What is an active lime production line?

1. What is active lime
Active lime (also known as quicklime or calcium oxide, chemical formula CaO) is a lime product with high reactivity. Due to its special physical and chemical properties, it is widely used in many fields such as industry, environmental protection, and construction. The following are its main characteristics and functions:

(1) Characteristics of active lime
High chemical activity
It is made by calcining high-quality limestone, with a high CaO content (usually ≥90%) and few impurities. It can react quickly with water, acid, etc.
It reacts faster and more efficiently than ordinary lime.

Porous and loose structure
CO₂is released during the calcination process, forming a porous structure with a large specific surface area and strong adsorption and reaction capacity.

Low impurity content
The content of harmful impurities such as sulfur and phosphorus is low, suitable for fields with high purity requirements (such as metallurgy and chemical industry).

Strong alkalinity
The aqueous solution is strongly alkaline (pH ≥ 12.5) and can neutralize acidic substances.

Strong hygroscopicity
It easily absorbs moisture and CO₂ in the air and needs to be stored in a sealed manner.

(2) The main role of active lime
Metallurgical industry
Steelmaking: as a slag-making agent, removes impurities such as sulfur and phosphorus, and improves the purity of molten steel.
Hot metal pretreatment: desulfurization (reacts with sulfur to form CaS), reducing subsequent smelting costs.

Environmental protection
Wastewater treatment: neutralizes acidic wastewater and precipitates heavy metals (such as generating Ca₃(PO₄)₂ to remove phosphorus).
Flue gas desulfurization (FGD): reacts with SO₂ to form gypsum (CaSO₄), reducing acid rain pollution.
Waste incineration: adsorbs harmful gases such as dioxins, reducing pollution emissions.

Chemical industry
Production of calcium carbide: reacts with coke to produce acetylene (CaO + 3C → CaC₂ + CO).
Preparation of calcium carbonate: reacts with CO₂ to form precipitated calcium carbonate (CaCO₃), which is used for fillers, coatings, etc.

Construction and building materials
Production of aerated concrete: reacts with siliceous materials to form cementitious substances (hydrated calcium silicate).
Soil solidification: improves acidic soil and improves foundation stability.

Other applications
Medicine/food: used as a desiccant or disinfectant (food grade purity required).
Agriculture: regulates soil pH, supplements calcium, and promotes crop growth.
Papermaking: used in alkali recovery processes and treats pulp black liquor.

(3) Precautions
Storage: must be moisture-proof and sealed to avoid contact with water and acid (exothermic reaction may cause danger).
Safety: wear protective equipment during operation to prevent dust inhalation or skin contact (highly corrosive).

2.Main process flow of an active lime production line
Active lime (quicklime, CaO) is produced by the pyrolysis of limestone (CaCO₃). The core process includes raw material pretreatment, calcination, cooling, and finished product processing. Limestone is stored in silos and lifted by an elevator to the top bin of the preheater. Two level gauges control the level in the top bin, and the limestone is evenly distributed to each preheater chamber through a discharge pipe. In the preheater, the limestone is heated to approximately 900°C, decomposing approximately 30% of the limestone. Hydraulic push rods push the limestone into the rotary kiln. The limestone sintered in the rotary kiln, decomposing it into CaO and CO₂. The decomposed limestone enters the cooler, where it is cooled by cold air blown into the cooler to below 100°C before being discharged. After heat exchange, the 600°C hot air enters the kiln and mixes with the coal gas for combustion. The exhaust gas mixes with the cold air and is passed through an induced draft fan to a bag filter, and then through an exhaust fan to the chimney. The lime from the cooler is transported to the finished lime storage bin via a vibrating feeder, chain bucket conveyor, bucket elevator, and belt conveyor. The following is a typical process flow and key equipment description of an active lime production line:

(1) Main process flow of an active lime production line
1)Raw material pretreatment
Limestone crushing and screening
Large limestone (≤1m) is crushed and medium-crushed to 30~50mm particles by jaw crushers, impact crushers, etc.
Screening through a vibrating screen removes dirt and impurities to ensure uniform particle size (too small affects air permeability, and too large calcination is not transparent).
Raw material storage
Qualified limestone is sent to the raw material warehouse to avoid mixing with impurities (such as SiO₂, Al₂O₃, etc. that affect lime activity).

