FIELD OF THE INVENTION
The present invention generally relates to fluidized bed coal gasification /
combustion systems. More particularly, the present invention relates to an
augmented water cooled flat plate distributor and support device for air / gas
/steam distribution in high pressure fluidized bed gasification systems.
BACKGROUND OF THE INVENTION
Pressurized Fluidized Bed Gasifiers generate fuel-gas 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.
Accordingly, the coal with bed material is uniformly fluidized by the stream of air/
air and the steam mixture with the required fluidization velocity admitted through
at least one bubble cap air / steam nozzles located in the distributor. The
resulting chemical reaction between the coal particles and the air / mixture of air
and steam, allows generation of a stream of high-pressure and high-temperature
raw synthesis gas also known as "Syngas" with specific chemical composition
and calorific value based on the coal composition and the proportion of the air /
mixture of air and steam. A plurality of bubble cap nozzles located at
predetermined locations in the distributor allow distribution of the air / mixture of
air and steam with uniform fluidization velocity and fluidize the bed. As a result,
the coal gets mixed with air / steam rapidly and thoroughly. The hot combustion
gas that is produced in the gasifier is supplied to the combustor of a gas turbine
engine, which powers a generator that supplies electrical power to a power grid.
In addition, the gas turbine engine exhaust is admitted to a heat recovery steam
generator that generates steam for driving a steam turbine. The power
generated by the steam turbine drives as electrical generator that provides
electrical power to the power grid. Thus, the electrical power so produced from
both the Gas turbine - Generator, and the steam turbine - Generator, is fed into
the power grid.
According to the prior art shown in Figure l,Figure 2 and Figure 3, the distributor
comprises; a cylindrical shaped fluidizing bed chamber (01) enclosed by a
refractory brick lined gasifier (02) to withstand high temperature of operation; a
non-fluidized bed material (03) uniformly spread over a number of flat plates
(07) acting as a thermal insulator and protecting the flat distributor plates (07)
from high temperature of operation; a plurality of bubble caps (04) having a
plurality of fluidizing nozzles (05) drilled at the upper periphery of the caps (04)
with desired diameter and pitch and welded to the top end of a plurality of stubs
(06) as shown in Figure 2 for uniform distribution of air / mixture of air and
steam, with optimum velocity known as the fluidization velocity for fluidizing the
bed in the chamber (01) the other end of the stubs (06) are attached to the
distributor plates (07) by a number of welds (08) to form a distributor grid.
Multiple cooling water tubes (09) welded to a number of bends (10), are welded
to the distributor plates (07) as shown in Figure 3, such that cooling water enters
at one end and leaves at the other end to safe guard the distributor plates (07)
from high temperature during bed heating phase of gasification. A pipe (11)
welded at the centre of the distributor grid allows removal of the bottom ash to
maintain the bed height during operation. Over a period of time, problems are
encountered due to distortion or warpage of the distributor plates including the
support plate. Because of this distortion or warpage, gaps or openings are
created between the two plates, allowing a portion of the process air and steam
mixture to pass through, resulting maldistribution of air / mixture of air and
steam in the fluidizing chamber leading to formation of agglomerates and
clinkers in the bed.
US Patent No. 4429471 dated February 7, 1984, entitled "FLUIDIZED BED AIR
DISTRIBUTOR" discloses a fluidized bed apparatus comprising a fluidized
chamber having a grid plate below said chamber, a feed gas channel beiow said
grid plate, and a fluidized bed distributor, said fluidized bed gas distributor
comprising a nipple, a cap and a bushing, wherein said cap is provided with at
least one gas distribution passage, and said nipple includes a central nipple
passage and said bushing includes a central bushing passage, said cap being
attached to a first end of said nipple said bushing being attached to a second
end of said nipple. However, the problem of forming agglomerates in the bed still
remains unsolved.
To overcome these problems an augmented water cooled flat plate distributor
and support device for air / gas / steam distribution in high pressure fluidized
bed gasification systems, is envisaged.
OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose an augmented
water cooled flat plate distributor and support device for air / gas / steam
distribution in high pressure fluidized bed gasification system, which improves
the life and function of the flat plate distributor by minimizing thermal stresses
and expansion by enhancing water cooling, thus eliminating the distortion or
warpage cause by thermal stresses.
