Treating process for recycling methanol synthesis purge gas and using part of same to prepare hydrogen products

Abstract

The invention provides a treating process for recycling methanol synthesis purge gas and using part of the same to prepare hydrogen products. The treating process includes that the methanol synthesis purge gas is firstly subjected to first-section-membrane separation treating, permeable gas, sufficient in hydrogen quantity, prepared in a lot of purge gas enters PSA (pressure swing adsorption), and first-section-membrane separation permeation gas is further purified to obtain high-purity hydrogen; most of the remaining purge gas serving as non-permeable gas continues to enter second-section-membrane separation, the permeable gas serving as hydrogen rich gas returns to a synthesis unit for recycling; second-section-membrane separation non-permeable gas and desorbed gas of the PSA both serving as fuel gas are sent out of a boundary region. The PSA and two-section-membrane separation are creatively and organically combined, and recycling of the methanol synthesis purge gas is realized while a certain amount of high-purity hydrogen is prepared in a more reasonable and economical manner. The treating process is especially suitable for occasions of recycling the methanol synthesis purge gas of a large-scale coal chemical plant and preparing a small amount of high-purity hydrogen at the same time.

Description

technical field [0001] The invention belongs to the technical field of coal chemical industry, and in particular relates to a process for recovering methanol synthesis purge gas and partially preparing hydrogen products. Background technique [0002] In the methanol synthesis unit of a coal chemical project, in order to prevent the accumulation of inert gas, a small amount of recycle gas is usually released after the reactor. This part of gas, due to the high hydrogen content, will cause a serious waste of useful gas if it is directly burned. For this reason, the current conventional practice of methanol synthesis units is to use low-investment membrane separation technology to filter out the macromolecular components in the released gas by using the difference in permeability of gas molecules in the membrane, and to concentrate the hydrogen in the released gas. It is returned to the methanol synthesis unit for recycling, and the remaining non-permeate gas is sent out of th...

AI Technical Summary

Problems solved by technology

Due to the high concentration of hydrogen in the permeate gas, the scale of the PSA device in this case is more reasonable; but in order to ensure that the pressure on the permeate side can meet the requirements of PSA to prepare higher pressure hydrogen products, the pressure drop on both sides of the membrane separation must be controlled at a low level Level, under the premise of ensuring the ideal hydrogen recovery rate, the number of required membranes increases, and the investment in membrane separation systems increases

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