Why Can Some Gas Coke be Used for Smelting Ferrosilicon?

Why Can Some Gas Coke be Used for Smelting Ferrosilicon?

Metallurgical coke is mostly used as the reducing agent for smelting ferrosilicon. Metallurgical coke is a coke formed at a coking temperature of about 1100-1300 °C in the coking process, so it is also called high-temperature coke or full coke. The coke formed at a coking temperature of about 600 to 800 ° C is called low-temperature coke or semi-coke. Gas coke is a kind of low-temperature coke. The so-called gas coke is a by-product of gas production.

The properties of gas coke and metallurgical coke are compared as follows:

1. Resistance

For various cokes with a particle size of 10-15 mm, the relationship between specific resistance and temperature is shown in Figure 4 according to actual measurements. The resistance of gas coke is greater than that of metallurgical coke, even at higher temperatures, its resistance is still greater than that of metallurgical coke. An important advantage of gas coke is when the resistance is large. The practice has proved that when smelting ferrosilicon, some gas coke is used, and the electrode can be deeply inserted into the charge, thereby reducing power consumption.

2. Chemical composition

It can be seen from Table 4 that the gas coke contains lower fixed carbon and higher ash content, which is not as good as metallurgical coke in terms of chemical properties. This is due to the lower coking temperature of gas coke. The carbon content of gas coke is low, so it should be added more when it is used as a reducing agent. At the same time, due to the high ash content in gas coke, the amount of slag during smelting also increases. On the other hand, due to the low carbon content in gas coke and its Mechanical strength is poor. In smelting, there is often a lack of carbon in the crucible and the lower part. It can be seen that gas coke is used as a reducing agent for smelting ferrosilicon, and the furnace condition is not easy to maintain.

3. Porosity and reactivity

The porosity of gas coke is 40-60% larger than that of metallurgical coke, which not only increases the resistance of gas coke, but also expands the reaction contact surface. conduct.

4. Cost

The price of gas coke is 10-20% lower than that of metallurgical coke.

The above-mentioned gas coke has the advantages of high porosity, high electrical resistance, and low cost, but it also has the disadvantages of low carbon content, high ash content, and poor mechanical strength. Therefore, it is not suitable to use all gas coke during smelting, but it can be used in combination with metallurgical coke. Practical experience has proved that the combined use of 30-40% gas coke and metallurgical coke has a better effect, and the unit power consumption is reduced to some extent.

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The Basic Structure of Submerged Arc Furnace

The Basic Structure of Submerged Arc Furnace

The submerged arc furnace is a kind of complicated electrical metallurgical machinery. It consists of the heating furnace itself, the transformer for the furnace, the high-current electrical conductor (short-circuit), the electrode system software, the submerged arc furnace charging system, the refrigeration system, and the high and low voltage power distribution system. Software, supervision and automation technology, tapping and slag removal system software, fume extraction system ash removal, and other system software.

The submerged arc furnace is an industrial electric furnace with huge power consumption. Mainly consists of a furnace shell, furnace cover, furnace lining, short net, water cooling system, smoke exhaust system, dust removal system, electrode shell, electrode pressing and lifting system, loading and unloading system, controller, burn-through device, hydraulic system, submerged arc furnace Transformers and various electrical equipment

The basic structure of the submerged arc furnace is shown in Figure 1 below. The high-voltage line provided by the power grid can be converted into low-voltage and high-current through the special transformer of the submerged arc furnace, and the current is sent to the electrode through the high-current electrical conductor. 

According to the carbon electrode input into the furnace, resistance is caused by the returned waste around the electrode. The heat of the furnace and the pulse heat caused by the end of the electrode convert the electromagnetic energy into thermal energy and then generate a high-temperature reaction zone in the furnace body to carry out the reduction reaction of metal oxide iron ore. 

Usually, carbon oxidants such as coke are used to continuously add coke and recovered metal oxide iron ore raw materials to the furnace, and the reduction reaction in the reflection area continues to develop, and the obtained liquid products are stored in the fusion furnace, and the furnace is opened on time. 

It is released through the mouth, the metal material is poured, cast, and rolled to obtain aluminum alloy products, and the coal ash is water quenched or poured before use.

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Blast Furnace Ironmaking Technology

Blast Furnace Ironmaking Technology

It mainly uses concentrate technology, high-pressure operation technology, high air temperature operation technology, fuel injection technology, oxygen-rich blast technology, long-life technology of blast furnace, etc.

(1) Concentrate Technology. 

That is, improve the quality of raw fuel, reduce coke ratio and improve smelting intensity. Blast furnace ironmaking requires high, clean, uniform, stable, less, and good quality raw fuel. High iron content is of high grade. Normal blast furnaces should reach 58% and super large blast furnaces 59%-60% or higher. The net result is that the powder content of charge is low, the iron content less than 5 mm should be less than 5%, and the super large blast furnace should be less than 3%. The Uniform size of all kinds of charges is equal. The average size of sinter entering the furnace is 18-20 mm, and the size > 40 mm is less than 10%. Stability is the chemical composition and performance stability of the charge. Fewer non-ferrous elements and fewer impurities of harmful elements; Fortunately, the metallurgical properties of the charge are better.

