A multi-fuel feeding system for cement kiln head

Abstract

This invention discloses a multi-fuel feeding system for a cement kiln head, belonging to the field of cement kiln technology. The cement kiln head includes several combustion zones. The system includes: a multi-channel burner, including a solid alternative fuel channel and a pulverized coal channel; a solid alternative fuel supply unit, providing high-calorific-value alternative fuel with a calorific value greater than 25 MJ / kg to the solid alternative fuel channel; a pulverized coal supply unit, providing pulverized coal to the pulverized coal channel; an oxygen-enriched supply unit, providing 28%~35% oxygen-enriched air to the multi-channel burner; and a calorific value compensation system, which controls the operating states of the solid alternative fuel supply unit, the pulverized coal supply unit, the multi-channel burner, and the oxygen-enriched supply unit based on the temperature distribution, bulk density, and moisture content of the solid alternative fuel within the combustion zones. By real-time analysis of the combustion parameters within the cement kiln head, combined with real-time detection of the bulk density and moisture content of the solid alternative fuel, calorific value compensation of the multi-fuel feeding system is achieved.

Description

Technical Field

[0001] This invention belongs to the field of cement kiln technology, and particularly relates to a multi-fuel feeding system for the kiln head of a cement kiln. Background Technology

[0002] The cement industry, a typical high-energy-consuming and high-carbon-emission sector, has energy costs accounting for 40% to 50% of its total production costs. Against this backdrop, the use of traditional fossil fuels is facing pressure from significant fluctuations in coal prices. Therefore, the application of alternative fuels (hereinafter referred to as "AFRs") has become a core path for cost reduction and carbon reduction in the industry. According to relevant statistics, leading global cement companies have achieved AFR heat substitution rates of 60% to 90%.

[0003] Currently, the common practice both domestically and internationally is to deliver AFRs (Alternating Flame Reactors) to the kiln tail for combustion. Due to its mature process adaptability and relatively low retrofitting costs, kiln tail combustion AFR technology remains the mainstream choice in the cement industry. This technology is particularly suitable for the large-scale application of low- to medium-calorific-value AFRs (12-20 MJ / kg). However, the use of high-calorific-value AFRs (such as plastics, fabrics, and biomass) is limited by the temperature constraints of the decomposer. Excessive injection can lead to problems such as localized overheating (>1000℃), premature sintering of raw materials, excessively rapid combustion of volatiles, a sharp drop in oxygen content, and a decrease in residual carbon burnout rate. In contrast, the kiln head, as the core high-temperature zone for clinker calcination (flame temperature >1800℃), can accommodate higher-calorific-value AFRs (>25 MJ / kg) under its high heat capacity conditions. The gas-solid two-phase flow extends the combustion residence time to 3-5 seconds, providing a unique advantage in the combustion environment.

[0004] While introducing AFRs into the main burner area of ​​the kiln head can overcome the technical bottleneck of using high-calorific-value AFRs, it also faces multiple technical obstacles:

[0005] AFR has a wide particle size distribution (0.5-50mm), low bulk density (0.2-0.5 t / m³), and poor flowability index (<50%), which makes it easy for problems such as pulse feeding to occur when feeding AFR.

[0006] The AFR calorific value fluctuates greatly (±15%), which leads to large fluctuations in kiln head temperature (>50℃).

[0007] The AFR volatile matter (30%–60%) is much higher than that of pulverized coal (15%–35%), which makes it easy for "flash ignition" to occur at the burner outlet, resulting in local high temperatures (>2200℃).

[0008] Large AFR particles (>10mm) require a longer combustion time, which is mismatched with the combustion rate of pulverized coal, leading to disordered temperature gradients within the kiln.

[0009] To address the significant technical obstacles to high-calorific-value AFR combustion at the kiln head, there is an urgent need to propose a solid alternative fuel feeding system for cement rotary kilns. Such a system would open up an efficient utilization channel for high-calorific-value AFR, construct a complete technical system for the graded utilization of AFR (a synergistic system of low-to-medium calorific-value combustion zones at the kiln tail and high-calorific-value combustion zones at the kiln head), and drive the cement industry to break through the 30% AFR thermal substitution rate technological inflection point, providing key path support for the cement industry to achieve its deep carbon reduction goals. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention provides a multi-fuel feeding system for cement kiln heads. By real-time analysis of combustion parameters (temperature distribution) within the cement kiln head and combined with real-time detection of the bulk density and moisture content of solid alternative fuels, the calorific value compensation of the multi-fuel feeding system is achieved.

