FIELD OF THE INVENTION
The present invention generally relates to Pressurized Fluidized Bed systems
usable with any grade of coal or other solid fuels. More particularly, the invention
relates to a Device for Cooling ash In Pressurized Fluidized Bed Gasification
Systems.
BACKGROUND OF THE INVENTION
Pressurized Fluidized Bed Gasifiers are adopted to generate Syngas from coal,
lignite or other carbonaceous solid fuels, for use in power, process and chemical
applications. In a refractory lined pressurized fluidized bed gasifier, during
gasification process, the crushed coal is continuously injected into the bed, air or
a mixture of air and steam is introduced through a distributor located at the
bottom of the gasifier, from which a stream of high-pressure and high-
temperature raw synthesis gas also called "Syngas" is generated. The hot
combustion gas is supplied to the combustor of a gas turbine engine, which
powers a generator that supplies electrical power to a power grid. Exhaust from
the gas turbine engine is admitted to a heat recovery steam generator that
generates steam for driving a steam turbine. Power generated by the steam
turbine also drives an electrical generator that provides electrical power to the
power grid.
During the gasification process, the bed ash is extracted from the bottom of the
gasifier to maintain the bed height, which is vital for ensuring better fluidization,
proper composition of fuel gas, maximum conversion of carbon and reduction in

the over loading of the equipments in the downstream of the gas path with fly
ash. The bed ash extraction system comprises auxiliary equipment like, ash
cooler, rotary extractor, receiver, lock, depressurizing vessel, ash hopper, and
ash disposal system.
In a typical pressurized fluidized bed gasifier, air or a mixture of air and steam is
passed through a distributor, which is provided with a plurality of bubble cap
nozzles arrangement to fluidize the bed. During gasification process, due to
partial combustion of the crushed coal, the mineral matter in the coal splits into
two streams namely "Bottom and ash" and "Fly ash". The heavier ash formed in
the bottom of the distributor is called "Bottom ash" and is extracted through a
plurality of pipes located at the various points of the distributor. Such removal of
heavier ash allows maintenance of an optimum bed height and desired
fluidization. The bottom ash is extracted and collected under high pressure in a
receiver, through a number of ash coolers using a number of bottom ash
extractors, at a desired rate to maintain the bed height. After cooling in the ash
cooler, and decreasing the pressure in a lock using a de-pressurizing vessel, the
ash is sent to a bottom ash disposal system. The lightweight particles and the
unburnt carbon particles called "fly ash" are carried away by the produced
stream of synthesis gas and passed through a group of serially disposed cyclones
and maintained at high pressure and temperature, thereby separating the fly ash
from the synthesis gas, which is, cooled in a number of ash coolers,
depressurized, purged of product and and/or toxic gases, collected in a fly ash
hopper, and converted to a form suitable for easy disposal.

As shown in figure 1, the prior art ash cooler comprises; an outer shell (01), an
inner shell (02), a plurality of smaller diameter metal tubes (03) arranged in a
staggered fashion and welded to said inner shell (02) maintaining a pitch and
slope suitable for smooth flow. The tubes (03) are grouped by a number of
horizontally and vertically arranged baffle plates (04 & 05) welded only in the
inner shell (02) to have a zigzag water path. As and when required, a quantity of
cold water is admitted between the outer and inner shells (01) and (02) through
a cooling water inlet pipe (06). The water flow takes place through the tubes
(03) in a zigzag manner, absorbing heat from the hot ash (08) and the hot water
leaves out through an outlet pipe (07), and the hot ash (08) falling/flowing in
between the tubes (03) gets cooled. Often problems are encountered with the
failure of the (03) tubes due to absence of flow of required quantity of water in
the tubes (03). The reason being, there are gaps between the baffle plates (04)
and the outer shell (01) allowing water to bypass instead of flowing only through
the tubes (03). Removing of failed tubes (03) and replacing the new tubes
involve gas cutting, grinding and welding in both outer & inner shells (01, 02).
The replacement work takes quite a long time. To overcome these problems,
device is necessary for Cooling the Ash in Pressurized Fluidized Bed Gasification
Systems.
U.S. Patent No. 6082442 dated July 4, 2000, entitled ' APPARATUS FOR
REMOVAL AND COOLING OF ASH FROM THE BED OF A FLUIDIZED BED
FURNACE' discloses a device for extracting and cooling dry ash from a fluidized
bed furnace. This prior art system consists of a combustion chamber, the
combustion chamber in the bottom surface is provided with a number of ash

