A control system and method for oxygen-enriched combustion process in a double-chamber lime kiln

Abstract

This invention relates to a control system and method for oxygen-enriched combustion in a double-chamber lime kiln. The system includes an oxygen-enriched supply unit, a combustion air duct, a mixing unit, and a control unit. The oxygen-enriched supply unit includes an oxygen production station and an oxygen delivery pipeline, with both ends of the pipeline connected to the oxygen production station and the combustion air duct, respectively. The oxygen-enriched supply unit injects oxygen-enriched gas into the combustion air duct. The mixing unit is located at the connection between the oxygen delivery pipeline and the combustion air duct, and is used to fully mix the oxygen-enriched gas with the combustion air to form oxygen-enriched combustion air. The oxygen delivery pipeline of the oxygen-enriched supply unit is equipped with a regulating valve and a shut-off valve. The control unit is electrically connected to the regulating valve and shut-off valve in the oxygen-enriched supply unit, and is used to automatically adjust the flow rate and on / off status of the oxygen-enriched gas according to the operating conditions of the double-chamber lime kiln. This invention achieves a synergistic improvement in energy saving, increased production, environmental protection, and safe operation by introducing oxygen-enriched gas into the combustion air duct and constructing a matching automatic control system.

Description

Technical Field

[0001] This invention relates to the field of industrial kiln combustion control technology, and more specifically, to a control system and method for oxygen-enriched combustion process in a double-chamber lime kiln. Background Technology

[0002] Double-chamber vertical kilns are important equipment for lime production. They are characterized by high thermal efficiency because they alternate between two kiln chambers for calcination and preheating. However, existing technologies generally suffer from problems such as large exhaust emissions, excessively high kiln pressure, severe dust and ash accumulation, high overall energy consumption, high exhaust gas temperature, and large emissions of nitrogen oxides (NOx) when maintaining a relatively high load of about 90% of the designed capacity.

[0003] The reason for this is that traditional combustion processes use ordinary air (with an oxygen content of about 21%) as a combustion-supporting agent. The nitrogen in the air, which makes up about 78% of the combustion process, is an inert gas and does not participate in the reaction. Instead, it absorbs a large amount of heat from the reaction and is discharged as a major component of the flue gas, carrying away significant heat. At the same time, nitrogen at high temperatures reacts with oxygen to produce thermal NOx.

[0004] Oxygen-enriched combustion technology, as a highly efficient, energy-saving, and environmentally friendly combustion technology, relies on using oxygen-enriched air with an oxygen content higher than 21% (typically 22%-30%) to replace ordinary air as the combustion-supporting gas. Theoretically, this technology offers advantages such as increased flame temperature, reduced flue gas volume, decreased exhaust heat loss, and suppression of thermal NOx formation. However, existing technologies lack a complete, reliable, and precisely matched control scheme for successfully applying oxygen-enriched combustion technology to the complex structure and variable operating conditions of double-chamber lime kilns, and achieving stable, efficient, and automated control. Simple introduction of oxygen-enriched gas can lead to uneven mixing, control mismatch, and even safety risks. Therefore, there is an urgent need in this field for a complete oxygen-enriched combustion process control system and method specifically tailored to the characteristics of double-chamber lime kiln processes. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a control system and method for oxygen-enriched combustion process in a double-chamber lime kiln, which aims to solve the problems existing in the prior art.

[0006] According to a first aspect of the present invention, a control system for an oxygen-enriched combustion process in a double-chamber lime kiln is provided, comprising: an oxygen-enriched supply unit, a combustion air duct, a mixing unit, and a control unit; The oxygen-enriched supply unit includes an oxygen-generating station and an oxygen-transmitting pipeline. The two ends of the oxygen-transmitting pipeline are respectively connected to the oxygen-generating station and the combustion-supporting air pipeline. The oxygen-enriched supply unit is used to inject oxygen-enriched gas into the combustion-supporting air pipeline. The mixing unit is located at the connection between the oxygen supply pipe and the combustion air pipe, and is used to fully mix the oxygen-enriched gas and the combustion air to form oxygen-enriched combustion air. The oxygen supply pipeline of the oxygen-enriched supply unit is equipped with a regulating valve and a shut-off valve. The control unit is electrically connected to the regulating valve and shut-off valve in the oxygen-enriched supply unit and is used to automatically adjust the flow rate and on / off state of the oxygen-enriched gas according to the operating conditions of the double-chamber lime kiln.

[0007] Preferably, the oxygen delivery pipeline is also equipped with a shut-off valve, a pressure reducing valve, a double pneumatic shut-off valve, and a flow detection device; the pressure reducing valve is configured to stabilize the delivery pressure of the oxygen-enriched gas at 0.3~0.5MPa.