[0011] The technical solution adopted in this invention is as follows:

[0012] The purpose of this invention is to provide a multi-fuel feeding system for a cement kiln head, wherein the cement kiln head includes several combustion zones; the system includes:

[0013] Multi-channel burner, including solid alternative fuel channel and pulverized coal channel;

[0014] The solid alternative fuel supply department supplies high-calorific-value alternative fuels with a calorific value greater than 25 MJ / kg to the solid alternative fuel channel;

[0015] The pulverized coal supply department supplies pulverized coal to the pulverized coal channel;

[0016] The oxygen-enriched supply section provides 28% to 35% oxygen-enriched air to the multi-channel burner;

[0017] The calorific value compensation system controls the operating status of the solid alternative fuel supply section, pulverized coal supply section, multi-channel burner, and oxygen-enriched supply section based on the temperature distribution in the combustion zone, the bulk density of the solid alternative fuel, and the moisture content.

[0018] The calorific value compensation system includes:

[0019] An infrared temperature sensor array, uniformly distributed in the combustion zone, is used to capture infrared images formed during AFR combustion. The detection range of the infrared images is 8μm~14μm infrared light.

[0020] The calorific value compensation module calculates the real-time calorific value based on the bulk density and water content of the solid alternative fuel.

[0021] The delivery air parameter control module controls the delivery air parameters of the oxygen-enriched supply unit based on the temperature distribution within the combustion zone.

[0022] The infrared image processing module acquires local overheated areas with temperatures above 1850℃ and low-temperature areas with temperatures below 1650℃ based on infrared images.

[0023] The calculation formula for the calorific value compensation module is as follows: In the formula, Q is the real-time calorific value, α is the calibration coefficient, the value of α ranges from 0.95 to 1.05, β is the moisture correction factor, the value of β ranges from 0.015 to 0.025, w is the water content, ρ is the bulk density, and C is the fuel type coefficient, the value of C ranges from 0.8 to 1.2.

[0024] Preferably, the solid alternative fuel supply unit includes:

[0025] Fuel storage section, used for storing solid alternative fuels;

[0026] A fuel delivery unit is used to transfer solid alternative fuels from a fuel storage unit to a solid alternative fuel channel;

[0027] Mass sensors are used to detect the mass of solid alternative fuels;

[0028] Humidity sensor used to detect the moisture content of solid alternative fuels;

[0029] Density sensor used to detect the bulk density of solid alternative fuels.

[0030] Preferably, the plurality of combustion zones include a primary AFR volatile matter slow-release combustion zone with a temperature requirement of 1200℃~1400℃, a secondary carbon skeleton gasification main combustion zone with a temperature requirement of 1600℃~1800℃, and a tertiary residual carbon burnout combustion zone with a temperature requirement greater than 1800℃.

[0031] Preferably, the calorific value compensation system includes:

[0032] An infrared temperature sensor array, uniformly distributed in the combustion zone, is used to capture infrared images formed during AFR combustion. The detection range of the infrared images is 8μm~14μm infrared light.

[0033] The infrared image processing module acquires local overheated areas with temperatures above 1850℃ and low-temperature areas with temperatures below 1650℃ based on infrared images.

[0034] The calorific value compensation module calculates the real-time calorific value based on the bulk density and water content of the solid alternative fuel.

[0035] The delivery air parameter control module controls the delivery air parameters of the oxygen-enriched supply unit based on the temperature distribution within the combustion zone.

[0036] Preferably, the calculation formula for the calorific value compensation module is as follows: In the formula, Q is the real-time calorific value, α is the calibration coefficient, the value of α ranges from 0.95 to 1.05, β is the moisture correction factor, the value of β ranges from 0.015 to 0.025, w is the water content, ρ is the bulk density, and C is the fuel type coefficient, the value of C ranges from 0.8 to 1.2.

[0037] Preferably, the multi-channel burner includes: an outer jet air channel, an outer swirl air channel, a pulverized coal conveying channel, an inner swirl air channel, an inner axial flow air channel, and an AFR conveying channel.

[0038] Preferably, the jet velocity in the outer jet air channel is greater than 300 m / s;

[0039] The jet wind speed range of the outer swirl channel is 60m / s to 180m / s, and it includes 24 guide vanes with a radius of curvature of 20mm and a tangential angle of 35°.

[0040] The jet velocity range of the pulverized coal conveying channel is 18m / s to 28m / s;

[0041] The jet wind speed range of the inner swirl channel is 60m / s to 180m / s, and the tangential angle range is 15° to 30°.

[0042] The jet velocity range of the inner axial flow channel is 30m / s to 180m / s;

[0043] The jet velocity range of the AFR delivery channel is 30~60m / s.

