Thermal characterization, gasification and kinetic studies of different sized Indian coal and char particles

不同尺度印度煤与煤焦颗粒的热特征、气化及动力学研究

International Journal of Advances in Engineering Sciences and Applied Mathematics, June 2014, Volume 6, Issue 1, pp 31-40

Abstract:Four different sizes of Indian high ash coal and char are investigated. A simultaneous thermal analyzer and mass spectrometer is used for the characterization of the coal and char samples and the identification of the volatiles evolved during the heating of the sample upto 1,050 °C under combustion cum gasification related conditions. The TG and DTA results are discussed for the investigations under air, oxygen, steam and blended gas atmospheres. The thermogravimetry—mass spectrum profile of the coal provides information on combustion performance (ignition, peak combustion and burnout temperatures) and on chemical changes to the volatile matter (H2, O, CO and CO2), char and minerals. The size effects of the coal and char during pyrolysis, combustion and gasification are discussed. The appropriate temperature ranges to the high ash coal gasification in the steam and steam blended gases are evaluated. The Arrhenius model is applied to determine the kinetic parameters from TG/DTG curves.

TG-FTIR/MS analysis of thermal and kinetic characteristics of some coal samples

7种煤样热动力学特征的TG-FTIR/MS分析

Journal of Thermal Analysis and Calorimetry, September 2013, Volume 113, Issue 3, pp 1063-1071

Abstract:Thermooxidative decomposition (TOD) of seven coal samples from different deposits (Bulgaria, Russia, Ukraine) was studied with the aim to determine characteristics of the process and the differences related to the origin of the coal samples studied. The experiments with a Setaram Setsys 1750 or Labsys Evo 1600 thermoanalyzers coupled to a Nicolet 380 FTIR spectrometer or Pfeiffer mass spectrometer, respectively, were carried out under non-isothermal heating conditions up to 1,000 °C at the heating rates of 1, 2, 5, 10, and 20 °C min−1 in an oxidizing atmosphere. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman was used to calculate the kinetic parameters. The combined TG-FTIR and TG-MS study of TOD of the coal samples made it possible to identify a number of gaseous species formed and evolved at that as well as to determine the differences in the thermal behavior of the coal samples and in the emission profiles of these species depending on their origin. The value of activation energy E along the reaction progress α varied more for the samples with higher content of organic matter and, especially, for the samples having at that also quite high content of mineral matter, indicating to the close association of mineral matter with organic matter and fixed carbon.

A comprehensive study on co-pyrolysis of bituminous coal and pine sawdust using TG

基于热重分析的烟煤与松木锯末共热解综合研究

Journal of Thermal Analysis and Calorimetry, June 2015, Volume 120, Issue 3, pp 1867-1875

Abstract:A sample consisting of woody biomass and bituminous coal was pyrolyzed in a lab-scale furnace in a nitrogen atmosphere with the temperature increasing by different heating rates of 5, 10, and 50 °C min−1 until the furnace wall temperature reached 900 °C. Five blending ratios (BRs) of coal–biomass were tested. For each BR, the mass loss of the sample and mole fractions of the gaseous species evolved from the sample were measured using a thermogravimetry (TG) and a real-time gas analyzer (GA). Reactivity, product yield, and activation energy were considered as index parameters to co-pyrolysis. While synergy (the difference between the experimental data and calculated results obtained using an additive model) of the reactivity of co-pyrolysis was observed only at specific temperatures, the TG results showed synergy at temperatures between 450 and 500 °C compared to between 450 and 600 °C seen with the GA method for all pyrolyzed gases, and especially between 350 and 650 °C for H2. While there was no synergy in the char yield of the co-pyrolysis, the liquid and total gas exhibited synergy for all three BRs. The pre-exponential factors and the activation energies of BRs of 0.25, 0.5, and 0.75 were obtained using a kinetic study of co-pyrolysis.

