Combustion Properties Of Coal Research Articles

Study on the influence of different acid and alkali environments on the spontaneous combustion properties of coal

To examine the impacts of diverse acid and alkali environments on the autothermal oxidation characteristics of coal, the microporous structure, active functional groups and oxidative thermodynamic parameters were investigated using SEM, TG-DSC and FTIR experimental methods. The results show that the number of pores on the eroded coal increases and the pore size increases compared to the neutral environment of pH = 7. The content of major oxygenated functional groups decreases and is converted to more reactive oxygenated alkali metal structures, with an approximate reduction of 35 % for ketone carbonyl CO and 57 % for acid carboxylic acid CO at pH = 10. The acidic environment promotes the combination of hydroxyl-hydrogen bonding functional groups with oxygen. The reactive exothermic process of eroded coal was promoted in pH = 4, 6, 8, and 10, and the combustion-promoting effect on NMG was more obvious, in which the ignition point temperature T6 of HG was reduced by 7.6 °C, 5.9 °C, 8.2 °C, and 5.1 °C, respectively. During the fitting process using the model-free method, the best fit for the oxygen uptake and weight gain stage and the combustion pyrolysis stage was achieved by the KAS and Friedman methods, respectively, and efficient fire extinguishing could be achieved in the pre-combustion pyrolysis stage (0.1<α < 0.2).

Analysis of pyrolysis and combustion characteristics of several coals with different coal properties

Studying the pyrolysis and combustion properties of coal is advantageous for promoting the environmentally friendly and effective exploitation of this resource. To investigate the pyrolysis and combustion characteristics of coal with varying types and properties, a thermal gravimetric experiment was conducted. This experiment aimed to determine the characteristic index and comprehensive combustion index. The pyrolysis characteristics of pulverized coal in a nitrogen atmosphere and the rapid combustion characteristics in an oxygen atmosphere were examined separately. The obtained results provide insights into the governing principles of the carbon content effect on the pyrolysis and combustion processes of pulverized coal particles. The findings indicate a positive correlation between the carbon content of coal and the efficiency of pyrolysis and combustion processes for pulverized coal particles. Moreover, a notable enhancement in the performance of pyrolysis and combustion is seen with increased carbon content.

Assessment of combustion characteristics of high ash Indian coal, petroleum coke and their blends for cement industry using TGA

This work investigates the combustion analysis of coal, petroleum coke and their blends. Coal and petroleum coke were characterized by proximate analysis, ultimate analysis, gross calorific value determination and ash analysis. Combustion performance of parent fuels and their blends were evaluated by thermogravimetric analysis followed by the analysis of different characteristics parameters, namely ignition temperature, peak temperature, burnout temperature and combustion efficiency. Results signify that petroleum coke has poor combustion characteristics compared to coal. After the rise in petroleum coke from 10 to 50 mass %, ignition temperature reduced from 413 to 385 °C, while insignificant variations occurred in peak temperature and burnout temperature. Such observations show natural reduction in ignition characteristics without significant modification in coal's burning profile. Combustion efficiency at 450 °C reduced from 46.18% to 34.77% as petroleum coke increased from 10 to 50 mass %, signifying decline in the combustion properties of coal. Kinetic analysis shows that petroleum coke has the maximum activation energy (182.11 kJ/mol) than coal (84.84 kJ/mol). Analysis of changes in enthalpy, Gibbs free energy and entropy inferred that individual combustion of both coal and petroleum coke is difficult, while blends have improved combustion characteristics than petroleum coke.

Evaluation of Synergy Between Lignite and Carbonized Biomass During Co-Combustion

Abstract Synergy often occurs between coal and biomass during co-utilization, and the combustion reactivity and combustion properties of coal are affected mainly due to high volatile matter in biomass. However, it is not clear that a synergistic interaction will be encountered if coal is processed with biochar that contains a limited amount of volatiles due to charring process. In this article, the existence of synergy was questioned based on the thermal analysis data obtained from the co-combustion of several biochars and lignite. The biochars produced at 400 °C from lignocellulosic biomasses such as Fraxinus (FR—ash tree), Populus hybrids (PO—hybrid poplar), and Rhododendron (RH) were blended with Turkish lignite (Adıyaman-Golbasi) to form blends that contain 5–15% biochars. These blends were burned in a thermogravimetric analyzer, and the combustion characteristics of the blends were evaluated, considering the criteria that include the reactivity and combustion performance indices including ignition index, comprehensive combustion index, burnout performance index, combustion stability indices, and rate and intensity index. Also, synergy indices such as synergy indicator, synergy factor, and interaction coefficient were calculated to identify the presence and intensity of synergy. It was concluded that depending on the type of biochar and the addition rate, changes occurred in the combustion properties of the coal, which can sometimes be considered as additive behavior and sometimes as a synergistic interaction. The presence of 5% or 10% PO biochar in the blends resulted in very obvious synergies in combustion characteristics according to all eight criteria considered.

