Full Process Optimization Of Tetrabromobisphenol-A Production

Tetrabromobisphenol A(TBBA),the largest bromine flame retardant in the world,is used in more than 70% of the world's electronic and electrical equipments.In recent years,the pressure of energy and environmental protection is becoming larger.As a result,the production of TBBA is faced with problems of rise in prices of raw materials,environmental protection,safety in production,and so on.The sysnthesis of TBBA by the chlorobenzene solvent method still exists the problems as following:1)The problem of low conversion rate and many impurities;2)The mother liquor which contains in the centrifugal filtration cake of crystallized wet material was more than 4-5% mass fraction.Dry energy consumption was high and exhaust gas collection was difficult.To the need of production safety,the exothermic reaction of bisphenol A(BPA)with an oxidizewas studied by the HEL parallel automated reactors & Calorimeters.The results showed that maximum temperature will reach to 150 ?if the cooling was failure,thus the actual production process must ensure the normal operation of cooling equipment.In order to solve the problems in the above TBBA production,the detailed study on the bromination reaction process of BPA by HPLC was carried out in this paper.The effects of bromination reaction heat,bromination reaction temperature,agitation,bromine and oxidant dropping ways and curing time on the conversion rate of BPA were studied.In addition,CFD was used to simulate the temperature distribution of bromide reaction,mixing paddle and bromine location and flow field.The results showed that the bromination reaction was affected by bromine and oxidant dropping ways mostly,and the conversion rate of BPA could be increased by 10% by adjusting the ways of bromine and oxidant dropping.Insufficient agitation leads to a 1-1.5%reduction in conversion rate.Finally,the crystallization of TBBA was studied in this paper.At first,the thermodynamic data of TBBA crystallization in chlorobenzene were measured.Then,the influence of stirring speed,cooling mode and cooling rate on the crystallization process were investigated.Results showed that the crystal integrity(mainly surface imperfection of crystals)are the main factors influencing the moisture content.The moisture content can be reduced to 0.5% by using programmed cooling crystallizationprocess,which will reduce the cost of drying about 3 million yuan each year.