Methods and systems for reducing pressure of natural gas and methods and systems of delivering natural gas

Methods and systems for reducing a pressure of compressed natural gas and for delivering natural gas are disclosed. A regulator comprising a vortex tube may be used to reduce the pressure of compressed natural gas while a temperature thereof is also reduced. The temperature reduction associated with a pressure drop in the compressed natural gas is achieved by throttling the gas at constant enthalpy from 3,000 PSIG to 150 PSIG through the regulator. At least one heat exchanger may be utilized to increase the temperature of the compressed natural gas to a temperature suitable for injection delivery. A pressure-reducing regulator may be used to further reduce a pressure of the gas to about 45 PSIG for delivery to an end-user.

TECHNICAL FIELD

Embodiments of the invention generally relate to methods and systems for reducing pressure of natural gas and, in particular, to methods and systems for injection delivery of compressed natural gas.

BACKGROUND

It is a well-known practice to compress non-ideal gases, including elemental and other gases for scientific or industrial purposes, for transport and delivery to consumers or other customers. For example, it is a known practice to transport compressed natural gas (CNG) by truck, ship, or similar delivery system to users that periodically require natural gas supply in excess of the supply available through existing pipelines. Further, there are areas in which natural gas service via pipeline is not available at all, due to remoteness, the high cost of laying pipelines, planned or unplanned outages, or other factors. In such cases, tanks of CNG transported by truck, for example, can be an economical way to provide the natural gas service required by such users.

To be economical, such tanks must be filled with large amounts of usable natural gas. Accordingly, full tanks of CNG are under very high pressure, commonly around 3000 pounds per square inch gauge (PSIG). However, in many cases natural gas under considerably lower pressure, e.g. from 20 to 100 PSIG, is required. Consequently, unloading a CNG tank requires a substantial reduction in the gas pressure prior to being received at a customer's intake. Currently, reducing the pressure of the CNG may be problematic due to substantial cooling of the natural gas caused by the Joules-Kelvin effect. Allowing a large volume of CNG to be depressurized results in a large temperature drop that can expose the material that comprises CNG tanks, valves, pipelines (particularly carbon steel pipes), customer equipment or other pieces of a natural gas system to low temperatures possibly exceeding safe operating ranges specified by manufacturers and codes.

Users of CNG supply systems may require volumes of natural gas that range from very low flow to flows in excess of 5,500 standard cubic feet per hour (SCFH). At such rates, the cooling resulting from depressurization may be transmitted a significant distance downstream from the point of regulation. This may increase the chance of failure if the material or equipment at the customer's intake is not rated for the extreme cold temperature of the gas. Such failures could result in a loss of a substantial volume of gas through a relief valve that releases gas to atmosphere when pressure is too high. At worst, a failure could result in irreparable damage or destruction of equipment and/or explosion.

It is understood that there are electric or electronic devices, control valves, and/or pressure controllers that may be able to accept the high-pressure CNG, depressurize it, and pass it to a standard natural gas intake at a relatively high rate of delivery. Such devices are extremely expensive, however, reducing or eliminating the profitability of truck-delivery of CNG. Further, devices capable of operating at the temperatures ranges produced by extreme depressurization of natural gas are not readily available.

Accordingly, there is a need in the industry for a reliable gas delivery system that provides depressurized gas at a steady rate with varying flow conditions.

SUMMARY

In some embodiments, the present invention includes a system for reducing a pressure of a gas. The system may include at least one vortex regulator, a heat exchange device and a pressure-reducing regulator. The at least one vortex regulator may include a vortex tube and may have at least one inlet to receive natural gas and at least one outlet for releasing the natural gas at a substantially decreased pressure and temperature. The heat exchange device may be configured to receive the natural gas from the at least one vortex regulator and to increase the temperature of the natural gas. The pressure-reducing regulator may be in fluid communication with the heat exchange device and may be configured for further reducing the pressure of the natural gas.

In additional embodiments, the present invention includes a method of reducing a pressure of natural gas that includes directing a natural gas stream into at least one vortex regulator comprising a vortex tube, reducing a pressure and a temperature of the natural gas stream using the at least one vortex regulator, heating the natural gas stream from the at least one vortex regulator using a heat exchanger in fluid communication with the vortex regulator and directing the natural gas stream from the heat exchanger to a pressure-reducing regulator to further reduce the pressure thereof.

In further embodiments, the present invention includes a method of delivering natural gas. The method may include directing a natural gas stream from at least one storage vessel to at least one vortex regulator comprising a vortex tube, decreasing a pressure of the natural gas stream while simultaneously reducing a temperature of the gas using the at least one vortex regulator and directing the natural gas stream to a heat exchanger having a surface in communication with a fluid having a temperature higher than that of the natural gas stream to heat the gas.

In yet another embodiment, the present invention may include a system for delivering natural gas that includes a mobile support. The system may include at least one storage vessel for containing the natural gas in a compressed form disposed on the mobile support and a vortex regulator including at least one vortex tube and disposed on the mobile support. The vortex regulator may be in fluid communication with the at least one storage vessel and a heat exchanger. The heat exchanger may be configured for exchanging heat between the natural gas and ambient air.

DETAILED DESCRIPTION OF THE INVENTION

The illustrations presented herein are not meant to be actual views of any particular material, apparatus, system, or method, but are merely idealized representations that are employed to describe embodiments of the present invention. Additionally, elements common between figures may retain the same numerical designation for convenience and clarity.

As used herein, the terms “compressed natural gas” and “CNG” mean and include natural gas, primarily methane, condensed under high pressure which may be stored, for example, in specially designed storage tanks at from about 2,000 PSIG to about 3,600 PSIG.

