Patent Application
20070266914
The invention disclosed and claimed herein deals with a method for gasifying solid organic materials, the novel apparatus for that purpose, and a system therefor. The instant invention is a unique method and apparatus that produces a high energy, low temperature, and low particulate-laden syngas by controlling the oxygen content in combustion air used for “starved air” combustion of biomass in a unique gasifier. Recirculated flue gas mixed with a predetermined amount of fresh air is utilized for providing the oxygen content therein and for controlling the method.
More particularly, this invention deals with a method for gasifying biomass materials, such as forestry and agricultural residues, industrial waste materials such as saw mill pulp, paper products, fowl litter, such as chicken litter and turkey litter, and hydrocarbon based plastics and the like.
This invention also deals with the apparatus that is used to convert the chemical energy into thermal energy or gaseous products, and specifically, syngas, that is also called production gas. Syngas is a compressible synthetic combustible gas containing very little particulate material. Thus, this invention can also be viewed as a method of producing syngas.
It has long been recognized that many industrial and agricultural solid organic by-products, such as forestry and agricultural residue, and the like, are a potential source of large amounts of chemical energy. The substantial increases in the cost of traditional fuels, such as fuel, oil and natural gas, which occurred during the 1970's, have provided substantial economic incentive to try to develop effective and efficient techniques for recovering the energy in these organic by-products, energy that traditionally was not recovered to any substantial extent. Such organic materials, frequently referred to as “biomass” materials, are now successfully utilized to some extent as fuel in some very large industrial systems, for example, in firing the power boiler and the recovery boiler in a pulp or paper mill. However the high capital cost that has heretofore been associated with biomass energy recovery systems has precluded their successful use in small or even medium size energy recovery systems.
Medium size energy recovery systems are used in community centers, schools, nursing homes, and small industrial and commercial establishments and, to date, biomass fuels have not been satisfactorily utilized as fuels in heating systems for such facilities. Among the U.S. patents that have issued on inventions relating to the recovery of energy from wood chips or similar organic materials are for example, U.S. Pat. No. 5,138,957 that issued to Morey, et al. on Aug. 18, 1992; U.S. Pat. No. 4,184,436 that issued to Palm, et al. Jan. 22, 1980; U.S. Pat. No. 4,312,278 that issued to Smith, et al. on Jan. 26, 1982; U.S. Pat. No. 4,366,802 that issued to Goodine on Jan. 4, 1983; U.S. Pat. No. 4,321,877 that issued to Schmidt, et al on Mar. 30, 1982; U.S. Pat. No. 4,430,948 that issued to Schafer, et al. on Feb. 14, 1984; U.S. Pat. No. 4,593,629 that issued to Pedersen, et al. on Jun. 10, 1986; U.S. Pat. No. 4,691,846 that issued to Cordell, et al. on Sep. 8, 1987, and U.S. Pat. No. 4,971,599 that issued to Cordell on Nov. 20, 1990.
However, it is not known that any of the inventions described in these patents have been successfully adapted to recover biomass energy on a cost-effective basis in small and medium size energy recovery systems.
Thus, gasifiers are not new in the art and there are many publications dealing with such pieces of equipment and systems in which they are used, but by way of illustration, attention can be directed to U.S. Pat. No. 4,691,846 that issued on Sep. 8, 1987 to Cordell, et al, in which there is described a method and apparatus for gasifying solid organic materials in which the system is described in detail with emphasis on the hopper and its manner of operation. It should be noted that the gasifier is shown and described as a dome-like structure with a bottom feed mechanism for the solid organic materials, and an upper exhaust system to remove the gaseous effluent to a secondary chamber.
A second disclosure can be found in U.S. Pat. No. 6,120,567 that issued on Sep. 19, 2000 to Cordell, et al in which there is described a method of gasifying solid organic materials and in which a similar apparatus and system as is disclosed in the '846 patent is set forth. The '567 patent is related to the '846 patent. Again, it should be emphasized that the gasifier is shown and described as a dome-like structure having a bottom feed and an upper exhaust for the gaseous effluent.
