US20110259250A1

US20110259250A1 - Systems And Methods For Converting Biomass In The Field To A Combustible Fluid For Direct Replacement Or Supplement To Liquid Fossil Fuels

Info

Publication number: US20110259250A1
Application number: US13/060,175
Authority: US
Inventors: James T. McKnight; Ken W. White
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-08-21
Filing date: 2009-08-21
Publication date: 2011-10-27
Also published as: WO2010022337A3; WO2010022337A2

Abstract

Methods, systems, and devices convert biomass from the field to provide heat, motive working gas, electrical energy, or fuel such that the biomass directly replaces or supplements liquid fossil fuels wherever these fuels may be used. The methods include procedures for harvesting the biomass, reducing it to a transportable form, purifying it and blending additives as necessary, and finally reducing the refined biomass to an explosible particle size distribution generally finer than 80 mesh for heating applications or 200 mesh for application in internal or external combustion engines. The present invention preferably includes transportation of the finished powder to storage units at the end user site, where the fuel is used by continuous delivery, metering, and dispersal in air to produce a continuous supply of an explosible fluid dispersion for direct energy conversion. Systems of automatic production for a variety of applications are also described.

Description

REFERENCE TO RELATED APPLICATIONS

This application claims one or more inventions which were disclosed in Provisional Application No. 61/090,714, filed Aug. 21, 2008, entitled “SYSTEMS AND METHODS FOR CONVERTING BIOMASS IN THE FIELD TO A COMBUSTIBLE FLUID FOR DIRECT REPLACEMENT OR SUPPLEMENT TO LIQUID FOSSIL FUELS”. The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.
The subject matter of this application is related to the subject matter in co-pending U.S. patent application Ser. No. 12/419,946, filed Apr. 7, 2009, entitled “POWDERED FUEL CONVERSION SYSTEMS AND METHODS”, which claims priority to U.S. Provisional Application No. 61/074,244, filed Jun. 20, 2008, and U.S. Provisional Application No. 61/042,996, filed Apr. 7, 2008. The subject matter of this application is also related to the subject matter in co-pending U.S. patent application Ser. Nos. 12/464,416, filed May 12, 2009, entitled “METHODS OF COMBUSTION OF POWDERED FUELS AND POWDERED FUEL DISPERSIONS”, 12/464,449, filed May 12, 2009, entitled “POWDERED FUELS AND POWDERED FUEL DISPERSIONS”, and 12/466,873, filed May 15, 2009, entitled “COMBUSTION DEVICES FOR POWDERED FUELS AND POWDERED FUEL DISPERSIONS”, all of which claim priority to PCT Patent Application No. PCT/US2007/024044, filed Nov. 16, 2007, which claims priority to U.S. Provisional Application No. 60/859,779, filed Nov. 17, 2006, U.S. Provisional Application No. 60/868,408, filed Dec. 4, 2006, and U.S. Provisional Application No. 60/993,221, filed Sep. 10, 2007. The above-mentioned applications are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention pertains to the field of fuels. More particularly, the invention pertains to methods and devices for providing energy from biomass as a replacement for energy from fossil fuels.
2. Description of Related Art
Fossil fuels are currently being used much more rapidly than they are being produced, and as such, fossil fuels are not a viable long term source of energy.
There is a need in the art for a renewable energy source capable of meeting the world's ever increasing demand for energy.

SUMMARY OF THE INVENTION

Methods, systems, and devices convert biomass from the field to provide heat, motive working gas, or electrical energy and for directly replacing or supplementing liquid fossil fuels wherever these fuels are used. The methods include procedures for harvesting the biomass, reducing it to a transportable form, purifying or enhancing it by removal or addition of certain volatile components or certain impurities by various procedures including aqueous extraction, and finally reducing the refined biomass to a particle size distribution generally finer than an explosible threshold, which, for example, is about 200 microns (0.2 mm) for wood. About 80 mesh is preferred for heating applications and about 200 mesh for application in internal or external combustion engines. Means to transport the finished powder to the site where the fuel is used, means to provide storage at the end user site, and means to continuously deliver, meter, and disperse the powdered fuel in air to produce a continuous supply of a combustible fluid are provided. The energy conversion is performed by devices and systems capable of performing sustained burning of explosible biomass with on/off control for a range of applications including heating, cooling and transportation for example. A system capable of automatic control for a variety of applications is also described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overview of a system of the present invention to convert biomass to energy.

FIG. 2 shows a detailed system of the present invention to convert biomass to energy.

