Biomass pyrolysis process

Summary

The biomass pyrolysis process involves several key stages, starting with the storage, drying, and transportation of raw biomass to a reactor. The biomass undergoes pre-drying, moisture evaporation, and degasification before reaching the carbonization stage, where elemental carbon is concentrated. This process enhances the grindability and calorific value of the material. After cooling, the carbonized biomass is either bagged, pelletized, or used for heat generation. The pyrolysis system can produce flammable gases for energy, with the efficiency of the process maximized by reusing hot air. The final gases are mixed and emitted through a common stack.

Takeaways

• 😀 Biomass is stored in a dedicated facility before being transported to the pyrolysis reactor via a bucket feeder.
• 😀 Biomass undergoes pre-drying in the feeder using hot, dry air, reducing moisture content and speeding up subsequent stages.
• 😀 Pre-dried biomass enters the pyrolysis reactor, where moisture evaporation, degasification, carbonization, and cooling occur.
• 😀 The moisture evaporation process is crucial for initiating carbonization, with time varying depending on biomass type and moisture content.
• 😀 Degasification occurs at temperatures between 370-400°C, removing volatile compounds like nitrogen, CO, CO2, and hydrogen.
• 😀 Approximately 40% of the energy produced in pyrolysis is consumed by the pyrolysis process itself.
• 😀 The gases generated during degasification can be mixed with humid air and used for energy purposes.
• 😀 Carbonization occurs at high temperatures, concentrating elemental carbon and improving the biomass's grindability.
• 😀 The resulting carbonized biomass has a calorific value of 21-29 MJ/kg, depending on the pyrolysis conditions.
• 😀 The cooling process uses a cross-flow water cooler to bring the biomass back to ambient temperature.
• 😀 The carbonized biomass can be further processed by pelletizing, bagging, or directly used for heat generation in boilers for district heating systems.

Q & A

What is the first step in the biomass pyrolysis process?

The first step is the storage of biomass in a dedicated facility. Afterward, the biomass is transported to the pyrolysis reactor via a bucket feeder.

How does the pre-drying process impact biomass during pyrolysis?

The pre-drying process reduces the moisture content of the biomass, which accelerates the subsequent processes in the pyrolysis reactor and improves the efficiency of carbonization.

What happens during the moisture evaporation stage of pyrolysis?

During the moisture evaporation stage, all accumulated moisture in the raw biomass is removed. This is necessary to initiate the carbonization process and can take several seconds to more than a dozen seconds, depending on the moisture content.

What is degasification in the biomass pyrolysis process?

Degasification occurs at temperatures between 370 to 400°C, where volatile gases such as nitrogen, carbon monoxide, carbon dioxide, and hydrogen are removed from the biomass. These gases are flammable and can be used for energy generation.

What role do volatile gases play in the biomass pyrolysis process?

The volatile gases removed during degasification contain energy. After mixing with humid air from the preceding process, they can be utilized for energy generation, providing approximately 40% of the energy needed for the pyrolysis process.

How does the carbonization process affect the biomass?

In the carbonization stage, the biomass is treated at high temperatures, which leads to the concentration of elemental carbon and the loss of its fibrous structure. This improves the grindability and calorific value of the material.

What is the range of calorific value of carbonized biomass?

The calorific value of the carbonized biomass can range from 21 to 29 megajoules per kilogram, depending on the temperature and duration of the carbonization process.

What happens during the cooling process in biomass pyrolysis?

After the biomass is carbonized, it is cooled to ambient temperature using a crossflow water cooler. This ensures the material is stable and ready for further processing or use.

How is the carbonized biomass used after pyrolysis?

The carbonized biomass can be loaded into big bags, pelletized, or transferred directly to a boiler for heat generation. The pyrolysis system can supply district heating networks with a capacity ranging from 1 to 3 megawatts.

What is the significance of using hot air in the biomass pyrolysis system?

Hot air is taken from the reactor to pre-dry the biomass, helping to reduce its moisture content. This process is crucial for maximizing the efficiency of the pyrolysis process and ensuring higher quality output.