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31.
A series of carbon dioxide gasification tests of waste biomass chars were performed in a thermogravimetric analysis system, at non-isothermal heating conditions. The effects of the inorganic constituents of the fuels on thermal conversion characteristics were examined. Reaction rates were determined by developing a power law model.The bulk of char gasification process occurred between 800 and 950 °C. Maximum reaction rate and conversion were exhibited by waste paper char, due to its higher surface area.Inherent alkaline and alkaline earth carbonates and sulphates acted as catalysts, by increasing the reactivity of the fuels in carbon dioxide and causing their degradation to start at lower temperatures (60-75 °C).The kinetic model fitted the experimental results accurately. Activation energy values and reaction order ranged from 180 to 370 kJ/mol and 0.4 to 0.6, respectively, among the chars, indicating a chemically controlled process. 相似文献
32.
The objective of this work was to promote the formation of the aragonite polymorph of calcium carbonate, which has some valuable applications in industry, via the mineral carbonation route. The combination of ultrasound with magnesium ions promoted the formation of pure aragonite crystals at optimum conditions. It was possible to synthesize high purity aragonite precipitates at temperatures ranging from 24 °C to 70 °C, with the resulting powders possessing varying particle size distributions (from sub-micron up to 20 μm) and crystal morphologies (from acicular needles to novel hubbard squash-like particles). Several process parameters were found to influence the produced calcium carbonate polymorph ratios (aragonite over calcite). Higher values of magnesium-to-calcium ratio, intermediate ultrasound amplitude (60%), continuous ultrasound application (100% cycle), introduction of ultrasound pre-breakage, lowering of the CO2 flow rate, and increase in the relative concentration (g/L Ca(OH)2), all promoted aragonite formation. A potential route for industrial production of this material has been identified via a fed-batch process, which effectively reutilizes magnesium chloride while maintaining high aragonite yield. The results presented herein are significantly superior to aragonite formation using only single promoting techniques, typically found in literature, and go beyond by focusing on pure (>99%) aragonite formation. 相似文献
33.
This paper presents a method for assessing the normalized age factors, which allow accelerated alkali-aggregate reaction (AAR) tests performed at various temperatures (20, 40 and 60 °C) to be related to the conditions encountered in situ in concrete structures. The evaluation of normalized age factors is based on the comparison of many experimental results taken from the literature concerning laboratory tests and in situ measurements. The use of these factors permits us to evaluate, from the results of an accelerated test performed at 60 °C, the protection time against AAR that could be expected for in situ concretes containing mineral admixtures (silica fume and fly ashes). The results show that, in addition to the inhibitory action of mineral admixtures leading to a strong decrease in the final AAR-swelling, the protection against abnormal expansion caused by AAR increases significantly when mineral admixtures are used. Abnormal expansion is expected at 2-4 years for plain concrete compared to 7-50 years for concrete with mineral admixtures. 相似文献
34.
从透辉石的结构特征探析其在陶瓷中的应用 总被引:1,自引:0,他引:1
透辉石为典型的热液接触变质矿物,系花岗岩浆与钙质白云岩接触交代的产物。多呈针柱状、柱粒状结构,富含SiO2、CaO、MgO,热性能好、烧失量低、资源丰富,是生产墙地砖的优质原料。含铁低的透辉石亦可用来生产日用细瓷,具有产品成本低、外观性能好、透光度高、机械强度高、热稳定性好等特点。 相似文献
35.
The mineralogy of clay-rich mineral matter isolated from a range of Australian bituminous coals has been evaluated in quantitative terms from X-ray powder diffraction (XRD) patterns using a Rietveld-based data processing technique. The chemical composition of coal ash derived from this mineral matter has been calculated and compared to the directly determined composition of the ash prepared from the same coal samples. Although there are some minor differences due in part to uncertainty regarding the actual composition of several minerals, the compositions indicated by the two methods show a relatively high correlation, suggesting that the Rietveld technique provides mineralogical analyses that are consistent with independently determined chemical data. Comparison of the normalised clay mineral percentages from the Rietveld analysis to quantitative interpretations based on a peak intensities in glycolated and heat-treated oriented aggregates of the respective clay fractions also shows a high correlation, confirming mutual consistency of the two different mineralogical analysis methods. Such quantitative mineralogical data are significant to a range of coal exploration, mining and utilization activities, including seam correlation, material handling and ash and slag formation in combustion processes. 相似文献
36.