DETAILED DESCRIPTION OF THE INVENTION

The term “ash” is used herein to describe the incombustible remains of combustion.
The term “biomass” is used herein to describe any organic matter available on a renewable, or recurring, basis. Biomass may include a wide variety of substances including agricultural residues such as grasses, nut hulls, oat hulls, corn stover, sugar cane, and wheat straw; energy crops such as grasses including but not limited to pampas grass, willows, hybrid poplars, maple, sycamore, switch grass, and other prairie grasses; animal waste from animals such as fowl, bovine, and horses; sewage sludge; wood residues (hardwood and/or softwood) from industries such as logging, milling, woodworking, construction, and manufacturing; and food products such as sugars and corn starch.
The term “combustion device” is used herein to include any system that burns and/or deflagrates a fuel of any type. Such combustion devices include internal combustion engines, furnaces, grain dryers, and generators.
The term “converting” as used in the language “converting said energy” is used herein to describe the act of harnessing or utilizing, for example, said energy, to produce a result, such as doing work or producing heat. In certain embodiments, the conversion of the energy may occur through the operation of a device, as measured by the action of the device, i.e., which will produce a measurable result.
The term “controlled stream” is used herein to describe a movement or stream of particles that may be directly controlled and modified, e.g., by feedback modification, based on parameters flow rate, mass transfer rates, power/heat output, temperature regulation, and the like. The stream may be finely or coarsely controlled as the particular application may require. Moreover, devices, such as sensors, may be used to provide the data necessary to control or modify the stream. In particular embodiments, the stream may be controlled for the purpose of producing consistent explosible powder dispersion.
The term “deflagrating” is art-recognized, and describes subsonic combustion that usually propagates through thermal conductivity (e.g., combusting material heats the next layer of cold material and ignites it). It should be understood that deflagration is distinguished from detonation in that detonation is supersonic and propagates through shock compression.
The term “explosible” as used herein describes a property of a powder, which, when dispersed under the appropriate conditions as a powder-gas mixture, is capable of deflagrating flame propagation after ignition. Explosible powders that form explosible powder dispersions are capable of flame propagation when mixed with the appropriate ratio of an oxidizing gas. Numerous explosible powders (which are distinguishable from ignitable powders) are described in Table A.1 of Rolf K. Eckhoff, Dust Explosions in the Process Industry (3d ed. 2003), the contents of which are hereby incorporated by reference herein.
The terms “gas” and “oxidizing gas” are used interchangeably herein to describe any substance in the gaseous state of matter, which contains a minimum amount of an oxidizing gas, e.g., O₂, to produce an explosible powder dispersion (i.e., even if insufficient to provide complete combustion). For example, the compressed gas from the compressed gas source, i.e., used to create explosible powder dispersions is an oxidizing gas, such as air. This term is intended to encompass gases of singular composition, e.g., O₂, and mixtures of gases, such as air. (This is in contrast to the use of this term as the abbreviated form of the word gasoline, liquefied petroleum gas, or natural gas.) In certain embodiments of the invention, a gas may be used to create a powdered fuel dispersion.
The term “mesh” is used herein to describe particle size by comparison to the open spacing of particle sieves as defined by a specific standard of mesh. A variety of standards for mesh scales exist including ISO 565, ISO 3310, and ASTM E 11-70. All mesh sizes referred to herein are measured using the ASTM E 11-70 standard.
The term “particle size” is used herein to describe the size of a particle, e.g., in terms of what size mesh screen the particle will pass through or by metric description of the size (e.g., in microns). Moreover, certain embodiments of the powdered fuel are defined, in part, by particle size. Particle size may be defined by mesh scales, in which larger numbers indicate smaller particles. As described herein, embodiments of powdered fuel may have a particle size smaller than or equal to 50 mesh. Powdered fuel also encompasses powdered fuels with more stringent requirements, for example, powdered fuels including particles smaller than approximately 80 mesh, e.g., smaller than approximately 200 mesh, e.g., 325 mesh, e.g., 400 mesh.
The term “particle size distribution” is used herein to describe the prevalence of particles of various size ranges, i.e., the distribution of the particles of various sizes, within a powder sample.
The term “powder”, is used herein to describe a solid compound composed of a number of fine particles that may flow freely when shaken or tilted. The powder composition and/or particulate size (and particulate size distribution) may be selected based on the application in which the powder is being used. For example, in certain embodiments the particle size distribution and/or particle material is purposefully selected based on the desired utility requiring a particular continuance, e.g., powdered fuel supplied to a four cycle engine may have a distribution of particles that is finer than the powdered fuel supplied to a furnace. The powders of the present invention are at least “substantially explosible”, in that the limited particles in the particle distribution that exceed the size limitations for explosibility amount to less than would prevent the powder dispersion from igniting to produce a sustainable stationary deflagrating combustion wave. In certain embodiments, the particles in the particle distribution that exceed the size limitations for explosibility are less than about 5% to less than about 0.25%. In a particular embodiment, the particles in the particle distribution that exceed the size limitations for explosibility are less than 2%. In another particular embodiment, there are no particles in the particle distribution that exceed the size limitations for explosibility. Fuels referred to as “powder” or “powdered fuel” meet the definition of “explosible” and as such are capable of deflagrating flame propagation after ignition and essentially complete combustion, with no sensible odor, smoke, or soot.
The terms “powdered fuel dispersion” and “powder dispersion” are used interchangeably herein to describe substantially uniform mixtures of powdered fuel and an oxidizing gas, which are selected to be explosible based on the nature of the powder (e.g., size and/or composition of the constituent particles) and the ratio of the powder to the oxidizing gas. The explosibility of the powdered fuel dispersion may be affected by a number of factors including, for example, the surface area of the powder particles, the energy content of the powder, the concentration of an oxidizer such as oxygen in the powder dispersion, the temperature of the powder and the oxidizer, the heat transfer rate, and the powder particle size. The terms “powdered fuel dispersion” and “powder dispersion” are also intended to cover those dispersions that include an imperfectly distributed mixture made with an imperfect distribution of an explosible powder, provided that such dispersions are explosible.
