1. What is the importance of using oxygen in electric furnaces?

Chemical reaction heat accounts for a considerable proportion of the energy input of electric furnaces, reaching 20%-30%; especially after the electric furnace uses molten iron, the proportion of chemical heat reaches 40%-50%, which is a modern electric arc furnace steelmaking process. Features: Oxygen technology is a concentrated expression of modern high-tech. The combination of power supply and oxygen supply is an important means for electric furnaces to improve production rhythm, save energy and reduce consumption.

2. Under oxygen blowing conditions, what is the theoretical calorific value generated when each element in the molten pool oxidizes 1k8?

Under oxygen blowing conditions, the theoretical calorific value generated when each element in the molten pool is oxidized by 1kg is shown in the following table:

Element Product Heat of reaction Relative cost① (reference value)

kJ/kg Kw·h/kg

Al Al2O3 30.995 8.61 3.7

Si SiO2 32.157 8.93 3.2

Mn MnO 6.992 1.94 6.0

Fe FeO 4.775 1.33 1.8

C CO 9.159 2.54 0.5～0.6

C CO2 32.761 9.10 0.3～0.6

① Assume that the electricity price per kw·h is 1.

3. What is the mechanical device of the electric furnace door gun?

Oxygen blowing in electric furnace steelmaking is one of the important means to strengthen electric furnace smelting. The use of steel pipe inserted into the molten pool to blow oxygen is the most commonly used method. In order to make full use of the chemical energy in the furnace, the amount of oxygen used per ton of steel has gradually increased in recent years; at the same time, taking into account the poor working conditions, unsafe, and unstable oxygen blowing efficiency of manual oxygen blowing, the electric furnace door gun mechanical device has been developed. Such as the self-consumable oxygen lance device developed by the German BSE company and the water-cooled oxygen lance device developed by the German Fuchs, the American Berry, and the American Combustion Company.

Since the self-consumable oxygen lance consumes a large amount of oxygen blowing pipes, new electric furnaces have been installed less frequently. The function of the furnace door gun device is to blow oxygen to assist melting and refining, and to blow carbon powder into the molten pool to create foam slag.

The use effect of the door gun of the integrated electric furnace is: improve the efficiency of oxygen blowing, shorten the smelting time by 5-15 minutes; save the oxygen blowing pipe by 80% to 90%, and reduce the cost by 15-30 yuan per ton of steel; improve the working conditions of workers and replace labor Blow 90% of oxygen.

4. What are the components of the electric furnace door gun device?

The furnace door gun is composed of the furnace door water-cooled oxygen lance and the furnace door gun; the mechanical system is composed of the boom rotation, the gun body rotation, the gun body swing and the lifting system; the oxygen lance equipped on the furnace door gun device can boost the melting during the melting period , The oxidation period can be decarburized and refined. The furnace door gun device is equipped with a carbon gun, which is mainly used to make foam slag.

5. What is a consumable electric furnace door carbon oxygen lance?

At present, the door gun of the electric furnace basically adopts a water-cooled design. As the water-cooled oxygen lance also has some shortcomings, Baden Steel has researched and applied a self-consumable furnace door lance, which has the function of injecting lime and injecting carbon powder to make foam slag.

Compared with the water-cooled oxygen lance, it has the advantages of large operating safety factor, large injection angle, and it can directly cut scrap steel. The disadvantage is that the cost of the oxygen blowing tube is high and the oxygen cannot be blown continuously.

6. What is oxy-combustion booster technology?

With the development of electric furnace steelmaking at home and abroad in the direction of large-scale and ultra-high power, large-scale electric furnaces and ultra-high-power electric furnace manufacturers have studied various smelting methods and adopted different enhanced smelting technology in order to improve production efficiency and reduce power consumption. And equipment. The electricity consumption of electric furnace smelting depends to a large extent on the time of the melting period, that is, it depends on the speed of melting of the scrap. The thermal characteristics of electric furnace steelmaking during the melting of steel materials make the furnace have three cold zones, especially after the use of high-power and ultra-high-power power supply, the influence of the cold zone is particularly prominent. Statistics show that the electricity consumption in the melting period accounts for 70% of the electricity consumption in the entire smelting cycle. For this reason, auxiliary energy fluxing technology is generally introduced at home and abroad to eliminate three cold zones, shorten the smelting time, and achieve the purpose of improving the production efficiency of electric furnaces and reducing the power consumption of smelting. According to reports, in the 1980s, 50% of electric arc furnaces in Europe and 80% of electric arc furnaces in Japan used oxygen-combustion smelting assisted steelmaking. In the 1990s, almost 100% of the large-scale electric furnaces newly put into production abroad adopted this technology, and the fuels used were generally natural gas and light diesel. In the 1980s, the domestic coal-to-oil fluxing technology was developed, and obvious results have been achieved on electric furnaces below 30t. Due to the low calorific value of coal, this technology is not suitable for large-scale electric furnaces, especially high-efficiency and fast-paced requirements for high-power and ultra-high-power electric furnaces. Therefore, at present, oil or gas is mainly used as a fluxing fuel for injection in China.

7. What are the oxygen-combustion booster fuels?

The fuel used in the burner has three types: solid, liquid and gas. Light diesel oil is currently more inclined to be used in liquid fuels, because it is convenient to use, clean, and easy to maintain, making it the first-choice auxiliary fuel. The main gas fuel is natural gas, and my country's current resources are limited and used less; while gas fuel such as coal gas is not used because of its low calorific value and large amount of exhaust gas. my country has developed solid fuel coal-oxygen technology in combination with resource conditions, but the thermal efficiency of injection is low, and the investment is large. Among them, the preparation, storage, transportation of pulverized coal and the removal and separation of sulfur and ash residues in combustion products And so on is more cumbersome.