Another object of the present invention is to propose an augmented water
cooled flat plate distributor and support device for air / gas / steam distribution
in high pressure fluidized bed gasification systems, that provides sturdy support
to hold the distributor including the deep bed firmly without deflection or
sagging, further allowing thermal expansion of the distributor, thereby
eliminating distortion or warpage caused by thermal stresses during gasifier
operation.
Yet another object of the present invention to propose an augmented water
cooled flat plate distributor and support device for air / gas / steam distribution
in high pressure fluidized bed gasification systems, in which castable refractory
and insulate lining over the distributor plate is provided to protect it from high
temperature during gasifier operation thereby minimizing the thermal stresses
and expansion and improves the life and function of the distributor.
Still another object of the present invention is to propose an augmented water
cooled flat plate distributor and support device for air /gas / stream distribution
in high pressure fluidized bed gasification systems, in which a plurality of
stiffeners are provided at the bottom of the distributor to support the distributor
and prevent the deflection or sagging, at various loads of gasification.
A further object of the present invention is to propose an augmented water
cooled flat plate distributor and support device for air / gas / steam distribution
in high pressure fluidized bed gasification systems that enables uniform flow
distribution of air / gas steam across the distributor plates along the entire bed
with a plurality of nozzle.
A still further object of the present invention is to propose an augmented water
cooled flat plate distributor and support device for air / gas / steam distribution
in high pressure fluidized bed gasification systems that reduces the repair and
maintenance time.
A further object of the present invention is to propose an augmented water
cooled flat plate distributor and support device for air / gas / steam distribution
in high pressure fluidized bed gasification systems that minimizes the formation
of agglomerates by enabling rapid and thorough mixing of the bed including an
easy extraction of bed ash to maintain bed height.
SUMMARY OF THE INVENTION
Accordingly, there is provided augmented water cooled flat plate distributor and
support device for air / gas / steam distribution in high pressure fluidized bed
gasification systems, the system comprising; a cylindrical shaped pressurized
fluidized bed gasifier to produce syngas from various grades of coal, a fluidizing
bed chamber encompassed by refractory and insulating brick lining to withstand
high temperature and high pressure fluidized bed; a non-fluidized bed material
uniformly spread over the bed, the device comprising a plurality of distributor
plate lined with castable refractory and insulite to act as a thermal insulator and
protect distributor plate from high temperature; a plurality of bubble caps having
a plurality of fluidizing nozzles configured at the upper periphery of the caps
through which the feed air or a feed mixture of air and steam is uniformly
distributor at an optimum velocity known as the fluidizing velocity for fluidizing
the material in the fluidizing bed chamber, a plurality of stubs attached to the
distributor plates by a number of welds, with the top ends welded to the bubble
caps to form a bubble cap nozzle assembly, a cooling water circuit with
continuous bent tubes welded to the distributor plate that protects the distributor
from high temperature during bed heating process by hot flue gases from the oil
burner; a pipe welded at the center of the distributor plate allowing easy
extraction of bed ash to maintain bed height during gasification process; a
support ring plate having a plurality of slotted bolt-holes to absorb thermal
expansion of the distributor plate during gasifier operation, and a plurality of
gusset plates welded at the bottom of the support ring plate, the support ring
plate placed below the fluidized bed chamber and welded to the gasifier to form
a rigid support for the distributor as well as for the gasifier bed; a ceramic ring
pad having corresponding slotted bolt-holes placed on top of the support ring
plate to act as a gasket for preventing leakage of air and steam mixture; the
distributor plate placed over the ceramic gasket and tightened with a number of
bolts, nuts and washers to firmly hold the distributor in position, the support ring
plate supporting the distributor and the entire bed to prevent sagging or
deflection at any point of time; a plurality of stiffener plates having contours
matching that of the cooling water pipes welded at the bottom of the distributor
plate to act as additional support for preventing sagging or deflection of the
distributor; a plurality of air / air and steam nozzles welded to a plenum to admit
air / mixture of air and steam during the gasification process. The configuration
and connectivity of the inventive device reduces the thermal expansion by
providing enhanced water cooling means including support means to
accommodate the thermal expansion of the distributor array, thereby improving
the life of the distributor array through elimination of distortion or warpage of
the distributor during gasifier operation.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - Shows a cross-sectional view of a high pressure fluidized bed coal
gasification system according to prior art.
