Utilization Of Coke Oven Gas Research Articles

Technical alternatives for coke oven gas utilization in China: A comparative analysis of environment-economic-strategic perspectives

China is the largest coke producer and consumer. There is a pressing need to address the high emissions of air pollutants and carbon dioxide associated with traditional coking production. As the nation pursues a transition towards carbon neutrality, expanding supply chains for coking plants to produce hydrogen, methanol, and other green alternatives has garnered significant attention. However, the relative advantages of these strategies have remained uncertain. In this study, we integrate a life cycle assessment-economic analysis-scenario analysis model to evaluate various coke oven gas (COG) utilization routes (COGtM: COG-to-methanol, COGtLNG: COG-to-liquefied natural gas, COGtSA: COG-to-synthetic ammonia, and COGtH: COG-to-hydrogen). The results indicate that COGtSA emerges as the preferred option for balancing environmental and economic benefits. Meanwhile, COGtM demonstrates economic viability but is associated with higher environmental impacts. Despite being recognized as a significant strategic direction under carbon neutrality initiatives, COGtH faces economic feasibility and risk resilience limitations. COGtLNG encounters both financial and environmental challenges, necessitating strategic development from an energy security perspective. The projected coking capacity is anticipated to experience a slight increase in the mid-term yet a significant decline in the long term, influenced by steel production capacity. In potential future markets, COGtM is estimated to potentially capture a maximum market share of 16–34% in the methanol market. Furthermore, against the backdrop of continuously expanding potential demand for hydrogen, COGtH holds advantages as a transitional solution, but in the long run, it can only meet a small portion of the market. COGtSA can meet 7–14% of market demand and emerges as the most viable pathway from the viewpoint of balancing environmental and economic aspects and covering future markets.

Life cycle analysis and economic evaluation of adsorptive removal of arsenic from groundwater using GAC and GAC-Fe adsorbents

The potential health effects associated with consumption of arsenic contaminated water have motivated chemical and energy intensive treatment processes. Granulated activated carbon (GAC) and iron impregnated granular activated carbon (GAC-Fe) are the two adsorbents which have shown significant removal of arsenic (As(V)). However, the synthesis of different adsorbents involves significant different materials and energy interactions which have different environmental and economic burdens. This study evaluates and compares the environmental impacts arising from treatment of arsenic containing water using GAC and GAC-Fe adsorbents, for the selection of more suitable one. The life cycle inventory pertaining to treatment through two adsorbents was prepared based on the data available in literature. The impacts were assessed utilizing ‘Sphera LCA for experts’ software with three midpoint methods i.e. CML 2001, TRACI 2.1 and ReCiPe 2016. Results show that chemically treated/impregnated adsorbents for arsenic contaminated water treatment not only have lesser environmental emissions but also reduces the treatment cost. The treatment with GAC-Fe has ∼30% lower impacts in GWP, AP, EP, MAETP, FAETP, ODP, ADP (E) and HTP categories than treatment with GAC, since increase in adsorbent's specific uptake in GAC-Fe reduces the amount of total adsorbent requirement. GAC-Fe based water treatment costs ∼23% less than with GAC. The main responsible parameters for emissions are synthesis of GAC from hard coal precursor, and electricity consumption in carbonization and drying operations. Apart from this, in case of GAC-Fe, additional impregnation and drying operation also contributes to emissions. The utilization of coke oven gas generated in adsorbent synthesis for energy credits has potentially reduced the emissions and operating cost. The less standard deviation (<10%) in Monte Carlo (MC) uncertainty analysis, indicated the reliability and robustness of LCA impacts. This study exemplified the environment friendliness of metal impregnated GAC based arsenic contaminated water treatment.

