Clean Coal Conversion: Road to Clean and Efficient Utilization of Coal Resources in China

Published: 06 May 2013
 

Clean Coal Conversion: Road to Clean and Efficient Utilization of Coal Resources in China

By Zhang Yuzhuo

President, Shenhua Group

Academician, Chinese Academy of Engineering

[Reprinted from Cornerstone - The Official Journal
of the World Coal Industry, October 2013]

In 2012, global coal consumption increased by 2.5%, far less than the average growth rate of 4.4% over the past decade, although it remained the fossil energy source undergoing the most rapid growth in consumption. In addition, in 2012 coal accounted for 29.9% of global primary energy consumption, the highest percentage since 1970.1 For the foreseeable future, the role of coal as an important global energy source, especially in non-OECD countries, will remain unchanged.

Clean and EfficientAs a principal non-OECD country, China’s coal-dominated energy mix will remain unchanged in the near term. At the same time, China’s impact on global coal production and consumption patterns will continue to increase. In 2012, the net growth in global coal consumption came exclusively from China, and, for the first time, coal consumption in China exceeded half of total global consumption. China’s coal utilization level relates not only to the healthy development of its own economy and society, but also has a significant impact on the development of the world’s economy and environment. Advancing clean coal conversion to facilitate a revolution in energy production and consumption, and thereby achieving the harmonious development of energy, economy, and the environment, is the only way to achieve clean, efficient utilization of coal in China as well as throughout the global energy system.2

Overview of the Clean Coal Conversion Industry

The coal conversion industry emerged in the 1950s, and chemicals production from coal at the commercial scale commenced during the 1990s. Since 2000, a continuous rise in the international price of crude oil and an ongoing increase in environmental global awareness have once again drawn significant attention to coal conversion, with a particularly strong emphasis on clean coal conversion. This has facilitated a fervor of coal conversion activity in China. Homegrown technologies have emerged based on research and development (R&D). Examples include packaged technologies such as Shenhua’s direct coal liquefaction technology, a coal-to-methanol-to-olefin technology (Dalian Institute of Chemical Physics of the Chinese Academy of Sciences), and a multi-nozzle coal/water slurry gasification technology (East China University of Science and Technology), as well as unit technologies such as methanation, coal-to-chemicals catalysts, and large-scale methanol synthesis. Plants that have been completed include the Shenhua Ordos 1080-ktpa (kilo tonnes per annum) direct coal liquefaction plant, three 160–180-ktpa indirect coal liquefaction plants, three large coal-to-olefin plants, one 200-ktpa coal-to-monoethylene glycol (MEG) plant, and several large coal-to-methanol and methanol-to-methyl ether plants with advanced gasification technologies. Four new coal-to-gas projects have been constructed. This progress has led to the formation of a commercial clean coal conversion industry enabled by coal gasification and based on C1 chemical technology to synthesize various low-carbon chemical products and clean petroleum substitutes (i.e., synthetic fuels); the industry is based on the philosophy of low-carbon, clean, and highly efficient energy utilization.3–5

The Evolution of Clean Coal Conversion

Coal Liquefaction

Coal liquefaction falls into two categories: direct and indirect liquefaction, both of which have been developed and commercialized in China.

For direct coal liquefaction, industrial-scale production was realized in Germany during World War II. After the first oil crisis, countries such as the U.S. and Japan successively developed many direct coal liquefaction technologies, with the largest pilot plant having a capacity of 600 t/d (tonnes per day). With an eye on its own industrial development needs, Shenhua Group in China independently developed the Shenhua Direct Coal Liquefaction Process and established the only 1080-ktpa direct coal liquefaction facility in the world. This facility was formally placed into commercial operation in January 2011; as of the end of June 2013 it had produced more than two million tonnes of synthetic fuel products, while achieving operational excellence. To build upon the commercial operation, further research and development are needed, such as reducing water consumption, improving product yield, reducing emissions, effluents, and wastes, and enhancing the development of premium and high-performance coal-based fuels.

