# Patent

## Title
Compact wastewater concentrator and pollutant scrubber

## Abstract

A compact and portable liquid concentrator includes a gas inlet, a gas exit and a flow corridor connecting the gas inlet and the gas exit, wherein the flow corridor includes a narrowed portion that accelerates the gas through the flow corridor. A liquid inlet injects liquid into the gas stream at a point prior to the narrowed portion so that the gas-liquid mixture is thoroughly mixed within the flow corridor, causing a portion of the liquid to be evaporated. A demister or fluid scrubber downstream of the narrowed portion removes entrained liquid droplets from the gas stream and re-circulates the removed liquid to the liquid inlet through a re-circulating circuit. Fresh liquid to be concentrated is also introduced into the re-circulating circuit at a rate sufficient to offset the amount of liquid evaporated in the flow corridor.

## Background
RELATED APPLICATIONS
This application is a continuation in part of U.S. patent application Ser. No. 12/705,462, filed on Feb. 12, 2010, which is a continuation in part of U.S. patent application Ser. No. 12/530,484, filed on Sep. 9, 2009, which is a U.S. national phase application of International (PCT) Patent Application No. PCT/US08/56702 filed Mar. 12, 2008 and which claims priority benefit of U.S. Provisional Patent Application No. 60/906,743, filed on Mar. 13, 2007. This application also claims priority benefit of U.S. Provisional Patent Application No. 61/229,650, filed Jul. 29, 2009. The entire disclosures of each of application Ser. Nos. 12/530,484; 60/906,743; 61/152,248; and 61/229,650 are hereby expressly incorporated by reference herein.


FIELD OF THE DISCLOSURE
This application relates generally to liquid concentrators, and more specifically to compact, portable, cost-effective wastewater concentrators that can be easily connected to and use sources of waste heat.
BACKGROUND
Concentration of volatile substances can be an effective form of treatment or pretreatment for a broad variety of wastewater streams and may be carried out within various types of commercial processing systems. At high levels of concentration, many wastewater streams may be reduced to residual material in the form of slurries containing high levels of dissolved and suspended solids. Such concentrated residual may be readily solidified by conventional techniques for disposal within landfills or, as applicable, delivered to downstream processes for further treatment prior to final disposal. Concentrating wastewater can greatly reduce freight costs and required storage capacity and may be beneficial in downstream processes where materials are recovered from the wastewater.
Characteristics of industrial wastewater streams are very broad as a result of the large number of industrial processes that produce them. In addition to wastewater produced by design under controlled conditions within industry, uncontrolled events arising from accidents and natural disasters frequently generate wastewater. Techniques for managing wastewater include: direct discharge to sewage treatment plants; pretreatment followed by discharge to sewage treatment plants; on-site or off-site processes to reclaim valuable constituents; and on-site or off-site treatment to simply prepare the wastewater for ultimate disposal. Where the wastewater source is an uncontrolled event, effective containment and recovery techniques must be included with any of these options.
An important measure of the effectiveness of a wastewater concentration process is the volume of residual produced in proportion to the volume of wastewater entering the process. In particular, low ratios of residual volume to feed volume (high levels of concentration) are the most desirable. Where the wastewater contains dissolved and/or suspended non-volatile matter, the volume reduction that may be achieved in a particular concentration process that relies on evaporation of volatiles is, to a great extent, limited by the method chosen to transfer heat to the process fluid.
Conventional processes that affect concentration by evaporation of water and other volatile substances may be classified as direct or indirect heat transfer systems depending upon the method employed to transfer heat to the liquid undergoing concentration (the process fluid). Indirect heat transfer devices generally include jacketed vessels that contain the process fluid, or plate, bayonet tube or coil type heat exchangers that are immersed within the process fluid. Mediums such as steam or hot oil are passed through the jackets or heat exchangers in order to transfer the heat required for evaporation. Direct heat transfer devices implement processes where the heating medium is brought into direct contact with the process fluid, which occurs in, for example, submerged combustion gas systems.
Indirect heat transfer systems that rely on heat exchangers such as jackets, plates, bayonet tubes or coils are generally limited by the buildup of deposits of solids on the surfaces of the heat exchangers that come into direct contact with the process fluid. Also, the design of such systems is complicated by the need for a separate process to transfer heat energy to the heating medium such as a steam boiler or devices used to heat other heat transfer fluids such as hot oil heaters. This design leads to dependence on two indirect heat transfer systems to support the concentration process. Feed streams that produce deposits on heat exchangers while undergoing processing are called fouling fluids. Where feed streams contain certain compounds such as carbonates for which solubility decreases with increasing temperature, deposits, generally known as boiler scale, will form even at relatively low concentrations due to the elevated temperatures at the surfaces of the heat exchangers. Further, when compounds that have high solubility at elevated temperatures such as sodium chloride are present in the wastewater feed, they will also form deposits by precipitating out of the solution as the process fluid reaches high concentrations. Such deposits, which necessitate frequent cycles of heat exchange surface cleaning to maintain process efficiency, may be any combination of suspended solids carried into the process with the wastewater feed and solids that precipitate out of the process fluid. The deleterious effects of deposition of solids on heat exchange surfaces limits the length of time that indirect heat transfer processes may be operated before these processes must be shut down for periodic cleaning. These deleterious effects thereby impose practical limits on the range of wastewater that might be effectively managed, especially when the range of wastewater includes fouling fluids. Therefore, processes that rely on indirect heat transfer mechanisms are generally unsuitable for concentrating wide varieties of wastewater streams and achieving low ratios of residual to feed volume.
U.S. Pat. No. 5,342,482, which is hereby incorporated by reference, discloses a particular type of direct heat transfer concentrator in the form of a submerged gas process wherein combustion gas is generated and delivered though an inlet pipe to a dispersal unit submerged within the process fluid. The dispersal unit includes a number of spaced-apart gas delivery pipes extending radially outwardly from the inlet pipe, each of the gas delivery pipes having small holes spaced apart at various locations on the surface of the gas delivery pipe to disperse the combustion gas as small bubbles as uniformly as practical across the cross-sectional area of the liquid held within a processing vessel. According to current understanding within the prior art, this design provides desirable intimate contact between the liquid and the hot gas over a large interfacial surface area. In this process, the intent is that both heat and mass transfer occur at the dynamic and continuously renewable interfacial surface area formed by the dispersion of a gas phase in a process fluid, and not at solid heat exchange surfaces on which deposition of solid particles can occur. Thus, this submerged gas concentrator process provides a significant advantage over conventional indirect heat transfer processes. However, the small holes in the gas delivery pipes that are used to distribute hot gases into the process fluid within the device of U.S. Pat. No. 5,342,482 are subject to blockages by deposits of solids formed from fouling fluids. Thus, the inlet pipe that delivers hot gases to the process fluid is subject to the buildup of deposits of solids.
Further, as the result of the need to disperse large volumes of gas throughout a continuous process liquid phase, the containment vessel within U.S. Pat. No. 5,342,482 generally requires significant cross-sectional area. The inner surfaces of such containment vessels and any appurtenances installed within them are collectively referred to as the “wetted surfaces” of the process. These wetted surfaces must withstand varying concentrations of hot process fluids while the system is in operation. For systems designed to treat a broad range of wastewater streams, the materials of construction for the wetted surfaces present critical design decisions in relation to both corrosion and temperature resistance which must be balanced against the cost of equipment and the costs of maintenance/replacement over time. Generally speaking, durability and low maintenance/replacement costs for wetted surfaces are enhanced by selecting either high grades of metal alloys or certain engineered plastics such as those used in manufacturing fiberglass vessels. However, conventional concentration processes that employ either indirect or direct heating systems also require means for hot mediums such as steam, heat transfer oil or gases to transfer heat to the fluid within the vessel. While various different high alloys offer answers in regard to corrosion and temperature resistance, the costs of the vessels and the appurtenances fabricated from them are generally quite high. Further, while engineered plastics may be used either directly to form the containment vessel or as coatings on the wetted surfaces, temperature resistance is generally a limiting factor for many engineered plastics. For example, the high surface temperatures of the inlet pipe for hot gas within vessels used in U.S. Pat. No. 5,342,482 imposes such limits. Thus, the vessels and other equipment used for these processes are typically very expensive to manufacture and maintain.
Moreover, in all of these systems, a source of heat is required to perform the concentration or evaporative processes. Numerous systems have been developed to use heat generated by various sources, such as heat generated in an engine, in a combustion chamber, in a gas compression process, etc., as a source of heat for wastewater processing. One example of such a system is disclosed in U.S. Pat. No. 7,214,290 in which heat is generated by combusting landfill gas within a submerged combustion gas evaporator, which is used to process leachate at a landfill site. U.S. Pat. No. 7,416,172 discloses a submerged gas evaporator in which waste heat may be provided to an input of the gas evaporator to be used in concentrating or evaporating liquids. While waste heat is generally considered to be a cheap source of energy, to be used effectively in a wastewater processing operation, the waste heat must in many cases be transported a significant distance from the source of the waste heat to a location at which the evaporative or concentration process is to be performed. For example, in many cases, a landfill operation will have electricity generators which use one or more internal combustion engines operating with landfill gas as a combustion fuel. The exhaust of these generators or engines, which is typically piped through a muffler and an exhaust stack to the atmosphere at the top of a building containing the electrical generators, is a source of waste heat. However, to collect and use this waste heat, significant amounts of expensive piping and ductwork must be coupled to the exhaust stack to transfer the waste heat to location of the processing system, which will usually be at ground level away from the building containing the generators. Importantly, the piping, ducting materials, and control devices (e.g., throttling and shutoff valves) that can withstand the high temperatures (e.g., 950 degrees Fahrenheit) of the exhaust gases within the exhaust stack are very expensive and must be insulated to retain the heat within the exhaust gases during transport. Acceptable insulating materials used for such purposes are generally prone to failure due to a variety of characteristics that add complexity to the design such as brittleness, tendencies to erode over time, and sensitivity to thermal cycling. Insulation also increases the weight of the piping, ducting, and control devices, which adds costs to structural support requirements.
SUMMARY
A compact liquid concentrating device disclosed herein may be easily connected to a source of waste heat, such as a landfill gas flare or a combustion engine exhaust stack, and use this waste heat to perform a direct heat transfer concentration process without the need of large and expensive containment vessels and without a lot of expensive high temperature resistant materials. The compact liquid concentrator includes a gas inlet, a gas exit and a mixing or flow corridor connecting the gas inlet and the gas exit, wherein the flow corridor includes a narrowed portion that accelerates the gas through the flow corridor. A liquid inlet located between the gas inlet and the narrowed portion of the flow corridor, injects liquid into the gas stream at a point prior to the narrowed portion so that the gas-liquid mixture is thoroughly mixed within the flow corridor, causing a portion of the liquid to be evaporated or concentrated. A demister or fluid scrubber downstream of the narrowed portion, and connected to the gas exit, removes entrained liquid droplets from the gas stream and re-circulates the removed liquid to the liquid inlet through a re-circulating circuit. Fresh liquid to be concentrated is also introduced into the re-circulating circuit at a rate sufficient to offset the combined total of liquid evaporated in the flow corridor and any concentrated liquid that is withdrawn from the process.
The compact liquid concentrator described herein includes a number of attributes that operate to cost-effectively concentrate wastewater streams having broad ranges of characteristics. The concentrator is resistant to corrosive effects over a broad range of feed characteristics, has reasonable manufacturing and operating costs, is able to operate continuously at high levels of concentration, and efficiently utilizes heat energy directly from a wide variety of sources. Moreover, the concentrator is compact enough to be portable, and so may be easily transported to locations where wastewater is generated through uncontrolled events and can be installed in close proximity to waste heat sources. Thus, the concentrator disclosed herein is a cost-effective, reliable and durable device that operates to continuously concentrate a broad range of different types of wastewater streams, and that eliminates the use of conventional solid-surface heat exchangers found in conventional indirect heat transfer systems which lead to clogging and deposit buildups.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a general schematic diagram of a compact liquid concentrator;
FIG. 2 depicts an embodiment of the liquid concentrator of FIG. 1 mounted on a pallet or skid for easy transportation on a truck;
FIG. 3 is a perspective view of a compact liquid concentrator which implements the concentration process of FIG. 1, connected to a source of waste heat produced by a landfill flare;
FIG. 4 is a perspective view of a heat transfer portion of the compact liquid concentrator of FIG. 3;
FIG. 5 is a front perspective view of an evaporator/concentrator portion of the compact liquid concentrator of FIG. 3;
FIG. 6 is a perspective view of easy opening access doors on a portion of the compact liquid concentrator of FIG. 3;
FIG. 7 is a perspective view of one of the easy opening access doors of FIG. 6 in the open position;
FIG. 8 is a perspective view of an easy opening latch mechanism used on the access doors of FIGS. 6 and 7;
FIG. 9 is a schematic diagram of a control system which may be used in the compact liquid concentrator of FIG. 3 to control the operation of the various component parts of the compact liquid concentrator;
FIG. 10 is a diagram of the compact liquid concentrator of FIG. 3 attached to a combustion engine stack as a source of waste heat;
FIG. 11 is a general schematic diagram of a second embodiment of a compact liquid concentrator;
FIG. 12 is a top view of the compact liquid concentrator of FIG. 11;
FIG. 13 is a schematic diagram of a third embodiment of a compact liquid concentrator, the third embodiment being a distributed liquid concentrator;
FIG. 14 is a side elevational cross-section of the liquid concentrating portion of the distributed liquid concentrator of FIG. 13;
FIG. 15 is atop plan view of the liquid concentrating section of FIG. 14; and
FIG. 16 is a close up side view of a quencher and venturi section of the distributed liquid concentrator of FIG. 13.
FIG. 17 is a perspective view of an alternate embodiment of a compact liquid concentrator that implements the concentration process of FIG. 1, and configured to remove ammonia from landfill leachate.



