Role of iron ore in enhancing gasification of iron coke:Structural evolution,influence mechanism and kinetic analysis

The utilization of iron coke provides a green pathway for low-carbon ironmaking.To uncover the influence mechanism of iron ore on the behavior and kinetics of iron coke gasification,the effect of iron ore on the microstructure of iron coke was investigated.Furthermore,a comparative study of the gasification reactions between iron coke and coke was conducted through non-isothermal thermogravimetric method.The findings indicate that compared to coke,iron coke exhibits an augmentation in micropores and specific surface area,and the micropores further extend and interconnect.This provides more adsorption sites for CO_(2) molecules during the gasification process,resulting in a reduction in the initial gasification temperature of iron coke.Accelerating the heating rate in non-isothermal gasification can enhance the reactivity of iron coke.The metallic iron reduced from iron ore is embedded in the carbon matrix,reducing the orderliness of the carbon structure,which is primarily responsible for the heightened reactivity of the carbon atoms.The kinetic study indicates that the random pore model can effectively represent the gasification process of iron coke due to its rich pore structure.Moreover,as the proportion of iron ore increases,the activation energy for the carbon gasification gradually decreases,from 246.2 kJ/mol for coke to 192.5 kJ/mol for iron coke 15wt%.

Gasification kinetics of bulk coke in the CO2/CO/H2/H2O/N2 system simulating the atmosphere in the industrial blast furnace

The gasification characteristics and gasification kinetics of coke in complex CO2/CO/H2/H2O/N2 systems similar to the gas system of industrial blast furnace (BF) were studied by the method of isothermal thermogravimetric analysis. The experimental gas compositions and the corresponding temperature were chosen according to data reported for industrial BFs. The gasification behavior of coke was described by the Random Pore Model (RPM), Volumetric Model (VM), and Grain Model (GM). Results showed that the gas composition of the coke gasification zone in BF changes slightly and that the temperature is the most important factor affecting coke gasification. The lower activation energy of coke samples (Coke Reaction Index (CRI)>50) is due to the high Fe2O3 in the ash, lower degree of graphitization, and larger pore structure. In addition, the choice of kinetic model does not differ substantially in describing the gasification mechanism of coke in a BF.

Effect of CO_2 and H_2O on gasification dissolution and deep reaction of coke

To more comprehensively analyze the effect of CO_2 and H_2O on the gasification dissolution reaction and deep reaction of coke, the reactions of coke with CO_2 and H_2O using high temperature gas–solid reaction apparatus over the range of 950–1250°C were studied, and the thermodynamic and kinetic analyses were also performed. The results show that the average reaction rate of coke with H_2O is about 1.3–6.5 times that with CO_2 in the experimental temperature range. At the same temperature, the endothermic effect of coke with H_2O is less than that with CO_2. As the pressure increases, the gasification dissolution reaction of coke shifts to the high-temperature zone. The use of hydrogen-rich fuels is conducive to decreasing the energy consumed inside the blast furnace, and a corresponding high-pressure operation will help to suppress the gasification dissolution reaction of coke and reduce its deterioration. The interfacial chemical reaction is the main rate-limiting step over the experimental temperature range. The activation energies of the reaction of coke with CO_2 and H_2O are 169.23 kJ ·mol-1 and 87.13 kJ·mol^(-1), respectively. Additionally, water vapor is more likely to diffuse into the coke interior at a lower temperature and thus aggravates the deterioration of coke in the middle upper part of blast furnace.

Effect of heat treatment on structure and gasification reactivity of petroleum coke

Petroleum coke was thermally treated on a fixed bed reactor in a temperature range of 1173-1673 K. The changes of the elemental composition and crystalline structure of petroleum coke, with heat treatments as well as the gasification reactivity of the heat-treated petroleum cokes were investigated. The results showed that the petroleum coke was carbonized and grapbitized to a higher degree with increasing heating temperature, while the gasification reactivity decreased. The treatment at temperatures of 1173 and 1473 K significantly enlarged the specific surface area and the pore volume of petroleum coke. Both the specific surface area and the pore volume decreased at 1673 K. An empirical normal distribution function model （NDFM） was found to fit the gasification rates of petroleum coke well. The correlation coefficient of petroleum coke by normal distribution function model at different heat treatment temperatures is between 0.93 and 0.95.

