Circulating water \"0 discharge, 0 pollution\" technology

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I. Properties and composition of coking wastewater Coking wastewater is a type of wastewater rich in toxic and harmful substances; it has a high concentration of NH3-N, a large amount of tar, and poor biodegradability, which makes biological treatment of this wastewater highly difficult and complex； Heterocyclic compounds, polycyclic aromatic hydrocarbons, cyanides, NH3-N, and other substances present in wastewater are toxic to microorganisms and can inhibit their growth. 1. Sources of coking wastewater 1) Excess ammonia aqueous waste generated from high-temperature pyrolysis and cooling of raw gas ； Water accounts for more than half of the total emissions from the plant; its quality is complex, with a wide variety of components and high concentrations of pollutants. In addition to inorganic pollutants such as ammonia, cyanide, and thiocyanate, it also contains phenols, oils, naphthalene, pyridine, quinoline, anthracene, and other polycyclic and heterocyclic aromatic compounds. 2) Water from devices such as the final cooling unit for gas in the gas purification process and the crude benzene separation tank, including the direct cooling water used for the final cooling of the gas, the direct cooling water used in the benzene and toluene washing processes, and the direct steam condensation water used in the crude benzene processing process. The pollutants it contains include phenols, cyanides, other CODcr components, etc., as well as ammonia. 3) Wastewater generated during the processing of crude tar, benzene refining, phenol production, and guaiacol production. The pollutants contained include phenols, cyanides, and other CODcr components, with a small volume of water. 4) Wastewater in contact with coal, coke dust, and similar substances: Dust removal and washing water used in the coal processing process, as well as dust removal and washing water used during coal loading or coke extraction from coke ovens; it is characterized by a high concentration of suspended solids ； The volume of wastewater generated in the dry quenching process for coking is relatively small. 2. Major pollutants in coking wastewater 1) Classification of major pollutants: Benzenes: benzene, toluene, xylene, etc ； Phenols: phenol, cresol, xylene, etc ； Quinolines: quinoline, isoquinoline, etc ； Naphthalenes: naphthalene, methylnaphthalene, etc ； Heterocyclic compounds: indole, carbazole, pyridine, benzofuran, etc.; polycyclic aromatic hydrocarbons ； Thiocyanides, cyanides, ammonia, ammonium salts, sulfides, etc ； 2) Pollutants with major toxicity and their hazards: Phenolic compounds: These are prototoxic substances that are harmful to all living organisms; they cause cells to lose their vitality, leading to damage and necrosis in deep tissues, and ultimately to systemic poisoning. It accounts for 60% of total organic pollutants and belongs to organics with easy detoxification. Cyanide: It is a highly toxic substance that, once it enters living organisms, can inhibit the respiratory enzyme systems within cells, thereby reducing microbial activity. Polycyclic aromatic hydrocarbons and heterocyclic compounds: They belong to persistent organic pollutants (POPs) and are difficult to degrade ； POPs degrade slowly and tend to accumulate in the environment; some of them can also transform into other substances with greater toxicity. Most POPs not only pollute the environment but also pose a direct threat to human health. Pollutants such as alkylphenols and pyridines belong to environmental endocrine disruptors (EEDCs) ； 3. Components of tar and their contribution to CODcr. Coal tar is one of the products obtained from the pyrolysis of coal in the coke-making industry; at room temperature, it is a black, viscous liquid. The coal tar produced at high temperatures during coke manufacturing has a higher density, ranging from 1.160 to 1.220 g/cm3. It is mainly composed of polycyclic aromatic compounds, with naphthalene being the predominant component; the other components are present in relatively smaller amounts, including 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, oxofluorene, anthracene, phenanthrene, carbazole, fluoranthene, quinoline, pyrene, and others. It can be inferred from the components of tar that the pollutants in coking wastewater mainly originate from the contamination by tar. The difficulty in treating coking wastewater is mainly due to the toxic CODcr generated by tar. Therefore, controlling the content of tar in wastewater is the key to solving the treatment of coking wastewater. 4. Basic categories of CODcr in coking wastewater. Chemical oxygen demand (CODCr) is one of the important indicators for describing organic pollution in water quality. It refers to the amount of potassium dichromate consumed in the oxidation of organic substances present in wastewater samples using a strong oxidizing agent, and it is expressed in terms of oxygen concentration (mg/L). Classification and degradation analysis of CODcr in coking wastewater: The impact of CODcr on microorganisms. II. Comprehensive solution: During the discussions between the two parties, after technical personnel from Jinniu Tiantie Coking conducted on-site inspections and investigations at the coking plant of Hanbao Iron and Steel Company, which is one of the customers using Wanhe’s technology, and taking into account the results of the on-site surveys at Jinniu Coking, its historical operation patterns, as well as the characteristics of coking wastewater and the methods used for its treatment, Shandong Wanhe developed a targeted solution for Jinniu Coking: a comprehensive approach that involves controlling the source of pollution, implementing multi-level interventions, and optimizing the quality of biochemical treatments and ammonia solutions. 1. Controlling the source: 1) Reducing the total amount of CODcr in the feedstock for biochemical treatment processes, thereby reducing the stress associated with decomposition and degradation in these processes ； The reduction of tar and suspended solids in ammonia water directly leads to a decrease in the CODcr of the coking wastewater entering the biochemical system. 2) Reduce the total amount of toxic CODcr, thereby minimizing microbial poisoning and death and maintaining microbial activity and biochemical capabilities ； Quinoline and indole inhibit the degradation of glucose ； Difficult-to-degrade organic compounds mainly include pyridine, carbazole, biphenyl, terphenyl, etc., which have a significant inhibitory effect on aerobic microorganisms. Easily degradable organic compounds are mainly phenolic compounds and benzene compounds ； Pyrroles, naphthalenes, furans, and imidazoles belong to degradable organic compounds. 2. Multi-level linkage: 1) Ensure the smooth operation of the coke oven nozzles, thereby enabling effective cooling of the gas and making the pressure and temperature inside the oven more stable ； Thereby maintaining the stable quality of tar ammonia solution ； 2) Effective and thorough separation of tar from ammonia water, reducing the tar content in ammonia water; this can effectively minimize the adverse effects of oils, sulfides, etc. on biochemical treatment ； 3) Ensure the efficient operation of ammonia evaporation to reduce the total amount of pollutants in the residual ammonia water. 3. Optimization of biodegradability: 1) Reducing the load on the anaerobic stage; 2) Reducing the load on the aerobic stage (by enhancing the separation of tar from ammonia water, thereby reducing the total amount of organic matter and thus decreasing the treatment load in the aerobic stage); 3) Increasing the activity and decomposition capacity of microorganisms; 4) Optimizing the key operational parameters of the biochemical processes; 5) It has been shown that after hierarchical removal and anaerobic treatment of coking wastewater, some toxic substances are converted into non-toxic ones, improving the biodegradability of the wastewater. This demonstrates that reducing the amount of toxic substances in wastewater plays a crucial role in enhancing the functions and decomposition capabilities of microorganisms. 15820013215 Yang