Abstract:

The cooling crystallization and alkaline removing process of methionine saponification solution was studied.The effects of crystallization parameters,such as cooling final temperature,cooling rate and seed addition amount,on the purity and removal rate of sodium carbonate from decahydrate of crystallization products were systematically investigated.Experimental results showed that the removal rate of sodium carbonate decreased gradually with the increase of the cooling terminal temperature. Meanwhile,the purity of sodium carbonate decahydrate increased firstly and then remained almost unchanged.As the cooling rate increases,the purity of sodium carbonate decahydrate decreased gradually,and the removal rate of sodium carbonate did not change much.With the increase of the number of crystal seeds of sodium carbonate decahydrate,the purity of sodium carbonate decahydrate increased first and then decreased,and the removal rate of sodium carbonate was almost unchanged.Optimization of process conditions were obtained: the cooling rate of 0.05 ℃/min,seed addition amount of 7.5%（based on the quality of the crystalline product）,the terminal temperature of frozen for-10 ℃. Under the conditions,the crystal purity of sodium carbonate decahydrate was 96.41%,and the removal rate of sodium carbonate in saponification solution was 81.2%.

Key words: methionine saponification solution, cooling crystallization, sodium carbonate decahydrate