The hot particles collected in the cyclone are recycled to the combustor through a recycle device. Hence, to minimize the maintenance of refractory laid on the surface of cyclone, an alternate water cooled design is employed in CFBC boilers but manufacturing of circular water cooled cyclone is a complicated and an expansive process. Uniform water/steam flow is to be ensured to avoid starvation of tubes. However, a thin layer of refractory on the surface of tubes is sufficient to prevent erosion. All the above mentioned prior art cyclones have a circular cross section and employ centrifugal forces for separating solids from the flue gas.
STATEMENT OF INVENTION
According to this invention there is provided an improved hot particle collection device for Circulating Fluidised Bed Combustion (CFBC) system comprising water cooled enclosure integral with combustor and elutriated particles collected in the separator is connected to recycle system, the said combustion system having a primary air fan for supplying air to fluidized the particle from the bottom of the combustor, a secondary air fan being provided for supplying air for secondary combustion of fuel at various elevation in said combustor and high pressure air used for recycling the particle collected in separator to combustor, the fuel being fed at the lower elevation of the combustor through rotary air lock feeders and recycle system, the said combustor being water cooled having height between 20 meters and 40 meters to allow particle to burn in the combustor, a feed point being provided for supplying feed material to the combustor against furnace pressure, the said combustor being connected to said water cooled particle separator as a part of evaporator to separate the particles and the said separator being provided with a separate duct being connected to the recycle device for recycling the particles, the said separator is connected to a flue gas outlet duct to recover the heat from the flue gas in second pass of boiler.
Summery of the Invention:
The present invention involves an improved and cost effective non circular ash separator with an unique inlet configuration and an appropriately located gas outlet pipe with a suitable ash reinjection device for a CFBC boiler.
According to the present invention, a circulating fluidized bed combustion (CFBC) boilers of a special design is used to separate fly ash and bed material for recirculation. The invention also includes suitable design features to couple the combustor and ash separator, etc.

The special design / constructional features include the following:
1) Design of an alternate ash separator.
2) Design of the ash separator integral to the water wall of combustor.
3) Flue gas inlet to the ash separator and its location.
4) Design of flue gas outlet from ash separator.
5) Sizing of ash separator.
6) Distance between the ash separator and the outlet of combustor.
The present invention will now be described in detail with reference to the accompanying drawings shows a schematic view of an alternate hot particle collection device for CFBC boilers.
With reference to the accompanying figure of the circulating fluidized bed boilers, the CFBC boiler of the present invention is provided with a primary air fan with sufficient pressure and flow to fluidize the material from the bottom; a secondary air fan (2) supplies air for secondary combustion of fuel at various elevations in the combustor and also supplies air for recycle device; the fuel is fed (3) at the lower elevation of combustor through a rotary air lock feeder; a water cooled combustor (4) with sufficient height to allow the particles to burn in the combustor; a feed point also available to feed bed material (5) against

furnace pressure; a water cooled ash separator as part of evaporator (6) to separate out the particles; an outlet of ash separator duct (7) connecting to recycle device; a recycle device (8) to recycle the particle with a suitable nozzle type air distributor (9); the fly ash return line (10) to recycle the particle; a gas outlet in ash separator with suitable height and diameter to leave out the clean gas (11) from the ash separator; a flue gas inlet to ash separator with suitable cross section and location (12); flue gas outlet duct connecting the second pass to recover the heat from the flue gas (13) and the location and size of ash drain (14).
The invention as described herein with reference to the drawing is not limitative, any modification and / or alteration of such will be well within the knowledge of a person skilled in the art.

WE CLAIM;
1. An improved hot particle collection device for Circulating Fluidised Bed Combustion (CFBC) system comprising water cooled enclosure integral with combustor (4) and elutriated particles collected in the separator (6) is connected to recycle system (8), the said combustion system having a primary air fan (1) for supplying air to fluidized the particle from the bottom of the combustor, a secondary air fan (2) being provided for supplying air for secondary combustion of fuel at various elevation in said combustor (4) and high pressure air used for recycling the particle collected in separator (6) to combustor (4), the fuel being fed at the lower elevation of the combustor through rotary air lock feeders and recycle system (8), the said combustor (4) being water cooled having height between 20 meters and 40 meters to allow particle to burn in the combustor, a feed point (5) being provided for supplying feed material to the combustor against furnace pressure, the said combustor (4) being connected to said water cooled particle separator (6) as a part of evaporator to separate the particles and the said separator being provided with a separate duct (7) being connected to the recycle device (8) for recycling the particles, the said separator (6) is connected to a flue gas outlet (13) duct to recover the heat from the flue gas (13) in second pass of boiler.
2. An improved hot particle collection device as claimed in Claim 1 wherein the device is provided with vortex finder, located away from the centre point of cross section of separator (6) to facilitate high collection of particles.

3. An improved hot particle collection device as claimed in claim 1 and 2, wherein the vortex finder is made of characteristics material with diameter between 300 m.m. to 1.0 meter and depth inside the ash separator (6) between 500 m.m. to 1.5 meter.
4. An improved hot particle collection device as claimed in Claim 1, wherein ash separate duct (7) is connected to recycle device (8) to recycle particles to the combustor (4) through ash return line (10).
5. An improved hot particle collection device as claimed in any one of the preceding claims wherein water cooled pipes forms as an enclosure with a special design to minimize erosion due to elutriated particles.
6. An improved hot particle collection device as claimed in claim 1 having a cross section to facilitate high rate of separation of particles from flue gas(13).
7. An improved hot particle collection device substantially as herein described and illustrated in the drawings of the Complete Specification.