Present day, the production of hot metal (HM) via the blast furnace route remains an integral part of the global steel industry. With global pressure to curb greenhouse gas emissions, injection of ...hydrogen is considered a promising solution while ironmaking transitions to alternate technologies. A comprehensive heat and mass balance model calibrated to an operating blast furnace was used to assess the operational limits of hydrogen injection through the tuyeres, replacing Pulverised Coal Injection (PCI). Constrained by a minimum top gas temperature and minimum Raceway Adiabatic Flame Temperature (RAFT), the maximum injection rate was determined to be 19.5 kg-H2/t-HM when replacing 37.4 kg-PCI/t-HM (i.e. a replacement ratio of 1.9 kg-PCI/kg-H2 or 1.54 kg-C/kg-H2). At the maximum hydrogen injection rate, the specific CO2,eq emissions were seen to decrease by 8% in the top gas. In the case where the increased level of hydrogen increases stack reduction efficiency, the maximum hydrogen injection rate is decreased, while the replacement ratio is increased significantly. A maximum hydrogen injection rate of 14.3 kg-H2/t-HM with a replacement ratio of 4.5 kg-PCI/kg-H2 was achieved when the stack reduction efficiency was 100%, with a CO2,eq emission decrease of 14%. The optimal scenario for injection of hydrogen was determined to be maintaining a constant production rate, allowing the RAFT to decrease, and replacing PCI.
Display omitted
•Torrefaction at higher temperatures positively enhances higher heating value.•Grinding energy reduced 8.5 times with the increase of torrefaction temperature.•Catalytic oxidation ...converts chemical energy in the volatiles into thermal energy.•1.25 GJ/tonne excess energy can be generated from torrefaction gas.
Using torrefied char, or biocoal, as solid fuel provides an opportunity to introduce a sustainable feedstock into the energy market. The goals of this study were to investigate how torrefaction improves the energy content and the grindability of a Malaysian bamboo along with understanding the potential for integrated energy recovery from torrefaction gases. The feedstock was torrefied at 250–290 °C for 1 h and the combustion characteristics and grindability of the solid products along with the composition of torrefied gas species were measured. The results showed a beneficial increase in elemental carbon increased from 47 to 63 wt% at 290 °C torrefaction, reflecting an increase in higher heating value from 17.8 to 25.6 MJ/kg. The combustion behavior of all the products showed three distinct zones, with increasing torrefaction severity leading to higher combustion temperature due to an increased fixed carbon content. This increase in severity also lead to more friable and grindable material, and the 290 °C condition required a factor of 2.7 less hold-up time in the mill compared to the raw bamboo, and a factor of 8.5 less energy (938 and 111 kWh/tonne respectively). Through analysis of the gas and volatile formation, a case study showed that catalytic oxidation can convert nearly 100% of the embodied chemical energy into usable thermal energy. These experimental findings were scaled to a 100,000 tonne/y capacity torrefaction plant and in the moderate case of 270 °C operating temperature, the plant has 1.25 GJ/tonne excess energy beyond what the process needs.
Present day, the production of hot metal (HM) via the blast furnace route remains an integral part of the global steel industry. With global pressure to curb greenhouse gas emissions, injection of ...hydrogen is considered a promising solution while ironmaking transitions to alternate technologies. A comprehensive heat and mass balance model calibrated to an operating blast furnace was used to assess the operational limits of hydrogen injection through the tuyeres, replacing Pulverised Coal Injection (PCI). Constrained by a minimum top gas temperature and minimum Raceway Adiabatic Flame Temperature (RAFT), the maximum injection rate was determined to be 19.5 kg-H2/t-HM when replacing 37.4 kg-PCI/t-HM (i.e. a replacement ratio of 1.9 kg-PCI/kg-H2 or 1.54 kg-C/kg-H2). At the maximum hydrogen injection rate, the specific CO2,eq emissions were seen to decrease by 8% in the top gas. In the case where the increased level of hydrogen increases stack reduction efficiency, the maximum hydrogen injection rate is decreased, while the replacement ratio is increased significantly. A maximum hydrogen injection rate of 14.3 kg-H2/t-HM with a replacement ratio of 4.5 kg-PCI/kg-H2 was achieved when the stack reduction efficiency was 100%, with a CO2,eq emission decrease of 14%. The optimal scenario for injection of hydrogen was determined to be maintaining a constant production rate, allowing the RAFT to decrease, and replacing PCI.
In the present study, theoretical and experimental investigations were carried out to examine the effect of changing the operating parameters of an air gap membrane distillation (AGMD) system on the ...performance of electrospun and commercial membranes. These parameters include feed, cooling water temperature and feed flow rate. Analytical models were used, with the aid of MATLAB, to predict the permeate flux of AGMD based on heat and mass transfer. Heat transfer was used to predict the temperature on the membrane surface on the feed side and the thin film layer in the cooling plate on the air gap side, which was used later to calculate the vapour pressure and the permeate flux. The molecular diffusion model corresponded well with the experimental measurements in terms of predicting the permeate flux by varying the feed temperature, while it was poor in term of coolant temperature and feed flow rate. The results also illustrate that high rejection rates of around 99% of heavy metals can be achieved by using superhydrophobic electrospun membranes. The electrospun membrane flux increased with increasing feed tank temperature and flow rate while it was reduced with an increase of cooling line temperature.
