BF Operation Research Articles

Study on the High-Temperature Interaction between Coke and Iron Ores with Different Layer Thicknesses.

Coke plays a key role as the skeleton of the charge column in BF. The gas path formed by the coke layer in the BF has a decisive influence on gas permeability. At high temperatures, the interface between coke and ore undergoes a melting reaction of coke and a reduction reaction of ore. The better the reducibility of the ore, the more conducive it is to the coupling reaction of ore and coke. The melting loss reaction of coke becomes more intense, and the corresponding strength of coke will decrease, which will affect the permeability of the blast furnace and is not conducive to the smooth operation of the blast furnace. Especially with a deterioration in iron ore quality, BF operation faces severe challenges, which makes it necessary to find an effective way to strengthen BF operation. In this study, a melting-dropping furnace was used to develop and clarify the high-temperature interaction between coke and iron ores with different layer thicknesses. The influencing factors were studied by establishing a gas permeability mathematical model and observing the metallographic microscope images of samples after the coke solution loss reaction. The relationships between coke layer thickness, distribution of gas flow, and pressure drop were obtained. The results showed that, under certain conditions, the gas permeability property of a furnace burden has been improved after the coke layer thickness increased. Upon observing the size of coke particles at the interface reaction site, the degree of melting loss reaction can be determined. A smaller particle size indicates more melting loss reaction. A dripping eigenvalue for molten metal was introduced to evaluate the dynamic changes in the comprehensive dripping properties of molten metal of furnace burden, which showed that the dripping eigenvalue for the molten metal could deteriorate because of the unruly thickness and the coke layer thickness should be limited through considering the operational indicators of the blast furnace.

Reduction in heat losses through air tuyeres in blast furnaces at DSP

Approximately 30 % of all the heat losses in a blast furnace may be attributed to the air tuyeres. Blast Furnace uses highly pure copper (>99.7 %), water-cooled nozzles (tuyeres) as the injection point for high velocity, pre-heated air mixture to the blast furnace for iron oxide reduction. These tuyeres periodically fails and failure introduces furnace instability, increased costs and fuel rate, lost productivity, and increased safety and environmental exposure. Heat flux has greater influence on blast furnace operation. Optimum heat flux is required for smooth BF operation. In a trial at DSP Blast Furnace No.3 & 4, around 50 % of the air tuyeres (existing) were replaced by modified designed tuyeres to decrease the heat losses. In the design modification of tuyeres, insulating inserts have been introduced in air channel (inner surface directly in contact with air blast). In addition to this hard facing of outer surface with Ni-Cr alloy have been carried out with suitable coating technology. Channelization of cooling water to the tip of tuyere and then to the body of tuyere has given added advantages in terms of efficient cooling to further decrease the heat loss as well as increasing the durability of tuyeres. Incorporation of modified designed tuyeres in place of existing tuyeres has given reduction in ΔT of individual tuyeres in the range of 2.0–3.0 % contributing to the average heat savings of ∼ 48500 kcal/hr/tuyere. This amounts to almost 30 % of the heat savings in trial period as compared to base values.

Modeling of hydrogen shaft injection in ironmaking blast furnaces

Hydrogen, as a carbon-free fuel and reducing agent, has the potential to mitigate carbon dioxide emission in BF ironmaking and the shaft injection is one of the promising and feasible processes; however, its effects on non-renewable fossil fuels saving in ironmaking process and the in-furnace phenomena are still not clear. In this study, a multi-fluid BF model is adopted to study hydrogen shaft injection's influence on in-furnace phenomena and BF performance, including flow-thermal-chemical behaviors and fossil fuel rate saving. The computational domain includes the industrial-scale BF regions from the slag surface in the hearth to the stock line near the furnace top, and the study is carried out under a fixed bosh gas flow rate. The simulation results show that compared with regular BF operation, hydrogen shaft injection can considerably affect BF performance, including the gas flow field, thermal field, and reduction behaviors. It is found that, as the injection rate increases, the penetration depth of hydrogen shows an increasing trend; the apex of cohesive zone shifts to a higher position with a more concave-shaped profile; moreover, both the reduction degree of iron oxides and thermal conditions in the shaft can be improved, which are accompanied with a significantly decreased fossil fuel rate. This study provides a quantitative tool to understand and optimize the hydrogen shaft injection into BFs towards a low-carbon ironmaking process.

