Coal gasification black/gray water system treatment method capable of lowering hardness, saving water and reducing sewage discharge

Abstract

The invention discloses a coal gasification black / gray water system treatment method capable of lowering hardness, saving water and reducing sewage discharge, comprising the following steps: (1) overflow gray water enters a gray water tank after black water produced from a coal gasification system is subjected to a flocculation and sedimentation treatment in a sedimentation tank; after being subjected to a scale inhibition and dispersion treatment, party of gray water in the gray water tank is recycled back to the coal gasification system, and discharged gray water in the gray water tank is cooled by a cooling device to a water temperature of not more than 35 DEG C; (2) the cooled gray water enters an electrodialysis device (EDR), a majority of calcium, magnesium, bicarbonate radical and chloridion are removed by means of electrodialysis, produced fresh water is recycled as replenishing water or is used for other systems; produced concentrated water partially or entirely returns to the sedimentation tank; a feeding device of a flocculating agent and a hardness lowering agent is arranged on the sedimentation tank; and a scale inhibition and dispersion agent feeding device is arranged on the gray water tank. According to the treatment method disclosed by the invention, hardness of circulating gray water in a coal gasification system is lowered effectively, scaling is relieved, continuous operation period of the system is prolonged, water consumption is saved, and sewage discharge is reduced.

Description

[0001] Technical field: [0002] The invention belongs to the water treatment technology of a coal gasification slag water system, and in particular relates to a treatment method for reducing the hardness of gray water in a coal gasification black ash water system and reducing the drainage volume and supplementary water volume of the coal gasification system. Background technique [0003] Coal gasification technology is a key common technology in the field of clean coal technology; it has the characteristics of high efficiency and ultra-clean, and is the mainstream of coal technology development in the world today. Among coal gasification technologies, entrained bed coal gasification technology is more suitable for large-scale industrial production. [0004] Coal gasification in foreign countries is mainly used to produce fuel gas and cycle power generation. The requirements for syngas purification are not particularly strict, and the treatment of slag water is relatively simp...

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Problems solved by technology

[0005] At present, due to the constraints of coal quality, water resources and environmental protection and other factors, the suspended solids, alkalinity and hardness in the gray water of the coal gasification system continue to increase, which makes the scaling and blockage of the entire coal gasification system increasingly serious, seriously affecting the coal gasification system. The long-term continuous and stable operation of the coal gasification system also causes a large amount of drainage and replenishment water in the coal gasification system. Therefore, in addition to the conventional flocculation and sedimentation and scale inhibition and dispersion treatment of the black ash water of the coal gasification system, a method of reducing gray water in the coal gasification black ash water system is developed. It is very necessary to treat the hardness and reduce the drainage and replenishment of the coal gasification system

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