RM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13)
GASIFICATION SYSTEM FOR GENERATING SYNTHESIS GAS AND PROCESS FOR RECOVERY OF CARBON VALUES FROM SOLID RESIDUES
THERMAX LIMITED
an Indian Company
of D-13, MIDC Industrial Area,
R.D. Aga Road, Chinchwad,
Pune-411019,
Maharashtra, India.
Inventors:
1. BASARGEKAR SUDHEER SHYAMRAO
2. GUPTA DEVKUMAR FULCHAND
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF DISCLOSURE
The present disclosure relates to a gasification system for generating synthesis gas and a process thereof. Particularly, the present disclosure relates to a gasification system for generating synthesis gas using a solid carbonaceous fuel, typically coal, and an improved process thereof.
BACKGROUND
Various apparatus and methods are known in the art for generating synthesis gas from solid carbonaceous materials such as coal by gasification. Generally, these apparatus are designed to recover the chemical energy stored in the carbonaceous material in a usable form, typically synthesis gas, either for use as fuel for powering an engine/ a gas turbine or as a feedstock for an operation. The conventional gasification apparatus use fixed bed, fluidized bed, jet stream or entrained bed gasifiers for gasifying the coal. Some of the known apparatus and methods are discussed in the prior art below.
In US Patent No. 3993583 a process for producing synthesis gas in a fluidized bed from carbon and steam is disclosed, wherein carbon fines, separated from the synthesis gas, are burned in a slagging combustor, and the resulting combustion gases are used to heat a recycle stream of carbon from the fluidized bed. The ash build-up in the gasifier is controlled by withdrawing a second stream of char from the fluidized bed; separating the second stream into an ash-rich portion and an ash-poor portion; feeding the ash-rich portion into the combustor; and feeding the ash-poor portion into the fluidized bed gasifier. US Patent No. 4386940 discloses a gasification system for converting ash containing carbonaceous solids into a gaseous mixture containing hydrogen and carbon monoxide by endothermic reaction of the solids with steam in a fluidized

gasification zone, wherein heat for the reaction is supplied by continuously circulating a recycle stream of the solids between the gasification zone and a combustion zone in which the recycle stream is heated by contact with hot combustion gases formed by burning at least a portion of carbonaceous fines elutriated from the gasification system. The entrainment of fines in the combustor is reduced by introducing the finest fines at the lower end of the combustor and the coarser fines at a point above the point where the finest fines are introduced.
US Patent No. 6117199 (hereinafter referred to as '199 US Grated Patent) discloses a method and apparatus for gasifying of a solid carbonaceous material in a fluidized bed reactor in which the solid particles entrained by the gases being removed from the upper part of the reactor are separated and returned to the lower part of the reactor. Oxygenous gas is supplied into the lower part of the reactor and the non-reacted carbonaceous material separated from the gases is oxidized in the lower part of the reactor. The carbonaceous material is introduced above the oxidizing zone into a zone substantially free of oxygen and the carbonaceous material is pyrolyzed and reduced by means of the hot gases and particles rising from the lower part of the reactor. However, the apparatus for gasifying of a solid carbonaceous material disclosed in the '199 US Grated Patent utilizes a gasifier in which fuel, hot air and un-burnt carbonaceous material is re-cycled to the gasifier. However, the gasifier of the apparatus for gasifying of a solid carbonaceous material is inefficient. Further, the apparatus for gasifying of a solid carbonaceous material utilizes syn-gas generated in the gasifier for preheating of the air, such a configuration is complex and energy in-efficient.

These known apparatus suffer from disadvantages like incomplete carbon utilization, high heating fuel requirement, low operation controllability and low gasification efficiency.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to provide a gasification system for generating synthesis gas by gasification of a solid carbonaceous material, typically coal, which provides high gasification efficiency in extracting heat energy from carbon contained in solid residues.
Still another object of the present disclosure is to provide a gasification system for generating synthesis gas by gasification of a solid carbonaceous material, typically coal, which reduces energy wastage due to chemical energy in the carbon carried away by solid residues in synthesis gas.
Another object of the present disclosure is to provide a gasification system that provides high carbon utilization.
Still another object of the present disclosure is to provide a gasification system that reduces the heating fuel requirement, and provides easy operation controllability.
Yet another object of the present disclosure is to provide a gasification system for generating synthesis gas by gasification of a solid carbonaceous material that achieves maximum utilization of carbon contained in the solid residues by

extracting heat from the flue gas generated in the combustor and utilizing the extracted heat for pre-heating the air and generation of steam which in turn is utilized for the efficient operation of the gasifier.
Another object of the present disclosure is to provide a gasification system for generating synthesis gas that has high cold gas efficiency.
Still another object of the present disclosure is to provide a gasification system for generating synthesis gas that produces synthesis gas of high calorific value and requires less fuel for operation.
Another object of the present disclosure is to provide a high performance gasification system for generating synthesis gas that exhibits high carbon conversion efficiency.
Still another object of the present disclosure is to provide a high performance gasification system for generating synthesis gas that requires less oxidant. These objects and other advantages of the present disclosure will be more apparent from the following description.
SUMMARY
A gasification system for generating syngas is disclosed in accordance with an embodiment of the present disclosure. The gasification system includes a gasifier, at least one cyclone separator and a combustor. The gasifier includes at least one inlet configured thereon for facilitating receiving of solid fuel, conveying air, and super-heated steam, wherein the solid fuel is processed in the controlled environment of said gasifier to produce synthesis gas. The at least one cyclone separator is functionally coupled to the gasifier and receives