Highly simplified and efficient process for methanol and ammonia synthesis from coke-oven gas and pulverized coke using chemical looping technology

The utilization of coke-oven gas (COG) to produce methanol requires external carbon supplementation and is associated with the wastage of hydrogen resources. COG chemical looping reforming (CGCLR) integrated with PC chemical looping combustion (PCCLC) is involved in this system and it is an effective solution to the poor carbon/hydrogen utilization and high process intensification. The CO2 generated from the PCCLC is recycled into the CGCLR to reformulate the methane in COG to alter the hydrogen-to-carbon ratio (R) of the syngas and thereby produce more methanol. The key operational parameters of the proposed system are analyzed to optimize the utilization of the elements in COG. This system exhibits utilization efficiencies of 85.4% and 63.9% for hydrogen and carbon, respectively, both of which are relatively high. The exergy efficiency is up to 77.5%. The new system has a reduced process complexity, and more amount of CO2 is recycled to produce value-added chemicals.

Hydrogen production from low pressure coke oven gas by vacuum pressure swing adsorption

Hydrogen is a major component of coke oven gas (COG) and can be used in gas-based direct reduction iron processes to help the steel industry achieve the carbon peaking and carbon neutrality goals. However, the high compression power consumption is the main drawback of the current PSA cycle since the COG needs to be compressed from atmospheric pressure to ∼18 bar to achieve a hydrogen production with purity >99.9% and recovery < 85%. Here in this study, we experimentally demonstrate by using a 4-bed 12-step lab-scale VPSA rig filled with activated carbon RB3 and can obtain a hydrogen product with a purity of 99.67% and a recovery of 91.97% at a feed pressure of only 5.17 bar. We then constructed a non-isothermal non-adiabatic VPSA model using our in-house code and validated the model against experimental breakthrough and VPSA cycles. Parametric optimization produced a H2 product of 99.995% purity and 92.29% recovery at a slightly increased adsorption pressure of 6 bar and a vacuum pressure of 0.02 bar with 10.21 mol.H2/kg.ads/hr productivity and 7.09 kJ/mole.H2 specific power. We also confirmed that light product purge at vacuum pressure can effectively improve the H2 purity and the gas flow direction of the pressure equalization step has a significant effect on the mass transfer front. Our research presents the success of low-pressure hydrogen production from COG, which will greatly accelerate the transformation of COG utilization and promote the decarbonization of the iron and steel industry.

Comparative life cycle assessment of ammonia production by coke oven gas via single and coproduction processes

As an abundant H2-rich byproduct from coking production, coke oven gas (COG) is a favorable feedstock for ammonia production. Recently, three COG-based ammonia processes have been applied, including single process, coproduction of ammonia with methanol, and coproduction of ammonia with liquefied natural gas (LNG). To systematically evaluate the environmental impacts of three COG routes, a comparative life cycle assessment was conducted with industrial data. Besides, the effects of ammonia synthesis pressure and electricity sources to the total LCA result were discussed. The results indicate that the environmental impacts of COG-based single ammonia route are mainly generated from ammonia production stage, accounting for 69.63 % of the overall normalized results, in which electricity and COG are the dominated contributors. Therefore, employing electricity from renewables like wind, solar, hydro and nuclear could dramatically mitigate the environmental impacts with a reduction of 36.3 %–70.7 % in most environmental indicators. Scenario analysis proves that reducing synthesis pressure from 31.4 MPa to 15 MPa does not show remarkable environmental benefits as expected since higher pressure is more conducive to ammonia synthesis. In comparison with coal based and natural gas-based ammonia routes, COG routes have obvious energy-saving benefit. In three COG-based ammonia routes, the two coproduction routes accounted for 49.1 % and 78.6 % of the energy depletion as single production due to highly efficient utilization of resources and energy. Coproduction of ammonia with methanol route exhibits better environmental performance than these in coproduction of ammonia with LNG route. Therefore, coproduction of ammonia with methanol route is more favorable in COG to ammonia processes. This study intends to provide a valuable reference for COG utilization and ammonia production options through the life cycle aspect.

