Cement kiln bypass venting dechlorination and waste heat recovery system and method

Abstract

The present application relates to the field of energy saving and environmental protection, and discloses a cement kiln bypass air release dechlorination and waste heat recovery system and method, which comprises a wind taking device, a probe assembly integrated on the wind taking device, and a first dust removal unit; a heat exchanger unit, a second dust removal unit, an induced draft booster fan arranged downstream of the second dust removal unit, an oxygen supplement circuit, and a control unit; the wind taking device draws high-temperature mixed flue gas containing dust into a cement kiln smoke chamber; the heat exchanger unit is in communication with the outlet of the first dust removal unit; the second dust removal unit is in communication with the outlet of the heat exchanger unit; the induced draft booster fan is used to provide power for the system and send the purified flue gas to a waste heat utilization device; the oxygen supplement circuit is used to take gas from a clean gas source and accurately inject the gas into the wind taking device through an oxygen supplement electric regulating valve; the control unit is electrically connected with the probe assembly, various sensors, a wind taking electric regulating valve, an oxygen supplement electric regulating valve, and the induced draft booster fan; according to real-time detection parameters, the bypass air release amount and the oxygen supplement amount are cooperatively controlled through an internal algorithm, thereby reducing the energy consumption cost of enterprises and reducing greenhouse gas emissions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy saving and environmental protection, and in particular to a cement kiln bypass air release dechlorination and waste heat recovery system and method. BACKGROUND

[0002] In modern cement production, in order to comprehensively utilize resources and reduce costs, alternative raw materials or fuels containing high levels of volatile components such as chlorine, alkali, sulfur, etc. are often used. During the high-temperature calcination process in the rotary kiln, these volatile components (especially chloride ions) will accumulate in the kiln, forming a cycle. Excessive accumulation of chloride ions can cause frequent skinning and clogging in the preheater, decomposer, and kiln tail smoke chamber, etc., seriously affecting the stable operation and efficiency of the kiln system. At the same time, high chlorine content can also adversely affect the final quality and performance of the cement product.

[0003] To solve this problem, the existing technology generally uses a bypass air release system, which extracts a portion of the flue gas carrying a large amount of high-temperature chlorine-containing dust from the kiln tail smoke chamber, cools and dedusts it, and then discharges it, thereby removing the chlorides from the kiln system and breaking the internal cycle.

[0004] However, the traditional bypass air release system has the following defects:

[0005] The extracted flue gas has a temperature of 900-1100℃, and direct cooling or water quenching can cause a huge loss of heat energy, increasing the total energy consumption of the system. Extracting gas from the kiln system reduces the oxygen content in the kiln, which can cause a local reducing atmosphere in the kiln, affecting the quality of the clinker calcination. To handle the high-temperature flue gas, high-temperature cooling and dedusting equipment are needed, increasing the investment cost, and to compensate for the heat loss caused by the extraction of air, more fuel needs to be consumed. SUMMARY

[0006] The present application provides a cement kiln bypass air release dechlorination and waste heat recovery system, which aims to solve the problems mentioned in the above-mentioned prior art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A cement kiln bypass air release dechlorination and waste heat recovery system, comprising:

[0009] An air extraction device in the form of a cylinder is arranged in an inclined manner on the side wall of the cement kiln smoke chamber, the air extraction device extends into the smoke chamber to extract high-temperature mixed flue gas containing dust, a probe assembly and an oxygen supplement inlet are provided on the air extraction device, the probe assembly integrates a gas analyzer for detecting HCl concentration, O2 content and CO content, and an air extraction electric regulating valve is provided between the air extraction device and the downstream short pipe;

[0010] The primary dust removal unit is a cyclone, and the gas outlet of the air taking device is connected to the straight cylinder section inlet of the cyclone through a short pipe to preliminarily separate the mixed flue gas, and the separated high-chlorine dust material is discharged to the chlorine bypass ash bin for separate treatment through the air lock device;

[0011] The heat exchanger unit has a hot side inlet connected to the gas outlet of the cyclone and a cold side inlet connected to the clean air supply device, and is used for heat exchange between the high-temperature flue gas and the clean air;

[0012] The secondary dust removal unit has an inlet connected to the hot side outlet of the heat exchanger unit, is used for further dust removal of the cooled flue gas, and has an outlet provided with an HCl concentration analyzer, and the collected high-chlorine ash is discharged to the chlorine bypass ash bin for treatment;

[0013] The waste heat recovery system includes an induced draft booster fan arranged downstream of the outlet of the secondary dust removal unit, and is used for sending the purified flue gas into the waste heat power generation device;

[0014] The oxygen supplement circuit includes a gas taking branch, the gas taking branch is taken from the heat exchanger hot side outlet or the clean air supply device, and is connected with a flow meter in series, the gas taking branch is connected with an oxygen supplement injection inlet of the air taking device, and an oxygen supplement electric regulating valve is arranged at the oxygen supplement injection inlet;

