A method for increasing the calorific value of converter flue gas

Abstract

The present invention discloses a method for increasing the calorific value of converter flue gas, belonging to the field of converter smelting technology. The method comprises a converter and a flue gas duct correspondingly disposed at the converter's open opening. The flue gas duct is connected to a primary dust removal fan, and an air volume control device is disposed at the throat portion connecting the flue gas duct and the dust hood to control the air volume entering the throat portion. The primary dust removal fan and the air volume control device are both interlocked with the converter's programmable logic controller (PLC) control mechanism. The PLC control mechanism interlocks and controls the primary dust removal fan's high-voltage frequency converter for multi-stage variable frequency speed regulation according to the converter's smelting stage. The air volume control device is adjusted accordingly based on the variable frequency speed regulation level of the primary dust removal fan to control the flue gas duct throat opening, thereby controlling the CO concentration and gas flow rate of the converter flue gas. The present invention implements multi-stage speed regulation for the primary dust removal fan in the flue gas duct, reducing equipment consumption. Furthermore, the flue gas duct throat opening is regulated based on changes in air volume at different speeds, extending the gas recovery period and thereby increasing the calorific value and quantity of the gas.

Description

Technical Field

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

[0002] During the converter blowing process, a large amount of flue gas containing CO is produced, which 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 meet strict requirements for O2 and CO content during the recovery process. The O2 content must be no 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 a low calorific value of the gas, which makes it difficult to meet the recovery standards. 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%. Since 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 the gas. Summary of the Invention

[0003] Technical problem to be solved: In response to 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 and utilize converter gas with a low CO content, but also reduce the energy consumption of equipment operation during the converter production process.

[0004] Technical solution: The method of improving the calorific value of converter flue gas according to the present invention comprises a converter and a flue gas duct corresponding to the open portion of the converter, the flue gas duct being connected to a primary dust removal fan, and an air volume control device for controlling the air volume entering the throat of the flue gas duct and the dust collection hood being provided at the throat thereof, the primary dust removal fan and the air volume control device being interlocked with a PLC control mechanism of the converter;

[0005] The method comprises the following steps:

[0006] 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;

[0007] Step 2: According to the variable frequency speed regulation level of the primary dust removal fan, the air volume control device is adjusted to control the flue gas duct throat opening, thereby controlling the CO concentration content and gas flow rate of the converter flue gas.

[0008] Preferably, in step 1, when the converter heat starts and is in the charging and iron adding stage, the high-voltage inverter of the primary dust removal fan is controlled by the PLC control mechanism to adjust the speed from 500r / min to 800r / min.

[0009] 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 to release the oxygen gun.

[0010] 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.

[0011] 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:

[0012] 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;

[0013] 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;

[0014] 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.

[0015] Preferably, in step 1, when the converter smelting enters the steel-tapping 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.

[0016] Preferably, in step 2, the throat opening is dynamically adjusted by the air volume control device according to the following rules:

[0017] When the speed of the primary dust removal fan is less than 600r / min, the flue gas duct throat opening is adjusted to 45%;

[0018] When the speed of the primary dust removal fan is 600~1050r / min, the flue gas duct throat opening is adjusted to 50%;

[0019] 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%;

[0020] When the primary dust removal fan speed is between 1200 and 1300 r / min, the flue gas duct throat opening is adjusted to 65%;

[0021] When the speed of the dust removal fan is reduced to 1030r / min after the converter taps steel, the flue gas duct throat opening is adjusted to 45%.

[0022] 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.

[0023] 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.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] 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 regulates the throat opening of the flue gas duct according to changes in air volume at different speeds, so that the converter furnace mouth is at a slightly positive pressure, reducing 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 longer period of time, thereby increasing the calorific value and quantity of the coal gas. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0027] Example 1: The present invention discloses a method for increasing the calorific value of coal gas from a converter, comprising a converter and a flue gas duct correspondingly disposed at an open portion of the converter, the flue gas duct being connected to a primary dust removal fan, and an air volume control device for controlling the air volume entering the throat being disposed at a throat portion connecting the flue gas duct to a dust collecting hood, the primary dust removal fan and the air volume control device being interlocked with a PLC control mechanism of the converter;

[0028] The method comprises the following steps:

[0029] 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-stage variable frequency speed regulation. Specifically, when the converter heat starts and is in the charging and iron adding stage, 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 iron adding is completed and the converter is shaken to 55°, the high-voltage inverter 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 lance (the interlocking condition for releasing the oxygen lance is that the speed of the primary dust removal fan is not less than 1000r / min); during the descent of the oxygen lance, 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.

[0030] 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 primary dust removal fan is in operation, the PLC control mechanism interlocks and controls the high-voltage inverter of the primary dust removal fan to adjust the speed to 1245r / min. When the coal gas recovery is completed, the PLC control mechanism interlocks and controls the high-voltage inverter of the primary dust removal fan to adjust the speed to 1030r / min. (Oxygen may be replenished in the later stages of converter smelting, and the oxygen lance cannot be released if the primary dust removal fan speed is less than 1000r / min.) When the converter smelting enters the steelmaking stage, the PLC control mechanism interlocks and controls the high-voltage inverter of the primary dust removal fan to adjust the speed to the initial speed of 500r / min.

