Osmotic reverse osmosis technology: a powerful tool for achieving zero discharge of coal chemical industry wastewater

Thread Content

Osmotic reverse osmosis technology: a powerful tool for achieving zero discharge of coal chemical industry wastewater. Author/Source: China Chemical Industry News. Date: December 23, 2015. Clicks: 11. The BOT project related to the supporting facilities and relocation projects in the Qingxu Chemical New Materials Park of Yangmei Group – namely, the concentrated brine treatment unit for boiler make-up water and the No. 1 evaporation crystallization treatment unit – was officially launched not long ago. The main process flow of this project is: water intake storage — softening — tubular microfiltration — secondary softening — reverse osmosis concentration — forward osmosis MBC concentration — evaporation crystallization. Thus, forward osmosis zero-discharge technology was introduced for the first time in the field of water treatment for coal chemical industries. The first pilot-scale seawater concentration unit using osmotic pressure technology in Huanghua, Hebei. 　　The Yangmei Chemical New Materials wastewater zero-discharge project is a zero-discharge initiative registered with the Ministry of Environmental Protection; it can serve as a reference for other coal chemical enterprises in the future, holding great significance as a model. So, why do companies adopt forward osmosis technology? What is forward osmosis technology? With doubts, the author conducted an on-site investigation. 　　Zero discharge treatment of coal chemical wastewater is an urgent necessity. According to relevant experts, developing the coal chemical industry is an inevitable path for China’s energy strategy transformation, as determined by the country’s current energy resource situation and the broader context of the energy revolution. In our country, coal resources and water resources are distributed in an inverse pattern. Taking the four provinces and regions of Shanxi, Shaanxi, Ningxia, and Inner Mongolia in the middle and upper reaches of the Yellow River as an example, these areas account for 67% of the country’s total coal resources. Due to their abundant coal resources, many coal chemical projects have been planned in these provinces in recent years; however, the water resources available there constitute only 3.85% of the country’s total water resources. Furthermore, coal chemical production generates large amounts of saline wastewater, and in conventional wastewater treatment processes, salts cannot be degraded. At present, the salt content accumulation in the Yellow River basin has approached the ecological red line. If strict controls are not implemented and zero emissions are not required, as coal chemical projects develop in these areas, environmental conflicts will become very severe, making ecological management in the Yellow River basin even more difficult. Oasys Company’s shale gas project in the Permian Basin is the world’s first to utilize forward osmosis membrane technology. 　　“At present, the shallow groundwater is the most vulnerable to pollution. Due to the widespread contamination of surface water, shallow groundwater becomes polluted quite frequently as well. In the north, over-extraction of groundwater is quite severe, resulting in large-scale loss of groundwater. Since the groundwater level is significantly lower than that in the surrounding areas, a funnel-shaped zone is formed; under pressure, surface water from the surrounding areas flows into this area, which makes the groundwater more susceptible to pollution. The pollution of drinking water sources is difficult to eliminate using traditional water treatment processes. ”Ma Jun, director of the Center for Public and Environmental Research, said. 　　To this end, in recent years, to promote the coordinated development of the industrial economy and water resources as well as the environment, **relevant authorities have issued a number of policies and regulations. 　　In 2005, the **National Development and Reform Commission and the Ministry of Science and Technology, in conjunction with the Ministry of Water Resources, the Ministry of Construction, and the Ministry of Agriculture, formulated and issued the \"Outline of China’s Water Conservation Policy,\" which called for the development of technologies for reusing wastewater and achieving zero discharge. Encourage and support the reuse of treated waste (polluted) water discharged by enterprises, and vigorously promote the technology for reusing such treated water in closed-loop cooling water systems. In areas facing water shortages and high environmental requirements, companies are encouraged to adopt zero-waste wastewater treatment technologies. Around 2006, **the prerequisite set by the National Development and Reform Commission for approving demonstration projects in modern coal chemical industry was that enterprises had to commit to zero emissions; otherwise, it was difficult to obtain approval for the environmental impact assessment of such projects. Ceremony to mark the start of the BOT project for the boiler make-up water brine concentration treatment unit and Unit 1 evaporation crystallization treatment unit, as part of the supporting infrastructure and relocation projects in Yangmei Group’s Qingxu Chemical New Materials Park. 　　With increasingly stringent environmental protection policies and standards, companies that launched coal chemical projects in the western regions in previous years have faced repeated obstacles in site selection and project approval, ending up in a difficult situation. Since the beginning of this year, the environmental impact assessment reports for Jiangsu Su New Energy’s 4 billion cubic meter coal-to-natural gas project, Ili Xintian’s 2 billion cubic meter coal-to-gas project, and Shanxi Lu’an’s coal-to-oil project have been rejected by the Ministry of Environmental Protection one after another, causing a stir in the industry. The reasons for the rejection of the environmental impact assessment mostly relate to the long-standing environmental issues associated with coal-to-gas production, namely water resource utilization and wastewater treatment. All issues boil down to one thing – whether zero emissions can be achieved. 　　