Method for stabilizing recovery of carbon dioxide in a twin hearth kiln

Abstract

The application discloses a method for stably recovering carbon dioxide in a double-hearth kiln, and comprises the following steps: using a double-hearth kiln carbon dioxide stable recovery device to control the stable recovery of carbon dioxide in the double-hearth kiln; the control step comprises the following steps: when No. 1 kiln or No. 2 kiln is in a production stop state, electric valve 1 and electric valve 2 on the flue gas outlet pipeline of No. 1 kiln or No. 2 kiln are closed; when No. 1 kiln and No. 2 kiln are both in production, the combustion time and the reversing time of the kiln are set to be the same, and the reversing of the two kilns is ensured to be different; before the reversing period, the cooling air electric valve on the cold air pipeline of No. 1 kiln and No. 2 kiln is closed, and the opening degree of electric valve 1 is set to be 60%; during the production of No. 1 kiln and No. 2 kiln, the detection data of the pressure gauge is greater than 0 kpa, and electric valve 2 is opened; otherwise, electric valve 2 is closed, and the carbon dioxide recovery fan is reduced in rotation speed, etc. The application can solve the problem that the carbon dioxide concentration is reduced and the stable recovery cannot be realized during the reversing period of the existing double-hearth kiln.

Description

Technical Field

[0001] This invention relates to the field of steel manufacturing and equipment technology, and in particular to a method for the stable recovery of carbon dioxide in a double-chamber kiln. Background Technology

[0002] The Maeltz vertical kiln has two kiln chambers, kiln 14 and kiln 25, connected by a central passage. Each kiln (14 and 15) has a flue gas dust collector (13) connected to its top via a pipe. A flue gas dust collector fan (1) is connected to the flue gas outlet pipe (2) of the dust collector (13). Cooling air pipes (4) are connected to the discharge hoppers at the bottom of kilns (14 and 15) via electric cooling air valves (5). Figure 1 As shown. The biggest advantages during calcination are co-flow and heat storage. "Co-flow" means that during calcination of the coal gas in the combustion chamber, the coal gas, combustion air, and limestone flow downwards side by side, and the combustion flue gas also flows downwards, which is beneficial for producing high-quality active lime. "Heat storage" refers to the fact that the high-temperature flue gas, the product of fuel combustion, enters the heat storage chamber through the connecting channel between the two kiln chambers inside the combustion chamber. In the heat storage chamber, the high-temperature flue gas flows upwards, transferring heat to the limestone raw material in the preheating zone, preheating the stone to a higher temperature. At the same time, the high-temperature exhaust gas, after heat exchange, drops to a lower temperature and is discharged into the atmosphere through the flue gas bag filter.

[0003] During combustion operation, the two kilns of the Maeltz kiln switch functions every 12-14 minutes, meaning that while one kiln is in calcination mode, the other is in heat storage mode. Under normal conditions, the system supplies a large amount of coal gas and combustion air to the combustion chamber to ensure normal combustion, while the flue gas dust collector ensures that the top of the heat storage chamber is in a negative pressure environment. Therefore, the pressure in the combustion chamber is always higher than that in the heat storage chamber, allowing the high-temperature flue gas to flow smoothly into the heat storage chamber, thus achieving heat storage.

[0004] After a calcination cycle is completed in the Maeltz kiln, the system enters the reversing period. The entire reversing period takes approximately 45 seconds. During the reversing period, the combustion air release valve and cooling air release valve of the Maeltz kiln open successively, releasing the pressure inside the kiln to zero, realizing the change in the position of the kiln release valve, and starting the next calcination cycle.

[0005] Inside the combustion chamber, fuel (pulverized coal or coal gas) is calcined to produce flue gas, which enters the regenerator through the intermediate channel. Together with the cooling air from the kiln bottom, it passes through the regenerator and dust removal system before being discharged into the atmosphere. During the reversal period, because the fuel system is cut off and the combustion chemical reaction ceases, various components of the flue gas flue gas will fluctuate, such as a decrease in carbon dioxide concentration. To ensure a stable carbon dioxide concentration in the flue gas recovered from the double-chamber kiln, a device specifically designed for flue gas recovery in double-chamber kilns is required. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a method for stable recovery of carbon dioxide in a double-chamber kiln, so as to solve the problem that the carbon dioxide concentration in the existing double-chamber kiln decreases during the commutation period and cannot be stably recovered.

