A device for dust collection of chlorination furnace flue gas and an operating method thereof

Abstract

The application discloses a device for dust collection of chlorination furnace flue gas and an operating method. The device comprises a chlorination furnace, a spraying chamber, a flue, a cyclone dust collector, a bag filter, a dust collection pulp tank, and a dust collection control system; the dust collection control system acquires a spraying chamber temperature signal to control the flow of titanium tetrachloride mud of the first spraying port for primary cooling, and acquires a flue temperature signal to control the flow of alkali solution of the second spraying port for secondary cooling and chemical reaction, and the cyclone dust collector and the bag filter receive the cooled flue gas and separate dust. The application can realize cascade separation and interception of high and low particle size section dust, reduce the content of impurity elements in titanium tetrachloride products through the cooperation of physical interception and chemical settlement, solve the technical problem of easy hardening and failure of the filtration system, and improve the long-term stable operation ability of the process.

Description

Technical Field

[0001] This application relates to the fields of chemical environmental protection equipment and titanium tetrachloride production processes, specifically to a device and operating method for dust collection from flue gas in a chlorination furnace. Background Technology

[0002] Titanium tetrachloride is a key raw material for industrial products such as titanium dioxide produced via the chloride process and sponge titanium. In conventional production systems, the main processes include fluidized bed chlorination and molten salt chlorination. Both processes involve a chemical reaction between titanium-containing raw materials and chlorine gas at high temperatures to produce gaseous titanium tetrachloride. In existing titanium tetrachloride production processes, the outlet at the top of the chlorination furnace is typically connected to a traditional cyclone dust collector or gravity dust collection chamber to separate the solid dust entrained in the airflow.

[0003] In actual industrial production, the dust particles entrained in the high-temperature flue gas generated by the chlorination furnace exhibit uneven particle size distribution. Monitoring data shows that a high proportion of dust particles with a diameter of less than 5 micrometers are present in the titanium tetrachloride flue gas. Traditional cyclone dust collectors and gravity dust collection chambers, limited by their physical separation mechanisms, have low dust collection efficiency for these fine dust particles. This results in a large amount of fine dust failing to be intercepted and instead entering the downstream condensation and rinsing process along with the titanium tetrachloride gas. This phenomenon leads to excessive solid particulate impurities in the titanium tetrachloride liquid produced in the subsequent process, typically exceeding 20 grams per liter. If the titanium raw material used in the upstream chlorination furnace itself has a high impurity content, the final solid particulate impurity content in the titanium tetrachloride liquid can even further increase to over 100 grams per liter. The high solid content slurry causes wear and frequent crystallization blockage in the precision condensation equipment and process pipelines of the downstream process during flow, reducing the continuous operational stability of the entire chlorination system and increasing the production, purification, and equipment maintenance costs of titanium tetrachloride products. Currently, there is a significant technical bottleneck in effectively separating fine dust and preventing bag clogging caused by highly viscous byproducts. Summary of the Invention

[0004] In order to solve the technical problems in the prior art of titanium tetrachloride gas causing wear and tear on downstream equipment, high impurity content, and easy caking and failure of filter equipment due to the large amount of fine dust it carries, this application provides a device and operating method for dust collection of flue gas from chlorination furnaces.

[0005] This application provides an apparatus for dust collection from flue gas of a chlorination furnace, comprising: a chlorination furnace; a spray chamber connected to the chlorination furnace, the spray chamber having a first spray port; a flue connected to the spray chamber, the flue having a second spray port; a cyclone dust collector connected to the flue; a bag filter connected to the cyclone dust collector; a dust collection slurry tank connected to both the discharge port of the cyclone dust collector and the discharge port of the bag filter; a dust collection control system configured to acquire the temperature signal of the spray chamber and control the flow rate of titanium tetrachloride slurry entering the first spray port to perform primary cooling of the flue gas; the dust collection control system is further configured to acquire the temperature signal of the flue, control the flow rate of alkaline solution entering the second spray port to perform secondary cooling of the flue gas, and control the alkaline solution to react chemically with aluminum chloride in the flue gas; the cyclone dust collector and the bag filter are configured to receive the cooled flue gas and separate dust.

[0006] Furthermore, the dust collection control system is configured to control the target temperature range of the first-stage cooling between 210 degrees Celsius and 260 degrees Celsius; the dust collection control system is configured to control the target temperature range of the second-stage cooling between 200 degrees Celsius and 250 degrees Celsius; a second spray valve is connected to the flue, and the second spray valve is connected to the second spray port; the dust collection control system is connected to the second spray valve, and the dust collection control system adjusts the opening of the second spray valve to control the injection amount of the alkali solution according to the actual temperature feedback signal of the flue.

[0007] Furthermore, the aforementioned dust collection and pulping tank is equipped with a dilute hydrochloric acid injection pipeline and a density monitoring instrument; the aforementioned dust collection control system is electrically connected to the aforementioned density monitoring instrument; the aforementioned dust collection control system is configured to control the discharge of pulp and the replenishment of pulping liquid based on the pulp density signal fed back by the aforementioned density monitoring instrument.

[0008] Furthermore, the aforementioned dust collection control system is preset with a first threshold and a second threshold for judging the slurry density signal; the first threshold is 1.4 kg / L and the second threshold is 1.3 kg / L; the dust collection slurry tank is connected to a slurry discharge pump, and the dilute hydrochloric acid injection pipeline is equipped with an inlet valve; the aforementioned dust collection control system is configured to start the slurry discharge pump to perform an outward slurry discharge action when the aforementioned slurry density signal is greater than or equal to the aforementioned first threshold; the aforementioned dust collection control system is configured to shut down the slurry discharge pump and open the inlet valve to replenish the slurry liquid to the aforementioned dust collection slurry tank when the aforementioned slurry density signal drops to less than or equal to the aforementioned second threshold.

