Method for increasing coal gas calorific value of converter flue gas

Abstract

The invention discloses a method for increasing the gas calorific value of converter flue gas, and belongs to the technical field of converter smelting, a converter and a flue gas pipeline correspondingly arranged at an opening of the converter are included, the flue gas pipeline is connected with a primary dust removal fan, and an air volume control device for controlling the air inlet volume of a throat part is arranged at the connecting throat part of the flue gas pipeline and a dust collection cover; the primary dust removal fan and the air volume control device are interlocked with a PLC (Programmable Logic Controller) control mechanism of the converter; according to different smelting stages of the converter, a PLC control mechanism is used for controlling a high-voltage frequency converter of a primary dust removal fan in an interlocking manner to carry out multi-stage frequency conversion speed regulation; the air volume control device is correspondingly adjusted according to the frequency conversion speed regulation level of the primary dust removal fan to control the throat opening degree of the flue gas pipeline, and then the CO concentration content of the converter flue gas and the coal gas flow speed are controlled. The primary dust removal fan of the flue gas pipeline is subjected to multi-stage speed regulation, so that the equipment consumption is reduced; and the throat opening degree of the flue gas pipeline is regulated and controlled according to air quantity changes at different rotating speeds, so that the gas recoverable range duration is prolonged, and the calorific value and quantity of the gas are further improved.

Description

Technical Field

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

[0002] The large amount of CO-containing flue gas produced during the converter blowing process is called converter gas. The CO content and the amount of gas are constantly changing during the converter blowing process. As a by-product of converter steelmaking, the gas must have strict requirements on its O2 and CO content during the recovery process. The O2 content must not be less than 1% and the CO content must be greater than 20% to ensure that the calorific value of the converter gas is greater than 5016kJ / m 3 The above. At present, the general smelting method has a low CO content and low calorific value of coal gas, which is difficult to meet the recovery standard. Therefore, in the existing converter gas recovery mode, only the converter gas with a higher calorific value is recovered, that is, in the process of blowing a furnace of steel, under the premise of qualified oxygen content (less than 1.5%), the converter gas is recovered when the CO content is ≥35%, and the converter gas is rejected when it is ≤35%. Because the CO content is low in the early and late stages of blowing, the calorific value cannot meet the production needs and is released. This method not only wastes energy but also causes serious air pollution. In addition, during the converter smelting process, the primary dust removal fan runs at high speed for a long time, resulting in a large amount of electrical energy waste; at the same time, the throat opening of the dust collection flue is relatively fixed, causing a large amount of wild wind to enter the flue, resulting in CO combustion and reducing the calorific value of coal gas. Summary of the invention

[0003] Technical problem to be solved: In view of the problems existing in the converter gas production process in the prior art, the present invention provides a method for improving the gas calorific value of converter flue gas, which can not only recycle the converter gas with a low CO content, but also reduce the energy consumption of equipment operation in the converter production process.

[0004] Technical solution: A method for improving the calorific value of coal gas of converter flue gas described in the present invention comprises a converter and a flue gas duct correspondingly arranged at the open part of the converter, the flue gas duct is connected to a primary dust removal fan, and a throat connecting the flue gas duct and the dust collecting hood is provided with an air volume control device for controlling the air volume of the throat, the primary dust removal fan and the air volume control device are interlocked with the PLC control mechanism of the converter; Wherein, the method comprises the following steps: Step 1: According to the different smelting stages of the converter, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to perform multi-level frequency conversion speed regulation; Step 2: According to the variable frequency speed regulation level of the primary dust removal fan, the air volume control device is adjusted accordingly to control the throat opening of the flue gas duct, thereby controlling the CO concentration content and gas flow rate of the converter flue gas.

[0005] Preferably, in step 1, when the converter furnace starts and is in the charging and iron adding stage, the high-voltage frequency converter of the primary dust removal fan is controlled by the PLC control mechanism to adjust the speed from 500r / min to 800r / min.

[0006] Preferably, in step 1, when the converter is finished adding iron and the converter is shaken to 55°, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed from 800r / min to 1030r / min, and prepare for releasing the oxygen gun.

