Experimental Study On Resource Utilization Of Ash

Coal, as the most important energy source in China, distributes in majority of north China with high ash content, which leads to large amounts of ash emission. However, Stone Coal, with low carbon content and low heat value, is comparatively abundant in south China. Vanadium, as an associated element of Stone Coal, is one kind of important strategic materials. Unfortunately, super-accumulation of leavings after extracting Vanadium will be overground stockpiled, which results in land occupation and environmental pullution. On the one hand, the current silicon aluminum material commonly uses clay in cement production. But due to its higher reaction activation energy, it needs excessive energy consumption during the process of calcinations, furthermore, clay mining destroys vegetation and farmland, therefore clay has been banned by many developed countries for cement production. On the other hand, cement production could consume large amounts of ash and leavings. Thus, ash used in cement production could not only saving rescources, but also improving environmental conditions, which is in accordance with the ideology of sustainable development strategy.To avoid the existing problems, such as low recovery rate of Vanadium, environmental pollution and small capacity in the conventional vanadium extraction processes, the calcium-modified roasting process in circulating fluidized bed was used. Mixed Dunhuang-Stone Coal with calcium-based additives as material ball, then put it in the circulating fluidized bed (thermal input power is 1MW) in order to study the Vanadium extraction characteristics of vanadium-containing stone coal calcination in CFB, ash characteristic and leaching characteristics of vanadium. The results showed that CFB had good effect on the roasting oxidation of Vanadium in stone coal because the main components of combustion products was fly ash with 70% Vanadium, which is 23.3% more than original Stone Coal and the V2O5 leaching rate of ash was close to 70% at a liquid-solid ratio of 2:1, sulfuric acid concentration of 15% and leaching temperature of 90℃. It is foresaw that the roasting oxidation and V2O5 leaching effect of Dunhuang Stone Coad could be better in the actual calcination of CFB.Physicochemical properties of Vanadium extraction leavings and gasified ash have been analyzed. It showed that the chemical constituents and mineral composition of these ash are very similar with the common argillaceous materials used in cement production, also contain lots of oxygen-rich minerals and trace elements which play a positive mineralization role in clinker calcination and cement hydration as well as the improvement of anti-pressure and anti-folded intensity. Besides, gasified fly ash contains 29.53% of carbon content and 8967kJ/kg of calorific value so that it can be uses as inferior coal for heat supply and ingredient for shaft kiln cement to save energy comsumption in cement industry.Based on the calcination process of Pre-calcining Kiln, we designed raw mix formula with Vanadium extraction leavings from the process of vanadium extraction by interim product with sulfuric acid leaching from ash of stone coal. We adopted Degression Making-up Method to optimize 15 formulations. Then we calcined it to be clinker under the calcination temperature of 1250℃,1300℃,1350℃,1400℃和1450℃. According to the analysis of fCaO, XRD, SEM and compression strength tests, comparing with the industry clinker, we can find that cement clinker is successfully calcined basically with the temperature of 50℃decreased. Therefore, we are sure that cement clinker with Vanadium extraction leavings as argillaceous material is successful and meaningful for the reason that it can reduce calcination time, save energy comsumption, increase burnability of raw meal and improve quality of clinker.Based on the erect kiln cement process, we designed raw mix formulations with fly ash.of ash-agglomerated gasifier. We set the three modulus KH=0.92-0.95, SM=1.8-2.2, IM=1.1-1.5. According to the different fly ash- anthracite ratio and fly ash replacement rate of clay, we adopted Equation-solving Method to optimize 91 formulations. It shows that gasified fly ash could be used as argillaceous material for erect kiln cement production and save energy for the remarkable reduction of Anthracite consumption.We have experimental study on the utilization of Vanadium extraction leavings from Acid Leaching Process as Cement Active Admixture. Vanadium extraction leavings used alone or mixed with stone coal ash in the weight ratio of 10%,15%, 25%,30%,35%,40% and 45%. According to the physical inspection of cement samples, we can find that Vanadium extraction leaving belongs to active admixture and whether it was used alone or mixed with stone coal ash, cement performances index met Ordinary Portland Cement Standard GB175-2007 and cement of 32.5 grade would be generated. Moreover, the 28d pressure intensity of Vanadium extraction leavings is far more than stone coal ash of cement factory, which makes Vanadium extraction leavings, used as cement active admixture, be sold at high price in order to greatly improve economic and environmental benefits of comprehensive utilization of Stone Coal.We have experimental study on the utilization of Vanadium extraction leavings from Second-calcination as Cement Active Admixture. The second Vanadium extraction leavings used alone or mixed with stone coal ash in the weight ratio of 10%, 20%,30% and 40%. According to the physical inspection of cement samples, we can find that whether the second Vanadium extraction leaving was used alone or mixed with stone coal ash, cement performances index met Ordinary Portland Cement Standard GB 175-2007 and cement of 32.5R grade would be generatedm, but the effect is still not as good as Vanadium extraction leavings from Acid Leaching Process. The results of R28 show that the second Vanadium extraction leaving belongs to active admixture. Gypsum, compositon of the second Vanadium extraction leavings, is enough to replace applied plaster.Therefore, the utilization of Vanadium extraction leavings from Second-calcination as Cement Active Admixture could not only use leavings entirely, but also reduce cost of gypsum in cement production.At last, we have experimental study on the utilization of bottom slag, which is the slag from CFB calcination of ash-agglomerated gasified slag, as Cement Active Admixture. The slag used alone or mixed with stone coal ash in the weight ratio of 10%,15%,25%,30%,35%,40% and 45%. According to the physical inspection of cement samples, we can find that whether the slag was used alone or mixed with the second stone coal ash, cement performances index met Ordinary Portland Cement Standard GB175-2007 and cement of 32.5R grade would be generatedm even up to 42.5R. Furthermore, the results of R28 also show that gasified bottom slag is more active than Vanadium extraction leavings from Acid Leaching Process. The results of R28 show that the second Vanadium extraction leaving belongs to active admixture.