DETAILED DESCRIPTION
FIG. 1 depicts a generalized schematic diagram of a liquid concentrator 10 that includes a gas inlet 20, a gas exit 22 and a flow corridor 24 connecting the gas inlet 20 to the gas exit 22. The flow corridor 24 includes a narrowed portion 26 that accelerates the flow of gas through the flow corridor 24 creating turbulent flow within the flow corridor 24 at or near this location. The narrowed portion 26 in this embodiment may be formed by a venturi device. A liquid inlet 30 injects a liquid to be concentrated (via evaporation) into a liquid concentration chamber in the flow corridor 24 at a point upstream of the narrowed portion 26, and the injected liquid joins with the gas flow in the flow corridor 24. The liquid inlet 30 may include one or more replaceable nozzles 31 for spraying the liquid into the flow corridor 24. The inlet 30, whether or not equipped with a nozzle 31, may introduce the liquid in any direction from perpendicular to parallel to the gas flow as the gas moves through the flow corridor 24. A baffle 33 may also be located near the liquid inlet 30 such that liquid introduced from the liquid inlet 30 impinges on the baffle and disperses into the flow corridor in small droplets.
As the gas and liquid flow through the narrowed portion 26, the venturi principle creates an accelerated and turbulent flow that thoroughly mixes the gas and liquid in the flow corridor 24 at and after the location of the inlet 30. This acceleration through the narrowed portion 26 creates shearing forces between the gas flow and the liquid droplets, and between the liquid droplets and the walls of the narrowed portion 26, resulting in the formation of very fine liquid droplets entrained in the gas, thus increasing the interfacial surface area between the liquid droplets and the gas and effecting rapid mass and heat transfer between the gas and the liquid droplets. The liquid exits the narrowed portion 26 as very fine droplets regardless of the geometric shape of the liquid flowing into the narrowed portion 26 (e.g., the liquid may flow into the narrowed portion 26 as a sheet of liquid). As a result of the turbulent mixing and shearing forces, a portion of the liquid rapidly vaporizes and becomes part of the gas stream. As the gas-liquid mixture moves through the narrowed portion 26, the direction and/or velocity of the gas/liquid mixture may be changed by an adjustable flow restriction, such as a venturi plate 32, which is generally used to create a large pressure difference in the flow corridor 24 upstream and downstream of the venturi plate 32. The venturi plate 32 may be adjustable to control the size and/or shape of the narrowed portion 26 and may be manufactured from a corrosion resistant material including a high alloy metal such as those manufactured under the trade names of Hastelloy®, Inconel® and Monel®.
After leaving the narrowed portion 26, the gas-liquid mixture passes through a demister 34 (also referred to as fluid scrubbers or entrainment separators) coupled to the gas exit 22. The demister 34 removes entrained liquid droplets from the gas stream. The demister 34 includes a gas-flow passage. The removed liquid collects in a liquid collector or sump 36 in the gas-flow passage, the sump 36 may also include a reservoir for holding the removed liquid. A pump 40 fluidly coupled to the sump 36 and/or reservoir moves the liquid through a re-circulating circuit 42 back to the liquid inlet 30 and/or flow corridor 24. In this manner, the liquid may be reduced through evaporation to a desired concentration. Fresh or new liquid to be concentrated is input to the re-circulating circuit 42 through a liquid inlet 44. This new liquid may instead be injected directly into the flow corridor 24 upstream of the venturi plate 32. The rate of fresh liquid input into the re-circulating circuit 42 may be equal to the rate of evaporation of the liquid as the gas-liquid mixture flows through the flow corridor 24 plus the rate of liquid extracted through a concentrated fluid extraction port 46 located in or near the reservoir in the sump 40. The ratio of re-circulated liquid to fresh liquid may generally be in the range of approximately 1:1 to approximately 100:1, and is usually in the range of approximately 5:1 to approximately 25:1. For example, if the re-circulating circuit 42 circulates fluid at approximately 10 gal/min, fresh or new liquid may be introduced at a rate of approximately 1 gal/min (i.e., a 10:1 ratio). A portion of the liquid may be drawn off through the extraction port 46 when the liquid in the re-circulating circuit 42 reaches a desired concentration. The re-circulating circuit 42 acts as a buffer or shock absorber for the evaporation process ensuring that enough moisture is present in the flow corridor 24 to prevent the liquid from being completely evaporated and/or preventing the formation of dry particulate.
After passing through the demister 34 the gas stream passes through an induction fan 50 that draws the gas through the flow corridor 24 and demister gas-flow corridor under negative pressure. Of course, the concentrator 10 could operate under positive pressure produced by a blower (not shown) prior to the liquid inlet 30. Finally, the gas is vented to the atmosphere or directed for further processing through the gas exit 22.
The concentrator 10 may include a pre-treatment system 52 for treating the liquid to be concentrated, which may be a wastewater feed. For example, an air stripper may be used as a pre-treatment system 52 to remove substances that may produce foul odors or be regulated as air pollutants. In this case, the air stripper may be any conventional type of air stripper or may be a further concentrator of the type described herein, which may be used in series as the air stripper. The pre-treatment system 52 may, if desired, heat the liquid to be concentrated using any desired heating technique. Additionally, the gas and/or wastewater feed circulating through the concentrator 10 may be pre-heated in a pre-heater 54. Pre-heating may be used to enhance the rate of evaporation and thus the rate of concentration of the liquid. The gas and/or wastewater feed may be pre-heated through combustion of renewable fuels such as wood chips, bio-gas, methane, or any other type of renewable fuel or any combination of renewable fuels, fossil fuels and waste heat. Furthermore, the gas and/or wastewater may be pre-heated through the use of waste heat generated in a landfill flare or stack. Also, waste heat from an engine, such as an internal combustion engine, may be used to pre-heat the gas and/or wastewater feed. Still further, natural gas may be used as a source of waste heat, the natural gas may be supplied directly from a natural gas well head in an unrefined condition either immediately after completion of the natural gas well before the gas flow has stabilized or after the gas flow has stabilized in a more steady state natural gas well. Optionally, the natural gas may be refined before being combusted in the flare. Additionally, the gas streams ejected from the gas exit 22 of the concentrator 10 may be transferred into a flare or other post treatment device 56 which treats the gas before releasing the gas to the atmosphere.
The liquid concentrator 10 described herein may be used to concentrate a wide variety of wastewater streams, such as waste water from industry, runoff water from natural disasters (floods, hurricanes), refinery caustic, leachate such as landfill leachate, flowback water from completion of natural gas wells, produced water from operation of natural gas wells, etc. The liquid concentrator 10 is practical, energy efficient, reliable, and cost-effective. In order to increase the utility of this liquid concentrator, the liquid concentrator 10 is readily adaptable to being mounted on a trailer or a moveable skid to effectively deal with wastewater streams that arise as the result of accidents or natural disasters or to routinely treat wastewater that is generated at spatially separated or remote sites. The liquid concentrator 10 described herein has all of these desirable characteristics and provides significant advantages over conventional wastewater concentrators, especially when the goal is to manage a broad variety of wastewater streams.
Moreover, the concentrator 10 may be largely fabricated from highly corrosion resistant, yet low cost materials such as fiberglass and/or other engineered plastics. This is due, in part, to the fact that the disclosed concentrator is designed to operate under minimal differential pressure. For example, a differential pressure generally in the range of only 10 to 30 inches water column is required. Also, because the gas-liquid contact zones of the concentration processes generate high turbulence within narrowed (compact) passages at or directly after the venturi section of the flow path, the overall design is very compact as compared to conventional concentrators where the gas liquid contact occurs in large process vessels. As a result, the amount of high alloy metals required for the concentrator 10 is quite minimal. Also, because these high alloy parts are small and can be readily replaced in a short period of time with minimal labor, fabrication costs may be cut to an even higher degree by designing some or all of these parts to be wear items manufactured from lesser quality alloys that are to be replaced at periodic intervals. If desired, these lesser quality alloys (e.g., carbon steel) may be coated with corrosion and/or erosion resistant liners, such as engineered plastics including elastomeric polymers, to extend the useful life of such components. Likewise, the pump 40 may be provided with corrosion and/or erosion resistant liners to extend the life of the pump 40, thus further reducing maintenance and replacement costs.
As will be understood, the liquid concentrator 10 provides direct contact of the liquid to be concentrated and the hot gas, effecting highly turbulent heat exchange and mass transfer between hot gas and the liquid, e.g., wastewater, undergoing concentration. Moreover, the concentrator 10 employs highly compact gas-liquid contact zones, making it minimal in size as compared to known concentrators. The direct contact heat exchange feature promotes high energy efficiency and eliminates the need for solid surface heat exchangers as used in conventional, indirect heat transfer concentrators. Further, the compact gas-liquid contact zone eliminates the bulky process vessels used in both conventional indirect and direct heat exchange concentrators. These features allow the concentrator 10 to be manufactured using comparatively low cost fabrication techniques and with reduced weight as compared to conventional concentrators. Both of these factors favor portability and cost-effectiveness. Thus, the liquid concentrator 10 is more compact and lighter in weight than conventional concentrators, which make it ideal for use as a portable unit. Additionally, the liquid concentrator 10 is less prone to fouling and blockages due to the direct contact heat exchange operation and the lack of solid heat exchanger surfaces. The liquid concentrator 10 can also process liquids with significant amounts of suspended solids because of the direct contact heat exchange. As a result, high levels of concentration of the process fluids may be achieved without need for frequent cleaning of the concentrator 10.
More specifically, in liquid concentrators that employ indirect heat transfer, the heat exchangers are prone to fouling and are subject to accelerated effects of corrosion at the normal operating temperatures of the hot heat transfer medium that is circulated within them (steam or other hot fluid). Each of these factors places significant limits on the durability and/or costs of building conventional indirectly heated concentrators, and on how long they may be operated before it is necessary to shut down and clean or repair the heat exchangers. By eliminating the bulky process vessels, the weight of the liquid concentrators and both the initial costs and the replacement costs for high alloy components are greatly reduced. Moreover, due to the temperature difference between the gas and liquid, the relatively small volume of liquid contained within the system, the relatively large interfacial area between the liquid and the gas, and the reduced relative humidity of the gas prior to mixing with the liquid, the concentrator 10 approaches the adiabatic saturation temperature for the particular gas/liquid mixture, which is typically in the range of about 150 degrees Fahrenheit to about 215 degrees Fahrenheit (i.e., this concentrator is a “low momentum” concentrator).
Moreover, the concentrator 10 is designed to operate under negative pressure, a feature that greatly enhances the ability to use a very broad range of fuel or waste heat sources as an energy source to affect evaporation. In fact, due to the draft nature of these systems, pressurized or non-pressurized burners may be used to heat and supply the gas used in the concentrator 10. Further, the simplicity and reliability of the concentrator 10 is enhanced by the minimal number of moving parts and wear parts that are required. In general, only two pumps and a single induced draft fan are required for the concentrator when it is configured to operate on waste heat such as stack gases from engines (e.g., generators or vehicle engines), turbines, industrial process stacks, gas compressor systems, and flares, such as landfill gas flares. These features provide significant advantages that reflect favorably on the versatility and the costs of buying, operating and maintaining the concentrator 10.
The concentrator 10 may be run in a start up condition, or in a steady state condition. During the startup condition, the demister 34 sump and re-circulating circuit 42 may be filled with fresh wastewater. During initial processing, the fresh wastewater introduced into the inlet 30 is at least partially evaporated in the narrowed portion 26 and is deposited in the demister 34 sump in a more concentrated form than the fresh wastewater. Over time, the wastewater in the demister sump 34 and the re-circulating circuit 42 approaches a desired level of concentration. At this point, the concentrator 10 may be run in a continuous mode where the amount of solids drawn off in the extraction port 46 equals the amount of solids introduced in fresh wastewater through the inlet 30. Likewise, the amount of water evaporated within the concentrator 10 is replaced by an equal amount of water in the fresh wastewater. Thus, conditions within the concentrator 10 approach the adiabatic saturation point of the mixture of heated gas and wastewater. As a result, the concentrator 10 is highly efficient.
FIG. 2 illustrates a side view of the liquid concentrator 10 mounted on a movable frame 60, such as a pallet, a trailer or a skid. The movable frame is sized and shaped for easy loading on, or connection to, a transportation vehicle 62, such as a tractor-trailer truck Likewise, such a mounted concentrator may easily be loaded onto a train, a ship or an airplane (not shown) for rapid transportation to remote sites. The liquid concentrator 10 may operate as a totally self-contained unit by having its own burner and fuel supply, or the liquid concentrator 10 may operate using an on-site burner and/or an on-site fuel or waste heat source. Fuels for the concentrator 10 may include renewable fuel sources, such as waste products (paper, wood chips, etc.), and landfill gas. Moreover, the concentrator 10 may operate on any combination of traditional fossil fuels such as coal or petroleum, renewable fuels and/or waste heat.
A typical trailer-mounted concentrator 10 may be capable of treating as much as one-hundred thousand gallons or more per day of wastewater, while larger, stationary units, such as those installed at landfills, sewage treatment plants, or natural gas or oil fields, may be capable of treating multiples of one-hundred thousand gallons of wastewater per day.
FIG. 3 illustrates one particular embodiment of a compact liquid concentrator 110 which operates using the principles described above with respect to FIG. 1 and which is connected to a source of waste heat in the form of a landfill flare. Generally speaking, the compact liquid concentrator 110 of FIG. 3 operates to concentrate wastewater, such as landfill leachate, using exhaust or waste heat created within a landfill flare which burns landfill gas in a manner that meets the standards set by the U.S. Environmental Protection Agency (EPA) and/or more local regulatory authority. As is known, most landfills include a flare which is used to burn landfill gas to eliminate methane and other gases prior to release to the atmosphere. Typically, the gas exiting the flare is between 1200 and 1500 degrees Fahrenheit and may reach 1800 degrees Fahrenheit. The compact liquid concentrator 100 illustrated in FIG. 3 is equally effective in concentrating flowback or produced water from natural gas wells and may be operated on exhaust gas from a natural gas flare, or a propane flare, at or near the well head. The natural gas flare may be supplied with natural gas directly from the natural gas well, in some embodiments.
