Industrial Burners In the industrial field, burner controls for

intermittent or continuous operation ensure safe burner operation.

 It’s ensuring optimum combustion processes.

For high firing rates we offer electronic air/fuel ratio control with optional oxygen trim for maximum combustion efficiency and low emission levels.

Industrial Burners contd.. Fuels: Solid (Coal), Liquid (Oil) and Gas Coal: Classification Peat: First stage,highly moisture

content,small % of volatile matter and fixed carbon,not suitable for power plant.

Industrial Burners contd.. Lignite: Second stages,highly moisture

content and ash but has higher heating values and fixed carbon.

Sub Bituminous coal: here coal have lost woody structure,moisture content from 17% to 20% and volatile matter from 35% to 45%,also known as black lignite.

Bituminous coal: low moisture content and non- disintegrating properties.

Industrial Burners contd.. Semi-Bituminous Coals:highest grade of

coals, when these burns small amount of smoke, content high fixed carbon and highest heating values.

Semi- Anthracite Coals: Harder than earlier one,found in small quantities so costly for power generation

Anthracite Coals; highest carbon content but don’t have highest heating values

Super-Anthracite Coals: very hard with shiny black surface,higher % of carbon content and the less than 8% volatile.

Fuel Combustion One of the chief factors in the economical working

of a power plant is the efficient combustion of fuel. Two most commonly used methods for burning of

coal are Stoker firing and Pulverized firing The selection of one of the above method depends

of the following factors Characteristics of the coal available Capacity of boiler unites Station load factor Load fluctuations Reliability and efficiency of the various types of

combustion equipment available

Methods for burning of coal Stoker Firing: is a power operated fuel

feeding mechanism and grate(metal framework keeping fuel in fireplace).

By the use of stokers, a cheaper grade of fuel can be used, a higher efficiency attained,greater flexibility of operation assured,better furnace conditions maintained and less smoke produced than is usual with hand firing.

Stoker Firing:Advantages Generally less building space is necessary. Can be used for small or large boiler units. Very reliable and maintenance charges are

reasonably low. Cheaper grade of fuel is used. Reduction in auxiliary plant. Less smoke produced. Higher efficiency attained.

Stoker Firing:Disadvantages With very large unites the initial cost may

be rather high than with pulverized fuel. Construction is complicated. Sudden variations in the steam demand

can't be met to the same degree. Banking and stand by losses are always

presents. Trouble due to sagging and clinkering of

combustion chamber walls are experienced.

Overfeed stokers:the coal is fed into the grate above the point of air admission ,mainly two types:

traveling grate stoker and spreader stoker. Underfed stokers: the coal is fed into

the grate below the point of air admissions, and suitable for non-clinkering,high volatile coals having coking properties and low ash content.

Classification of Stoker Firing

Pulverized Fuel Firing In this type firing system the coal is

reduced to a fine powder with the help of grinding mill and then projected into the combustion chamber with the help of hot air current.

Efficiency depends upon the size of the powder.

Use in modern thermal power plant where available coal is cheap.

Pulverized Fuel Firing: advantages Any grade of coal can be used since coal is

powder before use. Rate of feed of the fuel can be regulated properly

resulting in fuel economy. Higher boiler efficiency. Greater capacity to meet peak loads. Practically no ash handling troubles. No moving parts in the furnace subjected to high

temperatures. No standby losses due to banked fires. Practically free from sagging and clinkering

troubles. The external heating surfaces are free from

corrosions. This system works successfully with or in

combination with gas or oil.

Pulverized Fuel Firing: Disadvantages High capital cost. Lot of fly ash in the exhaust which makes

the removing of fine dust uneconomical. The possibilities of explosion are more as

coal burns like gas. Maintenance of furnace brick work is

costly. Special equipment is needed to start this

system. The skill operates are required.

Coal Burners Fires the pulverized coal along with

primary air into the furnace. The secondary air admitted separately

below the burner,around the burner or else where in the furnace.

Ignition takes place by means of radiation and flame propagation from the fuel already burning in the furnace.

Coal Burners contd.. Coal Burners may be classified according to their

design and by their arrangement in the furnace as follows

Opposite Firing:burners are placed on the opposite walls of the furnace and they fire directly against each other

Cross Firing:the burner fired in the vertical directions and in horizontal directions and the fuel stream intersect each other.

Tangential Firing: burner are placed at the corner of the furnace and they send horizontal streams of air and fuel tangent to an imaginary circle in the center of the furnace which results intense turbulence and thorough mixing of the fuel and air.

Coal Burners contd.. Cyclone burner:crushed coal is used and

not the pulverized fuel. This is done to eliminate pulverisers and

to reduce the fly ash difficulties. From the feeder the crushed coal and the

primary air enter with a vortex motion at the center of the cyclone.

The secondary air admitted separately aids in the vortex motion.

The fuel is quickly burned and ash in the form of motion slag drains down the inner wall of the cyclone.

Cyclone burner: Advantages Simplified coal crushing equipments can

be used instead of costly pulverized mills. Excess air required can be reduced to

15% minimum using forced draught fan The cyclone furnace can be use low

grade fuels,reduce the size of the steam generator and limits the fly ash emission so that excessive furnace cleaning and precipitations are not required.

Oil burning The function of the oil burner are to mix the fuel

and air in the proper proportion and to prepare the fuel for combustion.

Following are the two ways to achieved it: The oil may be vaporized or gasified by heating

within the burner The oil may be atomized by the burner and its

vaporization occurs in the combustion space Atomization of the oil is done in three basic ways The oil is broken into small droplets by using air or

steam under pressure. Forcing oil under pressure through a suitable

nozzles Tearing an oil film into drops by centrifugal force.

Gas Burning Simple and requires no preparation. The most familiar gas burner is the

atmospheric burner. Gas and air together pass through a

tube leading to the burner ports, mixing in the process.

The mixture burns at the ports or the opening in the burner head.

Secondary air is drawn into the flame from the surrounding atmosphere.

Gas Burning:Advantages

Cleanliness Ease of control of furnace

temperature Ability to produce a long slow

burning flame with uniform and gradual heat liberation.

Ease of temperature regulation.

Fluidized Bed Combustion Bed of solids particles behave as fluid. When an evenly distributed air is passed upward

through a finely divided bed of solid particles at low velocity,the particles are undisturbed.however,if the vel.is steadily increased,a stage is reached when the individual particles are suspended in the air stream.

If the vel. Further increased,the bed becomes highly turbulent and rapid mixing of particles occur which appear similar to the bubbles formed in a boiling liquid, a bed is to be fluidized.

In a fluidized bed, rapid mixing ensures uniformity of temperature.

Classification of FBC Atmospheric FBC: here,the pressure

inside the bed is atmosphere. The control systems are relatively conventional.

Pressurized FBC: here,double shell design is provided so that the thermal reactor stress is separated from the pressure stress.pressurized air is supplied to the system,the main advantages of this system is high burning rates,reduced volume,increase coal loading but control is difficult and plant life is low as compared to ATM FBC

Advantages of FBC Low combustion temp.(820 to 950 0c) inhibits

the formation of Nox Due to better heat transfer, the unit size and

hence the capital costs are reduced. Safe and efficient operation. Multifuel and fully automatic operation. Easy ash removal system Higher thermal efficiency. No moving parts,resulting in reduced

maintenance cost. Can meet the rapid changes of demand. Shorter erection and commissioning period.

Disadvantages of FBC

The major disadvantages is that since the air has to be supplied at a high pressure so as to support the bed, the fan power is increased sufficiently.