Regeneration Process Design Of Cleaning Agents In Polyurethane Hot Melt Adhesive Reactor

N-methylpyrrolidone(NMP)has been widely used in petrochemical,lithium battery,polymer synthesis and other processes due to its high thermal stability,high boiling point,low volatility and strong solubility.Because of its strong solubility to polyurethane,low toxicity and low corrosion to equipment,it is used as cleaning agent of polyurethane adhesive reactor.In the cleaning process,the consumption of NMP is large and the price of NMP is expensive,it is necessary to recycle and reuse to save production costs after cleaning.In this paper,according to NMP existing recovery methods,in order to avoid the plugging of distillation column,the NMP recovery rate is low and the separation energy consumption is large for the cleaning agent waste liquid containing polyurethane hot melt adhesive.At first,the method of adding water and stirring was adopted to remove the solid component of polyurethane in the waste solution of cleaning agents,the optimum addition amount was determined as the mass ratio of water to waste liquid 1:2,the temperature in the stirring process was 25℃,the open-type impeller with folded blades was selected as the stirring paddle,and the stirring time was 300r/min for20 min.However,there is a problem of solid agglomeration in the process of precipitation.To avoid this issue and not reduce the effect of solid removal by adding appropriate amount of ethanol to water.After filtration and separation of the solid and liquid suspension obtained by adding ethanol solution,vacuum rectification are carried out.Rectification under high vacuum can reduce the hydrolysis rate of NMP and reduce the heating energy consumption.In the rectification process,only the light component ethanol and water need to be evaporated to recover the NMP.The distillate from the top of the tower can be added to the waste cleaning agent,which reduce the cost of ethanol and water consumption.After vacuum distillation at 55℃ to 85℃,a recycled cleaning agent with water content of 0.25% was obtained.In this paper,the chemical process simulation software Aspen Plus was used to simulate the recovery process of the waste liquid of the reactor cleaning agents produced by the annual output of 50000 tons of polyurethane hot melt adhesive,Wilson activity coefficient model was selected as thermodynamic method.Under the initial conditions obtained by simple simulation,the effects of theoretical plate number,feed position and reflux ratio on separation efficiency and energy consumption were investigated by means of strict distillation calculation and sensitivity analysis tools.Finally,the optimized operation parameters of the distillation column were obtained.After rectification,the recovery solution of cleaning liquid with NMP purity of 96.48%and water content of 0.05% was obtained.In this paper,on the basis of the distillation simulation results,the material and energy in the recovery process were calculated,and then according to the material and energy balance results of the recovery process of equipment design and selection.The detailed equipment calculation and hydrodynamics check are carried out on the distillation tower,and the storage tank,heat exchanger and other equipment in the process are calculated and selected.After the calculation and selection of equipment,a preliminary technical and economic estimate is made for the whole recycling process.Finally,the economic benefit of the recycling process can be increased by about50,795,135 yuan per year after the adoption of the process.