Method and system for preparing liquefied natural gas from coal-to-oil purified synthesis gas

Abstract

The invention discloses a method and system for preparing liquefied natural gas from coal-to-oil purified synthesis gas. The method comprises the following steps that 1, methane in purified synthesis gas in the coal-to-oil technology is separated and extracted, and methane-rich gas is obtained; 2, the methane-rich gas obtained in the first step is compressed to remove impurities; 3, the methane-rich gas treated in the second step is cooled and rectified, and the liquefied natural gas and rectified tail gas are obtained. According to the method and system preparing the liquefied natural gas from the coal-to-oil purified synthesis gas, CH4 in the purified synthesis gas in the coal-to-oil technology is removed before the purified synthesis gas enters a synthesis unit, the content of inert gas is decreased, the partial pressure of H2 and CO is increased, and the yield of the synthesis process is improved; meanwhile, the power consumption of a recycle compressor of a subsequent synthesis system is reduced. Compared with a traditional method for enabling all gases to enter a cooling box, the gas entering the cooling box unit in the preparation method is less than 30% of that in the traditional method, the equipment dimension of the cooling box is greatly decreased, and the energy loss of the cooling box is greatly reduced; the pressure drop loss of the synthesis gas is small, the quantity of the rectified tail gas in the cooling box is small, and the compression work consumed during recycling is small.

Description

technical field [0001] The invention relates to a method and system for preparing liquefied natural gas from coal-to-oil purification synthesis gas. Background technique [0002] my country is relatively rich in coal resources and is one of the few countries in the world that uses coal as its main energy source. "Short of oil, less gas, rich in coal" (96% of coal, 4% of oil + gas) is the basic national condition of our country, and coal resources are important energy resources that our country can rely on in the medium and long-term development. At present, my country's oil demand is increasingly dependent on imports. By the end of 2014, China's oil dependence on foreign countries was close to 60%. Oil shortage has become the main structural contradiction in my country's energy supply and demand and the "bottleneck" restricting the rapid development of the national economy. . Unstable factors in the relationship between supply and demand in the international oil market, pol...

AI Technical Summary

Problems solved by technology

If you do not put CH in Aiki 4 Extraction will cause the conversion rate of the synthesis unit to be too low, while the CH 4 Cycling through the system increases the load on the compressor

The traditional direct cryogenic method is to pass all the purified syngas through the cold box unit. This method increases the equipment of the cold box unit, consumes more cooling capacity of the cold box, and loses the synthesized H at the same time. 2 and CO effective gas, a large amount of nitrogen stripping is also required

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