(2) High-pressure Operation Technology. 

That is, the operation technology of increasing the pressure on the top of the furnace and keeping the gas in the whole blast furnace under high pressure so as to improve the smelting intensity, increase the output and reduce the coke ratio. The top pressure of high-pressure operation of large blast furnaces ranges from 200 kPa to 300 kPa, and the top pressure of some blast furnaces with a capacity of less than 1000 cubic meters exceeds 120 kPa. In modern blast furnaces, every 10 kPa increase in top pressure can increase production and reduce the fuel ratio by 2%.

(3) High Air Temperature Operation Technology. 

That is, the operation of heating the blower temperature to over 1200C by means of a hot air stove. It is an important measure to reduce the coke ratio and strengthen smelting in BF. Using blast heating technology, the blast temperature of the blast furnace can be increased to 1300C. In modern blast furnaces, coke can be saved by 3% and the corresponding output can be increased with an increasing air temperature of 100 C.

(4) Fuel Injection Technology. 

An enhanced smelting technology for blast furnaces in which gas, liquid, or solid fuels are injected into the blast furnaces through special equipment to replace some coke in the charge of the blast furnaces. The purpose is to improve the operation of blast furnaces, increase the production of pig iron, expand the variety and source of fuel used in blast furnace smelting and reduce the cost of pig iron. The main types of fuel injected are heavy oil, natural gas, and coal powder.

(5)Oxygen-rich Blower Technology. 

That is, industrial oxygen is added to the blast furnace to make oxygen content in the blast exceed atmospheric oxygen content, strengthen fuel combustion in the air outlet area, so as to improve smelting intensity and increase pig iron output. With the development of blast furnace smelting technology, the combination of high air temperature, oxygen enrichment, and fuel injection is of great significance to the strengthening of blast furnace smelting.

(6)Long-life Technology of Blast Furnace. 

Comprehensive technical measures for increasing the age of blast furnaces. Reasonable design of blast furnace inner type, application of the non-superheated cooling system and closed circulating cooling technology with pure water (soft water), optimization of lining structure of hearth and bottom of blast furnace, and establishment of perfect automatic monitoring and control system of the blast furnace are the important characteristics for stable, smooth and efficient production of the blast furnace. The design life of large-scale blast furnaces is 20-25 years. The volume of iron yield per cubic meter of the first generation of blast furnaces should reach 15,000-20,000 tons.

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Cause Analysis of Breakage of Blast Furnace Air Nozzle

Cause Analysis of Breakage of Blast Furnace Air Nozzle

Preface

Blast furnace operation is a very continuous operation process. Generally, the small air outlet sleeves of the blast furnace are managed for life and replaced regularly. If abnormal damage occurs to the small nozzle sleeve of the blast furnace, it will seriously affect the normal production of the blast furnace. Besides the effect of air break on the production, it also includes the increase of fuel ratio caused by water leakage, the cooling of the blast furnace, and the damage to refractories of the hearth. Frequent air breaks can also cause changes in the position of the melting zone, resulting in wall thickness, nodulation, or inactivation of the hearth until the hearth accumulates. Therefore, the study of the mechanism and cause of air outlet breakage and the effective reduction of air outlet breakage in production is the focus of daily attention of furnace operators.

Causes of Breakage of Blast Furnace Air Nozzles

1) Objective Factors of Blast Furnace Air Nozzles Breakage

There are many reasons for air outlet breakage, many of which are caused by objective conditions, such as air outlet structure, manufacturing defects, the water quality of cooling water, pressure, flow rate, etc. These objective factors may cause air outlet breakage.

Firstly, with the development of technology, the structure of air outlets used in blast furnaces is also constantly improved, such as changing from cavity type to tubular type, at the same time, the manufacturing quality and processing technology are also continuously improved. The air outlet breakage caused by air outlet structure and manufacturing quality is no longer the main cause of air outlet breakage.

The air outlet is damaged due to quality reasons. Water leakage is treated. Pores such as pinholes are usually visible and the leakage holes are small outside and large inside. Crack water leakage caused by air quality, usually occurs at the welding seam. Of course, affected by blast furnace condition, cooling, and other factors, the air vent can also cause cracks and water leakage under the action of thermal gradient under momentary huge thermal load, which is not a quality problem of air vent.

Secondly, in terms of cooling, the formation of scale can generally be found at the air outlet or pipeline due to water quality problems such as air outlet breakage caused by excessive water quality. As for water pressure and water speed, the design standards for each blast furnace have been in place at the beginning of the construction of the furnace. Some fluctuations in production should also be able to meet the needs of air outlet cooling, so water pressure and water speed should not be the main cause of air outlet breakage.