Numerical Investigation of Blast Furnace Operation with Scrap Charging

One approach to reduce CO2 emission in the steelmaking industry is to recycle scrap to the blast furnace/basic oxygen furnace (BF/BOF) production system. This paper performed a numerical investigation on the BF operation with scrap charging. The investigated BF was with an inner volume of 820 m3, producing 2950 tons of hot metal per day (tHM/d). The simulated results indicated the following: Extra scrap addition in BF causes the decrease of shaft temperature, the decrease of local gas utilization, and the lowering of cohesive zone position, leading to an unstable BF running. The partial replacement of sinter with scrap in BF can mitigate the negative effects induced by scrap charging. The optimal scrap rate in the BF is 178 kg/tHM, under which the BF reaches a productivity of 3310 tHM/d, a top-gas utilization of 48.5%, and a top-gas temperature of 445 K. Compared to the base case, in the BF operation with scrap charging, the BF productivity is increased by 360 kg/tHM, its pulverized-coal rate and coke rate are decreased by 16.3 kg/tHM and 39.8 kg/tHM, respectively.

Energy efficient technology of hot metal smelting at PAO NLMK

Decrease of energy expenditure for hot metal smelting is an actual task in blast furnace technology perfection. Under conditions of PAO NLMK regimes with maximum forcing of the BF process at the expense of pressure increase under furnace mouth and coke hot strength increase were chosen as one of priority ways to increase the BF operation energy efficiency. Data on blast furnaces productivity, specific coke rate, quantity of blow-in oxygen and fuel at different gas pressure levels under the furnace mouth quoted. A dependence between pulverized coal rate and total carbon consumption determined. It was shown, that application in PAO NLMK blast furnaces of coke having hot strength of 60–65% at maximum possible pressure under the furnace mouth and application of pulverized-coal fuel enabled in the period from 2012 through 2018 to decrease the coke rate by more than 100 kg. Also the total carbon consumption decreased by more than 30 kg per hot metal ton and to increase smelting products chemical composition stability.

Control and Optimization of Melting Zone Parameters by Means of a Two-Dimensional Model in the Blast Furnace Automated Process Control System

A two-dimensional mathematical model of BF is developed that describes gas dynamic, heat and mass transfer processes over the height and cross section of a furnace from the charging level to the iron taphole. A two-dimensional mathematical model is implemented as part of five existing MMK blast-furnace production automatic control systems for the melting zone in real time. The systems used are already installed in the furnaces as means of automation, microprocessor and computer engineering. Continuous automatic control and quantitative evaluation of the parameters of the melting zone (MZ) shape, location, and thickness are provided. This makes it possible to compare these MZ parameters with smelting input and output parameters, reveal their effect on the melting parameters and to estimate them quantitatively, and to conduct continuous automatic monitoring of changes in MZ parameters in time. It is shown that a change in the shape of the MZ (increasing the angle at the periphery and axis of the furnace), its ascent over the height of the furnace (from the line of the combustion zone), and an increase in its thickness worsen furnace performance. Values of the MZ parameters are established that provide the best smelting indices. Continuous automatic monitoring of changes in MZ parameters over time and comparison of results with trends in the change of smelting parameters make it possible to identify the causes of disruption in BF operation and take timely measures to overcome them.

Computational Investigation of the Multiphase Flow Behavior in Ironmaking Blast Furnace

For studying the microscopic mechanism of pulverized coal injection (PCI) process to optimize BF operation further, the multiphase-coupled interactions and combustion phenomena is described by mathematical equations. Some assumptions are employed properly in simulation for solving the equations well. Some physical properties of per-phase obtained through simulating the typical flow behaviors in iron-making process were contrastive analyzed with the field data. The investigation shows that the complex phenomena in a BF can be presented by the computational approach which is proved virtual and robust. The computational results have shown that the gas-solid-powder flow varies spatially, particularly in the raceway; the powder flow is strongly affected by the air and coke particles under the cohesive zone, and by the ore particles upon the cohesive zone; the ability of BF could be enhanced with higher rate of coal injection to a certain extent.