[0009] Furthermore, the bag filter is equipped with a metal filter bag inside, and the bag filter is connected to an alternating backflushing cleaning system; the alternating backflushing cleaning system includes a first backflushing pipeline and a second backflushing pipeline connected in parallel; the first backflushing pipeline is connected to a hot nitrogen source, and the second backflushing pipeline is connected to a cold nitrogen source; the first backflushing pipeline and the second backflushing pipeline are respectively equipped with a first control valve and a second control valve, and both the first control valve and the second control valve are electrically connected to the dust collection control system.

[0010] Furthermore, the filter bag is made of nickel-based alloy; the hot nitrogen output from the hot nitrogen source is set to a temperature of 250 degrees Celsius, and the cold nitrogen output from the cold nitrogen source is set to a temperature of 25 degrees Celsius; the dust collection control system is configured to open the first control valve to inject hot nitrogen when the inlet and outlet pressure difference of the bag filter reaches a first preset pressure difference value, causing the filter cake layer to expand slightly; the dust collection control system is configured to close the first control valve after a first preset time period and open the second control valve to inject cold nitrogen pulses into the filter bag, causing the filter bag to undergo cold shrinkage deformation.

[0011] Furthermore, an online spectrometer and a flue gas flow meter are installed on the flue; the dust collection control system is electrically connected to the online spectrometer and the flue gas flow meter; the dust collection control system is configured to control the actual spraying volume of alkaline solution based on the flue gas flow data measured by the flue gas flow meter and the molar concentration data of aluminum chloride measured by the online spectrometer.

[0012] Furthermore, the aforementioned dust collection control system has a preset chemical reaction molar ratio constant; the value of the aforementioned chemical reaction molar ratio constant is between 1.5:1 and 2.5:1; the aforementioned dust collection control system is configured to multiply the obtained aluminum chloride molar concentration data by the aforementioned chemical reaction molar ratio constant to calculate the basic alkali injection amount as a feedforward control quantity; the aforementioned dust collection control system is configured to compare the actual temperature signal in the aforementioned flue with the preset secondary cooling target temperature range to generate a temperature deviation signal, and use a proportional-integral-differential algorithm to process the aforementioned temperature deviation signal to calculate a feedback correction quantity; the aforementioned dust collection control system superimposes the aforementioned feedforward control quantity and the aforementioned feedback correction quantity and outputs a control signal to the alkali spraying actuator.

[0013] This application embodiment also provides an operation method for dust collection from chlorination furnace flue gas, applied to a dust collection control system. The dust collection control system is electrically connected to a spray chamber, a flue, a dust collection slurry tank, a first spray port in the spray chamber, a second spray port in the flue, a density monitor in the dust collection slurry tank, and a slurry discharge pump. The method includes: the dust collection control system acquiring a temperature signal from the spray chamber and controlling the flow rate of titanium tetrachloride slurry entering the first spray port to perform a first-stage cooling of the flue gas; the dust collection control system acquiring a temperature signal from the flue and controlling the flow rate of alkaline solution entering the second spray port to perform a second-stage cooling of the flue gas; the dust collection control system acquiring a slurry density signal fed back by the density monitor; the dust collection control system starting the slurry discharge pump to discharge slurry when the slurry density signal is greater than or equal to a preset first threshold, and shutting off the slurry discharge pump when the slurry density signal is less than or equal to a preset second threshold.

[0014] Furthermore, the dust collection control system is electrically connected to a first control valve and a second control valve on the bag filter. The first control valve is connected to a hot nitrogen source, and the second control valve is connected to a cold nitrogen source. The operation method further includes: the dust collection control system acquiring the inlet and outlet pressure difference signal of the bag filter; in response to the inlet and outlet pressure difference signal reaching a preset pressure difference value, the dust collection control system opening the first control valve to inject hot nitrogen into the bag filter; and after a first preset time period, the dust collection control system closing the first control valve and opening the second control valve to inject cold nitrogen into the bag filter.

[0015] The device and operating method for dust collection in chlorination furnace flue gas provided in this application achieve cascaded separation and interception of dust with high and low particle sizes by setting a cyclone dust collector and a bag filter in series in the process flow; and integrates a two-stage fluid spray cooling module at the front end. Utilizing the combination of titanium tetrachloride slurry and alkaline solution, a step-wise and stable decrease in flue gas temperature is achieved, avoiding thermal stress damage to equipment caused by drastic temperature fluctuations. Alkaline solution spraying converts easily permeable gaseous aluminum chloride into solid alumina particles in situ, achieving a synergistic effect of physical interception and chemical sedimentation. This solution solves the industry problem of high impurities in crude titanium tetrachloride and easy caking and failure of the filtration system, reducing the content of impurity elements in titanium tetrachloride, lowering the purification cost of subsequent processes, and improving the long-term stable operation capability of the entire process. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the device for dust collection of chlorination furnace flue gas provided in the embodiments of this application.

[0017] Figure 2 This is a partially enlarged view of the variable temperature alternating backflushing cleaning system provided in the embodiments of this application.

[0018] Figure 3 This is a logical structure block diagram of the dust collection control system provided in the embodiments of this application.

[0019] Figure 4 This is a flowchart of the operation method for dust collection of flue gas from a chlorination furnace provided in the embodiments of this application.

