Abstract:
An apparatus, system, and method for subjecting biomass to pyrolysis to extract energy products using a pyrolysis unit comprising generally concentric chambers including a combustion chamber and at least one pyrolysis chamber. Each chamber is in communication with an adjacent chamber such that a directed, generally-deoxygenated heated gas stream passes through the combustion chamber to each of the pyrolysis chambers in turn. Additionally, each pair of adjacent chambers shares a heat-conducting wall, further promoting heat transfer throughout the unit. A heat source, which can be a burn enclosure configured as part of the pyrolysis unit, produces the heated gas stream. Biomass introduced into the pyrolysis unit is pyrolysized by the gas stream, resulting in exhaust containing non-condensing gases, bio-oil vapor, and entrained char. The exhaust is directed from the pyrolysis unit to other parts of the system where the bio-oil and char can be separated from the exhaust and collected.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to provisional application 61/053,386, filed May 15, 2008, entitled System, Apparatus, and Method for Optimizing the Economical Production of Ecologically-Sound Energy Products from Biomass, Such as Sawmill Waste or Byproducts. 
     
    
     BACKGROUND 
       [0002]    The present invention relates generally to systems, apparatus, and methods for the production of energy products from carbonizable material, such as biomass, particularly systems, apparatus, and methods that employ fast pyrolytic reactions. 
         [0003]    Today, the United States faces substantial environmental issues from continuing reliance on polluting energy sources such as coal, natural gas, nuclear power, and hydroelectric power. The burning of fossil fuels, such as coal and natural gas, results in the emission of excessive amounts of carbon dioxide into the atmosphere. The use of nuclear power raises the specter of ecological damage through the accidental release of radiation into the environment, as well as difficulties in safely disposing of spent nuclear fuel. Hydroelectric projects can disrupt local ecosystems, resulting in major reductions in fish populations, negative impacts on native and migratory birds, and damage to the dammed river itself. As a result, people are looking for alternatives to these ecologically-harmful sources of energy. In recent years, biomass has gained popularity as an environmentally-sound alternative. 
         [0004]    Biomass is commonly defined as living or recently-dead biological matter, generally vegetable matter. Biomass, or the fuel products derived from it, can be burned to produce power. Unlike fossil fuels, however, carbon dioxide released from the burning of biomass does not contribute to the overall carbon dioxide content of the atmosphere. This is true because biomass is part of the world&#39;s current atmospheric carbon cycle. For this reason, biomass is viewed as a renewable, carbon-neutral fuel. 
         [0005]    Substantial sources of biomass are available from forest products processing facilities. The typical facility uses some of its biomass in the creation of its products, while the remainder of the biomass is seen as a byproduct. One type of forest products processor that produces a large volume of biomass byproduct is a chip mill. The chip mill processes only small-sized timber. In the chip mill, logs are debarked and then ground into chips for transporting to other mills for further processing. Another type of forest products processor is a chip and saw facility (“CNS facility”). A CNS facility produces dimensional lumber from timber that has a diameter ranging from mid-sized to small. Substantial sources of biomass are also available from other facilities, such as large log processing plants, plywood plants, and OSB plants, among others. 
         [0006]    Throughout the year, a typical CNS facility will generate an average of more than five-hundred tons of dry biomass byproducts per day. (According to Marks Mechanical Engineering Handbook, the standard for “dry” is defined as twelve percent moisture content.) These biomass byproducts consist of white chips, bark, sawdust, and wood shavings. The white chips produced by a CNS facility are generally sold to paper-producing mills for processing into paper and cellulose products. The bark, sawdust, and shavings are either used at the CNS facility itself as a thermal energy source or sold as a byproduct. When sold as a byproduct, the biomass generally fetches less than twenty dollars a ton. This is far less than the value of its energy content, as shown by Table 1 below. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Typical Production and Pricing of Biomass from a CNS facility 
               
             
          
           
               
                   
                 Water 
                 Daily 
                 Value 
                 Energy 
                 Energy Val 
               