Figure 2 - Shows a cross-sectional and enlarged view of a bubble cap nozzle
of the system of figure 1.
Figure 3 - Shows a plan view of a water cooled distributor with bubble cap
nozzle for air / mixture of air and steam distribution in high
pressure fluidized bed gasification system of figure 1.
Figure 4 - Shows a cross-sectional view of an augmented water cooled flat
plate distributor and support device for air / gas / steam
distribution in high pressure fluidized bed gasification systems,
according to the present invention.
Figure 4a - Shows a cross-sectional and enlarged view of a bubble cap nozzle,
according to the present invention.
Figure 5 - Shows a plan view of the augmented water cooled flat plate
distributor and support device for air / gas / steam distribution in
high pressure fluidized bed gasification systems, according to the
present invention.
Figure 6 - Shows a plan view of the augmented Water Cooled Rat Plate
Distributor assembly of the device of Figure 4.
Figure 7 - Shows a segment of the augmented support ring plate assembly of
the device of Figure 4.
Figure 8 - Shows a segment of a ceramic ring pad of the device of Figure 4.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
PRESENT INVENTION
Figures 4,4a,5,6,7 and 8 show an augmented water cooled flat plate distributor
and support arrangement for air / gas / steam distribution in a high pressure
fluidized bed gasification systems, the system comprising; a cylindrical shaped
pressurized fluidized bed gasifier (12) to produce syngas from various grade of
coal, a fluidizing bed chamber (13) to accommodate the fluidized bed, the
fluidized bed having all-through a refractory brick lining (14) including an
insulating brick lining (15) to withstand high temperature fluidized bed; and a
non-fluidized bed material (16) to be uniformly spread, the device comprising a
plurality of shaped distributor plates (19) having multiple first holes (20) drilled
with a pitch and diameter, a plurality of first slotted bolt-holes (21) drilled with
corresponding pitch a the periphery, and a second hoie (22) drilled with diameter
larger than the first holes (20) at the center of the distributor plates for bed ash
extraction as shown in Figure 6; a castable refractory lining (17) including an
insulite lining (18) laid over the shaped distributor plates (19) to act as a thermal
insulator and protect the distributor plates (19) from high temperature; a
plurality of bubble caps (23) having a plurality of fluidizing nozzles (24)
constructed at the upper periphery of the caps (23) through which the feed air or
a mixture of air and steam is uniformly distributed at an optimum velocity known
as the fluidization velocity for fluidizing the material in the fluidizing bed chamber
(13) to minimize formation of agglomerates by allowing rapid and thorough
mixing of bed, a plurality of stubs (25) inserted into the first holes (20) of the
distributor plates (19) and firmly fixed by a number of welds (26), and the top
ends are welded to top ends of the bubble caps (23) to form bubble cap nozzle
assembly as shown in Figures 4 and 4a; an augmented cooling water-flow circuit
having a plurality of water circulating tubes (27) with bends (28) welded to the
distributor plates (19) to form the augmented cooling water flow-circuit as shown
in Figures 5 and 6, which protects the distributors from high temperature, reduce
thermal expansion during bed heating process by hot flue gases from the oil
burner and increase the life of the distributor by allowing consistent entry of the
cooling water at one end and leaving at the other end; a pipe (29) inserted and
welded into the second hole (22) at the centre of the distributor allows easy
extraction of bed ash and maintains bed height during gasification process; a
support ring plate (30), having a plurality of second slotted bolt-holes (31)
matching the first slotted bolt-holes (21) in the distributor plates (19), to
accommodate the thermal expansion of the distributor plates (19) during gasifier
operation; a plurality of gusset plates (32) welded at the bottom of the support
ring plate (30) to form of a support assembly, as shown in Figure 7. The support
assembly is placed below the fluidizing bed chamber (13) and welded into the
gasifier (12) to form a rigid support for the distributor as well as for the gasifier
bed as shown in Figure 4; a ceramic ring pad (33) having a number of third
slotted bolt-holes (34) drilled to match with the first and second slotted bolt-
holes (21,34) placed on top of the support ring plate (30) acting as a gasket and
preventing the air and steam mixture to pass through; the distributor plate is
located over the ceramic gasket (33) and tightened with a number of bolts, nuts
and washers (35,36,37) to firmly hold the distributor in position, the support ring
plate (30) firmly holding and supporting the distributor and the entire bed at any
point of time; a plurality of stiffener plates (38) having matching contours of that
of the cooling water pipes (27) welded at the bottom of the distributor plate as
shown in Figure 5, the stiffener plate assembly acting as an additional support
and preventing sagging or deflection of the distributor at various loads of
gasification; a plurality of air and steam nozzles (39) placed below the distributor
assembly and welded to a plenum (40) as shown in Figure 4, to admit air or air
and steam mixture for gasification process.