synthesis gas generated in the gasifier and separates solid residues from the synthesis gas to provide clean synthesis gas, and separate solid residues present in the synthesis gas for recovery of carbon values there-from. The combustor is functionally coupled to the gasifier and receives solid residues collected from the gasifier and at least one cyclone separator for combusting the carbon contained in the solid residues in the presence of air inside the combustor, wherein heat generated by combustion of the carbon contained in the solid residues is extracted and is at least partially utilized for pre-heating air and forming steam to be fed to said gasifier.
In accordance with one embodiment of the present disclosure, the combustor receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and fly ash and char from at least one cyclone separator, wherein carbon contained in the bottom ash, fly-ash and char received in the combustor is combusted in the presence of air and heat generated by combustion of the carbon contained in the bottom ash, fly-ash and char is partially extracted for generating steam and the remaining heat is extracted for pre-heating air, the steam and pre-heated air is utilized for operation of the gasifier, thereby facilitating recovery of carbon values from the bottom ash, fly-ash and char.
In accordance with another embodiment of the present disclosure, the combustor receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and the gasifier receives solid residues in form of fly ash and char from at least one cyclone separator along with air, wherein carbon contained in the bottom ash and char received in the combustor is combusted in the presence of air and heat generated by combustion of the carbon contained in the bottom ash and char is partially extracted for generating steam and remaining heat is extracted for pre-heating air, the steam and pre-

heated air is utilized for operation of the gasifier, thereby facilitating recovery of carbon values from the bottom ash and char, further, carbon contained in the fly-ash and char from at least one cyclone separator is recycled to the gasifier.
In accordance with yet another embodiment of the present disclosure, the combustor receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and fly ash and char from a second cyclone separator and the gasifier receives solid residues in the form of fly ash and char from a first cyclone separator along with air, wherein carbon contained in the char received in the combustor is combusted in the presence of air and heat generated by combustion of the carbon is partially extracted for generating steam and remaining heat is extracted for pre-heating air, the steam and pre¬heated air is utilized for operation of gasifier. Typically, the gasifier is a fluidized bed.
Preferably, the gasifier is a circulating fluidized bed type gasifier operating at pressures between atmospheric pressure and 30 bar and temperature in the range
of800°C to l025°C.
Generally, the combustor is operating at atmospheric pressure.
In accordance with another embodiment, the gasifier is a bubbling bed type gasifier.
Alternatively, the gasifier is a fluidized-bed type gasifier operating at temperature in the range of 800 -1025°C.

Generally, the gasifier processes solid fuel selected from a group consisting of high ash coal, sub-bituminous, bituminous coal, lignite and other rank coal.
Typically, the combustor is a fluidized bed type combustor.
Further, the gasification system includes a heat exchanger device, wherein heat generated by combustion of the carbon contained in solid residues is partially extracted for generating steam and the remaining heat is extracted for pre¬heating air.
Typically, the gasifier is provided with a plurality of inlets configured thereon for facilitating entry of air, steam and Nitrogen in the gasifier, wherein Nitrogen facilitates purging, feeding and lock hopper pressurization.
Further, the gasification system includes a depressurization system and a lock hopper disposed upstream of the combustor, wherein the lock hopper receives said solid residues before feeding to the combustor and the depressurizing system reduces the pressure of the solid residues received from the gasifier before feeding the solid residues to the combustor.
In accordance with one embodiment, the depressurization system and the lock hopper receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and fly ash and char from at least one cyclone separator, wherein the depressurization system reduces pressure of the bottom ash and char received from the gasifier.
In accordance with another embodiment, the depressurization system and the lock hopper receives solid residues in the form of bottom ash and char from an

operative bottom of the gasifier, wherein the depressurization system reduces pressure of the bottom ash and char received from the gasifier.
In accordance with another embodiment, the depressurization system and the lock hopper receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and fly ash and char from the second cyclone separator.
In accordance with another embodiment, the gasification system further includes a loop seal disposed between the at least one cyclone separator and the gasifier, wherein the loop seal receives solid residues separated in the at least one cyclone separator and recycles the solid residues to the gasifier, wherein the fly ash and char from the at least one cyclone separator are recycled to the gasifier.
A gasification process for generating syngas is disclosed in accordance with another embodiment of the present disclosure. The gasification process includes the steps of feeding solid fuel, pre-heated air and steam in a gasifier, processing of solid fuel in a controlled environment inside the gasifier to produce synthesis gas, separating solid residues from the synthesis gas generated in the gasifier in at least one cyclone separator and providing a stream of clean synthesis gas, receiving and collecting solid residues from different sources, optionally de-pressuring said solid residues, combusting carbon contained in the solid residues collected in a combustor, extracting heat generated by combustion of carbon contained in the solid residues and at least partially utilizing the heat generated by the combustion of the carbon contained in the solid residues for operating the gasifier.