[0008] Preferably, the mixing unit includes a nozzle disposed inside the combustion air duct, the nozzle being connected to one end of the oxygen supply pipe extending into the combustion air duct, and the nozzle having a plurality of spray nozzles evenly distributed at its outlet.

[0009] Preferably, the outlet of the nozzle faces the opposite direction to the flow direction of the combustion air in the combustion air duct.

[0010] Preferably, the control unit includes a PID controller, which receives a flow signal from the flow detection device and a preset oxygen enrichment concentration setpoint, and achieves closed-loop control of the oxygen enrichment gas flow rate by adjusting the opening of the regulating valve.

[0011] Preferably, the system also includes an oxygen content analyzer, which is installed on the combustion air duct downstream of the mixing unit to detect the oxygen content in the combustion air after mixing with oxygen-enriched gas, and feeds the detection signal back to the control unit to correct the oxygen enrichment concentration set value.

[0012] Preferably, the control unit is connected to the combustion air reversing valve of the double-chamber lime kiln and configured to execute the following interlocking logic: when a signal is received that the combustion air reversing valve has switched to the venting state, the control unit closes the shut-off valve and stops supplying oxygen-enriched gas; when a signal is received that the combustion air reversing valve has switched to the kiln-entry state, the control unit opens the shut-off valve and allows the supply of oxygen-enriched gas.

[0013] According to a second aspect of the present invention, a method for controlling the oxygen-enriched combustion process in a double-chamber lime kiln is provided. This method is implemented using the oxygen-enriched combustion process control system for a double-chamber lime kiln as described above, and includes the following steps: S1. Oxygen-enriched air is delivered to the combustion air duct; S2. The mixing unit fully mixes the oxygen-enriched air with the combustion-supporting air to form an oxygen-enriched combustion-supporting air. S3. The oxygen-enriched combustion air is sent into the combustion chamber of the double-chamber lime kiln to participate in combustion.

[0014] Preferably, in step S3, the control unit dynamically adjusts the injection flow rate of the oxygen-enriched gas according to the preset oxygen enrichment concentration setting value using PID regulation, so as to match the real-time combustion air volume and combustion conditions of the lime kiln.

[0015] Preferably, the oxygen-enriched gas is delivered at a pressure of 0.3~0.5MPa, the oxygen volume concentration of the oxygen-enriched combustion air is 22%~30%, and the injection point of the oxygen-enriched gas is located at the bottom of the combustion air duct after the combustion air vent valve.

[0016] Compared with the prior art, the present invention has the following beneficial effects: By introducing oxygen-enriched gas into the combustion air duct of a double-chamber lime kiln and constructing a matching automatic control system, a synergistic improvement in energy saving, increased production, environmental protection, and safe operation has been achieved. Specifically, the reduced nitrogen content in the oxygen-enriched combustion air formed after the oxygen-enriched gas mixes with the combustion air significantly reduces the volume of flue gas and exhaust heat loss, thereby lowering fuel consumption per unit product. Furthermore, the increased theoretical combustion temperature and faster combustion speed shorten calcination time, increasing kiln capacity. Simultaneously, a stable temperature field and uniform heat transfer ensure the quality of the lime product. In addition, reducing the total nitrogen content at the source effectively suppresses the formation of thermal NOx, reducing nitrogen oxide emissions. The reduction in exhaust gas volume directly leads to a decrease in kiln pressure, improving kiln operating conditions, reducing dust and ash accumulation, and enhancing operational stability. Through precise adjustment of the oxygen-enriched flow rate by the control unit and a safety interlock with the kiln reversing system, full automation and high safety of the process have been achieved. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0018] Figure 1 A schematic diagram of the structure of the oxygen-enriched combustion process control system for a double-chamber lime kiln according to an embodiment of the present invention is shown.

[0019] In the diagram: 1. Oxygen generating station; 2. Oxygen delivery pipeline; 21. Regulating valve; 22. Shut-off valve; 23. Gate valve; 24. Pressure reducing valve; 25. Dual pneumatic shut-off valve; 26. Flow transmitter; 27. Pressure gauge; 28. Manual valve; 29. ​​Exhaust valve; 3. Nozzle; 4. Combustion air duct; 41. Oxygen content analyzer. Detailed Implementation

