FIELD OF INVENTION
[001] The present invention relates to the method for improving the
quality of syngas in a fluidized bed gasification technology, thus,
reducing hazardous substances in the atmosphere. The present
disclosure is in the field of performance improvement of gasifier by
re-circulating the exhaust flue gases from syngas engine to fluidized
bed gasifier for power generation technology, particularly
gasification technology for power generation through syngas engine.
BACKGROUND AND THE PRIOR ART
[002] Coal is most important and abundant fossil fuel used for power
generation. Coal continues to occupy a pivotal role in world energy
scene. Conventional subcritical pulverized coal fired power plants
burn coal to generate steam and use generated steam for power
generation at an efficiency of around 30 - 35%. These power plants
emit large quantities of carbon dioxide which causes global warming
and oxides of sulphur and nitrogen which are responsible for acid
rains. Hence, it is essential to utilize coal more efficiently by reducing
the emission.
[003] To overcome the above problems, various clean coal
technologies are at various stages of development to utilize coal more

efficiently. One of the current concepts for utilizing coal more
efficiently with low emissions route is gasification process. In
gasification process the coal is used as a feed stock to generate the
synthesis gas (mixture of CO and H2) at elevated pressure and
temperature. Various gasification technologies are available for
gasification of different coals. The fluidized bed gasification (FBG)
has been identified and being used for gasification of high ash
content coals. The high ash coals are converted in to syngas in
gasification process and used for power generation through gas
engine for rural electrification or captive power applications. In
captive power applications, coal is gasified at elevated pressure and
temperature to generate coal syngas (mixture of CO and H2). The
generated syngas is cleaned to remove various contaminants such
as particulates, H2S, NH3 and alkali in gas clean-up system. After
cleaning the syngas in gas clean-up system, the cleaned gas is sent
as fuel to syngas engine for power generation.
[004] DE102016008835A1 titled “Integrated exhaust gas recycling
and fuel gasification plant for internal combustion engines of all
kinds” relates to integrated exhaust gas recycling and fuel
gasification plant for use on all types of internal combustion engines
or explosion. It is also the preferred liquid fuel by means of the waste
heat of the exhaust gassed and optimally prepared with the aid of
exhaust heat and catalysts for the combustion. The exhaust gas

from this combustion material has been recycled by the components
contained in this exhaust gas transformed water vapour, CO and
CO2 in new fuels and oxygen liberated from them again.
[005] JP2002004948 titled “A Power generating device and method
using hydrocarbon as material” improves gasification efficiency in
producing a combustible gas for an internal combustion engine by
gasifying a hydrocarbon material. A part of an exhaust gas from
the internal combustion engine has been introduced into a gasifying
device as a gasifying agent to be directly brought into contact with a
material composed of hydrocarbon in the gasifying device to produce
the combustible gas. The combustible gas has been refined to be
used as the fuel of the internal combustion engine itself with
releasing the remained exhaust gas to the atmospheric air. The
amount of the exhaust gas to be introduced into the gasifying device
and a rate of the distribution of the exhaust gas to be released to the
atmosphere can be adjusted by adjusting an opening of
the exhaust gas distribution valve.
[006] US20110315096A1 titled “Gasifier Hybrid combined cycle
power plant” provides a system and method for the efficient, clean
and simultaneous conversion of multiple fuels, including but not
limited to waste derived gas, liquid and solid phase fuels, to
electrical energy. The invention used a closely coupled combined

thermal cycle system based on an air fed gasifier and
an internal combustion engine. Steam generated by exhaust heat
from an internal combustion engine and from the combustion of
syngas produced by the gasifier is used to power an admission steam
turbine in an efficient system in which components such as water
treatment, heat recovery, and other components are common to
gasifier and the internal combustion engine.
[007] EP3214155A3 titled “Process and apparatus for the
production of synthesis gas for running an internal combustion”
discloses a method for producing synthesis gas for operating an
internal combustion engine from an organic solid fuel decomposed
into pyrolysis products in a pyrolysis reactor without an oxygen
supply, includes feeding the pyrolysis products from a bottom of the
pyrolysis reactor to a fluidized bed reactor. A synthesis gas produced
in the fluidized bed reactor is withdrawn as product gas. The
products gas is directly or indirectly fed to the internal combustion
engine. The pyrolysis reactor is operated using at least one pyrolysis
auger for conveying the solid fuel. The fluidized bed reactor is
fluidized by supplying air at a rate above a minimal loosening rate
of the bed material of the fluidized bed of the fluidized bed reactor.
[008] None of the prior art references have the characteristics of the
present invention that of the improving the syngas quality by

