Current Issue : October-December Volume : 2022 Issue Number : 4 Articles : 5 Articles
This publication presents changes in sawdust of selected deciduous trees as a consequence of impulse electric field (PEF) stimulation. The analyzed changes concerned the time–temperature characteristics created during the measurement of the heat of combustion of the audited material. Based on experience from previous studies, two alternatives of electric field strength and one variant of capacitor discharges (pulses) were adopted. The results were compared with the sample not treated with PEF. The selected parameters were the result of previous studies, in which the applied variants seemed to be the most promising, i.e., they gave the most diverse results. The research presented in this work has shown that the pulsed electric field affects the time and temperature characteristics of biological material. The changes are most pronounced for the last period of the combustion process, from the moment the maximum temperature was reached to the end of the process. The obtained results indicate that birch and ash react to PEF conditioning in a similar manner. The second group, due to the similarity of the obtained results, is oak and linden. It seems that, apart from the electric field strength, the obtained results are also influenced by the cellulose content in the tested wood. The described process has a very low energy-efficiency, but the reduction of the energy needed to generate the impulse could lead to the possibility of applying the obtained results in industry....
Studies show that accurate division of spontaneous combustion (SC) zones in the goaf and the determination of the prediction system of the SC index are of great significance to prevent spontaneous and unwanted combustions in the goaf. Aiming at resolving the problem of coal SC in the goaf of an “isolated-island” fully mechanized caving face, a multiphysics model coupled with gas flow field and gas concentration field was established in the present study. Taking the 8824 working face of Nanzhuang coal mine as the research object and the oxygen concentration as the division index, coal SC was simulated in the goaf. The obtained results show that the ranges of heat dissipation zone, oxidation zone, and the asphyxia zone on the air inlet side are around 0–107 m, 107–239 m, and beyond 239 m, respectively. Moreover, the ranges of the three zones on the return air side are 0–13 m, 13–189 m, and beyond 189 m, respectively. The ranges of the three zones in the middle of goaf are 0–52 m, 52–213 m, and beyond 213 m, respectively. The performed analyses demonstrate that the obtained simulation results are consistent with the experimental data. Meanwhile, the coal programmed temperature rise experiment was carried out to improve the prediction index gas system of SC. It was found that CO and C2H4 can be used as early warning indices of SC in the goaf, while C2H6, C3H8, and C2H4/C2H6 are auxiliary indices to master the coal SC....
An Ni-CeO2 catalyst with high Ni loading (50 wt.%) prepared by a salt-assisted solution combustion method was characterized by different methods and used for CO2 methanation. The specific surface area of the Ni-CeO2 catalyst prepared by salt-assisted solution combustion is 7 times that of the catalyst prepared by conventional solution combustion. The Ni-CeO2 catalyst prepared by salt-assisted solution combustion has smaller particle sizes of Ni and exhibits excellent activity at low temperatures. The high Ni loading and small Ni particle size can provide more metal Ni site and Ni-CeO2 interface, which help to improve the CO2 methanation performance....
Recently, an aerosol dynamics model—the Soot Aggregate Moment Model (SAMM)—that can efficiently trace the size distribution and morphology of soot particles was developed. In order to examine the applicability of SAMM in association with open-source CFD and combustion chemistry solvers, the formation and growth of soot particles in a premixed ethylene/air combustion were simulated by connecting SAMM with OpenSMOKE++ in this study. The simulation results were compared with available measurements and with the results of a previous study conducted using SAMM connected with an in-house CFD code and the CHEMKIN combustion chemistry package. Both CHEMKIN and OpenSMOKE++ underestimated C2H2 concentration compared to previous measurements, with deviation from the measured data being smaller for OpenSMOKE++. The chemical mechanism adopted in the CHEMKIN package was found to underestimate pyrene concentration by a factor of several tens. OpenSMOKE++ predicted much higher soot precursor concentrations than CHEMKIN, leading to a higher nucleation rate and a faster surface growth in the latter part of the reactor. This resulted in a reasonable soot production rate without introducing an artificial condensation enhancement factor. The overestimation of low-molecular-weight polycyclic aromatic hydrocarbons in the latter part of the reactor and the neglect of sintering led to an overprediction of soot production and primary particle number. This result indicates that accounting only for obliteration without sintering in SAMM could not simulate the merging of primary particles sufficiently. This indication merits further investigation....
The article presents the test results of the co-firing process of a glycerine fraction derived from the production of liquid biofuels (fatty acid methyl esters) with coal. The test was performed in industrial conditions using a steam boiler with a capacity of approx. 2 MW in one of the building materials manufacturing facilities. The process of co-firing a mixture of a 3% glycerine fraction and eco-pea coal was evaluated. The reference fuel was eco-pea coal. The combustion process, composition and temperature of exhaust gases were analyzed. Incorrect combustion of glycerine fraction may result in the emission of toxic, mutagenic, and carcinogenic substances, including polycyclic aromatic hydrocarbons. During the test of the combustion process of a mixture of glycerine fraction and eco-pea coal, a decrease in the content of O2, CO, and NOx was observed as well as an increase in the content of H2, CO2, and SO2 in the fumes and growth of temperature of exhaust gases in relation to the results of combustion to eco-pea coal. Reduced content of carbon monoxide in exhaust gases produced in the combustion could be caused by the high temperature of the grate or by an excessive amount of oxygen in the grate. The higher content of oxygen in glycerine changes the value of excess air coefficient and the combustion process is more effective. The bigger content of sulfur dioxide in burnt fuels containing the glycerine fraction could be caused by the presence of reactive ingredients contained in the glycerine fraction. The reduced content of nitrogen oxides in exhaust gases originating from the combustion of a fuel mixture containing a fraction of glycerine could be caused by lower content of nitrogen in the glycerine fraction submitted to co-firing with coal and also higher combustion temperature and amount of air in the combustion chamber. The increased content of carbon dioxide in exhaust gases originating from the combustion of fuel mixture containing glycerine fraction could be caused by the influence of glycerine on the combustion process. The increase of hydrogen in the glycerine fraction causes the flame temperature to grow and makes the combustion process more efficient....
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