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

Abstract

The invention relates to the technical field of energy conservation and environmental protection, and discloses a cement kiln bypass air discharge dechlorination and waste heat recovery system and method.The cement kiln bypass air discharge dechlorination and waste heat recovery system comprises an air taking device which stretches into a cement kiln smoke chamber to extract high-temperature mixed smoke containing dust, and a probe assembly and a first-stage dust removal unit are integrated on the air taking device; the heat exchanger unit is communicated with an outlet of the primary dust removal unit, and the secondary dust removal unit is communicated with an outlet of the heat exchanger unit, comprises an induced air booster fan arranged at the downstream of the secondary dust removal unit, and is used for providing power for the system and conveying purified flue gas to waste heat utilization equipment; the oxygen supplementation loop is used for taking air from a clean air source and accurately injecting the air into the air taking device through an oxygen supplementation electric control valve; and the control unit is electrically connected with the probe assembly, the sensors, the air taking electric control valve, the oxygen supplementing electric control valve and the induced air booster fan, and cooperatively controls the bypass air releasing amount and the oxygen supplementing amount through a built-in algorithm according to real-time detection parameters, so that the energy consumption cost of an enterprise is reduced, and greenhouse gas emission is reduced.

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: 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

[0005] 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.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A cement kiln bypass air release dechlorination and waste heat recovery system, comprising: An air extraction device in the shape of a cylinder and 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, an air extraction electric regulating valve is provided between the air extraction device and the downstream short pipe; A primary dedusting unit in the form of a cyclone, the gas outlet of the air extraction device is connected to the straight cylinder section inlet of the cyclone through a short pipe, for preliminary gas-solid separation of the mixed flue gas, and the separated high-chlorine dust material is discharged to the chlorine bypass ash bin for separate treatment through a wind lock device; a heat exchanger unit, a hot side inlet of which is communicated with the gas outlet of the cyclone, and a cold side inlet of which is communicated with the clean air supply device, for heat exchange between the high-temperature flue gas and the clean air; a secondary dust removal unit, an inlet of which is communicated with the hot side outlet of the heat exchanger unit, for further dust removal of the cooled flue gas, and an outlet of which is provided with an HCl concentration analyzer, and the collected high-chlorine ash is discharged to a chlorine bypass ash bin for treatment; a waste heat recovery system, comprising an induced draft booster fan arranged downstream of the outlet of the secondary dust removal unit, for sending the purified flue gas into a waste heat power generation device; an oxygen supplement loop, comprising a gas taking branch, the gas taking branch being taken from the heat exchanger hot side outlet or the clean air supply device, and being connected in series with a flow meter, and the gas taking branch being communicated with an oxygen supplement injection inlet of the air taking device, and the oxygen supplement injection inlet being provided with an oxygen supplement electric regulating valve; a control unit, comprising a PLC controller and an upper computer monitoring system, an input end of the PLC controller being 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 an output end of the PLC controller being electrically connected with an air taking electric regulating valve, an oxygen supplement electric regulating valve, and a frequency converter of the induced draft booster fan, and the control unit calculating a target bypass air discharge amount and an oxygen supplement amount according to the detected HCl concentration, O2 and CO content through a built-in control algorithm.

[0007] Preferably, the control algorithm of the control unit comprises: a chlorine content monitoring module for monitoring the HCl concentration C in the flue gas through the probe assembly; a bypass air discharge amount calculation module for calculating the required bypass air discharge amount Q1: when C>C1, Q1=(C-Ct)×Qt×K / C; when C≤C1, Q1=0; wherein C1 is the HCl concentration limit value, Ct is the target chlorine content, Qt is the total flue gas amount of the kiln system, and K is a correction coefficient; an oxygen content balancing module for calculating a basic oxygen supplement amount Q2b: when Os>Oa, Q2b=Q1×(Os-Oa) / (Oair-Oa); when Os≤Oa, Q2b=0; 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; a CO correction module for correcting the final oxygen supplement amount Q2 according to the CO content: when CO<COmax, Q2=Q2b; When CO≥COmax, Q2=Q2b×(1+β), wherein β=(CO-COmax) / COmax, and 0<β≤0.3; At the same time, limit 0≤Q2≤Q2max, Q2max is the 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 supplement electric regulating valve according to the calculation results of Q1 and Q2.

