Rotary Kiln Drying Operation Guide-GYF Technology
I. Preparations before kiln drying
To ensure the safe and smooth completion of the kiln drying process in the rotary kiln, the following preparations must be completed before ignition:
System check: Conduct a comprehensive inspection of the entire firing system to ensure that all equipment is in a condition suitable for continuous operation.
Inspection of kiln and preheater: Carefully inspect the interior of the preheater and rotary kiln, inspect the refractory bricks in each section and retighten them to prevent loosening; Remove all debris from the kiln.
Instrument calibration: Ensure that the temperature and pressure monitoring instruments within the system are functioning properly and that the data is accurate and reliable.
Fuel preparation: The coal powder storage bin at the kiln head should be stocked with sufficient coal powder that meets the quality requirements (with indicators such as moisture content, fineness, and calorific value meeting the standards); the coal grinding system should be in a ready-to-start state to ensure continuous supply of coal powder.
Ventilation and combustion system inspection: Open the maintenance door of the cooling machine to serve as the air intake channel for the combustion gas during the kiln drying process; The coal injection pipe and all pipelines should be kept unobstructed, sealed well, and adjustable flexibly.
Sealing and Positioning: Inspect and improve the sealing of all parts of the preheater; measure the curvature of the kiln cylinder, determine the initial position and make a record.
Preparation of ignition materials: Transport the firewood to the vicinity of the kiln and stack it as required; Prepare the ignition materials such as diesel and cotton yarn; The operators must wear complete labor protection equipment and implement safety protection measures.
II. Kiln Drying Method for Rotary Kilns
Depending on the type of kiln, the methods for drying the kiln can be mainly divided into two types:
Dry preheating kiln
Firing time: Approximately 3 days (72 hours)
Operation method: The ignition is carried out in segments from the tail to the head of the kiln, in sequence.
The first fire: Located at the tail of the kiln where the material is held, it is mainly used for drying the heating elements.
The second fire: Placed in the middle section of the kiln, to dry the refractory bricks at the rear of the kiln.
The third fire: Located in the cooling zone area, it is used to dry the refractory bricks in the first half of the drying kiln.
2. Wet kiln
Firing oven time: 8 to 16 hours
Operation method: Use direct injection of coal powder for ignition and dry the refractory bricks inside the kiln.
Heating requirements: The heating process should be carried out gradually from low to high. It is strictly prohibited to have a sudden increase in the temperature at the kiln tail. In the initial stage, the amount of coal used should be minimized to avoid engine shutdown. Within the first 8 hours, the temperature at the kiln tail should be kept below 150℃. During the entire drying process of the kiln, the tail temperature should not exceed 200℃.
Auxiliary measures: Slowly rotate the kiln body at an appropriate speed (rotate 1/4 circle every 30 minutes) to prevent the cylinder from deforming and ensure that the refractory bricks are heated evenly.
III. Operating Steps for Kiln Drying
1. Wood-fired kiln drying stage
Method for stacking firewood: Stack the firewood in a "well" shape about 2 meters away from the end of the kiln, with the height being approximately two-thirds of the effective inner diameter of the kiln; After lighting the fire, gradually add more firewood to gradually raise the temperature at the outlet of the mixing chamber to 200℃; According to the temperature rise curve requirements, advance one pile of firewood approximately every 5 meters towards the front; After each pile of firewood burns out, the kiln body rotates one-quarter of a circle; When the firewood reaches the kiln opening, fuel can be continuously replenished through the kiln door cover; During this stage, the kiln body should slowly rotate one-quarter of a circle every 30 minutes.
Note: If the coal powder flame is unstable, intermittent kiln rotation can be temporarily adopted. However, the single stay time must not exceed 30 minutes to prevent the kiln body from deforming.
2. Heating Temperature System
| Heating range (°C) | Heating rate (℃/h) | Fuel types | Required time (h) | Reference temperature point |
| 20～200 | 15 | Wood chips | 12 | Exit temperature of the mixing chamber |
| 200 | Insulation | Wood chips | 20 | Exit temperature of the mixing chamber |
| 200～300 | 20 | Wood chips | 10 | Tail of the kiln |
| 300 | Insulation | Wood chips | 16 | Firing zone/tail temperature of the kiln |
| 300～500 | 25 | Coal powder | 8 | Tail temperature of the kiln |
| 500 | Insulation | Coal powder | 10 | Tail temperature of the kiln |
| 500～700 | 25 | Coal powder | 8 | Tail temperature of the kiln |
| 700 | Insulation | Coal powder | 4 | Tail temperature of the kiln |
| 700～800 | 30 | Coal powder | 3 | Tail temperature of the kiln |
| 800～900 | 30 | Coal powder | 2 | Tail temperature of the kiln |
Explanation: When the temperature at the kiln tail reaches above 300℃, and the conditions are met, it is possible to switch to coal powder combustion.
III. Coal powder drying in the kiln stage
Fan operation: Gradually open the inlet air doors of the high-temperature fan and the exhaust fan of the bag dust collector to establish stable ventilation. Combustion control: Adopt stable long-flame combustion to avoid short flame and rapid burning that causes local overheating; control the amount of coal to ensure combustion and eliminate the phenomenon of black smoke emission.
System connection: Connect the discharge pipe of the pneumatic booster pump to the connection pipe of the preheater; install a drainage device inside the booster pump and assign a dedicated person to monitor and record.
Oven drying status judgment: By observing the temperature changes on the surface of the refractory bricks inside the oven and the concentration of water vapor, the drying progress can be determined; ensure that the refractory materials are dehydrated to avoid cracking or peeling during subsequent production.
IV. Precautions for Kiln Drying After Temporary Parking
When the rotary kiln is temporarily shut down for a long period due to some reason, measures to dry the kiln should be taken to maintain the temperature inside the kiln and prevent the kiln from going out. When operating, the following points should be noted:
Preheating the materials in the kiln: At a low temperature, first use the auxiliary drive to rotate the kiln body, moving the red-hot clinker to the top, which helps to ignite the coal powder.
Adjust ventilation: Open the exhaust valve appropriately to ensure that the flame can smoothly enter the kiln.
Control the amount of coal fed: In the initial stage, the amount of coal fed should be kept low to prevent intense combustion that could trigger explosions or backfires, causing the kiln coating to fall off.
Combustion management: Reasonably control the amount of coal to ensure complete combustion and avoid the emission of black smoke.
Temperature control: The kiln temperature must not exceed the normal production temperature range.
Using auxiliary transmission: It is recommended to use an auxiliary mechanism for kiln turning to facilitate the control of rotational speed and residence time.
End kiln drying: Once the temperature inside the kiln returns to normal and the combustion becomes stable, the kiln drying operation can be stopped and the normal production process can be initiated.
Important Notice: The kiln drying process is a crucial step during the start-up and shutdown of the rotary kiln, directly affecting the lifespan of refractory materials and the safety of the system. Please strictly follow the temperature rise curve for operation and strictly prohibit rapid temperature increase or uncontrolled temperature.