2)Calcination Process (Core Step)
Preheating Stage (100-900°C)
Limestone is preheated in a preheater using kiln exhaust gas to remove surface moisture and some volatile matter, improving thermal efficiency.
Pyrolysis (900-1200°C)
Limestone is calcined in a rotary kiln or shaft kiln, undergoing the decomposition reaction: CaCO₃ → CaO + CO₂↑ (endothermic reaction).
Key Control Parameters:
Temperature: Rotary kilns typically operate at 1050-1250°C, shaft kilns at 900-1100°C.
Retention Time: Rotary kilns typically operate at approximately 1-3 hours, shaft kilns at approximately 6-12 hours.
Fuel: Natural gas, pulverized coal, coke oven gas, etc. (Low-sulfur fuels are preferred to avoid sulfur contamination).

3)Cooling and Waste Gas Treatment
Lime Cooling
High-temperature lime (approximately 200-300°C) is cooled to below 80°C via a vertical cooler or air cooling system to prevent secondary carbonization (CaO + CO₂ → CaCO₃).
The recovered hot air can be fed into the calcination system for recycling.
Waste Gas Treatment
After cyclone and bag filter dust removal, the kiln exhaust gas is partially recovered for use in the chemical or food industries, with the remainder discharged in compliance with emission standards.

4)Finished Product Processing
Crushing and Classification
The cooled lime blocks are crushed to 1-10mm (particle size adjusted based on application) using a double-roll crusher or hammer crusher.
Vibrillation screening is used to select different product specifications (e.g., coarse granules for steelmaking, fine powder for environmental protection).
Storage and Packaging
Finished products are stored in sealed warehouses to prevent moisture and carbonization.
Some products can be briquetted or packaged in bags (special packaging is required for food-grade lime).

(2).Key equipment selection
Process Common equipment Function and features
Raw material crushing Jaw crusher, impact crusher Coarse to medium crushing, processing large limestone lumps
Calcination kiln Rotary kiln, double-chamber shaft kiln, beam shaft kiln Rotary kiln has high output (over 1,000 tons/day), while shaft kiln has high thermal efficiency
Cooling system Vertical cooler, air-cooled conveyor Rapid cooling, waste heat recovery
Dust removal system Cyclone dust collector, bag filter Exhaust gas purification to meet environmental requirements

(3). Key points of process control
Raw material quality: CaCO₃ content ≥ 95%, SiO₂ + Al₂O₃ ≤ 2%.
Calcination temperature: Too high will lead to over-burning (reduced densification activity), too low will lead to under-burning (residual CaCO₃).
Fuel selection: Low-sulfur fuel (sulfur content < 0.5%) to avoid the formation of CaSO₄ that affects activity.
Environmental requirements: Dust emission ≤ 10 mg/m³, CO₂ can be considered for capture and utilization (CCUS technology).

3.Active lime production process: How to systematically improve product quality?
Active lime (CaO) is a vital raw material for modern industry. Its quality directly impacts process efficiency and product quality in key areas such as steelmaking, environmental desulfurization, and chemical production. As industrial technological requirements continue to increase, systematically improving the quality of active lime products has become a key focus of the industry.

(1). Raw Material Selection
In an activated lime production line, selecting the appropriate limestone raw material requires a comprehensive consideration of its chemical composition, physical properties, and actual production conditions. First, the limestone's CaCO₃ content should be as high as possible, ideally above 95%, to ensure high-purity activated lime after calcination. Impurity levels such as SiO₂ and Al₂O₃ must be strictly controlled, generally requiring SiO₂ to be no more than 1% and Al₂O₃ to be less than 0.5%. These impurities react with CaO at high temperatures to form low-melting calcium silicate or calcium aluminate, which not only reduces lime activity but also easily causes kiln ringing or nodules, impacting production stability. The content of harmful elements such as sulfur and phosphorus must be below 0.03%, especially for activated lime used in steelmaking. Excessive sulfur content can directly affect steel quality.