Gasification of iron coke and cogasification behavior of iron coke and coke under simulated hydrogen-rich blast furnace condition

To explore the iron coke application in hydrogen-rich blast furnace,which is an effective method to achieve the purpose of low carbon emissions,the initial gasification temperature of iron coke in CO_(2) and H_(2)O atmosphere and its cogasification reaction mechanism with coke were systematically studied.Iron coke was prepared under laboratory conditions,with a 0-7wt%iron ore powder addition.The properties of iron cokes were tested by coke reactivity index(CRI)and coke strength after reaction(CSR),and their phases and morphology were evolution discussed by scanning electron microscopy and X-ray diffraction analysis.The results indicated that the initial gasification temperature of iron coke decreased with the increase in the iron ore powder content under the CO_(2) and H_(2)O_((g))atmosphere.In the 40vol%H_(2)O+60vol%CO_(2) atmosphere,CRI of iron coke with the addition of 3wt%iron ore powder reached 58.7%,and its CSR reached 56.5%.Because of the catalytic action of iron,the reaction capacity of iron coke was greater than that of coke.As iron coke was preferentially gasified,the CRI and CSR of coke were reduced and increased,respectively,when iron coke and coke were cogasified.The results showed that the skeleton function of the coke can be protected by iron coke.

Comparative evaluation for catalytic gasification of petroleum coke and asphaltene in subcritical and supercritical water

Subcritical and supercritical water gasification of petroleum coke and asphaltene was performed at variable temperatures(350–650°C),feed concentrations(15–30 wt%)and reaction times(15–60 min).Nickel-impregnated activated carbon(Ni/AC)was synthesized as a catalyst for enhancing syngas yields at optimal gasification conditions(650°C,15 wt%and 60 min).Structural chemistry of precursors and chars developed at different gasification temperatures was studied using physicochemical and synchrotronbased approaches such as carbon–hydrogen–nitrogen–sulfur(CHNS)analysis,thermogravimetric and differential thermogravimetric analysis(TGA/DTA),scanning electron microscopy(SEM),Fourier-Transform Infrared spectroscopy(FTIR),Raman spectroscopy,X-ray diffraction(XRD)and X-ray absorption spectroscopy(XAS).Asphaltene testified to be a better precursor for catalytic hydrothermal gasification leading to 11.97 mmol/g of total gas yield compared to petroleum coke(8.04 mmol/g).In particular,supercritical water gasification using 5 wt%Ni/AC at 650°C with 15 wt%feed concentration for 60 min resulted in 4.17 and 2.98 mmol/g of H_2from asphaltene and petroleum coke,respectively.Under the same conditions,the respective CH_4yields from catalytic gasification of asphaltene and petroleum coke were 2.54and 1.07 mmol/g.Nonetheless,asphaltene also seemed to an attractive feedstock for the production of highly aromatic chars through hydrothermal gasification.

Kinetics of petroleum coke/biomass blends during co-gasification

The co-gasification behavior and synergistic effect of petroleum coke, biomass, and their blends were studied by thermogravimetric analysis under CO2 atmosphere at different heating rates. The isoconversional method was used to calculate the activation energy. The results showed that the gasification process occurred in two stages： pyrolysis and char gasification. A synergistic effect was observed in the char gasification stage. This effect was caused by alkali and alkaline earth metals in the biomass ash. Kinetics analysis showed that the activation energy in the pyrolysis stage was less than that in the char gasification stage. In the char gasification stage, the activation energy was 129.1–177.8 k J/mol for petroleum coke, whereas it was 120.3–150.5 k J/mol for biomass. We also observed that the activation energy calculated by the Flynn–Wall–Ozawa（FWO） method were larger than those calculated by the Kissinger–Akahira–Sunosen（KAS） method. When the conversion was 1.0, the activation energy was 106.2 k J/mol when calculated by the KAS method, whereas it was 120.3 k J/mol when calculated by the FWO method.

