Treatment of lignite coke wastewater

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Lanchar wastewater, also known as semi-coke wastewater, refers to an industrial wastewater generated during the medium- and low-temperature carbonization of poorly metamorphosed coals (non-caking coal, weakly caking coal, long-flame coal) at temperatures of around 600–800 °C, as well as during gas purification and the process of quenching coke with lanchar steam. This type of wastewater has a complex composition, containing large amounts of pollutants that are difficult to degrade and highly toxic, such as organic pollutants like benzene derivatives, phenols, polycyclic aromatic hydrocarbons, and nitrogen-oxygen heterocyclic compounds, as well as inorganic pollutants such as heavy metals. It is a typical example of industrially generated wastewater with high pollution levels and high toxicity. After the **Ministry of Industry and Information Technology included semi-coke in the industrial catalog in 2008, the semi-coke industry experienced rapid growth due to strong market demand. However, research on semi-coke wastewater by environmental experts has not kept up with this development; most semi-coke production facilities in operation still use conventional biochemical treatment methods or incineration for wastewater treatment. The main type of carbonization furnace used by existing lignite (semi-coke) enterprises is the internally heated vertical furnace. Since the tar and water generated during the production process in vertical furnaces are difficult to separate, the COD level of the wastewater is as high as 30,000–40,000 mg/L; moreover, it contains large amounts of toxic substances that inhibit microbial growth, making it difficult to achieve the required standards through biological treatment. The incineration method, due to its high energy consumption, is only suitable for small enterprises with low water volumes. Moreover, during incineration, the harmful substances in the wastewater are released into the atmosphere as vapor, causing secondary pollution. In light of the characteristics of lignite coke wastewater, namely \"four highs and one low\" (high COD, high oil content, high ammonia nitrogen, high phenol levels, and low wastewater generation volume), our company has developed a comprehensive set of process technologies for pretreatment, ammonia evaporation for phenol removal, and precision filtration for decolorization. Through these combined new techniques, it is possible to achieve the resource utilization of high-concentration organic wastewater from lignite coke (semi-coke), thereby addressing the environmental challenges faced by the lignite coke industry and improving the quality of this product. Additionally, ammonia nitrogen, coal tar, and phenols in the wastewater can be recovered, which also generates certain economic benefits. Our company has built an industrial pilot plant for this technology in Shenmu, Shaanxi, and conducted numerous tests. The 72-hour on-site technical calibration conducted in late April this year showed that the device operates reliably, and its effluent parameters meet the requirements for biochemical treatment. Moreover, the three units of pretreatment, ammonia steaming for phenol extraction, and fine filtration for decolorization adopt a modular design and combination, enabling them to meet the treatment requirements of different scales and water qualities. Our company plans to install an industrial demonstration facility for wastewater treatment with a capacity of 300,000 tons per year for lignite coke in the Shenmu area in 2019; the project has already been submitted for approval. We welcome colleagues to engage in technical exchanges and learning.