The technology of Coal Gasification is to combust the Coal in a controlled oxygen environment. The resultant is the generation of Coal Gas whose primary constituent is CO instead of CO2. Coal gas is used extensively to replace high value fuels for thermal applications. This Gas can also be used to make fertilizers and Chemicals. The gasifiers listed below are primarily used for thermal applications.
Coal Gas Contains
Following Gases
Depending on the type of gasifier, the percentage of
these Gases Changes. So does the Calorific values.
Checklist for Gasifier Model and Technology
Selection:
CASE Coal Gasifier are of various types. Different types of Gasifiers
are used for different Applications depending on the following:
Type of Application:
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Gasifier Automation Required:
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Quantity of Gas Required:
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Gas Calorific Value Desired:
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Pressure at Burner Point Desired:
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Distance of user point from the Gasifier:
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Burner level Automation:
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Quality of Coal:
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Granularity of Coal:
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Economic Constraints:
On the basis of the
above information provided by the user, the gasification technologist at CASE
selects the optimum technology and type of gasifier suitable to meet the users’
demand.
CASE Hot Gasifier:
This
is the Basic type of Gasifier. This Gasifier Converts Coal into coal gas and
the Gas output temperature is over 450° C
and the pressure is about 150mmWC.
The gas composition is as follows. CO 20-25%, H2
15-18%, CH4 2-4%, N2 45-50%. The VM in the coal stays in
gaseous form which burns with the gas at the user point. These gasifiers need
to be close to the user point. Here Burner level automation is not possible;
However, Gasifier operations can be fully automatic. The calorific value of gas
without Considering VM is 1250Kcal/Nm3. Considering TAR caloric
value being part of Coal Gas in gaseous form, the overall calorific value of
the gas can be over and above 1800Kcal/Nm3.
The positive of this technology is low capex and Opex.
There is no Tar or Phenol water generated in this technology. The technology is
a hot favorite of Steel Rolling mills, Galvanizing Plants, Annealing lines etc.
The cons for this technology are that burner level
automation is not possible and these gasifiers need to be installed very close
to the user point.
This technology requires Lump coal of size 15mm – 50mm.
These gasifiers can be designed for a wide range of coals varying from high
grade Anthracite coals to low grade bituminous coals having high ash coal. The
Coal quantity required per NM3 of Coal Gas generated depends on the Quality of
coal.
CASE
Cold Pyrolysis Gasifier:
These Gasifiers are one generation above Hot Gasifiers. In this technology,
Gasifier gas can be scrubbed of the TAR and Clean cold Gas can be boosted to
any pressure as per user’s requirements. The phenol water is 100% recirculated
back into the system. The Gas composition is almost same as in Hot Gasifier
except high CH4 (4-6%) which results in Calorific value to be over
1400 Kcal/Nm3.
These Gasifiers are fully automatic and are preferably used where burner
level Automation is desired like in Automatic Steel Furnaces, Pellet Plants,
Glass Plants, Aluminum Calciners etc.
The Negatives of this technology is that if the Gas required is over
35000Nm3/hr, Battery of gasifiers are required resulting in
increasing costs on man power and Opex.
Just like hot gasifiers, the gas quantity generated in these gasifiers
are similarly dependent on the quality of coal used for gasification. Likewise,
coal used in these gasifiers is also of wide variety varying from low ash like
“Anthracite” or high ash like “Indian F Grade coal”.
Circulating
Fluidized Bed Gasifiers:
These
Gasifiers are the third-generation gasifiers where coal fines of 0mm-10mm size
can be used for gasification. These Gasifiers have Fluidized Bed where Coal
fines, Steam and Air are pumped from the bottom to the top. The gas comes out
from the top which needs to be filtered and can be compressed to any pressure
depending on the user requirements. In this
technology there is no generation of Tar or Phenols.
The calorific value of gas is about 1300Kcal/Nm3 and can be increased to
about 1800Kcal/Nm3 by adding oxygen in the air which is used as gasifying
agent.
These gasifiers involve a higher capex but they are low in opex as
compared to the other two variants explained above.
The coal used in these gasifiers can be fines below size of 10mm but the
ash content needs to be less than 25%. This technology is well established now
and many installations are available to vouch for the technology. This
technology can generate 60000Nm3/Hr gas in single cell. This is a
boon where gas requirement is in high quantities.
CASE Entrained
Flow Coal Gasifiers:
These gasifiers are Fourth-Generation Coal Gasifiers where the
technology is better than Circulating bed coal gasifiers. In this technology,
High ash coal can be used of size less than 100 microns.
The Gas is filtered and used by the user. The pressure of gas coming out
of the gasifier can be plus 80 KPA. In this technology 100% Oxygen can be used
instead of air as gasifying agent by which calorific value of plus 2400Kcal/Nm3
can be achieved in the gas. This is a boon where the thermal process requires
higher Calorimetric temperatures.
These gasifiers are down draft in contrast to all the above three
cousins. In these gasifiers the temperature is maintained over Ash fusion
temperature of coal used. The majority ash comes out in liquid form from the
bottom.
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117, Charmwood Plaza, CharmwoodVillage, Surajkund, Faridabad, Haryana -
121009, INDIA.
Tel.: +91-129-4266666
Telefax: +91-129-4266699
Email : info@casepl.com, case@casepl.com
Website: https://www.casepl.com