[0044] Preferably, the high-calorific-value alternative fuel includes one or more of plastics, textiles, and biomass.

[0045] Preferably, the high-calorific-value alternative fuel is a mixture of spheres with an outer diameter of less than 15 mm, or flakes with a diameter of less than 50 mm, or spheres with an outer diameter of less than 15 mm, or flakes with a diameter of less than 50 mm.

[0046] Preferably, the oxygen-enriched supply unit includes:

[0047] The No. 1 air supply system supplies air to the outer swirl channel through the No. 1 regulating valve and the No. 1 branch pipe; supplies air to the inner swirl channel through the No. 2 regulating valve and the No. 2 branch pipe; and supplies air to the inner axial channel through the No. 3 regulating valve and the No. 1 branch pipe.

[0048] The No. 2 air supply system provides oxygen-enriched air to the outer jet air channel through an oxygen-enriched air supply pipeline.

[0049] Compared with the prior art, the advantages and positive effects of this application are:

[0050] This invention employs an infrared temperature sensor array uniformly distributed throughout the combustion zone, enabling precise real-time monitoring of the combustion zone and detailed understanding of the specific temperature distribution. This real-time detection and control allows for a better understanding of the combustion process, thereby optimizing combustion efficiency and reducing energy waste.

[0051] This invention integrates a humidity sensor, a density sensor, and a calorific value compensation system. These sensors and systems can perform precise calculations and adjustments based on the humidity and bulk density of the AFR (Amount of Fuel Residue), as well as the temperature compensation requirements of the combustion zone. Using this data, the invention can obtain the required mass of AFR via a mass sensor and accurately deliver it to the cement kiln head as compensating fuel. This precise control method not only improves fuel efficiency but also ensures stable operation of the cement kiln and product quality.

[0052] Furthermore, this invention also relates to an oxygen-enriched supply unit, which plays a crucial role in improving fuel combustion efficiency. By precisely controlling the airflow direction and volume, the oxygen-enriched supply unit can ensure that the temperature distribution in the combustion zone reaches an ideal state, meeting the specific requirements of cement kiln operation. This optimized temperature distribution not only helps improve combustion efficiency but also reduces the emission of harmful gases, thus having a positive impact on the environment.

[0053] This invention opens up an efficient utilization channel for high-calorific-value AFR, which can increase the heat substitution rate of high-calorific-value AFR to more than 50%, shorten the burnout time of 10mm plastic particles to less than 2.4s, increase the residual carbon burnout rate to more than 99.5%, and control the kiln head temperature fluctuation within ±12℃, providing key path support for the cement industry to achieve the goal of deep carbon reduction. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a structural diagram of a preferred embodiment of this application;

[0056] Figure 2 This is an axial cross-sectional view of the multi-channel burner in a preferred embodiment of this application;

[0057] Figure 3 This is an end view of the multi-channel burner in a preferred embodiment of this application;

[0058] Figure 4 This is a schematic diagram of the thermal field monitoring arrangement of the 12-channel infrared temperature measurement array in a preferred embodiment of this application. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0060] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0061] Please see Figures 1 to 4 A multi-fuel feeding system for the kiln head of a cement kiln, comprising:

[0062] The cement kiln head includes several combustion zones; that is, the cement kiln head in this application adopts a gradient combustion technology based on combustion gradation, which divides the combustion zone into several stages; the gradient combustion technology achieves the surface gasification-core combustion process of large particle AFR by controlling the staged supply of air.

[0063] The system includes:

[0064] The multi-channel burner 3 includes a solid alternative fuel channel and a pulverized coal channel;

[0065] Solid alternative fuel supply unit 1 supplies high-calorific-value alternative fuel with a calorific value greater than 25 MJ / kg to the solid alternative fuel channel; solid alternative fuel refers to high-calorific-value alternative fuel with a calorific value (>25 MJ / kg) such as plastics, textiles, biomass, etc. (<15 mm spheres or <50 mm flakes or mixtures thereof), abbreviated as AFR; a high-pressure blower is used to transport the solid alternative fuel through pipelines to the burner at the kiln head of the cement kiln;

[0066] Coal powder supply unit 2 supplies coal powder to the coal powder channel;

[0067] The oxygen-enriched supply unit 4 provides 28% to 35% oxygen-enriched air to the multi-channel burner 3, thereby improving the residual carbon combustion rate.

[0068] The calorific value compensation system controls the working status of the solid alternative fuel supply unit 1, the pulverized coal supply unit 2, the multi-channel burner 3, and the oxygen-enriched supply unit 4 based on the temperature distribution in the combustion zone, the bulk density of the solid alternative fuel, and the moisture content.

