Reducing Agent Rate Research Articles

Automatic Control of Hot Metal Temperature

To achieve the automation of blast furnace operation, an automatic control system for hot metal temperature (HMT) was developed. Nonlinear model predictive control (NMPC) which predicts up to ten-hour-ahead HMT and calculates appropriate control actions of pulverized coal rate (PCR) was constructed. Simulation validation showed that the NMPC algorithm generates control actions similar to those by the operators and that HMT can be maintained within ±10 °C of the set point. The automatic control system using NMPC was then implemented in an actual plant. As a result, the developed control system suppressed the effects of disturbances, such as the changes in the coke ratio and blast volume, and successfully reduced the average control error of HMT by 4.6 °C compared to the conventional manual operation. The developed control system has contributed to the reduction of reducing agent rate (RAR) and CO2 emissions.

Thermodynamic study of oxide phase compositions at reducing iron ore coosit by coals of Karazhyra deposit

Application of coals as reducing agents in the direct iron reducing process is a perspective way. For solid-phase iron reducing from iron ore concentrate of Bapy deposit, Republic of Kazakhstan, application of coals of Karazhyra deposit was proposed. Chemical composition of iron ore concentrate of Bapy deposit is presented. By application of methods and means of thermodynamic simulation, analysis of oxide phase composition was carried out. As a result of thermodynamic studies, it was revealed that at reducing of concentrate of specified composition, iron and aluminum oxides, magnesium, calcium, barium, and alkaline metals silicates, sulfides and phosphor compounds are presented in the oxide phase. A dependence of oxide phase parameters on temperature and coal rate was established. It was shown that a number of aluminum oxide, titanium and barium compounds and calcium and magnesium silicates is not practically varying within the whole temperature interval. The number of compounds, containing phosphor, potassium, natrium is decreasing while temperature is increasing due to elements transferring in gas phase. The number of sulfides is decreasing with temperature increase till the whole disappearance in the condensed phase. The number of iron oxides at the temperature higher 872K depends only on reducing agent rate. The number of oxide phase at the temperature lower 853K is maximum, then begins to decrease while the temperature is increasing, the reducing processes are developing and at the temperature of 1013K after completion of reducing process it reaches its maximum value which is not changing then up to temperature 1773K. The studies carried out enable to evaluate slag properties at elaboration of resource-saving technologies of iron direct reducing and can be used at forecasting and evaluation of metallization processes and the further re-melting of materials obtained from Bapy deposit iron ore concentrate of and Karazhyra deposit coals.

Evaluating the behavior of catalyst coated nut-coke in blast furnace conditions

For efficient blast furnace ironmaking, it is desired to have low reducing agent rate, primarily coke rate. Developing technology to improve reaction efficiency of the blast furnace is extremely important as it has the potential to allow a decrease in the reducing agent rate as well as CO2 emissions. The reaction efficiency of blast furnace can be improved by lowering the Thermal Reserve Zone (TRZ) temperature; which is also the starting temperature of coke gasification reaction. In present study, nut-coke has been coated with in-plant waste, consisting mainly of iron oxide and calcium oxide, as catalyst. There was a clear increase of 10 points in the reactivity of coated nut-coke. The coated nut-coke have been subjected to non-standard high temperature experiments simulating blast furnace conditions with reducing gas consisting of CO, CO2 and N2 to capture the effect of catalytic coating on the onset of gasification reaction. The high temperature experiments carried out advise the following: i) A drop of 100 °C in the reaction beginning temperature of catalyst coated nut-coke as compared to non-coated one ii) A typical calculation shows that the lowering of reaction beginning temperature corresponds to a potential carbon rate savings of about 2.5 kg/ton of hot metal (thm). Furthermore, in a trial conducted at blast furnace with charging catalyst coated nut-coke, it has been observed that the carbon rate during the trial period was 3 kg/thm lower than the base period. The findings of blast furnace trial agree with that of the experimental one.

