Pilot operation of electrochemical descaling for circulating cooling water system of converter valve in converter station
The equipment corrosion and scaling,microorganism propagation and large amount of pollution often occurs during operation of the circulating cooling water system of converter valve in converter station.Using traditional chemical additive for scale inhibition involves high operating costs and is prone to causing secondary pollution.Electrochemical descaling technology has many functions such as scale removal,corrosion prevention and bactericidal,without causing secondary pollution.The three-month pilot test of electrochemical descaling technology used in the converter valve circulating cooling water system in a flexible DC converter station of Zhejiang State Grid was explored.At the optimal operating parameters as follows:current density of 5 A·m-2 and circulating flow rate of 15 m3·h-1,the effluent Ca2+,Mg2+and conductivity decreased gradually,and they were controlled below 22 mg·L-1,21 mg·L-1 and 2300 μS·cm-1,respectively;the residual chlorine concentration reached 6.80 mg·L-1 and the removal rate of COD reached 46.15％,the best specific energy consumption was 17.10 Wh·L·mg-1.After electrochemical treatment,the corrosion rates of circulating water on carbon steel and stainless steel were lower than 0.016 1 mm·a-1 and 0.000 03 mm·a-1,respectively,which could meet the industrial circulating cooling water treatment design code.Scanning electron microscope(SEM),Energy Dispersive Spectrometer(EDS)and X-Ray Diffraction(XRD)analysis were carried out on the scale deposited on the electrode of the pilot electrochemical device and the scale deposited in the cooling tower of the circulating water tank after long-term operation.It was found that after the electrochemical descaling process,the scale had smaller pores and loose structure,which is conducive to peeling and further removal.The comprehensive operation cost of the electrochemical descaling system is greatly reduced compared with the traditional chemical additive scaling control system.This study provides a technical basis for the application of electrochemical descaling technology in the circulating water system of converter valve in the converter station.
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