The term “disposed on,” as used herein, means and includes mounted on, placed on, positioned on, supported by, attached to, or otherwise connected to the mobile support, either directly or indirectly.

The phrase “in fluid communication,” as used herein, means to engaging in, or currently being available for, one-way or two-way movement of a liquid, gas, or both, as circumstances indicate. Fluid communication between two elements may be direct between the two elements (e.g., when the two elements are physically contacting each other in a functional manner) or indirect (i.e., when the two elements are not physically contacting each other but are connected in a functional manner via an intermediary element(s) such as a transferring means).

The phrase “in selective fluid communication,” as used herein, means that one of the two elements is ready for being placed in fluid communication with the other of the two elements, e.g., the one element would be in fluid communication with the other element if the two elements were connected, directly or indirectly, to each other as previously described.

The terms “Joule-Thompson effect(s)” and “Joule-Kelvin effect(s),” as used herein, mean and include the temperature change of a gas or a liquid when forced through a valve, a narrow jet, or a porous plug adiabatically (i.e., without loss or gain of heat to the system). The rate of change of temperature T with respect to pressure P in a Joule-Thomson process (that is, at constant enthalpy H) is the Joule-Thomson (Kelvin) coefficient μJT. This coefficient can be expressed in terms of the gas's volume V, its heat capacity at constant pressure Cp, and its coefficient of thermal expansion a as:

As used herein, the term “pounds force per square inch gauge,” or “PSIG,” means and includes the pressure in pounds force per square inch exceeding atmospheric pressure.

An embodiment of an embodiment of a system100for reducing a pressure of natural gas is shown in a simplified schematic view inFIG. 1. As shown inFIG. 1, the gas may be stored in a compressed form at least one storage vessel102and may be fed into the system100through a gas inlet104. The gas may enter the system100from the storage vessel102at a pressure of from about 2,000 PSIG to about 4,000 PSIG and, more particularly, about 3,000 PSIG. The system100may be configured to reduce the pressure of the gas by from about 3,000 PSIG to pressures ranging from 1,500 PSIG to 2,500 PSIG and, more particularly, by as much as 2,500 PSIG. After entering the system100, the gas may be fed through gas flow line106and may, optionally, be diverted to a bypass line108or a static pressure line110, as will be described in further detail. A flow rate of the gas within the system100may be less than or equal to about 5,500 standard cubic feet per hour (SCFH).

The gas may be directed though the gas flow line106to a first regulator112configured to substantially reduce the pressure of the gas. As a non-limiting example the first regulator112may be a Joule-Thomson expansion valve, a diaphragm regulator or a needle valve regulator, such as, those commercially available from Bryan Donkin RMG (Germany), Elster-Instromet A/S (Denmark) and Tescom-Emerson Process Management (Elk River, Minn.). The pressure of the gas may be reduced by the first regulator112such that the gas exiting the first regulator112has a pressure of from about 1,500 PSIG to about 2,500 PSIG at a location in the gas flow line106.

The gas may be fed from the first regulator112to a vortex regulator118by way of a first valve116a. Alternatively, a Venturi nozzle or any orifice, such as, a valve or a narrow jet, may be used instead of the vortex regulator118. For example, the vortex regulator118may include a vortex tube, examples of which are disclosed in U.S. Pat. No. 2,907,174 to Willem Peter Hendel, U.S. Pat. Nos. 5,911,740 and 5,749,231 to Tunkel et al., and U.S. Pat. No. 6,071,424 to Tuszko et al., each of which is hereby incorporated by reference in its entirety. A vortex tube, often referred to as the Ranque vortex tube, the Hilsch tube and the Ranque-Hilsch tube, is a static mechanical device that takes pressurized compressible fluid and derives a hot fluid and a cold fluid at a lower pressure. The mechanics by which the vortex tube separates a fluid into hot and cold parts through depressurizing are largely unknown, but empirical data validate that it is a measurable, repeatable and sustainable event. In operation, the pressurized compressible fluid is injected through tangential nozzles into a chamber in which the compressible fluid is simultaneously separated into a fluid stream higher in temperature than the inlet stream and a fluid stream that is cooler than the inlet stream. While not wishing to be bound by any particular scientific theory, tangential injection may set the pressurized compressible fluid stream in a vortex motion. This spinning stream of compressible fluid may turn about 90° and pass down the hot tube in the form of a spinning shell or vortex, similar to a tornado. A valve at one end of the tube allows some of the warmed fluid to escape. That portion of the warmed fluid that does not escape is directed back down the tube as a second vortex inside the low-pressure area of the larger vortex. The inner vortex may lose heat to the larger vortex and exhaust through the other end as a cold fluid stream. The gas in the vortex is cooled because part of its total energy converts into kinetic energy.

By way of non-limiting example, the vortex regulator118may be configured to substantially reduce the pressure of the gas using a method such as that disclosed in U.S. Pat. No. 5,327,728 to Lev E. Tunkel, which is hereby incorporated by reference in its entirety. Such a vortex regulator may be obtained from Universal Vortex, Inc. (Robbinsville, N.J.). The vortex regulator118is able to reduce the pressure of the gas from about 3,000 PSIG to about 150 PSIG for gas flows ranging from about 1,800 SCFH to about 5,500 SCFH without experiencing regulator freeze up. The vortex regulator118may produce a hot gas fraction during the pressure reduction process that is diverted onto surfaces of the vortex regulator118to prevent the formation of ice and mitigate the potential freeze up condition associated with high pressure reduction. The pressure of the gas may be reduced by the vortex regulator118so that the gas exiting therefrom has a pressure of from about 300 PSIG to about 50 PSIG and, more particularly, about 150 PSIG. The first valve116amay be, for example, a ball valve such as those commercially available from Swagelok Company (Solon, Ohio).

