Abstract:
An automated, computer-controlled landfill condensate injection system includes a pump that pumps condensate into a flare chamber at a pressure that is sufficiently high and through a nozzle that is configured to vaporize the condensate without requiring the use of high pressure air injected with the condensate. Secondary injection lines can also be provided that terminate in nozzles which are vertically staggered from each other along the chamber, to inject additional condensate into the flare and thus dispose of it at a higher rate depending on vaporization conditions. Computer-controlled valves can be provided in the lines for selectively opening and closing the lines.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to landfills, and more particularly to systems and methods for disposing of liquid condensate from landfill gas recovery systems. 
     BACKGROUND 
     Waste products decompose in landfills, and after the free oxygen in the landfill is depleted, the waste product decomposition generates methane gas. It is desirable to recover this methane gas for environmental and safety reasons. To this end, landfill gas recovery systems have been introduced which collect the gas generated in landfills and burn the gas in flares on the landfill. 
     Occasionally, gas in the recovery system condenses with other fluids such as water. This methane-based condensate, like the gas, must be removed from the landfill for safety and environmental reasons, and to ensure that blockage of gas piping and damage to the flare system does not occur. Typically, the condensate is simply pumped out of the gas recovery system and transported to a hazardous waste dump site, where it is disposed of. 
     As recognized herein, transporting hazardous condensate to another waste facility for disposal is not only expensive, it does not solve the environmental problem of disposing of the condensate, but rather only moves the problem to a hazardous waste disposal facility. With this in mind, the present invention recognizes the desirability of economically disposing of the condensate at the site at which it is recovered in an environmentally benign way. 
     As recognized herein, one method for disposing of the condensate is to burn it in the flare chamber that is used to burn the methane gas. Typically, a landfill gas recovery flare chamber includes a ring of vertically-oriented burners located near the bottom of the chamber, and methane gas is piped through the burners and oxidized, with the hot oxidation products exhausting upwardly up through the flare chamber and out of the open top end of the chamber. In such a flare chamber, the condensate can be injected radially into the flare chamber above the burners by entraining the condensate in a pressurized high velocity air stream above the flame of the flare. 
     Such a system, as understood by the present invention, unfortunately requires a relatively expensive air compressor to generate the pressurized air stream. Also, a portion of the high velocity condensate stream tends to impinge on the wall of the flare chamber that is opposite the condensate injection point, damaging the wall. 
     Alternatively, the present invention understands that condensate can be pumped upwardly into the flare chamber through a vertical pipe that is centrally located in the flare chamber below the ring of burners. As the condensate moves upwardly past the burners, it flashes into vapor. As recognized by the present invention, however, the injection rate of condensate sometimes must undesirably be limited to avoid excessively cooling the flare chamber as the latent heat of vaporization of the condensate is overcome. Excessively cooling the flare chamber could reduce the ability of the flare to burn the methane gas and condensate. Moreover, the present invention understands that landfill process controls, including those related to condensate injection systems, preferably be automatic, to more accurately control the processes and to avoid the necessity of personnel undertaking time consuming and repetitive process monitoring and adjustment. 
     As further recognized herein, it is possible to provide a condensate injection system having a relatively high condensate injection rate without excessively cooling a flare chamber, and to automatically control the condensate injection rate as appropriate for the particular energy level of the flare. Accordingly, it is an object of the present invention to address one or more of the abovenoted considerations. 
     SUMMARY OF THE INVENTION 
     A compressorless condensate injection system is disclosed for a landfill having a flare chamber including at least one wall that is heated when the flare chamber burns methane gas extracted from the well. The system includes a condensate reservoir and a condensate pump in fluid communication with the reservoir to pump condensate into the chamber at a high pressure, preferably 40-250 pounds or more. At least a first injection line is in fluid communication with the condensate pump but not with an air compressor. The first line terminates in a first nozzle that is positioned on the flare chamber for directing condensate into the chamber such that condensate from the nozzle is vaporized when it is sprayed into the chamber without requiring the use of compressed air. 
     In a preferred embodiment, the first line has a heat exchange segment that is curved, e.g., the segment can extend partially or completely around the flare chamber before terminating in a nozzle. In this way, fluid in the first line can be heated when the flare chamber burns gas extracted from the well. 
