Numerical Modeling Of Pulverized Coal Combustion In Blast Furnace

Pulverized coal injection technology is widely used in blast furnace ironmaking due to economic, operational and environmental benefits. In this process, coal powders is injected with gas into the blast furnace via a lance through a blowpipe and tuyere, and combusts in the raceway cavity and then in the surrounding packed coke bed. Under high PCI rate operation always follow low burnout, the unburnt coal powders may accumulate in the boundary of raceway, affecting the coke bed permeability and thereby the furnace stability. High burnout of coal powder is desired and necessary for high PCI rate operation, On the other hand, an appropriate distribution of gas composition is favourable for furnace stability. In practice, adjusting operating conditions in real time is the key countermeasures to optimise and control the furnace operation. Therefore, analyse the pulverized coal flow and combustion in the tuyere and raceway accurately and reliably is necessary for optimising coal properties and blast conditions.A three-dimensional mathematical model is developed to analyse gas-particle flow and combustion characteristics of coal particles, on the basis of experimental data to validate the pulverized coal combustion process, the pulverized coal combustion process and the effects of operating conditions analysed in detail.Pulverized coal injection under high hating rate of hot blast, the volatile release fast and burn followed, when comparing the combustion behaviour of various size groups, it is found that no matter the devolatilization and char combustion process and final bunout level varies depending on particle size groups. The contributions of VM are nearly the same for final burnout level, but char burnout level depend on particle diameter. Due to the mathematical model is mainly considered in additional heterogeneous reactions of char with steam and carbon dioxide, provide more complete and reliable predictions of gas species distributions, include H2and CO concentration.As blast temperature increases, the coal plume undergoes a shorter preheating stage, followed by a faster rate of volatile release and a hige level burnout, the introduction of a higher temperature blast affects coal burnout evolution more significantly in the upstream. A blast temperature of approximately1200℃is considered a transition point affects burnout evolution, and the primary temperature for pulverized coal burnout. By increasing oxygen enrichment, both the central coal plume and recirculating fine particles in the peripheral region increase the chances of contact with oxygen. Oxygen enrichment is also an effective way to obtain a high level burnout and to maintain the desired flame temperature within the raceway.The moisture in the blast have an less affects on the pulverized coal flow and combustion in the blowpipe and tuyere, and temperature field of recirculating region in the peripheral region. The moisture in the blast lower the temperature obviously in the main combustion region along the centraline. The moisture in the blast through endothermic reaction with char consume valuable hearth heat, and influence gas species distributions.As for the pulverized coal burnout, the coal rate have the most impact, the order of blast parameters on the burnout evalution ia ranked as oxygen enrichment, blast temperature, and blast moisture. The results confirm that notable improvements in final burnout can be achieved for coals with more fine particles and high volatile matter, and by higher oxygen enrichment. The use of high blast temperature can increase coal burnout, but the further increase in blast temperature over1200℃has little effect on final burnout.