High magnesium and low calcium desulfurization wastewater softening pretreatment device and method

Abstract

The invention relates to a high magnesium and low calcium desulfurization wastewater softening pretreatment device and a method. The high magnesium and low calcium desulfurization wastewater softening pretreatment device consists of a settling tank, a softening tank, a flocculation tank and a clarification tank that are communicated in order. The bottom of the settling tank is connected to a first sludge discharge pipeline. The top of the softening tank is connected to a seed crystal delivery pipeline and a first agent delivery pipeline, and the bottom of the softening tank is connected to a second sludge discharge pipeline. The top of the flocculation tank is connected to a second agent delivery pipeline, and the bottom of the flocculation tank is communicated with the second sludge discharge pipeline. The bottom of the clarification tank is communicated with the second sludge discharge pipeline. The invention also relates to a high magnesium and low calcium desulfurization wastewater softening pretreatment method carried out on the basis of the high magnesium and low calcium desulfurization wastewater softening pretreatment device. The device and the method provided by the invention can achieve selective separation of Ca<2+> in desulfurization wastewater, perform wastewater softening without affecting the concentration of Mg<2+>, and reduce sediment production and lower the softener delivery amount and cost.

Description

technical field [0001] The invention relates to a device and method for softening and pretreating desulfurization wastewater with high magnesium and low calcium content. The device can reduce the amount of sediment generated in the softening process, reduce the dosage and cost of softener, and belongs to the environmental protection technology field. Background technique [0002] In order to achieve the national SO 2 Due to increasingly stringent emission restrictions, most thermal power plants in China have installed flue gas desulfurization equipment. Among them, limestone-gypsum wet flue gas desulfurization technology has been the most widely used due to its mature and reliable technology and strong adaptability to coal types. This technology is effective in removing flue gas SO 2 At the same time, it also produces wastewater with complex components, poor water quality and great harm (high suspended solids, super high salt content, excessive heavy metal content, etc.)....

AI Technical Summary

Problems solved by technology

However, since the oxalic acid used in this study is an organic acid, in order to maintain a certain pH of the wastewater, it is necessary to add ammonia water to it for neutralization. If it is directly applied to the desulfurization wastewater, it will increase the cost of softening and the complexity of the process. At the same time, it will add to the wastewater NH 4 + , new pollutants need to be further treated; in addition, there is a big difference between the quality of the rare earth wastewater and the desulfurization wastewater (for example, the suspended solid content of the desulfurization wastewater is only below 4mg / L, while the suspended solid content of the desulfurization wastewater can reach thousands to Tens of thousands of mg / L; its magnesium-calcium ion concentration ratio is only 5:1, while the desulfurization wastewater with high magnesium and low calcium content Mg 2+ Concentrations up to Ca 2+ 15-20 times; its solution is neutral, while desulfurization wastewater is weakly acidic), and cannot be directly used for desulfurization wastewater softening

Images