Purifying device for wet-process flue gas desulfurization wastewater and using method thereof

Abstract

The invention relates to the wastewater multistage processing field, and particularly relates to a purifying device for wet-process flue gas desulfurization wastewater and a using method thereof. The purifying device for the wet-process flue gas desulfurization wastewater includes a wastewater regulation tank (1), and is characterized by also including a reaction flocculation tank (2), a precipitation tank (3), a first-stage fluorine removal reaction tank (41), a second-stage fluorine removal reaction tank (42) and the like. The using method of the purifying device for the wet-process flue gas desulfurization wastewater is characterized by successively comprising the following steps: a, adjusting the water quality and the water amount; b, carrying out Cr6<+> reduction and heavy metal ion reaction flocculation; c, carrying out first-stage precipitation; d, carrying out a fluorine removal reaction and COD degradation; e, carrying out second-stage precipitation; f, carrying out a neutralization reaction; g, carrying out sand filter processing; and h, draining water. The system operation is stable and reliable, the energy consumption is low, and the operation cost is low.

Description

technical field [0001] The invention relates to the field of multistage treatment of wastewater, in particular to a purification device for wet flue gas desulfurization wastewater and a method for using the same. Background technique [0002] The desulfurization wastewater in the wet flue gas desulfurization system comes from the discharge water of the absorption tower. In order to maintain the balance of materials in the slurry circulation system of the desulfurization unit, prevent the soluble part of the flue gas, that is, the chlorine concentration from exceeding the specified value, and ensure the quality of the gypsum, a certain amount of wastewater must be discharged from the system. The wastewater mainly comes from the gypsum dehydration and cleaning system. The impurities contained in wastewater mainly include suspended matter, supersaturated sulfite, sulfate and heavy metals. The main water quality characteristics of wet flue gas desulfurization wastewater are: hi...

AI Technical Summary

Problems solved by technology

However, this traditional process only targets suspended solids SS and heavy metal ions, and can still meet the requirements of effluent water quality, but it has disadvantages such as large consumption of chemicals, large amount of sludge, and high operating costs. The conventional treatment process is difficult to meet the water discharge requirements, and there are the following problems:

[0010] (1) Since the water contains heavy metal ions (including Cr 6+ ) and F - , the conventional system adopts one-stage mixed reaction and one-stage precipitation. On the one hand, a large amount of lime milk needs to be added to generate a large amount of sludge. At the same time, the primary reaction is not sufficient, making it difficult for F ions to reach the standard

[0011] (2) The SS of suspended matter in the wastewater influent is very high. After the primary sedimentation, the SS is difficult to reach the standard, which leads to more frequent backwashing in the filtration process, resulting in higher energy consumption of the system

[0012] (3) Since the COD of wastewater influent is 200mg / L, it is necessary to degrade COD. In the conventional process, chemical method is mainly considered for COD degradation, that is, a strong oxidant (such as sodium hypochlorite, etc.) is added to the mixed reaction stage for oxidation. Degrade COD, while Cr exists in wastewater 6+ need to be reduced to Cr 3+ It is necessary to add a reducing agent, so that the oxidizing agent is added first and then the reducing agent is added, so that the consumption of the agent is large

The main heavy metal pollutant Cr in wastewater 6+ reduced to Cr 3+ , you need to adjust the pH value of the wastewater to between 2 and 3 to achieve a better reduction reaction effect. After the reduction reaction is completed, to make the heavy metal ions produce the best precipitation effect, you need to control the pH value between 9.5 and 10.5. For this reason, it is necessary to add acid to the wastewater to adjust the pH value to 2-3 for Cr 6+ Reduction, adding alkali to adjust the pH value to 9.5-10.5 for precipitation reaction, the wastewater system will need to add a large amount of acid and alkali to repeatedly adjust the pH value, which will consume a large amount of acid and alkali agents, which will increase the operating cost , while a large amount of Ca(OH) 2 Dosing increases the subsequent sludge treatment load

[0014] (5) In the conventional process, due to the back-and-forth adjustment of several chemicals and the excessive dosing of lime milk, the sludge treatment system has a large load, which increases the operation and maintenance costs, and at the same time makes the sludge treatment system a large investment.

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