Effects of crude oil on the microstructure and spontaneous combustion characteristics of coal: a case study of weakly caking coal in the Huangling No. 2 mine, China

The effects of crude oil on the microstructure and spontaneous combustion characteristics of coal were assessed, using raw coal sample and coal samples containing 5%, 10% and 15% oil. The pore structures, oxygen adsorption capacity, surface functional groups and spontaneous combustion characteristics were characterized by the LP-N2A, TG, FTIR and temperature-programmed experiments. The LP-N2A and TG tests revealed that the presence of crude oil reduced the porosity, specific surface area and pore volume in the coal sample containing crude oil, which would suppress the transport capacity of oxygen in mesopores and micropores not to adsorb on the specific active sites of coal surfaces. FTIR analysis indicated that the amount of oxygen-containing functional groups and –OH groups decreased tremendously in the coals containing crude oil, but the content of aliphatic C–H groups showed an increasing trend. Moreover, the values of A(CH2)/A(CH3), Ahy/Aar, Aoxygen/Aar all decrease gradually with the rising crude oil contents, indicating that the crude oil reduced the average alkyl chain length and compressed the space between aromatic clusters. The results of temperature-programmed experiments showed that O2 consumption and CO production rates decreased gradually with the increase in crude oil content. The results were in agreement with the varying trend of characterization of microstructure and function groups obtained by LP-N2A, TG and FTIR tests. Furthermore, the Pearson correlation coefficient cleared that the breaking of long aliphatic chains of aromatic rings and reduction of hydrogen bonds content have a greater contribution to the suppression of spontaneous combustion than the attenuation of physical adsorption. This study concluded that crude oil lowers down the spontaneous combustion properties of coal, which could provide a reference for the prevention of spontaneous combustion of coal seam containing crude oil.

Variations in combustion properties of coal with average relative density and functional groups identified by FTIR analysis

ABSTRACT This work presents experimental results of combustion characteristics of low volatile Indian coal. Coal of different average relative density (ARD) varying from 1.35 to 2.0 was generated by density fractionation of the coal. Coal samples were characterized by proximate analysis, Fourier-transform infrared spectroscopy (FTIR), ultimate analysis, and gross calorific value (GCV). Combustion experiments were conducted to identify the effects of ARD and functional groups on combustion characteristics. It was observed that with the rise in ARD of coal from 1.45 to 2.0, the ignition temperature increased from 357°C to 417°C. Highest coal combustion rate was observed for 1.525 ARD coal, due to the presence of all types of hydrocarbons, alcoholic, aldehyde, and trisubstituted alkene (except primary amines) as seen from FTIR analysis. Analyses of coal combustion rate and GCV indicate that 1.45 ARD coal has the highest GCV, heat release rate, and lowest ash generation rate, properties that are best suitable for thermal utilities.

Assessing the effectiveness of a high-temperature-programmed experimental system for simulating the spontaneous combustion properties of bituminous coal through thermokinetic analysis of four oxidation stages

The spontaneous combustion of coal is characterized by high-temperature oxidation. This study used a self-made programmed experimental system to maintain temperature parameters at specified levels to simulate the combustion properties of coal. The oxygen concentration was determined to be inversely proportional to indicator gas concentrations. Five characteristic temperatures were achieved: critical temperature (97.45 ± 7.15 °C), crack temperature (149.28 ± 8.32 °C), active temperature (206.95 ± 15.05 °C), speedup temperature (263.45 ± 6.35 °C), and ignition temperature (390.85 ± 27.05 °C). Thermal characteristics were analyzed by dividing the oxidation into the following temperature stages: the critical temperature stage, crack–active–speedup temperature stage, speedup-ignition temperature stage, and combustion stage. Furthermore, the differential and integral kinetic methods were used to compute the apparent activation energy in the four aforementioned stages. The results indicated that the apparent activation energies decreased through the first three stages and then increased in the fourth stage. Therefore, the crack–active–speedup temperature stage was determined to be potentially dangerous during oxidation because gases increased rapidly at this stage; such gases included CO, which is particularly harmful to human health. The thermal energy release also increased gradually at this stage.

