Critical factors in Boiler Design & Operation

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

Fuel Additives -- Are they necessary ?

What are Fuel Additives
Fuel Additives are organic or inorganic chemical formulations mostly employed for the LOI reduction, clinker problems, reducing O2 in combustion, in Boilers.The formulations come in as liquids & powders or even as sticks.

What is the role & function of Fuel Additives in combustion ? Actually speaking none.

Boiler Operation Types
There are 27 distinct Boiler operation types, methods or conditions.
Out of these 13 cause higher flue gas or air velocity, another 13 cause deficient flue gas or air velocity. The 27th condition is where the flue gas velocity is neither higher or lower, it is exact.

Air or Flue gas velocity impact
Increased air velocity ejects the fuel out of the system & deficient air velocity produces un-burnt carbon. However both get classified as LOI.

How to check air velocity ?
When the LOI is segregated & checked for Volatile matter presence, the air velocity behaviour can be verified.

If the LOI shows VM presence, the boiler is working with higher air velocity & is ejecting the fuel out.

If the LOI shows no VM presence, the boiler is working with deficient air velocity.

For boilers where switching between high load & low load is frequent, the VM presence will be 50-50, means present in some samples & absent in some samples.

Fuel Additives -- Limitations
Fuel Additives can perform some what in the 13 conditions where there is deficient flue gas velocity. Deficient air velocity produces Fixed Carbon, no volatile matter ash which require higher combustion temperature.

However in the rest 14 conditions, there is no effect of Fuel Additives whatsoever.

If the Boiler employs a fuel additive and there is some result attributed, then the possibility is that the operation is of deficient air velocity types.

Clinker Problems -- the Truth & the Story
The ash fusion temperature, chemistry of fuel, ash, iron etc, causes clinkers is a good story. The truth is that deficient air velocity can only produce clinkers.

Deficient air velocity operations, produce Fixed carbon in Ash & also have clinker problems.

Deficient air velocity is produced by increased bed height or bed thickness, improper settings of PA, FD.

Clinker formation is caused primarily due to low FD or PA pressure & increased bed height.

The heat energy is like water, it flows. When the flue gases cannot pick up the heat due to low velocity, the heat flows to the ash & forms clinker.

The only heat carrier in the boiler is the flue gas only & it has to flow quite clear.

In some cases, the bed volume itself is very low, however the operating load of the boiler will be higher, meaning lower bed volume handles more heat energy, when load drops & heat has no flowing opportunity to water side, it flows to fuel and causes clinker.

I have solved many clinker formation problems in CFBC, AFBC, FBC, Manual fired boilers, by correction of bed thickness & air pressure.

Lowering O2% while using a Fuel Additive
Some Fuel Additive formulations have O2 releasing compounds, which release O2 or nascent Oxygen. The density of the flue gas is a very important parameter in heat carriage. If the density is higher, it carries more heat & vice versa.

When O2 is reduced due to Fuel Additive usage, the results may be good for Indirect Method assessment, which shows increase in Efficiency, however the reaction conditions will take a good beating, along with flue gas density.

Many times, reducing O2%, only will cause increase in fuel consumption & lower Direct Method Efficiency.

Where there is measurement of fuel, the activity of lowering O2% can be discarded, as the effect of increased consumption can be noticed.

However where is no measurement of fuel or the installation follows Indirect Method, the real effect cannot be known till very long time, as there is no counter check or verification.

Do Fuel Additives reduce fuel consumption ?
If there is LOI, due to deficient air velocity operations, Yes to an extent of 0.2 to 1%, as per the scale of LOI occurrence.
In all other cases, they have no effect

Fuel Additives are Combustion Catalysts ?
The Combustion reaction itself, happens very quickly. Catalyzing already an over speeding reaction only worsens the case. 
When already the combustion is suffering, employing a catalyst, only increases the suffering.

