What is the basic principle of overfeed stoker?

What is the basic principle of overfeed stoker?

In case of overfeed stokers, the coal is fed on the grate above the point of air admission. Working principle : In this type of fuel firing, the primary air enters the grate from the bottom. The air passing through the grate is heated by absorbing the heat from the ash and grates itself. So, the grate is cooled.

What is overfeed stoker?

Overfeed stoker is the type of stoker in which the coal is fed from the top and air is blown from below. Underfeed stoker is one where coal is fed from underneath and the air is fed from top.

What is meant by Underfeed coal firing?

A mechanical stoker suitable for small boilers, such as the vertical, water-tube, and locomotive types. Coal is conveyed direct from a bunker or hopper by a feed worm, which forces the fuel up through the bottom of the retort in which it is burned.

What is multi retort stoker?

Conventional multiple retort stokers comprise a number of retorts and tuyeres extending longitudinally of the furnace and arranged in alternation across the width of the furnace. The tuyeres adjacent each retort deliver air for combustion into the burning mass of fuel being moved along the retort.

What are the different methods of firing coal?

Methods of Firing Steam Boiler

  • Hand Firing.
  • Mechanical Stroke Firing.

What Stoker means?

(Entry 1 of 2) 1 : one employed to tend a furnace and supply it with fuel specifically : one that tends a marine steam boiler. 2 : a machine for feeding a fire.

What is the amount of air required to burn the Pulverised coal?

1 kg coal is 1/12 kmol coal (pure C assumed), needs 1/12 kmol O2 for combustion, or 1/12 * 100/21 kmol of air. This is roughly 0.4 kmol of air/hr, or 11.5 kg of air/hr. Taken as s volume, this amounts to roughly 9 m³/hr of air under normal conditions.

What stoker means?

What is fuel firing?

The essential feature of pulverized-coal firing is that throughout the combustion, the fuel is suspended as a cloud of small particles in the combustion air.

What is hand firing?

Hand-fired grates were made of cast iron. They varied in design to suit the type of fuel to be burned. The air openings in the grates varied from 1/8 to 1/2 in in width, and larger air openings were used for burning bituminous than for burning anthracite coal.

What can you say about Stoker?

Stoker, machine for feeding coal or other solid fuel into a furnace, usually supporting the fuel during combustion. A good stoker also supplies air for combustion and regulates the rate of burning and, in large installations, disposes of the ashes.

How is coal introduced into an underfeed stoker?

UNDERFEED STOKERS In an underfeed stoker, the fuel is introduced through long troughs, called “retorts”, at a level below the location of air admission to the fuel bed. Thus, the green coal (or raw coal) is at the bottom, the ash moves away from the retort]

What does it mean to Stoke a fire?

To stoke a fire meant to do whatever was necessary to keep it burning properly, including poking, stirring, and supplying it with fuel. Eventually these “stokers” were replaced with mechanical devices which automatically fed fuel to the furnaces, and in some cases automatically disposed of the ash.

What did a stoker do in the early days?

——-f SECTION 2 STOKERS IN USE TODAY In the early days, a “stoker” was someone employed to tend a furnace. To stoke a fire meant to do whatever was necessary to keep it burning properly, including poking, stirring, and supplying it with fuel.

What is the combustion chart for a coal stoker?

Combustion Chart for Determining Excess Air from either Flue Gas Oxygen or Carbon Monoxide (Dry Basis) while Firing a Bituminous Coal 34 18. Combustion Chart for Determining Total Air from an Orsat Flue Gas Analysis 35 19.

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