Linz-Donawitz Converter Research Articles

Hydrogen production and CO2 capture from Linz-Donawitz converter gas via a chemical looping concept

Linz-Donawitz converter gas (LDG), an important by-product in the steel industry with CO (55–60 vol%) and CO2 (15–20 vol%) as the main components, is usually used as fuel for heating or power generation, releasing massive of diluted CO2 with the concentration lower than 15 % that is difficult to capture. Herein, we propose a method to produce pure H2 via chemical looping water splitting by using LDG as reducing agent, which can easily concentrate CO2 for capture. Fe2O3, one of the most environmentally friendly and low-cost oxides, was chosen as the oxygen carrier to perform this concept. It was found that the addition of small amounts of Ce0.75Zr0.25O2 solid solution could strongly improve the activity of Fe2O3 for CO conversion, especially at relatively low temperatures. Compared with pure Fe2O3, the CO conversion and H2 yield were increased from 39.5 % and 0.34 mmol·g−1 to 100 % and 2.32 mmol·g−1 at 650 °C, respectively, after adding 5 wt% of Ce0.75Zr0.25O2. The strong interaction between the two oxides contributed to the enhanced performance via promoting CO adsorption and lattice oxygen releasing. Water splitting assisted by air oxidation could fully regenerate the reduced oxygen carrier, and the oxygen carrier was stable during the long-term chemical looping process, with the CO2 capture rate at ca. 95.8 %. In situ DRIFTS results showed that CO2 was producedthrough a direct reaction of lattice oxygen with CO, and the decomposition of carbonate species intermediate by adsorption of CO on the surface of oxygen carriers. This study gave full evidence that it was feasible for achieving H2 generation and CO2 capture in one step via chemical looping reforming of reducing exhaust gases (e.g., LDG) from industrial emissions.

Mechanisms and kinetics of a new cleaner single cyclic roasting-leaching process for the extraction of vanadium from Linz–Donawitz converter slag using CaCO3 and H2SO4

Prevailing alternative technologies of vanadium extraction from vanadium slag that suffer from high production costs, energy consumption and serious environmental pollution due to the large production of toxic solid-liquid-gaseous effluents are that non-environmental-friendly. This study implemented a new, cleaner, more effective and environmentally-friendly method of the single cyclic roasting-acid leaching, where vanadium clinker, residue and liquor can be recycled as roasting additive and leaching agent to enhance the roasting-leaching effect. The complete single cyclic roasting-acid leaching process of the chemicals, mechanisms and the maximum roasting conversion efficiency achieved in the case of vanadium is 88.86%–92.39% and leaching efficiency of 93.77%–97.61%. Herein, the recycling and reuse of all the liquor and leaching residue result in the zero-liquid discharge, solid waste reduction, significant cleanliness, and high resource utilization. This work has opened a new pathway of establishing a significantly cleaner production process for environmental sustainability via design and incorporation of inner recycling of wastes into the process in which these wastes are produced. In addition, the thermodynamics and kinetics of the whole single cyclic roasting-acid leaching process analysis can help us understand the mechanisms. All results and conclusions have guiding significance to industrial production of V2O5 from vanadium slag.

Slopping index for LD converters based on sound and image data fusion by fuzzy Kalman filter

ABSTRACT The LD (Linz Donawitz) steelmaking process is the most used in the steel industry due to its high-volume capacity and low cost per ton of steel produced. However, the basic oxygen steelmaking process in LD converters is subjected to potential steel charge overflows, often called ‘slopping’. Besides yield losses, slopping events can damage the environment and expose employees to danger. More than ever, steelmaking plants need to avoid this type of event to keep producing as environmental impacts are no more tolerable by society. Steelmaking plants already use different methods to monitor and detect slopping events, but they are often limited and unreliable. Therefore, this paper proposes a multi-sensor data fusion process to generate a reliable slopping index to warn operators of potential slopping events and detect the triggered ones. The work is based on sound and image data (67 heats with 27 slopping events) collected on previous trials at a 350-ton LD converter. The Kalman filter was applied as a data fusion agent of two indexes, one resulted from computer vision analysis of the LD converter mouth (image data), the other resulted from digital signal analysis of sound captured on the converter’s hood (sound data). Fuzzy sets were applied for adaptative tuning of the Kalman filter to improve the data fusion process. Besides the increase of alarm accuracy and heat classification, the data fusion index worked better on different scenarios and produced a more reliable indicator for a slopping prevention system.

