Method for increasing calorific value of converter gas

Abstract

The invention provides a method for increasing the calorific value of converter gas. The method comprises the following steps: S1) setting the distance between a movable smoke hood of a converter and a furnace mouth to be 50-100 mm from the lower limit; in the smelting process of the converter, after addition of scrap steel and molten iron is finished, an oxygen lance descends to start oxygen ignition for 20-30 s, then a movable smoke hood of the converter is adjusted to the lower limit, and the included angle of the oxygen lance ranges from 13 degrees to 15 degrees; (S2) in the oxygen supply blowing process of the converter, after ignition is normal, the oxygen pressure is adjusted to 0.80-0.95 MPa; the rotating speed of the dust removal fan is controlled by stages to ensure that the furnace mouth is at micro-positive pressure; s3, after converter smelting is completed, the hot slag is reserved in the converter, and lime is added in batches according to the slag remaining amount and the silicon content of molten iron. By adopting the measures in the converter process, the amount of CO2 generated by combustion of CO in converter gas is reduced, and the calorific value of the gas is increased.

Description

Technical Field

[0001] The invention relates to the technical field of converter steelmaking, and in particular to a method for improving the calorific value of converter coal gas. Background Art

[0002] During the converter smelting process, operators judge the reaction conditions in the molten pool by observing the flame at the furnace mouth. When the distance between the furnace mouth and the active smoke hood is large, more air is inhaled through the gap between the furnace mouth and the active smoke hood during the smelting process, and part of the CO produced by the carbon-oxygen reaction in the molten pool is burned to generate CO2, resulting in a decrease in the calorific value of the gas. The carbon-oxygen reaction rates at different stages of converter smelting are different, and the CO content produced is also different. If the fan speed of the gas recovery system is too high, more air will be inhaled, and if it is too low, the CO cannot be fully recovered by the system, affecting the calorific value of the gas. The converter smelting process is restricted by the previous slag reduction process. The oxygen utilization rate will be low, causing unused oxygen to enter the flue gas, and partially burning the CO produced by the carbon-oxygen reaction in the molten pool to produce CO2, resulting in a decrease in the calorific value of the gas; the converter smelting process will have different iron-to-metal ratios at different stages according to the production requirements. When the molten iron is relatively small, the initial temperature of the molten pool will be relatively low; in addition, when the molten iron temperature is relatively low, the initial temperature of the molten pool will also be relatively low. The low molten pool temperature causes the slag added in the early stage of smelting to melt slowly, which will reduce the oxygen utilization rate, causing oxygen to enter the flue gas to partially burn CO and reduce the calorific value of the gas.

[0003] To this end, those skilled in the art have proposed a method for reducing the CO2 content in the flue gas generated during the converter smelting process to solve the above-mentioned problem of reduced calorific value of coal gas. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for improving the calorific value of converter gas, so as to solve the problem that low oxygen utilization rate causes CO combustion, and excessive air inhalation during smelting causes CO combustion, resulting in reduced calorific value of converter gas.

[0005] In view of this, the present application provides a method for improving the calorific value of converter gas, comprising the following steps:

[0006] S1) Set the distance between the converter movable smoke hood and the furnace mouth to the lower limit of -50~-100mm;

[0007] During the converter smelting process, after adding scrap steel and molten iron, the oxygen lance is lowered to start oxygen ignition for 20 to 30 seconds before adjusting the converter movable smoke hood to the lower limit, where the oxygen lance angle is 13° to 15°;

[0008] S2) During the oxygen supply blowing process of the converter, the oxygen pressure is adjusted to 0.80~0.95MPa after normal ignition;

[0009] Control the speed of the dust removal fan in stages to ensure that the furnace mouth is at a slight positive pressure;

[0010] S3) After the converter smelting is completed, the hot slag is retained in the furnace;

[0011] Lime is added in batches according to the amount of slag retained and the silicon content of molten iron.

[0012] In some specific embodiments, the speed of the dust removal fan is controlled in stages as follows:

[0013] During the oxygen blowing process of the converter, the speed of the dust removal fan before oxygen blowing is 38~40% of the maximum speed, the speed of the dust removal fan during iron adding is 52~54% of the maximum speed, the speed of the dust removal fan during the oxygen blowing stage is 54~74% of the maximum speed, and the speed of the dust removal fan during the steel releasing stage is 59~61% of the maximum speed.