recirculating the exhaust gases coming from the syngas engine.
Through the present invention, the quality of the syngas gets
improved which in turn increases the gas engine efficiency and also
decreases the hazardous gases like carbon di-oxide, carbon
monoxide and hydro carbons in the atmosphere. The present
invention can overcome the drawbacks of the above mentioned prior
arts.
OBJECTS OF INVENTION
[009] Therefore, the objective of the present invention is to increase
the quality of the syngas in a fluidized bed gasifier by utilizing the
waste heat energy available in the flue gas.
[010] Another objective of the present invention is to increase the
efficiency of gas engine by utilizing the qualitative syngas as a fuel
for gas engine.
[011] A further objective of the present invention is to reduce the
CO2 gases in the atmosphere by recycling the exhaust flue gases
coming from the gas engine to fluidized bed gasification process.
[012] Yet another objective of the present invention is to reduce the
Nitrogen Oxides (NOx) concentration by avoiding the utilization of
air in a fluidized bed gasification process.

[013] Yet another objective of the present invention is to increase
the calorific value of syngas by utilizing the oxygen in place of air in
a gasification process.
SUMMARY OF THE INVENTION
[014] In the present invention, in syngas engine, the cleaned
synthesis gas is burnt for power generation and converted in to flue
gas. The temperature of the flue gas at the exhaust of the gas engine
is approximately in the range of 300-350 Degree C and the
composition is carbon di-oxide, carbon monoxide and hydro
carbons. Since the exhaust gases are having 300-350 Degree C,
these gases are re-used as fluidizing media by adding required
quantity of oxygen content for generation of synthesis gas in
fluidized bed gasification process.
[015] In an aspect, the heat which is available in flue gas is used for
synthesis gas production which in turn improves the quality of
syngas. Also the hazardous gases like carbon di-oxide, carbon
monoxide and hydro carbons are reduced in the atmosphere by
utilizing as a fluidizing media in the fluidized bed gasifier.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[016] It is to be noted, however, that the appended drawings
illustrate only typical embodiments of the present subject matter
and are therefore not to be considered for limiting of its scope, for
the invention may admit to other equally effective embodiments. The
detailed description is described with reference to the accompanying
figures. In the figures, a reference number identifies the figure in
which the reference number first appears. The same numbers are
used throughout the figures to reference like features and
components. Some embodiments of system or methods or structure
in accordance with embodiments of the present subject matter are
now described, by way of example, and with reference to the
accompanying figures, in which:
[017] FIGURE 1 shows a Schematic view of the Re-circulation of
exhaust flue gases from syngas engine to fluidized bed gasifier for
power generation.
[018] The figures depict embodiments of the present subject matter
for the purposes of illustration only. A person skilled in the art will
easily recognize from the following description that alternative
embodiments of the structures and methods illustrated herein may
be employed without departing from the principles of the disclosure
described herein.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF
THE PRESENT INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
[019] While the embodiments of the disclosure are subject to various
modifications and alternative forms, specific embodiment thereof
have been shown by way of example in the figures and will be
described below. It should be understood, however, that it is not
intended to limit the disclosure to the particular forms disclosed, but
on the contrary, the disclosure is to cover all modifications,
equivalents, and alternative falling within the scope of the
disclosure.
[020] The terms “comprises”, “comprising”, or any other variations
thereof used in the disclosure, are intended to cover a non-exclusive
inclusion, such that a device, system, assembly that comprises a list
of components does not include only those components but may
include other components not expressly listed or inherent to such
system, or assembly, or device. In other words, one or more elements
in a system or device proceeded by “comprises… a” does not, without
more constraints, preclude the existence of other elements or
additional elements in the system or device.
[021] The present invention provides the method for improving the
quality of syngas by re-circulating the exhaust flue gases from

