FIELD OF THE INVENTION:
The present invention relates to a novel method for methanol production from high ash Indian coal or more specifically related to conversion of coal to methanol through fluidized bed gasification technology.
BACKGROUND OF THE INVENTION:
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 in 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.
This invention primarily focuses on conversion of Syngas generated through fluidized bed gasification using high ash (upto 40%) Indian coal as feed by employing oxygen as gasifying agent and carbon dioxide and steam as fluidizing medium. The generated syngas consists majorly of carbon monoxide, carbon dioxide, hydrogen, methane along with trace quantities of hydrogen sulfide, ammonia and alkali metals. The fluidized bed gasifier operates at temperature of 1000- 1050°C and gasifying agent generally used is air.
Us Patent No. 4,017,272 dated 12th April 1977, claimed to have developed a process to convert carbonaceous fuel into syngas consisting of rich carbon monoxide and hydrogen. It was also claimed to have used air and steam as fluidizing medium to convert feed to synthesis gas. The corresponding operating procedure in detail has been claimed in this patent. This invention has used air and steam as medium but not carbon dioxide and pure oxygen.
US Patent No. 4,211,669 dated 8th July 1980, has claimed that by using steam and carbonaceous material in presence of alkali-metal catalyst, a high purity syngas can be produced at a temperature and pressure of 1000 deg F and 100 psia respectively. However in this invention to generate syngas and does not speak about utilization of carbon dioxide as fluidizing medium.

In continuation to aforesaid patent, another US patent No 4,348,487 dated 7th September, 1982, has claimed to develop a process to utilize the generated synthesis gas by means of converting it into methanol. It claimed that methanol can be generated by integrating catalytic gasification with methanol synthesis loop. The syngas generated from catalytic gasification is cleaned using scrubber and packed columns. The methane present in the syngas is separated through cryogenic gasification before admitting into methanol loop. In this invention, carbon dioxide not separated to there is no water gas shift reactor to condition the gas.
US Patent No 4,227,416 dated 7th July, 1981 has claimed to have developed a process to convert syngas from downgraded coal to methanol in order to use it for processing and transport of slurry based coal. It was also claimed that part of synthesis gas was used to run the gas turbine to produce power. This patent does not talk about separation of carbon dioxide, hydrogen sulfide and water gas shift reactor etc.
US Patent No. 4, 407, 973 dated 4th October, 1983 is falls under category of integration of two methanol plants one being natural gas as feed and second one being coal based. This patent claims to have developed the process to generate methanol from coal gasification. The part of syngas got used for another methanol plant. This patent claims to have developed the syngas generation from coal gasification and used water gas shift reactor to condition the gas. However in this invention utilization of carbon dioxide as fluidizing medium is missing.
International Patent No. WO 2016/180812 Al, dated 17th November, 2016 has claimed to have developed a novel process to convert syngas into methanol by sending the combined stream of make-up gas and recycled gas into sulfur reactor before admitting it into methanol reactor and by replacing carbon dioxide that is added to recycle gas with water in an amount of 0.1-5 mol% so that poisonous sulfur in the makeup gas is reduced and carbon dioxide

compressor cost is saved. This patent only talks about syngas to methanol but not coal to methanol.
But these conventional technologies are often complex and does not provide the sufficient yield. Hence, there is always a need for developing a simple yet effective method to cover the shortcoming.
The present invention meets the long felt need.
SUMMARY OF THE INVENTION:
A novel method for converting high ash Indian coal into methanol comprises the steps of : i) feeding of coal through stream using carbon dioxide as transporting medium and combination of steam, carbon dioxide and oxygen through a stream to the fluidized bed gasifier; ii) gasifying high ash Indian coal at a particular gasification temperature for generating syngas with the help of sand; iii) cleaning of said syngas using series of cyclones, candle filter and fine ash filter to reduce particulates concentration to less than 2 mg/nm3; iv) passing of syngas into heat exchanger, where the temperature is recued to owing heat transfer; v) passing of syngas to scrubber to bring down the ammonia substantially by introduction of water coming through stream for absorbing ammonia and other alkali metal as well; vi) introduction of syngas from scrubber to another hear exchanger where the temperature is increased from 40 to 60°C to 190°C before admitting it into carbonyl sulfide hydrolysis reactor; vii) transferring of syngas into hydrogen sulfide removal unit to remove hydrogen sulfide with the help of methyl-di ethanol amine (MDEA) trough chemical absorption where the amine is regenerated with removal and separation of hydrogen sulfide vapors; viii) introduction of syngas to compressor for compression and heated and subsequently syngas is transferred to water gas shift reach where available carbon monoxide gets converted to hydrogen; ix) passing of conditioned syngas into packed column for removal of carbon dioxide by absorption into mono ethanol amine solution; x) utilization of separated carbon dioxide from step (ix) as fluidizing medium to maintain