As illustrated in FIG. 3, the compact liquid concentrator 110 generally includes or is connected to a flare assembly 115, and includes a heat transfer assembly 117 (shown in more detail in FIG. 4), an air pre-treatment assembly 119, a concentrator assembly 120 (shown in more detail in FIG. 5), a fluid scrubber 122, and an exhaust section 124. Importantly, the flare assembly 115 includes a flare 130, which burns landfill gas (or other combustible fuel) therein according to any known principles, and a flare cap assembly 132. The flare cap assembly 132 includes a moveable cap 134 (e.g., a flare cap, an exhaust gas cap, etc.) which covers the top of the flare 130, or other type of stack (e.g., a combustion gas exhaust stack), to seal off the top of the flare 130 when the flare cap 134 is in the closed position, or to divert a portion of the flare gas in a partially closed position, and which allows gas produced within the flare 130 to escape to the atmosphere through an open end that forms a primary gas outlet 143, when the flare cap 134 is in an open or partially open position. The flare cap assembly 132 also includes a cap actuator 135, such as a motor (e.g., an electric motor, a hydraulic motor, a pneumatic motor, etc., shown in FIG. 4) which moves the flare cap 134 between the fully open and the fully closed positions. As shown in FIG. 4, the flare cap actuator 135 may, for example, rotate or move the flare cap 134 around a pivot point 136 to open and close the flare cap 134. The flare cap actuator 135 may utilize a chain drive or any other type of drive mechanism connected to the flare cap 134 to move the flare cap 134 around the pivot point 136. The flare cap assembly 132 may also include a counter-weight 137 disposed on the opposite side of the pivot point 136 from the flare cap 134 to balance or offset a portion of the weight of the flare cap 134 when moving the flare cap 134 around the pivot point 136. The counter-weight 137 enables the actuator 135 to be reduced in size or power while still being capable of moving or rotating the flare cap 134 between an open position, in which the top of the flare 130 (or the primary combustion gas outlet 143) is open to the atmosphere, and a closed position, in which the flare cap 134 covers and essentially seals the top of the flare 130 (or the primary combustion gas outlet 143). The flare cap 134 itself may be made of high temperature resistant material, such as stainless steel or carbon steel, and may be lined or insulated with refractory material including aluminum oxide and/or zirconium oxide on the bottom portion thereof which comes into direct contact with the hot flare gases when the flare cap 134 is in the closed position.
If desired, the flare 130 may include an adapter section 138 including the primary combustion gas outlet 143 and a secondary combustion gas outlet 141 upstream of the primary combustion gas outlet 143. When the flare cap 130 is in the closed position, combustion gas is diverted through the secondary combustion gas outlet 141. The adapter section 138 may include a connector section 139 that connects the flare 130 (or exhaust stack) to the heat transfer section 117 using a 90 degree elbow or turn. Other connector arrangements are possible. For example, the flare 130 and heat transfer section 117 may be connected at virtually any angle between 0 degrees and 180 degrees. In this case, the flare cap assembly 132 is mounted on the top of the adaptor section 138 proximate the primary combustion gas outlet 143.
As illustrated in FIGS. 3 and 4, the heat transfer assembly 117 includes a transfer pipe 140, which connects to an inlet of the air pre-treatment assembly 119 to the flare 130 and, more particularly, to the adaptor section 138 of the flare 130. A support member 142, in the form of a vertical bar or pole, supports the heat transfer pipe 140 between the flare 130 and the air pre-treatment assembly 119 at a predetermined level or height above the ground. The heat transfer pipe 140 is connected to the connector section 139 or the adapter section 138 at the secondary combustion gas outlet 141, the transfer pipe forming a portion of a fluid passageway between the adapter section 138 and a secondary process, such as a fluid concentrating process. The support member 142 is typically necessary because the heat transfer pipe 140 will generally be made of metal, such as carbon or stainless steel, and may be refractory lined with materials such as aluminum oxide and/or zirconium oxide, to withstand the temperature of the gas being transferred from the flare 130 to the air pre-treatment assembly 119. Thus, the heat transfer pipe 140 will typically be a heavy piece of equipment. However, because the flare 130, on the one hand, and the air pre-treatment assembly 119 and the concentrator assembly 120, on the other hand, are disposed immediately adjacent to one another, the heat transfer pipe 140 generally only needs to be of a relatively short length, thereby reducing the cost of the materials used in the concentrator 110, as well as reducing the amount of support structure needed to bear the weight of the heavy parts of the concentrator 110 above the ground. As illustrated in FIG. 3, the heat transfer pipe 140 and the air pre-treatment assembly 1119 form an upside-down U-shaped structure.
The air pre-treatment assembly 119 includes a vertical piping section 150 and an ambient air valve (not shown explicitly in FIGS. 3 and 4) disposed at the top of the vertical piping section 150. The ambient air valve (also referred to as a damper or bleed valve) forms a fluid passageway between the heat transfer pipe 140 (or air pre-treatment assembly 119) and the atmosphere. The ambient air valve operates to allow ambient air to flow through a mesh bird screen 152 (typically wire or metal) and into the interior of the air pre-treatment assembly 119 to mix with the hot gas coming from the flare 130. If desired, the air pre-treatment assembly 119 may include a permanently open section proximate to the bleed valve which always allows some amount of bleed air into the air pre-treatment assembly 119, which may be desirable to reduce the size of the required bleed valve and for safety reasons. A pressure blower (not shown) may be connected to the inlet side of the ambient air valve, if desired, to force ambient air through the ambient air valve. If a pressure blower is implemented, the bird screen 152 and permanently open section (if implemented) may be relocated to the inlet side of the pressure blower. While the control of the ambient air or bleed valve will be discussed in greater detail hereinafter, this valve generally allows the gas from the flare 130 to be cooled to a more desirable temperature before entering into the concentrator assembly 120. The air pre-treatment assembly 119 may be supported in part by cross-members 154 connected to the support member 142. The cross-members 154 stabilize the air pre-treatment assembly 119, which is also typically made of heavy carbon or stainless steel or other metal, and which may be refractory-lined to improve energy efficiency and to withstand the high temperature of the gases within this section of the concentrator 110. If desired, the vertical piping section 150 may be extendable to adapt to or account for flares of differing heights so as to make the liquid concentrator 110 easily adaptable to many different flares or to flares of different heights and also to improve efficiency when erecting concentrators by correcting for slight vertical and/or horizontal misalignment of components. This concept is illustrated in more detail in FIG. 3. As shown in FIG. 3, the vertical piping section 150 may include a first section 150A (shown using dotted lines) that rides inside of a second section 150B thereby allowing the vertical piping section 150 to be adjustable in length (height).
Generally speaking, the air pre-treatment assembly 119 operates to mix ambient air provided through the ambient air valve beneath the screen 152 and the hot gas flowing from the flare 130 through the heat transfer pipe 140 to create a desired temperature of gas at the inlet of the concentrator assembly 120.
The liquid concentrator assembly 120 includes a lead-in section 156 having a reduced cross-section at the top end thereof which mates the bottom of the piping section 150 to a quencher 159 of the concentrator assembly 120. The concentrator assembly 120 also includes a first fluid inlet 160, which injects new or untreated liquid to be concentrated, such as landfill leachate, into the interior of the quencher 159. While not shown in FIG. 3, the inlet 160 may include a coarse sprayer with a large nozzle for spraying the untreated liquid into the quencher 159. Because the liquid being sprayed into the quencher 159 at this point in the system is not yet concentrated, and thus has large amount of water therein, and because the sprayer is a coarse sprayer, the sprayer nozzle is not subject to fouling or being clogged by the small particles within the liquid. As will be understood, the quencher 159 operates to quickly reduce the temperature of the gas stream (e.g., from about 900 degrees Fahrenheit to less than 200 degrees Fahrenheit) while performing a high degree of evaporation on the liquid injected at the inlet 160. If desired, but not specifically shown in FIG. 3, a temperature sensor may be located at or near the exit of the piping section 150 or in the quencher 159 and may be used to control the position of the ambient air valve to thereby control the temperature of the gas present at the inlet of the concentrator assembly 120.
As shown in FIGS. 3 and 5, the quencher 159 is connected to liquid injection chamber which is connected to narrowed portion or venturi section 162 which has a narrowed cross section with respect to the quencher 159 and which has a venturi plate 163 (shown in dotted line) disposed therein. The venturi plate 163 creates a narrow passage through the venturi section 162, which creates a large pressure drop between the entrance and the exit of the venturi section 162. This large pressure drop causes turbulent gas flow and shearing forces within the quencher 159 and the top or entrance of the venturi section 162, and causes a high rate of gas flow out of the venturi section 162, both of which lead to thorough mixing of the gas and liquid in the venturi section 162. The position of the venturi plate 163 may be controlled with a manual control rod 165 (shown in FIG. 5) connected to the pivot point of the plate 163, or via an automatic positioner that may be driven by an electric motor or pneumatic cylinder (not shown in FIG. 5).
A re-circulating pipe 166 extends around opposite sides of the entrance of the venturi section 162 and operates to inject partially concentrated (i.e., re-circulated) liquid into the venturi section 162 to be further concentrated and/or to prevent the formation of dry particulate within the concentrator assembly 120 through multiple fluid entrances located on one or more sides of the flow corridor. While not explicitly shown in FIGS. 3 and 5, a number of pipes, such as three pipes of, for example, 1⁄2 inch diameter, may extend from each of the opposites legs of the pipe 166 partially surrounding the venturi section 162, and through the walls and into the interior of the venturi section 162. Because the liquid being ejected into the concentrator 110 at this point is re-circulated liquid, and is thus either partially concentrated or being maintained at a particular equilibrium concentration and more prone to plug a spray nozzle than the less concentrated liquid injected at the inlet 160, this liquid may be directly injected without a sprayer so as to prevent clogging. However, if desired, a baffle in the form of a flat plate may be disposed in front of each of the openings of the 1⁄2 diameter pipes to cause the liquid being injected at this point in the system to hit the baffle and disperse into the concentrator assembly 120 as smaller droplets. In any event, the configuration of this re-circulating system distributes or disperses the re-circulating liquid better within the gas stream flowing through the concentrator assembly 120.
The combined hot gas and liquid flows in a turbulent manner through the venturi section 162. As noted above, the venturi section 162, which has a moveable venturi plate 163 disposed across the width of the concentrator assembly 120, causes turbulent flow and complete mixture of the liquid and gas, causing rapid evaporation of the discontinuous liquid phase into the continuous gas phase. Because the mixing action caused by the venturi section 162 provides a high degree of evaporation, the gas cools substantially in the concentrator assembly 120, and exits the venturi section 162 into a flooded elbow 164 at high rates of speed. In fact, the temperature of the gas-liquid mixture at this point may be about 160 degrees Fahrenheit.
As is typical of flooded elbows, a weir arrangement (not shown) within the bottom of the flooded elbow 164 maintains a constant level of partially or fully concentrated re-circulated liquid disposed therein. Droplets of re-circulated liquid that are entrained in the gas phase as the gas-liquid mixture exits the venturi section 162 at high rates of speed are thrown outward onto the surface of the re-circulated liquid held within the bottom of the flooded elbow 164 by centrifugal force generated when the gas-liquid mixture is forced to turn 90 degrees to flow into the fluid scrubber 122. Significant numbers of liquid droplets entrained within the gas phase that impinge on the surface of the re-circulated liquid held in the bottom of the flooded elbow 164 coalesce and join with the re-circulated liquid thereby increasing the volume of re-circulated liquid in the bottom of the flooded elbow 164 causing an equal amount of the re-circulated liquid to overflow the weir arrangement and flow by gravity into the sump 172 at the bottom of the fluid scrubber 122. Thus, interaction of the gas-liquid stream with the liquid within the flooded elbow 164 removes liquid droplets from the gas-liquid stream, and also prevents suspended particles within the gas-liquid stream from hitting the bottom of the flooded elbow 164 at high velocities, thereby preventing erosion of the metal that forms the portions of side walls located beneath the level of the weir arrangement and the bottom of the flooded elbow 164.
After leaving the flooded elbow 164, the gas-liquid stream in which evaporated liquid and some liquid and other particles still exist, flows through the fluid scrubber 122 which is, in this case, across-flow fluid scrubber. The fluid scrubber 122 includes various screens or filters which serve to remove entrained liquids and other particles from the gas-liquid stream. In one particular example, the cross flow scrubber 122 may include an initial coarse impingement baffle 169 at the input thereof, which is designed to remove liquid droplets in the range of 50 to 100 microns in size or higher. Thereafter, two removable filters in the form of chevrons 170 are disposed across the fluid path through the fluid scrubber 122, and the chevrons 170 may be progressively sized or configured to remove liquid droplets of smaller and smaller sizes, such as 20-30 microns and less than 10 microns. Of course, more or fewer filters or chevrons could be used.
As is typical in cross flow scrubbers, liquid captured by the filters 169 and 170 and the overflow weir arrangement within the bottom of the flooded elbow 164 drain by gravity into a reservoir or sump 172 located at the bottom of the fluid scrubber 122. The sump 172, which may hold, for example approximately 200 gallons of liquid, thereby collects concentrated fluid containing dissolved and suspended solids removed from the gas-liquid stream and operates as a reservoir for a source of re-circulating concentrated liquid back to the concentrator assembly 120 to be further treated and/or to prevent the formation of dry particulate within the concentrator assembly 120 in the manner described above with respect to FIG. 1. In one embodiment, the sump 172 may include a sloped V-shaped bottom 171 having a V-shaped groove 175 extending from the back of the fluid scrubber 122 (furthest away from the flooded elbow 164) to the front of the fluid scrubber 122 (closest to the flooded elbow 164), wherein the V-shaped groove 175 is sloped such that the bottom of the V-shaped groove 175 is lower at the end of the fluid scrubber 122 nearest the flooded elbow 164 than at an end farther away from the flooded elbow 164. In other words, the V-shaped bottom 171 may be sloped with the lowest point of the V-shaped bottom 171 proximate the exit port 173 and/or the pump 182. Additionally, a washing circuit 177 (FIG. 9) may pump concentrated fluid from the sump 172 to a sprayer 179 within the cross flow scrubber 122, the sprayer 179 being aimed to spray liquid at the V-shaped bottom 171. Alternatively, the sprayer 179 may spray un-concentrated liquid or clean water at the V-shaped bottom 171. The sprayer 179 may periodically or constantly spray liquid onto the surface of the V-shaped bottom 171 to wash solids and prevent solid buildup on the V-shaped bottom 171 or at the exit port 173 and/or the pump 182. As a result of this V-shaped sloped bottom 171 and washing circuit 177, liquid collecting in the sump 172 is continuously agitated and renewed, thereby maintaining a relatively constant consistency and maintaining solids in suspension. If desired, the spraying circuit 177 may be a separate circuit using a separate pump with, for example, an inlet inside of the sump 172, or may use a pump 182 associated with a concentrated liquid re-circulating circuit described below to spray concentrated fluid from the sump 172 onto the V-shaped bottom 171.
As illustrated in FIG. 3, a return line 180, as well as a pump 182, operate to re-circulate fluid removed from the gas-liquid stream from the sump 172 back to the concentrator 120 and thereby complete a fluid or liquid re-circulating circuit. Likewise, a pump 184 may be provided within an input line 186 to pump new or untreated liquid, such as landfill leachate, to the input 160 of the concentrator assembly 120. Also, one or more sprayers 185 may be disposed inside the fluid scrubber 122 adjacent the chevrons 170 and may be operated periodically to spray clean water or a portion of the wastewater feed on the chevrons 170 to keep them clean.
