boilers basics
TRANSCRIPT
BOILERBoiler is a closed fired pressure vessel
for Generating Steam
Hot Pressurized Water Vaporizing Fluid
THE BOILER
PARTS
Boiler has two types of components
Mountings&Accessories
MOUNTINGS
Mountings are the components that are required to operate the boiler regularly and to examine the process and conditions to operate in a proper way safely
Essential part of boiler
Mountings includeSafety ValveCheck ValvePressure GaugeTemperature GaugeLevel Glass
SAFTY VALVE
It releases the extra steam generated so that bursting is safe
CHECK VALVE
Check valve controls the one dimensional flow and let not allow fluid to be back on same side
PRESSURE GAUGE
Indicates the pressure so easy to check the presser of steam and if some wrong to designate and see the real problem to resolve
TEMPARATRE GAUGE
Indicates temperature may e a outlet or if more are there at different stages like flue gas and furnace
LEVEL GLASS
It Indicates the level of water in steam drum so that if the level is fluctuating it should e controlled
ACCESSORIES
Accessories improves the efficiency of boiler by value addition via processing the steam or may be the heat going to be lose
Auxiliary to Boiler
These includeSuper HeaterAir Pre-HeaterEconomizerFeed Pump
SUPER HEATER
Super Heats steam for process at outlet of steam drum to dry it at certain temperature
AIR PREHEATER
Heats air before entering to make air fuel mixture to achieve temperature as soon
Exhaust gases are used for heating urpose
ECONOMIZER
Preheats water before entering to the drum
Exhaust gases are used for heating
FEED PUPM
Feeds water at a pressure to steam drum more than seam drum
Used for forces circulation
BOILER CLASSIFICATION
Boiler are classified according to some criteria likeMaterialPressureTube Contents
MATERIAL
Cast Iron BoilerTheses are castled and are solid piecesWere used long ago
Steel BoilersThese are made by steel sheet rolling,
welding and rivetingThese days mostly in use
PRESSURE
On Base of pressure we can classify Low Pressure 25 Kg/cm2
Medium Pressure 40 High Pressure 100 Sub Critical 140 Super critical 170
TUBE CONTENTS
The classification on base of tube contents is as below
Fire Tube Water Tube
Fire Tube
The water is in drum and flue gases in tubes
Water tube
The water in tubes and flue gases on outside of tubes
DRY & WET BACK
This is sub classification of Fire tube boiler on the bases of reversing chamber type
DRY BACK
The reversing chamber is dry (insulated)
WET BACK
Reversing chamber side is water in drum that makes it more heat transfer rate for higher efficiency
BOILER DESIGN
When boiler is designed it consist of two portion
o Thermal designo Mechanical design
THERMAL DESIGN
In thermal design we have the input data as steam fuel composition, outlet temperature, feed temperatures, pressure, evaporation rate, load consideration
Here we assume some parameters and stat our calculations
By using iteration we calculate some parameters as BOT
In thermal balance we see that our assumed parameters fulfill the condition or not here we have 2-3 % error to avoid he calculation confliction
Then we see furnace and each pass separately to calculate their temperatures and other parameters
MECHANICAL DESIGN
Here on base of our desired shape of boiler using SME code we calculate for the stresses and thickness of all components like
furnaceShellTubesStay rods
ASME
American Society of Mechanical Engineers founded in 1880
Responsible for coding and standardizing about boilers and pressure vessels
STAMPING
For manufacturers they should have facility to fabricate the boiler according to the ASME code to fulfill the international standard
STAMPS
Power BoilerMiniature boilersElectrical boilersBoiler assemblyWelded PipingSafety valve
BOILER APPLICATIONS
Boiler are used in almost all types of industry
HEATING
For central heating of buildings where open firing is dangerous
ENGINE DRIVING
Steam is used to drive engines as in MERINES
Also to drive reciprocating machines
PWER GERATION
Boilers are widely used for power generation at power stations
PROCESS INDUSTRY
In process industry for many purposesWashingPurificationConcentrationProcess Activation
EVAPORATION
Boiler is used to evaporate some fluid for process where that have to be injected in vapor form
Like NH3 in fertilizer plant is injected in vapor form so the fluid used in boiler will be NH3
BOILER CLEANING
When boilers work for a long time then it need cleaning because with time the deposition of insoluble contents are there to decrease efficiency of boiler
So scheduled cleaning is performed
WTB CLEANING
In water tube boilers the smoke that is on fire side. That deposition is to be removed for proper functioning
There is a nozzle provided on fire side there the steam under pressure is fired over the outside of tubes that washes that fumes
MECHANICAL CLEANING
Fouling is the deposition of insoluble contents of water that are here in tubes and drums that causes the reduction of heat transfer so that is cleaned by mechanical means of scraping or vibrations
CHEMICAL CLEANING
The deposits are acidic in nature so the asdic solution is added to the water and filled boiler then heating to a certain time the depositions are solved in water then that water is removed and after washing the boiler it is again ready for use
FIRETUEB BOILER CLEANING
Small fire tube boiler does not need cleaning but if the cleaning is desired then it is washed to use again
BOILER PROBLEMS
Problems in boiler can be
Thermal or
Operational
DESIGN PROBELMS
When the boiler is to design we have some problems like
Thermal BalanceSulpher ContentsEfficiency AchievementAir Leakage
THERMAL BALANCE
For thermal iteration procedure we assume a temperature ad then we define the thermal properties to calculate the temperature again to get exact value of temperature
Ideally these are equal but in real we can have 2-3 % error allowance to avoid from too much complicated calcualtions
SULPHER CONTENTS
The presence of Sulpher in fuel which after burning causes SO3 during combustion. With reaction of water to this it will result corrosive H2SO4
BOT is taken higher than Due Point of Sulpher
OPERATIONAL PROBLEMS
When boiler is working there so many problems are to face and they must be immediately to resolve or made safe before the boiler is let to start
Operational problems areInefficient CombustionBack FiringProcess DynamicsExplosionAdjustment of Air Fuel ratioPower failure & Shut Down
INEFFICEINT COMBUSTION
Non homogeneous mixture of fuel due to mechanical parts or Non availably of fuel contents in combustion zone causes inefficient combustion
So proper equipment is to be used
BACK FIRING
Continuous running of boiler some times causes the low velocity of flue gases than the combustion flam that results in travel of flam to the chimney and firing sounds can be heard
Explosion door is provided that efficiently breaks that pressuedriffrence
PROCESS DYNAMICS
Process variables like Level, Pressure, Temperature fluctuate during its operation so the associated problems occurs and they should have be controlled
LevelPressureBlow DownWater QualityPower failureShut Down