[0015] The control unit includes a PLC controller and an upper computer monitoring system, the input end of the PLC controller is electrically connected with a probe assembly at the air taking device, an HCl concentration analyzer at the outlet of the secondary dust removal unit, and temperature sensors and pressure sensors distributed at the outlet of the air taking device, the inlets and outlets of the heat exchanger, and the inlet of the secondary dust removal unit, and the output end of the PLC controller is electrically connected with an air taking electric regulating valve, an oxygen supplement electric regulating valve, and an induced draft booster fan frequency converter, and the control unit calculates a target bypass air discharge amount and an oxygen supplement amount through a built-in control algorithm according to the detected HCl concentration, O2 and CO content.

[0016] Preferably, the control algorithm of the control unit includes:

[0017] A chlorine content monitoring module is used for monitoring the HCl concentration C in the flue gas through the probe assembly;

[0018] A bypass air discharge amount calculation module is used for calculating a required bypass air discharge amount Q1:

[0019] When C>C1, Q1= (C-Ct) x Qt x K / C;

[0020] When C≤C1, Q1=0;

[0021] Wherein, C1 is an HCl concentration limit value, Ct is a target chlorine content, Qt is a total flue gas amount of the kiln system, and K is a correction coefficient;

[0022] An oxygen content balance module for calculating a basic oxygen make-up Q2b:

[0023] When Os > Oa, Q2b = Q1 x (Os - Oa) / (Oair - Oa);

[0024] When Os ≤ Oa, Q2b = 0;

[0025] Wherein, Os is the set oxygen content of the kiln system, Oa is the measured oxygen content of the kiln system, and Oair is the oxygen content of the air;

[0026] A CO correction module for correcting the final oxygen make-up Q2 according to the CO content:

[0027] When CO < COmax, Q2 = Q2b;

[0028] When CO ≥ COmax, Q2 = Q2b x (1 + β), wherein β = (CO - COmax) / COmax, and 0 < β ≤ 0.3;

[0029] At the same time, limit 0 ≤ Q2 ≤ Q2max, and Q2max is the maximum oxygen make-up;

[0030] A coordinated control module for synchronously adjusting the opening of the air taking electric regulating valve and the oxygen make-up electric regulating valve according to the calculation results of Q1 and Q2.

[0031] Preferably, the control unit further comprises:

[0032] A temperature protection module for monitoring the inlet temperature T of the secondary dust removal unit, and adjusting the air flow on the cold side of the heat exchanger for temperature adjustment when T is lower than the sum of the dew point temperature Td and the safety margin ΔT;

[0033] A pressure balance module for monitoring the pressure at each point of the system, and maintaining the negative pressure at the air taking point stable by adjusting the frequency of the induced draft booster fan;

[0034] An abnormality processing module for processing abnormal working conditions:

[0035] When the CO content exceeds COmax, the CO correction module is called to increase the oxygen make-up;

[0036] When the sensor fails, switch to manual control mode and maintain the operating parameters before the failure.

[0037] Preferably, the inner wall of the hot side of the heat exchanger unit is provided with a wear-resistant lining, and a compressed air soot blowing device is installed, which is automatically started according to the pressure difference ΔP of the heat exchanger, and the soot blowing program is executed when ΔP exceeds the set threshold value ΔPmax.

[0038] Preferably, the secondary dust removal unit is a bag filter or an electric dust collector, and the high-chlorine ash collected by the chlorine bypass ash bin is sent to a special storage facility through a closed conveying system for harmless treatment or sold as a chemical raw material.

[0039] Preferably, the oxygen supplement inlet is arranged on the cylinder of the air taking device at a position 50-150 mm away from the air taking port, is arranged vertically between the oxygen supplement inlet and the cylinder, and is provided with a wind baffle on the side close to the smoke chamber inside the cylinder. A flow meter is arranged on the oxygen supplement pipeline for monitoring and controlling the oxygen supplement amount.

[0040] Preferably, the induced draft booster fan is a centrifugal fan with a built-in frequency drive.

[0041] Preferably, the system further comprises a chlorine removal optimization module, which calculates, based on the HCl concentration Cin detected by the probe assembly at the air taking device and the HCl concentration Cout detected by the analyzer at the outlet of the secondary dust removal unit:

[0042] the chlorine load FCl=Cin×Q1;

[0043] the chlorine removal efficiency ηCl= (Cin-Cout) / Cin×100%;

[0044] the correction factor update value K is updated according to the chlorine removal efficiency ηCl.

[0045] wherein Q1 is the actual bypass air discharge amount.

[0046] When ηCl is lower or higher than ηt, the target chlorine removal efficiency, the chlorine removal optimization module outputs a correction instruction to the control unit to optimize the bypass air discharge amount Q1, the oxygen supplement amount Q2, and the rotation speed of the induced draft booster fan.

