chain grate stoker [ ′chān ‚grāt ‚stōk·ər] (mechanical engineering) A wide, endless chain used to feed, carry, and burn a noncoking coal in a furnace, control the air for combustion, and discharge the ash.
What is the difference between chain-grate and travelling grate stokers?
Over-fire air injection and a high furnace (8) The travelling-grate stoker is similar in general appearance and operation to the chain-grate stoker except that individual grate bars or keys are mounted on carrier bars which extend across the width of the stoker and are attached to and driven by several parallel chains.
How do the grate bars of a stoker work?
The shearing action of adjacent grate bars as they pass around the curved supporting member at the rear of the stoker provides a self-cleaning action for the grate bars. (3) Thus the supply of air to various sections of the fuel bed may be adjusted to suit the combustion requirements.
What are the different types of stokers?
The main types of stokers are: 1 Chain-grate or travelling-grate stoker 2 Spreader stoker boiler More ...
What is an spreader stoker?
Spreader stokers utilize a combination of suspension burning and grate burning. The coal is continually fed into the furnace above a burning bed of coal. The coal fines are burned in suspension; the larger particles fall to the grate, where they are burned in a thin, fastburning coal bed.
How does the chain run in travel Grate Stoker?
How does the chain run in travelling grate stoker? Explanation: The chain travels over two sprockets. In both chain type and in bar type stokes. One sprocket is placed at the front end and other sprocket is placed at the rear end of the furnace.
What are the two types of stoker fired boiler?
Travel Grate Stoker Solid Coal Firing.
What is grate of boiler?
Grates are provided in solid fuel boilers to help with the fuel-burning such as biomass or coal. It is designed to enable the passing of air for combustion.
What is Stoker power plant?
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.
What is stoker fired?
Stoker-fired boilers are used in many applications with thermal capacities below 50 MW. In these boilers, the fuel is fed by a stoker onto the grate, where it is ignited by heat from the refractory above. As the fuel travels down the grate, it continues to burn, with primary air coming from below.
What are the various types of stokers used for coal firing?
Types of Overfeed Stokers • Travelling Grate Stoker – Chain Grate Stoker – Bar Grate type Stoker • Spreader Stoker Chain Grate Stoker Chain Grate Stoker • Traveling or chain grate stokers feed coal out onto a rotating metal belt that supports the fire.
What is the function of grate?
Gratings over drains and air vents are used as filters, to block movement of large particles (such as leaves) and to allow movement of small particles (such as water or air).
What is grate area?
The grate area is the area of the grate (length x width). The larger the grate area, the more fuel can be burned per hour. The amount of fuel burned also depends on the fuel or bed movement velocity.
What is flue gas in boiler?
Flue gas refers to a chemical byproduct substance that is generated as a result of a combustion reaction that has escaped through long pipes such as those in boilers, furnaces or steam generators. Flue gas may also be referred to as exhaust gas and may act as a reactor agent for atmospheric corrosion.
What are the principles of stokers?
Explanation: In under feed type of stokers, the fuel and air move in the same direction. In this stoker air after passing through the holes in the grate comes in contact with the raw coal. As air diffuses through the bed of raw coal, it mixes with the volatile matter generated by the raw coal.
What is difference between overfeed and underfeed stoker?
In case of overfeed stokers, the coal is fed into the grate above the point of air admission. While in case of underfeed stokers, the coal is admitted into the furnace below the point of air admission.
What is stoker coal used for?
Steam coal refers to coal used in boilers to generate steam to produce electricity or for other purposes. Stoker coal refers to coal that has been crushed to specific sizes (but not powdered) for burning on a grate in automatic firing equipment.
What is a spreader stoker boiler?
In spreader stoker boilers, solid fuel particles are spread uniformly over the grate area as they are thrown into the furnace. Primary combustion air enters from below through the grate and the fuel on it.
What type of Stoker that utilize a combination of suspension burning and grate burning?
Spreader stokersSpreader stokers utilize a combination of suspension burning and grate burning. The coal is continually fed into the furnace above a burning bed of coal.
How does a coal stoker work?
0:031:19Harman® Technology: VertiFlow™ Coal Stoker System - YouTubeYouTubeStart of suggested clipEnd of suggested clipHere the coal gets hot and starts releasing gases before it reaches the fire. This unique ignitionMoreHere the coal gets hot and starts releasing gases before it reaches the fire. This unique ignition process allows the call to already be lit. When it reaches the burn pot.
What is meant by overfeed and underfeed principle of coal firing?
In case of overfeed stokers, the coal is fed into the grate above the point of air admission. While in case of underfeed stokers, the coal is admitted into the furnace below the point of air admission.
What Is Chain Grate Stoker Boiler
Chain grate stoker boiler features: high in heat efficiency. Safe and reliable in running. Reasonable structure. Stoker boiler types can be classified based on its type and based on the method of feeding fuel to the furnace. Stoker boiler types are generally classified as chain-gate or traveling-gate stoker boiler and spreader stoker boiler.
Fuel Options in a Stoker Grate Boiler
Agricultural residue (bagasse, stover, rice hulls), biomass ,coal, natural gas, oil, wood waste (forestry, pulp and paper) and so on. Zhengzhou Boiler Co., Ltd. founded in 1945, 72 years' experience of industrial steam boiler and pressure vessel design and manufacture.
What is the purpose of a coal grate?
A coal grate is used to control the rate at which coal is fed into the furnace, and to control the thickness of the coal bed and speed of the grate.
What are the different types of stokers?
Stoker Fired Boiler are classified according to the method of feeding fuel to the furnace and by the type of grate. The main types of stokers are: 1 Chain-grate or travelling-grate stoker 2 Spreader stoker boiler
What is coal spreader feeder?
Spreader feeders have the capability to uniformly feed coal into a device that can propel it along the depth of a grate in an evenly distributed pattern. Many designs have been used successfully over the years. The coal feed mechanisms include gravity reciprocating plates and metering chain conveyors. The mechanisms that propel the coal into the furnace include steam and air injection as well as underthrow and overthrow rotors. Steam or air assist can be used with the rotor systems.
What is spreader stoker?
Spreader stokers utilize a combination of suspension burning and grate burning. The coal is continually fed into the furnace above a burning bed of coal. The coal fines are burned in suspension; the larger particles fall to the grate, where they are burned in a thin, fastburning coal bed. This method of firing provides good flexibility to meet load fluctuations, since ignition is almost instantaneous when firing rate is increased. Hence, the spreader stoker is favored over other types of stokers in many industrial applications.
What happens when a boiler grate moves?
As grate moves along the length of the boiler furnace, the coal burns before dropping off at the end as ash. Some degree of skill is required, particularly when setting up the grate, air dampers and baffles, to ensure clean combustion leaving minimum of unburnt carbon in the ash.
What are the mechanisms used to feed coal?
The coal feed mechanisms include gravity reciprocating plates and metering chain conveyors. The mechanisms that propel the coal into the furnace include steam and air injection as well as underthrow and overthrow rotors. Steam or air assist can be used with the rotor systems.
