Water Treatment & Chemicals for Boiler Water Systems

Boiler is an apparatus to produce steam.

Thermal energy released by combustion of fuel issued to make steam at the desired temperature and pressure.

The steam produced is used for : 1). For generating power in steam engines or steam turbines. 2). Heating the residential and industrial buildings. 3). Performing certain processes in the sugar mills, chemical and textile industries.

BoilerBoiler

• The working pressure & quality of steam.

• Steam generation.

• Floor area available.

• Accessibility for repair & inspection.

• Comparative initial cost.

• Erection facilities.

• The probable load factor.

• The fuel & water available. Operating &

maintenance cost.

Selection of boiler

a). Safety : The boiler should be safe under the operating conditions.

b). Accessibility : the various part of boiler should be accessible for

repair & maintenance.

c). Capacity : Should be capable of supplying Steam according to the

requirements.

d). Efficiency : Should be able to absorb a maximum amount of heat

produced due to burning of fuel in the furnace.

e). It should be simple in construction .

f). Its initial cost and maintenance cost is low.

g). It should be capable of quick starting and loading .

Boiler properties

•A boiler is used to heat water and generate re- quired steam or hot water

•There are various types of boilers according to their uses, boilers are classified according to :

1.their structures,

2.the methods of water circulation,

3.the types of fuels,

4.the kinds of the materials used

Types of BoilerTypes of Boiler

The boiler may be classified as :

a.Horizontal, vertical or inclined

b.Fire tube & water tube

c.Externally fired & internally fired

d.High pressure & low pressure

e.Forced circulation & natural circulation

f.Stationary & portable

g.Single tube & multi tube boilers

Classification of Boilers

If the axis of boiler is horizontal, the boiler is called

horizontal.

If the axis is vertical then it is called vertical.

If the axis is inclined then it is called inclined.

Advantage of horizontal boiler:

a.it should be repaired easily.

b.occupies less floor area.

Disadvantage:

a. it occupies more space

a. Horizontal , vertical or inclined

In the fire tube boiler the hot gases are inside

the tubes & the water surrounds in the tube.

ex. Cochran, locomotive etc.

In the water tube boiler the water is inside the

tube & the hot gases are surround them.

ex. Stirling

b. Fire tube & water tube boiler

The boiler is known as externally fired if the fire

is outside the shell.

ex. Babcock & wilcox

In case of internally fired boilers, the furnace is

located inside the boiler shell.

ex: cochran, lancashire etc.

c. Externally & internally fired boiler

 In forced circulation type of boilers the

circulation of water is done by forced pumps.

ex. Velox, lamont

In natural circulation type of boiler the

circulation of water in boiler takes place due to

natural convention. ex. Lancashire, babcock

d. Forced circulation & natural circulation

 The boilers which produce steam at pressure

of 80 bar and above are called high pressure

boiler.

ex. Velox

The boiler which produce steam at pressure

below 80 bar are called low pressure boiler.

ex. cochran

e. High pressure & low pressure boilers

 Stationary boilers are used for power plant-

steam, for central station utility power plants,

for plant process steam etc.

Portable boilers are include locomotive type &

other small units for temporary use at sites.

f. Stationary & portable boilers

The fire tube boilers are classified as single tube

& multi tube boilers, depending upon the fire

tube is one more than one.

Ex: cornish boiler

g. Single tube multi-tube boilers

In general, they are roughly classified into :1.cylindrical boilers and 2.water-tube boilers

Boiler mainly classified as: a.fire tube b.water tube

Types of BoilerTypes of Boiler

a.

Fire tube boilerFire tube boiler

• Horizontal return fire tube boiler is most suitable for low capacity thermal power plant.

• The main constructional features of this boiler are one big size steam drum which lies horizontally upon supporting structures.

• There are numbers of fire tubes come from furnace and also aligned horizontally inside the drum. When the drum is filled with water these tubes are submerged in water.

Fire tube boilerFire tube boiler

• Horizontal return fire tube boiler is most suitable for low capacity thermal power plant.

• The main constructional features of this boiler are one big size steam drum which lies horizontally upon supporting structures.

• There are numbers of fire tubes come from furnace and also aligned horizontally inside the drum. When the drum is filled with water these tubes are submerged in water.

Fire tube boilerFire tube boiler

• The fuels (normally coal) burnt in the furnace and combustible gasses move into the fire tubes, travel through these tubes from rear to front of the boiler drum and finally the gases come into the smoke box.

• The hot gasses in the tubes under water transfer heat to the water via the tube walls.

• Due to this heat energy steam bubbles are created and come up upon the water surface.