2) Breakage of Blast Furnace Air Nozzle Caused by Operation

For general blast furnaces, the breakage of the air outlet caused by the operation is the main cause at present. The breakage of the air outlet caused by the improper operation is mainly manifested in the following aspects:

The first, is excessive development of gas flow at the edge of the blast furnace. Due to excessive airflow at the edge, the reaction at the edge of the blast furnace increases, resulting in a large amount of slag iron. In contrast to normal conditions, when slag iron enters the hearth along the surface of the swing zone of the air outlet, a small amount of slag iron will drip down the furnace wall. When a small amount of slag iron drips down the upper end of the air outlet, the air outlet will be damaged.

The burned parts of the air outlet caused by this reason are mostly on the upper part of the air outlet. Most of the burned holes are large outside and small inside, similar to the phenomenon of droplets passing through. When the edges are over-developed, frequent rises and falls in front of the air vents can also be seen through the air vent mirrors.

In addition, excessive development of edge airflow often results in unstable slag skin at the furnace belly, frequent shedding, and falling slag skin running down the furnace wall. On the one hand, it causes wear and water leakage at the front of the air outlet. On the other hand, a large number of slag blocks that are not fully preheated melt in front of the air outlet, which makes the temperature of the molten slag iron droplets decrease rapidly, resulting in poor fluidity and can not rapidly penetrate into the lower part of the furnace cylinder and accumulate in front of the air outlet, thus causing the air outlet to burn out.

Second, the BF hearth is inactive and accumulated. The volume of the hearth decreases as a result of central or edge accumulation. As the number and time of blast furnaces are usually fixed, under the same circumstances, the slag iron surface will be higher than the original one after the hearth is accumulated, and the pressure relationship will be tense outside the blast furnaces, slow charging and other phenomena will appear, so the slag iron in the furnace is easy to burn out the air vent. Sometimes, due to peripheral accidents, the iron tapping time is delayed and the air vent may be burned out.

However, the main reason for the damage to the air outlet caused by the accumulation of hearth is that after the accumulation of hearth, the permeability of the dead coke reactor of the blast furnace is poor, resulting in the accumulation of slag iron in front of the air outlet, which burns out the air outlet.

If the condition of the blast furnace is restored after it is cooled, a large number of airports will be damaged. The main reason is the poor liquid permeability of dead coke in the hearth, as well as the low physical heat and poor fluidity of the newly formed slag iron, which can not penetrate the hearth in time and the slag iron accumulates in front of the airports. The burned area of the air outlet caused by this kind of reason is usually the lower part of the air outlet.

Third, the kinetic energy of the blast furnace is insufficient. For example, for long-term air reduction of the blast furnace, the area of the air outlet is not adjusted in time. Due to insufficient dynamic energy of the blast, the swing area of the air outlet becomes smaller and slag iron may burn the front end of the air outlet.

When the wind speed of the fourth blast furnace is too high and the kinetic energy of the blast is too high, when the wind speed is too high, a negative pressure zone will be formed around the air outlet. The higher the wind speed, the higher the negative pressure around the air outlet. When the negative pressure is high to a certain extent and has a certain attraction to the slag iron dripped from the upper part, the slag iron dripped from the upper part will be absorbed on the surface of the air outlet and burned out. At the same time, the high air speed will also cause turbulence in the air outlet area. This changes the dripping direction of slag iron and burns the air vent. There are a number of cases where blast furnaces were forced to blow because they wanted to penetrate the center, resulting in a large number of burned air outlets.

Fifth, BF is not smooth and the reason for the suspended charge. After suspension, air-reducing and even air-resting materials may be filled with slag from the air outlet, which will burn the air outlet. It is also possible that the material column suddenly falls from the upper part, causing the air vent to break, especially if the suspension is stubborn for a long time, which is even more dangerous. There have been incidents in which enterprises smashed air vents while sitting down due to long-term vicious suspension.

Improper operation of the sixth flushing furnace results in slag peel falling off, burnout air vent, long-term addition of fluorite, and development of edge airflow, which is also liable to burnout. The burnout mechanism can be seen in << Hazard of fluorite to furnace smelting >>

Seventh, the cause of coal powder scouring in the coal injection process. After pulverized coal is injected into the blast furnace, the air vent can be worn out in a short time due to the improper position of the lance. Even if the gun position is correct, the friction of pulverized coal on the air vent is very serious. Statistics from enterprises show that the wear of pulverized coal can enlarge the inner diameter of the air vent by 0.5-0.8 mm every month. Therefore, when coal is relatively high, the influence of coal powder scouring can not be neglected.

The reason for the damage to the air outlet is summarized in the hope that in our daily operation, it can be prevented slightly and gradually, and the operation with the possibility of burning the air outlet can be avoided as far as possible so as to reduce the loss in production. The unnecessary wind break in the village will create conditions for stable production and the long life of the blast furnace.

