Investigation Into The Material Process Engineering Of Converting Coal Into Electricity

Both available resources and environment are the two essential issues that are closely related to the sustainable development. In this paper, the process of converting coal into electricity is optimized and integrated by employing the methodology of material process engineering, together with scientific survey and experiments. In the study, all the sub-processes involved in the process of converting coal into electricity are taken into account, under the principles of resource minimization, reuses of product wastes and resources, while the resource conservation and recycling are taken as the core value, leading to low consumption, low discharges, and high efficiency. The impact on environment by pollutants is analyzed and evaluated, in order to conform to the requirements of a comprehensive utilization of resources, energy conservation, clean production, and sustainable development, meeting the need of establishing an ecological, environmental friendly and sustainable economy. It is aimed at developing an ecological industry in the industrial region or level, by taking products and in particular the wastes from the upstream production process as the raw materials for the downstream production process, establishing an industrial metabolism and co-existence relationship.The material process engineering's frame system has be studed on the basis of the process engineering. Intersection between power industry and cement industry- residue of resources is exemplified,and the process of converting coal into electricity is optimized and integrated .Each sub-process involved in the process of converting coal into electricity is analyzed and investigated, including coal selection and blending, coal-fired power generation, comprehensive utilization of the solid wastes by coal formation, desulphurization and denitration. While the problems in each of these sub- processes are revealed, the strategies for solving them by applying new technologies and policies are suggested.The behavior and properties of fly ash produced in the pulverized coal stove (PFA) and circulation fluid bed boiler (AFBCA) have been analyzed and compared, by using the cement experimental method, chemical, XRD and SEM analyses. There is no obvious difference in chemical composition between PFA and AFBCA. PFA exhibits finer particles, a relatively smaller proportion of mineral contents, larger activeness, larger strength contribution and a smaller water requirement as compared to AFBCA. It also consists of smaller spherical particles and smoother surface. In contrast, AFBCA is associated with larger and coarser particles with porous surface.A new classification system for fly ash is proposed in this study, namely the high calcium PFA, the low calcium PFA, the high calcium AFBCA and the low calcium AFBCA, according to the ways of electricity generation and the calcium proportion. The new classification system will benefit their uses and applications in building engineering and building materials industry.Coal burning in pulverized coal fired boilers and calcination of Portland cement clinker are similar in temperature conditions, while the fly ash and cement clinker have similar chemical compositions. Taking pulverized coal fired boiler as a reactor, compound coal is burnt under combustion condition similar to that of the pulverized coal stove. On the basis of XRD phase analysis, one can conclude that with the increase in calcium content, the amount of 3Al₂O₃·2SiO₂ in coal ash gradually disappears, replaced by 2CaO·Al₂O₃·2SiO₂. With further increase in the calcium content, the 2CaO·Al₂O₃·2SiO₂ content also gradually decreases, giving rise to the belite minerals. The experimental results show that in the certain doping range of the powdered coal, the rapid combustion at high temperature generates belite minerals, suggesting that the feasibility of joint production of coal-burning electricity generation and manufacture of cement. Preliminary experimental study has been done on the property and utilization of cogeneration ash.On the basis of the current status of study on the technology of joint production of the coal-burning electricity generation and cement manufacture, some of the key existing problems have been identified. Indeed, the feasible joint production of coal-burning electricity generation and cement manufacture is a system engineering. It is necessary to integrate with the development of thermal power technology, and to organize experts and scholars from related disciplines and joint efforts in order to complete this project. The idea of the integrated production of coal-burning electricity and cement manufacture has to comply with the types of coal and furnace, the temperatures involved and other conditions, where the behavior of coal-slag changes under the boiler combustion condition has to be studied, in order to select the appropriate coal composition and to obtain the clinker of different hydraulicity ingredients safely. The exergy efficiency of two different processes of converting coal into electricity is analyzed and determined according the exergy balance principle. From the exergy of pollutants emitted, the environmental impact of converting coal into electricity is analyzed and determined. The impacts on environment and human health are also evaluated by considering the environmental negative effects, on the basis of the mathematical model combining non-carcinogenic pollutant health hazards and airborne effluents, with reference to the "ambient air quality standards" and "power plant air pollution emission standards".Having studied the technological development of generating electricity by coal-burning in our country, it is concluded that the main electricity generation techniques will be the super (super) critical technology for power generation which is better in technology inheritance, scale-up in short time, optimization in thermal power structure, and the CFB boiler power generation technology which has better environmental results. By taking the two electricity generation techniques as the centre of development, the entire process of converting coal into electricity will be optimized and integrated, leading to the realistic joint process of converting coal into electricity and the comprehensive utilization of the solid wastes.