Improved low-energy-consumption CO2 stripping method urea process

Abstract

According to the technical scheme, urea synthesis liquid is divided into two parts, one part of urea synthesis liquid is fed into a high-pressure CO2 stripping tower in a high-pressure decomposition and recovery system to be subjected to high-pressure CO2 stripping, and the other part of urea synthesis liquid is fed into a high-pressure CO2 stripping tower in a high-pressure decomposition and recovery system to be subjected to high-pressure CO2 stripping; the other part of the urea synthesis liquid is fed into a medium-pressure decomposition tower of the medium-pressure decomposition recovery system for medium-pressure decomposition, and a medium-pressure gas phase and a medium-pressure decomposition liquid phase are obtained. High-pressure stripping liquid flowing out of the bottom of the high-pressure CO2 stripping tower and the other part of urea synthesis liquid are decompressed and then are respectively fed into the middle section and the upper section of a medium-pressure decomposition tower for medium-pressure gas-liquid separation, and medium-pressure decomposition liquid led out of the bottom of the medium-pressure decomposition tower is fed into a low-pressure decomposition tower for low-pressure decomposition. The method is simple in process, easy to transform, capable of further saving energy and reducing consumption, capable of improving productivity and low in investment and operation cost.

Description

technical field [0001] The invention relates to a urea process, in particular to an improved low-energy CO 2 Stripping urea process. Background technique [0002] Industrial urea production is based on CO 2 Gas and liquid ammonia are used as raw materials, which are processed into solid urea products through high-pressure synthesis, medium-pressure or / and low-pressure decomposition and recovery, vacuum concentration, and granulation. [0003] At present, the production process of urea plant at home and abroad mainly includes the CO produced by Stamicarbon in the Netherlands. 2 Steam stripping process, Italian Snamprogetti ammonia stripping process, Japan TOYO's ACES21 process, China's five-ring high-efficiency synthesis, low-energy urea process, aqueous solution method full cycle process, etc., among which CO 2 The stripping process and the ammonia stripping process are the most competitive. [0004] Traditional CO 2 The process flow of the stripping method is that the ...

AI Technical Summary

Problems solved by technology

However, there are the following problems: (1) high-pressure CO 2 The liquid phase of the stripper and the medium pressure CO 2 The liquid phase of the stripping tower is sent to the low-pressure decomposition tower together, and no medium-pressure decomposition and recovery is carried out. On the one hand, this will lead to a large amount of water returned to the high-pressure ring, and the ammonia-to-carbon ratio in the high-pressure ring is relatively high, which is unfavorable to the urea reaction and affects to a certain extent On the other hand, the load of low-pressure decomposition and recovery will be heavy, which is not conducive to further shifting the load of the high-pressure stripper, resulting in limited expansion capacity or limited energy-saving effect; (2) the medium-pressure carbamate condenser The heat of reaction is directly taken away by circulating water. On the one hand, high-quality low-temperature heat is wasted, and on the other hand, more circulating water is consumed, resulting in insufficient energy recovery and high operating costs.

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