Method for calcining lime by using biomass
By using precise pulverization and injection technology for biomass fuel, the problems of difficult-to-regenerate fuel sources and high production costs in double-chamber vertical kiln calcination of lime have been solved, achieving stable combustion, low carbon emissions, and waste residue utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-10
AI Technical Summary
The use of fossil fuels in the calcination of lime in double-chamber vertical kilns results in the difficulty of regenerating fuel sources, the difficulty of waste disposal, high production costs, and a lack of compliance with the concept of sustainable development.
Using biomass (such as forestry processing residues and woody crop straw) as fuel, the process involves crushing, drying, grinding, finished product collection, and injection conveying to ensure that the wood powder burns evenly in the furnace and controls the temperature at 1150℃ to produce lime products.
It achieves stable combustion and precise temperature control of biomass fuel, reduces carbon emissions, and the waste residue can be used as agricultural fertilizer, reducing production costs and making it suitable for large-scale industrial production.
Smart Images
Figure CN121627322A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metallurgical technology, and in particular to a method for calcining lime using biomass. Background Technology
[0002] A double-chamber vertical kiln is a lime calcination device. Its core structure consists of two interconnected kiln chambers that share a combustion system and discharge device. During calcination, it employs an "alternating calcination-preheating" mode. While one kiln chamber is in calcination mode, the other chamber uses the high-temperature flue gas discharged from the calcining chamber to preheat the newly added limestone raw material. The two kiln chambers periodically switch operating states via a reversing valve. The raw material is evenly distributed into the kiln chambers from the top, and after three stages—preheating, calcination, and cooling—the finished lime is discharged from the bottom outlet.
[0003] The use of fuel in calcining lime in a double-chamber vertical kiln has significant drawbacks. The suitable fuels are mostly high-quality gas or pulverized coal. These fuels have limited reserves, high procurement costs, and easily generate a large amount of dust and harmful gases during combustion, resulting in significant environmental protection pressure and not conforming to the current green production concept.
[0004] The use of traditional fossil fuels such as gas and solid (coal) in the calcination of lime in double-chamber vertical kilns faces many restrictions. The fuel source is not easily renewable, which is not in line with the concept of sustainable development. The waste residue is not easy to handle, and the production cost is high.
[0005] Therefore, it is necessary to provide a method for calcining lime using biomass to solve the above-mentioned technical problems. Summary of the Invention
[0006] This invention provides a method for calcining lime using biomass, which solves the problems of high production costs associated with calcining lime in double-chamber vertical kilns, which commonly use fossil fuels such as gas and solid (coal) that are not easily renewable, thus failing to meet the concept of sustainable development, and also results in difficult waste disposal.
[0007] To solve the above technical problems, the present invention provides a method for calcining lime using biomass, comprising the following steps: S1: coarse crushing process; selecting biomass raw materials such as forestry processing residues and woody crop straw, removing mud, stones and metal impurities, and then feeding them into a double roller crusher for coarse crushing to crush the biomass raw materials into granular materials with a particle size ≤25mm.
[0008] S2: Drying process; The coarsely crushed granular biomass material is fed into a dryer for drying. Hot air circulation drying is used, and the drying temperature is controlled at 120-130℃ for 30-60 minutes.
[0009] S3: Powdering process; The dried material is fed into a mill for powdering, and a classifying screen is used for online classification.
[0010] S4: Finished Wood Dust Collection Process; Graded and qualified wood dust is sent to the finished product storage silo through a negative pressure collection pipeline. A pulse-jet dust collector is installed on the top of the storage silo to collect the airborne wood dust.
[0011] The bottom of the storage silo adopts a conical structure and is equipped with a screw feeder to ensure smooth discharge of wood powder. At the same time, the storage silo is equipped with a gas detection device and a multi-point temperature monitoring device to control the temperature inside the storage silo to ≤50℃ and the oxygen content to ≤10% to prevent the wood powder from spontaneously combusting.