RESEARCH ON THE MANUFACTURING MAGNESIUM FROM THANHHOA DOLOMITE BY PIDGEON PROCESS


 The magnesium and magnesium alloys has applied widely in different industrial aspects in Vietnam in the modern life. Especially, the products from magnesium alloys implementing in the automotive have increased rapidly since the car elements tend to be generated by the light alloys in order to save the fuel. However, in the current time, Vietnam has no factories to produce the magnesium to adapt the domestic demand although it owns an enrich resource of raw materials. This research indicates the possibility of using the dolomite ore in Thanhhoa – Vietnam to make the magnesium as well as evaluate the primary factors like recovering temperature, reducing agent rate, recovering time having effect on the reduction efficiency of Thanhhoa dolomite by metallothermic method in vacuum (Pidgeon Process). This is basic process, low investment and suitable for the small and medium scales in Vietnam. The experiment includes heating, indicating the chemical ingredients and recovering experiment on the dolomite after calcination (dolime) by using ferrosilicon. The thermodynamic model is created to estimate the recovering efficiency in the Pidgeon. The result shows that the CaO/MgO molar ratio of calcination dolomite in Thanhhoa is nearly 1.5 which is suitable to produce magnesium in the case of highly-required efficiency and pureness. Besides, the result from the furnace of the experiment is lower than the one in the model. The samples are set up to check the influence of the rate of ferrosilicon in the compound. The result indicates that the ideal efficiency reaches 85 % with 30 % ferrosilicon. Moreover, the study confirms that the optimal operating conditions in this process are recovering during three hours at 1200 °C and 100 Pa pressure. This result proves the potential application of Thanhhoa dolomite in the industry suitable with the current condition in Vietnam

Smelting practice of scrap addition in blast furnace and theoretical analysis of cost saving

The recycling of scrap has attracted more attention in recent years, and scrap can be used as iron-bearing material to smelt hot metal. The smelting practice of blast furnace (BF) with scrap addition in China was investigated, with the types of scrap being small pieces of scrap, such as crushed materials, light and thin materials, and small compacts which were easy to be added into BFs. The higher productivity of BFs with scrap addition was observed compared with that of BFs without scrap addition at the same volume, and the positive correlation between production increase rate and addition amount of scrap was found. The reducing agent rate of most BFs with scrap addition was lower than the average reducing agent rate at the same volume, while the gas utilization of BFs with scrap addition would not be reduced significantly. The theoretical analysis of cost saving was carried out as well, and the results indicated that the cost could be saved by scrap addition. The melting and carburizing were the two main processes of scrap in BF, in which three steps were involved in the melting process of scrap. The amount of carburization depended on the carbon content of hot metal in hearth and the original carbon content in scrap. The calculation showed that the coke rate could be reduced by 27 kg with 100 kg scrap addition per ton of hot metal, and the saving cost was decided by the amount of scrap and the actual situation of BF.

Effect of Coke Particle Arrangement on Reduction and Gasification Reaction in Mixed Layer of Ore and Coke

To reduce CO2 emissions from steel works, low reducing agent rate (low coke rate) operation of the blast furnace is desired. Mixing nut coke in the ore layer is one effective measure for realizing this type of operation. Therefore, the effect of coke mixing on the reduction reaction rate of ore and the gasification reaction rate of coke in the mixed layer of ore and coke was investigated. The reduction rate of the ore and the gasification rate of the coke in the mixed layer of ore and coke was estimated by a reduction and gasification experiment, and the packing structure of the coke in the mixed layer was estimated by a mathematical model analysis using the discrete element method. The reduction rate of the ore and the gasification rate of the coke in the mixed layer was affected by the degree of contact between the ore and coke. In addition, the reduction rate of the ore and the gasification rate of the coke in the mixed layer was accelerated by the effects of mutual utilization of the gases generated by the reactions.