[0014] In some specific embodiments, the oxygen blowing stage includes 1 section, 2 sections, 3 sections, 4 sections, 5 sections and 6 sections. The speed of the dust removal fan in section 1 is 54-56% of the maximum speed, the speed of the dust removal fan in section 2 is 61-63% of the maximum speed, the speed of the dust removal fan in section 3 is 65-67% of the maximum speed, the speed of the dust removal fan in section 4 is 72-74% of the maximum speed, the speed of the dust removal fan in section 5 is 66-68% of the maximum speed, and the speed of the dust removal fan in section 6 is 61-63% of the maximum speed.

[0015] In some specific embodiments, the reserved amount of hot slag is 3-8 kg / t steel.

[0016] In some specific embodiments, the amount of lime added is calculated based on alkalinity: if the residual amount of hot slag is less than 3t, the amount of lime added is calculated based on alkalinity of 2.2; if the residual amount of hot slag is 3-5t, the amount of lime added is calculated based on alkalinity of 2.1; if the residual amount of hot slag is greater than 5t, the amount of lime added is calculated based on alkalinity of 2.0.

[0017] In some specific embodiments, the first batch of lime added is 60-80% of the total amount of lime added.

[0018] In some specific embodiments, the oxygen pressure is adjusted by adjusting the position of the oxygen lance.

[0019] In some specific embodiments, the oxygen lance position adjustment is specifically as follows:

[0020] The iron consumption is 820~860kg / t, and the oxygen lance position is 2.0m; the iron consumption is 860~900kg / t, and the oxygen lance position is 1.9m; ​​the iron consumption is 900~950kg / t, and the oxygen lance position is 1.8m.

[0021] In some specific embodiments, for a 150t converter, the angle of the oxygen lance is 13.5-14.0°.

[0022] In some specific embodiments, the converter is supplied with oxygen for blowing for 200 seconds, and the CO2 content in the converter flue gas is reduced to an average of 22-24%.

[0023] The present application provides a method for improving the calorific value of converter gas, which includes the following means: first, the distance between the converter movable smoke hood and the furnace mouth is set to a lower limit of -50~-100mm; during the converter smelting process, after the scrap steel is mixed with steel, the oxygen lance is lowered to open the oxygen ignition 20~30s later, and then the converter movable smoke hood is adjusted to the lower limit; during the converter oxygen supply and blowing process, the oxygen lance angle and oxygen pressure are controlled, and the speed of the dust removal fan is controlled in stages; finally, after the converter smelting is completed, the hot slag is reserved in the furnace and lime is added in batches; the present application reduces the intake of air during the converter smelting process by adjusting the distance between the movable smoke hood and the furnace mouth, controlling the speed of the fan in stages during the smelting process, etc., so as to avoid air entering the flue and causing CO combustion; at the same time, by recycling the hot slag, controlling the low alkalinity of the converter slag, adding lime in batches, etc., the oxygen utilization rate is improved, and the CO combustion caused by the unused oxygen entering the oxygen is reduced; finally, the calorific value of the converter gas is improved. DETAILED DESCRIPTION

[0024] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0025] In view of the problem in the prior art that the combustion of CO in the flue gas generated during the converter smelting process increases the CO2 content, thereby reducing the calorific value of the converter gas, the present application provides a method for improving the calorific value of the converter gas, which avoids the combustion of CO caused by the entry of air into the flue and improves the oxygen utilization rate by adjusting the position of the converter movable smoke hood, the angle of the oxygen lance, the oxygen pressure, the staged control of the dust removal fan, the recycling of hot slag and the staged addition of lime, thereby finally improving the calorific value of the converter gas; specifically, an embodiment of the present invention discloses a method for improving the calorific value of the converter gas, comprising the following steps:

[0026] S1) Set the distance between the converter movable smoke hood and the furnace mouth to the lower limit of -50~-100mm;

[0027] During the converter smelting process, after adding scrap steel and molten iron, the oxygen lance is lowered to start oxygen ignition for 20 to 30 seconds before adjusting the converter movable smoke hood to the lower limit, where the oxygen lance angle is 13° to 15°;

[0028] S2) During the oxygen supply blowing process of the converter, the oxygen pressure is adjusted to 0.80~0.95MPa after normal ignition;

[0029] Control the speed of the dust removal fan in stages to ensure that the furnace mouth is at a slight positive pressure;

[0030] S3) After the converter smelting is completed, the hot slag is retained in the furnace;

[0031] Lime is added in batches according to the amount of slag retained and the silicon content of molten iron.