[0012] S5: Wood flour calorific value testing process; randomly sample wood flour from the mill outlet and test its lower heating value (HV) using an oxygen bomb calorimeter. If the test result meets HV≥3200Kcal / kg, the wood flour calorific value meets the standard and can be directly used in subsequent calcination processes; if the test result is HV<3200Kcal / kg, activate the calorific value blending mechanism and add coal powder with HV≥6000Kcal / kg into the mill. Calculate the blending ratio based on the calorific value difference. During the blending process, turn on the stirring device in the storage silo at a speed of 60-80 r / min for 20-30 min to ensure uniform mixing of wood flour and coal powder. After blending, take samples again for testing until the lower heating value of the mixed fuel reaches HV≥3200Kcal / kg.
[0013] S6: The prepared wood powder is injected and transported to the furnace for combustion. Qualified wood powder is then transported to the lime calcination furnace via dilute phase injection, powered by a Roots blower. The gas-to-solid mass ratio μ is controlled to be ≤4. The wood powder conveying speed in the pipeline is controlled to ν = 10-15 m / s, a speed range sufficient to overcome pipeline resistance and prevent excessive wear due to excessive wood powder speed. The conveying pressure is controlled to be ≥0.5 MPa, and must be 0.15 MPa higher than the kiln pressure to ensure smooth injection of wood powder into the furnace and prevent backflow of high-temperature flue gas. After entering the furnace, adjust the air distribution ratio within the furnace. The ratio of primary air to secondary air is controlled at 1:1.2-1:1.5. Primary air provides oxygen for the initial combustion of wood powder, while secondary air is introduced from the annular channel at the top of the furnace to promote complete combustion of wood powder and agitate the airflow, ensuring uniform temperature within the furnace. The temperature is monitored in real time by a multi-point temperature monitoring device installed within the furnace, and the amount of wood powder injected is adjusted to ensure that the temperature in the limestone thermal decomposition zone in the middle of the furnace is stably maintained at 1100℃. The calcination time is controlled at 2-3 hours to complete the calcination of limestone to produce lime products.
[0014] Preferably, the discharge particle size of the double-roll crusher is 25-30mm.
[0015] Preferably, the dryer is equipped with an online humidity monitor at the discharge end to detect the moisture content of the material in real time and control the moisture content of the material after drying.
[0016] Preferably, the main shaft speed of the mill is 1200-1500 r / min, the grading screen adopts an 80-100 mesh stainless steel screen, and the grading screen speed is controlled by a variable frequency motor to 800-1000 r / min to accurately control the fineness of the wood powder. Coarse particles that do not pass through the grading screen are returned to the mill for re-grinding via a return pipeline.
[0017] Preferably, the coal powder with HV≥6000Kcal / kg added to the finished product storage silo via a spiral mixer can be either anthracite or bituminous coal.
[0018] Preferably, the controlled gas-solid mass ratio is μ≤4 / 1, kg / kg. This ratio ensures that the wood powder is suspended in the conveying pipeline, avoiding sedimentation and pipe blockage.
[0019] Preferably, in the drying process of S2, a dryer is required to dry the coarsely crushed granular biomass material. The dryer includes: a hot air furnace, a rotary drying drum, and an online detection system.
[0020] Hot blast furnace: generates high-temperature flue gas at 800℃, which is then mixed with air (kiln tail flue gas can be used for mixing) to adjust the temperature to 120-150℃ (depending on the moisture content of the raw materials), with an oxygen content of ≤12%, and then dried in a drying drum;
[0021] Rotary drying drum: equipped with lifting plates, the rotation speed is linked to the final moisture content, and frequency conversion is used for regulation;
[0022] Online monitoring system: Three parameters are monitored inside the rotary drying drum: temperature, oxygen content (or CO content), and moisture content;
[0023] The internal operating temperature is 120-130℃, with a dangerous value of 150℃. When the temperature is >150℃, nitrogen purging is required. The operating oxygen content is 8%-12%; when the oxygen content is ≥12%, nitrogen purging is required.
[0024] Preferably, in step S6, a calcination device is used to calcine limestone by burning wood powder, and the calcination device includes a kiln body;
[0025] The raw material silo is located at the top center of the kiln body. A fire observation hole is provided on one side of the top of the kiln body. A discharge port is provided at the bottom of the kiln body. The kiln body is equipped with a smoke exhaust chimney.