     A first control valve preferably is in fluid communication with the first injection line for selectively blocking fluid flow therethrough, with the first control valve being responsive to electrical control signals. Indeed, secondary injection lines with respective solenoid valves and nozzles can be provided for selectively injecting even greater amounts of condensate into the chamber, depending on vaporization conditions. These secondary nozzles can be oriented to direct condensate upwardly and radially inwardly into the flare chamber. If desired, a ring line can communicate with the condensate pump, and the ring line terminates in a ring line nozzle disposable adjacent the burners of the flare. 
     Additional features can include a methane gas inlet line and a methane sensor for measuring a methane concentration in the inlet line, a flow sensor for measuring gas flow rate in the inlet line, and a temperature sensor for sensing temperature in the flare chamber. Also, condensate temperature and pressure can be measured in each heat exchange segment. Electrical control signals for controlling the solenoid valves can be generated by a computer based on these signals. 
     In another aspect, a computer program device can include a computer program storage device readable by a digital processing system, and a computer program on the program storage device and including instructions executable by the digital processing system for performing method steps for controlling at least one control valve disposed in at least one condensate injection line in a landfill flare chamber. The method undertaken by the computer includes determining a gas volume burn rate based on a combination of methane concentration in gas to be burned in the chamber, flow rate of gas, and flare chamber temperature. Also, the computer generates one or more control signals to control the valve or valves in response to the determination of gas volume burn rate. 
     In still another aspect, a condensate injection nozzle includes a nozzle body defining a pathway therethrough, and an orifice element disposed in the pathway. An diversion plate is also disposed in the pathway. In accordance with present principles, the diversion plate causes turbulent flow of the condensate, prior to the condensate passing through the orifice element and being injected into the flare chamber. 
     The details of the present invention, both as to its structure and its operation, can best be appreciated in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of the present condensate injection system shown in one intended environment with a flare chamber and accompanying gas injection components, with portions of the flare chamber insulation layer broken away; 
     FIG. 2 is a schematic view from an elevational perspective of the present flare chamber, showing the condensate nozzles, with the heat exchange segments of the secondary injection lines schematically shown as winding once around the inside of the flare chamber, it being understood that further coils can be provided for each segment if desired; 
     FIG. 3 is a flow chart of the present logic; 
     FIG. 4 is a cross-sectional diagram of the preferred nozzle; 
     FIG. 5 is a top plan view of the diversion plate; and 
     FIG. 6 is a side elevational view of the diversion plate, showing one of the slots in phantom. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1, a system is shown and generally designated  10  for burning methane gas from a landfill  12 . As shown, the system  10  includes a condensate injection system, generally designated  14 , and a gas injection system, generally designated  16 . As disclosed in detail below, the injection systems  14 ,  16  respectively inject liquid condensate from the landfill  12  and gas from the landfill  12  into a cylindrical metal flare chamber  18 , for disposal of the condensate and gas by vaporization. 
     In one embodiment, the flare chamber of the present invention can be a conventional candle flare chamber or enclosed flare chamber that is conventionally affixed to the landfill  12 . Or, the flare chamber  18  with condensate injection system  14  can be mounted on a flat movable trailer. In such an embodiment, the flare chamber  18  can be tiltably mounted on the trailer. 
     With regard to the gas injection system  16 , gas from the landfill  12  enters a main gas inlet pipe  20  under vacuum supplied by a blower  22 . The gas first passes through a condensate extractor or filter  24  that removes condensate from the gas, the effluent of which is pumped by a pump  25  to a condensate storage tank  26  in the condensate injection system  14 . If desired, the storage tank  26  can be omitted. 
     In the preferred embodiment, the gas passes through a flow metering device  28 , preferably one of the devices disclosed in U.S. Pat. No. 5,616,841, owned by the assignee of the present invention and incorporated herein by reference. Then, the gas passes through a flame arrestor  30  that establishes a fire boundary to prevent flames from the flare chamber  18  from propagating past the arrestor  30 , and the gas then flows into the chamber  18 . 
     As shown in FIG. 1, a temperature sensor  32  and a methane concentration sensor  34  are disposed in the flare inlet pipe or other suitable location (i.e., directly on the flare chamber  18 ) to sense the temperature inside the flare chamber  18  and the methane concentration of the gas entering the chamber  18 . It is to be understood that the sensors  28 ,  32 ,  34  are in data communication with a computer  36  via RF, IR, or electric wire for sending their respective output signals to the computer  36  as described below. 