[0032] The method for improving the calorific value of converter gas provided in the present application is applicable to converter steelmaking process and has no special restrictions on the type of steel.

[0033] In the method for improving the calorific value of converter gas provided in the present application, the distance between the converter movable smoke hood and the furnace mouth is first set to a lower limit of -50~-100mm. During the smelting process, the furnace mouth is covered by the movable smoke hood to reduce the intake of air during the smelting process. Specifically, the lower limit is -80~-100mm.

[0034] During the converter smelting process, after the addition of scrap steel and molten steel is completed, the oxygen lance is lowered to start the oxygen ignition for 20 to 30 seconds and then the converter movable smoke hood is adjusted to the above-mentioned lower limit position to reduce the amount of air sucked in through the gap between the movable smoke hood and the furnace mouth; in this process, the oxygen lance angle involved is 13 to 15°, specifically, the oxygen lance angle is 13.5 to 14°.

[0035] During the oxygen blowing process in the converter, the starting temperature of the molten pool is estimated based on the molten iron ratio and the molten iron temperature. After the converter is started and ignited normally, the oxygen pressure is adjusted to 0.80~0.95MPa to promote rapid slag formation in the early stage, improve oxygen utilization, and reduce CO combustion caused by the use of oxygen entering the flue. Furthermore, the position of the oxygen lance is controlled to be 1.5~2.5m. Specifically, taking a 150t converter as an example, the iron consumption is 820~860kg / t, the blowing lance position is 2.0m, the iron consumption is 860~900kg / t, the blowing lance position is 1.9m, the iron consumption is 900~950kg / t, and the blowing lance position is 1.8m.

[0036] According to the present invention, based on the influence of the carbon-oxygen reaction law of the converter, molten iron problems, molten iron silicon content and molten iron ratio on the initial temperature of the molten pool, the dust removal fan is set in different modes in stages to ensure that the furnace mouth is at a slightly positive pressure, thereby preventing CO from escaping through the furnace mouth and reducing air intake. Specifically, the speed of the dust removal fan before oxygen blowing is 38-40% of the maximum speed, the speed of the dust removal fan during iron addition is 52-54% of the maximum speed, the speed of the dust removal fan in the oxygen blowing stage is 54-74% of the maximum speed, and the speed of the dust removal fan in the steel release stage is 59-61% of the maximum speed. The oxygen blowing stage includes 1, 2, 3, 4, 5 and 6 stages. The speed of the dust removal fan in stage 1 is 54-56% of the maximum speed, the speed of the dust removal fan in stage 2 is 61-63% of the maximum speed, the speed of the dust removal fan in stage 3 is 65-67% of the maximum speed, the speed of the dust removal fan in stage 4 is 72-74% of the maximum speed, the speed of the dust removal fan in stage 5 is 66-68% of the maximum speed, and the speed of the dust removal fan in stage 6 is 61-63% of the maximum speed. In a specific embodiment, the corresponding fan operation mode is selected according to the iron consumption. Taking a 150t converter as an example, if the iron consumption is ≥920Kg, the upper limit of the fan speed corresponding to each stage is selected; if the iron consumption is 860≤ and the fan speed is less than 920Kg / t, the middle limit of the fan speed corresponding to each stage is selected; if the iron consumption is less than 860Kg / t, the lower limit of the fan speed corresponding to each stage is selected.

[0037] After the converter smelting is completed, the present application reserves hot slag in the furnace. Specifically, the reserved amount of hot slag is 3~8kg / t steel, and further, the reserved amount of hot slag is 4~7kg / t steel; in the present application, the reserved amount of hot slag is estimated by adjusting the angle of the converter. At the same time, lime is added in batches according to the amount of slag left and the silicon content of molten iron to improve the oxygen utilization rate and reduce the unused oxygen entering the flue gas to cause CO combustion. The amount of lime added is calculated based on the alkalinity of 2.0~2.2. Specifically, the residual amount of hot slag is less than 3t, and the amount of lime added is calculated based on the alkalinity of 2.2; the residual amount of hot slag is 3~5t, and the amount of lime added is calculated based on the alkalinity of 2.1; the residual amount of hot slag is greater than 5t, and the amount of lime added is calculated based on the alkalinity of 2.0 (alkalinity = CaO / SiO2). The lime is added in batches, and the first batch, i.e. the first batch, is added according to the temperature of the molten iron, and the amount added is 60-80% of the total amount added to promote rapid temperature rise of the molten pool.