[0020] In the diagram: 101-Chlorination furnace, 102-Spray chamber, 103-First spray port, 104-Slurry supply pipe, 105-Slurry regulating valve, 107-Flue, 108-Second spray port, 110-Second spray valve, 111-Cyclone dust collector, 112-Bag filter, 113-Transition flue, 114-First discharge rotary valve, 115-Second discharge rotary valve, 116-Dust collection and slurry preparation tank, 117-Slurry discharge pump, 118-Dilute hydrochloric acid injection pipeline, 119-Liquid inlet valve, 120-Dust collection control system, 122-Density monitor, 123-Online spectrometer, 124-Flue gas flow meter, 125-First backflush pipeline, 126-Second backflush pipeline, 127-Hot nitrogen source, 128-Cold nitrogen source, 129-First control valve, 130-Second control valve. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the application.

[0022] Example 1

[0023] Reference Figures 1 to 3 This application provides a device for dust collection from chlorination furnace flue gas. This device is mainly used in the post-processing of crude titanium tetrachloride in the chlorination process titanium dioxide industry or sponge titanium industry. From a physical structural perspective, the device mainly comprises sequentially connected physical gas-liquid-solid treatment components and a supporting electrical automation control network.

[0024] like Figure 1As shown in the embodiment of this application, the device for dust collection of flue gas from a chlorination furnace includes a chlorination furnace 101, a spray chamber 102, a flue 107, a cyclone dust collector 111, a bag filter 112, a dust collection slurry tank 116, and a system-level core brain, namely a dust collection control system 120. In the process pipeline connection structure, the air inlet of the spray chamber 102 is directly and sealed to the top exhaust port of the chlorination furnace 101 via a high-temperature resistant ceramic flange to receive the raw mixed flue gas containing a large amount of high-temperature dust from the chlorination furnace 101. A first spray port 103 for injecting cooling fluid is provided axially or radially inside the spray chamber 102. The flue 107 is located between the spray chamber 102 and subsequent dust removal equipment, with one end connected to the exhaust end of the spray chamber 102 and the other end connected to the inlet tangential port of the cyclone dust collector 111. Second spray ports 108 are evenly distributed on the inner wall or cross-section of the flue 107.

[0025] The cyclone dust collector 111 relies on the centrifugal force generated by its internal flow field to separate coarse-diameter dust particles by gravity. Its top exhaust port is connected to the inlet chamber of the final fine dust collection device, the bag filter 112, via a sealed transition flue 113. Through this series structure, the flue gas escaping from the chlorination furnace 101 undergoes a complete process flow, including high-temperature chemical reaction, primary spray cooling, secondary spray cooling and chemical solidification, centrifugal interception of coarse particles, and surface filtration of ultrafine particles. To achieve a closed-loop treatment of the separated solid impurities, discharge ports are provided at the dust collection cone at the bottom of the cyclone dust collector 111 and the ash hopper at the bottom of the bag filter 112. These discharge ports are collected and connected to the dust collection and slurry tank 116 below via corrosion-resistant gravity discharge pipes.

[0026] To achieve highly automated temperature and fluid coupling control, this embodiment constructs an electrical automation execution loop. The dust collection control system 120 is configured to acquire the airflow temperature signal inside the spray chamber 102 in real time through thermocouples or platinum resistance sensors installed inside the corresponding cavities, and control the mass flow rate of titanium tetrachloride slurry entering the first spray port 103 based on the temperature signal. The injection of titanium tetrachloride slurry absorbs heat through latent heat vaporization, achieving primary cooling of the original high-temperature flue gas and preventing high-temperature creep deformation in subsequent pipelines. The dust collection control system 120 is also configured to acquire the temperature feedback signal of the flue 107 and control the flow rate of alkaline solution entering the second spray port 108 to perform secondary cooling of the flue gas after the initial cooling. In this stage, in addition to using the water evaporation of alkaline solution to further reduce the temperature, the sprayed alkaline solution is controlled to undergo gas-liquid two-phase contact with the high-temperature mixed flue gas, causing the active components in the alkaline solution to undergo a chemical precipitation reaction with the free aluminum chloride entrained in the mixed flue gas, converting it into solid alumina particle crystals. This dual-track mechanism of physical cooling and chemical reaction ensures that the flue gas temperature is reduced to a safe range before entering the subsequent dust removal equipment, and that previously difficult-to-filter gaseous metal chlorides are solidified. Ultimately, the cyclone dust collector 111 and the bag filter 112 are configured to receive the flue gas after two stages of cooling and chemical precipitation solidification, and utilize their respective physical separation mechanisms to intercept and separate the dust and generated alumina particles.

[0027] In a preferred engineering structure arrangement, an array of mud nozzles is axially arranged inside the spray chamber 102. This array is connected to the supply source of titanium tetrachloride mud via an external mud supply pipe 104. An electro-proportional regulating valve, namely a mud regulating valve 105, is installed on the main line of the mud supply pipe 104. The signal control terminal of the mud regulating valve 105 is connected to the analog output module of the dust collection control system 120. A dual-fluid alkaline spray gun for injecting alkaline solution is arranged inside the flue 107. The gas interface of the dual-fluid alkaline spray gun is connected to an industrial compressed nitrogen network, and its liquid interface is connected to an alkaline solution storage tank via a second spray valve 110. Through the shearing action of the high-speed airflow generated by compressed nitrogen, the injected alkaline solution is atomized under the spray of the dual-fluid alkaline spray gun, and the particle size distribution range of the atomized alkaline solution droplets is controlled within 30 to 50 micrometers. By using micron-sized atomized droplets, the specific surface area contact rate between the alkaline solution and the high-temperature flue gas is increased, avoiding the phenomenon of crystallization and blockage caused by excessively large local droplets forming a crust on the surface instantly at high temperatures, resulting in unreacted crystals inside. It should be noted that the above-described dual-fluid spray gun is only one example of atomization with high dispersion. Those skilled in the art can also achieve similar large-area atomization coverage using a high-pressure recirculation single-fluid atomizing nozzle.

