Why we use boiler ?
A boiler is a device used for generating:
a) Steam for power generation
b) Hot water for heating purpose
PRIMARY REQUIREMENT OF BOILER
The primary requirements of steam generators or
a) The water must be contained safely
b) The steam must be delivered safely in desired
conditions as regards its pressure, temperature, quality
and required rate
FACTORS AFFECTING THE CHOICE OF
The selection of type and size of a steam boiler depends upon
the following factors:
The power required and the working pressure
Geographical position of the plant
Availability of fuel
Supply and quality of feed water
The probable load factor
Steam pressure and superheat desired
The Boilers may be classified as under:
Horizontal boiler, vertical or inclined boilers
Fire tube and water tube boilers
Externally fired and internally fired boilers
Forced circulation and natural circulation boilers
High, medium and low pressure boilers
Stationary boiler and portable boiler
Single tube boilers and multi tube boilers
Its a pump which is used to
deliver feed water to the boiler.
The appliances in common use
for delivering the feed-water
into the steam boilers are:
a) Reciprocating pump
b) Rotary pump
The function of an injector is to feed water into the
boiler. It is also used where the space is not available for
the installation of a feed pump.
An economizer is a device in which the waste heat of the
flue gases is utilized for heating the feed water.
Economizer are of two types :
Independent type, and
The function of the air pre-heater is to increase the
temperature of air before it enters the furnace.
It is generally placed after the economizer.
HORIZONTAL, VERTICAL OR INCLINED BOILER
If the axis of the boiler is horizontal, the boiler is called
horizontal if the axis is vertical, it is called vertical boiler
and if the axis is inclined it is called as inclined boiler.
The parts of horizontal boiler is can be inspected and
repaired easily but it occupies more space. The vertical
boiler occupies less floor area.
FIRE TUBE BOILER
In the fire boilers, the hot
gases flows inside the tubes
and the water surrounds the
Relatively small steam
capacities (12,000 kg/hour)
Low to medium steam
pressures (18 kg/cm2)
Operates with oil, gas or
Fire tube boiler is so easy to use, operate, clean and
Fire tube boiler can be used in small scale industries.
Fire tube boiler is relatively cheaper than water tube
A fire tube boiler costs 25 to 40 percent less than a
comparatively sized water tube boiler.
The fire tube boiler can not produce steam at a
pressure higher than 250 pounds per square inch.
Capacity of generated steam is limited. Fire tube
boilers are limited to approximately 2,500 HP, or
about 86,000 lb/hr.
Steam quality less as compared to WTB
WATER TUBE BOILER
In the water tube boilers, the
water is inside the tubes and
hot gases surround them.
Used for high steam demand
and pressure requirements
Capacity range of 4,500 –
enhanced by induced draft
Lower tolerance for water
quality and needs water
To operate boiler at a high capacity, the water tube
packaged boiler is best.
Water tube boiler packages are designed to handle larger
capacities, up to approximately 650,000 lb/hr, which is
equivalent to about 19,000 HP.
A water tube boiler also is superior for high temperature
and steam pressure.
It can operate at pressures up to 1,500 psi.
For large-capacity loads, large design pressure
requirements, tracking rapid load swings or extreme
horsepower needs, the water tube boiler essentially is the
EXTERNALLY FIRED AND INTERNALLY FIRED
The boiler is known as externally fired if the fire
is outside the shell.
In case of internally fired boilers, the furnace is
located inside the shell.
FORCED CIRCULATION AND NATURAL CIRCULATION
In forced circulation type of boilers, the circulation
of water is done by forced pump.
In natural circulation type of boilers, circulation of
water in the boiler takes place due to natural
convention currents produced by the application of
HIGHER PRESSURE AND LOW PRESSURE
The boiler which produce steam at pressures of 80
bar and above are called high pressure boilers.
The boilers which produce steam at pressure below
80 bar are called low pressure boilers.
STATIONARY AND PORTABLE
Primarily, the boilers are classified as either
stationary or mobile.
Stationary boilers are used for power plant steam,
for central station utility power plants, for plant
process steam etc.
Mobile boilers or portable boilers include
locomotive type, and other small units for
temporary use at sites.
SINGLE TUBE AND MULTI TUBE BOILER
THE fire tube boilers are classified as single tube and
multi-tube boilers, depending upon whether the fire
tube is one or more than one.
1. Boiler Performance
2. Boiler blow down
3. Boiler feed water treatment
ASSESSMENT OF BOILER
• Causes Of Poor Boiler Performance
- Poor combustion
- Heat transfer surface fouling
- Poor operation and maintenance
- Deteriorating fuel and water quality
• Heat Balance : Identify heat losses
• Boiler Efficiency: Determine deviation from best
BOILER BLOW DOWN
• Controls ‘total dissolved solids’ (TDS) in the water
that is boiled
• Blows off water and replaces it with feed water
• Conductivity measured as indication of TDS levels
• Calculation of quantity blow down required:
Feed water TDS x % Make up water
Maximum Permissible TDS in Boiler water
• Lower pretreatment costs
• Less make-up water consumption
• Reduced maintenance downtime
• Increased boiler life
• Lower consumption of treatment chemicals
Boiler Feed Water Treatment
Quality of steam depend on water treatment to
Efficient heat transfer only if boiler water is free
from deposit-forming solids