How challenging is water treatment in coal chemical industries?

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How challenging is water treatment in coal chemical industries? Author/Source: Date: 2016-02-17 Click-through rate: 28 Currently, China’s coal chemical industry stands at a crossroads in its development. On the one hand, since last year, the environmental impact assessments for many coal chemical projects have been rejected by the Ministry of Environmental Protection ； On the other hand, due to the decline in international oil prices, the economic viability of coal chemical industry has been greatly affected. In any case, for the coal chemical industry to develop, environmental protection is an issue that the industry cannot ignore; in particular, wastewater treatment has become a hurdle that coal chemical companies must overcome. Is there really an effective way to help the coal chemical industry solve its wastewater treatment problems? With profits shrinking significantly, can companies still maintain their investments in environmental protection? The reporter conducted a special investigation. Wastewater treatment is handled in a reactive manner. Xu Yanhua, dean of the School of Environment at Nanjing Tech University, was involved in a survey of coal chemical enterprises in four western provinces and regions organized by the China Petroleum and Chemical Industry Federation. He told reporters that the focus of this investigation is the environmental problems faced by the coal chemical industry. “After seven or eight days of research, the overall impression is that there are both positive aspects and concerns. It is gratifying that many coal chemical enterprises have made significant breakthroughs in the localization and scaling up of key technologies and equipment such as gasification and conversion. Some coal chemical industry clusters have carried out active and fruitful explorations in coal-power cogeneration, the development and expansion of coal-based products, as well as the complementary coexistence between coal chemistry and petrochemistry. The concern is that the industry faces severe environmental problems; water scarcity and water pollution have become key factors hindering its development. In the locations where some coal chemical projects are being built, there is a severe shortage of water resources on one hand, and the ecosystem is fragile with no remaining environmental capacity on the other. ”Xu Yanhua said. It is reported that many coal chemical enterprises also adopt a passive approach when it comes to water usage, water conservation, the reuse of treated wastewater, and near-zero emissions. Some enterprises claim in their summary reports that they have achieved zero discharge of wastewater; however, the actual treatment processes and the destinations of the reclaimed water remain unclear and indefinable, failing to stand up to scrutiny. Due to the lack of effective monitoring and regulatory mechanisms, it is difficult to determine the actual efficiency of wastewater treatment in enterprises, the rate of recycled water reuse, and the water consumption per unit of product, resulting in a concerning situation. Furthermore, the problem of pollution in the evaporation ponds affecting the Tengger Desert has also become a target of criticism. In the northwestern regions of our country, where evaporation rates are high, utilizing solar energy to enable the natural evaporation and concentration of wastewater can **save companies the costs associated with installing evaporation equipment as well as the operating expenses related to it. The purpose of establishing the evaporation ponds was to accommodate wastewater with low chemical oxygen demand and high salinity. For coal chemical projects that require large investments but yield relatively low returns, the use of evaporation ponds provides a practical solution for companies to treat high-salinity wastewater at low costs. Regrettably, some enterprises mistakenly use evaporation ponds as temporary wastewater storage areas or accident ponds, discharging large amounts of highly concentrated wastewater into them; in some cases, this has even led to environmental pollution incidents, completely going against the original purpose for which these evaporation ponds were approved for construction. As a result, some places have outright banned evaporation ponds and required companies to achieve absolute zero wastewater discharge. However, the occurrence of pollution incidents in evaporation ponds is due to various factors; the fault lies not with the evaporation ponds themselves. Inadequate monitoring and supervision, as well as insufficient supporting policies, are important causes. There are many challenges associated with near-zero emissions. \"True zero discharge of wastewater in coal chemical industries is not achievable, but near-zero emissions is still possible.\" ”Industry insiders said in interviews with reporters. Nevertheless, Xu Yanhua said that there are still many issues regarding near-zero wastewater discharge in current coal chemical projects. Firstly, the design of wastewater treatment and the design of the main processing processes are usually not carried out by the same entity, resulting in a disconnect between the design tasks and a lack of seamless integration. For a near-zero emission project, the wastewater treatment system should be highly integrated and coupled with the main production equipment. The water intake points, pollution generation points, reclaimed water reuse points, as well as sewage collection, treatment, and reuse should form an organic whole. Only by considering wastewater treatment and the main process design in an integrated manner and designing them simultaneously is it possible to achieve true near-zero emissions. Secondly, existing wastewater treatment processes generally suffer from problems in terms of specificity and effectiveness. Coal-to-gas (Ruhrgas or British liquid slag Ruhrgas gasifiers), coal-to-oil (direct liquefaction), and coal-to-coke projects generally generate toxic wastewater containing high concentrations of phenols and amines, and traditional processes involving simple pretreatment followed by biological treatment often fail to operate in a stable and effective manner. Even with complete subsequent membrane treatment and evaporation desalination facilities, it is difficult to achieve near-zero emissions. One of the prominent technical issues is the lack of necessary preprocessing. Once again, current wastewater treatment processes often suffer from technical fragmentation and low integration levels. Existing coal chemical projects are implemented in segments by multiple units, resulting in poor compatibility among the technologies of these various units, difficulties in effective integration, and a low level of integration overall. Some enterprises fail to properly separate pollutants from clean water, collect wastewater in a categorized manner, or treat it according to its different qualities; they focus on end-stage treatment while neglecting water conservation during the processing process. Gasification technology determines the difficulty of treatment. Hu Qianlin, deputy secretary-general of the China Petroleum and Chemical Industry Federation, emphasized that the waste gases and solid wastes generated by coal chemical industries are controllable, but wastewater – namely high-concentration, hard-to-degrade organic wastewater and highly saline wastewater – represents a challenge. If the problem of pollution in the coal chemical industry cannot be resolved, it will hinder the development of this industry. For example, in coal gasification, different gasification techniques result in varying levels of pollution, and accordingly, the measures required for pollution control as well as the difficulty of such control also differ. The most difficult-to-treat coal chemical wastewater is that generated from the gasification process using Ruhr gasifiers and from the production of coal-based semi-coke. Such wastewater often contains not only high concentrations of organic toxins, but also large amounts of oily substances and suspended solids (coal dust and coal powder). This frequently leads to scaling and clogging of phenol-ammonia recovery units, preventing the system from operating stably. Tang Hongqing, consultant at Sinopec Synthetic Oil Co., Ltd., told reporters that at the end of last year, relevant personnel from several coal chemical enterprises met in Shanghai to discuss the issue of wastewater treatment in the coal chemical industry. In reality, the discussion centered on treating wastewater generated by the Lurgi gasification process. This type of wastewater is extremely difficult to treat, as it contains phenols and tar. “In fact, not all coal chemical enterprises have severe wastewater treatment problems. Companies like Yitai Coal-to-Oil, which use water-coal slurry gasification, have done an excellent job in wastewater pretreatment. By further employing ion exchange membranes in the final treatment stage, along with measures such as multi-effect evaporation, it is possible to achieve discharge levels that meet regulatory requirements, resulting in very little wastewater that actually needs to be discharged. The reason companies need to discuss this is mainly because there are several coal-to-natural gas plants that use the Lurgi gasification process. Such as the coal-to-natural gas project in Datang Keqi, etc. ”Tang Hongqing said. Tang Hongqing analyzed that, from the perspective of current technology, even if everyone discusses it together, no conclusions will be reached. Because for this type of toxic wastewater containing high levels of oil and concentrated phenols and ammonia, there is still no more feasible technology to completely treat it. Tang Hongqing told reporters that some coal chemical enterprises chose the Lurgi furnace process route when building their plants, and this decision was problematic in itself. But this is not a company’s problem, and the companies cannot be blamed. Because they were not aware at the time of building the factory that this process would lead to serious consequences. Now that the factory has been built, the sewage problem has arisen. It’s not possible to spend another 20 billion yuan to dismantle this furnace and replace it with a new one; that would be equivalent to building a new factory from scratch. “For new enterprises, rather than trying to deal with this problem, it is better to start at the source and prevent such wastewater from being generated, that is, by not using the Lurgi process. Furthermore, coal should be used wisely; lignite should no longer be employed in coal chemical industries. Companies can use bituminous coal and fluidized bed processes to produce coal chemical products, thereby avoiding the generation of wastewater containing phenols and tar, and thus solving the problem. Even if lignite must be used, every effort should be made to make it suitable for pulping; it is worthwhile despite the relatively high energy consumption. Overall, the wastewater problem in the coal chemical industry is not serious. However, at present, there is no way to treat 100% of the wastewater generated by the Lurgi furnace process. ”Tang Hongqing emphasized. Insufficient investment hinders near-zero emissions. Yang Chuanwu, vice president of China National Chemical Engineering Group Corporation, told reporters that the issue of wastewater treatment in coal chemical industries is essentially a matter of investment. To treat wastewater thoroughly and achieve near-zero emissions, investment is required. Now, **the environmental requirements for coal chemical industries have increased, but some projects that are under construction or have already been completed were built in accordance with the old standards; they certainly would not meet the new