Resid Contact Cracking and Coke Gasification Integrated Technology

In order to utilize petroleum resources efficiently and greenly,and solve the problems of high coke yield,highsulfur coke utilization,and environmental protection concerns in China’s refineries,a resid contact cracking and coke gasification integrated technology is being developed by the Research Institute of Petroleum Processing(RIPP).Based on the three technical characteristics including thin films cracking,partial oxidation,and rapid cracking,this technology not only can reduce the production rate of coke and dry gas formed during the process,but also can increase the liquid yield.Moreover,the in-situ low-temperature gasification technology is used to solve the clean utilization of high-sulfur petroleum coke,which can play the role of“Utility Island”and is a green and low-carbon technology for low-quality heavy oil upgrading.

Coke behavior with H_(2)O in a hydrogen-enriched blast furnace:A review

Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO_(2)emissions in the ironmaking process.However,hydrogen-enriched reduction produces large amounts of H_(2)O,which places new demands on coke quality in a blast furnace.In a hydrogen-rich blast furnace,the presence of H_(2)O promotes the solution loss reaction.This result improves the reactivity of coke,which is 20%-30%higher in a pure H_(2)O atmosphere than in a pure CO_(2)atmosphere.The activation energy range is 110-300 kJ/mol between coke and CO_(2)and 80-170 kJ/mol between coke and H_(2)O.CO_(2)and H_(2)O are shown to have different effects on coke degradation mechanisms.This review provides a comprehensive overview of the effect of H_(2)O on the structure and properties of coke.By exploring the interactions between H_(2)O and coke,several unresolved issues in the field requiring further research were identified.This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.

Characterization of Catalytic Cracking Catalysts Regenerated by Gasifying Deposited Coke

Partially or fully regenerated catalytic cracking catalysts were prepared by gasifying the coke deposited on coked catalysts with a gaseous mixture of oxygen and steam in a fixed fluidized bed （FFB）. The resultant samples were characterized by different methods such as the nitrogen adsorption-desorption analysis, the X-ray diffractometry, the infrared spectroscopy, the ammonia temperature-programmed desorption （NH3-TPD） method, the X-ray fluorescence （XRF） analysis, the transmission electron microscopy and energy dispersive X-ray spectroscopy （TEM-EDX）, the thermal-gravimetric analysis （TGA） and the differential thermal analysis （DTA）. The results showed that exposure of catalyst to steam for about 10 minutes at temperature ≥ 800 ℃ could not cause too much destruction of the catalysts, and an amount of coke equating to about 0.27 m% was enough to block approximately all acid sites in micro-pores of the zeolite catalyst. Coke didn＇t show equal reactivity during coke burning-off that could be accelerated by the catalytic action of nearby metal atoms. However, when the carbon content on the catalyst reached about 2.44 m%, the catalytic action of metals on the catalyst was not evident. The severe thermal and hydrothermal environment during exposure of the catalyst to steam at a temperature in the range of about 860--880 ℃ for 30 minutes could lead to collapse of pore structure and transformation of crystal phase and consequently decrease of the surface area and acid amount on the catalyst.

An Energy Analysis on Gasification of Sewage Sludge by a Direct Injection in Supercritical Water

Supercritical Water Gasification is an efficient technology in converting wet biomass into H2 and CH4 in comparison to other conventional thermochemical processes. Coke deposition, however, remains as a major challenge in this technology. Coke formation is the result of polymerization reactions that take place at sub-critical conditions. Directly injecting the relatively unheated wet biomass feed into supercritical water increases the heating rate and reduces the residence time of the feed in the sub-critical condition. This leads to a minimized coke formation in the process. However, a non-isothermal mixing takes place during this direct injection that is less energy-efficient. In addition, the biomass feedstream experiences less pre-heating that means less heat recovery from the product gas. These two aspects might reduce the overall process performance. Parametric studies of key operating parameters, such as operating temperature, dry matter content, bypass water ratio and heat exchanger effectiveness, are carried out to investigate the influence of direct injection to the thermal efficiency of the system. Subsequently, optimization using pinch analysis is conducted to the system with direct injection. Finally, an operating window for optimum performance of the optimized direct injection gasification system is proposed.

