FIELD OF INVENTION
This invention relates to integrated gasification based power generation in high pressure
fluidized bed gasification system using any grade of coals/bio mass. More particularly, the
invention relates to a high temperature bulk-solid recirculator for high pressure fluidized bed
gasification system.
BACKGROUND OF INVENTION
Combined Cycle increasingly being used to generate electricity through integrated
gasification. Such combined cycles are capable of using various grades of low calorific value
and high ash content coals.
In a fluidized bed gasifier the air and steam mixture is introduced through a distributor
located at bottom of the gasifier. Coal is continuously injected to the gasifier through at least
one ejector using compressed air. Coal gas is produced due to the chemical reaction of coal
with air and steam. The fly ash and unburnt carbon particles in fuel gas are separated by a
plurality of cyclones disposed in series in the gasifier/ The coal gas at the exit of the cyclone
is cooled in a Heat Recovery Boiler (HRB), The gas is further cooled in a cooler
simultaneously superheating the saturate.- steam of HRB. Part of the superheated steam is
utilized for gasification process and the rest is caused to expand in the steam turbine to
generate electricity. The gas is further processed in a gas cleaning system and admitted to
a gas turbine combustion chamber to generate electricity.
The collected fly ash having sizable amount of char/unburnt carbon which is recycled back
to the gasifier through a non mechanical High temperature bulk solid recirculator to utilize
the unburnt carbon in the fly ash.
In typical pressurized fluidized bed gasifiers, the fly ash collected in a cyclone having
considerable amount of unburnt carbon is recycled back to the gasifier through a fly ash
cooler, a rotary bucket type extractor and an ejector use the compressed gas. A double
shelled fly ash cooler generally is provided with a number of water tubes staggerly, arranged
in the inner shell, wherein the required quantity of water is

admitted between the shells which flow through the tubes, and the ash flowing
in between the tubes gets cooled. Problems are encountered in respect of
bridging of the ash accumulated above the buckets of rotary extractor, and
further respecting the larger size foreign materials like refractory pieces which
get locked in the bucket causing an arresting of the rotation of the bucket
leading to stoppage of extraction. Moreover, in this system considerable amount
of heat is removed from the fly ash by the cooler and the cooled fly ash perforce
recycled back to the gasifier at a lower temperature thus reducing the possibility
of optimum burning/gasification of the recycled char.
SUMMARY OF INVENTION
Accordingly there is provided a high temperature bulk-solid recirculator adaptable
to high pressure fluidized bed gasification systems, comprising at least one
bubble cap distributor for fluidizing bulk-solid, the distributor receiving a coal
gas/inert gas/air/steam via inlet pipes at a pressure higher than the operating
pressure of the gasification system; a dual gas chamber for admitting coal
gas/inert gas/air/steam to the distributor via inlet pies; two fluidizing pipes
disposed vertically in respect of the dual gas chamber for collecting the bulk
solids from atleast one cyclone of the system, fluidizing the bulk-solid and
thereby causing an upward transmittal of the fluidized material; a pipe angularly
disposed and flowably inter connecting the atleast one cyclone and the fluidizing
pipe for downlink transportion of the ash particles separated in atleast one
cyclone; and an inclined pipe disposed at an angle from 40° to 80° with
reference to the other fluidizing pipe of the two fluidizing pipes for recycling back

the ash particulates continuously to the gasification system. The high
temperature bulk solid recirculator in a fluidizing condition acts as a one way
seal, thereby allowing material flow to the gasifier and preventing material/gas
flow in the opposite direction.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Fig. - Shows an elevational and side view of a high temperature bulk-solid
recirculator of the present invention (without the gasifier)

