Chapter 20 - Utilization of biomass as an alternative fuel in iron and steel making

Growing concerns over fossil CO2 emissions has created a considerable interest in an efficient utilization of renewable biomass in steel industry. Biomass lignin can be used as binder and reducing ...

This paper considers the utilisation of forest biomass in iron and steel making by putting focus on the supply of available raw biomass assortment, biomass conversion technologies, and distribution of biomass-based products towards reduced fossil CO2 emissions in the iron and steel industry. Biomass-based products are produced by converting biomass assortments from forestry operations and forest industries via slow pyrolysis and gasification technologies. Using a spatially explicit cost optimisation model, biomass supply is optimised to suit the corresponding demand for energy and material substitution, and the extent to which biomass can be a tool in CO2 abatement is explored. The study findings show that maximum use of biomass-based products result in a 43% reduction in CO2 emissions across the existing steel producing technologies. Results also show that increasing the rate of biomass utilisation via substitution targets is more effective than the use of a carbon pricing policy, since the maximum CO2 reduction is unmet even with very high CO2 prices. In the scenario analysis, it is found that low fossil fuel prices constitute a barrier to adopting biomass as an alternative to fossil energy use. Compared to the business-as-usual case, a maximum of 27% increase in energy-related costs was calculated for the industry.

Current status and development trends of innovative blast furnace ironmaking technologies aimed to environmental harmony and operation intellectualization

The iron and steel industry is still dependent on fossil coking coal. About 70% of the total steel production relies directly on fossil coal and coke inputs. Therefore, steel production contributes by ~7% of the global CO2 emission. The reduction of CO2 emission has been given highest priority by the iron- and steel-making sector due to the commitment of governments to mitigate CO2 emission according to Kyoto protocol. Utilization of auxiliary carbonaceous materials in the blast furnace and other iron-making technologies is one of the most efficient options to reduce the coke consumption and, consequently, the CO2 emission. The present review gives an insight of the trends in the applications of auxiliary carbon-bearing material in iron-making processes. Partial substitution of top charged coke by nut coke, lump charcoal, or carbon composite agglomerates were found to not only decrease the dependency on virgin fossil carbon, but also improve the blast furnace performance and increase the productivity. Partial or complete substitution of pulverized coal by waste plastics or renewable carbon-bearing materials like waste plastics or biomass help in mitigating the CO2 emission due to its high H2 content compared to fossil carbon. Injecting such reactive materials results in improved combustion and reduced coke consumption. Moreover, utilization of integrated steel plant fines and gases becomes necessary to achieve profitability to steel mill operation from both economic and environmental aspects. Recycling of such results in recovering the valuable components and thereby decrease the energy consumption and the need of landfills at the steel plants as well as reduce the consumption of virgin materials and reduce CO2 emission. On the other hand, developed technologies for iron-making rather than blast furnace opens a window and provide a good opportunity to utilize auxiliary carbon-bearing materials that are difficult to utilize in conventional blast furnace iron-making.

In blast furnace ironmaking, coke can be partially replaced by injected natural gas. Tuyere injection of cold natural gas is commonly practiced in North America. In this work, limits to the tuyere injection rate have been quantified with mass and energy balances. The fundamental origin of the limits is the endothermicity of methane injection. In principle, shaft injection of preheated and partially combusted methane would obviate the endothermic effect. However, the thermal and chemical energy parameter indicates that the energy requirement in the lower part of the furnace—to melt hot metal and slag—might not be met in the case of shaft injection. Tuyere injection of preheated methane might be a feasible alternative. Calculated combustion kinetics support the feasibility of partial combustion of preheated methane (with sub-stoichiometric oxygen) before injection.

Increased utilization of natural gas in blast furnace ironmaking can decrease both the cost and the carbon intensity of ironmaking, given current US natural gas prices. In this paper, three ways to utilize natural gas are compared: tuyere injection, prereduction of iron ore, and shaft injection. The basis for comparison includes coke replacement ratios, carbon intensity and furnace productivity. These were calculated using relevant mass and energy balances, a blast furnace productivity correlation based on the bosh gas flow rate, and measured and modeled prereduction kinetics. Of the natural gas utilization methods, prereduction has the highest effective coke replacement ratio (and hence the largest advantage in raw material cost), but is likely to have the highest capital requirement.

