COREX竖炉中烧结矿的还原过程及其对综合炉料还原性能的影响

为了降低COREX炼铁工艺的成本,中国在综合炉料中加入了烧结矿。本文研究了烧结矿在COREX竖炉中的还原过程,阐明了其还原性质的变化,并研究了烧结矿配比对综合炉料冶金性能的影响。结果表明,在COREX竖炉中烧结矿的还原过程与其在高炉中类似,但还原粉化发生得更快;在模拟COREX竖炉还原条件下,与球团矿和块矿相比,烧结矿的还原粉化性能(RDI)最差而还原性能(RI)差别不大。宏观和微观矿相分析表明,还原时烧结矿呈现整体开裂而球团矿和块矿均呈现表面开裂,炉料自身产生的裂纹与其最终还原粉化性能之间不存在简单的对应关系。COREX竖炉综合炉料与单一种类炉料之间存在部分冶金性能叠加性,配入烧结矿时综合炉料的低温还原粉化性能RDI_(+6.3)和RDI_(+3.15)应分别不低于70%和80%。

Nanosize-effect on the distribution of heavy metals in copper smelting dust:Based on sophisticated dust sorting approach

Dust particles emitted from smelters can be hazardous to ecosystems and humans,as they are often enriched in metallic compounds.Here,we combined multi-method mineralogical analysis with a sophisticated size sorting approach for copper smelting dust to study the nanosize-effect on heavy metal distribution,which has hitherto been underestimated.Three types of dust were collected from a copper flash smelter and then size-sorted using a Dekati low-pressure impactor.Results showed that all three samples could easily sort out nanoscale dust particles(<1μm,grades 10–2)and even those smaller than 100 nm(grades 5–2).Especially for electrostatic precipitators dust,the mass fraction of nanoscale dust(<1μm)could reach 10.71%.The presence of heavy metals(Pb,Zn,Cu,and As)and their mineral species in dust was examined at various particle sizes.It was discovered that different heavy metals are enriched on nanoparticles in specific sizes.In micron-sized particles,heavy metals are generally found in discrete phases(e.g.,CuSO_(4),PbSO_(4),and As_(2)O_(3)).In nanoscale particles,the dominant phase is Fe_(3)O_(4),while heavy metals are mostly found in lattice substitution(e.g.,CuFe_(2)O_(4)and ZnFe_(2)O_(4)).Two distinct nano-dust morphologies were found:One with irregular mesh or chain structures consisting of particles of a few nanometers,and the other with polygonal crystals in larger sizes of hundreds of nanometers.The enrichment of heavy metals in the latter morphology is more pronounced,possibly because lattice substitution of heavy metals is more likely to occur when polycrystalline particles are formed.

Direct reduction of carburized pre-reduced pellets by microwave heating

A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated.The pre-reduced pellets,with a porous structure,and fine particles are carburized homogeneously at 400-650 °C in a CO atmosphere.The carburized carbon not only acts reaction as a reduction agent,but also absorbs microwave in the reduction process.Hence,the carburized pre-reduced pellets can be rapidly reduced by microwave heating.There are three procedures involved in the process,namely,gas-based pre-reduction,low-temperature carburization and deep reduction by microwave heating.Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory.This not only improves the efficiency of the microwave heating,but also accelerates the reduction of iron oxides.The temperature of the pre-reduced pellets rises to 1050 °C in 45 min when the carburization rate is 2.02%,and the metallization rate and compressive strength reach 94.24% and 1725 N/pellet,respectively.