A typical and general process in the prior art can be found in Canadian patent 2,058,103 that issued on Oct. 14, 1997 in the name of Morey, et al. in which a bottom feed, biomass materials, and gasification system is set forth. The system feeds fuel such as green and wet woodchips from below, up through a central opening in a stationary, perforate fire table that supports the mound-like fuel bed that is formed thereby. A plurality of ring-like manifolds below the fire table, and surrounding the fuel supply tube are separately provided with air in a controlled manner according to the demand for the combustible gas produced.
Thus this invention deals with a method for gasifying solid organic materials, the apparatus used in such a method, and a system therefor and with specificity, it deals with, in one embodiment, a gasifier for gasifying solid organic materials comprising in combination a housing, wherein the housing has a lower portion and an upper portion and a circular side wall supported by the lower portion and attached to the upper portion.
There is a roof for the housing, the roof being supported by and integral with the circular sidewall. There is at least one opening through the roof for exiting syngas effluent and at least one opening for a sensing device and located at, and connected to, the roof opening, is a device for removing the syngas from the gasifier.
Located at, and associated with the sensing device opening, there is at least one device for sensing the elevation of any mass of any solid organic material contained in the housing, the sensing device being a radar device that is mounted over any sensing device opening and surmounts a non-metallic plate that covers the opening.
Located in the lower housing there is at least one opening for supporting a device for determining the amount of non-combustible material remaining within the gasifier, and located at, and connected to, the lower portion of the housing, and within the opening for supporting a device for determining the amount of non-combustible material remaining within the gasifier there is at least one device for determining the amount of non-combustible material remaining within the gasifier.
Located in the circular wall, there is at least one opening for supporting at least one device for providing oxidative gas to the solid organic materials, the oxidative gas being recirculated flue gas containing a predetermined portion of fresh air. Located in, and connected to the oxidative gas opening is a device for providing an oxidative gas to the solid organic materials.
There is a floor for the gasifier located in the lower portion of the gasifier, the floor having a top surface and a bottom surface, the floor having at least one opening through it to allow for the passage of solid organic material into the interior of the gasifier, wherein the top surface of the floor has a retaining wall on the outside of each of the floor openings to form a retention basin to retain the solid organic materials in the lower portion of the gasifier to form a floorless hearth.
There is a device for moving solid organic materials through the floor opening and into the gasifier in an upwardly motion and a device for providing and retaining a cone structure to the underside of the solid organic materials.
The gasifier has a device for containing the solid organic materials while above the retention basin and at least one opening in the lower portion of the gasifier to allow movement of non-combustibles out of the gasifier, along with a device in the retention basin for removing non-combustible materials out of the gasifier.
Finally, there is a control and monitor for the amount of mass of solid organic material within the gasifier and a control and monitor for the amount of non-combustibles in the gasifier that are inter-related. This type of gasifier is known in the art as a circular gasifier.
In another embodiment, the invention deals with a square or rectangular “loaf” gasifier. Thus, this embodiment deals with a gasifier for gasifying solid organic materials comprising a housing, wherein the housing has a lower portion and an upper portion and the housing has four side walls supported by the lower portion and attached to the upper portion, thus differing from the above-mentioned circular gasifier.
The loaf gasifier has a roof, the roof being supported by and integral with the four side walls and the gasifier has at least one opening through a side wall for exiting syngas effluent and at least one opening through the roof for a sensing device.
Located at, and connected to the side wall opening, is a device for removing the gaseous effluent from the gasifier and located at, and associated with the sensing device opening, there is at least one device for sensing the elevation of any mass of any solid organic material contained in the housing, said sensing device being a radar device that is mounted over any sensing device opening and that surmounts a non-metallic plate that covers the opening.
Located in the lower housing there is at least one opening for supporting a device for determining the amount of non-combustible material remaining within the gasifier and located at, and connected to the lower portion of the housing, and within the opening described just Supra, there is at least one device for determining the amount of non-combustible material remaining within the gasifier.
Located in the sidewalls there is at least one opening for supporting at least one device for providing oxidative gas to the solid organic materials, the oxidative gas being recirculated flue gas containing a predetermined portion of fresh air. Located in, and connected to the oxidative gas opening, is a device for providing an oxidative gas to the solid organic materials.