In terms of physical properties, the limestone's particle size should be moderate, typically within the 30-50mm range. Too large a particle size prevents heat from reaching the core during calcination, resulting in premature burning. Too small a particle size can affect kiln ventilation and increase energy consumption. The hardness and porosity of the limestone also require attention. Moderate hardness and porosity help improve calcination efficiency and finished product quality. Furthermore, the limestone's mineral structure and crystallinity influence calcination results. Limestone with a finer grain structure is generally easier to decompose and more active after calcination.

In actual production, raw material selection must be considered in conjunction with the kiln type. Rotary kilns are more adaptable to limestone particle sizes, while vertical kilns require a more uniform particle size distribution. Raw material supply stability and cost are also important considerations to ensure long-term economic and sustainable production. Laboratory analysis and industrial trials can further verify the suitability of limestone, ultimately selecting a raw material that meets quality requirements and is economically viable.

(2). Raw material pretreatment In the active lime production line, the raw material pretreatment process is a key link to ensure the subsequent calcination efficiency and product quality. After the limestone raw materials are mined from the mine, they first need to be crushed and screened. The large pieces of limestone are crushed by jaw crusher, and then crushed by impact crusher or cone crusher. Finally, the raw materials are crushed to a uniform particle size of 30-50mm. This process must ensure that the particle size is moderate and avoid excessive crushing to produce too much powder, because too large particles will affect the calcination effect, and too small particles will lead to poor ventilation in the kiln. The crushed raw materials are graded and screened by vibrating screen to remove particles that are too large or too small that do not meet the requirements, and at the same time separate impurities such as soil and gravel to ensure the purity of the raw materials. 
The qualified limestone after screening needs to go through a cleaning process to remove the soil and dust attached to the surface by water washing or dry cleaning. This step is particularly important for improving the purity of the raw materials and reducing impurity reactions during the calcination process. The cleaned raw materials enter the drying system, where rotary dryers or other drying equipment are used to control the moisture content to below 1%. Excessive moisture not only increases calcination energy consumption but can also cause preheater blockage. The pretreated limestone is transported to the raw material silo for temporary storage. During this process, special attention must be paid to moisture and dust prevention measures to prevent secondary contamination of the raw materials and moisture absorption and agglomeration. The entire pretreatment process requires strict control of parameters at each stage to ensure that the raw materials' chemical composition, particle size, and moisture content meet calcination requirements, ensuring high-quality raw materials for the subsequent high-temperature calcination process.

4.Active Lime Production Line Maintenance Guide
The activated lime production line is a core production facility in the steel, chemical, environmental protection and other industries. Its stable operation is directly related to product quality, production efficiency and economic benefits. The maintenance and management of scientific systems can significantly reduce equipment failure rates, extend service life, and reduce energy consumption and production costs.

(1) Main equipment and maintenance priorities of the production line
The activated lime production line consists of multiple key equipment, each with its own specific maintenance requirements and priorities. Only by ensuring that every link is properly maintained can we ensure the efficient and stable operation of the entire production line.

1）. Raw material pretreatment system
The raw material pretreatment system is the front-end link of the production line and mainly includes crushing equipment and screening equipment. Crushing equipment usually uses jaw crushers, impact crushers or cone crushers to crush limestone raw materials to appropriate particle size. The focus of maintenance is to regularly check the wear of the crusher jaw or hammer head, and it needs to be replaced in time when the wear on one side exceeds 15 mm. At the same time, attention should be paid to the bearing temperature and lubrication conditions. The bearing temperature should be controlled below 75 degrees Celsius, and the lubricating grease needs to be replenished or replaced regularly. The screening equipment is mainly a vibrating screen. It is necessary to check whether the screen is damaged every day. If the screen hole deformation exceeds 10%, it should be replaced immediately. In addition, the performance of the damper spring also needs to be tested regularly to ensure screening efficiency.