[0031] Step 2: Adjust the air volume control device to control the flue gas duct throat opening according to the variable frequency speed regulation level of the primary dust removal fan at different stages of converter smelting, thereby controlling the CO concentration and gas flow rate of the converter flue gas. The flue gas duct throat opening is dynamically adjusted by the air volume control device according to the following rules: when the primary dust removal fan speed is less than 600 r / min, the flue gas duct throat opening is adjusted to 45%; when the primary dust removal fan speed is 600-1050 r / min, the flue gas duct throat opening is adjusted to 50%; when the primary dust removal fan speed is between 1050-1200 r / min, the flue gas duct throat opening is adjusted to 60%; when the primary dust removal fan speed is between 1200-1300 r / min, the flue gas duct throat opening is adjusted to 65%; and when the primary dust removal fan speed is reduced to 1030 r / min after converter tapping, the flue gas duct throat opening is adjusted to 45%.

[0032] It should be noted that during the 6-level speed regulation process 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 adjusted to 50% accordingly. 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 lance 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.

[0033] In a preferred embodiment, the air volume control device is a plurality of air inlet control valves arranged along the circumference of the flue gas duct throat. 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.

[0034] In a preferred embodiment, the air volume control device is a plurality of annular blades and a driving mechanism arranged along the circumference of the flue gas duct throat. When the plurality of annular blades are in a closed state, the side wall of the flue gas duct throat can be in a completely closed state. The driving mechanism can use a driving cylinder, a hydraulic cylinder or a driving electric cylinder to control the opening of the annular blades to control the air volume entering the flue gas duct throat.

[0035] In a specific implementation process of the method of the present invention, its energy consumption parameters are shown in Table 1:

[0036] .

[0037] As can be seen from Table 1, the targeted hierarchical 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, thereby 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. The CO concentration in 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.

[0038] The present method reduces power consumption from 466 kilowatt-hours (KWh) to 376 KWh within 23 minutes of using a six-stage dust removal fan from scrap steel loading to steel tapping in the converter. This reduces power consumption by 90 KWh per heat of steel, a reduction of over 10%. Based on comparative analysis of tracking data, assuming an annual output of 4.3 million tons, the calculation is: 90 / 135 * 4,300,000 = 2,866,666.67 kWh; at 0.65 yuan per kilowatt-hour, the calculation is: 2,866,666.67 * 0.65 = 1,863,333.336 yuan. The average calorific value of recovered coal gas in the workshop was 5,600 kcal / Nm³ before implementation, but 6,300 kcal / Nm³ after implementation.

[0039] The present invention uses multi-stage speed regulation of the primary dust removal fan and regulation of the throat opening of the converter flue gas duct at different stages of smelting, so that the coal gas CO in the converter furnace is quickly formed and rises rapidly, shortening the gas recovery conditioning time, avoiding the decrease in CO concentration caused by charging in the early stage of converter smelting and thus affecting the coal gas recovery, and improving the calorific value of the coal gas and the amount of recovery; at the same time, the throat opening of the flue gas duct is optimized according to the different stages of smelting, so as to always maintain a slight positive pressure at the furnace mouth of the converter, and avoid the reduction of the calorific value of the coal 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 of the primary dust removal fan per ton of steel.

[0040] The above is a preferred embodiment 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 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 corresponding to the open part of the converter, the flue gas duct is connected to a primary dust removal fan, and an air volume control device for controlling the air volume of the throat is provided at the throat where the flue gas duct is connected to the dust collecting hood, and the primary dust removal fan and the air volume control device are interlocked with the PLC control mechanism of the converter; 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; the specific steps are: (1) When the converter heat starts and is in the charging and iron adding stage, the high-voltage inverter of the primary dust removal fan is controlled by the PLC control mechanism to adjust the speed from 500r / min to 800r / min; (2) When the converter is finished adding iron and the converter is shaken to 55°, the high-voltage inverter 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 to release the oxygen lance; (3) During the descent of the oxygen lance, the high-voltage inverter 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; (4) 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 When the PLC control mechanism is interlocked, the high-voltage inverter of the primary dust removal fan is controlled 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; (5) When the converter smelting enters the steel tapping 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 500r / min; Step 2: According to the variable frequency speed regulation level of the primary dust removal fan, the air volume control device is adjusted to control the flue gas duct throat opening, thereby controlling the CO concentration and gas flow rate of the converter flue gas; 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 flue gas duct throat opening is adjusted to 45%; When the speed of the primary dust removal fan is ≥600 and <1050r / min, the flue gas duct throat opening is adjusted to 50%; When the speed of the primary dust removal fan is ≥1050 and <1200r / min, the flue gas duct throat opening is adjusted to 60%; When the speed of the primary dust removal fan is ≥1200 and <1300r / min, the flue gas duct throat opening is adjusted to 65%; When the speed of the dust removal fan is reduced to 1030r / min after the converter taps steel, the flue gas duct throat opening is adjusted to 45%.

2. The method for increasing the calorific value of converter flue gas according to claim 1, 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.

3. The method for increasing the calorific value of converter flue gas according to claim 1, 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.