Clean Coal Conversion Research Articles

Research on the Optimization and Application of New Energy Technologies in Clean Coal Conversion

With the continuous growth of global energy demand and increasingly severe environmental issues, clean coal technology has garnered significant attention as a crucial means to mitigate the negative environmental impacts of coal utilization. However, traditional clean coal conversion technologies often suffer from low energy utilization efficiency and insufficient environmental pollution control. In recent years, the application of new energy technologies in the clean coal conversion process has shown tremendous potential, significantly optimizing energy conversion efficiency, reducing emissions, and enhancing economic benefits. This paper systematically explores the application of solar energy, wind energy, and biomass energy in clean coal conversion, analyzes the mechanisms and methods through which new energy technologies optimize the clean coal conversion process, and proposes future research directions and policy recommendations.

Insight into Ca-based compounds on different coal devolatilization behavior by TG-MS

Catalytic pyrolysis, as an indispensable technology, can efficiently achieve clean coal conversion. In this work, the effect of calcium-based compounds (CaO and CaCl2) on devolatilization characteristics and gas evolution behavior of three coals were investigated by thermogravimetry-mass spectrometry (TG-MS). The catalytic mechanism was further explored in combination with the bond cleavage and gas kinetics. The results showed that both catalysts increased the weight loss rate and pyrolysis characteristic index, which also promoted the early release of CH4, H2, CO2 and C6H6, leading to an increase on the amount of CH4 and H2 production. CaO had a better catalytic effect than that of CaCl2. In addition, the kinetic results indicated that both compounds significantly reduced the activation energy of the methane I and IV stages, by 21.33%–34.66 % and 0.8%–18.60 %, respectively. And the activation energy of hydrogen III stage evolution was also reduced by 2%–18.98 % with catalysts. The calcium-based compounds tended to act on the Cal-O, Cal-Car and Car-H structures, improved the coal devolatilization behavior. The results aim to provide theoretical understanding for the practical application of catalytic pyrolysis technology.

Pure hydrogen gas production in a coal supercritical water gasification system with CO2 as transporting medium

Supercritical water gasification (SCWG) technology was a clean coal conversion and utilization technology, which could decompose low-grade coal into gaseous products and make efficient and clean use of them. However, system with H2O transporting had much energy consumption on heating transporting medium and side reactions at heating process would weaken the gasification effect. Considering the advantages of low critical point and low specific heat capacity of CO2, and the precedent of CO2 as a transport medium in non-supercritical systems, CO2 was expected to become a transport medium in supercritical water gasification systems and to achieve the goal of improving the gasification effect of heating process and reducing energy consumption. A supercritical water coal gasification system of was established with lignite as raw material in this paper. Production yields of gasification with CO2 as the transporting medium at different working conditions were investigated. CO2 and H2O were used as the transporting medium of the system, contrastively. Compared with H2O-transporting system, production of H2 and CO2 in CO2-transporting system decreased while that of CH4 and CO increased as well. Furthermore, both energy and exergy efficiency of CO2-transporting system were higher than that of H2O-transporting system. The result proved the superiority of CO2 as the transport medium of supercritical water gasification system.

Coal-Based Carbon Nanomaterials: En Route to Clean Coal Conversion toward Net Zero CO2.

As the world is committed to reach carbon peak by 2030 and net zero by 2050, the use of coal as an energy source is facing unprecedented challenges. According to the International Energy Agency (IEA), global annual coal demand is estimated to drop from more than 5640 million tonnes of coal equivalent (Mtce) in 2021 to 540 Mtce in 2050 under the net zero emission scenario, mostly being replaced by renewable energy such as solar and wind. Therefore, the coal industry is vigorously seeking alternative applications to keep it thriving, and nanotechnology can be one of the contributors. Herein, the challenges to coal-based carbon nanomaterials syntheses are outlined, along with a path toward commercialization. Coal-based carbon nanomaterials can be promising contributors to the concept of clean coal conversion, initiating its migration from an energy source to a high-value-added carbon source.

