Study On Acrylamide Polymerization Process Based On Thermal Characteristics Of Phase Transition

As a kind of water-soluble polymer,polyacrylamide is widely used in all walks of life.The polymerization of acrylamide with high monomer concentration releases huge polymerization heat,and the high temperature of acrylamide polymerization system causes the branching and crosslinking of acrylamide.The research on polymerization heat treatment of high monomer concentration acrylamide aqueous solution has become a research trend.In this paper,the suspended phase conversion heat reactor and plate heat transfer reactor use the energy storage advantages of phase change materials to transfer the excessive polymerization heat generated by the polymerization of acrylamide aqueous solution,to realize temperature control of the polymerization system of acrylamide aqueous solution.Moreover,through the numerical analysis of the heat transfer process of plate heat exchanger,the main heat transfer modes during the heat transfer process are determined.The energy consumption in the drying process of polyacrylamide was calculated.In this paper,the good energy storage capacity of paraffin wax was determined by differential scanning calorimetry(DSC).A suspended phase conversion thermal reactor was designed using paraffin wax as phase change material.The synthetic polymer was determined to be polyacrylamide by infrared spectroscopy.Through the influence of phase change dosage and heat transfer area on heat transfer and temperature control in polymerization process,it is found that heat transfer area is the key factor affecting heat transfer process.With the increase of the amount of paraffin wax,the total heat transfer capacity of phase change material increases,the heat transfer effect is enhanced,the temperature of acrylamide polymerization process decreases,and the molecular weight and conversion rate of polyacrylamide are improved compared with the traditional process.In this paper,a new type of plate type reactor suitable for acrylamide polymerization and heat transfer was designed based on the suspension phase conversion reactor.Through the phase transformation thermal layer and polymerization reaction layer in full contact storage,transfer of acrylamide polymerization heat,through the plate heat exchanger plate,plate thickness,polyacrylamide colloidal thickness of the experiment,determine the thickness of polyacrylamide colloidal thickness is the key factor limiting heat transfer,internal heat transfer distance is shorter,heat transfer effect is more obvious,can realize the temperature control of acrylamide polymerization process.Thermogravimetric analysis and repeated experiments on paraffin showed that the repeated experiments had little effect on the thermal properties of paraffin.As a phase change material,paraffin had good repeatability and stability.The experimental results of old and new acrylamide processes under different monomer concentrations show that the polymerization heat of acrylamide polymerization is more with the increase of monomer concentration.Under the new process conditions,the heat transfer effect of acrylamide polymerization system is more obvious,and the system temperature is in the best polymerization temperature range as far as possible.Under the new process conditions,the molecular weight of acrylamide copolymerized with 40%monomer concentration was 13.3×10~6,which was 38.5%higher than that of the traditional process.In this paper,the numerical calculation of the phase conversion heat process in the plate heat transfer reactor is guided by the enthalpy method model,and the theoretical temperature of polyacrylamide colloid at different time periods in the heat transfer process is calculated according to the energy equation and the thermal conduction differential equation.By comparing the numerical temperature curve of the heat transfer process between paraffin and polyacrylamide with the experimental temperature curve,it is found that the curve is highly consistent,and the main heat transfer mode of the paraffin-polyacrylamide polymerization system is determined to be heat conduction.The thermal conductivity of paraffin and polyacrylamide was calculated by DSC and thermal diffusion.The thermal conductivity of solid paraffin was 0.583 W/(m·°C),and the average thermal conductivity of liquid paraffin was 0.287 W/(m·°C).The energy consumption required in the product drying process was calculated,and the standard coal consumption of 40%monomer concentration of acrylamide polymerization process drying was 58370 g per 1000 g of polyacrylamide(44%at the highest coal-fired power efficiency).The new process reduces the standard coal consumption by 19%compared with the old process.The new technology of acrylamide polymerization can save energy and protect environment effectively.