The term “ultra clean coal” is used herein to describe any coal having a low ash content by weight, for example, less than 1.00% to less than 0.05%.
The term “volatile mass” is used herein to describe the mass of the powder fuel particles that includes material or compounds, such as water, which vaporize or volatilize at or below the combustion temperature of the powdered fuel.
Many forms of biomass have been used to produce heat via combustion over the years. Scrap from the pulp and paper industry and lumber and wood products industries has been a staple fuel source to supplement the use of fossil fuels. Common practice has been to chip and reduce the particle size below one inch using chippers and hogs and then use the sawdust and chip combination to fire a variety of large combustion devices, such as boilers to produce steam.
U.S. Pat. No. 4,532,873, “SUSPENSION FIRING OF HOG FUEL, OTHER BIOMASS OR PEAT”, issued in 1985 to Rivers et al., is an excellent example of the previous and current art for the direct burning of various types of biomass for heat recovery, in this case in a water-wall boiler. Today, rotary biomass driers are typically fired by large and expensive, refractory lined cyclonic Webb Burners™ fed by relatively large particles from sawdust to tiny chips.
Systems and methods of the present invention rely on using just the explosible nature of finely ground biomass to produce a sustained, stationary combustion wave, fed by a moving dispersion of explosible powder in air. For wood biomass, particle sizes are generally below 200 microns, the explosibility threshold for wood. These explosible powder burners are tiny compared to Webb Burners™ and very low cost.
The hog fuel burner system requires a distribution with particle sizes much larger than burner systems of the present invention, allowing for up to an estimated 75% of the particles outside the explosible range (“15-85% less than 150 microns”) and “65 to 100% less than 1000 microns”, meaning 35% could be larger than 1 millimeter (1000 microns), a size that is 4 to 5 times the boundary between explosible and non-explosible wood powders.
The stability of the prior art two-phase combustion regime operates in a narrow 2.5:1 turndown ratio compared to our single-phase-like 10:1 turndown ratio, and prior art burner cannot tolerate cold secondary air unlike the powder burner used by the present invention. While this hog fuel biomass burning system may superficially appear similar to burners of the present invention, it is clear that this entire prior art system operates using a totally different combustion regime and substantially different operating principles, burner hardware, and fluid mechanic processes in its two-phase operation.
The particle size region claimed by Rivers, et al. (“at least 60% by weight of the particles are finer than about 1000 microns”) allows for a significant portion of non-explosible particles. “A fines portion including at least 15% by weight less than 150 microns was found suitable” makes it clear there is no requirement for significant or substantial use of “fines”. The hog fuel burner does not operate in what we call the explosible range, a term they never use.
Today biomass is slowly finding applications in a wide variety of heating applications. Power plants in Europe are leading the way in co-firing applications. The present disclosure focuses on both production and combustion of substantially explosible mixtures. Other art, including the hog fuel patent just described and co-firing designs, specify the use of a distribution of a mixed particle size fuel, often called “powder”. Only some component segments of the broad, larger fuel particle size distribution are “fine powders” that may, only when used alone, actually be explosible. Units called “powder burners” from Thermix Combustion Systems and Elster LBE in Germany, are usually multi-fuel capable and examples of burners using significant non-explosible powder components.
A burner of the present invention has numerous features and benefits: instant cold start ON-OFF control; stable combustion the moment the powder-air mix is ignited; use in either vertical and horizontal modes; burning solid fuel in a single-phase mode as if it were a vaporized liquid or gas; completeness of combustion within the burner housing itself, rather than in a large high temperature furnace reactor; an ultra-short particle residence time requirement; burning substantially explosible powders; and smaller and simpler than prior art solid fuel systems. The burner and fuel in combination are important to operation of a burner used the present invention standalone system.
The present invention provides methods, processes, and systems for energy production from raw harvested biomass and other carbonaceous sources. Biomass, as used herein, is preferably any harvestable crop or portion of a crop which can be grown on a renewable basis, preferably in the field, but also potentially in a water environment. Biomass includes, but is not limited to, portions of trees, agricultural crops, and fast growing plant species such as willow, or switch grass, which may be grown on a wide range of soil qualities and, attractively, on marginal fields not well suited for food crops with the intention of supplying raw biomass for fuel production.
A wide range biomass sources are available for use in the present invention, many on a regional basis, including certain grasses already referred to as “energy grass”. Biomass feedstock materials for use in the present invention include, but are not limited to, crops, wastes, residues, starch crops, grains, rice, barley, rye, oats, soybean, maize, wheat, sugar cane, sugar, cocoa bean, sugar crops, corn, grasses, switchgrass, Miscanthus grass, elephant grass, Orchardgrass, many perennial grasses including Timothy grass tall fescue, prairie grass, Abfrageergebnisse (offered for license by a Hungarian research institute as “energy grass”), Reed canarygrass, industrial hemp, Giant reed, cotton, seeds, husks, seaweed, water hyacinth, algae, microalgae, herbaceous and woody energy crops, wood chips, bamboo, wood, stem wood, cellulose, and lignin, hardwoods, American sycamore, black locust, eucalyptus, hybrid poplar, hybrid willow, silver maple, softwoods, cedar, pine, Monterey pine, invasive types of brush, fishmeal, fat, whey, agricultural wastes, rice straw, chaff, wheat straw, sugar cane bagasse, corn stover, corn stalks, biochar, forestal wastes, sawdust, shavings, lumber wastes, pulp, pulp waste, mill wastes, thinned woods, brush solid wastes, municipal solid wastes, industrial solid wastes, construction wastes, demolition wood wastes, urban wood wastes, yard wastes, agricultural residues, livestock wastes, dry manure solids, poultry wastes, and intermediate enzymatic and acid hydrolysis bio-solid byproducts and waste solids from biological processes of ethanol fermentation, methane production, and anaerobic digestion.