2）. calcination system
The calcination system is the core part of the activated lime production line and mainly includes rotary kilns or vertical kilns. The maintenance of rotary kilns focuses on the mechanical condition of the kiln body and refractory materials. The ovality of the kiln body needs to be tested monthly, and the deviation should not exceed 0.2% of the kiln diameter. The wear of the contact surface between the supporting wheel and the belt should be checked regularly, and the gap should be controlled between 1-2 mm. The sealing device at the kiln head and kiln tail must maintain good sealing performance, and the air leakage rate must be controlled below 5%. The maintenance of refractory materials is particularly critical. The remaining thickness of the kiln lining should not be less than 80 mm. When local high temperature points are found by infrared temperature measurement, it often indicates that the refractory materials have fallen off and need to be treated in time.

The maintenance of vertical kilns focuses on the combustion system and refractory materials. The nozzle of the burner needs to be cleaned weekly to prevent carbon deposits from affecting combustion efficiency. When the crack width of the hot surface layer of refractory materials exceeds 1 mm, it needs to be replaced. The temperature distribution in the kiln should be monitored through infrared temperature measurement, and the local temperature difference should not exceed 50 degrees Celsius.

3）. thermal system
The thermal system includes preheaters, coolers and various fans and other equipment. The focus of the preheater maintenance is to prevent the cyclone from forming skin. It is necessary to shut down every 72 hours for air gun purging, and the accumulated thickness is controlled below 50 mm. The cooler should regularly check the wear of the grate plates, and the wear on one side should not exceed 5 mm, otherwise it will affect the cooling efficiency. The focus of fan maintenance is on the bearing vibration value and lubrication condition. The bearing vibration value should be controlled below 4.5 mm/s, and the lubricating grease needs to be replaced regularly.

4）. electrical control system
The stable operation of the electrical control system is crucial to the entire production line. The DCS control cabinet needs to be cleaned every month to ensure good heat dissipation. Temperature, pressure and other sensors must be calibrated regularly, and the calibration period shall not exceed 3 months. The insulation resistance of the motor should be tested regularly, and the resistance value should not be lower than

(2) Daily maintenance procedures
Daily maintenance is the first line of defense to prevent equipment failures. Through standardized daily inspection and maintenance, potential problems can be discovered and dealt with in a timely manner, preventing minor failures from turning into major problems.

1）. Daily inspection content
Systematic inspection of the entire line of equipment needs to be carried out every day. The raw material handling system must check the crusher bearing temperature, belt tension and screen condition. The calcination system must record the bearing temperature of supporting wheels at each stage of the rotary kiln and the movement of the kiln body, and check the sealing status of the kiln head and kiln tail. The thermal system shall monitor the preheater pressure difference, the cooler grate plate operation status and the fan vibration value. The electrical system must check whether the display of each instrument is normal and whether the operating current of the motor is within the rated range.

Special attention needs to be paid to lubrication conditions. There are about 120-200 lubrication points in the entire production line, and lubricants need to be filled or replaced regularly according to equipment requirements. High-temperature parts such as kiln head bearings require high-temperature resistant grease, and lithium-based grease can be used for ordinary parts. The amount and cycle of lubricant filling must strictly comply with the requirements of the equipment manual. Too much or too little will affect the life of the equipment.

2）. Key parameter monitoring
Several key parameters should be monitored in daily operation. The axial movement of the rotary kiln should be controlled within plus or minus 5 mm and achieved by adjusting the inclination angle of the supporting wheel. The range of motor current fluctuations should not exceed 10% of the rated value. Abnormal fluctuations often indicate mechanical blockage or electrical failure. The oxygen content of the exhaust gas should be maintained between 2-5%. If too high, it indicates that the system is leaking; if too low, it may be incomplete.

3）. Handling common problems
Some common problems encountered in daily maintenance need to be dealt with in a timely manner. If it is found that the discharge particle size of the crusher has become larger, it may be that the hammer head or jaw plate is excessively worn and needs to be inspected and replaced. When uneven contact between the rotary kiln wheel and the supporting wheel causes abnormal noise, the kiln body may be deviated and requires calibration with a laser centering instrument. The pressure difference of the dust collector suddenly increases. The filter bag may be damaged and needs to be stopped for inspection and replacement.

