Papers by Keyword: Co-Processing

Abstract: Municipal solid waste incineration fly ash (MSWIFA) is a kind of hazardous waste. In the recent years, the demand for the disposal of MSWIFA has gradually increased with the increase of its production. The co-processing of MSWIFA in cement kiln has become the future development trend in this field due to the advantages of large disposal capacity, thorough disposal and low secondary pollution. In this paper, the life cycle assessment (LCA) was used to analyze the environmental impact of cement kiln co-processing MSWIFA, and the influence of allocation method of by-products in pretreatment process on calculation results was discussed. The results of analysis on the pretreatment of MSWIFA using the water-washing process showed that the allocation method of by-products will affect the calculation results to a certain extent, especially in the toxicity-related indicators, and for pretreatment process, electricity production process is the key link to causing environmental impact. The environmental analysis for clinker product shows that the contribution ratio of pretreatment process calculated by extended boundary method was 3.33% larger than that of mass allocation method in acidification potential(AP), and 3.32% smaller than that in WCP.

Abstract: Bamboo is a prospective biomass fuel due to its high heating value and growth rate. The addition of kaolin is necessary in the thermal conversion of biomass to increase its ash fusion temperature (AFT), thus reducing fouling and corrosion of the combustion system. This study evaluates the feasibility of utilizing bamboo-kaolin co-processing residue for geopolymer synthesis. Thermochemical calculations suggest that bamboo culm ash liquidus increases by 15% by adding kaolin during combustion at a biomass to kaolin mass ratio of 95:5%. A 2³ full factorial experiment measures the effect of activator Na₂SiO₃:KOH ratio, KOH concentration, and heat-curing period at 60 °C on the early strength of geopolymer mortars. Co-processing residue of bamboo-kaolin at a mass ratio of 95:5% produces geopolymer mortars with compressive strengths in the 10.7-40.3 MPa range. ANOVA treatment of the data indicate strong positive effect of KOH concentration. Crystalline phase characterizations indicate that the co-processing is able to convert kaolin to the amorphous, more reactive metakaolin. A shift in the IR absorption band from 1034 to 1008 cm^-1 is attributed to the conversion of Si-O-Si bonds of the co-processing residue into Si-O-Al and Si-O-K bonds of the geopolymer gel phase. These results suggest the feasibility of geopolymerization as a waste valorization pathway to ensure the sustainability of the biomass-based energy production.

Abstract: The national general survey manifests that the Chinese soil is suffering from serious contamination, mainly arising from heavy metals (HM). Due to the large amount of heavy metal waste, many researchers have performed the feasibility studies on co-processing this kind of waste in cement kilns. In this paper, we review these results from the perspectives of national standards, the crystal structure of clinker, and the volatility of metals in cement kiln system. The crystal structure of clinker mineral offers physical possibility for the solidification of HM atoms. The volatility studies also indicate that most of the metals will not emit from the kiln system. For the incorporated metals in clinker, their release ratio is very low, and the leaching HM atoms can be immediately enclosed by the cement hydration products. Based on these theoretical results, we measured the HM in the raw materials and in the cement product for 1 year in a cement plant. The bag filter dust contained high level of Tl with an average of 219.30 ppm. The other metals were almost solidified by the clinker. With the vaporization of Tl in the raw materials, the circulation pattern causes the accumulation and buildup of Tl in the system. The incorporation capacity of clinker on HM is predicted in this paper, but the incorporation ratio of HM from contaminated soil, the circulation pattern of HM in cement kiln system, and the emission of HM is currently not clear and further work is in progress.

Abstract: As China develops its economy, hazardous waste generation is expected to increase rapidly. Recovery and recycling, i.e. co-processing of Alternative Fuels and Raw materials (AFRs) and treatment of hazardous waste in energy-and resource-intensive industries such as the cement industry seems to be an supplementary option to conventional technologies which can increase the overall waste management capacity in China significantly. With the largest cement production in the world, the industry can save significant amounts of non-renewable coal and raw materials by substitution with wastes which needs treatment. However, co-processing requires appropriate regulations and policies to support its development and safe and sound implementation.

Abstract: First of all, hazards of mined-out areas and municipal solid waste are analyzed. Then according to the research status of municipal solid waste processing and mine filling technologies, both of the environmental issues are researched. From the point of view that municipal solid waste and mined-out areas can be regarded as resources to each other, co-processing technology of mining and municipal solid waste is proposed. Research contents and key techniques of this technology are discussed, which contain classification and preprocessing technologies of the filled waste, experiment of filling materials ratio and the techniques of filling municipal solid waste. This technology can not only help to process the municipal solid waste cleanly, but also control the disasters of mined-out areas, so it has an important practical significance.

Abstract: The incorporation of cadmium into clinker during the co-processing of waste with cement kiln was investigated. Cadmium contained reagent was added to the cement raw meal to produce clinkers after clinkerization process. XRD analysis and SEM-EDS analysis were employed to indentify the major mineral phase of clinker and the cadmium contained mineral phase. Leaching test, sequential extraction procedures were employed to evaluate the leaching potential of cadmium in clinker. The results show the stabilization rate of cadmium during the clinkerization process is low. The incorporation ratio of cadmium in C2S is 0.32%~1.14%, the incorporation ability of cadmium in C2S is higher than C3S. The major mineral phases of clinker with the incorporation of cadmium were CH, C3S and C2S. The average leaching concentration of cadmium of clinker was 1.4 μg/L, which was higher than the blank samples. BCR Sequential extraction procedures analysis of the clinkers show exchangeable, water and acid-soluble fraction and residual fraction were very small, while the reducible phase of cadmium was up to 95.13%.