Reduction of NO_(x)emission based on optimized proportions of mill scale and coke breeze in sintering process

Reducing NO_(x) emission of iron ore sintering process in a cost effective manner is a challenge for the iron and steel industry at present.Effects of the proportion of mill scale and coke breeze on the NO_(x) emission,strength of sinter,and sinter indexes were studied by com-bustion and sinter pot tests.Results showed that the peak value of NO concentration,total of NO emission,and fuel-N conversion rate gradu-ally decreased as the proportions of the mill scale increased because NO was reduced to N_(2) by Fe_(3)O_(4),FeO,and Fe in the mill scale.The strength of sinter reached the highest value at 8.0wt%mill scale due to the formation of minerals with low melting point.The fuel-N conver-sion rate slightly fluctuated and total NO_(x) emission significantly decreased with the decreased proportions of coke breeze because CO forma-tion and content of N element in the sintered mixture decreased.However,the sinter strength also decreased due to the decrease in the amount of the melting minerals.Furthermore,results of the sinter pot tests indicated that NO_(x) emission decreased.The sinter indexes performed well when the proportions of mill scale and coke breeze were 8.0wt%and 3.70wt%respectively in the sintered mixture.

Thermal analysis and kinetic modeling of pulverized coal combustion accompanied with coke breeze

Pulverized coal injection technique has been widely used as a means of reducing coke consumption during ironmaking process.Owing to the increasing shortage of fossil fuels,other substitutes such as biomass,plastic,and waste tires have been studied in recent years.Coke breeze as one of the by-products of coking industries has been investigated as a substitute for partial pulverized coals.The combustion characteristics of blended fuels were estimated based on the flammability index C and the combustion characteristic index S.For different coke breeze additions,the combustion was divided into two stages,and the apparent kinetic parameters of the two stages were estimated by fitting the experimental data to the shrinkage reaction model and shrinkage diffusion model,respectively.Results showed that with the increase in coke breeze addition from 15% to 60%,the indexes C and S decrease,and the activation energy of the first stage remains almost constant,while that of the last stage increases from 16.89 up to 67.18 kJ mol^(-1),which indicates that adding coke breeze decreases the combustion efficiency of pulverized coal.Comparing the combustion and kinetic parameters under different coke breeze addition conditions,the optimal addition amount is suggested to be within 15%.

Process control technology of low NO_x sintering based on coke pretreatment

Process control is an effective approach to reduce the NOx emission from sintering flue gas.The effects of different materials adhered on coke breeze on NOx emission characteristics and sintering performance were studied.Results showed that the coke breeze adhered with the mixture of CaO and Fe2O3 or calcium ferrite significantly lowers the NOx emission concentration and conversion ratio of fuel-N to NOx.Pretreating the coke with the mixture of lime slurry and iron ore fines helped to improve the granulation effect,and optimize the carbon distribution in granules.When the mass ratio of coke breeze,quick lime,water and iron ore fines was 2:1:1:1,the average NOx emission concentration was decreased from 220 mg/m3 to 166 mg/m3,and the conversion ratio of fuel-N was reduced from 54.2%to 40.9%.

NO_x reduction in the sintering process

A new process, NOx reduction with recycling flue gas and modifying coke breeze, was proposed. The effects of modified coke breeze and recycled flue gas on NOx reduction were investigated by sinter pot tests. The results show that the NOx reduction rate is over 10wt% in the sintering of modified coke breeze, the effects of the additives on NOx reduction are： CeO2〉CaO〉K2CO3. The NOx reduction rate increases with the amount of recycled flue gas, and is 22.35wt% in the sintering with recycling 30vol% of the flue gas. When 30vol% of the flue gas is recycled into the sintering of CeO2, CaO, and K2CO3 modified coke breeze, the NOx reduction rates are 36.10wt%, 32.56wt%, and 32.17wt%, respectively.

Evaluation of granulability and absorbtivity of biomass in agglomeration mixture

The granulability and absorbtivity of sawdust and coke breeze were investigated.These properties are important within the preparation of agglomeration charge.They have a significant impact on plynodynamic batch conditions.Ability of materials to wet is a fundamental condition of granulability of materials.Wettability and water absorption of wood with liquids is generally significantly affected by their chemical structure.The important factors affecting the wetting process are undoubtedly the wood moisture content,the value of the surface tension of liquid media and their chemical composition.With increasing moisture content of wood,the time to equilibrium rises.Determination of water absorption and granulability of sawdust was conducted to seek their possible use as a partial replacement of coke dust in the production of the agglomerate.Experiments have been realized with alder,oak and pine sawdust and reference material-coke breeze.These materials were divided to four classes of granularity:supplied material,1-2 mm,0.5-1 mm and less than 0.5 mm.And different liquid media were used:water 16°C,water 60°C,soapy water,lime milk and surfactant.