Process optimization and thermodynamic analysis of autothermal coal chemical looping gasification industrial demonstration system

Chemical looping gasification (CLG) is an innovative clean coal conversion technology with industrial application prospects. The technical reliability of coal CLG (CCLG) in an autothermal state remains to be investigated. To clarify the process characteristics of an autothermal CCLG process, a CCLG autothermal operation system was established based on a CLG industrial demonstration unit. Process modeling of the CCLG reactor system and economizer, air preheater, and other heat exchange units was performed, to ensure autothermal operation of the global CCLG process. The optimal operating parameters of the system were established, the optimal heat exchange network was designed, and the source and distribution of thermodynamic irreversibility were clarified. The results showed that the optimal coal feed flow rate, air feed temperature and flue gas circulation temperature were 437.07 kg/h, 550 °C and 450 °C, respectively. The fuel reactor (FR) flue gas circulation was not conducive to system autothermal, resulting in weakened gasification performance. The optimal heat exchange plan allowed the system to operate without an external heat source. The thermodynamic irreversibility mainly originated from the redox process. The system heat efficiency was 81.63 %, the product exergy efficiency was 78.06 %, the total exergy efficiency was 41.10 %, and the total exergy destruction rate was 55.40 %. Additionally, the FR flue gas circulation caused high exergy loss, resulting in reduced system thermodynamic efficiency.

Exploring molecular structure characteristics and chemical index of Qinghua bituminous coal: A comprehensive insight from single molecule of macerals to particles with various sizes

Understanding the relationship between the coal structure and its reactive behaviour is of great significance to achieve clean coal conversion and its efficient utilisation. One of the key tasks is to elucidate the molecular structure and chemical bonding information of coal. Owing to the complexity of the chemical structure of coal, studies on the molecular structure of coal, especially coal models with complex particle structures of different sizes for bituminous coal from northwest China, are highly warranted. In this work, the molecular structure characteristics and chemical index of a Qinghua bituminous coal sample collected from the Ningdong area, China, were assessed. Using a combination of material characterization, computation, and molecular modelling methods, a standard method for modelling complex coal structures from single molecules of macerals to particles of various sizes was developed. The single molecular structure of vitrinite and inertinite present in Qinghua coal can be expressed as C269H196N4O13S and C255H179N3O14S, respectively. Then, a series of complex particle models of various sizes were established based on the single molecular structure models of vitrinite and inertinite. Among these models, the size of the complex particles was as large as 11 nm, with the total atomic number approaching 60,000. Furthermore, the energetic and structural features of the complex coal particle structures were also explored based on their energy decomposition and radial distribution function analysis. In addition, the chemical structure index analysis was performed for different coal macerals to further understand the internal relationship between its structure and application.

Reviews of clean coal conversion technology in China: Situations & challenges

It is important to develop the advanced coal to chemicals industry (ACCI) against a backdrop of coal-based energy structures, excessive imported oil and natural gas, and strict environmental constraints in China. In this study, the technology and industry of China's ACCI are reviewed to explain the effect of using coal to replace oil and natural gas, and the corresponding resource and environmental burdens that this will create. Development trends in technology and industry are also proposed to explore future scenarios. The review shows that although excellent progress has been made on an industrial scale, demonstrative level, and in terms of technology and equipment, the lack of strategic understanding, severe external constraints, partly underdeveloped technologies, and weak foundations must be immediately addressed. Therefore, it is necessary to clarify the importance that the ACCI has on the energy revolution and energy system. Based on technological innovation, a variety of external factors should be considered as a whole with emphasis on filling the knowledge gap of theoretical foundations and industry standards to support high-quality development for ACCI.

Breakthrough and innovative clean and efficient coal conversion technology from a chemical engineering perspective

To adapt to the needs of a developing global society and provide water and ecological environmental protection, it is necessary to enhance technological innovations for clean coal conversion to achieve the basic requirements of “clean and low carbon, safe and efficient”. This paper puts forward a new idea of the chemical conversion of coal in terms of the material conversion efficiency and energy utilization efficiency of common key technologies, forward leading technologies, modern engineering technologies, and disruptive technologies. In addition, it is pointed out that there are many chemistry and chemical engineering problems restricting the innovation and breakthrough of new clean coal technologies. In view of this problem, we carry out an in-depth study of the main processes used in the coal chemical industry, and find that understanding the structure–activity relationship, designing ideal catalysts, strengthening the main reaction processes, and promoting the integration of processes used in other chemical fields into the coal chemical industry are helpful for realizing the steady development of the modern coal chemical industry. Such approaches can lead to improved economic benefits, and provide means for realizing the clean and efficient transformation of coal.