[0069] In one specific embodiment, the solid alternative fuel supply unit 1 includes:

[0070] Fuel storage section, used for storing solid alternative fuels;

[0071] A fuel delivery unit is used to transfer solid alternative fuels from a fuel storage unit to a solid alternative fuel channel;

[0072] Mass sensors are used to detect the mass of solid alternative fuels;

[0073] Humidity sensor used to detect the moisture content of solid alternative fuels;

[0074] Density sensor used to detect the bulk density of solid alternative fuels.

[0075] These sensors can acquire the humidity, bulk density, and mass of the AFR in a timely manner, providing timely and accurate numerical analysis data for the calorific value compensation system.

[0076] In one specific embodiment, the solid alternative fuel supply unit 1 includes a dual-metering device consisting of a twin-screw weighing feeder and a nuclear weighing device. The twin-screw weighing feeder is the main control signal, and the nuclear weighing device performs dynamic compensation (correcting the density fluctuation error of the screw scale) to achieve AFR metering with a metering accuracy of ±1.0%.

[0077] In one specific embodiment, the fuel storage unit includes a steady flow silo 101 and a fluidization silo 105. The outlet of the steady flow silo 101 is connected to the inlet of the fluidization silo 105 via a solid alternative fuel conveying line. The fuel conveying unit includes a solid alternative fuel conveying line, a rotary feeder 106, and a pneumatic conveying system RB01 assembly. The outlet of the fluidization silo 105 is connected to the inlet of the rotary feeder 106 via the solid alternative fuel conveying line.

[0078] In one specific embodiment, the solid alternative fuel supply unit 1 includes:

[0079] The steady-flow silo 101 stores solid alternative fuels and maintains a stable material level of 30-70%.

[0080] The twin-screw weighing feeder 102 is used to detect the quality of solid alternative fuels.

[0081] The online microwave moisture analyzer 103 is used to detect the moisture content of solid alternative fuels;

[0082] The Nuclear Scale 104, based on gamma-ray density measurement, is used to detect the density of solid alternative fuels. The Nuclear Scale 104 is a non-contact continuous metering device that utilizes the absorption principle of gamma rays emitted from Cs-137 or Am-241 radioactive sources. The gamma-ray module measures the density in real time and performs dynamic compensation (correcting the density fluctuation error of the screw scale) to achieve a metering system with a measurement accuracy of ±1.0%.

[0083] This invention employs a double-helix weighing feeder 102 and a nuclear scale 104 based on gamma-ray density measurement to correct measurement errors caused by density in real time, achieving an accuracy of ±1.0%.

[0084] The online microwave moisture analyzer 103 and the γ-ray density measurement module of the nucleus scale 104 based on γ-ray density measurement are integrated with a calorific value compensation module to establish an AFR calorific value compensation function model, that is, to adopt the microwave-γ-ray dual-mode detection online calorific value compensation algorithm model.

[0085] The fluidization silo 105 and the outlet of the steady-flow silo 101 are connected to the inlet of the fluidization silo 105 via a solid alternative fuel conveying line. Air in the pneumatic conveying system RB01 component pipeline is injected into it via a rotary feeder 106, thus fluidizing the AFR within the silo. Its function is to solve the problem of pulse-type AFR feeding. It should be noted that the upper part of the fluidization silo 105 is connected to a dust collector via a pipe.

[0086] The discharge port of the rotary feeder 106 and the fluidization silo 105 are connected to the inlet of the rotary feeder 106 via a solid alternative fuel conveyor line.

[0087] The pneumatic conveying system RB01 component receives the solid alternative fuel output from the rotary feeder 106 and outputs it to the solid alternative fuel channel. The pneumatic conveying system RB01 component mainly includes a Roots blower, silencer, valves, instruments, conveying pipelines, etc.

[0088] The invention may also include a separator for separating alternative fuels from the delivery gas, ensuring that there is no gas interference when the fuel enters the burner.

[0089] The inner wall of the burner is made of high-temperature and corrosion-resistant materials, which are suitable for the high-temperature combustion environment of alternative fuels.

[0090] This invention enables continuous and uniform feeding of AFR: it is equipped with a stable flow bin to solve the upstream material flow fluctuation, and adopts a redundant metering system composed of a screw scale and a nuclear scale to improve metering accuracy. It is also equipped with a fluidized bin to solve the problem of pulse feeding in AFR.

