Lingzhi Yang

Influence of bottom-blowing gas species on the nitrogen content in molten steel during the EAF steelmaking process

ABSTRACT In modern EAF steelmaking process, control of the nitrogen content of molten steel has become more and more important and bottom-blowing technique has been widely applied to promote the molten bath fluid flow, accelerate the metallurgical reaction and improve the quality of molten steel. In this study, the influence of bottom-blowing gas species on the nitrogen content in molten steel during EAF steelmaking was systematically investigated and analysed. Combining the induction furnace experiments and theoretical analysis, the kinetic models of nitrogen change in molten steel with bottom blowing N2, Ar and CO2 were established theoretically and validated experimentally. Meanwhile, the thermodynamic laws and agitation capacity of different bottom-blowing gases were also clarified. Then, based on the industrial application research, the metallurgical effects, especially nitrogen removal, with different bottom-blowing gases were also studied and finally, a new concept was proposed for cyclic utilisation of CO2 in the EAF steelmaking process.

A novel process for preparation of titanium dioxide from Ti-bearing electric furnace slag: NH 4 HF 2 -HF leaching and hydrolyzing process

A novel process to prepare titanium dioxide from Ti-bearing electric furnace slag by NH4HF2-HF leaching and hydrolyzing process has been developed. In this present study, the effects of [NH4+]/[F] mXolar ratio, leaching temperature, [F] concentration, liquid/solid mass ratio, leaching time on the Ti extraction, and the phase transformations have been investigated to reveal the leaching mechanism of Ti-bearing electric furnace slag in NH4HF2-HF solution. In the NH4HF2-HF leaching process, the MgTi2O5 and Al2TiO5 are converted to TiF62- and Mg-Al-bearing precipitate. Ti extraction rate reached 98.84% under the optimal conditions. In addition, 98.25% iron ions can be removed in the presence of NaCl prior to hydrolysis process. The effects of pH and temperature on the selective hydrolysis of TiF62- during hydrolysis process were also studied. In the hydrolysis process, the TiF62- is converted to (NH4)2TiOF4. By calcination, high grade TiO2 powder with its purity of 99.88% was obtained, using which the products, well crystallized anatase and rutile, were obtained through roasting at 800°C and 1000°C, respectively.

Alloy Yield Prediction Model Based on the Data Analysis in EAF Steelmaking Process

In this paper, based on the big data in steelmaking process, equation about the relationship between steel composition (especially the oxygen content) and the element yield is established by using mathematical analysis method to analyze the factors influencing yield. Meanwhile, combining the alloy yield database that were established based on self-learning of historical data and computer technology in steelmaking process, a method of yield prediction of alloy elements is studied. To provide support for this method, alloying elements yield prediction software is developed to realize the rapid and intuitive site operation guidance, and to realize the precise control of dosage of alloy material.

Effects of high pressure roller grinding on size distribution of vanadium-titanium magnetite concentrate particles and improvement of green pellet strength

The vanadium-titanium magnetite concentrate from Panxi region of China was pretreated by high pressure roller grinding (HPRG) and then used in pelletization. Size distribution change of the vanadium-titanium magnetite concentrate after HPRG and the improvement of its green pellet strength were investigated. The results indicated that, besides the increase of fine particles, the vanadium-titanium magnetite concentrate after HPRG had a smaller size ratio of fine particle to coarse particle of 0.126, meaning a lower porosity, compared with the size ratio of raw material of 0.157. The concentrate particles were more closely packed when there was a smaller size ratio of fine particle to coarse particle. The particle packing in the green pellets was closer after HPRG, which strengthened the green pellets with an average drop number of 5.1 (drop height of 0.5 m) and average compressive strength of 13.1 N per pellet of 11 mm in diameter.

Discussion of Carbon Emissions for Charging Hot Metal in EAF Steelmaking Process

Abstract As the cost of hot metal is reduced for iron ore prices are falling in the international market, more and more electric arc furnace (EAF) steelmaking enterprises use partial hot metal instead of scrap as raw materials to reduce costs and the power consumption. In this paper, carbon emissions based on 1,000 kg molten steel by charging hot metal in EAF steelmaking is studied. Based on the analysis of material and energy balance calculation in EAF, the results show that 146.9, 142.2, 137.0, and 130.8 kg/t of carbon emissions are produced at a hot metal ratio of 0 %, 30 %, 50 %, and 70 %, while 143.4, 98.5, 65.81, and 31.5 kg/t of carbon emissions are produced at a hot metal ratio of 0 %, 30 %, 50 %, and 70 % by using gas waste heat utilization (coal gas production) for EAF steelmaking unit process. However, carbon emissions are increased by charging hot metal for the whole blast furnace–electric arc furnace (BF–EAF) steelmaking process. In the condition that the hot metal produced by BF is surplus, as carbon monoxide in gas increased by charging hot metal, the way of coal gas production can be used for waste heat utilization, which reduces carbon emissions in EAF steelmaking unit process.