基于焦粉预处理的低NO_x烧结过程控制技术（英文）

过程控制是降低烧结烟气NOx排放的有效途径。研究了焦粉粘附不同物质时对NOx排放和烧结指标的影响。结果表明,当焦粉粘附CaO和Fe2O3的混合物或者铁酸钙时能减少燃料氮向NOx的转化从而降低NOx排放浓度。用石灰浆和铁矿粉的混合物对焦粉进行预处理,有助于改善制粒效果,优化制粒小球中的碳分布。当焦粉、生石灰、水、铁矿粉以质量比2:1:1:1进行混合预处理后参与烧结,NOx平均排放浓度可由220 mg/m3降至166 mg/m3,燃料氮转化率可由54.2%降至40.9%。

Preparation of sinter with low reduction degradation index for COREX reduction in a high proportion

The sinter with low reduction degradation index(RDI)for COREX reduction was prepared by separated granulation sintering process.The results illustrate that the productivity and tumble index are attained to be 1.64 t m^(-2)h^(-1)and 59.25%,respectively,in pot tests under the optimal conditions.Under the reducing condition simulating COREX shaft furnace,RDI_(+6.3 mm),RDI_(+3.15 mm),and reducibility index of the sinter reach 63.05%,81.52%,and 83.65%,respectively.Compared with traditional sintering process,the productivity rose by 14.69%,and RDI_(+6.3) mm and RDI_(+3.15) mm were increased by 157.54%and 32.70%,respectively.In addition,as the proportion of sinter reached 60%,RDI_(+6.3 mm)and RDI_(+3.15 mm)of comprehensive burden were achieved to be 73.39%and 84.28%,respectively,which could completely meet the requirement of COREX shaft furnace for RDI.The mechanism was demonstrated that the more silicoferrites of calcium and aluminum and silicate phase occurred as well as magnetite,and the amount of Fe_(2)O_(3)decreased substantially in the sinter by separated granulation sintering process.Hence,the low-temperature reducing stress is restrained,with the increase in sinter strength.

Control of nitrogen oxides emission by selective non-catalytic reduction in preheating section during iron ore pellets production

Reducing the NO_(x) emission from pelletizing process is of great importance to the green development of iron and steel industry.The flue gas temperature of preheating(PH)section during grate-kiln iron ore pelletizing process typically ranges within 850–1050℃,which meets the temperature requirements of selective non-catalytic reduction(SNCR)for NO_(x).The in-bed SNCR behavior of NO_(x) in the PH section was investigated,and the influence of relevant parameters was revealed.Results show that with the flue gas temperature rising,the denitration rate reached a peak value and then declined,where the appropriate temperature range was 950–1000℃.Increasing the NH_(3)/NO ratio(NSR)contributed to improving the denitration rate,and the appropriate NSR was 1.0.Oxygen content in the flue gas also showed an important influence on denitration rate,which reached a peak value and then dropped with the oxygen content rising.Under the condition of 18 vol.%oxygen content,the denitration reaction mainly occurred in the form of 4NO+4NH_(3)+O_(2)=4N_(2)+6H_(2)O.For restricting the competitive reaction of NH_(3) oxidation,the oxygen content in flue gas of PH section should be kept at an appropriate range.In general,the denitration rate reached about 25%in the PH section through spraying ammonia.

Life Cycle Assessment of Iron Ore Sintering Process

Iron ore sintering is an energy＇intensive process associated with emission of pollutants in iron and steel in- dustry. In order to comprehensively evaluate the environmental impacts of sintering, a detailed life cycle assessment of a sintering plant was conducted. Life cycle inventory showed that, in the production of 1 t sinter ore, 241.53 kg CO2 , 22.68 kg CO, 0. 294 kg SO2 , 0.63 kg NO, , 1.18 /lg dioxin and 0.48 kg dust were discharged. Global war- ming potentials, acidification potentials, photochemical ozone creation potentials and human toxicity potentials were selected as four impact categories, and the evaluation index for the sintering plant was calculated as 3.45 × 10 ^-12. Fi nally, based on the environmental impact analysis, several measures of reducing environmental [oadings of the sinte- ring plant were provided, which included the utilization of denitrification equipment, recirculation of the hot waste gas and process improvement to reduce fuel consumption.