CFB Steam Boiler Manufacturer in Namibia

The CFB boiler manufactured in Namibia has been based on an internally recirculating circulating fluidized bed system. Discussions with manufacturers indicated that this system is best suited for the application which involves a low moisture content fuel.

The CFB is a circulating fluidized bed boiler in which a portion of the bed media (sand) is recirculated in the main furnace chamber. Primary fluidizing air is supplied below the bed with sufficient velocity to force the bed media and fuel particles upward through the furnace. Due to an expansion in cross-sectional area at the top of the furnace, the velocity of the existing flue gas is decreased causing sand and particles to drop out of the flow and fall back down the furnace. Some media and particles will continue onward toward the heat exchanger tubes and are collected using a series of U-beams designed to separate particulate and sand from the flow.

These materials fall back down into the main furnace as well. These two components make up the primary recirculation loop. Bed media, fuel particles and ash escaping this primary collection mechanism will be collected using cyclone separators following the superheaters and delivered back the bed. This is the secondary recirculation loop. The boiler will be supplied with superheaters, economizers, refractory lined water wall and steam drum. Primary and secondary combustion air will be preheated by exiting flue gas following the economizer.

Thermoflex has the ability to create a thermodynamic model of a CFB system and this model will provide a reasonably accurate estimate of the heat and mass balance for a CFB. Detailed technical operating and performance data was not provided by suppliers at the time of the study, so a number of assumptions were made and Thermoflex was used to model the optimized performance of the system and determine some of these parameters.