Comparative study on life cycle energy consumption, carbon emissions and economic performance of various coke-oven gas utilization schemes

Coke-oven gas (COG) is the by-product of coking process and can be used as feedstock in energy and chemical processes. However, the relative advantages and comprehensive competitiveness of various mature and widely-used utilization schemes still need to be investigated, which will be helpful in exploring better ways to use COG. From the perspective of energy supply, this paper investigated the energy consumption, carbon emissions, capital investment and product cost of COG-to-hydrogen (COGtH), COG-to-natural gas (COGtNG), COG-to-methanol (COGtM) and COG-to-power (COGtP) through LCA method, and compared the comprehensive competitiveness using entropy weight method. The results show that COGtP performs better in all aspects, only consumes 2.669 MJ of energy and generates 0.14 kg CO2-eq of carbon emissions when outputting 1 MJ of energy, and product cost is only 1.11E-02 RMB/MJ, making it the most competitive utilization scheme. COGtM consumes the highest 8.525 MJ of energy and generates 0.708 kg CO2-eq of carbon emissions when outputting 1 MJ of energy, and it is superior to COGtNG only in terms of capital investment, making it the least competitive utilization scheme. The comprehensive competitiveness of COGtNG is slightly higher than COGtH, with comprehensive score of 0.49 and 0.46 respectively, and it can be further improved by reducing the equipment investment of methanation, while the performance of COGtH in economic aspect needs to be improved, especially to reduce product cost. Further analysis shows the extent to which the energy consumption and carbon emissions is affected by allocation principle is determined by the proportion of energy consumption and carbon emissions in the coking and upstream coal mining, washing and transportation stages, and under value allocation, the energy consumption and carbon emissions is almost directly linearly proportional to COG price, but non-linearly inversely proportional to coke price. In addition, the value allocation is favorable than mass and energy allocation in view of its reduced energy consumption and carbon emissions of utilization schemes if COG price decreases to 0.38 RMB/Nm3 and 0.47 RMB/Nm3 respectively, or coke price increases to 1122 RMB/t and 899 RMB/t respectively.

Environmental and economical assessment of high-value utilization routes for coke oven gas in China

The high-value utilization of coke oven gas (COG) has been widely investigated because of abundant resource shortage and serious environmental pollution. Comparative environmental and economic analysis of various COG utilization routes (i.e., COG-to-methanol, COG-to-hydrogen, and COG-to-synthetic natural gas) in China was conducted to identify the optimized route via China's regionalized life cycle assessment coupled economic assessment. Results showed that the COG-to-hydrogen route presents the lowest environmental and economic effects. Fossil depletion category was the main contributor for the three COG utilization scenarios, accounting for approximately 60% of the total environmental burden. Electricity dominated the environmental and economic burden with the proportion of approximately 90% and 30%, respectively. COG-based routes reduced the energy consumption by 83.4%–87.1% and carbon emissions by 41.4%–88.4% than coal-based routes. The recycling of unused COG for hydrogen production can substantially reduce the CO2 emissions by 11.87, 4.94, 6.39, 7.48 and 4.70 million tons in the provinces of Shanxi, Hebei, Shandong, Shaanxi, and Inner Mongolia, respectively. “Green hydrogen” route relying on hydropower shows higher environmental superiority than other routes, whereas COG-to-hydrogen route is regarded as an important breakthrough for large-scale transformation and application of “green hydrogen”. Optimizing the industrial layout and vigorously promoting the recycling of COG by enterprises are conducive to increasing the environmental and economic benefits.