[0047] The application also discloses a method for bypass air discharge and chlorine removal and waste heat recovery of a cement kiln, which comprises the following steps:

[0048] S1: continuously monitoring the HCl concentration C, the O2 content, the CO content, the temperature, and the pressure of the kiln tail flue gas through a probe assembly;

[0049] S2: starting a bypass air discharge program when the HCl concentration C exceeds a set limit value C1;

[0050] S3: calculating the required bypass air discharge amount Q1 according to the formula Q1= (C-Ct) ×Qt×K / C;

[0051] calculating the basic oxygen supplement amount Q2b according to the oxygen content and correcting the final oxygen supplement amount Q2 according to the CO content;

[0052] S4: outputting a control signal by a PLC controller to synchronously adjust the opening degrees of the air taking electric regulating valve and the oxygen supplement electric regulating valve;

[0053] S5: Monitor the pressure difference of the cyclone inlet and outlet and the temperature of the discharge port. When the pressure difference abnormally increases or the temperature abnormally decreases, it is judged that a blockage occurs and an alarm is given;

[0054] S6: Monitor the temperature T of the secondary dust removal unit inlet to ensure that T >= Td+DeltaT;

[0055] S7: Monitor the pressure difference DeltaP of the heat exchanger. When DeltaP> DeltaPmax, start the soot blowing program;

[0056] S8: Adjust the speed of the induced draft fan to maintain the negative pressure of the air intake point within the set range;

[0057] S9: Send the purified flue gas to the waste heat power generation device for energy recovery;

[0058] S10: Based on the HCl concentration Cin at the air intake device and the HCl concentration Cout at the outlet of the secondary dust removal unit, calculate the dechlorination efficiency etaCl=(Cin-Cout) / Cin*100% in real time;

[0059] S11: Send the high-chlorine ash collected by the primary and secondary dust removal units to the chlorine bypass ash bin for separate treatment;

[0060] S12: Execute the abnormal processing program:

[0061] When the CO content exceeds COmax, increase the oxygen supplement amount according to the CO correction module algorithm;

[0062] When the temperature T < Td, adjust the cold side air intake of the heat exchanger or open the hot flue gas bypass valve;

[0063] When the pressure is out of limit, automatically adjust the frequency of the induced draft fan;

[0064] When the sensor fails, switch to manual control mode and issue an alarm;

[0065] S13: Update the correction coefficient K value according to the dechlorination efficiency etaCl to optimize the control parameters;

[0066] S14: Record the operation data and generate a report, and return to S1 to continue monitoring.

[0067] The technical effects and advantages of the present application are:

[0068] 1、The present application can effectively control the chlorine circulation enrichment problem in the kiln system by precise bypass air release technology, and maintain the chlorine content in a safe range. The design of two-stage dust removal system ensures that the high-chlorine dust is fully separated and collected, reducing the accumulation of chlorine elements in the system from the source. The problem of preheater skinning and blocking that has long plagued cement enterprises is solved, greatly extending the skinning cleaning cycle and significantly reducing the frequency of kiln shutdown and blockage. The stable operation of the system not only improves the operation rate of the production line, but also effectively reduces the corrosion of high-chlorine environment on equipment, prolonging the service life of key components such as the inner cylinder of the preheater, the material distribution plate, and the cyclone. At the same time, stable chlorine content control creates good conditions for clinker calcination, improves the mineral composition of clinker, and improves the quality stability and strength grade of cement products.

[0069] 2. The bypass air release and chlorine removal technology is deeply integrated with waste heat recovery technology, forming a complete energy cascade utilization system. High-temperature air release flue gas is first exchanged with clean air through a high-efficiency heat exchanger, and the recovered high-grade heat energy can be directly used for raw material drying, coal powder preparation and other processes in the production system, replacing the original heat source provided by additional fuel. The medium and low temperature flue gas after heat exchange and cooling is further sent to the waste heat power generation system, realizing the conversion of heat energy to electric energy and increasing the enterprise's self-generation capacity. The originally discarded heat energy is converted into valuable energy resources. The entire system forms a closed-loop energy utilization chain, not only reducing the enterprise's energy consumption cost, but also reducing greenhouse gas emissions.

[0070] 3. The bypass air release and chlorine removal process is realized through the control system. The multi-parameter online monitoring device provided by the system can real-time collect key process parameters such as chlorine content, oxygen content, and carbon monoxide content, and quickly analyze and decide through the built-in intelligent algorithm. The oxygen supplement control strategy can dynamically adjust the oxygen supplement amount according to the actual working condition, ensuring that the combustion in the kiln is always in the best state, avoiding the problem of incomplete combustion caused by lack of oxygen. The automatic collection, storage and analysis of all operation data provide a scientific basis for production management and promote the transformation and upgrading of cement enterprises to intelligent manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 The system schematic diagram of the present application.