[0038] The present application provides a method for improving the calorific value of converter gas, comprising the following aspects: S1) setting the distance between the converter movable smoke hood and the furnace mouth to a lower limit of -50 to -100 mm; during the converter smelting process, after the scrap steel is mixed with steel, the oxygen lance is lowered to start oxygen ignition for 20 to 30 seconds, and then the converter movable smoke hood is adjusted to the lower limit; S2) during the converter oxygen supply and blowing process, the oxygen lance angle is controlled to be 13 to 15 degrees, and the oxygen pressure is adjusted to 0.80 to 0.95 MPa after the converter is blown and ignited normally; the speed of the dust removal fan is controlled in stages to ensure that the furnace mouth is at a slightly positive pressure; S3) after the converter smelting is completed, the hot slag is reserved in the furnace; lime is added in batches according to the amount of slag left and the silicon content of molten iron. The present invention reduces air intake during the smelting process and prevents air from entering the flue to cause CO combustion by adjusting the distance between the movable smoke hood and the furnace mouth, controlling the speed of the fan in stages during the smelting process, and other measures; at the same time, through the recycling of hot slag, low alkalinity control of converter slag, batch addition of lime, operation models corresponding to different molten iron ratios, optimization of oxygen lance nozzles, and other measures, the oxygen utilization rate is improved and unused oxygen entering the oxygen to cause CO combustion is reduced.

[0039] In order to further understand the present invention, the method for improving the calorific value of converter gas provided by the present invention is described in detail below in conjunction with embodiments, and the protection scope of the present invention is not limited by the following embodiments.

[0040] Example

[0041] This embodiment provides a method for improving the calorific value of converter gas, which specifically involves adjusting the converter steelmaking process, molten iron + scrap steel → converter (oxygen blowing);

[0042] Specifically, the method for improving the calorific value of converter gas includes the following aspects:

[0043] S1: Set the distance between the converter movable smoke hood and the furnace mouth to the lower limit of -100mm to reduce the air intake during the smelting process;

[0044] S2: After adding scrap steel and iron, the oxygen lance is lowered to start oxygen ignition for 30 seconds, and then the movable smoke hood is lowered to the lower limit to reduce the air inhaled through the gap between the movable smoke hood and the furnace mouth;

[0045] S3: During the normal blowing process, the corresponding fan operation mode is selected according to the charging structure (iron consumption). If the iron consumption is ≥920Kg, the upper limit of the fan speed corresponding to each stage is selected; if the iron consumption is 860≤ and <920Kg / t, the middle limit of the fan speed corresponding to each stage is selected; if the iron consumption is <860Kg / t, the lower limit of the fan speed corresponding to each stage is selected. The dust removal fan speed is controlled in stages under different modes to ensure that the furnace mouth is in a slightly positive pressure state, which prevents CO from escaping through the furnace mouth and reduces air intake;

[0046] S4: For 150-ton converter, select oxygen lances with angles of 13.5°~14° according to the loading structure to promote rapid slagging and improve oxygen utilization;

[0047] S5: After the smelting of the previous furnace in the converter is completed and the steel is tapped, the converter is tilted to 105-110° to reserve 5-10t of hot slag and splash-dryness is ensured;

[0048] S6: Lime is added according to the amount of slag left and silicon in molten iron. When calculating the amount of lime added, the alkalinity is calculated as 2.0~2.2; if the slag left is ≤3 tons, the alkalinity is calculated as 2.2; if the slag left is 3 tons~5 tons, the alkalinity is calculated as 2.1; if the slag left is ≥5 tons, the alkalinity is calculated as 2.0.

[0049] Lime is added in batches, with the first batch accounting for 60-80% of the total amount, to promote rapid temperature rise of the molten pool;

[0050] S7: During the whole process of oxygen blowing in the converter, the lance position is 1.8~1.9 meters, the process is 1.4~1.5 meters, and the oxygen pressure is 0.85~0.95Mpa, in order to promote rapid slag formation in the early stage, improve oxygen utilization, and reduce unused oxygen entering the flue to cause CO combustion.