Life cycle assessment of liquefied natural gas production from coke oven gas in China

Producing liquefied natural gas (LNG) from coke oven gas (COG) is a promising option to partly alleviate the shortage of natural gas supply and effectively utilize the byproduct of coking production in China. In order to systematically evaluate the energy consumption and environmental impact of COG-based LNG process, the life cycle assessment (LCA) method was introduced in this study. Two synthesized approaches were considered and compared, namely decarbonization process and methanation process. Besides, whether with or without H2 extraction in methanation process is also discussed. Inventory data are obtained from onsite investigations of representative enterprises in China. The results indicate that, LNG production stage is the dominated unit in the overall environmental impacts of decarbonization process, next is LNG evaporation stage, while coking stage only contributes 2.38%. The reason is that COG is only responsible for less upstream environmental burdens as a byproduct. In LNG production stage, medium pressure steam, COG and electricity are the key substances. Comparative LCA shows that methanation process shows better environmental performance than decarbonization process in COG-based LNG production since more LNG product are produced. It is suggested that methanation process with H2 extraction is more desirable considering economic performance. This work intends to provide useful insights on the sustainability development of COG utilization in coking industry.

Technology-environment-economy assessment of high-quality utilization routes for coke oven gas

Coke oven gas (COG) is an important energy resource that rich in hydrogen and methane, which is conventionally used for industrial heating but is embarking on high-quality utilization routes to produce bulk energy and materials. Previous work emphasized the comparison of COG utilization with external competitors but has limited understanding of the internal competitiveness of different COG utilization routes, making it impossible to scientifically guide the high-quality utilization of COG. This study proposed a technology-environment-economy assessment framework to compare the competitiveness of six high-quality COG utilization routes called COG to electricity (COGTE), COG to methanol (COGTM), COG to hydrogen (COGTH), COG to synthetic natural gas (COGTSNG), COG to synthetic ammonia (COGTSA), and COG to olefins (COGTO). The framework employed the life cycle assessment method based on an economic functional unit to calculated individual indicators and used the entropy weight method to integrate these indicators to a comprehensive score. The results show that energy consumption, water consumption, and carbon emission are critical defects of COGTSNG, COGTM, and COGTE, respectively. Net present value rate, internal rate of return, and dynamic payback period are common but differentiated disadvantages of the five COG utilization routes other than COGTO with the current market price, which are the main factors of their weaker comprehensive competitiveness. COGTO is expected to be the most promising high-quality COG utilization route thanks to its excellent competitiveness, handsome market demand, and special policy preferences. In addition to COGTM, any of the other five COG utilization routes are likely to be most competitive when raw material and product prices fluctuate by 25%, which suggests that the investment should be tailored to local specific prices, demand, and policies.

Techno-Economic and Carbon Footprint Analyses of a Coke Oven Gas Reuse Process for Methanol Production

This paper focuses on the best way to produce methanol by Coke Oven Gas (COG) conversion and by carbon dioxide capture. The COG, produced in steelworks and coking plants, is an interesting source of hydrogen that can be used to hydrogenate carbon dioxide, recovered from flue gases, into methanol. The architecture of the reuse process is developed and the different process units are compared by considering a hierarchical decomposition. Two case studies are selected, process units are modelled, and flowsheets are simulated using computer-aided design software. A factorial techno-economic analysis is performed together with a preliminary carbon balance to evaluate the economic reliability and the environmental sustainability of the proposed solutions. The production costs of methanol are equal to 228 and 268 €/ton for process configurations involving, respectively, a combined methane reforming of COG and a direct COG separation to recover hydrogen. This cost is slightly higher than the current price of methanol on the market (about 204 €/ton for a process located in the USA in 2013). Besides, the second case study shows an interesting reduction of the carbon footprint with respect to reference scenarios. The carbon dioxide capture from flue gases together with COG utilization can lead to a competitive and sustainable methanol production process depending partly on a carbon tax.

