Abstract: The invention comprising a drying and sorting apparatus for preparation of solid fuel prior to firing in a combustion furnace. Unsaturated air/gas is passed through a bed containing a mixture of solid fuel and inert material particles, fluidizing them. The unsaturated air/gas is the drying vehicle. When in a fluidized state, the lighter organically derived solid fuel particles separate from the heavier inert material particles. The air/gas is admitted to the bed directionally in a manner which drives the mixture in a retraceable path to outlet points downstream of the point of feedstock entry, the heavier inert material settling at the bottom and the lighter solid fuel particles rising in the bed. Means are provided in the sorter floor for selectively concentrating and directing the solid inert material to the collection point transversely to the direction of particle flotation.

Abstract: The invention comprises a dense pack heat exchanger for a steam generator having a circulating fluidized bed combustion system whereby a bed of solid particles comprising fuel and inert material is entrained in the furnace gas stream. Means are provided for collecting high temperature bed solid particles downstream of the furnace. The dense pack heat exchanger directs the hot collected particles down over heat transfer surface, such surface being a portion of the steam generator fluid circuits. Flow is induced by gravity means. The dense compaction of the solid particles around the fluid heat exchange circuits results in high heat transfer rates as the fluid cools the compacted solid material. The heat exchange surface is arranged to facilitate flow of the solid particles through the heat exchanger.

Abstract: The invention comprises an integrated control means, and particularly at partial loads, for a steam generator having a circulating fluidized bed combustion system wherein gas recirculation means is used to supplement combustion air flow to maintain gas velocity in the circulation loop sufficient to entrain and sustain particle mass flow rate at a level required to limit furnace gas temperature to a predetermined value as 1550 F. and wherein gas recirculation mass flow apportions heat transfer from the gas and recirculated particles among the respective portions of the steam generator fluid heat absorption circuits, gas and circulating particle mass flow rates being controlled selectively in a coordinated manner to complement each other in the apportionment of heat transfer optimally among the fluid heat absorption circuits while maintaining furnace gas temperature at a predetermined set point.

Abstract: The invention comprises a drying and sorting apparatus which is integrated with a conventional steam generator for separating organically derived solid fuel from solid inert materials and for removal of moisture from the solid fuel prior to feeding such fuel to a combustor. Low level heat in the steam generator combustion gases, after heat exchange with the steam generator fluid circuits, provides the means for removing moisture from the solid fuel when hot air/gas (unsaturated with respect to moisture) is passed through a bed containing a mixture of solid fuel and waste inert material particles, fluidizing them. When in a fluidized state the lighter organically derived solid fuel particles separate from the heavier inert material particles.

Abstract: The invention comprises a steam generator fluidized bed which recirculates through a major portion of the normal gas to fluid heat transfer circuits. Solid bed material is separated, collected and recirculated. Bed temperatures are limited by regulation of density of bed inert material to inhibit the radiant aspects of combustion. Gas recirculation is used to supplement air flow to achieve higher than entrainment bed gas velocity in the fuel ignition and reaction zone. Fuel ignition and reaction are controlled by limiting the amount of atmospheric air flow to the circulating fuel rich bed mixture to regulate extent of propagation of the ignition and reaction zone into the initial portion of the circulating bed loop, starting from the point of highest gas pressure.

Abstract: The invention comprises a steam generator having a circulating fluidized bed firing system. Particles of fuel and solid inert material are recirculated in a furnace wherein gas velocities are maintained at levels sufficient to entrain the fuel and inert material particles in the gas stream. A plenum is provided at the furnace outlet wherein gas velocity drops below entrainment level and the particles are directed to a collection hopper for recycle. The gas is withdrawn from the plenum through ducting in a manner to assure uniform gas distribution through the plenum. High gas velocity through the ducting improves heat transfer in the fluid cooled enclosure surface where such surface is incorporated into the ducting. The ducting connect to the downstream gas path.

Abstract: The invention comprises a steam generator having a migrating fluidized bed combustor system. The bottom, head end of the bed incorporates a support floor system through which air is admitted tangential to the floor in a manner which causes the bed to migrate in a retraceable track. Tangential admission of air cools the floor and inhibits reverse flow down through the floor when the bed is slumped. Particle entrainment velocities are developed at mid-point in the bed. Tangential entrainment gas flow assures uniform distribution of combustibles and inert material throughout the lower bubbling bed and furnace area above the mid-point. Platens in the furnace zone straighten gas flow for gravity separation of particulate at the outlet of heat transfer surface above the furnace.

Abstract: The invention provides a means for more effectively adapting fluidized bed combustors for retrofit of existing boilers for burning of low grade inexpensive solid fuels. The operating discharge gas from a fluidized bed combustor is substantially lower in temperature from what exists at the furnace gas outlet of a conventional steam generator. Thus, outlet gas from fluidized bed combustors needs to be placed in the downstream gas path differently from conventional practice. The external combustors of the present invention permit placement of hot gas in the steam generator gas path where it can be effectively utilized. The invention also teaches how new steam generators can be configured advantageously to accommodate multiple fluidized bed combustors particularly as pertains to larger capacity steam generators in the 200 MW electrical and larger range.