In some embodiments, where a volumetric flow demand of the gas may be sufficiently high, the gas may be diverted to the bypass line108, which circumvents the first regulator112. The gas may be fed through the bypass line108and back to the gas flow line106by a second valve116b. After re-entering the gas flow line106, the gas may be fed into the vortex regulator118at a pressure of from about 2,000 PSIG to about 4,000 PSIG and, more particularly, about 3,000 PSIG.

A temperature of the gas is substantially reduced during pressure reduction by the vortex regulator118and the first regulator112. After exiting the vortex regulator118, the temperature of the gas may be from about −78.9° C. (about −110° F.) to about −56.7° C. (about −70° F.) and, more particularly, about −67.8° C. (about −90° F.). The reduction in pressure is advantageous to the system due to the significant temperature drop that occurs due to Joule-Kelvin effect. The temperature reduction associated with the pressure reduction in the gas is achieved by throttling the gas at a constant enthalpy from through the vortex regulator118and the first regulator112. The temperature gradient between the gas exiting the vortex regulator118and ambient air heater120enables for significant heat input into the system100via ambient heater120. The ambient heater120may be a heat exchanger having a forced convection surface area, or any other device configured for exchanging heat between gas and ambient air. The ambient heater120may be in fluid communication with the vortex regulator118and a surface of the ambient heater120may be in communication with the ambient air for transfer of heat from the ambient air to the gas. The system100may further include a fan (not shown) or other device for circulating the ambient air over the surface of the ambient heater120. Energy transferred from the surrounding environment (i.e., ambient air) into the system100at a high rate through a convection process via the ambient heaters120and124may be determined using the following equation:
Q=H(ΔT)

The variable H is the convection coefficient and is dependent on the gas and geometry of the device it is flowing through. The reduced temperature of the gas resulting from the pressure reduction by the vortex regulator118and the first regulator112creates a large temperature gradient (ΔT) between the gas and the ambient air. The energy transfer direction (Q) should increase based on the available energy in the ambient environment. Typically the sign of the temperature gradient (ΔT) predicts the direction of energy transfer. Therefore, if the temperature of the gas is less than that of the surroundings, energy is transferred into the system.

By achieving a large temperature gradient from rapid two stage pressure reduction with the primary pressure reduction occurring in the vortex regulator118, gas heating may be achieved efficiently. The large temperature gradient achieved through pressure reduction by the vortex regulator118enables a substantial portion of the heating process to take place in the ambient heater120.

The ambient heater120may be modeled by using a closed loop energy balance that encompass the working fluids (i.e., natural gas) and ambient air. The fundamental equation that describes the required heat input for the heat transfer process associated with the ambient heater120is as follows:
Q=UAΔTm,
wherein Q is an overall heat transfer, U is the heat transfer coefficient for the ambient heater, ΔTm is a log mean temperature difference between the gas and the ambient air and A is an overall heat transfer area of the ambient heater120. By way of non-limiting example, the ambient heater120may have a heat transfer coefficient (U) of from about 0.75 to about 1.2 and, more particularly, about 0.965 and a heat transfer area (A) of from about 50 ft3to about 400 ft3and, more particularly, about 214.63 ft3.

For example, if the temperature of the ambient air is about 10° C. (50° F.) and the temperature of the gas is about −67.8° C. (−90° F.), the gas may be heated to ambient temperature (i.e., about 10° C.) using about 11,986 BTUs. In some embodiments, an external heat source may be supplied to the ambient heater120to increase the efficiency of heating.

The gas exiting the ambient heater120may have a temperature of from about 0° C. to about 20° C. (about 68° F.) and, more particularly, about 10° C. (about 50° F.). The gas may be directed from the ambient heater120to a second regulator122configured to substantially reduce the pressure of the gas. Additionally, the gas, or a portion thereof, may be directed from the inlet104to the static pressure line110. The static pressure line110may maintain a constant pressure, the purpose of which is to control the outlet pressure of the second regulator122. Gas may be directed through the static pressure line110by a valve123.

The second regulator122may be a Joule-Thomson expansion valve, a diaphragm regulator or a needle valve regulator such as, for example, a 26-1200 SERIES high flow regulator which is commercially available from Tescom-Emerson Process Management. The second regulator122may control the pressure of the gas to enable for a large flow differential while substantially reducing or eliminating pressure spikes suing incremental flow changes. As a non-limiting example, the second regulator122may reduce the pressure of the gas to from about 20 PSIG to about 100 PSIG and, more particularly, about 45 PSIG.

The gas may then be directed to another ambient heater124configured to increase the temperature of the gas within about 28.9° C. (about 20° F.) of an ambient temperature, such as, from about 28.9° C. (about 20° F.) to about 10° C. (about 50° F.). The gas exiting the system100may be conveyed to a gas main to be directed to residential, commercial and industrial applications.

In some embodiments, the system100may be disposed on a mobile support, such as, a vehicle or a trailer. The ambient heaters120and124may also be disposed on the mobile support or, alternatively, may be separate from the mobile support. The system100may further include a heat source that provides heat to the ambient heaters120and124. For example, the heat source may be suitable an internal combustion engine125used to provide power for transporting the system100on the mobile support. As a non-limiting example, heat source may besuch as used on a flameless nitrogen skid unit such as those described in U.S. Pat. No. 5,551,242 to Loesch et al., the entirety of which is hereby incorporated by reference in its entirety.

