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