[0007] Preferably, in step 1, during the descent of the oxygen lance, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed from 1030 r / min to 1100 r / min, and the converter is started for preliminary smelting.

[0008] Preferably, in step 1, when the converter smelting enters the gas recovery stage, the speed of the primary dust removal fan is adjusted according to the following rules: When the CO concentration in the gas is 15% <C CO When the speed is less than 40%, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1165r / min; When the CO concentration in the gas is 40% <C CO At this time, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1245r / min; When the gas recovery is completed, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1030r / min.

[0009] Preferably, in step 1, when the converter smelting enters the steel-out stage, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 500r / min.

[0010] Preferably, in step 2, the throat opening is dynamically adjusted by the air volume control device according to the following rules: When the speed of the primary dust removal fan is less than 600r / min, the throat opening of the flue gas duct is adjusted to 45%; When the speed of the primary dust removal fan is 600~1050r / min, the flue gas duct throat opening is adjusted to 50%; When the speed of the primary dust removal fan is between 1050 and 1200 r / min, the flue gas duct throat opening is adjusted to 60%; When the speed of the primary dust removal fan is between 1200 and 1300 r / min, the flue gas duct throat opening is adjusted to 65%; When the dust removal fan speed drops to 1030r / min after steel is tapped from the converter, the flue gas duct throat opening is adjusted to 45%.

[0011] Preferably, the air volume control device is a plurality of air inlet control valves arranged along the circumference of the throat of the flue gas duct.

[0012] Preferably, the air volume control device is a plurality of annular blades and a driving mechanism arranged along the circumference of the throat of the flue gas duct.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects: The method of the present invention performs multi-stage speed regulation on a primary dust removal fan of a flue gas duct according to different smelting stages of an actual converter smelting process, thereby reducing equipment consumption; and according to changes in air volume at different speeds, regulates the throat opening of the flue gas duct, so that the converter furnace mouth is at a slightly positive pressure, reduces the entry of external wild wind into the flue gas duct, thereby controlling the CO concentration in the flue gas to be within a recoverable range for a relatively long time, thereby increasing the calorific value and quantity of coal gas. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention is clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0015] Embodiment 1: A method for improving the calorific value of coal gas of converter flue gas disclosed in the present invention comprises a converter and a flue gas duct correspondingly arranged at the open part of the converter, the flue gas duct is connected to a primary dust removal fan, and a throat portion where the flue gas duct is connected to a dust collecting hood is provided with an air volume control device for controlling the air volume of the throat portion, and the primary dust removal fan and the air volume control device are both interlocked with a PLC control mechanism of the converter; Wherein, the method comprises the following steps: Step 1: According to the different smelting stages of the converter, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to perform multi-level frequency conversion speed regulation. Specifically, when the converter starts and is in the stage of charging and adding iron, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed from 500r / min to 800r / min; when the converter is finished adding iron and the converter is shaken to 55°, the speed of the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust from 800r / min to 1030r / min, and prepare for releasing the oxygen gun (the interlocking condition for releasing the oxygen gun is that the speed of the primary dust removal fan is not less than 1000r / min); during the descent of the oxygen gun, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed from 1030r / min to 1100r / min, and start the converter for preliminary smelting.

[0016] When the converter smelting enters the gas recovery stage, the speed of the primary dust removal fan is adjusted according to the following rules: When the CO concentration in the gas is 15% <C CO <40%, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1165r / min; when the CO concentration in the gas is 40%, <C CO When the gas recovery is finished, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1245r / min; when the gas recovery is finished, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1030r / min (oxygen may be replenished in the later stage of converter smelting, and the oxygen gun cannot be released when the speed of the primary dust removal fan is less than 1000r / min). When the converter smelting enters the steel-making stage, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to the initial speed of 500r / min.