In other embodiments, the system100may be used to provide an uninterrupted natural gas source to end-users. For example, such a system100may be used to provide natural gas to power generation facilities, residences, local distribution companies, service centers, manufacturing plants, hospitals, and the like. The system100may be installed in a location in which a natural gas source is desired and compressed natural gas may be stored in containers, such as storage tanks.

The system100may further include monitoring equipment127, such as, sensors, computers and the like for monitoring the pressure, temperature, flow rate and the like, of the natural gas at various points in the system100. Such monitoring equipment127is well known in the art and is, thus, not described in detail herein.

The system100enables the pressure of natural gas to be reduced from about 3,000 PSIG to about 45 PSIG while substantially reducing or eliminating freeze up conditions that may result in loss of control or interruption of gas flow. For example, the temperature of the gas exiting the system100may be greater than or equal to about −28.9° C. (about −20° F.). The system100may be used to reduce the pressure of natural gas at flows less than or equal to about 5500 SCFH.

Another embodiment of an embodiment of a system200for reducing a pressure of natural gas is shown in a simplified schematic view inFIG. 2. The gas may enter the system200through a gas inlet valve202at a pressure of from about 2,000 PSIG to about 4,000 PSIG and, more particularly, about 3,000 PSIG. The gas may be fed through a high pressure-reducing regulator204such as, for example, a diaphragm regulator or a needle valve regulator. The high pressure-reducing regulator204may reduce a pressure of the gas to from about 1,000 PSIG to about 3,000 PSIG. From the high pressure-reducing regulator204, the gas may be fed into a gas flow line206or may, optionally, be diverted to a bypass line208. A flow rate of the gas within the system200may be less than about 1,800 mSCFH.

The system200may include a first pressure relief valve210aalong the gas flow line206that may be used to release excess pressure from the system200. The pressure relief valve210amay be, for example, a pilot-operated or spring-operated pressure relief valve. Examples of pressure relief valves include Anderson Greenwood valves, which are available from Tyco Flow Control (Princeton, N.J.). A portion of the gas may be directed through the gas flow line206through a first valve212ato a high flow vortex regulator218. The first valve212amay be, for example, a ball valve. The gas flow line206may, optionally, include a first temperature gauge214aand a first pressure gauge216athat may be used to determine at least one setting of the high flow vortex regulator218. The high flow vortex regulator218may include a vortex tube and may be configured to substantially reduce the pressure and temperature of the gas. By way of non-limiting example, the high flow vortex regulator218may reduce the pressure and temperature of the gas so that the gas exiting therefrom has a pressure of from about 300 PSIG to about 50 PSIG and, more particularly, about 150 PSIG and a temperature of from about −78.9° C. (about −110° F.) to about −56.7° C. (about −70° F.) and, more particularly, about −67.8° C. (about −90° F.).

In some embodiments, where a volumetric flow demand of the gas may be sufficiently low, at least a portion of the gas may be diverted to the bypass line208, which circumvents the high flow vortex regulator218. The gas may be fed through the bypass line208to a low flow vortex regulator220by a second valve212b. The reduced pressure gas may be fed from the low flow vortex regulator220to the gas flow line206at a pressure of from about 300 PSIG to about 50 PSIG and, more particularly, of about 150 PSIG and a temperature of about −78.9° C. (about −110° F.) to about −56.7° C. (about −70° F.) and, more particularly, about −67.8° C. (about −90° F.).

The gas flow line206may include a second temperature gauge214b, a second pressure gauge216b, a second pressure relief valve210band a third pressure relief valve210c. The gas may be directed to an outlet222via a system200at a substantially reduced pressure, such as, a pressure of from about 5 PSIG to about 200 PSIG.

Another embodiment of a system300for reducing pressure of a gas, such as natural gas, is shown in a simplified schematic view inFIGS. 3A and 3B.FIG. 3Ais a side view of the system300whileFIG. 3Bis a perspective view of the system300. The system300may include a gas inlet302which may be connected to a gas source such as, for example, a storage tank (not shown). The system300may also include a high flow vortex regulator304, a primary ambient heater (not shown), a static pressure line306, a high flow bypass line308and a gas outlet310. The system300may also, optionally, include a first pressure gauge312, a first pressure relief valve314, a pressure controller316, a low flow vortex regulator318, a second pressure gauge320, a pressure regulator322, a second ambient heater (not shown), a third pressure gauge324and a second pressure relief valve326. The static pressure line306may include an injection regulator328.

Upon entering the gas inlet302, a portion of the gas may be directed to the pressure controller316or the static pressure line306. For example, the gas may be directed to at least one of the pressure controller316and the static pressure line306by a t-shaped connector330a, such as, an SS-1610-1-16 connector that is available from Swagelok Company. The pressure of the gas entering the pressure controller316may be determined using the first pressure gauge312, or other pressure measuring device. As a non-limiting example, the first pressure gauge312may be a PGI-115P industrial pressure gauge available from Swagelok Company. For example, the first pressure gauge312may be connected to the gas inlet302by way of a t-shaped connector330b, similar to that previously described, and reducing bushing333a. The reducing bushing333amay be, for example, an SS-4-RB-2 stainless steel pipe fitting-reducing bushing or an SS-8-RB-4 stainless steel pipe fitting-reducing bushing, each of which is available from Swagelok Company. The t-shaped connectors330aand330bmay be connected to one another by way of a fitting332asuch as, for example, an SS-8-CN stainless steel pipe fitting, close nipple, available from Swagelok Company.

