Field of Invention
[0001] The present invention relates to ‘Generation of syngas using chemical
looping gasification method and allied areas of applications of syngas’. More
specifically, this invention relates to conversion of Coal to Methanol through
chemical looping gasification method”. The invention covers overall process
development of converting Coal through chemical looping method to syngas and
subsequent conversion of syngas to methanol.
Background of Invention
[0002] Gasification is a process of converting any carbonaceous material such
as coal, petcoke, biomass etc into a usable fuel gas called syngas by oxidizing
the material partially. The gasifying agents used for this process are combination
of air (oxygen), steam and carbon dioxide. The generated syngas has broad range
of applications such as liquid fuels production, chemicals productions, hydrogen
gas production and electricity production etc. The syngas is generated by partial
oxidation of carbonaceous material (feed). Therefore it is required to have oxygen
to oxidize the fuel, but the capital cost incurred to set up oxygen plant is
significant. This can be avoided by employing a method called “Chemical Looping
Gasification (CLG)”.
[0003] CLG is a novel technology to convert any carbonaceous material into
syngas by employing oxygen carrier (OC) that has lattice oxygen to supply
required oxygen to the gasification process. A CLG process employs two reactors
one in which the OC oxidizes the feedstock by getting itself reduced called
Reducer (Fuel reactor) and another in which the OC is oxidized using air called
Oxidizer (Air reactor).
[0004] The selection of suitable carrier for CLG is crucial as it determines the
gasification characteristics. The selected carrier should have characteristics
such as minimal reaction with syngas, easy regeneration (by reacting with air),
low reaction with fuel ash etc. The OC should react with fuel (solid-solid reaction)

directly in the atmospheres of CO2 or steam or in their combination. The OCs
used for CLG include oxides of Fe, Co, Cu, Mn and Ni etc.
[0005] This invention primarily focuses on generation of syngas from feedstock
(eg. Coal, biomass, lignite) continuously using CLG method and conversion of
generated syngas into methanol. The concept of CLG is similar to chemical
looping combustion (CLC) but the objective in CLG is syngas generation than
heat. The objective is met by controlling the flows of feedstock and OC. By
supplying lower quantities of OC than stoichiometric quantity results in partial
oxidation of coal and hence syngas is formed. Either steam or CO2 or blend of
these is used as fluidizing medium. The generated syngas consists majorly of
carbon monoxide, carbon dioxide, H2 and methane. The fuel reactor operates at
temperature of 800-1000oC depending on kind of OC chosen. The OC is reduced
to lower oxidation state in fuel reactor as it supplies oxygen to feedstock. The
reduced OC is transferred to air reactor where it reacts with air and oxidized.
The regenerated OC is recycled to fuel reactor for the gasification.
[0006] In the prior art US Patent No. 2012/0214106 A1 dated 23rd August 2012,
claimed to have developed a process to convert carbonaceous fuel into syngas
consisting of rich carbon monoxide and hydrogen. It was claimed that 1st
reduction of metal oxide occurs in the fuel reactor and 2nd reduction occurs in
a dip leg of a fuel reactor cyclone or loop seal of fuel reactor. It was also claimed
that reduced metal oxide is admitted to air reactor to produce N2, O2, heat, and
the metal oxide. This invention purely aims to produce heat than syngas or
syngas applications.
[0007] Another prior art US Patent No. 8,771,549 B2 dated 8th July 2014 has
claimed to have developed method for chemical looping combustion of at least
one hydrocarbon feed with independent control of the circulation of the solid
active mass particles between the fluidized bed reaction Zones, by means of one
or more non-mechanical valves of L-valve type. Though this prior art talks about
synthesis gas generation but two fuel reactors have not been used.