Concentrated liquid also may be removed from the bottom of the fluid scrubber 122 via the exit port 173 and may be further processed or disposed of in any suitable manner in a secondary re-circulating circuit 181. In particular, the concentrated liquid removed by the exit port 173 contains a certain amount of suspended solids, which preferably may be separated from the liquid portion of the concentrated liquid and removed from the system using the secondary re-circulating circuit 181. For example, concentrated liquid removed from the exit port 173 may be transported through the secondary re-circulating circuit 181 to one or more solid/liquid separating devices 183, such as settling tanks, vibrating screens, rotary vacuum filters, horizontal belt vacuum filters, belt presses, filter presses, and/or hydro-cyclones. After the suspended solids and liquid portion of the concentrated wastewater are separated by the solid/liquid separating device 183, the liquid portion of the concentrated wastewater with suspended particles substantially removed may be returned to the sump 172 for further processing in the first or primary re-circulating circuit connected to the concentrator.
The gas, which flows through and out of the fluid scrubber 122 with the liquid and suspended solids removed therefrom, exits out of piping or ductwork at the back of the fluid scrubber 122 (downstream of the chevrons 170) and flows through an induced draft fan 190 of the exhaust assembly 124, from where it is exhausted to the atmosphere in the form of the cooled hot inlet gas mixed with the evaporated water vapor. Of course, an induced draft fan motor 192 is connected to and operates the fan 190 to create negative pressure within the fluid scrubber 122 on as to ultimately draw gas from the flare 130 through the transfer pipe 140, the air pre-treatment assembly 119 and the concentrator assembly 120. As described above with respect to FIG. 1, the induced draft fan 190 needs only to provide a slight negative pressure within the fluid scrubber 122 to assure proper operation of the concentrator 110.
While the speed of the induced draft fan 190 can be varied by a device such as a variable frequency drive operated to create varying levels of negative pressure within the fluid scrubber 122 and thus can usually be operated within a range of gas flow capacity to assure complete gas flow from the flare 130, if the gas being produced by the flare 130 is not of sufficient quantity, the operation of the induced draft fan 190 cannot necessarily be adjusted to assure a proper pressure drop across the fluid scrubber 122 itself. That is, to operate efficiently and properly, the gas flowing through the fluid scrubber 122 must be at a sufficient (minimal) flow rate at the input of the fluid scrubber 122. Typically this requirement is controlled by keeping at least a preset minimal pressure drop across the fluid scrubber 122. However, if the flare 130 is not producing at least a minimal level of gas, increasing the speed of the induced draft fan 190 will not be able to create the required pressure drop across the fluid scrubber 122.
To compensate for this situation, the cross flow scrubber 122 is designed to include a gas re-circulating circuit which can be used to assure that enough gas is present at the input of the fluid scrubber 122 to enable the system to acquire the needed pressure drop across the fluid scrubber 122. In particular, the gas re-circulating circuit includes a gas return line or return duct 196 which connects the high pressure side of the exhaust assembly 124 (e.g., downstream of the induced draft fan 190) to the input of the fluid scrubber 122 (e.g., a gas input of the fluid scrubber 122) and a baffle or control mechanism 198 disposed in the return duct 196 which operates to open and close the return duct 196 to thereby fluidly connect the high pressure side of the exhaust assembly 124 to the input of the fluid scrubber 122. During operation, when the gas entering into the fluid scrubber 122 is not of sufficient quantity to obtain the minimal required pressure drop across the fluid scrubber 122, the baffle 198 (which may be, for example, a gas valve, a damper such as a louvered damper, etc.) is opened to direct gas from the high pressure side of the exhaust assembly 124 (i.e., gas that has traveled through the induced draft fan 190) back to the input of the fluid scrubber 122. This operation thereby provides a sufficient quantity of gas at the input of the fluid scrubber 122 to enable the operation of the induced draft fan 190 to acquire the minimal required pressure drop across the fluid scrubber 122.
FIG. 6 illustrates the particular advantageous feature of the compact liquid concentrator 110 of FIG. 3 in the form of a set of easy opening access doors 200 which may be used to access the inside of the concentrator 110 for cleaning and viewing purposes. While FIG. 6 illustrates easy opening access doors 200 on one side of the fluid scrubber 122, a similar set of doors may be provided on the other side of the fluid scrubber 122, and a similar door is provided on the front of the flooded elbow 164, as shown in FIG. 5. As illustrated in FIG. 6, each of the easy access doors 200 on the fluid scrubber 122 includes a door plate 202, which may be a flat piece of metal, connected to the fluid scrubber 122 via two hinges 204, with the door plate 202 being pivotable on the hinges 204 to open and close. A plurality of quick-release latches with pivoting handles 206 are disposed around the periphery of the door plate 202 and operate to hold the door plate 202 in the closed position and so to hold the door 200 shut when the fluid scrubber 122 is operating. In the embodiment shown in FIG. 6, eight quick-release latches 206 are disposed around each of the door plates 202, although any other desired number of such quick-release latches 206 could be used instead.
FIG. 7 illustrates one of the doors 200 disposed in the open position. As will be seen, a door seat 208 is mounted away from the wall of the fluid scrubber 122 with extension members 209 disposed between the door seat 208 and the outer wall of the fluid scrubber 122. A gasket 210, which may be made of rubber or other compressible material, is disposed around the circumference of the opening on the door seat 208. A similar gasket may additionally or alternatively be disposed around the outer circumference of inner side of the door plate 202, which provides for better sealing when the door 200 is in the closed position.
Each quick-release latch 206, one of which is shown in more detail in FIG. 8, includes a handle 212 and a latch 214 (in this case a U-shaped piece of metal) mounted on a pivot bar 216 disposed through the handle 212. The handle 212 is mounted on a further pivot point member 218 which is mounted on the outer wall of the door plate 202 via an attachment bracket 219. The operation of the handle 212 up and around the further pivot member 218 (from the position shown in FIG. 8) moves the latch 214 towards the outer wall of the fluid scrubber 112 (when the door plate 202 is in the closed position) so that the latch 214 may be disposed on the side of a hook 220 away from the door plate 202, the hook 220 being mounted on the extension member 209. Rotation of the handle 210 back in the opposite direction pulls the latch 214 up tight against the hook 220, pulling the further pivot member 218 and therefore the door plate 202 against the door seat 208. Operation of all of the quick-release latches 206 secures the door plate 202 against door seat 208 and the gasket 210 provides for a fluidly secure connection. Thus, closing all eight of the quick-release latches 206 on a particular door 200, as illustrated in FIG. 6, provides a secure and tight-fitting mechanism for holding the door 200 closed.
The use of the easy opening doors 200 replaces the use of a plate with holes, wherein numerous bolts extending from the outer wall of the concentrator are fitted through the holes on the plate and wherein it is necessary to tighten nuts on the bolts to draw the plate against the wall of the concentrator. While such a nut and bolt type of securing mechanism, which is typically used in fluid concentrators to allow access to the interior of the concentrator, is very secure, operation of this configuration takes a long time and a lot of effort when opening or closing an access panel. The use of the quick opening doors 200 with the quick-release latches 206 of FIG. 6 may be used in this instance because the interior of the fluid scrubber 122 is under negative pressure, in which the pressure inside the fluid scrubber 122 is less than the ambient air pressure, and so does not need the security of a cumbersome bolt and nut type of access panel. Of course, as will be understood, the configuration of the doors 200 allows the doors 200 to be easily opened and closed, with only minimal manual effort, and no tools, thereby allowing for fast and easy access to the structure inside of the fluid scrubber 122, such as the impingement baffle 169 or the removable filters 170, or other parts of the concentrator 110 on which an access door 200 is disposed.
Referring back to FIG. 5, it will be seen that the front the flooded elbow 164 of the concentrator assembly 120 also includes a quick opening access door 200, which allows easy access to the inside of the flooded elbow 164. However, similar quick opening access doors could be located on any desired part of the fluid concentrator 110, as most of the elements of the concentrator 10 operate under negative pressure.
The combination of features illustrated in FIGS. 3-8 makes for a compact fluid concentrator 110 that uses waste heat in the form of gas resulting from the operation of a landfill flare burning landfill gas, which waste heat would otherwise be vented directly to the atmosphere. Importantly, the concentrator 110 uses only a minimal amount of expensive high temperature resistant material to provide the piping and structural equipment required to use the high temperature gases exiting from the flare 130. For example, the small length of the transfer pipe 140, which is made of the most expensive materials, is minimized, thereby reducing the cost and weight of the fluid concentrator 110. Moreover, because of the small size of the heat transfer pipe 140, only a single support member 142 is needed thereby further reducing the costs of building the concentrator 110. Still further, the fact that the air pre-treatment assembly 119 is disposed directly on top of the fluid concentrator assembly 120, with the gas in these sections flowing downward towards the ground, enables these sections of the concentrator 110 to be supported directly by the ground or by a skid on which these members are mounted. Still further, this configuration keeps the concentrator 110 disposed very close to the flare 130, making it more compact. Likewise, this configuration keeps the high temperature sections of the concentrator 110 (e.g., the top of the flare 130, the heat transfer pipe 140 and the air pre-treatment assembly 119) above the ground and away from accidental human contact, leading to a safer configuration. In fact, due to the rapid cooling that takes place in the venturi section 162 of the concentrator assembly 120, the venturi section 162, the flooded elbow 164 and the fluid scrubber 122 are typically cool enough to touch without harm (even when the gases exiting the flare 130 are at 1800 degrees Fahrenheit). Rapid cooling of the gas-liquid mixture allows the use of generally lower cost materials that are easier to fabricate and that are corrosion resistant. Moreover, parts downstream of the flooded elbow 164, such as the fluid scrubber 122, induced draft fan 190, and exhaust section 124 may be fabricated from materials such as fiberglass.
The fluid concentrator 110 is also a very fast-acting concentrator. Because the concentrator 110 is a direct contact type of concentrator, it is not subject to deposit buildup, clogging and fouling to the same extent as most other concentrators. Still further, the ability to control the flare cap 134 to open and close, depending on whether the concentrator 110 is being used or operated, allows the flare 130 to be used to burn landfill gas without interruption when starting and stopping the concentrator 110. More particularly, the flare cap 134 can be quickly opened at any time to allow the flare 130 to simply burn landfill gas as normal while the concentrator 110 is shut down. On the other hand, the flare cap 134 can be quickly closed when the concentrator 110 is started up, thereby diverting hot gasses created in the flare 130 to the concentrator 110, and allowing the concentrator 110 to operate without interrupting the operation of the flare 130. In either case, the concentrator 110 can be started and stopped based on the operation of the flare cap 134 without interrupting the operation of the flare 130.
If desired, the flare cap 134 may be opened to a partial amount during operation of the concentrator 110 to control the amount of gas that is transferred from the flare 130 to the concentrator 110. This operation, in conjunction with the operation of the ambient air valve, may be useful in controlling the temperature of the gas at the entrance of the venturi section 162.
Moreover, due to the compact configuration of the air pre-treatment assembly 119, the concentrator assembly 120 and the fluid scrubber 122, parts of the concentrator assembly 120, the fluid scrubber 122, the draft fan 190 and at least a lower portion of the exhaust section 124 can be permanently mounted on (connected to and supported by) a skid or plate 230, as illustrated in FIG. 2. The upper parts of the concentrator assembly 120, the air pre-treatment assembly 119 and the heat transfer pipe 140, as well as a top portion of the exhaust stack, may be removed and stored on the skid or plate 230 for transport, or may be transported in a separate truck. Because of the manner in which the lower portions of the concentrator 110 can be mounted to a skid or plate, the concentrator 110 is easy to move and install. In particular, during set up of the concentrator 110, the skid 230, with the fluid scrubber 122, the flooded elbow 164 and the draft fan 190 mounted thereon, may be offloaded at the site at which the concentrator 110 is to be used by simply offloading the skid 230 onto the ground or other containment area at which the concentrator 110 is to be assembled. Thereafter, the venturi section 162, the quencher 159, and the air pre-treatment assembly 119 may be placed on top of and attached to the flooded elbow 164. The piping section 150 may then be extended in height to match the height of the flare 130 to which the concentrator 110 is to be connected. In some cases, this may first require mounting the flare cap assembly 132 onto a pre-existing flare 130. Thereafter, the heat transfer pipe 140 may be raised to the proper height and attached between the flare 130 and the air pre-treatment assembly 119, while the support member 142 is disposed in place. For concentrators in the range of 10,000 to 30,000 gallons per day evaporative capacity, it is possible that the entire flare assembly 115 may be mounted on the same skid or plate 230 as the concentrator 120.
Because most of the pumps, fluid lines, sensors and electronic equipment are disposed on or are connected to the fluid concentrator assembly 120, the fluid scrubber 122 or the draft fan assembly 190, setup of the concentrator 110 at a particular site does requires only minimal plumbing, mechanical, and electrical work at the site. As a result, the concentrator 110 is relatively easy to install and to set up at (and to disassemble and remove from) a particular site. Moreover, because a majority of the components of the concentrator 110 are permanently mounted to the skid 230, the concentrator 110 can be easily transported on a truck or other delivery vehicle and can be easily dropped off and installed at particular location, such as next to a landfill flare.
FIG. 9 illustrates a schematic diagram of a control system 300 that may be used to operate the concentrator 110 of FIG. 3. As illustrated in FIG. 9, control system 300 includes a controller 302, which may be a form of digital signal processor type of controller, a programmable logic controller (PLC) which may run, for example, ladder logic based control, or any other type of controller. The controller 302 is, of course, connected to various components within the concentrator 110. In particular, the controller 302 is connected to the flare cap drive motor 135, which controls the opening and closing operation of the flare cap 134. The motor 135 may be set up to control the flare cap 134 to move between a fully open and a fully closed position. However, if desired, the controller 302 may control the drive motor 135 to open the flare cap 134 to any of a set of various different controllable positions between the fully opened and the fully closed position. The motor 135 may be continuously variable if desired, so that the flare cap 134 may be positioned at any desired point between fully open and fully closed.
Additionally, the controller 302 is connected to and controls the ambient air inlet valve 306 disposed in the air pre-treatment assembly 119 of FIG. 3 upstream of the venturi section 162 and may be used to control the pumps 182 and 184 which control the amount of and the ratio of the injection of new liquid to be treated and the re-circulating liquid being treated within the concentrator 110. The controller 302 may be operatively connected to a sump level sensor 317 (e.g., a float sensor, anon-contact sensor such as a radar or sonic unit, or a differential pressure cell). The controller 302 may use a signal from the sump level sensor 317 to control the pumps 182 and 184 to maintain the level of concentrated fluid within the sump 172 at a predetermined or desired level. Also, the controller 302 may be connected to the induced draft fan 190 to control the operation of the fan 190, which may be a single speed fan, a variable speed fan or a continuously controllable speed fan. In one embodiment, the induced draft fan 190 is driven by a variable frequency motor, so that the frequency of the motor is changed to control the speed of the fan. Moreover, the controller 302 is connected to a temperature sensor 308 disposed at, for example, the inlet of the concentrator assembly 120 or at the inlet of the venturi section 162, and receives a temperature signal generated by the temperature sensor 308. The temperature sensor 308 may alternatively be located downstream of the venturi section 162 or the temperature sensor 308 may include a pressure sensor for generating a pressure signal.
