Natural gas temperature and pressure regulating system based on recovering pressure energy and absorbing heat from ultralow temperature ambient environment

Abstract

The natural gas temperature and pressure regulating system based on recovering pressure energy and absorbing heat from ultralow temperature ambient environment. A pressure driven heating system of pipeline natural gas pressure regulation or liquid natural gas regasification process. This system adopts vortex tube, ambient air heat exchanger and ejector that constitute the pressure driven heating unit to replace the existing heater. The two kinds of pressure driving devices of an ejector and a vortex tube are adopted, transmit the low temperature NG at the cold end of the vortex tube into the ambient air heat exchanger to absorb heat from the ambient continuously; at the same time, make temperature of the gas from the hot end of the vortex tube increase to meet the required temperature of pipeline directly, then achieve the purpose of no heater energy consumed.

Claims

1. A natural gas temperature and pressure regulating system based on recovering pressure energy and absorbing heat from ultralow temperature ambient environment, comprising an inflow high-pressure natural gas and a pressure regulating device; wherein the natural gas temperature and pressure regulating system comprises a pressure-driven heating and pressure regulating unit; wherein the inflow high-pressure natural gas is heated, gasified or decompressed by the pressure-driven heating and pressure regulating unit and then connected to the pressure regulating device; the inflow high-pressure natural gas includes compressed natural gas, pipeline natural gas and liquefied natural gas; the pressure-driven heating and pressure regulating unit consists of a vortex tube, an air-temperature heat exchanger and an ejector; an inlet of the ejector is connected with an outlet of the air-temperature heat exchanger, an outlet of the ejector is connected with an inlet of the vortex tube; a cold end of the vortex tube is connected with an inlet of the air-temperature heat exchanger, and a hot end of the vortex tube is connected with the pressure regulating device; the inflow high-pressure natural gas and a low-pressure natural gas discharged from the air-temperature heat exchanger are mixed in the ejector to form a medium-pressure natural gas which is then discharged from the outlet of the ejector into the vortex tube; a high-speed vortex is formed after going through a tangential nozzle of the vortex tube and the medium-pressure natural gas is depressed, and the medium-pressure natural gas is separated into two low-pressure streams inside the vortex tube due to an energy separation effect of the vortex tube, one stream from the vortex tube goes to the hot end is heated by the heating action in the vortex tube, and a temperature of the one stream of the low-pressure natural gas is adjusted to an allowable temperature of the pipe network through a hot-end control valve of the vortex tube, and then sent to the pressure regulating device; the other stream of the low-pressure natural gas from the vortex tube goes to a cold-end of the vortex tube, then, enters into the air-temperature heat exchanger to absorb heat from the air; and the low-pressure natural gas from the outlet of the air-temperature heat exchanger is injected into the ejector by a high-speed jet from the ejector; the natural gas discharged from the hot end of the vortex tube enters the regulating device for pressure reduction, so as to reach a delivery pressure and eventually enter a downstream of a sub-station or an urban pipeline network.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 Schematic diagram of the natural gas temperature and pressure regulating system based on recovering pressure energy and absorbing heat from ultralow temperature ambient environment

(2) In the diagram: 1-1 vortex tube; 1-2 ambient air heat exchanger; 1-3 ejector.

(3) FIG. 2 Schematic diagram of the system of this invention at the CNG decompression station.

(4) In the diagram: 2-1 CNG Storage tank; 2-2 ejector; 2-3 ambient air heat exchanger; 2-4 vortex tube; 2-5 pressure regulating device

(5) FIG. 3 Schematic diagram of the system of this invention at the PNG decompression/distribution station.

(6) In the diagram: 3-1 incoming flow PNG; 3-2 ejector; 3-3 vortex tube; 3-4 ambient air heat exchanger; 3-5 downstream pressure regulating

(7) FIG. 4 Schematic diagram of the system of this invention at the LNG decompression station.