УДОСКОНАЛЕННЯ ВИПУСКНОЇ РІДКОЇ ФОРМИ КАТIОННИХ БАРВНИКIВ І ЛАКІВ

Improved composition of final forms of cationic dyes and their mixtures in liquid form when mixed to expand the colors of such classes as azine, oxazine, acridine, triazole, triazine, benthiazole and polymethine with reduced foaming and increased resistance to storage of roses. The improved composition allows to expand the color range of mixed dyes for dyeing and printing of fabrics from polyacrylonitrile fiber with high quality indicators. Options for utilization of coke oven gas and resin components isolated from coal coking waste by synthesis of intermediates based on it for the synthesis of triarylmethane dyes are considered. The main directions of improvement of technology of their production for various areas of application are defined. The reactions of aniline, phenol, toluene and their derivatives, naphthalene from coke chemical resin with subsequent production of target dyes from yellow to blue and violet colors are shown. Physicochemical and technological features of the formed tungsten-molybdenum varnishes on the basis of cationic basic dyes are resulted.

Techno-economic evaluation of the integrated polygeneration system of methanol, power and heat production from coke oven gas

This study aims to develop novel high energy-efficient and economically viable methanol production processes form coke oven gas. To pursue this goal, two process schemes for the coke oven gas utilization, namely a highly integrated polygeneration of methanol, power, and heat, are proposed. The optimal system configuration and operating conditions for maximizing methanol amount or the total energy production were identified through the development of rigorous process models. The capability of the proposed processes was analyzed with different criteria: energy efficiency, carbon balance and minimum selling price of the produced methanol. As a result, the energy efficiency of the proposed processes is analyzed to range from 53 to 71%, which are greatly improved compared to the base process (38%). An economic evaluation study revealed that the minimum selling price of the methanol of the proposed processes was 0.23–0.29 USD/kg, which are competitive with conventional methanol production processes.

A thermodynamic performance analysis on influence parameters of COG-CCHP based on exergy

PurposeThe purpose of this paper is to investigate the performance of coke oven gas (COG)-combined cooling, heating and power (CCHP) system and to mainly focus on studying the influence of the environmental conditions, operating conditions and gas conditions on the performance of the system and on quantifying the distribution of useful energy loss and the saving potential of the integrated system changing with different parameters.Design/methodology/approachThe working process of COG-CCHP was simulated through the establishment of system flow and thermal analysis mathematical model. Using exergy analysis method, the COG-CCHP system’s energy consumption status and the performance changing rules were analyzed.FindingsThe results showed that the combustion chamber has the largest exergy loss among the thermal equipments. Reducing the environmental temperature and pressure can improve the entire system’s reasonable degree of energy. Higher temperature and pressure improved the system’s perfection degree of energy use. Relatively high level of hydrogen and low content of water in COG and an optimal range of CH4volume fraction between 35 per cent and 46 per cent are required to ensure high exergy efficiency of this integration system.Originality/valueThis paper proposed a CCHP system with the utilization of coke oven gas (COG) and quantified the distribution of useful energy loss and the saving potential of the integrated system under different environmental, operating and gas conditions. The weak links of energy consumption within the system were analyzed, and the characteristics of COG in this way of using were illustrated. This study can provide certain guiding basis for further research and development of the CCHP system performance.

A novel coke-oven gas-to-natural gas and hydrogen process by integrating chemical looping hydrogen with methanation

The coke-oven gas (COG)-to-natural gas (CGtNG) is a promising process of chemical industry. However, the CGtNG suffers from low hydrogen utilization efficiency and natural gas capacity due to the high ratio of hydrogen to carbon of the COG. The CO2 derived from chemical looping hydrogen process can be an effective carbon source to optimize syngas composition for high efficient natural gas production. Therefore, a novel process of COG chemical looping hydrogen assisted COG-to-natural gas (CGCLH-CGtNG) is proposed in this paper. The key parameters are optimized for maximizing COG utilization and natural gas production in the novel process. Results show that the novel process could solve the issues of CO2 utilization in the chemical looping hydrogen process and low natural gas production in the CGtNG. At the cost of additional 4.36 t/h COG consumption, the novel process produce about 19% more natural gas and additional 1.39 t/h hydrogen compared with the conventional CGtNG process. The corresponding hydrogen utilization and exergy efficiencies of the novel process are increased from 61.1% to 78.5% in the CGtNG to 82.4% and 87.6% through intensive mass and energy integration, respectively.

