Abstract: A fluidized bed combustion system in which a separator receives a mixture of flue gases and entrained particulate material from a fluidized bed in a furnace. A loop seal valve, in the form of three ducts, connects an outlet of the separator to the furnace for recycling the separated particulate material back to the furnace. One of the ducts extends vertically from the separation and another duct extends horizontally from the latter duct and connects this latter duct to an angled duct which registers with an opening in the furnace wall. The last duct is angled downwardly to provide an increased throughput when compared to standard loop seal devices.

Abstract: A valve is provided preferably having a moulded plastic valve plug with a plurality of preferably arcuate grooves circumferentially spaced in the forward surface of the plug. The arcuate grooves distribute fluid flowing between the plug and valve seat substantially equally about the periphery of the valve plug. Fluid is also directed by the grooves to flow between a sealing surface of the plug and the valve seat in an outward radial direction substantially parallel to the valve seat. The resulting fluid flow reduces cavitation, valve stem chatter, noise and vibrations as well as reducing erosiion of the valve seat. An inner portion of the plug is made of a relatively high tensile strength material having a low thermal expansion rate whereas an outer portion of the plug including the plug sealing surface is made of a material having a relatively low surface hardness.