[0028] To ensure efficient precipitation reaction and prevent excessive cooling that could lead to acidic gas condensation and corrosion, the dust collection control system 120 incorporates a stepped closed-loop control logic. Specifically, the system is configured to control the target temperature range of the first-stage cooling within 210°C to 260°C; simultaneously, the dust collection control system 120 is configured to control the target temperature range of the second-stage cooling within 200°C to 250°C. At the control execution level, the dust collection control system 120 continuously calculates the deviation value based on the actual temperature feedback signal transmitted from the sensors inside the flue 107, and generates corresponding continuous control signals to adjust the opening of the second spray valve 110, thereby achieving stepless closed-loop adjustment of the alkaline solution injection volume. Through this tight temperature control range, the temperature range of the flue gas entering the subsequent cyclone dust collector 111 is locked between 200 and 250°C, ensuring that gaseous substances do not liquefy and guaranteeing the safe operation of the filtration equipment.

[0029] To achieve targeted interception of dust particles with different particle sizes, the dust removal equipment in this embodiment adopts a cascaded specialized design. The aforementioned cyclone dust collector 111 is mainly used to collect and intercept large dust particles with a diameter of 5 micrometers or more in the flue gas flow. In terms of its structural parameter design, the height-to-diameter ratio of the internal cyclone cavity is configured to be 5 to 6:1, and based on the negative pressure suction effect of the induced draft fan, the tangential airflow velocity of the dust-laden flue gas at its inlet is limited to the range of 15 to 20 meters per second. Its body material is configured as a high-strength carbon steel shell lined with a wear-resistant ceramic composite plate. Through this combination of high diameter-to-diameter ratio and high air velocity design, a strong double-vortex cyclone centrifugal field can be formed inside, ensuring the cyclone centrifugal dust collection efficiency while utilizing the ultra-high hardness of the inner ceramic lining to ensure that the inner wall of the equipment is not worn by hard dust particles entrained by high flow velocity, ensuring a long-term maintenance-free operating life of the equipment.

[0030] Subsequently, the aforementioned bag filter 112 is specifically designed to collect and intercept fine dust particles with a diameter of less than 5 micrometers that escape from the cyclone dust collector 111, as well as newly generated micro-alumina particles from chemical reactions. The bag filter 112 contains a filter bag made of a high-temperature corrosion-resistant metal material. Its outer shell is constructed of carbon steel lined with ceramic. To withstand the combined effects of strong acidity and high temperature, the filter bag and its internal supporting frame are made of nickel-based alloy material. In this embodiment, the filter bag is specifically manufactured using a process of interweaving nickel-based alloy wire and nickel-based alloy steel wire rope. This high-strength mixed weaving structure can balance the high pore density required for intercepting fine dust with the high mechanical tensile strength required to resist frequent backflushing.

[0031] After dust collection is complete, the collected dust mixture, containing ferric chloride, ferrous chloride, alumina, calcium chloride, magnesium chloride, sodium chloride, as well as unreacted residual petroleum coke and waste titanium slag, will fall by gravity through the lower pipeline into the dust collection and slurry tank 116. To prevent short-circuiting of flue gas during the material discharge process, multiple star-shaped airlock structures, such as the first discharge rotary valve 114 and the second discharge rotary valve 115, are connected in series at the bottom of the cyclone dust collector 111 and the discharge pipe from the bottom of the bag filter 112 to the dust collection and slurry tank 116. By intermittently and alternately opening these discharge rotary valves, a sealed material column with static pressure can be maintained in the vertical drop section of the discharge pipe, preventing leakage and cross-contamination of process gases.

[0032] To address the challenge of harmlessly disposing of solid dust collection residue, this application's device constructs a fully automated closed-loop pulping and discharging system. The side wall or top of the aforementioned dust collection and pulping tank 116 is equipped with a dilute hydrochloric acid injection pipeline 118 connecting to the liquid acid storage area. To detect changes in internal physical properties, an ultrasonic density monitor 122 is installed on the side wall of the tank, which is electrically connected to the data acquisition terminal of the aforementioned dust collection control system 120. The aforementioned dust collection control system 120 is configured to determine, based on the continuous pulp density signal fed back in real time by the density monitor 122, whether to trigger the operation of the discharge pump 117 and control the replenishment of pulping liquid in a closed loop using internal logic calculations. During normal operation, dilute hydrochloric acid with a concentration of approximately 10% is continuously introduced into the pulping tank. The liquid level at the internal liquid interface is maintained at approximately 60% under servo control, and a gas-liquid-solid three-phase reaction pulping is carried out in conjunction with a stirring mechanism. The acidic volatile gas produced during the pulping process is extracted into a separate exhaust gas system for purification and washing treatment.

