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In the current global context, there is a pressing need to curtail greenhouse gas emissions, making the utilization of a coal and zero-carbon energy blend an imperative strategy for reducing carbon emissions from coal-fired power generation. The planar flame burner serves as a tool to simulate the temperature and atmospheric conditions within the reburning zone, facilitating extensive examination of the physical and chemical structural alterations, as well as the nitrogen oxide reduction potential, during NH 3 /CH 4 activation for reburning pulverized coal. Experimental results underscore that blending high-activity fuels optimizes the combustion performance of coal char. Through the addition of NH 3 and CH 4 , the NO reduction capability of coal char is bolstered by approximately 0.67 times compared to sole reliance on recirculating flue gas transport. Furthermore, NH 3 introduction facilitates the conversion of C]O double bonds into C–O single bonds, rendering them more amenable to reduction by NO. While the joint influence of NH 3 and CH 4 does not significantly impact char particle size, it does foster the evolution of N-Q to N-5 and N-6 on the char surface. Furthermore, there was a significant increase in the BET-specific surface area, which rose by 50%. Additionally, the total pore volume increased by approximately 21.43%. The comprehensive understanding of NH 3 and CH 4 modified pulverized coal reburning technology holds significant promise for optimizing power plant operations and mitigating carbon dioxide and nitrogen oxide emissions. [Display omitted] • The addition of CH 4 has no significant effect on the particle size of char. • The reducibility of coal char modified by NH 3 &CH 4 increased by nearly 0.67 times. • The addition of NH 3 promotes the conversion of C]O to C–O. • The addition of NH 3 &CH 4 promotes the evolution of N-Q to N-5 and N-6. • The specific surface area and total pore volume of char were both increased. [ABSTRACT FROM AUTHOR]

To address the issues of ignition difficulty, incomplete burnout, and high NOx emissions during coal char combustion in industrial applications, a series of co-firing experiments involving bituminous coal and its medium-temperature pyrolysis char were conducted using a micro fluidized bed analysis system. The experiments explored co-firing behaviors and NOx emission characteristics for five different fuel blending ratios in an environment with 21 % oxygen concentration, across temperatures between 923 K and 1223 K. The study delved into the synergistic effects of coal and char co-firing, as well as the influence of combustion temperature and fuel blend ratio on the co-firing efficiency and NOx emissions. The results show a synergistic effect in the co-firing of bituminous coal and char, influenced by reaction temperature and coal-to-char blend ratio, which evolves as combustion progresses. In the 923–1073 K range, initial coal addition to the blend enhances reactivity. However, as the reaction advances or coal content exceeds 75 %, this synergy shifts to an inhibitory effect. At temperatures above 1023 K, increased proportions of coal in the blend are associated with improved burnout rates, especially when the coal content is at or above 50 %. Moreover, at a combustion temperature of 1123K, there is a marked decrease in nitrogen oxide emissions, with coal blend ratio of 25 % and 50 % showing particular efficacy in reducing these emissions. These results provide valuable insights for the efficient and clean utilization of coal char in industrial combustion processes. • The synergistic effect of co-firing depends on the temperature and the blend ratio, and changes with the reaction process. • Between 923 and 1073K, bituminous coal initially enhances fuel reactivity but later or above 75 % content, it hinders the reaction. • Temperatures over 1023 K combined with coal contents at or exceeding 50 % lead to increased burnout rates. • NOx emissions attain lowest value at 1123 K, with coal proportions of 25 % and 50 %. [ABSTRACT FROM AUTHOR]