extraction pipes and an intake and an outlet for cooling medium. A housing is
provided with a plurality of said bottom surface, a chain conveyor, a motorized
driving wheel and an ash discharge port. The chain conveyor is a drag conveyor
and comprises at least two parallel and circulating chains connected together at
intervals by a plurality of scrapers. When the cooling system leaks, water
penetrates into the interior and soaks the ash. The wet ash cakes up on the wall
of the housing and clogs the conveyor, which breaks down.
The combustion and operation of the device of prior US Patent teaches away
from the objects and solutions of the present invention.
U.S. Patent No. 4601730 dated July 22,1986, entitled 'AIR SUPPLY GRATE AND
ASH REMOVAL SYSTEM FOR WOOD GASIFIER' discloses an air supply grate, a
reactor vessel provided with several ring sections and a floor section called ash
pit, a vertical axis rotating an ash plow carried by a shaft, an ash extraction
auger (screw conveyor) and a sealed ash tank. Provisions of ash plow & ash
auger, however, makes the operation substantially costly and complex.

OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose a device for
improved cooling of the generated ash in operation of Pressurized fluidized bed
gasification systems which eliminates the disadvantages of the prior art.
Another object of the present invention is to propose a device for improved
cooling of the ash generated in operation of Pressurized Fluidized Bed
Gasification Systems, which reduces the repair and maintenance time of failed
tubes.
A still another object of the present invention is to propose a device for improved
cooling of the generated ash in operation of pressurized fluidized bed gasification
systems, which eliminates firing of ash in the receiver or in hopper, to prevent
failure of the pressure vessels due to overheating.
Yet another object of the invention is to propose a novel device for improved
cooling of the generated ash in operation of pressurized fluidized bed gasification
systems, which increases the life of down stream equipment like receiver, lock
vessel, hopper etcetera by proper cooling of ash and preventing over heating of
equipment.
A further object of the present invention is to propose a novel device for
improved cooling of the generated ash in operation of pressurized fluidized bed
gasification systems, in which there is no lining to handle high temp ash.

A still further object of the present invention is to propose a novel device for
improved cooling of the generated ash in operation of pressurized fluldized bed
gasification systems, which allows disposal of the ash to atmosphere with highest
safety and in a environmentally friendly operation.
SUMMARY OF THE INVENTION
Accordingly, there is provided a device for improved cooling of the generated ash
in operation of pressurized fluidized bed gasification systems. The invention
implements a process for the partial combustion of carbonaceous materials such
as crushed coal, petroleum or biomass converted into carbon monoxide (CO) and
hydrogen (H2) by reacting the raw material at high temperatures with a
controlled amount of steam, oxygen and/or air, the resulting gas mixture being a
fuel and is called synthesis gas or 'syngas'. The mineral matter in the coal splits
into two streams namely "Bottom ash" and "Fly ash". The heavier ash formed in
the bottom of the distributor is called "Bottom ash" and is extracted through a
plurality of ash coolers, which enables to maintain the bed height and optimum
fluidization. The lightweight particles and the unburnt carbon particles called
"fly ash" formed are carried away by the stream of synthesis gas through the
exit of the gasifler. The product synthesis gas and fly ash with unburnt carbon or
char are passed through a cyclone at high pressure and temperature, thereby
separating the fly ash with unburnt carbon or char. The fly ash is either
recirculated or extracted through the fly ash coolers and discharged to ash yard.