[0020] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0021] This invention provides a control system for oxygen-enriched combustion process in a double-chamber lime kiln, see [link / reference]. Figure 1 The oxygen-enriched combustion process control system for the double-chamber lime kiln includes: an oxygen-enriched supply unit, a combustion air duct 4, a mixing unit, and a control unit. The oxygen-enriched supply unit includes an oxygen production station 1 and an oxygen delivery pipe 2. The two ends of the oxygen delivery pipe 2 are connected to the oxygen production station 1 and the combustion air duct 4, respectively. The oxygen-enriched supply unit is used to inject oxygen-enriched gas into the combustion air duct 4. The mixing unit is located at the connection between the oxygen delivery pipe 2 and the combustion air duct 4 to ensure that the oxygen-enriched gas and the combustion air are fully mixed to form oxygen-enriched combustion air. The oxygen delivery pipe 2 of the oxygen-enriched supply unit is equipped with a regulating valve 21 and a shut-off valve 22. The control unit is electrically connected to the regulating valve 21 and the shut-off valve 22 in the oxygen-enriched supply unit and is used to automatically adjust the flow rate and on / off state of the oxygen-enriched gas according to the operating conditions of the double-chamber lime kiln.

[0022] The mixing unit includes nozzles 3 disposed inside the combustion air duct 4. The nozzles 3 are connected to one end of the oxygen supply pipe 2 that extends into the combustion air duct 4. Several jet outlets are evenly distributed at the outlet of the nozzles 3. That is, the outlet of the nozzles 3 has a honeycomb structure, allowing the oxygen-enriched gas ejected through the nozzles 3 to be dispersed, enabling the oxygen-enriched gas to quickly and thoroughly mix with the combustion air in the combustion air duct 4. In this embodiment, the outlet direction of the nozzles 3 is opposite to the flow direction of the combustion air in the combustion air duct 4. This design causes the oxygen-enriched gas to be ejected in the form of multiple fine jets, impacting the upward-flowing mainstream of the combustion air head-on, thereby achieving rapid and thorough mixing.

[0023] A flow detection device is installed on the oxygen supply pipeline 2. The control unit receives the flow signal from the flow detection device and a preset oxygen enrichment concentration setpoint, and achieves closed-loop control of the oxygen enrichment gas flow rate by adjusting the opening of the regulating valve 21. The opening of the regulating valve 21 on the oxygen enrichment pipeline is adjusted by PID control based on the preset oxygen enrichment concentration setpoint (the amount of oxygen enrichment required per unit time). Specifically, the operator sets the target oxygen enrichment concentration (e.g., 25%), and the system calculates the required oxygen enrichment gas volumetric flow rate as the setpoint based on the current total combustion air volume. The control unit receives the actual flow signal detected by the flow detection device, compares it with the setpoint, and its output signal drives the regulating valve 21 to operate, so that the actual flow rate accurately tracks the setpoint. In this embodiment, the flow detection device is a flow transmitter 26 installed on the oxygen supply pipeline 2.

[0024] The double-chamber lime kiln oxygen-enriched combustion process control system also includes an oxygen content analyzer 41. The oxygen content analyzer 41 is installed on the combustion air duct 4 downstream of the mixing unit. It is used to detect the oxygen content in the oxygen-enriched combustion air after mixing with oxygen-enriched gas in real time, and feeds the detection signal back to the control unit to correct the oxygen concentration setpoint. Specifically, the control unit compares the oxygen content in the oxygen-enriched combustion air measured by the oxygen content analyzer 41 with the target value. If there is a deviation, the control unit fine-tunes the setpoint of the oxygen-enriched gas volume flow rate, forming an outer loop correction. This overcomes the interference caused by fluctuations in the combustion air volume or changes in the oxygen purity of the oxygen-enriched gas, ensuring the accurate and stable mixing concentration.

[0025] Furthermore, the control unit is connected to the combustion air reversing valve of the double-chamber lime kiln and configured to execute the following interlocking logic: when a signal is received that the combustion air reversing valve has switched to the venting state, the control unit closes the shut-off valve 22 and stops supplying oxygen-enriched gas; when a signal is received that the combustion air reversing valve has switched to the kiln-entry state, the control unit opens the shut-off valve 22 and allows the supply of oxygen-enriched gas.