There is a floor for the gasifier located in the lower portion of the gasifier, the floor having a top surface and a bottom surface. The floor has at least one opening through it to allow for the passage of solid organic material into the interior of the gasifier, wherein the top surface of the floor has a retaining wall on the outside of each of the floor openings to form a retention basin to retain the solid organic materials in the lower portion of the gasifier to form a floorless hearth.
There is a device for moving solid organic materials through the floor opening and into the gasifier and a device for providing and retaining a cone structure to the underside of the solid organic materials.
In addition, there is a device for heating the solid organic materials while above the retention basin and at least one opening in the lower portion of the gasifier to allow movement of non-combustibles out of the gasifier, along with a device in the retention basin for removing non-combustible materials out of the gasifier.
Finally, there is a control and monitor for the amount of mass of solid organic material within the gasifier and a control and monitor for the amount of non-combustibles in the gasifier that are inter-related.
In another embodiment, the circular gasifier described Supra is modified to alter the flow of effluent by providing a constriction in the midsection of the gasifier. Thus, there is a gasifier for gasifying solid organic materials comprising a housing wherein the housing has a lower portion having a top part and an upper portion having a bottom part and the housing has a circular side wall supported by the lower portion and attached to the upper portion, wherein the circular side wall has a constricted section where the top part of the lower portion and the bottom part of the upper portion meet and join.
In yet another embodiment of this invention, the loaf gasifier described Supra is also modified. Thus, there is a gasifier for gasifying solid organic materials comprising a housing wherein the housing has a lower portion with a top part and an upper portion with a bottom part and the housing has four side walls supported by the lower portion and attached to the upper portion and the side walls have a constricted section where the top part of the lower portion and the bottom part of the upper portion meet and join.
There is still another embodiment of this invention, said embodiment being a method of gasifying solid organic materials to produce a gaseous effluent and a solid residue, the method comprising providing a supply of solid organic material and providing a circular gasifier as set forth in this disclosure.
Thereafter, the solid organic materials are introduced into the gasifier upwardly from a lower portion of the gasifier to provide a mass of solid organic materials in the gasifier. The solid organic materials are ignited and then heated in the gasifier while providing an oxidative gas to the gasifier, the oxidative gas being recirculated flue gas from a flue stack located in a system in which the gasifier is operating and, the oxidative gas is flue gas containing a predetermined portion of fresh air.
There is provided an effluent path of flow within the gasifier for a portion of the gaseous effluent to migrate, mix, and react through the heated solid organic materials and the syngas formed thereby is transferred outwardly from the gasifier and any non-combustible solids are transferred out of the gasifier.
A further embodiment of this invention is a method of gasifying solid organic material to produce a gaseous effluent and a solid residue, said method comprising providing a supply of solid organic material and providing a loaf gasifier as set forth in this disclosure and introducing the solid organic materials into the gasifier upwardly from a lower portion of the gasifier to provide a mass of solid organic materials in the gasifier.
The solid organic materials are ignited and then heated in the gasifier while providing an oxidative gas to the gasifier to provide a gaseous effluent, wherein the oxidative gas is recirculated flue gas from a flue stack located in a system in which the gasifier is operating and, the oxidative gas is flue gas containing a predetermined portion of fresh air.
There is provided an effluent path of flow within the gasifier for a portion of the gaseous effluent to migrate, mix, and react through the heated solid organic materials and the syngas formed thereby is transferred outwardly from the gasifier and any non-combustible solids are transferred out of the gasifier.
It is contemplated within the scope of this invention to provide systems that utilize each of the various gasifiers disclosed and claimed in this invention.
Turning now to
Thus, there is shown a gasifier 1 of this invention that is a circular gasifier that is equipped with a solid mass feeder 2 (shown in
The solid mass materials are first comminuted or chopped, if it is forestry product, so that it will flow and be ignited readily. Generally this chopped material is best handled if the pieces are at least 3 inches or less in any dimension. If the solid mass material is chicken litter or turkey litter, then chopping is not required.
