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A Brief Discussion on Boilers

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Page 1: Boilers NFC

A Brief Discussion on Boilers

Page 2: Boilers NFC

Abdul HannanWaheed Ahmad

Taha KhanHassan Mahmood

Fakhar AnwaarNafees Ahmad

Page 3: Boilers NFC

IntroductionTypes of BoilersAssessments of BoilersEnergy efficiency opportunities

Page 4: Boilers NFC

What is a Boiler?

It is a closed vessel in which the heat produced by the combustion of fuel is transferred to water for its conversion into steam at the desired temperature & pressure.

At atmospheric pressure the water volume increases to 1,600 times.

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Boilers, were a major part of the Industrial Revolution beginning about 1700 A.D. They are major consumers of industry & building energy consumption today

Industry boilers are used for power generation process heat(e.g., refineries, petrochemical, paper mills, tire manufacturing etc) & heating

In buildings, boilers are used for steam primary heat, terminal reheat systems. Water heating & absorption chillers

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Horizontal and Vertical boilerFire tube and water tube BoilerExternally and Internally fired boilerForced and Natural Circulation boilerHigh, Medium and Low pressure boilerStationary and Portable boilerSingle and Multi tube boiler

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If the axis of the boiler is vertical then its called vertical boiler. E.g. Cochran boiler

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If the axis of the boiler is horizontal then its called the horizontal boiler. E.g. Locomotive boiler, Lancashire boiler.

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The fire tube boiler, the oldest design, is made so the products of combustion pass through tubes surrounded by water in a shell

The furnace/flame volume can either be inside or external to the shell that contains the water.

The upper steam capacity of fire tube boiler is about 20,000 lbm/hr, & the peak pressure obtainable is limited by their large shells to about 300 psi.

Fire-tube boilers are used for heating systems

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Horizontal, four pass, forced draft fire tube boiler

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It can be seen here that the hot gases are in the tube & water is surrounding them

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A water-tube boiler is one in which the products of combustion pass around the outside & heat tubes containing the water

The water tube diameter is much smaller than the shell diameter of a fire-tube boiler, so much higher pressures can be obtained, well over 2000 psi

The furnace & boiler tube area must be surrounded by a heavily insulated refractory wall to prevent heat transfer through the boiler walls

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The boiler in which the water is inside the tube &hot gases surround them is called water-tube boiler

E.g., Babcock & Wilcox Boiler

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All the largest boilers used for heating & industrial purpose are packaged boilers

They are factory built & shipped whole or in modular components to the customer.

Many are constructed in an elongated shape that will fit through large building doors with minimal fitting adjustment required

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In the boiler if the fire is outside the shell, that boiler is known as externally fired boiler. E.G., Babcock & Wilcox boiler

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The boiler in which the furnace is located inside the boiler shell it is known as internally fired boiler E.g. , Cochran Boiler, Lancashire Boiler

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In the boiler if the circulation of water is done by a pump ten they are known as forced circulation boiler.

E.g. , Benison Boiler, Lamont Boiler

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In the boiler if the circulation of water takes place due to difference in density resulting from different in temperature, it is known as natural circulation boiler

E.g. , Lancashire Boiler

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It is one in which the working pressure of the boiler is more than 25 bar.

E.g. , Babcock & Wilcox boiler

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It is that boiler whose working pressure is between 10-25 bars

E.g. , Lancashire Boiler & Locomotive Boiler

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It is that boiler whose working pressure is between 3.5-10 bar.

E.g. , Cochran boiler

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The boilers having only one fired tube or water tube are called single tube boilers.

E.g. , Cornish Boiler

The boilers having two or more fire or water tube for the circulation of hot gases or water are called multi tube boiler

E.g. , Lancashire boiler, Babcock boiler & Wilcox boiler

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Thermal efficiency of boiler is defined as the percentage heat input that is effectively utilized to generate steam. There are two methods to calculate the boiler efficiency

1.The Direct Method2.The Indirect Method

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Boiler Efficiency = Q * (H-h)/(q * GCV) * 100Where

Q = quantity of steam generated per hour (kg/hr)H = Enthalpy of saturated steam (kcal/kg)h = Enthalpy of feed water (kcal/kg)q = Quantity of fuel used per hour (kg/hr)GCV = Gross Calorific Value of the fuel (kcal/kg)

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Page 27: Boilers NFC

Air preheater. Economizer. Super heater. De-super heater. Boiler feed pump. Forced draft and induced draft fans. Mechanical separator. Equipment tanks Feed water tanks De-aerator Continuous blow down expander Drainage expander Chemical dosing system. Soot blowers and wall blowers. Pressure reduction valve. Pulverizers and fuel firing system. Ash handling systems.

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Thanks for your Attention