[0008] Preferably, the control unit further comprises: The temperature protection module is configured to monitor the inlet temperature T of the secondary dust removal unit, and perform temperature adjustment 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 ΔT; The pressure balance module is configured to monitor the pressures at various points of the system, and maintain the negative pressure stability at 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 supplement amount; When the sensor fails, the system switches to a manual control mode and maintains the operating parameters before the failure.

[0009] 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 performs a soot blowing program when the pressure difference ΔP exceeds a set threshold value ΔPmax.

[0010] Preferably, 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.

[0011] Preferably, the oxygen supplement injection inlet is arranged on the cylinder of the air taking device at a position 50-150 mm away from the air taking port, and is arranged vertically between the oxygen supplement injection inlet and the cylinder. A wind baffle is arranged on the side of the cylinder close to the smoke chamber, and a flowmeter is arranged on the oxygen supplement pipeline for monitoring and controlling the oxygen supplement amount.

[0012] Preferably, the induced draft booster fan is a centrifugal fan with a built-in frequency drive.

[0013] 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: Chlorine load FCl=Cin×Q1; Chlorine removal efficiency ηCl=(Cin-Cout) / Cin×100%; According to the dechlorination efficiency ηCl, the correction coefficient update value K is updated; Wherein, Q1 is the actual bypass air volume; When ηCl is lower or higher than ηt, the target dechlorination efficiency, the dechlorination optimization module outputs a correction instruction to the control unit to optimize the bypass air volume Q1, the oxygen supplement volume Q2 and the induced draft fan speed.

[0014] The application also discloses a cement kiln bypass air dechlorination and waste heat recovery method, comprising the following steps: S1: continuously monitoring the HCl concentration C, O2 content, CO content, temperature and pressure of the kiln tail flue gas through a probe assembly; S2: when the HCl concentration C exceeds the set limit value C1, starting the bypass air program; S3: calculating the required bypass air volume Q1 according to the formula Q1= (C-Ct) × Qt × K / C; Calculating the basic oxygen supplement volume Q2b according to the oxygen content, and correcting to obtain the final oxygen supplement volume Q2 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 supplement electric regulating valve; S5: monitoring the pressure difference between the inlet and outlet of the cyclone and the temperature of the discharge port, and when the pressure difference abnormally increases or the temperature abnormally decreases, judging that a blockage occurs and alarming; S6: monitoring the inlet temperature T of the secondary dust removal unit to ensure that T≥Td+ΔT; S7: monitoring the pressure difference ΔP of the heat exchanger, and when ΔP>ΔPmax, starting the soot blowing program; S8: adjusting the speed of the induced draft fan to maintain the negative pressure at the air taking point within the set range; S9: sending the purified flue gas into a waste heat power generation device for energy recovery; 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, calculating the dechlorination efficiency ηCl=(Cin-Cout) / Cin×100% in real time; S11: sending the high-chlorine ash collected by the primary dust removal unit and the secondary dust removal unit to a chlorine bypass ash bin for separate treatment; S12: executing an abnormality processing program: When the CO content exceeds COmax, increasing the oxygen supplement volume according to the CO correction module algorithm; When the temperature T<Td, adjusting the air inlet on the cold side of the heat exchanger or opening the hot flue gas bypass valve; When the pressure exceeds the limit, automatically adjusting the frequency of the induced draft fan; When the sensor fails, switching to a manual control mode and alarming; 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 to continue monitoring.