[0072] Figure 2 The system flowchart of the present application. DETAILED DESCRIPTION

[0073] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0074] In the production process of cement clinker, the raw materials (such as limestone, clay) and fuels (such as coal) used usually contain a certain amount of chlorine (Cl) element. In the high-temperature calcination environment of the rotary kiln, chlorine will combine with alkali metals (potassium, sodium) to form volatile chlorides. These chlorides are enriched in the kiln system, and when the concentration is too high, they will condense and crystallize in the preheater, the decomposition furnace and the flue chamber and other parts with lower temperature, causing serious skinning and plugging problems. Skin plugging will worsen the system ventilation and affect the material conveying, and in severe cases, it can even cause the kiln to stop, greatly affecting the continuity and stability of cement production.

[0075] Embodiment one

[0076] Please refer to Figure 1 and Figure 2 A cement kiln bypass air-bleeding chlorine removal and waste heat recovery system, comprising: an air-bleeding device, a primary dust removal unit, a heat exchanger unit, a secondary dust removal unit, a waste heat recovery system, an oxygen supplement loop and a control unit, wherein:

[0077] The air-bleeding device is in the shape of a cylinder and is arranged on the side wall of the cement kiln flue chamber in an inclined manner. The cylinder body of the air-bleeding device is made of high-temperature-resistant and wear-resistant alloy steel material. The diameter of the cylinder body is 400-800 mm. The cylinder body is installed on the side wall of the cement kiln flue chamber at an inclination angle of 15-60°. The air-bleeding opening extends into the interior of the flue chamber, and the depth of the extension can be adjusted. The air-bleeding device extends into the flue chamber to extract high-temperature mixed flue gas containing dust. A probe assembly and an oxygen supplement inlet are arranged on the air-bleeding device. The oxygen supplement inlet is arranged on the cylinder body of the air-bleeding device at a distance of 50-150 mm from the air-bleeding opening. The oxygen supplement inlet is arranged vertically with the cylinder body. A wind shield is arranged on the side of the cylinder body close to the flue chamber to prevent dust and impurities from blocking the interior of the oxygen supplement inlet during the air extraction process. A flow meter is arranged on the oxygen supplement pipeline to monitor and control the oxygen supplement amount.

[0078] The probe assembly integrates a gas analyzer, comprising:

[0079] The HCl concentration sensor adopts an online infrared absorption spectrum sensor, the O2 sensor adopts a zirconia or electrochemical sensor, the CO sensor adopts an online infrared absorption spectrum sensor, a temperature sensor and a pressure sensor, which are used to detect the HCl concentration, the O2 content and the CO content. An air-bleeding electric regulating valve is arranged between the air-bleeding device and the downstream short pipe.

[0080] The primary dust removal unit is a cyclone, and a lock star type discharger is installed at the bottom of the cyclone cone to discharge the separated high-chlorine dust material to a chlorine bypass ash bin. The outlet of the air taking device is connected to the inlet of the straight cylinder section of the cyclone through a short pipe to preliminarily separate the mixed flue gas, and the separated high-chlorine dust material is discharged to the chlorine bypass ash bin through the lock device for separate treatment.

[0081] The heat exchanger unit is connected to the gas outlet of the cyclone at the hot side inlet and connected to the clean air supply device at the cold side inlet to exchange the high-temperature flue gas with the clean air. The inner wall of the hot side of the heat exchanger unit is provided with a wear-resistant lining, and a compressed air blowing device is installed. The blowing device is automatically started according to the pressure difference ΔP of the heat exchanger, and the blowing program is executed when the ΔP exceeds the set threshold value ΔPmax. The blowing device is a common blowing nozzle.

[0082] Specifically, the heat exchanger is equipped with 6-12 blowing nozzles uniformly distributed in the heat exchanger. The compressed air pressure is 0.5-0.8 MPa, and the single blowing time is 30-60 s. When the pressure difference ΔP of the heat exchanger exceeds the set value 800 Pa, the blowing program is automatically started, and the blowing period can be adjusted according to the actual dust accumulation.

[0083] The secondary dust removal unit is connected to the hot side outlet of the heat exchanger unit to further remove dust from the cooled flue gas. The outlet of the secondary dust removal unit is provided with an HCl concentration analyzer, and the collected high-chlorine ash is discharged to the chlorine bypass ash bin for treatment.

[0084] The waste heat recovery system includes an induced draft booster fan arranged downstream of the outlet of the secondary dust removal unit to send the purified flue gas into a waste heat power generation device.

[0085] The oxygen supplement circuit includes a gas taking branch connected to the outlet of the heat exchanger or the clean air supply device and connected in series with a flow meter. The gas taking branch is connected to an oxygen supplement injection inlet of the air taking device, and an oxygen supplement electric regulating valve is arranged at the oxygen supplement injection inlet.