The first pressure relief valve314may be connected to the first pressure gauge312by a fitting332band a t-shaped connector330csimilar to those previously described. The first pressure relief valve314may be a direct spring operated pressure relief valve such as an Anderson Greenwood Type 81 pressure relief valve which is available from Tyco Flow Control. The first pressure relief valve314may be in fluid communication with the high flow bypass line308via t-shaped connector330dand valve334a. For example, the valve334amay be a ball valve such as a three-piece high-pressure alternative fuel service valve, which is available from Swagelok Company. The first pressure relief valve314may be in fluid communication with the pressure controller316via the t-shaped connector330dand tube connectors336aand336b. The tube connectors336aand336bmay be stainless steel connectors such as, for example, an SS-810, SS-1610 and SS-400 tube fitting connectors available from Swagelok Company. The pressure controller316may be used, for example, to control the flow of the gas into the high flow vortex regulator304. The pressure controller316may be a high flow, pressure-reducing regulator or Joule-Thomson expansion valve and may have an inlet pressure of from about 3,570 PSIG to about 6,000 PSIG, an outlet pressure of from about 10 PSIG to about 2,500 PSIG and a flow capacity (Cv) of from about 0.8 to about 2. By way of non-limiting example, the pressure controller316may be a 44-1300 Series high flow/high pressure-reducing regulator, which is available from Tescom-Emerson Process Management. The pressure controller316may, optionally, be connected to or in fluid communication with a check valve338such as, for example, a SS-58S8-SC11 lift check valve that is available from Swagelok Company. The pressure controller316may prevent the gas pressure on the outlet of the check valve338from exceeding about 2,500 PSIG. A tube connector336c, such as that previously described, may connect the pressure controller316and the check valve338. The inlet302may be in connected to or in fluid communication with the high flow bypass line308and in selective fluid communication with a low flow bypass line342via a cross-shaped connector340, such as, an SS-8-VCR-CS 316 SS face seal fitting, which is available from Swagelok Company.

A valve334bmay, respectively, be disposed between the cross-shaped connector340and the high flow vortex regulator304, and may be used to control fluid communication therebetween. The valve334bmay be connected to the high flow vortex regulator304by tube connectors336dand336e, such as those previously described. The high flow vortex regulator304may be obtained from Universal Vortex and may have a maximum flow volume of about 29 thousand cubic feet per hour (about 821.188 cubic meters per hour). Optionally, a reducing bushing333bmay be disposed between the valve334band the high flow vortex regulator304.

Another valve334cmay be disposed between the low flow bypass line342and the cross-shaped connector340, and may be used to control fluid communication therebetween. As a non-limiting example, the valve334cmay be connected to the low flow bypass line342by a tube connector336f, similar to those previously described, and may connected to the cross-shaped valve340by a fitting332d, similar to those previously described. The low flow vortex regulator318may have a maximum flow rate of about 9 thousand cubic feet per hour (about 254.851.6 cubic meters per hour).

The low flow vortex regulator318and the high flow vortex regulator304may each be in fluid communication with the first ambient heater (not shown) via an ambient heater inlet344. The ambient heater inlet344may include a fitting, such as, an SS-8-SE street elbow fitting which is available from Swagelok Company, which may be connected to the low flow bypass line342and the high flow vortex regulator304by a t-shaped connector330e, similar as those previously described.

The ambient gas heater may be in fluid communication with the pressure regulator322via an ambient gas flow outlet346. The ambient gas flow outlet346may include a fittings such as those previously described with respect to the ambient heater inlet334. The pressure regulator322may be, for example, a regulator having an inlet pressure of from about 6,000 PSIG to about 10,000 PSIG, an outlet pressure of from about 55 PSIG to about 6,000 PSIG and a flow capacity (Cv) of from about 3.3 to about 12. As a non-limiting example, the pressure regulator322may be a diaphragm sensed pressure-reducing regulator such as a 26-1200 Series high flow regulator, which is commercially available from Tescom-Emerson Process Management. The second pressure valve320, or other pressure measuring apparatus, and a reducing bushing333cmay, optionally, be disposed between the ambient gas outlet346and the pressure regulator322. The pressure regulator322or the reducing bushing333c, if present, may be connected to the t-shaped connector330eby a fitting332e.

The pressure regulator322may be in fluid communication with a second ambient heater (not shown) and a heater bypass line348via a second heater inlet350and a second heater outlet352. The second ambient heater may, optionally, be connected to a third pressure gauge324or other similar pressure measuring device, through a t-shaped connector330fand a reducing bushing333d, similar to those previously described.

The heater bypass line348may be in fluid communication with the pressure regulator322via a t-shaped connector330g, similar to those previously described. The heater bypass line348may be connected to the pressure regulator322at one end and to the t-shaped connector330gat an opposite end by tube connectors332fand332g. Optionally, a reducing bushing333emay be disposed Fittings332eand332gmay be used to interconnect the t-shaped connectors330fand330gand a fitting332hconnected to the second pressure relief valve326. By way of non-limiting example, the second pressure relief valve326may be a direct spring operated valve, such as, an Anderson Greenwood Type 81 pressure relief valve which is available from Tyco Flow Control.

The static pressure line306may include the injection regulator328having an inlet pressure of from about 6,000 PSIG to about 10,000 PSIG, an outlet pressure of from about 5 PSIG to about 6,000 PSIG and a flow capacity (Cv) of from about 0.02 to about 0.12. The static pressure line306and the injection regulator328may be used to maintain a static pressure on the high flow regulator322. For example, the injection regulator328may be a 44-1100 Series high pressure-reducing regulator, which is available from Tescom-Emerson Process Management. As a non-limiting example, the static pressure line306may be connected to the gas inlet302by a tube connector336hand may be connected to the pressure regulator322by tube connectors336iand336j, such as those previously described.