[0015] Technical effects and advantages of the present application: 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 within a safe range. The design of two-stage dust removal system ensures that 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, significantly extending the skinning cleaning cycle and significantly reducing the frequency of kiln shutdown for cleaning. 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.

[0016] 2. The bypass air release dechlorination and waste heat recovery technology is deeply integrated to build 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 to realize the conversion of heat energy to electric energy, 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.

[0017] 3. The bypass air release dechlorination process is realized through the control system to achieve full-automatic operation. The multi-parameter online monitoring device equipped in the system can collect key process parameters such as chlorine content, oxygen content, and carbon monoxide content in real time, and quickly analyze and make decisions through the built-in intelligent algorithm. The oxygen supplement control strategy can dynamically adjust the oxygen supplement amount according to the actual working conditions to ensure that the kiln combustion is always in the best state, avoiding 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

[0018] Figure 1 The system schematic diagram of the present application.

[0019] Figure 2 The system flowchart of the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0021] 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 parts such as the preheater, the decomposing furnace and the flue, causing serious skinning and plugging problems. Skin plugging will worsen the system ventilation and affect material transportation, and in severe cases, it can even cause the kiln to stop, greatly affecting the continuity and stability of cement production.

[0022] Embodiment one 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: The air-bleeding device is in the shape of a cylinder and is arranged in an inclined manner on the side wall of the cement kiln flue. The cylinder of the air-bleeding device is made of high-temperature-resistant and wear-resistant alloy steel material. The diameter of the cylinder is 400-800 mm. The cylinder is installed on the side wall of the cement kiln flue at an inclination angle of 15-60°. The air-bleeding opening extends into the interior of the flue, and the depth of the extension can be adjusted. The air-bleeding device extends into the flue 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 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. A baffle is arranged on the side of the cylinder close to the flue 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.

[0023] The probe assembly integrates a gas analyzer, comprising: The HCl concentration sensor uses an online infrared absorption spectrum sensor, the O2 sensor uses a zirconia or electrochemical sensor, the CO sensor uses 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. The primary dust removal unit is a cyclone, a lock star type discharger is installed at the bottom of the cyclone cone, and the separated high-chlorine dust material is discharged to the 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, which is used for the preliminary gas-solid separation of the mixed flue gas. The separated high-chlorine dust material is discharged to the chlorine bypass ash bin through the lock device for separate treatment. The heat exchanger unit is connected to the gas outlet of the cyclone at the hot side inlet, and is connected to the clean air supply device at the cold side inlet, which is used for heat exchange between the high-temperature flue gas and the clean air. The inner wall 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.

[0024] Specifically, the heat exchanger is equipped with 6-12 blowing nozzles, which are 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.

[0025] The secondary dust removal unit is connected to the hot side outlet of the heat exchanger unit, which is used for further dust removal of 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. The waste heat recovery system includes an induced draft booster fan arranged downstream of the outlet of the secondary dust removal unit, which is used to send the purified flue gas into the waste heat power generation device. The oxygen supplement loop includes a gas taking branch, which is taken from the heat exchanger hot side outlet or the clean air supply device, and is connected in series with a flow meter. The gas taking branch is connected to the oxygen supplement injection inlet of the air taking device, and an oxygen supplement electric regulating valve is arranged at the oxygen supplement injection inlet. 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 according to the detected HCl concentration, O2 and CO content through the built-in control algorithm.

[0026] The traditional system often only focuses on chlorine removal, and ignores its influence on the stability of the kiln system.

[0027] The present application integrates the 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.

[0028] The coordinated design of "air extraction-oxygen supplement" solves the problem of disturbance of the kiln atmosphere (especially O2 content) caused by bypass air release, ensuring the stable operation of the main production line and the quality of clinker.

[0029] 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.

