Combustion compartment types and the coal usage

1.Pulverized Combustion
  source :
  www.lanl.gov
  www.pi.hitachi.co.jp/rd-eng/development/development13
   
 
 
 

Principles: Being a coal combustion of fine particles like face powder, the system must have a pounding unit to crush the coal to become fine powder, by passing the coal powder through the coal-powder-spraying nozzle for feeding the powder into the furnace. The air using for combustion will gather itself at the coal-powder-spaying nozzle, then combustion will take place at the nozzle.

Combustion effectiveness.   : Very high
Costs.                                    : Very high
Coal size suitable for usage. :  200Mesh or about 70 micron

 
 
2. Fluidized Combustion
 
Principle: Being a coal combustion of tiny size, whereas the coal is dry and flammable, which can evenly spread out and blend with air thoroughly for a long period of time. For this method of combustion, it may need solid matters, such as sand or ash derived from combustion to be used for the purpose of being the heat spreader, distributing heat to thoroughly cover the entire area. This type of combustion will have the nature like boiling lava.
   
Combustion effectiveness. : Very High
Costs.  : Medium – High
Coal size suitable for usage.    : 0 –10 mm.

 

  source
  http://nett21.gec.jp/JSIM_DATA/WASTE/WASTE_3/img/Fig_458-2_ing
   
 

3.Travelling Grate Stroker

 

Principle: consisting of metal-plate grates connected in the form of conveyor belts for doing the function of conveying coals being burnt. Coals will then be completely burnt and become ash, which will fall down at the area, at the end of the metal plate grates.
 

 
Combustion effectiveness. : High
Costs.  : Medium
Coal size suitable for usage.    : 10 -20 mm. 
 
  source : http://cyberlab.lh1.ku.ac.th/elearn/faculty/science/sci35/homepage/page/chapter_6.htm
 
 

4.Step Grate & Pushing Grate Stroker


Principle: This system of combustion uses its conveying nature to feed coals into the combustion compartment, by employing a grate having the feature of a ramp like a ladder. Coals will fall down from the upper part to the lower part in descending order the same way as the ladder steps are. Coals will be completely burnt until such coals become ash at the lowest part of ladder steps.
Combustion effectiveness. : High
Costs.  : Medium
Coal size suitable for usage.    : 210 -20   mm.
 source: www.gec.jp/JSIM_DATA/WASTE/WASTE_5/html/Doc_515.html
 
 
5.Underfeed Stroker

Working principle: In this system, coals will be fed into the combustion compartment from the lower part of the combustion compartment and then those coals will be piled up at the central area of the combustion compartment, while the ash is being pushed to fall down to the area beside the heap of coals. This will need the combustion compartment to be open for removing the ash (this is for the old version, but the current version will be equipped with a grate, which will automatically turn over itself, without opening the furnace), thereby this will cause the effectiveness of this boiler type to be low.

   
Combustion effectiveness. : Low
Costs.  : Low
Coal size suitable for usage.    : 20 50 mm.
 
 
6.Spreader Stroker

Working principle: Coals will be fed into the combustion compartment by the spreader. Coals of each size will be swung into the combustion compartment. The big-sized coals will be swung farther, while the smaller size will be fallen in the area close to the spreader. Coals will then fall on the back of the sliding rail for further burning.

   
Combustion effectiveness. : High
Costs.  : Medium-High
Coal size suitable for usage.    : 0- 50 mm.
source : http://www.fao.org/docrep/P2396E/p2396e03.jpg