Combustion performance of pulverized coal and corresponding kinetics study after adding the additives of Fe_(2)O_(3) and CaO

Combustion performance of pulverized coal(PC)in blast furnace(BF)process is regarded as a criteria parameter to assess the prop-er injection dosage of PC.In this paper,effects of two kinds of additives,Fe_(2)O_(3) and CaO,on PC combustion were studied using the thermo-gravimetric method.The results demonstrate that both the Fe_(2)O_(3) and CaO can promote combustion performance index of PC including igni-tion index(C_(i)),burnout index(D_(b)),as well as comprehensive combustibility index(S_(n)).The S_(n) increases from 1.37×10^(−6) to 2.16×10^(−6)%2·min^(−2)·℃^(−3) as the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%.Additionally,the combustion kinetics of PC was clarified using the Coats-Redfern method.The results show that the activation energy(E)of PC combustion decreases after adding the above additives.For instance,the E decreases from 56.54 to 35.75 kJ/mol when the Fe_(2)O_(3) proportion increases from 0 to 5.0wt%,which supports the improved combustion per-formance.Moreover,it is uneconomic to utilize pure Fe_(2)O_(3) and CaO in production.Based on economy analysis,we selected the iron-bearing dust(IBD)which contains much Fe_(2)O_(3) and CaO component to investigate,and got the same effects.Therefore,the IBD is a potential option for catalytic PC combustion in BF process.

Numerical simulation of the effect of coaxial and cross-axis injection modes on pulverized coal combustion in the raceway of blast furnace tuyere

The aim of this study is to investigate the influence of the angle of the pulverized coal (PC) injection lance on the combustion characteristics of fuel in the raceway of blast furnace tuyeres. Using FLUENT software, a Euler-Lagrange three-dimensional numerical model was constructed to analyze the influence of different positions of blast furnace tuyere coal powder injection lance (coaxial and cross-axis) on key parameters such as temperature distribution, gas flow, and combustion efficiency. The results demonstrate that adjusting the angle of the injection lance significantly modifies the average and peak temperatures in the raceway, while the composition of gas components remains relatively stable. When the injection lance angle is 10°, the average temperature and peak temperature in the raceway are 2294 K and 2747 K, respectively. When the injection lance angle is 12°, the combustion efficiency of the PC reaches 80.8%. This study reveals the significant impact of the injection lance angle on the combustion process. Especially at an angle of 12°, the combustion efficiency of the blast furnace significantly improves. With coaxial injection, the combustion rate increases as the distance between the injection lance tip and the tuyere increases. This paper is instructive for the optimization of the blast furnace combustion system, which improve fuel utilization efficiency and reduce environmental emissions. This paper provides practical recommendations for adjusting blast furnace operational parameters, offering insights for achieving more efficient and environmentally friendly industrial production.

Numerical Modelling of Coal Combustion Processes in the Vortex Furnace with Dual-Port Loading

The work is devoted to numerical simulation of pulverized-coal combustion processes in the vortex furnace which is a prospective design of a boiler unit for thermal power plants. New modification of this design characterized by additional tangential-injection nozzle located at the bottom of combustion chamber has been studied. Numerical results for the case of Siberian brown coal combustion in this vortex furnace with dual-port loading are presented, including 3-D aerodynamic structure, the fields of temperatures, radiated heat fluxes, species and dispersed phase concentrations, and NOx emissions.

Gas-Particle Flow and Combustion Characteristics of Pulverized Coal Injection in Blast Furnace Raceway

The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles, as well as components concentration and temperature distribu- tion of coal gas in the process of pulverized coal injection of blast furnace raceway. The results show that a great deal of coal gas discharges on the top of raceway away from the tuyere, and the residence time of coal particles in the re- gion of blowpipe and tuyere is 20 ms or so and 50 ms when it reaches raceway boundary. The pressure is the highest at the bottom of raceway and the maximal temperature is about 2 423 K. The char combustion is mainly carried out in the raceway and the maximum of char burn-out rate attains 3× 10-4 kg/s.

Combustion characteristics of semicokes derived from pyrolysis of low rank bituminous coal

Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal.The proximate analysis,calorific value and Hardgrove grindability index(HGI) of semicokes were determined,and the ignition temperature,burnout temperature,ignition index,burnout index,burnout ratio,combustion characteristic index of semicokes were measured and analyzed using thermogravimetry analysis(TGA).The effects of pyrolysis temperature,heating rate,and pyrolysis time on yield,composition and calorific value of long flame coal derived semicokes were investigated,especially the influence of pyrolysis temperature on combustion characteristics and grindability of the semicokes was studied combined with X-ray diffraction(XRD) analysis of semicokes.The results show that the volatile content,ash content and calorific value of semicokes pyrolyzed at all process parameters studied meet the technical specifications of the pulverized coal-fired furnaces(PCFF) referring to China Standards GB/T 7562-1998.The pyrolysis temperature is the most influential factor among pyrolysis process parameters.As pyrolysis temperature increases,the yield,ignition index,combustion reactivity and burnout index of semicokes show a decreasing tend,but the ash content increases.In the range of 400 and 450 °C,the grindability of semicokes is rational,especially the grindability of semicokes pyrolyzed at 450 °C is suitable.Except for the decrease of volatile content and increase of ash content,the decrease of combustion performance of semicokes pyrolyzed at higher temperature should be attributed to the improvement of the degree of structural ordering and the increase of aromaticity and average crystallite size of char.It is concluded that the semicokes pyrolyzed at the temperature of 450 °C is the proper fuel for PCFF.

Pulverized Coal Combustion of Nitrogen Free Blast Furnace

The efficiency of coal combustion is an important factor for the blast furnace process.The influence of low xO/xC on coal combustion performance under nitrogen free blast furnace condition was researched through the self-developed pulverized coal burning device.The results show that the coal combustion rate reduces with xO/xC decreasing,and the combustion rate of bituminous coal is higher than that of anthracite.The coal combustion rate ascends with the rise of volatile matter,but when volatile matter of pulverized coal is more than 18%,the combustion rates will not increase correspondingly.Small amount of CaCO3 and CO2 additions can promote coal combustion,and the effect of CaCO3 is more apparent,which can increase the pulverized coal combustion rate by 15%-18% or so.

Kinetic study on co-combustion of pulverized anthracite and bituminite for blast furnace injection

Combustion behavior of single pulverized coals(PCs)and co-combustion characteristics of anthracite(AT)and bituminite(BT)blends with 20 wt.%volatile were studied by thermogravimetric experiments.The results indicated that reaction characteristics of PCs were closely related to their functional group structure and consequently,the pyrolysis of PCs with highly active functional groups initiated at lower temperatures.It was also noticed that the discrepancy of functional group structures between AT and BT might impair their interaction during combustion.The early exhaust of BT at low temperatures would possibly lead to an independent combustion of volatile and residual carbon and eventually the inefficient combustion of their blend.However,the mixing of AT and BT with similar functional group structures was more likely to achieve blends with superior combustion property.Simultaneously,non-isothermal kinetic analysis mani-fested that the combustion of blends followed random pore model(RPM),and therefore,the parameters calculated by RPM were more accurate to describe their combustion behavior.The kinetic calculation results showed that the activation energy required for decomposition of blends in early combustion stage was much lower owing to the excellent activity of volatile,while residual carbon with stable aromatic hydrocarbon demanded more energy to initiate its combustion.

Investigation on Pulverized Coal Combustion Behavior by Non-Isothermic Integral Thermogravimetry Method

The combustion process of pulverized coal was investigated by non-isothermic integral thermogravimetry. The thermogravimetry curves were fitted by the Coats-Redferm approximation function, and kinetic parameters and characteristic temperatures were obtained. The optimal mixing ratio and particle size can be ascertained. The characteristic temperature of pulverized coal can be obtained from the thermogravimetry curve, and the combustion of coal can be divided into homogeneous and heterogeneous combustion according to the differential thermal analysis curve. The activation energy of a single type of coal ranking from low to high is as follows： bituminous coal, meager-lean coal, and anthracite. In the first mixing method, with more low-price meager-lean coal B replacing high price anthracite A, the activation energy slightly decreases; with more bituminous coal replacing meager-lean coal, total tendency makes a declining of activation. In the later mixing method, with an increase in particle size, a declining activation energy can be seen in total tendency.

Comparison of semi-coke with traditional pulverized coal injection and iron ore sintering fuels based on chemical structure and combustion behavior

Substantial semi-coke has been produced through the industrialized low-temperature pyrolysis process,which has great potential as an alternative fuel for pulverized coal injection(PCI)and iron ore sintering.X-ray diffraction,Raman spectroscope,and thermal analysis were used to compare the carbon chemical structure and combustion reactivity of semi-coke,pulverized coal,and coke breeze.The results show that the average volatile matter content in 46 types of semi-cokes is 8.94 wt.%.The fluctuation range of the characteristic parameters of the semi-coke chemical structure is d_(002)=(0.352–0.379)nm and A_(D1)/A_(G)=(2.51–7.92),while the fluctuation range of the characteristic parameters of pulverized coal is d_(002)=(0.348–0.373)nm and A_(D1)/A_(G)=(1.71–9.03)(where d_(002)means the interlayer spacing between the aromatic planes,and A_(D1)/A_(G)is an index that characterizes the degree of disorder of the char structure through the area ratio of the defect peak band D1 to the perfect graphite peak band G);the overlap between these ranges is relatively high.Contrarily,the fluctuation range of the characteristic parameters of coke breeze is d_(002)=(0.343–0.350)nm and A_(D1)/A_(G)=(0.75–2.51),which is markedly different from that of semi-coke.Semi-coke combustion reactivity is close to that of pulverized coal,but considerably better than that of coke breeze.In terms of chemical structure and combustion reactivity,semi-coke can be used as an alternative fuel for PCI;however,when used for sintering alternative fuel,matching of the heat supply and demand in the later sintering stage must be scrupulously analyzed.

