Method for reducing smelting power consumption of submerged arc furnace

Abstract

The invention discloses a method for reducing smelting power consumption of a submerged arc furnace, which comprises the following steps of: batching pellets, preparing cured pellets, feeding and preheating the pellets, smelting in the submerged arc furnace and the like, and is characterized in that a roasting link of carbonate auxiliary materials during smelting in the submerged arc furnace is transferred to a preparation link of pellets from the inside of the submerged arc furnace; when the roasting furnace is used for heating and firing the pellets, a byproduct coal gas generated by smelting of the submerged arc furnace is used, so that not only can the tail gas resource of the submerged arc furnace be fully utilized for heating and temperature rise, but also other energy consumption is not additionally increased, and the power consumption of iron alloy smelting is effectively reduced. In addition, the added coke powder generates a pre-reduction effect on the chromium ore pellets, and then the power consumption and the production cost of iron alloy smelting are greatly reduced in the mode that clinker entering the furnace and furnace material preheating are combined.

Description

Technical Field

[0001] The invention relates to the technical field of ferroalloy smelting, and in particular to a method for reducing power consumption in smelting in a submerged arc furnace. Background Art

[0002] Ferroalloy refers to a product that is added to molten iron as a deoxidizer or element additive during steelmaking to give the steel certain characteristics or meet certain requirements. The melting point of the main elements of ferroalloys is generally high, and its oxides are difficult to reduce, so it is difficult to smelt pure metals. Ferroalloys are easier to reduce and smelt with iron, so ferroalloys are often used in steelmaking. The iron content is not only harmless, but also beneficial because it is easy to melt in molten steel.

[0003] However, ferroalloy smelting mainly relies on electric heating, which consumes a lot of electricity. How to reduce the ferroalloy production cost by reducing the smelting power consumption has become an effective means to improve the competitiveness of enterprises. Usually, when smelting in a submerged arc furnace, the auxiliary materials (dolomite, magnesite, lime) and the original ore are directly put into the furnace, which is called raw material smelting, while the chromium ore and a variety of auxiliary materials are first mixed evenly, and then roasted at high temperature to make artificial block ore into the furnace, which is called clinker smelting. The process of heating the pellets and the charge with high-temperature flue gas is called the charge preheating process. Since the roasting treatment of carbonate auxiliary materials such as limestone, magnesite and dolomite added to the pellets is a highly endothermic decomposition process, it is also the process link that consumes the most heat in the charge maturation process. Therefore, it is urgent to optimize the preparation process of raw and auxiliary materials for pellets to reduce the energy consumption of submerged arc furnace smelting. Summary of the invention

[0004] The invention provides a method for reducing the power consumption of smelting in an ore-bearing furnace, aiming at reducing the power consumption of smelting in an ore-bearing furnace by adjusting the preparation and preheating process of raw and auxiliary materials in pelletized ore, thereby reducing the production cost of ferroalloy.

[0005] To achieve its purpose, the present invention adopts the following technical solution: (1) preparing pellets; mixing and grinding 86.7-95.4% of chromium ore powder, 1.9-2.6% of coke powder, 0.7-1.0% of bentonite, 3.2-5.8% of dolomite, 0-3.6% of magnesite and 0-2.1% of limestone powder according to mass percentage, and forming pellets to obtain pellets; (2) Screening; the pellets obtained in step (1) are screened to obtain qualified pellets and unqualified pellets, the qualified pellets are sent to a roasting furnace, dried, roasted and consolidated to obtain mature pellets; the unqualified pellets are returned to step (1) to be re-pelletized; (3) Loading and preheating: According to the mass percentage, 70-73% of the slaking pellets obtained in step (2), 18-21% of coke, 3-7% of silica and 2-5% of the recycled slag are added to the preheating kiln for preheating to obtain 100% raw materials and auxiliary materials; (4) Smelting in an ore-fired furnace; adding 100% of the raw and auxiliary materials preheated in step (3) into an ore-fired furnace for smelting to obtain a ferrochrome alloy.

[0006] Furthermore, in step (1), a ball mill is used for mixing and grinding, and balls are formed when the proportion of grinding particle size ≤ 200 mesh reaches more than 78%.

[0007] Furthermore, in step (1), the pelletizing is performed using a pelletizing machine.

[0008] Furthermore, a roller screen is used for screening in step (2).

[0009] Furthermore, the particle size of the qualified pellets in step (2) is 12-16 mm.

[0010] Furthermore, the strength of the qualified pellets in step (2) is ≥1800N.

[0011] Furthermore, the roasting furnace in step (2) is a steel belt roasting furnace.

[0012] Furthermore, in step (2), the calcination temperature of the calcination furnace is 1220-1280° C., and the calcination time is 30-50 min.

[0013] Furthermore, in step (3), the preheating temperature of the preheating kiln is 450-550°C, and the preheating time is 3-4h.

