Electric Power ›› 2022, Vol. 55 ›› Issue (4): 221-228.DOI: 10.11930/j.issn.1004-9649.202103028

• Generation Technology • Previous Articles    

Water Balance Model and Water-Saving Analysis for Coal-fired Power Plants

LIU Guangjian1, YUE Fengzhan1, ZHOU Shuo1, WANG Lin1, GAN Xue2   

  1. 1. School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China;
    2. Gongcheng Management Consulting Co., Ltd., Beijing 510610, China
  • Received:2021-03-10 Revised:2022-02-21 Online:2022-04-28 Published:2022-04-24
  • Supported by:
    This work is supported by National Key R&D Program of China (Heat and Mass Distribution Law and Energy Efficiency Evaluation in Water Recovery and Treatment Process of Coal-fired Power Plants, No.2018 YFB0604301).

Abstract: With the increasing shortage of water resources and the continuous increase of thermal power installed capacity, the application of water-saving technology is an essential issue for the sustainable development of the thermal power industry. The water balance model and water flow diagram is proposed based on coal type, meteorological conditions, and power plant performance parameters. From the water flow diagram, the water balance relationship is intuitively reflected between entering and leaving streams. The key processes to reduce system water use were identified. The energy and water-saving effects of flue gas waste heat and water recovery system are quantitatively analyzed. For supercritical power plant burning bituminous coal, about 60% water losses come from cooling tower evaporation and wind blowing, while cooling tower blowdown accounts for 20%. The moisture content in exhaust fluegas accounts for 15%. The critical points of water saving in thermal power plants are cooling systems, wastewater discharge, and moisture recovery from flue gas. This paper presents a waste heat and moisture recovery from flue gas system. The preliminary analysis shows that, for wet-cooled units, the water consumption per MW·h will drop by 19.2% with flue gas moisture recovered by 60%. For air-cooled units, if the flue gas moisture is recovered by 60%, the water withdraw of the power plant will be zero. If the semi-dry or dry desulfurization system is adopted at the same time, the power plant can become the water supplier.

Key words: water balance, water flow chart, deepwater conservation, water consumption index, flue gas moisture recovery