syngas engine to fluidized bed gasifier for power generation. As
shown in Figure 1, the present invention comprises of a fluidized
bed gasifier (14) where the gasification process takes place with the
generation of the synthesis gas or syngas. A subbituminous coal of
size (0-6) mm is used as a feed stock and is fed in to gasifier using
coal hopper (9), coal lock (10) and rotary feeder (11). The gasification
process takes place by admitting coal from coal hopper (9), coal lock
(10) and rotary feeder (11) in to fluidized bed gasifier (14). A lime
stone is added to the gasification process through sorbent hopper
(6), sorbent lock (7) and sorbent feeder (8) in order to capture the
SOX concentration in syngas. The generated syngas is cleaned from
dust particles in a cyclone-1 (15), cyclone-2 (17) and candle filter
system (19) and is sent to the gas cooler (21) for cooling the said
syngas. The cooled syngas is sent to the knock out drum (22)
thereafter for removing the moisture content in the synthesis gas. A
multiple unit of ash locks are provided as (16) from (15), (18) from
(17) and (20) from (19) where the fly ashes are collected by ash
removal system. After receiving the fly ash from the ash removal
system, the ashes are withdrawn in a predetermined period.
[022] Removing the dust particles and moisture content in the
synthesis gas thereupon, it is passed into a syngas receiver (23)
where the syngas is stored. The stoichiometric required syngas from
the syngas receiver (23) is sent to the syngas inlet manifold (25) at

60 degree C through mass flow meter (24). The mass flow meter (24)
measures the flow rate of synthesis gas that is sent into the said gas
engine inlet manifold (25). The stoichiometric air is admitted into the
gas engine manifold (25) that mixes with the entered synthesis gas.
After mixing the synthesis gas and air in the gas engine inlet
manifold (25), the said mixed gas combination enters into a
cylindrical chamber syngas engine (26) for power generation
through power stroke. Thereafter, the waste (waste or flue) gases
comes out from the syngas engine cylinder (26) through exhaust
stroke.
[023] After power stoke in the gas engine (26), the waste gases or
flue gases are sent to the flue gas receiver (29) through exhaust
muffler (27) and non-return valve (28). A non-return valve (28) is
provided at the end of syngas engine (26) for not entering the
exhaust gases back into the syngas engine (26) due to pressurization
of flue gas receiver (29). The flue gas receiver (29) is insulated with
ceramic wool to avoid the heat loss. Storing the flue gas in a flue gas
receiver (29), a blower (1) is used to suck the flue gas from the flue
gas receiver (29), to compresses in the range of 1.2 to 1.5 bar
pressure and is sent to the system receiver (2) therefrom. The system
receiver (2) is vessel where the flue gas is stored and utilized for
gasification purpose. From the system receiver (2), the flue gas is
sent to the fluidized bed gasifier (14) as a fluidizing media for

fluidizing the bed material. Another stream of flue gas from (2) is
used as a transport of air or secondary air to push the feed stock
into the fluidized bed gasifier (14). A flow control valve (30) controls
the flue gas flow rate from syngas receiver (29) to system receiver
(2).
[024] The oxygen from the oxygen receiver (4) and steam from steam
generator (3) is added to gasifier plenum (5) through flow control
valve (FCV). By mixing oxygen in place of air, the gasification
reactivity is increased as the carbon available in coal is converted
into synthesis gas. When the carbon conversion rate is increased,
the calorific value of synthesis gas also increases. The method
disclosed herein involves increase of the caloric value of syngas from
1100 kcal/nm3 to 1250 kcal/nm3. Addition of super-heated steam
from steam generator (3) increases the hydrogen concentration in
synthesis gas. A unit of ash locks (13) is provided at plenum (5)
where the bottom ashes are collected therefrom through ash
extractor (12).
[025] The valves attached to system receiver (2), steam generator (3),
sorbent hopper (6), sorbent feeder (8), coal hopper (9) and rotary
feeder (11) act as both way flow in the required direction.
[026] In the present disclosure the synthesis gas is generated in a
fluidized bed gasification process and is used as a fuel for a gas

engine where electrical energy or power is generated. The syngas
engine (26) emits the flue gases at a temperature range of 300-350
Degree C and is used as a fluidizing media for gasification process.
The flue gases sent into gasifier (14) at 180-250 degree C carries
sensible heat to the process. By utilizing the heat from flue gas, the
quality of the synthesis gas is improved. In the present invention,
the gasification reactivity increases due to presence of oxygen and
carbon dioxide in flue gas where carbon dioxide replaces the
nitrogen. Hence the quality of synthesis and also reactivity of coal
increases. The exhaust gases composition consists of Carbon di-
oxide (CO2), carbon monoxide (CO) and hydrocarbons (HC) and these
are very harmful for environment. By recycling the exhaust flue
gases from the gas engine (26) to fluidized bed gasifier (14), the heat
which is available in the flue gas is utilized in the gasification
process which in turn improves the quality of syngas and also
minimizes the release of hazardous substance into the environment.
[027] It should be noted that the description and figures merely
illustrate the principles of the present subject matter. It should be
appreciated by those skilled in the art that conception and specific
embodiment disclosed may be readily utilized as a basis for
modifying or designing other structures for carrying out the same
purposes of the present subject matter. It should also be appreciated
by those skilled in the art that by devising various arrangements