[0026] The wood powder silo is located at the bottom left side of the outer surface of the kiln body. A compressed air conveying device is installed at the bottom of the wood powder silo, and one end of the compressed air conveying device is fixedly connected to the kiln body. A combustion-supporting fan device is installed on one side of the left side of the kiln body.
[0027] Compared with related technologies, the method for calcining lime using biomass provided by the present invention has the following beneficial effects:
[0028] This invention provides a method for calcining lime using biomass. Through precise control of the moisture content, fineness, and lower heating value of wood flour via a pulverizing process, coupled with optimized injection and conveying parameters, the method ensures uniform dispersion and complete combustion of wood flour within the furnace. This maintains a stable furnace temperature of approximately 1150℃ to meet the thermal decomposition requirements of limestone, improving the lime product qualification rate and achieving stable combustion and precise temperature control of wood flour. Simultaneously, the use of biomass (wood flour) to replace fossil fuels reduces carbon emissions compared to traditional all-fossil fuel calcination methods. Furthermore, the waste residue generated during calcination can be directly used as agricultural fertilizer, achieving significant carbon reduction and emission reduction effects with low or even zero emissions. The cost of obtaining wood flour is lower than that of coal, reducing production costs. The calorific value adjustment mechanism can adapt to biomass raw materials from different sources and with different physicochemical properties, addressing the challenge of complex biomass composition. Moreover, the injection and conveying parameters can be flexibly adjusted according to furnace specifications and limestone throughput, making it suitable for large-scale industrial production. This demonstrates strong process adaptability and offers the advantages of stable wood flour combustion and precise temperature control, significant carbon reduction and emission reduction, substantial reduction in production costs, and strong process adaptability. Attached Figure Description
[0029] Figure 1 A schematic flow diagram of a method for calcining lime using biomass provided by the present invention;
[0030] Figure 2 A schematic diagram of a co-current calcination device for a method of calcining lime using biomass provided by the present invention;
[0031] The following are labeled in the diagram: 1. Compressed air conveying device, 2. Combustion fan device, 3. Fire observation hole, 4. Raw material silo, 5. Kiln body, 6. Exhaust chimney, 7. Discharge port, 8. Wood powder silo. Detailed Implementation
[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0033] First Embodiment
[0034] Please refer to the following: Figure 1 ,in, Figure 1 This is a schematic flowchart of a method for calcining lime using biomass, provided by the present invention.
[0035] A method for calcining lime using biomass includes the following steps: S1: coarse crushing process; selecting biomass raw materials such as forestry processing residues and woody crop straw, removing mud, stones and metal impurities, and then feeding them into a double roller crusher for coarse crushing to crush the biomass raw materials into granular materials with a particle size ≤25mm.
[0036] S2: Drying process; The coarsely crushed granular biomass material is fed into a dryer for drying. Hot air circulation drying is used, and the drying temperature is controlled at 120-130℃ for 30-60 minutes.
[0037] S3: Powdering process; The dried material is fed into a mill for fine powdering, and a classifying screen is used for online classification.
[0038] S4: Finished Wood Dust Collection Process; Graded and qualified wood dust is sent to the finished product storage silo through a negative pressure collection pipeline. A pulse-jet dust collector is installed on the top of the storage silo to collect the airborne wood dust.
[0039] The bottom of the storage silo adopts a conical structure and is equipped with a screw feeder to ensure smooth discharge of wood powder. At the same time, the storage silo is equipped with a gas detection device and a multi-point temperature monitoring device to control the temperature inside the storage silo to ≤50℃ and the oxygen content to ≤10% to prevent the wood powder from spontaneously combusting.
[0040] S5: Wood flour calorific value testing process; randomly sample wood flour from the mill outlet and test its lower heating value (HV) using an oxygen bomb calorimeter. If the test result meets HV≥3200Kcal / kg, the wood flour calorific value meets the standard and can be directly used in subsequent calcination processes; if the test result is HV<3200Kcal / kg, activate the calorific value blending mechanism and add coal powder with HV≥6000Kcal / kg into the mill. Calculate the blending ratio based on the calorific value difference. During the blending process, turn on the stirring device in the storage silo at a speed of 60-80 r / min for 20-30 min to ensure uniform mixing of wood flour and coal powder. After blending, take samples again for testing until the lower heating value of the mixed fuel reaches HV≥3200Kcal / kg.
