Heating System of Batch-Type Pyrolysis Oil Refining Equipment

Heating System of Batch-Type Pyrolysis Oil Refining Equipment

The heating system is the core unit of batch-type waste tire pyrolysis oil refining equipment. Its function is to provide a stable and controllable high-temperature environment for the pyrolysis reactor, promoting the cleavage and decomposition of macromolecular hydrocarbons in waste tires. The heating method, heat source selection, and temperature control logic must be adapted to the batch production characteristics of the intermittent process: charging - heating pyrolysis - discharging. The specific technical points are as follows:

Heating Method and Core Structure

Indirect heating is the primary heating method for batch-type pyrolysis reactors, while direct heating is rarely adopted (direct heating tends to cause local overheating and coking of raw materials, as well as the emission of large amounts of harmful gases).

The reactor is typically designed with a jacketed structure or a configuration of refractory brick lining plus an external heating chamber: the inner layer is the pyrolysis chamber loaded with waste tire raw materials, and the outer layer is the heating chamber. The heating medium or heat source acts on the outer layer, transferring heat to the inner raw materials through thermal conduction and thermal radiation.

Some small-scale equipment employs electric heating tubes directly installed in the heating chamber, while large-scale equipment mostly adopts fuel combustion heating. A comparison of the two methods and their applicable scenarios is provided below:

Electric Heating: High-temperature resistant electric heating tubes/rods are built into the heating chamber, converting electrical energy into thermal energy. Its advantages include high temperature control precision, no combustion exhaust gas emissions, and convenient and clean operation, making it suitable for small and medium-sized batch-type equipment and areas with stringent environmental protection requirements. The disadvantage is relatively high energy consumption costs and strict requirements for power supply stability, with the power of a single set of equipment usually ranging from 300kW to 500kW.

Fuel Heating: The pyrolysis non-condensable gas produced by the project is used as the primary fuel, supplemented by diesel or natural gas as backup. Fuel is burned in the heating chamber to generate high-temperature flue gas. Its advantages are low energy consumption costs and the realization of resource recycling. The disadvantage is the need to configure a flue gas purification system (desulfurization, denitrification, dust removal), and its temperature control precision is slightly lower than that of electric heating. It is suitable for large-scale batch-type pyrolysis equipment.

Temperature Control Logic of the Heating Process

The heating process of the batch-type process requires precise stage-by-stage temperature control to avoid reduced pyrolysis efficiency or equipment failures caused by temperature fluctuations. A typical temperature control process is as follows:

Preheating Stage: The pyrolysis reactor is heated from room temperature to 200–250℃. This stage mainly removes moisture and light volatile components from waste tires. The heating rate is controlled at 10–15℃ per hour to prevent sudden pressure rise inside the reactor due to rapid vaporization of moisture.

Main Pyrolysis Stage: The temperature is raised to 450–550℃ (the core temperature range for waste tire pyrolysis) and maintained at a constant temperature for 8–12 hours. At this temperature, a large number of macromolecular chains of rubber break, generating pyrolysis oil, non-condensable gas, and carbon black. Excessively high temperature (above 600℃) will cause excessive gasification of pyrolysis products, reducing the oil phase yield and accelerating the wear of reactor materials. Excessively low temperature will result in insufficient pyrolysis reaction and low raw material conversion rate.

Cooling Stage: After the completion of the pyrolysis reaction, heating is stopped, and the reactor is cooled naturally or forcedly to below 100℃ before subsequent discharging operations, preventing safety risks caused by discharging at high temperatures.

Safety Guarantee Design of the Heating System

Dual-channel temperature control sensors are equipped to monitor the temperature of the heating chamber and pyrolysis chamber in real time. When the temperature exceeds the set threshold, the heat source is automatically cut off, and the alarm device is activated.

The heating chamber is equipped with an explosion-proof pressure relief valve and a flue gas waste heat recovery device. Waste heat can be used for preheating raw materials or factory heating, improving energy utilization efficiency.

The electric heating system is configured with overload and short-circuit protection devices; the fuel heating system is equipped with gas leakage detection probes and flame monitors to ensure the safe and controllable operation of the combustion process.