Hot Blast Temperature Research Articles

3D thermodynamics and parameters analysis of the external combustion hot blast stove

The external combustion hot blast stove is widely used in the steelmaking industry due to the advantage of providing a large amount of high-temperature and stable hot blast for blast furnaces. To research the thermal efficiency and stability of external combustion hot blast stoves, the non-equilibrium porous medium model coupled with transient thermal analysis is used to discuss the characteristics of two types of external combustion hot blast stoves during the cyclic operation process. In this paper, a comparison of the numerical data and in situ data during one cycle to ensure the accuracy of the calculation, which of the results showed that the temperature maximum relative error value is within 3%. The numerical results displayed that the velocity and temperature distribution of fluid are mainly affected by pressure, flow rate, cycle time, and geometric structure, where the hot blast temperature is affected by the cycle time but the distribution of velocity and relative pressure are affected by the height of hot blast branch. It can be concluded that the flow field and the structure of type A hot blast stove are more stable than that of type B by comparing the results of two types of hot blast stoves.

Synergistic enhancement for energy-saving, emission reduction and profit improvement in iron and steel manufacturing system: Strategies for parameter regulation and technologies integration

The steel industry, characterized by high energy consumption and carbon emission, poses a significant threat to global energy and environmental security. In response to the energy conservation and dual-carbon targets, the steel industry must urgently find sustainable pathways for transformation and development. Steel production structure optimization and the application of cutting-edge technologies have been proven to be highly effective. However, the complexity and variability of actual production conditions highlight the absence of a methodology capable of adapting to real production scenarios, elucidating influencing principles across multiple factors, analyzing synergistic mechanisms of multiple indicators, and proposing collaborative control strategies. Furthermore, the potential for technology applications that are closely integrated with the company’s resource endowment remains uncertain, leading to an unclear overall strategy for energy saving and carbon reduction. This study develops a multi-scale optimization and evaluation model for ISMP, incorporating interconnected and matching processes, as well as nested multi-indicators, in response to the context. Subsequently, the disturbance mechanisms of various factors are accurately identified and a multi-indicator synergistic control strategy and framework are proposed. Following optimization, the exergy loss, energy consumption, carbon emission intensity, cost, and pollutant emissions of ISMP per tonne of steel are reduced by 1418.70 MJ, 42.93 kgce, 154.79 kg, 171.21 CNY, and 0.0168 kg, respectively. Additionally, measures such as reducing moisture content in coking coal can effectively regulate multiple indicators. Based on the proposed sensitivity quantification method, the temperature of hot blast is identified as the most effective controllable factor. Technologies like hydrogen-rich fuel injection, integrated waste heat recovery, and solar photovoltaic & energy storage have shown favorable prospects, according to analysis conducted from various angles regarding economic viability and potential for energy-saving and carbon reduction. However, the application of aforementioned technologies may be limited by financial consideration, necessitating cautious and judicious investment choices.

Numerical investigation of the limit of coke rate reduction in an ironmaking blast furnace (BF)

Blast furnace (BF) ironmaking maintains its role as the predominating process for producing hot metal (HM) from iron ore. The process is highly carbon-consumption and emission intensive. Considering its massive production scale, any improvement of the process in terms of the operational parameters could results in significant social, environmental and economical benefits. The most concerned operational parameters of the BF is the coke rate, with the reduction of the coke rate being long time pursued. However, the limit of coke rate reduction for an operating BF is rarely attempted for safety and stability. Therefore, the limit for coke rate reduction for an operating BF largely remains implicit, with the underlying mechanism being unknown. In this work, a previously developed multifluid BF process model is used to investigate the limit of coke reduction on an experimental scale BF. With the gradual reduction of the coke rate, the BF is analysed in detail in terms of in-furnace multiphase flow, thermochemical behaviors as well as overall performance indicators. The minimum coke rate to maintain a targeted production is identified with the underlying mechanism for the BF operated with a coke rate at its limit explained. Also, possible measures for increasing the limits of coke reduction are proposed. This is done by increasing the hot blast temperature, which proves to be useful based on the simulation results. The results generated from this work should be useful to improve the BF ironmaking process efficiency, hence cutting CO2 emission and guiding green production in the future.