The core technology of commercial-scale indirect coal liquefaction was first mastered in South Africa. Over the last decade, China has made breakthroughs in commercial indirect coal liquefaction through independent R&D. Three 160–180-ktpa indirect liquefaction projects have been placed in operation. Now efforts are being made to speed up the implementation of a large demonstration project, which is focused on solving key technical issues such as the design and manufacturing of large-scale Fischer–Tropsch (F-T) synthesis slurry bed reactors, catalytic oxidation of alcohol byproducts, methane conversion and utilization of synthesis tail gas, production and application of new F-T synthesis catalysts, process optimization and integration of a heat recovery system, and engineering design for major project deployment. Progress is also being made to improve process integration and optimization, further reduce the required unit investment, reduce water and coal consumption per unit product, establish a high-temperature F-T synthesis demonstration plant, and achieve safe and stable long-term operation of large (e.g., >1 MMtpa) plants.

Clean and Efficient Image 1

Shenhua’s groundbreaking 1080-ktpa Ordos direct coal liquefaction facility is an example of the major CTL advancements occurring in China.

Coal-to-Olefins

Currently, there are two commercial coal-to-olefin technologies: the coal-to-methanol-to-olefin (MTO) process and the coal-to-methanol-to-propylene (MTP) process. Globally, many companies are investigating and optimizing olefin production processes. Today, the most successful include the methanol-to-olefin (DMTO) technology (Dalian Institute of Chemical Physics of the Chinese Academy of Sciences), Sinopec methanol-to-olefin (S-MTO) technology, U.S. UOP/HYDRO methanol-to-olefin (MTO) technology, and the German Lurgi MTP technology. Based on the existing technologies, China has established and put into commercial operation four coal-to-olefin projects, such as Shenhua Baotou’s 600-ktpa MTO and Shenhua Ningmei’s 500-ktpa MTP. In addition, China is actively pursuing new technologies for the optimization of catalyst production, reduction of water and coal consumption, improvement of production selectivity and yield, etc. Shenhua Group has independently developed a next-generation methanol-to-olefin (SHMTO) technology, and the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences has completed the R&D leading to the second generation of methanol-to-olefin (DMTO-II) technology. Both technologies have been applied at commercial plants that are currently under construction. There are plans for further optimization and improvement of the entire process, including gasification, purification, and methanol synthesis, so as to form a complete process package with intellectual property rights that improves the stability and economics of large plants.

Coal-to-Gas

Methanation, a key coal-to-gas process, is a mature, proprietary technology currently deployed commercially in China. The first phase, including commissioning, of the Datang Keqi Project, with a capacity of 1.33 billion m3/yr, has been completed, while the second phase, with a capacity of 1.33 billion m3/yr, is nearing completion. The first phase of the Datang Fuxin Project, with a capacity of 1.33 billion m3/yr, has been completed and the commissioning is currently underway. The first phase of the Inner Mongolia Huineng Project with a capacity of 0.4 billion m3/yr and the first phase of the Xinjiang Qinghua Project with a capacity of 1.75 billion m3/yr, are also nearing completion. When all the above-mentioned projects are running at full capacity, there are plans in China to further develop, through R&D, the key aspects of the methanation technology, such as improvements in fixed bed gasification pressure, efficient wastewater treatment and reuse, and a portfolio of coal gasification technologies, to demonstrate integrated gas, electricity, and chemical polygeneration and comprehensive peaking-shaving regulation technology and to improve energy efficiency and overall financial return.

Coal-to-MEG

Coal-to-MEG technology is available in Japan and the U.S. The first coal-to-MEG commercial-scale demonstration project in the world (i.e., Tongliao GEM Chemical 200 ktpa) was built in China and includes several technologies with Chinese intellectual property rights. At the industrial scale, the economic feasibility and actual operation of MEG production through carbonylation and hydrogenation of synthesis gas will be demonstrated. In addition, the focus of R&D includes the scale-up of major equipment, such as dimethyl oxalate synthesis reactors and dimethyl oxalate hydrogenation reactors, optimization of technologies for wastewater treatment and reuse, MEG distillation efficacy and product quality improvements, and identification of other economic and practical coal-to-MEG routes.

Coal-to-Aromatics

Tsinghua University, Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, and others have developed a coal-to-aromatics technology. Huadian Coal Industry Group Co., Ltd. has constructed and successfully commissioned the world’s first 10-ktpa pilot plant. Moreover, efforts will be made to eventually develop the first industrial-scale coal-to-aromatics demonstration project, which will focus on key technologies such as design and enlargement of the methanol-to-aromatics reactor, reaction heat control, engineering optimization, as well as industrial application of paraxylene catalysts.

