Rotary Kiln (Oven Drying) Installation and Operation Manual

Ⅰ. Preparations before drying in a rotary kiln

To ensure a safe and smooth kiln drying process, the following preparations must be completed before firing:

System check: Check the entire kiln system to ensure that all equipment is working smoothly.

Kiln and preheater check: Carefully inspect the preheater and the inside of the rotary kiln, check the firebricks one by one and tighten them to prevent loosening. Remove all debris from the kiln.

Instrument calibration: Ensure that the temperature and pressure control instruments in the system are working properly and that the data is accurate and reliable.

Fuel preparation:

There should be sufficient pulverized coal in the pulverized coal silo in the kiln head that meets the quality requirements (moisture, fineness, calorific value, etc.).

The coal mill system should be ready to start at any time to ensure the smooth supply of pulverized coal.

Checking the ventilation and combustion system:

Open the inspection hatch of the cooler, which serves to take in air for combustion products during drying in the kiln.

The coal inlet pipe and other pipes should be free, tight and flexible. Sealing and positioning:

Inspect and install the sealing of all parts of the preheater;

Measure the deflection of the kiln shell, determine the initial position and record it.

Preparing the kindling material:

Deliver firewood to the kiln entrance and stack it in the required piles;

Prepare diesel fuel, cotton yarn and other kindling materials;

Operators should use all necessary labor protection equipment and observe safety precautions.

Ⅱ. Rotary Kiln Drying Methods

There are two main drying methods according to the kiln type:

1. Dry kiln with preheater

Drying time: about 3 days (72 hours)

Process: Ignition is carried out in stages, starting from the tail of the kiln and moving towards the kiln head:

First firebox: located at the stop ring of the tail of the kiln, and is mainly used for drying the preheater;

Second firebox: located in the middle of the kiln, and is used for drying the refractory bricks in the back of the kiln;

Third firebox: located in the cooling zone, and is used for drying the refractory bricks in the front half of the kiln.

2. Wet kiln

Drying time: 8-16 hours

Process: Ignition is carried out by directly blowing coal powder to dry the refractory bricks in the kiln. Heating requirements:

The temperature should be gradually increased from low to high. A sharp increase in the temperature in the tail of the kiln is strictly prohibited.

At the initial stage, coal consumption should be minimized to prevent the fire from dying out.

During the first 8 hours, the temperature in the tail of the kiln should be maintained below 150 °C.

During the entire kiln drying process, the temperature in the tail should not exceed 200 °C.

Auxiliary measures:

Slowly rotate the kiln (1/4 turn every 30 minutes) to prevent its deformation and ensure uniform heating of the refractory bricks.

III. Rotary Kiln Drying Steps

1. Firewood Drying Step

Firewood Stacking Method:

Stack the firewood in a well about 2 meters from the tail of the kiln, with a height of about 2/3 of the effective inner diameter of the kiln.

After ignition, gradually add firewood to raise the temperature at the outlet of the mixing chamber to 200 °C.

According to the heating curve, advance the stack about every 5 meters.

After each stack of firewood burns out, rotate the kiln a quarter turn.

When the firewood reaches the entrance of the kiln, continue to add fuel through the kiln door cover.

At this stage, the kiln should slowly rotate a quarter turn every 30 minutes.

Note: If the pulverized coal flame is unstable, intermittent rotation of the kiln can be used temporarily, but the holding time of one time should not exceed 30 minutes to prevent deformation of the kiln.

Note: When the kiln tail temperature exceeds 300°C, switch to pulverized coal combustion if conditions permit.

3. Kiln Pulverized Coal Drying Stage

Fan Operation: Gradually open the high-temperature fan and the inlet damper on the bag filter exhaust fan to ensure stable ventilation.

Combustion Control:

Use a long flame to ensure stable combustion to avoid short, sharp flame flashes that may cause local overheating.

Control the coal amount to ensure combustion and eliminate black smoke.

System Connection:

Connect the outlet pipe of the pneumatic lifting pump to the connection pipe of the preheater.

Install a drainage device in the lifting pump and assign a person in charge of monitoring and recording the data.

Kiln Drying Status Evaluation:

Observe the surface temperature and moisture content of the refractory bricks in the kiln to evaluate the progress of firing.

Ensure dehydration of refractory material to prevent cracking and chipping during subsequent manufacturing.

IV. Precautions for Drying in the Kiln after Temporary Shutdown

When the rotary kiln is shut down for a long time, measures must be taken to maintain the kiln temperature and prevent flame failure.

The following precautions must be taken during kiln operation:

Kiln Preheating: While the kiln is still cold, tilt the kiln body with the auxiliary drive, moving the hot clinker upward to facilitate the ignition of coal dust.

Ventilation Adjustment: Open the exhaust damper properly to allow the flame to enter the kiln freely.

Coal Feed Adjustment: A small amount of coal should be added at the beginning to prevent intense combustion, which may cause flame backfire and peeling of the kiln lining.

Combustion Control: Control the amount of coal to ensure complete combustion and avoid the formation of black smoke.

Temperature Control: The kiln temperature should not exceed the normal working range.

Use of auxiliary drive: It is recommended to use auxiliary drive to tilt the kiln to facilitate the control of kiln speed and holding time.

Completion of drying: Once the kiln temperature is normalized and combustion is stabilized, drying can be stopped and normal production can be resumed. Reminder: Drying is a critical step in the start-up and shutdown of the rotary kiln, directly affecting the service life of refractory materials and the safety of the system. Strictly follow the heating curve. Rapid heating or temperature exceeding the allowable range is strictly prohibited.