Of course, there are many reasons why air vents are damaged, but they are usually shown by the above forms, such as harmful elements in raw materials and fuels which cause slag to stick, lead to cylinder accumulation, and damage air vents. In production, it is necessary to make specific analyses according to actual conditions so as to avoid a large number of burns of air outlets affecting the smooth running of the blast furnace.

Conclusion

(1) A large number of air outlets are damaged, which is very disadvantageous to the continuous production of blast furnace technology. Effective measures must be taken to reduce the breakage rate of air outlets.

(2) Damage to the air vent is closely related to the operation of the blast furnace, but only by changing the original and fuel conditions, can the blast furnace adopt the most economical operation system and fundamentally eliminate the cause of air vent breakage.

(3) It is also an effective way to reduce the burning of air nozzles by properly increasing the water pressure and flow rate of cooling water, strengthening the cooling, and improving the cooling conditions from the outside.

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Blast Furnace Lining

Blast Furnace Lining

Blast Furnace

The blast furnace is made of steel plate with refractory brick lining inside.

From top to bottom, the blast furnace body is divided into 5 parts: furnace throat, furnace shaft, furnace waist, furnace bosh, and furnace hearth. Due to the advantages of good technical and economic indicators, simple process, large production capacity, high labor production efficiency, and low energy consumption, the iron produced by this method accounts for the vast majority of the world's total iron output.

Blast Furnace Lining

A layer of 345 ~ 1150mm thick refractory bricks is laid inside the blast furnace shell to reduce the heat dissipation of the furnace shell. Cooling equipment is set in the bricks to prevent the furnace shell from deformation.

The damage mechanism of each part of the blast furnace brick lining is different. In order to prevent the local brick lining from being damaged first and shorten the service life of the blast furnace, different refractory brick lining must be selected according to the factors such as damage, cooling, and blast furnace operation.

The hearth and bottom traditionally use high-grade and super high-grade clay bricks. This part of the bricks gradually melted away. Due to shrinkage and poor bricklaying quality, major burn-through accidents were often caused in the past. Carbon refractories are mostly used for hearth and bottom, basically solving the burn through the problem of furnace bottom.

There are three types of carbon bricks used in furnace bottom: all are carbon bricks; Around and above the furnace bottom are carbon bricks, and the lower part is clay bricks or high alumina bricks; Around and below the furnace bottom are carbon bricks, and the upper part is clay bricks or high alumina bricks. The latter two are also called integrated furnace bottoms.

The design furnace bottom thickness tends to decrease (from 0.5d to about 0.3d or 1/4 of the furnace shell inner diameter, D is the hearth diameter).

The disadvantage of carbon bricks is that they are easily eroded by air, carbon dioxide, water vapor, and alkali metals. The furnace waist, especially the brick lining at the lower part of the furnace body, is easy to be damaged due to wear, thermal stress, chemical erosion, etc.

When the blast furnace with cooling staves is put into operation for about two years, the brick lining at the lower part of the furnace body is often eroded. The upper part of the furnace body and the furnace throat brick lining shall be made of materials with abrasion resistance and thermal stability, and the clay brick is preferred. After the bosh brick lining is eroded, the production is maintained by "slag skin".

In recent years, the application of gunning technology to repair brick lining has been quite common. Gunning high alumina refractory (including Al2O3 340 ~ 60%), with a service life of 3/4 of that of the lining.

The main products of Hani Metallurgy are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

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Reasons for High Power Consumption of Electric Arc Furnace Steelmaking

Reasons for High Power Consumption of Electric Arc Furnace Steelmaking

The reasons for the high power consumption of electric arc furnace steelmaking are rough as follows.

Raw Material Conditions

For the scrap steel used in electric furnace steelmaking, since the raw materials are required to use light and thin materials, briquettes, etc., it is often easy to cause high material feed and thermal shutdown, resulting in large heat loss. 

In the case of insufficient charging once, a second feeding is required. In some cases, there have been three feedings, which also increases the heat loss. Each additional charging (the average charging time is 5min) increases the power consumption by about 7-12KWh/T. 

In addition, it is found that C and P are relatively high after the raw materials are purified. 

After entering the oxidation period, the removal of C and P will require a longer time and higher energy consumption.

Operator Skills

The power consumption during the melting period accounts for 60%-70% of the total power consumption, and the power is mainly wasted after the chemical cleaning. energy.

Objective Conditions

During the smelting process, due to the shortage of electric power, the phenomenon of power outage occurs suddenly. After a long time, the molten steel cools and solidifies and needs to be remelted. This process wastes a lot of electric energy.

Other Accidents

If the operator does not operate properly, the electrode will be broken, and a lot of heat will be lost in the process of processing the electrode. 

When the reduction sample is taken in the reduction period, it is found that the composition is unqualified, and the secondary oxidation must be carried out, which will also waste a lot of money. thermal energy. 

