Progress of the Great Wall Energy Chemicals High-Salinity Wastewater Zero-Discharge Project
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It describes the technical process for the \"zero discharge\" of high-salinity water in one of the companies under Great Wall Energy Chemical Co., Ltd., namely the treatment process of \"pre-treatment via medium-high pressure membrane concentration, mechanical vapor compression cycle evaporation, and forced circulation crystallization\", and outlines the progress and trial operation status of this project. At the same time, suggestions for optimizing the management of “zero-emission” projects were put forward, including cost control, process optimization, improvement of personnel competence, and policy guidance. 1 Project Overview China Petrochemical Great Wall Energy Chemical Co., Ltd. (hereinafter referred to as Great Wall Energy Chemical) is a wholly-owned subsidiary of Sinopec Corporation. It serves as a platform for investment in the coal chemical industry, responsible for the investment and operation of coal chemical projects, organizing and coordinating project construction, and providing professional management for its subsidiaries and enterprises in which it holds shares. At present, Great Wall Energy Chemical has established and built multiple coal chemical projects in Xinjiang, Inner Mongolia, Anhui, Guizhou, Ningxia and other regions, with some of them already in full production and operation or in the final stages of trial operation. In the early stages of project decision-making and during production operation management, Great Wall Energy Chemical has consistently paid close attention to and vigorously promoted the \"zero discharge\" project for high-salinity wastewater, primarily for the following reasons. Firstly, in recent years, **strict control criteria have been established for water usage and wastewater discharge in new coal chemical projects. For example, in 2012, the State Council issued the \"Opinions on Implementing the Strictest Water Resources Management System,\" setting a ceiling for the total amount of water used across the country by 2030. Restrictions on water use mean that the project must not only adopt extensive water-saving measures such as air cooling, but also ensure the complete reuse of wastewater. In 2015, the Ministry of Environmental Protection issued the \"Environmental Access Requirements for Modern Coal Chemical Industry Projects (Trial)\\", which stipulated that coal chemical projects must take on a leading role in areas such as wastewater treatment technologies, wastewater disposal plans, and the utilization and disposal of crystalline salts. It can be said that \"zero discharge\" of high-salinity wastewater has become an essential part of environmental impact assessments submitted by enterprises, as well as a requirement for their sustainable development.
Secondly, as one of the largest energy and chemical companies in China, Sinopec bears significant social responsibilities, and it has an undeniable duty and obligation to protect the environment as well as to save water and reduce energy consumption. “The implementation of the \"Clear Waters and Blue Skies\" environmental protection program – which involved investing nearly 23 billion yuan between 2013 and 2015 in environmental projects aimed at reducing pollutant emissions by Sinopec’s enterprises and ensuring that such emissions meet regulatory standards, as well as at improving the environmental quality in the workplaces and surrounding areas and addressing potential environmental hazards – represents Sinopec’s solemn commitment to society and the environment. Sinopec Group’s headquarters and Great Wall Energy Chemicals attach great importance to environmental protection efforts within the company, and are determined to prevent any environmental incidents or potential hazards. Finally, some of the companies under Great Wall Energy Chemical have entered the trial production phase. The main processing units, wastewater treatment systems, and wastewater recycling facilities have been put into operation, generating concentrated water with a high salt content. The plan to have this water treated centrally by municipal authorities has not seen any progress; as there are no outlets for discharging this concentrated water, it can only be stored temporarily in makeshift storage facilities. This situation is likely to force a complete shutdown of the processing units, thus becoming a bottleneck that hinders the normal operation of the project. “The site for constructing the “zero emissions” facility has been leveled, and the external conditions required for its construction and operation are generally met. The facility’s needs for utilities such as water, electricity, and gas can be met through the existing supply systems within the plant, providing a solid foundation for this company’s zero emissions project.
2 Project Commissioning Examples 2.1 Introduction to the “Zero Emission” Process Technology As mentioned earlier, the company’s wastewater treatment and reuse system is already in operation; after double-membrane treatment, brine with a total dissolved solids (TDS) level of 330–450 m3/h and a TDS concentration of 3800–4500 mg/L is produced. To address the issue of what to do with highly saline water, a two-step approach is adopted for the \"zero discharge\" project: first, a medium-high pressure membrane concentration and reduction system is installed downstream of the wastewater treatment facility, to recover approximately 90% of the water for use as recycled water or as makeup water for the primary desalinated water, thereby reducing the TDS level of the highly saline water to around 45,000 mg/L ； Thereafter, the reduced-concentration high-concentration water is subjected to evaporation crystallization to produce solid crystalline impurities, while the evaporated water is returned to the reduction system, thereby achieving full reuse of the water.