The distributor assembly with the plurality of bubble cap nozzles (23,24) and
stubs (25) is welded at the bottom of the gasifier (12) and thereafter the cooling
water inlet and outlet connections are made. It holds the bed to a particular
height with high temperature.
During the gasification process, the air / mixture of air and steam is admitted to
the plenum (40) through the air + steam nozzles (39), and flows through the
distributor nozzles (24), coal is injected to the gasifier (12) through an ejector
using compressed air with the bed material already filled in the gasifier, the
distributor creates uniform flow distribution of the air / mixture of air and steam
with high velocity and ensures uniform temperature distribution above the bed
which in turn allows production of fuel gas with desired composition. The device
minimizes or avoids formation of agglomerates by allowing rapid and thorough
mixing of the bed with the use of the bubbles cap air / steam nozzles. The device
also holds the bed to a particular height with high temperature by allowing easy
removal of bed ash, and maintains uniform fluidization velocity. The augmented
water cooling circuit of the device enables the distributor to withstand high
temperature and reduces thermal expansion. Also due to the sturdy support
assembly of the device allows absorption of thermal expansion of the distributor.
Thus, the invention device eliminates distortion or warpage of the distributor
during gasifier operation. The device also acts as a strong support means to hold
the distributor firmly and maintain the deep bed without deflection or sagging.
The invention substantially reduces the repair and maintenance time and cost
and provides easy maintenance.
WE CLAIM
1. An augmented water cooled flat plate distributor and support device for
air / gas / steam distribution in high pressure fluidized bed gasification
systems, the system comprising:
- a cylindrical shaped pressurized fluidized bed gasifier (12) to produce
syngas from various grades of coal, a fluidizing bed chamber (13) to
accommodate the static and fluidized bed, encompassed by a
refractory brick lining (14) including an insulating brick lining (15) to
withstand high temperature and high pressure fluidized bed, a non-
fluidized bed material (16) uniformly spread over the bed;
- the device comprising a plurality of shaped distributor plates (19)
having multiple first holes (20) drilled with a diameter and pitch in
which the plurality of stubs (25) are inserted and firmly fixed by a
number of welds (26), a plurality of first slotted bolt-holes (21) drilled
a the periphery, a second hole (22) drilled at the center of distributor
plate for bed ash extraction, the second hole (22) having a diameter
larger than the first hole (20);
- a castable refractory lining (17) including an insulite lining (18)
disposed over the plurality of flat distributor plates (19) to act as a
thermal insulator and protect the distributor plates (19) from high
temperature;
- a plurality of bubble caps (23) having a plurality of fluidizing nozzles
(24) constructed at the top periphery of the caps (23), through which
the feed air or a mixture of air and steam is uniformly distributed at an
optimum velocity for fluidizing the material in the fluidizing bed
chamber (13) and minimize formation of agglomerates due to rapid
and thorough mixing of the bed including fast extraction of bed ash;
- a support ring plate (30), having a plurality of second slotted bolt-
holes (31) drilled to match with the first slotted bolt-holes (21) and
accommodates thermal expansion of the distributor plates (19) during
gasifier operation;
- a plurality of gusset plates (32) welded at the bottom of the support
ring plate (30) to form a support assembly, and placed below the
fluidizing bed chamber (13) and welded into the gasifier (12) to firmly
hold and support the distributor including the entire bed without
sagging or deflection of the distributor during gasifier operation;
- a plurality of stiffener plates (38) having contours matching with that
the cooling water pipes (27) of a cooling water flow circuit welded at
the bottom of the distributor plate to act as an additional support for
preventing sagging or deflection of the distributor array at various
loads of gasification.