[0041] S6: The prepared wood powder is injected and transported to the furnace for combustion. Qualified wood powder is then transported to the lime calcination furnace via dilute phase injection, powered by a Roots blower. The gas-to-solid mass ratio μ is controlled to be ≤4. The wood powder conveying speed in the pipeline is controlled to ν = 10-15 m / s, a speed range sufficient to overcome pipeline resistance and prevent excessive wear due to excessive wood powder speed. The conveying pressure is controlled to be ≥0.5 MPa, and must be 0.15 MPa higher than the kiln pressure to ensure smooth injection of wood powder into the furnace and prevent backflow of high-temperature flue gas. After entering the furnace, adjust the air distribution ratio within the furnace. The ratio of primary air to secondary air is controlled at 1:1.2-1:1.5. Primary air provides oxygen for the initial combustion of wood powder, while secondary air is introduced from the annular channel at the top of the furnace to promote complete combustion of wood powder and agitate the airflow, ensuring uniform temperature within the furnace. The temperature is monitored in real time by a multi-point temperature monitoring device installed within the furnace, and the amount of wood powder injected is adjusted to ensure that the temperature in the limestone thermal decomposition zone in the middle of the furnace is stably maintained at 1150℃. The calcination time is controlled at 2-3 hours to complete the calcination of limestone to produce lime products.
[0042] The discharge port of the double-roll crusher is 25-30mm.
[0043] The dryer is equipped with an online humidity monitor at the discharge end to detect the moisture content of the material in real time and control the moisture content of the material after drying.
[0044] The mill's main shaft speed is 1200-1500 r / min, and the grading screen uses an 80-100 mesh stainless steel screen. The grading screen speed is controlled by a variable frequency motor to 800-1000 r / min, which precisely controls the fineness of the wood powder. Coarse particles that do not pass through the grading screen are returned to the mill for re-grinding via a return pipeline.
[0045] The finished product storage silo is filled with pulverized coal with HV≥6000Kcal / kg via a spiral mixer, which can be replaced by anthracite or bituminous coal.
[0046] The preferred gas-solid mass ratio is μ≤4 / 1, kg / kg. This ratio ensures that the wood powder is suspended in the conveying pipeline, preventing sedimentation and pipe blockage.
[0047] The mill can be vertical or tubular.
[0048] Compared with related technologies, the method for calcining lime using biomass provided by the present invention has the following beneficial effects:
[0049] This invention provides a method for calcining lime using biomass. Through precise control of the moisture content, fineness, and lower heating value of wood flour via a pulverizing process, coupled with optimized injection and conveying parameters, the method ensures uniform dispersion and complete combustion of wood flour within the furnace. This maintains a stable furnace temperature of approximately 1150℃ to meet the thermal decomposition requirements of limestone, improving the lime product qualification rate and achieving stable combustion and precise temperature control of wood flour. Simultaneously, the use of biomass (wood flour) to replace fossil fuels reduces carbon emissions compared to traditional all-fossil fuel calcination methods. Furthermore, the waste residue generated during calcination can be directly used as agricultural fertilizer, achieving significant carbon reduction and emission reduction effects with low or even zero emissions. The cost of obtaining wood flour is lower than that of coal, reducing production costs. The calorific value adjustment mechanism can adapt to biomass raw materials from different sources and with different physicochemical properties, addressing the challenge of complex biomass composition. Moreover, the injection and conveying parameters can be flexibly adjusted according to furnace specifications and limestone throughput, making it suitable for large-scale industrial production. This demonstrates strong process adaptability and offers the advantages of stable wood flour combustion and precise temperature control, significant carbon reduction and emission reduction, substantial reduction in production costs, and strong process adaptability.
