Practical optimization of scale removal in circulating cooling water: Electrochemical descaling-filtration crystallization coupled system

Abstract

• Superior removal rates of EC-FC system compared with EC system. • Effective interception of scale particles in effluent of EC module. • The function of FC module to alleviating ohmic heat from EC reactor. • More efficient operation in high current density of EC-FC system than EC. Targeting for the problems in industrial circulating cooling water system resulted from scale formation, researchers have proposed a variety of treatment solutions, among which electrochemical descaling is one of the most promising technology. At present, the main barrier in electrochemical scale removal is relatively insufficient treatment efficiency. One possible reason for this is that the scale particles generated by electrochemical process cannot be effectively deposited on the cathode of the reactor but flow out of the electrochemical reactor. To this problem, this paper proposed a coupled system that connected the filter crystallization module after the electrochemical descaling process. By doing so, it was expected to filter and intercept scale particles, thus improving the overall performance of treatment. The experimental results attested that the introduction of filtration crystallization (FC) system could improve the performance of electrochemical-filtration crystallization (EC-FC) system in hardness removal rate, alkalinity removal rate, total dissolved solids (TDS) removal rate and water sample temperature difference. With the promotion effect from FC system, the scale particles in the effluent from the EC system can be effectively intercepted, and inductive crystallization of the scale ions can be achieved for further purification. Different from EC system, the descaling efficiency of EC-FC system escalated continuously with the rise of current density, while decreased first and then went up with the shortening of hydraulic retention time. However, EC system determined the upper limit of the treatment performance of the whole system. It was because FC system can only deposit the scale particles that were not deposited on the cathode plate on the filler, but cannot react to produce new scale formation ions. Through our proposal and investigation, this work provides an original facile idea for the practical application of electrochemical scale removal technology with proved feasibility.