     Having described the gas injection system  16  and turning now to the condensate injection system  14 , a condensate pump  38  is provided for pumping condensate through the injection system  14 . In one preferred embodiment, the pump  38  is a rotary vane pump that discharges condensate such that the condensate is injected into the chamber  18  at 40-250 pounds pressure or more. Alternatively the pump  38  can be a diaphragm pump or other suitable device. This high pressure, in addition to the nozzle structure shown below, ensures that the condensate will be vaporized without requiring the use of a high pressure air compressor. Accordingly, the injection system  14  is a compressorless system. 
     The flow path of condensate through the preferred condensate injection system  14  is as follows. From the storage tank  26 , condensate flows past a manually operated tank outlet isolation valve  40  to a flow switch  42 . It is to be understood that the flow switch outputs a signal representative of whether condensate is in the system  14 . This switch can be sent to the computer  36  and used by the computer  36  to deenergize the motor of the pump  38  when no condensate is available, to protect the pump  38 . 
     From the flow switch  42  the condensate flows to a particulate filter  44 , which extracts large particles from the condensate. If desired, a differential pressure sensor  46  can sense the differential pressure across the filter  44  to indicate whether the filter  44  requires cleaning or maintenance. Sensor isolation valves  48 ,  50  are provided in the sensor  46  line to isolate the sensor  46 . 
     Next, the condensate flows through a manually operated pump inlet isolation valve  52  to the pump  38 . From the discharge of the pump  38 , condensate flows to a T connector or other three-way connector  54 . Condensate can flow from the connector  54  through a recirculation line  56  to a back pressure regulator valve  58 , which senses pressure at the discharge of the pump  38  and opens and closes as appropriate to ensure that a predetermined high discharge pressure is not exceeded. As shown in FIG. 1, condensate flowing through the regulator valve  58  flows through a tank inlet isolation valve  60  back to the condensate storage tank  26 . 
     A main injection line  62  branches from the T connector  54 , and a first pressure indicator  64  communicates with the line  62  by means of a first tap line  66  with isolation valve  68 , to sense pressure in the line  62 . Condensate flows past the first tap line  66  to a flow adjusting valve  70 . In one embodiment, the flow adjusting valve  70  can be a needle-type valve which is manually set to establish a predetermined flow rate through the line  62 . Or, the flow adjusting valve  70  can be a solenoid valve that is controlled by the computer  36  to dynamically establish a flow rate through the line  62 . 
     Still referring to FIG. 1, a flow rate meter  72  is downstream of the flow adjusting valve  70  for measuring the flow rate of condensate through the main line  62 . The flow rate meter  72  can communicate with a flow rate totalizator  74 , which in turn can present a visual display of instantaneous flow rate and total flow and/or communicate with the computer  36  to send a flow rate signal thereto. In one embodiment, the flow rate meter  72  is a turbine-type meter. 
     A second pressure indicator  76  communicates with the main injection line  62  by means of a second tap line  78  with isolation valve  80 , to sense pressure in the line  62  and to provide a visual indication thereof and/or electrical indication to the computer  36 . Condensate flows past the second tap line  78  to a manually operated injection isolation valve  82 , and thence to a solenoid-controlled main injection valve  84 . 
     From the main injection valve  84 , the condensate flows through a primary injection line  86  into the chamber  18 , into which it is injected at high pressure through a vertically-oriented main nozzle  88 . Moreover, FIG. 1 shows that the main condensate injection line  86  directs condensate to a valve manifold that includes at least first through third secondary control valves  90 ,  92 ,  94 . In the preferred embodiment, the control valves  86  and  90 - 94  are solenoid valves that are in data communication with the computer  36  for opening or shutting the control valves on an individual basis. 
     The secondary control valves  90 - 94  lead to respective first through third secondary injection lines  96 ,  98 ,  100 . As can be appreciated in reference to FIG. 1, the secondary injection lines  96 - 100  direct condensate into the flare chamber  18  in accordance with disclosure below. 