微粉炭燃焼性に及ぼす高炉への都市ガス吹き込みの影響

Reducing CO2 emission in ironmaking process is pressing issue. Low RAR (reducing agent rate) operation of the blast furnace and the utilization of hydrogenous reducing agent are effective to reduce CO2 emission. In this study, the influence of the hydrogenous reducing agent on the combustibility of the pulverized coal was examined by using a small scale combustion furnace. As a result, the combustibility of the pulverized coal was improved by simultaneous injection of the pulverized coal and the hydrogenous reducing agent. Furthermore, the fundamental study about the effect of natural gas (CH4) injection point on the combustibility of the pulverized coal was conducted by experiment using above mentioned small scale combustion furnace and by three-dimensional numerical analysis for further high efficiency. In the case of the relative position of CH4 injection point and the pulverized coal injection point being near, the ignition point of the pulverized coal came closer to lance tip. Especially, in the case of CH4 injection point being upstream in blow pipe about 0 to 20 mm from the pulverized coal injection point, the fastest ignition of the pulverized coal was confirmed by experimental and calculation results.

Influence of Coke Reactivity Improved on High Temperature Properties of Iron-bearing Burden

The influence of different reactivity coke on reduction, softening, melting and dropping properties of iron-bearing burden were studied by melting and dropping experiment, meanwhile reduction mechanism and softening-melting mechanism of stock column, as well as stock column pressure difference were also analyzed. The results show that reduction degree at 1000°C increases, softening-melting start temperature and dropping temperature decrease, and melting temperature rises, when the coke reactivity increases from 24.76% to 56.28%. Softening and melting temperature interval increases, melting and dropping temperature interval reduces and stock column permeability is improved as the coke reactivity increased, which lead to softening-melting and dropping properties value of iron-bearing burden reducing. In addition, industrial experimental analysis shows that reducing agent rate (RAR) can be reduced by 8.26 kg/t using high reactivity coke (HRC) of 12%. Therefore, the appropriate increase of coke reactivity could improve stock column permeability and high temperature properties of iron-bearing burden, so as to reduce RAR.

Reduction Behavior of Self-Reducing Pellet (SRP) for Low Height Blast Furnace

One way to decrease the reducing agent rate in a blast furnace (BF) is the lowering of thermal reserve zone (TRZ) temperature by using self-reducing pellets (SRP). The lower strength requirement of raw materials for small BFs allows the charging of SRP. In the scope of the current study, the behavior of SRP under the TRZ simulated conditions has been investigated. Coal, charcoal, and coke breeze were used as embedded reducing agents. The reduction experiments have been performed under different iso- and non-isothermal scenarios. A Tammann furnace laboratory rig and a simultaneous Thermogravimetric/Differential Thermal Analysis (TG/DTA) experimental set were used for investigations. Mass loss, reduction degree, metallization degree, volume change, and reaction heat flow were examined. The results from experiments with TRZ condition show that embedded reducing agents, especially charcoal, promote iron oxide reduction in pellets. The crushing strengths of SRPs after both methods of hardening, fire-hardening and cement-bonded curing, and the reduction of cement-bonded SRP after curing have been investigated as well.

Effect of Hydrogen Addition on Reduction Behavior of Ore Layer Mixed with Coke

Low RAR (reducing agent rate) operation of the blast furnace is one of effective techniques for reducing CO2 emissions. Coke mixed charging is a well-known and available measure to achieve low RAR operation by improving permeability and reducibility. Utilization of hydrogenous reducing agents is also an efficient measure. A reduction test under load was performed to investigate the effect of coke mixing with hydrogen addition on reduction behavior of the ore. Simultaneous use of coke mixing and hydrogen addition accelerated the reduction rate through the carbon gasification rate, and it was also decreased pressure drop. The effect of coke mixing and hydrogen addition on blast furnace operation was examined using a two-dimensional mathematical simulation model. In case of the ore layer mixed with coke, hydrogen addition in the reduction gas increased the hydrogen reduction ratio and decreased the direct reduction ratio. As a result, RAR decreased and permeability improved.

