【Haichuan Chemical Salary Updates】The Difficulties in Coal Chemicals: The Hidden Challenges Related to Salts and the Environmental Issues of the \"Last Kilometer\"

Reporters have learned from industry sources that the number of coal-based chemical projects that actually achieve \"salt separation\" is currently in the single digits. As **requirements for the disposal of hazardous waste become stricter, the hidden problems faced by the coal chemical industry need to be addressed urgently. “The \"last mile\" environmental challenge: Where do mixed salts come from? This is closely related to the high water consumption \"nature\" of coal chemical projects. On the one hand, the water used for operation contains salts, and the vaporized wastewater and condensed water discharged contain a certain amount of various salts naturally ； On the other hand, the high-salt wastewater generated in some stages due to the addition of catalysts, chemicals, and other reagents contains large amounts of various impurity salts. The miscellaneous salts produced as by-products of coal chemical processing did not initially receive sufficient attention. Yu Bin, president of Botian Environmental Design Institute, told reporters that when new coal chemical projects emerged in 2008, the concept of \"zero emissions\" did not exist; wastewater could be discharged after meeting the required treatment standards, and there was no issue with residual salts. “In recent years, **environmental regulations have become increasingly stringent, and coal chemical projects have begun to focus on achieving ‘near-zero wastewater discharge’. This is a process that involves a long sequence of steps, presents high technical challenges, and features a complex system; any issue within one of these components can affect the overall results. Therefore, true ‘near-zero emissions’ encompass not only the recycling of wastewater but also take into account high-salinity wastewater that is difficult to reuse. ”

In December 2015, the former Ministry of Environmental Protection issued the \"Environmental Access Requirements for Modern Coal Chemical Industry Projects (Trial)\\", which explicitly stated at the policy level that \"effective measures must be taken to deal with high-salinity wastewater, so as to prevent pollution of groundwater, air, soil, etc.\"”； By-product salts that cannot be recycled are temporarily managed as hazardous waste. Coal chemical projects that obtained environmental approval after 2016 have begun to explore routes for the recycling of mixed salts. In response to this, Liu Zhixue, a member of the Special Committee of the Petrochemical Federation and an environmental protection expert, pointed out that some enterprises and regions have proposed so-called \"zero wastewater discharge\" solutions in order to promote the implementation of coal chemical projects. However, the pilot projects that have been put into operation all face issues such as poor wastewater quality, unstable operating systems, and high treatment costs; moreover, the crystallized impure salts are stored in an unorganized manner, posing significant environmental risks. “When formulating the \"Environmental Access Requirements for Modern Coal Chemical Industry Projects (Trial)\\", sufficient consideration was given to future possibilities for technological advancement, in order to provide technical pathways for the recycling of salt resources. ”On this basis, some companies took the lead in attempting salt separation and crystallization techniques, enabling the crystallized salts, which are temporarily classified as hazardous waste, to be repurposed as resources. It can be said that how to truly achieve resource-based disposal is the ‘last mile’ challenge in the environmental protection of coal chemical industries at present.

There are many technical challenges and the systems need improvement; the disposal of mixed salts presents difficulties in various aspects. The reporter learned that there are reasons related to salt itself, as well as external challenges such as current technologies and systems. High yield and complex composition – these are the primary challenges that need to be addressed when dealing with mixed salts. “A coal-to-olefins project with a capacity of 600,000 tons per year, producing 30,000–50,000 tons of salt annually ； A coal-to-natural gas project with a capacity of 4 billion cubic meters per year, producing 50,000 to 80,000 tons of salt annually. This means that for each coal chemical project, tens of thousands of tons of miscellaneous salts need to be disposed of each year. ”**Xiong Rihua, director of the water treatment platform at the Beijing Low-Carbon Clean Energy Research Institute of the Energy Group, gave an example. Due to their complex composition, it is difficult to recycle mixed salts; \"even in the best cases, only 70%-80% of them can be reused, with the remaining part still being mixed salts for which there is currently no effective treatment method.\" ”

“To achieve zero emissions, many projects opt to build ‘evaporation ponds’, allowing water to evaporate naturally first and then storing the remaining salt. It has low costs and a simple manufacturing process, but it also has disadvantages such as large space requirements and limited durability. Some companies have lax management, which even leads to new problems such as leaks. ”Yu Bin explained that the evaporation ponds were abandoned in favor of a \"crystallization\" technique, which involves extracting impure salts in crystalline form through methods such as concentration and distillation. After the mixed salts crystallize, they are piled up for storage as required or further processed. Xiong Rihua said that the latter refers to the purification of sodium chloride and sodium sulfate present in mixed salts to produce reusable industrial salts; the most common method used at present is called \"salt separation crystallization\". “However, due to the complexity of the post-treatment process, the technology not being fully mature yet, as well as high additional investment and operating costs, industrial application has not been achieved at present. ”

