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Co-combustion Characteristics Of Oil Shale Retorting Solid Waste And Biomass

Posted on:2013-11-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:H P LiuFull Text:PDF
GTID:1262330392969742Subject:Thermal Engineering
Abstract/Summary:PDF Full Text Request
As the important supplementary energy of conventional oil and gas resources, oilshale shows more and more important status in the global resource strategy. However,a huge quantity of retorting solid waste will be formed in thermal processing of oilshale in vertical retorts. The retorting solid waste will gradually become thebottleneck in the development and utilization of oil shale. At the same time, it is notonly a waste of energy and resources, but also poses a great threat to the environment.As the low grade fuel with high ash content, low calorific value and low volatile, ithas been shown that circulating fluidized bed combustion of retorting solid wastecould be a promising technology. In this thesis, the co-combustion way of retortingsolid waste with high calorific value biomass has been proposed, and theco-combustion characteristics and interactions between oil shale retorting solid wasteand biomass have been deeply studied in the theory and experiment aspects.A detailed analysis of the basic fuel properties of the oil shale retorting solidwaste and biomass has been made. A large number of experimental studies onco-combustion characteristics of retorting solid waste and biomass have beenconducted and the effect of fuel type, mixing ratio and heating rate on co-combustioncharacteristics have been systematically discussed. The TG-DTG results show that,with the increase of biomass mixing proportion, the ignition temperature and burnouttemperature are reduced, and the burning rate are increased, and the combustioncharacteristics get improved. With the increase of the heating rate, the combustion TGcurves shift to the high temperature range, and the ignition temperature, burnouttemperature and the temperature corresponding to the maximum burning rate areincreased. Meanwhile, the dehydration peak, volatile release peak and the fixedcarbon burning peak all get broaden, and all the peak values are increased.In theory, based on the single scan rate method (Coats-Redfern equation),iso-conversional method (KAS equation and DAEM model), the co-combustionkinetic characteristics of retorting solid waste and biomass have been studied in detail.The results show that the dynamic characteristic obtained from iso-conversionalmethod is relatively close, while the difference exists compared with the method ofsingle scan rate method, but the regularity is consistent.The synergy of co-combustion process between the oil shale retorting solid waste and biomass has been investigated in detail and the interaction effect of the mixingratio, heating rate, types of biomass and other factors on the co-combustioncharacteristics has been revealed. Based on the Avrami transformation kinetic theory,the TG combustion process is simulated. The simulation results of free energy ofactivation are consistent with that obtained by KAS equation. This provides atheoretical basis for further exploration of co-combustion characteristics ofmulti-component of oil shale retorting solid waste and biomass.On the basis of the co-combustion mechanism, the combustion experiment of oilshale retorting solid waste with cornstalk particles is finished on circulation fluidizedbed test pilot. A comprehensive and systematic research of fuel proportion, a primaryair ratio on combustion temperature, slag, recycle, combustible content in fly ash andcombustion efficiency. The results show that, in the oil shale retorting solid wastemixed with a certain proportion of cornstalk particles, it can be completely stable andefficient combustion.Based on Euler closed two-fluid model, the numerical simulation for a65t/h oilshale-fired high-low bed CFB boiler that has been put into operation has beenperformed and verified with the actual operating data. A new130t/h oil shale retortingsolid waste-fired and cornstalk particles-fired high-low bed CFB boiler has beendeveloped. The flow characteristics of the boiler have been simulated and predicted.
Keywords/Search Tags:oil shale, retorting solid waste, biomass, co-combustion, CFB
PDF Full Text Request
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