Handling of Rice Husk to Production Process
 
 
  Production Procedures
 
 
  
  Detail of Production Units
 

Boiler or Fuel Combustion System
After the combustion chamber is started up by fuel oil until reaching a temperature of 700-800 degrees C, then ground rice husks will be fed from a service silo while the use of fuel oil is gradually decreased until all rice husks ignite continuously, then a complete stop of fuel oil can be carried out.
The combustion system in the combustion chamber is a suspension-fired combustion, where ground husks from a service silo are fed to a fuel-air mixing system and are compressed by air from a primary air fan which is injected through a burner and then the mixture is carried into the boiler furnace on the front portion about the furnace's middle height. The burner has adjustable vanes to force the fuel-air mixture to circulate for proper combustion in the combustion chamber at temperature around 800-900 degrees C. At the lower side of the combustion chamber, there is a compression port where outside air is drawn by a forced draft fan and blown through an economizer in the exhaust port to preheat the air. Subsequently, the hot air will be compressed through this port in a quantity of 30 percent in excess of the need of the system to prevent incomplete combustion which will result in the occurrence of carbon monoxide (CO) and, at the same time, the air will suspend the husks in the suspension firing zone. Husks subjected to grinding will be broken into small lightweight particles, thus enabling faster combustion while those with more weight and mass will become bottom ash after burning and fall to the inclined bottom of the furnace and flow out through the ash port to be swept by a screw conveyor for removal. Lightweight husks, after burring, will be mixed in the flue gases and are carried out of the combustion chamber through the flue port. These so-called "fly ashes" will be collected by an electrostatic precipitator (ESP) before the flue is discharged to tht' atmosphere. Air which is being compress~d into a combustion chamber by a forced draft fan will be controlled by inlet guide vanes. When the pressure inside the combustion chamber is in balance with outflowing flue gases, the heat obtained from flue gases will be used to vaporize water to become steam having temperature of 480 degrees C. Then the flue gases used in heating water will be released through an economizer to exchange remaining heat for efficient heat recovery. An induced draft fan will draw the flue gases to an ESP to trap fly ash in flue gases before they are released from the stack.

Steam Turbine and Generator
Hot steam from a boiler will be transferred to a steam turbine where the thermal energy of the steam is converted to mechanical energy. Inside the boiler, a governor is fitted to regulate the steam flow rate and the speed of rotors to be at 15,000 rpm and subsequently this speed will be reduced to 3,000 rpm by a reduction gear unit in order to turn a 11.5 KV turbine generator. Then the mechanical energy will be converted to electric energy which is transmitted by a generator breaker and a step-up transformer to generate a voltage of 115 KV for subsequent distribution through the transmission line of the Provincial Electricity Authority (PEA).

Condenser
Steam that has been used in the process will be sent to a condenser where it is liquefied to become condensate flowing into a holding reservoir. The resultant water which is still hot will be recycled to the boiler for generating steam.

Cooling Tower
This cooling system removes heat from water coming out off a condenser where the cooling water has cooled steam used in turning a turbine. Heat will be transferred from steam to the cooling water (the temperature of the incoming cooling water is 37.5 degrees C) and the heat in the cooling water is removed by a fan blower and will be dissipated together with evaporated water into the atmosphere. The outgoing cooling water now will a temperature of 32 degrees C will be combined with madeup water supplied from the a water reservoir to compensate for evaporating water and subsequently it will be fed to a condenser to remove heat from steam in the process circuit for another cycle. In this regard, water from this system will be recycled at a daily rate of about 1,922 cubic meters and use in the cooling system for not less than 10 times.

 
  Combustion Technology
 
 
 

Rice Husk Power Plants Employing the Same Furnace System as that Used in the Power
Plant of A.T. Biopower Company Limited

 
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  Model 1
  Model 2
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