Particular aspects of the present invention include methods of harvesting and processing the specific biomass source. Furthermore, the present invention provides devices and methods for performing the steps in this process as a continuous, automated system, which is capable of producing energy for local use or exported as electrical power or powdered fuel for use elsewhere. The complete system preferably links the initial biomass processing steps to the ultimate production of power through various energy conversion means at the site of harvest and processing. Certain materials of the wide range of biomass supply feedstock materials may require special equipment for preprocessing, for example demolition wastes or manure. Such equipment and techniques are known to those in the relevant art and will not be detailed in this disclosure.
The method and system begin with collection of the raw biomass and the first stage of size reduction of the biomass, sufficient to permit drying, and proceed to the stages of fine grinding followed by storage or immediate application for heat or mechanical power generation. In an automated system, the power required for the initial and subsequent biomass size reduction and drying steps is preferably provided by the final power producing step. In a continuously operating system, surplus power is preferably used locally, exported as electrical power, and inventoried as powdered fuel. In a preferred embodiment, if the inventory of stored power or powdered fuel drops below a set minimum, this automatically starts up the power production step and the process of reducing the dried biomass material to powder as needed, or initiates a manual start-up of the process.
The conversion of the collected biomass and other fuel sources to powder, the combination with an oxidizing gas to form a combustible fluid, the energy conversion, and the subsequent power generation at the site of the biomass is preferably a unified system combining devices which are linked by automatic controls and operated automatically in response to the demand for power or powder, as illustrated in FIG. 1 and FIG. 2.
FIG. 1 shows an overview of a system for converting biomass in the field into energy in an embodiment of the present invention. The biomass is first harvested or collected by a harvesting device 10 in the field where it has grown. The harvested biomass may then be transported by a vehicle or other means 12 to a central processing site, where the remaining processes, including grinding the biomass in a coarse grinder 14 are preferably automated or automatable. Alternatively, the biomass may be fed in the field by hand, auger, conveyor belt, the harvest device itself, or other device 12 to a coarse grinder 14 followed by transport of the biomass by a vehicle or other means 16, 20 to the central processing site, where the remaining preferably automated processes, including drying and fine grinding in a dryer 18 and fine grinder 22, respectively. If the biomass has been coarsely ground at the central site, the biomass is transferred by an automated device 16, 20, preferably by a metering auger or conveyor belt, to the dryer 18 or fine grinder 22.
The biomass is transferred by a second automated device 24, preferably by a conveyor belt or metering system, for one or more steps of finer grinding in grinders 22 after drying. After being finely ground to a substantially explosible size distribution, the biomass is automatedly transferred, preferably by an auger, a conveyor belt, or an air stream 26, to a storage unit 28 for the biomass. The biomass is transferred as needed from storage 28, preferably using a metered auger 30, dispersed in a mixing zone 32 with an oxidizing gas stream, and transported, preferably in a gas stream 34 to a burner 36 for energy conversion by combustion. The heat energy from burning is then transferred or transported 38 and applied as needed. The heat energy is used for a device requiring energy 40 including, but not limited to, a heating unit for heating or an engine for a motive working gas or for conversion to electrical energy for storage, transmission, or immediate use.
FIG. 2 shows a detailed system to convert certain types of biomass to energy in an embodiment of the present invention. When the biomass comes from a forest source, waste from a forest harvest or a forest harvest itself is collected by a forest harvester 50 and preferably fed directly to or transported to a chipper 52. The chipper loads a vehicle, preferably a truck, which compresses the chips and transports the compressed chips to central processing. Alternatively, the harvested biomass, including logs, is trucked to central processing and fed to a chipper 52 there, with optional debarking of the logs prior to chipping. When the biomass comes from a field source, the corn harvested-stalks, cut switch grass, or other field biomass source may be left in the field by a harvester machine and then raked and baled by a grass harvester 54 and transported to central processing, where the bales are opened and the biomass is fed to a shredder 56 or other particle size reduction means. Biomass with particle sizes above those required for optimal drying to a target of 10% moisture for example, may be subject to a coarse hammer mill reduction step following an optional size sorting and foreign material removal step (not shown).
The chipped or shredded material is then augered, blown, or conveyed to a horizontal or vertical drying and storage facility 58, where warm air is introduced counter-current to movement of the chips or chopped stalks. Dried material is continuously augered or conveyed from the storage facility to a rough grinder 60, preferably a hammer mill with a ⅜-inch screen opening, for initial grinding. In an alternative embodiment, rotary drying systems that are run either directly or indirectly by biomass combustion are used. The material passing through the screen may be blown directly to a fine grinder system or to a storage hopper. Various metal and foreign material detection and removal systems, dust collection plus spark detection systems, and mitigation systems known to those skilled in the relevant art are inherent to these designs and are preferably used in systems and methods of the present invention.
The coarsely ground material is fed to at least one fine grinder 62, preferably to a hammer mill with 40-mesh screens whose output is then fed directly to a third hammer mill with 80-mesh screens, whose output may be used directly as heating fuel or inventoried for similar use. Alternatively, the roughly ground material may be fed to an impact or attrition mill with an air classifier set to recycle particles larger than 100 mesh for heating fuel or 200 mesh for heating, internal combustion, or external combustion. Non-biomass fuels such as ultra clean coal powder or other additives may be introduced and mixed with the biomass during or after the fine grinding process. The outputs from fine grinding may be inventoried.