During operation and at, for example, the initiation of the concentrator 110, when the flare 130 is actually running and is thus burning landfill gas, the controller 302 may first turn on the induced draft fan 190 to create a negative pressure within the fluid scrubber 122 and the concentrator assembly 120. The controller 302 may then or at the same time, send a signal to the motor 135 to close the flare cap 134 either partially or completely, to direct waste heat from the flare 130 into the transfer pipe 140 and thus to the air pre-treatment assembly 119. Based on the temperature signal from the temperature sensor 308, the controller 302 may control the ambient air valve 306 (typically by closing this valve partially or completely) and/or the flare cap actuator to control the temperature of the gas at the inlet of the concentrator assembly 120. Generally speaking, the ambient air valve 306 may be biased in a fully open position (i.e., may be normally open) by a biasing element such as a spring, and the controller 302 may begin to close the valve 306 to control the amount of ambient air that is diverted into the air pre-treatment assembly 119 (due to the negative pressure in the air pre-treatment assembly 119), so as to cause the mixture of the ambient air and the hot gases from the flare 130 to reach a desired temperature. Additionally, if desired, the controller 302 may control the position of the flare cap 134 (anywhere from fully open to fully closed) and may control the speed of the induced draft fan 190, to control the amount of gas that enters the air pre-treatment assembly 119 from the flare 130. As will be understood, the amount of gas flowing through the concentrator 110 may need to vary depending on ambient air temperature and humidity, the temperature of the flare gas, the amount of gas exiting the flare 130, etc. The controller 302 may therefore control the temperature and the amount of gas flowing through the concentrator assembly 120 by controlling one or any combination of the ambient air control valve 306, the position of the flare cap 134 and the speed of the induced draft fan 190 based on, for example, the measurement of the temperature sensor 308 at the inlet of the concentrator assembly 120. This feedback system is desirable because, in many cases, the air coming out of a flare 130 is between 1200 and 1800 degrees Fahrenheit, which may be too hot, or hotter than required for the concentrator 110 to operate efficiently and effectively.
In any event, as illustrated in FIG. 9, the controller 302 may also be connected to a motor 310 which drives or controls the position of the venturi plate 163 within the narrowed portion of the concentrator assembly 120 to control the amount of turbulence caused within the concentrator assembly 120. Still further, the controller 302 may control the operation of the pumps 182 and 184 to control the rate at which (and the ratio at which) the pumps 182 and 184 provide re-circulating liquid and new waste fluid to be treated to the inputs of the quencher 159 and the venturi section 162. In one embodiment, the controller 302 may control the ratio of the re-circulating fluid to new fluid to be about 10:1, so that if the pump 184 is providing 8 gallons per minute of new liquid to the input 160, the re-circulating pump 182 is pumping 80 gallons per minute. Additionally, or alternatively, the controller 302 may control the flow of new liquid to be processed into the concentrator (via the pump 184) by maintaining a constant or predetermined level of concentrated liquid in the sump 172 using, for example, the level sensor 317. Of course, the amount of liquid in the sump 172 will be dependent on the rate of concentration in the concentrator, the rate at which concentrated liquid is pumped from or otherwise exists the sump 172 via the secondary re-circulating circuit and the rate at which liquid from the secondary re-circulating circuit is provided back to the sump 172, as well as the rate at which the pump 182 pumps liquid from the sump 172 for delivery to the concentrator via the primary re-circulating circuit.
If desired, one or both of the ambient air valve 306 and the flare cap 134 may be operated in a fail-safe open position, such that the flare cap 134 and the ambient air valve 306 open in the case of a failure of the system (e.g., a loss of control signal) or a shutdown of the concentrator 110. In one case, the flare cap motor 135 may be spring loaded or biased with a biasing element, such as a spring, to open the flare cap 134 or to allow the flare cap 134 to open upon loss of power to the motor 135. Alternatively, the biasing element may be the counter-weight 137 on the flare cap 134 may be so positioned that the flare cap 134 itself swings to the open position under the applied force of the counter-weight 137 when the motor 135 loses power or loses a control signal. This operation causes the flare cap 134 to open quickly, either when power is lost or when the controller 302 opens the flare cap 134, to thereby allow hot gas within the flare 130 to exit out of the top of the flare 130. Of course, other manners of causing the flare cap 134 to open upon loss of control signal can be used, including the use of a torsion spring on the pivot point 136 of the flare cap 134, a hydraulic or pressurized air system that pressurizes a cylinder to close the flare cap 134, loss of which pressure causes the flare cap 134 to open upon loss of the control signal, etc.
Thus, as will be noted from the above discussion, the combination of the flare cap 134 and the ambient air valve 306 work in unison to protect the engineered material incorporated into the concentrator 110, as whenever the system is shut down, the flare cap and the air valve 306 automatically immediately open, thereby isolating hot gas generated in the flare 130 from the process while quickly admitting ambient air to cool the process.
Moreover, in the same manner, the ambient air valve 306 may be spring biased or otherwise configured to open upon shut down of the concentrator 110 or loss of signal to the valve 306. This operation causes quick cooling of the air pre-treatment assembly 119 and the concentrator assembly 120 when the flare cap 134 opens. Moreover, because of the quick opening nature of the ambient air valve 306 and the flare cap 134, the controller 302 can quickly shut down the concentrator 110 without having to turn off or effect the operation of the flare 130.
Furthermore, as illustrated in the FIG. 9, the controller 302 may be connected to the venturi plate motor 310 or other actuator which moves or actuates the angle at which the venturi plate 163 is disposed within the venturi section 162. Using the motor 310, the controller 302 may change the angle of the venturi plate 163 to alter the gas flow through the concentrator assembly 120, thereby changing the nature of the turbulent flow of the gas through concentrator assembly 120, which may provide for better mixing of the and liquid and gas therein and obtain better or more complete evaporation of the liquid. In this case, the controller 302 may operate the speed of the pumps 182 and 184 in conjunction with the operation of the venturi plate 163 to provide for optimal concentration of the wastewater being treated. Thus, as will be understood, the controller 302 may coordinate the position of the venturi plate 163 with the operation of the flare cap 134, the position of the ambient air or bleed valve 306, and the speed of the induction fan 190 to maximize wastewater concentration (turbulent mixing) without fully drying the wastewater so as to prevent formation of dry particulates. The controller 302 may use pressure inputs from the pressure sensors to position the venturi plate 163. Of course, the venturi plate 163 may be manually controlled or automatically controlled.
The controller 302 may also be connected to a motor 312 which controls the operation of the damper 198 in the gas re-circulating circuit of the fluid scrubber 122. The controller 302 may cause the motor 312 or other type of actuator to move the damper 198 from a closed position to an open or to a partially open position based on, for example, signals from pressure sensors 313, 315 disposed at the gas entrance and the gas exit of the fluid scrubber 122. The controller 302 may control the damper 198 to force gas from the high pressure side of the exhaust section 124 (downstream of the induced draft fan 190) into the fluid scrubber entrance to maintain a predetermined minimum pressure difference between the two pressure sensors 313, 315. Maintaining this minimum pressure difference assures proper operation of the fluid scrubber 122. Of course, the damper 198 may be manually controlled instead or in addition to being electrically controlled.
Thus, as will be understood from the above discussion, the controller 302 may implement one or more on/off control loops used to start up or shut down the concentrator 110 without affecting the operation of the flare 130. For example, the controller 302 may implement a flare cap control loop which opens or closes the flare cap 134, a bleed valve control loop which opens or begins to close the ambient air valve 306, and an induced draft fan control loop which starts or stops the induced draft fan 190 based on whether the concentrator 110 is being started or stopped. Moreover, during operation, the controller 302 may implement one or more on-line control loops which may control various elements of the concentrator 110 individually or in conjunction with one another to provide for better or optimal concentration. When implementing these on-line control loops, the controller 302 may control the speed of induced draft fan 190, the position or angle of the venturi plate 163, the position of the flare cap 134 and or the position of the ambient air valve 306 to control the fluid flow through the concentrator 110, and/or the temperature of the air at the inlet of the concentrator assembly 120 based on signals from the temperature and pressure sensors. Moreover, the controller 302 may maintain the performance of the concentration process at steady-state conditions by controlling the pumps 184 and 182 which pump new and re-circulating fluid to be concentrated into the concentrator assembly 120. Still further, the controller 302 may implement a pressure control loop to control the position of the damper 198 to assure proper operation of the fluid scrubber 122. Of course, while the controller 302 is illustrated in FIG. 9 as a single controller device that implements these various control loops, the controller 302 could be implemented as multiple different control devices by, for example, using multiple different PLCs.
As will be understood, the concentrator 110 described herein directly utilizes hot waste gases in processes after the gases have been thoroughly treated to meet emission standards, and so seamlessly separates the operational requirements of the process that generates the waste heat from the process which utilizes the waste heat in a simple, reliable and effective manner.
In addition to being an important component of the concentrator 110 during operation of the concentrator 110, the automated or manually actuated flare cap 134 described herein can be used in a standalone situation to provide weather protection to a flare or to a flare and a concentrator combination when the flare stands idle. With the flare cap 134 closed, the interior of the metal shell of the flare 130 along with the refractory, burners and other critical components of the flare assembly 115 and the heat transfer assembly 117 are protected from corrosion and general deterioration related to exposure to the elements. In this case, the controller 302 may operate the flare cap motor 135 to keep the flare cap 134 fully open or partially closed during idling of the flare 130. Moreover, beyond using a flare cap 134 that closes automatically when the flare 130 shuts down or that opens automatically when the flare 130 is ignited, a small burner, such as the normal pilot light, may be installed inside of the flare 130 and may be run when the flare 130 is shut down but while the flare cap 134 held closed. This small burner adds further protection against deterioration of flare components caused by dampness, as it will keep the interior of the flare 130 dry. An example of a stand alone flare that may use the flare cap 134 described herein in a stand-alone situation is a stand-by flare installed at a landfill to ensure gas control when a landfill gas fueled power plant is off-line.
While the liquid concentrator 110 has been described above as being connected to a landfill flare to use the waste heat generated in the landfill flare, the liquid concentrator 110 can be easily connected to other sources of waste heat. For example, FIG. 10 illustrates the concentrator 110 modified so as to be connected to an exhaust stack of a combustion engine plant 400 and to use the waste heat from the engine exhaust to perform liquid concentration. While, in one embodiment, the engine within the plant 400 may operate on landfill gas to produce electricity, the concentrator 110 can be connected to run with exhaust from other types of engines, including other types of combustion engines, such as those that operate on gasoline, diesel fuel, etc.
Referring to FIG. 10, exhaust generated in an engine (not shown) within the plant 400 is provided to a muffler 402 on the exterior of the plant 400 and, from there, enters into a combustion gas exhaust stack 404 having a combustion gas exhaust stack cap 406 disposed on the top thereof. The cap 406 is essentially counter-weighted to close over the exhaust stack 404 when no exhaust is exiting the stack 404, but is easily pushed up by the pressure of the exhaust when exhaust is leaving the stack 404. In this case, a Y-connector is provided within the exhaust stack 404 and operates to connect the stack 404 to a transfer pipe 408 which transfers exhaust gas (a source of waste heat) from the engine to an expander section 410. The expander section 410 mates with the quencher 159 of the concentrator 110 and provides the exhaust gas from the engine directly to the concentrator assembly 120 of the concentrator 110. It is typically not necessary to include an air bleed valve upstream of the concentrator section 120 when using engine exhaust as a source of waste heat because exhaust gas typically leaves an engine at less than 900 degrees Fahrenheit, and so does not need to be cooled significantly before entering the quencher 159. The remaining parts of the concentrator 110 remain the same as described above with respect to FIGS. 3-8. As a result, it can be seen that the liquid concentrator 110 can be easily adapted to use various different sources of waste heat without a lot of modification.
Generally, when controlling the liquid concentrator 110 of FIG. 10, the controller will turn on the induced draft fan 190 while the engine in the plant 400 is running. The controller will increase the speed of the induced draft fan 190 from a minimal speed until the point that most or all of the exhaust within the stack 404 enters the transfer pipe 408 instead of going out of the top of the exhaust stack 404. It is easy to detect this point of operation, which is reached when, as the speed of the induced draft fan 190 is increased, the cap 406 first sits back down on the top of the stack 404. It may be important to prevent increasing the speed of the induced draft fan 190 above this operational point, so as to not create any more of a negative pressure within the concentrator 110 than is necessary, and thereby assuring that the operation of the concentrator 110 does not change the back pressure and, in particular, create undesirable levels of suction experienced by the engine within the plant 400. Changing the back pressure or applying suction within the exhaust stack 404 may adversely effect the combustion operation of the engine, which is undesirable. In one embodiment, a controller (not shown in FIG. 10), such as a PLC, may use a pressure transducer mounted in the stack 404 close to the location of the cap 406 to continuously monitor the pressure at this location. The controller can then send a signal to the variable frequency drive on the induced draft fan 190 to control the speed of the induced draft fan 190 to maintain the pressure at a desirable set point, so as to assure that undesirable back pressure or suction is not being applied on the engine.
