System and method for cryogenic separation and recovery of reformed hydrogen

Abstract

The invention discloses a system for cryogenic separation and recovery of reformed hydrogen. The system specifically comprises a pretreatment unit, an oil washing unit, a drying unit and a cryogenic separation unit, The invention also discloses a method for cryogenic separation and recovery of reformed hydrogen by using the system. Reformed hydrogen and hydrogen in low-pressure separation gas are recovered by using a mixed refrigerant refrigeration separation technology, most of light hydrocarbons such as methane, ethane, propane and butane can be removed, hydrogen with the purity of 97% or above is obtained, and the recovery rate of hydrogen reaches 99.5%. The oil washing unit is connected with an LPG storage tank through an LPG inlet to form circulation, and through repeated material circulation, liquefied petroleum gas generated by primary separation can be used for washing and pre-cooling feed gas, so that benzene in the feed gas is washed away. Due to the fact that benzene is easy to crystallize at the temperature of 5 DEG C, the process is easy to influence in the subsequent drying and cryogenic separation process, benzene in the feed gas can be removed through repeated washing of the oil washing unit, and material recycling is achieved.

Description

technical field [0001] The invention relates to the technical field of hydrogen recovery, in particular to a system and method for cryogenic separation and recovery of reformed hydrogen. Background technique [0002] With the enhancement of people's awareness of environmental protection, the quality index of refined oil is increasing day by day, and the demand for improving the quality of refined oil is increasing day by day. At present, the main way to upgrade refined oil at home and abroad is to improve the quality through hydrogenation. Hydrogen has become a very valuable resource for refineries, and most of hydrogen is currently obtained through hydrogen reforming. [0003] However, the supporting processing device for reforming hydrogen in the industry is a PSA device, which uses pressure swing adsorption technology to purify hydrogen to obtain analyte gas with a hydrogen purity ≥ 99.9%. The hydrogen yield is generally around 92%, and the lost hydrogen is about 8-12%. ...

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Problems solved by technology

[0003] However, the supporting processing device for reforming hydrogen in the industry is a PSA device, which uses pressure swing adsorption technology for hydrogen purification to obtain analyte gas with a hydrogen purity ≥ 99.9%. The hydrogen yield is generally around 92%, and the lost hydrogen is about 8~12%

Analytical gas is generally used as fuel gas for combustion, and the hydrogen in it cannot be rationally utilized, resulting in waste of hydrogen resources

Moreover, in the actual operation process, due to raw material gas fluctuations, device load changes, etc., as time goes by, the operating parameters of the pressure swing adsorption device will gradually change, and the adsorption time will become shorter and the analytical pressure will increase, resulting in The recovery rate of hydrogen decreases gradually, and the loss of hydrogen increases gradually

[0004] Further, the reason for the low recovery rate of hydrogen purification by pressure swing adsorption technology is analyzed, mainly because a small amount of hydrocarbon molecules are not easy to resolve and adhere to the inner surface of the molecular sieve, and gradually accumulate, resulting in a decrease in the adsorption effect of the molecular sieve on hydrocarbons

For this reason, the existing technology proposes the method of replacing the adsorbent, or adopts the method of multiple purging and analysis with hot nitrogen. Although the hydrogen recovery rate can be improved to a certain extent, it will increase the production cost of the enterprise.

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