Concept design and techno-economic performance of hydrogen and ammonia co-generation by coke-oven gas-pressure swing adsorption integrated with chemical looping hydrogen process

The coke-oven gas direct chemical looping hydrogen generation is a promising process for chemical industry; however, it still suffers from high energy consumption and low hydrogen production. The chemical looping-derived H2 and N2 can be used to produce ammonia. Therefore, a new process for coke-oven gas chemical looping hydrogen and ammonia co-generation integrated with pressure swing adsorption technology, which can flexibly adapt to market demand, is proposed in this paper. The new process has two extreme configurations to produce hydrogen or ammonia only. A thorough analysis of key operational parameters of the proposed systems has been conducted to optimize coke-oven gas utilization, and maximize hydrogen and subsequent ammonia production. The maximal hydrogen and ammonia productions are 7126 and 4784 kmol/h of 5532 kmol/h coke-oven gas consumption for the two extreme configurations, respectively. Moreover, an exergy efficiency of 68.5–73.6% and about 100% direct CO2 capture efficiency are obtained when switching between hydrogen and ammonia production in the novel process. These values are compared to those of the coke-oven gas chemical looping hydrogen generation process (hydrogen production of 6613 kmol/h per 6276 kmol/h coke-oven gas consumption, 66.0% exergy efficiency, and 73.3% CO2 capture efficiency). Finally, the economic and sensitive analyses of the novel process are also conducted in this paper.

Parameter optimization and thermodynamic analysis of COG direct chemical looping hydrogen processes

Coke-oven gas (COG) is largely by-produced in coking plants, being most burnt and resulting in serious energy waste and air pollutant emissions. Producing high-value hydrogen from COG is therefore promising, however, the traditional processes via steam methane reforming still suffer from high energy consumption and CO2 emissions. In this work, we propose efficient COG-to-hydrogen processes by chemical looping hydrogen technology. Parameter optimization of the proposed systems without and with support has also been conducted for the optimum COG utilization and maximum hydrogen production. The optimum molar ratios for the oxygen carrier/COG, steam/oxygen carrier, and air/oxygen carrier were found to be 2.0, 1.2, and 0.81, respectively, for the process without support. In the supported system, due to the presence of the high-temperature support, the optimum molar ratio of the oxygen carrier/COG is decreased to 1.1, while the steam/oxygen carrier ratio is increased to 3.9. The exergy efficiency, and CO2 capture efficiency, and hydrogen purity of the system with support are 63.8%, 73.3%, and 99.4 mol.%, respectively. It was found that the process including an intercooling between fuel reactor and steam reactor, and oxygen-enriched combustion in the heating air reactor provides a further improved exergy efficiency of 66.2% and CO2 capture efficiency of about 100%.

Life cycle assessment and economic analysis of methanol production from coke oven gas compared with coal and natural gas routes

Abstract Coke oven gas (COG), a considerable byproduct in coke production, has been utilized as the feedstock for methanol production. A “cradle-to-gate” life cycle assessment (LCA) of COG-based methanol production (COG route) was conducted and compared with the coal and natural gas routes by applying CML 2001 method with GaBi 6.0 software. Besides, the economic analysis of the three methanol routes were performed. The results indicate that COG route shows lower impacts than coal route to all the selected environmental categories. Moreover, the average methanol production cost of COG route is lower than that of coal and natural gas routes by 25.1% and 19.8%, respectively. In COG route, 82.1% of the overall normalized environmental burden occurs at methanol production stage dominated by electricity and steam consumption. The environmental impact of COG route could be reduced by supplying medium-pressure steam from coke dry quenching system for methanol production. This work intends to provide useful insights on the sustainability development of COG utilization in coke industry.