The application of molecular simulation in ash chemistry of coal

One of the crucial issues in modern ash chemistry is the realization of efficient and clean coal conversion. Industrially, large-scale coal gasification technology is well known as the foundation to improve the atom economy. In practice, the coal ash fusibility is a critical factor to determine steady operation standards of the gasifier, which is also the significant criterion to coal species selection for gasification. Since coal behaviors are resultant from various evolutions in different scales, the multi-scale understanding of the ash chemistry is of significance to guide the fusibility adjustment for coal gasification. Considering important roles of molecular simulation in exploring ash chemistry, this paper reviews the recent studies and developments on modeling of molecular systems for fusibility related ash chemistry for the first time. The discussions are emphasized on those performed by quantum mechanics and molecular mechanics, the two major simulation methods for microscopic systems, which may provide various insights into fusibility mechanism. This review article is expected to present comprehensive information for recent molecular simulations of coal chemistry so that new clues to find strategies controlling the ash fusion behavior can be obtained.

Carbon Nanomaterials: Opening a Path to a Sustainable Future

Research & Development in Material Science Carbon Nanomaterials: Opening a Path to a Sustainable Future Jianbo Zhang* Department of Chemical Engineering, Northwest University, China *Corresponding author: Jianbo Zhang, Department of Chemical Engineering, Shaanxi Research Center of Engineering Technology for Clean Coal Conversion, School of Chemical Engineering, Northwest University, China Submission: August 27, 2017; Published: September 08, 2017 DOI: 10.31031/RDMS.2017.01.000502 ISSN : 2576-8840Volume1 Issue1

Hydrogen production by non-catalytic partial oxidation of coal in supercritical water: The study on reaction kinetics

Supercritical water gasification (SCWG) has attracted great attention for efficient and clean coal conversion recently. A novel kinetic model of non-catalytic partial oxidation of coal in supercritical water (SCW) that describes formation and consumption of gas products (H2, CO, CH4 and CO2) is reported in this paper. The model comprises 7 reactions, and the reaction rate constants are obtained by fitting the experimental data. Activation energy analysis indicates that steam reforming of fixed carbon (FC) is the rate-determining step for the complete gasification of coal. Once CH4 is produced by pyrolysis of coal, steam reforming of CH4 will be the rate-determining step for directional hydrogen production.

Pressurized Thermogravimetric Study on the Hydropyrolysis and Hydrogasification Kinetics of a Bituminous Coal

Coal hydropyrolysis (CHP) and coal hydrogasification (CHG) are two important processes during coal conversion in a hydrogen atmosphere. Much attention has been paid on this clean coal conversion technology because of its advantages. In this work, the CHP and CHG kinetic characteristics of a bituminous coal are studied in a pressurized thermogravimetric analyzer (P-TGA). The effects of the pressure on the CHP and CHG kinetics of the bituminous coal are detected with the non-isothermal thermogravimetric method. In addition, the kinetic compensation effect (KCE) and isokinetic points of the two processes are investigated. Besides, the kinetic triplets, including the pre-exponent factor, the activation energy and mechanism function are also calculated and defined for all of the cases during the CHP and CHG processes. Meaningful and interesting conclusions are finally obtained from this study. The initial pyrolysis temperature will increase with the reaction pressure when the pressure is within 3 MPa. The appe...

Initial Chemical Reaction Simulation of Coal Pyrolysis via ReaxFF Molecular Dynamics

Mechanisms investigation of coal pyrolysis will aid efficient and clean coal conversion and utilization. However, coal pyrolysis is a complex process involving myriad coupled reaction pathways such that the deeper understanding of its mechanism is still limited even with state-of-the-art experimental approaches. In this paper, ReaxFF molecular dynamics simulation was employed to perform simulation of chemical reactions in pyrolysis of a bituminous coal model with 4976 atoms to examine the nascent decomposition mechanisms and product profiles at temperatures from 1000 to 2000 K over a 250 ps simulation period. It is found that more than 900 reactions may occur at the temperature 2000 K within the simulation period with a trajectory output interval of 12.5 ps, and a detailed chemical reaction network was obtained by further analysis of the trajectory using a newly created C++ program. The product profile evolution tendency with temperature observed in the simulation agrees well with what was obtained experi...

Calcium Looping Process for Clean Coal Conversion: Design and Operation of the Subpilot-Scale Carbonator

The calcium looping process (CLP), which is being developed at The Ohio State University (OSU), is a clean coal technology for the production of hydrogen (H2) and electricity from coal-derived syng...

