The challenge of brown coal gasification solved with a “spaceflight approach””

Thread Content

The challenge of lignite gasification solved through a “space technology approach” Author/Source: Sinochem News Network Date: 2019-09-25 Clicks: 57 On September 3, Aerospace Changzheng Chemical Engineering Co., Ltd. (referred to as Aerospace Engineering) announced the results of research on clean and efficient conversion technologies for lignite using space-related furnace technologies in Songyuan City, Jilin Province. This technology was first applied to the urea expansion project at Sinochem Jilin Changshan Chemical Co., Ltd. (referred to as Sinochem Changshan), where it achieved excellent operational results, providing a solution to the challenge of processing large quantities of low-quality coal resources on a large scale. After visiting the site and engaging in in-depth discussions, the delegates from various parts of the country gained a thorough understanding of this technology. They concluded that it requires low investment, has a short implementation process, and can operate stably over long periods of time, making it highly valuable and promising for widespread adoption. Untitled2.png shows the scene of the presentation on the results of the assessment. Given China’s resource profile, characterized by abundant coal, limited oil, and scarce gas, as well as the fact that renewable energy accounts for only a small proportion of the total energy supply, coal will remain the primary energy source in China for a long time to come. Although our country is generally rich in coal, the quality of this coal is not always satisfactory. Low-grade coals, including lignite, high-sulfur raw coal, and high-ash raw coal, account for about 40% of the total coal resources in the country. 　　To date, the proven reserves of lignite across the country amount to approximately 130 billion tons, accounting for 13% of China’s total coal resource reserves. It is mainly found in regions such as eastern Mongolia, Heilongjiang, and Yunnan, where resources are abundant and extraction costs are low. Promoting the local conversion and utilization of lignite in these areas is an important approach to implementing the energy security strategy and fostering sustainable economic and social development in those regions. 　　Lignite, being the coal with the lowest degree of coalification, has a low carbon content and high hydrogen and oxygen contents. It features high levels of moisture and volatiles, a wide range in ash fusion properties, low calorific value, poor thermal stability, and high reactivity. Compared to bituminous coal and anthracite, it differs significantly in quality whether used as fuel coal or as raw material coal, and it is also more difficult to process in a clean and efficient manner for resource utilization. For this reason, the development and utilization of lignite in China are not sufficient at present, and it is common for lignite resources to remain underutilized or to be used in a suboptimal manner. 　　How to effectively develop and utilize lignite resources has become one of the key strategies for improving the utilization rate of coal resources in China and for more effectively implementing the energy security strategy. It is also an important aspect of the supply-side structural reforms in the coal and deep-processing industries, and it has remained a focus of attention in the energy sector in recent years. 　　Wang Xianzheng, honorary president of the China Coal Industry Association, explained that, considering transportation safety and economic efficiency, the use of lignite is closely related to its effective utilization radius; therefore, on-site processing and conversion are essential. There are two approaches to the in-situ conversion of lignite: power generation and coalification integration. Relatively speaking, through the coal gasification furnace as a conversion medium, the integrated coal chemical process enables coal to shift from being primarily a fuel to serving both as a fuel and a raw material, and to transform from a traditional energy source into a clean energy source. It allows for the production of oil, gas, olefins, as well as coal-based chemicals and new coal-based materials; thus, it offers a huge market potential along with improved economic benefits. 　　Zhu Yuying, deputy general manager of the aerospace engineering company, pointed out that there are four main technical challenges associated with lignite gasification: first, the high reactivity leads to intense combustion, resulting in high thermal stress at the burner tip; second, the low stiffness of the flame makes it easy for the flame to touch the wall of the burner; third, the high content of volatiles poses significant safety and environmental issues during drying and transportation processes; fourth, the physical and chemical properties of lignite powder differ, leading to problems in matching the upstream and downstream processes. 　　Changshan makes its debut with impressive operational performance. Located in Songyuan City, Jilin Province, Sinochem Changshan has a production capacity of 600,000 tons per year of urea, 250,000 tons per year of compound fertilizers, and 3,000 tons per year of refined morpholine; it also produces by-products such as liquid oxygen, liquid nitrogen, and liquid argon. 　　The Sinochem Changshan urea expansion project involved the construction of a new urea production facility with an annual capacity of 300,000 tons. This facility consisted of units for air separation, gasification, purification, ammonia synthesis, and urea production. Work on this project began in 2009, construction started in 2013, it was completed in July 2015, and synthetic ammonia production commenced in October 2015. Its gasification unit uses advanced space-based lignite conversion technology to produce crude syngas, marking the first application of this technology in the field of lignite gasification. 　　Zhou Qihang, director of the gasification workshop at Sinochem Changshan, explained that the drying process for this gasification unit employs the \"drum pre-drying\" technology. The gasification process adopts the technical approach of \"top-mounted single burner + pressurized coal gasification + downward water quenching,\" which enables the conversion and utilization of a wide range of lignites. It features advanced technology, high carbon conversion efficiency, and low oxygen consumption per unit volume. It also has a high degree of domestic production, reduces construction costs, and lowers operational and maintenance expenses. The plant operates in a stable and reliable manner. 　　