Not long ago, Shanxi Jincheng, a key coal chemical base in China, held a special meeting to promote the implementation of zero-emission wastewater processes across its coal chemical enterprises. This move has sparked widespread interest: can the coal chemical industry truly achieve zero wastewater discharge? To find out, reporters conducted an in-depth investigation.
Water is a critical resource for coal chemical projects, and the Shangma Coal Chemical Project is no exception. It not only consumes large amounts of water but also produces significant volumes of wastewater. For instance, producing one ton of methanol requires 10–15 tons of water, and a plant with an annual output of 200,000 tons generates 100 tons of wastewater per hour. A "18·30 project" (producing 180,000 tons of synthetic ammonia and 300,000 tons of urea) recycles 20,000 cubic meters of water hourly. Meanwhile, a dimethyl ether plant producing 10,000 tons annually uses 8,000 tons of water daily. According to data from Jincheng City, as of last year, the city had an annual capacity of 2.92 million tons of urea and 380,000 tons of methanol. By 2010, this was expected to grow to 6 million tons of urea, 2 million tons of methanol, 400,000 tons of dimethyl ether, and 100,000 tons of coal-based oil. As the scale of these projects expands, so do the challenges to the local water environment.
The Dan and Yan Rivers, two major waterways in the city, are already at saturation levels, with the Dan River exceeding its environmental carrying capacity. If all coal chemical companies in Jincheng implement zero-waste-water discharge, they could save up to 1 billion cubic meters of cooling water annually—equivalent to the volume of water transferred through the South-to-North Water Transfer Project to Beijing by 2010.
In fact, the National Development and Reform Commission had already encouraged water-saving technologies and wastewater reuse as early as 2006, aiming to promote sustainable development in the coal chemical industry.
According to experts, achieving zero wastewater discharge requires addressing desalination first. While the treated wastewater meets environmental standards, it still contains salts like NaCl, Na₂SO₄, CaCl₂, MgSO₄, and MgCl₂. These salts remain dissolved and do not evaporate, leading to scaling, corrosion, and sludge buildup if reused directly. Desalination is essential, but it comes at a high cost. For example, a methanol plant producing 200,000 tons annually would need at least 3 million yuan in investment, with treatment costs reaching 2–3 yuan per ton of water—higher than the price of fresh water. Many companies are reluctant to invest due to economic concerns.
Even after desalination, only 60–70% of water can be reused, leaving 30–40% as concentrated brine that must be discharged. Experts warn that improper handling of this brine can cause severe equipment damage and environmental issues. Some companies use the concentrated water for coal and ash humidification, but such usage is limited by weather and conditions. In winter, less water is needed, making full utilization difficult. Excess waste water often ends up being discharged into the environment, potentially causing soil salinization.
To truly achieve zero wastewater discharge, experts suggest focusing on source control, improving water efficiency, and minimizing waste. Treated wastewater should be processed through membrane concentration to recover fresh water for production, while the remaining brine can be partially recycled or used for non-critical purposes. Any excess that cannot be reused should be treated further—through pretreatment, evaporation, and salt removal—before being released. This comprehensive approach represents the most effective path toward true "zero discharge."
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