Biomass applications in iron and steel industry: An overview of challenges and opportunities

A review on reduction technology of air pollutant in current China's iron and steel industry

ABSTRACTThe steel industry accounts for 5% of the world's total energy consumption and contributes 6% of the world's anthropogenic CO2 emissions. The control of CO2 emissions has become increasingly stringent in various countries. The most advanced CO2 emission reduction technology in the steel industry has reached a bottleneck; therefore, many countries have begun developing breakthrough CO2 emission reduction technologies to cope with the current global climate change. Blast furnace (BF) ironmaking is the key production process in steel manufacturing. The development of low-carbon ironmaking technology based on the BF is an effective way to realize green evolvement of iron and steel industry. The current hot technologies of low-carbon BF ironmaking and innovative low-carbon BF ironmaking processes of the steel industry in various countries (including Europe, USA, Japan, etc.) are summarized in this paper; in addition, new ideas for China's steel industry to reduce CO2 emissions are provided.

Two key variables in blast furnace ironmaking - silicon content in hot metal ([Si]) and hot metal temperature (FeW) are considered and used to represent the thermal state in hot metal, while hourly output of hot metal (Fe/H) is used to represent the efficiency of ironmaking. The data is preprocessed by wavelet analysis to denoise and remove outliers. Fuzzy C-means clustering (FCM) is then used to identify the relation between efficiency of ironmaking and smelting intensity by using the processed data. Simulation based on data collected from No.7 blast furnace of Handan Steel show that the mean value of historical data (0.45) is not the stable thermal state of blast furnace. The system is more stable and has higher smelting intensity when silicon content is around 0.41, which shows that “low silica smelting practice” attempt in the steel industry can lower the energy consumption while keeping the smelting intensity and smooth production. It is proved that appropriate level of silicon content will lead to safe, smooth production with lower energy consumption and higher production.

Most modern blast furnaces (BFs) operate with Pulverized Coal Injection (PCI), but renewable and carbon neutral biochar could be applied to reduce the fossil CO2 emission in the short term. In the present study, heat and mass balance-based model (MASMOD) is applied to evaluate the potential of biochar in partial and full replacement of injected pulverized coal (PC) in the ironmaking BF. The impact of biochar injection on the raceway adiabatic flame temperature (RAFT) and top gas temperature (TGT) is evaluated. Three grades of biochar, produced from the pyrolysis of sawdust, were evaluated in this study. The total carbon content was 79.2%, 93.4% and 89.2% in biochar 1, 2 and 3, respectively, while it was 81.6% in the reference PC. For each type of biochar, 6 cases were designed at different injection levels from 30 kg/tHM up to 143 kg/tHM, which represent 100% replacement of PC in the applied case, while the top charged coke is fixed in all cases as reference. The oxygen enrichment, RAFT, and TGT are fixed for certain cases, and have been calculated by MASMOD in other cases to identify the optimum level of biochar injection. The MASMOD calculation showed that as the injection rate of biochar 1 and biochar 2 increased, the RAFT increased by ~190 °C, while TGT decreased by ~45 °C at 100% replacement of PC with biochar. By optimizing the moisture content of biochar and the oxygen enrichment in the blast, it is possible to reach 100% replacement of PC without much affecting the RAFT and TGT. Biochar 3 was able to replace 100% of PC without deteriorating the RAFT or TGT.

Low-carbon production of iron and steel: Technology options, economic assessment, and policy

Biomass Supply Chain in Asian and European Countries

In view of scarcity and depletion in the quality of raw materials as well as stringent environmental regulations, judicious use of resource and adoption of optimal operating practices have become the prime concern in iron and steel industries. Real time forecasting and supervision of the process behavior is an important step in addressing these issues. As a part of the tool termed “Real Time Process Simulator (RTPS)”, containing several reduced order models for real time monitoring and prediction of the internal dynamics of iron making blast furnace, a mathematical model for material and thermal analysis has been developed, mainly to predict the top gas composition, raw material consumption and overall heat balance. The model predictions have been tested against actual plant data. The raceway adiabatic flame temperature has been calculated using data similar to that of an operating plant. The calculated heat distribution of the process has been presented in the form of a SHANKEY diagram. The RTPS, containing the present model has been implemented in an Indian integrated steel plant. Prior to implementation, the model has been tested and validated in the plant operational range with the help of a virtual platform.

Chapter 13 - Biomass gasification: a step toward cleaner fuel and chemicals