DETAILED DESCRIPTION OF AN PREFERRED EMBODIMENT OF THE
INVENTION
In a fluidized bed bulk solid recirculator, when controlled quantity of clean coal gas/inert
gas/air is admitted to a bubble cap distributor (01) through a gas inlet pipe (02) and a
dual gas chamber (03) at a slightly more than the system pressure, fluidization velocities
are generated in both left and right vertical limbs (04,05), the diameter 'd' of the vertical
limbs (04,05) ranging from 100mm 500mm. The bulk solids in both the limbs (04,05)
start fludizing and rise upward. The ash particles collected in atleast one cyclone and flow
through a pipe (06) having an angle a ranging from 40° to 80°. The ash particles in the
other limb (05) over flow into the gaslfier through an inclined pipe (07), having an angle
6 ranging from 40° to 80°. Above the bubble cap distributor (01), a plurality of cooling
water jacket pipes (08,09,10 and 11) are configured for cooling the inner pipes (04,05,06
and 07). A plurality of fluidizing distributor nozzles are arranged in a middle portion of the
distribution (01), for example at a height ranging from 0.8d to 1.2d. This process
continues for the entire operation of the system and the unburnts in the fly ash are
recycled back to the gasifier. The cooling water enters through an iniet pipes (12) and
hot water exit from an outlet pipe (13). An auxiliary fresh coal injection pipe (14) enables
fuel supplementing. Atleast one each inspection port (15) and pressure and temperature
measuring port (16) is provided to said high temperature bulk solid recirculator.
The high temperature bulk solid recirculator in a fluidizing condition acts as an one way
seal, thereby allowing materiaf flow to the gasifier, and preventing material/gas flow in
the opposite direction. The invention has additional features in the fluidizing distributor
nozzle design, water cooling arrangement and the application for higher pressure.

WE CLAIM
1. A high temperature bulk-solid recirculator adaptable to high pressure
fluidized bed gasification systems, comprising:
- at least one bubble cap distributor (01) for fluidizing bulk-solid, the
distributor receiving a coal gas/inert gas/air/steam via inlet pipes
(02) at a pressure higher than the operating pressure of the
gasification system;
- a dual gas chamber (03) for admitting coal gas/inert gas/air/steam
to the distributor (01) via inlet pipes (02);
- two fluidizing pipes disposed vertically in respect of the dual gas
chamber (03) for collecting the bulk solids from atleast one cyclone
of the system, fluidizing the bulk-solid and thereby causing an
upward transmittal of the fluidized material;
- a pipe (06) angularly disposed and flowably inter connecting the
atleast one cyclone and the fluidizing pipe (04) for downlink
transportion of the ash particles separated in atleast one cyclone;
and
- an inclined pipe (07) disposed at an angle from 40° to 80° with
reference to the other fluidizing pipe (04) of the two fluidizing pipes
(04, 05) for recycling back the ash particulates continuously to the
gasification system, characterized in that high temperature bulk
solid recirculator in a fluidizing condition acts as a one way seal,
thereby allowing material flow to the gasifier and preventing
material/gas flow in the opposite direction.

2. The recirculator as claimed in claim 1, comprising a plurality of water
jacket pipes (08,09,10,11) disposed above the distributor (01) for cooling
the inner pipes (04,05,06 and 07).
3. The recirculator as claimed in claim 1 or claim 2, wherein said plurality of
water jacket pipes (03,09,10,11) have two inlet pipes (12) and one outset
pipe (13) for entry and exit of cooling water and hot water respectively.
4. The recirculator as claimed in claim 1, comprising an axilliary fresh coa.
injection pipe (13) for supplementing fuel supply.
5. The recirculator as claimed in claim i, comprising atleast one each
inspection port (15) and pressure and temperature measuring port
(16).
6. The recirculator as claimed in claim 1, wherein the re-circulator is
provided with a refractory lining.
7. A high temperature bulk-solid recirculator for high pressure fluidized bed gasification system as herein described and illustrated with the
accompanying drawing.

ABSTRACT

TITLE "HIGH TEMPERATURE BULK SOLID RECIRCULATOR FOR HIGH
PRESSURE FLUDIZED BED GASIFICATION SYSTEM"
The invention relates to a high temperature bulk-solid recirculator adaptable
to high pressure fluidized bed gasification systems, comprising: at least one
bubble cap distributor (01) for fluidizing bulk-solid, the distributor receiving a
coal gas/inert gas/air/steam via inlet pipes (02) at a pressure higher than the
operating pressure of the gasification system; a dual gas chamber (03) for
admitting coal gas/inert gas/air/steam to the distributor (01) via inlet pipes
(02); two fluidizing pipes disposed vertically in respect of the dual gas
chamber (03) for collecting the bulk solids from atleast one cyclone of the
system, fluidizing the bulk-solid and thereby causing an upward transmittal of
the fluidized material; a pipe (06) angularly disposed and flowably inter
connecting the atleast one cyclone and the fluidizing pipe (04) for downlink
transportion of the ash particles separated in atleast one cyclone; and an
inclined pipe (07) disposed at an angle from 40° to 80° with reference to the
other fluidizing pipe (04) of the two fluidizing pipes (04, 05) for recycling back
the ash particulates continuously to the gasification system, characterized in
that high temperature bulk solid recirculator in a fluidizing condition acts as a
one way seal, thereby allowing material flow to the gasifier and preventing
material/gas flow in the opposite direction.