[0033] In the specific automatic slurry discharge control logic, the internal memory of the aforementioned dust collection control system 120 presets a first threshold and a second threshold for comparison and judgment. In this embodiment, to ensure a balance between slurry flowability and processing efficiency, the first threshold is set to 1.4 kg / L, and the second threshold is set to 1.3 kg / L. A high-flow-rate slurry discharge pump 117 is connected to the bottom outlet of the aforementioned dust collection slurry tank 116, and an electromagnetically or pneumatically driven inlet valve 119 is installed on the aforementioned dilute hydrochloric acid injection pipeline 118. During system operation, when the aforementioned dust collection control system 120 receives a signal indicating that the solids in the tank have dissolved and accumulated to a higher concentration, and the slurry density signal value is greater than or equal to the aforementioned first threshold, the system outputs a drive voltage to start the aforementioned slurry discharge pump 117, executing the slurry discharge and conveying action to the downstream slag treatment process. As the high-concentration slurry is discharged, the density inside the tank naturally decreases. When the dust collection control system 120 detects that the slurry density signal has dropped to less than or equal to the second threshold, the system outputs a shutdown signal to shut down the discharge pump 117 and simultaneously or after a delay opens the inlet valve 119 to continue to replenish 10% of fresh dilute hydrochloric acid slurry into the dust collection slurry tank 116 for dilution, thereby forming a continuous slurry preparation and quantitative discharge circulation system that does not require manual intervention.

[0034] Based on the aforementioned basic solution, and addressing the technical bottleneck of incomplete system corrosion or dealuminization caused by crude alkaline spray control under certain abnormal operating conditions, this application introduces a deep cascade coupling computational structure based on chemical reaction kinetics into the dust collection control system in a preferred embodiment. The specific solution includes: an online spectrometer 123 and a flue gas flow meter 124 are installed on the aforementioned flue duct 107. The aforementioned dust collection control system 120 establishes a high-speed data electrical connection with the aforementioned online spectrometer 123 and the aforementioned flue gas flow meter 124 via an industrial bus. The dust collection control system 120 deploys a feedforward and feedback cascade algorithm model based on mass conservation, configured to dynamically solve and control the final actual spray volume of the alkaline solution based on the real-time flue gas volumetric flow rate data measured by the aforementioned flue gas flow meter 124 and the molar concentration data of the harmful component, namely aluminum chloride, measured by the aforementioned online spectrometer 123.

[0035] To achieve feedforward calculation, the non-volatile memory of the dust collection control system 120 presets a chemical reaction molar ratio constant. This molar ratio refers to the stoichiometric ratio between the combined amount of the reactive substances sodium hydroxide and water in the alkali solution and the target removed product aluminum chloride in the flue gas. Through experimental calculations, the value range of this chemical reaction molar ratio constant is limited to between 1.5:1 and 2.5:1 to ensure that the reaction has sufficient driving force. In each scan cycle of the program, the dust collection control system 120 performs calculations according to the following formula model, multiplying the obtained aluminum chloride molar concentration data by the chemical reaction molar ratio constant and other parameters to calculate the basic alkali solution injection amount as the feedforward control quantity.

[0036] Specifically, the system performs mathematical calculations on the basic alkali injection volume by multiplying the instantaneous flue gas volumetric flow rate measured by the flue gas flow meter 124, the instantaneous molar concentration of aluminum chloride resolved by the online spectrometer 123, and the set chemical reaction molar ratio constant, and then dividing by the inherent molar concentration of sodium hydroxide and water in the alkali solution:

[0037]

[0038] Among them, M base V represents the calculated basic alkali solution injection volume; gas Indicates instantaneous flue gas volumetric flow rate; C Al Indicates the instantaneous molar concentration of aluminum chloride; C alkali K represents the inherent molar concentration of sodium hydroxide and water in the alkaline solution measured inside the storage tank. ratio This indicates the molar ratio constant set by the system.

[0039] To eliminate system inertial errors and meet temperature redline requirements, the dust collection control system 120 is also configured to perform feedback fine-tuning: the actual temperature signal measured inside the flue 107 is compared in real time with a preset secondary cooling target temperature range, such as 225 degrees Celsius, generating a temperature deviation signal. This temperature deviation signal is then processed using a proportional-integral-derivative (PID) algorithm to calculate the feedback correction amount. Finally, the dust collection control system 120 mathematically integrates the feedforward control quantity derived from chemical concentration with the feedback correction amount derived from temperature deviation, outputting the final current or voltage control signal to the second spray valve 110 and other alkaline spraying actuators. This cascaded computing structure with feedforward compensation ensures complete and thorough chemical precipitation of aluminum chloride in the flue, avoiding the fatal flaw of traditional single-loop regulation relying solely on temperature, where excessive alkaline injection due to sudden changes in flue gas composition leads to localized liquid accumulation and corrosion. It should be noted that the aforementioned PID algorithm is only one feedback correction mechanism; those skilled in the art can replace it with other equivalent deviation adjustment models, such as fuzzy neural network control.

[0040] In an advanced preferred embodiment, addressing the technical challenge of conventional pulse cleaning failing to dislodge the highly adhesive alumina-coated dust, resulting in a stubborn "bag-clogging" layer on the filter bag surface, this embodiment designs a variable-temperature alternating backflushing cleaning system based on a thermal expansion stress difference destruction mechanism. For example... Figure 2As shown, the bag filter 112 is connected to the alternating backflushing cleaning system. The alternating backflushing cleaning system, in its air path topology, includes a first backflushing pipe 125 and a second backflushing pipe 126 arranged in parallel. These two pipes converge and share the same set of cleaning jet ejectors that extend deep into the filter bag. The input end of the first backflushing pipe 125 is connected to a low-pressure hot nitrogen source 127, and an electric heater is connected in series at the front end of this pipe for temperature control. The input end of the second backflushing pipe 126 is connected to a high-pressure cold nitrogen source 128. The first backflushing pipe 125 and the second backflushing pipe 126 are respectively equipped with a first control valve 129 and a second control valve 130 as on / off control elements. The solenoid coils of both the first control valve 129 and the second control valve 130 are electrically connected to the relay output port of the dust collection control system 120. Simultaneously, differential pressure transmitters are connected to both sides of the inlet and outlet tube sheets of the bag filter to monitor operating resistance.

