Diesel exhaust fluid production method

Abstract

The invention provides a diesel exhaust fluid production method. The method comprises the following steps: sending an ammonia-and-carbon dioxide removed urea synthesis reaction liquid from the synthesis workshop section of a urea production device to a crystallization kettle, carrying out vacuum flash evaporation crystallization, centrifuging the obtained crystallization kettle material after the vacuum flash evaporation crystallization to obtain separated crystals as a diesel exhaust fluid product, and returning the obtained liquid phase material to the urea production device. The method uses a flash evaporation cooling effect to make a urea solution supersaturated and crystallized in order to obtain the high quality diesel exhaust fluid product, so the energy utilization efficiency is increased, and the diesel exhaust fluid yield is obviously higher than that in the prior art at a same crystallization temperature.

Description

technical field [0001] The invention relates to a crystallization method of urea solution, in particular to a production method of adiabatic vacuum flash crystallization of urea used as raw material for diesel vehicle tail gas treatment liquid. Background technique [0002] According to the regulations of the national environmental protection department, all heavy-duty diesel vehicles sold from July 1, 2013 must meet the National IV emission standard. Compared with the National III emission standard, the National IV emission of heavy-duty diesel vehicles. Reduced by about 30%, particulate matter (PM) emissions reduced by more than 80%. In order to reduce the nitrogen oxides and particulate matter in diesel vehicle exhaust emissions, at present, automobile manufacturers in Europe, the United States and other countries generally use selective catalytic reduction (SCR) technology to treat diesel vehicle exhaust, so that it can reach Euro IV, Euro V or even higher standards. Em...

AI Technical Summary

Problems solved by technology

[0005] Chinese patent CN101695669A discloses a method for preparing urea for vehicles, which uses activated carbon adsorption and recrystallization to remove impurities; the problem with this method is that recrystallization energy consumption is high, and the introduction of activated carbon for adsorption increases the cost of raw materials Consumption, so its production cost is higher; and the content of biuret in the mother liquor after recrystallization is higher, it can no longer be sold as ordinary urea, and it is difficult to handle

[0006] Chinese patent CN101811065A discloses a method for preparing diesel vehicle exhaust treatment fluid. The method uses industrial urea or agricultural urea as raw material, and uses ion resin exchange technology to remove impurities. The main problem of this method is that the urea dissolution process requires a large amount of heat absorption. Leads to higher energy consumption, and the ion resin needs to be regenerated, resulting in higher cost

[0007] Chinese patent CN102806011A discloses a method for preparing urea for vehicles. This method uses cooling crystallization and solid-liquid separation to obtain solid urea for vehicles. Compared with the previous patent, this method simplifies the process and reduces the cost. However, it is necessary to introduce a cooling medium-low temperature water to cool down, which increases the steps of energy exchange and reduces the efficiency of energy utilization

Images