Typically, the collective steps of collecting solid residues from different sources, combusting carbon contained in the solid residues, extracting heat generated by combustion of carbon contained in the solid residues and utilizing the heat generated by the combustion of carbon contained in the solid residues for operating the gasifier involves collecting solid residues in the form of bottom ash and char from an operative bottom of the gasifier and fly ash and char from a cyclone separator and receiving the bottom ash, fly ash and char in the combustor, wherein carbon contained in the bottom ash, fly ash and char is combusted in the combustor in the presence of air and the heat generated by combustion of the carbon contained in the bottom ash, fly-ash and char is at least partially utilized by partially extracting the heat for generating steam and extracting the remaining heat for pre-heating air, wherein the steam and pre¬heated air is utilized for operation of the gasifier.
In accordance with another embodiment, the collective steps of collecting solid residues from different sources, combusting carbon contained in the solid residues, extracting heat generated by combustion of carbon contained in the solid residues and utilizing the heat generated by the combustion of carbon contained in the solid residues for operating the gasifier involves directing the solid residues in the form of bottom ash and char from an operative bottom of the gasifier to a combustor and re-cycling solid residues in form of fly ash and char from at least one cyclone separator to the gasifier, wherein the carbon contained in the bottom ash and char is combusted in the combustor in the presence of air and the heat generated by combustion of the carbon contained in the bottom ash and char is at least partially utilized by partially extracting the heat for generating steam and extracting the remaining heat for pre-heating air, wherein the steam and pre-heated air is utilized for Operation of the gasifier.

In accordance with still another embodiment, the collective steps of collecting solid residues from different sources, combusting carbon contained in the solid residues, extracting heat generated by combustion of carbon contained in the solid residues and utilizing the heat generated by the combustion of the carbon contained in the solid residues for operating the gasifier involves directing the solid residues in the form of bottom ash and char from an operative bottom of the gasifier to the combustor and directing solid residues in form of fly ash from second cyclone separator to the combustor and fly ash and char from first cyclone separator to the gasifier, wherein carbon contained in the bottom ash, the fly-ash from the second cyclone separator and char received in the combustor is combusted in the presence of air and heat generated by combustion of the carbon contained in the bottom ash, fly-ash from the second cyclone separator and char is partially extracted for generating steam and remaining heat is extracted for pre-heating air, the steam and pre-heated air is utilized for operation of gasifier, thereby facilitating recovery of carbon values from the bottom ash, fly-ash from the first cyclone separator and char.
The gasification process for generating syngas further includes the step of recycling at least a portion of solid residues separated in the at least one cyclone separator to the gasifier, wherein the rate at which the portion of solid residues are recycled to the gasifier is at most three to twenty times the rate at which solid fuel, pre-heated air and steam is fed to the gasifier.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The disclosure will now be described with the help of the accompanying drawings, in which,

FIGURE 1 illustrates a schematic representation of a gasification system for generating synthesis gas by gasification of a solid carbonaceous material in accordance with a preferred embodiment of the present disclosure, wherein the combustor receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and fly ash and char from a cyclone separator for combustion there inside, the combustion of the carbon contained in the bottom ash, fly-ash and char generates heat that is utilized for operation of the gasifier;
FIGURE 2 illustrates a schematic representation of a gasification system for generating synthesis gas by gasification of a solid carbonaceous material in accordance with another embodiment of the present disclosure, wherein the combustor receives solid residues in the form of bottom ash and char from an operative bottom of the gasifier and the gasifier receives solid residues in form of fly ash and char from first and second cyclone separators along with air for extracting the carbon values of solid residues;
FIGURE 3 illustrates a schematic representation of a gasification system for generating synthesis gas by gasification of a solid carbonaceous material in accordance with still another embodiment of the present disclosure.
FIGURE 4 illustrates a graphical representation depicting variation in cold gas efficiency with respect to air inlet temperature to the gasifier, in order to substantiate advantageous effect of the pre-heating of the inlet air on the cold gas efficiency;
FIGURE 5 illustrates a graphical representation depicting variation of equivalence ratio with respect to air inlet temperature to the gasifier, in order to

substantiate advantageous effect of the pre-heating of the inlet air to gasifier on the equivalence ratio; and
FIGURE 6 illustrates a graphical representation depicting variation of syngas heating value with respect to air inlet temperature to the gasifier, in order to substantiate advantageous effect of the pre-heating of the inlet air to gasifier on the syngas heating value.
DESCRIPTION OF THE ACCOMPANYING DRAWINGS
A gasification system for generating synthesis gas by gasification of a solid carbonaceous material" will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the disclosure. The gasification system for generating synthesis gas utilizes the solid residues separated from the synthesis gas for recovery of carbon values from the solid residues. More specifically, the gasification system collects solid residues from different sources, such as bottom ash and char from an operative bottom of a gasifier and fly ash and char from at least one cyclone separator and the carbon contained in the solid residues undergoes combustion in the presence of air inside the combustor, wherein heat generated by combustion of the carbon contained in the solid residues is partially extracted for generating steam and the remaining heat is extracted for pre-heating air, the steam and pre-heated air is utilized for operation of the gasifier, thereby facilitating recovery of carbon values from the bottom ash, fly-ash and char. The description provided is purely by way of example and illustration.
FIGURE 1 of the accompanying drawings illustrates a schematic representation of a gasification system 100 for generating synthesis gas by gasification of a solid carbonaceous material in accordance with a preferred embodiment of the