The oxidation reaction order (n) and activation energy (E a) are the primary parameters in the global carbon/oxygen reaction model. However, these parameters continue to be a subject of argument due to the problems of experimental technology and kinetic analysis methods. This paper used a micro fluidized bed reaction analysis system to study the reaction kinetics of bituminous coal char with a median particle size of 75 μm at 923–1223 K and 2%–21% oxygen concentration. The effects of temperature and oxygen concentration on the combustion characteristics of char were analyzed. The real n value and main kinetic parameters in the n th-order Arrhenius model were measured, and the transition temperatures of the combustion control zone were determined. Results showed that the position of the maximum combustion reactivity occurs in the range of 20–30% of carbon conversion, which decreased slightly with the increase of temperature and increased slightly with the increase of oxygen concentration. The intrinsic reaction zone is below 1023 K, the intrinsic reaction order is between 0.64 and 0.71, and the intrinsic activation energy is about 106 kJ/mol. This study contributes to improve the precision and practicality of the n th-order Arrhenius model. • Measured the real reaction order n and main kinetic parameters of coal char by a micro fluidized bed system • Determined the transition temperatures of the combustion control zone, and the intrinsic reaction zone I is below 1023 K • The n value at the same conversion in the same combustion control zone is almost the same • In zone I n =0.64–0.71, activation energy E a =97–117 kJ/mol, pre-exponential factor A 0 =130–836 mol/(s·m2·atm n) [ABSTRACT FROM AUTHOR]

Reburning technology combining coal and biomass can effectively reduce NOx emissions and promote carbon neutrality in coal-fired systems. This work is based on the flat-flame burner test bench that decoupled the process of biomass-coal reburning effect on coal in the initial stage. The changes in surface functional groups and carbon skeleton structure of coal char were analyzed using FTIR, XPS, and Raman detection methods. The char's combustion reactivity and NO reduction ability were analyzed based on the micro-reactive fluidized bed test bench. The results showed that biochar and syngas would react with oxygen in the transport medium, and the resulting reactive species would activate the char. The activated effect of syngas is significantly better than that of biochar. The syngas reacts with oxygen while protecting the unnecessary consumption of the coal particle surface, and the generated active substances are enriched on the surface of the coal char to enhance its reactivity. The disordered structure of char was enhanced, and the number of small aromatic ring clusters increased by about 28%. The total alkane group content on the char surface increased by nearly 140%, and the total oxygen-containing group content decreased by nearly 17.8%. The combustion reactivity of char is increased by nearly 44.6%, and the reduced ability of NO is increased by nearly 23.4%. Theoretically, the reburned pulverized coal is reduced by 23.4%. [Display omitted] • Study on the interaction of biomass and coal co-reburning. • In co-reburning, biochar competes with biomass syngas and coal for O 2. • Biomass syngas has a better activation effect on coal than biochar. • Syngas enhances the combustion reactivity and NO reduction ability of coal char. • The reducing intermediates produced by syngas will be enriched on the char. [ABSTRACT FROM AUTHOR]

Pressurized O 2 /H 2 O combustion is a potential CCS technology. In this study, a pressurized horizontal furnace was used to prepare pyrolysis char under pressurized inert atmosphere, and then a pressurized drop tube furnace was used to carry out char combustion under pressurized O 2 /H 2 O atmosphere (5% O 2 , 20% H 2 O) at the same pressure and temperature as the pyrolysis process. The carbon conversion of char under different pressures (0.4/0.7/1.0 MPa), temperatures (900/950/1000 °C), and residence time (1.38/2.76/4.14 s) was studied by proximate analysis. The random pore model was used to calculate reaction kinetic parameters of char combustion at different pressures. The results show that when the pressure increased from 0.4 MPa to 0.7 MPa, the carbon conversion increased significantly, with the increment reaching up to 9.90 percentage points. The marginal diminishing effect became significant when the pressure was greater than 0.7 MPa. The reaction activation energy and pre-exponential factor at 0.4/0.7/1.0 MPa were 66.53/66.29/35.79 kJ/mol and 20.54/36.84/1.69 s−1, respectively. • Pressurization promote carbon conversion of char combustion in O 2 /H 2 O atmosphere. • The promotion of pressurization weakened when pressure was greater than 0.7 MPa. • Activation energy at 0.4/0.7/1.0 MPa was 66.53/66.29/35.79 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]