Display omitted
•Environmentally friendly Superhydrophobic composite electrospun membrane for AGMD.•Comparison between different models for flux prediction.•Investigating AGMD parameters.•Composite electrospun membrane ahiwed high flux and rejection at high lead concentration.
Soft sensors are powerful tools for the implementation of process analytical technology (PAT). They are categorized into white-box (first-principle), black-box (statistical), and gray-box models. ...Gray-box models integrate white-box and black-box models to address each drawback, i.e., prediction accuracy and intuitiveness. Although they have been applied to various industrial processes, their applicability to water content monitoring in fluidized bed granulation has not been reported. In this study, we evaluated three types of gray-box models, i.e., parallel, serial, and combined gray-box models, in terms of prediction accuracy using real operating data on a commercial scale with two formulations. The gray-box models were constructed by integrating the heat and mass balance model (white-box model) and locally weighted partial least squares regression (LW-PLSR) model (black-box model). LW-PLSR was utilized to cope with collinearity and nonlinearity. In the serial gray-box models, LW-PLSR models adjusted the fitting parameters of the white-box model depending on the process parameters for each query. In the parallel gray-box or combined gray-box models, LW-PLSR models compensated for the output error of the white-box or serial gray-box models, respectively. The results demonstrated that all three types of gray-box models improved the prediction accuracy of the white-box models regardless of the formulation. Besides, we proposed the assessment method based on Hotelling’s T2 and Q residual for gray-box models using LW-PLSR, which contributes decision support to select gray-box or white-box model. The accurate and descriptive gray-box models are expected to enhance process understanding and precise quality control in fluidized bed granulation.
Bio-SRF based on livestock waste has low heating value and high moisture content. The concentration of toxic gases such as SOx, NOx, and HCl in the flue gas is changed according to the composition of ...fuel, and it has been reported. Therefore, the study of fuel combustion characteristics is necessary. In this study, we investigated combustion characteristics on the blended firing of coal and Bio-SRF (bio-solid refused fuel) made from livestock waste fuel in CFBC (circulating fluidized bed combustor). The raw materials for manufacturing Bio-SRF include agricultural waste, herbaceous plants, waste wood, and vegetable residues. Bio-SRF, which is formed from organic sludge, has a low heating value and a high moisture content. Bio-SRF of livestock waste fuel is blended with different ratios of coal based on heating values when coal is completely combusted in CFBC. In the result of experiment, the combustor efficiency of calculated unburned carbon concentration in the fly ash shows 98.87%, 99.04%, 99.64%, and 99.71% when the multi co-combustion ratio of livestock waste fuel increased from 100/0 (coal/livestock waste) to 70/30 (coal/livestock waste). In addition, the boiler efficiency is shown to be 86.23%, 86.30%, 87.24% and 87.27%. Through the experimental results, we have identified that co-combustion of livestock waste fuel does not affect boiler efficiency. We have systematically investigated and discussed the temperature changes of the internal combustor, compositions of flue gases, solid ash characteristics, and the efficiency of combustion and of the boiler during co-combustion of coal and Bio-SRF.
A Static Model for Energy‐Optimizing Furnace Vidhyasagar, Malaiyappan; Kumar, Deepoo; Viswanathan, Nurni Neelakantan ...
Steel research international,
September 2022, 2022-09-00, 20220901, Volume:
93, Issue:
9
Journal Article
Peer reviewed
In an integrated steel‐making plant, crude steel is produced mainly through a basic oxygen furnace (BOF) and an electric arc furnace (EAF). Apart from these two, energy‐optimizing furnace (EOF) is ...also evolving as a competent technology in the primary steel‐making process. Currently, a few plants are using the EOFs for crude steel production. The process control tools available in the EOFs are also limited, which may be the reason for limited reported attempts to improve this process. Mass and heat balance are essential methodologies to understand the mass flow of a process much better. Many mass and heat balance‐based studies have been carried out for the BOFs and EAFs, which can aid the operation of these furnaces toward process optimization. The present work focuses on developing a static model for the EOF process that can give a better understanding of the process and can aid the operation. A Microsoft Excel‐based model has been developed considering heat and mass balance coupled with thermodynamic data and operating conditions of the furnace from the plant scale experiments. The present model can predict the entire mass flow in the process and its accuracy is also assessed. The possible reasons for the present accuracy level were also elaborated.
The present study explains the detailed modeling of the inputs and outputs of the furnace named energy‐optimizing furnace (EOF), which produces crude steel. Only a few furnaces are available in the world and its control tools are also fewer. So, this study helps in better understanding the furnace and its operation.
PDF