present disclosure. The gasification system 100 includes a coal gasifier 104, a combustor 102, and a cyclone separator 106. The combustor 102 receives solid residues in the form of bottom ash and char 124 from an operative bottom of the gasifier 104 and fly ash and char 126 from at least one cyclone separator 106 for combustion there inside, the combustion of the carbon contained in the bottom ash, fly-ash and char generates heat that is at least partially utilized for operation of the gasifier 104. The combustor 102 is placed spaced apart from the coal gasifier 104. The coal gasifier 104 is provided in operative communication with the combustor 102. The cyclone separator 106 is provided in operative communication with the coal gasifier 104. A stream of air, particularly hot air 116 and steam 118 is provided proximal to the operative bottom of the coal gasifier 104 at the plenum 110. A plurality of inlets 120 are configured on the gasifier 104 for feeding coal and conveying air/superheated steam to the coal gasifier 104. Nitrogen can be purged into the coal gasifier 104 from plurality of inlets 122 schematically shown in Figure 1.
The coal gasifier 104 is a high pressure bubbling-bed type gasifier and is provided in communication with at least one cyclone separator 106. The air and steam is fed at the plenum 110 near the operative bottom of the coal gasifier 104, The coal is fed from the plurality of inlets 120 along with air. The cyclone separator 106 receives the synthesis gas stream 125 produced in the coal gasifier 104. The cyclone separator 106 separates fly ash and char from the synthesis gas stream 125 to produce clean synthesis gas stream 130 and a recycle stream 126 containing the fly ash and char. The recycle stream 126 containing the fly ash and the char is discharged from the operative bottom of the cyclone separator 106. The recycle stream 126 containing the fly ash and the char is subsequently fed to the combustor 102 after depressurization in a depressurizing system 109 via a lock hopper 108 for effecting complete burning of the char. A bottom ash and char stream 124 is discharged from the operative bottom of the

coal gasifier 104. The bottom ash and char stream 124 is also fed to the combustor 102 after depressurization in the depressurizing system 109 via the lock hopper 108. The depressurization system 109 and the lock hopper 108 receive bottom ash and char 124 from an operative bottom of the gasifier 104 and fly ash and char 126 from the cyclone separator 106. The depressurization system 109 reduces pressure of the bottom ash and char 124 received from the gasifier 104 before feeding it into the combustor 102 as the pressure inside the gasifier 104 is far higher than the pressure inside the combustor 102, particularly, the pressure inside the gasifier 104 is in between atmospheric pressure and 30 bar while the pressure inside the combustor is atmospheric pressure. The depressurization system 109 is an optional element of the gasification system and hence is represented by phantom lines in the Figures and may not be required in case the gasifier 104 is operated at atmospheric or near to sub-atmospheric pressure. The de-pressurization in the depressurization system 109 may be step wise de-pressurization. The lock hopper 108 receives the fly-ash, bottom ash and char before feeding to the combustor 102.
The combustor 102 receives solid residues in the form of ash and char mixture, particularly, the combustor 102 receives at least a portion of the fly-ash and char 126 separated from the synthesis gas 125 in the at least one cyclone separator 106 and also receives bottom-ash and char 124 directly from the gasifier 102. The lock hopper 108 receives the fly-ash and char 126 and the bottom-ash and char 124 before feeding to the combustor 102.
The coal gasifier 104 is operated at pressures between 1 atmospheric pressure and 30 bar and at a temperature between 800 -1025°C. The combustor 102 is of the fluidized-bed type and is operated at a temperature between 800 - 950 °C and at atmospheric pressure. The air for gasification is preheated by exchanging heat from the flue gas stream 128 discharged from the combustor 102. A stream

of water 114 is provided to the combustor 102 to produce steam 118; the steam 118 can further be superheated and is supplied to the gasifier 104. The air entering the combustor from the stream of air 112 is heated in the combustor 102 to provide a stream of hot air 116 that again is supplied to the gasifier 104. The hot air 116 and the superheated steam 118 are supplied to the coal gasifier 104 at the plenum 110 as fluidizing media for the bubbling-bed type gasifier 104. Accordingly, the carbon contained in the bottom ash, fly-ash and char received in the combustor 102 is combusted in the presence of air and heat generated by combustion of the carbon contained in the bottom ash, fly-ash and char is partially extracted for generating steam 118 and the remaining heat is extracted for pre-heating air and generating stream of pre-heated air 116, the steam 118 and pre-heated air 116 is utilized for operation of the gasifier 104, The ash 132 is removed from the combustor 102 by means of a conveyor, particularly a screw type conveyor. Additional air 134 may be provided to the combustor 102.
The gasification system 100 thus provides a separate combustor 102 which extracts the heat from the carbon contained in the solid residues, particularly from the carbon contained in the bottom ash, fly-ash and char for generating hot air 116 and the steam 118 that in turn is fed to the coal gasifier 104. The carbon conversion in the coal gasifier 104 is at least 80 %. The remaining carbon (char) along with the solid residues is sent to the combustor 102 from the coal gasifier 104 bottom and after separation in the cyclone separator 106. Thus, maximum energy content of the carbon contained in the solid residues is extracted and the energy so extracted from the carbon contained in the bottom ash, fly-ash and char is utilized for generating steam and pre-heating air that is fed to the coal gasifier 104 so as to maximize the carbon conversion and increasing the cold gas efficiency.