     Further inventive features of the condensate injection system  14  can be appreciated in cross-reference to FIGS. 1 and 2. As shown, the three secondary injection lines  96 ,  98 ,  100  are all higher than the main nozzle  88  and are vertically staggered relative to each other. The secondary lines include respective first through third curved heat exchange segments  96   a ,  98   a ,  100   a . The segments  96   a ,  98   a ,  100   a  can be serpentine-shaped as shown, or as schematically shown in FIG. 2 they can extend around the inside periphery or the inner refractory of the chamber parallel to the ground or slanted with respect to the ground, prior to terminating in respective nozzles. In any case, the length of the segments ensures that heat from the flare will be transferred through the segments into the condensate that is carried in the segments. In one preferred embodiment, each heat exchange segment  96   a ,  98   a ,  100   a  includes a respective condensate injection temperature monitor “T” and a respective condensate injection pressure monitor “P” which can be in data communication with the present computer. 
     If desired, the heat exchange segments  96   a ,  98   a ,  100   a  can be sandwiched between the wall of the flare chamber  18  and an insulation layer, for shielding the wall of the flare chamber  18  from people. With this structure, fluid in the heat exchange segments  96   a ,  98   a ,  100   a  of the condensate injection lines  96 - 100  can be heated by the wall of the flare chamber  18  when the flare chamber  18  burns gas that is extracted from the landfill, to thereby preheat the condensate prior to injection into the flare. As recognized by the present invention, such preheating reduces the amount of heat necessary to burn the condensate, thereby increasing the capacity of the flare to burn condensate. Moreover, should it be desired to dispose of landfill leachate in lieu of or in addition to condensate, the leachate is filtered to remove heavy metals and particles, with the above-described preheating effectively facilitating leachate disposition in the flare. 
     Desirably, to promote heat transfer the heat exchange segments  96   a - 100   a  are radially staggered from each other relative to the flare chamber  18 . It is to be understood that the heat exchange segments  96   a ,  98   a ,  100   a  can be disposed on the interior surface of the chamber  18 , and that the segments  96   a - 100   a , instead of being serpentine-shaped, can be wound around the wall  18   a  in respective helical patterns or other patterns that optimize preheating condensate before it is injected into the flare. 
     In cross-reference to FIGS. 1 and 2, each secondary injection line  96 - 100  passes through the wall of the flare chamber  18  and terminates in a respective secondary nozzle  102 ,  104 ,  106 , with the secondary nozzles being positioned near the interior surface of the flare chamber  18 . The secondary nozzles can be identical in configuration to the main nozzle  88 , described in greater detail below. 
     As best shown in FIG. 2, the higher three (i.e., secondary) nozzles  102 ,  104 ,  106  are oriented to direct condensate upwardly and radially inwardly into the flare chamber  18 . Moreover, the nozzles are vertically staggered with respect to each other. Thus, the highest nozzle  102  is higher than the next highest nozzle  104  and so on. 
     In contrast, the lowest, i.e., main, nozzle  88  is positioned below and radially central to a ring of burners  108 , in the flare chamber  18  near the bottom thereof. Accordingly, the main condensate injection line  86  establishes a ring line that is in communication with the condensate pump  38 . If desired, the main injection line  86  may include a heat exchange segment. 
     With the above disclosure in mind, the present invention envisions regulating condensate flow into the flare chamber  18  based on a gas oxidation rate in the flare chamber  18 . More specifically, 
     As best shown in FIG. 2, the higher three (i.e., secondary) nozzles  102 ,  104 ,  106  are oriented to direct condensate upwardly and radially inwardly into the flare chamber  18 . Moreover, the nozzles are vertically staggered with respect to each other. Thus, the highest nozzle  102  is higher than the next highest nozzle  104  and so on. 
     In contrast, the lowest, i.e., main, nozzle  88  is positioned below and radially central to a ring of burners  108 , in the flare chamber  18  near the bottom thereof. Accordingly, the main condensate injection line  86  establishes a ring line that is in communication with the condensate pump  38 . If desired, the main injection line  86  may include a heat exchange segment. 
     With the above disclosure in mind, the present invention envisions regulating condensate flow into the flare chamber  18  based on a gas oxidation rate in the flare chamber  18 . More specifically, the higher the gas oxidation rate, the more condensate may be injected into the flare chamber  18 , and vice versa. Accordingly, the condensate control valves  84  and  90 - 94  receive electrical control signals from the computer  36  to either individually open or individually shut the valves, based on the oxidation rate, although in other embodiments the control valves might be throttled based on the control signals. As disclosed in detail below, the computer  36  determines the oxidation rate and generates the control signals based on one or more of the signals from the temperature sensor  32 , the methane concentration sensor  34 , and the gas flow meter  28 . 