[0086] The control unit includes a PLC controller and an upper computer monitoring system. The input end of the PLC controller is electrically connected to the probe assembly at the air taking device, the HCl concentration analyzer at the outlet of the secondary dust removal unit, and the temperature sensors and pressure sensors distributed at the outlet of the air taking device, the inlet and outlet of the heat exchanger, and the inlet of the secondary dust removal unit. The output end of the PLC controller is electrically connected to the air taking electric regulating valve, the oxygen supplement electric regulating valve, and the frequency converter of the induced draft booster fan. The control unit calculates the target bypass air discharge amount and the oxygen supplement amount through the built-in control algorithm according to the detected HCl concentration, O2 content, and CO content.

[0087] The traditional system often only focuses on chlorine removal, ignoring its influence on the stability of the kiln system.

[0088] The present application integrates the three functions of chlorine removal, waste heat recovery and atmosphere compensation into a closed loop system, solves the problem of single function, and realizes the maximization of comprehensive benefits.

[0089] The synergistic design of "air extraction-oxygen compensation" solves the problem of disturbance of the atmosphere (especially the O2 content) in the kiln caused by bypass air release, ensuring the stable operation of the main production line and the quality of the clinker.

[0090] The bypass air release system is transformed from a pure "energy consumption unit" to an "energy recovery unit", which converts waste heat into heat energy through heat exchangers and waste heat recovery systems, achieving significant economic and environmental benefits.

[0091] The control algorithm of the control unit includes:

[0092] A chlorine content monitoring module for monitoring the HCl concentration C in the flue gas through a probe assembly;

[0093] A bypass air release amount calculation module for calculating the required bypass air release amount Q1:

[0094] When C>C1, Q1=(C-Ct)×Qt×K / C;

[0095] When C≤C1, Q1=0;

[0096] Wherein, C1 is the HCl concentration limit, Ct is the target chlorine content, Qt is the total flue gas amount of the kiln system, and K is the correction coefficient;

[0097] An oxygen content balancing module for calculating the basic oxygen compensation amount Q2b:

[0098] When Os>Oa, Q2b=Q1×(Os-Oa) / (Oair-Oa);

[0099] When Os≤Oa, Q2b=0;

[0100] Wherein, Os is the set oxygen content of the kiln system, Oa is the measured oxygen content of the kiln system, and Oair is the oxygen content of air;

[0101] A CO correction module for correcting the final oxygen compensation amount Q2 according to the CO content:

[0102] When CO<COmax, Q2=Q2b;

[0103] When CO≥COmax, Q2=Q2b×(1+β), wherein β=(CO-COmax) / COmax, and 0<β≤0.3;

[0104] At the same time, limit 0≤Q2≤Q2max, and Q2max is the maximum oxygen compensation amount;

[0105] The coordination control module is used for synchronously adjusting the opening degrees of the air taking electric regulating valve and the oxygen supplementing electric regulating valve according to the calculation results of Q1 and Q2. The chlorine load is quantified as the bypass air discharge amount, avoiding over-discharge / under-discharge caused by experience, and taking into account the chlorine removal efficiency and heat loss control.

[0106] O2 and CO double-variable coordination ensures that oxygen supplementing meets the combustion safety and avoids excessive oxygen leading to increased energy consumption and secondary reaction.

[0107] The coordination control reduces coupled oscillation, shortens the recovery time after disturbance, and improves the stability of the kiln tail working condition and the utilization rate of the production line.

[0108] Preferably, the control unit further comprises:

[0109] The temperature protection module is used for monitoring the inlet temperature T of the secondary dust removal unit, and when T is lower than the sum of the dew point temperature Td and the safety margin ΔT, temperature adjustment is performed by adjusting the air flow of the cold side of the heat exchanger;

[0110] The pressure balance module is used for monitoring the pressure at each point of the system, and the negative pressure stability at the air taking point is maintained by adjusting the frequency of the induced draft booster fan;

[0111] The abnormality processing module is used for processing abnormal working conditions:

[0112] When the CO content exceeds COmax, the CO correction module is called to increase the oxygen supplementing amount;

[0113] When the sensor fails, the manual control mode is switched to and the operating parameters before the failure are maintained. Avoiding the secondary dust removal low-temperature condensation causing filter material paste bag, acid corrosion. Ensure that the secondary dust removal is in the best temperature window, stabilize the low emission, and prolong the service life of the filter bag / electrode.

[0114] Maintain system availability under high humidity / load fluctuation conditions and reduce unplanned downtime.

[0115] The bypass air discharge amount calculation module accurately maps the chlorine concentration deviation to the required gas flow, realizing "on-demand chlorine removal" based on real-time load, thereby avoiding under-discharge or over-discharge caused by traditional fixed proportion or stepwise regulation, and optimizing the economic efficiency of operation.

