Theoretical And Experimental Study On Oxygen Enriched Combustion Technology In Cement Industry

Reducing and capture of CO₂ emissions in the industrial production process is an important way to improve the greenhouse effect.As a pillar of construction industry in China,the cement industry emits 15%of the total CO₂ amount in China,the development of cement industry CO₂ capture technology has become one of the key issues for sustainable development.Therefore,based on the existing XDL technology,Institute of Powder Engineering,Xi'an University of Architecture and Technology,proposed a novel method for flue gas CO₂ capture technology at oxygen enriched combustion in order to reduce CO₂ emission of the cement industry.In this dissertation,limestone calcining thermo-gravimetric has been studied at high concentration CO₂ atmosphere.The technical parameters of oxygen enriched combustion at a real 5000 t/d-XDL cement clinker production system were collected.The material balance and heat balance were established by mathematical model.Finally,the research offered an applicable CO₂ capture,separation,utilization and storage technology?CO₂-EOR technology?,and gave a technical and economic analysis and evaluation as well.Based on the experiments of TGA and the simulation integrated multifunction test platform at dilute suspension,The research of limestone reaction kinetic at accumulated/suspended state,high CO₂ concentration and N₂/CO₂ atmosphere was conducted.The effects of CaCO₃calcination processed at high concentration of CO₂ are listed in the following:1)when the CO₂ concentration is in the range from 30%to 100%,the mechanism of accumulated limestone calcining reaction function fits for the Avrami-Erofeev equation,G?7???8??28?[-ln?7?1-??8?]n,the reaction order is from 2/5 to 2/3.The reaction mechanism model is random nucleation and subsequent growth model.The relation between CO₂ concentration and apparent activation energy,pre-exponential factor,reaction rate constant isE_??0?28?655.19e.^1396CCO2,lnA?28?71.56e.^1254CCO2and lnk?28?71.56e.^1254CCO2-78806e.^1395CCO2/T.2)When the CO₂ concentration is in the range from 50%to 80%,the mechanism of suspended limestone calcining reaction function fits for the Avrami-Erofeev equation,reaction order is 2/5 and 3/4.The reaction mechanism model is random nucleation and subsequent growth model.The apparent activation energy is 1255.3 kJ·mol^-1 and 1808.8kJ·mol^-1,where lnA is 127.86 and 159.37.3)As the concentration of CO₂ increasing,the reaction difficulty increases correspondingly.The maximum weight loss rate is increased from 1163K to 1209K when the CO₂ concentration increased from 40%to 100%.Using the 5000 t/a-XDL semi industrial test platform,the experiment of oxygen enriched combustion under various conditions had been developed.It is concluded that:1)As the increasing of O₂ concentration,the apparent decomposition rate of cement was meal increases gradually;when the O₂ concentration increased from 21.2%to 25%,the apparent decomposition rate of cement raw meal increased from 44.8%to90.1%correspondingly.2)As the increasing of O₂ concentration,the concentration of CO₂ in the flue gas increases gradually.When the O₂ concentration increased from 21.2%to 25%,the concentration of CO₂ in the flue gas increased from 24.3%to 40.8%correspondingly.3)At the optimum conditions,compared to the traditional technology,the unit coal consumption of limestone decomposition process under the condition of oxygen enriched combustion technology reduced 5.85%,the apparent decomposition rate increased 10.79%,and flue gas CO₂ concentration increased 2.19 times comparing to the original one.Based on the experimental results from 2500 t/d cement industry,i.e.,semi-industrial line based on the XDL technology from Xi'an University of Architecture and Technology,the optimum oxygen enriched combustion technology model was established and calculated by Matlab 7.0.It showed:1)with the increasing of O₂ concentration,the air supply,gas amount,gas emissions as well as the energy consumption of per unit cement clinker decreased,CO₂concentration in flue gas and production capacity gradually increased;2)As the increasing of air leakage coefficient,system air amount,CO₂concentration in flue gas and production capacity gradually decreased.The amount of flue gas,flue gas emissions and unit production energy consumption cement clinker for gradually increased.3)After the oxygen enriched combustion from the 2500 t/d XDL cement industry,when the O₂ concentration is 30%,air leakage coefficient is 3%and O₂ excess coefficient is 1.05,system capacity can be improved to 3550 t/d,CO₂ concentration in flue gas is 76.57%.The flue gas emissions reduced 55.50%and 16.36 kg standard coal was saved for unit cement clinker production,and the standard coal saving rate is as high as 16.35%.The dissertation presented the technology route of CO₂ capture,utilization and storage in cement industry.The cryogenic freezing liquefaction and separation of CO₂?CO₂-EOR?is used to improve the oil recovery.The evaluation shows that:1)The cost of CO₂ capture is 101.22 yuan/?t·CO₂?which saved 25.55 yuan/?t·CO₂?;2)The cost of CO₂ capture,utilization and storage in cement industry is 831.41yuan/?t·CO₂?,the CO₂ capture cost,transportation cost and enhanced oil cost is 75.67yuan/?t·CO₂?,30.24yuan/?t·CO₂?and 725.50 yuan/?t·CO₂?respectively,which bring economic benefits at 1665.39 yuan/?t·CO₂?.So the comprehensive benefit of the CO₂capture,utilization and storage technology of the cement industry is 833.98yuan/?t·CO₂?.