A new method for calculating the theoretical dry flue gas volume of metallurgical gas

Aimed at the limited engineering condition that only gas calorific value but not gas composition can be provided, a new theoretical combustion calculation method based on gas calorific value was proposed, which is suitable for calculating the theoretical dry flue gas volume of metallurgical gas. In the new method, three simplified models were proposed, including blast furnace gas (BFG) model, Linz–Donawitz converter gas (LDG) model and coke oven gas (COG) model. The simplified models were respectively derived from the original model of theoretical combustion calculation, according to the composition characteristics of each metallurgical gas. Finally, the proposed models were verified through large sample of BFG, LDG and COG. The verification results show that the new models for calculating the theoretical dry flue gas volume of metallurgical gas all have high accuracy. The average relative errors of BFG model, LDG model and COG model are only 0.35%, 0.12%, 0.64% respectively. Thus, the new method proposed in this paper is reasonable and feasible. It can meet the accuracy requirement of engineering and can provide a new way for theoretical combustion calculation of metallurgical gas.

Ca- and Mg-rich waste as high active carrier for chemical looping gasification of biomass

Chemical looping gasification (CLG) is a promising technology for high-quality syngas production. One key issue to successful CLG is the selection of high-performance oxygen carrier. In this study, several Ca- and Mg-rich steelmaking wastes from steel industry, such as blast furnace slag (BF slag), blast furnace dust (BF dust) and Linz-Donawitz converter slag (LD slag), were used as oxygen carriers in chemical looping gasification of biomass. The results showed that the reducibility of Ca- and Mg-rich waste, especially LD slag and BF dust, was superior to that of hematite. Considering long-term operation, the cyclic stability of steelmaking waste was tested. BF dust showed a poor stability, while the other carrier (hematite, BF slag or LD slag) presented an excellent stability during multiple redox cycles in spite of partial sintering and agglomeration. Moreover, the effects of supply oxygen coefficient (O/B ratio) and reaction temperature on CLG of biomass were investigated. The results revealed that Ca- and Mg-rich waste exhibited a higher syngas production compared to hematite. The higher performance could be attributed to the improved reduction rate of Fe2O3 and gasification rate of biomass by Ca or Mg in steelmaking waste. In addition, LD slag exhibited the higher gas value at the O/B ratio of 1 at 900 °C. As a consequence, LD slag was an appropriate oxygen carrier for CLG of biomass in terms of perfect reducibility, superior cyclic stability and high reactivity.

Techno-economic evaluation of polygeneration system for olefins and power by using steel-mill off-gases

Utilization of industrial off-gases to produce valuable chemicals has the advantages of reducing dependence on fossil fuels. Despite many studies of off-gas utilization, production of secondary chemicals including detailed kinetic models integrated with a power-generation system to fully utilize byproducts has not been considered. The goal of this study was to techno-economically evaluate a polygeneration system to produce olefins and power from steel-mill off-gases. Two process cases were evaluated; they use carbon monoxide-rich Linz-Donawitz converter gas with either hydrogen or coke oven gas as feed. The hydrogen was concentrated from coke oven gas by using membrane-separation technology. These gases reacted with Linz-Donawitz converter gas to yield methanol, which was then converted to olefins. Kinetic models were applied for methanol synthesis and methanol-to-olefin reaction. Heat exchanger networks are designed to minimize utility usage, and a power generation system that uses the Rankine cycle to fully utilize byproduct stream. Calculated minimum selling prices of ethylene by discounted cash flow analysis were US$ 2030∙tonne−1 when hydrogen was the feed gas, and US$ 1064∙tonne−1 when coke oven gas was the feed gas; both were higher than the current minimum selling price (~US$ 720∙tonne−1) of ethylene derived from naphtha. The reduction in minimum selling price by use of coke oven gas is due to the revenue of power generation from coke oven gas retentate. Linz-Donawitz converter gas production with hydrogen is the most sensitive to feed price, whereas Linz-Donawitz converter gas-with- coke oven gas is the most sensitive to capital investment. The analysis demonstrates that neither system is economically viable under the current condition. The findings of this study represent a basic analysis for future improvements of the off-gas to olefins process, especially highly integrated system with power generation.