A portion of the finely ground biomass may be transferred off-site for off-site usage including, but not limited to, usage as a fuel for a heating unit or an engine 64. The remaining portion may be kept on-site in a storage unit 66 for later use on-site or transfer off-site or be fed directly to a burner 68 for conversion to heat energy. For transfer off-site, inventoried powdered biomass may be transferred to a chambered hopper truck capable of delivering multi-ton quantities of powder to storage hoppers of individual retail, commercial, or industrial customers. Alternatively, powder may be transferred to hopper rail cars for transport to a central retail distribution facility from which it is then loaded into retail delivery hopper trucks. For storage on-site, the powder is preferably stored in a retail storage tank 66.
The powder is transported from the retail storage tank by at least one auger or an air flow system to at least one burner hopper, whenever the burner 68 needs to be resupplied with the substantially explosible powder fuel. Alternatively, the powder is transported, for example by auger, to the storage tank of a four cycle engine 68 if 200-mesh powder is used or to a turbine. A burner, internal combustion engine, or external combustion engine 68 is operated using the powdered biomass as the primary fuel source. At least a portion of the produced powdered fuel is burned as a stationary deflagrating combustion wave in a burner as described in co-pending U.S. patent application Ser. Nos. 12/419,946, 12/464,416, 12/464,449, and 12/466,873.
The energy from combustion of the powdered fuel may be stored on-site in an energy storage unit 70, preferably as electrical energy from a generator, or transferred off-site, preferably as electrical energy for usage 72 by nearby residents. The energy may also be used on-site for any of the processing, storage, or transportation steps for the biomass or for any other processes at the central processing site requiring energy. About a quarter of the raw biomass energy is preferably used to complete the drying and grinding processes of the present invention.
While FIG. 2 depicts both forest and grass harvesters as input gathering devices to systems of the present invention, it is understood that other types of biomass feedstock sources may utilize different collection devices. Although not shown diagrammatically, the overall process to “harvest”, process and utilize such biomass, scrap wood for example, will remain essentially the same, however, for the fundamental steps remain: gather 50, 54, reduce particle size for drying and handling 52, 56, dry to approximately 10% moisture 58, interim storage if desirable 58, then further reduce to the end use application driven particle size distribution specification 60, 62. Beyond finished product grinding, the system process and methods are the same. The more general nature of FIG. 1 likewise applies to all biomass and non-biomass sources, with minor differences in processing on a material specific basis known by those skilled in the relevant art.
The energy from combustion may be provided as thermal, mechanical, or electrical energy. The electrical power generated via an external or internal combustion engine may be used locally or stored in a quantity sufficient to start the burner or generator to permit initiation of further powder production. In a preferred embodiment, the central processing site is powered exclusively by energy from combustion of powdered fuel such that it does not rely on any other outside source of energy under normal operating conditions.
For a small scale unit in an embodiment of the present invention, i.e. a power utility unit for an isolated village in a developing country, the process begins by collecting and coarsely grinding various locally available biomass materials, including, but not limited to, banana stalks, corn stalks, harvested reeds, mangrove cuttings, eucalyptus cuttings, and waste from coconut harvest and processing, in a small chipper/shredder, such as the Northern Industrial PTO Wood Chipper, Model# 1104S001 from Northern® Tool+Equipment (Burnsville, Minn.), or, for somewhat larger eucalyptus cuttings, a larger chipper, such as the 8-inch wood chipper from Liberty Implements (Phoenix, Ariz.). Both of these units require approximately 30-horsepower (HP) engines which may be driven directly from a steam engine or by electrical power from a generator as outlined herein. This coarsely ground material is blown into a drying bin heated by the flue gas from the burner powering the steam boiler or dried in other types of drying devices known to those skilled in the relevant art, including, but not limited to, rotary single-pass or multi-pass biomass dryers. At this point, an inventory of the starting material is preferably taken. The dried material at the output of the drying bin or other dryer may be delivered by conveyor belt or metering system to the first stage of grinding, preferably a hammer mill with ⅜-inch screen openings, such as the Universal Mill from Bauermeister USA (Memphis, Tenn.), which is designed to process 200 lbs/hr using approximately 15 HP. The output of this mill is directly delivered in the product air stream to a second mill, such as the Classifier Mill BM-CLM 0 from Bauermeister USA (Memphis, Tenn.), which transfers the approximately 200-mesh finished powder to the powder storage hopper. This is preferably followed by a second inventory step.
In an alternative embodiment, systems and methods of the present invention include a KDS Micronex system supplied by First American Scientific Corporation. The KDX Micronex system is a cyclonic impact and classifying mill capable of handling a wide range of particle sizes and percent moisture levels at increased throughput rates. A large KDS system, driven by a 400 HP main drive, can process 55% moisture wet wood chips at a rate of 2080 lb/hr with a resulting output of 10 percent moisture powder at 1040 lb/hr, substantially reduced to a preferred explosible powder specification. A customized KDS Micronex system of selectable throughput may be used as a replacement for, or as an adjunct to, other particle size reduction equipment and technologies available, depending on the specific application.
From the powder storage hopper, the powder is transferred by auger as needed to supply a burner, such as described in co-pending U.S. patent application Ser. Nos. 12/419,946, 12/464,416, 12/464,449, and 12/466,873, which preferably burns the substantially explosible powdered fuel in a stationary deflagrating combustion wave. The burner may heat a boiler, such as the 50-125 HP Monotube Boiler from the Reliable Steam Engine Co. (Tidewater, Oreg.). The steam from the boiler may be used to power an engine, such as the V-4 Single Acting Compound Engine from the Reliable Steam Engine Co. (Tidewater, Oreg.), which drives a generator, such as the 25 kW 540 RPM Tractor Driven PTO Generator, Model 25PTOC-3, from Winco, Inc. (Le Center, Minn.).
