Dual-refrigeration cycle methane washing synthesis gas cryogenic separation device and separation method

Abstract

The invention provides a dual-refrigeration cycle methane washing synthesis gas cryogenic separation device and a separation method. The separation device comprises a methane washing tower, a flash tower, a first separation tower, a second separation tower, a first circulating refrigeration system and a second circulating refrigeration system, wherein the methane washing tower, the flash tower, the first separating tower and the second separating tower are sequentially communicated, the first circulating refrigerating system comprises a methane circulating refrigerating system, and the second circulating refrigerating system comprises a nitrogen circulating refrigerating system or a carbon monoxide circulating refrigerating system. The invention also provides a separation method which is carried out in the separation device. According to the method, the synthesis gas with high methane content and nitrogen content can be efficiently separated, a hydrogen-rich product, a pure methane product and a pure carbon monoxide product are prepared at the same time, and the relatively high carbon monoxide recovery rate is ensured while the energy consumption is greatly reduced.

Description

technical field [0001] The invention relates to the technical field of gas cryogenic separation, in particular to a double refrigeration cycle methane washing synthesis gas cryogenic separation device and separation method. Background technique [0002] At present, it is widely used in syngas (containing H 2 , CO, CH 4 , C2H6, N 2 , AR and other components) cryogenic separation is liquid nitrogen washing, partial condensation process, methane washing process, and carbon monoxide washing derived from methane washing. Partial condensation process, methane scrubbing process or carbon monoxide scrubbing process are often used in the process. [0003] When the chemical synthesis unit needs a large amount of high-purity carbon monoxide products, and at this time the raw material synthesis gas contains higher methane / nitrogen components (such as CH 4 >7v%, N 2 >4v%), neither pressure swing adsorption nor membrane separation should be used. When the scale of carbon monoxi...

AI Technical Summary

Problems solved by technology

[0017] Since the raw material synthesis gas contains more CH 4 and N 2 , the existing partial condensation or methane washing process of conventional cryogenic separation has high energy consumption, and high-pressure nitrogen or high-pressure carbon monoxide cycle refrigeration is required, but the amount of circulating gas is often large, so the energy consumption is also high, and the downstream device has a high impact on the product. When the carbon monoxide purity requirement is high, pressure swing adsorption and membrane separation can no longer meet the requirements. At this time, the cryogenic separation device often causes a very high investment in driving equipment due to the large circulation of refrigeration gas.

In addition, due to the influence of impurities, the recovery rate of CO is often not high, and only the content of CO is higher than that of H 2 The recovery rate of CO in the raw material synthesis gas is relatively high. Taking dry coal gasification as an example, the recovery rate of CO in the partial condensation process can usually reach about 90% (while the raw material with H2 component content in the raw gas is higher than the CO component The recovery rate of CO in syngas is usually about 80%. If it is to be increased to 90%, more energy consumption needs to be paid; conventional methane washing process CO can achieve 90% recovery rate, but the treatment of the above-mentioned CH 4 and N 2 More components, often the energy consumption of conventional methane washing process is higher

Images