Method of and Arrangement for Feeding Fuel Into a Circulating Fluidized Bed Boiler

A method of feeding at least one of light, fine, volatile and moist fuel into a furnace of a circulating fluidized bed boiler, the method comprising:

• introducing a fuel flow into a furnace of a circulating fluidized bed boiler, the fuel flow being selected from at least one of light, fine, volatile and moist fuel;
• combusting the fuel in the presence of a fluidized bed material in the furnace of the boiler to form flue gases;
• circulating the fluidized bed material both inside the furnace in an internal circulation, in which bed material returns along walls of the furnace down to the bottom of the furnace, and outside the furnace in an external circulation that includes at least a solids separator arranged in flow communication with the furnace;
• separating bed material from the flue gases in the separator;
• removing the flue gases from the separator for further treatment;
• returning the separated bed material to the furnace;
• collecting circulating bed material from at least the internal circulation flowing down along the furnace walls to a return flow;
• and
• introducing the return flow in consolidated form into communication with the fuel being introduced in the furnace, so that the bed material return flow and the fuel flow are mixed together and flow downwards in the furnace, in order to increase the residence time of the fuel in the furnace.

An arrangement for feeding at least one of light, fine, volatile and moist fuel into a furnace of a circulating fluidized bed boiler, the boiler comprising:

• a furnace delimited at least by a grid at the bottom of the boiler, side walls, and a roof;
• a solids separator arranged in flow communication with an upper portion of the furnace;
• at least one air feed for providing the furnace with primary and secondary air;
• a return for returning the solids separated from the flue gases in the separator into the furnace;
• a feed for feeding fuel into the furnace, the fuel being selected from at least one of light, fine, volatile and moist fuel;
• and
• a conduit for introducing in consolidated form at least solids circulating inside the furnace and flowing down along the furnace walls into communication with the fuel to force the fuel flow down towards the grid in order to increase the residence time of the fuel in the furnace.