               
                 Byproduct 
                 Content 
                 Production 
                 Per Ton 
                 Per Pound 
                 Per Ton * 
               
               
                   
               
             
          
           
               
                 Bark 
                 10% 
                 300 tons 
                 $9.91 
                 6,500 Btu 
                 $224.91 
               
               
                 White Chips 
                 40% 
                 700 tons 
                 $19.13 
                 5,000 Btu 
                 $173.00 
               
               
                 Sawdust 
                 40% 
                 120 tons 
                 $13.00 
                 5,000 Btu 
                 $173.00 
               
               
                 Shavings 
                 10% 
                 120 tons 
                 $24.50 
                 8,666 Btu 
                 $299.86 
               
               
                   
               
               
                 * The dollar value of the energy contained within a ton of a given type of biomass is based on a sale price of $100 for a 42-gallon barrel of crude oil having an energy content of 5,780,000 Btu. 
               
             
          
         
       
     
         [0007]    One process used to produce energy products from biomass, and thus capture its energy content, is a process known as fast pyrolysis. Fast pyrolysis utilizes temperatures of between four-hundred-fifty and six-hundred degrees Celsius to rapidly heat biomass in the absence of oxygen. This results in the creation of three products: bio-oil, char, and non-condensing gases. All three products are combustible. The energy content of each of these products is listed in Table 2 below, along with the approximate percentage of each product typically yielded by the process. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Energy Content of Products Produced by Fast Pyrolysis 
               
             
          
           
               
                   
                   
                   
                 % of Product 
               
               
                   
                 Product 
                 Energy Content 
                 Yielded 
               
               
                   
                   
               
               
                   
                 Bio-oil 
                 8,000 Btu per pound 
                 70.0% 
               
               
                   
                 Char 
                 12,000 Btu per pound  
                 14.3% 
               
               
                   
                 Non-condensing Gases 
                 4,000 Btu per pound 
                 13.4% 
               
               
                   
                   
               
             
          
         
       