[0017] Step 2: According to the variable frequency speed regulation level of the primary dust removal fan at different stages of converter smelting, the air volume control device is adjusted to control the throat opening of the flue gas duct, thereby controlling the CO concentration content and gas flow rate of the converter flue gas. The throat opening of the flue gas duct is dynamically adjusted by the air volume control device according to the following rules: when the speed of the primary dust removal fan is <600r / min, the throat opening of the flue gas duct is adjusted to 45%; when the speed of the primary dust removal fan is 600~1050r / min, the throat opening of the flue gas duct is adjusted to 50%; when the speed of the primary dust removal fan is between 1050~1200r / min, the throat opening of the flue gas duct is adjusted to 60%; when the speed of the primary dust removal fan is between 1200~1300r / min, the throat opening of the flue gas duct is adjusted to 65%; when the speed of the primary dust removal fan is reduced to 1030r / min after the converter taps steel, the throat opening of the flue gas duct is adjusted to 45%.

[0018] It should be noted that during the 6-level speed regulation of the primary dust removal fan, the throat opening of the flue gas duct is dynamically adjusted according to the air volume. For example, the initial speed of the primary dust removal fan in the smelting preparation stage is 500r / min, and the throat opening is 45% at this time. When the converter is charged with iron, the speed of the primary dust removal fan is adjusted to 800r / min, and the PLC control mechanism monitors the actual speed of the primary dust removal fan in real time. When the speed of the primary dust removal fan is greater than 600r / min, the throat of the flue gas duct is correspondingly adjusted to 50%. When the converter is shaken to 65°, the speed of the primary dust removal fan is adjusted to 1030r / min again. At this time, the throat opening of the flue gas duct is not adjusted. When the oxygen gun descending height interlock is started, the speed of the primary dust removal fan is adjusted from 1030r / min to 1100r / min. When the speed of the primary dust removal fan is higher than 1050r / min, the throat opening of the flue gas duct is adjusted to 60% accordingly.

[0019] In a preferred embodiment, the air volume control device is a plurality of air inlet control valves arranged along the circumference of the throat of the flue gas duct. The air inlet control valve is an electric valve, and the opening of the electric valve can be remotely controlled by a PLC control mechanism.

[0020] In a preferred embodiment, the air volume control device is a plurality of annular gap blades and a driving mechanism arranged along the circumference of the throat of the flue gas duct. When the plurality of annular gap blades are in a closed state, the side wall of the throat of the flue gas duct can be in a completely closed state. The driving mechanism can use a driving cylinder, a hydraulic cylinder or a driving electric cylinder and other structures to realize the opening control of the annular gap blades, so as to control the air volume entering from the throat of the flue gas duct.

[0021] In a specific implementation process of the method of the present invention, its energy consumption parameters are shown in Table 1:

[0022] .

[0023] As can be seen from Table 1, the targeted use of graded control of the speed of the primary dust removal fan and the throat opening of the flue gas duct according to the converter smelting process can meet the power consumption of different smelting stages, thereby reducing the overall power consumption. The CO atmosphere in the converter furnace is quickly formed by regulating the speed of the primary dust removal fan and adjusting the opening of the converter throat at different stages, and the wild wind entering the flue gas duct to burn CO is reduced, reducing the waste of gas calorific value. In addition, the gas recovery time after releasing the oxygen gun is advanced from 100 seconds to 50 seconds to meet the gas recovery conditions, and the CO concentration of the gas rises rapidly, avoiding the adverse effect of the CO concentration drop in the early stage of converter smelting on gas recovery, and the gas recovery quantity increases by 10~20m 3 / ton of steel.

[0024] In the process of adding scrap steel to the converter and tapping steel, the dust removal fan adopts 6-level speed regulation within 23 minutes, and the power consumption is reduced from 466KWH before implementation to 376KWH. After the implementation of the method of the present invention, the power consumption of each furnace of steel is reduced by 90KWh, and the power consumption is reduced by more than 10%. Based on the comparative analysis of tracking data, according to the annual output of 4.3 million tons: 90 / 135*4300000=2866666.67kwh; according to 0.65 yuan per kilowatt-hour: 2866666.67*0.65=1863333.336 yuan. Before the implementation of the method of the present invention, the average calorific value of the recovered coal gas in the workshop was 5600kcal / Nm³, and after the implementation of the method of the present invention, the average calorific value of the recovered coal gas was 6300kcal / Nm³.