For this boiler/steam engine combination, the burner combustion chamber may include cyclonic removal of ash particles or droplets. Alternatively, the temperature of the burner exhaust may be controlled to ensure that the ash particles are solids, which may subsequently be collected from the flue gas, if necessary, via an electrostatic precipitator, in a manner such as described by Neundorfer, Inc. (Willoughby, Ohio). A portion of this power may be used to maintain a charge in a bank of storage batteries sufficient to start up the electrical system required to operate the burner and associated control system. The largest part of this electrical power supply may be distributed throughout the village for uses including, but not limited to, powering hot plates to provide smoke-free cooking, powering electrical lighting, powering a cell phone-based communication system, and most importantly powering a well pump, which may feed a bank of several reverse osmosis water purifiers, such as Model RO-Pump from APEC (Industry, Calif.). The excess power may be transmitted into an electrical power network if one exists or the excess powder may be delivered to neighboring villages for use in a smaller burner, steam engine, and generator to power the local village water supply and lighting services. The excess powder may also be shipped to supply other higher capacity power-generating centers.
The operation of the complete system as described above is preferably automated as much as possible. In one embodiment, when the power storage level in the batteries drops below a predetermined level, the burner, the steam engine, and the generator are automatically started up to increase the power storage in the batteries. In one embodiment, when the amount of finished powdered fuel in storage drops below a predetermined level, the powder milling process is automatically started up. In one embodiment, when the amount of coarse ground dry raw material drops below a predetermined level, such as a one day supply, the power system may be shut down, and additional harvesting and coarse grinding is triggered, while assuring that there is sufficient stored fuel available to drive the automated coarse grinding and drying step.
In developed countries needing additional peak power for the summer air conditioning months, the forests and wood lots for local biomass-fueled power generation stations preferably increase their production of pulp wood harvesting and forest thinnings, for example tree weeding, by a factor of two or more and transport this shippable biomass to peak demand power generation centers, which are preferably located just at the outskirts of suburbs of major metropolitan centers, close enough to the metropolitan centers to keep significant transmission losses to a minimum.
The addition of environmentally clean peak power generation units or centers of the present invention to the existing network of old, inefficient power plants and generators as backup units to the nation's power grid is an attractive technical and capital investment option. These units are capable of coming up to generating status extremely quickly and automatically, preferably in the time it takes to heat the minimum amount of water or other fluid used to generate adequate steam to run and synch their generators, or to simply start an explosible powder powered internal combustion engine to directly drive and synch an electrical generator.
At these peak power generation centers, the process preferably begins by reducing these pulp wood logs to chips and smaller particles, such as mulch, suitable for drying using chippers or grinders, such as the 3600 Chipper/Grinder from Morbark, Inc. (Winn, Mich.), which is fed by a log loader, such as the SK210 LL Kobelco (Carol Stream, Ill.). The scale at which chips, mulch, and powder is produced depends on the scale of the peak power requirements for the unit/center. It has been suggested that supplemental power units with capacities as low as 250 kwatt/hr would be helpful in some smaller metro areas, while in larger locations, 2,500 kwatt/hr or more would be needed.
For smaller scale units, the powder production rate is preferably about 1000 lbs/hr for a system based on three 200-HP boilers, such as from Reliable Steam Engine Co. (Tidewater, Oreg.). For larger scale centers, the powder production rate is preferably about 5 tons/hr with the power generation based on three 2000-HP boilers, such as from Hurst Boiler & Welding Company (Coolidge, Ga.) and steam turbine generators from Skinner Power Systems (Erie, Pa.). Again, the burner combustion chamber exhaust system may include cyclonic removal of ash components, preferably prior to contact with the heat transfer surfaces or ash particle collection from the flue gas as outlined above.
As in the small scale unit described above, the reduced particle size chips or mulch is conveyed to a large drying bin which is heated either directly or by the flue gas from the burner heating the boiler. Alternatively, a direct heated biomass powder fired rotary drying system may be used in place of the drying bins. For a 250-kwatt system, the dried mulch is preferably conveyed to the input of one or more Universal Mills with the capacity to produce at least 0.5 ton/hr of coarsely ground wood powder which is then fed directly to a second Universal Mill set to produce powder through 80-mesh screens, which is then inventoried for delivery to three separate 200-HP burner/boiler/generator units including generators such as the 150 kW 1,000 RPM Tractor-Driven PTO Generator from Winco, Inc. (Le Center, Minn.).
Again, this system is preferably automated using the control principles described above and control hardware and software known to those skilled in the relevant art with the additional specification that the signal to start operation is derived from the demands placed on the local power network. Specifically, one or more of the three boiler/generator units in this embodiment would be fired up as needed.
For the large scale power generation centers, a preferred design uses a system offered by, or similar to, Alternative Green Energy Systems Inc. (Boucherville, QB), which fuels 2000-HP boilers, such as from Hurst Boiler & Welding Company (Coolidge, Ga.), and steam turbine generators, such as from Skinner Power Systems (Erie, Pa.). In one embodiment, these 200-HP boilers are fed by multiple burners of the present invention, preferably five burners, each burner preferably being independently controlled and consuming about 10 pounds of powdered fuel per minute. This system may be scaled up simply by adding more boiler turbine units. It may be that local supplies of pulpwood logs are insufficient for larger metropolitan centers, but pulpwood logs may be transported by railroad such that, for example in the northeastern United States, Canada, western Pennsylvania, Maine, and the Carolinas supply the Washington to Boston megalopolis.
Although several systems have been described herein for predetermined energy production levels, other systems for energy production on other scales may be used within the spirit of the present invention.
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention.
Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.