     
         [0008]    Fuel needed to create and maintain such high temperatures in systems utilizing fast pyrolysis can represent a major operational expense. For this reason, it is recognized as desirable in the art to create systems that make the most of the heat they produce. There are a number of strategies used to accomplish this. 
         [0009]    One strategy employs techniques meant to optimize the transfer of thermal energy to individual particles of biomass within a pyrolysis chamber. This can be accomplished through the use of organic heat carriers, like hot char, and inorganic heat carriers, like sand. These particularized heat carriers circulate within the pyrolysis chamber and radiate their heat to the particles of biomass. Other techniques involve rapidly moving particles of feedstock within a pyrolysis chamber so as to force the particles into nearly continual contact with the hot walls of the chamber. Still other techniques circulate a heated gas stream through a pyrolysis chamber to transfer heat to the particles of biomass. Another strategy involves capturing the hot exhaust resulting from pyrolytic reactions in the pyrolysis chamber and recirculating that hot exhaust to other parts of the system. Yet another more basic strategy involves simply insulating the pyrolysis chamber to deter heat loss through the walls of the chamber. 
         [0010]    Given the desirability to make efficient use of the heat produced by systems employing fast pyrolysis to convert biomass into energy products, what is needed is a fast pyrolysis system that improves upon the conservation and reuse of a system&#39;s existing heat in a manner that is compatible with other recognized techniques for conserving and reusing the heat generated by the system. 
       BRIEF SUMMARY 
       [0011]    In accordance with the present invention, an apparatus, system, and method are provided that employs a pyrolysis unit comprising concentric, or generally concentric, intercommunicating chambers for pyrolysizing biomass to create energy products. The pyrolysis unit captures and reuses heat that might otherwise be lost to the outside environment through the walls of a single-chambered unit. In addition, the unique, generally concentric construction of the intercommunicating chambers is compatible with other techniques used for conserving and reusing system-generated heat, such as the recirculation of hot exhaust resulting from pyrolytic reactions. 
         [0012]    A pyrolysis unit embodying features of the present invention includes an elongated, tubular combustion chamber and at least one elongated, tubular pyrolysis chamber. The chambers are configured generally concentrically so that the combustion chamber is located substantially within the larger-diameter pyrolysis chamber. In embodiments including multiple pyrolysis chambers, each of the elongated, tubular pyrolysis chambers will be arranged with the combustion chamber in a generally concentric manner such that the combustion chamber is the innermost chamber, an inner pyrolysis chamber substantially surrounds the combustion chamber, and each successive pyrolysis chamber substantially surrounds a previous pyrolysis chamber. 
         [0013]    One end of the combustion chamber is in communication with a proximate end of the pyrolysis chamber. In embodiments including multiple pyrolysis chambers, an opposite end of the innermost pyrolysis chamber is also in communication with a proximate end of a next-innermost pyrolysis chamber. An opposite end of the next-innermost pyrolysis chamber is, in turn, in communication with a proximate end of a successive pyrolysis chamber, and so on for each successive pyrolysis chamber. In this way, a directed, generally-deoxygenated, heated gas stream flowing from the combustion chamber flows through each pyrolysis chamber in turn. The heated gas stream reverses direction at each junction of chambers such that the stream flows in a first direction through one chamber, and then flows in a second direction opposite to the first direction through an adjacent chamber. 
         [0014]    Each pair of adjacent chambers shares a common wall that separates the gas in each chamber while still conducting heat. For example, the wall of the combustion chamber and the inner wall of the inner pyrolysis chamber are both the same wall. In addition to heat radiating from the heated gas stream passing through the chambers, each common wall of the pyrolysis unit also conducts heat through itself from one chamber to the next. At the designed temperature of the combustion exhaust, the wall of the combustion chamber will also provide significant radiant heat transfer to the biomass flowing through the first pyrolysis chamber, thereby increasing the rate of heat transfer to the biomass. 