8. What factors depend on the efficiency of the burner?

Electric furnaces produce steel by generating heat through electrode arcing. The steel material is slowly melted from the center of the electrode to the surrounding area, resulting in greater heat loss and longer melting time. Oxygen burner, also known as oxygen burner, is arranged on the furnace wall in the cold zone of the electric furnace. It relies on the reasonable matching of burner and electric arc power supply to achieve balanced melting of scrap steel. The use efficiency of the burner depends on:

(1) Scrap steel temperature and heating area. If the scrap steel temperature is high at the initial stage of melting and the heating area is large, the burner efficiency can reach 80%;

(2) Determine the appropriate oxygen-oil ratio at different stages. When the scrap is close to melting, the burner oil volume should be reduced. In addition to oil, the fuel used in the burner includes natural gas or pulverized coal. Oxygen burners are also used in the flue to preheat scrap steel, but environmental protection should be paid attention to.

9. What is an electric furnace cluster jet oxygen lance?

CoherentJet oxygen lance technology is a new type of oxygen injection technology, which can solve the shortcomings of traditional supersonic oxygen lances of short injection distance, small impact force, and low oxygen utilization rate. It mainly uses the envelope formed by the combustion of the medium to protect the main body. Oxygen flow. The exit Mach number of the cluster jet oxygen lance can reach about 2.0, and the jet distance in the technical state can reach 1.2-2.1m, and it can be directly installed on the furnace wall to achieve functions such as fluxing and decarburization.

10. What are the main benefits of the cluster jet oxygen lance applied to electric furnaces?

The main benefits of the cluster jet oxygen lance applied to electric furnaces are reflected in:

(1) It has multiple functions such as oxygen blowing, combustion and post-combustion, and realizes centralized automatic control, thereby reducing the cost of facilities and the process cost of separate operations for each system.

(2) Due to the setting of the combustion function, the scrap steel can be preheated and melted in advance, thereby reducing power consumption (at least 20kW·h per ton of steel).

(3) Due to the strong impact and stirring ability, the utilization rate of oxygen and sprayed carbon powder is increased, thereby reducing the consumption of oxygen and carbon powder.

(4) Due to the setting of the secondary combustion function, the CO combustion in the furnace is fully utilized to increase the furnace temperature, thereby reducing energy consumption.

(5) Due to the reduction of splashing, the iron content in the slag is reduced, the metal recovery rate is improved and the maintenance cost of the furnace body is reduced.

11. How to control the operation of the cluster oxygen lance?

The cluster oxygen lance cuts and melts the scrap more quickly, can blow oxygen into the molten pool more effectively, and greatly improve the utilization rate of oxygen. First turn on the auxiliary oxygen system, turn on the compressed air system after a certain time delay, and then turn on the fuel (or gas) system after a certain time delay, and at the same time supply the main oxygen. When shutting down, the fuel and main oxygen should be turned off first, and then the compressed air and secondary oxygen should be turned off in sequence. Automatic alarm processing to prevent serious safety accidents caused by oil pressure exceeding compressed air pressure.

12. What is the metallurgical principle of secondary combustion?

The secondary combustion can be divided into the following processes:

2[C]+{O2}=2{CO}

Among them, C comes from carbon powder, fuel, pig iron or molten steel, and 02 comes from oxygen, air, slag or molten steel.　

2[C]+{O2}=2{CO}

Among them, theoretically comes from the aforementioned dedicated oxygen source for secondary combustion, but in actual situations there is no strict source limit, and the two are carried out at the same time.

13. What is the secondary combustion rate?

The index to evaluate the progress of the reaction is called the secondary combustion rate, which is expressed by the following formula:

PCR=%CO2/ (%CO+%CO2)×100%　　　 (4.3)

In the formula, PCR is the rate of secondary combustion; %CO and %CO2 are the volume percentages of CO and CO2 in the combustion products, respectively.

14. What is an EBT oxygen lance?

In order to achieve slag-free tapping, modern electric arc furnaces all use eccentric bottom tapping (EBT) technology. This not only reduces the amount of slag in the tapping process, but also shortens the smelting cycle and reduces the temperature drop during tapping. But at the same time, the EBT zone has become one of the cold zones of UHP-EAF, resulting in a slower melting rate of scrap steel in this zone, and a large difference between the composition of the molten pool and the central zone.

In order to solve the problem of the EBT cold zone, an EBT oxygen lance can be installed above the side of the eccentric furnace to blow oxygen to the zone. The EBT oxygen lance can promote the melting of the scrap steel in this area, and after the molten pool appears, it can increase the temperature of the molten pool in the EBT zone, uniform the composition of the molten pool, and realize the reburning of CO.

In practical applications, the use of EBT oxygen lance completely solves the problems of the scrap steel in the EBT area that has not melted during tapping and the tapping opening cannot be opened. At the same time, the temperature and composition of the EBT area during tapping and the temperature of the furnace door area And the error of the composition is only 0.5% to 1.0%.

The impact force of the EBT oxygen lance needs to be considered in the design. Due to the shallow molten pool in the EBT zone, the penetration depth of the oxygen jet of the EBT oxygen lance cannot exceed 2/3 of the depth of the molten pool in the EBT zone in design, and the tapping area should be avoided at the same time. Taking into account the attenuation of the oxygen jet, a telescopic drive EBT oxygen lance is used, and the position of the lance is adjusted according to the smelting situation.