During the smelting process, the coal-oxygen burner leaks water, which interrupts the fluxing; when the furnace wall is hung with materials, the furnace cover needs to be unscrewed for processing, which delays the smelting time to varying degrees and increases the heat loss.

The main products of Hani Metallurgy are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

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Scrap Steel is the Most Important Raw Material for Electric Arc furnace Smelting. What are its Substitutes?

Scrap Steel is the Most Important Raw Material for Electric Arc furnace Smelting. What are its Substitutes?

Scrap steel is the most important raw material for electric arc furnace smelting. The lack of scrap steel resources is one of the main reasons affecting the development of electric arc furnace steelmaking. Generally, there are three sources of scrap steel, i.e. self-produced scrap steel in the production process of steel enterprises, processing scrap steel in the production process of industrial and mining enterprises, social (production, life, national defense, etc.) scrap steel materials (including scrap steel, such as scrap automobiles, ships, steel bridge, and construction steel, etc.). Due to the progress of technology, the amount of steel scrap produced for the first two reasons decreases and the amount of social steel scrap increases continuously. As social waste steel is reused or contains more harmful elements such as Cu, Sn, As, and Pb which are difficult to remove, some harmful elements are enriched in the steel and the quality of waste steel is reduced. In order to solve the problems of shortage and quality reduction of scrap steel, scrap steel substitutes must be developed. At present, the main alternatives to scrap steel are molten iron (pig iron), direct reduction iron (DRI), decarburized granular iron, iron carbide, composite metal, etc.

Hot Metal (Pig Iron)

Modern electric arc furnaces widely use the carbon-oxygen gun, secondary combustion, oxygen burner technology, secondary combustion technology of furnace gas, etc. They absorb and integrate the enhanced smelting technology of the converter, especially the intensity of oxygen supply is greatly improved. The oxygen consumption is as high as about 30Nm3/t, and some even exceed 40Nm3/t, which is close to the oxygen consumption of the converter. Correspondingly, the amount of carbon distribution is increased and hot metal (pig iron) is the most effective method. When molten iron is added in large quantities, a large amount of chemical heat is generated due to the elements (mainly carbon) in the molten steel oxidized, and power supply is not available for some time during smelting, i.e. electric furnace converting smelting, and even all-iron hydroelectric furnace converting smelting mode appears in China. Electric arc furnaces in long-process iron and steel enterprises basically adopt the process of adding iron. In addition, some new blast furnaces of electric arc furnace process steel plants provide iron to solve the problems of shortage of waste steel resources and high production cost of electric arc furnace process. It is not advisable to build a new blast furnace to supply molten iron for electric arc furnaces from present and future development.

The Electric Arc Furnace Steelmaking Plus Hot Metal Technology has the Following Advantages:

1) For the non-flat pool smelting furnace type, the power supply can be optimized, the molten pool can be formed in advance, the power supply time of high power can be increased and the smelting cycle can be shortened;

2) Increase physical and chemical heat to improve thermal efficiency;

3) The content of harmful metal impurities in liquid steel can be diluted.

It is more suitable to control the molten iron ratio between 30% and 50%. When the oxygen supply intensity is low, the optimum molten iron ratio is about 30%. When the oxygen supply intensity is high, the molten iron ratio can reach 50%. Quantum electric arc furnace developed by Printer Company of Germany put forward that scrap steel should be used at least 50% in order to obtain sufficient preheating benefit. Electric arc furnaces have lost their superiority in sustainable development due to the converter smelting mode of all-iron hydroelectric furnaces.

Pig iron is mainly produced by casting molten iron (liquid iron) into ingots. The average usage of pig iron in electric arc furnaces worldwide is 5% to 10% of the total amount of metal.

Direct Reduced Iron

At present, 95% of direct reduced iron is used in electric arc furnace production. Direct reduction refers to the ironmaking process in which iron ore and iron-bearing oxides are reduced to metal products below the melting temperature, usually in a shaft furnace or rotary kiln. According to the product, it can be divided into sponge iron, metalized pellet, and hot-pressed block iron. The production methods include gas-based direct reduction and coal-based direct reduction.

Advantages of Using Direct Reducing Iron in Electric Arc Furnace Steelmaking:

1) Constant chemical composition and less harmful impurities, especially P, S, and N content, are conducive to the production of high value-added products;

2) Stable quality and low residual elements (e.g. copper less than 0.002%) can dilute harmful elements in waste steel well and increase the selection space of waste steel supply;

3) Sponge iron and hot-pressed lump iron can be continuously loaded into the furnace, with less power-off time and less heat loss, which is conducive to saving power, shortening the smelting time of the electric furnace, and increasing output.

4) It is beneficial for foam slag making and prolonging the service life of refractories and electrodes in the furnace.