Shown in
The control of pile height is of critical importance for combustion control and the release of gaseous combustibles, i.e., the “product gas”. The location of feed cone(s) 25 and vertical auger(s) are designed to provide a pile having a generous depth, and which has a generally flat upper periphery. This flat, mesa-like upper surface extends over 60 to 70 percent of the floor area, generally filling the lower portion of gasifier 1, and sharply tapers downward adjacent wall 11. This downward taper, referred to as the angle of repose, is dependent upon the type of fuel used. A flat fuel pile is key to achieving uniform combustion without bridging. This flat configuration results in a uniform pile depth, which in turn results in uniform air pressure within the pile 18, thus minimizing channeling of the pile. Maintaining pile depth is very important. About 6 inches or more of ash is maintained below the actively burning portion of the pile so as to prevent heat damage to feed cone 25 and ash removal system 4.
As the feed material in the 18 in gasifier 1 moves to the feed cone 25 to the center and top of the mass, it gets hotter and hotter, and volatile components in such material and combustion products begin to dissipate from the surface of the pile, partly being assisted by the gases that are rising through such material. As the feed material in the pile 18 loses more and more of the volatile and pyrolytic ingredients it will begin to form high molecular weight carbonaceous derivatives and char until, eventually, it is exposed to the full operating temperature inside gasifier 1. This material moves generally horizontally outward and then downward toward the outer wall and lower floor where it is exposed to further oxidation agents via tuyere arrays 32 and 34 for a more complete reaction, at which time all of the organic constituents of such feed material will gasify and will pass from gasifier 1 as an incompletely oxidized gaseous effluent of combustibles (syngas), the effluent leaving gasifier 1 through an insulated exit duct 52. The velocity of the effluent above the fuel pile and out the exit duct is kept low, reducing particulate carryover.
It is contemplated within the scope of this invention to provide air-modified flue gas (oxidative gas), steam modified ambient air or steam modified pure oxygen to the burning piles 18 and 71 through the respective tuyeres fitted on the gasifiers 1 and 60.
Feed rate into gasifier 1 is monitored and controlled by monitoring and controlling fuel pile height within gasifier 1. Suitable instrumentation, not shown, is provided to control the rate of the delivery of the feed material into gasifier 1 by the feed assembly as a function of the elevation of the top of the feed material in the height of pile 18 to maintain such elevation at a substantially constant value, and thereby to contain the pile 18 of feed material at a substantially constant shape
Turning to
As the solid mass pile 18 burns, it creates a certain amount of ash that must be removed from the gasifier 1. Therefore, there is at least one trench 24 provided in the gasifier floor featuring one or more devices for removal of ash and combustion residues and for control of the elevation of the “moving bed of ash” hearth. A most adaptable device is an auger 26 shown in
The formation of the ash creates a floorless hearth in the gasifier 1 on which the burning solid mass pile 18 is situated. By intermittent or continuous ash removal, there is created a “moving bed of ash” which is essentially the floorless hearth 30 of this invention.
Alternatively, the control of the “moving bed of ash” level that creates the hearth 30, and the removal of the ash, can be accomplished by a conveyor or conveyors moving across the entire floor, or section thereof, from side to side, or end to end of the gasifier as deemed most suitable for the dimensions and shape of the “moving bed of ash” hearth 30, or alternatively, a set, or sets, of dump grates can be inserted under the “moving bed of ash” hearth 30 to facilitate and control removal of the ash.
Preferred for this invention when forestry products are used as the feed, is a peppermill grate 40 ash system (see
Another grate system 84 for the invention disclosed herein that is similar to a peppermill grate is shown in
The top grate 86 has wedge plates 89 mounted on top of it. These plates 89 are installed in such a way that when the top grate 86 is rotating towards the openings 88, the wedge plates 89 push the ash in front of them towards the openings 87 in the bottom grate 85. The movement and height of the wedge plates 89 ensure measurable and constant ash removal from the bottom of the pile, preventing the ash bridging above the ash grate openings. As the bottom layer of the ash is discharged, the mixture of ash and unburned carbon from the above drops down lower. As the carbon burns, the process temperature in the vicinity of the ash discharge thermocouples becomes higher indicating that the system has to wait for the next ash dump.
As the carbon is more and more combusted and disintegrates, the bottom of the gasifier becomes colder and colder indicating that the ash only is left at the bottom of the gasifier and it is time for a new ash dump.