Modeling on the blast furnace with CO2-enriched hot blast

Ironmaking and steelmaking are resource- and energy-intensive industries and major sources of CO2 emissions. We investigated the use of recycled CO2 gas to replace some of the air in the hot blast under smelting conditions in a blast furnace. CO2 reacts with carbon in the raceway zone; hence, a kinetic model of the CO2-enriched hot blast reaction with coke in the raceway zone was established. At the end of the raceway and its influence area, newly added CO2 gas reacts with carbon to form CO gas. A blast furnace mass and energy balance calculation model was established by assuming that all CO2 gas reacted to produce CO gas in the raceway zone based on the above conclusion. These CO molecules were oxidized into CO2 gas by the indirect reduction of iron ore in the middle and upper parts of the blast furnace; the conversion ratio from newly added CO2 to CO at the top of the blast furnace was approximately 50%. The conversion of CO2 to CO gas absorbed physical heat, which cooled the furnace; this may affect the normal operation of the blast furnace. Therefore, before using CO2 gas to replace part of the air in the blast furnace, it is necessary to evaluate the heat conditions of the blast furnace. To partially offset this heat loss, three heat supplementation methods were compared. For every 1% increase in the CO2 enrichment rate, the coke ratio needs to be increased by approximately 5 kg/THM, the hot blast temperature needs to be increased by approximately 65 °C, or the coal ratio needs to be increased by approximately 5.5 kg/THM.

The design characteristic of the hot blast valve and its effect on blast furnace temperature during the switching period of the air heaters

The article considers the structure and characteristics of a hot blast valve which is traditionally installed on air heaters of blast furnaces of domestic metallurgical plants. The hot blast valve connects the heated air heater of the blast furnace to the hot blast pipeline, that is, it transfers the air heater from the heating mode to the blowing mode. It is a water-cooled gate valve with a round bore and a semicircular movable gate, which is moved by an electric actuator. The main characteristics of any valve are its constructive, throughput and working characteristics. Constructive characteristics establish the dependence of the flow area on the movement of its gate, and the working characteristics establish the dependence of the flow rate of the substance on the movement of its gate under operating conditions. The cold blast valve is installed at the inlet of the air heater and during the period of its opening the cold blast is supplied to both air heaters, cooled and hot. As this takes place, there is no blast pressure drop between the air heaters valves, since we have a parallel connection of the blast pipelines with fully open hot blast valves of the cooled and heated air heater. Under such operating conditions of the air heater valves, the design characteristic of the valve becomes its working characteristics and its area determines the flow rate of the blast through it. In this regard, in order to analyze the effect of the valve operation on the hot blast temperature during the air heater switching period, it is necessary to find its design characteristic. For this, an analytical method was used to find a mathematical expression for this characteristic, an analysis was made of the change in the flow rate of blast through the cold blast valve when it was opened and closed during the air heater switching period. In this case, in the process of opening the cold blast valve of the heated air heater, the ratio of the amount of blast, which passes through the heated and cooled air heater, changes, which causes an increase in the blast temperature and reaching a certain maximum of it. The availability of a mathematical description of the working characteristic of the cold blast valve makes it possible to further analyze the temperature change during the air heater switching period and prevent its uncontrolled change

Prediction of Blast Furnace Thermal State in Real-Time Operation

The paper gives a general description of the dynamic model of the blast-furnace process that enables to calculate transition processes of the blast furnace thermal state, evaluated by the content of silicon in hot metal. It provides calculation results of the transition processes to be subjected to changes in control actions: ore load from the top and oxygen concentration in blast, natural gas flow rate and hot blast temperature from the bottom. Specific features of these transition processes during blast-furnace smelting are analyzed. The paper shows that the dynamic characteristics of blast furnaces change are subjected to control actions and depend significantly on properties of melted raw materials and operating parameters of blast furnaces. The oscillatory transition process in the blast furnace is observed in the case after disturbance it has an opposite influence on the thermal state of the lower and uppers stages of heat exchange. The paper presents prediction results of the silicon content in hot metal. It gives practical recommendations for selection of control actions.

