Responses Laws Of High Organosulfur Coking Coal To Microwave

Coking coal is scarce in China. In the process of coking, the sulfur remained in coke could make the steel hot-short and reduce the production capacity of the blast furnace and the SO2produced in the process could corrode the equipments and pollute the environment, which thereby limit the use of high-sulfur coking coal. Therefore, the effective removal of sulfur-containing components in coking coal is of great significance for the full use of resources and environmental protection.The removal of sulfur in coal by microwave has been proved to be feasible both theoretically and technologically. It has the advantages including mild reaction conditions, less reaction time, easy to be controlled, high reaction yield and low damage to the organic matter of the coal. However, its reaction mechanism and optimal technological conditions have not been specifically identified yet, especially the optimum working frequency, the influencing factors and microcosmic mechanism of microwave desulfurization which are difficult to be ascertained need to be studied further.Researches have been carried out to study the typical Shanxi high-sulfur coking coal in this paper, including systematic analyzation of the occurrence state of the sulfur-containing components and the relative contents of various forms of sulfur in the coal samples, so as to ascertain the organic sulfur occurrence regularity and screen out suitable sulfur-containing model compounds. Dielectric properties tests have been done to the typical high-sulfur coal samples and the model compounds to identify its microwave frequency response. The influence of additional energy field on the removal process of sulfur-containing components has been studied on the basis of microscopic quantum-mechanical calculations. Microwave desulfurization experiments have been conducted to the high-sulfur coal in order to establish matching relationship between microwave irradiation conditions and microwave desulfurization reactions, which consequently provides technical support and theoretical guidance for the industrial tests of microwave desulfurization. The main research results include:1. The occurrence states of sulfur-containing components in typical high-sulfur coal: inorganic sulfur which is of low content is mainly composed of sulfates and organic sulfur is mainly composed of thiols thioethers, thiophenes, sulfones and sulfoxides, in which thiophenes are the majority. While the content of thiophenes is on the rise when the density of the coal samples increases, the content of thiols thioethers decreases and that of sulfoxides increases after showing a downward trend. After being dealt with nitric acid and microwave irradiation, all inorganic sulfur is removed while organic sulfur is partially removed, among which thiols thioethers have the best removal effect, sulfoxides comes second, and thiophenes is of the worst.2. The results of the dielectric properties tests on typical high-sulfur coal samples are listed as follows. In the frequency range of0.2-18GHz, dielectric response peaks of different coal samples appear in1.357GHz,2.581GHz,13.728GHz and15.8GHz, etc. The increasing content of Kaolinite results in the increase of both ?' and ?". While quartz has less effect on the dielectric properties, calcite almost has on effect on it. ?" becomes lower when the particle size of coal samples increases, but it increases quickly along with the increase of moisture content in coal samples. The ?' of high density coal sample is higher than that of low density coal sample. The microwave response of high-sulfur coal is superior to that of low sulfur coal.3. Along with the change of frequency, the permittivity real parts of the five sulfur-containing model compounds basically have consistent variation tendencies. Absorption peak occurs in the range of0-3GHz, and while the range of3-8GHz remains stable the range of10-18GHz receives a few obvious absorption peaks. The strongest absorption range of model compounds by microwave is9-11GHz and in the range of0.5-2GHz, model compounds have obvious loss of microwave. The size comparison of the permittivity real parts among the model compounds is as following:Diphenyl sulfoxide> Diphenyl sulfone> Diphenyl disulfide> Dibenzothiophene> N-octadecyl mercaptan. The addition of sulfur-containing model compounds improves the dielectric polarization ability of coal. The loss angle tangent of sulfur-containing model compounds and non-sulfur model compounds are quite different along with the change of frequency, which shows that sulfur bond has obvious response to the microwave.4. Analysis of quantum mechanics simulation software:the structural optimization results of sulfur-containing model compounds show that the C-S bond length is longer than other bonds. More specifically, the C-S bond length of aliphatic model compounds is longer than that of aromatic model compounds and the C-S bond length in the ring structure is shorter than that in branched chains. In the thiophene ring structure the C-S bond order is equal to the C-C bond order and meanwhile it is larger than that in the non-ring structure. The S atoms of the model compounds with comparatively large HOMO stretch take the giving electrons positions and they lose electrons easily and react with others. Transition state path analysis shows that H2S produced by microwave heating the S radicals generated by benzene thiol and the H radicals has the minimum energy barrier57.652kcal/mol, relative to the energy of reactants. As the strength of electric field increases, the required transition state energy barrier diminishes. Considering the solvation effect, transition state requires lower energy barrier and with the increase of the solvent's permittivity, reaction energy barrier becomes larger.5. The results of microwave irradiation experiments on the typical high-sulfur coal are illustrated as follows. The coal with a particle size of1-3mm has the best desulfurization effect and the coal with a moisture content of10%possesses the maximum rate of desulfurization. The microwave irradiation desulfurization effects of840MHz and915MHz are significantly higher than that of2450MHz. After being irradiated by microwave, the relative content of mercaptan (sulfide) sulfur decreases obviously while that of thiophene sulfur increases. The desulfurization rate reaches the maximum when the ratio of HAC and H2O2additives is1:1. The desulfurization rate is constantly on the rise along with the increase of the concentration of sodium hydroxide, but the rising rate gradually decreases.