Natural gas isobaric liquefaction apparatus

Abstract

This invention is about a natural gas isobaric liquefaction apparatus, which is based on the Rankine cycle system of similar thermal energy power circulation apparatus at cryogenic side, a cryogenic liquid pump is used to input power and the refrigerating media makes up cold to the natural gas liquefying apparatus, so as to realize the isobaric liquefaction of natural gas. The natural gas liquefying apparatus of this invention can save energy by over 30% as compared with the traditional advanced apparatus with the identical refrigerating capacity, therefore it constitutes a breakthrough to the traditional natural gas liquefaction technology, with substantial economic, social and environmental protection benefits.

Claims

1. A natural gas isobaric liquefaction apparatus, comprising: a natural gas pretreatment system for removing moisture and CO.sub.2 in the natural gas; a refrigerant tank storing a liquid refrigerant; a cryogenic liquid pump fluidly connected with an outlet of the refrigerant tank; a cold regenerator having a first inlet for receiving the liquid refrigerant from the cryogenic liquid pump and a first outlet for outputting a stream of mixed gaseous and liquid refrigerant; a liquefying system comprising a first chamber, a second chamber, a condensing evaporator fluidly connected to the second chamber, wherein the first chamber has an inlet for receiving the stream of mixed gaseous and liquid refrigerant from the cold regenerator and an outlet for outputting a low temperature refrigerant, the second chamber has an inlet fluidly connected with the natural gas pretreatment system and an outlet for outputting a liquefied natural gas, and wherein the condensing vaporizer cools the natural gas received from the second chamber to form the liquefied natural gas; and an expander having an inlet fluidly connected with the outlet of the first chamber and an outlet connected to a second inlet of the cold regenerator, wherein a second outlet of the cold regenerator is connected to an inlet of the refrigerant tank.

2. The apparatus of claim 1, further comprising: a throttle valve installed in a line connecting the second outlet of cold regenerator and inlet of the liquid refrigerant tank.

3. The apparatus of claim 1, wherein the expander comprises a braking equipment that is a fan, a motor, a hydraulic pump, or a gas compressor.

4. The apparatus of claim 2, wherein the expander comprises a braking equipment that is a fan, a motor, a hydraulic pump, or a gas compressor.

5. The apparatus of claim 1, wherein, in the liquefying system, the second chamber, the condensing evaporator (9), and the first chamber are integrated in one housing.

6. The apparatus of claim 2, wherein, in the liquefying system, the second chamber, the condensing evaporator, and the first chamber are integrated in one housing.

7. The apparatus of claim 3, wherein, in the liquefying system, the second chamber, the condensing evaporator (9), and the first chamber are integrated in one housing.

8. The apparatus of claim 4, wherein, in the liquefying system, the second chamber, the condensing evaporator (9), and the first chamber are integrated in one housing.

9. The apparatus of claim 1, wherein said refrigerant has a boiling point lower than or equal to that of methane under the standard atmospheric pressure, and is a mixture comprising one or more gases selected from methane, nitrogen, argon, helium, and hydrogen.

10. The apparatus of claim 1, further comprising one or two heat exchangers for precooling the natural gas prior to entering the liquefying system using the refrigerant from the outlet of the first chamber to the inlet of the expander.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 is a schematic diagram of cascade natural gas liquefying process;

(2) FIG. 2 is a schematic diagram of APCI propane precooling mixed refrigerant liquefying process;

(3) FIG. 3 shows the natural gas expansion liquefying process:

(4) In FIG. 3: 301dehydrating agent, 302carbon dioxide removal column, 303water cooler, 304returns to the gas compressor, 305, 306, 307heat exchangers, 308subcooler, 309tank, 310expander, 311compressor.

(5) FIG. 4 shows the nitrogen gas expansion liquefying process:

(6) In FIG. 4: 401pre-treatment apparatus, 402, 404, 405heat exchanger, 403heavy hydrocarbon separator, 406nitrogen stripper, 407turbine expander, 408nitrogen-methane separating column, 409circulation compressor.

