The circulating spray mother liquor used in flue gas wet desulfurization will increase the concentration of sulfite and sulphate as the number of cycles increases, eventually causing crystallization and clogging of the piping of the circulating sprinkler system. After several cycles of spraying, the chloride ions in the solution are continuously enriched and the concentration rises sharply. And the ultra-high concentration of chloride ions will cause serious corrosion to the circulation pump and the spray system.

Therefore, for the specificity of desulfurization wastewater combined with the degree of treatment required by the owner, there are currently two conventional treatment methods:

I. Conventional process treatment (concentration and clarification after three reactors)

The pH of the desulfurization wastewater is adjusted to a suitable range by adding lime milk (in the process, most of the metal ions such as iron and copper are precipitated), and then a heavy metal capture agent is added (the generally added agent is organic sulfur). ) Remove more than 95% of heavy metal ions from wastewater. After the coagulation reaction, it enters the concentrated clarifier. After a long period of clarification, the supernatant is used for spraying the coal field through PH reconciliation. The sludge is subjected to pressure filtration treatment.

Although the process is simple, with the continuous improvement of environmental protection requirements and avoiding secondary pollution (dissolved chloride ions are completely untreated and directly infiltrated into the ground), the desulfurization wastewater will be gradually sprayed after conventional simple treatment. Prohibited.

Second, zero discharge of desulfurization wastewater

Zero discharge is the further intensive treatment of the desulfurization wastewater after the conventional treatment process, so that the effluent can fully meet the requirements of reclaimed water.

The permanent hardness of the water is removed by deep softening; the COD is removed by a strong oxidation system; the suspended solids and residual chlorine are removed by a filtration system and an adsorption system; and the final effluent quality is ensured by a double membrane method (ultrafiltration, reverse osmosis). The reverse osmosis concentrated water enters the evaporation system to prepare the crystallization mother liquid, and then enters the centrifuge, and is separated by a centrifuge to finally obtain an industrial salt.

The process is complex, with one-time investment and high operating costs. However, with the increasing emphasis on environmental protection and increasingly strict emission standards, the process has completely solved all kinds of pollutants in desulfurization wastewater, and has truly achieved zero emissions and reuse of water, which will surely be in the country. Promote popularization within the scope.