Revamping of CSN BF2 hot blast stove no. 1

CSN BF no. 2 has only three hot blast stoves. Owing to the operational risks as well as output losses associated with the BF operation with just two hot blast stoves, the revamping time of this equipment becomes a crucial issue, requiring special attention in each phase of the project from planning to execution so as to shorten the time as much as possible. According to this context, the present paper describes in detail the main technologies used in the last revamping of hot blast stoves carried out in February 2007. These technologies included an accelerated cooling down curve, air conditioning system (good working condition) and convection heating system, which in association with an innovative construction methodology, involving movable and multilevel platforms, has allowed the project to be completed from blow to blow in a record time of just 67 days and 10 h, resulting in a reduction of costs around R$3·4m.

Mathematical Modeling and Exergy Analysis of Blast Furnace Operation With Natural Gas Injection

AbstractBlast furnace operation with natural gas (NG) injection is one of the effective measures to save energy, reduce CO2 emission, and decrease environmental load for iron and steel industry. Numerical simulations on blast furnace operation with NG injection through tuyeres are performed in this paper by raceway mathematical model, multi‐fluid blast furnace model, and exergy analytical model. With increasing NG injection volume, the simulation results are shown as follows: (1) the theoretical flame temperature and bosh gas volume can be constant by decreasing blast volume and increasing oxygen enrichment. (2) The utilization rate of CO enhances while that of H2 decreases. The proportion of H2 in indirect reduction tends to be increased, which accelerates the reduction of burdens. The pressure drop shows that the permeability of blast furnace gets better. The blast furnace productivity is increased from 2.07 to 3.08 t · m−3 · day−1. The silicon content in hot metal is decreased from 0.26% to 0.05%. When BF operation with 125.4 kg · tHM−1 NG injection, coke rate and carbon emission rate are decreased by 27.2% and 32.2%, respectively. (3) The thermodynamic perfection degree is increased from 88.40% to 90.50%, the exergy efficiency is decreased from 51.94% to 49.02% and the chemical exergy of top gas is increased from 4.69 to 6.22 GJ · tHM−1. It is important to strengthen the recycling of top gas.

Study on Technology of Blast Furnace Energy Saving and Consumption Reduction

By study the development situation of blast furnace smelting in china and the blast furnace operation system and technology, combined with production conditions of JISC BF, based on a large number of the production data, the comparison analysis test on JISC BF operation system and technology was did. Through continuously optimization and practice, the relatively suitable operation system and technology of JISC BF at present was explored, which could reduce the coke ratio into furnace while increasing the coal injection ratio and making great economic effect.

Research on Technology of Blast Furnace Optimization of Operation Principle

By study the development situation of blast furnace smelting in china and the blast furnace operation system and technology, combined with production conditions of JISC BF, based on a large number of the production data, the comparison analysis test on JISC BF operation system and technology was did. Through continuously optimization and practice, the relatively suitable operation system and technology of JISC BF at present was explored, which could reduce the coke ratio into furnace while increasing the coal injection ratio and making great economic effect.

Effect of Magnesium and Aluminum Oxides on Fluidity of Final Blast Furnace Slag and Its Application

The experimental results indicated that the lower liquidus temperature and the better viscosity stability lay in the area of MgO = 5.4%, Al2O3 = 10­15% ,T iO2 = 0.5% and C/S = 1.2 for the range of composition studied. Several observations in the iso-fluidity diagrams of blast furnace final slag have shown that liquidus temperature decreased with decreasing MgO content and the viscosity of slag could be regarded as being independent of MgO content in the range of MgO = 5­9% ,A l 2O3 = 15% ,C /S = 1.0­1.2. And, slag fluidity became worse with increasing Al2O3 content under the conditions of MgO = 5.4% ,C /S = 1.2. This study suggested the MgO contents could be lowered from current 6.5 to 5.4% in the conditions of Al2O3 = 15% ,C /S = 1.2 under the stable blast furnace operation with high thermal level. Furthermore, this recipe of lower MgO content (5.4%) had been implemented in CSC’s BF operation to reduce the slag volume, and the formula of fluidity developed in this study had been installed in the process computer of all CSC’s BFs to present slag fluidity in real time.

Investigation of Cost Optimization of Pig Iron

Since the pig iron cost is the major cost of steel, reducing the pig iron cost is the key of reducing the cost and enhancing the competitive capacity of iron and steel enterprise. The law of the cost of pig iron change with time was analysed in the paper. The major factors which affect the cost of pig iron are confirm by the analysis the composition of the cost of pig iron, then the measures such as reducing material fee, injecting pulverized coal economically, improving BF operation and strengthening management are advised.