FIGURE 2 illustrates a schematic representation of a gasification system 200 for generating synthesis gas by gasification of a solid carbonaceous material in accordance with another embodiment of the present disclosure. The gasification system 200 includes a coal gasifier 204, a combustor 202, and a pair of cyclone separators 206a and 206b. In case of the gasification system 200, the combustor 202 receives solid residues in the form of bottom ash and char 224 from an operative bottom of the gasifier 204 and the gasifier 204 receives solid residues in form of fly ash and char 207 from first and second cyclone separators 206a and 206b. More specifically, the stream of fly ash and char 207a from the cyclone separators 206a and the stream of fly ash and char 207b from the cyclone separators 207a are fed to a loop seal 245 via an intermediate seal 240 and thereafter recycled to the gasifier 204. The loop seal 245 receives fly-ash and char 207a, 207b separated in the cyclone separators 206a and 206b respectively and recycles the fly-ash and char 207 to the gasifier 204 along with air inducted via air stream 247. The fly-ash and char 207 along the air fed to the gasifier 204 are utilized in the gasifier 204. The combustor 202 is placed spaced apart from the coal gasifier 204. The coal gasifier 204 is provided in operative communication with the combustor 202. The cyclone separators 206a and 206b are provided in operative communication with the coal gasifier 204. More specifically, a synthesis gas stream 225 from the gasifier 204 is fed to the first cyclone separator 206a, wherein fly-ash and char 207a are separated from the synthesis gas stream 225 and the synthesis gas stream with partially removed fly-ash and char is forwarded to the second cyclone separator 206b, wherein again fly-ash and char is separated and a stream of clean synthesis gas 230 is obtained.
A stream of hot air 216 and a stream of steam 218 are provided proximal to the operative bottom of the coal gasifier 204 at the plenum 210 from the combustor 202. At least one inlet 220 is configured on the gasifier 204 for feeding coal and

conveying air to the coal gasifier 204. Nitrogen can be purged into the coal gasifier 204 from plurality of inlets 222.
The coal gasifier 204 is a circulating fluidized-bed type gasifier with multiple cyclones. The gasification system 200 further includes the loop seal 245 that receives fly-ash and char separated in the cyclone separators 206a and 206b and recycles the fly-ash and char 207 to the gasifier 204. The coal gasifier 204 is operated at pressures between atmospheric pressure and 30 bar and at a temperature between 800 - 1025 °C. The air, particularly hot air 216 and steam 218 is fed at the plenum 210 near the operative bottom of the coal gasifier 204 from the combustor 202. The coal is fed from the plurality of inlets 220 along with air. Bottom ash and char stream 224 is discharged from the operative bottom of the coal gasifier 204 which is fed to the combustor 202 after depressurization in the depressurizing system 209 via the lock hopper 208. More specifically, the depressurization system 209 and the lock hopper 208 receive solid residues in the form of bottom ash and char 224 from an operative bottom of the gasifier, wherein the depressurization system 209 step-wise reduces pressure of the bottom ash and char 224 received from the gasifier 204. The lock hopper 208 receives the bottom ash and char 224 before feeding to the combustor 202. The depressurization system 209 reduces pressure of the bottom ash and char 224 received from the gasifier 204 before feeding it into the combustor 202 as the pressure inside the gasifier 204 is far higher than the pressure inside the combustor 202, particularly, the pressures inside the gasifier 204 is between atmospheric pressure and 30 bars while the pressure inside the combustor 202 is atmospheric pressure. The depressurization system 209 is an optional element of the gasification system 200 and hence is represented by phantom lines in the Figures and may not be required in case the gasifier 204 is operated at atmospheric or near to sub-atmospheric pressure. The lock hopper 208 received the bottom ash and char before feeding to the combustor 202.The

cyclone separators 206a and 206b receives the synthesis gas stream 225 produced in the coal gasifier 204. The cyclone separators 206a and 206b separates the bed material, fly ash and char from the synthesis gas 225 to produce clean synthesis gas stream 230. The stream of fly ash and char 207a and stream of fly ash and char 207b are fed to or recycled back to the coal gasifier 204 after passing through the intermediate seal 240 and after addition of air to it in the loop seal 245. More specifically, in case of gasification system 200, two cyclone separators 206a and 206b are used, the intermediate seal 240 is provided to collect the ash-char mixture 207a and 207b from the two cyclone separators 206a and 206b and then the ash-char mixture 207a and 207b is sent to the loop seal 240 from where the ash-char mixture 207 is circulated back to the gasifier 204. The rate at which the portion of solid residues removed in the cyclone separators 206a and 206b, particularly are fed to the gasifier 204, the rate at which the fly ash and char 207 is recycled to the gasifier 204 is at most three to twenty times the rate at which solid fuel, pre-heated air and steam is fed to the gasifier 204. The combustor 202 is operated at 850-950 °C and 10 bar pressure. The burnt ash 232 is discharged from the combustor 202 with the help of the lock hopper. The air for gasification is preheated by exchanging heat from the flue gas stream 228 discharged from the combustor 202. The steam 218 for gasification is generated in the combustor 202 and is superheated, if required. The hot air 216 and the superheated steam 218 are supplied to the plenum 210 of the coal gasifier 204 as fluidizing media. The combustion air 234 is provided to the combustor 202. The combustor 202 receives solid residues in the in the form of bottom ash and char 224 from an operative bottom of the gasifier 204 and the gasifier 204 receives solid residues in form of fly ash and char 207 from first and second cyclone separators 206a and 206b along with air, wherein carbon contained in the bottom ash and char 224 received in the combustor 202 is combusted in the presence of air 212 and heat generated by combustion of the carbon contained in the bottom ash and char 224 is partially

