A liquefaction process for deoxygenation and denitrification of oxygen-containing coalbed methane

Abstract

The invention discloses a liquefaction process for oxygen-containing coal bed gas deoxidation and denitrification. Including liquefaction, deoxygenation and denitrogenation steps of oxygen-containing coalbed methane and nitrogen refrigerant circulation step: liquefaction, deoxygenation and denitrogenation of oxygen-containing coalbed methane Step: input oxygen-containing coalbed methane into a cold box, cool down and then enter rectification Oxygen and nitrogen are removed in the tower; then it enters the cryogenic section of the cold box to continue cooling, and finally enters the LNG storage tank after throttling; the nitrogen refrigerant cycle steps are as follows: the nitrogen compressed and cooled by the nitrogen expansion compressor enters the cold A part of the nitrogen is cooled and then throttled by expansion to provide cooling capacity for the cryogenic section, liquefaction section and precooling section of the cold box, and then returns to the secondary inlet of the nitrogen compressor; the other part of the nitrogen is throttled after being liquefied. After the subcooling section, subcooling section, liquefaction section and precooling section of the recondenser and cold box provide cooling capacity, it returns to the primary inlet of the nitrogen compressor. The process of the invention fully considers the applicability of domestic equipment, improves the automation of process control, and reduces the start-up time.

Description

technical field [0001] The invention relates to a liquefaction process for oxygen-containing coal bed gas deoxidation and denitrification, and belongs to the technical field of natural gas liquefaction. Background technique [0002] The coalbed methane extracted during the coal mining process has relatively low methane content, usually 30% to 70% (volume fraction), and other components mainly include carbon dioxide and air. In 2013, 12.6 billion cubic meters of coalbed methane was extracted underground in my country, and the utilization amount was about 4.3 billion cubic meters, which was less than 35%. my country's coalbed methane resources are abundant, but relatively little development, almost no industrial application. Because coalbed methane pours into the coal mine roadway or explodes, it will cause disasters. Therefore, the coal industry has always regarded coalbed methane as a disaster gas. At present, the drainage treatment of oxygen-containing coalbed methane mix...

AI Technical Summary

Problems solved by technology

[0003] At present, there are several invention patents related to the separation process and equipment of oxygen-containing coalbed methane, such as Chinese patent application 200610080889.4. The distillation process is complicated, there are many equipments, and the pressure loss of the distillation tower is relatively large. Since the system adopts a low-pressure process, the energy consumption of the process is relatively high

Chinese patent 200610103425.0 adopts cryogenic rectification method for the separation and liquefaction of oxygen-containing coalbed methane, but this process adopts conventional refrigeration methods such as mixed refrigeration or expansion refrigeration, and the refrigeration temperature that can be achieved by single mixed refrigerant refrigeration or turbine expansion It cannot meet the requirements of high-precision removal of nitrogen and oxygen in coalbed methane, resulting in high methane content in the discharge, which has certain safety problems and also reduces the processing capacity of separation and liquefaction

This process is relatively complicated, and it needs to consume a large amount of methane to react with oxygen, and the contained N 2 still needs further processing

Images