[0116] The oxygen content balance module is used for feedforward compensation based on the air discharge amount, and actively maintains the stoichiometric combustion; the CO correction module is used as a safety feedback loop, and when signs of incomplete combustion are detected, the gain of the compensation amount is amplified, ensuring the combustion efficiency and operation safety.

[0117] The coordination control module ensures the high synchronization and proportional accuracy of the actions of the two actuators, i.e., the air intake valve and the oxygen supplement valve. The module solves the instantaneous pressure, temperature or component fluctuations that may be caused by the execution delay or mismatch in the multivariable control system, ensures the smooth implementation of the control strategy, and avoids secondary disturbance to the main system.

[0118] The temperature protection module effectively inhibits the condensation of HCl and other acidic gases by maintaining the flue gas temperature above the safety margin, thereby fundamentally slowing down the chemical corrosion rate of the equipment.

[0119] The pressure balance module realizes the dynamic pressure decoupling between the bypass system and the main flue by closed-loop control of the negative pressure at the air intake point. The module ensures that the operation of the bypass system does not significantly affect the ventilation resistance curve of the main kiln system, and maintains the stability of the pressure difference at key positions in the kiln, such as the kiln head and the kiln tail.

[0120] The secondary dust removal unit is a bag-type dust collector or an electric dust collector. The high-chlorine ash collected in the chlorine bypass ash bin is sent to a special storage facility through a sealed conveying system for harmless treatment or sold as a chemical raw material.

[0121] The induced draft booster fan is a centrifugal fan with a built-in frequency drive.

[0122] The system further comprises a chlorine removal optimization module. Based on the HCl concentration Cin detected by the probe assembly at the air intake device and the HCl concentration Cout detected by the analyzer at the outlet of the secondary dust removal unit, the following calculations are performed:

[0123] Chlorine load FCl = Cin x Q1;

[0124] Chlorine removal efficiency ηCl = (Cin - Cout) / Cin x 100%;

[0125] According to the chlorine removal efficiency ηCl, the updated value K of the correction coefficient is updated.

[0126] Wherein, Q1 is the actual bypass air volume calculated by the formula.

[0127] When ηCl is lower or higher than ηt, the target chlorine removal efficiency, the chlorine removal optimization module outputs a correction instruction to the control unit to optimize the bypass air volume Q1, the oxygen supplement volume Q2 and the speed of the induced draft booster fan.

[0128] The chlorine removal optimization module introduces the chlorine removal efficiency ηCl as feedback to iteratively update the correction coefficient K in the core control model, solving the problem of accuracy decline of the static model in long-term operation. This enables the entire system to have the ability of continuous self-optimization.

[0129] The application also discloses a cement kiln bypass air discharge and waste heat recovery method, comprising the following steps:

[0130] S1: Continuously monitor the HCl concentration C, O2 content, CO content, temperature and pressure of the kiln tail flue gas through the probe assembly;

[0131] S2: When the HCl concentration C exceeds the set limit C1, start the bypass bleeder program;

[0132] S3: Calculate the required bypass bleeder quantity Q1 according to the formula Q1= (C-Ct) x Qt x K / C;

[0133] Calculate the basic oxygen supplement quantity Q2b according to the oxygen content, and obtain the final oxygen supplement quantity Q2 by correction according to the CO content;

[0134] S4: The PLC controller outputs a control signal to synchronously adjust the opening degree of the air taking electric regulating valve and the oxygen supplement electric regulating valve;

[0135] S5: Monitor the pressure difference between the inlet and outlet of the cyclone and the temperature at the discharge port. When the pressure difference abnormally increases or the temperature abnormally decreases, it is judged that a blockage has occurred and an alarm is issued;

[0136] S6: Monitor the inlet temperature T of the secondary dust removal unit to ensure that T≥Td+ΔT;

[0137] S7: Monitor the pressure difference ΔP of the heat exchanger. When ΔP>ΔPmax, start the soot blowing program;

[0138] S8: Adjust the speed of the induced draft booster fan to maintain the negative pressure at the air taking point within the set range;

[0139] S9: Send the purified flue gas to the waste heat power generation device for energy recovery;

[0140] S10: Based on the HCl concentration Cin at the air taking device and the HCl concentration Cout at the outlet of the secondary dust removal unit, calculate the dechlorination efficiency ηCl= (Cin-Cout) / Cin x 100% in real time;

[0141] S11: Send the high-chlorine ash collected by the primary and secondary dust removal units to the chlorine bypass ash bin for separate treatment;

[0142] S12: Execute the abnormal handling program:

[0143] When the CO content exceeds COmax, increase the oxygen supplement quantity according to the CO correction module algorithm;

[0144] When the temperature T<Td, adjust the cold side air intake of the heat exchanger or open the hot flue gas bypass valve;

[0145] When the pressure exceeds the limit, automatically adjust the frequency of the induced draft booster fan;

[0146] When the sensor fails, switch to manual control mode and issue an alarm;

[0147] S13: Update the correction coefficient K value based on the dechlorination efficiency ηCl and optimize the control parameters;

[0148] S14: Record runtime data and generate reports, then return to S1 to continue monitoring.