Effect of coal blending on ash fusion behavior for blast furnace injection of high calcium bituminous coal

AbstractIn order to expand the range of bituminous coal injected into blast furnace, the ash melting behavior and regulation mechanism of bituminous with high calcium and low ash fusion temperature (AFT) were investigated by coal blending. And the mineral transformation behavior in the blended ashes was investigated by X‐ray powder diffractometry with normalized reference intensity ratio software and FactSage software. The experimental results manifest that the softening temperature (ST) of coal D is 8°C lower than that of the hot blast temperature. By adequately mixing coal B and coal D, it is easy to meet the requirements of pulverized coal injection. And coal D has become a standard bituminous for blast furnace injection. However, the high content of CaO in the coal S ash makes the AFT much lower than the hot blast temperature, which leads to the reluctance of the steel industry to inject coal S. With the increase of coal B mass ratio, the content of high‐melting eutectic matters (3Al2O3·2SiO2 and tridymite) increases at high temperature, while the content of low‐melting anorthite, andradite, gehlenite, and grossularite decreases, which leads to the increase of AFTs. The variation in the liquid phase under certain conditions reflects the change in AFT. In summary, by blending with coal B, the ST of blended coals S/B is higher than the hot blast temperature (1250°C), so that coal S can be applied to blast furnace injection. And the injection ratio of coal S in blended coals can reach about 50%.

Mathematical simulation of BF hot blast temperature influence on variations of silicon content in hot metal

The problem of influence of sinter production technological factors on silicon content and particularly variations of Si (ΔSi) in hot metal is actual for the up-to-date metallurgy.Traditional methods and plans of studies of BF heat running at present are considered less precise and effective comparing with up-to-date methods of mathematical and computer simulation, since the last provide an ability to forecast and optimize numerous parameters of BF process.A complex mathematical analysis of dependence between hot blast temperature and ΔSi by application of the universal mathematical model, specially elaborated and adapted for industrial conditions of sinter plant operation of Alchevsk steel-works was the task of the study.Influence of hot blast temperature (X-Factory) on minimization of ΔSi (Y-Factory) studied. Complex mathematical analysis was carried out using statistical data collected during 65 months of Alchevsk steel-works blast furnace of 3000 m3 operation. Results of calculation of influence of hot blast temperature on ΔSi by application of the universal mathematical model presented. Minimization of ΔSi when optimizing hot blast temperature reached. Accuracy of calculation using the elaborated model was more 99% of actual operational statistic.

Investigation of the influence of fuel consumption and geometric dimensions of the refractory blocks of the blast furnace nozzle on the blast-heating temperature

At present, the average temperature of hot blast on blast furnaces in Ukraine has significantly decreased and is about 1000°C. This is not related to the possibilities of its heating, but is caused by the shortage and cost of natural gas, the irregular feed of raw materials and thеir quality. An increase in the blast-furnace heating temperature in blast-furnace production is one of the effective ways to reduce the expensive coke rate and improve the parameters of the blast furnace operation. The common ways to increase the blast temperature, such as enrichment with natural gas or oxygen, are very expensive, and therefore are not currently in practice at industrial enterprises. Due to that, alternative low-cost ways to increase the blast temperature and methods for evaluating their effectiveness become relevant. The influence of the geometric dimensions of the air heater nozzle and the fuel consumption on the blast temperature have been analyzed. For this, a two-dimensional mathematical model of the operation of the blast air heater was used. The model results from the operation of the air heaters at the blast furnace No. 3 of «Ilyich iron and steel works». An increase in the blast furnace gas consumption by 30% makes it possible to increase the blast temperature by 137°C. In this case, heat losses with outgoing gases increase by 2,6%. However, an increase in blast furnace gas consumption is restricted by the following factors: blast furnace gas proper reserve at the plant, the capacity of the burner, the operational features of the fan for supplying air and exhaust gases. The change-over from the standard 6-gang block with a 41 mm cell size to the same block with a 30 mm cell size makes it possible to raise the temperature by 33°C due to the intensification of heat exchange from the combustion products to the nozzle and to reduce heat losses with the outgoing gases. In this case, owing to the volume reduction of the nozzle solid body, its thermal power will decrease

A method for controlling the surface morphology of centrifugally spun starch‐based fibers

ABSTRACTIn the present study, we provide a method for controlling the surface morphology of centrifugally spun starch‐based fibers by adjusting the ratio of amylopectin/amylose in starches and combining with a hot blast temperature. The effects of hot blast temperature, amylopectin, and amylose on fiber surface morphologies are investigated. Scanning electron microscopy is used to characterize the morphology of the prepared fibers. The results show that fibers with burr‐shaped nanostructures on the surface can be fabricated by adding amylopectin to starches and are promoted by increasing the hot blast temperature. However, amylose in starches plays the role of smoothing the fiber surfaces. X‐ray diffraction reveals that the fibers are amorphous. Through Fourier transform infrared spectroscopy analysis, it was found that some physicochemical changes occur during centrifugal spinning. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45810.