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%.

高炉喷吹煤粉预热工艺技术进展及应用

煤粉预热可提高高炉喷吹煤粉的初始温度,加强煤粉在风口前的气化热解过程,降低喷煤对风口区域热风的冷却效应,进而提高煤粉燃烧率,为高煤比创造条件。对现有几种煤粉预热工艺,如高炉废烟气对流预热、电磁感应预热、立式筒仓管板预热和流化床预热技术特点依次进行了分析。高炉废烟气对流预热工艺,充分利用高炉煤气和热风炉废烟气余热,既能提高煤粉初始温度,又能减少能源浪费。攀钢钒高炉和舞钢高炉预热煤粉工业试验结果表明,提高煤比和降低焦比的效果良好,应用前景广阔。

煤粉炉掺烧造纸污泥的污染物排放

燃煤锅炉掺烧是一种经济可行的污泥处置方式,由于造纸污泥有机质含量较高,采用造纸厂内已建成的燃煤供热锅炉掺烧造纸污泥,既可以减少造纸厂处理污泥的成本,又能利用污泥热能。掺烧造纸污泥可能会使锅炉产生的烟气和灰渣等固体废物中的污染物有所变化。利用造纸厂2×300 MW机组锅炉进行掺烧造纸污泥试验,检测产生污染物的变化情况。掺烧试验共掺烧造纸污泥755 t,燃煤与掺烧污泥的掺混比为22∶1,混合燃料相比燃煤热值稍下降。掺烧试验持续3 d,对烟气、干化污泥、炉渣和粉煤灰进行样品采集,共采集掺烧前3个烟气样品、3个干化污泥样品,各采集1个炉渣粉煤灰的空白样品,共采集掺烧后6个烟气样品、16个炉渣样品及50个粉煤灰样品。检测结果显示,烟气中常规性气体污染物如NOx增加1.5倍,SO2浓度略增加,检测出重金属Ni、Zn、Ba、Se、Cr、Mn、Sb、Pb、Cu,其中重金属Ba和Zn浓度较高,空白组烟气未检测出二噁英,掺烧组二噁英类平均质量浓度为1.20 pg/m^(3)(以TEQ计)。相比空白组,掺烧后炉渣中Pb浓度增加最明显,增长2.5倍;而Cu、Ni、Co、Al、Ti重金属浓度下降,空白组炉渣中二噁英质量分数为2.10 pg/g,掺烧组炉渣中二噁英质量分数为2.00 pg/g;相比空白组,粉煤灰中重金属元素Ba、Mn、As浓度增加明显,增长1.5~2.0倍,而Cu、Zn、Ni、Pb、Co、Ti、Al浓度下降,空白组粉煤灰中未检出二噁英,掺烧组粉煤灰中二噁英质量分数为2.00 pg/g。本次掺烧试验产生的污染物均未超过国家标准限值。

基于煤质特性的京唐高炉喷吹煤结构优化

为优化首钢京唐高炉喷吹煤结构和降低冶炼成本,对京唐高炉喷吹煤粉的煤质特性进行了分析,用煤焦置换比理论公式计算了单种煤的理论置换比,并计算了京唐高炉喷吹煤的煤粉利用率。认为,随着高炉煤比的提高,煤焦置换比逐步降低;通过对配煤结构及高炉操作参数进行优化,京唐三座高炉的煤粉利用率得到进一步提升。1号高炉煤粉利用率达到了97.64%,2号高炉达到了97.58%,3号高炉达到了98.14%,较2022年6月分别提高了3%左右。

流化床-煤粉复合燃烧锅炉的炉膛传热计算方法

:针对流化床 -煤粉复合燃烧锅炉的特点 ,在综合考虑流化床、火焰和受热面之间换热的基础上 ,推导了流化床 -煤粉复合燃烧锅炉炉膛传热计算的基本方程 ,得到了复合燃烧锅炉炉膛传热计算的零维模型半经验法。以某 75 t/h树皮流化床 -煤粉复合燃烧锅炉为例 ,进行了炉膛传热计算。图 1表 6参