[0008] Yet another prior art US Patent No. 9,481,837 B2 dated 1st Nov 2016 has
claimed to have developed chemical looping process to convert fuel into gas
which primarily consists of CO and H2. It is also claimed to have developed
different configuration to convert fuel to CO and H2. This patent also claimed the
said gas coming from chemical looping process can be used for different
applications such as for Fischer-Tropsch. However, this patent has not
discussed about converting the obtained gas from chemical looping process to
methanol.
Objectives of Invention
[0009] The primary object of the present invention is to convert coal to methanol
using chemical looping gasification method.
[0010] Another object of the present invention is the development of process
scheme to convert coal to syngas using chemical looping gasification method
which utilizes metal oxide called oxygen carrier (OC) and syngas to methanol,
utilization of CO2 separated from syngas in the downstream process for fuel
reactor as fluidizing medium, utilization of N2 stream from air reactor to produce
the steam and utilization of the same for fuel reactor as gasifying medium.
[0011]Another object of the present invention is development of method for
continuous operation of fuel reactor by adopting two fuel reactors.
Summary of the invention
[0012] The present invention relates to a novel process to convert coal (any
carbonaceous feedstock) into methanol using chemical looping gasification
method. It avoids air separation unit instead metal oxides of Fe, Cu, Mn, Co and
Ni etc are employed for partial oxidation of carbonaceous feedstock into syngas.
The process comprises of
a) Utilization of metal oxide coming from air reactor to provide required
oxygen for partial oxidation of fuel in the fuel reactor where complex reactions
occurs among metal oxide, fuel, steam/CO2 (supplied as gasifying medium) to

generate syngas consists of carbon monoxide, carbon dioxide, hydrogen and
methane;
b) Switching of operation of fuel reactor of process (a) to second fuel reactor
when the reactor is filled with ash to enable separate ash along with any OC left
out from the fuel reactor which enables the continuous operation to produce
syngas of process (a)
c) Regeneration of metal oxide (which is reduced in the fuel reactor as
described in (a)) in air reactor by employing air which oxidizes reduced metal
oxide and supplying the regenerated metal oxide to fuel reactor;
d) Passing of air reactor outlet gas which primarily consists of N2 to steam
generator (which is heat exchanger) where the heat will be used to convert water
into steam which in turn will be used as gasifying medium in fuel reactor of (a)
and water gas shift reactor;
e) Passing of said syngas of process (a) catalytic water gas shift reactor where
available carbon monoxide gets converted to hydrogen;
f) Passing of conditioned syngas from step (e) to packed column to remove
carbon dioxide present in the syngas using MEA (Mono Ethanol Amine) solvent
and re-generation of solvent in the packed column;
g) Utilization of separated carbon dioxide from step (f) as gasification medium
for the two fuel reactors and
h) Passing of said conditioned syngas from step (g) to methanol loop to
convert syngas into methanol and subsequent separation of methanol.
Brief Description of the Drawings
[0013] The nature and scope of the present will be better understood from
accompanying drawings which are by way of illustration of a preferred
embodiment and not by way of any sort of limitation.

[0014] Figure 1 shows the process scheme to convert coal into methanol using
chemical looping gasification method.
Detailed Description of the invention
[0015] The present invention mainly focuses on generation of syngas from
feedstock (eg. Coal, biomass, lignite) continuously using CLG method and
conversion of generated syngas into methanol. The concept of CLG is similar to
chemical looping combustion (CLC) but the objective in CLG is syngas generation
than heat. The objective is met by controlling the flows of feedstock and OC. By
supplying lower quantities of OC than stoichiometric quantity results in partial
oxidation of coal and hence syngas is formed. Either steam or CO2 or blend of
these is used as fluidizing medium. The generated syngas consists majorly of
carbon monoxide, carbon dioxide, H2 and methane. The fuel reactor operates at
temperature of 800-1000oC depending on kind of OC chosen. The OC is reduced
to lower oxidation state in fuel reactor as it supplies oxygen to feedstock. The
reduced OC is transferred to air reactor where it reacts with air and oxidized.
The regenerated OC is recycled to fuel reactor for the gasification.
[0016] The process shown in the Fig.1. depicts the method of conversion of coal
into methanol using chemical looping gasification method which employs oxygen
carrier for partial oxidation of fuel and avoids expensive air separation unit. The
process is broadly classified into four modules namely, chemical looping
gasification module, Water gas shift reactor system, Carbon dioxide removal
system and Methanol generation system and Methanol separation system. Each
of these modules are explained in detail in the following sections.
[0017] The crushed and sieved coal or any carbonaceous feedstock flows through
the stream 1. The feedstock is admitted to two fuel reactors 4 and 5 through
streams 2 and 3 respectively. The fresh OC flows through stream 10 and it is
admitted to fuel reactors 4 and 5 through streams 12 and 11 respectively. The
oxygen required to partially oxidise the feedstock is supplied by metal oxide (OC)
supplied. The metal oxide reduces in the process to lower oxidation state.