Modelling and Analysis of Oxygen Enrichment to Hot Stoves

The paper presents some research work on applying the oxygen enrichment technique to hot stoves that was carried out in one European RFCS project. In the presented work, both theoretical and practical work was studied. A dynamic model was used to investigate the effects of oxygen enrichment on hot stoves’ performance under the condition that only blast furnace gas was used as the fuel gas. The modelling results showed that SOE will enhance the combustion process in hot stoves by increasing hot blast temperature and shortening the on-gas time, which were further verified by industrial trials performed at an iron-making plant. In addition, CFD modelling was performed by simulating different oxygen levels and lance positions at the burner to avoid the hot spot formation during the combustion.

Model Development of a Blast Furnace Stove

A large amount of energy is required in the production of steel where the preheating of blast in the hot blast stoves for iron-making is one of the most energy-intensive processes. To improve the energy efficiency it is necessary to investigate how to improve the hot blast stove operation.In this work a mathematic model for evaluating the performance of the hot blast stove was developed using a finite difference approximation to represent the heat transfer inside the stove during operation. The developed model was calibrated by using the process data from the stove V26 at SSAB Oxelösund, Sweden. As a case study, the developed model was used to simulate the effect of a new concept of OxyFuel technique to hot blast stoves. The investigation shows that,by using the OxyFuel technique, it is possible to maintain the blast temperature while removing the usage of coke oven gas. Additionally, the hot blast temperature increases while the flue gas temperature decreases, which allows for an increase of the blast temperature, leading to improved energy efficiency for the hot stove system.

Boosting the hot-blast temperature in blast furnaces by means of an optimal control system

Thermal analysis of the air heater for 2038-m3 blast furnace 1 at OAO Chelyabinskii Metallurgicheskii Kombinat confirms that the hot-blast temperature may be increased by at least 30–40°C on introducing an optimal control subsystem designed by OAO VNIIMT. This reduces expenditures on coke by 75 million rub/yr.

Study on High Temperature Air Combustion of Hot Blast Stove

NOx is the major technical barrier to increase hot blast temperature and prolong campaign life of hot blast stove (HBS) at present. In order to restrain the amount of NOx formation during combustion process in the HBS, the paper studies and analyses the generation mechanism of NOx production, and calculates NOx generation rate and amount in HBS by means of thermodynamic generation model. A new dome combustion stove is developed based on high temperature air combustion (HTAC) technology. A comparison on the combustion process and characteristic of conventional HBS and HTAC HBS is performed by application of CFD numerical simulation model. Temperature and concentration field distribution, flame shape and NOx concentration distribution of two kinds of stove are calculated. The result shows quite symmetrical HTAC stove temperature field distribution. Under the same dome temperature, NOx generation is 80ppm only, reduced by approximate 76% in comparison with conventional stove. HTAC HBS can obtain higher temperature, energy-saving, emission-reducing, and decrease NOx emission efficiently, as well as realize long campaign life of HBS.

Effect of Preheated Top Gas and Air on Blast Furnace Top Gas Combustion

The coke consumption in blast furnaces (BF), directly related to the energy consumption and CO2 emission from BF, is reduced with the increase of hot blast temperature. To establish the flame temperature of more than the blast furnace gas (BFG) adiabatic flame temperature of 1 587 K by using only BFG without any additional high calorific value gases such as coke oven gas, the effect of preheating of BFG and/ or air on the BFG combustion temperature was investigated based on thermodynamic heat balance and the computational fluid dynamic (CFD) simulations. Thermodynamic evaluation and CFD simulated results showed that air preheating was not effective to raise the BFG combustion temperature compared with BFG preheating or simultaneous preheating of air and BFG at the same preheating temperature. The less efficiency of air preheating was explained based on the small heat content of preheated air. The blast temperature of 1 700 K was obtained without adding high calorific value gases by preheating only BFG to 873 K or simultaneous preheating both BFG and air to 700 K. Compared with air or simultaneous preheating of air and BFG, BFG preheating will be a suitable approach to increase BFG combustion temperature. This is not only because the supply of heat content to the combustion zone, but also the enhanced mixing introduced by the large inlet gas velocity difference between air and BFG promotes rapid CO burn-up.