In order to utilize the solid residues simultaneously with clean and high-combustion efficiency when firing high sulfur and ash coal sludge generated in coal washing process in China, the mineral composition and usability of combustion solid products were investigated when injecting compound additives into series of coals or coals blended with sludges. In this study, a single burner furnace was used for combustion test and the solid residues were analyzed by means of X-ray powder diffraction method. The influences of temperature, residence time, and compound additives on mineral characteristics of the residues have been discussed. The results indicate that, the compositions of solid products are principally free oxides and a small amount of gehlenite, dicalcium silicate, etc. below 1000 °C; when the firing temperature increases above 1100 °C, the major minerals are gehlenite and dicalcium silicate. Also it can be found that several seconds is not enough for mineral complete reaction, and suitable calcium oxide content and particles fineness are recommended. The result of combustion test shows that there is no evident effect on ignition and combustion when the additive/coal (a/c) ratio is below 30% by weight; and the normal stable combustion with ignition delay can be achieved when the a/c ratio is ranging between 30 and 50%; but the a/c ratio exceeding 50% will damage combustion and even result in fire extinction. Industrial test results indicated that the solid residues was composed of silicate mineral rich in belite by adopting compound additives, but the comprehensive reaction mechanism needs further studies as well as the effect of additives on combustion should be concerned. 相似文献
37.
This study focuses on the determination and concentration of twelve elements (Na, K, Ca, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn and Cd) occurring in sub-bituminous Assam coals and their geochemical association. Distribution of these elements between organic and mineral matters was studied. Comparison of the results of three coals has shown that three elements (Mg, Ca and Mn) are significantly organic bound, while five elements (Fe, Co, Ni, Cu and Zn) are significantly mineral bound; Cd is 50% bound to either organic or mineral matter. FTIR and XRD studies reveal qualitative information about the bonding pattern and nature of components of the mineral matters. The results obtained in this study have considerable geochemical and technological interests. 相似文献
38.
The mineral transition mechanism and self-pulverization property of the sintered products in the Ca2Al2SiO7-CaO system were systematically studied using pre-synthesized gehlenite determined by XRD, SEM, FTIR and particle size analyses. The minerals of Ca12Al14O33, CaAl2O4, Ca3SiO5 and Ca2SiO4 are formed by the direct reactions of Ca2Al2SiO7 with CaO. CaAl2O4 reacts with CaO to form Ca12Al14O33 or Ca3Al2O6, while Ca3SiO5 reacts with Ca2Al2SiO7 to form Ca2SiO4 and calcium aluminate compounds. The sintered products mainly contain CaAl2O4, Ca12Al14O33 and Ca2SiO4 at 1350?°C or above 1500?°C when the molar ratio of CaO to Al2O3 is 1.0. Increasing the sintering duration or the CaO consumption promotes the transition of Ca2Al2SiO7 to Ca2SiO4 and calcium aluminate compounds when sintered at 1350?°C, which accordingly improves the self-pulverization property of the sintered products. The formed minerals of Ca12Al14O33, CaAl2O4 and Ca2SiO4 transform into Ca2Al2SiO7 again when the sintering temperature is between 1400?°C and 1450?°C, and the corresponding self-pulverization property of the sintered products deteriorates sharply. 相似文献
39.
Marta K. Schütz Natália F. Lopes Angélica Cenci João Marcelo M. Ketzer Sandra Einloft Jeane Dullius Rosane Ligabue 《化学工程与技术》2018,41(3):573-579
Carbon dioxide (CO2) gas is the main contributor to climate change. CO2 storage in underground brines and oil‐field brines by mineral trapping has been considered as a promising alternative in order to reduce CO2 emissions. However, permanent storage of CO2 in stable carbonate minerals is greatly dependent on brine pH, being favored over an alkaline pH. The effect of alkaline additives (NaOH, KOH, CaO) and buffer solutions (NaHCO3/NaOH, Na2HPO4/NaOH, NH4Cl/NH4OH) on the mineral trapping of CO2 under mild conditions using a synthetic brine is investigated. The results indicate that both NaOH+NH4Cl/NH4OH and KOH+NH4Cl/NH4OH mixtures promote precipitation mainly of calcium carbonate (CaCO3). 相似文献
40.
转炉钢渣粉磨性能的实验研究 总被引:16,自引:1,他引:16
对转炉钢渣粉磨性能进行了实验研究。结果表明,钢渣的易磨性比熟料差,但优于矿渣。在钢渣所合矿物中,硅酸盐矿物易磨,含铁矿物难磨。通过粉后方式,可以将钢渣中具有胶凝活性的矿物选择性分离出来。 相似文献