Fundamental Study on Carbon Composite Iron Ore Hot Briquette Used as Blast Furnace Burden

AbstractCarbon composite iron ore hot briquette (CCB) is the product of fine iron ore and fine coal by hot briquetting process, which attracts more and more attention as a new type of ironmaking raw materials aiming to improve the operation efficiency and reduce the coke consumption of blast furnace. This paper is devoted to experimental study on metallurgical properties of CCB and numerical simulation of the BF operation with CCB charging. At first, the metallurgical properties of CCB, including cold crushing strength, RDI, RSI, reducibility, high temperature strength, and softening and dripping are experimentally tested and compared with the common burdens, which revealed that the CCB possesses the required metallurgical properties and is suitable to use as the blast furnace burden. Then, the effects of charging CCB on the dripping properties of comprehensive burdens are elucidated based on the experiments under simulated blast furnace conditions. The results showed that the maximum charging ratio of CCB in the iron burdens is 40%–50% for achieving appropriate dripping properties of the mixed burdens. Finally, a multi‐fluid blast furnace model is used to simulate BF operation with CCB charging. According to model simulations, charging CCB will cause the temperature level to decreases in the furnace and the location of the cohesive zone shifts downward. On the other hand, the productivity tends to increase while coke rate and total reducing agent rate decrease, the heat efficiency improves remarkably and the operation performance of BF is effectively enhanced.

New Evaluation Index of Blast Furnace Raceway Activity

The shape feature of tuyere raceway possesses an important effect on hearth state and BF operation. With analyzing channel for permeating gas and liquid in the hearth section in the position of tuyere raceway, it can be seen that the channel amount is mainly determined by section of raceway and section between the raceways. On the basic of theoretical and statistical analysis on practical production data, the new evaluation index of indicating tuyere raceway shape feature was proposed. In the condition of high blast volume, the new index AITR tended to increase and BF production was improved gradually as blast volume increases. The good evaluation character of this new index AITR has been validated with practical production data in this work.

Ironmaking Process Parameter Analysis and Optimization for the Blast Furnace

With practical data of the BF ironmaking from Jiuquan Iron&Steel Cooperation Ltd. (JISC), taking the quality of pig iron as evaluation indicator, mathematical models based on the least square regression and partial least square regression were set up respectively by co-relation analysis of feeding-to-product interval of the BF processing. The calculation results showed that the reasonable description can be obtained by the partial least square regression model; and 10 of 29 parameters with obvious impact on the BF operation were listed accordingly. Meanwhile, an optimal group of parameters was found by genetic algorism calculation method. The optimal index of the group was 99.13％. This study is beneficial to the improvement of feeding adjustment and optimal operation of BF ironmaking.

Research on Technology of Blast Furnace Energy Saving and Optimization of Operation Principle

By study the development situation of blast furnace smelting in china and the blast furnace operation system and technology, combined with production conditions of JISC BF, based on a large number of the production data, the comparison analysis test on JISC BF operation system and technology was did. Through continuously optimization and practice, the relatively suitable operation system and technology of JISC BF at present was explored, which could reduce the coke ratio into furnace while increasing the coal injection ratio and making great economic effect.

Intensifying Smelting Synthesis Technique of 2500m<sup>3</sup> Blast Furnace

Based on the existing smelt condition, after exploring and practicing, 2500m3BF of the Stainless Steel Branch of Baosteel procured breakthrough on the intensifying smelting. By researching technologies of compounding many coke kinds for lessening the effect to the BF, adjusting the proportion of each ore to optimize the structure of charging, increasing the gas using ratio for cutting down fuel ratio, and taking low silicon smelting to optimize BF operation, the general indicators in the top position among the same type blast furnaces in china.

99/01683 Development of BF tuyere monitor : Sha, Y. et al. Gangtie, 1997, 32, (12), 12–15. (In Chinese)

A BF tuyere monitor has been developed to realize continuous monitoring of tuyere inner situation,instead of manual observation.The main functions are coal injection monitoring,abnormal BF operation monitoring,diagnosing coke movement and tuyere temperature etc.The fix protecting apparatus can ensure the detector to work well under hard conditions of tuyere.There is no disturbance to manual observation and tuyere replacement.