Study On Purifying Process Of Crystallization For PIA Equipment Of 30,000 Tons Per Year

M-phthalic acid(IPA) is an intermediate raw material with great foreground, it can be used to produce raw material of polyester, dope, special type fibre, thermographic adhesive agent, printing ink, polyester fibre dyeing modifying agent and resin plasticity agent. In present, IPA is mainly produced by high temperature liquid air oxidation method in which crude IPA must be refine by hydroprocessing to get high pure IPA. Solution crystallization method is used to purify IPA.The research of crystallization process is mainly basis on supersaturation theory, the simulation of crystallizer depends mainly on experimental data. The moisture percentage, flow parameters, particle shape and size distribution of the product were measured. It is found that irregular surface shape, broad particle size distribution, especially high small particles concentration can bring about serious cluster and adherence in flow process. Furthermore, the factors affecting IPA's particle size were analyzed in terms of particle formation process—crystallization. The different processing parameters affect crystallization process was discussed according to industrial trial, the particle size under different operating conditions were analyzed.In present controlling condition, the percent crystallization in the first crystallizer is about 60% to total. The increase of the first stage crystallizer's supersaturation degree can raise percent crystallization, total crystal nucleus content and decrease the formation of big particles.Under present operating parameters, the effect of production charge on particle size shows trinomial relation. The more uniform particle can be obtained in 90% charge to total.The crystallizer volume is a important factor in multistage crystallization. Because of the little volume of the fifth stage crystallizer, it is easy to...