Zero-discharge advanced treatment method of desulfurized wastewater

Abstract

The invention provides a zero-discharge advanced treatment method of desulfurized wastewater. The method comprises the following steps: 1, primary acidizing treatment; 2, primary dechlorination with an electrochemical reactor; 3, alkalization treatment; 4, elimination of calcium and magnesium ions; 5, secondary acidizing treatment; 6, secondary dechlorination with the electrochemical reactor; 7, settling and filtration; 8, first-stage electrodialysis, second-stage electrodialysis...N-stage electrodialysis; and 9, reclamation of clear water. The method solves a series of problems such as high treatment cost, high requirements on pretreatment, short service life of products, high replacement cost, serious scaling of an evaporator and pipelines, difficulty in treatment of solid mixture wastes and the like in the prior arts such as chemical softening plus hyperfiltration plus reverse osmosis, chemical softening plus multiple-effect evaporation, and the like, and the treatment cost of the method is about 1 / 3 of that of the existing methods.

Description

[0001] Technical field: [0002] The invention relates to the field of environmental protection wastewater treatment, in particular to a zero-discharge method for advanced treatment of desulfurization wastewater. [0003] Background technique: [0004] The limestone-gypsum wet flue gas desulfurization process in various flue gas desulfurization processes has the advantages of mature technology, wide range of coal types, and high desulfurization efficiency, and the utilization rate in practical engineering applications reaches more than 85%. However, in the process of using this method for desulfurization, a certain amount of desulfurization wastewater containing high concentrations of sulfates, sulfites, various heavy metals and suspended solids and with a low pH value will inevitably be produced. The total salt content (TDS) of power plant desulfurization wastewater desulfurization by this method is generally 20,000 ~ 50,000 mg / L, the total hardness is about 10,000 ~ 25,000 mg / L (ca...

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Problems solved by technology

[0006] At present, the advanced treatment methods for power plant desulfurization wastewater mainly include chemical softening + ultrafiltration + reverse osmosis; chemical softening + multi-effect evaporation. Practice has proved that these technologies mainly have the following shortcomings: The hardness, suspended solids, salinity, turbidity and other indicators have high requirements, the pre-treatment requirements are high, and the process is complicated; the service life of the product is short, and the replacement cost is high; reverse osmosis can only recover about 60% of the wastewater, and the concentrated Water still needs to be treated by other methods and cannot meet the requirements of zero discharge

[0007] The main problem of the chemical softening + multi-effect evaporation method is that the hardness of the wastewater after chemical softening is generally 20-300 mg / L (calculated as CaCO3). Phosphate, etc. will gradually crystallize out and adhere to the evaporation wall, which will form serious scaling in the evaporator and pipeline process

According to practice, under this condition, the evaporator needs to be shut down for cleaning after 3 or 4 months of operation, resulting in uncontinuous production; compared with single-effect evaporation, the steam consumption of multi-effect evaporation is reduced, but regardless of However, the cost of the above method of evaporating is very high (generally around 50 yuan / ton of water)

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