Claims

1. A system for converting raw biomass to heat energy comprising:

a harvester, wherein the harvester harvests at least one raw biomass material;

a transporter, wherein the transporter transports the raw biomass material to a central processing facility; and

the central processing facility comprising:

a fine grinding system, wherein the fine grinding system grinds the raw biomass material to a predetermined size distribution to form a substantially explosible powdered fuel; and

at least one burner system comprising:

a positive displacement powder dispersion feed system comprising:

an oxidizing gas feed system supplying a flow of an oxidizing gas;

a powder fuel feed system regulating a powder flow rate of the explosible powdered solid fuel; and

a mixing zone having inputs coupled to the oxidizing gas feed system and the powder fuel feed system and an output comprising a moving stream of a dispersion of particles of the powdered solid fuel in the oxidizing gas;

a flame stabilizing combustion system fed by the mixing zone for directing the moving stream toward a stationary deflagrating flame; and

an ignition source for initiating the deflagrating flame;

wherein the powder flow rate and a gas feed rate for the oxidizing gas feed system are selected such that the dispersion of particles is explosible and sustains the stationary deflagrating flame.

2. The system of claim 1 further comprising an engine run using heat energy produced in the burner system.

3. The system of claim 2, wherein the engine is selected from the group consisting of an external combustion engine and an internal combustion engine.

4. The system of claim 2 further comprising a generator run by the engine for generating electrical power.

5. The system of claim 1 further comprising a rough grind system, wherein the rough grind system grinds the raw biomass material to a predetermined drying size for drying to remove moisture.

6. The system of claim 5 further comprising a dryer, wherein the dryer removes moisture to a predetermined moisture level from the raw biomass material ground to the predetermined drying size.

7. The system of claim 1 further comprising at least one transfer device for transferring biomass within the central processing facility.

8. The system of claim 7, wherein the transfer device is selected from the group consisting of a conveyor belt, a metering auger, a blower, a truck, and a multi-wheeled transport device.

9. The system of claim 1 further comprising an inventorying device for inventorying an amount of the biomass material in the system.

10. The system of claim 1 further comprising at least one storage device, wherein the storage device stores the substantially explosible powdered fuel until energy is needed.

11. The system of claim 1, wherein the system produces energy by a continuous process of linked components.

12. A method of delivering an explosible mixture comprising a substantially explosible powdered fuel to an ignition source inside a combustion enclosure in a self-sustainable system to generate power, the method comprising the steps of:

a) harvesting at least one raw biomass material;

b) transporting the raw biomass material to a central processing facility;

c) drying the raw biomass material to a predetermined moisture level;

d) reducing at least a portion of the biomass material to a predetermined particle size for use as the substantially explosible powdered fuel;

e) mixing the powdered fuel with an oxidizing gas to form the explosible mixture;

f) igniting the explosible mixture in the combustion enclosure such that a stationary deflagrating combustion wave is formed; and

g) consuming the powdered fuel to produce energy to generate power.

13. The method of claim 12, wherein the step of harvesting is performed such that the raw biomass material is transportable to the central processing facility.