extracted for generating steam 218 and remaining heat is extracted for pre-heating air 216, the steam 218 and pre-heated air 216 is utilized for operation of the gasifier 204, further, carbon contained in the fly-ash and char 207 from the first and second cyclone separators 206a,206b is recycled to the gasifier 204 and utilized in the gasifier 204.
The gasification system 200 thus provides a separate combustor 202 which extracts the heat from the carbon contained in the solid residues, particularly from the carbon contained in the bottom ash and char for generating hot air 216 and the steam 218 that in turn is fed to the coal gasifier 204. The carbon conversion in the coal gasifier 204 is at least 90 %. The remaining carbon (char) along with the solid residues is sent to the combustor 202. The gasification system 200 provides control over the amount of char fed to the combustor 202 so as to maintain the ash balance in the system.
FIGURE 3 illustrates a schematic representation of a gasification system 300 for generating synthesis gas by gasification of a solid carbonaceous material in accordance with still another embodiment of the present disclosure. In case of the gasification system 300, the char ash mixture 307a from the first cyclone 306a is re-circulated or recycled to the gasifier 304 using the loop seal 345 after adding air stream 347 thereto. The char ash mixture 307b arrested in the second cyclone separator 306b is send to the common char ash mixture collection and depressurization system along with the bottom ash 324 coming from the bottom of the gasifier 304. The char ash mixture is fed to the combustor 302. More specifically, the gasification system 300 includes a coal gasifier 304, a combustor 302, and a pair of cyclone separators 306a and 306b. The combustor 302 receives solid residues in the form of bottom ash and char 324 from an operative bottom of the gasifier 302 and fly ash and char 307b from the second cyclone separator 306b and the gasifier 304 receives solid residues in the form

of fly ash and char 307a from the first cyclone separator 306a along with air, wherein carbon contained in the bottom ash 324, the fly-ash and char 307b from the second cyclone separator 306b is combusted the combustor 302 in the presence of air and heat generated by combustion of the carbon contained in the bottom ash 324, fly-ash and char 307b from the second cyclone separator 306b is partially extracted for generating steam 318 and remaining heat is extracted for pre-heating air 316, the steam 318 and pre-heated air 316 is utilized for operation of the gasifier 302. Further, the fly-ash and char 307a from the first cyclone separator 306a is recycled to the gasifier 304 and is utilized in the gasifier 304.
FIGURE 4 illustrates a graphical representation depicting variation in cold gas efficiency with respect to air inlet temperature to the gasifier based on numerical simulation results. More specifically, the cold gas efficiency increases with increase in air inlet temperature to gasifier, such graphical representations of the results substantiate the advantageous effect of the pre-heating of the inlet air on the cold gas efficiency. FIGURE 5 illustrates a graphical representation depicting variation of equivalence ratio with respect to air inlet temperature to the gasifier based on results. More specifically, the equivalence ratio decreases with increase in air inlet temperature to gasifier, such graphical representations of the results substantiate advantageous effect of the pre-heating of the inlet air to gasifier on the equivalence ratio.
FIGURE 6 illustrates a graphical representation depicting variation of syngas heating value with respect to air inlet temperature to the gasifier. More specifically, the syngas heating value increases with increase in air inlet temperature to gasifier, such graphical representations of the test results substantiate advantageous effect of the pre-heating of the inlet air to gasifier on the syngas heating value.

The following table depicts a comparative analysis of the various operational parameters associated with Gasification system with combustor in accordance with present invention and Conventional Gasification System without
combustor.

Gasification system with
combustor in accordance
with present invention Conventional Gasification System without combustor
Coal, [kg/hr] 400 407
Air, [kg/hr] 790 820
Steam, [kg/hr] 30 30
Syngas, [kg/hr] 1066.18 1100
Cold gas efficiency,[%] 65.7 64.6
Syngas heating value,[kcal/kg] 862.31 835.85
Carbon conversion[%] >98 90
Based on the comparative analysis provided in the above table it is clear that with use of the gasification system of the present disclosure, the amount of air and coal required for the gasification is reduced. More specifically, the gasification system of the present disclosure requires coal input of 400kg/hr as compared to 407 kg/hr coal input required in the conventional gasification systems and the gasification system of the present disclosure requires air input of 790 kg/hr as compared to 820 kg/hr air input required in the conventional
T
gasification systems. Further, with use of the gasification system of the present disclosure the cold gas efficiency and carbon conversion percentage is enhanced. More specifically, with use of the gasification system of the present disclosure, the carbon conversion percentage is more than 98 percent as compared to the carbon conversion percentage of 90 percent as is in the case of conventional gasification system and the cold gas efficiency of the gasification system of the present disclosure is 65.7 percent as compared to 64.6 percent cold gas efficiency in case of the conventional gasification system. Further, the syngas produced by the gasification system of the present invention has more calorific value than the syngas produced by conventional gasification systems.