[0014] The beneficial effects of the present invention are as follows: 1. This method transfers the roasting process of carbonate auxiliary materials from the ore-heating furnace to the preparation process of pellets, and the roasting furnace uses the byproduct gas produced by the ore-heating furnace to heat and burn the pellets. It can not only make full use of the tail gas resources of the ore-heating furnace for heating and temperature increase, but also does not increase other energy consumption, effectively reducing the power consumption of ferroalloy smelting. In addition, the added coke powder has a pre-reduction effect on the chrome ore pellets, which can effectively improve the reaction activity of the pellets and improve their metallurgical effects.

[0015] 2. This method loads the prepared mature pellets to the preheating kiln on the top of the furnace, and also uses the by-product gas produced by the smelting in the smelting furnace to heat the mature pellets. The preheating temperature is 450-550°C. The combination of charge aging + charge preheating is adopted to reduce the power consumption and production cost of ferroalloy smelting.

[0016] 3. In the pellet preparation process of the present invention, the sulfur brought into the ore powder and coke powder can react with the alkaline substances in the auxiliary materials (dolomite, magnesite, limestone powder) after roasting, thereby effectively reducing the emission of sulfur dioxide in the roasting furnace exhaust gas, saving energy and protecting the environment. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be further described below in conjunction with the examples, but this description does not constitute an improper limitation on the technical solution of the present invention. The amounts of each substance added in the following examples are all in mass percentage.

[0018] Example 1 A method for reducing electric power consumption of smelting in a submerged arc furnace comprises the following steps: (1) Preparing pellets; 89.88% chromium ore powder, 2.1% coke powder, 0.82% bentonite, 4.1% dolomite, 2.0% magnesite and 1.1% limestone powder are first sent to a ball mill for mixing and grinding, and after the mixing, the grinding particle size of the mixture is ≤200 mesh and the proportion of the mixed material reaching the standard is 83%, and then sent to a ball making machine for ball making to obtain pellets; (2) Screening; the pellets obtained in step (1) are sent to a roller screen for screening to obtain qualified pellets and unqualified pellets, wherein the qualified pellets have a particle size of 12-16 mm and a compliance rate of 86%, and the strength of the qualified pellets is 2170N; the qualified pellets are sent to a steel belt roasting furnace at a roasting temperature of 1250°C for roasting for 30 minutes, and the matured pellets are obtained after drying, roasting and consolidation; the unqualified pellets are returned to the pelletizing machine in step (1) for re-pelletizing; (3) Loading and preheating: 72.4% of the slaking pellets obtained in step (2) are added to a preheating kiln at a temperature of 478° C. and preheated for 4 hours to obtain 100% raw materials and auxiliary materials; (4) Smelting in an ore-fired furnace; adding 100% of the raw and auxiliary materials preheated in step (3) into an ore-fired furnace for smelting to obtain a ferrochrome alloy.

[0019] After testing, it was found that the final power consumption of the smelting ton of iron in the ore-fired furnace using this method was 3215 kwh / t.

[0020] Example 2 A method for reducing electric power consumption of smelting in a submerged arc furnace comprises the following steps: (1) Preparing pellets; 88.15% chromium ore powder, 2.5% coke powder, 0.95% bentonite, 5.8% dolomite and 2.6% magnesite are first sent to a ball mill for mixing and grinding, and after the mixing, the grinding particle size of the mixture is ≤200 mesh and the proportion of the qualified rate is 83%, and then sent to a ball making machine for ball making to obtain pellets; (2) Screening; the pellets obtained in step (1) are sent to a roller screen for screening to obtain qualified pellets and unqualified pellets, wherein the qualified pellets have a particle size of 12-16 mm and a compliance rate of 84%, and the strength of the qualified pellets is 2030N; the qualified pellets are sent to a steel belt roasting furnace at a roasting temperature of 1280°C and roasted for 50 minutes, and the matured pellets are obtained after drying, roasting and consolidation; the unqualified pellets are returned to the pelletizing machine in step (1) for re-pelletizing; (3) Loading and preheating: 71.8% of the slaking pellets obtained in step (2) are added to a preheating kiln at a temperature of 550° C. and preheated for 4 hours to obtain 100% raw materials and auxiliary materials; (4) Smelting in an ore-fired furnace; adding 100% of the raw and auxiliary materials preheated in step (3) into an ore-fired furnace for smelting to obtain a ferrochrome alloy.

[0021] After testing, it was found that the final power consumption of the smelting ton of iron in the ore-fired furnace using this method was 3187 kwh / t.

[0022] Example 3 A method for reducing electric power consumption of smelting in a submerged arc furnace comprises the following steps: (1) Preparing pellets; 90.46% chromium ore powder, 2.0% coke powder, 0.74% bentonite, 3.6% dolomite, 1.5% magnesite and 1.7% limestone powder are first sent to a ball mill for mixing and grinding, and after the mixing, the grinding particle size of the mixture is ≤200 mesh and the proportion of the mixed material reaching the standard rate is 81%, and then sent to a ball making machine for ball making to obtain pellets; (2) Screening; the pellets obtained in step (1) are sent to a roller screen for screening to obtain qualified pellets and unqualified pellets, wherein the qualified pellets have a particle size of 12-16 mm and a compliance rate of 82%, and the strength of the qualified pellets is 2232N; the qualified pellets are sent to a steel belt roasting furnace at a roasting temperature of 1260°C and roasted for 47 minutes, and the matured pellets are obtained after drying, roasting and consolidation; the unqualified pellets are returned to the pelletizing machine in step (1) for re-pelletizing; (3) Loading and preheating: 72.2% of the slaking pellets obtained in step (2) are added to a preheating kiln at a temperature of 525° C. and preheated for 3 hours to obtain 100% raw and auxiliary materials; (4) Smelting in an ore-fired furnace; adding 100% of the raw and auxiliary materials preheated in step (3) into an ore-fired furnace for smelting to obtain a ferrochrome alloy.

