Experimental Investigation Of Continuous Multistage Countercurrent Crystallizer For Separation P-Nitrochlorobenzene And O-Nitrochlorobenzene

O-nitrochlorobenzene and some other impurities are easily introduced during the synthesis of p-nitrochlorobenzene, which results in lower product purity. In addition, it is difficult to separate p-nitrochlorobenzene and o-nitrochlorobenzene by traditional methods because they are isomers with highly similar physicochemical properties. Therefore, the melting crystallization method was adopted. In order to better apply the melt crystallization technology, a set of tower melt crystallizer with height of 1350 mm and diameter of 50 mm was designed according to the melt crystallization principle. The process of continuous purification of p-nitrochlorobenzene by multi-stage counter-current in a tower crystallizer was studied. The effects of operation conditions including the bed height of crystal, reflux ratio, the composition of feed, stirring speed were investigated on the crystallization. Finally, under the following conditions: crystal bed height of 600 mm, reflux ratio of 2.5, feed mass fraction of 90.85%, stirring speed of 12 rpm, the purity of p-nitrochlorobenzene could exceed 99.9%, the product liquid flow rate was 13.74 g/min. The above results indicated that the tower crystallizer based on the melt crystallization principle could effectively separate and purify p-nitrochlorobenzene and onitrochlorobenzene.