In addition, there are also deficiencies at the institutional level. The environmental protection officer in charge of the aforementioned coal chemical project admitted that although mixed salts are classified as hazardous waste, there are no clear guidelines for their disposal. “A series of issues remain unclear, such as the criteria for processing, whether purification is necessary, and how to sell the products after recovery. Due to the lack of specific disposal standards for the coal chemical industry, it is necessary to temporarily rely on industrial salt standards; however, the two are not identical, which inevitably leads to confusion in the processing process. ”

Reduction and resource utilization are the directions. Once the challenges have been identified, how can coal chemical enterprises overcome these difficulties? “The approaches being discussed now basically start from the end. If considered at the source, salt production can be reduced from the beginning, which will effectively ease the burden of subsequent treatment. ”Yu Bin suggested that rather than investing a great deal of effort and resources in dealing with salt, it would be better to optimize production processes so as to use less salt during manufacturing; less salt being emitted means less need for treatment. Liu Zhixue agreed with this view; the front-end process should use \"less salt\" while meeting the process requirements, and at the same time ensure proper coordination and communication between upstream and downstream processes. “For high-salinity water treatment, it is necessary to identify the core technologies, optimize and integrate them through repeated testing and verification, and explore new ways to reduce the amount of impurities in the saltwater. ”At the same time, wastewater treatment in the coal chemical industry involves multiple stages and various technologies. On the one hand, it is necessary to focus on optimizing and coordinating the entire process, by collecting wastewater in a categorized manner and treating it according to its different qualities, thereby reducing the burden on downstream treatment facilities ； On the other hand, systematic consideration should be given to the efficient use of water; the water pinch point theory should be applied to make use of water just as effectively as steam, increase its reuse rate, and minimize wastewater discharge.

Xiong Rihua’s focus is more on how to reduce costs, improve the quality of crystalline salts, and increase the rate of resource utilization. He said that in coal chemical projects where salt separation by crystallization has been achieved, the recovery rate of crystallized salts is generally in the range of 50%-60%; if this efficiency can be increased to over 80%, the costs associated with dealing with impure salts are expected to drop further. “In other words, it is necessary to determine how much product can be obtained per ton of inorganic salts; the higher the yield, the less residual salt waste there will be, and thus the lower the potential environmental impact. ” It is also understood that the Ministry of Ecology and Environment has recently placed standard-setting on its agenda – two draft standards, namely \"Sodium Chloride as a By-product of Coal Chemical Industry\" and \"Sodium Sulfate as a By-product of Coal Chemical Industry\", have entered the expert evaluation stage as part of the first batch of regulations to be established.

The salt separation and crystallization process currently has industrial-scale facilities in projects such as Shenhua Baotou Coal Chemical, Shenhua Yulin Coal Chemical, and GCL Xinjiang Polysilicon.

The disposal of high-salt wastewater is a global challenge. In China, more than 300 million cubic meters of such wastewater are generated each year, resulting in over 10 million tons of high-salt hazardous waste. Most of this waste is not properly disposed of, placing significant strain on the ecological environment. In the interviews, industry experts generally agreed that at present, there are no economical or systematic methods for dealing with high-salt wastewater, and the by-products generated during treatment are difficult to identify; moreover, the waste salt is often treated as hazardous waste, preventing its economic value from being maximized. Lack of core technologies: High-salinity wastewater refers to wastewater that contains organic substances and has a total dissolved solids (TDS) content of more than 3.5% by mass. This is because such wastewater contains not only organic pollutants but also a large amount of soluble inorganic salts. Salt-containing wastewater in our country accounts for over 5% of the total amount of wastewater generated, and its volume continues to increase at a steady rate. Wu Gang, deputy director of the Technology Department of the China Chemical Industry Environmental Protection Association, said that high-salt wastewater is primarily associated with fine chemical industries such as those producing pesticides, dyes, and pharmaceutical intermediates, as well as with the coal chemical and refining industries. The wastewater from these industries contains complex components, making it difficult to treat; this leads to significant water pollution problems. In particular, effective and economical treatment methods have long been lacking for specific pollutants.