Research On The On-line Anti-fouling Technology Of Heat Exchanger

Fouling is formed on the tube wall when the heat exchanger in the N, N-dimethylformamide(DMF)production process is cooled down,which can lead to decline of production capacity,material loss,increased energy consumption,rise of production cost.In order to solve this problem,some innovative anti-fouling methods were put forward in this paper,and experiments were conducted in our lab.First,the composition of fouling was analyzed.The result shows that the fouling is composed of sodium formate,sodium carbonate and sodium bicarbonate.The experiment showed that the scaling mechanism was crystallization scaling combined with particulate scaling.The effects of inlet temperature of DMF(T),liquid velocity(u),ratio of spring diameter and tube diameter(r),ratio of screw-pitch and tube diameter(φ)on the anti-fouling of heat exchangers were investigated and analyzed.The optimal parameters were gotten through the orthogonal experiment:u=1.0 m/s,T=50℃,φ=1.5,r=0.8.The experiment of liquid-solid fluidized bed showed that:the fluidized particles can reduce the scale by 40%,the rate of sacling forming and the fouling weight decreased with the increase of particle number and particle diameter.The scaling mechanism was not affected by inserting spring,but the method of liquid-solid fluidized bed combined with inserted spring can improve the anti-fouling effect by 20%-50%comparing with method of liquid-solid fluidized bed under the same experimental conditions.The effects of particle number,length of spring,off- time of pump,pump operating time on anti-fouling of heat exchanger were investigated through pulse experiment,the results showed that the anti-fouling effect increased with the increase of particle number and length of spring.Finally,five on-line methods were compared and evaluated,improvement idea of industrial plant was proposed and its principle was simply introduced.