China goes green: cleaner production of chemicals

The effort that China is making for cleaner production of chemicals especially based on technology innovations of green processing and synthesizing methods, is reviewed. An example is the rapidly expanding chlor-alkali industry in China, which manufactures a large volume of products of caustic soda, polyvinyl chloride (PVC), etc. With a distinct difference from conventional technologies, a series of novel processes are under investigation, both in academic research and in industrial demonstrations, such as clean coal conversion to acetylene using thermal plasma, mercury free catalysis to synthesize vinyl chloride monomer (VCM) and a plasma-assisted gas-solid contacting process to make chlorinated PVC (CPVC). All efforts are directed to improving the process efficiency, saving the materials and energy cost, and accordingly to reducing the emission/disposal of waste gases, liquids and solid residues. We try to address the significance of technology innovations to drive the industry reformation, in order to fully update the outdated processes with heavy pollution and energy consumption, to the state of the art green process and synthesis techniques.

Clean coal conversion processes – progress and challenges

Although the processing of coal is an ancient problem and has been practiced for centuries, the constraints posed on today's coal conversion processes are unprecedented, and utmost innovations are required for finding the solution to the problem.With a strong demand for an affordable energy supply which is compounded by the urgent need for a CO2 emission control, the clean and efficient utilization of coal presents both a challenge and an opportunity to the current global R&D efforts in this area. This paper provides a historical perspective on the utilization of coal as an energy source as well as describing the progress and challenges and the future prospect of clean coal conversion processes. It provides background on the historical utilization of coal as an energy source, along with particular emphasis on the constraints in current coal conversion technologies. It addresses the energy conversion efficiencies for current coal combustion and gasification processes and for the membrane and looping based novel processes which are currently under development at various stages of testing. The control technologies for pollutants including CO2 in flue gas or syngas are also discussed. The coal conversion process efficiencies under a CO2 constrained environment are illustrated based on data and ASPEN Plus® simulations. The challenges for future R&D efforts in novel coal conversion process development are also presented.

Clean coal conversion options using Fischer–Tropsch technology

Material and energy balances were prepared for two coal conversion options for the co-production of liquid hydrocarbon products and electricity. The results are compared to the alternative approach of producing liquid hydrocarbons from natural gas. It is concluded that the capital cost for coal conversion must be higher but that cash operating costs may be similar. There are important synergistic effects so that facilities co-producing liquid hydrocarbons and electricity from coal are more efficient than facilities producing these products individually. There may be good strategic reasons to use clean coal conversion plants co-producing liquid hydrocarbons and electricity. Due to the huge capital investments required, some form of government assistance will be needed.

Clean Coal Technologies in Japan

Coal provided 16·1% (116·3 million tons) of the energy for Japan in FY 1992. According to the long-term energy supply and demand outlook in Japan, prepared and revised in June 1994 by the Advisory Committee for Energy, it is estimated that coal will provide 16·4% (130 million tons) of the energy in 2000 and 15·4% (134 million tons) in 2010, and that coal demand will increase. Japan imports one-third of the amount of international coal trade and depends heavily on overseas coals. In FY 1993, Japan imported 112 million tons of overseas coals and depended on foreign countries for about 94% of coal used. Coal provides about 30% of the energy for the world. Owing to the stable supply of coal and its economic efficiency for the middle and long term, technologies for coal utilization such as clean coal conversion, including liquefaction, gasification, etc., and efficient combustion processes are being developed in Japan as the chief substitute for petroleum to reduce the excessive dependence on petroleum. Clean coal technologies being developed in Japan will spread widely throughout the world and are expected to create sustainable growth while solving energy and environmental issues.

A clean coal conversion technology

Technical feature:The Ralph M. Parsons Co. and the U.S. Dept. of Energy are developing preliminary designs and economic evaluations of commercial coal conversion facilities. The commercial designs already completed include a Fischer-Tropsch facility producing liquid hydrocarbons plus substitute natural gas by indirect coal liquefaction. More specifically, this facility will produce carbon dioxide-carbon monoxide-hydrogen syngas, which will then be purified and converted into hydrocarbon liquids. Part of the unreacted syngas will be upgraded to substitute natural gas by methanation. The Parsons design incorporates advanced technology and satisfies strict environmental requirements. Major pollution abatement efforts include: desulfurization of gases generated during coal conversion; removal of acid gases; and a combination of recycling and discharge of aqueous effluents. Of particular concern is the possible formation of carcinogenic compounds in coal tar. (2 diagrams, 1 drawing, 2 tables)