that, although not explicitly described or shown herein, embody the
principles of the present subject matter.
[028] Although embodiments for the present subject matter have
been described in language specific to package features, it is to be
understood that the present subject matter is not necessarily limited
to the specific features described. Rather, the specific features and
methods are disclosed as embodiments for the present subject
matter. Numerous modifications and adaptations of the method of
the present invention will be apparent to those skilled in the art, and
thus it is intended by the appended claims to cover all such
modifications and adaptations which fall within the scope of the
present subject matter.
[029] It will be understood by those within the art that, in general,
terms used herein, and especially in the appended claims (e.g.,
bodies of the appended claims) are generally intended as “open”
terms (e.g., the term “including” should be interpreted as “including
but not limited to,” the term “having” should be interpreted as
“having at least,” the term “includes” should be interpreted as
“includes but is not limited to,” etc.). It will be further understood by
those within the art that if a specific number of an introduced claim
recitation is intended, such an intent will be explicitly recited in the
claim, and in the absence of such recitation no such intent is
present. For example, as an aid to understanding, the following

appended claims may contain usage of the introductory phrases “at
least one” and “one or more” to introduce claim recitations. However,
the use of such phrases should not be construed to imply that the
introduction of a claim recitation by the indefinite articles “a” or “an”
limits any particular claim containing such introduced claim
recitation to inventions containing only one such recitation, even
when the same claim includes the introductory phrases “one or
more” or “at least one” and indefinite articles such as “a” or “an”
(e.g., “a” and/or “an” should typically be interpreted to mean “at
least one” or “one or more”); the same holds true for the use of
definite articles used to introduce claim recitations. In addition, even
if a specific number of an introduced claim recitation is explicitly
recited, those skilled in the art will recognize that such recitation
should typically be interpreted to mean at least the recited number
(e.g., the bare recitation of “two recitations,” without other modifiers,
typically means at least two recitations, or two or more recitations).
Furthermore, in those instances where a convention analogous to
“at least one of A, B, and C, etc.” is used, in general such a
construction is intended in the sense one having skill in the art
would understand the convention (e.g., “a system having at least one
of A, B, and C” would include but not be limited to systems that have
A alone, B alone, C alone, A and B together, A and C together, B and
C together, and/or A, B, and C together, etc.). In those instances

where a convention analogous to “at least one of A, B, or C, etc.” is
used, in general such a construction is intended in the sense one
having skill in the art would understand the convention (e.g., “a
system having at least one of A, B, or C” would include but not be
limited to systems that have A alone, B alone, C alone, A and B
together, A and C together, B and C together, and/or A, B, and C
together, etc.). It will be further understood by those within the art
that virtually any disjunctive word and/or phrase presenting two or
more alternative terms, whether in the description, claims, or
drawings, should be understood to contemplate the possibilities of
including one of the terms, either of the terms, or both terms. For
example, the phrase “A or B” will be understood to include the
possibilities of “A” or “B” or “A and B.”
[030] It will be further appreciated that functions or structures of a
plurality of components or steps may be combined into a single
component or step, or the functions or structures of one-step or
component may be split among plural steps or components. The
present invention contemplates all of these combinations. Unless
stated otherwise, dimensions and geometries of the various
structures depicted herein are not intended to be restrictive of the
invention, and other dimensions or geometries are possible. In
addition, while a feature of the present invention may have been
described in the context of only one of the illustrated embodiments,

such feature may be combined with one or more other features of
other embodiments, for any given application. It will also be
appreciated from the above that the fabrication of the unique
structures herein and the operation thereof also constitute methods
in accordance with the present invention. The present invention also
encompasses intermediate and end products resulting from the
practice of the methods herein. The use of “comprising” or
“including” also contemplates embodiments that “consist essentially
of” or “consist of” the recited feature.
ADVANTAGE OF INVENTION
[031] The advantage of the present invention is that it increases the
quality of the syngas in a fluidized bed gasifier by utilizing the waste
heat energy available in the flue gas.
[032] Another advantage of the present invention is that it increases
the efficiency of gas engine by utilizing the qualitative syngas as a
fuel for gas engine.
[033] Yet another advantage of the present invention is that it
reduces the CO2 gases in the atmosphere by recycling the exhaust
flue gases coming from the gas engine to fluidized bed gasification
process.