At present, the amount of DRI used in electric arc furnaces abroad basically exceeds 50%, and some even use 100% DRI.

Decarburized Granular Iron

Decarburized granulated iron, fully known as decarburized granulated pig iron, is produced by quenching with high pressure water when the blast furnace is tapped to produce granulated pig iron of different grain sizes (3-10mm). Then it is loaded into rotary kiln, filled with a certain amount of mixed gas, heated to a certain temperature, and decarbonized by pig iron to obtain the raw material for electric arc furnace steelmaking.

The Use of Decarburized Granular Iron in Electric Arc Furnaces has the Following Advantages:

1) The content of gangue is 1%-3% lower than that of direct reducing iron, which can reduce power consumption by about 10%.

2) The content of S and P is low, and the impurity elements are also lower than that of direct reducing iron.

3) A small amount of FeO on the surface of granular iron is favorable for making foam slag in electric arc furnace.

Ferric Carbide

The basic principle of producing iron carbide is to feed iron ore into a fluidized bed reactor with a certain temperature and pressure and to react with preheated industrial gases (CO, CO2, CH4, H2, H2O steam) to form iron carbide. The reaction formula is:

3Fe2O3+ H2+ CH4= 2Fe3C+9H2O

3Fe2O3+H2+CH4= 2Fe3C+9H2O

The content of carbon in iron carbide is as high as 6%, which meets the requirements of high carbon distribution in modern electric arc furnace steelmaking and has the following advantages:

1) It is beneficial to the production of low nitrogen steel in electric furnace. When the electric arc furnace sprays iron carbide steel making, the nitrogen content in steel decreases from 0.007% to 0.003% - 0.004%;

2) It is advantageous to make foam slag. When using iron carbide as raw material, foam slag can be made well even if carbon powder is not sprayed into the molten pool.

3) It is beneficial to reduce the cost of desulfurization. Ferric carbide is clean with low content of sulfur and phosphorus. It is easy to reduce desulfurization cost per ton of steel for some flat material plants to replace hot metal in charge with partial iron carbide.

4) Benefit energy saving. Ferric carbide can be added on the top of the electric arc furnace without opening the furnace cover, thus reducing the temperature loss.

Composite Metal Material

Composite metal charge is a new type of charge successfully developed in Russia to replace steel-making pig iron, pellets, qualified billets and scrap steel. It is formed by cooling and consolidating a 15% - 25% filler (sinter or pellet) on a cast iron machine using molten iron and a certain mixing process. It consists mainly of steel-making pig iron and sealed iron oxide. The composition of the developed composite metal material is shown in Table 4.

When applied in electric arc furnace, foam slag can be formed at lower temperature (1150-1200 C). When the composite metal blocks are melted, when the temperature of iron oxide in the filler material which is "sealed up" is higher than 1100 C, chemical reaction with impurities in iron begins, and slag phase and CO are formed. At temperatures higher than 1200 C (lower than the melting temperature of scrap steel), a flowable foaming liquid slag has been formed in the electric arc furnace, which continuously releases carbon monoxide bubbles. Practice shows that the application of composite metal material can reduce oxygen consumption, power consumption and smelting time.

In conclusion, the addition of a part of scrap steel substitutes in electric arc furnace not only makes up for the shortcomings of low residual element scrap steel, but also improves the purity of steel. The slag material used in the electric arc furnace is basically similar to that used in the converter.

The main products of Hani Metallurgy are: 

electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanmetallurgy.com/

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What is the Gantry Mechanism in Electric Arc Furnace?

What is the Gantry Mechanism in Electric Arc Furnace?

At present, electric arc furnaces use furnace top charging. 

In the earliest days, the furnace top and the upper structure of the furnace such as the electrode lifting mechanism were installed on a gantry, like a gantry crane, which was driven out to the direction of the tapping slot, exposing the furnace, so that scrap steel could be added from the furnace top. The furnace body open type is that after the furnace top is raised, the furnace body mounted on the trolley is opened from the gantry frame and above the cradle, and opens towards the furnace door.

  The top swing type has been widely adopted now, and the main advantage is that the metal structure of the furnace is the lightest in weight. 

The top swing type can be divided into two types, namely floor type, and common platform type. 

① There is a vertical rotating shaft in the furnace top lifting and turning mechanism installed on the foundation, which can lift the entire top structure of the furnace top, and then the rotating shaft rotates to unscrew the furnace top. 

②The upper structure of the common platform furnace (electrode lifting and furnace roof lifting) is installed on the cantilever gantry. After the furnace roof is raised, the cantilever gantry rotates around the axis, and the wheels on the gantry can roll along the arc track on the platform. 

On small stoves, the lifting and rotating mechanism of the roof is mounted directly on the furnace shell. 

In this case, the furnace shell is subjected to heavy mechanical loads, and this part of the furnace shell has poor heat dissipation. 

The result is a tendency to deform, requiring special cooling and reinforcement. Both floor-standing and co-platform solutions have a wide range of applications. 