More specifically, the calorific value of the syngas produced by the gasification system of the present disclosure is 862.31 kcal/kg as compared to 835.85 kcal/kg calorific value of the syngas produced by the conventional gasification system. With all these advantages of the gasification system of the present disclosure, the syngas output of the gasification system of the present disclosure is still comparable to the syngas output of the conventional gasification system.
TECHNICAL ADVANTAGES
A gasification system for generating synthesis gas by gasification of a solid carbonaceous material, typically coal, as described in the present disclosure has several technical advantages. The technical advancements offered by the present disclosure include the realization of:
• the gasification system provides high gasification efficiency in extracting heat energy from carbon contained in solid residues;
• the gasification system reduces energy wastage due to chemical energy of carbon carried away by solid residues in the synthesis gas;
• the gasification system reduces solid residues such as fly-ash, bottom ash and char in the synthesis gas;
• the gasification system provides high carbon utilization;
• reduces the heating fuel requirement, and provides easy operation controllability;
• a gasification system for generating synthesis gas by gasification of a solid carbonaceous material that achieves maximum utilization of carbon contained in the solid residues by extracting heat from the flue gas generated in the combustor and utilizing the extracted heat for pre-heating

the air and generation of steam which in turn is utilized for the efficient operation of the gasifier;
• provide a gasification system for generating synthesis gas that has high cold gas efficiency;
• a gasification system for generating synthesis gas that produces synthesis gas of high calorific value and requires less fuel for operation;
• a high performance gasification system for generating synthesis gas that exhibits high carbon conversion efficiency; and
• a high performance gasification system for generating synthesis gas that requires less oxidant.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters,

dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
In view of the wide variety of embodiments to which the principles of the present disclosure can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

We Claim:
1. A gasification system for generating syngas, said gasification system
comprising:
• a gasifier with at least one inlet configured thereon for facilitating receiving of solid fuel, conveying air and super-heated steam, wherein said solid fuel is processed in the controlled environment of said gasifier to produce synthesis gas;
• at least one cyclone separator functionally coupled to said gasifier and adapted to receive synthesis gas generated in said gasifier and separates solid residues from said synthesis gas to provide clean synthesis gas, and separate solid residues present in said synthesis gas for recovery of carbon values there-from; and
• a combustor functionally coupled to said gasifier and adapted to receive solid residues collected from said gasifier and said at least one cyclone separator for combusting the carbon contained in said solid residues in the presence of air inside the combustor, wherein heat generated by combustion of the carbon contained in the solid residues is extracted and is at least partially utilized for pre-heating air and forming steam to be fed to said gasifier.
2. The gasification system as claimed in claim 1, wherein said combustor is
adapted to receive solid residues in the form of bottom ash and char from
an operative bottom of said gasifier and fly ash and char from at least one
cyclone separator, wherein carbon contained in the bottom ash, fly-ash
and char received in said combustor is combusted in the presence of air
and heat generated by combustion of the carbon contained in the bottom
ash, fly-ash and char is partially extracted for generating steam and
remaining heat is extracted for pre-heating air, the steam and pre-heated

air is utilized for operation of the gasifier, thereby facilitating recovery of carbon values from the bottom ash, fly-ash and char. The gasification system as claimed in claim 1, wherein said combustor is adapted to receive solid residues in the form of bottom ash and char from an operative bottom of said gasifier and said gasifier is adapted to receive solid residues in form of fly ash and char from at least one cyclone separator along with air, wherein carbon contained in the bottom ash and char received in said combustor is combusted in the presence of air and heat generated by combustion of the carbon contained in the bottom ash and char is partially extracted for generating steam and remaining heat is extracted for pre-heating air, the steam and pre-heated air is utilized for operation of the gasifier, thereby facilitating recovery of carbon values from the bottom ash and char, farther, carbon contained in the fly-ash and char from at least one cyclone separator is recycled to said gasifier. The gasification system as claimed in claim 1, wherein said combustor is adapted to receive solid residues in the form of bottom ash and char from an operative bottom of said gasifier and fly ash and char from a second cyclone separator and said gasifier is adapted to receive solid residues in the form of fly ash and char from a first cyclone separator along with air, wherein carbon contained in the char received in said combustor is combusted in the presence of air and heat generated by combustion of the carbon is partially extracted for generating steam and remaining heat is extracted for pre-heating air, the steam and pre-heated air is utilized for operation of said gasifier.
The gasification system as claimed in claim 1, wherein said gasifier is a fluidized bed.
The gasification system as claimed in claim 1, wherein said gasifier is a circulating fluidized bed type gasifier (CFBG) operating at pressures

between atmospheric pressure and 30 bar and temperature in the range of 800°Ctol025°C.
7. The gasification system as claimed in claim 1, wherein said combustor is operating at atmospheric pressure.
8. The gasification system as claimed in claim 1, wherein said gasifier is a bubbling bed type gasifier.
9. The gasification system as claimed in claim 1, wherein said gasifier is a
fluidized-bed type gasifier operating at temperature in the range of 800°C
to 1025°C.
10. The gasification system as claimed in claim 1, wherein said gasifier is adapted to process solid fuel selected from a group consisting of high ash coal, sub-bituminous coal, bituminous coal, lignite and other rank coal.
11. The gasification system as claimed in claim 1, wherein said combustor is a fluidized bed type combustor.
12. The gasification system as claimed in claim 1 further comprising a heat exchanger device, wherein heat generated by combustion of carbon contained in said solid residues is partially extracted for generating steam and the remaining heat is extracted for pre-heating air.
13. The gasification system as claimed in claim 1, wherein said gasifier is provided with a plurality of inlets configured thereon for facilitating entry of air, steam and Nitrogen in said gasifier, wherein Nitrogen facilitates purging, feeding and lock hopper pressurization.
14. The gasification system as claimed in claim 1 further comprising a depressurization system and a lock hopper disposed upstream of said combustor, wherein said lock hopper receives said solid residues before feeding to said combustor and said depressurizing system reduces the