(3) Regular maintenance plan
In addition to daily maintenance, regular maintenance is a necessary measure to ensure long-term stable operation of equipment. According to the depth and scope of maintenance, it can be divided into monthly maintenance and annual overhaul.

1）. monthly maintenance
Monthly inspections are mainly aimed at wearing parts and key components. Refractory materials should be comprehensively inspected. The remaining thickness of rotary kiln lining should not be less than 50% of the original thickness. If the crack width of vertical kiln refractory bricks exceeds 1 mm, it needs to be treated. The transmission system must check the gear engagement of the reducer, and the contact area must reach more than 60%. The coupling alignment deviation should be controlled within 0.05 mm/meter. The insulation resistance of the motor should be tested, and the value should not be less than 100 megohm.

During monthly maintenance of the lubrication system, the lubrication oil must be completely replaced and the oil circuit must be cleaned. The filter elements of the hydraulic system must be replaced, and the oil quality must meet the NAS 8 standard. The electrical system must check whether the wiring terminals are loose and whether the grounding resistance is qualified.

2）. annual overhaul
The annual overhaul is the time to carry out a comprehensive overhaul of the production line. The bending degree of the kiln body shall be tested with a laser straightener, and the deviation shall not exceed 0.1‰ of the kiln length. The preheater should be replaced with the wear-resistant lining of the cyclone. It is recommended to use ceramic wear-resistant materials, and the service life can reach 5 years. The electrical system must undergo comprehensive testing, including cable insulation testing, control system module testing, etc.

During the overhaul, necessary renovations and upgrades will also be carried out to the equipment. If the three-level preheater is upgraded to a five-level preheater, the thermal efficiency can be increased by 25%; the ordinary cooler can be transformed into a push-rod cooler, the cooling efficiency can be increased by 40%. Although these renovations have a large one-time investment, they have significant long-term benefits.

3）. spare parts management
Sound spare parts management is the foundation for ensuring smooth maintenance. Wearing parts such as crusher hammers and grate cooler grate plates should be kept in proper stock and purchased in advance according to the service life. Bulk spare parts such as refractories must be ordered 3-6 months in advance to ensure that they can be delivered in time during maintenance. Detailed warehouse entry and exit records must be established for all spare parts, and the principle of first-in, first-out shall be implemented.

Through scientific daily maintenance and regular maintenance, the equipment failure rate of the activated lime production line can be reduced by more than 40%, the equipment life can be extended by 30%, and energy consumption can be reduced by 15%. Enterprises should establish a sound maintenance management system, form closed-loop management of point inspection, lubrication, overhaul, analysis and other aspects, and gradually introduce intelligent maintenance methods, such as predictive maintenance systems, digital twin technologies, etc., to further improve maintenance efficiency and accuracy. Only by maintaining equipment well can we ensure long-term stable and efficient operation of the production line and create maximum value for the company.

5.Common troubleshooting of active lime production line
As an industrial system for continuous production, the activated lime production line will inevitably encounter various failures during long-term operation. Timely and accurate diagnosis and handling of these faults is the key to ensuring stable production and reducing downtime losses.

(1) Fault handling of raw material pretreatment system
1）. Crusher blockage failure
Failure symptoms:
Abnormal increase in current (exceeding 15% of rated value)
Ununiform discharge particle size or completely interrupted
Increased equipment vibration accompanied by abnormal noise

Reason analysis:
The feed particle size is too large (exceeds the equipment design maximum)
Material moisture content is too high (>5%)
Foreign matter is stuck in the crushing chamber
Severe wear of hammer/jaw plates leads to reduced crushing efficiency

Treatment measures:
Shut down immediately and cut off the power
Clean the crushing chamber, inspect and remove foreign objects
Check the status of the worn parts. The hammer head has a single side worn by more than 15mm and needs to be replaced.
Adjust the feeding device to ensure that the material particle size is ≤ 80% of the design value
Pre-drying the wet material