standards. If a company fails to meet the standards and is required to add more facilities, it will have to spend money, which will affect its economic efficiency to some extent. Currently, the economic viability of the coal chemical industry has been greatly affected by falling oil prices; it is very difficult for companies to invest in technologies that achieve zero or near-zero emissions. Only if there are mandatory requirements imposed by **the authorities at the local level**, or if certain policy-based subsidies are provided to enterprises, can their burden be reduced. But if companies are left to handle it on their own, the profitability of coal chemical industries is already low; adding more costs will further remove any incentive for them to proceed. Furthermore, there is no mandatory requirement for companies to do this, and the costs involved are relatively high, making it difficult to promote emission reductions. “Now I think the main bottleneck in wastewater treatment for coal chemical industries is not technology, but rather funding issues. Now that the emission standards have been raised, and unlike the previous basic treatment methods, in order to meet these new standards, companies must also incur higher costs for the ‘final stage’ of wastewater treatment, resulting in an unproportional cost-benefit ratio. For enterprises, whether state-owned or privately owned, it is essential to prioritize efficiency above all else. Therefore, **some mandatory requirements should be introduced to intervene with these investors. ”Yang Chuanwu emphasized. Yang Chuanwu suggested that, first and foremost, controls should be implemented at the source: conducting proper environmental acceptance checks and increasing the proportion of environmental protection investments by enterprises. If an enterprise fails to pass the environmental protection inspection, it must absolutely not be allowed to commence production; this loophole must be plugged. Otherwise, once the enterprise starts production, it will be difficult to stop it. Even if a company’s emissions do not meet the standards, it can only be forced to continue operating. He definitely can’t go any further back; the investment would exceed the budget. Therefore, it is necessary to ensure that environmental protection measures are incorporated from the initial design and construction phase of enterprises, so as to meet the new environmental standards; this will make subsequent emission control easier. Instead of building first and then attempting to modify and upgrade it once the standards are not met, this approach would result in significantly higher costs for the company. Secondly, **the fines should be reinvested in those companies that proactively practice environmental protection. The current situation is that companies are fined whenever their emissions do not meet the standards, and all such fines are deposited in the state treasury. Creating a blockage is a passive approach that does not achieve the goal fundamentally. For example, many companies do not carry out discharges during the day but do so secretly at night, or they discharge only once a week while stopping for five or six days; fines are not sufficient to put an end to such practices. True resolution lies in raising enterprises’ awareness, making them understand the consequences of pollution, so that they will proactively handle wastewater properly. Yang Chuanwu hopes that **the fines collected will be awarded to enterprises that conscientiously engage in environmental protection and carry out renovation and improvement efforts, rather than being turned over to the state treasury.** Otherwise, companies will be unwilling to bear the costs associated with pollution control; **they really don’t want to do so, and this is not conducive to the development of the entire environmental protection industry. But if the fines can be reinvested in these companies, they will feel that \"by taking environmental actions, I not only get paid but also fulfill my social responsibilities,\" which can help achieve the desired environmental outcomes. Xu Yanhua suggested that pollution incidents at evaporation ponds are closely related to inadequate monitoring and supervision, as well as unsupportive policies. Wastewater with truly low chemical oxygen demand, low toxicity, and high salinity in evaporation ponds generally does not pose a serious threat to the ecological environment. Therefore, a one-size-fits-all approach to evaporation ponds has certain issues in terms of scientific validity, rationality, and practical feasibility. The key is to strengthen monitoring and supervision to ensure that the water quality and quantity of wastewater discharged into the evaporation ponds meet the specified requirements. Furthermore, appropriate supporting policies should be introduced: enterprises that discharge pollutants in excess of the allowed limits should be subject to higher pollution fees or penalties, while those that meet the emission standards should receive corresponding subsidies and incentives. At the same time, a tiered pricing system should be implemented for enterprises’ fresh water consumption based on the approved standard levels. Such measures will help to address the current situation in coal chemical enterprises, where there is an abuse of evaporation ponds, resulting in a lack of pressure and motivation to save water and reduce emissions. Furthermore, to achieve water conservation and emission reduction, it is also necessary to optimize the entire process of wastewater treatment, apply principles of systems engineering, actively introduce the \"water pinch point\" technology, and vigorously promote the hierarchical use of water as well as its recycled use based on different quality levels. On this basis, a plant-level water balance is established, a reclaimed water island is built, and flexible scheduling of recycled water throughout the plant is achieved.