[0018] The fluidizing medium/gasifying medium for gasification of feedstock is
mixture of carbon dioxide and steam. Mixed stream of carbon dioxide line 7 and
steam line 25 introduced into reactors 4 and 5 through lines 8 and 9 respectively.
The complex reactions occur among feedstock, OC, steam and CO2 in the fuel
reactors and produces syngas. The ash released in the reactors 4 and 5 is
separated through the line 14 and 13 respectively. To make the process of
generation of syngas continuous, reactor 4 has to be operated first and after it
is filled with ash, then operation has to be switched to reactor 5. When the
reactor 5 is in operation, the ash has to be separated in the fuel reactor 4. After
reactor 5 is filled with ash, then operation has to be switched to reactor 4 to
remove ash from fuel reactor 4. This process has to be repeated without any
interruption of syngas generation in this method.
[0019] Gasification occurs because of complex reactions among coal, oxygen,
carbon dioxide and steam. The insufficient flow of OC makes the feedstock to
partially oxidize. The heat required to support endothermic gasification reactions
is provided by oxidized metal oxides coming through the line 19 and 18. As a
result of these complex reactions syngas is generated. The syngas majorly
consists of carbon monoxide, hydrogen, carbon dioxide and methane leaves the
fuel reactors 4 and 5 through a line 21 and 20 respectively. The residue left out
after the reactions is nothing but ash and some unburnt carbon particles which
needs to be removed as described above.
[0020] The reduced OC from fuel reactors 4 and 5 is admitted to air reactor 22
through the streams 16 and 15 respectively. The reduced OC is oxidized by air
which is entering into the air reactor 22 through the stream 17. The flow of air
has to be controlled in such a way that OC is completely oxidized. Air also
oxidizes if any unburnt carbon particles enters into reactor 22 along with
reduced OC. As air oxidizes OC, it gets reduced to N2 and leaves through the
reactor through the stream 23. The outlet gaseous stream of air reactor has high
temperature as oxidation reactions are highly exothermic. The heat of the stream
23 is extracted in the heat exchanger 23a by converting water coming through

line 24 into steam. The steam generated in the heat exchanger 23a is send to the
fuel reactors through the stream 25. The cooled stream leaves the heat exchanger
through 26.
[0021] The combined syngas stream of 27 (mixture of streams 20 and 21) is
introduced to water gas shift reactor 29. The purpose is to obtain hydrogen to
carbon monoxide ratio to be more than two in the stream 30. The reactor 29 is
filled with Fe based catalyst and operates adiabatically to convert carbon
monoxide to hydrogen through water gas shift reaction by utilizing moisture
present in the syngas stream 27 and externally supplied steam 28 that is coming
from the steam converter 23a.
[0022] The hydrogen rich syngas stream 30 leaves the reactor 29 with a
temperature of 400oC and exchanges heat with stream 31 in the heat exchanger
31a. The cooled syngas is introduced to absorber 34 of carbon dioxide removal
unit through a stream 33. The syngas separated from carbon dioxide is
introduced to knockout drum 42 through a stream line 35.
[0023] The carbon dioxide present in the syngas is absorbed into Mono Ethanol
Amine (MEA) solution by chemical absorption. The absorbed MEA solution is
introduced to stripper column 38 for regeneration through a line 37. The
separated carbon dioxide vapours leaves stripper through line 39 and admitted
to the knockout drum 40. The liquid stream is recycled back to the stripper 35
through a line 36. The separated carbon dioxide is introduced to the compressor
6 through a line 41. The compressed carbon dioxide leaves the compressor
through a stream line 7 and admitted to fuel reactors 4 and 5 as explained
earlier.
[0024] The syngas from knockout drum 42 is admitted to compressor 44 through
a line 43 and to compress the gas upto 70 kg/cm2. The compressed syngas leaves
the compressor 44 through a line 45 to join the stream 58 that is coming from
compressor 57. The combined stream 45a is introduced to the heat exchanger
46 to absorb the heat of stream 63. The heated stream leaves the heat exchanger