Will increased reactivity improve the combustion ?
Yes. Only in 3T condition. A Fuel Additive cannot produce a 3T condition.
3T condition is a physical reaction environment condition produced by fans, WBP & fuel

IS CATALYSIS OF COMBUSTION REACTION REQUIRED ?
Not at all. Only correction of reaction conditions is required, which takes care of every thing.

How to eliminate Fuel Additives usage

Fuel Additives are only needed when there are incorrect Boiler operation which cause deficient air or flue gas velocity. 

Deficient air velocity correction or boiler switching to 3T operations, eliminate usage of Fuel Additives, once & for all.

In 3T condition,
1. the air velocity is exact, therefore raising the reaction efficiency of Carbon & oxygen
2. high reaction efficiency conditions or environment exists, the LOI is automatically near zero
3. the air pressure is right, the clinker formation also gets eliminated

Fuel Additives are not needed, however become compulsive due to improper operational issues.

The above information is for solid fuel fired boilers.

For Oil fired & Gas fired Boilers
Turbulence correction or 3T operation, eliminates all the combustion issues


Any comments write to sap@chargewave.in

SAP

Power Plants CO2 emissions -- Challenges & Opportunities

In the present moment, the CO2 emissions are taking center stage in every discussion. What are the challenges & opportunities ?

Challenges : As the power demand is ever increasing, so are the CO2 emissions as most of the plants are either coal or biomass based ones

What are the opportunities for CO2 reduction ?
Is the CO2 capture alone the solution ?
Are there any other options ?

While CO2 capture is expensive to invest, the cheapest alternative is to employ the 3T (time, turbulence, temperature) equilibrium condition in Boiler Operations.

What 3T can achieve is much bigger as an immediate alternative, as it brings down the Boudouard Reaction to within the theoretical limits and the fuel consumption itself is reduced.

While the CO2 emission is directly proportional to the fuel employed per ton of Steam, when the fuel consumption itself lowers, the CO2 gets lowered too.

We also manufacture chemicals, which can block Boudouard Reaction & lower the fuel consumption.

Together 3T + chemicals the is maximum reduction option at hand.

The biggest challenge is not measuring the fuel or its GCV and the employment of Indirect Method.

Unless the Indirect Method is debated, unshackled, understood & restructured, the possibility of CO2 emissions reduction is remote.

Any queries ?

You can contact me at sap@chargewave.in

SAP

Thermal Efficiency & Indirect Method -- Limitations & Opportunities

Thermal Efficiency -- Limitations & Opportunities

Thermal Efficiency, is a term which has to be clearly understood in relationship with Boiler Operations.

What does it indicate ?
1. Boiler is first a carbon & oxygen reactor, where the energy generation is taking place
2. After the energy is generated, it is exchanged throughout the boiler in different thermal zones

So, we can measure two efficiencies based upon 2 different phenomenon

1. Efficiency of the reaction (carbon & oxygen reactor)
2. Efficiency of the heat capture or heat exchange

The Indirect method focusses on Efficiency of heat exchange part and assumes 100% energy is generated from the combustion of fuel.

What is considered in the Indirect Method
Losses from stack, LOI, radiation, blowdown, moisture, Hydrogen etc., so these are the energy losses what the boiler cannot capture.

Where is the energy generation here ??? 
Energy generation has no mention. 100% energy generation is an assumption. 

What is ignored in the Indirect Method

 Reaction conditions created in the furnace by the fans
 Reaction Efficiency of Carbon & oxygen
 Boudouard Reaction (CO2 + C --> 2CO -- 6000 Kcal / Kg) condition assessment
 Actual measurement of energy generated in the reaction

My question is why assume that Energy generated is 100% ?. What is the guarantee that it has been generated & is available ?

If the Boudouard Reaction is higher than the theoretical limit, more heat is consumed in the Endothermic reaction & less is available for heat transfer.
 
If only 85% energy has been generated in the furnace, then 85% minus losses will be the Thermal Efficiency.