(8) In the diagram: 4-1 LNG Storage tank; 4-2 LNG Storage tank with supercharger; 4-3 ambient air vaporizer; 4-4 cryogenic liquid booster pump; 4-5 pressure regulating device; 4-6 vortex tube; 4-7 ambient air heat exchanger; 4-8 ejector;

DETAILED DESCRIPTION

(9) Specific implementation method of this invention are described in detail combined with the technical solutions and the accompanying diagram.

(10) Natural gas pressure regulating system using pressure of the incoming flow natural gas and absorbing heat from ultralow temperature ambient environment, which is mainly consisted of vortex tube 1-1, ambient air heat exchanger 1-2 and ejector 1-3.

(11) The incoming high pressure natural gas enters the heating and pressure regulating system that driven by pressure at this invention.

(12) This pressure driven heating and pressure regulating unit is consisted of ejector 1-3, vortex tube 1-1, ambient air heat exchanger 1-2, they are connected sequentially to form a closed loop. The cold end of vortex tube 1-1 is connected to the ambient air heat exchanger 1-2, and the hot end of vortex tube 1-1 flows out of the system into the subsequent device; the high pressure incoming natural gas enters into the ejector 1-3 and becomes the main working fluid. The fluid expands and accelerates in the Laval nozzle in the injector 1-3 to form a supersonic jet that injects the low pressure natural gas discharged from the outlet of the ambient air heat exchanger 1-2, the two stream of natural gas exchange momentum and energy to become one stream in the mixing chamber of ejector 1-3, and then the stream experiences pressure recovery in the diffuser of ejector 1-3, and a medium-pressure fluid is formed at the outlet of ejector 1-3, and then transmit the stream into the vortex tube 1-1; After the natural gas enters the vortex tube 1-1, it expands and decompresses through the tangential nozzle in the vortex tube 1-1 to form a high-speed vortex. Due to the energy separation effect of the vortex tube 1-1, the natural gas is separated into two streams. One is heated by the heating effect of the vortex tube 1-1, and the temperature is adjusted to the allowed temperature of the pipe network through control valve at the hot end of vortex tube and then enter the subsequent downstream device; due to the cooling effect inside of the vortex tube 1-1, the other stream is cooled and enters into ambient air heat exchanger 1-2 through the cold end of vortex tube 1-1 to absorb heat from air, then the heated natural gas is discharged from the outlet of the ambient air heat exchanger 1-2, and return to the ejector 3 from the injecting fluid inlet of the injector 1-3.

(13) Based on the system above, three specific implementation solutions are listed below for different incoming natural gas conditions.

(14) (1) The Incoming Flow is Compress Natural Gas (CNG)

(15) When the application background is compressed natural gas, the decompression system that can use the pressure of the storage tank itself to achieve the heat extraction from low temperature air, mainly consisted of 2-1 CNG storage tank; 2-2 ejector; 2-3 ambient air heat exchanger; 2-4 vortex tube; 2-5 pressure regulating device.

(16) The compressed natural gas transported from the CNG storage tank 2-1 into the heating pressure regulating unit driven by pressure described in this invention, and then is transmitted to the pressure regulating device 2-5;