particular velocity and as transporting medium for coal and sorbent; xi) passing of said conditioned syngas to a methanol loop and reaction occurs in the reactor where the formed methanol leaves the reactor and subjected to condensation; characterized in that pure oxygen is used as gasifying agent and carbon dioxide obtained in the downstream process act as fluidizing medium alongwith steam.
OBJECTS OF THE INVENTION:
It is therefore, the primary object of the present invention to provide a novel method of converting high ash Indian coal into methanol through fluidized bed gasification technology.
Another object of the present object of the present invention to provide a novel method of converting high ash Indian coal into methanol where high ash Indian coal is transferred to methanol through oxy-blown fluidized bed gasification.
Yet another object of the present invention to provide a novel method of converting high ash Indian coal into methanol which is simple yet rapid.
Further object of the present invention to provide a novel method of converting high ash Indian coal into methanol, where feeding system of coal and sorbent are fed to the gasifier to maintain the operating temperature and to control the temperature.
Another object of the present invention to provide a novel method of converting high ash Indian coal into methanol, where the syngas obtained from gasification is used to generate steam that in-turn used as gasifying medium and for the regeneration process of amine solvents used in the hydrogen sulfide removal process and carbon dioxide removal process.
Yet another object of the present invention to provide a novel method of converting high ash Indian coal into methanol which provides substantially higher yield and also environment friendly.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
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. Some embodiments of system or methods 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:
Fig. 1 illustrates a process scheme to convert coal to methanol.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The present subject matter relates to a novel method for conversion of high ash Indian coal into methanol though bed gasification technology.
The present invention covers overall process development of converting high ash Indian Coal through gasification using bubbling fluidized bed reactor to syngas and subsequent conversion of syngas to methanol.
The novel method includes use of pure oxygen as gasifying agent, employment of water gas shift reactor, utilization of carbon dioxide separated from syngas in the downstream process as fluidizing medium and use of syngas heat to generate steam which in turn to get used for fluidization along with carbon dioxide.
The novel process is broadly classified into six subdivision namely
i) Gasification of coal
ii) Gas clean up
iii) Water gas shift reactor system
iv) Carbon dioxide removal system
v) Methanol generation system and
vi) Methanol separation system.

The novel process utilizes oxy-blown fluidized bed gasification by using combination of carbon dioxide and steam as gasifying medium.
The process comprises of :
a) Gasifying (partial oxidation) high ash Indian coal using oxygen as gasifying agent and combination of carbon dioxide obtained in the downstream process and steam as fluidizing medium to maintain particular velocity at a gasification temperatures of 1000-1050°C to generate syngas primarily consists carbon monoxide, carbon dioxide, hydrogen, methane and trace quantities of hydrogen sulfide, ammonia and alkali metals;
b) Cleaning of said syngas (a) using cyclones, candle filter and fine ash filter to reduce the particulates concentration to less than 2 mg/nm3;
c) Passing said syngas to scrubber to remove ammonia, where water is used to absorb ammonia and alkali metals present in the syngas;

d) Passing of said syngas (c) to carbonyl sulfide hydrolysis vessel to convert carbonyl sulfide present to hydrogen sulfide through catalyst means and admitting treated gas to packed bed column where hydrogen sulfide is absorbed into Mono-Di-ethanol Amine (MDEA) solvent and the solvent is regenerated in the stripping column;
e) Passing said treated gas to catalytic reactor to adsorb remaining hydrogen sulfide present before sending it to 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 fluidizing
medium to maintain particular velocity and as transporting medium for coal
and sorbent and