pressure of said solid residues received from said gasifier before feeding said solid residues to said combustor.
15. The gasification system as claimed in claim 14, wherein said depressurization system and said lock hopper are adapted to receive solid residues in the form of bottom ash and char from an operative bottom of said gasifier and fly ash and char from at least one cyclone separator, wherein said depressurization system reduces pressure of the bottom ash and char received from the gasifier.
16. The gasification system as claimed in claim 14, wherein said depressurization system and said lock hopper are adapted to receive solid residues in the form of bottom ash and char from an operative bottom of said gasifier, wherein said depressurization system reduces pressure of the bottom ash and char received from said gasifier.
17. The gasification system as claimed in claim 14, wherein said depressurization system and said lock hopper are adapted to receive solid residues in the form of bottom ash and char from an operative bottom of said gasifier and fly ash and char from the second cyclone separator.
18. The gasification system as claimed in claim 1 further comprising a loop seal disposed between said at least one cyclone separator and said gasifier, wherein said loop sea] receives solid residues separated in said at least one cyclone separator and recycles the solid residues to said gasifier, wherein the fly ash and char from said at least one cyclone separator are recycled to said gasifier.
19. A gasification process for generating syngas, said gasification process comprising the steps of:

• feeding solid fuel, pre-heated air and steam in a gasifier;
• processing of solid fuel in a controlled environment inside said gasifier to produce synthesis gas;

• separating solid residues from said synthesis gas generated in said gasifier in at least one cyclone separator and providing a stream of clean synthesis gas;
• receiving and collecting solid residues from different sources;
• optionally de-pressuring said solid residues;
• combusting carbon contained in the solid residues collected in a combustor; and
• extracting heat generated by combustion of carbon contained in said solid residues and at least partially utilizing the heat generated by the combustion of carbon contained in said solid residues for operating said gasifier.

20. The gasification process for generating syngas as claimed in claim 19, wherein said collective steps of collecting solid residues from different sources, combusting carbon contained in said solid residues, extracting heat generated by combustion of carbon contained in said solid residues and utilizing the heat generated by the combustion of said solid residues for operating the gasifier involves collecting solid residues in the form of bottom ash and char from an operative bottom of said gasifier and fly ash and char from a cyclone separator and receiving the bottom ash, fly ash and char in the combustor, wherein carbon contained in the bottom ash, fly ash and char is combusted in said combustor in the presence of air and the heat generated by combustion of the carbon contained in the bottom ash, fly-ash and char is at least partially utilized by partiallyextracting the heat for generating steam and extracting the remaining heat for pre¬heating air, wherein the steam and pre-heated air is utilized for operation of said gasifier.
21. The gasification process for generating syngas as claimed in claim 19, wherein said collective steps of collecting solid residues from different sources, combusting carbon contained in said solid residues, extracting

heat generated by combustion of carbon contained in said solid residues and utilizing the heat generated by the combustion of said solid residues for operating the gasifier involves directing the solid residues in the form of bottom ash and char from an operative bottom of the gasifier to a combustor and re-cycling solid residues in form of fly ash and char from at least one cyclone separator to said gasifier, wherein the carbon contained in the bottom ash and char is combusted in said combustor in the presence of air and the heat generated by combustion of the carbon contained in the bottom ash and char is at least partially utilized by partially extracting the heat for generating steam and extracting the remaining heat for pre-heating air, wherein the steam and pre-heated air is utilized for operation of said gasifier.. 22. The gasification process for generating syngas as claimed in claim 19, wherein said collective steps of collecting solid residues from different sources, combusting carbon contained in said solid residues, extracting heat generated by combustion of carbon contained in said solid residues and utilizing the heat generated by the combustion of said solid residues for operating the gasifier involves directing the solid residues in the form of bottom ash and char from an operative bottom of said gasifier to said combustor and directing solid residues in form of fly ash from a second cyclone separator to said combustor and fly ash and char from a first cyclone separator to said gasifier, wherein carbon contained in the bottom ash, the fly-ash from said second cyclone separator and char received in said combustor is combusted in the presence of air and heat generated by combustion of the carbon contained in the bottom ash, fly-ash from said second cyclone separator and char is partially extracted for generating steam and remaining heat is extracted for pre-heating air, the steam and pre-heated air is utilized for operation of said gasifier, thereby facilitating

recovery of carbon values from the bottom ash, fly-ash from the first cyclone separator and char.
23. The gasification process for generating syngas as claimed in claim 19, further includes the step of recycling at least a portion of solid residues separated in said at least one cyclone separator to said gasifier, wherein the rate at which said portion of solid residues is recycled to said gasifier is at most three to twenty times the rate at which solid fuel, pre-heated air and steam is fed to said gasifier.