CLIAMS:CLAIMS

We Claim:

1. An apparatus for gasification and combustion of fuel comprising of a central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and combustion zone; and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash.

2. An apparatus for gasification and combustion of fuel comprising of a central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of first set of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and plurality of second set of spaced apertures arranged in one circumferential path extending up the wall providing air to the combustion zone above the gasification zone and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash.
3. An apparatus for gasification and combustion of fuel as claimed in claim 1 or 2, where in the said the inner wall is sloping.

4. An apparatus for gasification and combustion of fuel gas as claimed in any of the preceding claims wherein the top end of the central enclosure is open to the atmosphere.

5. An apparatus for gasification and combustion of fuel as claimed in any of the preceding claims wherein the said fuel may be a bio-fuel

6. An apparatus for gasification and combustion of fuel as claimed in claim any of the preceding claims, where in the said the number of apertures and the size of the aperture is pre-determined and corresponds to the amount of air to be fed in to the gasifier.

7. A method of for gasification and combustion of fuel comprising the steps of :

a. supplying fuel to a gasification zone in central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and combustion zone; and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash;
b. producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the apertures in the inner wall; and
c. combusting the resultant the producer gas in the combustion zone.

8. A method of for gasification and combustion of fuel comprising the steps of :

a. supplying fuel to a gasification zone in central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of first set of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and plurality of second set of spaced apertures arranged in one circumferential path extending up the wall providing air to the combustion zone above the gasification zone and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash;
b. producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the first set of apertures in the inner wall; and
c. supplying pre-determined of air through the second set of apertures and combusting the resultant the producer gas in the combustion zone.

9. A method as claimed in claim 7 or 8 wherein the said the inner wall is sloping.

10. A method as claimed in claims 7, 8 or 9 wherein the top end of the central enclosure is open to the atmosphere.

11. A method as claimed in claims 7, 8, 9 or 10 wherein the said fuel may be a bio-fuel

12. A method as claimed in claims 7, 8, 9, 10 or 11, wherein the said the number of apertures and the size of the aperture is pre-determined and corresponds to the amount of air to be fed in to the gasifier.
,TagSPECI:FIELD OF THE INVENTION
The present invention relates to apparatuses and methods for combustion of solid fuels; particularly to combustion apparatuses for gasification and combustion of multiple solid fuels and the methods thereof; more particularly to apparatuses and methods for complete gasification and combustion of solid fuels.

BACK GROUND OF THE INVENTION
There is a dire need for the use and adaption of cleaner and environment-friendly power generation methods. Due to fast depletion of the fossil fuel, there is an acute need to make use efficient of renewable sources of energy. Energy in crop residues, Wood residues, and biomass crops all present attractive possibilities for reducing our dependence on fossil fuels.

Gasification of solid bio-fuels for production of producer gas and its consequent combustion is known. It is an established technology for power generation and has undergone number of improvements over the years to overcome many of the limitations of the conventional combustion systems with highest efficiency which converts solid fuels in to a clean gas that can be used 100% Gas Engine mode for power generation.

US2354963 teaches a combustion device comprising of a gasification chamber generating producer gas and having a grate for the supply of air with a mixing and ignition. chamber (or more such chambers) having an opening or more openings to the gasification chamber and serving to mix the gases with air and to ignite the mixture so that the final combustion is effected in a fire box or the like arranged after the mixing and ignition chamber. A partial vacuum is produced in the reactor space by the jet of air, which sucks along product gas from the reactor space to cause a so-called ejector action according to Bernoulli's principle. This device is not suitable for high temperature operations as at high temperatures in the feed column, pellets would disintegrate long before they reach the grate.

Gasifiers are usually classified as being counter-current, co-current, or side-draft (cross-current). With counter-current gasifiers, air is blown or drawn up through a grate supporting the feedstock, producing producer gas by gasification of the bio-fuels. This producer gas passes up through to the combustion zone for combustion. The unburned fuel exits at the top for further use.

Co-current gas reactor, on the other hand force the producer gas down through the combustion area by means of air pressure or air suction to an exit for use. Co-current gas reactors were developed in an effort to reduce tar content in gas used to power internal combustion engines. In conventional co-current systems, the air enters through peripheral jets directed toward the centre of the air-tight cylindrical fuel and combustion chamber just above a funnel-shaped or conical bottom to initiate gasification. As the feedstock is devolatized by combustion and heat, it shrinks into pieces of carbon or char which accumulate in a conical bottom and are supported on a grate below the throat. The chars form a red-hot bed which reduces CO2 to combustible CO and also cracks the tars into stable gases. This gas can be cleaned and cooled for use in an engine to generate power by mitigating emissions compared over conventional route.

