Monitoring the Blast furnace working state by a combination of innovative measurement techniques

At blast furnace B at Salzgitter Flachstahl a series of innovative measuring techniques are installed to monitor the processes at the blast furnace top, making this furnace one of the best equipped furnaces in Europe. These techniques comprise full 2D measurement of the temperature profile of the top gas shortly above the burden surface, 3D radar scan of the whole burden surface and online measurement of the dust concentration in the top gas. After more than 5 years’ experience with most of these techniques, they enable to better understand the complex chemical and physical interrelations occurring in the BF stack between the ascending process gas and the descending solid burden. A couple of examples of incidents that were monitored are presented in this article, including influences of charging programmes on top gas temperature profiles and influences of disturbed gas solids interaction on the BF working state. The new measuring techniques with tailor-made data processing enable the operators to gain a better picture of the processes currently occurring in the blast furnace, consequently supporting them in keeping the blast furnace operation as stable and efficient as possible.

Development of iron ores sintering machine for blast furnace process

There must be proper means to sinter and, agglomerated iron ore concentrate before it can be further processed in the blast furnace. A Sintering machine of 5kg capacity of agglomerated ore was designed and fabricated using mild steel material, which was locally sourced. The machine was fabricated with a combustion chamber of 30 by 30 cm and with 15cm depth. It was also lined with refractory material to reduce the chamber to the volume of 3375 cm3. However, the sintering chamber was designed to have a truncated square pyramid shape to the volume of 2150 cm3 after lining with refractory material. The design was made to utilize coke and palm kernel shell char as fuel which will be ignited to produce heat into the sintered material by suction of the heat into the agglomerated sintered ore. Tests such as tumbler index, abrasion, and porosity test were carried out on the sintered products in agreement with ASTM E276 and E389 standards. The results from the test gave a tumbler index of 70.2% and 65.7% for coke and palm kernel shells respectively. Also, abrasion index of 5.1% and 4.6% for coke and palm kernel char, and porosity of 6.8% and 6.5% for coke and palm kernel char respectively. The results from the experimental test were in agreement with other research work. Therefore, the developed iron ore sintering machine has a better efficiency of producing sinter for blast furnace operation.

In Situ Observation of the Carbothermic Reduction and Foaming of Slags in Silicomanganese Production

The carbothermic reduction of slag in silicomanganese production is accompanied by the release of carbon monoxide. This gas can accumulate as bubbles within the slag, leading to foaming and, potentially, disturbances to furnace operation. This study investigated the reduction in the slag together with its foaming using a sessile drop furnace. Five silicomanganese slags produced from industrial raw materials (Assmang ore, Comilog ore, high-carbon FeMn slag with quartz, and FeS additions) were reduced by a graphite substrate at isothermal conditions (i.e., 1540–1660 °C) under CO atmosphere. The reduction reaction was tracked by photographing the slag droplet, and the cyclic expansion and burst of the droplet were used to estimate the gas evolution. The reacted samples were analyzed by wavelength-dispersive X-ray spectroscopy (WDS) to determine MnO and SiO2 reduction. While no foaming was observed using Comilog ore, extensive retention of CO in the slag phase was observed when using Assmang ore or Assmang with high-carbon FeMn slag. The beginning of foaming was attributed to an increase in the reaction rate; the absence of foaming when using Comilog can be attributed to the acidity of the charge. Addition of sulfur to the Comilog-based charge did not influence the reduction.

Reducing Furnace Operating Costs: IGBT/MFDC Technology Saves on Energy

Real power savings are observed in a case study comparing a VRT (Variable Reactance Transformer) and an IGBT/MFDC power supply in a furnace retrofit. The IGBT (Insulated Gate Bipolar Transistor) is the power controller and MFDC (Mid Frequency Direct Current) is the transformer portion of the power supply. The VRT was replaced with a similarly sized IGBT/MFDC power supply. Other variables remained essentially equivalent and provided a good comparison between the power consumption of a VRT versus an IGBT/MFDC system in an equivalent furnace. IGBT/MFDC offers cost savings through less kilowatt usage, lower peak demand, and better power factor when compared to other power controls. From this case study, we will demonstrate a 40 percent reduction in kilowatt consumption, a 14 percent reduction peak demand, and a high displacement power factor throughout the cycle. All of this results in lower costs for furnace operation.

Efficiency Gains and Reductions in Furnace Maintenance Through the Use of High Temperature Ceramic Coating Technology

Unique high temperature, energy efficient ceramic coatings are being used in heat treating and forging furnaces around the globe to reduce the high cost of refractory maintenance, reduce fuel consumption and improve furnace efficiencies as well as product quality. In addition, these coatings also protect metal from oxidation when used at elevated temperatures as well as corrosion in caustic environments. We will show how these specialized ceramic coatings can provide energy savings depending on the fuel being used, the furnace operation, furnace configuration, and production schedule of at least up to 20%. Additionally, we will show that furnace heat up and turn-around times are decreased and how the service life of ceramically coated refractories are extended.