The portion of a segment of a feed cone 25 is shown surmounting the grate 42. The grate 42 is surmounting the flat plate 39. At one edge 44 of the grate 42, there is a pin 45 that attaches the grate 42 to the flat plate 39 and the grate 42 partially swings around the pin 45 such that the grate 42 moves in an oscillating motion. The swinging motion of the grate 42 moves the ashes that pile on the grate 42 and the flat table 39 and the ash falls through holes 41 and 43 into a bin below. Also shown are the bottom tuyeres 34.
It is preferred within the scope of this invention to eliminate the peppermill grate system when the feed material into the gasifier 1 is soft, easily combustible materials, such as chicken litter, turkey litter, or plastics, and the like.
As indicated supra, the gasifier 1 has a centrally located feed cone 25 arranged along the centerline of the chamber and protruding above the general elevation of the “moving bed of ash” hearth 30. The feed cone 25 is serviced by a single, or twin set, of fuel feed augers 31 entering vertically from below.
The feed cone 25 is circular (See
It is contemplated within the scope of this invention to have the feed cones 25 be utilized as one single piece, that is a unitary article, for example those shown in
Also contemplated within the scope of this invention is the use of such feed cones 25 as non-moveable articles when in use in the gasifier. However, preferred for this invention are feed cones 25 that are moveable, that is are moveable in a partial circular motion within the gasifier 1, such that they oscillate. (See
In the gasifier, a partial primary method is one in which the combustion is carried out sub-stoichiometrically with the application of an oxidizing agent, which in this invention is flue gas mixed with a predetermined portion of fresh air, wherein the solid organic materials are transferred continuously or intermittently to the gasifier 1 at a predetermined rate to maintain a mass of solid organic materials in the gasifier, and further wherein the oxidant is continuously added to the gasifier 1 to continuously gasify the solid organic materials in the mass, and still further the solid residue (non-combustibles) are transferred out of the gasifier. The oxidizing agent is administered through a set or sets of suitable ducts connected to nozzles, preferably tuyeres and injection points located within, around and between the feed cones 25, and to a row, or line of nozzles and/or tuyeres in the surrounding walls of the gasifier 1.
Thus shown in
As can be observed from
The gasifier 1 is equipped with an opening 15 for the movement of the syngas produced by the method. The opening 15 has surmounted on it, a fixture 52 for allowing the attachment of components that are used to handle the syngas, which will be described infra.
Located in the lower portion of the housing 10 of the gasifier 1 is a device for determining the amount of non-combustibles within the gasifier 1. Thus probes 53 can be used to monitor the level of moving ash bed defined by the upper elevation of the accumulated ash. As an example of probes 53, there are used thermo elements in pairs located one above the other, distanced sufficiently such that the level of the moving ash bed will be in between them, and capable of characterization by the difference in temperatures and the temperature of the material above the moving ash bed while in operation. Said temperature difference will then be the offset that will dictate the degree of auger 26 movement required to control the level of the moving ash bed between the probes. In this representation, it is assumed that gasifier 1 is equipped with several sets of probes 53, inserted through openings 55, around the perimeter of the chamber and an average of probe 53 input data will determine the auger 26 movements.
The floor 57 for the gasifier is located in the lower portion 12 of the gasifier 1, the floor 57 having a top surface and a bottom surface. The floor 57 has at least one opening through it to allow for the passage of the solid organic material into the interior of the gasifier 1.
To bring gasifier 1 to an operational condition on start up, the feed assembly 3 is activated to form the pile 18 of feed material in the gasifier 1 in preparation of development of a “moving ash bed” above bottom 9. The pile 18 of feed material is ignited. To facilitate bringing the pile 18 of feed material up to its normal operating temperature, fuel oil or other readily combustible supplemental fuel may be added to it. As an example, this may be done manually through an opening 54 provided in the wall of the gasifier 1.
As the oxidation proceeds and the temperatures elevate the solid mass 18 will pyrolyze and gasify. Gas produced in the starved combustion sifts through the burning pile and into the upper portion of the burning pile 18, the upper pile 18 acting as a filter for particulate material. It is important to conduct the combustion of the solid mass below the pile 18. The products of combustion rise through the pile 18 and cools because the latent heat of water absorbs the energy. As fuel comes, it gets pyrolyzed and the fuel moisture and volatile hydrocarbons get separated from the non-volatile components. These processes are driven by the hot gases that result from the combustion of the fixed carbon, which takes place below the pile 18.