“In 2008, GB/T21534-2008 \"Terms for Water Conservation in Industrial Water Use\", issued by the General Administration of Quality Supervision, Inspection and Quarantine, defined zero discharge as a situation in which the production water system of an enterprise or operational unit generates no industrial wastewater that is discharged outside. It can be understood that zero emissions mean concentrating industrial wastewater into solid or concentrated form for further treatment, rather than discharging it in wastewater form into natural water bodies. Currently, domestic zero-waste wastewater treatment projects generally require substantial investment and high costs. ”Guo Youzhi, secretary-general of the Desalination Branch of the China Water Resources Society, gave an example: the coal-to-oil project of Shenhua Group Co., Ltd., the first such project in China to have been built yet not to achieve true zero wastewater discharge, invested 1.34 billion yuan in environmental protection measures, accounting for 10% of the total project cost. During the trial operation period, the cost of treating each ton of organic wastewater exceeded 5 yuan, while the cost of treating each ton of saline water was over 38 yuan. 　　Demonstrations of forward osmosis technology applications have been carried out in multiple fields. “Traditional treatment technologies for coal chemical industry wastewater have drawbacks such as high investment costs, elevated operating expenses, and unstable system performance.” Forward osmosis technology is a groundbreaking new technology developed in light of the current state of the zero-discharge field. ” Li Suqing, technical director of Colek Environmental Resources Technology (Beijing) Co., Ltd., explained that osmotic process technology makes use of the natural phenomenon of osmosis; through semipermeable membranes created through chemical polymerization, water molecules naturally diffuse from liquids with lower salt concentrations to those with higher salt concentrations due to the difference in osmotic pressure, without the need for external equipment such as high-pressure pumps to provide the driving force for separation. Furthermore, this technology causes relatively less contamination of the membrane, allowing the permeation membrane to operate for extended periods without the need for cleaning, thereby resulting in significant reductions in investment and operating costs. Huaneng Changxing Waterlet forward osmosis equipment. 　　It is understood that the shale gas project of the American company Oasys in the Permian Basin is the world’s first to utilize forward osmosis membrane technology. This technology treats high-salinity wastewater from the petrochemical industry, achieving zero discharge. The treated water meets the quality standards for drinking water. In 2013, Beijing Water Technology Co., Ltd. invested in the American company Oasys Water and introduced positive osmosis membrane treatment technology to China. By combining this technology with the company’s own lime coagulation and clarification methods, it developed a unique solution for achieving zero discharge of industrial wastewater with high COD levels and high salt content. 　　Since then, there have been two technical approaches for zero discharge of high-salt wastewater in China: one is lime softening + forward osmosis membrane concentration + crystallization drying ； Another method is lime softening + evaporation + crystallization drying. There are currently demonstration projects for these two technical approaches in coal-fired power plants in China; Huaneng Changxing Power Plant uses the forward osmosis + crystallization technology, while a power plant in Guangdong employs the conventional evaporation + crystallization process. 　　“The biggest difference between these two technical approaches is that traditional evaporation crystallization technology has high energy consumption, while forward osmosis membrane concentration technology has relatively lower energy consumption. ”Li Suqing explained that the evaporation crystallization process involves using evaporators to concentrate wastewater to a salt content of around 15%; the highly concentrated saline solution is then converted into solid salt through crystallization and drying for disposal. Since the evaporator converts wastewater into water vapor through phase change and then recovers water after condensation, a large amount of steam is required to vaporize the wastewater; in this process, the wastewater undergoes 100% phase change, which results in high energy consumption. For instance, in a zero-discharge demonstration project at a power plant in Guangdong, the operating cost of using this technology amounts to 180 yuan per ton of wastewater. The forward osmosis membrane concentration process draws water molecules into the extract; without the need for large amounts of steam or electricity, it is possible to increase the salt content of wastewater to around 25%. The gas-water separation in the extract occurs at a lower phase transition temperature compared to that in the wastewater, accounting for only 1/3 of the wastewater volume. This reduces both the amount of water that needs to be processed in the crystallizer and the energy consumption. For example, the operating cost for Huaneng Changxing Power Plant to use this technology is 45 yuan per ton of wastewater. 　　Additionally, the forward osmosis membrane has high resistance to impact loads, and its operation and maintenance are simple. The evaporation crystallization process relies on steam for heating; a cooling cycle is required before shutting down, while a large amount of steam is needed for preheating before starting up. The entire start-up and shutdown process is complex to operate ； The forward osmosis membrane concentration process can automatically adjust the concentration ratio based on the salt content in the wastewater, thereby ensuring the appropriate salt content in the crystals. It requires no complex operating procedures for starting or stopping, allowing for one-click operation. 　　