高炉の還元材比におよぼすフェロコークス多量装入の影響

高炉の還元材比におよぼすフェロコークス多量装入の影響

試験高炉による焼結鉱，コークス品質評価

The use of high reactivity coke is proposed to realize low reducing agent rate blast furnace operation. The reducing agent rate was reduced by use of high reactivity coke in an actual blast furnace. The reduction of reducing agent rate is caused by the improvement of the reaction efficiency due to the decrease of the thermal reserve zone temperature. On the other hand, it is suggested that sinter reducibility will affect on the effect of the high reactivity coke. Therefore, in this paper, the quality of high reducibility sinter and the effectiveness of high reactivity coke coexistence of high reducibility sinter were verified by the experimental blast furnace and following results were obtained.1) The top gas utilization was improved and the reducing agent rate was reduced by use of high reducibility sinter.2) The permeability was improved by use of high reducibility sinter. The improvement of permeability will be expected in actual blast furnaces.3)The top gas utilization was improved by use of high reactivity coke. The improvement was caused by the improvement of reaction efficiency due to the decrease of the thermal reserve zone temperature.4) The degradation of coke was decreased due to the decrease of the amount of reaction.5) The high reactivity coke works effectively when high reducibility sinter co-exists.

Simulation of Blast Furnace Operation with Intensive Hydrogen Injection

Recent years various trials to decrease carbon dioxide emission from iron and steelmaking industries have been made. One of these trials is utilization of hydrogen in blast furnace process, and this study performed numerical simulation of blast furnace operation with hydrogen injection through tuyere. The simulations were carried out under the conditions of constant bosh gas flow rate, adiabatic flame temperature and hot metal temperature. The simulation results showed that the temperature level in the stack part was decreased with increase in the hydrogen injection ratio. This resulted in the lowering of the top gas temperature and retarded the reduction of iron oxide especially one of magnetite. The injection of the hydrogen remarkably decreased the coke rate. The converted reducing agent rate, that is sum of coke rate and six times (molecular weight ratio of carbon to hydrogen gas) as hydrogen rate showed small change. Although this decrease in coke rate deteriorated the permeability of the burden materials in the furnace, pressure drop in the furnace was reduced. Since the molar flow rate of the reducing gas was kept constant, the decrease in the gas density due to the increase in the hydrogen content was mainly considered to lead the decrease in the pressure drop. The water gas shift reaction played an important role in the generation of the field of gas composition, thus this reaction has to be carefully discussed for further utilization of hydrogen in blast furnace.

フェロコークスによる高炉内低温度域でのガス化，還元反応の促進

Iron-coke having various amount of M.Fe were produced in laboratory scale and the influence of M.Fe content in Iron-coke on reaction behavior under the condition simulating blast furnace has been investigated. Cold strength of Iron-coke products was decreased with an increase of mixing ratio of iron ore mostly due to a prevention of dilatation of coal particles by iron ore, resulting in weak bonding of coal particles. Nevertheless formed Iron-coke with iron ore in the fraction up to 30% would have enough strength for use in blast furnace as nut coke. Both CRI and JIS-reactivity were enhanced by increasing ratio of mixed iron ore, confirming the catalysis effect of M.Fe. The temperature at which carbon consumption started was lowered with an increase of T.Fe in coke. Formed Iron-coke containing 43% of T.Fe started reaction consuming its carbon at lower temperature than conventional coke by 150°C. Furthermore, consumed carbon ratio was improved by M.Fe installation to coke due to increasing gasification. Process evaluation with using Iron-coke in blast furnace was performed by BIS test. It was revealed that using formed Iron-coke having 43% of T.Fe for blast furnace resulted in an increase of shaft efficiency by 6.8%. It was found that to lower the reducing agent rate in blast furnace by decreasing the temperature of thermal reserve zone, lowering the beginning temperature of coke reaction was effective. Usage of Iron-coke having M.Fe catalyst within coke matrix is one of the methods.

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.

Enhancement of Low-temperature Gasification and Reduction by Using Iron-coke in Laboratory Scale Tests