Gasifiers and their improvements are further described in US6112677; US6336449; WO9426849A1 and US2010/03236338. None of the devices described above significantly decreases the problems related to gasification of solid fuel, particularly with regard to feeding of secondary air into the product gas and/or the structural solutions of the reactor space, because a mixing of combustion air and product gas that is sufficient to ensure complete combustion and optimum efficiency cannot be achieved. They are cumbersome and require large set-up as well. Scaling down and scaling up of the device based on the requirement is impossible.

Therefore there is a need the art to overcome technical problems of the prior art. There is a further need in the art to develop an efficient, economical and environment friendly solution to the problems associated with the prior art.

OBJECTS OF THE INVENTION
It is an object of the invention to develop an efficient and environmental friendly bio mas gasifiers.

It is yet another object of the invention to provide a novel gasifier whose linear design allows for compact modular design in order to accommodate a wide variety of energy demands for the single size product unit that can be “stacked” with others for producing different energy output demands.

It is yet another object of the invention to produce heat and power at all levels of industries from flexible conditions.

It is another object of the invention to develop an apparatus that can handle optimum size, extreme moisture and high bulk density feedstock in proposition with low bulk density feed materials like leafy/powdery feedstock e.g. sugarcane trash and bagasse, cow dung and other agro waste materials in balled or briquetted forms.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art and meet the objects of the invention it is disclosed herein an apparatus for gasification and combustion of fuel comprising of a central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and combustion zone; and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash.

It is herein disclosed an apparatus for gasification and combustion of fuel comprising of a central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of first set of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and plurality of second set of spaced apertures arranged in one circumferential path extending up the wall providing air to the combustion zone above the gasification zone and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash.

Also disclosed is a method of for gasification and combustion of fuel comprising the steps of: a) supplying fuel to a gasification zone in central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and combustion zone; and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash; b) producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the apertures in the inner wall; and c) combusting the resultant the producer gas in the combustion zone.

Also disclosed is a method of for gasification and combustion of fuel comprising the steps of: a) supplying fuel to a gasification zone in central enclosure having a gasification zone and combustion zone; the said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of first set of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and plurality of second set of spaced apertures arranged in one circumferential path extending up the wall providing air to the combustion zone above the gasification zone and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash; b) producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the first set of apertures in the inner wall; and c) supplying pre-determined of air through the second set of apertures and combusting the resultant the producer gas in the combustion zone.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG 1 is a perspective view of one of the embodiments of the invention
FIG 1A is a cross-sectional view of one of the embodiments of the invention
FIG 1B is a cross-sectional view of one of the embodiments of the invention
FIG 2 is a perspective view of one of the embodiments of the invention
FIG 2A is a cross-sectional view of one of the embodiments of the invention
FIG 2B is a cross-sectional view of one of the embodiments of the invention

DETAILED DESCRIPTION OF THE INVENTION

Gasifiers disclosed here operates on counter-current gasification to generate tar free gas. The design of the gas reactor is particularly flexible to scale-up for any rated capacity.

Referring to Figs. 1, 1A and 1B, an apparatus(101) for gasification and combustion of fuel comprising of a central enclosure having a gasification zone(6) and combustion zone(5) is disclosed. The said enclosure comprises of inner (4) and outer walls (3) spaced apart defining an annular space between them. The annular space is closed at the top and bottom ends and has an inlet (2) on the outer wall (3) to receive air from an external blower or fan. Fuel to the enclosure is supplied by a conveyor through a fuel inlet (1) till the upper limit of the gasification zone. The inner wall(4) has a plurality of spaced apertures(7) arranged in one circumferential path extending up the wall providing air to the gasification and combustion zone and an ash door(8) may be provided at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash.

The feedstock for gasification is conveyed to a hopper through suitable conveying device from ground level and the hopper gets closed with a top slide door by motorized or pneumatic or hydraulic mechanism based operation on the top after filling the chamber. The bottom slide door is opened after ensuring the closing of top slide door. These arrangements are made to ensure uniform charging of feedstock into the gas reactor which prevents feedstock load on the gasification zones and moving grate assembly. The top slide door and the bottom slide door arrangement of the hopper ascertains leak proof environment inside the gas reactor which are operating under pressure mode. One more slide door can be provided between the top and bottom slide door assembly if needed for added safety.

Referring to Figs.1, 1A, 1B, a method for gasification and combustion of fuel by supplying fuel to a gasification zone in central enclosure having a gasification zone and combustion zone as described above, producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the apertures in the inner wall and combusting the resultant the producer gas in the combustion zone is disclosed. The said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and combustion zone. An ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash; producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the apertures in the inner wall; and combusting the resultant the producer gas in the combustion zone.