[0025] The present invention uses multi-stage speed regulation of a primary dust removal fan and throat opening regulation of a converter flue gas duct at different stages of smelting, so that the gas CO in the converter is rapidly formed and rises, shortening the gas recovery condition time, avoiding the impact of CO concentration drop due to feeding in the early stage of converter smelting and thus affecting gas recovery, thereby improving the calorific value of gas and the amount of gas recovery; at the same time, the throat opening of the flue gas duct is optimized according to different stages of smelting, so as to always maintain a slight positive pressure at the converter mouth, and avoid the reduction of the calorific value of gas due to the inhalation of external wild wind during the smelting process; the primary dust removal fan adopts multi-stage variable frequency speed regulation, and can adjust the speed according to the demand for air volume at different stages of converter smelting, thereby reducing the power consumption per ton of steel of the primary dust removal fan.

[0026] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for increasing the calorific value of converter flue gas, characterized in that: It includes a converter and a flue gas duct correspondingly arranged at the open part of the converter, the flue gas duct is connected to a primary dust removal fan, and a wind volume control device for controlling the wind volume at the throat is arranged at the throat where the flue gas duct is connected to the dust collecting hood, and the primary dust removal fan and the wind volume control device are interlocked with the PLC control mechanism of the converter; Wherein, the method comprises the following steps: Step 1: According to the different smelting stages of the converter, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to perform multi-level frequency conversion speed regulation; Step 2: According to the variable frequency speed regulation level of the primary dust removal fan, the air volume control device is adjusted accordingly to control the throat opening of the flue gas duct, thereby controlling the CO concentration content and gas flow rate of the converter flue gas.

2. The method for improving the calorific value of converter flue gas according to claim 1, characterized in that: In step 1, when the converter furnace starts and is in the charging and iron adding stage, the high-voltage frequency converter of the primary dust removal fan is controlled by the PLC control mechanism to adjust the speed from 500r / min to 800r / min.

3. The method for improving the calorific value of converter flue gas according to claim 2, characterized in that: In step 1, when the converter is added with iron and the converter is shaken to 55°, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed from 800r / min to 1030r / min, and prepare for releasing the oxygen gun.

4. The method for improving the calorific value of converter flue gas according to claim 3, characterized in that: In step 1, during the descent of the oxygen lance, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed from 1030r / min to 1100r / min, and the converter is started for preliminary smelting.

5. The method for improving the calorific value of converter flue gas according to claim 4, characterized in that: In step 1, when the converter smelting enters the gas recovery stage, the speed of the primary dust removal fan is adjusted according to the following rules: When the CO concentration in the gas is 15% <C CO When the speed is less than 40%, the high-voltage inverter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1165r / min; When the CO concentration in the gas is 40% <C CO At this time, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1245r / min; When the gas recovery is completed, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 1030r / min.

6. The method for increasing the calorific value of converter flue gas according to claim 5, characterized in that: In step 1, when the converter smelting enters the steel-out stage, the high-voltage frequency converter of the primary dust removal fan is interlocked and controlled by the PLC control mechanism to adjust the speed to 500r / min.

7. The method for improving the calorific value of converter flue gas according to any one of claims 1 to 6, characterized in that: In step 2, the throat opening is dynamically adjusted by the air volume control device according to the following rules: When the speed of the primary dust removal fan is less than 600r / min, the throat opening of the flue gas duct is adjusted to 45%; When the speed of the primary dust removal fan is 600~1050r / min, the flue gas duct throat opening is adjusted to 50%; When the speed of the primary dust removal fan is between 1050 and 1200 r / min, the flue gas duct throat opening is adjusted to 60%; When the speed of the primary dust removal fan is between 1200 and 1300 r / min, the flue gas duct throat opening is adjusted to 65%; When the dust removal fan speed drops to 1030r / min after steel is tapped from the converter, the flue gas duct throat opening is adjusted to 45%.

8. The method for improving the calorific value of converter flue gas according to claim 7, characterized in that: The air volume control device is a plurality of air inlet control valves arranged along the circumference of the throat of the flue gas duct.

9. The method for improving the calorific value of converter flue gas according to claim 7, characterized in that: The air volume control device comprises a plurality of annular blades and a driving mechanism arranged along the circumference of the throat of the flue gas duct.