In contrast, the advantage of the floor type is that the electrode and the furnace top are not affected by the mechanical impact caused by the falling material during the top charging, and the problem lies in the conical column head on the upper end of the rotating shaft that lifts the upper structure of the furnace, which needs to be connected with the upper structure. Match the corresponding holes in the shelf.

 In some cases, the shaft may be caught by the hole and cannot be dropped. When the furnace is rotating, the upper structure of the furnace must fit well with the furnace shell and must not move. 

In principle, the furnace roof can also be turned away in the direction of the furnace door, but it is not suitable from a safety point of view. 

Therefore, in most furnaces, the top of the furnace is turned about 70° to the tapping direction. 'Before the furnace top is turned away, it should be lifted upwards, 300~500mm away from the upper edge of the furnace shell.

On floor-mounted furnaces, the upper structure and the furnace roof are hard-connected and lift upwards together. 

On the furnace with the common platform structure, there is another furnace roof lifting mechanism on the door frame, and the furnace roof is suspended by a chain. 

The ease of roof replacement must of course also be considered when designing a furnace. Before the top of the furnace is turned away, the electrode needs to be raised so that its lower edge exceeds the upper edge of the furnace shell. 

When the furnace top is turned to one side, the center of gravity of the furnace will move to this side. In order to prevent the electric furnace from tilting to the side, the furnace body and the column of the workshop should be locked before charging.

In order to prevent sideways tipping, the distance between the arc-shaped plates of the cradle of some large furnaces is wide, or the cradle is composed of three arc-shaped plates.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

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Electric Furnaces with the Largest Production Capacity in the World

Electric Furnaces with the Largest Production Capacity in the World

The Algerian project under construction of China Steel Equipment is the largest comprehensive steel mill for ironmaking, steelmaking and rolling under overseas general contracting of Chinese enterprises. Among them, the annual production of DRI is 3 million tons, that of steel-making and continuous casting is 2.15 million tons, and that of bar is 2 million tons. China Steel Equipment Centralized Advantage Team has overcome the difficulties of overseas construction and tight construction period, produced qualified products in the shortest time, achieved a number of world first, and created good economic benefits, which has been praised by the owner.

One 240t electric furnace is the main process equipment in the steel-making and continuous casting workshop of SISCO Algeria Project. 1 240t ladle furnace; 1 set of raw material treatment system (MHS), the main raw material for steel making is 100% H/CDRI; 1 8-Strands Continuous Caster with 180 Casting Sections × 180mm-200 × 200mm, fixed length 9-12m, arc radius R=10.25m. This project EAF is currently the world's largest electric furnace per unit capacity.

This project adopts the process flow of direct reducing iron-steelmaking-continuous casting-rolling steel, and adopts the process of direct reducing iron hot discharging, hot conveying and hot charging electric furnace in gas-based shaft furnace. Using DRI as raw material, 700-900 C direct reduction iron is heated to the high-level bin of electric furnace. It enters the electric furnace steel-making by continuous feeding. The power consumption per ton of steel can be reduced by 150kWh, the melting time can be shortened by 17%, and the capacity of electric furnace steel can be increased by more than 17%. The comprehensive cost of power consumption for high-speed bar rolling with 2-slitting is reduced by more than 15% compared with traditional non-slitting high-speed bar rolling.

The main products of Hani Metallurgy are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanmetallurgy.com/

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Production Methods of Ferroalloys

Production Methods of Ferroalloys

There are many production methods of ferroalloys, most of which are produced by pyrometallurgy.

The production methods of ferroalloys are mainly divided into the following according to the smelting equipment, operation methods, and heat sources used:

I. Classification by Production Equipment

According to production equipment, it can be divided into blast furnace method, electric furnace method, out-of-furnace method, converter method, and vacuum resistance furnace method.

1. Electric Furnace Method. 

The electric furnace is the main method to produce ferroalloys, and its output accounts for about 80% of all ferroalloys.

2. Blast Furnace Method. 

The main equipment used in the blast furnace method is the blast furnace. The blast furnace method is the earliest ferroalloy production method. The blast furnace process has the advantages of high labor productivity and low cost. However, in view of the limitation of the temperature of the blast furnace hearth and the fact that the metal is fully saturated with carbon during the smelting process of the blast furnace, the blast furnace method is generally only used to produce ferroalloys with reducing elements and low-grade ferroalloys.

3. Off-furnace Method (Metal Thermal Method). 

The out-of-furnace method uses silicon, aluminum, or aluminum-magnesium alloy as a reducing agents and relies on chemical heat generated by reduction reaction to smelt. The main equipment used is the cylindrical furnace. Raw materials used include concentrate, reducing agent, flux, heating agent, steel chips, iron ore, etc.