[0050] Second Embodiment
[0051] Please refer to the following: Figure 2Based on the first embodiment of this application, which provides a method for calcining lime using biomass, the second embodiment of this application proposes another method for calcining lime using biomass. The second embodiment is merely a preferred embodiment of the first embodiment, and the implementation of the second embodiment will not affect the separate implementation of the first embodiment.
[0052] Specifically, the second embodiment of this application provides a method for calcining lime using biomass, which differs in that step S6 requires the use of a calcination device to calcine limestone by burning wood powder, and the calcination device includes a kiln body 5;
[0053] Raw material bin 4 is located at the top center of the kiln body 5. A fire observation hole 3 is provided on one side of the top of the kiln body 5. A discharge port 7 is provided at the bottom center of the kiln body 5. A smoke exhaust chimney 6 is provided on the right side of the kiln body 5.
[0054] Wood powder silo 8 is located at the bottom left side of the outer surface of the kiln body 5. A compressed air conveying device 1 is provided at the bottom of the wood powder silo 8. One end of the compressed air conveying device 1 is fixedly connected to the kiln body 5. A flame-retardant fan device 2 is provided on one side of the left side of the kiln body 5.
[0055] The working principle of the method for calcining lime using biomass provided by this invention is as follows:
[0056] During operation, the wood powder in the wood powder silo 8 is first precisely sprayed into the kiln body 5 through the compressed air conveying device 1. The combustion fan device 2 provides sufficient oxygen for the combustion of the wood powder, ensuring that the wood powder can burn completely. The observation hole 3 allows the operator to observe the combustion situation in the kiln body 5 in real time, so as to adjust the relevant parameters in a timely manner. The limestone undergoes a thermal decomposition reaction in the high temperature environment inside the kiln body 5, and the generated lime product is discharged from the discharge port 7. The exhaust gas generated by combustion is discharged from the kiln body 5 through the exhaust chimney 6.
[0057] Compared with related technologies, the method for calcining lime using biomass provided by the present invention has the following beneficial effects:
[0058] This invention provides a method for calcining lime using biomass. A complete calcination system is formed by the coordinated operation of a compressed air conveying device 1, a combustion fan device 2, a fire observation hole 3, a raw material silo 4, a kiln body 5, a flue gas chimney 6, a discharge port 7, and a wood powder silo 8. During the calcination process, the entire process is stable and efficient, meeting the needs of large-scale industrial production. By using biomass (wood powder) as fuel, carbon emissions are significantly reduced compared to traditional all-fossil fuel calcination methods. Furthermore, the waste residue produced during calcination can be directly used as agricultural fertilizer, achieving significant carbon reduction and emission reduction effects with low or even zero emissions of pollutants.
[0059] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.
Claims
1. A method of calcining lime with biomass, characterized by, The method comprises the following steps: S1: coarse crushing process; The biomass raw material is selected from forestry processing residues, woody plants, and shell crops, and after removing soil, stones, and metal impurities, the biomass raw material is sent to a double-roller crusher for coarse crushing treatment, so that the biomass raw material is crushed into granular material with a particle size of less than or equal to 25 mm; S2: drying process; the granular biomass material after coarse crushing is sent to a dryer for drying treatment, a hot air circulation drying method is adopted, the drying temperature is controlled to be 105-120 ℃, and the drying time is 30-60 min; S3: powder making process; the dried material is sent to a mill for powder making, and a classification screen is matched for online classification treatment; S4: finished wood powder collection process; the wood powder that passes the classification is sent to a finished product storage bin through a negative pressure collection pipeline, a pulse dust collector is arranged at the top of the storage bin to collect the flying wood powder, a conical structure is arranged at the bottom of the storage bin and matched with a screw feeder to smoothly discharge the wood powder, and a gas detection device and a multi-point temperature monitoring device are arranged in the storage bin to control the temperature in the storage bin to be less than or equal to 50 ℃ and the oxygen content to be less than or equal to 10%; and the wood powder is prevented from self-ignition; S5: wood powder heat value testing process; wood