46 through a stream 47 and introduced to the reactor 48. The methanol reaction
occurs in this reactor 48 and the formed methanol leaves the reactor through a
stream line 63. Since per pass conversion of carbon monoxide in the reactor is
low and therefore it is to be recycled. Methanol reactions are exothermic and the
heat is to be removed. The methanol reactor 48 is filled with Cu based catalyst.
The methanol reactor 48 temperature is maintained by admitting steam through
a line 49. The heat liberated from the exothermic reactions is absorbed by the
stream 49. The heated steam leaves the reactor 48 through a stream line 50.
[0025] The methanol containing gas is introduced to the heat exchanger 46 to
reduce its temperature and subsequently it is admitted to condenser 52 through
the stream 51 to cool it further. The condensed stream 53 contains liquid
methanol and water along with unreacted gases. To increase the conversion
these gases are to be recycled. The liquids and gases are separated in the
knockout drum 54. The gas leaves the drum 54 through a line 55 and liquid
leaves through a stream 59. To avoid accumulation of gases and for balance, a
part of gas stream 55 is purged through a line 56. Remaining syngas is
compressed in the compressor 57 and compressed gas passes through a line 58
to join the stream 45a.
[0026] The liquid stream from drum 54 leaves through stream line 59 and
admitted to methanol distillation column 60. The liquid stream 59 contains
methanol and water. These separated in the tray column 60. The light fraction
that is methanol comes from top through a stream line 61 and water comes from
bottom through a line 62.
[0027] Any carbonaceous feedstock can be converted to methanol through
chemical looping gasification method. High purity methanol can be obtained
from this process that can be blended with gasoline through which dependency
on crude oil can be reduced.

[0028] It will be appreciated by those skilled in the art that the present invention
can be embodied in other specific forms without departing from the essential
characteristics thereof. The presently disclosed embodiments are therefore
considered in all respects to be illustrative and not restricted. The scope of the
invention is indicated by the appended claims rather than the foregoing
description and all changes that come within the meaning and range and
equivalence thereof are intended to be embraced therein.
Advantages of the Invention
[0029]The conventional gasification of feedstock involves expensive air
separation unit for oxygen which is required to gasify feedstock. The present
invention avoids the use of air separation unit instead the required oxygen is
supplied by metal oxide and therefore capital cost of overall plant reduces. The
mechanism provided in the invention will be useful to continuous operation of
fuel reactor in chemical looping gasification process. The methanol generated
though the invention can pave the way to reduce crude oil imports as methanol
can be blended with gasoline.

We Claim
A process for the production of methanol from carbonaceous feedstock
through chemical looping gasification method, the process comprises the steps
of :
a. Utilization of metal oxide coming from air reactor to provide required
oxygen for partial oxidation of fuel in the fuel reactor,
b. Switching of operation of fuel reactor of process (a) to second fuel
reactor when the reactor is filled with ash,
c. Regeneration of metal oxide (which is reduced in the fuel reactor as
described in (a)) in air reactor by employing air,
d. Passing of air reactor outlet gas which primarily consists of N2 to steam
generator (which is heat exchanger)
e. Passing of said syngas of process (a) catalytic water gas shift reactor
where available carbon monoxide gets converted to hydrogen;
f. Passing of conditioned syngas from step (e) to packed column to
remove carbon dioxide present in the syngas using MEA (Mono
Ethanol Amine) solvent and re-generation of solvent in the packed
column;
g. Utilization of separated carbon dioxide from step (f) as gasification
medium for the two fuel reactors and
h. Passing of said conditioned syngas from step (g) to methanol loop to
convert syngas into methanol and subsequent separation of
methanol.
2. The process as claimed in claim 1, wherein two fuel reactors are
used for the continuous supply of syngas by switching mechanism.

3. The process as claimed in claim 1, wherein ash is removed from first
fuel reactor when second reactor is in operation.
4. The process as claimed in claim 1 wherein the gasifying medium
used is mixture of carbon dioxide and steam.
5. The process as claimed in claim 1 where in the carbonaceous
material used is coal.
6. The process as claimed in claim 1(a) wherein complex reactions
occurs among metal oxide, fuel, steam/CO2 (supplied as gasifying
medium) to generate syngas consists of carbon monoxide, carbon
dioxide, hydrogen and methane;