Prevention recommendations:
Install metal detectors and iron removal devices
Establish a sampling system for feeding particle size (once every 2 hours)
Set automatic overload protection device

2）. Vibration screen is damaged
Failure symptoms:
Large particulate material appears in the undersize
Abnormal movement trajectory of sieve body
Reduced screening efficiency

Solution:
Immediately stop the machine and replace the screen (when the damaged area is greater than 10%)
Adjust the tensioning device to ensure that the screen installation flatness error is ≤3mm
Check the stiffness of the damping spring and replace the deformed spring

(2) Troubleshooting of calcination system faults
1）. Rotary kiln body deviation
Typical performance:
Uneven wear on the contact surface between the belt and the supporting wheel
The axial movement of the kiln body exceeds ±5mm
Driving motor current fluctuates cyclically

Processing steps:
Use a laser centering instrument to detect the straightness of the kiln body (deviation>3mm/m needs to be adjusted)
Corrected by the supporting roller adjustment device (each adjustment angle ≤0.5°)
Check the wear condition of the wheel pad (gap>3mm needs to be replaced)
Re-adjust the hydraulic gear pressure to 1.8-2.2MPa

Key technical parameters:
Kiln body ovality ≤0.2%D (D is kiln diameter)
Roller bearing temperature ≤65℃
Clearance between wheel and backing plate 1.5-2.5mm

2）. Shaft kiln nodules (kiln wall hanging material)
Fault characteristics:
Increase in resistance in the kiln (pressure difference> 30% of normal)
The activity of lime exiting the kiln suddenly dropped below 280ml
Infrared temperature measurement shows local high temperature area

Emergency response plan:
Reduce production by 20-30%
Increase the temperature in the calcination zone by 50-80℃
Put into operation the kiln wall vibrating device (frequency adjusted to 8-10Hz)
Stop the kiln for manual cleaning if necessary (CO protection is required)

Fundamental solutions:
Control the content of SiO ˇ +Al ˇ O in raw materials to ≤2.5%
Optimize the burner angle (tilt 5-8° is appropriate)
Improve raw material pre-homogenization process

(3) Thermal system fault handling
1）. Preheater blockage
Failure signs:
Abnormal increase in system negative pressure (>6500Pa)
The temperature of the lower cyclone dropped sharply
Material mobility deteriorates

Emergency handling process:
Stop feeding immediately
Turn on the air cannon blocking system (cyclic action every 15 minutes)
Use high-pressure water gun (pressure>10MPa) for remote cleaning
Check whether the spreader box is deformed (if the deformation exceeds 5mm, it needs to be replaced)

Preventive maintenance:
Check the skin formation of the cyclone every shift
Control the kiln tail exhaust gas temperature ≤350℃
Optimize raw material composition (avoid enrichment of low-melting-point minerals)

2）. Grate cooler failure
Common problem types:
Grate plate falling off: It is manifested by a short circuit of cooling air and an increase in discharge temperature
Hydraulic system loss of pressure: abnormal running speed of grate bed
Transmission chain breaks: equipment completely stops

Treatment plan:
Grate plate replacement standard: wear>5mm or through cracks appear
Hydraulic system maintenance:
The oil temperature is controlled at 35-55℃
Filter element replacement cycle ≤200 hours
Chain tension adjustment: sag ≤ 2% of center distance

(4) Electrical control system failure
1）. DCS system signal abnormal
Failure performance:
Display value jumps or freezes
Control instruction execution delay
Module communication interruption

Diagnosis steps:
Check the grounding of the signal wire shielding layer (resistance ≤4Ω)
Test channel isolator working status
Verify sensor output (4-20mA signal deviation ≤1%)
Check the power supply quality of the control system (voltage fluctuation ≤±10%)

2）. Motor windings are overheated
Processing process:
Immediately stop the machine and measure the insulation resistance (≥100MΩ is qualified)
Check the cooling system:
Air-cooled motor: Clean up dust accumulated in air duct
Water-cooled motor: check water pressure (≥0.2MPa) and flow rate
Check the mechanical load:
Coupling alignment deviation ≤0.05mm
Bearing clearance meets standard