[0149] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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 process, method, article, or apparatus.

[0150] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cement kiln by-pass dechlorination and waste heat recovery system, characterized in that, The application relates to a cement kiln exhaust gas treatment system. The system comprises: an air extraction device in the shape of a cylinder and arranged in an inclined manner on the side wall of a cement kiln flue, the air extraction device extending into the flue to extract high-temperature mixed flue gas containing dust, a probe assembly and an oxygen supplement inlet being arranged on the air extraction device, the probe assembly integrating a gas analyzer for detecting HCl concentration, O2 content and CO content, an air extraction electric regulating valve being arranged between the air extraction device and a downstream short pipe; a primary dust removal unit, the gas outlet of the air extraction device being connected to the inlet of a straight cylinder section of a cyclone through a short pipe, the primary dust removal unit being used for primary gas-solid separation of the mixed flue gas, and high-chlorine dust materials separated after the primary dust removal being discharged to a chlorine bypass ash bin through a lock air device for separate treatment; a heat exchanger unit, a hot side inlet of the heat exchanger unit being connected to the gas outlet of the cyclone, and a cold side inlet of the heat exchanger unit being connected to a clean air supply device; a secondary dust removal unit, an inlet of the secondary dust removal unit being connected to the hot side outlet of the heat exchanger unit, the secondary dust removal unit being used for further dust removal of the cooled flue gas, and an HCl concentration analyzer being arranged at the outlet of the secondary dust removal unit, high-chlorine ash collected by the secondary dust removal unit being discharged to the chlorine bypass ash bin for treatment; a waste heat recovery system, the waste heat recovery system comprising an induced draft fan arranged downstream of the outlet of the secondary dust removal unit, the induced draft fan being used for sending the purified flue gas into a waste heat power generation device; an oxygen supplement circuit, the oxygen supplement circuit comprising a gas extraction branch, the gas extraction branch being taken from the hot side outlet of the heat exchanger or the clean air supply device, the gas extraction branch being connected to the oxygen supplement inlet of the air extraction device, and an oxygen supplement electric regulating valve being arranged at the oxygen supplement inlet; a control unit, the control unit comprising a PLC controller and an upper computer monitoring system, input ends of the PLC controller being electrically connected to the probe assembly at the air extraction device, the HCl concentration analyzer at the outlet of the secondary dust removal unit, and temperature sensors and pressure sensors distributed at the outlet of the air extraction device, the inlets and outlets of the heat exchanger, and the inlet of the secondary dust removal unit, and output ends of the PLC controller being electrically connected to the air extraction electric regulating valve, the oxygen supplement electric regulating valve and the frequency converter of the induced draft fan, the control unit calculating target bypass air discharge and oxygen supplement amount through a built-in control algorithm according to the detected HCl concentration, O2 content and CO content; the control algorithm of the control unit comprises: a chlorine content monitoring module for monitoring HCl concentration C in flue gas through the probe assembly; a bypass air discharge calculation module for calculating required bypass air discharge Q1: when C>C1, Q1= (C-Ct) x Qt x K / C; when C<=C1, Q1=0; wherein C1 is an HCl concentration limit value, Ct is a target chlorine content, Qt is total flue gas volume of a kiln system, and K is a correction coefficient; an oxygen content balancing module for calculating basic oxygen supplement Q2b: when Os>Oa, Q2b=Q1 x (Os-Oa) / (Oair-Oa); when Os<=Oa, Q2b=0; wherein Os is a set oxygen content of the kiln system, Oa is a measured oxygen content of the kiln system, and Oair is oxygen content of air; a CO correction module for correcting final oxygen supplement Q2 according to CO content: when CO<COmax, Q2=Q2b; when CO>=COmax, Q2=Q2b x (1+beta), wherein beta=(CO-COmax) / COmax, and 0<beta<=0.3; at the same time, Q2 is limited to 0<=Q2<=Q2max, and Q2max is maximum oxygen supplement amount. The coordination control module is configured to synchronously adjust the opening degrees of the air taking electric regulating valve and the oxygen supplementing electric regulating valve according to the calculation results of Q1 and Q2.

2. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1, wherein, The control unit further comprises: The temperature protection module is configured to monitor the inlet temperature T of the secondary dust removal unit, and to adjust the temperature by adjusting the air flow of the cold side of the heat exchanger when the temperature T is lower than the sum of the dew point temperature Td and the safety margin AT; The pressure balance module is configured to monitor the pressures at various points of the system, and to maintain the negative pressure stability of the air taking point by adjusting the frequency of the induced draft booster fan; The abnormality processing module is configured to process abnormal working conditions: When the CO content exceeds COmax, the CO correction module is called to increase the oxygen supplementing amount; When the sensor fails, the system switches to a manual control mode and maintains the operating parameters before the failure.

3. The cement kiln by-pass dechlorination and waste heat recovery system of claim 2, wherein, The inner wall of the hot side of the heat exchanger unit is provided with a wear-resistant lining, and a compressed air soot blowing device is installed, which is automatically started according to the pressure difference AP of the heat exchanger, and the soot blowing program is executed when the pressure difference AP exceeds the set threshold APmax.

4. The cement kiln by-pass dechlorination and waste heat recovery system of claim 3, wherein, The secondary dust removal unit is a bag-type dust collector or an electric dust collector, and the high-chlorine ash collected in the chlorine bypass ash bin is sent to a special storage facility through a sealed conveying system for harmless treatment or sold as a chemical raw material.

5. The cement kiln by-pass dechlorination and waste heat recovery system of claim 4 wherein, The oxygen supplementing injection inlet is arranged on the barrel of the air taking device at a position 50-150 mm away from the air taking port, and is arranged vertically between the barrel and the oxygen supplementing injection inlet. A baffle is arranged on the side of the barrel close to the smoke chamber, and a flowmeter is arranged on the oxygen supplementing pipeline for monitoring and controlling the oxygen supplementing amount.

6. The cement kiln by-pass dechlorination and waste heat recovery system of claim 5, wherein, The induced draft booster fan is a centrifugal fan with a built-in frequency converter.

7. The cement kiln by-pass dechlorination and waste heat recovery system of claim 6 wherein, The system further comprises a chlorine removal optimization module, which calculates based on the HCl concentration Cin detected by the probe assembly at the air taking device and the HCl concentration Cout detected by the analyzer at the outlet of the secondary dust removal unit: The chlorine removal efficiency ηCl= (Cin-Cout) / Cin×100%; According to the chlorine removal efficiency ηCl, the correction coefficient update value K is updated; Wherein, Q1 is the required bypass air volume; When ηCl is lower or higher than ηt, the target chlorine removal efficiency, the chlorine removal optimization module outputs a correction instruction to the control unit to optimize the bypass air volume Q1, the oxygen supplementing amount Q2 and the speed of the induced draft booster fan.

8. A method for dechlorination and waste heat recovery system for bypassing a cement kiln based on the system as claimed in claim 7, characterized in that, The method comprises the following steps: S1: continuously monitoring the HCl concentration C, the O2 content, the CO content, the temperature and the pressure of the kiln tail flue gas through the probe assembly; S2: when the HCl concentration C exceeds the set limit value C1, the bypass air program is started; S3: the required bypass air volume Q1 is calculated according to the formula Q1= (C-Ct) ×Qt×K / C; The basic oxygen supplementing amount Q2b is calculated according to the oxygen content, and the final oxygen supplementing amount Q2 is obtained by correction according to the CO content; S4: the PLC controller outputs a control signal to synchronously adjust the opening degrees of the air taking electric regulating valve and the oxygen supplementing electric regulating valve; S5: the pressure difference between the inlet and the outlet of the cyclone barrel and the temperature at the discharge port are monitored, and when the pressure difference abnormally increases or the temperature abnormally decreases, it is judged that a blockage occurs and an alarm is given; S6: the inlet temperature T of the secondary dust removal unit is monitored to ensure that T≥Td+AT; S7: the pressure difference AP of the heat exchanger is monitored, and the soot blowing program is started when AP>APmax. S8: Adjust the speed of the induced draft fan to maintain the negative pressure at the air intake point within the set range; S9: Send the purified flue gas to the waste heat power generation device for energy recovery; S10: Based on the HCl concentration Cin at the air intake device and the HCl concentration Cout at the outlet of the secondary dust removal unit, calculate the dechlorination efficiency ηCl = (Cin-Cout) / Cin × 100% in real time; S11: Send the high-chlorine ash collected by the primary and secondary dust removal units to the chlorine bypass ash bin for separate treatment; S12: Execute the abnormal handling program: When the CO content exceeds COmax, increase the oxygen supplement amount according to the CO correction module algorithm; When the temperature T < Td, adjust the cold side air intake of the heat exchanger or open the hot flue gas bypass valve; When the pressure is out of limit, automatically adjust the frequency of the induced draft fan; When the sensor fails, switch to manual control mode and issue an alarm; S13: Update the correction coefficient K value according to the dechlorination efficiency ηCl to optimize the control parameters; S14: Record the operation data and generate a report, and return to S1 for continuous monitoring.

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