Can the formula be modified to Heat generated minus Losses = Thermal Efficiency ? to include what they have forgotten ?

CO2 is measured & assumed that it is formed by C + O2 reaction only, where as there are two routes for CO2 formation, one directly by C + O2 reaction & another by 2CO + O2 reaction.

The question is how heat capture efficiency can explain heat generation as an assumption, when there are two distinct processes happening.

Is heat absorption more critical than its generation ?
Is the reaction condition not at all important ?
Is the heat generation so simple and easy that it could be assumed to be 100% always ?


Questions ?
I was asked at one of the presentations, that the Indirect Method is the only reliable method to assess the Thermal Efficiency ?

I replied, how the boiler designer would assess the efficiency on the drawing board or at the designing stage ?
Is the Indirect Method assessment the only way after commissioning of the Boiler, for derivation ?
How the designer would know, the efficiency at the design stage ?
Is there another possibility or processes of derivation ?

In fact, the Boiler has to have the necessary combustion air + excess air. How do we assess this ? In the boiler if you reduce excess air, combustion air is also reduced, & when it happens it promotes Boudouard Reaction.

Higher Thermal Efficiency by design is a factor of excess air, lower the excess air, higher is the heat capture, this is an offshoot of heat exchanger.

Does higher Thermal Efficiency mean the reaction efficiency is high enough ? Not at all.

There are 27 different or distinct ways or methods, a boiler can be operated, in which only 1 method aligns the 3T's & the rest do not.


Interesting facts about Indirect Method
1. Even if the load of the boiler is 10% or 20% or < 60% or 100% the Efficiency is always higher than 82% plus & does not change
2. Design Efficiency of the boiler can be exceeded in this method ?
    Several commissioning reports of boiler installations & also in Energy Audit reports, this is observed, is this true ?
3. Can the boiler function higher than its design efficiency ?
4. 100% energy generation is assumed in 100 minus losses formula
5. Fuel, GCV of fuel can be back calculated without consideration to reaction efficiency, actual fuel GCV or actual fuel quantity fired
6. Time, turbulence & temperature equilibrium present or absent, it has no effect on heat generation
7. In precise measurement of fuel, fuel GCV, the Thermal Efficiency is always greater than Direct Method Boiler Efficiency
8. In all the 27 types of Boiler operations, the Indirect Method shows similar values
9. Lesser Direct Method Efficiency does not raise the stack temperature or other losses (again indicating it is a measurement of heat exchange capacity)
10. Fuel density, furnace draft, operating loads etc. have no impact on the Efficiency

Is the Indirect Method so efficient ?
1) does it mean that there is no need to use Bomb Calorimeters, fuel measurement systems, Boiler instrumentation ? Is the design enough ?
2) does it mean that it has all solutions for combustion problems ?
3) does it mean following the Indirect Method has no validation system vis-a-vis measurement of fuel & its CV


Why is the Indirect Method followed ?
1) Heat exchange capacity of the Boiler does not change & very stable
2) It is easy to report & measure
3) Everyone says it is scientific so, it has to be
4) Everyone follows it
5) No one asks for validation, includes Managements, Auditors, Operators
6) Method is recommended by OEM's & Auditors
7) Fuel quantification & its CV have lot of variations, is cumbersome which justifies not validating it & hence forth skipped altogether
8) Reason no. 7 justified & supported by OEM's, Auditors & others irrespectively 

It is a fact that in 98% of the installations, the Indirect Method cannot be validated in the input fuel or its CV, as the boilers function at much lower efficiency than what is factually reported. Observations show that the fuel quantities & its CV's are tailored when Efficiencies are low.

If the Indirect Method cannot be validated in the input fuel or its CV, why do we follow it in the first place ?


Fuel can be measured precisely by weight by bunker weighing systems instead of belt weighing systems which have errors, stacking fuel in separate identifiable lots, will resolve fuel measurement. Frequent sampling from feeders & increasing no. of samples, will lower the error in the CV measurement.