气化渣基脱硫活性焦制备工艺与性能评价

煤气化过程中产生的气化渣的处置问题日趋严重。气化渣中的残余炭具有较发达的孔隙结构和较大的比表面积,具有制备活性炭和其他高附加值碳材料的潜质。通过水介重力分选方法得到高品质气化渣分离炭后,采用配煤法制备脱硫活性焦,可实现气化渣的高附加值利用。通过单因素试验法及正交试验法考察在气化渣分离炭高掺比条件下配煤种类、比例及炭化、活化工艺条件对脱硫活性焦结构和性能影响。研究表明,气化渣分离炭在掺入比例为50%时,活性焦的最佳配煤组成为:焦煤29%、长焰煤8%、煤沥青13%;最佳炭化条件为:升温速率5℃/min、炭化温度700℃、炭化时间30 min;最佳活化条件为:活化温度900℃、升温速率8℃/min、活化时间120 min、活化水量1.0 mL/(g·h)。利用固定床反应装置对气化渣基脱硫活性焦进行脱硫和再生性能评价,在最佳配方和工艺条件下,公斤级试验制备的脱硫活性焦耐磨强度为97.26%,耐压强度为696.3 N(实测值),灰分为11.66%,碘吸附值为378.78 mg/g,脱硫值为28.5 mg/g,满足脱硫用煤质颗粒活性炭指标A型优级品的技术指标且再生性能良好。以气化渣分离炭作为碳源制备脱硫活性焦在大幅降低活性焦生产成本的同时,也为气化渣的高值化利用提供了一条可行途径,对气化渣的减量化、资源化、高值化利用具有重要意义。

基于Aspen Plus的煤部分气化氢电联产系统模拟

为了提高煤制氢系统的能源利用效率,减少碳排放,构建了4种以煤部分气化为基础的新型氢电联产系统.基于Aspen Plus软件,采用系统效率、制氢效率作为评价标准,对各系统进行模拟与对比分析.结果表明:存在不同氧煤比与碳转化率使得系统效率达到最高,系统1~4分别在碳转化率为60%、85%、65%、60%时达到最高系统效率;各系统效率与气化效率随着气化温度的提高,呈先迅速增长后趋于平稳趋势;各系统效率与气化效率随着气化压力的提高,呈先迅速减少后趋于平稳趋势;在氧煤比为0.33,气化压力为2 MPa,气化温度为1000℃工况下系统1~4效率分别为59.12%、66.13%、62.21%和58.57%;采用CO_(2)与O_(2)作为气化剂,且CO_(2)与O_(2)的质量比为4∶1的煤部分气化加压富氧燃烧循环系统(系统2)在各项标准下具有优势,为最佳氢电联产系统.

焦炭-水蒸气催化气化反应特性研究

采用碱性待生剂为气化原料,考察焦炭与水蒸气催化气化反应特性。在消除内外扩散影响的前提下,探讨了气化反应温度、进水蒸汽、混合气体比例及气化时间对焦炭水蒸气催化气化反应的影响。结果表明,碱性待生剂上焦炭催化气化反应速率与气化反应温度成正比,进水蒸汽速率为2.5 L/min时,可基本消除水蒸气的扩散效应对焦炭催化气化反应的影响,碱性待生剂上焦炭转化率基本趋于稳定,气化反应时间30 min,可较好转化碱性待生剂上焦炭,产品气以H_(2)组成为主(含量约60%)。水蒸气/氧气混合气为气化剂可显著提高焦炭催化气化转化率,同时,氧气的加入会影响合成气组成。合成气中H 2和CO含量降低,CO_(2)含量升高。

不同焦炭光学组织的气化反应性分析

焦炭光学组织是影响焦炭反应性的内在因素,对不同焦炭光学组织的气化反应性分析可为更好地指导配煤炼焦生产,即通过合理配煤控制和改善焦炭反应性指标以实现降低配煤成本、稳定和提高焦炭质量。选择10种不同变质程度的炼焦煤,利用煤岩显微镜和焦炭反应性实验定量分析每种光学组分的相对反应性,并建立基于镜质体反射率和焦炭光学组织相对反应速率的焦炭反应性预测方程。结果发现,不同焦炭中不同光学组织的气化反应速率(绝对值)差别较大,但相对反应速率基本恒定,与焦炭类型无关。各向同性组织、镶嵌状组织、流动状组织、丝质及破片组织的相对反应速率比值为K_(ISO)∶K_(M)∶K_(F)∶K_(FF)=2.5∶1.0∶0.6∶2.6。光学组织相对反应速率对焦炭反应性(CRI)的影响高于变质程度,基于镜质体反射率(R^(o)_(max))和焦炭光学组织相对反应速率(K)的焦炭反应性预测方程为CRI=-14.73 R^(o)_(max)+17.21 K+30.78。