14. The method of claim 13, wherein the step of harvesting comprises a sub-step selected from the group consisting of:

a) chipping a plurality of waste wood from a forest harvest into a truck equipped to compress and transport the waste wood;

b) collecting a plurality of pulpwood logs for transportation;

c) collecting and baling a plurality of waste corn stalks from a harvest;

e) cutting, windrowing, and baling switch grass;

f) collecting scrap wood, construction debris, or demolition debris; and

g) any combination of a) through f).

15. The method of claim 12 further comprising the step of reducing the raw biomass to a form that can be easily dried and transported by auger, air, or conveyor.

16. The method of claim 15 further comprising the step of drying the form as needed depending on timing requirements for harvesting the biomass and producing the substantially explosible powdered fuel.

17. The method of claim 15 further comprising the step of inventorying the form to determine timing requirements for harvesting additional biomass material and delivering the substantially explosible powdered fuel to the ignition source.

18. The method of claim 15, wherein the step of reducing comprises at least one sub-step of grinding at least a portion of the form to a predetermined dimension to form the substantially explosible powdered fuel.

19. The method of claim 18, wherein the sub-steps of grinding are separated by intermediate steps of transporting using augers or air and inventorying using a plurality of bins.

20. The method of claim 18, wherein the sub-steps of grinding are continuous such that an output of a courser grinding mill is fed directly to a finer grinding mill.

21. The method of claim 12 further comprising the step of inventorying the powdered fuel.

22. The method of claim 12 further comprising the step of transporting the powdered fuel to at least one distribution center or to a storage facility of at least one final user.

23. The method of claim 12 further comprising the step of transferring the powdered fuel by auger or blower to a storage hopper of a final application at the central processing facility.

24. The method of claim 12, wherein the step of mixing the powdered fuel with an oxidizing gas further comprises the sub-steps of metering the powdered fuel, metering the oxidizing gas, and mixing the powdered fuel with the oxidizing gas to form the explosible mixture.

25. The method of claim 12, wherein the step of burning the explosible mixture further comprises the sub-step of blowing the explosible mixture past an ignition source.

26. The method of claim 12, wherein the raw biomass material is selected from the group consisting of wheat straw, rice straw, a portion of a plurality of trees left after a forest harvest, a portion of a forest, a portion of pulpwood harvested for paper making or particle board production, a fast growing plant species, any other waste biomass stream that can be readily harvested and driedcrops, wastes, residues, starch crops, grains, rice, barley, rye, oats, soybean, maize, wheat, sugar cane, sugar, cocoa bean, sugar crops, corn, grasses, switchgrass, Miscanthus grass, elephant grass, Orchardgrass, perennial grasses, Timothy grass tall fescue, prairie grass, Abfrageergebnisse, Reed canarygrass, industrial hemp, Giant reed, cotton, seeds, husks, seaweed, water hyacinth, algae, microalgae, herbaceous and woody energy crops, wood chips, bamboo, wood, stem wood, cellulose, and lignin, hardwoods, American sycamore, black locust, eucalyptus, hybrid poplar, hybrid willow, silver maple, softwoods, cedar, pine, Monterey pine, invasive types of brush, fishmeal, fat, whey, agricultural wastes, rice straw, chaff, wheat straw, sugar cane bagasse, corn stover, corn stalks, biochar, forestal wastes, sawdust, shavings, lumber wastes, pulp, pulp waste, mill wastes, thinned woods, brush solid wastes, municipal solid wastes, industrial solid wastes, construction wastes, demolition wood wastes, urban wood wastes, yard wastes, agricultural residues, livestock wastes, dry manure solids, poultry wastes, intermediate enzymatic and acid hydrolysis bio-solid byproducts and waste solids from biological processes of ethanol fermentation, methane production, and anaerobic digestion, and any combination of the above.

27. The method of claim 12 further comprising the step of providing electricity using energy released in the step of combustion of the explosible mixture.

28. The method of claim 12 further comprising the step of burning a portion of the explosible mixture in a combustion chamber of an internal combustion engine to generate a mechanical power.

29. The method of claim 12 further comprising the step of burning a portion of the explosible mixture to generate steam to run a steam turbine or to power an external combustion engine.

30. The method of claim 12 further comprising the step of using energy generated from the step of consuming the powdered fuel to operate at least one machine selected from the group consisting of a grinding mill, an electrical generator for powering electric motors driving a plurality of equipment needed to produce the powdered fuel, a battery used to start up the burner, an electric cooking unit, a pump for pumping well water, a water purification system, electrical lighting, a cellular phone system, and any combination of the above.

31. The method of claim 12 further comprising the step of adding at least one additive to the raw biomass material selected from the group consisting of boron, calcium, phosphorus, magnesium, silicon, sulfur, aluminum, iron, titanium, tantalum, zirconium, zinc, and compounds and alloys thereof, bronze, titanium dioxide, coal, ultra clean coal, metal, plastic, sulfur dust, phosphorus dust, polyester dust, a hydrocarbon-bearing solid, polypropylene, polystyrene, acrylonitrile butadiene styrene, polyethylene terephthalate, polyester, polyamides, polyurethanes, polycarbonate, polyvinylidene chloride, polyethylene, polymethyl methacrylate, polytetrafluoroethylene, polyetheretherketone, polyetherimide, phenolics, urea-formaldehyde, melamine formaldehyde, and polylactic acid, and any combination of the above.