[0041] In terms of operating parameter matching settings, coupled with the high thermal conductivity of the nickel-based alloy filter bag, the hot nitrogen source 127 is filled with nitrogen gas at a pressure ranging from 0.2 to 0.3 MPa, and its output hot nitrogen gas temperature is forced to be constant at 250 degrees Celsius by an electric heater; conversely, the cold nitrogen source 128 is filled with nitrogen gas at a higher pressure ranging from 0.5 to 0.7 MPa, and its output cold nitrogen gas temperature is set to room temperature at 25 degrees Celsius. At the dust removal execution logic level, the dust collection control system 120 is configured to continuously monitor the differential pressure signal. When the differential pressure between the inlet and outlet of the bag filter 112 is detected to rise and reach a first preset differential pressure value, such as 1000 Pascals, the system outputs a command to open the first control valve 129, injecting the 250-degree Celsius hot nitrogen gas into the filter bag at a low speed. The continuous injection of hot nitrogen lasts approximately 2 to 3 seconds. This process transfers a large amount of heat energy to the filter cake layer on the surface of the filter bag. While maintaining the chloride components in the dust layer in an absolutely dry state to prevent deliquescence, it also causes the clumped filter cake to undergo thermal micro-expansion, generating minute structural cracks. The dust collection control system 120 is configured to, after completing the first preset time period of thermal pretreatment, instantly close the first control valve 129 to cut off the heat source and open the second control valve 130 to inject a brief 0.1 to 0.2-second pulse of high-pressure, room-temperature cold nitrogen into the filter bag. Through this cold impact, the specific linear expansion coefficient of the nickel-based alloy skeleton and the metal wires is fully utilized, causing the metal filter bag matrix to undergo rapid contraction deformation after encountering the cold pulse. At this time, thermomechanical shear peeling stress is generated between the thick dust filter cake that expands due to heat on the outside and the metal skeleton that contracts violently inside. Through the physical tearing effect of this alternating stress, the highly viscous dust shell layer can be forcibly peeled off from the metal surface. Tests show that by adopting this alternating cleaning architecture based on the physical phenomenon of thermal expansion and contraction, the filter bag clogging caused by blind purging with a single high-pressure airflow is avoided. The long-term cleaning recovery rate of the bag filter is increased to over 98%, ensuring long-term low-resistance operation of the system. This results in a stable reduction of solid impurities in the final titanium tetrachloride product to below 5 grams per liter, meeting the requirements for high-purity industrial applications.

[0042] Example 2

[0043] Based on the above hardware architecture, such as Figure 3 Control diagram and Figure 4As shown in the flowchart, this application embodiment also provides an operation method for dust collection in chlorination furnace flue gas. The method operates as a whole and relies on a dust collection control system. In terms of hardware communication topology, the dust collection control system is bidirectionally electrically connected to physical entities on site, including spray chamber 102, flue 107, dust collection slurry tank 116, and actuators and sensors such as mud regulating valve 105 installed in spray chamber 102, second spray valve 110 installed in flue 107, density monitor 122 installed in dust collection slurry tank 116, and slurry pump 117 for draining liquid, through an industrial control network.

[0044] The operation method provided in this embodiment, after system initialization and normal ignition and smoke generation of the chlorination furnace, mainly follows the steps below in a cyclical manner:

[0045] The system enters the pulping preparation subroutine S401. The dust collection control system drives the relevant valves to quantitatively introduce approximately 10% concentration dilute hydrochloric acid into the dust collection pulping tank, and activates the liquid level control loop to dynamically maintain the pulping liquid level at around 60%. At the same time, the internal mechanical stirring mechanism of the dust collection pulping tank is activated, and the relevant valves of the discharge pump are opened to establish an internal liquid circulation channel to prevent heavy particles from prematurely settling and solidifying at the bottom of the tank.

[0046] The system enters the flue gas cascade cooling and chemical sedimentation procedure S402. The dust collection control system acquires the temperature signal of the mixed gas inside the spray chamber in real time through sensors. The dust collection control system has a preset start-up threshold. When the temperature signal is determined to rise and reach above 300 degrees Celsius, the system triggers the first-stage cooling procedure. Based on the deviation of the temperature signal, it uses an internal regulator to output a control signal to adjust the opening of the mud regulating valve 105, controlling the injection of titanium tetrachloride cold mud to perform first-stage cooling of the flue gas. Through closed-loop regulation, it strives to stabilize the spray chamber temperature within the range of 210 to 260 degrees Celsius. After the flue gas enters the next stage pipeline, the dust collection control system continues to acquire the temperature signal of the flue. Similarly, when the flue temperature reaches a high-temperature warning state above 260 degrees Celsius, the system triggers the second-stage chemical sedimentation procedure. Based on the temperature signal of the flue, the dust collection control system continuously adjusts the opening of the second spray valve 110 to perform a deeper second-stage cooling of the initially cooled flue gas. In this process, by controlling the flow rate of alkaline solution, the overall temperature in the mixing flue is precisely controlled at 200 to 250 degrees Celsius. At the same time, the alkaline solution is used to cause the gaseous aluminum chloride in the flue gas to undergo a precipitation reaction and be converted into solid particles, thus completing the pretreatment stage.