Iron-coke having various amount of M.Fe were produced in laboratory scale and the influence of M.Fe content in Iron-coke on reaction behavior under the condition simulating blast furnace has been investigated. Cold strength of Iron-coke products was decreased with an increase of mixing ratio of iron ore mostly due to a prevention of dilatation of coal particles by iron ore, resulting in weak bonding of coal particles. Nevertheless formed Iron-coke with iron ore in the fraction up to 30% would have enough strength for use in blast furnace as nut coke. Both CRI and JIS-reactivity were enhanced by increasing ratio of mixed iron ore, confirming the catalysis effect of M.Fe. The temperature at which carbon consumption started was lowered with an increase of T.Fe in coke. Formed Iron-coke containing 43% of T.Fe started reaction consuming its carbon at lower temperature than conventional coke by 150°C. Furthermore, consumed carbon ratio was improved by M.Fe installation to coke due to increasing gasification. Process evaluation with using Iron-coke in blast furnace was performed by BIS test. It was revealed that using formed Iron-coke having 43% of T.Fe for blast furnace resulted in an increase of shaft efficiency by 6.8%. It was found that to lower the reducing agent rate in blast furnace by decreasing the temperature of thermal reserve zone, lowering the beginning temperature of coke reaction was effective. Usage of Iron-coke having M.Fe catalyst within coke matrix is one of the methods.

Reduction of Reducing Agent Rate in Blast Furnace Operation by Carbon Composite Iron Ore Hot Briquette

Reduction of Reducing Agent Rate in Blast Furnace Operation by Carbon Composite Iron Ore Hot Briquette

Numerical Evaluation of Blast Furnace Performance under Top Gas Recycling and Lower Temperature Operation

AbstractThe new process of top gas recycling by hot reducing gas (HRG) injection has been developed in this study in order to overcome the disadvantageous problems under the lower temperature operation, to enhance the utilization of top gas carbon and to reduce carbon dioxide emission of blast furnaces. Numerical evaluation of blast furnace top gas recirculation together with lower‐temperature operation was performed by means of a multi‐fluid blast furnace model. The simulation results show that, (1) under the lower temperature operation, the shaft injection, or simultaneous shaft and tuyere injection of hot reducing gas is effective to increase the heat supply and to enrich the reduction atmosphere in the shaft zone, to improve the reduction of iron burdens, and enhance the efficiency of the shaft zone. (2) If top gas is recirculated by HRG on the basis of lower temperature operation, a highly efficient low‐carbon blast furnace is obtained. The productivity of the furnace shows a remarkable increase and the total reducing agent rate shows a considerable decrease. Furthermore, the top gas carbon utilization is enhanced and the carbon dioxide emission rate is lowered. (3) Generally, shaft efficiency, carbon emission and heat efficiency under simultaneous tuyere and shaft injection are comparatively better than in the other two methods of single injection.

Reaction behavior of Formed Iron Coke and Its Effect on Decreasing Thermal Reserve Zone Temperature in Blast Furnace

Usage of highly reactive coke in order to decrease the thermal reserve zone temperature in blast furnaces is promising to increase reaction efficiency in blast furnaces and to decrease the reducing agent rate. We focused on the catalytic effect of iron and succeeded in producing highly reactive formed iron coke with high iron content. In this paper the reaction behavior of formed iron coke when mixed with conventional coke and in the presence of alkali was investigated and the following results were obtained. When the mixture of iron coke and conventional coke is heated in a reaction gas, iron coke selectively and preferentially reacts near the thermal reserve zone temperature (900°C), which causes a decrease in the thermal reserve zone temperature, while conventional coke barely reacts and is protected from degradation. It was also confirmed that the catalytic activity of Fe and that of K is independent of each other and that in the presence of alkali, the reaction beginning temperature of iron coke is lower than that of conventional coke. These results show that the use of formed iron coke could decrease the thermal reserve zone temperature in an actual blast furnace where coke reactivity is promoted by condensed alkali vapor.

Advanced Supporting System for Burden Distribution Control at Blast Furnace Top

Burden distribution control is one of main technologies to keep the good permeability and the high reaction efficiency in a blast furnace. However, in actual blast furnace operation, there are variations in burden distribution due to various factors, such as fluctuations in condition of the raw materials, fluctuations of the mechanical properties of charging devices, the changes of charging devices due to abrasion and so forth. Such variations could be a negative factor to conduct blast furnace operation in high productivity and low reducing agent rate. The advanced supporting system for burden distribution control at blast furnace top regards those variational factors as the characteristic parameters of burden distribution formation through analyzing on-line monitoring probe data to make effective supports for a proper burden distribution control. In this paper, the composition of the supporting system and the results of applying this system to actual blast furnace are described.