A scheduling approach with uncertainties in generation and consumption for converter gas system in steel industry

Linz–Donawitz converter gas (LDG) is a class of significant secondary energy in steel enterprises, and its adequate recycling can help save energy, reduce emission and improve profit. Aiming at the scheduling problem with uncertainties in both gas generation and consumption, a three-layer-causal-network-based approach for LDG system is proposed in this study. Two causality-based methods by employing causal exception estimation and working condition clustering are designed to construct the prediction intervals (PIs) of the gas generation and consumption flows respectively. Given that the surplus or shortage range of the LDG that can keep the tank levels balance can be calculated, a three-layer causal network of “generation-storage-consumption” is established to describe and evaluate the scheduling rules. Then, the solution is finally optimized based on the objective function and its corresponding constraints constructed by the safety, environmental and economic indicators. To verify the performance of the proposed method, the experiments by using real-world data coming from a steel plant are carried out, where the manual approach and the existing mixed-integer-linear-programming-based one in literature are also employed as comparative ones. The results indicate that the proposed method is capable of providing superior performance for such an industrial application.

A Mixed Integer Linear Programming Model for the Optimization of Steel Waste Gases in Cogeneration: A Combined Coke Oven and Converter Gas Case Study

Off-gas is one of the by-products of the steelmaking process. Its potential energy can be transformed into heat and electricity by means of cogeneration. A case study using a coke oven and Linz–Donawitz converter gas is presented. This work addresses the gas allocation problem for a cogeneration system producing steam and electricity. In the studied facility, located in northern Spain, the annual production of the plant requires 95,000 MWh of electrical energy and 525,000 MWh of thermal energy. The installed electrical and thermal power is 20.4 MW and 81 MW, respectively. A mixed integer linear programming model is built to optimize gas allocation, thus maximizing its benefits. This model is applied to a 24-h scenario with real data from the plant, where gas allocation decision-making was performed by the plant operators. Application of the model generated profit in a scenario where there were losses, increasing benefits by 16.9%. A sensitivity analysis is also performed. The proposed model is useful not only from the perspective of daily plant operation but also as a tool to simulate different design scenarios, such as the capacity of gasholders.

Techno-economic evaluation of methanol production using by-product gases from iron and steel works

Aiming at achieving large-scale CO2 mitigation in the iron & steel industries via efficient utilization of the by-product gases such as the coke oven gas (COG) and Linz-Donawitz converter gas (LDG) in the iron & steel works, conceptual design of a LDG-to-methanol process (option 1) and two LDG/COG-to-methanol processes (options 2 and 3 without or with H2 purification, respectively) was implemented using the process simulator Aspen Plus. Both the process development and economic analysis for all the three proposed options were conducted to determine the technical performance via indicators such as the energy efficiency and CO2 reduction rate, and the profitability via indicators such as the total capital investment and the net methanol production cost. Meanwhile, six case studies under different recycle ratios (0.5–0.95) were conducted for each proposed option to investigate the effects of recycle ratio on the technical and economic performance. The techno-economic analysis results clearly show that all the three proposed options are highly efficient for CO2 mitigation via methanol production using the by-product gases LDG and COG. More specifically, options 1 and 3 seem to be more energy efficient and eco-friendly than option 2, in terms of energy efficiency and CO2 reduction rate. Whereas, options 2 and 3 seem to be more economically feasible than option 1, considering the net methanol production cost. From the aspects of both technical and economic performance, option 3 is considered as the most competitive process. This work provides candidate process routes for the iron & steel industries to become more sustainable and profitable, especially in the event of a high carbon tax and a low H2 price in the future.

Granular-Causality-Based Byproduct Energy Scheduling for Energy-Intensive Enterprise