[0047] Once the flue gas temperature fluctuations decrease and stabilize within the range of 200 to 250 degrees Celsius, the system transitions to the mechanical feeding and dust collection discharge procedure S403. The dust collection control system sends an enable signal, driving the rotary valves located below the downstream physical separation equipment—the cyclone dust collector and bag filter—to begin mechanically discharging the collected dust. During this process, the system controls the discharge valves to open and close intermittently at a set interval, ensuring that a certain height of material gravity seal is maintained in the conveying pipeline at all times. This prevents corrosive, high-temperature flue gas from leaking into the pulping tank and causing system malfunctions due to material leakage.

[0048] The system transitions to closed-loop density control slurry discharge procedure S404. The aforementioned dust collection control system continuously acquires the real-time slurry density signal fed back by the density monitor at a preset sampling frequency. Internally, the dust collection control system performs logic comparison. When it determines that the slurry density signal has become viscous due to the dissolution of a large amount of dust residue, and the value is greater than or equal to a preset first threshold, the system immediately outputs a relay closing signal to start the slurry discharge pump 117, performing the action of discharging high-concentration slurry into the external pipeline network. During discharge, the control system simultaneously opens the replenishment valve to inject fresh dilute hydrochloric acid. As discharge and dilution proceed, the dust collection control system continuously monitors density changes. When it determines that the slurry density signal has dropped to less than or equal to a preset second threshold for further dilution, the system disconnects the output relay, shuts down the slurry discharge pump 117, and stops the discharge operation, completing an unattended automated discharge cycle, ensuring the smooth flow of waste liquid treatment and the safety of the pipeline.

[0049] As a complementary dust removal and recovery method, when the system is equipped with the variable temperature alternating backflushing hardware described in Embodiment 1, the dust collection control system is also electrically connected to a first control valve for connecting to a hot nitrogen source and a second control valve for connecting to a cold nitrogen source, both installed above the tube sheet of the bag filter, via an extended control module. In this advanced operating state, the above operation method also includes a parallel backflushing control branch, i.e., entering the variable temperature alternating backflushing dust removal procedure S405.

[0050] When the system is in filtration operation, the aforementioned dust collection control system continuously acquires the inlet and outlet differential pressure signals on both sides of the bag filter's air chamber via a differential pressure transmitter. When dust accumulation causes resistance to rise, in response to detecting that the inlet and outlet differential pressure signals have reached the internally set preset differential pressure value, the system suspends the current timestamp and enters the dust removal alternation sequence. The aforementioned dust collection control system sends an on level, preferentially opening the aforementioned first control valve to inject preheated 250°C hot nitrogen gas at low pressure into the bag filter's blowpipe system, performing filter cake drying and slight thermal expansion loosening steps. The internal timer of the aforementioned dust collection control system begins to accumulate. After the first preset time period expires, the system immediately sends a off level to close the aforementioned first control valve to stop heating, and seamlessly opens the aforementioned second control valve to instantaneously inject a high-energy pulse of room-temperature, high-pressure cold nitrogen gas into the bag filter. The duration of the cold nitrogen gas pulse is short. This controlled heating followed by rapid cooling, combined with the natural contraction properties of metal, tears apart the strongly adhesive alumina dust mixture coating the filter bag surface at a microscopic level, causing it to pulverize and fall into the ash hopper. After the cold pulse jet is completed, the control valve resets and closes, the system exits the cleaning sequence and resumes normal filtration and detection.

[0051] In summary, the operating method and control device provided in this application are closely integrated. Through cascaded cooling, feedback regulation of cascaded chemical reactions, and closed-loop cleaning logic based on physical phase changes, the synergistic response capabilities of various sensors and controllers are fully utilized. This achieves automated closed-loop management from initial cooling and dealuminization of high-temperature flue gas, to cascade separation of large and small particles, to automatic waste liquid slurry preparation and discharge, and thorough descaling and anti-clogging of metal filter bags. This improves the purity of titanium tetrachloride products and ensures the long-term stable and reliable operation of the entire chlorination production system.

[0052] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A device for dust collection from flue gas in a chlorination furnace, characterized in that, include: Chlorination furnace; A spray chamber is connected to the chlorination furnace, and the spray chamber is provided with a first spray port; A flue is connected to the spray chamber, and the flue is provided with a second spray port; A cyclone dust collector is connected to the flue. The bag filter is connected to the cyclone dust collector; The dust collection and pulping tank is connected to both the discharge port of the cyclone dust collector and the discharge port of the bag filter. The dust collection control system is configured to acquire the temperature signal of the spray chamber and control the flow rate of titanium tetrachloride slurry entering the first spray port to perform primary cooling of the flue gas; the dust collection control system is also configured to acquire the temperature signal of the flue and control the flow rate of alkaline solution entering the second spray port to perform secondary cooling of the flue gas, and control the alkaline solution to react chemically with aluminum chloride in the flue gas; the cyclone dust collector and the bag filter are configured to receive the cooled flue gas and separate dust.

