Coalbed methane liquefaction process

Abstract

The invention discloses a coalbed methane liquefaction process. A feeding unit, a mercury removing unit, a CO2 removing unit, a drying unit, a liquefaction unit, a refrigerant circulation unit, a refrigerant supplementing unit, a storage unit, a storage tank return gas compression unit, a hot oil unit and a torch unit are included. The feeding unit is sequentially connected with the mercury removing unit, the CO2 removing unit, the drying unit, the liquefaction unit and the storage unit; the liquefaction unit is pre-cooled, liquefied and supercooled through the refrigerant circulation unit; refrigerants are supplemented to the refrigerant circulation unit through the refrigerant supplementing unit; and the storage tank return gas compression unit is connected with the storage unit.

Description

technical field [0001] The invention relates to the technical field of liquefied gas, in particular to a coal bed gas liquefaction process. Background technique [0002] At present, in the liquefaction process of natural gas, the raw natural gas needs to be pretreated first, enter the liquefaction system at a certain flow rate, and then undergo precooling, liquefaction, supercooling and other cooling processes in the liquefaction system, and finally obtain LNG at -162.5°C. [0003] However, the existing natural gas liquefaction process has the following disadvantages: [0004] (1) The raw natural gas after pretreatment contains a small amount of impurities, which are attached to the pipes in the coiled heat exchanger. These accumulated impurities are likely to cause damage to the coiled heat exchanger during the long-term system cycle. Freeze. [0005] (2) After removing acid gas from natural gas, the MDEA-rich amine solution needs to be regenerated, and the acid gas remov...

AI Technical Summary

Problems solved by technology

At present, the existing technology does not have a good recovery method for the acid gas containing no sulfur and only carbon dioxide, so this part of the acid gas is discharged, which not only pollutes air and water, but also leads to waste of resources, making it impossible to reduce production costs.

[0006] (3) The five-component refrigerant cycle refrigeration is commonly used in natural gas liquefaction plants, and most of the mixed refrigeration natural gas liquefaction systems have complicated process flow, large engineering volume, and complicated start-up and shutdown procedures

[0007] (4) The operation of the mixed refrigerant refrigeration process is very flexible. When the production capacity is adjusted, that is, the load of the factory area, it is necessary to maintain the efficiency of mixed refrigerant refrigeration by changing the composition of the refrigerant. The operation level is relatively high, and automatic adjustment cannot be realized. When the adjustment is wrong, it is easy to cause large fluctuations in the parameters of the factory, resulting in unstable production.

[0008] (5) During the production of LNG, BOG gas will be produced in the LNG storage tank, thereby causing the pressure in the LNG storage tank to increase. In the existing technology, the BOG gas is usually drawn out from the LNG storage tank and discharged or Combustion treatment not only causes environmental pollution, but also leads to a great waste of energy, which indirectly increases the manufacturing cost of LNG

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