Characteristics comparison of tar from lignite pyrolysis with inherent and simulated moisture for adopting a two-stage gasification process

Zhang, Lijuan; Zeng, Xi; Wang, Jiale; Wang, Fang; Zhang, Jianling; Guo, Minchen; Peng, Cuina; Wu, Rongcheng; Xu, Guangwen

doi:10.1016/j.fuel.2018.09.056

Cited by 25 publications

(2 citation statements)

References 40 publications

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“…Liu et al [126] creatively developed a coal-coke-hydrogen-iron system that employs low-rank coal pyrolysis coupled with gasification to produce hydrogen-rich gas for direct reduced iron, and the exergy loss and greenhouse gas per unit product are greatly reduced compared to the traditional coking blast furnace ironmaking process. Xu et al [127][128][129][130][131][132] designed a novel two-stage fluidized gasification system consisting of a downer pyrolyzer and a riser gasifier to investigate the performance of coal conversion utilization for the polygeneration of high-value tar and clean gaseous products. The process principle of the technology is shown in Figure 18.…”

Section: Decoupling Gasificationmentioning

confidence: 99%

Recent Progress on Hydrogen-Rich Syngas Production from Coal Gasification

et al. 2023

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Coal gasification is recognized as the core technology of clean coal utilization that exhibits significant advantages in hydrogen-rich syngas production and CO2 emission reduction. This review briefly discusses the recent research progress on various coal gasification techniques, including conventional coal gasification (fixed bed, fluidized bed, and entrained bed gasification) and relatively new coal gasification (supercritical water gasification, plasma gasification, chemical-looping gasification, and decoupling gasification) in terms of their gasifiers, process parameters (such as coal type, temperature, pressure, gasification agents, catalysts, etc.), advantages, and challenges. The capacity and potential of hydrogen production through different coal gasification technologies are also systematically analyzed. In this regard, the decoupling gasification technology based on pyrolysis, coal char–CO2 gasification, and CO shift reaction shows remarkable features in improving comprehensive utilization of coal, low-energy capture and conversion of CO2, as well as efficient hydrogen production. As the key unit of decoupling gasification, this work also reviews recent research advances (2019–2023) in coal char–CO2 gasification, the influence of different factors such as coal type, gasification agent composition, temperature, pressure, particle size, and catalyst on the char–CO2 gasification performance are studied, and its reaction kinetics are also outlined. This review serves as guidance for further excavating the potential of gasification technology in promoting clean fuel production and mitigating greenhouse gas emissions.

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Section: Decoupling Gasificationmentioning

confidence: 99%

Recent Progress on Hydrogen-Rich Syngas Production from Coal Gasification

et al. 2023

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“…Coal is the main traditional energy source, which dominates the world’s energy consumption, especially in China . Lignite is a kind of widely used low-rank coal that has large reserves, low cost, high chemical reactivity, and low pollution. , However, it also has some defects, such as low calorific value, high moisture content, and high spontaneous combustion tendency . The process of coal spontaneous combustion is very complex.…”

Section: Introductionmentioning

confidence: 99%

Study on the Formation Mechanism of the Pyrolysis Products of Lignite at Different Temperatures Based on ReaxFF-MD

Zhu

Huo

et al. 2021

ACS Omega

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The internal part of coal that is not in contact with oxygen will undergo pyrolysis reaction due to heat conduction, and the active groups generated can reverse-aggravate the degree of coal spontaneous combustion. At present, a few studies have been conducted on the pyrolysis mechanism of coal at different temperatures by using mutually validated experimental and simulation methods, resulting in the mismatch between the microscopic mechanism and macroscopic characteristics. In this paper, DH lignite is taken as the research object, and its macromolecular model is established. The pyrolysis reaction of lignite is studied by the experimental methods of coal pyrolysis index gas collection and detection experimental and thermogravimetric analyses and the simulation method of ReaxFF-MD. The influence of temperature on lignite pyrolysis is explored by analyzing the distribution of products at different temperatures and the formation mechanism of typical products, so as revealing the microscopic mechanism of lignite pyrolysis. The results show that 110–500 K of experimental temperature corresponds to 1400–2400 K of simulation temperature. CO 2 and C 2 H 4 are the main gas products during pyrolysis simulation. Carboxyl and ester groups are the main source of CO 2 , which gradually increases with the rise of temperature. Since CO 2 can be reduced to produce CO, H 2 O, and C 2 H 2 O at high temperatures, the yield decreases when the temperature is higher than 2000 K. C 2 H 4 is derived from the decomposition of long-chain aliphatic hydrocarbons, and its yield fluctuation rises with the rise of temperature. The formation of H 2 O and H 2 mainly occurs in the secondary pyrolysis stage. When 1400 K < T < 2100 K, the primary pyrolysis is the main reaction, where the weak bridge bonds and macromolecular structure undergo cleavage to form gas products and tar free radical fragments. When T > 2100 K, the secondary pyrolysis reactions were significant. Tar free radicals and char undergo decomposition, hydrogenation, and polymerization reaction, gas products and tar free radicals increase, and the char yield decreases compared with the primary pyrolysis stage, so 2100 K is the key temperature of the pyrolysis reaction. The research is of great importance in improving the accurate control of coal spontaneous combustion.

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