[0091] In one specific embodiment, the pulverized coal supply unit 2 includes a pulverized coal silo 201, a pulverized coal valve 202, a pulverized coal metering scale 203, and a pneumatic conveying system RB02 assembly. The pneumatic conveying system RB02 mainly includes a Roots blower, a silencer, valves, instruments, and conveying pipelines.

[0092] In one specific embodiment, the cement kiln head employs a gradient combustion technology based on combustion gradation, dividing the combustion zone into three stages:

[0093] The primary AFR volatile matter slow-release combustion zone requires a temperature of 1200℃~1400℃; AFR conveyor air, inner axial flow air, and inner swirl flow air are introduced to achieve slow-release combustion of AFR volatile matter;

[0094] The main combustion zone of the secondary carbon skeleton gasification requires a temperature of 1600℃~1800℃; pulverized coal conveying air, outer swirl air and secondary air at about 1000℃ are introduced to complete the carbon skeleton gasification.

[0095] The three-stage residual carbon burnout combustion zone requires a temperature greater than 1800℃; high-speed injection of 28%~35% oxygen-enriched air at a speed greater than 300m / s is introduced to ensure complete combustion of residual carbon.

[0096] The gradient combustion technology is explained using three-stage combustion to illustrate the surface gasification-core combustion process of large-particle AFRs.

[0097] In one specific embodiment, the oxygen-enriched supply unit 4 can improve the residual carbon burnout rate by introducing 28%~35% oxygen-enriched air into the injection air channel outside the multi-channel burner and injecting it into the three-stage residual carbon burnout combustion zone at a speed of more than 300m / s, thereby reducing the residual carbon burnout time and improving the residual carbon burnout rate.

[0098] Depending on the type of fuel and combustion requirements, the nozzle size and angle can be adjusted to optimize the flame shape and temperature distribution.

[0099] In one specific embodiment, the calorific value compensation system includes:

[0100] An infrared temperature sensor array, evenly distributed in the combustion zone, is used to capture infrared images formed during AFR combustion. The detection range of the infrared images is 8μm~14μm infrared light. For ease of understanding, the infrared temperature sensor array is illustrated by a 12-channel infrared temperature measurement array monitoring module, which uses a 12-channel infrared temperature measurement array (100Hz sampling rate) arranged in a circular array in the kiln head hood, corresponding to the clock's hour direction, to capture the 8μm~14μm long-wave infrared light (weak dust scattering) released during AFR combustion. Figure 4The thermometers 501 (No. 1), 502 (No. 2), 503 (No. 3), 504 (No. 4), 505 (No. 505), 506 (No. 6), 507 (No. 7), 508 (No. 8), 509 (No. 9), 510 (No. 10), 511 (No. 11), and 512 (No. 12) are evenly distributed in the circular arrangement of the infrared temperature measurement array, corresponding to the hour direction of the clock.

[0101] The infrared image processing module acquires local overheated areas with temperatures above 1850℃ and low-temperature areas with temperatures below 1650℃ based on infrared images; that is, based on infrared images, it can quickly locate the local overheated areas (>1850℃) or low-temperature areas (<1650℃) caused by flash burning of AFR volatiles or unburned large particles.

[0102] The calorific value compensation module calculates the real-time calorific value based on the bulk density and water content of the solid alternative fuel.

[0103] The air delivery parameter control module controls the air delivery parameters of the oxygen-enriched supply unit 4 based on the temperature distribution within the combustion zone.

[0104] In one specific embodiment, the calculation formula of the calorific value compensation module is as follows:

[0105] ;

[0106] In the formula, Q is the real-time calorific value, α is the calibration coefficient, the value of α ranges from 0.95 to 1.05, β is the moisture correction factor, the value of β ranges from 0.015 to 0.025, w is the water content, ρ is the bulk density, and C is the fuel type coefficient, the value of C ranges from 0.8 to 1.2.

[0107] In one specific embodiment, the multi-channel burner 3 includes: an outer jet air channel 301, an outer swirl air channel 302, a pulverized coal conveying channel 303, an inner swirl air channel 304, an inner axial flow air channel 305, and an AFR conveying channel 306.

[0108] The outer jet air duct 301 has a jet air velocity greater than 300 m / s; it sprays 28%~35% oxygen-enriched air, the jet air duct is lined with Al2O3-ZrO2 high temperature resistant ceramic, and the spraying uses independent oxygen-enriched nozzles.

[0109] The jet wind speed range of the outer swirl channel 302 is 60m / s to 180m / s, and it includes 24 guide vanes with a radius of curvature of 20mm and a tangential angle of 35°.