Failure Mechanism and Material Requirements for Coal Lance in Blast Furnace

Pulverized coal injection (PCI) is a key technology in modern ironmaking by blast furnace (BF) and the life of injection lance has a great influence on PCI operation and on normal running of blast furnace. It is found that the main reasons for the failure of the lances are their outer surface oxidation and the inner surface erosion through monitoring some lances used in BF. The outer surface oxidation of the lances made of lCr18Ni9Ti is inevitable under high hot blast temperature condition through thermodynamics analysis. A mathematical model for calculating the temperature of common monocular coal lance had been developed according to the principles of mass and energy balance. Increasing temperature and flow velocity of the hot blast would cause a rise in the lance temperature. The influence of hot blast temperature is more obvious. The lance temperature would decline when compressed air flux increases. Conveying technology of dense phase pulverized coal is beneficial to extending lance's life because decreasing solid-gas ratio would intensify erosion and burning loss. The anti-oxidation temperature of lance materials needs to be over 1000 °C for BF intensified smelting. In order to increase the resistance to oxidation of the coal lance's outer surface, oxidation-resistant steel or Al coating stainless steel is the appropriate material for BF use. Employing the metal surface treatment technology to enhance the hardness of the coal lance's internal surface could prolong the service life of coal lance.

Damage Analysis for Coal Lance in Blast Furnace

Pulverized Coal Injection (PCI) is a key technology in modern ironmaking by blast furnace and the life of injection lance has a great influence on PCI operation and on normal running of blast furnace. It is found that the main reasons for the failure of the lances are their outer surface oxidation and the inner surface erosion through monitoring some lances used in BF. The outer surface oxidation of the lances made of lCr18Ni9Ti is inevitable under high hot blast temperature condition through thermodynamics analysis. Increasing the inner surface hardness by surface treatment would prolong the service life of coal lance. The anti-oxidation temperature of lance materials needs to be over 1000°C for BF intensified smelting.

Study of a ceramic burner for shaftless stoves

A multi-burner-port annular flameless ceramic burner (MAFCB) of the shaftless stove for blast furnaces was designed. The characteristics of pressure drop, homogeneousness of the flows at burner ports, and distribution of the flows in the chambers and joint were studied by cold model experiments. This type of ceramic burner was successfully applied in 6# blast furnace at Liuzhou Iron & Steel Co. Ltd. (LISC) and this practice proved that it could be used in the hot blast stove and other stoves with a higher efficiency and a higher steadiness of hot blast temperature at 1200°C. With the combustion of blast furnace gas alone, the thermal efficiency was up to 78.95%, saving energy remarkably.

Performances of pulverized coal injection in blowpipe and tuyere at various operational conditions

Combustion efficiencies of pulverized coal in blowpipes and tuyeres under various operational conditions are numerically predicted to recognize the performance of pulverized coal injection in a blast furnace. A variety of parameters including the injection pattern of the pulverized coal, oxygen content in the hot blast, inlet temperature of the hot blast and mass flow rate of coal carrier gas are taken into consideration. The effect of installing a ceramic sleeve around the tuyere on pulverized coal combustion is also evaluated. The predictions indicate that pulverized coal combustion is highly related to the injection pattern, hot blast temperature, mass flow rate of the carrier gas and installation of the ceramic sleeve, whereas it is insensitive to the oxygen concentration. The present study is conducted based on the practical operational conditions of the blast furnace at the China Steel Corporation. Consequently, the obtained results have provided a useful insight into the operation of pulverized coal injection, and they enable us to further improve the blast furnace performance in the future.

Modelling and analysis of blast furnace performance for efficient utilization of energy

A simple model is presented to assess thermal performance of blast furnace (BF) for efficient utilization of energy with an integrated view to improving the productivity of the plant. The model is developed using the mass, energy and availability balance equations and is applied to an existing Iron and Steel industry in India. A comparison of the actual operation of the BF is made with that of the model prediction. The model provides a reasonable agreement with the real time (on-site) data of the BF operation. The predicted values of BF coke rate and blast rate are 8.6% and 5.11% higher than that of the actual values, respectively. The First and Second law efficiencies of the BF operating system were found to be 77.3% and 39.13%, respectively. Irreversibility of the actual operation of BF was found to be 18.9%, which included the irreversibility due to the transformation of chemical energy and promotion of reduction reactions. The main cause of the irreversibility in the process was the conversion of chemical energy of the fuel (coke) to thermal energy. The effect of the changing operating parameters on the plant productivity is also investigated. This study suggests that the plant productivity can be improved by increasing the hot air blast temperature, reducing hot metal silicon level, reducing coke ash level and increasing sinter volume in the charge.