Study of the thermal behaviour of coal/biomass blends during oxy-fuel combustion by thermogravimetric analysis

基于热重分析的全氧燃烧过程中煤与生物质混合热特性研究

Journal of Thermal Analysis and Calorimetry, February 2016, Volume 123, Issue 2, pp 1643-1655

Abstract:During oxy-fuel combustion, the gas composition inside the boiler differs greatly from that of conventional combustion with air, involving consequences for different aspects in fuel combustion. Research on oxy-fuel combustion is needed to understand which factors influence the process, especially for coal and biomass co-firing. In this study, the combustion behaviour of coal/biomass blends was determined by thermogravimetric studies (TG) with different CO2/O2 mixtures and compared with similar results for conventional combustion. This approach determines the appropriate conditions for the oxy-fuel combustion for future studies that will be carried out in lab- and bench-scale combustors. One sub-bituminous coal (Puertollano coal) and two Spanish biomasses (olive grove and thistle) were the fuels selected for the study. The combustion behaviour of each pure fuel and several coal/biomass blends, under air and oxy-fuel conditions (70 %CO2–30 %O2, 60 %CO2–40 %O2), was studied. Results obtained for the pure fuels have shown that the temperatures of maximum reaction rate, T max, determined under oxy-fuel combustion were lower than those found during conventional combustion. Similar pattern was encountered for the different coal/biomass blends studied (varying from 80 % coal/20 % biomass to 20 % coal/80 % biomass), with a more reactive behaviour in oxy-fuel conditions than in conventional air combustion. The values of temperatures at maximum mass loss, T m, obtained for these blends in an oxy-fuel atmosphere were 100–200 °C lower than the values found for the air atmosphere. T m values determined for the blends were also dependent on the oxy-fuel conditions, with larger differences observed with the 60 %CO2–40 %O2 mixture than with the 70 %CO2–30 %O2 atmosphere with respect to air combustion. However, the greatest decreasing effect compared to air of biomass addition on T m values was found for the blend with the lowest biomass content (20 % biomass w/w).

Numerical modeling of pulverized coal combustion at thermal power plant boilers

热发电厂锅炉粉煤燃烧的数值模拟

Journal of Thermal Science, June 2015, Volume 24, Issue 3, pp 275-282

Abstract:The paper deals with development and application the numerical model for solution of processes at combustion chamber of the thermal power plant boiler. Mathematical simulation is based on solution of physical and chemical processes occuring at burning pulverized coal in the furnace model. Three-dimensional flows, heat and mass transfer, chemical kinetics of the processes, effects of thermal radiation are considered. Obtained results give quantitative information on velocity distributions, temperature and concentration profiles of the components, the amount of combustion products including harmful substances. The numerical model becomes a tool for investigation and design of combustion chambers with high-efficiency and reliable operation of boiler at thermal power plants.

Numerical Simulation of Pulverized Coal MILD Combustion Using a New Heterogeneous Combustion Submodel

基于新非均质燃烧子模型的粉煤MILD燃烧数值模拟

Flow, Turbulence and Combustion, January 2014, Volume 92, Issue 1, pp 319-345

Abstract:The scope of this investigation is the application and analysis of a recently developed submodel (Schulze et al., Oil Gas Science Technol, 2013, doi:10.2516/ogst/2012069) for char particle combustion and gasification. The distinguishing feature of this model is a detailed representation of the diffusion and convection processes as well as the homogeneous reactions in the boundary layer around the char particle. These processes are fully coupled to the heterogeneous particle kinetics. The model was implemented into the CFD code ANSYS-Fluent. The coupled solver is used for simulating the IFRF full scale pulverized coal combustion MILD furnace, for which detailed experimental data are available for model evaluation (Orsino et al., IFRF Doc. No F46/y/3, 2000) The new model yields improved agreement with measured data as compared to the standard modeling approach. This can be directly related to the prediction of the char burnout rate. For further analysis, the mixing field in the IFRF furnace is investigated in detail by introducing four mixture fractions for pyrolysis products, char burn-off gases, primary and secondary air, respectively. The solutions of the respective transport equations are used to define the local stoichiometry both in the gas phase and on the particle surface in such a multi-stream system. The conditions in the particle surrounding gas phase as well as on the particle surface are used to define the regime of particle-gas interaction based on the simulations with the new submodel. It can be shown that for certain conditions the homogeneous reactions in the particle boundary must be accounted for.