[0110] The jet velocity range of the pulverized coal conveying channel 303 is 18m / s to 28m / s;

[0111] The jet wind speed range of the inner swirling air channel 304 is 60m / s to 180m / s, and the variable angle swirler has a tangential angle range of 15° to 30°.

[0112] The jet velocity range of the inner axial flow channel 305 is 30m / s to 180m / s;

[0113] The jet velocity range of the AFR delivery channel 306 is 30~60m / s.

[0114] The high-calorific-value alternative fuels include one or more of plastics, textiles, and biomass.

[0115] The high-calorific-value alternative fuel is a mixture of spheres with an outer diameter of less than 15 mm, or flakes with a diameter of less than 50 mm, or spheres with an outer diameter of less than 15 mm, or flakes with a diameter of less than 50 mm.

[0116] In one specific embodiment, the oxygen-enriched supply unit 4 includes:

[0117] The No. 1 air supply system supplies air to the outer swirl channel 302 through the No. 1 regulating valve 401 and the No. 1 branch pipe; supplies air to the inner swirl channel 304 through the No. 2 regulating valve 402 and the No. 2 branch pipe; and supplies air to the inner axial flow channel 305 through the No. 3 regulating valve 403 and the No. 1 branch pipe.

[0118] The No. 2 air supply system provides oxygen-enriched air to the outer jet air channel 301 through the oxygen-enriched air supply pipeline.

[0119] This invention uses an infrared temperature sensor array to monitor the thermal field, which can capture temperature fluctuations in different areas. Then, it can adjust the ratio and angle of the inner axial flow air, inner swirl air, and outer swirl air as needed, and adjust the oxygen content of the outer jet air to maintain a stable kiln head temperature gradient.

[0120] Explanation of working principle:

[0121] AFR enters the steady flow bin 101, which has a built-in material level display and high / low material level alarms, ensuring that the material level is always within a suitable range (30~70%), resolving upstream material flow fluctuations, and eliminating external interference for the weighing and metering of the double helix weighing feeder 102.

[0122] The double helix weighing feeder 102 and the nuclear scale 104 form a redundant metering system. The double helix weighing feeder uses a load cell for weighing and metering, which is the main control signal. The nuclear scale performs dynamic compensation (corrects the density fluctuation error of the helix scale) to improve the reliability of AFR metering. The metering accuracy can reach ±1%. When the deviation between the two scales is >1.5%, the weighted average mode is triggered or an alarm prompts manual intervention.

[0123] An AFR calorific value compensation function model was established. An online calorific value compensation system based on an online microwave moisture analyzer 103 and a nucleus scale 104 for gamma-ray density measurement was developed. A calorific value compensation module based on calorific value, moisture content, and density was established. The formula for the calorific value compensation module is as follows:

[0124] ;

[0125] In the formula, Q is the real-time calorific value (MJ / kg), α is the calibration coefficient, the value of α ranges from 0.95 to 1.05, β is the moisture correction factor, the value of β ranges from 0.015 to 0.025, w is the water content (%), ρ is the bulk density (t / m³), and C is the fuel type coefficient, the value of C ranges from 0.8 to 1.2.

[0126] The precisely weighed AFR enters the fluidization silo 105, where it is fluidized. It is then fed into the pneumatic conveying system (RB01 component) via a rotary feeder, thus solving the problem of pulse feeding.

[0127] The No. 1 pneumatic conveying system RB01 component conveys the AFR to the multi-channel burner AFR conveying channel 306, where it enters the kiln head for combustion, with a conveying air velocity of 30~60m / s.

[0128] The coal powder stored in the coal powder silo 201 is metered and fed through the coal powder valve 202 and the coal powder metering scale 203 with a metering accuracy of ±1%. Parameters such as calorific value are tested by the laboratory.

[0129] The No. 2 pneumatic conveying system RB02 component conveys pulverized coal to the pulverized coal conveying channel 303 of the multi-channel burner for combustion at the kiln head, with a conveying air velocity of 18~28m / s.

[0130] The No. 3 pneumatic conveying system RB03 simultaneously supplies air to the inner axial flow, inner swirl flow, and outer swirl flow. The No. 4 pneumatic conveying system RB04 supplies air only to the outer jet flow. The inner axial flow velocity is 60m / s~180m / s, the inner swirl flow velocity is 60m / s~180m / s, the outer swirl flow velocity is 60m / s~180m / s, and the outer jet flow velocity is greater than 300m / s.

[0131] Adjusting the opening of regulating valve 403 can adjust the initial wind speed of the inner axial flow channel 305 of the multi-channel burner, which can change the length of the first-stage volatile matter combustion slow release zone and adjust the residence time of the AFR in the first-stage volatile matter combustion slow release zone to prevent volatile matter flashover.