         [0015]    A heat source is used to produce the directed, generally-deoxygenated, heated gas stream. In one embodiment, this heat source is a burn enclosure with an igniter and is configured as part of the pyrolysis unit. A fuel-air mixture is injected under pressure into a first end of the burn enclosure and ignited by the igniter. A second opposite end of the burn enclosure joins one end of a combustion chamber. The heated gas stream flows through the combustion chamber and out of the opposite end where it enters one or more pyrolysis chambers, each in turn. Alternate embodiments use other heat sources, such as a gas turbine in conjunction with a burn enclosure. 
         [0016]    Biomass is introduced into the pyrolysis unit and pyrolysized by the generally-deoxygenated, combusted gas stream, resulting in the creation of primarily non-condensing gases and bio-oil vapor, along with entrained char. This exhaust and its entrained matter are collected from the pyrolysis unit and directed to other parts of the system where the bio-oil vapor and char are both separated from the exhaust and collected. 
         [0017]    In some embodiments, a cyclone separator is used to separate entrained char from the exhaust. Also used in some embodiments is a biomass feed bin used to hold biomass for introduction into the pyrolysis unit. Exhaust separated from its bio-oil vapor and char is passed through the biomass feed bin whereupon the biomass acts as a filter, cleaning remaining entrained matter from the exhaust. Also in some embodiments, char separated from the exhaust is introduced back into the pyrolysis unit to aid in producing the generally-deoxygenated, heated gas stream. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which: 
           [0019]      FIG. 1  is a schematic view of a concentric-chambered pyrolysis system, in accord with the present invention; 
           [0020]      FIG. 2  is a schematic view of a pyrolysis unit used in the concentric-chambered pyrolysis system of  FIG. 1 ; 
           [0021]      FIG. 3  is a cross-sectional perspective view of  FIG. 2 , taken along line  3 - 3 ; 
           [0022]      FIG. 4  is a schematic view of a cyclone separator used in the concentric-chambered pyrolysis system of  FIG. 1 ; and 
           [0023]      FIG. 5  is a schematic view of a second embodiment of a concentric-chambered pyrolysis system, in accord with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Embodying the principles of the present invention is a system comprising a pyrolysis unit having concentric, or generally concentric, intercommunicating chambers in which biomass is pyrolysized to recover bio-oil and other products. A preferred embodiment of the system is depicted in  FIGS. 1-4  and designated generally by reference numeral  10 . 
         [0025]    Referring now to  FIG. 1 , the concentric-chambered pyrolysis system  10  includes a biomass feed bin  20  for receiving and delivering biomass  12  that is to be pyrolysized. The biomass feed bin  20  is generally enclosed to provide greater control over the channeling of exhaust  18  (shown as an arrow) from pyrolytic reactions that is fed into the feed bin  20 , as described below with reference to  FIG. 1 . The biomass  12  is fed through a top  21  of the feed bin  20  using a rotary air lock  70 . The biomass  12  is delivered from the feed bin  20  by an auger  68  attached to a lower portion  22  of the biomass feed bin  20 , as described below with reference to  FIGS. 1 and 2 . In this way, the biomass feed bin  20  continually cycles new biomass  12  through the system  10 . 
         [0026]    Continuing with  FIG. 1 , the biomass feed bin  20  accepts raw biomass  12 . The present embodiment envisions receiving this biomass  12  primarily from sawmills, particularly chip and saw facilities. The biomass  12  will typically not need to be ground to a smaller size because it will already be of a size suitable for use in the system  10 . If the biomass  12  does need to be ground, however, the biomass  12  will be ground prior to placing the biomass  12  in the biomass feed bin  20 . Note that in the present embodiment, an optimal size for particles of biomass  12  used in the concentric-chambered pyrolysis system  10  are envisioned to be particles  12  having no side generally greater than one-quarter inch in length. In alternate embodiments, however, items of biomass  12  having substantially larger dimensions are possible. Note also that in the present embodiment, items of biomass  12  are envisioned to consist generally of wood chips, sawdust, bark, wood shavings, and the like. Note further that in alternate embodiments, the use of biomass  12  of varying types received from numerous different sources is possible. Note in addition that in other alternate embodiments, carbonizable material other than just biomass can be used as input to the system  10 . 
