【作者】 段培清；

【导师】 南碎飞；

【作者基本信息】 浙江大学 ， 化学工程， 2008， 硕士

【摘要】 N,N-二甲基甲酰胺(N,N-dimethyllformamide)又名甲酰二甲胺,简称DMF,DMF生产工艺中的换热器在换热冷却过程中在换热管内壁生成一层污垢,造成设备生产能力下降、物料流失、能耗增大、生产成本上升。为解决此问题,提出了内置弹簧和液固流态化结合除垢以及脉冲除垢新方法,并进行了实验研究。首先分析了实际工业换热器中结垢物的成分,结果表明结垢物主要由甲酸钠、碳酸钠和碳酸氢钠组成。结垢机理为结晶结垢和微粒沉积结垢混合机理。内置弹簧除垢实验,研究了DMF溶液进口温度T、流体流速u、弹簧直径与换热管内径之比r、弹簧螺距与换热管内径之比φ对换热器在线防、除垢效果的影响,通过正交试验得到了一组最优组合条件:u=1.0 m/s、T=50℃、φ=1.5、r=0.8。液固流态化实验表明,在一定的操作条件下,流化颗粒可以使污垢减少40%左右,起到一定的防、除垢效果,随着颗粒数目的增加和颗粒直径的增大,污垢形成速率降低,结垢量减少。内置弹簧和液固流态化结合除垢实验表明,加入弹簧后污垢的形成机理并没有发生变化,在相同实验条件下,与单独液固流态化除垢方法相比,两者结合的方法可以使污垢减少20%—50%。脉冲防、除垢实验研究了球形钢珠的数量、弹簧的长度、泵的停止时间、泵的运行时间等因素对除垢效果的影响,颗粒数量越多、弹簧越长,除垢效果越好。脉冲实验结果表明该方法可以使换热器污垢减少50%—70%。对五种换热器在线防、除垢技术进行了对比与评价,提出工业装置改进思路,并简述其工作原理。更多还原

【Abstract】 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.更多还原