1. Carbonization is the process by which coal is heated
and volatile products—gaseous and liquid—are driven
off, leaving a solid reside called char or coke.
The coke produced by carbonization of coal is used in
the iron and steel industry and as a domestic smokeless
fuel
Only a limited range of coals produces acceptable
metallurgical cokes.
These coals are in the bituminous rank range but not all
bituminous coals are caking coals.
2. Coal carbonization processes are classified into
i. high-temperature
ii. low-temperature
High-temperature
Carbonization processes performed at temperatures in
the range of 900 − 1200°
C.
The main purpose of high-temperature carbonization is
the production of metallurgical coke for use in blast
furnaces and foundries.
3. Low-temperature
In low temperature carbonization heating is carried out at
500-700°
C.
Coke produced is not mechanically strong so it is not
used as metallurgical coke.
Low-temperature carbonization was originally developed
to provide town gas for residential and street lighting and
to manufacture a smokeless fuel for domestic and
industrial heating
5. )
The ability of a coal to melt upon heating and to form a
coherent residue on cooling is termed caking;
caking is an essential prerequisite for a coking coal that
it should cake or fuse when heated.
Coals that are low in rank, such as lignites, or high in
rank, such as anthracites, do not cake and therefore are
not capable of forming coke.
Several properties of coals are measured to identify
appropriate coking coals, including swelling, fluidity,
composition etc.
6.
7. What is Biomass?
— Any organic material derived from plants
(botanical) or animals (biological)
— A non-fossilized fuel source that is
biodegradable
— Excludes materials normally used as foods
8. Thermodynamic Properties of Biomass
— Heat of combustion
— Heat released/absorbed in a chemical reaction
without a change in temperature
— Ignition temperature
— The temperature of the biomass at which the
combustion reaction becomes self sustaining
— Heating value
— HHV – heat released by combustion of a fuel at
25rC and returned to 25rC
— LHV – heat released by combustion of a fuel at
25rC and returned to 150rC
— LHV = HHV – latent heat of vaporization
9. Other Properties of Biomass
— Bases of expressing biomass composition
— “As received” basis
— Ultimate analysis
— Determines the composition of the biomass
fuel in terms of basic elements
— C + H + O + N + S + A + M = 100%
10. Other Properties of Biomass
— Bases of expressing biomass composition
— “As received” basis
— Proximate analysis
— Determines the composition of the biomass
fuel in terms of gross components
— VM + FC + A + M = 100%
11. A Renewable Energy Source
— When biomass dies it is naturally broken
down and releases H2O, CO2, and energy
— The same change happens when used for
chemical or energy purposes
— Net pollution contribution is zero!
12. How is Biomass Formed?
— Botanical (plant) biomass converts CO2 and
H2O to carbohydrate and oxygen with energy
from the sun through photosynthesis
— Biological (animal) species grow by
consuming botanical species or other
biological species
13. Biomass Classification
A. Virgin Biomass
1. Terrestrial
— Forest
— Grasses
— Energy crops
— Cultivated crops
2. Aquatic
— Algae
— Water plants
15. Thermodynamic Properties of Biomass
— Heat of combustion
— Heat released/absorbed in a chemical reaction
without a change in temperature
— Ignition temperature
— The temperature of the biomass at which the
combustion reaction becomes self sustaining
— Heating value
— HHV – heat released by combustion of a fuel at
25rC and returned to 25rC
— LHV – heat released by combustion of a fuel at
25rC and returned to 150rC
— LHV = HHV – latent heat of vaporization
16. Other Properties of Biomass
— Bases of expressing biomass composition
— “As received” basis
— Ultimate analysis
— Determines the composition of the biomass
fuel in terms of basic elements
— C + H + O + N + S + A + M = 100%
17. Other Properties of Biomass
— Bases of expressing biomass composition
— “As received” basis
— Proximate analysis
— Determines the composition of the biomass
fuel in terms of gross components
— VM + FC + A + M = 100%
19. Biomass has higher H/C & O/C
ratio than fossil fuels
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20. Why is it important?
• Biomass is a renewable energy
• No net greenhouse contribution to
atmosphere
• Locally available
• Less fuel processing energy
consumption for absence of mining or
extraction
21.
22. Why Co-firing is important
1. It is one of the most effective practical
means for greenhouse gas reduction
2. It offers the highest electrical conversion
efficiency of any biomass power options
3. Co-firing in existing coal fired boiler is
among the lowest cost biomass power
production options
4. It is the lowest technical risk option
23. Co-firing concerns
• Potential cost of interference with coal
plant operation may out weigh additional
revenues from co-firing
• Risks
1. Reduced availability & flexibility
2. Increased O&M of biomass associated equipment
• Technical issues
a) fuel preparation & handling
b) Combustion related issues
c) Ash related issues
d) environmental issues
24. Options for Electricity generation
from Biomass
• Gasification + Gas engine
• Combustion + Steam generation + Steam
turbine
• Co-firing in existing fossil fuel power
plant
26. Co-firing options
1. Direct firing - feed biomass in pulverizers-
2. Indirect firing - Gasify biomass in a CFB
gasifier and reburn it in the furnace
3. Parallel firing –
a) Burn biomass in an external hot gas
generator and feed the gas into the furnace
b) Burn biomass in an external boiler and use
that steam for heating / generation