h) Passing of said conditioned syngas from step (g) to methanol loop to convert syngas into methanol and subsequent condensation.
The detailed of this novel process of conversion of high ash Indian coal into methanol is given in figure 1 with the structural components.
The size of crushed coal used is 0.5 to 4mm.
The crushed and sieved coal of 0.5-4 mm size is introduced to coal hopper la through a line 1. The feed is sent through the line 1b into a vessel called coal lock 2 which is used as mediator between lock (la) and receiver (3). The coal lock (2) is used as storage vessel for feed coal. The coal from the vessel 2 is introduced into coal receiver 3 through line 2a. The feed from the coal receiver is transported to fluidized bed gasifier (9) with the help of carbon dioxide available in the stream 4 which is coming from the carbon dioxide storage tank 53. The flow rate of carbo dioxide in the stream 4 is such that it can carry the coal load coming from the receiver 3. The coal from the lock la is admitted to gasifier (9) with the transporting medium of carbon dioxide through a line 4a.
Similarly sieved sand of size 0.5-4 mm is introduced through a line 5 to a hopper 5a. Subsequently sand is introduced to a lock 6 through a line 5b and from where, sand flows to receiver 7 through a line 6a. Finally if temperature in the gasifier (9) increases beyond 1050°C, sand is admitted into gasifier through a line 7a to contain the gasifier temperature immediately. The feeding of sand into gasifier reduces temperature as it absorbs quantum of heat available in the gasifier immediately.
The fluidizing medium for gasification of coal is a mixture of carbon dioxide and steam.
The gasifying agent used here is pure oxygen. Mixed stream of carbon dioxide line 4b and oxygen line 54 introduced into furnace 55 to get heated upto a temperature of 350°C. The heated stream of carbon dioxide and oxygen introduced into gasifier (9) through a stream 8. The flow of carbon dioxide from storage tank 53 is controlled depending on gasifier temperature, performance

and requirement. The steam is introduced to furnace 55 to make it super¬heated steam before admitting it into gasifier (9) through a line 56a. The steam flow to gasifier is controlled from storage vessel (tank) 57 is controlled depending on requirement.
Gasification occurs because of complex reactions occurs among coal, oxygen, carbon dioxide and steam. The insufficient flow of oxygen partially oxidizes coal by reacting with it. Considering exothermic nature of combusting reaction, the heat liberated is absorbed by endothermic gasification reactions. As a result of these complex reactions syngas is generated. The syngas comprising carbon monoxide, hydrogen, carbon dioxide and methane along with traces of hydrogen sulfide, ammonia and alkali metals is leaves the gasifier through a line 11. The composition range of syngas in volume basis is carbon monoxide: 25-30%, hydrogen: 14-20%, carbon dioxide: 40-50%, nitrogen: 0-5%, hydrogen sulfide: 3000 PPM, carbonyl sulfide: 200 PPM and ammonia: 200 PPM.
The residue left out after the reactions is nothing but ash and some unburnt carbon particle. These have to be removed frequently to maintain certain bed height. These are removed regularly from the bottom of the gasifier and extracted through stream 10.
The particulates of syngas generated in the gasifier are removed through series of cyclones and filters. The stream 11 is introduced to cyclone 12 to remove higher size particulates and leaves the cyclone 12 through stream 13. Since refractory lining and insulation are there for gasifier (9), stream 11 pipeline, cyclone 12 and stream 13 and therefore the temperature of syngas leaving cyclone will be not less than 900°C. This heat is transferred to stream 19a that is saturated steam coming from heat exchanger 19. The saturated becomes super-heated steam in the heat exchange 14 and introduced to the receiver 57 through stream 14a.
The temperature of syngas leaving heat exchanger 14 is reduced to 600°C owing heat transfer occurred to the stream 19a. This syngas is admitted to

second cyclone 6 nd barrier filters 17 and 18 to remove particulates present in the syngas. The second cyclone outlet goes introduced to candle filter 17 through line 16a. The cleaned gas in the candle filter is introduced to second candle filter assembly 18, through line 18a. The particulate free syngas has temperature of 400°C and this heat is extracted in the heat exchanger 19 by transferring heat to hot water stream 19c that is coming from receiver 19b. The particles removed in the cyclones and filters are removed from the bottom.
The syngas from heat exchanger 19 is introduced to scrubber 20a through a line 20 to bring ammonia level to below 100 PPM otherwise it is harmful to catalyst present in the downstream processes. The ammonia present in the syngas is absorbed into the inlet water coming through stream 20b. The absorbed ammonia water is drawn from scrubber through a line 20c.
The syngas coming from scrubber 20a is introduced to heat exchanger 22 through a stream line 21. The syngas inlet temperature to heat exchanger 22 is in the range of 40-60°C. This syngas is required to heat to the temperature of 190°C before admitting it into carbonyl sulfide hydrolysis reactor. Syngas has approximately 200 PPM of carbonyl sulfide that has to be converted to hydrogen sulfide before sending the syngas into amine based hydrogen sulfide removal unit. The carbonyl sulfide present in the syngas is reacts with water present in presence of catalyst and converts to hydrogen sulfide. The moisture present in the syngas is not sufficient and therefore extra steam is added to the reactor 24 through stream line 24a. The outlet of carbonyl sulfide converter 24 is admitted to heat exchanger 22 to reduce the temperature to 40°C.
The syngas coming from the heat exchanger 22 is admitted to an absorber 26 of hydrogen sulfide removal unit. The syngas gas leaves hydrogen sulfide removal system through a line 27 and admitted to knockout drum 36. The amine used to remove hydrogen sulfide present in the syngas is Methyl Di Ethanol Amine (MDEA). The hydrogen sulfide is absorbed preferentially into MDEA solution through chemical absorption. The amine used is regenerated in the system. The

