Rotating Machines in Boilers

7/22/2019 Rotating Machines in Boilers

http://slidepdf.com/reader/full/rotating-machines-in-boilers 1/23



This project entitled “ROTATING MACHINES IN

BOILERS” is framed on the needs of boiler auxiliaries for a

power plant.

A boiler is defined as “a closed vessel in which steam is

produced from water by the combustion of fuel.”

Here the discussions are made on major components ofrotating machines in boilers. It includes maintenance of

boilers in power plant.



The following parts come under major rotating

machines in boilers :

Coal mills Fans

Air pre-heater



Coal mill is a machine in which the 20mm size of

coal from the coal feeder is grounded into fine

powder.

Coal mill contains four pipes surrounding a centerone. Through the center pipe coal enters the mill and

fine coal powder is taken to the furnace through

surrounding pipes.

Ungrounded particles of coal come out through theBottom Reject Gate (BRG).



The main functions of fans are:

To supply to the furnace the required quantity of air

for complete combustion of fuel.

To remove the gaseous products of combustion fromthe furnace and throw these through chimney or stack

to atmosphere.



Primary air fan

Forced draft fan

Induced draft fan Seal air fan

Scanner air fan



The main purpose of the primary air fan is to supply

primary air to carry the pulverized fuel from the mill

and to discharge into the furnace.

It is a radial type. Primary air fan sucks the air from atmosphere

pressurizes it and sends it to coal mill through

primary air preheater which heats up this pressurized

air.



The main purpose of this fan is to supply adequate

amount of air to the furnace for maximum

combustion.

It is an axial type fan. The air supplied by the PAF is not sufficient for

combustion process. The additional air required is

supplied using FD fans.



The main purpose of this fan is to suck the flue gases

from the furnace and send it to the atmosphere

through chimney and maintain furnace draft.

It is an axial entry and radial discharge type. It also maintains the pressure inside the furnace.



The main purpose of this fan is to supply seal air to

mills to avoid contamination of gear box oil and

bearings by coal entry.

It is a centrifugal type fan.



The furnace consists of scanners to sense the

flame.

The main purpose of this fan is to supply air

cleaning and cooling the flame scanners.



Air pre-heater is a general term to describe any devicedesigned for heating air before any other process (here

combustion in the boiler).

The purpose of air pre-heater is to recover the heat from the

flue gases exiting the boiler and transferring it to air beingsupplied for combustion of fuel in the boiler, thus increasing

the efficiency of the boiler, and reducing useful heat loss from

flue gas in the form of radiation

Thus the gases are sent to chimney at a lower temperature,hence meeting the emission regulations.



20% of Total heat transfer in the boiler by APH.

Decrease in boiler efficiency due to poor performance of APH

1% decrease in efficiency due to 20 oC rise in flue gas

temperature.

1% improvement in boiler efficiency for each 22 oC rise in thecombustion air temperature.

The total fuel saving due to pre heating combustion air may be

5 to 10 %.

Air heaters also make pulverized coal firing practical bydrying and providing transport medium.



Fans are helpful in the regulation of pressure inside the boiler.

Fans are also used in providing excess air for complete

combustion.

Air pre-heaters are responsible for the increase of boiler

efficiency. Air pre-heaters are employed for waste heat recovery.

Coal mills are used for crushing the coal into fine powder i.e.

pulverization.

Therefore rotating machines namely air pre-heater, fans andcoal mills are necessary for the generation of steam efficiently



THANK YOU

Rotating Machines in Boilers

Documents

Transcript of Rotating Machines in Boilers