Simulation of Velocity Field of Molten Steel in Electric Arc Furnace Steelmaking

The application of the bottom-blowing in the steelmaking process of EAF can effectively shorten the mixing time of the molten bath, accelerate the removal of carbon, phosphorus and sulfur, and improve the production efficiency and product quality. Information about the effects of changing molten steel velocity during the smelting process would help to accurately model molten bath dynamics. In this study, numerical simulation software was employed to simulate the EAF steelmaking process under variable eccentric bottom-blowing gas flow situations. Velocity field data were obtained for the different bottom-blowing schemes. When other nozzles’ bottom-blowing gas flow rates were maintained at 133 L/min, the average velocity of molten steel in EBT (Eccentric Bottom Tapping Area) was increased from 2.8 × 10−3 to 3.4 × 10−3 m/s with the eccentric gas flow rate of bottom-blowing from 100 to 267 L/min, the average velocity of molten steel in the bath increased from 4.3 × 10−3 to 4.6 × 10−3 m/s with the eccentric gas flow rate of bottom-blowing from 100 to 267 L/min.

Hybrid Modeling for Endpoint Carbon Content Prediction in EAF Steelmaking

Considering the complicated and harsh conditions in the electric arc furnace (EAF) steelmaking process, the precise endpoint control technology is a crux that influences the product quality and production costs of the molten steel because precise endpoint control can control the endpoint carbon content and the endpoint oxidation. In this paper, a new hybrid prediction model was established to predict the endpoint carbon content in EAF steelmaking, which included the mechanism model based on the mass transfer process and the Extreme Learning Machine (ELM) optimized by the Evolving Membrane Algorithm (EMA). The mechanism model was calibrated with corrected parameters obtained from the ELM-EMA algorithm. As a result, the shortages that the mechanism model can’t work precisely and that the single mathematical algorithm model lacks the analysis of the metallurgy process were overcome by the hybrid prediction model. Meanwhile, modifying ELM algorithm by EMA algorithm can improve the generalization performance of single-hidden-layer feed-forward neural networks. The experiments on a 50t EAF demonstrated that the proposed model had a good generalization performance and good prediction accuracy.

Research of Digital Platform and Process Guidance Model in EAF Steelmaking Process

As a shortage of information technology support, steel plant is unable to real-time tracking production cost of each working procedure, and can’t form the information feedback in time. Information integration technology for dynamic monitoring becomes a development trend of process control in advanced iron and steel enterprise. The paper based on the characteristics of EAF steelmaking process and requirements build the digital platform and process guidance model, which is designed to solve for smelting composition control, cost control, and optimizing guide in EAF steelmaking process. The model is including: data acquisition module, cost monitoring and calculation module, EAF endpoint carbon control module, alloy material optimization module, component monitoring and forecast module, process guidance module, data maintenance and query module.

Present Situation and Prospect of EAF Gas Waste Heat Utilization Technology

Abstract With the increase of hot metal ratio in electric arc furnace (EAF) steelmaking process, physical sensible heat and chemical latent heat of gas increased significantly. As EAF raw material condition is similar to basic oxygen furnace (BOF), and the condition of BOF gas waste heat utilization technology is mature, waste heat utilization technology in EAF steelmaking will be getting more and more attention. Scrap preheating and steam production as mature technology is the main way of EAF gas waste heat utilization. Power generation converted high temperature steam to electricity will further improve the EAF gas utilization value. The previous ways are to recycle physical sensible heat of EAF gas. To use chemical latent heat of gas, the secondary combustion technology is usually adopted to make CO fully burn into CO2. Coal gas production can fully recycle the chemical latent heat of gas theoretically, which is higher efficiency than other ways. Coal gas production needs a stable steelmaking process to stabilize high temperature gas. And the way need to develop EAF sealing technology, oxygen removal technology and gas purification technology, to make gas content meet the requirements of coal gas production in EAF steelmaking process.

The Extraction of Zinc from Zinc Ferrite by Calcified-Roasting and Ammonia-Leaching Process

Zinc ferrite (ZnFe2O4), one of the major forms of zinc in Electric Arc Furnace (EAF) dust and zinc leaching residue, is very difficult to chemically dissolve in either acidic or alkaline solutions. In spite of the zinc resources in the Electric Arc Furnace (EAF) dust and zinc leaching residue are abundant, there is no mature utilization technology. This situation not only causes the waste of resources, but also produces the harm to the environment. In the paper, the basic principle of this process has been established by revealing the phase equilibria in the CaO–Fe2O3–ZnO system, where Ca2Fe2O5 can be in equilibrium with ZnO rather than ZnFe2O4 at higher CaO region. It has also been demonstrated that the formed ZnO can be solved by ammonia-leaching and Ca2Fe2O5 keep in solid residue, which can be used as a flux for steel refining.