【作者】 王丽萍；

【导师】 蔡晓君； 肖涤；

【作者基本信息】 北京化工大学 ， 机械工程（专业学位）， 2017， 硕士

【摘要】 工业应用广泛的换热器在运行中产生的污垢导致其工作性能下降、能耗增大。本课题以乙烯装置换热器在五种工况下形成的复合污垢为研究对象,从预防和治理污垢角度出发,运用理论、实验及数值模拟等手段对换热器结垢、除垢、防垢进行系统研究,主要工作如下:(1)文献调研发现,延长污垢诱导期是防垢的最有效措施。理论与实验研究得出流速、温差是污垢在诱导期内作用的主要影响因素:保持流体温度不变,温差越大,垢层越厚,结垢量越多;且存在某一时刻,在零到该时刻内垢层和结垢量增加缓慢,超过该时刻则垢层和结垢量加速增长,该时刻之前即为诱导期;温差一定下,流速增大、结垢量减少。(2)基于结垢机理得到五种工况下产生的污垢形态不同,通过垢样和设备介质组分检测,五种垢样主要成分均为芳香聚合物;采用前期同类污垢清洗配方对五种垢样进行了溶垢实验分析,结果表明:该配方溶垢率下降一倍,溶垢时间增加两倍。结合该溶垢配方优缺点和溶垢理论,运用正交法配置了适用于五种以上污垢的绿色清洗试剂:以柴油为清洗基液,3:1:1复配OP-10、JFC、SAS三种助剂。(3)基于溶垢机理,结合现场情况,通过拟定的在线清洗流程方案,设计了清洗储槽并选配了输送泵型号,对乙烯装置的待洗换热器进行了现场在线清洗,结果表明:清洗效果达到预期目标,大大降低成本。(4)运用CFD软件对生产工况下的换热器进行数值模拟,通过流速和折流板的变化,比较分析得到换热器最优防垢策略:适当减小流速的同时减小折流板间距。本研究成果不仅可适用于同类生产装置的多种换热器的清洗,并且可推广至其他生产装置的清洗,为污垢在线清洗数据库奠定基础,推动在线化学清洗的工业化,还为后续换热器强化传热、预防结垢的研究提供了科学的数据支持。更多还原

【Abstract】 The fouling produced during the operation of heat exchangers which have been widely applied results in the decrease of their performances and the increase of energy consumption.In this paper,the fouling produced by ethylene heat exchanger in the five conditions was taken as research object,and the research of heat exchanger fouling,fouling prevention and cleaning system had been done by using the theory,experiment and numerical simulation from the perspective of the prevention and control of dirt angle,the main work is as follows:(1)The literature research found that the extension of the dirt induction period is the most effective anti fouling measures.Theoretical and experimental research showed that the velocity and temperature are the main factors influencing the effect of fouling during the induction period:the bigger the difference in temperature,the thicker the fouling layer is when keeping the temperature of fluid constantly;there exists a moment to the moment of the scale layer and scaling in zero increase slowly,the time is over fouling and scaling amount of accelerated growth,before the time is the induction period;under certain temperature,flow rate increases,the amount of scale reduction.(2)Based on different dirt form scaling mechanism of five operating conditions,through the scale and medium component detection equipment,the five main constituents of the scale are aromatic polymers;analysis of five kinds of scale were done with the same dirt cleaning formula for the scale experimental,the results showed that the the rate of decline of that formula a time as scale increased two times.According to the advantages and disadvantages of the fouling formula and the theory of scale deposition,the green cleaning agents suitable for more than five kinds of fouling were prepared by orthogonal method:diesel oil was used as cleaning base liquid,3:1:1 was compounded with OP-10,JFC,SAS.(3)Based on the fouling dissolution mechanism,combined with the site conditions,through the on-line cleaning process plan,this part has designed the cleaning tank and selected the delivery pump type.Then,the heat exchanger in the ethylene plant is performed by on-line cleaning on site,and the results show that the cleaning effect achieves the desired goal,meanwhile,the cost is greatly reduced.(4)This part uses the CFD software to simulate the heat exchanger under the production conditions,and then get the optimum fouling prevention strategy,which is decreasing velocity and decreasing the baffle spacing,by changing the velocity and baffle plate heat exchanger,a comparative analysis of the optimal scale strategy:decreasing velocity and decreasing the baffle spacing.This research results can be applied to the cleaning of heat exchanger of the similar production device,and extended to the cleaning of other types of production equipment.It lays the foundation for the database of on-line cleaning fouling,promotes the industrialization of on-line chemical cleaning,and also provides the scientific data support for the follow-up research of heat exchanger fouling prevention and enhancement of heat transfer.更多还原