INFLUENCE OF BLOWING PARAMETERS AND SLAG REGIME ON SILICON AND SULFUR CONTENT IN BLAST-FURNACE CAST IRON

At two blast furnaces (BF) with a volume of 1386 and 1500 m³, the influence of the parameters of blast and slag modes on the content of silicon and sulfur in cast iron was investigated. The blast mode was evaluated by the consumption of pulverized coal fuel (PCF) and oxygen, the slag mode was evaluated by its basicity CaO / SiO₂. It was found that the injection of pulverized coal into the hearth of 1500 m³ BF in the range of flow rates from 108 to 120 g/m³·s, and in the hearth of 1386 m³ BF in the range from 90 to 110 g/m³·s was accompanied by a decrease in the silicon content in cast iron. The deterioration of the transition of silicon into cast iron with an increase in the consumption of pulverized coal is explained by the complex effect of factors that retard the reduction of its oxides. Extreme relationships were also established between the intensity of melting in terms of oxygen consumption and the silicon content in the cast iron of the furnaces under study. The extreme dependences of the studied variables are due to the dual effect of the melting intensity on the reduction of silicon oxides: a reduction in the time of contact of the metal with furnace gases reduces the possibility of transition of silicon into metal, and an increase in the volume of the silicon reduction zone improves these possibilities. When operating a 1386 m³ furnace on calcium slag in the range of CaO / SiO₂ basicity change from 0.9 to 1.3 without removing the blast furnace operation periods associated with a change in operating conditions, the absence of dependence of the silicon content in cast iron on the CaO/SiO₂ modulus was found/ In its turn this indicated the complexity of factors influencing the reduction of silicon oxides. In the same range of changes in basicity and different operating modes of the furnace, a noticeable effect of basicity on the sulfur content in cast iron was observed, which indicates the decisive role of basicity in the process of blast-furnace desulfurization.

Fired Heater Simulation, Modelling and Optimization

In this study a dynamic model Simulation was carried out using ASPEN HYSY for industrial refinery fired heater, PID controller was applied to control the flue gas exit temperature. the simulation shows perfect agreement with the datasheet of the furnace. It was found that Increasing the number of the tube rows in convection bank from 2 to 3 allows us to recover approximately 5% of the overall efficiency, hence the duty furnace has increased from 65.9MW to 68.1MW and the fuel flow in like manner has increased from 5597kg/h to 5807kg/h moreover Adding more rows has a reverse return as we start to notice increase on the flue gas temperature. Furthermore, sensitivity analysis was conducted with HYSYS to determine one of the most important parameters that affect the performance of the heater based on the data generated from the simulation. MATLAB code was generated for efficiency calculation and for parameter manipulation, the code was designed to be flexible as possible, user will just need to replace the nominal fuel and air characteristics. for gaining optimum furnace operation the heat transfer inside the furnace was studied, and the results were compared with previous research involving furnace analysis to validate models, the heat transfer coefficient is determined by analysis of conductive heat transfer through the boundary layer. well-stirred model was used for mathematical model calculations and for optimization of furnace operation, the models were validated with ASPEN Exchanger Design and Rating(EDR) alongside ASPEN HYSYS

Application and Evaluation of Mathematical Models for Prediction of the Electric Energy Demand Using Plant Data of Five Industrial-Size EAFs

The electric arc furnace (EAF) represents the most important process route for recycling of steel and the second most productive steelmaking process overall. Considering the large production quantities, the EAF process is subject to continuous optimization, and even small improvements can lead to a significant reduction in resource consumption and operating cost. A common way to investigate the furnace operation is through the application of mathematical models. In this study the applicability of three different statistical modeling approaches for prediction of the electric energy demand is investigated by using more than 21,000 heats from five industrial-size EAFs. In this context, particular consideration is given to the difference between linear and nonlinear regression models. Detailed information on the treatment of the process data is provided and the applied methods for regression are described in short, including information on the choice of hyperparameters. Subsequently, the results of the models are compared. Gaussian process regression (GPR) was found to yield the best overall accuracy; however, the benefit of applying nonlinear models varied between the investigated furnaces. In this regard, possible reasons for the inconsistent performance of the methods are discussed.

Tuyere-Level Syngas Injection in the Blast Furnace: A Computational Fluid Dynamics Investigation

With the recent push towards high injection rate blast furnace operation for economic and environmental reasons, it has become desirable in North America to better understand the impacts of alternate injected gas fuels in comparison to the well-documented limitations of natural gas. The quenching effects of gas injection on the furnace present a functional limit on the maximum stable injection rate which can be utilized. With this in mind, researchers at Purdue University Northwest’s Center for Innovation through Visualization and Simulation utilized previously developed computational fluid dynamics (CFD) models of the blast furnace to explore the impacts of replacing natural gas with syngas in a blast furnace with a single auxiliary fuel supply. Simulations predicted that the syngas injection can indeed reduce coke consumption in the blast furnace at similar injection rates to natural gas while maintaining stable raceway flame and reducing gas temperatures. The coke rates predicted by modeling using similar injection rates indicated an improvement of 8 to 15 kg/thm compared to baseline conditions when using the syngas of various feedstocks. Additionally, syngas injection scenarios typically produced higher raceway flame temperatures than comparable natural gas injection cases, indicating potential headroom for reducing oxygen enrichment in the hot blast or providing an even higher total injection rate.