• As the amount of steam is increased in that closed drum, steam pressure inside the drum increases which increase significantly the boiling temperature of the water and hence rate of production of steam is reduced. In this way a fire tube boiler controls its won pressure. In other words this is a self pressure controlled boiler.

Fire tube boilerFire tube boiler

• The fuels (normally coal) burnt in the furnace and combustible gasses move into the fire tubes, travel through these tubes from rear to front of the boiler drum and finally the gases come into the smoke box.

• The hot gasses in the tubes under water transfer heat to the water via the tube walls.

• Due to this heat energy steam bubbles are created and come up upon the water surface.

• As the amount of steam is increased in that closed drum, steam pressure inside the drum increases which increase significantly the boiling temperature of the water and hence rate of production of steam is reduced. In this way a fire tube boiler controls its won pressure. In other words this is a self pressure controlled boiler.

Fire tube boilerFire tube boiler

Fire tube boilerFire tube boilerAdvantage of fire tube boiler1) Compact in construction.2) Fluctuation of steam demand can be met easily.3) Cheaper than water tube boiler.

Disadvantage of fire tube boiler1)Due to large water the required steam pressure rising time quite high.2)Output steam pressure cannot be very high since the water and steam are kept in same vessel. 3)The steam received from fire tube boiler is not very dry. 4)In a fire tube boiler, the steam drum is always under pressure, so there may be a chance of huge explosion which resulting to severe accident.

Fire tube boilerFire tube boilerRelationship between the heating surface area and the

evaporation rate of water-tube boilers

Lihat file

Relationship between the heating surface area and the evaporation rate of fire and flue-tube boilers

Lihat file

Water tube boiler Water tube boiler lihat filelihat file

• A water tube boiler is such kind of boiler where the water is heated inside tubes and the hot gasses surround them. This is the basic definition of water tube boiler. Actually this boiler is just opposite offire tube boiler where hot gasses are passed through tubes which are surrounded by water.

Advantages of Water Tube BoilerThere are many advantages of water tube boiler due to which these types of boiler are essentially used in large thermal power station.

1.Larger heating surface can be achieved by using more numbers of water tubes

2.Due to convectional flow, movement of water is much faster than that of fire tube boiler; hence rate of heat transfer is high which results into higher efficiency

3.Very high pressure in order of 140 kg/cm2 can be obtained smoothly

Water tube boilerWater tube boilerTypes of Water Tube BoilerThere are many types of water tube boiler .They can be sub-categorized in three types, namely, 

1) Horizontal Straight Tube Boiler 

2) Bent Tube Boiler 

3) Cyclone Fired Boiler

Water tube boilerWater tube boilerHorizontal Straight Tube Boiler again can be sub-divided into two different types, such as 

i. Longitudinal Drum Boiler

ii. Cross Drum Boiler

Bent Tube Boiler also can be sub-divided into four different types, such as 

i. Two Drum Bent Tube Boiler 

ii. Three Drum Bent Tube Boiler 

iii. Low Head Three Drum Bent Tube Boiler 

iv. Four Drum Bent Tube Boiler

Comparison between Comparison between fire tube & water tube fire tube & water tube boilerboiler

No. Particulars Fire tube boilers Water tube boilers 1.Mode of firing Internally fired Externally fired 2.Rate of steam production lower Higher 3.Construction Difficult Simple 4.Transportation Difficult Simple 5.Treatment of water Not so necessary More necessary 6.Operating pressure Limited to 16 bar Under high pressure as

100 bar7.Floor area More floor area Less floor area 8.Shell diameter Large for same power Small same power 9.Explosion Less More 10.Risk of bursting lesser More risk

Boiler PerformanceBoiler Performance

1). Evaporative capacity : It can be expressed in terms of : a.kg of steam/hr b.kg of hour/hr/m2 of heating surface c.kg of steam/kg of fuel fired

2). Factor of Evaporation It is defined as the ratio of the heat received by 1kg of water at the working

conditions to that received by 1 kg of water evaporated from and at 100 degree.

TugasTugas

Jelaskan cara kerja dan gambar :

FIRE TUBE BOILERS 1). Simple vertical boiler 2). Cochran boiler 3.) Cornish boiler 4). Lancashire boiler 5). Locomotive boilers

TugasTugas

Jelaskan cara kerja dan gambar :

WATER TUBE BOILERS 1). Horizontal Straight tube boiler : a.Longitudinal drum b.Cross drum,

Types of cross drum boiler : 1.two drum 2.three drum 3.four drum

2). Bent tube boiler , Type of bent tube boiler adalah Low head three drum