[0132] Adjusting the opening of regulating valve 402 (No. 2) and regulating valve 401 (No. 1) can adjust the initial wind speed of the internal and external airflow.

[0133] The inner swirl channel 304 of the multi-channel burner is equipped with a variable angle swirler, and the outer swirl channel 302 is equipped with guide vanes with a tangential angle of 35°.

[0134] Changing the speed and angle of the swirling airflow can adjust the flame shape and the combustion conditions of the secondary main combustion zone (carbon skeleton gasification combustion zone).

[0135] Introducing 28%–35% oxygen-enriched air into the outer air jet channel 301 of the multi-channel burner, and injecting it into the tertiary combustion zone at a speed greater than 300 m / s, can increase the residual carbon burnout rate in the tertiary combustion zone to greater than 99.5% and reduce the residual carbon burnout time to 1.6 s. The high-speed injected air creates a low-pressure zone outside the primary and secondary combustion zones, enhancing the turbulent mixing of secondary air and AFR in the primary and secondary combustion zones.

[0136] A 12-channel infrared temperature measurement array is arranged in a circular array on the kiln head hood, such as... Figure 4 As shown, thermometers 501 (No. 1), 502 (No. 2), 503 (No. 3), 504 (No. 4), 505 (No. 505), 506 (No. 6), 507 (No. 7), 508 (No. 8), 509 (No. 9), 510 (No. 10), 511 (No. 11), and 512 (No. 12) correspond to the hourly clock direction, capturing the 8μm-14μm long-wave infrared radiation (weak dust scattering) released during AFR combustion. This allows for rapid location of monitoring modules in areas of localized overheating (>1850℃) or underheating (<1650℃) caused by flashover of AFR volatiles or incomplete combustion of large particles.

[0137] Two initial AFR implementation schemes were designed:

[0138] Option 1: Waste plastics (25%) + biomass pellets (25%) + coal powder (50%);

[0139] Option 2: Waste textiles (25%) + biomass pellets (25%) + coal powder (50%).

[0140] In the initial implementation phase, the proportion of pulverized coal blending should not be less than 50%. As production data accumulates, the proportion of pulverized coal blending can be gradually reduced to not less than 20%, and a model of AFR type C, calorific value Q and pulverized coal blending ratio should be established in actual operation.

[0141] The results of this invention, obtained through simulations on a 5000t / d production line using Scheme 1 and Scheme 2, show that the burnout time of 10mm plastic granules can be shortened from 3.2s to less than 2.4s, the burnout rate can be increased to >99.5%, the burnout rate of large granules (15mm) can be greater than 99.2%, and the residual carbon content can be reduced to <0.5%. The kiln head temperature fluctuation can be reduced from ±50℃ to ±12℃, and the flame length can be shortened by 20% (8m → 6.4m).

[0142] The technical solution of the present invention has the following technical features:

[0143] 1. The pneumatic conveying system enables efficient and stable delivery of alternative fuels, solving the problems of easy clogging and high wear in traditional mechanical conveying.

[0144] 2. The kiln head burner is reasonably designed to meet the combustion requirements of various alternative fuels, thereby improving combustion efficiency and temperature uniformity within the kiln.

[0145] 3. The process control system has achieved intelligent operation, reducing the difficulty and error of manual operation.

[0146] 4. The system has good overall environmental performance, reducing carbon emissions and pollutant emissions, and meets the requirements of green production.

[0147] The implementation process mainly includes:

[0148] 1. Store alternative fuels (such as biomass pellets) in storage bins.

[0149] 2. Start the pneumatic conveying system and use a high-pressure blower to deliver the alternative fuel to the kiln head burner.

[0150] 3. Inside the burner, the alternative fuel mixes with the combustion air and is ignited to form a high-temperature flame.

[0151] 4. The control system adjusts the fuel flow and combustion air volume in real time according to the kiln temperature to ensure stable combustion.

[0152] 5. The exhaust gas after combustion is discharged after dust removal and desulfurization treatment.

