Stoker moving

Co-Combustion of Different Waste Wood Species With Lignite in an Industrial Steam Boiler with a Moving Stoker Firing System... 

Fig. 1 Measuring sites at the moving stoker boiler of PINDOS ...

Table 1. Fuel test matrix of the co conAustion trials at the moving stoker.

Table 2, Proximate and ultimate analyses (%wt) and calorific values of the fuels used during the co-combustion trials, at the moving stoker boiler.

The fuel flows at right angles to the air flow. Only a small amount of air is fed at the front of the stoker, to keep the fuel mixture rich, but as the coal moves toward the middle of the furnace, the amount of air is increased, and most of the coal is burned by the time it gets halfway down the length of the grate. Fuel-bed depth varies from 100 to 200 mm (4 to 8 in), depending on the fuel, which can be coke breeze, anthracite, or any noncaking bituminous coal. 

The spreader stoker operated as a continuous system, with ash removal doors. The conversion concept corresponds to updraft-downfeed (countercurrent), moving bed. Secondary air (overfire air) entered at 42 inches above the grate. The overfire air ports were directed slightly downward (12°). 

Cocurrent moving-beds exist in different commercial PBC systems. The most typical example is the so-called underfeed stoker (see Figure 35), which applies screw technology to convey the solid fuel into the conversion system. 

Figure 35 A screw conveyor technology (underfeed stoker) with a cocurrent moving bed. [32]...

Continuous movins conversion systems cocurr homog moving bed homog fixed batch bed screw technology pellet burners, underfeed stokers (pellets), see Figure 35. 

If petroleum coke is used on moving grate stokers rather than as a powdered fuel, it must be given close supervision and care. Unless this is done, the grate life may be unduly short (33, 41). 

The principle of the moving bed of Fig. 3.37a in cross-flow to the air supply is used for roasting zinc blende and for the combustion of large coal on chain grate stokers. Another kind of moving bed is found in hopper-type reactors in which particles are fed at the top and continuously move downwards to be discharged at... 

Spreader stoker 55 Hogged fuel High High Moving... 

The emissions of two different commercially available types of wood chip combustion systems were analysed one boiler with a power output of 70 kW with a stoker type burner, the other boiler with a power output of 600 kW and a moving grate burner. Both systems had a computer controlled feed rate and combustion air supply. 

Camera approach Observe material, such as trash in waste-to-energy plants, as it moves through burn zone on traveling grates or stoker. Camera can detect overheat situations close to boiler tube walls. 

For example, coal combustion may be achieved using pulverized coal in entrained systems or as sized particles in fixed or slowly moving beds larger pieces may, in certain instances, also be used. In the case of the fixed- or slowly moving bed combustor, it is usual to employ a mechanical stoker to feed the coal and a grate to support the coal particles as well as to admit air for the combustion process. With regard to the pulverized systems, coal that has been crushed to ca. 200 mesh is carried into the system entrained by the air. 

In the underfeed stoker, coal is fed by a worm feeder into the bottom of a retort (Figure 14.15). The coal rises vertically in the retort and air enters through tuyeres in the sides. The fire is ignited at the top and the flame front moves downward and its speed is matched by the rising flow of coal, fulfilling the requirement of the flame front traveling in the opposite direction of the primary air. 

The first type of furnace was the spreader stoker, in which a mechanical shovel moved between a fuel hopper and the fixed grate, spreading the coal onto the burning zone (Chapter 14). Later improvements in ash handling and coal feeding, however, have made this early stoker design obsolete. 

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