The energy-intensive enterprises (EIEs), such as iron and steel enterprises, account for a significant part of the total energy consumption in society. The Linz–Donawitz converter gas (LDG) is a kind of crucial byproduct energy resource recycled during the steelmaking process, and its reasonable scheduling can effectively reduce the LDG emission and increase its efficiency. In this study, a granular-causality-based scheduling approach for the LDG system in steel industry is proposed. A granular causality technique is modeled to confirm the casual relationship of the LDG system based on the discontinuous production characteristic, in which a causality diagram is established and the phase space of the training sample is reconstructed to improve the prediction accuracy. Then, a multioutput least-square support vector machine model is constructed for the prediction of the gas tank levels. In order to consider the impact of multiple solutions on the scheduling result in a period of time, a scheduling objective function that combines the economy criterion and the safety one is designed and optimized by a modified particle swarm optimization (PSO) algorithm. The validation experiments using real-world data coming from the energy data center of a steel plant are carried out, and the results indicate that the proposed method exhibits reliable performance. Moreover, an application software system based on the proposed method is developed and implemented, which demonstrates the applicability of the proposed approach. Note to Practitioners —Given that the steelmaking process is a discontinuous one and the LDG system can hardly be described by a physical or mechanism-based model, its energy scheduling works is usually operated by the manual method currently, which leads to low accuracy and a waste of energy. Since a large number of real-time data had been accumulated by the existing SCADA system implemented in most steel plants, a data-driven long-term scheduling approach is proposed in this study. The proposed method aims at the long-term scheduling of the LDG system in steel industry, and the acquisition frequency of the real-time data is 1 min. The application system designed on the basis of the proposed method can provide effective scheduling solutions. Furthermore, it is necessary to ensure the data integrity and reliability via data imputation and filtering methods since there may exist some missing data or outliners in the acquired data from the SCADA system onsite. This study avoids the redundant introduction of such preliminary preprocessing methods for the sample data.

Diffusive Steel Scrap Melting in Carbon-Saturated Hot Metal-Phenomenological Investigation at the Solid⁻Liquid Interface.

The oxygen steelmaking process in a Linz-Donawitz (LD) converter is responsible for more than 70% of annual crude steel production. Optimization of the process control and numerical simulation of the LD converter are some of the current challenges in ferrous metallurgical research. Because of the process conditions and oxidation of impurities of the hot metal, a lot of chemical heat is generated. Therefore, steel scrap is charged as a coolant with the economical side aspect of its recycling. One of the more complex aspects is, among others, the dissolution and melting behaviour of the scrap in carbon-saturated hot metal. Heat and mass transfer act simultaneously, which has already been investigated by several researchers using different experimental approaches. The appearances at the interface between solid steel and liquid hot metal during diffusive scrap melting have been described theoretically but never investigated in detail. After an experimental investigation under natural and forced convective conditions, the samples were further investigated with optical microscopy and electron probe microanalysis (EPMA). A steep carbon concentration gradient in the liquid appeared, which started at an interface carbon concentration equal to the concentration on the solid side of the interface. Moreover, the boundary layer thickness moved towards zero, which symbolized that the boundary layer theory based on thermodynamic equilibrium was not valid. This fact was concluded through the prevailing dynamic conditions formed by natural and forced convection.

Evaluation of the synergies in cogeneration with steel waste gases based on Life Cycle Assessment: A combined coke oven and steelmaking gas case study

Steel making processes dispose large volumes of waste gases whose potential energy can be transformed into heat and electricity by means of cogeneration. A case study using coke oven and Linz-Donawitz converter gas is presented here. The data is obtained from an existing plant located in Northern Spain. The engines are adapted for its operation with converter gas, and steam is generated in boilers that consume coke gas, converter gas and natural gas in the absence of waste gases. The actual influence on the environmental behaviour of the process is analysed considering the benefits but also the drawbacks derived from the gases low calorific value, toxicity and polluting. The work constitutes the first study in an installation with these characteristics and burning this combination of gases. The functional unit is represented by 1 MWh of thermal energy. The analysis has been developed mainly on the bases of the following sources: site-specific measured or calculated data directly from the process of cogeneration, life-cycle inventory databases and bibliographical information. Operating parameters, as well as production data (thermal and electric energy), emissions of NOX, SO2 and CO2, discharges and wastes associated with this process are exposed. The system boundaries were considered gate to gate, so the results are useful for the integration with other global scenarios. Midpoint and endpoint characterisation factors for humans, ecosystems and resources are given. The main effects are related to Climate change, Ionising radiation, Human toxicity and Fossil and Ozone depletion. The results indicate that the usage of these gases implies an environmental benefit. The operational data belonging to 2014 shows a reduction of more than 100 points in the global impact of the functional unit. In the best scenario, 169.42 Nm3/MWh of natural gas may be saved with the consequent reduction in natural resources and ozone depletion.

Environmental risk assessment of steel-making slags and the potential use of LD slag in mitigating methane emissions and the grain arsenic level in rice (Oryza sativa L.)

