CHEE2695 – Lecture 6
Pyrolysis:
- There are two main types:
o Slow pyrolysis is used for agricultural biochar and renewable energy
generation. It is quite a simple technology.
o Fast pyrolysis’ main product of interest is ‘bio-oil’ or syngas (depending
on temperature). It requires fast heat transfer to the particle. For bio-oil
production, volatiles must be quickly removed to avoid secondary
reactions.
- Fast pyrolysis has many different methods:
o Vacuum pyrolysis,
o Screw and auger kilns,
o Microwave pyrolysis,
o Molten salts.
Gasification:
- The main output of gasification is Syngas and ash.
- The type of gasifier used will depend on:
o Feedstock type,
o Output products (temperature, residence time, and gasification agent
control).
o Required capacity.
- Types of gasifiers include:
o Fixed bed,
o Fluidised bed,
o Entrained flow.
- Entrained flow gasifiers require very fine particles. This creates a high level of
mixing/contact with the gasifying agent at high temperature, meaning the gas
produced is tar free. This type of gasification is most popular for coal
gasification applications.
- Integrated gasification combined cycle (IGCC) is a way to extract energy from
fuels that is more efficient and environmentally superior to combustion. The
mass flow rate to a gasifier is much lower than a combustor, as it operates
sub-stoichiometrically. It extracts more energy per unit mass of coal than
combustion and generates a cleaner burning gaseous fuel that can be
transported.
Industrial use of combustion:
- The majority of the world’s electricity demands are met by combustion.
Pyrolysis:
- There are two main types:
o Slow pyrolysis is used for agricultural biochar and renewable energy
generation. It is quite a simple technology.
o Fast pyrolysis’ main product of interest is ‘bio-oil’ or syngas (depending
on temperature). It requires fast heat transfer to the particle. For bio-oil
production, volatiles must be quickly removed to avoid secondary
reactions.
- Fast pyrolysis has many different methods:
o Vacuum pyrolysis,
o Screw and auger kilns,
o Microwave pyrolysis,
o Molten salts.
Gasification:
- The main output of gasification is Syngas and ash.
- The type of gasifier used will depend on:
o Feedstock type,
o Output products (temperature, residence time, and gasification agent
control).
o Required capacity.
- Types of gasifiers include:
o Fixed bed,
o Fluidised bed,
o Entrained flow.
- Entrained flow gasifiers require very fine particles. This creates a high level of
mixing/contact with the gasifying agent at high temperature, meaning the gas
produced is tar free. This type of gasification is most popular for coal
gasification applications.
- Integrated gasification combined cycle (IGCC) is a way to extract energy from
fuels that is more efficient and environmentally superior to combustion. The
mass flow rate to a gasifier is much lower than a combustor, as it operates
sub-stoichiometrically. It extracts more energy per unit mass of coal than
combustion and generates a cleaner burning gaseous fuel that can be
transported.
Industrial use of combustion:
- The majority of the world’s electricity demands are met by combustion.
