Pilot Evaluation of DSA Anode Electrochemical Scaling Applied in a Cooling Water Circulation System

Abstract

Scale deposition in circulate cooling water system is a terrible problem which could result in the reduction of heat transfer efficiency and increasing of operational consumption. In this paper, based on the Lab scale experiment, the DSA electrodes was evaluated in cooling water scaling by pilot experiment. The experimental results indicated that, the hardness removal rate appeared approximately linear relationship with the current density, and the hardness removal rate increased rapidly with the increasing of the residence time and then tends to be stable. According to the scaling requirement and economic consumption in practical application, under the experimental condition, current density of 25.56A/m 2 and the residence time of 4min was the best working condition with the hardness removal rate of 22.87%. The research results could provide important practical basis for the development, design and commissioning of electrochemical equipment in the future. Introduction Scale deposition results problems such as heat exchangers efficiency decay, membrane clogging, pipe blocking, equipment life shortening, etc.[1]. The traditional scale control process applied in water treatment is based on the dosage of anti-scalants which is able to restrain scale precipitation up to a certain degree, and among with the dosage of these kinds of chemical compounds, this technique would result in harmful effects on environment, high power consumption and expenses to operate the treatment system[2-4]. In recent years, a electrochemical technique to control the scaling potential of water circulating was applied in cooling water system by the precipitation of hardness forming ions on the cathode zone, which can decrease the water hardness of the system[5-7]. Dimensionally stable anode (DSA), which has excellent corrosion resistance, high electrocatalytic activity, and stable mechanical characteristics, has been probed to be applied in water scaling system[8-10]. Compared with other methods, this electrochemical scale removal process offers many advantages such as accessibility to automation, environmental compatibility, no need to chemical dosage, convenient process control, and convenient wastes handle[11,12]. The former Lab scale experimental results has been indicated that, the main influencing factors of DSA electrochemical scaling process are electrode spacing, current density, and electrolysis time. In this study, to prove the conclusion drawn in the Lab, pilot scale experiments have been put into effect to evaluate the effect of the above factors in a circulate cooling water system. Materials and Methods Pilot Experimental System The experimental system consisted of a pilot electrolyser which electrodes dimension is 300×500mm 2 , and a DC power supply. Between the cathode and the anode plate, there exits 20 cm space in the electrolyser. The DC power supply (Yizhan Electronic Instrument Co., Ltd, Shenzhen of China) was used to supply power at a constant current intensity. The cathode was a 300×500mm 2 ferric plated and the anode plate was a same dimension Ti/IrO2-RuO2 electrode. The pilot electrolysis experimental system was shown as Fig. 1.