2. The device as claimed in claim 1, wherein a plurality of stubs (25) are
inserted and welded into the first holes (20) of the distributor plates (19),
and wherein the top ends of the stubs (25) are welded to the bubble caps
(23) to form a bubble cap nozzle assembly.
3. The device as claimed in ciaim 1 or 2, wherein a plurality of said cooling
water tubes (27) are welded to corresponding number of bends (28) and
the weld assembly is further welded to the distributor plates (19) to form
an augmented cooling water circuit, the cooling water entering at one end
and leaving at the other end, which circuit providing protection to the
distributor from high temperature including reduction in the thermal
expansion during bed heating process by the hot flue gases.
4. The device as claimed in any of the preceding claims, wherein a pipe (29)
is inserted into the second hole (22) and welded at the center of the
distributor array to allow easy extraction of the bed ash to maintain the
bed height including maintenance of an improved calorific value of the
coal gas during gasification process.
5. The device as claimed in claim 4, wherein the plurality of distribution
plates (19) are welded in between the cooling water circuit pipes (27) to
form a water cooled distributor array.
6. The device as claimed in claim 5, wherein a ceramic ring pad (33) having
multiple third slotted bolt-holes (34) are drilled to match with the first and
second slotted bolt-holes (21,31) constructed on the distributor array and
support plate respectively and disposed on top of the support ring plate
(30) to act as a gasket for preventing the air and steam mixture to pass
through.
7. The device as claimed in claim 6, wherein the distributor plate assembly is
placed over the ceramic gasket (33) and tightened with a number of bolts,
nuts and washers (35,36,37).
8. The device as claimed in claim 7, wherein a plurality of air and steam
nozzles (39) are welded to a plenum (40) to admit air and steam mixture
for gasification process.
9. The device as claimed in claim 8, wherein the bubble cap nozzles (23) are
supported by the distributor plates (19), and wherein the water cooling
circuit (27,28), refractory and insulate lining (17,18) in the distributor
plates (19) increase the life of distributor by minimizing the thermal
stresses during gasifier operation.

ABSTRACT

The invention relates to an augmented water cooled flat plate distributor and
support device for air / gas / steam distribution in high pressure fluidized bed
gasification systems, the system comprising a cylindrical shaped pressurized
fluidized bed gasifier (12) to produce syngas from various grades of coal, a
fluidizing bed chamber (13) to accommodate the static and fluidized bed,
encompassed by a refractory brick lining (14) including an insulating brick lining
(15) to withstand high temperature and high pressure fluidized bed, a non-
fluidized bed material (16) uniformly spreadover the bed; the device comprising
a plurality of shaped distributor plates (19) having multiple first holes (20) drilled
with a diameter and pitch in which the plurality of stubs (25) are inserted and
firmly fixed by a number of welds (26), a plurality of first slotted bolt-holes (21)
drilled at the periphery, a second hole (22) drilled at the center of distributor
plate for bed ash extraction, the second hole (22) having a diameter larger than
the first hole (20); a castable refractory lining (17) including an insulite lining
(18) disposed over the plurality of flat distributor plates (19) to act as a thermal
insulator and protect the distributor plates (19) from high temperature; a
plurality of bubble caps (23) having a plurality of fluidizing nozzles (24)
constructed at the top periphery of the caps (23), through which the feed air or
a mixture of air and steam is uniformly distributed at an optimum velocity for
fluidizing the material in the fluidizing bed chamber (13) and minimize formation
of agglomerates due to rapid and thorough mixing of the bed including easy
extraction of bed ash; a support ring plate (30), having a plurality of second
slotted bolt-holes (31) drilled to match with the first slotted bolt-holes (21) and
accommodate thermal expansion of the distributor plates (19) during gasifier
operation; a plurality of gusset plates (32) welded at the bottom of the support
ring plate (30) to form a support assembly, and placed below the fluidizing bed
chamber (13) and welded into the gasifier (12) to firmly hold and support the
distributor including the entire bed without sagging or deflection of the
distributor during gasifier operation; a plurality of stiffener plates (38) having
contours matching with that the cooling water pipes (27) of a cooling water flow
circuit welded at the bottom of the distributor plate to act as an additional
support for preventing sagging or deflection of the distributor array at various
loads of gasification.