Research On Process Optimization Of Turbulence Pickling By Hydrochloric Acid Based On Frequency Conversion Technology

Pickling by hydrochloric acid (HC1) is widely adopted to remove the oxide scale. Turbulence pickling based on frequency conversion technology is a kind of new pickling method in recent years, which can increase the effiency of acid pickling process and reduce the consumption of heat and hydrochloric acid. Methods of weight loss and microstructure analysis were carried out to analysis pickling process. In order to dicuss the effect of pickling parameters on the pickling efficiency, an accurate method for measuring the pickling time based on electrochemistry theory was proposed to research on acid flow and concentration and temperature. The experimental pickling data were fitted using modified mathematical modeling, including acid flow term. While easily online detected parameters, such as plate thickness, coiling temperature, acid temperature and flow, were selected using orthogonal test method to predict the acid endpoint based on BP neural network. The effect of acid flow heat transfer performance on acid flow was studied by fluent software and the combination of acid incident angle and flow was optimized based on iSIGHT platform.The results showed that acid temperature is the most important parameter to efficiency of acid pickling, and follewed by acid concentration and flow. The modified mathematcial modeling, considering the influence of acid flow, can predict endpoint of pickling time according to given process parameters, with the correlation coefficient 0.96 between predicted values and experimental values. And 4-7-1 BP network can predict the endpoint with prediction error less than 10%. At the given acid incidence angle, the increase of acid flow can help to improve the average nusselt number near incidence point. The maximum average nusselt number 224.69 can be achived at the optimized angle 83.7°, flow 193.6m3/h by iSIGHT platform, which increased by 24.2% compared with the initial angle 90°, flow 200m3 /h.This research can help to understand the core technology of variable frequency turbulence pickling and to optimize pickling process parameters for further improvement of pickling efficiency.