[0007] To solve the above problems, the technical solution of the present invention is as follows: The method for stable carbon dioxide recovery in a double-chamber kiln includes using a double-chamber kiln stable carbon dioxide recovery device to control the stable recovery of carbon dioxide in the double-chamber kiln; the double-chamber kiln stable carbon dioxide recovery device includes a No. 1 kiln and a No. 2 kiln connected by an intermediate channel; the tops of the No. 1 kiln and the No. 2 kiln are respectively connected to flue gas dust collectors via pipes; the flue gas dust collectors are connected to flue gas outlet pipes with flue gas dust collectors connected to them ...

[0008] The control steps include:

[0009] When kiln No. 1 or kiln No. 2 is shut down, electric valve 1 and electric valve 2 on the flue gas outlet duct of kiln No. 1 or kiln No. 2 are closed.

[0010] When both kilns No. 1 and No. 2 are in production, the combustion time and reversing time of the kilns are set to be the same to ensure that the two kilns do not reverse at the same time during the reversing period. Before the reversing period, the cooling air electric valves on the cold air ducts of kilns No. 1 and No. 2 are closed, and the opening degree of electric valve one is set to 60%.

[0011] Start the carbon dioxide recovery fan on carbon dioxide recovery pipeline 2 to recover the flue gas from the two kilns;

[0012] 20 seconds before the changeover, the No. 1 kiln cuts off fuel, and the carbon dioxide concentration in the flue gas decreases. When the carbon dioxide detector of the No. 1 kiln reads low, the No. 1 kiln electric valve decreases its opening, and the No. 2 kiln electric valve increases its opening. When the carbon dioxide detector of the No. 1 kiln reads high, the No. 1 kiln electric valve increases its opening, and the No. 2 kiln electric valve decreases its opening.

[0013] During the production process of kilns No. 1 and No. 2, when the pressure gauge reading is >0 kPa, electric valve 2 opens to ensure that outside air does not enter; when the pressure gauge reading is <0 kPa, electric valve 2 closes and the carbon dioxide recovery fan reduces its speed; when the pressure gauge reading is <-10 kPa, if reducing the frequency of the carbon dioxide recovery fan to below 20 Hz cannot meet the production requirements, the cooling air electric valve opens.

[0014] A more specific embodiment of the above technical solution may be that the electric valve one, the carbon dioxide detector one, the pressure gauge, and the electric valve two are connected to a control unit.

[0015] Furthermore, the carbon dioxide detector and the carbon dioxide recovery fan are connected to the control unit.

[0016] Furthermore: the control unit is a PLC.

[0017] Furthermore: the carbon dioxide recovery fan is a variable frequency fan.

[0018] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0019] This method for stable carbon dioxide recovery in a double-chamber kiln utilizes electrical instrumentation and interlocking control of electric valves to effectively control the carbon dioxide recovery concentration and stabilize it within a certain range. Addressing the instability of carbon dioxide in flue gas during periods of switching between multiple double-chamber kilns, this method achieves stable carbon dioxide recovery through controlled procedures. This device can be applied to simultaneously recover flue gas from two or more kilns, stably controlling the recovered carbon dioxide concentration and ensuring its stability. Stable carbon dioxide recovery will benefit carbon dioxide production and subsequent lime deep processing carbonization steps. Attached Figure Description

[0020] Figure 1 This is the main view of the existing technology;

[0021] Figure 2 This is a front view of the dual-chamber kiln stable carbon dioxide recovery device according to an embodiment of the present invention;

[0022] The diagram shows: 1. Flue gas dust removal fan; 2. Flue gas outlet duct; 3. Electric valve 1; 4. Cooling air duct; 5. Cooling air electric valve; 6. Carbon dioxide detector 1; 7. Pressure gauge; 8. Electric valve 2; 9. Carbon dioxide recovery duct 1; 10. Carbon dioxide detector 2; 11. Carbon dioxide recovery duct 2; 12. Carbon dioxide recovery fan; 13. Flue gas dust collector; 14. Kiln No. 1; 15. Kiln No. 2; 16. Control unit. Detailed Implementation

[0023] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0024] This method for the stable recovery of carbon dioxide in a double-chamber kiln includes controlling the stable recovery of carbon dioxide in the double-chamber kiln using a double-chamber kiln stable carbon dioxide recovery device.

