With the acceleration of global industrialization, the amount of plastic, oil sludge and tyre produced has shown an increasing trend year by year. In the face of the ecological challenges brought by these solid wastes, pyrolysis technology has received widespread attention. It converts waste into fuel oil, which is an important measure to achieve sustainable development. Therefore, it is of great significance to explore the changes in plastic, oil sludge and tyre during the pyrolysis process.
Basic Steps of Pyrolysis Process
Pyrolysis process splits waste into syngas, pyrolysis oil and solid residues at high temperature under micro-oxygen conditions. The whole pyrolysis process not only includes the thermal decomposition of raw materials, but also includes the collection of products, the treatment of waste gas and the back-end deep processing of oil products, etc. The following will reveal the pyrolysis technology through workflow of Beston pyrolysis plant.
Raw Material Feeding
This process is to transport the raw materials into the reactor. The main transportation methods include:
- Manual feeding: The operator puts the raw materials directly into the reactor. Due to the low degree of automation, it is usually suitable for small-scale pyrolysis machine.
- Hydraulic feeding: A hydraulic system pushes materials into the reactor. The pressure generated by the hydraulic device allows for even material feeding into the reactor.
- Screw feeding: A screw conveyor transports materials into the reactor. Automatically, the rotating screw pushes the material forward.
Pyrolysis Reaction
The pyrolysis reaction in the reactor is a key part of the pyrolysis plant process. Because it determines the efficiency of the entire process. It mainly involves the following stages:
- Preheating: First, turn on the burner to preheat the main furnace. This is to ensure uniform heating of the pyrolysis raw materials. Usually, the preheating time is 2-4h.
- Reaction Starts: The raw materials enter the combustion furnace. When the temperature reaches 180℃, oil gas is formed. Next, when the temperature reaches 280℃-350℃, the reaction tends to stabilize.
- Reaction Completion: When the temperature of the main furnace increases, while the manifold temperature & pressure decreases, the reaction ends.
End Product Collection
The end products of pyrolysis include liquid (pyrolysis oil), gas (syngas), and solid (residue). They have their own collection facilities:
- Pyrolysis Oil: First, the oil gas produced by the pyrolysis reaction enters the manifold to separate impurities. Subsequently, the oil gas enters the oil condenser to form pyrolysis oil, which is stored in the oil storage tank.
- Syngas: The non-condensable components in the high-temperature oil gas enter hydroseal for purification. Subsequently, the formed syngas enters the burner to power the pyrolysis reactor.
- Solid Residue: After the reaction is completed, the screw conveyor discharges the solid residue in the furnace. The use of a water-cooled screw conveyor can reduce the temperature of the slag and reduce the cooling time.
Tail Gas Treatment
First, the tail gas is cooled by the flue condenser. Then, the cooled gas enters the spray tower, which removes fine particles and residual pollutants. Finally, the chimney discharge the gases. If you need higher emission standards, you can use a high-end exhaust gas treatment system. This system can achieve the following emission standards:
| Pollutant | Emission Standard |
|---|---|
| Sulfur Dioxide (SO₂) | ≤ 50 mg/m³ |
| Nitrogen Oxides (NOx) | ≤ 200 mg/m³ |
| Particulate Matter | ≤ 10 mg/m³ |
| Hydrochloric Acid (HCl) | ≤ 10 mg/m³ |
| Hydrofluoric Acid (HF) | ≤ 1 mg/m³ |
Pyrolysis Process Insights: A Raw Material Perspective
The common point of the composition of the three wastes, plastics, oil sludge and waste tires, is high molecular weight hydrocarbons. This makes them very suitable for recycling by pyrolysis. However, these types of pyrolysis technologies is different:
Pyrolysis Process of Waste Plastic
The main components of plastics are long-chain polymers, such as PE, PS and PP. When pyrolyzing these materials, the polymer chains are broken to form low molecular weight hydrocarbons. Due to the high carbon-hydrogen ratio of plastics, it can produce a large amount of syngas and oil products during the the process of pyrolysis. However, the formation of wax oil often affects the efficiency of plastic pyrolysis. Therefore, plastic pyrolysis equipment using a catalytic tower is often used to solve this problem. The specific process is as follows:
Pyrolysis Process of Oil Sludge
Oil sludge is a byproduct produced during the extraction, processing and storage of oil. It contains rich organic matter (such as petroleum hydrocarbons) and a certain amount of inorganic matter (such as industrial residues). The equipment that treats this waste is usually called TDU. Various oil sludges can produce considerable oil yields during the pyrolysis process. More importantly, pyrolysis can also solidify harmful substances such as heavy metals in oil sludge in the residue, reducing the risk of secondary pollution. The specific process is as follows:
Pyrolysis Process of Waste Tyre
The main components of waste tires are natural & synthetic rubber, steel wire and various additives, which will decompose into carbon black, pyrolysis oil, syngas and steel wire during pyrolysis. Carbon black can be recycled for the production of rubber products. Oil can be further processed into non-standard diesel and heavy oil generator fuel. Steel wire can be reused in steel products. The complex organic structure makes the products produced in the tire pyrolysis plant have high added value. The tyre pyrolysis process is as follows:
Different Types Pyrolysis Process Description: Batch Vs. Continuous
As a sustainable method for recycling waste, pyrolysis technology for waste operate in two main modes: batch and continuous. Understanding the basic characteristics of these two methods will help you choose the right process to meet different processing needs.
Batch Pyrolysis Process
Batch pyrolysis process refers to the processing of a fixed amount of raw materials in a closed pyrolysis reactor. In each processing batch cycle, the loading, preheating, reaction, cooling and unloading stages need to be carried out separately. Each stage takes a certain amount of time. Only when the pyrolysis process of the previous batch is completed can the operator start the next batch.
Features
- High Flexibility: The operator can adjust the configuration scheme and processing parameters according to the raw materials and production needs.
- Easy Operation: Layout and structure of the equipment required for this process are simple, which is convenient for operation and maintenance.
- High Cost Performance: The initial equipment investment is small and the return on investment is fast. Therefore, it is suitable for small and medium-sized production.
Continuous Pyrolysis Process
The continuous pyrolysis process involves the uninterrupted processing of raw materials in a continuous flow through a pyrolysis reactor. Unlike batch processes, materials are fed into the reactor continuously and the products are simultaneously extracted. This method is designed to operate in a steady-state mode, with the process stages (heating, reaction, and cooling) occurring in a continuous sequence.
Features
- High Efficiency: Continuous processing allows for a constant flow of materials and products, optimizing the overall processing time and increasing throughput.
- Lower Operating Costs: Although the initial investment is higher, continuous pyrolysis plant can achieve economies of scale for large volumes of material.
- Stable Operation: The continuous nature of the process provides more consistent product quality and reduces the risk of process interruptions, leading to improved reliability.
Pyrolysis Process Opens the Way to Sustainable Recycling
Pyrolysis process is a promising solution for treating a variety of waste materials, including plastics, sludge, and tires. By converting these challenging materials into valuable products, pyrolysis not only solves the problem of waste disposal. It also contributes to sustainable resource recovery. In addition, each process has unique advantages in flexibility, efficiency, and cost-effectiveness. If you want to start a pyrolysis recycling project, please consult Beston Group Co., Ltd. for solutions.