Simulation Of New Energy-saving And Emission-reduction PTA Process

Purified terephthalic acid(PTA)is an important raw material for the production of polyethylene terephthalate(PET).The consumptions and emissions of the PTA process are the core competitiveness of PTA plant.Therefore,it is of great significance to develop a new energy-saving,low-consumption and emission-reducing PTA process.According to the existing PTA process,this work proposed a new PX oxidation process coupled with multistage distillation,i.e.multi-stage dehydration towers was added at the top of the oxidation reactor.The obtained water solvents could be used as the washing water,and the oxidation heat could be used as dehydrate energy.Therefore energy consumption and the wastewater discharge of the process was reduced greatly.A full process modeling and flowsheeting for PTA production process was completed,and the specific contents included the following:(1)Comparing three different integrated PX oxidation and dehydration processes,it was shown that the oxidation+dehydration coupling process could greatly reduce the consumption of energy,deionized water and raw material,i.e.directly using the oxidation heat as the rectification heat source,and the refined mother liquor as the dehydration tower reflux.The process parameters of the dehydration towers were optimized and the tower equipment was designed.(2)The oxidation and refining unit was integrated.Schemes of RPF+acid washing+drying and RPF?water washing were compared,and the operating parameters of the filter was optimized.The feasibility analysis of the refined mother liquor reflux was investigated and the water circulation was proposed.Then the indexs of water consumption,PX material consumption and acetic acid consumption of the PTA process was simulated and analyzed.(3)Energy-saving and consumption-reducing plans were proposed.The effect of 4-CBA and methyl acetate(MA)concentration on combustion reactions was analyzed,and the function of PX and acetic acid consumption on the 4-CBA and MA concentration were obtained.The formation mechanism of the MA were analyzed,and the MA recovery unit(the key stripping towers)were calculated and designed.