Referring to Figs. 2, 2A and 2B, an apparatus (201) for gasification and combustion of fuel comprising of a central enclosure having a gasification zone (26) and combustion zone (25) is disclosed. The said enclosure comprises of inner (24) and outer walls (23) spaced apart defining an annular space between them. The annular space being closed at the top and bottom ends and having an inlet(22) on the outer wall(23) to receive air from an external blower or fan. Fuel to the enclosure is supplied by a conveyor through a fuel inlet (21) till the upper limit of the gasification zone; The inner wall(24) has a plurality of first set of spaced apertures(27) arranged in one circumferential path extending up the wall providing air to the gasification and plurality of second set of spaced apertures(28) arranged in one circumferential path extending up the wall providing air to the combustion zone above the gasification zone and an ash door(29) at the bottom of the gasification/combustion chamber may be provided for holding solid fuel and removal of ash.

Referring to Figs.2, 2A, 2B, a method for gasification and combustion of fuel by supplying fuel to a gasification zone in central enclosure having a gasification zone and combustion zone as described above, producing producer gas by pyrolysis of said fuel in the gasification zone by supplying pre-determined amount of air through the first set of apertures in the inner wall and supplying pre-determined of air through the second set of apertures and combusting the resultant the producer gas in the combustion zone is disclosed. The said enclosure comprises of inner and outer walls spaced apart defining an annular space between them, said annular space being closed at the top and bottom ends and having an inlet on the outer wall to receive air from an external blower or fan; a means to supply fuel to the enclosure till the upper limit of the gasification zone; the said inner wall has a plurality of first set of spaced apertures arranged in one circumferential path extending up the wall providing air to the gasification and plurality of second set of spaced apertures arranged in one circumferential path extending up the wall providing air to the combustion zone above the gasification zone and an ash door at the bottom of the gasification/combustion chamber for holding solid fuel and removal of ash.

The shell of the high temperature Biomass gas reactor designed is constructed using Mild Steel (MS) and Stainless Steel (SS) sheet with suitable thickness. The MS/SS plate is rolled have a single joint welding. This approach in designing instigates production cost and time reduction. It augments the pyrolyzed products to flow freely downwards in stratified reactor avoiding edge losses and prevents clinker formation on sharp edges. Thus, it is a square, rectangular, round shape in cross section with perfect dimensions based on combustion engineering calculations and the scaling-up of this design is highly acceptable and easy. The interior of the gas reactor shell inner surface is lined with multi-composition layers of fire crate grade, glass powder, wood ash, refractory brick powder and whytheat-A (90% alumina) dense castable to suitable thickness depending of models respectively. The exterior of the shell is lined glass wool (20), ceramic blanket supported by chicken mesh enclosed in an aluminium cladding

The proposed invention deals with a multi-condition acceptable advanced biomass gas reactor which is a square, rectangular, outer round shaped which can be operated on all types of firewood, coal, coconut husk, coconut shell, coconut fronds, mango seed, cow dung and any powdery bio-fuel or agro-wastes in bailed briquetted or pellet form that generates tar free gas while removing ash and particulate in the proficient manner. This reactor operates on stratified counter-current gasification mode operating slightly above atmospheric pressure for flexible rating with combined draft gasification and single conical gas outlet. The gasification zone temperature is maintained above 1000oC and above to achieve tar-free gas.

The invention is advantages in that the enclosure is linear or rectangular shape to provide feedstock introduction into the gasification area without deterioration of the air injection flow path or the grates. The invention can combine the use of a pre-heater that is self-sustained to give greater gasification efficiency and to allow the use of a moist fuel.

The apparatus of the invention is fully insulated by a special surface lining methodology to achieve maximum thermal efficiency on hot gas condition as well as cold gas efficiency with tar-free gas.

ADVANTAGES
1. The invention combines the operational advantages of counter-current and co-current gasification.
2. It can be operated on all types of firewood, coal, refused derived fuel, rubber waste, leather waste, coconut husk, coconut shell, coconut fronds, mango seed, cow dung and any powdery bio-fuel or agro-wastes in balled, briquetted or pellet form converted to a free gas by removing ash and particulate in the proficient manner.
3. This system can handle optimum size, extreme moisture and high bulk density feedstock in proportion with low bulk density feed materials like leafy trash/powdery feedstock e.g. sugarcane trash and bagasse, and other agro-waste materials in bailed or briquetted forms.
4. This gas reactor can accommodate any kind of feedstock feed on optimum size (from 50mm of length X 50mm of diameter to 300mm of length X100mm of diameter)even with higher bulk density (from 350 to 1500 Kg/m3) that is highly comparable over woody feedstock (i.e., around 400kg/m3) and powdery feedstock (i.e., around 60kg/m3) and acceptable with large woods and large sticks with higher moisture (up to 50%) acceptability compared against earlier works.
5. The oxidizing agent (Air) inlet temperature for sustained gasification can be achieved at ambient temperature regimes and even at extreme temperatures below 280C also without any pre-heating process. The rating capacity with feedstock can be doubled while using wood chips or pellets. It works under pressure below 300 mm of water column. The gas reactor with moving gate mechanism with adjustable options based on size feedstock for gasification are designed operated at low speed to minimise char ash generation and thus achieved a very high gasification efficiency.