Main Causes of Incomplete Slag Discharge in Tire Pyrolysis Furnaces

Main Causes of Incomplete Slag Discharge in Tire Pyrolysis Furnaces

Incomplete slag discharge from pyrolysis furnaces is usually the result of combined effects from process operation, equipment status, and raw material characteristics, as detailed below:

I. Improper Process Operation

Insufficient Pyrolysis Temperature and Time

If the furnace temperature fails to reach the standard for complete pyrolysis (typically 450–550℃) or the pyrolysis duration is too short, some heavy oil and carbon black remain undecomposed, forming viscous slag that adheres to the furnace walls.

Incorrect Timing of Cooling and Slag Discharge

Slag discharge started before the furnace temperature drops below 60℃ will cause high-temperature slag to have poor fluidity and easily stick to the furnace bottom and slag outlet. Alternatively, if a slight positive pressure is not maintained during discharge, external air can enter and cause slag to harden.

Imbalanced Gas Flow Regulation

When gas output decreases in the later stage of pyrolysis, failing to adjust the vent valve in a timely manner can create negative pressure inside the furnace, causing slag to be adsorbed onto the walls and preventing it from falling na

turally to the slag outlet.

II. Abnormal Equipment Status

Design Flaws in Slag Discharge System

Insufficient furnace bottom slope, undersized slag outlet diameter, or worn blades in the screw slag extractor can hinder smooth slag discharge, leading to accumulation in dead corners of the furnace bottom.

Equipment Sealing and Deformation

Long-term high-temperature operation can cause local deformation of the furnace body, creating concave areas where slag accumulates. Aging seals that leak allow cold external air to enter, cooling and hardening the slag.

Auxiliary System Malfunctions

Cooling system failures result in excessively high furnace temperatures, increasing slag viscosity. Damage to the internal stirring device prevents uniform slag distribution, leading to localized accumulation that is difficult to discharge.

III. Raw Material Characteristics

Excessive Impurities in Raw Materials

Failure to fully remove hard impurities such as metals and gravel from waste tires causes carbon black particles to combine with these impurities during pyrolysis, forming hard slag that adheres to the furnace walls.

High Moisture Content in Raw Materials

Moisture in raw materials vaporizes at high temperatures, mixing with carbon black and heavy oil to form viscous sludge with stronger adhesion, which is difficult to remove via conventional slag discharge methods.

Contamination with Chlorine-Containing Plastics

Mixing PVC or other chlorine-containing plastics into the raw materials produces hydrogen chloride during pyrolysis, which corrodes the furnace walls. The corrosion products then bind with slag, exacerbating adhesion issues.