Water treatment issues in coal-based ethylene glycol production

According to Sinochem New Network, the long-standing problem of wastewater treatment in coal-based ethylene glycol production projects has been solved. A reporter from China Chemical Industry News learned yesterday from Dalian Rick Technology Co., Ltd. that the catalytic reduction technology for nitric acid it has developed enables the nitric acid content in the wastewater generated during the coal-based ethylene glycol production process to be reduced to below 0.1%, while the consumption of raw materials such as sodium nitrite, nitric acid, and sodium hydroxide is reduced by over 90% at the same time. Currently, this technology has been applied industrially at Puyang Yongjin Chemical Co., Ltd. and Luoyang Yongjin Chemical Co., Ltd. 　　According to the person in charge of Dalian Rick, Henan Energy and Chemical Group operates 5 coal-to-ethylene glycol plants with an annual production capacity of 200,000 tons each. Since their commissioning, the problem of wastewater containing high concentrations of nitrates has been affecting the normal operation of these plants. In October 2014, Dalian Rike partnered with Henan Nenghua to apply nitric acid reduction technology to the 200,000-ton coal-to-ethylene glycol production process at Puyang Yongjin. The nitric acid reduction unit was successfully started up for the first time. The device operates stably, and the nitric acid content in the process wastewater has dropped from 1.2% to below 0.1%, thus resolving the issue of environmental treatment for the wastewater. At the same time, after nitric acid reduction, the consumption of raw materials such as sodium nitrite, nitric acid, and sodium hydroxide is reduced by over 90%, saving more than 40 million yuan in raw material costs each year. 　　In recent years, many domestic research institutions have been developing coal-based ethylene glycol production processes. The principles of these processes are essentially the same, involving a synthesis route of methyl nitrite carbonylation, methyl nitrite regeneration, and oxalate hydrogenation. According to the researchers at Dalian Rick, during the regeneration of methyl nitrite, the main components of the resulting liquid phase are methanol and water; in addition, there is 0.5%–2% nitric acid produced as a by-product of the reaction. The regeneration liquid is distilled to recover organic substances such as methanol, while the wastewater containing nitric acid is neutralized with alkali before undergoing environmental protection treatment. This type of wastewater containing nitrates and nitrites has a complex composition and high toxicity, making it extremely difficult to treat. Due to the neglect of nitrogen oxide treatment in wastewater, environmental protection has become a major challenge faced after the coal-based ethylene glycol plant went into operation, preventing the plant from functioning properly. Previously, technology suppliers for coal-based ethylene glycol both domestically and internationally also did not possess applicable technologies in this area. 　　To address this challenge, Dalian Rike organized researchers to conduct scientific research on wastewater treatment technologies for the coal-based ethylene glycol production process, and was the first in the world to successfully develop nitric acid-catalyzed reduction technology. This technology can reduce nitric acid in the regenerated coal-based ethylene glycol solution to nitrites, which are then returned to the system as raw materials; as a result, the nitric acid content in the treated process wastewater is reduced to below 0.1%.

Is there an oil removal issue with this water? If the oil content is high, it should also have an impact on nitric acid catalysis.