Over the past decades, with increasing steel manufacturing, the huge amount of by-products (slags) generated need to be reused in an efficient way not only to reduce landfill slag sites but also for sustainable and eco-friendly agriculture. Our preliminary laboratory study revealed that compared to blast furnace slag, electric arc furnace slag and ladle furnace slag, the Linz-Donawitz converter (LD) slag markedly decreased CH4 production rate and increased microbial activity. In the greenhouse experiment, the LD slag amendment (2.0 Mg ha−1) significantly (p < 0.05) increased grain yield by 10.3–15.2%, reduced CH4 emissions by 17.8–24.0%, and decreased inorganic As concentrations in grain by 18.3–19.6%, compared to the unamended control. The increase in yield is attributed to the increased photosynthetic rates and increased availability of nutrients to the rice plant. Whereas, the decrease in CH4 emissions could be due to the higher Fe availability in the slag amended soil, which acted as an alternate electron acceptor, thereby, suppressed CH4 emissions. The more Fe-plaque formation which could adsorb more As and the competitive inhibition of As uptake with higher availability of Si could be the reason for the decrease in As uptake by rice cultivated with LD slag amendment.

Oxidation kinetics of vanadium-bearing LD converter slag by mechanical activation

ABSTRACTA thermogravimetric investigation was performed to evaluate the kinetic and thermodynamic parameters and the influence of mechanical activation on oxidation of vanadium-bearing LD (Linz–Donawitz) converter slag. Results indicate that the particle size of d0.5 significantly decreased from 29 μm to 0.266 μm after activation, and the specific surface area based on the BET model increased from 1.324 m2/g to 3.289 mm2/g. Thermogravimetric investigations were separately performed at 650, 700, 750, 800, 850, 900, 950 and 1000°C. Two distinct stages in the oxidation process were identified. The first stage was controlled by nucleation and growth and the second stage was controlled by 3D diffusion. However, the first stage relatively contributed more to the entire process than the second stage. Kinetic study also reveals that mechanical activation exhibited a significant effect on the oxidation of LD converter slag. Mechanical activation significantly reduced the roasting temperature and shortened the roasting time. The corresponding apparent activation energy Ea and frequency factor A changed from 13.01 kJ/mol to 6.59 kJ/mol and 0.247 min−1 to 0.141 min−1 for unmilled and milled slags, respectively.

Optimization and dissolution kinetics of vanadium recovery from LD converter slag in alkaline media

Alkaline roasting-alkaline leaching process was used to recover vanadium from LD (Linz Donawitz) converter slag. The independent leaching parameters investigated were liquid to solid ratio (L/S) (10–20 mL/g), temperature (40–60°C), NaOH concentration (1.0–3.0 M), and time (60–120 minutes). Response surface methodology (RSM) was utilized to optimize the leaching parameters and as a result, the most influencing parameter was found to be liquid to solid ratio. Based on the results, the optimum recovery condition (approx. 99%) was obtained with L/S ratio of 20, temperature of 40°C, NaOH concentration of 3.0M, and leaching time of 100 minutes, respectively. Furthermore, the kinetics of alkaline leaching process was investigated using shrinking core model (SCM) equations. It was found that the rate of vanadium leaching is controlled by a mixed controlling mechanism which is comprised of chemical reaction and diffusion through the solid product layer.

A biological process effective for the conversion of CO-containing industrial waste gas to acetate

Acetogens have often been observed to be inhibited by CO above an inhibition threshold concentration. In this study, a two-stage culture consisting of carboxydotrophic archaea and homoacetogenic bacteria is found to be effective in converting industrial waste gas derived from a steel mill process. In the first stage, Thermococcus onnurineus could grow on the Linz-Donawitz converter gas (LDG) containing ca. 56% CO as a sole energy source, converting the CO into H2 and CO2. Then, in the second stage, Thermoanaerobacter kivui could grow on the off-gas from the first stage culture, consuming the H2 and CO in the off-gas completely and producing acetate as a main product. T. kivui alone could not grow on the LDG gas. This work represents the first demonstration of acetate production using steel mill waste gas by a two-stage culture of carboxydotrophic hydrogenogenic microbes and homoacetogenic bacteria.