absorbed stream 26a is introduced to heat exchanger 28 to get heated to 110°C. This heated stream 29 is introduced to the other packed column called stripper 29 where desorption of hydrogen sulfide occurs at this temperature. This hydrogen sulfide vapors leaves stripper through line 30 and cooled in the condenser 30a and finally hydrogen sulfide separated in the knockout drum 31. The liquid stream is recycled back to the stripper 29 through a line 31a. To maintain the temperature in the stripper 29, a re-boiler 33 is used which is heated by steam introduced through a stream 34 coming from receiver 57. The saturated steam leaves the re-boiler through as stream 35 to a receiver 19b. The stripped MDEA solution is admitted to heat exchanger 28 through a stream 28c to reduce the temperature before sending it into trim cooler 28b through a line 28a. In trim cooler 28b, the MDEA solution temperature is reduced to 40°C and admitted to absorber 26. The overall hydrogen sulfide removal is expected to be 95% in this system. In this hydrogen sulfide removal unit, part of carbon dioxide is also removed.
In the knockout drum 36, the moisture is removed. The syngas is introduced to the compressor 37a through the stream 37. The compressed syngas 37b is admitted to heat exchanger 38 to get heated to a temperature of 200°C. Heating occurs because of heat transfer from the stream 42. The heated syngas is introduced to hydrogen sulfide absorber 39 whose purpose is to bring the hydrogen sulfide present in the syngas to below 0.1 PPM level. Subsequently syngas is introduced to water gas shift reactor 41 through a stream 40. The purpose is to obtain hydrogen to carbon monoxide ratio to be more than two in the stream 43. The reactor 41 is filled with iron based catalyst and operates adiabatically to convert carbon monoxide to hydrogen through water gas shift reaction by utilizing moisture present in the syngas stream 40 and externally supplied steam 41a.
The hydrogen rich syngas stream 42 leaves the reactor 41 with a temperature of 400°C and exchanges heat with stream 37b in the heat exchanger 38 and cooler 43a. The cooled syngas is introduced to absorber 46 of carbon dioxide

removal unit through a stream 44. The syngas separated from carbon dioxide is introduced to knockout drum 60 through a stream line 47.
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 49 for regeneration through a line 45a. The solution leaves from absorber 46 through a line 45 to heat exchanger 48 to get heated up to 110°C. This heated solution introduced to the stripper 49 in a line 45a. The desorbed solution stream 48a leaves the column 49 with a temperature of 120°C and loses the heat in the heat exchanger to the stream 45. Further this solution introduced to the trim cooler 48c through the stream line 48b to make its temperature of 40°C before introduced to the absorber column 46 through stream line 48d. The expected carbon dioxide removal from this unit is 95%.
The carbon dioxide vapors leaves stripper through line 50a and cooled in the condenser 50 and subsequently carbon dioxide separated in the knockout drum 51. The liquid stream is recycled back to the stripper 49 through a line 51a. To maintain the temperature in the stripper 49, a re-boiler 60 is used which is heated by steam introduced through a stream 58 coming from receiver 59. The saturated steam leaves the re-boiler through stream 59 to a receiver 19b. The separated carbon dioxide is introduced to the compressor 52a through a line 52. The compressed carbon dioxide leaves the compressor through a stream line 53a and stored in the vessel 53 from where it is fed to the gasifier 9 as explained earlier.
The syngas from knockout drum 60 is introduced to receiver 61a through a line 61. This receiver acts as buffer vessel to the methanol loop. The syngas composition leaving receiver in volume basis is carbon monoxide: 15-25%, H2:50-60%, carbon dioxide: 0-5%, water: 5-10%, nitrogen: 5-10%, methane:0-3%. This syngas is admitted to compressor 62 through a line 61b and to compress the gas upto 70 kg/cm2. The compressed syngas leaves the