Combustion characteristics of palm pressed fibres biochar and sub-bituminous Malaysian coal

In this research, the combustion properties of coal and biochar were investigated and compared to identify the potentiality of biochar for coal replacement application. Biochar is derived from the pyrolysis of palm pressed fibre (PPF) at 400 oC. Thermogravimetric analysis (TGA) was used to study the combustion profiles of the materials. The biochar and coal were combusted via thermogravimetric analysis from ambient temperature to 800 oC at 10 oCmin-1 of heating rate. From the results, biochar showed the high calorific value of 27.30 MJkg-1compared to that of coal 26.21 MJkg-1. Furthermore, biochar comprised the greater content of carbon and fixed carbon. Although, during combustion, coal releases high heat of 0.052 W than biochar which gave 0.049 W. This reveals that the biochar produced from PPF can be a perfect competitor against coal for heat generation. This finding could assist in promoting the application of biomass as an alternative to fossil fuel.

Surface physicochemical properties of semi-anthracitic coal from Painan-Sumatra during air oxidation

Painan coals of West Sumatra were selected as semi-anthracitic coal sample for studying the physicochemical properties such as measurement, evaluation and description of the changes of surface characteristic of coal sample and their oxidation in the atmospheric air at a temperature ranging from 105 to 400 °C for 30 min. Several methods are adopted to analyze and discuss several phenomena of the oxidized Painan coal surface during oxidation process for the change in the physicochemical properties as determined by Atomic Force Microscope (AFM), contact angle, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric and Differential Thermal Analysis (TG–DTA) analyses as well as other supporting analytical equipment. AFM analyses revealed some changes in adhesion force and surface morphology with more adhesion force available between 0.6 and 8.6 nN on polished coal surfaces due to the increased oxidation temperature. The study revealed that the extent of hydrophobicity of coal surface decreased with the increased of oxidation temperature expressed as contact angles at about 80° and 20°. Another phenomenon occurred during the experiment was hydrophilicity index of coal surface increase at approximately 1.3 and 2.9. Oxidation of coal that occurred with increased temperature also indicated an increase in oxygen content from 3.8% to 22.9 wt%. Increased oxygen functional group also noted that oxidation of coal took place during the treatment. We also found that oxidation treatment also affected the combustion properties of coal: decreasing ignition temperature between 452.9 and 317.6, lowering the reactivity of coal at maximum combustion rate temperature, and reflecting their char characteristics as burnt out, ranging from 652.3 to 648.5 °C.

Comparative study on structural properties and combustion kinetics of Chinese Shenhua long flame raw coal and its pyrolytic char

Research on the structural and combustion properties of coal is of great importance for its conversion and applications in view of fundamental studies. In this work, we conducted the first detailed study on the structural properties and combustion kinetics of Chinese Shenhua raw coal (RC) and its pyrolytic char (PC). The combustion kinetics was simulated by using the random pore model (RPM). The results showed that RC and PC were composed of both a plant‐cell‐like structure and a discrete particulate structure. In addition, PC had a larger specific surface area, finer particles, higher aromaticity, and higher degree of aromatic ring condensation than those of RC. Combustion of PC showed higher ignition temperature, lower burnout temperature, and a higher combustion index compared to RC. A high correlation coefficient R2 (0.999) and a low average error θ (0.008) were obtained using the RPM. The combustion apparent activation energy E and the structural parameter ψ of RC were 40.30 kJ mol−1 and 0.53, respectively. For PC, the values of E and ψ were estimated to be 60.01 kJ mol−1 and 0, respectively. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 766–774, 2017

98/03173 Effect of particle size on the thermal and combustion properties of coal

98/03173 Effect of particle size on the thermal and combustion properties of coal

Effect of particle size on the thermal and combustion properties of coal

Abstract In this research effect of particle size on the combustion properties of Cayirhan coal sample was studied. Non-isothermal thermogravimetry and derivative thermogravimetry (TG/DTG) experiment were carried out for twelve different size fractions of the Cayirhan coal sample. Thermogravimetry experiments were performed from ambient to 900°C in air atmosphere. Differential thermogravimetric data were analysed using an Arrhenius type reaction model assuming a first-order reaction. Kinetic parameters of the samples are determined and the results are discussed.

Thermogravimetric analysis and its application for estimating the combustion properties of coal from the study of small samples

The mass dispersion of a 300 mg coal sample, which is heated at a constant rate of temperature increase, is sampled and stored as a data string, along with the sample and furnace temperatures. The data are processed to produce mass dispersion, DTG and D2TG curves. From this information quasi proximate analysis indexes are computed along with several others which derive from the curve features. The indexes are used as a group, to select from a specially prepared data bank, standard reference information from all S.A. coals which compare best with those of the sample. The anticipated combustion characteristics of the sample are estimated by analogy with the standards and by analytical calculations.