Abstract:

Direct electrochemical softening cannot perform itself effectively for the typical ash water with high hardness and low carbonate alkalinity. Herein，an enhancing method was proposed through adding CO₂ into the ash water before electrochemical process. Firstly，the feasibility was verified experimentally. Then，the influence of CO₂ adding amount on hardness removal efficiency，current efficiency and energy consumption was investigated under different current and flow rate conditions. The results indicated that adding CO₂ could evidently enhance hardness removal effect. When the concentration of inorganic carbon was equivalent to the total hardness under 5 A-5 L/h，the hardness removal rate increased to about 60%，current efficiency increased to 50%，scale precipitation rate increased to 470 g/（m²·h） （in CaCO₃） and meanwhile corresponding energy consumption of CaCO₃ removal decreased to around 13.5 kW·h/kg. Reducing the current and flow rate in the same proportion could further reduce energy consumption，while the current efficiency remained stable at 50%，but corresponding scale precipitation rate decreased proportionally. With a fixed flow rate （5 L/h），further adding CO₂ to make pH=5.57 and increasing current to 10 A could further enhance hardness removal efficiency to 80.6%，but companied by the increase of energy consumption. Therefore，reasonable regulation of CO₂ addition amount and current could significantly contribute to the removal of hardness. For all that，the ionic conductivity of the diaphragm，current efficiency and the crystallization rate still needed to be improved to enhance the performance of the electrochemical equipment，which was a key for its engineering application.

Key words: ash water, electrochemical, hardness removal, carbon dioxide, high hardness, low carbonate alkalinity

摘要：

针对典型高硬度、低碳酸盐碱度的煤气化灰水直接电化学除硬效果差的问题，提出在隔膜法电化学除硬之前预补加CO₂来提升除硬效果。实验首先验证了该方法的可行性，然后在不同电流-流量条件下考察了CO₂补加量对电化学除硬率、除硬速率、电流效率及能耗的影响。结果表明，补加CO₂能明显提升除硬效果，在5 A-5 L/h电流-流量下，当补加CO₂使总无机碳含量接近总硬度时，除硬率提升至60%左右，电流效率提升至50%，除硬速率提升至470 g/（m²·h）（以CaCO₃计），去除单位质量CaCO₃的能耗降至13.5 kW·h/kg。同比例降低电流-流量可进一步降低能耗，同时电流效率仍稳定在50%，但除硬速率也同比例降低。固定流量（5 L/h），进一步补加CO₂使pH=5.57，并提升电流至10 A，除硬率增至80.6%，但能耗增加明显。因此，合理调控CO₂补加量和电解电流是提升灰水电化学除硬效果的关键，后续研究可关注提升隔膜离子导电性、电流效率或加速垢晶析出，以降低能耗、提升设备性能。

关键词: 煤气化灰水, 电化学, 除硬, CO₂, 高硬度, 低碳酸盐碱度

CLC Number: 

• X703.1