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Method for preparing liquefied natural gas by using coke-oven gas

A technology of liquefied natural gas and coke oven gas, which is applied in the direction of gas fuel, petroleum industry, fuel, etc., can solve the problem of low energy consumption of liquefaction, achieve the effects of reduced cycle ratio, reduced consumption cost, and stable operation

Active Publication Date: 2010-05-19
SOUTHWEST RES & DESIGN INST OF CHEM IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0009] The above two types of liquefaction and refrigeration cycles are based on the fact that natural gas itself has a relatively high pressure (2.8-4.0MPa), so the total energy consumption for liquefaction is low, and the coke oven gas is only at normal pressure, which needs to be purified and pressurized, and then methanized Low-temperature separation, liquefaction and production of LNG have not been reported yet

Method used

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Embodiment 1

[0034] The cryogenic separation (rectification separation) flow process of the present embodiment is as follows:

[0035] Composition (%) (volume percent) of coke oven gas after methanation: H 2 35.1,N 2 5.9, CH 4 59. Air volume 10000Nm 3 / h, pressure 1.75MPa, temperature 40°C.

[0036] Its process is as follows figure 1 shown. 10000Nm 3 / h Methanated gas is pressurized to 3.0MPa, dehydrated and dried, then enters heat exchanger E1 through pipeline 1 and is cooled to -89°C, and passes through pipeline 4 as a heat source for rectification column reboiler R, and is cooled to - 98°C, enters the heat exchanger E2 through the pipeline 5, and is cooled to -150°C ~ -155°C by the negative pressure methane evaporation gas of the pipeline 15, the liquid methane of the pipeline 20, the hydrogen nitrogen expansion gas of the pipeline 10 and the hydrogen nitrogen gas of the pipeline 8, saving Flow to 2.5MPa into the rectifying tower T. The methane with a purity greater than 99....

Embodiment 2

[0040] The cryogenic separation (rectification separation) flow process of the present embodiment is as follows:

[0041] Composition (%) (volume percent) of coke oven gas after methanation: H 2 35.1,N 2 5.9, CH 4 59. Air volume 10000Nm 3 / h, pressure 1.75MPa, temperature 40°C.

[0042] Its process is as follows figure 2 shown. 10000Nm 3 / h The gas after methanation is pressurized to 3.0MPa, dehydrated and dried, then enters the heat exchanger E1 through the pipeline 1 and is cooled to -89°C, and passes through the pipeline 4 as a heating source for the reboiler R of the rectification tower, and is cooled to -98°C, enter the heat exchanger E2 from the pipeline 5 for further cooling, throttle to 2.5MPa through the pipeline 6, and enter the rectification tower T through the pipeline 7. Under the action of rectification, methane with a purity greater than 99.5% is obtained in the tower kettle, and the liquid methane in the tower kettle is throttled to 0.14MPa through ...

Embodiment 3

[0046] The liquefaction process of the present embodiment is as follows:

[0047] Its process is as follows image 3 shown. The methane 5729Nm that obtains by embodiment 1 3 / h enters compressor COM from pipeline 1, compresses to 0.35MPa, mixes with methane from pipeline 18 (mixed gas of methane after expansion and vaporized methane of V2) and enters the second stage of compressor, then pressurizes to 5.0MPa, and cools Then it enters the heat exchanger E1 from the pipeline 2, then enters the precooler E2 from the pipeline 3, cools down to -45°C, enters the heat exchanger E3 from the pipeline 4 for further cooling, throttles it to 3.0MPa from the pipeline 5, and enters it through the pipeline 6 In the gas-liquid separator V1, the uncondensed gas enters the heat exchanger E3 from the pipeline 13, is heated to -49°C, and enters the expander EXP through the pipeline 14. After expansion, the pressure is 0.4MPa, and the expanded gas is mixed with the gas from the pipeline 15 and t...

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Abstract

The invention discloses a method for preparing liquefied natural gas by using coke-oven gas, which mainly comprises the steps of methanation reaction, rectification separation and liquefaction, wherein the methanated gas first enters a rectification column after heat exchange and cooling; a tower kettle reboiler is heated by the methanated gas; liquid methane flows to an overhead condenser to evaporate to provide cold; under the rectification action of the rectification tower, methane with a purity of over 99.5 percent is obtained and a mixture of H2, N2 and a small amount of methane is obtained in the tower top; and the methane is heated again and delivered to a liquefying device to be liquefied. The method has the advantages that: the separation and liquefaction are separate, so the operation is smooth and flexible; LNG and methane gas can be output; the refrigerant is derived from the product methane rather than external supply, so investment is reduced and the cost for other refrigerants is saved; and in addition, according to an preferred scheme, a rear methane expander is adopted, the amount of methane entering the methane expander is increased and the refrigerating capacity is increased, so a circulation ratio is reduced to 4.0 to 4.5.

Description

technical field [0001] The invention relates to the technical field of preparation of liquefied natural gas, in particular to a method for preparing liquefied natural gas by using coke oven gas. Background technique [0002] my country is a big country of coke production, with an annual production capacity of more than 300 million tons, and coke oven gas produced by each ton of coke is about 400m 3 . In addition to self-use, domestic and commercial fuels, more than 20 billion m of gas is released every year 3 . [0003] The composition of coke oven gas is relatively complex, among which CH 4 , CO, CO 2 , the CnHm volume fraction is nearly 40%, and the hydrogen content is high (volume fraction 54%-59%, the same below), through the methanation reaction, namely: [0004] CO+3H 2 =CH 4 +H 2 o [0005] and CO 2 +4H 2 =CH 4 +2H 2 o [0006] CO, CO 2 converted to methane and make CO 2 content reduced to 50×10 -6 Below, the coke oven gas becomes mainly CH 4 、H 2 a...

Claims

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Application Information

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IPC IPC(8): C10L3/08
Inventor 陶鹏万黄维柱黄建彬冉崇慧杨先忠周君
Owner SOUTHWEST RES & DESIGN INST OF CHEM IND
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