Research On The Recovery Of Methanol From Methanol-Isopropanol-Water Waste Water

Methanol is an important industrial material.The recovery of methanol from methanol-isopropanol-water waste water can not only reduce the environment pollution to water,but also reduce the production cost .So the research of the dissertation will be valuable both in cleaning production and in environment protection.In the dissertation, the influence of pressure,reflux ratio to separation effect of methanol batch distillation in laboratory is investigated. The Vapor-Liquid Equilibrium theory of methanol distillation is studied in detail and the parameters of Wilson and NRTL model are correlated with the simplex method. The VLE data are treatad in the Wilson and the NRTL model Programmes. The influence of reflux ratio, theoretical plate, feed position and feed temperature to distillation process are discussed. Preferred process operation parameters, which have guiding meaning to practical production of distillation tower are obtained. Basic data for the process amplifying design of methanol distillation tower are provided. The primary technical design of methanol distillation tower is carried out based on the result of simulation. The type of major auxiliary equipments and inner parts of packed tower are selected.The research results are as follows:(1) Methanol is recovered in a laboratory batch distillation and the operation condition is as follows: the pressure is 101.3Kpa, the number of theoretical plates is 20.3 and reflux ratio is 5.0. In this way, the purity of the recoverd methanol is more than 99% and the recovery efficiency is more than 87.3%.(2) The NRTL model which calculated the VLE data by using the parameters correlated by the ternary VLE data for system methanol-isopropanol-water is the first choice for the simulation calculation of methanol distillation, the average deviation of mole fraction in compounds is 0.0042.(3) When methanol distillation is simulated, the NRTL model is used to correct the nonideality of liquid phase. The preferred condition of methanol distillation is obtained as follows: reflux ratio is 4.5-5.0 and the number of theoretical plate is 30-33. Optimum feed position is 13 when reflux ratio is 5.0. When feed is situated in optimum position, separation effect is best. Separation effect became worse when feed position rose or fell from optimum position. With increasing of feed temperature, methanol concentration of tower top decreased and methanol concentration of tower bottom increased, separation affect became worse. The operation parameters are given when reflux ratio is 5.0.(4) Technical parameters of methanol distillation tower are obtained when reflux ratio is 5.0. packing is 250Y stainless steel corrugated-plate packing. Diameter of tower is 1.0m, and height of packing is 12m. The pressure drop of packing is 6960Pa. Average flood point gas velocity of rectification part and raiseing steaming part of packed tower are 3.75m/s, 2.54 m/s. Average liquid holdup of rectification part and raising steaming part of packed tower are 0.045m3/m3, 0.050 m3/m3.