The clean gas is passed to a next processing unit. The invention allows cooling of
bottom ash and fly ash in the pressurized fluidized bed gasifiers.
The inventive device for cooling ash in Pressurized Fluidized Bed Gasification
Systems, comprising; an outer shell, an inner shell, a cone shaped perforated
sheet, a plurality of horizontal and vertical baffle plates, a plurality of cooling
water inlet pipes, a plurality of staggerdly arranged ash cooling tubes, a plurality
of hot water outlet pipes, a number of access openings fitted with corresponding
number of doors, a number of man holes closed with dummy flanges, a plurality
of support plates placed at predetermined locations on the ash cooling device
and welded to the inner shell. The support plates prevent sagging of the coding
tubes by supporting the same during operation, a plurality of stubs and ash
measuring probe is capable of cooling the bed ash and fly ash in the pressurized
fluidized bed gasification system. The configuration and connectivity of the
device substantially reduces the repair & maintenance time by providing easy
access.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.01 - shows an elevational view of a device for cooling the ash in pressurized
fluidized bed gasification system according to the prior art.

Fig.02 - shows elevation, plan and end views of a device for cooling the ash in
pressurized fluidized bed gasification system, according to the present invention.
Fig.03 - shows elevation and end views of supporting arrangement for the
cooling water tube in the device of Fig.02
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
PRESENT INVENTION
According to the present invention, there is provided a device for cooling ash in
pressurized fluidized bed gasification systems. "An outer shell (09)" shown in
Fig.02, acts as a water jacket; an inner shell (10) through which the ash (24)
flows from top to bottom; a cone shaped perforated sheet (11) configured with
an optimum cone angle and hole diameter with corresponding pitch to uniformly
distribute the incoming hot ash (24); a plurality of horizontal and vertical baffle
plates (12 & 13) designed, arranged and welded in both the inner and outer shell
(09, 10) in such a fashion so that cooling water flow takes place at a desired
rate; a plurality of cooling water inlet pipes (14) placed in predetermined
locations along the ash cooling device and welded both in the outer shell and
flanged door (09 & 18) to admit the cooling water; a plurality of (cooling water)
metal tubes (15) staggeredly arranged with predetermined pitch and slope, and

welded in the mid portion of the inner shell (10) to allow sufficient quantity of
cold water to pass through and to cool the hot ash by absorbing heat from the
hot ash (24) falling from top to bottom of the ash cooling device; as and when
required, a quantity of cold water is admitted between the shells (09) and (10)
through the plurality of cooling water inlet pipes (14), water flow taking place
through the metal tubes (15) absorbing heat from the hot ash (24) and the hot
water leaves out through a plurality of hot water outlet pipes (16); a plurality of
access openings (17) placed along the ash cooling device and welded to the
outer shell (09); the access openings (17) fitted with a plurality of flanged doors
(18) by a number of bolts & nuts , and gaskets to provide easy access to
carryout repair and maintenance work in time; a number of man holes (19)
closed with dummy flanges placed at different locations of the ash cooling device
and welded in the outer shell (09) to remove the ash and clean the ash cooling
device during maintenance; a plurality of support plates (20, 21 & 22) placed
along the ash cooling device and welded to the inner shell (10) as shown in
Fig.3 to prevent sagging of tubes (15) by supporting the same during operation;
and a plurality of stubs (23) welded to both the inner and outer shell (09 & 10)
to install ash temperature measuring probes which measures the temperature of
hot ash (24) falling from the top of the cooler, which is cooled and leaves at the
bottom. Thus, the device is capable of cooling the bed ash and fly ash in
pressurized fluidized bed gasification systems and substantially reduce the repair
& maintenance time by providing easy access.

