Study On On-line Cleaning Technology Of Heat Exchanger Based On Scaling And Descaling Mechanisms

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.