(17) The pressure driven heating and pressure regulating unit is consisted of an ejector 2-2, a vortex tube 2-4, and an ambient air heat exchanger 2-3, they are connected sequentially to form a closed loop, the cold end of the vortex tube 2-4 is connected to the ambient air heat exchanger 2-3, and the hot end of the vortex tube 2-4 is connected to the pressure regulating device 2-5; the high pressure natural gas discharged from the CNG storage tank 2-1 enters the ejector 2-2 and becomes main working fluid. The fluid expands and accelerates in the Laval nozzle in the injector 2-2 to form a supersonic jet that injects the low pressure natural gas discharged from the outlet of the ambient air heat exchanger 2-3, the two stream of natural gas exchange momentum and energy to become one stream in the mixing chamber of ejector 2-2, and then the stream experiences pressure recovery in the diffuser of ejector 2-2, and a medium-pressure fluid is formed at the outlet of ejector 2-2, and then transmit the stream into the vortex tube 2-4; After the natural gas enters the vortex tube 2-4, it expands and decompresses through the tangential nozzle in the vortex tube 2-4 to form a high-speed vortex. Due to the energy separation effect of the vortex tube 2-4, the natural gas is separated into two streams. One is heated by the heating effect of the vortex tube 2-4, and the temperature is adjusted to the allowed temperature of the pipe network through control valve at the hot end of vortex tube 2-4 and then enter the subsequent downstream device 2-5; due to the cooling effect inside of the vortex tube 2-4, the other stream is cooled and enters into ambient air heat exchanger 2-3 through the cold end of vortex tube 2-4 to absorb heat from air, then the heated natural gas is discharged from the outlet of the ambient air heat exchanger 2-3, and return to the ejector 2-2 from the injecting fluid inlet of the injector 2-2.

(18) (2) The Incoming Flow is Pipeline Natural Gas (PNG)

(19) The high pressure natural gas that has been transported into the distribution station or the city gate station from the incoming PNG 3-1 enters the heating and pressure regulating unit driven by pressure described in this invention, and then is transmitted to the pressure regulating device 3-5.

(20) The pressure driven heating and pressure regulating unit is consisted of an ejector 3-2, a vortex tube 3-3, and an ambient air heat exchanger 3-4, they are connected sequentially to form a closed loop, the cold end of the vortex tube 3-3 is connected to the ambient air heat exchanger 3-4, and the hot end of the vortex tube 3-3 is connected to the pressure regulating device 3-5; the high pressure natural gas discharged from the incoming flow PNG 3-1 enters the ejector 3-2 and becomes main working fluid. The fluid expands and accelerates in the Laval nozzle in the injector 3-2 to form a supersonic jet that injects the low pressure natural gas discharged from the outlet of the ambient air heat exchanger 3-4, the two stream of natural gas exchange momentum and energy to become one stream in the mixing chamber of ejector 3-2, and then the stream experiences pressure recovery in the diffuser of ejector 3-2, and a medium-pressure fluid is formed at the outlet of ejector 3-2, and then transmit the stream into the vortex tube 3-3; After the natural gas enters the vortex tube 3-3, it expands and decompresses through the tangential nozzle in the vortex tube 3-3 to form a high-speed vortex. Due to the energy separation effect of the vortex tube 3-3, the natural gas is separated into two streams. One is heated by the heating effect of the vortex tube 3-3, and the temperature is adjusted to the allowed temperature of the pipe network through control valve at the hot end of vortex tube 3-3 and then enter the subsequent downstream device 3-5; due to the cooling effect inside of the vortex tube 3-3, the other stream is cooled and enters into ambient air heat exchanger 3-4 through the cold end of vortex tube 3-3 to absorb heat from air, then the heated natural gas is discharged from the outlet of the ambient air heat exchanger 3-4, and return to the ejector 3-2 from the injecting fluid inlet of the injector 3-2.

(21) (3) The Incoming Flow is Liquid Natural Gas (LNG)

(22) As shown in FIG. 2, a pressure driven liquid natural gas regasification heating system of the this invention is mainly consisted of an LNG storage tank 4-1 with a supercharger 4-2, and an ambient air vaporizer 4-3, a cryogenic liquid booster pump 4-4, a pressure regulating device 4-5, a vortex tube 4-6, an ambient air heat exchanger 4-7, and an ejector 8.

