PV panel pyrolysis represents one of the most practical recycling solutions for end-of-life photovoltaic modules. In an oxygen-free atmosphere, controlled heating enables clean separation between organic and inorganic materials. This technology addresses both resource recovery and environmental protection targets, boasting an energy conversion efficiency of over 75%, far superior to conventional incineration.
A typical crystalline silicon PV module consists of roughly 75% glass, 10% polymeric materials (EVA, TPT) and 8% metallic materials. The pyrolysis process is tailored for these organic fractions. When temperature rises to 300–320°C, molecular chains of EVA encapsulant break down and generate hydrocarbon vapors, while inorganic fractions including silicon wafers and glass remain physically and chemically stable. Such selective decomposition differentiates pyrolysis from other recycling routes.
Table 1 Main Components of PV Panels and Their Pyrolysis Behaviors
| Material Category | Main Components | Mass Ratio | Pyrolysis Temperature Range | Product Form |
|---|---|---|---|---|
| Organic Materials | EVA encapsulant | 6–8% | 280–350°C | Oil-gas mixture |
| TPT backsheet | 3–4% | 320–400°C | Cracked gas | |
| Metallic Materials | Aluminum frame & solder ribbon | 8–10% | No reaction | Solid recyclate |
| Inorganic Materials | Tempered glass | 65–70% | No reaction | Solid recyclate |
5-Step Pyrolysis Process
1. Pre-treatment: Aluminum Frame Removal
Machine vision positioning and high-precision grippers are applied on dedicated framing removal equipment for non-destructive stripping of aluminum frames. The latest model processes 2–3 standard modules per minute, with metal recovery rate exceeding 98%. During this stage, the laminated structure of PV panels must stay intact to avoid fragment-induced uneven pyrolysis in subsequent steps.
2. Core Pyrolysis Reaction
Frameless PV modules are fed into custom pyrolysis furnaces. A notable equipment innovation is the integrated pyrolysis furnace developed by Jiangsu Jiangwan Circular Technology (Patent No. CN121067336A). Equipped with circular plate racks, it automatically sorts broken and intact modules to guarantee even hot gas distribution. A gradual heating curve is strictly controlled to prevent premature carbonization of EVA and preserve oil quality. A full pyrolysis cycle lasts 4–6 hours, producing 45–55 kg pyrolysis oil per ton of PV panels.
3. Oil-Gas Condensation & Refining
Mixed vapors from pyrolysis pass through multi-stage condensers with circulating cooling water below 80°C for gradient cooling. Premium condensation systems keep the dew point deviation within ±5°C and lift oil yield by more than 15%. The recovered pyrolysis oil has a calorific value of 42 MJ/kg, close to the specification of No.4 fuel oil.
4. Solid Residue Sorting
Solid residuals after pyrolysis go through a three-stage separation workflow:
- A vibrating sieve with 3 mm mesh separates glass particles;
- Air gravity separators extract silicon wafers with 92% recovery rate;
- High-voltage electrostatic separation (15–25 kV) recovers copper and other metals.
The system delivers metal recyclates with purity up to 99.7%, which can be directly reused.
5. Tail Gas Treatment & Energy Recirculation
Pyrolysis gas is treated by desulfurization towers (desulfurization efficiency＞95%) and activated carbon adsorbers. The cleaned gas is reused as fuel for furnace heating. Flue gas meets emission standard GB16297-1996, with particulate matter below 20 mg/m³. This closed-loop design cuts external energy consumption by over 40%.
Technological Innovation & Equipment Evolution
New-generation pyrolysis equipment features three major trends:
- Modular design: The EHZG series from Damuzhi Drying Technology supports flexible capacity of 5–20 tons per day.
- Intelligent temperature control: PID algorithm stabilizes furnace temperature fluctuation within ±3°C.
- Waste heat recovery: Flue gas waste heat is used for pre-treatment drying, improving overall energy efficiency by 15–20%.
The dynamic rack system in patented designs matches rotation speed (0.5–2 rpm) with pyrolysis progress, solving material caking issues in traditional processes. Field data proves this design improves pyrolysis uniformity by 30% and reduces residual oil content below 0.5%.
Industrial Application & Economic Evaluation
Life cycle analysis shows pyrolysis reduces carbon emissions by 92% compared with landfilling. For retired modules from a 10 MW PV power station, pyrolysis recycling delivers around 850,000 CNY gross profit, with an investment payback period of 2–3 years. The main technical bottleneck lies in catalysts for EVA pyrolysis. Once breakthroughs are achieved, processing temperature can drop below 280°C.
For well-equipped pyrolysis recycling plants, overall operating cost stands at 1200–1500 CNY per ton, much lower than chemical recycling at 2500–3000 CNY per ton. With the global wave of retired PV panels arriving after 2025, pyrolysis will become a key pillar of circular economy, and the market size is expected to exceed 10 billion CNY.
Three R&D priorities for continuous technical upgrading:
- Develop low-temperature high-efficiency catalysts;
- Optimize non-destructive silicon wafer separation processes;
- Establish refining standards for pyrolysis oil.
Full-chain technical collaboration is essential to build a truly green closed loop covering PV panel manufacturing and end-of-life recycling.