compressor 62 through a line 62a to join the stream 77 that is coming from compressor 76. The combined stream 63 is introduced to the heat exchanger 63a to absorb the heat of stream 69a. The heated stream leaves the heat exchanger 63a through a stream 64 and introduced to the reactor 65. The methanol reaction occurs in this reactor 65 and the formed methanol leaves the reactor through a stream line 69a. 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 66 is filled with copper based catalyst. The methanol reactor 66 temperature is maintained by admitting steam through a line 67 that is coming from vessel 57. The heat liberated from the exothermic reactions is absorbed the stream. The heated steam leaves the reactor 66 through a stream line 68 and send to vessel 19b.
The methanol containing gas is introduced to the heat exchanger 69 to reduce its temperature and subsequently it is admitted to condenser 70 to cool it further. The condensed stream 71 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 72. The gas leaves the drum 72 through a line 73 and liquid leaves through a stream 78. To avoid accumulation of gases and for balance, a part of gas stream 73 is purged through a line 74. Remaining gas is recycled through a stream 75. This syngas is compressed in the compressor 76 and compressed gas is passes through a line 77 to join the stream 62a.
The liquid stream from drum 73 leaves through stream line 78 and admitted to methanol distillation column. The liquid stream contains methanol and water. These separated in the tray column 79. The light fraction that is methanol comes from top through a stream line 81 and water comes from bottom through a line 80.

It was clear from this invention that, high ash Indian Coal can be converted to methanol through fluidized bed gasification method. High purity methanol can be obtained from this process that can be blended with gasoline through which India can reduce its imports bill.
Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features 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.

WE CLAIM:
1. A novel method for converting high ash Indian coal into methanol comprises the steps of :
i) feeding of coal through stream (3a) using carbon dioxide as transporting medium (4) and combination of steam, carbon dioxide and oxygen through a stream (8) to the fluidized bed gasifier (9);
ii) gasifying high ash Indian coal at a particular gasification temperature for generating syngas with the help of sand;
iii) cleaning of said syngas using series of cyclones, candle filter and fine ash filter to reduce particulates concentration to less than 2 mg/nm3 ;
iv) passing of syngas into heat exchanger (14), where the temperature is recued to owing heat transfer;
v) passing of syngas to scrubber (20a) to bring down the ammonia substantially by introduction of water coming through stream (20b) for absorbing ammonia and other alkali metal as well;
vi) introduction of syngas from scrubber to another hear exchanger (22) where the temperature is increased before admitting it into carbonyl sulfide hydrolysis reactor;
vii) transferring of syngas into hydrogen sulfide removal unit to remove hydrogen sulfide with the help of methyl-di ethanol amine (MDEA) trough chemical absorption where the amine is regenerated with removal and separation of hydrogen sulfide vapors;
viii) introduction of syngas to compressor (37a) for compression and heated and subsequently syngas is transferred to water gas shift reach where available carbon monoxide gets converted to hydrogen;
ix) passing of conditioned syngas into packed column for removal of carbon dioxide by absorption into mono ethanol amine solution;

x) utilization of separated carbon dioxide from step (ix) as fluidizing medium to maintain particular velocity and as transporting medium for coal and sorbent;
xi) passing of said conditioned syngas to a methanol loop and reaction occurs in the reactor where the formed methanol leaves the reactor and subjected to condensation;
characterized in that pure oxygen is used as gasifying agent and carbon dioxide obtained in the down stream process act as fluidizing medium alongwith steam.
2. The method as claimed in claim 1, wherein the gasification temperature is 1000 to 1050°C.
3. The method as claimed in claim 1, wherein the sand is utilized is of size 0.5 to 4 mm which introduced to lock, flows to receiver and facilitates controlling the temperature of gasifier.
4. The method as claimed in claim 1, wherein the syngas is admitted to cyclone (16) barrier candle filter where the temperature of syngas is 400°C.
5. The method as claimed in claim 1, wherein the heat is extracted in the heat
exchanger by transferring heat to hot water stream.
6. The method as claimed in claim 1, wherein the syngas is required to heated for increasing the temperature from 40 to 60°C to 190°C before admitting it into carbonyl sulfide hydrolysis reactor.
7. The method as claimed in claim 1, wherein the methanol reactor is filled with copper based catalyst.
8. A method as claimed in claim 1, wherein the conversion of carbon monoxide to hydrogen through catalytic water gas shift reaction to meet the required hydrogen to carbon monoxide ratio by supplying little quantity of steam.

9. A method as claimed in claim l, wherein the hot syngas of water gas shift reactor is used to obtain desirable temperature of catalytic hydrogen sulfide adsorber reactor.