FBC COOLING TUBES
The main function of FBC tubes is to regulate and/or maintain the bed temperature so as not to reach the adiabatic temperature. Another function is to generate more steam because it has 5 - 6 times better co-efficient of heat transfer, thus enable to maintain the temperature of combustion zone below 1000 oC which is below the ash coagulation / melting point of most of the biomass and fossil fuels. About 40% of steam generation emanates from the FBC tubes, which was installed on both side of the furnace and directly in the line of fire. It has protective fins to prevent from abrasion due to constant movement of the sand surrounding the furnace sand bed.

CIRCULATING SAND BED CLEANER:
This system was primarily designed in order to burn fossil fuels with lots of inherent impurities like soil, sand stone, etc., which could not be burned. With its system, the impurities can be removed from the furnace WITHOUT SHUTTING DOWN THE BOILER and thus, it could be operated ON-LINE. When the sand bed have already substantial amount of impurities on it, it can be noticed from the furnace pressure indicator from the control panel. It has a HIGH, NORMAL and LOW level. When the indicator shows HIGH level, the operator will open the shutter below the sand belly and the sand with lots of impurities was drained to the oscillating sand screen cleaner where the impurities goes down to the dirt bin, while the clean sand goes back again to the furnace by means of a pneumatic conveyor/blower. This could be done WITHOUT SHUTTING DOWN THE BOILER. It only takes about 10 - 15 minutes every cleaning time, and the sequence depends on the purity and/or dirtiness of the coal. Based on experience, 2 - 3 times cleaning of the sand has been observed every 24 hours of operation.

FURNACE AIR DISTRIBUTION AND NOZZLE:
The air distribution design is of zig-zag configuration allowing to put as many nozzles as possible. In doing so, the sand bed has an even distribution of air pressure thus assuring uniform sand movement through the bed. It also assure the fuel to freely move from one place to another due to constant turbulence of the bed brought about by the rapid pulsation of the sand velocity from multiple and evenly distributed air nozzles throughout the furnace bed area.

FBC NOZZLE: The FBC nozzle are made from Carbonized Cast Steel designed for power plant boilers and can withstand temperature up to 1300 oC and designed to last for 3 years. It was located about 400 mm below the sand bed where the temperature is only 600 oC. Replacing the nozzle is so easy because it has a thread for easy removal and replacement.