         [0027]    Still referring to  FIG. 1 , some biomass  12  fed into the system  10  might require drying prior to undergoing pyrolysis. Biomass  12  with a moisture content of approximately fifteen percent or less by weight can be subjected to pyrolysis without prior drying. Green biomass  12 , however, will generally have a moisture content of about fifty percent by weight, as opposed to dry biomass  12  that generally will have a moisture content of about ten percent. The green biomass  12  can be blended with the drier biomass  12  to achieve a combined moisture content of fifteen percent or less. If such blending of the biomass  12  is insufficient to achieve a fifteen percent moisture content by weight, then the biomass  12  will need to be dried prior to subjecting the biomass  12  to pyrolysis. Optimally, the biomass  12  subjected to pyrolysis will have a moisture content of no more than twelve percent by weight. Note that in some cases the biomass  12  could be too dry, in which case moisture might need to be added. 
         [0028]    Referring now to  FIG. 2 , the concentric-chambered pyrolysis system  10  also includes a pyrolysis unit  30 . The pyrolysis unit  30  is made up of a burn enclosure  44 , an igniter  49 , a combustion chamber  31 , an inner pyrolysis chamber  35 , and an outer pyrolysis chamber  39 . The burn enclosure  44  is in the general shape of an elongated tube open at opposing ends  45 . A fuel-air input duct  74  is attached to the end  45  of a forward portion  46  of the burn enclosure  44 , while the igniter  49  is attached proximate to the end  45  of the forward portion  46 . Insulation  72  (see  FIG. 1 ) is installed around the burn enclosure  44  to reduce the amount of heat lost to the surrounding environment. 
         [0029]    Continuing with  FIG. 2 , the combustion chamber  31 , the inner pyrolysis chamber  35 , and the outer pyrolysis chamber  39  are each also in the general shape of an elongated tube, with the three chambers  31 ,  35 ,  39  arranged generally concentrically. The combustion chamber  31  is innermost, the inner pyrolysis chamber  35  surrounds the combustion chamber  31 , and the outer pyrolysis chamber  39  is outermost, surrounding both the combustion chamber  31  and the inner pyrolysis chamber  35 . An end  45  of a rearward portion  47  of the burn enclosure  44  is connected to a proximate end  32  of the combustion chamber  31 , while an opposing distal end  32  of the combustion chamber  31  extends into but is not attached to a proximate end  36  of the inner pyrolysis chamber  35 . An opposing distal end  36  of the inner pyrolysis chamber  35  extends into but is not attached to a proximate end  40  of the outer pyrolysis chamber  39 . 
         [0030]    Regarding  FIG. 2 , note that in alternate embodiments it is possible for a pyrolysis unit  30  to comprise as few as two chambers, for example a combustion chamber  31  and a pyrolysis chamber. In other alternate embodiments, it is possible that a pyrolysis unit  30  will have additional chambers, for example chambers in addition to a combustion chamber  31 , an inner pyrolysis chamber  35 , and an outer pyrolysis chamber  39 . Note also that the inventor recognizes that chambers of a pyrolysis unit can be arranged in a generally eccentric configuration, as opposed to a generally concentric configuration, even though it is likely that the eccentric configuration would be less efficient. 
         [0031]    Referring now to  FIG. 3 , each of the three chambers  31 ,  35 ,  39  of the pyrolysis unit  30  shares a wall  33 ,  37  with one other chamber  31 ,  35 ,  39 . A common wall  33  forms the wall  33  of the combustion chamber  31  as well as the inner wall  33  of the inner pyrolysis chamber  35 . Another common wall  37  forms the outer wall  37  of the inner pyrolysis chamber  35  and also the inner wall  37  of the outer pyrolysis chamber  39 . In this way, the three chambers  31 ,  35 ,  39  function as a heat exchanger, promoting heat transfer in three ways. First, conductive heat transfer through the common walls  33 ,  37  of the chambers  31 ,  35 ,  39 . Second, concurrent flow heat transfer is effected by the combusted gas stream  28 ,  29  (shown as arrows in  FIG. 2 ) and char  14  to the biomass undergoing pyrolysis, as described below with reference to  FIGS. 1 and 2 . Third, countercurrent flow heat transfer is effected by the gas stream  28 ,  29  flowing throughout the chambers  31 ,  35 ,  39 . Insulation  72  (see  FIG. 1 ) is installed adjacent an interior surface  42  (see  FIG. 2 ) of an outer wall  41  of the pyrolysis unit  30  to reduce the amount of heat lost to the surrounding environment. Note that the generally concentric configuration of the pyrolysis unit  30  allows for reuse of heat that would otherwise be lost to the surrounding environment through an outer wall of a single-chambered pyrolysis unit. 