An Overview of Use of Linz-Donawitz (LD) Steel Slag in Agriculture

Slag generated from basic oxygen furnace (BOF) or Linz-Donawitz (LD) converter is one of the recyclable wastes in integrated steel plants. This paper deals with the present and possible use of LD slag in agriculture. At present, the amount of slag deposited in storage yard, leading to the occupation of farm land and serious pollution to the environment. Improving the slag utilization is an important way to resolve these problems. The physical and chemical characteristics of steel slag were analyzed and then the research progress of steel slag utilization in agriculture as fertilizer introduced. Due to increasing awareness of the environment, disposal, reuse of wastes without harming the environment has became a prime concern for the industry. The local availability of non conventional sources of plant nutrients and soil conditioners plays a vital role because of the non availability and higher price of environmental fertilizers. Therefore, this waste can be utilized for enhancing yield as well as solving the disposal problem and improve the environment.

Comparative assessment on greenhouse gas emissions of end-of-life vehicles recycling methods

The ‘whole recycling method’, in which an end-of-life vehicle (ELV) is pressed and transferred to an electric furnace or converter, simultaneously recycles iron and treats automotive shredder residues. This contrasts with the usual practice of shredding ELVs to produce scrap. An advanced dismantling process is required to recycle pressed ELVs using a converter because the quality of scrap entering a converter is restricted (the copper content must be low). Here, life cycle assessments are performed to determine the amounts of greenhouse gases (GHGs) emitted recycling an ELV using the whole recycling method and using the shredding method. Recycling a pressed ELV in a converter was found to cause GHG emissions approximately 320 kg-CO2e lower than caused by the recycling of the pressed ELV in an electric furnace. Approximately, 120 kg-CO2e less GHGs were emitted when recycling in a converter than when using the shredding method. However, the amount of greenhouse gases reduced by a converter depends on the conditions used, such as the presence of a Linz–Donawitz converter gas recovery facility. It is hoped that incentives can be developed to improve scrap metal quality by encouraging automobile manufacturers to design for disassembly and recyclers to disassemble more ELV components.

Granular-computing based hybrid collaborative fuzzy clustering for long-term prediction of multiple gas holders levels

Linz–Donawitz converter Gas (LDG), regarded as an essential secondary energy resource, plays a significant role for the entire production process of steel industry. In a LDG system, the gas holders are crucial equipment for temporary energy storage and buffers connecting with the gas generation units and the gas users. The accurate long-term prediction for the holders levels of such a system would be very necessary for energy scheduling and its optimal decision making. Given the practical characteristics of the LDG system in a steel plant, a granular-computing (GrC)-based hybrid collaborative fuzzy clustering (HCFC) algorithm is proposed in this study for the long-term prediction of the multiple holders levels. The hybrid structure considers the features regarding to a gas holder, of which the horizontal part elaborates the mutual influences among different time spaces of a holder level, while the vertical one describes them among the influence factors (denoting the gas generation units or the users). Then, the modeling algorithm is also explicitly derived in this study. To verify the performance of the proposed approach, two groups of simulation are carried out by employing the real-world industrial data coming from this plant, in which the single-output method and the iterative computing-based one are comparatively analyzed. The results indicate that the proposed approach provides a remarkable accuracy for such an industrial application.

Performance Assessment of Partially Pre-fused Synthetic Flux in Basic Oxygen Steel Making

Lump lime as the most common flux and iron ore as a coolant are used in basic oxygen steel making. However, high melting point, poor dissolution property, fines generation tendency and hygroscopic nature of lump lime often create problems in operation. As the combination of both iron oxide (Fe2O3) and CaO shows eutectic at 1 230 °C, a combined mass of iron oxide and lime melts at lower temperature and dissolves faster in a molten bath. A partially pre-fused synthetic flux (PSF) was prepared through an innovative way in combination of iron oxide fines viz. Linz Donawitz converter sludge and blast furnace flue dust and lime fines by micro-pelletization of the mix followed by coke breeze free sintering. The developed PSF shows good cold handling strength, low melting point (1 180 °C), good thermal shock resistance, etc. As a low melting synthetic flux, its performance was assessed through dissolution/melting study in hot metal bath and refining of hot metal in a simulated bottom blown converter using (i) PSF, (ii) only lump lime and (iii) lump lime with iron ore when keeping other conditions identical. Very fast dissolution (27–80 s for 1–3 g lumps), enhanced removal of C and P (11–12 min), controlled slag foaming, and reduced oxygen consumption was obtained for using PSF.