[0153] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A multi-fuel feeding system for a cement kiln head, the cement kiln head comprising a plurality of combustion zones; the system comprising: The multi-channel burner (3) includes a solid alternative fuel channel and a pulverized coal channel; The solid alternative fuel supply unit (1) supplies high-calorific-value alternative fuels with a calorific value greater than 25 MJ / kg to the solid alternative fuel channel; The pulverized coal supply department (2) supplies pulverized coal to the pulverized coal channel; The oxygen-enriched supply unit (4) supplies 28% to 35% oxygen-enriched air to the multi-channel burner (3); characterized in that: The system also includes a calorific value compensation system, which controls the working status of the solid alternative fuel supply unit (1), the pulverized coal supply unit (2), the multi-channel burner (3) and the oxygen-enriched supply unit (4) based on the temperature distribution in the combustion zone, the bulk density and water content of the solid alternative fuel; The solid alternative fuel supply unit (1) includes: A nuclear scale based on gamma-ray density measurement is used to detect the bulk density of solid alternative fuels; An online microwave moisture analyzer is used to detect the moisture content of solid alternative fuels; A double-screw weighing feeder is used to detect the mass of solid alternative fuels; the double-screw weighing feeder, together with a nuclear scale based on gamma-ray density measurement, corrects for measurement errors caused by density in real time, to an accuracy of ±1.0%. The calorific value compensation system includes: An infrared temperature sensor array, uniformly distributed in the combustion zone, is used to capture infrared images formed during AFR combustion. The detection range of the infrared images is 8μm~14μm infrared light. The calorific value compensation module calculates the real-time calorific value based on the bulk density and water content of the solid alternative fuel. The air delivery parameter control module controls the air delivery parameters of the oxygen-enriched supply unit (4) based on the temperature distribution in the combustion zone. The infrared image processing module acquires local overheated areas with temperatures above 1850℃ and low-temperature areas with temperatures below 1650℃ based on infrared images. The calculation formula for the calorific value compensation module is as follows: In the formula, Q is the real-time calorific value, α is the calibration coefficient, the value of α ranges from 0.95 to 1.05, β is the moisture correction factor, the value of β ranges from 0.015 to 0.025, w is the water content, ρ is the bulk density, and C is the fuel type coefficient, the value of C ranges from 0.8 to 1.

2.

2. The multi-fuel feeding system for the cement kiln head according to claim 1, characterized in that, The solid alternative fuel supply unit (1) includes: Fuel storage section, used for storing solid alternative fuels; The fuel delivery unit is used to transfer solid alternative fuels from the fuel storage unit to the solid alternative fuel channel.

3. The multi-fuel feeding system for the cement kiln head according to claim 1, characterized in that, The combustion zones include a primary AFR volatile matter slow-release combustion zone with a temperature requirement of 1200℃~1400℃, a secondary carbon skeleton gasification main combustion zone with a temperature requirement of 1600℃~1800℃, and a tertiary residual carbon burnout combustion zone with a temperature requirement greater than 1800℃.

4. The multi-fuel feeding system for the cement kiln head according to claim 1, characterized in that, The multi-channel burner (3) includes: an outer jet air channel (301), an outer swirl air channel (302), a pulverized coal conveying channel (303), an inner swirl air channel (304), an inner axial flow air channel (305), and an AFR conveying channel (306).

5. The multi-fuel feeding system for the cement kiln head according to claim 4, characterized in that: The jet velocity of the outer jet air channel (301) is greater than 300m / s; The jet wind speed range of the outer swirl channel (302) is 60m / s to 180m / s, and it includes 24 guide vanes with a vane curvature radius of 20mm and a tangential angle of 35°. The jet velocity range of the pulverized coal conveying channel (303) is 18m / s to 28m / s; The jet wind speed range of the inner swirl air channel (304) is 60m / s to 180m / s, and the tangential angle range is 15° to 30°. The jet velocity range of the inner axial flow air duct (305) is 30m / s to 180m / s; The jet velocity range of the AFR conveying channel (306) is 30~60m / s.

6. The multi-fuel feeding system for the cement kiln head according to any one of claims 1-5, characterized in that: The high-calorific-value alternative fuels include one or more of plastics, textiles, and biomass.

7. The multi-fuel feeding system for the cement kiln head according to claim 6, characterized in that: The high-calorific-value alternative fuel is a mixture of spheres with an outer diameter of less than 15 mm, or flakes with a diameter of less than 50 mm, or spheres with an outer diameter of less than 15 mm, or flakes with a diameter of less than 50 mm.

8. The multi-fuel feeding system for the cement kiln head according to claim 1, characterized in that: The oxygen-enriched supply unit (4) includes: The No. 1 air supply system supplies air to the outer swirl channel (302) through the No. 1 regulating valve (401) and the No. 1 branch pipe; supplies air to the inner swirl channel (304) through the No. 2 regulating valve (402) and the No. 2 branch pipe; and supplies air to the inner axial channel (305) through the No. 3 regulating valve (403) and the No. 1 branch pipe. The No. 2 air supply system provides oxygen-enriched air to the outer jet air channel (301) through the oxygen-enriched air supply pipeline.

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