[0023] After testing, it was found that the final power consumption of the smelting ton of iron in the ore-fired furnace using this method was 3164 kwh / t.

[0024] Comparative Example 1 According to the traditional smelting method, 96.3% chromium ore powder, 2.3% coke powder and 1.4% bentonite required for smelting are sent to a ball mill for mixing and grinding. After the grinding particle size reaches 78%, it is sent to a ball making machine for ball making. After screening by a roller screen, qualified pellets with a particle size of 12-16 mm are directly sent to a steel belt roasting furnace for roasting at a roasting temperature of 1280°C to obtain chromium ore pellets without adding auxiliary materials such as lime and magnesite. The particle size of the pellets is 12-16 mm and the standard rate is 84%, and the pellet strength is 2230N. 0% of auxiliary materials are added to the chrome ore pellets entering the furnace, and the prepared 66.2% chrome ore pellets, 16.9% coke, 7.8% silica, 2.1% magnesite, 4.1% dolomite, 0.6% limestone and 2.3% returned slag are directly added to the submerged arc furnace for smelting to obtain ferrochrome without being preheated in a preheating kiln.

[0025] After testing, it was found that the actual power consumption of the smelting ton of iron in the submerged arc furnace using traditional smelting methods was 3628kwh / t.

[0026] Combining Examples 1-3 and Comparative Example 1, it can be seen that the method moves the roasting and maturing process of carbonate raw materials from the ore-fired furnace to the pellet preparation process, and uses the by-product gas of the ore-fired furnace for firing. The pre-molded pellets and other raw materials required for smelting, such as coke, silica, and recycled slag, are all preheated in the preheating kiln on the top of the ore-fired furnace before being added to the furnace for smelting, that is, a combination of furnace charge maturation and furnace charge preheating is adopted, thereby greatly reducing the power consumption of ore-fired furnace smelting. In addition, the sulfur brought in by the ore powder and coke powder is roasted and reacted with the alkaline auxiliary materials together, which can also effectively reduce the emission of sulfur dioxide in the tail gas of the roasting furnace in the pellet preparation process.

Claims

1. A method for reducing power consumption of smelting in a submerged arc furnace, characterized in that: The following steps are involved: (1) preparing pellets; mixing and grinding 86.7-95.4% of chromium ore powder, 1.9-2.6% of coke powder, 0.7-1.0% of bentonite, 3.2-5.8% of dolomite, 0-3.6% of magnesite and 0-2.1% of limestone powder according to mass percentage, and forming pellets to obtain pellets; (2) Screening; the pellets obtained in step (1) are screened to obtain qualified pellets and unqualified pellets, the qualified pellets are sent to a roasting furnace, dried, roasted and consolidated to obtain mature pellets; the unqualified pellets are returned to step (1) to be re-pelletized; (3) Loading and preheating: According to the mass percentage, 70-73% of the slaking pellets obtained in step (2), 18-21% of coke, 3-7% of silica and 2-5% of the recycled slag are added to the preheating kiln for preheating to obtain 100% raw materials and auxiliary materials; (4) Smelting in an ore-fired furnace; adding 100% of the raw and auxiliary materials preheated in step (3) into an ore-fired furnace for smelting to obtain a ferrochrome alloy.

2. A method for reducing power consumption in a submerged arc furnace according to claim 1, characterized in that: In step (1), a ball mill is used for mixing and grinding, and balls are formed when the proportion of grinding particle size ≤ 200 mesh reaches more than 78%.

3. A method for reducing power consumption in a submerged arc furnace according to claim 2, characterized in that: In step (1), a pelletizing machine is used for pelletizing.

4. A method for reducing power consumption in a submerged arc furnace according to claim 3, characterized in that: In step (2), a roller screen is used for screening.

5. A method for reducing electric power consumption in a submerged arc furnace according to claim 4, characterized in that: The particle size of the qualified pellets in step (2) is 12-16 mm.

6. A method for reducing power consumption in a submerged arc furnace according to claim 5, characterized in that: The strength of the qualified pellets in step (2) is ≥1800N.

7. A method for reducing power consumption in a submerged arc furnace according to claim 6, characterized in that: The roasting furnace in step (2) is a steel belt roasting furnace.

8. A method for reducing electric power consumption in a submerged arc furnace according to claim 7, characterized in that: The calcination temperature of the calcination furnace in step (2) is 1220-1280°C, and the calcination time is 30-50 minutes.

9. A method for reducing power consumption in a submerged arc furnace according to any one of claims 1 to 8, characterized in that: In step (3), the preheating temperature is 450-550°C and the preheating time is 3-4h.