[0051] As can be seen from the above, CO is produced by the carbon-oxygen reaction in the converter smelting process, and the CO is recycled through the coal gas recovery system. The present invention reduces the amount of air sucked into the smelting process and the problem of CO combustion caused by entering the flue by adjusting the distance between the movable smoke hood and the furnace mouth, controlling the speed of the fan in the smelting process in stages, and other measures; at the same time, through the recycling of hot slag, low alkalinity control of converter slag, batch addition of lime, operation models corresponding to different molten iron ratios, optimization of oxygen lance nozzles and other measures, the oxygen utilization rate is improved, the problem of CO combustion caused by the entry of unused oxygen into the flue gas is reduced, the CO2 content in the coal gas is reduced, and the calorific value of the coal gas is increased while the CO2 content in the coal gas is reduced. Through the above adjustments, it is detected that the CO2 content in the converter flue gas is reduced from an average of 27.5% to an average of 22.5% after blowing for 200 seconds, further improving the calorific value of the converter coal gas.

[0052] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0053] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for increasing the calorific value of converter gas, comprising the following steps: S1) Set the distance between the converter movable smoke hood and the furnace mouth to the lower limit of -50~-100mm; During the converter smelting process, after adding scrap steel and molten iron, the oxygen lance is lowered to start the oxygen ignition for 20 to 30 seconds before adjusting the converter movable smoke hood to the lower limit, in which the oxygen lance angle is 13° to 15°; S2) During the oxygen supply blowing process of the converter, the oxygen pressure is adjusted to 0.80~0.95MPa after normal ignition; Control the speed of the dust removal fan in stages to ensure that the furnace mouth is at a slight positive pressure; S3) After the converter smelting is completed, the hot slag is retained in the furnace; Lime is added in batches according to the amount of slag retained and the silicon content of molten iron.

2. The method according to claim 1, characterized in that: The speed control of the dust removal fan in stages is specifically as follows: During the oxygen blowing process of the converter, the speed of the dust removal fan before oxygen blowing is 38~40% of the maximum speed, the speed of the dust removal fan during iron adding is 52~54% of the maximum speed, the speed of the dust removal fan during the oxygen blowing stage is 54~74% of the maximum speed, and the speed of the dust removal fan during the steel releasing stage is 59~61% of the maximum speed.

3. The method according to claim 2, characterized in that The oxygen blowing stage includes 1st section, 2nd section, 3rd section, 4th section, 5th section and 6th section. The speed of the dust removal fan in 1st section is 54-56% of the maximum speed, the speed of the dust removal fan in 2nd section is 61-63% of the maximum speed, the speed of the dust removal fan in 3rd section is 65-67% of the maximum speed, the speed of the dust removal fan in 4th section is 72-74% of the maximum speed, the speed of the dust removal fan in 5th section is 66-68% of the maximum speed, and the speed of the dust removal fan in 6th section is 61-63% of the maximum speed.

4. The method according to claim 1, characterized in that: The reserved amount of the hot slag is 3-8 kg / t steel.

5. The method according to claim 1, characterized in that The amount of lime added is calculated based on alkalinity: if the residual amount of hot slag is less than 3t, the amount of lime added is calculated based on alkalinity of 2.2; if the residual amount of hot slag is 3-5t, the amount of lime added is calculated based on alkalinity of 2.1; if the residual amount of hot slag is greater than 5t, the amount of lime added is calculated based on alkalinity of 2.

0.

6. The method according to claim 1, characterized in that The first batch of lime added is 60-80% of the total amount of lime added.

7. The method according to claim 1, characterized in that The oxygen pressure is adjusted by adjusting the position of the oxygen lance.

8. The method according to claim 7, characterized in that The oxygen lance position adjustment is specifically as follows: The iron consumption is 820~860kg / t, and the oxygen lance position is 2.0m; the iron consumption is 860~900kg / t, and the oxygen lance position is 1.9m; ​​the iron consumption is 900~950kg / t, and the oxygen lance position is 1.8m.

9. The method according to claim 1, characterized in that: For a 150t converter, the angle of the oxygen lance is 13.5-14.0°.

10. The method according to claim 1, characterized in that The converter is supplied with oxygen for blowing for 200 seconds, and the CO2 content in the converter flue gas is reduced to an average of 22-24%.