A bold, factual assessment will reveal all the short comings of the Indirect Method, open opportunities for correction & cost savings.

The reverse ash reconciliation method also can be employed, to calculate the coal input. There are options for measurement, however they have to exercised.

Its time, there is a thorough review of this method, which does not allow actual heat generation assessment in the Boiler & change the operations which support the 3T condition.

What if the the formula is changed to

"Heat generated minus Losses = Thermal Efficiency %"

Heat generated = Fuel Quantity x Fuel CV
Losses = The same as in the Indirect Method

A MAGIC WILL UNFOLD WITH LOT OF OPPORTUNITY 

Opportunity to see a great magic in the above formula, as the heat generated can be increased by invoking the 3T equilibrium. I have already done this in many boilers. There is a great cost saving when you adopt the above change.

It is not all that difficult, it is the first step to Boiler Operation mastery.

Start the step for fuel measurement & the guarantee is that you can save a min. of 4 to 5% fuel in this method. The average saving I got is > 8% till date, only by tuning the boilers for 3T.

If you have questions, please write to sap@chargewave.in

Regards
SAP

TurCom Software -- Run Highest Boiler Efficiency in Direct Method

TurCom Software

Welcome to the world of Boiler Operations.

Introduction : There are 27 distinct Boiler Operation combinations that can be derived from

1) One PA or FD fan, One SA fan & Wind Box Pressure, for CFBC Boilers
2) One PA fan, One FD fan & Wind Box Pressure, for AFBC Boilers
3) One FD fan, One SA fan & Wind Box Pressure, for FBC Boilers
4) One FD fan, One SA fan & Wind Box Pressure, for Stoker Boilers

PA fan can be operated as PA Exact, PA High, PA Low
FD fan can be operated as FD Exact, FD High, FD Low
SA fan can be operated as SA Exact, SA High, SA Low
WBP can be operated as WB Exact, WB High, WB Low

Only one combination PA Exact, FD Exact, SA Exact & WB Exact is the right combination, in consideration to the input fuel density & this combination produces, the 3T (time, turbulence & temperature) alignment.

All other combinations do not align the 3T's. Most of the other combinations either produce excess air or flue gas velocity or deficient flue gas velocity.

Only in 3T condition the following results are possible
1) Highest Efficiency in the Direct Method
2) Lowest LOI
3) High reaction efficiency of Carbon & Oxygen
4) Real or true excess air in the stack
5) Lowest consumption of Coal or biomass
6) No adjustments needed for Coal or Biomass CV or their quantities to match the Indirect Method Efficiency
7) Very low erosion for FBC, AFBC & CFBC boilers
8) Perfect air & flue gas velocities
9) All thermal zones take their place (no zone shifts)

Do the DCS or any other software which is available today, measure the 3T's ?

No.They dont. The DCS's today are offer more functional control rather than give a picture of what's right or not in the system.

The 3T's has been a Boiler operation concept for very long time, many times heard in lectures & never ever in operational experience or assessments.

TurCom, gives you that strength of 3T alignment, what is missing out in the entire Boiler operation & knowledge spectrum.

TurCom Introduction : TurCom is a software which calculates the 3T's alignment or misalignment & then guides the operator for adjusting the fans & WBP to deliver the objectives.

Advantages of TurCom :
1) No learning curve or experienced operators required for operations
2) Boiler is very stable
3) Lowest LOI
4) Operation flexibility of fuels
5) High Efficiency in the Direct Method
6) Low erosion as excess or deficient air or flue gas velocities are corrected
7) Straight advisory
8) Lowest costs in energy as every calorie the fuel offers is extracted

TurCom is available as 3 options
a) Consultancy
b) Software Installation
c) Software Installation + proof of performance

If you have any questions, please write to sap@chargewave.in


PS Anand Prakash

O2 in Stack, True or False value ?

Oxygen Measured in Boiler Stacks -- Is the captured value true or false ?

