【Ten Years of Rapid Development in Chemical Processing Equipment】1371–2023: Screw press dryers and high-efficiency oil-water purification equipment for the treatment of sludge and scum

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On December 22, 2023, the “take-on-the-challenge” project aimed at solving the problems associated with the disposal of sludge and scum at Yan’an Refinery was approved by Shaanxi Yanchang Petroleum Refining Company. The acceptance team believes that this project is the first to adopt the process technology of \"stacked spiral dewaterers + high-efficiency oil-water purification equipment,\" which enables effective separation of oil, water, and sludge from oily sludge, achieving the desired objectives and filling a gap in the domestic oil refining industry regarding the treatment of oily sludge during wastewater processing. This technology transports the oil-containing sludge feed and the heated diluted water in proportion through a screw pump to a stacked screw dehydrator for treatment, thereby separating out most of the sludge, which is then conveyed by a screw conveyor to a sludge tank for storage and subsequent removal ； The separated oily wastewater enters an oil-water adjustment tank; through mechanical stirring, it is processed by high-efficiency oil-water purification equipment, which breaks down the oily sludge into oil of higher purity, clean water, and a small amount of washing residue water. The oil is sent directly to storage tanks, while the clean water is returned to the sewage system for further treatment. The washing residue water is pumped back to the spiral press using a screw pump for additional processing, thereby effectively solving the problem of difficult separation of sludge and residues that plagues the oil refining industry. In the process of treating water from upstream sources, the wastewater treatment system at Yan’an Refinery encounters complex compositions resulting from the mixture of water dehydrated in the oil storage tanks, water from electrodesalination processes, and sludge and scum generated by the air flotation system. This makes it difficult to settle and concentrate such water, thus posing challenges to the operation of the system. Previously, this sludge and scum could only be stored in regulation and homogenization tanks as well as oily waste tanks; after processes such as heating and dehydration, it turned into wet sludge that was difficult to handle and had to be disposed of as hazardous waste, resulting in high costs associated with transporting it for disposal each year. Yanlian engages in technical exchanges and field studies with industry experts and design firms by going out and inviting them in. After comparing various sludge and scum treatment technologies and taking into account the actual conditions of the plant, Jiangsu Xinyu Tiancheng Environmental Protection Co., Ltd. was ultimately selected as the partner enterprise to work on this project. The teams from both sides conducted in-depth research and analysis on the issue of dealing with sludge and scum, identified the technical approach, and through numerous experiments, jointly developed this new process technology consisting of a spiral press dehydrator and high-efficiency oil-water purification equipment. Yanlian began construction of a system for dealing with oil sludge and scum; it was completed and put into trial operation in July 2023, and has generated benefits totaling over 3 million yuan in the past 3 months. It is reported that this technology features excellent separation efficiency, small space requirements, a high degree of automation, low energy consumption, and low noise levels. A utility model patent was officially applied for with the **Intellectual Property Office in November 2023.