Simulation And Optimization Of Flue Gas Circulation Sintering Process Based On Fuel Layered Distribution

Abstract:The steel production of China ranking first in the world last for many years, but the energy consumption and emissions in steel production process are much higher than the advanced level of the world. This creates a huge potential for energy-saving and emission-reduction. In China, iron ore sintering plays a crucial role in iron and steel industry for its energy consumption ranking second and emissions ranking first in the steel production process. Therefore, it is of great significance for sustainable development of iron and steel industries to research and develop improved iron ore sintering technology which can reduce energy consumption and flue gas emissions.Flue gas circulation sintering (FGCS) technology can improve the stability of the sintered bed temperature and reduce emissions by recycling flue gas. Fuel layered distribution (FLD) technology can reduce the consumption of solid fuel and rationalize the distribution of sintered bed temperature through distributing solid fuel reasonably. Till now, research and application of the two technologies are still in infancy and most of the research methodologies are semi-industrial tests. Due to the development of computer simulation technique and the intensive study of various mechanisms in sintering process, it is more convenient and direct to study the energy-saving and emission-reduction in iron ore sintering.An unsteady mathematical model and numerical methods of transport process in iron ore sintering are established through intensively studying the mechanisms of flow, heat and mass transfer as well as structure change. The conventional sintering process is simulated with this model. The FGCS process of mixing flue gas in sintering and exhaust gas in sinter cooling and fuel layered distribution sintering (FLDS) process are proposed according to the distribution of sintered bed temperature in the depth direction and the flue gas changes over time. In researching the FGCS process, three schemes are proposed in accordance with different emphasis of waste heat utilization and emission-reduction in sintering system, and the quality evaluating indicator of sinter based on sintered bed temperature is first put forward., The FLD technology based on depth unit is proposed in researching the FLDS process, and its control target is the highest temperature of sintered. The synthetical optimization sintering process (SOSP) is innovatively proposed based on the two technologies above. Simulation and benefit analysis of the processes in the thesis are accomplished.The research result reveals that the improvements of sintering by using the FGCS process are reducing the flue gas emissions and improving the temperature of top sintered bed, the FLDS process can ameliorate the sintering through uniformizing the highest temperature distribution in depth direction and promoting the rational use of fuel, the SOSP can comprehensively improve quality evaluating indicator of sinter and waste heat utilization and decrease sintering cycle, solid fuel usage, flue gas emissions and total emissions of sulfur dioxide. In the above three processes, the SOSP is optimum in improving sinter quality and the effect of energy-saving and emission-reduction, and the FGCS process is optimum in increasing production.This study will help to understand the mechanisms of complex transport process in iron ore sintering and providing references for studing on sintering energy-saving and emission-reduction. The research is significant in increasing productivity, decreasing operating costs and improving competitiveness of iron and steel enterprise.