A preparing method of a urea solution used for vehicles

Abstract

The invention relates to a crystallizing method of a urea solution and particularly relates to a producing method of urea that is a raw material of a diesel vehicle exhaust treating liquid. The method includes (1) a step of preparing urea, namely a step of conveying a urea synthesis reaction solution in a synthesis stage of a urea production device into a urea solution tank to obtain an initial urea solution, (2) a step of removing excessive ammonium and carbon dioxide from the initial urea solution through flash evaporation, (3) a step of conveying the urea synthesis reaction solution into a vacuum flash evaporation crystallization kettle and performing vacuum flash evaporation crystallization, (4) a step of preparing high-purity water, namely a step of desalting industrial water, filtering the water with activated carbon, removing macro-molecule substances through a reverse osmosis membrane apparatus, removing TOC, deoxygenizing the water, disinfecting the water and filtering the water, and (5) a step of mixing crystallized urea and the high-purity water, and fully stirring the crystallized urea and the high-purity water to obtain the urea solution used for vehicles. The urea solution used for vehicles can reduce environment pollution, saves a cost and is of great significance for environment protection.

Description

technical field [0001] The invention relates to a crystallization method of urea solution, in particular to a production method of urea used as raw material for diesel vehicle tail gas treatment liquid. Background technique [0002] Diesel vehicle exhaust treatment fluid is a reductant that cooperates with SCR technology to convert nitrogen oxides in engine exhaust into harmless nitrogen and water. The main raw materials of diesel vehicle exhaust treatment fluid are urea and water for vehicles. Urea for vehicles is not an ordinary Agricultural urea or industrial urea is not a chemical analysis reagent, but a special chemical with certain added value that can be produced in large scale. [0003] The urea solution for vehicles is strictly controlled on impurities. Since ordinary tap water contains other trace elements such as inorganic salts and chlorides, it cannot be directly used to prepare urea solutions for vehicles. Purification of urea and water treatment are key steps...

AI Technical Summary

Problems solved by technology

Urea for vehicles is a relatively common production process in the Chinese market. It uses commercially available urea as raw material to produce urea after filtration and crystallization. The main problem is that the scale is small, the pollution generated by the treatment is not concentrated, and the waste liquid is difficult to recycle.