Coal-to-Hydrogen

Coal-to-hydrogen is already a mature technology, and is an important means of obtaining a cheap and steady supply of significant quantities of hydrogen. In 2007, Shenhua Group built the world’s largest coal-to-hydrogen plant, with a capacity up to 600 t/d, which is mainly used to provide hydrogen for Shenhua’s direct coal liquefaction plant.

With a continuous, strong demand for clean fuel, hydrogen cells, hydrogen gas turbines, and hydrogen-powered automobiles are gradually moving toward large-scale commercial production, and hydrogen will become an important source of clean energy. Therefore, coal-to-hydrogen is a viable technology based on the realistic possibility of large-scale commercial operation.

Clean and Efficient Image 2

Today the Shenhua Baotou MTO Plant produces 300 ktpa of polypropylene and 300 ktpa of polyethylene.

Prospects for Clean Coal Conversion

Today, the world is increasingly attentive to the development of low-carbon, high-efficiency, and clean energy. The future of energy development lies in the establishment of a new energy ecosystem (a term widely used in China and elsewhere that refers to an integrated energy system that is in balance with the environment), which will be centered on more efficient utilization of energy (including higher efficiency energy conversion and improved resource utilization), and can be built based on effective integration of various energy sources, so as to form a low-carbon, efficient, clean polyproduction system featuring “near-zero emissions”.

Given that coal will continue to play a dominant role for the long term, clean coal conversion is the key to the establishment of the new energy ecosystem. At the same time, attention should also be focused on near-zero emissions during fossil energy utilization, so as to realize the green and collaborative development of fossil energy, unconventional energy, and renewable energy, as well as advance the energy production and consumption revolution.

To achieve a successful energy revolution in China, a country where energy is dominated by coal, clean coal conversion has been included as an integral part of national energy strategies. The government is working actively to propel independent R&D of associated technologies and equipment, support growth of relevant industries, and establish an energy ecosystem based on clean coal conversion. The prospects for clean coal conversion involve four coal-related shifts, described briefly below.

Shift from Fuel to a Combination of Fuel and Feedstock

It is critical to continue the research, development, and demonstration of modern coal conversion technologies to achieve clean and efficient coal conversion and utilization. The overall arrangement of the coal-to-chemicals industry must be rationally planned to facilitate the construction and sound development of an integrated large-scale coal-to-chemicals industrial base. In 2012, the production capacity of coal-to-liquid fuels in China increased to 1.6 million tpa, coal-to-methanol increased to 55 million tpa, and coal-to-olefins (ethylene + propylene) production increased to 1.8 million tpa. Coal consumption for coal conversion is projected to reach 40–50 billion tpa in the next 40 years.

In this way, the role of coal is changed. Coal is not merely a fuel, but also a feedstock if we make full use of the C, H, and other elements found in coal for chemical synthesis and their heating value. Once market demands for electricity and heat are met, various clean energies and industrial raw materials, including natural gas, liquid fuels with ultra-low emissions, aviation and specialty fuels, and chemicals can be produced via coal gasification.

Shift from a Singular Energy System to a Component in an Integrated Coal–Unconventional Energy–Renewable Energy System

Unconventional energy and renewable energy are vigorously being developed via proactively pursuing hydroelectric power, safely and efficiently developing nuclear power, developing wind power projects in an orderly manner, and accelerating the utilization of solar power. In addition, shale gas, shale oil, biomass energy, geothermal energy, and other unconventional energy sources are also being actively pursued as well as promoting a distributed energy grid, so as to enable unconventional energy and renewable energy to take an increasingly prominent role in the restructuring of the energy mix. Moreover, an in-depth investigation will be completed for energy integration and optimization technologies with the objective of enhancing energy conversion and utilization efficiency—the coupling of shale gas and coal-to-chemicals processing, combining nuclear energy-to-hydrogen and coal polyproduction, combining solar energy-to-hydrogen and coal polyproduction, and combining utilization of coal, waste, and biomass, all of which are shown in Figure 1.

Clean and Efficient Figure 1

Figure 1. Framework for new coal-based polygeneration

The development of unconventional energy and renewable energy can change not only the coal-dominated energy mix. It can also bring about multiple possibilities for coal conversion pathways to realize the combined utilization of various energy resources and to establish a new coal-based polyproduction system with more efficient utilization and conversion of energy resources.

