Primary Research of a New Zero-Liquid-Discharge Technology of Wet Flue Gas Desulfurization Wastewater by Low-Rank Heat from Flue Gas

Wet flue gas desulfurization (WFGD) wastewater treatment is a key problem in coal-fired plants. Traditional chemical precipitation methods cannot reach zero-liquid discharge (ZLD). In this paper, a new technology using the low-rank heat from flue gas to concentrate the wastewater for ZLD is proposed...

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Bibliographic Details
Published in:Energies (Basel) 2021-07, Vol.14 (14), p.4259
Main Authors: Yao, Xuan, Zhang, Man, Deng, Boyu, Yang, Xinhua, Yang, Hairui
Format: Article
Language:English
Subjects:
Air pollution control
Calcium chloride
Calcium hydroxide
Chemical precipitation
Chloride
Coal-fired power plants
concentrate
Desulfurization
Desulfurizing
Dosage
Environmental policy
Evaporation
Filter presses
Flow rates
Flow velocity
Flue gas
Flue gas desulfurization
flue gas waste heat
Heat
Industrial plant emissions
Lime
New technology
Pollution control equipment
Salt
Slaked lime
Sludge
Sodium
System reliability
wastewater
Wastewater treatment
Water reuse
Water treatment
WFGD
zero liquid discharge (ZLD)
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Summary:Wet flue gas desulfurization (WFGD) wastewater treatment is a key problem in coal-fired plants. Traditional chemical precipitation methods cannot reach zero-liquid discharge (ZLD). In this paper, a new technology using the low-rank heat from flue gas to concentrate the wastewater for ZLD is proposed. A scrubber was built to verify the concentrating process, and the characteristics of the concentrated water were analyzed. The concentrated water was neutralized by adding Ca(OH)2 to raise the pH value. The wastewater can be concentrated 10~25 times to reduce the flow rate. The characteristics of the concentrated wastewater were studied by dosing lime. Then, liquid and solids were separated by filter pressing, the liquid was mainly composed of CaCl2, which accounts for 73.6%. The sludge is composed of CaSO4 and Mg(OH)2, depending on the lime consumption of the dosing process. Finally, the filter liquor after the filter press was mixed with ash to reach zero liquid discharge, and the sludge could be burnt after mixing with the coal or disposed by third-part vendor. This technology is demonstrated in one 600 MW unit and shows a high system reliability. The clean water is recycled by the WFGD wastewater during the evaporation. Binding on the environmental policies and large market demand of the WFGD wastewater, this technology shows a great application prospect in the future.
ISSN:1996-1073
1996-1073
DOI:10.3390/en14144259