A system301for reducing the pressure of a gas similar to that shown inFIGS. 3A and 3Bis shown inFIG. 3C. The system301may include gas inlet302, pressure relief valve314, high flow vortex regulator304, low flow vortex regulator318, ambient heater (not shown), second regulator322and outlet310. Optionally, the system301may include a first, second and third temperature gauges313,315and317and first, second and third pressure gauges312,320and324.

Referring toFIGS. 3A-3C, after entering the gas inlet302, the pressure of the gas entering gas inlet302may be determined using the first pressure gauge312. For example, the pressure of the gas may enter the gas inlet302at a pressure of from about 1,500 PSIG to about 4,500 PSIG and, more particularly, about 3,000 PSIG. As the gas is directed in through the inlet302, excess pressure may be released by the first pressure relief valve314. As shown inFIGS. 3A and 3B, the gas may, optionally, be directed to the pressure controller316that may reduce a pressure of the gas such that the gas exiting therefrom has a pressure of from about 1,500 PSIG to about 2,500 PSIG. Where a volumetric flow demand of the gas may be sufficiently low, at least a portion of the gas may be diverted to the gas bypass line308, which circumvents the pressure controller316.

Optionally, the gas, or a portion thereof, may be directed to the low flow bypass line342, and may be passed though the low flow vortex pressure reducer318, which substantially reduces the pressure of the gas. As a non-limiting example, the gas exiting the low flow vortex pressure reducer318may have a pressure of from about 150 PSIG to about 2,000 PSIG. The gas may be directed to the high flow vortex regulator304wherein the pressure of the gas is substantially reduced. For example, the gas entering the high flow vortex regulator304may exhibit a pressure of from about 500 PSIG to about 2,500 PSIG and may exit having a pressure of from about 50 PSIG to about 2,000 PSIG and, more particularly, about 145 PSIG. A temperature of the gas may also be substantially decreased during pressure reduction by the high flow vortex regulator304For example, the gas exiting the high flow vortex regulator304may have a temperature of from about −78.9° C. (about 110° F.) to about −56.7° C. (about −70° F.) and, more particularly, about −67.8° C. (about −90° F.).

The gas may be directed through the ambient heater inlet344to the first ambient heater which may substantially increase the temperature of the gas. For example, the gas exiting the ambient heater may have a temperature of from about 0° C. to about 20° C. and, more particularly, about 10° C. The gas may then be directed through the ambient gas flow outlet346to the high flow regulator322wherein the pressure of the gas may be reduced to from about 15 PSIG to about 75 PSIG and, more particularly, about 45 PSIG. Optionally, the pressure of the gas may be determined before entering the pressure regulator322using the second pressure gauge320.

The gas exiting the pressure regulator322may, optionally, be directed to the second ambient heater by the second heater inlet350, as shown inFIGS. 3A and 3B, wherein a temperature of the gas may be increased. As a non-limiting example, gas exiting the secondary heater outlet352may have a temperature of within about −7° C. (about 20° F.) of ambient temperature. A portion of the gas may be directed around the second ambient heater by the heater bypass line348. After exiting the second ambient heater via the second heater outlet352, a pressure of the gas may be determined using the third pressure gauge324. The gas may be directed through the outlet310. Excess pressure may be released from the system300by the second pressure relief valve326.

Another embodiment of a system400for reducing pressure of a gas, such as natural gas, is shown in a simplified schematic view inFIG. 4. The system400may include an inlet402, a low flow vortex regulator404, a high flow vortex regulator406, a series of pressure-reducing regulators408a,408b,408c,408dand408e, another pressure-reducing regulator410, pressure relief valves412a,412band412cand an outlet414. The inlet402may be connected to a first pressure gauge415afor example, by a t-shaped connector416aand a reducing bushing418a. As a non-limiting example, the first pressure gauge415amay be a PGI Series pressure gauge, which is available from Swagelok Company. The t-shaped connector416amay be, for example, an SS-8-T, an SS-4-T, an SS-16-T, an SS-8-ST, an SS-8-BT, an SS-400-3 tube fitting, each of which is available from Swagelok Company, or any other suitable t-shaped connector. The reducing bushing418amay be, for example, an SS-8-RB reducing bushing or an SS-16-RB reducing bushing, each of which is available from Swagelok Company. The inlet402may be in fluid communication with a first temperature gauge421ato which it is connected by a fitting420aand a t-shaped connector416b. For example, the fitting420amay be an SS-8-HLN hex-reducing nipple, an SS-16-HRN hex-reducing nipple, an SS-810 connector, or an SS-400 connector, each of which is available from Swagelok Company, or an NPT fitting, which is available from Omega Engineering (Stamford, Conn.), or any other suitable fitting. As a non-limiting example, the first temperature gauge421amay be obtained from DURATEMP® thermometer from Ashcroft, Inc. (Stratford, Conn.). The first temperature gauge421amay be connected to the t-shaped connector416bby fittings420b,420cand420dwhich are similar to the fittings previously described.