FIGS. 11 and 12 illustrate a side cross-sectional view, and a top cross-sectional view, of another embodiment of a liquid concentrator 500. The concentrator 500 is shown in a generally vertical orientation. However, the concentrator 500 shown in FIG. 11 may be arranged in a generally horizontal orientation or a generally vertical orientation depending on the particular constraints of a particular application. For example, a truck mounted version of the concentrator may be arranged in a generally horizontal orientation to allow the truck-mounted concentrator to pass under bridges and overpasses during transport from one site to another. The liquid concentrator 500 has a gas inlet 520 and a gas exit 522. A flow corridor 524 connects the gas inlet 520 to the gas exit 522. The flow corridor 524 has a narrowed portion 526 that accelerates the gas through the flow corridor 524. A liquid inlet 530 injects a liquid into the gas stream prior to the narrowed portion 526. In contrast to the embodiment of FIG. 1, the narrowed portion 526 of the embodiment of FIG. 11 directs the gas-liquid mixture into a cyclonic chamber 551. The cyclonic chamber 551 enhances the mixing of the gas and liquid while also performing the function of the demister in FIG. 1. The gas-liquid mixture enters the cyclonic chamber 551 tangentially (see FIG. 12) and then moves in a cyclonic manner through the cyclonic chamber 551 towards a liquid outlet area 554. The cyclonic circulation is facilitated by a hollow cylinder 556 disposed in the cyclonic chamber 551 that conducts the gas to the gas outlet 522. The hollow cylinder 556 presents a physical barrier and maintains the cyclonic circulation throughout the cyclonic chamber 551 including the liquid outlet area 554.
As the gas-liquid mixture passes through the narrowed portion 526 of the flow corridor 524 and circulates in the cyclonic chamber 551, a portion of the liquid evaporates and is absorbed by the gas. Furthermore, centrifugal force accelerates movement of entrained liquid droplets in the gas towards the side wall 552 of the cyclonic chamber 551 where the entrained liquid droplets coalesce into a film on the side wall 552. Simultaneously, centripetal forces created by an induction fan 550 collect the demisted gas flow at the inlet 560 of the cylinder 556 and direct the flow to the gas outlet 522. Thus, the cyclonic chamber 551 functions both as a mixing chamber and a demisting chamber. As the liquid film flows towards the liquid outlet area 554 of the chamber due to the combined effects of the force of gravity and the cyclonic motion within cyclonic chamber 551 toward the liquid outlet area 554, the continuous circulation of the gas in the cyclonic chamber 551 further evaporates a portion of the liquid film. As the liquid film reaches the liquid outlet area 554 of the cyclonic chamber 551, the liquid is directed through a re-circulating circuit 542. Thus, the liquid is re-circulated through the concentrator 500 until a desired level of concentration is reached. A portion of the concentrated slurry may be drawn off through an extraction port 546 when the slurry reaches the desired concentration (this is called blowdown). Fresh liquid is added to the circuit 542 through a fresh liquid inlet 544 at a rate equal to the rate of evaporation plus the rate of slurry drawn off through the extraction port 546.
As the gas circulates in the cyclonic chamber 551, the gas is cleansed of entrained liquid droplets and drawn towards the liquid discharge area 554 of the cyclonic chamber 551 by the induction fan 550 and towards an inlet 560 of the hollow cylinder 556. The cleansed gas then travels through the hollow cylinder 556 and finally vents through the gas exit 522 to the atmosphere or further treatment (e.g., oxidization in a flare).
FIG. 13 illustrates a schematic view of a distributed liquid concentrator 600 configured in a manner that enables the concentrator 600 to be used with many types of sources of waste heat, even sources of waste heat that are located in places that are hard to access, such as on the sides of buildings, in the middle of various other equipment, away from roads or other access points, etc. While the liquid concentrator 600 will be described herein as being used to process or concentrate leachate, such as leachate collected from a landfill, the liquid concentrator 600 could be used to concentrate other types of liquids as well or instead including many other types of wastewaters.
Generally speaking, the liquid concentrator 600 includes a gas inlet 620, a gas outlet or a gas exit 622, a flow corridor 624 connecting the gas inlet 620 to the gas exit 622 and a liquid re-circulating system 625. A concentrator section has a flow corridor 624 that includes a quencher section 659 including the gas inlet 620 and a fluid inlet 630, a venturi section 626 disposed downstream of the quencher section 659, and a blower or draft fan 650 connected downstream of the venturi section 626. The fan 650 and a flooded elbow 654 couple a gas outlet of the concentrator section (e.g., an outlet of the venturi section 626) to a piping section 652. The flooded elbow 654, in this case, forms a 90 degree turn in the flow corridor 624. However, the flooded elbow 654 could form a turn that is less than or more than 90 degrees if desired. The piping section 652 is connected to a demister, in this case illustrated in the form of a crossflow scrubber 634, which is, in turn, connected to a stack 622A having the gas exit 622.
The re-circulating system 625 includes a sump 636 coupled to a liquid outlet of the crossflow scrubber 634, and a re-circulating or recycle pump 640 coupled between the sump 636 and a piping section 642 which delivers re-circulated fluid to the fluid inlet 630. A process fluid feed 644 also delivers leachate or other liquid to be processed (e.g., concentrated) to the fluid inlet 630 to be delivered to the quencher section 659. The re-circulating system 625 also includes a liquid takeoff 646 connected to the piping section 642, which delivers some of the recycled fluid (or concentrated fluid) to a storage, settling and recycle tank 649. The heavier or more concentrated portions of the liquid in the settling tank 649 settle to the bottom of the tank 649 as sludge, and are removed and transported for disposal in concentrated form. Less concentrated portions of the liquid in the tank 649 are delivered back to the sump 636 for reprocessing and further concentration, as well as to assure that an adequate supply of liquid is available at the liquid inlet 630 at all times so to ensure that dry particulate is not formed. Dry particulate can form at reduced ratios of process fluid to hot gas volumes.
In operation, the quencher section 659 mixes fluid delivered from the liquid inlet 630 with gas containing waste heat collected from, for example, an engine muffler and stack 629 associated with an internal combustion engine (not shown). The liquid from the fluid inlet 630 may be, for example, leachate to be processed or concentrated. As illustrated in FIG. 13, the quencher section 659 is connected vertically above the venturi portion 626 which has a narrowed portion that operates to accelerate the flow of gas and liquid through a section of the fluid flow corridor 624 immediately downstream of the venturi portion 626 and upstream of the fan 650. Of course, the fan 650 operates to create a low pressure region immediately downstream of the venturi portion 626, drawing gas from the stack 629 through the venturi portion 626 and the flooded elbow 654 and causing mixing of the gas and liquid.
As noted above, the quencher section 659 receives hot exhaust gas from the engine exhaust stack 629 and may be connected directly to any desired portion of the exhaust stack 629. In this illustrated embodiment, the engine exhaust stack 629 is mounted on an outside of a building 631 that houses one or more electric power generators that generate electric power using landfill gas as a combustion fuel. In this case, the quencher section 659 may be connected directly to a condensate take off (e.g., a weep leg) associated with the stack 629 (i.e., a lower portion of the exhaust stack 629). Here, the quencher section 659 may be mounted immediately below or adjacent to the stack 629 requiring only a few inches or at most a few feet of expensive, high temperature piping material to connect the two together. If desired, however, the quencher section 659 may be coupled any other portion of the exhaust stack 629, including, for example, to the top or to a middle portion of the stack 629 via appropriate elbows or takeoffs.
As noted above, the liquid inlet 630 injects a liquid to be evaporated (e.g., landfill leachate) into the flow corridor 624 through the quencher section 659. If desired, the liquid inlet 630 may include a replaceable nozzle for spraying the liquid into the quencher section 659. The liquid inlet 630, whether or not equipped with a nozzle, may introduce the liquid in any direction, from perpendicular to parallel to the gas flow as the gas moves through the flow corridor 624. Moreover, as the gas (and the waste heat stored therein) and liquid flow through the venturi portion 626, the venturi principle creates an accelerated and turbulent flow that thoroughly mixes the gas and liquid in the flow corridor 624 immediately downstream of the venturi section 626. As a result of the turbulent mixing, a portion of the liquid rapidly vaporizes and becomes part of the gas stream. This vaporization consumes a large amount of the heat energy within the waste heat as latent heat that exits the concentrator system 600 as water vapor within the exhaust gas.
After leaving the narrowed portion of the venturi section 626, the gas/liquid mixture passes through the flooded elbow 654 where the flow corridor 624 turns 90 degrees to change from a vertical flow to a horizontal flow. The gas/liquid mixture flows past the fan 650 and enters a high pressure region at the downstream side of the fan 650, this high pressure region existing in the piping section 652. The use of a flooded elbow 654 at this point in the system is desirable for at least two reasons. First, the liquid at the bottom portion of the flooded elbow 654 reduces erosion at the turning point in the flow corridor 624, which erosion would normally occur due to suspended particles within the gas/liquid mixture flowing at high rates of speed through a 90 degree turn and impinging at steep angles directly on the bottom surfaces of a conventional elbow were the flooded elbow 654 not employed. The liquid in the bottom of the flooded elbow 654 absorbs the energy in these particles and therefore prevents erosion on the bottom surface of the flooded elbow 654. Still further, liquid droplets which still exist in the gas/liquid mixture as this mixture arrives at the flooded elbow 654 are more easily collected and removed from the flow stream if they impinge upon a liquid. That is, the liquid at the bottom of the flooded elbow 654 operates to collect liquid droplets impinging thereon because the liquid droplets within the flow stream are more easily retained when these suspended liquid droplets come into contact with a liquid. Thus, the flooded elbow 654, which may have a liquid takeoff (not shown) connected to, for example, the re-circulating circuit 625, operates to remove some of the process fluid droplets and condensation from the gas/liquid mixture exiting the venturi section 626.
Importantly, the gas/liquid mixture while passing through the venturi section 626 quickly approaches the adiabatic saturation point, which is at a temperature that is much lower than that of the gas exiting the stack 629. For example, while the gas exiting the stack 629 may be between about 900 and about 1800 degrees Fahrenheit, the gas/liquid mixture in all sections of the concentrator system 600 downstream of the venturi section 626 will generally be in the range of 150 degrees to 190 degrees Fahrenheit, although it can range higher or lower than these values based on the operating parameters of the system. As a result, sections of the concentrator system 600 downstream of the venturi section 626 do not need to be made of high temperature resistant materials and do not need to be insulated at all or to the degree that would be necessary for transporting higher temperature gases if insulation were to be applied for the purpose of more fully utilizing the waste heat content of the inlet hot gas. Still further the sections of the concentrator system 600 downstream of the venturi section 626 disposed in areas, such as along the ground that people will come into contact with, without significant danger, or with only minimal exterior protection. In particular, the sections of the concentrator system downstream of the venturi section 626 may be made of fiberglass and may need minimal or no insulation. Importantly, the gas/liquid stream may flow within the sections of the concentrator system downstream of the venturi section 626 over a relatively long distance while maintaining the gas/liquid mixture therein at close to the adiabatic saturation point, thereby allowing the piping section 652 to easily transport the flow stream away from the building 631 to a more easily accessible location, at which the other equipment associated with the concentrator 600 can be conveniently disposed. In particular, the piping section 652 may span 20 feet, 40 feet, or even longer while maintaining the flow therein at close to the adiabatic saturation point. Of course, these lengths may be longer or shorter based on ambient temperature, the type of piping and insulation used, etc. Moreover, because the piping section 652 is disposed on the high pressure side of the fan 650, it is easier to remove condensation from this stream. In the example embodiment of FIG. 13, the piping section 652 is illustrated as flowing past or beneath an air cooler associated with the engines within the building 631. However, the air cooler of FIG. 13 is merely one example of the types of obstructions that may be located close to the building 631 which make it problematic to place all of the components of the concentrator 600 in close proximity to the source of the waste heat (in this case, the stack 629). Other obstructions could include other equipment, vegetation such as trees, other buildings, inaccessible terrain without roads or easy access points, etc.
In any event, the piping section 652 delivers the gas/liquid stream at close to the adiabatic saturation point to the demister 634, which may be, for example, a crossflow scrubber. The demister 634 operates to remove entrained liquid droplets from the gas/liquid stream. The removed liquid collects in the sump 636 which directs the liquid to the pump 640. The pump 640 moves the liquid through the return line 642 of the re-circulating circuit 625 back to the liquid inlet 630. In this manner, the captured liquid may be further reduced through evaporation to a desired concentration and/or re-circulated to prevent the formation of dry particulate. Fresh liquid to be concentrated is input through the fresh liquid inlet 644. The rate of fresh liquid input into the re-circulating circuit 625 should be equal to the rate of evaporation of the liquid as the gas-liquid mixture flows through the flow corridor 624 plus the rate of liquid or sludge extracted from the settling tank 649 (assuming the material within the settling tank 649 remains at a constant level). In particular, a portion of the liquid may be drawn off through an extraction port 646 when the liquid in the re-circulating circuit 625 reaches a desired concentration. The portion of liquid drawn off through the extraction port 646 may be sent to the storage and settling tank 649 where the concentrated liquid is allowed to settle and separate into its component parts (e.g., a liquid portion and a semi-solid portion). The semi-solid portion may be drawn from the tank 649 and disposed of or further treated.
As noted above, the fan 650 draws the gas through a portion of the flow corridor 624 under negative pressure and pushes gas through another portion of the flow corridor 624 under positive pressure. The quencher section 659, venturi section 626, and fan 650 may be attached to the building 631 with any type of connecting device and, as illustrated in FIG. 13, are disposed in close proximity to the source of waste heat. However the demister 634 and the gas outlet 622, as well as the settling tank 649, may be located some distance away from the quencher section 659, venturi section 626, and fan 650, at for example, an easy to access location. In one embodiment, the demister 634 and the gas outlet 622 and even the settling tank 649 may be mounted on a mobile platform such as a pallet or a trailer bed.
FIGS. 14-16 illustrate another embodiment of a liquid concentrator 700 which may be mounted on a pallet or trailer bed. In one embodiment, some of the components of the concentrator 700 may remain on the bed and be used to perform concentration activities, while others of these components may be removed and installed near a source of waste heat in the manner illustrated in, for example, the embodiment of FIG. 13. The liquid concentrator 700 has a gas inlet 720 and a gas exit 722. A flow corridor 724 connects the gas inlet 720 to the gas exit 722. The flow corridor 724 has a narrowed or venturi portion 726 that accelerates the gas through the flow corridor 724. Gas is drawn into a quencher section 759 by an induction fan (not shown). A liquid inlet 730 injects a liquid into the gas stream in the quencher section 759. Gas is directed from the venturi section 726 into the demister (or cross flow scrubber) 734 by an elbow section 733. After exiting the demister 734, the gas is directed to the gas exit 722 through a stack 723. Of course, as described above, some of these components may be removed from the bed and installed in close proximity to a source of waste heat while others of these components (such as the demister 734, the stack 723 and the gas exit 722) may remain on the bed.
As the gas-liquid mixture passes through the venturi portion 726 of the flow corridor 724, a portion of the liquid evaporates and is absorbed by the gas, thus consuming a large portion of heat energy within the waste heat as latent heat that exits the concentrator system 700 as water vapor within the exhaust gas.