(5) Principles for handling systemic faults
1）. hierarchical fault response mechanism
Level 1 failure (risk of shutdown across the line): Activate emergency team within 15 minutes
Level 2 failure (partial shutdown): Develop a treatment plan within 2 hours
Level 3 failure (operation can be maintained): included in the next maintenance plan

2）. Root Cause Analysis (RCA)
Apply the 5Why analysis method for repetitive faults:
Why did this happen?→ Direct cause
Why wasn't it discovered?→ Detect system defects
Why not prevent it?→ Management system loopholes

3）. Emergency management of spare parts
Safety inventory of critical spare parts (e.g. kiln head seals, hydraulic valve sets)
Establish a regional spare parts sharing alliance
Promote standardized spare parts (reduce the proportion of special parts)

(6) Intelligent fault early warning technology
1）. on-line monitoring system
Vibration analysis: Capture early bearing defects (3-6 months warning before failure)
Thermal imaging monitoring: identify refractory material falling off (alarm with temperature difference>50℃)
Acoustic emission testing: crack propagation signal found

2）. Digital Twin Applications
Simulate through a virtual model:
Equipment stress distribution
Wear trend
fault propagation path

6.Frequently Asked Questions about Active Lime Production Line
Q1: What is the optimal particle size range for limestone raw materials?
A: Generally, it should be between 10-40mm. Particles that are too large (>50mm) will result in incomplete calcination, while particles that are too small (<5mm) will increase ventilation resistance in the kiln. Specific requirements for different kiln types are:
Rotary kiln: 15-35mm
Vertical kiln: 20-40mm

Q2: How should high mud content in raw materials be handled?
A: The following measures are recommended:
① Install a drum stone washer (mud removal efficiency can reach 80%)
② Add pre-screening with a vibrating screen (3-5mm mesh)
③ Control rainwater drainage from the storage yard (to avoid secondary pollution)

Q3: What are the possible causes of large fluctuations in lime activity? A: The following factors need to be investigated:
① Raw material factors: CaCO₃ content fluctuation > 3%, sudden increase in SiO₂
② Thermal parameters: Calcination zone temperature fluctuation > ±30°C
③ Cooling rate: Lime leaving the kiln does not cool to below 100°C within 90 seconds

Q4: How should excessive free calcium oxide (f-CaO) in the finished product be handled?
A: Control in stages:
Short-term: Increase calcination temperature by 20-30°C and extend residence time by 10%
Long-term: Optimize raw material ratio (control MgO content <; 2%)

Q5: Is the inverter frequently reporting overcurrent faults?
A: Resolve these issues in this order:
Check motor insulation (≥100MΩ)
Test encoder feedback signal (deviation <0.5%)
Optimize acceleration and deceleration times (>30s recommended for heavy-load starting).

Q6: How should the CO concentration alarm (>50ppm) in the kiln be handled? A: Emergency Procedures:
Immediately activate emergency ventilation (air volume ≥ 20 m³/min)
Evacuate personnel and check oxygen levels (do not enter if oxygen levels < 19.5%)
Check for gas pipeline leaks (soap and water leak detection method)

Q7: How can I prevent refractory collapse during maintenance?
A: Required procedures:
① Ensure the kiln is fully cooled (internal temperature < 60°C)
② Use support frames (spacing ≤ 1.5m)
③ Strictly prohibit the simultaneous removal of more than three adjacent refractory bricks

Q8: How to reduce coal consumption? (Currently > 120 kg standard coal per ton)
A: Recommended Modification Options:
Add a five-stage preheater (increase thermal efficiency by 25%)
Install a kiln radiant heat recovery device (save coal by 8-12%)
Use a low-NOx burner (save fuel by 5% and reduce NOx emissions)

Practical Advice
Establish a fault code library: Digitize historical faults and solutions for quick retrieval.
Spare parts classification management: Category A spare parts (e.g., kiln main reducer gears) must be stocked on-site, while Category C spare parts can be purchased through negotiation.
Weekly technical workshops: Analyze weekly faults and develop preventative measures