     Now turning to the condensate injection control regime of the present invention, the computer  36  can be a personal computer (PC), a laptop computer, or other microprocessing device having an associated man-machine interface such as a video monitor and an associated input device such as a keyboard, mouse, touch screen, ball, or other appropriate input device. Additionally, the computer  36  can include an associated modem for communicating with a computer network (not shown). 
     As described in detail below, the computer  36  has a control module  110  that controls the control valves based on gas flow properties of the flare. The control module  110  of the present invention can be embodied in computer program software. Manifestly, the invention is practiced in one essential embodiment by a machine component that renders the computer program code elements in a form that instructs a digital processing apparatus (that is, a computer) to perform a sequence of operational steps corresponding to those disclosed herein. 
     These instructions may reside on a program storage device including a data storage medium, such as a computer diskette. The machine component can be a combination of program code elements in computer readable form that are embodied in a computer-usable data medium on the computer diskette. Alternatively, such media can also be found in semiconductor devices, on magnetic tape, on optical disks, on a DASD array, on magnetic tape, on a conventional hard disk drive, on electronic read-only memory or on electronic ransom access memory, or other appropriate data storage device. In an illustrative embodiment of the invention, the computer-executable instructions may be lines of compiled C ++  language code. 
     It is to be understood that the present invention alternatively can be implemented by logic circuits. As yet another alternative, the present invention can be implemented by a circuit board, and the operative components of the control module  110  accordingly would be electronic components on the circuit board. 
     Referring now to FIG. 3, the overall logic of the module  110  of the computer  36  receives signals at block  112  from the sensors described above. These signals, as mentioned, can include gas inlet methane concentration, gas inlet temperature, gas flow rate, condensate injection temperature and/or pressure, and condensate flow rate. Using these signals, the computer can, as but one example, determine a gas volume burn rate. Then, at block  114  the computer  36  outputs control signals to maintain one or more parameters at predetermined levels. The computer  36  can output control signals to the secondary injection valves  96 - 100  in response to the gas volume burn rate. Alternatively or in addition, the computer  36  can cause the control valves to sequentially open, from, e.g., lowest to highest, based on gas inlet temperature, with higher temperatures indicating that more condensate can be disposed of and thus causing the computer  36  to open the control valves more rather than less. Or, the computer  36  might seek to establish a predetermined condensate flow rate based on one or more of gas temperature, condensate temperature, gas and/or condensate flow rate, etc. 
     Now referring to FIG. 4, the details of the preferred nozzles of the present invention can be seen. As shown, a hollow metal nozzle body  120  can be threaded to a hollow nozzle base  122 , with a central fluid pathway  124  being defined therethrough. In turn, the nozzle base  122  can have internal threads  126  for engaging the end of an injection line. If desired, a compression washer can be sandwiched between the body  120  and base  122 . 
     The nozzle body  120  is formed with an outwardly expanding spray end  128  as shown. Specifically, the spray end  128  expands radially outwardly from a smaller medial opening  130  to a larger distal opening  132 . A retaining lip  134  circumscribes the medial opening  130 . 
     As shown in FIG. 4, an orifice element  136  is juxtaposed with the medial opening  130  in the pathway  124 , and the orifice element  136  is retained in the body  120  by the retaining lip  134 . The orifice element  136  defines a central orifice  138  that communicates with the central pathway  124 . In the preferred embodiment, the orifice  138  defines a cylindrical, relatively narrow proximal portion  140  that terminates in an outwardly tapering frusto-conical portion  142 . 
     Proximal to the orifice element  136  and disposed within the central pathway  124  is a metal disc-shaped diversion plate  144 . As described more fully below, the plate  144  is formed with several obliquely-oriented slots to create swirling turbulence as the condensate passes therethrough, such that the condensate is atomized when it passes through the orifice element  136 . 
     More specifically, in cross-reference to FIGS. 5 and 6, the plate  144  is formed with slots  146  that are oriented at an oblique angle a relative to the longitudinal axis  148  of the pathway  124  when viewed from the edge of the plate  144 . In one preferred embodiment, six slots  146  are shown, and the angle α is between 30°-60°, and more preferably is 45°. 
     While the particular LANDFILL CONDENSATE INJECTION SYSTEM as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited as a “step” instead of an “act”.