In the embodiment shown in FIGS. 14-16, portions of the liquid concentrator 700 may be disassembled and mounted on a pallet or trailer skid for transportation. For example, the quenching section 759 and the venturi section 726 may be removed from the elbow section 733, as illustrated by the dashed line in FIG. 14. Likewise, the stack 723 may be removed from the induction fan 750 as illustrated by the dashed line in FIG. 14. The elbow section 733, demister 734, and induction fan 750 may be secured on a pallet or trailer skid 799 as a unit. The stack 723 may be secured separately to the pallet or trailer skid 799. The quenching section 759 and venturi section 726 may also be secured to the pallet or trailer skid 799, or alternately transported separately. The compartmentalized construction of the liquid concentrator 700 simplifies transportation of the liquid concentrator 700.
Embodiments of the devices and processes described above can be readily modified to accommodate the removal of pollutants from the wastewater being concentrated and also from the exhaust gas employed to concentrate that wastewater. Such modifications are contemplated to be particularly advantageous where the pollutants sought to be removed are among those whose emissions are typically regulated by governmental authorities. Examples of such pollutants include oxides of sulfur (SOx) commonly present in the exhaust gas from the combustion of landfill gas, and ammonia (NH3). Described below are modifications that may be made to the embodiments of the devices and processes described above to accommodate removal of SOx and NH3, but that description is not intended to be limiting to the removal of only those pollutants.
Removal of SOx
Hydrogen sulfide (H2S) is a known poisonous gas that can be generated by bacterial decomposition (chemical reduction) of compounds containing sulfur, sulfites, and sulfates that are present within wastes that have been placed in a landfill. Thus formed, H2S joins with other gases produced by all forms of bacterial action carried out in the landfill to form landfill gas. Generally, the greater the amount of wastes that contain sulfur, sulfites, and sulfates, the greater the amount of hydrogen sulfide that may be expected. For example, landfills may have quantities of sulfates from sources of calcium sulfate (e.g., gypsum wallboard materials) that contribute as much as 10,000 parts per million (weight basis) or greater H2S to the landfill gas. The hydrogen sulfide is part of the landfill gas that is burned in the landfill gas flare, as described herein, for example. Burning the H2S in a gas flare, reciprocating engine, or turbine is beneficial because the H2S is converted to oxides of sulfur (SOx), thus avoiding expensive pretreatment of the landfill gas to remove the H2S. However, the oxides of sulfur may be a regulated air pollutant in some countries. Another benefit of burning the H2S in a flare is that the H2S adds heat value to the flare exhaust that may be used to concentrate the landfill leachate, thus reducing the amount of overall fuel required.
Wet scrubbers are commonly employed to remove SOx from the exhaust gases produced by burning fuels that contain sulfur compounds including H2S. Examples of such scrubbers include spray- and packed-towers that contact (wet) alkaline materials (e.g., solutions or slurries of sodium hydroxide or lime (CaCO3)) directly with the exhaust gas to “scrub” (i.e., remove) SOx from the gas. The principle underlying wet scrubbing can be employed in the context of the wastewater concentrator described herein.
An alkaline material of known concentration can be added to the wastewater feed in a quantity sufficient to react with the SOx present in the exhaust gas and convert it to sodium sulfite and sodium sulfate (where the alkaline is NaOH) and calcium sulfate (CaSO4) where the alkaline is lime. Once formed, the sodium sulfite/sulfate and calcium sulfate salts will be removed from the process as part of the liquid concentrate. Ultimately, the sodium sulfite/sulfate and calcium sulfate salts can be disposed at chemical waste treatment facilities, or further converting into a higher-content solids stream (e.g., up to 100% solids) that can be placed into a special dedicated cell of the landfill to preclude recycling the sulfite/sulfate back into landfill gas as H2S. Because the volume of residual produced from landfill leachate, generally a very dilute aqueous waste stream, is typically only 3% or less of the feed volume, even with the added sulfite/sulfate salts the costs of transportation and disposal at off-site chemical waste treatment facilities, or the costs of building and operating special landfill cells to contain 100% solids should be quite economical, especially when compared to the costs of scrubbing the combustion gas emissions or removing the hydrogen sulfide prior to combustion without applying the waste heat from the combustion process as the principal energy source to treat the wastewater (e.g., leachate).
This dual purpose use for a wastewater treatment system offers tremendous benefits to landfill owners who find that emissions from their flare(s) or landfill gas fueled power plants exceed regulatory limits for SOx emissions. Conversion of the concentrator to function in the combined concentration/scrubbing modes involves only the addition of a metering system (e.g., a pump operatively connected to the controller of the concentrator) and supply tank for the selected alkaline reagent used for scrubbing. Likewise, operational changes to monitor the addition of an SOx removal stage to the concentration process does not add great complexity in that simple on-site analytical tests can be applied to monitor both the hydrogen sulfide levels in the landfill gas and the amount of sulfate in the concentrate produced in the process.
Referring again to FIGS. 3 and 10, the concentrator section 120 may include a caustic (or alkali) inlet 187 that is connected to a supply of caustic (or alkali) material 193 (e.g., sodium hydroxide or lime) by a supply line 189. A pump 191 may pressurize the supply line 189 with caustic or alkali material from the supply of caustic or alkali material 193 so that the caustic or alkali material is ejected into the concentrator section 120 (e.g., proximate the venturi 162) to mix with the exhaust gas from the flare 130 or generator. In other embodiments, the caustic or alkali material may be mixed with the leachate in the leachate input line 186 prior to being delivered to the concentrator section 120. Regardless, once the caustic or alkali material is delivered to the concentrator section 120, the caustic or alkali material rapidly mixes with the exhaust gas in the concentrator section 120 along with the leachate, as described above. Once mixed, the caustic or alkali material reacts with the oxides of sulfur, converting the oxides of sulfur to sodium sulfate and sodium sulfite or calcium sulfate as described above. Once converted the sodium sulfate, sodium sulfite and/or calcium sulfate immediately transfer into the liquid phase where they either remain dissolved or precipitate out of the gas/liquid mixture in the concentrator section 120. Thus, sulfur that was originally in the form of H2S within the landfill gas phase is transferred to the liquid phase as sodium sulfate/sulfite and calcium sulfite salts and is ultimately captured along with the concentrated leachate in the sump 172 of the demister section 122 and may be drawn off along with concentrated leachate for later disposal. As illustrated in FIG. 9, the controller 302 may be operatively connected to the pump 191 to control the rate at which caustic or alkali material is metered into the concentrator section 120. The controller 302 may determine a proper metering rate for the caustic based at least in part on the mass flow of exhaust gas through the concentrator section 120 and the percentage of oxides of sulfur within the exhaust gas. Thus, the disclosed concentrator is readily adaptable to variations in exhaust gas components and/or differing mass flow rates of the exhaust gas. As a result, the disclosed concentrator is capable of simultaneously concentrating landfill leachate and removing pollutants, such as oxides of sulfur, from landfill gas flare exhaust or reciprocating engine or turbine exhaust.
Removal of Ammonia
Ammonia is an air pollutant and a precursor of particulate formation in exhaust gases when released to atmosphere. Because ammonia is soluble in water, it is normally found in the wastewater (e.g., leachate) at landfill facilities, as opposed to the landfill gas
Known principles for the removal of ammonia from can be employed in the context of the concentrator and fluid scrubber described herein. For example, the wastewater feed containing ammonia can be treated with an agent (e.g., a caustic or alkali, such as sodium hydroxide or lime) capable of raising pH of the leachate. The increased-pH leachate can be passed into an air stripper where ammonia in the wastewater will migrate into the air stripper's exhaust air. The exhaust air from the air stripper can be combined with the combustion and excess air employed in the operation of a flare, reciprocating engine or turbine responsible for providing heat to the concentration process.
Within the flare, reciprocating engine or turbine, the ammonia introduced via the combustion air may beneficially reduce another pollutant, oxides of nitrogen (NOx), that may be present in the combustion. That reduction can be accomplished through a process known as selective non-catalytic reduction of NOx emissions. As ammonia passes from the waste heat source into the concentration process with the hot gas, a reagent suitable to convert the ammonia to a stable salt (as in the removal of SOx with alkaline scrubbing compounds) can be introduced to the process. For example, sulfuric acid can be introduced into the wastewater (e.g., leachate) after it exits the air stripper. That acid can be used to sequester the ammonia as ammonium sulfate (NH4)2SO4 within the concentrated liquid.
As illustrated in FIG. 17, an alternate embodiment of the concentrator used to scrub ammonia from landfill leachate may include a caustic or alkali inlet 195 connected to the leachate input line 186. The combined caustic/leachate may be routed through an in line air stripper 201 before continuing on to the concentrator section 120. The air stripper 201 may draw off gaseous ammonia which is released into the stripping gas by the previously added caustic or alkali. The drawn off gaseous ammonia may be delivered back to the landfill gas flare 130 or reciprocating engine or turbine through an ammonia delivery line 194. As described above, the ammonia in the flare 130, reciprocating engine, or turbine may beneficially reduce NOx emissions. Regardless, the ammonia may be sequestered as a stable salt with the addition of a reagent from a reagent source 197 through a reagent inlet 199 in the concentrator section 120. In this manner, the disclosed concentrator may scrub ammonia from the leachate stream while converting the ammonia into a byproduct that is easily disposed.
One aspect of the process for removing sulfur from landfill gas described herein includes combining the heated gas and a liquid flow of wastewater under pressure to form a mixture, reducing the static pressure of the mixture to vaporize a portion of the liquid in the mixture yielding a partially vaporized mixture comprising entrained concentrated liquid and a liquid concentrate, contacting with the partially vaporized mixture an alkaline agent to reduce the oxides of sulfur in the partially vaporized mixture, and, removing a portion of the entrained concentrated liquid and reduced oxides of sulfur from the vaporized mixture to provide a demisted gas.
Another aspect of the process for removing sulfur from landfill gas described herein includes re-circulating and combining with the liquid flow of wastewater the liquid concentrate.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes removing a portion of the entrained concentrated liquid and reduced oxides of sulfur from the partially vaporized mixture and passing the partially vaporized mixture through a cross flow scrubber operable to remove a portion of the entrained concentrated liquid and reduced oxides of sulfur from the partially vaporized mixture.
In yet another aspect of the process for removing sulfur from landfill gas described herein the partially vaporized mixture has a temperature of about 150° F. to about 190° F. (about 66° C. to about 88° C.).
Yet another aspect of the process for removing sulfur from landfill gas described herein includes producing an exhaust gas from the combustion of a fuel.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes selecting the fuel from the group consisting of landfill gas, natural gas, propane, and combinations thereof.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes combusting landfill gas.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes combusting natural gas.
In yet another aspect of the process for removing sulfur from landfill gas described herein, the heated gas has a temperature of about 900° F. to about 1200° F. (about 482° C. to about 649° C.).
In yet another aspect of the process for removing sulfur from landfill gas described herein, the wastewater comprises about 1 wt. % to about 5 wt. % solids based on the total weight of the leachate.
In yet another aspect of the process for removing sulfur from landfill gas described herein, preferably the liquid concentrate comprises at least about 10 wt. % solids, based on the total weight of the concentrate, more preferably the liquid concentrate comprises at least about 20 wt. % solids, based on the total weight of the concentrate, even more preferably the liquid concentrate comprises at least about 30 wt. % solids, based on the total weight of the concentrate, and even more preferably the liquid concentrate comprises at least about 50 wt. % solids, based on the total weight of the concentrate.
In yet another aspect of the process for removing sulfur from landfill gas described herein, the partially vaporized mixture comprises about 5 wt. % to about 20 wt. % liquid, based on the total weight of the partially vaporized mixture, and more preferably the partially vaporized mixture in comprises about 10 wt. % to about 15 wt. % liquid, based on the total weight of the partially vaporized mixture.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes combusting natural gas directly from a natural gas well head.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes selecting the wastewater from the group consisting of leachate, flowback water, produced water, and combinations thereof.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes selecting the alkaline agent from the group consisting of sodium hydroxide, calcium carbonate, and mixtures thereof.
Yet another aspect of the process for removing sulfur from landfill gas described herein includes combining the heated gas and a liquid flow of wastewater comprising an alkaline agent under pressure to form a mixture thereof and to reduce the oxides of sulfur, reducing the static pressure of the mixture to vaporize a portion of the liquid in the mixture yielding a partially vaporized mixture comprising entrained concentrated liquid and a liquid concentrate, and, removing a portion of the entrained concentrated liquid and reduced oxides of sulfur from the vaporized mixture to provide a demisted gas.
An aspect of the process for ammonia from landfill leachate described herein includes combining with a liquid flow of the wastewater a pH-raising agent to form a flow of increased-pH wastewater, contacting with the flow of increased-pH wastewater an air stream under conditions sufficient to remove ammonia from the wastewater yielding an ammonia-rich air exhaust stream and an ammonia-lean, increased-pH wastewater, combining the heated gas and a flow of the ammonia-lean, increased-pH wastewater under pressure to form a mixture thereof, reducing the static pressure of the mixture to vaporize a portion of the liquid in the mixture yielding a partially vaporized mixture comprising entrained concentrated liquid and a liquid concentrate, and, removing a portion of the entrained concentrated liquid from the vaporized mixture to provide a demisted gas.
Yet another aspect of the process for removing ammonia from landfill leachate includes combining the ammonia-rich air exhaust stream with a combustion air stream, and combusting a fuel in the presence of the combined air stream to form an exhaust gas comprising the heated gas.
Yet another aspect of the process for removing ammonia from landfill leachate includes selecting a caustic as the pH increasing agent.
Yet another aspect of the process for removing ammonia from landfill leachate includes selecting one of sodium hydroxide and lime as the caustic.
Yet another aspect of the process for concentrating wastewater according to the disclosure includes combining a heated gas and a liquid wastewater within a sealed section of duct to form a mixture that flows through the sealed duct under the influence of negative pressure applied by an induced draft fan located downstream of the sealed duct, drawing the flowing mixture through a section of duct with restricted cross-sectional area compared to the cross-sectional area where the mixture is created thereby accelerating the flow rate and creating turbulence that induces shearing forces between the continuous gas phase and surfaces of the restricted duct opening in contact with the discontinuous liquid phase that breaks droplets and other geometric shapes of the flowing liquid into very small droplets thereby creating extended interfacial surface area between the flowing gas and liquid wastewater that allows rapid approach to the adiabatic saturation temperature of the gas-liquid mixture through rapid heat and mass transfer from gas-to-liquid and liquid-to-gas, respectively, yielding a partially vaporized mixture comprising entrained concentrated liquid and a liquid concentrate, and removing a portion of the entrained concentrated liquid from the vaporized mixture to provide a demisted gas.
While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the methods and apparatus disclosed herein may be made without departing from the scope of the invention.

