Waste Aluminum Plastic Pyrolysis Plant

Step 1: Raw Material Pretreatment – Lay the Foundation for Efficient Pyrolysis

1. • Crushing and Sorting: First, the waste aluminum-plastic products (such as aluminum-plastic panels, medical blister packs, food packaging) are sent to a crusher to be crushed into uniform particles with a particle size of 5 – 20mm. This increases the contact area between the raw materials and heat, accelerating the pyrolysis reaction. During the crushing process, manual or mechanical sorting is used to remove obvious impurities such as metal blocks, glass, and stones mixed in the raw materials.
   • Cleaning and Drying: The crushed aluminum-plastic particles are cleaned by a washing machine to remove surface dust, oil stains, and residual adhesives. Then they are sent to a rotary dryer for drying treatment. The moisture content of the materials after drying is controlled below 10%, which avoids energy waste caused by water evaporation during the pyrolysis process and prevents equipment corrosion.
   • Screening and Grading: The dried particles are screened by a vibrating screen to separate unqualified large particles and re-crush them, ensuring that all the raw materials entering the next process meet the uniform particle size standard.

Step 2: Pyrolysis Reaction – Core Link of Aluminum-Plastic Separation

This is the core stage of the whole workflow, which realizes the decomposition of plastic components and the retention of aluminum components through anaerobic high-temperature cracking.

1. • Feeding and Sealing: The qualified aluminum-plastic particles are sent to the sealed pyrolysis reactor through an automatic feeder. The reactor is strictly sealed to ensure an oxygen-free or low-oxygen environment inside, which fundamentally avoids the generation of dioxins and prevents the oxidation of metal aluminum.
   • High-Temperature Cracking: The reactor is heated by an external heating system (the heat source is usually the synthetic gas recovered in the later stage). The temperature inside the furnace is gradually raised to 400 – 700℃. Under this temperature and anaerobic condition, the plastic components (such as PE, PP, PS) in the aluminum-plastic materials undergo thermal decomposition. Their macromolecular chains are broken into small-molecule gaseous products (such as hydrocarbons), while the metal aluminum has high thermal stability and remains in a solid state without any chemical change.
   • Temperature Control: The whole pyrolysis process is equipped with an intelligent temperature control system. The temperature in the reactor is monitored in real-time and adjusted dynamically. Different temperature stages correspond to different pyrolysis stages, ensuring the full decomposition of plastic and avoiding incomplete pyrolysis or over-pyrolysis.

Step 3: Product Separation – Collect Gas and Liquid Products

The gaseous products generated by pyrolysis are cooled and separated to obtain liquid pyrolysis oil and gaseous synthetic gas.

1. • Flue Gas Conduction: The gaseous products (mainly small-molecule hydrocarbons) generated in the reactor are introduced into the condensation system through a sealed pipeline. The condensation system is composed of a primary condenser and a secondary condenser, adopting a multi-stage cooling design to improve the condensation efficiency.
   • Pyrolysis Oil Collection: When the gaseous products pass through the condenser, they are cooled and liquefied into liquid pyrolysis oil. The pyrolysis oil flows into the oil storage tank through a pipeline after being filtered by an oil filter to remove impurities. The collected pyrolysis oil has a calorific value of 4200 – 4800 kcal/kg and can be directly used as industrial fuel or further refined into bio-diesel.
   • Synthetic Gas Recovery: The non-condensable gas that cannot be liquefied after multi-stage condensation is synthetic gas, whose main components are hydrogen, carbon monoxide, and methane, with a calorific value of 1200 – 1600 kcal/Nm³. The synthetic gas is purified by a desulfurization and deodorization device and then sent to the heating system of the reactor as a fuel, realizing energy self-sufficiency and reducing operating costs. Excess synthetic gas can also be stored in a gas storage tank for power generation or heating.

Step 4: Solid Residue Treatment – Extract High-Purity Recycled Aluminum

After the pyrolysis reaction, the solid residue in the reactor is mainly high-purity aluminum particles and a small amount of carbon black. This stage focuses on separating and purifying the aluminum.

1. • Cooling and Discharging: After the pyrolysis reaction is completed, the reactor is cooled to a safe temperature through a water cooling system. Then the solid residue is discharged into the cooling bin through an automatic discharge device to avoid oxidation of aluminum due to high-temperature contact with air.
   • Aluminum-Carbon Separation: The cooled solid residue is sent to a vibrating separator or electrostatic separator. Due to the different physical properties of aluminum and carbon black, aluminum particles and carbon black are efficiently separated. The separated carbon black can be sold as a raw material for rubber fillers or activated carbon.
   • Aluminum Purification: The separated aluminum particles are further purified by a magnetic separator to remove a small amount of iron impurities mixed in them. Finally, high-purity recycled aluminum with a purity of more than 95% is obtained, which can be directly sold to aluminum processing plants for remelting and reuse or processed into aluminum ingots and aluminum powder.

Step 5: Energy Recycling – Achieve Low-Carbon Operation

The plant integrates an energy recycling system to maximize the utilization of waste heat and by-product gas, reducing external energy input.

1. • Waste Heat Utilization: The waste heat generated during the operation of the reactor and condenser is collected by a waste heat recovery device and used to preheat the dried raw materials, improving the thermal efficiency of the whole system.
   • Synthetic Gas Circulation: As mentioned earlier, the synthetic gas generated in the pyrolysis process is the main fuel for the reactor, which can meet more than 80% of the heating demand of the plant. This not only saves the cost of purchasing external fuels but also reduces the emission of greenhouse gases.

Step 6: Environmental Protection Treatment – Ensure Compliance with Emissions

The whole process is equipped with a complete environmental protection system to ensure that all emissions meet the national and industrial environmental protection standards.

• • Tail Gas Treatment: A small amount of residual tail gas after synthetic gas recovery is treated by a desulfurization, denitration, and dust removal integrated device to remove sulfur dioxide, nitrogen oxides, and particulate matter in the tail gas. After treatment, the tail gas can be directly discharged into the atmosphere, and the emission indicators are far lower than the national standard.
  • Wastewater Treatment: The plant basically has no wastewater discharge during the operation process. The cooling water and cleaning water can be recycled after sedimentation and filtration, realizing zero wastewater discharge.
  • Solid Waste Disposal: The small amount of waste residue generated in the separation process is non-toxic and harmless, and can be used as a raw material for building materials or sent to a landfill for harmless disposal.