(7) FIG. 5 is a schematic diagram of natural gas expansion and liquefying process with propane precooling:

(8) In FIG. 5: 501, 503, 505, 506, 507heat exchangers, 502, 504propane heat exchangers, 508water cooler, 509compressor, 510braking compressor, 512, 513, 514gas-liquid separators.

(9) FIG. 6 is a schematic diagram of a natural gas isobaric liquefying apparatus of this invention:

(10) In FIG. 6: 601raw natural gas, 602pretreatment apparatus, 603cold exchanger, 604heavy hydrocarbon separator, 605liquid heavy hydrocarbon component, 606cold exchanger, 607precooled column feeding raw gas, 608lower column, 609condensing evaporator, 610upper column, 611LNG, 612LNG tank, 613pure liquid methane, 614pure liquid methane tank, 615column outflow cryogenic refrigerant, 616refrigerant superheated vapor, 617expander, 618cold regenerator, 619refrigerant tank, 620liquid refrigerant, 621cryogenic liquid pump, 622refrigerant gas-liquid mixture, 623throttle valve, 624braking equipment.

EMBODIMENTS

(11) In the following, this invention is further described in detail in conjunction with figures and embodiments.

Embodiment 1

(12) As shown in FIG. 6, a natural gas isobaric liquefying apparatus, with nitrogen gas as refrigerant, with the specific embodiment as follows:

(13) (1) The raw natural gas 601 flows via the pre-treatment apparatus 602 to remove moisture and carbon dioxide, enters the cold exchanger 603 and heavy hydrocarbon separator 604 to separate the liquid heavy hydrocarbon component 605, and then passes through cold exchanger 606 to become the precooled column feeding raw gas 607;

(14) (2) The precooled column feeding raw gas 607 enters the lower column 608, flows via condensing evaporator 609 to produce supercooled methane liquid, which flows back for rectification and isobaric condensation to produce liquefied natural gas 611 or LNG 601, the LNG is sent to LNG tank 612;

(15) (3) In the condensing evaporator, the pure methane liquid 613 produced from isobaric condensation is led to the liquid pure methane tank 614;

(16) (4) The liquid refrigerant 620 from refrigerant tank 619 is made into a refrigerant gas-liquid mixture 622 via the cryogenic liquid pump 621 and cold regenerator 618, and enters the upper column 610, the condensing evaporator 609 condenses the methane gas in the lower column to produce liquid methane, the column outflow cryogenic refrigerant 615 from the upper column 610 flows via the cold exchanger 606 and cold exchanger 603 to cool down the raw natural gas 601, to form the refrigerant superheated vapor 616, which flows via the expander 617 to reduce pressure and temperature, and returns via cold regenerator 618 and throttle valve 623, to the refrigerant tank 619, the cold quantity required by the natural gas liquefying system is made up via condensing evaporator 609, cold exchanger 606 and cold exchanger 603, so as to form the cold dynamic cycle circuit of the refrigerant; the pressure of the cold makeup system can be conveniently regulated via throttle valve 623.

(17) The braking equipment 624 of the said expander 617 is gas compressor, which is used to boost the raw natural gas.

(18) The said refrigerant tank 619 is provided with necessary thermal and cold insulation, such as thermal isolated vacuum container, and insulation materials such as pearlite.

(19) The equipment and their backup systems, pipes, instruments, valves, cold insulation and bypass facilities with regulation functions not described in this invention shall be configured with mature technologies of generally known traditional natural gas liquefying systems.

(20) Safety and regulation and control facilities associated with the natural gas liquefying apparatus of this invention are provided, so that the apparatus can operate economically and safely with high thermal efficiency, to achieve the goal of energy conservation, consumption reduction and environmental protection.

(21) This invention has been made public with an optimum embodiment as above, however, it is not used to restrict this invention, all variations or decorations made by those familiar with this technology without deviating from the spirit and scope of this invention also falls into the scope of protection of this invention. Therefore, the scope of protection of this invention shall be that defined by the claims in this application.