WE CLAIM:
1. A Device for Cooling Ash in Pressurized Fluidized Bed Gasification
Systems, comprising:
- an outer shell (09) acting as a water jacket;
- an inner shell (10) accommodating the ash and cooling water tubes
(15) to form a part of the ash path;
- a cone shaped perforated sheet (11) with a cone angle, and a hole
diameter with "suitable" pitch to uniformly distribute the incoming hot
ash (24) over the cooling tubes (15);
- a plurality of baffle plates (12) horizontally placed at predetermined
locations along the ash cooling device and welded both in outer an
inner shells (09 & 10) to configure a desired cooling water circuit,
- a plurality of vertical baffle plates (13) placed vertically along the ash
cooling device and welded both in the outer and inner shells (09 & 10);
- a plurality of cooling water inlet pipes (14) placed along the ash

cooling device and welded to the outer shell (09) and a plurality of
flanged doors (18) to admit the cooling water at an optimum pressure
and temperature;
- a plurality of metal cooling water tubes (15) staggeredly arranged with
"suitable'' pitch and slope angle and welded in the mid portion of the
inner shell (10) to allow sufficient quantity of cold water to pass
through at optimum pressure and cool the hot ash by absorbing heat
from the hot ash (24) falling from top to bottom of the ash cooling
device;
- a plurality of hot water outlet pipes (16) placed along the ash cooling
device and welded to the outer shell (09), the access openings (17)
being fitted with a plurality of access doors (18) by a number of bolts
& nuts and gaskets to provide easy access to carryout repair and main-
tenance work in time;
- a number of man holes (19) along different locations of the ash cooling
and welded to the outer shell (09), the manholes (19) being removably
closed with dummy flanges;

- a plurality of support plates (20, 21 & 22) placed along the ash cooling
device and welded to the inner shell (10) to prevent sagging of the tubes
(15) by supporting the same during operation; and
- a plurality of stubs (23) welded to both the inner and outer shell (09 & 10)
to allow installation of ash temperature measuring probes.
2. A Device for Cooling Ash in Pressurized Fluidized Bed Gasification systems
substantially as herein described and illustrated with reference to the
accompanying drawings.

A Device for Cooling Ash in Pressurized Fluidized Bed Gasification Systems,
comprising: an outer shell (09) acting as a water jacket; an inner shell (10)
accommodating the ash and cooling water tubes (15) to form a part of the ash
path; a cone shaped perforated sheet (11) with a cone angle, and a hole
diameter with pitch to uniformly distribute the incoming hot ash (24)
over the cooling tubes (15); a plurality of baffle plates (12) horizontally placed
at predetermined locations along the ash cooling device and welded both in
outer an inner shells (09 & 10) to configure a desired cooling water circuit a
plurality of vertical baffle plates (13) placed vertically along the ash cooling
device and welded both in the outer and inner shells (09 & 10); a plurality of
cooling water inlet pipes (14) placed along the ash cooling device and
welded to the outer shell (09) and a plurality of flanged doors (18) to admit the
cooling water at an optimum pressure and temperature; a plurality of metal
cooling water tubes (15) staggeredly arranged with suitable
pitch and slope angle and welded in the mid portion of the inner shell
(10) to allow sufficient quantity of cold water to pass through at

optimum pressure and cool the hot ash by absorbing heat from the hot ash (24)
falling from top to bottom of the ash cooling device; a plurality of hot water
outlet pipes (16) placed along the ash cooling device and welded to the outer
shell (09), the access openings (17) being fitted with a plurality of access doors
(18) by a number of bolts & nuts and gaskets to provide easy access to carryout
repair and maintenance work in time; a number of man holes (19) along
different locations of the ash cooling and welded to the outer shell (09), the
manholes (19) being removably closed with dummy flanges a plurality of
support plates (20, 21 & 22) placed along the ash cooling device and welded to
the inner shell (10) to prevent sagging of the tubes (15) by supporting the same
during operation; and a plurality of stubs (23) welded to both the inner and
outer shell (09 & 10) to allow installation of ash temperature measuring probes.