The moderately slow burning lower portion of the pile will serve to establish a quiet oxidation zone whereby entrainment of particulate matter and fly ash is minimized. Syngas with a maximum of combustible gaseous components and a minimum of particulate matter is one key objective of this invention.
Turning now to
Wall 61 is made up of a multiplicity of layers. In the preferred embodiment,
A second embodiment of wall 61 is shown in
With further regard to
As in the gasifier 1 described Supra, the control of pile height is of importance for combustion control and the release of gaseous combustibles. The principles discussed Supra for the gasifier 1 apply equally well for the gasifier 60 and will not be repeated herein.
Returning to
As in the gasifier 1, Supra, the oxidizing agent is administered through a set or sets of suitable ducts connected to nozzles, preferably tuyeres and injection points located within, around and between the feed cones 59, and to a row, or line of nozzles and/or tuyeres in the surrounding walls of the gasifier 1.
Thus shown in
The modified flue gas return system useful in gasifier 60 shown in
It should be noted that the upper part of the lower portion 12 and the lower part of the upper portion 13 of the gasifier (
Feed rate into gasifier 60 is monitored and controlled by monitoring and controlling fuel pile height within gasifier 60 using the same radar devices 16 as set forth Supra. Suitable instrumentation, not shown, is provided to control the rate of the delivery of the feed material into gasifier 60 by the feed assembly as a function of the elevation of the top of the feed material in the height of pile 71 to maintain such elevation at a substantially constant value, and thereby to contain the pile 71 of feed material at a substantially constant size.
Turning now to
Turning now to
Thus, shown in
The syngas 90 is provided to the syngas burner 91 at a temperature of about 500° F. to about 600° F. and is in a starved air condition. This part of the system is unique to this type of gasifier system in that the normal temperature of the air from prior art devices is in the range of 1200° F. to 1400° F., and in prior art systems, this air is not “starved air”, and before the prior art air can be used, it has to be cooled and compressed, which means that additional and expensive equipment has to be added to the system in prior art processes. The syngas burner 91 heats and combusts the syngas 90 up to a temperature in the range of 1200° F. to 1400° F. before the heated air 97 is provided to a low NOx oxidizer 96.
In a further embodiment, the syngas 90 can be provided to a kiln 98 using a syngas blower 99 that moves the syngas 90 to a nozzle mix syngas burner 100. Thereafter the syngas 90 is moved through the nozzle mix syngas burner 100 into the kiln 98. The heated air (about 2200° F.) from the kiln 98 is moved to the low NOx oxidizer 96 and combined with the starved air coming from the syngas burner 91.
The heating and movement of the heated air in the kiln 98 is aided by passing heated air 101 from a heat exchanger 102 (see
The heated air 107 from the kiln 98 is fed into the low NOx oxidizer 96 and mixed therein with the air 97 being fed into the top portion of the low NOx oxidizer 96. The low NOx oxidizer 96 is fed ambient air 108 using a combustion/tempering air fan 109, through manifolds 110 and tuyeres (not shown) and the air 111 that exits the low NOx oxidizer 96 does so at about 2000° F. and passes to the heat exchanger 102 shown in
Turning now to
Exchanged air having a temperature in the range of about 400° F. to 1200° F. is the air 101 that is passed back to the kiln 98. The air 101 has to be occasionally vented in order to control the temperature and pressure of the air 101 and this is shown at 116.
The heat-exchanged air 127 from the metal heat exchanger 113 is moved to an induction draft fan 115 before it enters the stack 117. Prior to air exiting 122 the flue stack 117, a portion of the flue gas 120 is withdrawn from the stack 117 and moved to a flue gas eductor 118, which is aided by a an induced draft fan 119. At this point, fresh air 128 is inducted and mixed with the flue gas 120 and it is this flue gas modified with fresh air 121 that is moved back to the gasifier 1 as the oxidative gas for use in the gasifier 1. Also shown in
This application claims priority from U.S. Provisional Patent Application 60/801,574 filed May 18, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60801574 | May 2006 | US |