(23) After the LNG exchanges heat with air in the ambient air vaporizer 4-3, the LNG converts into gaseous because of phase changing, and the temperature is raised. When the temperature meets the allowed temperature of pipe network after being heated by the ambient air vaporizer 4-3, then enter the pressure regulating device 4-5 directly; while the natural gas vaporized by the ambient air vaporizer 4-3 fails to reach the allowed temperature of the pipe network, the cryogenic liquid booster pump 4-4 is started. After pressurization, the natural gas is discharged from the ambient air vaporizer 4-3 and enters the pressure driven heating unit then is transmitted to the pressure regulating device 4-5;

(24) The pressure driven heating unit described in this invention is consisted of an ejector 4-8, a vortex tube 4-6, and an ambient air heat exchanger 4-7, they are connected sequentially to form a closed loop, the cold end of the vortex tube 4-6 is connected to the ambient air heat exchanger 4-7, and the hot end of the vortex tube 4-6 is connected to the pressure regulating device 4-5; the high pressure natural gas discharged from the ambient air vaporizer 4-3 enters the ejector 4-8 and becomes main working fluid. The fluid expands and accelerates in the Laval nozzle in the injector 4-8 to form a supersonic jet that injects the low pressure natural gas discharged from the outlet of the ambient air heat exchanger 4-7, the two stream of natural gas exchange momentum and energy to become one stream in the mixing chamber of ejector 4-8, and then the stream experiences pressure recovery in the diffuser of ejector 4-8, and a medium-pressure fluid is formed at the outlet of ejector 4-8, and then transmit the stream into the vortex tube 4-6; After the natural gas enters the vortex tube 4-6, it expands and decompresses through the tangential nozzle in the vortex tube 4-6 to form a high-speed vortex. Due to the energy separation effect of the vortex tube 4-6, the natural gas is separated into two streams. One is heated by the heating effect of the vortex tube 4-6, and the temperature is adjusted to over 5 C. through control valve at the hot end of vortex tube 4-6 and then enter the subsequent downstream device 4-5; due to the cooling effect inside of the vortex tube 4-6, the other stream is cooled and enters into ambient air heat exchanger 4-7 through the cold end of vortex tube 4-6 to absorb heat from air, then the heated natural gas is discharged from the outlet of the ambient air heat exchanger 4-7, and return to the ejector 4-8 from the injecting fluid inlet of the ejector 4-8.

(25) According to the mass conservation of the inlet and outlet, the pressure-driven heating unit proposed by the invention is systematically analyzed. The relationship between the cold flow ratio of the swirl tube and the ejector ejection coefficient is obtained as follows:
(1+)(1)=1 or =11/(1+)(1)

(26) Among them, is the cold flow ratio of the vortex tube, defined as the ratio of the mass flow at the outlet of the cold end to the mass flow at the inlet; is the ejector injection coefficient, defined as the ratio of the mass flow rate of the injected gas to the mass flow rate of the injected gas.

(27) It can be seen from the formula (1) that the cold flow ratio is proportional to the injection coefficient , that is, increasing the injection coefficient can increase the cold flow ratio.

(28) For the vortex tube energy separation performance, for a fixed structure vortex tube, the means for improving the hot end heating capacity of the vortex tube can increase the inlet pressure or increase the cold flow ratio. If the inlet pressure of the vortex tube is increased, since the inlet of the vortex tube 4-6 is connected to the outlet of the ejector 8, the ejector 8 injects fluid requires a large pressure drop in order to ignite the low pressure fluid, and the vortex tube 4-6 is increased under the same injection coefficient. The inlet pressure is bound to increase the injector 8 injection pressure. For the ejector ejector performance, under the condition that the ejector structure is fixed and the ejector fluid condition is constant, the ejector injection coefficient can be increased to increase the injector inlet pressure. In summary, in order to enhance the heating capacity of the hot end of the vortex tube 4-6 and make the outlet gas temperature reach the allowable temperature of the pipeline network, the method of increasing the pressure of the ejector 8 injecting the inlet fluid can be adopted. Therefore, a cryogenic liquid booster pump 4-4 is arranged between the storage tank 4-1 and the air-temperature gasifier 4-3 to boost the cryogenic LNG flowing from the outlet of the storage tank 4-1 so that the pressure of the gaseous natural gas flowing from the outlet of the air-temperature gasifier 4-3 reaches the design pressure value of the ejector 8 ejecting the inlet fluid.