powder samples are randomly taken from the mill outlet, and a bomb calorimeter is used to detect the low heat value (HV) of the wood powder; if the detection result satisfies HV≥3200 Kcal / kg, the wood powder heat value meets the standard, and the wood powder is directly used in the subsequent calcination process; if the detection result is HV<3200 Kcal / kg, a heat value blending mechanism is started, and coal powder with HV≥6000 Kcal / kg is added to the mill; the blending ratio is calculated according to the heat value difference; during the blending process, the stirring device in the storage bin is started, the stirring speed is 60-80 r / min, and the stirring time is 20-30 min; the wood powder and the coal powder are uniformly mixed; after blending, the mixed fuel is again sampled and detected until the low heat value of the mixed fuel reaches HV≥3200 Kcal / kg; S6: injection and delivery to the furnace for combustion; the qualified wood powder is delivered to the lime calcining furnace through a dilute phase injection method, a Roots blower is used to provide the delivery power, the gas-solid mass ratio μ is controlled to be less than or equal to 4; the wood powder delivery speed v in the pipeline is controlled to be 10-15 m / s, the speed range can overcome the pipeline resistance, and the pipeline wear caused by excessive speed of the wood powder is prevented; the delivery pressure is controlled to be greater than or equal to 0.5 MPa, and the delivery pressure needs to be 0.15 MPa higher than the pressure in the kiln, so that the wood powder can be smoothly injected into the furnace and the high-temperature flue gas in the furnace is prevented from backflowing; after the wood powder is injected into the furnace, the air distribution ratio in the furnace is adjusted, the air volume ratio of the primary air to the secondary air is controlled to be 1:1.2-1:1.5, the primary air is also the wood powder blowing air, which provides oxygen for the initial combustion of the wood powder, the secondary air is sent into the furnace from the top annular passage, which promotes the complete combustion of the wood powder and disturbs the air flow, ensures the uniform temperature in the furnace, and through the multi-point temperature monitoring device arranged in the furnace, the wood powder injection amount is adjusted in real time to ensure that the temperature in the middle part of the furnace where the limestone is thermally decomposed is stably maintained at about 1100 ℃, the calcination time is controlled to be 2-3 h, and the limestone calcination is completed to generate lime products.
2. The method of claim 1, wherein the biomass is selected from the group consisting of corn stover, switchgrass, miscanthus, willow, poplar, and combinations thereof. The outlet particle size of the double-roller crusher is 25-30 mm.
3. The method for calcining lime using biomass according to claim 1, characterized in that, The drying machine discharge end is provided with an online humidity monitor for real-time detection of material moisture content to control the moisture content of the dried material.
4. A method for calcining lime using biomass according to claim 1, characterized in that, The main shaft rotation speed of the grinder is 1200-1500 r / min, the grading screen uses a 80-100 mesh stainless steel screen, the grading screen rotation speed is controlled by a frequency conversion motor to be 800-1000 r / min, the wood powder fineness is accurately controlled, and the coarse particle material not passing through the grading screen is returned to the grinder through a reflux pipeline for re-pulverization.
5. A method for calcining lime using biomass according to claim 1, characterized in that, The finished product storage bin is provided with a spiral mixing machine for adding coal powder with HV≥6000 Kcal / kg, which can be selected from anthracite or bituminous coal.
6. A method for calcining lime using biomass according to claim 1, characterized in that, The control gas-solid mass ratio is preferably μ≤4 / 1, kg / kg, which can ensure that the wood powder is in a suspended state in the conveying pipeline to avoid deposition and pipe blockage.
7. A method for calcining lime using biomass according to claim 1, characterized in that, The S6 step needs to use a calcining device to calcine limestone by burning wood powder, and the calcining device comprises a kiln body. An ore intermediate bin is arranged at the top middle of the kiln body, one side of the top of the kiln body is provided with a fire hole, the bottom of the kiln body is provided with a discharge port, and the kiln body is provided with a smoke stack. A wood powder bin is arranged at the bottom of the left side of the outer surface of the kiln body, the bottom of the wood powder bin is provided with a compressed air conveying device, one end of the compressed air conveying device is fixedly connected to the kiln body, and one side of the left side of the kiln body is provided with a combustion air fan device.