Thanks to the adaptive development of the brown coal gasification process for aerospace engineering, the Sinochem Changshan project has achieved stable operation over long periods of time, with excellent technical performance. According to Zhou Qihang, no safety incidents have occurred with the installation, and its VOC emissions are within the specified limits. In 2018, it operated for a total of 304 days, with a carbon conversion rate of around 98.7% and an effective gas content of 88.5%. By the end of July 2019, it had been in operation for 199 days, with a carbon gasification conversion rate of around 98.8% and an effective gas content of 88.7%. 　　Xie Dequan, chief engineer at Sinochem Changshan, said, “After the new project featuring space furnaces came online, the production cost of synthetic ammonia dropped by 500–600 yuan per ton.” After experiencing the downturn in the fertilizer industry and urea market from 2016 to 2017, the company came to fully understand the energy efficiency advantages of space heaters. ” 　　Zhou Qihang noted that Sinochem Changshan had achieved profits of nearly 80 million yuan in the first seven months of this year, with annual profits expected to reach 150 million yuan. untitled.png Customers’ representatives witnessed the Sinochem Changshan aerospace gasification unit in person. By addressing each issue individually, the overall technology reaches an internationally advanced level. Zhu Yuying said that in order to overcome these challenges, aerospace engineering has conducted in-depth research on the characteristics of lignite in eastern Mongolia over the years, gaining a thorough understanding of the gasification properties of lignite, the characteristics of slag, as well as the physical and chemical properties of coal powder. On this basis, new types of burners, new gasification furnaces, as well as pre-drying and transportation processes for lignite were developed, enabling the efficient, clean, safe, and stable operation of the lignite gasification plant. 　　Aerospace Engineering has established databases on the gasification characteristics and slag properties of typical lignite, as well as the transportation characteristics of lignite powder, thereby providing a foundation for the promotion of lignite gasification projects in other regions of China and abroad. Song Gaopeng from the Market Development Department of the aerospace engineering industry said that elemental and industrial analyses of the lignite in eastern Mongolia have shown that the raw coal in this region has a high moisture content, around 30%, a low calorific value, large variations in ash content, a high volatile matter content, and is easy to grind into coal powder. 　　Based on a thorough study of lignite data, Aerospace Engineering has outlined an approach for the efficient and clean conversion of lignite in eastern Mongolia. Song Gaopeng said that Mongolian eastern lignite has a high moisture content and low calorific value; therefore, coal with a moisture content of around 30% and a calorific value of over 3500 KCal/kg should be given priority, and it should be processed locally, with the transportation distance kept within a radius of 200–300 km. Mengdong lignite slag has good viscosity-temperature properties and a wide operating range; coal types with an operating range of over 80°C are preferred as raw material coal. The ash content and ash fusion point of lignite in eastern Inner Mongolia vary considerably; it is preferable to use coal with a basic ash content of 8%–15% and an ash fusion point of 1200°C–1350°C as the raw material coal. Mengdong lignite has a high volatile content and high reactivity, and its physicochemical properties differ significantly from those of bituminous coal. The drying and transportation processes require careful attention to ensure safety and environmental protection, as well as to optimizing the process parameters of the system. 　　In response, Wang Xianzheng pointed out that the industry suffered in its earlier development because it first built the gasification furnaces before finding suitable raw coal, which led to more and more problems as testing progressed. The biggest advantage of space furnaces is that the raw materials are thoroughly studied first before the furnace design is carried out, which is one of the key factors to achieving success. 　　Song Gaopeng explained that during the development of new types of burners, the company focused its research and development on aspects such as thermal protection for the burner head, the structure of the burner nozzle, and the distribution pattern of the coal powder channels in the burner. Through the development of the burner nozzle structure, an appropriate design for such a structure was determined, which enabled the high-temperature zone inside the furnace to move downward; this approach effectively extended the burner’s lifespan and improved its performance in gasification processes. Through the development of a uniform structure for the pulverized coal passage in the burner, the carbon conversion rate and combustion efficiency are ensured, and uneven burning of the burner is avoided; the average relative standard deviation was reduced from approximately 49.16% to 6.75%. 　　Song Gaopeng explained that in the development of new types of gasification furnaces, the company utilized the design of structural parameters for the gasification chamber and conducted simulation experiments to determine the general patterns of flow of lignite slag along the water-cooled walls. By combining simulation analysis with the characteristics of lignite ash, the diameter and length-to-diameter ratio of the water-cooled walls were determined. Through the design of the slag outlet in the gasification chamber, the structural form and key dimensions of the slag outlet were determined. In addition, a contingency plan for dealing with slag blockage at the slag outlet was developed to address any issues arising from fluctuations in the ash content of the coal used, ensuring proper slag discharge during the operation of the gasification furnace. In addition, the company has also developed a combined process route of \"drum pre-drying + sealed transportation of lignite + drying of lignite during grinding,\" which addresses the issues related to safety in the pre-drying and transportation stages as well as ensuring compliant VOC emissions. 　　