Shift from High-Carbon Development to Efficient Utilization of Coal with Near-Zero Emissions

It is necessary to develop technologies to control pollutants throughout all coal conversion processes. It is important to implement technologies for efficient and clean combustion, coordinated pollutant control and reuse of wastes, and reclamation of wastes for comprehensively controlling pollutants from coal-fired power plants. Technologies for clean energy substitution/large-scale application, efficient removal of pollutants, and coordinated control of multiple pollutants with byproduct recycling can also be applied to control pollutants from industrial boilers. Similarly, advanced process technologies for efficient removal of pollutants with coordinated control of pollutants with byproduct recycling can be applied for controlling pollutants from industrial kilns. Finally, modern coking pollution control technology includes large-scale application, reclamation, and cleaning. All of the technology pathways are shown in Figure 2.

Clean and Efficent Figure 2

Figure 2. Polyproduction based on coal gasification

To achieve improved, cleaner coal conversion, additional R&D and the application of new coal-associated technologies, such as CO2capture, utilization, and storage (CCUS) and reclamation and comprehensive recycling of wastes or pollutants, will be required to achieve increased commercial deployment of coal conversion. For example, with efficient extraction and comprehensive utilization of aluminum, gallium, germanium, uranium, sulfur, and other resources in coal, the coal and its associated resources can be used efficiently and completely with the realization of near-zero emissions of pollutants.

Increasingly Intelligent Coal-Based Energy Production and Consumption

It is essential to promote the application of big data, Internet of Things, mobile Internet, and other information technologies throughout the process of coal conversion to maximize the intelligent features utilized in clean coal conversion. Increased use of intelligent technology is necessary to realize effective integration of clean and efficient coal conversion with unconventional energy and renewable energy as well to function in real time and adjust for the valleys and peaks caused by dynamic energy consumption. In addition, energy production and consumption with better safety and reliability performance, matching accuracy, and integration are necessary to form a new model such that a low-carbon, efficient, and clean energy system, meeting development needs of our economy and society, is indeed created, which can launch a revolution in the energy industry and transform the development path of society.

Clean and Efficient Image 3

The first production line of the Datang Keqi coal-to-gas facility has been completed and the second line is nearing completion.

Conclusions

Considering that China’s energy mix is dominated by coal, great efforts are being made to develop clean energy options to accompany the global tide of low-carbon development. Clean coal conversion can lead to the realization of the transformation from high carbon, to low carbon, to carbon-free coal utilization with broad prospects for technological and commercial markets in the future. It is expected that China’s clean energy development route will be focused mainly on the acceleration of clean coal conversion. There are several pathways for clean coal conversion, including increasing integration of coal and unconventional energy and renewable energy, development of coal-associated resources (e.g., CCUS and other technologies), and making the full industrial chain of clean energy more intelligent through technology. All these options are also essential to meet energy demand, optimize the global energy mix, and sustainably and soundly develop the global economy of future.

Shenhua Group, the world’s largest coal-based energy supplier and the leading coal conversion technology developer, will, via independent innovation and industrial upgrading, remain committed to R&D and the implementation of clean coal conversion. Shenhua Group is also committed to promotion of an intelligent clean energy system featuring near-zero emissions, so as to make unremitting progress for not only the development of the global energy industry, but also a brighter future for society.

 

REFERENCES

1. BP, Statistical Review of World Energy 2013, 2013, www.bp.com/en/global/corporate/about-bp/statistical-review-of-world-energy-2013.html
2. Comprehensive Research Report of Major Consulting Project for Strategic Research on Clean, Efficient, Sustainable Development and Utilization of Coal in China, 2012: Chinese Academy of Engineering.
3. Zhang Yuzhuo, Clean Coal Conversion Project, 2011: China Coal Industry Publishing House.
4. Zhang Yuzhuo, Prospects of Clean Coal Conversion from High-Carbon Energy to Low-Carbon Energy, Energy of China2008, 30 (4), 20–22, 37.
5. National Development and Reform Commission, Coal Intensive Processing Demonstration Project Planning (Exposure Draft), March, 2012.

The content included in Cornerstone  is based on the opinion of the authors, and does not necessarily reflect the views of the World Coal Association or its members.

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