Brief Principle Overview

(Also known as: molten salt pyrolysis furnace, molten salt pyrolysis oil refining furnace, combined spiral pyrolysis furnace, series-connected spiral propulsion carbonization furnace, top‑and‑bottom combined cracking furnace, spiral carbonization furnace, etc.)

After eight years of development and more than a dozen rounds of technical refinement, Jufeng Technology has independently developed molten salt pyrolysis equipment that utilizes molten salt as a heat transfer medium. The equipment is designed as a multi‑stage spiral‑push furnace, featuring an upper‑lower combined configuration with multiple sets of spirals that reciprocate back and forth. Materials enter from the top and exit from the bottom, while the heating method employs external heating of the spiral outer cylinder, with molten salt serving as the heat transfer medium. Key features include: it provides forced propulsion for a wide range of viscous and sticky materials, making it particularly suitable for plastics, large chunks of organic matter, and sticky substances—especially effective in strongly viscous plastic materials—but less well suited for powdered materials. This equipment is used for the treatment of various organic wastes, including waste tires (yielding 40–45% oil through pyrolysis), waste plastics (with a conversion rate exceeding 90%), industrial organic sludge, medical waste (without secondary pollution), waste lithium batteries, municipal and industrial waste, municipal sludge, oilfield oil mud, waste electronic circuit boards, hazardous waste containing organic compounds, various organic materials, hazardous waste containing organic pesticides, agricultural waste (such as straw and rice husks), and oil‑contaminated metal chips, among others.

Advantages of Molten Salt Pyrolysis

Using molten salt as a heat transfer medium to supply heat to an oxygen‑free pyrolysis furnace is an advanced and highly advantageous technical solution. Molten salts—typically mixtures of nitrates, nitrites, or carbonates—exhibit exceptional properties at high temperatures, making them ideally suited for such applications.

Here are several major applications of molten salt for heat supply: Core Advantages:  

1. Excellent temperature control and uniform heating, featuring a wide and stable operating temperature range. Common molten salts—such as Solar Salt (60% NaNO₃ + 40% KNO₃)—have a melting point of approximately 200°C and can provide stable heat output below 600°C. This temperature range perfectly covers the temperatures required for the pyrolysis of most organic materials—including biomass, plastics, rubber, and sludge—which typically range from 350–600°C.

2. Extremely High Heat Capacity: Molten salts possess a high specific heat capacity, meaning they can store and transfer large amounts of heat. This ensures that the reactor walls or heat exchangers are heated uniformly and steadily, preventing temperature fluctuations caused by localized overheating or overcooling, thereby making the properties of pyrolysis products—especially biochar—more stable and controllable.

3. Higher Product Yield: By precisely controlling the temperature at the optimal pyrolysis range, the yield of target products—such as bio-oil or biochar—can be maximized, while minimizing impurities like tar that arise from temperature inconsistencies.

4. Efficient and Safe Indirect Heating: Molten salt is circulated between an external heater—such as an electric furnace or gas furnace—and the pyrolysis reactor via a pump, with heat being transferred to the feedstock indirectly through the reactor walls or built‑in coils. This physically isolates oxygen, ensuring that pyrolysis proceeds in an oxygen‑free environment, thereby enhancing safety and guaranteeing product purity.

5. Compared to directly heating with high‑temperature flue gas, indirect molten salt heating does not dilute the combustible gases produced during pyrolysis, reduces the formation of non‑condensable gases, ensures a high oil yield, and maintains the high calorific value of the combustible non‑condensable gases, facilitating their efficient subsequent utilization.

6. Powerful Heat Storage Capacity and System Stability: Acting as a “Thermal Battery”: Molten salt systems are typically equipped with storage tanks that allow excess heat to be generated and stored during periods of low electricity demand or when solar energy is abundant. By storing heat using off-peak electricity or renewable energy sources, energy costs can be significantly reduced.

7. Safety and Reliability: Molten salts operate at atmospheric pressure within a high-temperature range, reducing the pressure requirements for reactors and pipelines and thereby lowering equipment costs and safety risks.

8. Excellent Heat Transfer and Compatibility: Molten salts have low viscosity and good fluidity, making them easy to pump and delivering high heat transfer efficiency; their chemical properties are relatively stable, resulting in minimal corrosion to common heat‑resistant stainless steels.

The equipment’s overall advantages are evident.

1. Dual Enhancement of Product Quality and Process Safety: Precise molten salt temperature control effectively prevents material coking and carbonization caused by localized overheating, ensuring long‑term stable operation of the equipment. The stringent anaerobic environment fundamentally eliminates oxidation reactions, not only improving the quality of pyrolysis oil, gas, and other products, but also significantly inhibiting dioxin formation, yielding substantial environmental benefits.

2. Outstanding Operational Efficiency and Economic Benefits: The continuous feed and discharge design significantly boosts processing capacity compared to traditional batch furnaces. The excellent thermal stability of molten salts ensures a constant reaction temperature, allowing the cracking reaction to proceed more thoroughly and completely, thereby enhancing both the yield and quality of the desired products. Certain system designs even enable the recycling of cracked gas as a heating medium, further improving overall thermal energy utilization.

3. Flexible Modularity and Adaptability: The multi‑stage spiral design allows for the adjustment of operating parameters at each stage—such as temperature and rotational speed—to create varying temperature gradients, thereby flexibly accommodating the optimal pyrolysis process requirements for different feedstocks, including biomass, waste tires, and organic solid waste. This modular approach also facilitates subsequent capacity scaling and equipment maintenance.

4. Thermal Efficiency and Energy Consumption Advantages: The heat transfer coefficient of molten salt is twice that of conventional organic heat transfer fluids, reducing heat loss by more than 40%. Counterflow heat exchange boosts energy utilization efficiency by 30%, while maintaining the same amount of material results in an approximate 25% reduction in energy consumption. The large contact area between the material and the molten salt ensures uniform heating with no localized overheating, leading to a 20% increase in pyrolysis efficiency.

5. Product Quality Advantages: The oxygen‑free environment effectively inhibits the formation of toxic substances such as dioxins, significantly enhancing the quality of pyrolysis oil, with a calorific value reaching 42 MJ/kg. Precise temperature control (±3°C) ensures product consistency; the carbon black exhibits low volatile matter and excellent fluidity, making it directly applicable to the rubber industry. The multi‑stage pyrolysis process boosts the feedstock conversion rate to over 95%, representing an improvement of 15–20% compared to conventional processes.

6. Operational and Maintenance Advantages: Continuous production (7×24 hours), large processing capacity, low unit energy consumption, significant economies of scale, modular design for easy equipment maintenance and upgrades, and a service life of over 10 years for key components.

7. Environmental and Safety Advantages: Oxygen‑free pyrolysis eliminates the combustion process, reducing exhaust emissions by 90% while completely excluding sulfur oxides and nitrogen oxides. The system operates at low pressure, posing no risk of explosion and ensuring high safety. The combustible gas generated during pyrolysis can be recovered and reused, enabling “zero energy consumption” operation, with surplus energy available for external supply.

Four-Group Helical Propulsion Molten Salt Pyrolysis Furnace – Photo