On August 31, 2019, China’s first set of powder coal water-cooled wall pressurized gasification technology developed independently by the aerospace industry for lignite processing passed the evaluation of scientific and technological achievements organized by the China Petroleum and Chemical Industry Federation. The expert opinion from the appraisal committee is that this technology possesses independent intellectual property rights, enables the safe, clean, and efficient conversion of lignite, and has reached an internationally advanced level; it is recommended to accelerate its promotion and application. Untitled3.png shows customer representatives listening to a live demonstration of Sinochem Changshan’s aerospace gasification unit. The response was positive, prompting increased efforts to promote and apply this technology. On September 3, at the conference announcing the achievements of research on clean and efficient conversion of lignite using aerospace furnaces, representatives from across the country gained an in-depth understanding of this technology as well as the operation status of Sinochem Changshan’s facility, and they exchanged views on these topics. A representative from a coal chemical enterprise told reporters that this technology requires low investment, has a short process, and can operate stably over long periods of time, making it highly promising for widespread adoption. 　　Taking the opportunity of the visit, a representative from a coal chemical enterprise in Xinjiang had an in-depth discussion with the operators in the control room regarding the parameters of the dryer. He told the reporters that although the coal used in his company locally is not lignite, its moisture content is similar to that of lignite. He came here specifically to examine the operation of lignite-based space furnaces, and he will consider using such furnaces in new projects. 　　In addition, representatives from several companies took this opportunity to exchange knowledge and inspect the operation of the space furnace. A representative from a company specializing in brown coal gasification technology told reporters that it was very rewarding to take this opportunity to learn and exchange knowledge regarding aerospace-related brown coal technologies. 　　Regarding the key directions for the future development of clean and efficient conversion technologies for lignite in space-related applications, Zhu Yuying said that space engineering will accelerate the promotion and application of such technologies in China’s lignite-producing areas, and actively explore overseas markets with abundant lignite resources such as Indonesia and Australia. Enterprise standard systems for lignite pre-drying, transportation, gasification design, and operation and maintenance will be established, and the database on the characteristics of lignite gasification will be further expanded. Efforts will also be made to implement larger-scale lignite gasification projects in order to achieve greater economies of scale. 　　Notes on the Selection of the Aerospace Furnace for Zhonghua Changshan Lignite Zhonghua Jilin Changshan Chemical Co., Ltd. (abbreviated as Zhonghua Changshan) was established in 1969. Over the several decades since it began operations in 1976, its gasification units have been replaced several times. 　　Xie Dequan, the chief engineer of Sinochem Changshan, said, “Due to rising crude oil prices, Sinochem Changshan switched from using oil to coal in 2000 and installed 6 oxygen-enriched continuous gasification furnaces, using Shanxi white coal and coking coal as raw materials.” Just two years after operation, prices of white coal and coke soared, leading to the installation of two Endre furnaces in 2003. From 2003 until January 2018, two sets of Endu furnaces solved the survival issues faced by Sinochem Changshan at that time. ” 　　He said, “But as the environmental problems caused by the high energy consumption associated with the use of Endo furnaces became increasingly apparent, Sinochem Changshan began researching gasification furnaces in 2008.” It took 3 to 4 years to conduct the research, requiring great patience and diligence. After examining various types of coal and the actual operating conditions of gasification furnaces, a decision was finally made to submit a report to headquarters recommending the use of pressurized coal gasification technology. ” 　　After selecting the gasifier, the issue of coal type compatibility becomes a top priority. Xie Dequan explained, “The space furnaces that were in use previously burned bituminous coal and anthracite, but the lignite from eastern Mongolia has a moisture content of over 30%, making it a challenge to convert it into coal powder for use in gasification furnaces.” Coincidentally, at that time, a coal-to-olefins project at a chemical company was operating successfully, and the pre-drying system used was capable of reducing 40% of the water content to around 8%. Inspired by aerospace engineering, we developed a drying process route and applied it at the front end of aerospace furnaces to solve the problem of coal drying. ” 　　At the same time, aerospace engineering also carried out adaptive modifications to the burners and gasification chambers; after overcoming numerous technical challenges, the gasification furnace was successfully put into operation. 　　He said, “After the space furnace was put into use, the operators of the device could control it from the main control room, and all personnel on site were evacuated.” At the beginning of 2018, the Endu furnace was completely shut down. This is mainly due to two reasons: first, the Endre furnace incurs high costs in terms of gas production, environmental protection, safety, and other aspects; second, the production processes of the two systems are completely different and independent of each other, making it difficult to assign staff appropriately. ” 　　Over the past two years, guided by Sinochem Group’s strategy of \"science first,\" Sinochem Changshan has continued to innovate and improve its operational metrics. Since 2018, the project has operated in a safe, stable, efficient, and high-performing manner, achieving excellent economic and social benefits.