2. The apparatus for dust collection from chlorination furnace flue gas as described in claim 1, characterized in that, The dust collection control system is configured to control the target temperature range of the first-stage cooling between 210 degrees Celsius and 260 degrees Celsius; the dust collection control system is configured to control the target temperature range of the second-stage cooling between 200 degrees Celsius and 250 degrees Celsius; a second spray valve is connected to the flue, and the second spray valve is connected to the second spray port; the dust collection control system is connected to the second spray valve, and the dust collection control system adjusts the opening of the second spray valve to control the injection amount of the alkali solution according to the actual temperature feedback signal of the flue.

3. The apparatus for dust collection of chlorination furnace flue gas as described in claim 2, characterized in that, The dust collection and pulping tank is equipped with a dilute hydrochloric acid injection pipeline and a density monitor; the dust collection control system is electrically connected to the density monitor; the dust collection control system is configured to control the discharge of pulp and the replenishment of pulping liquid based on the pulp density signal fed back by the density monitor.

4. The apparatus for dust collection of chlorination furnace flue gas as described in claim 3, characterized in that, The dust collection control system is preset with a first threshold and a second threshold for judging the slurry density signal; the first threshold is 1.4 kg / L and the second threshold is 1.3 kg / L; the dust collection slurry tank is connected to a slurry discharge pump, and the dilute hydrochloric acid injection pipeline is equipped with an inlet valve; the dust collection control system is configured to start the slurry discharge pump to perform an outward slurry discharge action when the slurry density signal is greater than or equal to the first threshold; the dust collection control system is configured to shut down the slurry discharge pump and open the inlet valve to replenish the slurry liquid to the dust collection slurry tank when the slurry density signal drops to less than or equal to the second threshold.

5. The apparatus for dust collection of chlorination furnace flue gas as described in claim 1, characterized in that, The bag filter is equipped with a metal filter bag inside, and the bag filter is connected to an alternating back-flushing cleaning system. The alternating back-flushing cleaning system includes a first back-flushing pipeline and a second back-flushing pipeline connected in parallel. The first back-flushing pipeline is connected to a hot nitrogen source, and the second back-flushing pipeline is connected to a cold nitrogen source. The first back-flushing pipeline and the second back-flushing pipeline are respectively equipped with a first control valve and a second control valve, and both the first control valve and the second control valve are electrically connected to the dust collection control system.

6. The apparatus for dust collection of chlorination furnace flue gas as described in claim 5, characterized in that, The filter bag is made of nickel-based alloy; the hot nitrogen source outputs a hot nitrogen gas at a temperature of 250 degrees Celsius, and the cold nitrogen source outputs a cold nitrogen gas at a temperature of 25 degrees Celsius; the dust collection control system is configured to open the first control valve to inject hot nitrogen gas when the inlet and outlet pressure difference of the bag filter reaches a first preset pressure difference value, causing the filter cake layer to expand slightly; the dust collection control system is configured to close the first control valve after a first preset time period and open the second control valve to inject a cold nitrogen gas pulse into the filter bag, causing the filter bag to undergo cold shrinkage deformation.

7. The apparatus for dust collection of chlorination furnace flue gas as described in claim 6, characterized in that, An online spectrometer and a flue gas flow meter are installed on the flue; the dust collection control system is electrically connected to the online spectrometer and the flue gas flow meter; the dust collection control system is configured to control the actual amount of alkaline solution sprayed based on the flue gas flow data measured by the flue gas flow meter and the molar concentration data of aluminum chloride measured by the online spectrometer.

8. The apparatus for dust collection of chlorination furnace flue gas as described in claim 7, characterized in that, The dust collection control system has a preset chemical reaction molar ratio constant; the value of the chemical reaction molar ratio constant is between 1.5:1 and 2.5:1; the dust collection control system is configured to multiply the acquired aluminum chloride molar concentration data by the chemical reaction molar ratio constant to calculate the basic alkali injection amount as a feedforward control quantity; the dust collection control system is configured to compare the actual temperature signal in the flue with the preset secondary cooling target temperature range to generate a temperature deviation signal, and use a proportional-integral-differential algorithm to process the temperature deviation signal to calculate the feedback correction quantity; the dust collection control system superimposes the feedforward control quantity and the feedback correction quantity and outputs a control signal to the alkali spraying actuator.

9. An operating method for dust collection from flue gas in a chlorination furnace, characterized in that, An instrument is applied to a dust collection control system, wherein the dust collection control system is electrically connected to a spray chamber, a flue, a first spray port of the dust collection system, a second spray port located in the flue, a density monitoring instrument located in the dust collection and slurry preparation tank, and a slurry discharge pump, including: The temperature signal of the spray chamber is acquired, and the flow rate of titanium tetrachloride slurry entering the first spray port is controlled to perform primary cooling of the flue gas. The temperature signal of the flue is acquired, and the flow rate of the alkaline solution entering the second spray port is controlled to perform secondary cooling of the flue gas; Obtain the slurry density signal fed back by the density monitor; The slurry discharge pump is started to discharge slurry when the slurry density signal is greater than or equal to a preset first threshold, and the slurry discharge pump is turned off when the slurry density signal is less than or equal to a preset second threshold.

10. The operating method for dust collection of chlorination furnace flue gas as described in claim 9, characterized in that, The dust collection control system is also electrically connected to a first control valve and a second control valve on the bag filter. The first control valve is connected to a hot nitrogen source, and the second control valve is connected to a cold nitrogen source. The operation method further includes: Obtain the inlet and outlet pressure difference signals of the bag filter; In response to the inlet and outlet pressure difference signal reaching a preset pressure difference value, the first control valve is opened to inject hot nitrogen into the bag filter. After a first preset time period, the first control valve is closed, and the second control valve is opened to inject cold nitrogen gas into the bag filter.

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