Coke oven gas to methanol process integrated with CO2 recycle for high energy efficiency, economic benefits and low emissions

A process of CO2 recycle to supply carbon for assisting with coke oven gas to methanol process is proposed to realize clean and efficient coke oven gas utilization. Two CO2 recycle schemes with respect to coke oven gas, namely with and without H2 separation before reforming, are developed. It is revealed that the process with H2 separation is more beneficial to element and energy efficiency improvement, and it also presents a better techno-economic performance in comparison with the conventional coke oven gas to methanol process. The exergy efficiency, direct CO2 emission, and internal rate of return of the process with H2 separation are 73.9%, 0.69t/t-methanol, and 35.1%, respectively. This excellent performance implies that reforming technology selection, H2 utilization efficiency, and CO2 recycle ways have important influences on the performance of the coke oven gas to methanol process. The findings of this study represent significant progress for future improvements of the coke oven gas to methanol process, especially CO2 conversion integrated with coke oven gas utilization in the coking industry.

Utilization of Coke Oven Gas and Converter Gas in the Direct Reduction of Lump Iron Ore

The application of off-gases from the integrated steel plant for the direct reduction of lump iron ore could decrease not only the total production cost but also the energy consumption and CO2 emissions. The current study investigates the efficiency of reformed coke oven gas (RCOG), original coke oven gas (OCOG), and coke oven gas/basic oxygen furnace gas mixtures (RCOG/BOFG and OCOG/BOFG) in the direct reduction of lump iron ore. The results were compared to that of reformed natural gas (RNG), which is already applied in the commercial direct reduction processes. The reduction of lump ore was carried out at temperatures in the range of 1073 K to 1323 K (800 °C to 1050 °C) to simulate the reduction zone in direct reduction processes. Reflected light microscopy, scanning electron microscopy, and X-ray diffraction analysis were used to characterize the microstructure and the developed phases in the original and reduced lump iron ore. The rate-controlling mechanism of the reduced lump ore was predicted from the calculation of apparent activation energy and the examination of microstructure. At 1073 K to 1323 K (800 °C to 1050 °C), the reduction rate of lump ore was the highest in RCOG followed by OCOG. The reduction rate was found to decrease in the order RCOG > OCOG > RNG > OCOG-BOF > RCOG-BOFG at temperatures 1173 K to 1323 K (900 °C to 1050 °C). The developed fayalite (Fe2SiO4), which resulted from the reaction between wustite and silica, had a significant effect on the reduction process. The reduction rate was increased as H2 content in the applied gas mixtures increased. The rate-determining step was mainly interfacial chemical reaction with limitation by gaseous diffusion at both initial (20 pct reduction) and moderate (60 pct reduction) stages of reduction. The solid-state diffusion mechanism affected the reduction rate only at moderate stages of reduction.

Reduction Behavior of Iron Ore Pellets with Simulated Coke Oven Gas and Natural Gas

Recently a special attention is being paid on the combination of different ironmaking technologies in the integrated steel plant to maximize the efficiency of the overall process. The utilization of coke oven gas for production of direct reduced iron (DRI) in the integrated steelmaking route is still under evaluation and discussion. In this study, iron ore pellets were isothermally reduced with simulated original and reformed coke oven gas (RCOG) at 700–980°C. The results were compared with those obtained by the reduction of pellets with the original and reformed natural gas (RNG). The highest reduction degree was obtained for the pellets reduced with RCOG while the lowest reduction degree was exhibited by original natural gas. On the other hand the rate of reduction with original coke oven gas was sharply increased at temperature of about 900°C to become higher than that of RNG. A slow down phenomenon appeared at the later stage of reduction due to the intensive carbon deposition. The soot formation increased as CH4 content and/or the temperature of reducing gas increased. Reflected light microscope, scanning electron microscope with EDX, and high performance X-ray diffraction analysis were used to estimate the reduction kinetics and mechanism.