4. Oxygen Converter Method. 

The main equipment used in the oxygen converter method is the converter. According to the oxygen supply mode, there are top-bottom, side-blowing, and top-bottom composite blowing methods. The raw materials used are liquid high-carbon ferroalloy, pure oxygen, coolant and slag-making materials, etc. The liquid high-carbon ferroalloy is added to the converter, and the high-pressure oxygen is blown into the furnace through the oxygen gun. The production is carried out intermittently depending on the heat from the oxidation reaction.

5. Vacuum Resistance Furnace Method. 

Vacuum resistance furnace is used to produce micro-carbon ferrochromium, ferrochromium nitride, and ferromanganese nitride products with very low carbon content. The main equipment is vacuum resistance furnace.

II. Classification by Heat Source

According to different heat sources, it can be divided into carbon thermal method, electrothermal method, electro-silicon thermal method, and metal thermal method.

1. Carbon Thermal Method. 

The heat source of the carbothermal smelting process is mainly the combustion heat of coke. Coke is used as reducing agent to reduce oxides in ores. The production by this method is carried out continuously in the blast furnace.

2. Electrothermal Method. 

Electric energy is the main heat source in the electrothermal smelting process. The oxides in ores are reduced with carbon reducing agent and the continuous operation process is adopted in the reduction furnace.

3. Electro-silicothermal Method. 

Electric energy is the main heat source in the smelting process of electro-silicon thermal process, while the rest is the heat released when silicon is oxidized. Silicon (ferrosilicon, manganese-silicon alloy and silicon-chromium alloy), as reducing agent, is used to reduce oxides in ores. Production is an intermittent operation in a refining furnace.

4. Metal Thermal Method. 

The heat source of the metallurgical process is mainly the heat emitted by metal reducing agents such as silicon and aluminium when reducing oxides in concentrates. The production is carried out in a tubular furnace in an intermittent manner.

III. Classification by Operation Method and Process

According to the characteristics of production and operation process, it can be divided into flux method, solvent-free method, slag-free method, slag-free method and continuous and intermittent smelting method.

1. Flux Method. 

Ferrous alloy smelting by flux method uses carbon material, silicon or other metal as reducing agent. Slag-making material should be added to adjust composition and properties of slag during production. If alkaline slag is used, high carbon ferromanganese can be produced.

2. Flux-free Method. 

In general, carbon material is used as reducing agent in the production of ferroalloys without flux. Slag composition and properties are not regulated by adding slag-making material in the production. If high quality manganese ore is used, acid slag is used to produce high carbon ferromanganese and low phosphorus and rich manganese slag is obtained.

3. Sludge-free Process. 

Sludge-free smelting of ferrous alloys is a continuous smelting process in a reduction furnace using carbon reducing agent, silica or remanufactured alloys as raw materials. The products include ferrosilicon, industrial silicon, silicon-chromium alloys, etc.

4. Sludge Method. 

Slag smelting of ferroalloys is to produce ferroalloys in reducing or refining electric furnaces by selecting reasonable slag type system and alkalinity. The slag-iron ratio is affected by different varieties and corresponding raw material conditions. Products include high carbon ferromanganese, manganese silicon alloy, high carbon ferrochromium, etc.

5. Continuous Smelting. 

Continuous smelting method is to continuously charge the furnace according to the falling charge level at the furnace mouth, while the alloy and slag accumulated in the furnace pool are discharged regularly. With submerged arc reduction smelting, the operating power is almost equalized and stable.

6. Intermittent Smelting. 

Intermittent smelting is a process in which charge is concentrated or batched into the furnace. It is generally divided into two stages: melting and refining, in which the electrode is buried in the furnace charge.

The main products of Hani Metallurgy are: electric arc furnace, LF ladle refining furnace, electro slag furnace, submerged arc furnace, metallurgical electric furnace short network system, submerged arc furnace short network system, water-cooled cable, bare copper stranded wire air-cooled cable, rotatable water-cooled cable , high-current copper tube busbar, insulated copper tube busbar, copper-steel composite conductive cross arm, water-cooled compensator, water-cooled furnace cover, water-cooled furnace shell, water-cooled furnace wall, fully enclosed combined handle, direct-cooled forged copper tile, electrode Chuck, electrode holding ring, pressure ring, hydraulic brake, collector ring, conductive element, ladle, tundish, ladle car, cross flat car, steel pouring car, furnace door water-cooled carbon-oxygen gun, furnace wall speed oxygen collector Electric furnace accessories such as guns, ladles, scrap steel tanks, ladle roasters, ladle gantry hooks, water-cooled cable jacket hoses, jacket protection rings and insulating materials.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

Free send inquiries to stella@hanrm.com  or inquiry99@hanmetallurgy.com if any needs.

Email: stella@hanrm.com Or stellarollingmill@gmail.com                              inquiry99@hanmetallurgy.com

Whatsapp/Wechat:+8615877652925

Website:  https://www.hanmetallurgy.com/

                https://www.hanrm.com