唐钢新区高炉提升煤比的措施及效果

唐钢新区高炉投产以来,原燃料质量波动导致了炉况不稳定,主要表现为煤气流不稳定,操作炉型不受控,为保持顺行主要采用轻负荷操作,煤比在125~135kg/t。通过采取改善原燃料质量、改进炉前出铁操作、优化工艺参数及调整操作制度等措施,煤比由130kg/t逐步提升到150kg/t以上,并稳定在160~170kg/t,同时实现了燃料比下降。认为:①高炉煤气流稳定、操作炉型规整是提升煤比的关键;②良好的原燃料质量是高炉稳定顺行的基础;③稳定的外部条件,减少操作影响,发展两股气流的上下部制度,有利于提升煤粉利用率。

核桃壳炭与煤粉混合燃烧特性及协同作用研究

在“双碳”目标积极推进背景下,节能减排已经成为当前钢铁工业绿色低碳发展的首要目标。生物质作为可再生碳源,应用于高炉冶炼可有效降低高炉冶炼过程的CO_(2)排放。本文选取农业生物质核桃壳为原料,深入研究高温条件下煤粉和核桃壳炭的热化学行为,研究不同比例混合燃料的燃烧特性,探讨煤粉与核桃壳炭共燃的协同作用,确定最优混合比例范围。结果表明,核桃壳炭的加入可以改善高炉喷吹煤粉的燃烧性能,核桃壳炭与煤粉的最佳掺混比例为25%,此时混合燃料的综合燃烧性能指数为6.253×10^(-10)(min^(-1)·℃^(-3));可燃性指数为3.715×10^(-6)(min^(-1)·℃^(-2))。核桃壳炭的掺入,有利于高炉生产实现节能减排,推动废弃物资源化处理和钢铁行业绿色低碳发展。

75 t/h煤气-煤粉混烧锅炉提效改造技术研究及应用

针对75 t/h煤气-煤粉混烧锅炉焦煤使用能力有限、排烟温度高和热效率低等问题,通过问题分析、方案研究和组织实施,并结合最新低氮燃烧技术,对75 t/h锅炉进行了纯烧煤气改造,提高了锅炉煤气使用能力,减少了热损失,降低了NOx排放指标,社会效益与经济效益明显。

高炉混合喷吹上湾高钙烟煤的性能研究

通过上湾矿烟煤和目标高炉常用煤种的混煤搭配实验,系统研究了不同方案下混煤的着火点、爆炸性、燃烧性和灰熔特性,实验结果表明:当上湾烟煤含量配比为40%时,上湾烟煤与ES无烟煤的混煤着火点最低,为370.8℃,并且没有爆炸性;上湾烟煤+ES无烟煤在混煤挥发分为18.6%时,混煤燃烧性最好;当上湾烟煤配比超过30%后,混煤软化温度会明显下降。

一维炉内煤粉气流富氧着火距离试验

针对火电锅炉在深度调峰过程中存在煤粉着火稳定性差的问题,提出富氧稳燃方法,并在一维炉内进行了煤粉气流点火试验,主要研究氧气浓度、一次风速和煤粉浓度对煤粉气流着火距离的影响。其中氧气浓度共取21%(空气)、25%、30%和35%,4个工况;一次风速共取18、23、28和33 m/s 4个工况;煤粉质量分数共取0.2、0.3、0.4、0.5和0.6 kg/kg(以每千克空气携带的煤粉质量计)5个工况。研究不同工况下煤粉气流着火距离的试验数据,并对试验数据及其变化规律进行详细分析。结果表明,氧气浓度每增加1%,着火距离缩短82.5 mm,但随氧气浓度的持续增大,对着火距离的影响逐渐变小;着火距离的变化率随风速的增加而增大,尤其当风速大于28 m/s后,风速对着火距离的影响非常大;煤粉浓度对着火距离的影响相对复杂,最佳煤粉浓度随氧气浓度的增大而增大;对比试验数据发现氧气浓度和一次风速对着火距离的影响大于煤粉浓度。最后利用试验数据拟合了氧气浓度和煤粉着火距离的数学模型,发现着火距离和氧气浓度之间存在指数函数关系。

基于数学建模的煤粉加热炉燃烧状态模拟研究

以获取准确的煤粉燃烬率,掌握煤粉加热炉燃烧状态为研究目的,提出基于数学建模的煤粉加热炉燃烧状态模拟方法。通过构建连续性方程、能量方程、动量方程、湍动能耗散率方程以及湍动能方程,描述煤粉加热炉内煤粉的燃烧过程。将煤粒在加热炉中的燃烧过程分为两个阶段,第一个阶段为热解挥发阶段,第二个阶段为残碳氧化阶段,依据双挥发反应模型构建热解挥发模型,对原煤热解挥发过程进行模拟。设置边界条件,进行实验研究,结果表明:颗粒粒径与煤粉燃烬率之间呈反比关系,温度与煤粉燃烬度之间成正比关系。所提方法的模拟结果与实际结果之间的拟合度较高,说明其模拟结果更加准确,可以促进工业加热中煤粉加热炉燃烧状态优化。