According to Shao Guohua, the technical supervisor at Huaneng Changxing Power Plant, the plant’s zero-discharge system for desulfurization wastewater with a capacity of 22 cubic meters per hour utilizes forward osmosis membrane treatment technology; as a result, 18 tons of desulfurization brine per hour can be concentrated to 3–4 tons. The wastewater is reused 100%, and all pollutants in it can be separated in the form of crystals and sludge. Moreover, during operation, the consumption of steam, chemicals, and electricity **decreases**. For example, the energy consumption required to treat one ton of wastewater is reduced from 20–40 kilowatt-hours in the traditional evaporation-crystallization method to 10 kilowatt-hours, resulting in a 30% reduction in operating costs. It is estimated that the company can recover 180,000 tons of high-quality fresh water per year, producing around 2,000 tons of industrial-grade salt suitable for sale, thereby achieving a win-win situation in terms of social benefits, environmental protection, and economic benefits. 　　Furthermore, osmotic reverse osmosis technology has also demonstrated its potential application value in the field of seawater desalination. Currently, the first pilot-scale osmotic desalination unit using positive osmosis technology, established in Huanghua, Hebei, has been put into operation, providing reliable operational data for the research activities in the seawater desalination and comprehensive utilization laboratory. 　　It is understood that osmotic reverse osmosis technology can increase the water production rate from desalination from 40% with current technologies to 85%, while also raising the concentrations of bromine, magnesium, and potassium in the concentrated brine. This facilitates the extraction and utilization of these resources, significantly reduces the operating costs of desalination, and minimizes environmental pollution caused by highly saline water. Its energy consumption is 70% of that of current desalination technologies. 　　Creating a model project for zero-emission coal chemical processing: It is based on these successful application examples that the wastewater treatment project in Yangmei Group’s Coal Chemical New Materials Park has chosen osmotic reverse osmosis technology. 　　Li Kai, the chief engineer of the Adipic Acid Branch responsible for the construction of the wastewater treatment project in the Yangmei Chemical New Materials Park, explained that the design capacity of the brine treatment unit for boiler make-up water in this park is 50 cubic meters per hour, with the output water being concentrated to 5 cubic meters per hour ； The required quality of the effluent water is a TDS level of over 2.4×105 ppm, while the reclaimed water must meet the quality standards specified in **GB/T19923-2005 “Quality Standards for Industrial Water Using Recycled Urban Sewage Water”** for water intended to be used as make-up water in open-loop cooling systems. The New Materials Zero-Emission Project has pledged to the **Ministry of Environmental Protection to build a model project for zero emissions in the coal chemical industry. The Ministry of Environmental Protection stated that after the plant is completed and put into operation, it will organize a meeting with representatives from the coal chemical industry here; therefore, the company has very high requirements regarding the selection of zero-emission technologies. 　　“Osmotic zero-discharge technology is one of the most cutting-edge technologies in the world today, and it is also the only technology available that can concentrate highly saline water with a TDS level of over 5×104 ppm to a level above 2.4×105 ppm. This is an important reason why we are optimistic about forward osmosis technology. The second reason is the industry’s recognition of forward osmosis technology. Oasys Water (a company in which Beijing Water Technology Co., Ltd. has made an investment in the U.S.) was awarded the ‘Best Water Technology Company of 2014’ prize by Global Water Intelligence magazine’ ； The Permian Basin project won the ‘2014 Global Best Engineering Award’ for its revolutionary positive osmosis membrane concentration (MBC) technology’ ； In 2014, this technology was identified by the China Petroleum and Chemical Industry Federation as a key technology for environmental protection in the coal chemical industry ； The zero-discharge technology for lime coagulation-sedimentation and forward osmosis concentration treatment of wastewater developed by Beijing Watertech Co., Ltd. has been recognized as a new technology and new product (service) in Beijing... Thirdly, there’s its performance within the industry. The zero-discharge project for flue gas desulfurization wastewater at the Huaneng Changxing Power Plant, which has already been put into operation in China; the zero-discharge project for flue gas desulfurization wastewater at the Shenhua Wangqu Power Plant, currently under design; as well as several successful implementation examples in the United States. Our company has boldly adopted osmotic pressure technology, believing that this technology can also create miracles in achieving zero discharge of wastewater from coal chemical industries, and thus develop model projects for zero-discharge operations in such industries. ”Li Kai said. 　　“Osmotic reverse osmosis technology makes use of the increasingly mature pre-treatment and pre-concentration techniques to improve existing evaporation-crystallization zero-discharge technologies. It enables the reuse and high-rate concentration of coal chemical wastewater without relying on evaporators, thereby significantly reducing investment and operating costs and meeting the demands of market development. Furthermore, relying on its forward osmosis zero-emission laboratory and R&D center, the company is able to develop customized zero-emission technology solutions for coal chemical enterprises. Through pilot tests and scale-up trials, these solutions can ultimately be applied in actual production, thereby significantly reducing the risks associated with their implementation. Currently, dozens of enterprises in industries such as coal chemical processing in China have shown great interest in forward osmosis technology. Moreover, the company’s various business models, including EPC, BT, BOT, and PPP, will also be an important factor contributing to the rapid adoption of this technology. ”Gao Feiyi, General Manager of Colek Environmental Resources Technology (Beijing) Co., Ltd., said. 　　Yang Huaheng, the chief marketing officer of Beijing WaterTech Co., Ltd., said with confidence: \"Osmosis technology is very popular at the moment, and it will become even more popular in the future.\" Because it meets the requirements of the development of **environmental protection policies, and satisfies the needs of industries such as coal chemical processing for wastewater reduction, resource utilization, and zero emissions.