The t-shaped connector416bmay be connected to another t-shaped connector416cby a fitting420e. The t-shaped connector416bmay be connected to a valve422aleading to a bypass line424and to another t-shaped connector416cconnected to a first pressure release valve412a. The valve422amay be, for example, an SS-AFSF8 ball valve or an SS-AFSS8 ball valve, which are available from Swagelok Company, or any other device suitable for controlling gas flow. The bypass line424may include the low flow vortex regulator404coupled thereto by fittings420fand420gsimilar to those previously described. The bypass line424may be in fluid communication the high flow vortex regulator406via a t-shaped connector416d. The bypass line424and the first pressure relief valve412amay be in selective fluid communication with the high flow vortex regulator406via valves422band422ca t-shaped valve416d. The high flow vortex regulator406and the low flow vortex regulator404may each be in fluid communication with a series of pressure-reducing regulators408a,408b,408c,408dand408e. The low flow vortex regulator404may have a maximum flow rate of about 9 million cubic feet per hour (about 254,851.6 cubic meters per hour). The high flow vortex regulator406may have a maximum flow volume of about 25 million cubic feet per hour (about 707921.175 cubic meters per hour).

Optionally, a second pressure gauge415bmay be disposed between the high flow vortex regulator406and at least one of the pressure-reducing regulators408a,408b,408c,408dand408e. As a non-limiting example, each of the pressure-reducing regulators408a,408b,408c,408dand408ehas a maximum inlet pressure of 3,600 PSIG, a pressure control range of from about 0 PSIG to about 250 PSIG, a flow coefficient of about 1.0 Cvand a maximum operating temperature of about 200° C. Each of the pressure-reducing regulators408a,408b,408c,408dand408emay be, for example, a high-flow, high-sensitivity, diaphragm-sensing pressure regulator, such as, a KHF Series pressure-reducing regulator available from Swagelok Company. The pressure-reducing regulators408a,408b,408c,408dand408emay be connected via t-shaped connectors416e,416f,416g,416hand416iand fittings420h,420i,420jand420k. Each of the pressure-reducing regulators408a,408b,408c,408dand408emay be connected to one of valves422d,422e,422f,422g, and422h. Each of the valves422d,422e,422f,422g, and422hmay be connected to connector, such as elbow connector428aand t-shaped connectors416j,416k,416land416mand via fittings420l,420m,420n,420oand420pand tubing426a,426b,426c,426dand426e. The t-shaped connectors416j,416k,416land416mand via fittings420l,420m,420n,420oand420pmay be similar to those previously described. The elbow connector428amay be, for example, a SS-16-E fitting available from Swagelok Company. The elbow connector428aand each of the t-shaped connectors416j,416k,416land416mand may be connected to another via fittings420q,420r,420sand420t.

A third pressure gauge415cmay, optionally, be disposed between the second pressure relief valve412band the series of pressure-reducing regulators408a,408b,408c,408dand408e. For example, the third pressure gauge415cmay be connected to t-shaped connector416oby fitting420u, elbow connector428band a reducing bushing418c. A t-shaped valve416pand a reducing bushing418dmay connect the second pressure relief valve412b. The second pressure relief valve412bmay be, for example, an Anderson Greenwood Series 800 pilot operated pressure relief valve, which is available from Tyco Flow Control. A second temperature gauge421bmay, optionally, be disposed between the second pressure relief valve412band the pressure-reducing regulator410. As a non-limiting example, the second temperature gauge421band the pressure-reducing regulator410may each be connected to a t-shaped connector416q. A reducing bushing418eand a fitting420wmay be used to connect the second temperature gauge421bto the t-shaped connector416q. By way of example and not limitation, the pressure-reducing regulator410may have a maximum inlet pressure of about 2,000 PSIG, an outlet pressure of about 5 to about 500 PSIG and an operating temperature range of from about 29° C. to about 82° C. The pressure-reducing regulator may be, for example, a 627 Series pressure-reducing regulator available from Tescom-Emerson Process Management.

Optionally, the third pressure relief valve412c, a fourth pressure gauge415d, a plug valve430and a fifth pressure gauge415emay be included in the system400. By way of non-limiting example, the third pressure relief valve412cmay be connected to the system400by way of a t-shaped connector416r, an elbow connector428c, fitting420xand reducing bushing418f. The fourth pressure gauge415dmay be in fluid communication with the pressure-reducing regulator410and the second pressure release valve412bby way of a t-shaped connector416r. For example, elbow connectors428d,428e, and428f, fittings420yand420z, t-shaped connector416sand reducing bushing418gmay connect the fourth pressure gauge415dto the t-shaped connector416r. The plug valve430may be connected to the t-shaped connector416sby a fitting420aa. The plug valve430may be, for example, a Class-300 XENITH® plug valve, which is available from Xomox Corporation (Cincinnati, Ohio). The fifth pressure gauge415emay be connected to the plug valve430by a fitting420ab, a t-shaped connector416tand a reducing bushing418h.

The outlet414may comprise a reducing bushing418i, such as that shown inFIG. 4. As a non-limiting example, the outlet414may be connected to the fifth pressure gauge415eby fittings420acand420ad, t-shaped valve416u, and elbow connector428g. Optionally, a close nipple432may be connected to the t-shaped connector416u.

Natural gas having a pressure of about 3,000 PSIG and a temperature of about 15.6° C. (about 60° F.) may be injected in to the system400through the inlet402. The natural gas injected into the system400may be obtained, for example, from a storage container (not shown).

The natural gas, or portions thereof, may be passed to the low flow bypass line424or to the high flow vortex regulator406, each of which is in selective fluid communication with the inlet402. If the pressure of the natural gas in the system400exceeds about 3,500 PSIG, sufficient pressure may be released by the first pressure relief valve412asuch that the pressure of the gas entering the high flow vortex regulator406is less than or equal to about 3,000 PSIG. In the low flow bypass line424, the natural gas may be directed through the low flow vortex regulator404by valve422a. The natural gas exiting the low flow vortex regulator404may have a substantially decreased pressure and temperature. For example, the temperature of the gas exiting the low flow vortex regulator404may be about −51.1° C. (−60° F.) while the pressure may be from about 150 PSIG to about 2,000 PSIG.