[0026] See Figure 1In this embodiment, the oxygen supply pipeline 2 is a DN80mm pipe, and the oxygen supply pipeline 2 is sequentially equipped with a shut-off valve 23, a pressure reducing valve 24, a dual pneumatic shut-off valve 25, a flow transmitter 26, a pressure gauge 27, a regulating valve 21, a shut-off valve 22, an exhaust valve 29, and a manual valve 28. The shut-off valve 23 is used to cut off the entire oxygen supply pipeline 2 during equipment maintenance or long-term shutdown to ensure maintenance safety. The pressure reducing valve 24 is used to reduce and stabilize the high-pressure oxygen from the self-made oxygen station 1 to a safe pressure suitable for subsequent kiln processes, ensuring a stable supply of oxygen-enriched gas and the safety of the oxygen supply pipeline 2; in this embodiment, the pressure reducing valve 24 is configured to stabilize the delivery pressure of oxygen-enriched gas at 0.3~0.5MPa. This is the core to ensure a stable supply and pipeline safety. The dual pneumatic shut-off valve 25 consists of two pneumatic shut-off valves arranged in parallel, used for quick and reliable dual shut-off of the oxygen-enriched supply. The dual-valve design provides redundant safety protection to prevent single valve failure. The flow transmitter 26 can measure the instantaneous flow rate of oxygen-enriched gas in real time and continuously, and convert it into a standard electrical signal to be sent to the control unit. It is a necessary feedback signal source for realizing precise PID regulation. The pressure gauge 27 is used to display the pressure of oxygen-enriched gas in the oxygen supply pipeline 2 in real time. The operator can use this to judge whether the pressure reducing valve 24 is working properly and whether the pressure in the oxygen supply pipeline 2 is within the safe range. The regulating valve 21 can be used to receive the command signal from the control unit and dynamically and accurately adjust the opening of the valve 21 to control the flow rate of oxygen-enriched gas at the set value. It is a key actuator for achieving a precise and stable oxygen enrichment ratio. In this embodiment, the regulating valve 21 is a pneumatic regulating valve. The shut-off valve 22 is an interlocked execution structure that can receive emergency signals from the control unit, such as combustion air release and fault alarm, and quickly and reliably shut off the supply of oxygen-enriched gas. In this embodiment, the shut-off valve 22 is a pneumatic shut-off valve. The exhaust valve 29 is used to remove air from the oxygen supply pipeline 2 before oxygen supply or to vent residual gas in the oxygen supply pipeline 2 when the machine is shut down, so as to facilitate safe maintenance. The manual valve 28 is used to fine-tune the flow rate during the initial commissioning of the system, or as a manual bypass when the automatic valve fails, or for local isolation when repairing specific components.

[0027] The present invention also provides a method for controlling the oxygen-enriched combustion process in a double-chamber lime kiln. This method is implemented using the oxygen-enriched combustion process control system for a double-chamber lime kiln as described above, and includes the following steps: S1. Oxygen-enriched air is delivered to the combustion air duct 4.

[0028] S2. The mixing unit fully mixes the oxygen-enriched air with the combustion-supporting air to form an oxygen-enriched combustion-supporting air.

[0029] S3. The oxygen-enriched combustion air is sent into the combustion chamber of the double-chamber lime kiln to participate in combustion.

[0030] Specifically, in step S3, the control unit dynamically adjusts the injection flow rate of the oxygen-enriched gas using a PID control method based on a preset oxygen enrichment concentration setting, so as to match it with the real-time combustion air volume and combustion conditions of the lime kiln. Preferably, the delivery pressure of the oxygen-enriched gas is 0.3~0.5MPa, the oxygen volume concentration of the oxygen-enriched combustion air is 22%~30%, and the injection point of the oxygen-enriched gas is located at the bottom of the combustion air duct 4 after the combustion air vent valve.

[0031] In summary, the present invention has the following beneficial effects: Significant energy-saving and consumption-reducing effects: Due to the reduced nitrogen content in the oxygen-enriched combustion air formed by mixing oxygen-enriched gas and combustion air, the volume of flue gas generated after combustion of a unit of fuel is significantly reduced (by approximately 15%-25%), greatly reducing the heat loss carried away by the flue gas (i.e., exhaust heat loss). At the same time, the theoretical combustion temperature is increased, and the heat is more concentrated in the calcination of materials, thereby reducing the fuel consumption (heat consumption) per unit of product.

[0032] Improving production capacity and product quality: Increased combustion speed and flame temperature shorten the calcination time of limestone, allowing more material to be processed in the same amount of time. Furthermore, stable calcination temperature and uniform heat transfer contribute to improved lime product quality.

[0033] Significant environmental benefits: Due to the reduction in the total amount of nitrogen involved in the reaction, the generation of thermal NOx is suppressed at the source, effectively reducing the emission concentration of nitrogen oxides in flue gas.

[0034] Improve kiln working conditions and operational stability: The reduction in exhaust gas directly leads to a decrease in kiln pressure, which is conducive to the stable operation of the kiln and reduces dust and ash accumulation.

