What is the Working Principle of a Waste Tire Pyrolysis Plant?
The core principle of waste tire pyrolysis plant is to force the large molecular rubber in tires to be broken down into small molecules under oxygen-free (or oxygen-deficient) and high-temperature (usually 300-500℃) conditions, and then convert them into three products: reusable pyrolysis oil, combustible gas and carbon black.
The entire process is like "dry steaming" the tires in a sealed container, and can be broken down into the following three key steps:
Pretreatment and Feeding
Waste tires first need to be crushed, the steel wires separated by magnetic separation and then pulverized to obtain uniform rubber granules or powder. The raw materials are then continuously fed into a closed reactor via a screw conveyor or similar method to ensure the reaction takes place in an oxygen-free environment.
Pyrolysis Reaction
This is the most critical step in the entire process. After the raw materials enter the reactor, heating triggers a complex chemical bond breaking reaction. The following points need to be carefully considered during operation:
Oxygen-free conditions: The system must maintain a strictly oxygen-free state, otherwise the tires will burn directly. This is usually achieved by purging with inert gases such as nitrogen, or by using non-combustible gases produced during the reaction process to create a protective atmosphere to isolate the system from air.
Reaction temperature: Temperature is the core indicator that determines the product trend. When the furnace temperature is controlled in the range of 300-500℃, the rubber macromolecular chains break down, and the main product is liquid pyrolysis oil. Once the temperature rises above 700℃, the gas yield increases significantly, and the tendency to form by-products such as polycyclic aromatic hydrocarbons (PAHs) also increases.
Residence time: The length of time materials remain in the reactor also affects the product structure. If the residence time is too short, the pyrolysis reaction may not be complete; if the residence time is too long, secondary pyrolysis is easily induced, causing substances that should have become oil to further decompose into gas.
Currently, the mainstream waste tire pyrolysis plant can be mainly classified into the following types based on the form of its core reactor:
|
Reactor type |
Working principle and characteristics |
|
Spiral/Hollow Spiral Reactor |
It utilizes spiral blades to propel and agitate materials. This method ensures uniform heat transfer, is suitable for continuous production, and is currently one of the most common types in research and application. |
|
Rotary kiln reactor |
The material is tumbled inside the slowly rotating cylinder, resulting in uniform heating, large processing capacity, and mature technology. |
|
Moving bed reactor |
Materials move downwards due to gravity, while gas flows upwards, resulting in good gas-solid contact and controllable temperature distribution. |
|
Microwave pyrolysis reactor |
Microwave energy is used to directly heat materials, resulting in rapid heating and selective heating, which can significantly shorten reaction time. |
Product Separation and Energy Self-circulation
After pyrolysis, the reactor outputs a high-temperature mixed product, which then enters the separation system：
Gas-solid separation: High-temperature oil gas and solid carbon black are separated first. After cooling and collection, the solid carbon black can be used as working material or fuel.
Oil and gas condensation: High-temperature oil and gas enter the condensation system and are cooled to obtain pyrolysis oil. This non-condensable gas is called pyrolysis non-condensable gas.
Energy self-sufficiency: The brilliance of this device lies in the fact that the separated pyrolysis non-condensable gas (mainly composed of methane, hydrogen, etc.) has a high calorific value and can be directly used as fuel to heat the pyrolysis reactor. This allows the entire system to operate on its own, greatly reducing external energy consumption.