The key to achieve zero discharge of desulfurization wastewater is to realize the removal of chloride ions. The high hardness and poor stability of desulfurization wastewater, which contains a large amount of heavy metals and high chlorine radicals, is scaling and corrosive, and is also a technical difficulty in wastewater treatment. The process system is compared according to the application of domestic industrial wastewater and zero discharge technology for desulfurization wastewater. Based on the operating parameters of conventional 300 MW thermal power units, the economic benefits were analyzed based on the addition of zero-discharge treatment of desulfurization wastewater. There are three main treatment options: 1) evaporation treatment technology for desulfurization wastewater; 2) evaporation treatment technology for spraying flue gas; 3) evaporation membrane treatment technology for high salinity wastewater.
The type and content of pollutants in desulfurization wastewater are to some extent governed by factors such as coal type, desulfurization process and method, flue gas dust content, limestone quality and dewatering effect, and rate of ammonia volatilization for nitrogen removal. The quality of desulfurization wastewater from the same generating unit varies greatly. In the treatment of zero discharge of desulfurization wastewater, the commonly used treatment process is desulfurization wastewater, which has a generally high chloride ion concentration and salt content, and is prone to corrosion and some scaling when the water is reused, which seriously hinders desulfurization.
Desulfurization wastewater zero discharge treatment technology we mainly talk about two kinds.
One is evaporation crystallization method, which can recover water resources and crystallization salt, and high energy consumption is the main reason to limit its large-scale application. In addition, in order to ensure the normal operation of evaporative crystallizer and the quality of crystallized salt, strict pretreatment of desulfurization wastewater is required, such as removal of hardness, organic matter and heavy metals in the wastewater. Therefore, in order to realize the large-scale application of evaporation crystallization method, the research and development of wastewater reduction pretreatment technology shall be paid attention to reduce the construction and operation cost of evaporation section, and the high efficiency of desulfurization wastewater pretreatment technology shall be researched at the same time.
Another method of zero discharge of desulfurization wastewater is flue evaporation treatment, which is simple to operate and has low operation cost, but the flue treatment method cannot recover water resources, and there are many potential impacts that cannot be determined, including the impact on subsequent processes such as dust removal, and possible flue corrosion problems. Therefore, in the flue gas evaporation treatment of zero-discharge desulfurization wastewater, attention should be paid to studying the impact of wastewater entering the flue gas on flue gas emissions and flue gas treatment systems. If the flue treatment method is to be widely adopted, a large number of long-term and complete economic and technical studies and evaluations are required.
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