The natural gas exiting the low flow vortex regulator404may be directed to the high flow vortex regulator406. The gas exiting the high flow vortex regulator406may have a substantially decreased pressure and temperature. For example, the temperature of the gas exiting the low flow vortex regulator404may be about −51.1° C. (−60° F.).

The natural gas may be directed from the low flow vortex regulator404and the high flow vortex regulator406to the series of pressure-reducing regulators408a,408b,408c,408d, and408e. Each of the pressure-reducing regulators of the series of pressure-reducing regulators408a,408b,408c,408d, and408emay be in selective fluid communication with the second pressure relief valve412band the pressure-reducing regulator410by way of the valves422a,422b,422c,422d, and422e. The natural gas exiting the series of pressure-reducing regulators408a,408b,408c,408d, and408emay exhibit a pressure of about 225 PSIG.

The second pressure relief valve412bmay be used to reduce the pressure of the natural gas within the system400. For example, if the pressure of the natural gas exiting the series of pressure-reducing regulators408a,408b,408c,408d, and408eis greater than about 300 PSIG, a portion of the natural gas may be release through the second pressure relief valve412b.

The natural gas may then be directed to the pressure-reducing regulator410wherein the pressure of the gas is reduced from about 225 PSIG to about 60 PSIG. The third pressure relief valve412cmay be used to release a portion of the natural gas, for example, if the pressure exceeds about 75 PSIG. The natural gas may exit the system400at a substantially reduced pressure and temperature.

FIG. 5is a simplified schematic illustration of a natural gas delivery system500for transport and delivery of natural gas. The system500may include a trailer502(FIGS. 5A and 5B), a self-propelled vehicle503(FIG. 5C) or a stationery unit505(FIG. 5D), a storage box504, hose reels506, a storage assembly508, a control cabinet512and a pressure reduction system (not shown) for-reducing pressure of natural gas, such as those described with respect toFIGS. 1-4, may be adapted for mounting on or connecting to the trailer502. The manifold may include a heat exchanger514which is disposed on or connected to the trailer502. The system500may be configured to reduce the pressure of compressed natural gas having a pressure of about 3,000 PSIG to about 45 PSIG while maintaining an operating temperature of greater than about −40° C. to prevent components of the system500from freezing. The reduced pressure natural gas may be injected into a gas distribution line at a temperature of about −28.9° C. (about −20° F.). For example, such a system may be mounted or disposed on a wall, a support or a floor of the trailer502.

The hose reels504, or other suitable device, may be used to store hose for connecting an outlet of the system500to the gas distribution line. The storage assembly508may be configured to hold storage containers for storing the compressed natural gas. For example, the storage containers may be steel cylinders or bottles516in selective fluid communication with the pressure reduction system by way of connective tubing518. The control cabinet512may include controls for operating the pressure reduction system. The system500may further include monitoring equipment520, such as, sensors, computers and the like for monitoring the pressure, temperature, flow rate and the like, of the natural gas at different points of the pressure-reducing system. Such monitoring equipment520is well known in the art and is, thus, not described in detail herein.

FIG. 6is a plot of a temperature of the gas released from a high flow vortex regulator (outlet temperature) versus a change in pressure (PSIG) of the gas (ΔP). The change in pressure was determined by subtracting the pressure of the gas entering the high flow vortex regulator from the pressure of the gas exiting the high flow vortex regulator. As shown inFIG. 6, the outlet temperature of the gas is substantially reduced as the change in pressure increases.

FIG. 7is a plot of a temperature of gas exiting a vortex pressure regulator702and a temperature of gas exiting an ambient heater704versus a pressure of gas entering a system such as that described with respect toFIG. 1.

FIG. 8is a plot of a pressure of gas stored in a storage tank as the pressure of the natural gas is reduced by the vortex pressure regulator at various flow rates in a system such as that described with respect toFIG. 1. As shown inFIG. 7, the flow rate may be held at about 4,500 mSCFH during pressure reduction by the vortex pressure regulator with only a differential change in tank pressure.

FIG. 9includes plots of pressure versus temperature of the natural gas after pressure reduction by the second regulator122and the vortex regulator118in the system100shown inFIG. 1. The second regulator122was a 44-1300 Series high flow/high pressure-reducing regulator. The plot902corresponds to the pressure versus temperature for the natural gas exiting the second regulator122while the plot904corresponds to the pressure versus temperature for the natural gas exiting the vortex regulator118.

FIG. 10is a plot of pressure versus flow rate of the gas exiting a 44-1300 Series high flow/high pressure-reducing regulator used as the second regulator122of a system100similar to that shown inFIG. 1

FIG. 11includes plots of time versus pressure at various points in a system for reducing a pressure of natural gas similar to that shown inFIG. 3C. The pressure of the natural gas was determined at an inlet of the system1302and an outlet of a vortex regulator1352at various times. The difference in pressure from the inlet350of the vortex regulator to the outlet352of the vortex regulator1305was also determined. The system included a TESCOM 44-1300 as the second regulator1322, which was set at a static pressure of 45 PSIG1322. As shown inFIG. 11, as the change pressure by the vortex pressure regulator1305approaches the inlet pressure of the gas into the system1302, the vortex pressure regulator may provide substantially all of the pressure reduction which enables a broader range of pressure control by the system.