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 refrigerant 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 refrigerant tank storing a liquid refrigerant; a cryogenic liquid pump fluidly connected with an outlet of the refrigerant tank; a cold generator having a first inlet for receiving the liquid refrigerant from the cryogenic liquid pump and a first outlet for outputting a stream of mixed gas and liquid refrigerant; a liquefying system comprising an upper column and a lower column connected by a conduit disposed external to the upper column and the lower column, wherein the lower column has a first outlet for introducing natural gas into the upper column, a second outlet for outputting a first liquefied natural gas stream, and an inlet fluidly connected with the natural gas pretreatment system; and wherein the upper column has an inlet for receiving the refrigerant containing gas and liquid from the cold generator, a first outlet for outputting a low temperature refrigerant, and a second outlet for outputting a second liquefied natural gas stream; and an expander having an inlet fluidly connected with the first outlet of the upper column and an outlet connected to a second inlet of the cold generator, wherein a second outlet of the cold generator 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 generator 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 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 chosen from methane, nitrogen, argon, helium, or hydrogen.

6. 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 first outlet of the upper column to the inlet of the expander.

7. The apparatus of claim 1, wherein the second outlet of the lower column is fluidly connected with a liquid methane storage tank.

8. The apparatus of claim 1, wherein the second outlet of the upper column is fluidly connected with a LNG storage tank.

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: 401, 403, 405, 406, 407heat exchangers, 402, 404propane heat exchangers, 408water cooler, 409compressor, 410braking compressor, 412, 413, 414gas-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, 602pre-treatment apparatus, 603cold exchanger, 604heavy hydrocarbon separator, 605liquid heavy hydrocarbon component, 606cold exchanger, 607precooled column feeding raw gas, 608lower column, 609upper column, 610methane gas diverting pipeline, 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 upper column 609 for liquid nitrogen wash, the produced supercooled methane liquid flows back for rectification, and isobaric condensation to produce liquefied natural gas 611 or LNG, and the LNG is sent to LNG tank 612;

(15) (3) The methane gas diverted from the middle of lower column 608 flows via methane gas outlet pipeline 610 and enters upper column 609, after liquid nitrogen washing and isobaric condensation to produce pure methane liquid 613, and it is diverted out and sent to 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 609, to condense the raw natural gas in lower column 608 and produce liquid pure methane and LNG, the column outflow cryogenic refrigerant 615 from upper column 609, flows via cold exchanger 606 and cold exchanger 603 to cool down raw natural gas 601, and forms the refrigerating media superheated vapor 616, which, after expansion, pressure reduction and temperature reduction via expander 617, flows through cold regenerator 618 again and throttle valve 623, returns to the refrigerant tank 619, and makes up the required cold energy to the natural gas liquefying system via upper column 609, cold exchanger 606 and cold exchanger 603, so as to form the cold dynamic cycle circuit of the refrigerant.

(17) The braking equipment 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.