[0030] The control algorithm of the control unit includes: A chlorine content monitoring module for monitoring the HCl concentration C in the flue gas through a probe assembly; A bypass air release amount calculation module for calculating the required bypass air release amount Q1: When C > C1, Q1 = (C - Ct) x Qt x K / C; When C ≤ C1, Q1 = 0; Where 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; An oxygen content balancing module for calculating the basic oxygen supplement amount Q2b: When Os > Oa, Q2b = Q1 x (Os - Oa) / (Oair - Oa); When Os ≤ Oa, Q2b = 0; Where 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; A CO correction module for correcting the final oxygen supplement amount Q2 according to the CO content: When CO < COmax, Q2 = Q2b; When CO ≥ COmax, Q2 = Q2b x (1 + β), where β = (CO - COmax) / COmax, and 0 < β ≤ 0.3; At the same time, limit 0 ≤ Q2 ≤ Q2max, Q2max is the maximum oxygen supplement amount; A coordinated control module for synchronously adjusting the opening of the air intake electric regulating valve and the oxygen supplement electric regulating valve according to the calculation results of Q1 and Q2. The chlorine load is quantified as bypass air release amount, avoiding over-release / under-release caused by "experience", and balancing chlorine removal efficiency and heat loss control.

[0031] O2 and CO double variable coordination ensures that oxygen supplement meets the safety of combustion and avoids excessive oxygen leading to increased energy consumption and secondary reactions.

[0032] Coordinated control reduces coupled oscillation, shortens recovery time after disturbance, and improves kiln tail working condition stability and production line availability.

[0033] Preferably, the control unit further comprises: a temperature protection module for monitoring the inlet temperature T of the secondary dust removal unit, and adjusting the air flow of the cold side of the heat exchanger when T is lower than the sum of the dew point temperature Td and the safety margin ΔT; a pressure balance module for monitoring the pressure at various points in the system, and maintaining the negative pressure at the air intake point stable by adjusting the frequency of the induced draft booster fan; an abnormality handling module for handling abnormal conditions: when the CO content exceeds COmax, a CO correction module is called to increase the oxygen supplement; when a sensor fails, the system switches to manual control mode and maintains the operating parameters before the failure. This avoids the secondary dust removal low-temperature condensation causing filter material paste bags and acid corrosion. It ensures that the secondary dust removal is in the optimal temperature window, stabilizes the low emission, and prolongs the service life of the filter bag / electrode.

[0034] maintains system availability under high humidity / load fluctuation conditions and reduces unplanned downtime.

[0035] The bypass air release amount calculation module accurately maps the chlorine concentration deviation to the required gas flow, achieving "on-demand chlorine removal" based on real-time load, thereby avoiding under-release or over-release caused by traditional fixed proportion or stepwise adjustment, and optimizing the economic efficiency of operation.

[0036] The oxygen content balance module performs feedforward compensation based on the air release amount, actively maintaining stoichiometric combustion; the CO correction module acts as a safety feedback loop, amplifying the compensation amount when signs of incomplete combustion are detected, ensuring combustion efficiency and operational safety.

[0037] The coordinated control module ensures high synchronicity and proportional accuracy of the actions of the two actuators, the air intake valve and the oxygen supplement valve. It solves the transient pressure, temperature, or component fluctuations that may be caused by execution delays or mismatches in multivariable control systems, ensuring smooth implementation of the control strategy and avoiding secondary disturbances to the main system.

[0038] The temperature protection module effectively suppresses the condensation of HCl and other acidic gases by maintaining the flue gas temperature above the safety margin, fundamentally slowing down the chemical corrosion rate of the equipment.

[0039] The pressure balance module achieves dynamic pressure decoupling between the bypass system and the main flue by closed-loop control of the negative pressure at the air intake point. It ensures that the operation of the bypass system does not significantly affect the ventilation resistance curve of the main kiln system, maintaining the stability of the pressure difference at key positions in the kiln (such as the kiln head and kiln tail).

[0040] The secondary dust removal unit is a bag filter or an electric dust collector, high-chlorine ash collected by the chlorine bypass ash bin is sent to a special storage facility through a closed conveying system, and is treated for harmless treatment or sold as a chemical raw material.