[034] Yet another advantage of the present invention is that it
reduces the Nitrogen Oxides (NOx) concentration by avoiding the
utilization of air in a fluidized bed gasification process.
[035] Yet another advantage of the present invention is that it
increases the calorific value of syngas by utilizing the oxygen in place
of air in a gasification process.

WE CLAIM:
1. A method of recirculation of exhaust flue gases from synthetic
gas engine to fluidized bed gasifier and improvement of syngas
quality, comprising the steps of:
- Generating the synthesis gas (syngas) in fluidized bed gasifier
(14) upon gasification process by admitting coal from coal hopper
(9), coal lock (10) and rotary feeder (11) into fluidized bed gasifier
(14) for gasification and with feeding sorbent through sorbent
feeder (8) from sorbent hopper (6) and sorbent lock (7) into the
gasifier (14) for absorption of sulphur content available in coal,
wherein the generated syngas from (14) gets cleaned from dust
particle by passing through cyclone-1 (15), cyclone-2 (17) and
candle filter system (19) attached with fly ash lock unit (16, 18,
20) configured in the path of generated syngas from (14), gets
cooled by gas cooler (21) and gets dried by passing through a
knock out drum (22) attached to the said gas cooler (21);
- Storing the said syngas into a syngas receiver (23) and Sending
stoichiometric syngas therefrom to the syngas inlet manifold (25)
at 60 degree C through mass flow meter (24) with measurement
of the flow rate of synthesis gas;
- Admitting stoichiometric air into the gas engine manifold (25) to
mix with the entered synthesis gas and Passing the said syngas

and air mix combination therefrom into a gas engine (26) cylinder
chambers for power generation through power stroke;
Producing the waste or flue gases from the syngas engine cylinder
(26) through exhaust stroke and Sending the said waste or flue
gases to the flue gas receiver (29) through exhaust muffler (27)
and non-return valve (28) therefrom,
wherein non-return valve (28) embedded at the end of syngas
engine (26) prohibits entering of the exhaust gases back into the
syngas engine (26) due to pressurization of flue gas receiver (29)
attached with a blower (1) and insulated with ceramic wool to
avoid the heat loss;
Sending the said flue gas to the system receiver (2) therefrom in
controlled flow rate through flow control valve (30), for storing
and utilizing the flue gas for gasification, wherein it follows one
stream to the fluidized bed gasifier (14) as a fluidizing media for
fluidizing the bed material and second stream as a transport of
air or secondary air to push the feed stock into the fluidized bed
gasifier (14);
Adding oxygen from the oxygen receiver (4) and steam from
steam generator (3) to gasifier plenum (5) through flow control
valve (FCV) in fluidized bed gasifier (14), wherein (5) embedded
with fly ash lock unit (12, 13); and

- Generating qualitative synthesis gas by utilizing the heat from
the flue gas,
wherein synthesis gas (syngas) from fluidized bed gasifier (14)
generates waste or flue gases that upon addition of stoichiometric
air at gas engine manifold (25) and passing into the gas engine (26)
therefrom, gets recirculated back to the said fluidized bed gasifier
(14) as a fluidizing media for fluidizing the bed material.
2. The method as claimed in claim 1, wherein the blower (1)
attached to (29) performs suction of the flue gas from (29) and
compresses the syngas in the range of 1.2 to 1.5 bar pressure.
3. The method as claimed in claim 1, wherein mixture of the pure
oxygen from the oxygen receiver (4) to gasifier plenum (5) through
flow control valve (FCV) in fluidized bed gasifier (14) in place of
air in a gasification process increases the gasification reactivity
by converting available carbon into synthesis gas and increases
its calorific value from 1100 kcal/nm3 to 1250 kcal/nm3
thereupon.
4. The method as claimed in claim 1, wherein recycled exhaust flue
gases from the gas engine (26) to fluidized bed gasifier (14) carries
the available heat ranging 180-250 degree C for the gasification
process.

5. The method as claimed in claim 1, wherein addition of super-
heated steam from steam generator (3) to gasifier plenum (5)
develops the hydrogen concentration in synthesis gas.
6. The method as claimed in claim 1, wherein the valves attached
to system receiver (2), steam generator (3), sorbent hopper (6),
sorbent feeder (8), coal hopper (9) and rotary feeder (11) act as
both way flow in the required direction.
7. The method as claimed in claim 1, wherein fly ash lock unit (13)
and ash extractor (12) attached with the gasifier plenum (5) and
(16, 18, 20) attached with member unit (15), (17) and (19)
respectively collects generated fly ash during syngas productio