Consider the Reaction C + O2 --> CO2, the following conditions are available in the furnace

Condition     Carbon         Oxygen          Carbondioxide      Reaction

       1             Reactive          Reactive           100% probability      Successful

       2             Reactive          Non-reactive     0% probability         Fail

       3             Non-reactive   Reactive            0% probability         Fail

       4             Non-reactive   Non-reactive     0% probability         Fail

In the boiler furnace only 25% probability exists for a successful carbon & oxygen reaction.

What if conditions 2, 3 & 4 are present in the furnace, then the following is probable

a) Carbon showing up as LOI
b) Reaction failure O2 shows up as a component of excess air

Hence the indication of O2% in stack, may not be true if the reaction conditions are not examined & also if LOI is present.If LOI is present, the fact is that there is reaction failure O2 showing up as excess air.

So, what is excess air now ?. True excess air is obtained only when the LOI is near zero, till then it is only a mixture of excess air + reaction failure O2.

How do we achieve true excess air ?
Can be achieved by synchronizing 3T's, time, turbulence & temperature.
In 3T alignment, the reaction condition 1, prevails.

There are 27 types of Boiler Operation combinations considering
1) PA or FD Fan, SA Fan & WBP for CFBC boilers
2) PA Fan, FD Fan & WBP for AFBC boilers
3) FD Fan, SA Fan & Bed thickness for Stoker boilers
4) PA Fan, FD Fan & WBP for PF boilers

In 26 Boiler operation combinations conditions, improper reaction conditions reign & reaction failure O2 shows up as excess air.

How to recognize, that the O2% indication is true excess air ?
If 
         1. LOI is near zero for CFB & PF boilers
         2. LOI is < 2% for AFBC & FBC boilers
         3. LOI is < 4% for Stoker Boilers
         4. Direct Method efficiency is 1.5% to 2% less than Indirect Method Efficiency
         5. No adjustments made for CV of coal, Coal quantity or Steam quantity & real data has been considered
         6. 3T's are in alignment

If you have any questions on the same, write to me at sap@chargewave.in

Thanks for reading

PS Anand Prakash

Boiler Automation Equipment to run the FBC, AFBC, CFBC Boilers Efficiently in Direct Method

After years of solving combustion related problems in FBC, AFBC & CFBC boilers, I have developed an algorithm to calculate required turbulence for given boiler design & operating fuel.

Turbulence in the boiler is the key vertice in the triangle of Turbulence -- Time & Temperature.

It is the turbulence which controls rate of reaction of C & O2, & responsible for Reaction Efficiency of C & O2.

If turbulence is high, it leads to unburnt fuel being shot out of the bed, incorrect reaction efficiency, higher fuel consumption, higher Boudouard reaction, incorrect draft.

If turbulence is low, it leads to unburnt carbon being generated in the bed, incorrect reaction efficiency, higher fuel consumption, higher Boudouard reaction, adjusted draft.

Detailed analysis of turbulence conditions show that the boiler can be operated in 27 turbulence combinations.

Out of the above combination 26 attribute to incorrect operation contributed by increased or reduced fuel density, bed height, bed density, incorrect fans settings, furnace draft  & only 1 combination corresponds to the right operation of the boiler.

This means the boiler can be operated incorrectly in 26 ways & it can never be realized unless the last option is exercised which is the correct one.

Trial & errors can be eliminated directly with an equipment which can provide guidance in setting right the turbulence in the system.

The system which is being run following the Indirect method of Boiler Efficiency often fall into the trap of these 26 incorrect ways, since the Indirect Method is incapable of detecting operational probabilities.

If interested the equipment is available as a stand alone Automation System, or Add on to an existing operation system, which on command can take over the operation & set it perfectly.

For an Add On system, this equipment requires entire boiler design data & will capture the operational data from the DCS & then advise the operators to correct the operations.

Any inquiries can be sent to sap@chargewave.in or sashank@exaact.co