Thursday 22 November 2012

FUEL Combustion & Control IN BOILER

Combustion & Control

What are the most important factors influencing the combustion process?
What if any of these factors is not correct?

How do you determine whether the combustion in a boiler is with too little air or excess air, or good combustion, just by looking at the stack (chimney)?

Your boilers flue gas temperature went up.  Give reasons for this.

Discuss need of providing excess air for combustion.  What is the disadvantage of providing too much of excess air.
Does excess air in combustion affect boiler efficiency?
How do you calculate the percentage of excess air?
What is the excess air required when burning natural gas? Why excess air is required in combustion?
What is the excess air required when burning fuel oil? Why excess air is required in combustion?

What are the causes of incomplete combustion of solid, liquid, and gaseous fuels?
What is the composition of natural gas?
What are the properties of medium fuel oil (MFO)?
What is the percentage of CO2 if burned in natural gas?
What are the advantages and disadvantages of natural gas compared with fuel oil?
Why does combustion efficiency of natural gas lower than for fuel oil?
What is the dry composition of the flue gas?
What is stoichiometric combustion?
What is fully automatic burner?
What are the features every fully automatic burner should have?
What is a semi-automatic burner?
What are the features every semi-automatic burner should have?
What is the equation of combustion for MFO?
What is the equation of combustion for Natural Gas?
What is pulverized coal and fluidized bed?

What is the equation of combustion for Natural Gas?  How much CO2 and H2O is released if 1 kg of natural gas burned? How much combustion air is required?

What do you find in flue gas analysis?  Explain
What is NOx and what effect does NOx have to the environment?
What is the most reliable means of analyzing flue gas? Describe its function.
Which is the more reliable indicator of excess air, CO2 or O2? Give your reason.
What is the difference between “flash point” and “fire point”?
What is Pensky-Martens apparatus?
What is “closed flash point” and what is the minimum temperature of flash point of any fuel fired in a steam boiler, and why?
Why is the knowledge of flash point important?
What is the flash point of natural gas and is natural gas more dangerous than fuel oil in term of flash point?
For fuel oil and NG combustion, natural gas such as methane or butane is used for a pilot.  Give two reasons gas is used for a pilot?

When firing boiler from cold, when steam is still not available, how would you atomize the oil?
Why it is not recommended to open the damper wide during lighting off boiler?
Why is it necessary to ensure the damper at minimum firing position before firing?
What is the purpose of diffuser plate (or impeller plate) in a burner? Are burner register and diffuser are the same?
What is burner turndown ratio?
Is burner with high turndown ratio good?
List the safety devices used with an automatic combustion control.

What does the term “ramp rate” on boilers mean?

What are the three ways to control combustion output?
What are the types of oil burners used in modern boilers?
What are three ways to atomize oil?
Describe the steam-atomizing burner in detail.
Describe the pressure-jet (Mechanical pressurized atomizing) burner.

What difficulties can be affected with water in fuel oil?

Describe the rotary-cup (rotary-atomizing) burner.

What is the maintenance required to oil burners?
What is a flame failure indicating device, and what are the three most commonly used flame scanners?
What is the function of a flame detector? How do you maintain the photocell to perform satisfactorily?

Between ultraviolet and infrared (IR) flame scanners, which is most frequently used and why?

What are the types of gas burners used in modern boilers?
What is the difference between rotary soot blower and retractable soot blower?
There are 2 types of soot blowers, stationary and retraction. Where would you install the stationary and where would you install the retraction soot blower in a watertube boiler?
What is soot?
Why is soot blow important?
How do you operate soot blower?

Why is it important to have soot blower for superheater tubes?

Why is it important to have soot blower for superheater tubes?

What is the harmful effect of sulfur in a fuel?
What is the harmful effect of vanadium in a fuel?

How do you manually clean soot from the firetube boiler, and how often?
Can soot blowing cut tubes?
What is the frequency for soot blower?
What are the designs of soot blowers?
Describe precautions to be taken when using soot blower.
What is sonic soot blower? What is the advantage of sonic soot blowers used in boilers or economizers?
What is “flame-brushing”?
How does a smoke density meter work?
What functions does draft play in the combustion of fuel?
Name and explain three types of draft.
What do you understand by “balanced draft”?
Why must the draft be carefully controlled?
Show the installation of force-draft fan in solid fuel boiler
Show the installation of force-draft fan in liquid/gas boiler.
What is the sequence of stopping the draft fan?
Have you heard about clinkers in solid-fuel boiler? How do you prevent clinkers from happening?
What are the HEAT losses on a boiler?   Name seven and explain each loss.
What are the factors to consider when calculating steam cost dollar per ton product?
What is the difference between m3, Sm3 and Nm3?

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