[0025] like Figure 2 The double-chamber kiln carbon dioxide recovery device shown includes a No. 1 kiln 14 and a No. 2 kiln 15, which are connected by an intermediate channel. The top of the No. 1 kiln 14 and the No. 2 kiln 15 are respectively connected to a flue gas dust collector 13 through a pipe. The flue gas dust collector 13 is connected to the flue gas outlet pipe 2, which is connected to the flue gas dust collector 13, and a flue gas dust collector fan 1 is connected to it. The cooling air pipe 4 is connected to the unloading hopper at the bottom of the No. 1 kiln 14 and the No. 2 kiln 15 through a cooling air electric valve 5.

[0026] After connecting to the flue gas dust removal fan 1, the flue gas outlet duct 2 is sequentially equipped with an electric valve 3, a carbon dioxide detector 6, a pressure gauge 7, and an electric valve 8. A carbon dioxide recovery duct 9 is connected between the carbon dioxide detector 6 and pressure gauge 7 on the flue gas outlet duct of kiln 14 and the carbon dioxide detector 6 and pressure gauge 7 on the flue gas outlet duct of kiln 25. A carbon dioxide recovery duct 11 extends from the carbon dioxide recovery duct 9, and a carbon dioxide detector 10 and a carbon dioxide recovery fan 12 are sequentially installed on the carbon dioxide recovery duct 11. The electric valve 3, carbon dioxide detector 6, pressure gauge 7, electric valve 8, carbon dioxide detector 10, and carbon dioxide recovery fan 12 are connected to a control unit 16, which is a PLC; the carbon dioxide recovery fan 12 is a variable frequency fan.

[0027] The control steps of the control unit 16 include:

[0028] When kiln 14 or kiln 2 is shut down, the electric valve 3 and electric valve 8 on the flue gas outlet duct of kiln 1 or kiln 2 will be closed because no flue gas is generated.

[0029] When both kiln 14 and kiln 25 are in production, in order to ensure that the carbon dioxide recovery concentration of flue gas from kiln 1 and kiln 2 is uniform, the two parameter values ​​of kiln combustion time and reversal time are set to be consistent to ensure that the two kilns do not reversal at the same time. Before the reversal period, the cooling air electric valve 5 on the cold air duct of kiln 1 and kiln 2 is closed, and the opening degree of electric valve 3 is set to 60%.

[0030] Start the carbon dioxide recovery fan 12 on carbon dioxide recovery pipeline 2 11 to recover flue gas from the two kilns.

[0031] 20 seconds before the changeover, fuel is cut off in kiln 14, reducing the carbon dioxide concentration in the flue gas. When the data detected by carbon dioxide detector 6 in kiln 14 is low, electric valve 3 in kiln 1 decreases its opening, while electric valve 3 in kiln 2 increases its opening to ensure a stable carbon dioxide concentration in the carbon dioxide recovery pipeline. When the data detected by carbon dioxide detector 6 in kiln 14 is high, electric valve 3 in kiln 14 increases its opening, while electric valve 3 in kiln 2 decreases its opening to ensure a stable carbon dioxide concentration in the carbon dioxide recovery pipeline (this can be determined by carbon dioxide detector 210).

[0032] During the production process of Kiln 14 and Kiln 25, the flue gas outlet duct 2 is under positive pressure, i.e., the reading of pressure gauge 7 is >0 kPa, and electric valve 2 8 is opened to ensure that outside air does not enter. When the reading of pressure gauge 7 is <0 kPa, electric valve 2 8 is closed, and carbon dioxide recovery fan 12 reduces its speed to ensure that the flue gas generated by Kiln 14 and Kiln 25 can be fully utilized, ensuring the safety of the entire system and a stable concentration of recovered carbon dioxide. When the reading of pressure gauge 7 is <-10 kPa, if reducing the frequency of carbon dioxide recovery fan 12 to below 20 Hz cannot meet the production requirements, cooling air electric valve 5 is opened to prevent the pipeline pressure from being too low and causing the pipeline to be flattened and damaged by atmospheric pressure.

