Harmless Treatment of Coking Wastewater

Firstly, the source of coking wastewater

Coking plants mainly produce coke and coal gas, and also recycle chemical products such as benzene, tar, ammonia, phenol, cyanide, etc. A large amount of wastewater is generated during the processes of gas washing, cooling, purification, and chemical product recovery and refining. The main component of wastewater is the moisture in coking coal, which is formed by the escape and condensation of coal gas during high-temperature dry distillation. There are thousands of organic compounds in coal gas, and any substance that is soluble or slightly soluble in water forms extremely complex residual ammonia water in the condensate, which is the largest amount of coking wastewater. Next is the wastewater formed during the gas purification process, such as desulfurization, ammonia removal, and extraction of refined benzene, naphthalene, and crude pyridine. The wastewater generated from tar processing and crude benzene refining is not large in quantity, but its composition is complex.

Figure 1 Coking Production Process Flow and Wastewater Source

Secondly, the technical conditions and control requirements for harmless and resourceful treatment of coking wastewater

Coking wastewater has complex components, high concentrations, and numerous toxic and harmful substances. The ammonia nitrogen in coking wastewater exists in two forms: free ammonia and fixed ammonium, the latter of which includes ammonium chloride, ammonium carbonate, ammonium sulfide, and ammonium polysulfide. In addition, in chemical and biochemical treatment reactions, other nitrogen-containing compounds such as dicyanide, thiocyanate, nitric acid and nitrite, as well as organic nitrogen compounds such as pyridine, quinoline, indole, carbazole, acridine, etc. in wastewater can also be converted into ammonia nitrogen.

Example of Pre treatment+Activated Sludge Process+Oxidation Pond Process+Adsorption Process for Treating Coking Wastewater Mooring Project

1) Preprocessing and Primary Processing

Coking phenol cyanide wastewater not only contains various pollutants, but also contains a large amount of suspended substances such as oil, tar, coke particles, coal dust, etc. The presence of this substance has inhibitory and toxic effects on the microorganisms of activated sludge in biochemical treatment. When their concentration in wastewater reaches a certain level, a certain amount of tar and other substances will adhere to the surface of activated sludge microbial aggregates, hindering the uptake of dissolved oxygen in water by microorganisms, reducing the effectiveness of biochemical treatment, and causing sludge to float and lose.

Figure 2 Schematic Diagram of the Process Flow of Coking Wastewater Treatment Unit

2) Biochemical treatment operation

The biochemical treatment of wastewater is the use of microorganisms that are abundant in nature to decompose pollutants dissolved in wastewater, and through biochemical processes, convert them into stable non-toxic inorganic substances to purify wastewater.

3) Deep treatment of wastewater

Haipu Company's deep adsorption process further removes ammonia nitrogen and COD components from water, achieving the conditions for qualified discharge.

Haipu Company's Tail Water Upgrading and Reuse Process

Advantages and Features:

Process (1) Ultrafiltration+Special Adsorbent: After pre-treatment such as coagulation and multi-media filtration (or ultrafiltration), the biochemical effluent is directly subjected to special adsorption process, and the COD can be reduced to below 50mg/L, which can be directly discharged or reused.

Process (2) Ultrafiltration+special adsorbent+reverse osmosis: To meet further reuse requirements, a combined process of ultrafiltration membrane+adsorption+reverse osmosis can be used. After adding special adsorbent adsorption, the reverse osmosis membrane can be protected, and its water production rate is increased by more than 40% compared to the "double membrane method" (ultrafiltration+reverse osmosis). COD is reduced to below 5mg/L, and the reverse osmosis concentrated water is nearly colorless.