不同条件下焦炭的高温反应行为及热态性能评价

针对某钢铁企业四种捣固焦,研究了不同条件下焦炭高温气化反应行为,从不同角度评价焦炭热态性能。结果表明,在国标条件下,四种焦炭的CRI和CSR分别在21%~31%和54%~68%范围内。随着焦炭反应性的升高,气化溶损反应开始温度和激烈温度均降低,且两者分别在887~948℃和1315~1423℃范围内。随着溶损率的增加,焦炭C和D的固定溶损率反应后强度均降低,且前者大于后者,但两者差值明显低于国标条件下的差值。高炉实际运行结果显示,在其他条件不变的情况下,使用焦炭C和D时高炉技术经济指标相差不大。采用高温下固定溶损率反应后强度和平均反应速率评价焦炭的热态性能更符合炉内情况,推荐的检测条件为温度1200~1400℃、固定溶损率为20%~30%。

CaO添加量对焦炭反应性和反应动力学的影响

近年来,研究表明利用高反应性焦炭进行高炉炼铁不仅可以降低燃料比,而且可以降低碳排放。因此,开发高反应性焦炭的研究受到关注。本工作在不同变质程度煤中添加CaO进行炼焦,研究CaO添加量对焦炭反应性和反应后强度的影响。同时,研究添加不同含量CaO的焦炭在不同升温速率下的焦炭与CO_(2)非等温气化反应行为,分析了CaO对焦炭气化反应特征参数以及动力学过程的影响规律。

危险废物综合利用中的废气污染物解析——以焙烧石油焦和煤气化灰渣为例

石油焦和煤气化制氢产生的灰渣属于非典型危险废物。目前,国内利用气化灰渣进行钒、镍等金属的提取以达到综合利用目的的案例极少。在总结石油焦和煤气化灰渣来源和其固废属性的基础上,以国外某同类电厂石油焦和煤气化灰渣为研究对象的类比源,分析了气化灰渣中各元素的含量;根据预处理装置的运行参数以及各污染因子的产生机理,通过类比法,推断出焙烧脱碳工序废气的污染因子为烟尘、二氧化硫、二氧化氮、重金属及二噁英等。研究结论为我国石油焦和煤气化灰渣综合利用过程污染物的推断及环保管理提供了一定的思路。

兰炭在固定床碎煤加压气化炉的应用分析与探讨

晋控金石园区分公司采用固定床碎煤加压气化技术生产合成氨、甲醇,气化炉原料煤为无烟块煤。为进一步拓展气化炉原料煤种,公司开展了掺烧兰炭的试烧试验。介绍了兰炭掺烧比例为20%、30%、50%、100%等不同条件下的气化炉运行工况、煤气组分、吨氨消耗、煤气水产量变化情况,分析了气化炉掺烧兰炭的经济性,试烧数据可为同类型企业的原料煤结构调整提供实践指导。

粉焦在粉煤气化装置中的应用

在全球能源危机的背景下,能源价格不断上涨,实现能源的综合利用,显得尤其重要。粉焦是煤炭产业生产过程中的一种附属产品,在煤炭转变的工业生产中合理利用粉焦,不仅有助于缓解能源供应压力,同时还可以更好的达到节约煤炭的目的,因此粉焦的合理利用有非常突出的价值和意义。陕煤集团榆林化学有限责任公司将粉煤热解过程中产生的粉焦通过粉焦称重螺旋输送机送到磨煤系统,经过研磨、干燥、筛选,最终送到气流床煤气化炉内完成气化反应,实现粉焦在粉煤气化装置的综合利用,不仅实现粉焦利用价值的提升,同时实现企业经济效益的改善,最终达到节约能源的目的。