[0033] This method for stable carbon dioxide recovery in a double-chamber kiln utilizes electrical instrumentation and interlocking control of electric valves to effectively control the carbon dioxide recovery concentration and stabilize it within a certain range. Addressing the instability of carbon dioxide in flue gas during periods of switching between multiple double-chamber kilns, this method achieves stable carbon dioxide recovery through controlled procedures. This device can be applied to simultaneously recover flue gas from two or more kilns, stably controlling the recovered carbon dioxide concentration and ensuring its stability. Stable carbon dioxide recovery will benefit carbon dioxide production and subsequent lime deep processing carbonization steps.

Claims

1. A method for stable carbon dioxide recovery in a double-chamber kiln, comprising controlling the stable carbon dioxide recovery in the double-chamber kiln using a double-chamber kiln stable carbon dioxide recovery device; the double-chamber kiln stable carbon dioxide recovery device comprises a No. 1 kiln and a No. 2 kiln connected by an intermediate channel, the tops of the No. 1 kiln and the No. 2 kiln respectively connected to flue gas dust collectors via pipes, the flue gas dust collectors connected to the flue gas outlet pipes are connected to flue gas dust removal fans, and cooling air pipes are respectively connected to the bottoms of the No. 1 kiln and the No. 2 kiln via cooling air electric valves, characterized in that: After the flue gas outlet duct is connected to the flue gas dust removal fan, an electric valve one, a carbon dioxide detector one, a pressure gauge and an electric valve two are installed in sequence. A carbon dioxide recovery duct one is installed between the carbon dioxide detector one and the pressure gauge on the flue gas outlet duct of kiln one and between the carbon dioxide detector one and the pressure gauge on the flue gas outlet duct of kiln two. A carbon dioxide recovery duct two is led out from the carbon dioxide recovery duct one. A carbon dioxide detector two and a carbon dioxide recovery fan are installed in sequence on the carbon dioxide recovery duct two. The control steps include: When kiln No. 1 or kiln No. 2 is shut down, electric valve 1 and electric valve 2 on the flue gas outlet duct of kiln No. 1 or kiln No. 2 are closed. When both kilns No. 1 and No. 2 are in production, the combustion time and reversing time of the kilns are set to be the same to ensure that the two kilns do not reverse at the same time during the reversing period. Before the reversing period, the cooling air electric valves on the cold air ducts of kilns No. 1 and No. 2 are closed, and the opening degree of electric valve one is set to 60%. Start the carbon dioxide recovery fan on carbon dioxide recovery pipeline 2 to recover the flue gas from the two kilns; 20 seconds before the changeover, the No. 1 kiln cuts off fuel, and the carbon dioxide concentration in the flue gas decreases. When the carbon dioxide detector of the No. 1 kiln reads low, the No. 1 kiln electric valve decreases its opening, and the No. 2 kiln electric valve increases its opening. When the carbon dioxide detector of the No. 1 kiln reads high, the No. 1 kiln electric valve increases its opening, and the No. 2 kiln electric valve decreases its opening. During the production process of kilns No. 1 and No. 2, when the pressure gauge reading is >0 kPa, electric valve 2 opens to ensure that outside air does not enter; when the pressure gauge reading is <0 kPa, electric valve 2 closes and the carbon dioxide recovery fan reduces its speed; when the pressure gauge reading is <-10 kPa, if reducing the frequency of the carbon dioxide recovery fan to below 20 Hz cannot meet the production requirements, the cooling air electric valve opens.

2. The method for stable carbon dioxide recovery in a double-chamber kiln according to claim 1, characterized in that: The electric valve one, the carbon dioxide detector one, the pressure gauge and the electric valve two are connected to a control unit.

3. The method for stable carbon dioxide recovery in a double-chamber kiln according to claim 2, characterized in that: The carbon dioxide detector and the carbon dioxide recovery fan are connected to the control unit.

4. The method for stable carbon dioxide recovery in a double-chamber kiln according to claim 3, characterized in that: The control unit is a PLC.

5. The method for stable recovery of carbon dioxide in a double-chamber kiln according to any one of claims 1-4, characterized in that: The carbon dioxide recovery fan is a variable frequency fan.

Images