## Claims

1. A process for concentrating wastewater with a heated gas comprising oxides of sulfur (SOx) and reducing SOx therein, the process comprising:
(a) combining the heated gas and a liquid flow of wastewater under pressure to form a mixture thereof at a first location upstream of a narrowed portion of a mixing corridor;
(b) drawing the mixture through the mixing corridor, and reducing the static pressure of the mixture in the narrowed portion to vaporize a portion of the liquid in the mixture yielding a partially vaporized mixture comprising entrained concentrated liquid;
(c) contacting with the partially vaporized mixture an alkaline agent to reduce the oxides of sulfur in the partially vaporized mixture;
(d) removing a portion of the entrained concentrated liquid and reduced oxides of sulfur from the vaporized mixture to provide a demisted gas, and
(e) returning a portion of the concentrated liquid to the mixing corridor at a second location, downstream of the first location.

2. The process of claim 1 further comprising re-circulating and combining with the liquid flow of wastewater the removed entrained concentrated liquid.

3. The process of claim 1, wherein removing a portion of the entrained concentrated liquid and reduced oxides of sulfur from the partially vaporized mixture comprises passing the partially vaporized mixture through a cross flow scrubber operable to remove a portion of the entrained concentrated liquid and reduced oxides of sulfur from the partially vaporized mixture.

4. The process of claim 1, wherein the partially vaporized mixture has a temperature of about 150° F. to about 190° F. (about 66° C. to about 88° C.).

5. The process of claim 1, wherein the heated gas comprises an exhaust gas from the combustion of a fuel.

6. The process of claim 5, wherein the fuel is selected from the group consisting of landfill gas, natural gas, propane, and combinations thereof.

7. The process of claim 6, wherein the fuel is landfill gas.

8. The process of claim 6, wherein the fuel is natural gas.

9. The process of claim 1, wherein the heated gas has a temperature of about 900° F. to about 1200° F. (about 482° C. to about 649° C.).

10. The process of claim 1, wherein the wastewater is selected from the group consisting of leachate, flowback water, produced water, and combinations thereof.

11. The process of claim 10, wherein the wastewater is leachate.

12. The process of claim 1, wherein the removed entrained concentrated liquid comprises about 1 wt. % to about 5 wt. % solids based on the total weight of the removed entrained concentrated liquid.

13. The process of claim 12, wherein the removed entrained concentrated liquid comprises at least about 10 wt. % solids, based on the total weight of the removed entrained concentrated liquid.

14. The process of claim 13, wherein the removed entrained concentrated liquid comprises at least about 20 wt. % solids, based on the total weight of the removed entrained concentrated liquid.

15. The process of claim 14, wherein the removed entrained concentrated liquid comprises at least about 30 wt. % solids, based on the total weight of the removed entrained concentrated liquid.

16. The process of claim 15, wherein the removed entrained concentrated liquid comprises at least about 50 wt. % solids, based on the total weight of the removed entrained concentrated liquid.

17. The process of claim 1, wherein the partially vaporized mixture in step (b) comprises about 5 wt. % to about 20 wt. % liquid, based on the total weight of the partially vaporized mixture.

18. The process of claim 17, wherein the partially vaporized mixture in step (b) comprises about 10 wt. % to about 15 wt. % liquid, based on the total weight of the partially vaporized mixture.

19. The process of claim 1, wherein the alkaline agent is selected from the group consisting of sodium hydroxide, calcium carbonate, and mixtures thereof.

20. The process of claim 19, wherein the alkaline agent further comprises a solution of sodium hydroxide.

21. The process of claim 19, wherein the alkaline agent further comprises a slurry of calcium carbonate.

22. A process for concentrating wastewater with a heated gas comprising oxides of sulfur (SOx) and reducing SOx therein, the process comprising:
(a) combining the heated gas and a liquid flow of wastewater comprising an alkaline agent under pressure at a first location upstream of a narrowed portion of a mixing corridor to form a mixture of heated gas and liquid thereof and to reduce the oxides of sulfur;
(b) drawing the mixture through the mixing corridor, and reducing the static pressure of the mixture in the narrowed portion to vaporize a portion of the liquid in the mixture yielding a partially vaporized mixture comprising entrained concentrated liquid;
(c) removing a portion of the entrained concentrated liquid and reduced oxides of sulfur from the vaporized mixture to provide a demisted gas; and,
(d) returning a portion of the concentrated liquid to the mixing corridor at a second location, downstream of the first location.

23. A process for concentrating wastewater with a heated gas comprising oxides of sulfur (SOx) and reducing SOx therein, the process comprising:
(a) combining the heated gas and a liquid flow of wastewater under pressure at a first location upstream of a narrowed portion of a mixing corridor;
(b) passing the combined heated gas and liquid flow of wastewater through the mixing corridor to form a gas-liquid mixture having a liquid concentration of about 5 weight percent (wt. %) to about 20 wt. %, based on the total weight of the mixture, and accelerating the gas and liquid flow within the narrowed portion, causing a portion of the liquid to evaporate;
(c) contacting with the gas-liquid mixture an alkaline agent to reduce the oxides of sulfur in the gas-liquid mixture;
(d) separating a portion of the liquid from the gas-liquid mixture to provide a gas mixture entrained with liquid droplets, wherein one of the liquid and the liquid droplets comprises reduced oxides of sulfur;
(e) removing liquid droplets entrained in the gas mixture obtained in step (d) to provide a concentrated liquid and a substantially liquid-free and substantially SOx-free gas; and,
(f) returning a portion of the concentrated liquid to the mixing corridor at a second location, downstream of the first location.

24. The process of claim 23, further comprising re-circulating and combining with the liquid flow of wastewater in step (a) the concentrated liquid obtained in step (e).

25. A process for removing ammonia from wastewater and concentrating the wastewater with a heated gas, the process comprising:
(a) combining with a liquid flow of the wastewater a pH-raising agent to form a flow of increased-pH wastewater;
(b) contacting with the flow of increased-pH wastewater an air stream under conditions sufficient to remove ammonia from the wastewater yielding an ammonia-rich air exhaust stream and an ammonia-lean, increased-pH wastewater;
(c) combining the heated gas and a flow of the ammonia-lean, increased-pH wastewater under pressure to form a mixture thereof at a first location upstream of a narrowed portion of a mixing corridor;
(d) drawing the mixture through the mixing corridor, and reducing the static pressure of the mixture in the narrowed portion to vaporize a portion of the liquid in the mixture yielding a partially vaporized mixture comprising entrained concentrated liquid; and,
(e) removing a portion of the entrained concentrated liquid from the vaporized mixture to provide a demisted gas; and
(f) returning a portion of the concentrated liquid to the mixing corridor at a second location, downstream of the first location.

26. The process of claim 25 further comprising combining the ammonia-rich air exhaust stream obtained in step (b) with a combustion air stream, and combusting a fuel in the presence of the combined air stream to form an exhaust gas comprising the heated gas employed in step (c).

27. The process of claim 25, wherein the pH-increasing agent is a caustic.

28. The process of claim 27, wherein the caustic is one of sodium hydroxide and lime.

29. The process of claim 8, wherein the natural gas is unrefined and supplied directly from a well head.

30. The process of claim 8, wherein the natural gas is refined.