[0035] High level of automation and safety: The control unit enables automatic and precise adjustment of the oxygen-enriched gas flow rate and is interlocked with the kiln reversing system, ensuring the synchronization and safety of oxygen-enriched gas supply with the kiln process and avoiding errors and risks from manual operation.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0037] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A control system for oxygen-enriched combustion process in a double-chamber lime kiln, characterized in that, include: Oxygen-enriched supply unit, combustion air duct, mixing unit, and control unit; The oxygen-enriched supply unit includes an oxygen-generating station and an oxygen-transmitting pipeline. The two ends of the oxygen-transmitting pipeline are respectively connected to the oxygen-generating station and the combustion-supporting air pipeline. The oxygen-enriched supply unit is used to inject oxygen-enriched gas into the combustion-supporting air pipeline. The mixing unit is located at the connection between the oxygen supply pipe and the combustion air pipe, and is used to fully mix the oxygen-enriched gas and the combustion air to form oxygen-enriched combustion air. The oxygen supply pipeline of the oxygen-enriched supply unit is equipped with a regulating valve and a shut-off valve. The control unit is electrically connected to the regulating valve and shut-off valve in the oxygen-enriched supply unit and is used to automatically adjust the flow rate and on / off state of the oxygen-enriched gas according to the operating conditions of the double-chamber lime kiln.

2. The oxygen-enriched combustion process control system for a double-chamber lime kiln according to claim 1, characterized in that, The oxygen delivery pipeline is also equipped with a shut-off valve, a pressure reducing valve, a double pneumatic shut-off valve, and a flow detection device; the pressure reducing valve is configured to stabilize the delivery pressure of the oxygen-enriched gas at 0.3~0.5MPa.

3. The oxygen-enriched combustion process control system for a double-chamber lime kiln according to claim 1, characterized in that, The mixing unit includes a nozzle disposed inside the combustion air duct. The nozzle is connected to one end of the oxygen supply pipe that extends into the combustion air duct. Several jet nozzles are evenly distributed at the outlet of the nozzle.

4. The oxygen-enriched combustion process control system for a double-chamber lime kiln according to claim 3, characterized in that, The nozzle outlet faces the opposite direction to the flow direction of the combustion air in the combustion air duct.

5. The oxygen-enriched combustion process control system for a double-chamber lime kiln according to claim 2, characterized in that, The control unit includes a PID controller, which receives a flow signal from the flow detection device and a preset oxygen enrichment concentration setpoint, and achieves closed-loop control of the oxygen enrichment gas flow rate by adjusting the opening of the regulating valve.

6. The oxygen-enriched combustion process control system for a double-chamber lime kiln according to claim 5, characterized in that, It also includes an oxygen content analyzer, which is installed on the combustion air duct downstream of the mixing unit to detect the oxygen content in the combustion air after mixing with oxygen-enriched gas, and feeds the detection signal back to the control unit to correct the oxygen enrichment concentration set value.

7. The oxygen-enriched combustion process control system for a double-chamber lime kiln according to claim 2, characterized in that, The control unit is connected to the combustion air reversing valve of the double-chamber lime kiln and configured to execute the following interlocking logic: when a signal is received that the combustion air reversing valve has switched to the venting state, the control unit closes the shut-off valve and stops supplying oxygen-enriched gas; when a signal is received that the combustion air reversing valve has switched to the kiln-entry state, the control unit opens the shut-off valve and allows the supply of oxygen-enriched gas.

8. A method for controlling the oxygen-enriched combustion process in a double-chamber lime kiln, characterized in that, The implementation of the double-chamber lime kiln oxygen-enriched combustion process control system as described in any one of claims 1-7 includes the following steps: S1. Oxygen-enriched air is delivered to the combustion air duct; S2. The mixing unit fully mixes the oxygen-enriched air with the combustion-supporting air to form an oxygen-enriched combustion-supporting air. S3. The oxygen-enriched combustion air is sent into the combustion chamber of the double-chamber lime kiln to participate in combustion.

9. The method for controlling the oxygen-enriched combustion process in a double-chamber lime kiln according to claim 8, characterized in that, In step S3, the control unit dynamically adjusts the injection flow rate of the oxygen-enriched gas according to the preset oxygen concentration setting value using PID regulation, so as to match it with the real-time combustion air volume and combustion conditions of the lime kiln.

10. The method for controlling the oxygen-enriched combustion process in a double-chamber lime kiln according to claim 8, characterized in that, The oxygen-enriched gas is delivered at a pressure of 0.3~0.5MPa, the oxygen volume concentration of the oxygen-enriched combustion air is 22%~30%, and the injection point of the oxygen-enriched gas is located at the bottom of the combustion air duct after the combustion air vent valve.

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