Middle-grade magnesia ball magnesia desulphurization technology has been applied in many places around the world, among which it has been applied in more than 100 projects in 13 countries. 95% of power stations in Taiwan use magnesia method, and it has been applied in the United States, Germany and other places. At present, China has begun to promote it, and has been applied in a few areas. Magnesium oxide method desulfurization relative to calcium method desulfurization, to avoid a series of problems existing in simple wet method, such as pipeline blockage, smoke temperature is too low, smoke with water and the existence of secondary water pollution; The process maturity is second only to calcium method, simple structure, small area, sufficient source of raw materials, low operating costs, good safety performance, investment significantly reduced, and can reduce the secondary pollution, desulfurization agent recycling, reduce the cost of desulfurization, comprehensive economic benefits have been greatly improved.
The flue gas desulfurization transformation project (FGD) of power plant (2x225MW) unit adopts magnesium oxide wet desulfurization technology. The process system is mainly composed of desulfurizer slurry preparation system, flue gas system, SO2 absorption system, desulfurization tower drainage system, magnesium sulfite dehydration system, process water system, wastewater treatment system, utility and meter compressed air system. The whole FGD basically adopts the closed circuit water circulation mode, and the waste water mainly comes from the desulfurization process of desulfurization tower. The water in the slurry of desulfurization unit will enrich heavy metal elements and F-,C1- during the continuous circulation process, which on the one hand accelerates the corrosion of desulfurization equipment, and on the other hand affects the quality of desulfurization byproducts. Therefore, a certain amount of waste water discharged by desulfurization unit obviously has high salt characteristics. The content of heavy metal ions, acid ions and ss exceeds the standard, and the pH value does not meet the discharge standard, so it needs to be targeted treatment. In this paper, the design of waste water treatment system of flue gas desulphurization transformation project is briefly introduced.
Design water quantity and quality
According to the information provided by a power plant in Shandong, the total displacement of desulfurization device is 144t/d, the average displacement is 6t/h, continuous discharge, the design of the device processing capacity of 8t/h.
Water quality of desulfurization wastewater: temperature 49℃, pH2-3, suspended matter 5900mg/L, SO42-<10000mg/L, C1-10000mg/L, F-1000mg/L.