[0041] The induced draft booster fan is a centrifugal fan with a built-in frequency drive.

[0042] 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: chlorine load FCl = Cin x Q1; chlorine removal efficiency ηCl = (Cin - Cout) / Cin x 100%; According to the chlorine removal efficiency ηCl, the updated value K of the correction coefficient is updated. Wherein, Q1 is the actual bypass air volume calculated by the formula; 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.

[0043] 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.

[0044] The application also discloses a cement kiln bypass air discharge and waste heat recovery method, comprising the following steps: S1: continuously monitor the HCl concentration C, O2 content, CO content, temperature and pressure of the kiln tail gas through the probe assembly; S2: when the HCl concentration C exceeds the set limit value C1, start the bypass air discharge program; S3: calculate the required bypass air discharge volume Q1 according to the formula Q1 = (C - Ct) x Qt x K / C; Calculate the basic oxygen supplement volume Q2b according to the oxygen content, and correct the final oxygen supplement volume Q2 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 supplement electric regulating valve; S5: monitor the pressure difference between the inlet and outlet of the cyclone and the temperature of the discharge port, and when the pressure difference abnormally increases or the temperature abnormally decreases, it is judged that blockage occurs and an alarm is given; S6: monitor the inlet temperature T of the secondary dust removal unit to ensure that T ≥ Td + ΔT; S7: monitor the pressure difference ΔP of the heat exchanger, and when ΔP > ΔPmax, start the soot blowing program; S8: Adjust the speed of the induced draft fan to maintain the negative pressure of 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, the dechlorination efficiency ηCl=(Cin-Cout) / Cin×100% is calculated in real time; S11: The high-chlorine ash collected by the primary and secondary dust removal units is sent to the chlorine bypass ash bin for separate treatment; S12: Execute the exception 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 booster 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 to continue monitoring.

[0045] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0046] The above is only the preferred embodiment of the present application, and it should be noted that for ordinary skilled persons in the art, without departing from the technical principles of the present application, a number of improvements and refinements can be made, which should also be considered as the protection scope of the present application.

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 being integrated with 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, and the control unit calculating target bypass air discharge and oxygen supplement according to the detected HCl concentration, O2 content and CO content through a built-in control algorithm.

2. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1, wherein, 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; 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.

3. The cement kiln by-pass dechlorination and waste heat recovery system of claim 2, 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 ΔT; 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.

4. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1 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 ΔP of the heat exchanger, and the soot blowing program is executed when ΔP exceeds the set threshold ΔPmax.

5. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1 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.

6. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1 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.

7. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1 wherein, The induced draft booster fan is a centrifugal fan with a built-in frequency converter.

8. The cement kiln by-pass dechlorination and waste heat recovery system of claim 1 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: chlorine load FCl=Cin×Q1; chlorine removal efficiency ηCl=(Cin-Cout) / Cin×100%; correction coefficient update value K according to the chlorine removal efficiency ηCl; wherein Q1 is the actual 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.

9. A method for dechlorination and waste heat recovery in a bypass system of a cement kiln according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1: continuously monitoring the HCl concentration C, O2 content, CO content, temperature and 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: calculating the required bypass air volume Q1 according to the formula Q1=(C-Ct)×Qt×K / C; calculating the basic oxygen supplementing amount Q2b according to the oxygen content and the final oxygen supplementing amount Q2 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: monitoring the pressure difference between the inlet and outlet of the cyclone barrel and the temperature at the discharge port, and determining that a blockage occurs and alarming when the pressure difference abnormally increases or the temperature abnormally decreases; S6: monitoring the inlet temperature T of the secondary dust removal unit to ensure that T≥Td+ΔT; S7: monitoring the pressure difference ΔP of the heat exchanger, and starting the soot blowing program when ΔP>ΔPmax. 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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