When anyone thinks about a boiler, the first thing which flashes is the steam, steam quality, turbine etc.
However when the Boiler Design aspects are looked into, the most critical factors are presented in ascending order
1) Density of the fuel
a) Fuel density is the most critical factor, as increase in density reduces flame throw for PF boilers, reduces fluidization in FBC, AFBC & CFBC boilers, reduces fuel flows
b) The PA Fans are designed for the fuel density & volume delivery
c) The furnace dimensions (more width or height) are determined again by fuel density & volume delivery
d) The FD fans are designed for handling the fuel density & its reactivity patterns
e) reactivity and reaction efficiency of the fuel is also a function of its density, as higher density slows the combustion reactions & lower density speeds it up
f) The air & flue gas velocities are also determined as a function of fuel density
g) The air duct dimensions are also function of fuel density
h) Direct Method Efficiency of the boiler also is a dependent parameter of fuel density
i) Time, turbulence & temperature or the 3T equilibrium is a dependent parameter of fuel density
j) LOI in the fly ash, clinker, etc., density of the fuel plays a major role
k) Flue gas density which is the heat carrier in the furnace also is dependent upon fuel density
The density of the fuel commands the entire combustion process, hence it is the most critical parameter. Most of the combustion related problems arise from change in density of the fuel.
In fact 70% to 80% design work is attributed to combustion related issues, fuel handling etc..
In almost every Boiler installation, the density goes unchecked & is not reported. Many times, when I ask what is the fuel density, it is checked almost the first time ever.
Ask the OEM, what is the fuel density consideration for design.
2) The rest of the boiler, viz., bank, bed tubes, etc. fall in the reminder work
3) Critical parameter is also the steam drum size, ensure the steam drum size is big enough to hold at least 20% to 30% of the steaming capacity as water holding capacity.
When the boiler drum is small, the thermal stresses get created, as there will always be conditions where heat produced > heat absorption. If this condition occurs, if clinker is formed, it is good, as the heat has been removed through clinker.
If the clinker has not formed, then there is a good chance of the tube surfaces getting heated up, becoming red hot & become stressed, readying them for failure.
As the water is the only coolant removing the heat in the whole boiler system, water supply or its velocity >> steam velocity. This measure will keep thermal stresses at bay.
In big steam drum boilers, the boiler tube failure is a slow or remote possibility, due to more than sufficient cooling arrangement.
In small steam drum boilers, the tube failures are high, as the tubes display highest characteristics for easy erosion only when they are red hot.
Steam drum size is a determinant factor in natural circulation rates, which is never measured in Boiler operation.
4) Fuel density in usage : This is also a very critical parameter. Often it happens, that the fuel for which the boiler stands designed, is no longer available. The decisions for purchasing a fuel should include its density as a parameter, which removes much of the anxiety in operations
5) 3T condition : The Boiler should operate in 3T condition, this is most critical parameter in operation
If you have any comments or queries, please send to sap@chargewave.in
SAP
However when the Boiler Design aspects are looked into, the most critical factors are presented in ascending order
1) Density of the fuel
a) Fuel density is the most critical factor, as increase in density reduces flame throw for PF boilers, reduces fluidization in FBC, AFBC & CFBC boilers, reduces fuel flows
b) The PA Fans are designed for the fuel density & volume delivery
c) The furnace dimensions (more width or height) are determined again by fuel density & volume delivery
d) The FD fans are designed for handling the fuel density & its reactivity patterns
e) reactivity and reaction efficiency of the fuel is also a function of its density, as higher density slows the combustion reactions & lower density speeds it up
f) The air & flue gas velocities are also determined as a function of fuel density
g) The air duct dimensions are also function of fuel density
h) Direct Method Efficiency of the boiler also is a dependent parameter of fuel density
i) Time, turbulence & temperature or the 3T equilibrium is a dependent parameter of fuel density
j) LOI in the fly ash, clinker, etc., density of the fuel plays a major role
k) Flue gas density which is the heat carrier in the furnace also is dependent upon fuel density
The density of the fuel commands the entire combustion process, hence it is the most critical parameter. Most of the combustion related problems arise from change in density of the fuel.
In fact 70% to 80% design work is attributed to combustion related issues, fuel handling etc..
In almost every Boiler installation, the density goes unchecked & is not reported. Many times, when I ask what is the fuel density, it is checked almost the first time ever.
Ask the OEM, what is the fuel density consideration for design.
2) The rest of the boiler, viz., bank, bed tubes, etc. fall in the reminder work
3) Critical parameter is also the steam drum size, ensure the steam drum size is big enough to hold at least 20% to 30% of the steaming capacity as water holding capacity.
When the boiler drum is small, the thermal stresses get created, as there will always be conditions where heat produced > heat absorption. If this condition occurs, if clinker is formed, it is good, as the heat has been removed through clinker.
If the clinker has not formed, then there is a good chance of the tube surfaces getting heated up, becoming red hot & become stressed, readying them for failure.
As the water is the only coolant removing the heat in the whole boiler system, water supply or its velocity >> steam velocity. This measure will keep thermal stresses at bay.
In big steam drum boilers, the boiler tube failure is a slow or remote possibility, due to more than sufficient cooling arrangement.
In small steam drum boilers, the tube failures are high, as the tubes display highest characteristics for easy erosion only when they are red hot.
Steam drum size is a determinant factor in natural circulation rates, which is never measured in Boiler operation.
4) Fuel density in usage : This is also a very critical parameter. Often it happens, that the fuel for which the boiler stands designed, is no longer available. The decisions for purchasing a fuel should include its density as a parameter, which removes much of the anxiety in operations
5) 3T condition : The Boiler should operate in 3T condition, this is most critical parameter in operation
If you have any comments or queries, please send to sap@chargewave.in
SAP
I must say, I thought this was a pretty interesting read when it comes to this topic. Liked the material. . .
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