         [0032]    Referring now to  FIG. 1 , fuel  17  (shown as an arrow), along with outside air  16  (shown as an arrow) propelled by a blower  66 , are introduced into the burn enclosure  44  under pressure through the fuel-air input duct  74 . Combustion of the fuel-air  17 ,  16  mixture produces heat and removes oxygen from the burn enclosure  44  and the attached combustion chamber  31 . Note that a variety of fuels  17  can be used for this purpose, such as fuel oil or bio-oil  15 . 
         [0033]    Continuing with  FIG. 1 , the char  14  along with air  16  are also introduced into the burn enclosure  44 . The air  16  need not necessarily be preheated. The char  14  is fed from a char bin  24  by a first auger  68  attached to a middle portion  25  of the char bin  24 . The first auger  68  conveys the char  14  out of the char bin  24  and into a proximate rotary air lock  70 . A second auger  68  receives the char  14  from the rotary air lock  70  and delivers the char  14  into a char-air input duct  78  that leads into the burn enclosure  44 . The preheated air  16  comes from a cooling duct  83  (see  FIG. 4 ) of a cyclone separator  80  that is used to separate entrained char  14  from the exhaust  18  (shown as an arrow) of previous pyrolytic reactions, as described below with reference to  FIG. 4 . The cooling duct  83  connects to the char-air input duct  78  to convey the preheated air  16  to the burn enclosure  44 . An end of the char-air input duct  78  is attached to a top  48  of the burn enclosure  44 . The char-air  14 ,  16  mixture exits the end of the duct  78  and enters the burn enclosure  44  through the top  48 . Note that a key function of the char-air  14 ,  16  mixture is to burn off any excess oxygen that would otherwise remain in the burn enclosure  44  and combustion chamber  31  following combustion of the fuel-air  17 ,  16  mixture. 
         [0034]    Still referring to  FIG. 1 , the igniter  49  ignites the fuel-air  17 ,  16  mixture. The ignited fuel-air  17 ,  16  mixture, in turn, ignites the char-air  14 ,  16  mixture. Combustion begins generally in the burn enclosure  44  and continues into the combustion chamber  31  where the fuel-air  17 ,  16  and char-air  14 ,  16  mixtures are substantially fully combusted. Note that although it is preferable that all of the oxygen remaining in the burn enclosure  44  and combustion chamber  31  be consumed, it is not required. Note also that feeding of the fuel-air  17 ,  16  and char-air  14 ,  16  mixtures, along with ignition of the mixtures, is done in a continual sequence during system  10  operation. 
         [0035]    Continuing with  FIG. 1 , to burn off any excess oxygen that would otherwise remain in the burn enclosure  44  and combustion chamber  31  following ignition of the fuel-air  17 ,  16  mixture requires that a certain minimum amount of char  14  be present in the burn enclosure  44 . During typical system  10  operation, however, more than this minimum amount of char  14  is introduced into the burn enclosure  44 . This results in excess char  14  being present in the combustion chamber  31  following combustion of the fuel-air  17 ,  16  and char-air  14 ,  16  mixtures. Individual particles of this excess char  14  are greatly heated by the combustive reaction. These particles of excess char  14  radiate heat to their surroundings as the char  14  travels through the combustion  31 , inner pyrolysis  35 , and outer pyrolysis chambers  39 . Eventually, the excess char  14  becomes entrained within exhaust  18  of a new pyrolysis reaction, with the excess char  14  mixing with newly-pyrolysized char  14 , as described below with reference to  FIGS. 1 and 2 . Note that in alternate embodiments, a gas turbine can be used as a combustion source for providing heat and deoxygenation in addition to, or in place of, a burn enclosure  44 . 
         [0036]    Referring now to  FIG. 2 , the substantially deoxygenated, continuous heated gas stream  28 ,  29  (shown as arrows) produced from the continual combustion of the fuel-air  17 ,  16  and char-air  14 ,  16  mixtures (see  FIG. 1 ) flows out of the rearward portion  47  of the burn enclosure  44  and throughout the combustion chamber  31 . The continual production of the heated gas stream  28 ,  29  from the burn enclosure  44  and the combustion chamber  31 , together with an impetus provided by injection of the fuel-air  17 ,  16  mixture into the burn enclosure  44  under pressure, propels the heated gas stream  28 ,  29  in a first direction  28  through the combustion chamber  31  and into the inner pyrolysis chamber  35 . In the inner pyrolysis chamber  35 , the heated gas stream  28 ,  29  changes to a second direction  29  that is opposite to that of the first direction  28  of the stream  28 ,  29  through the combustion chamber  31 . The heated gas stream  28 ,  29  exits the distal end  36  of the inner pyrolysis chamber and enters the outer pyrolysis chamber  39 . In the outer pyrolysis chamber  39 , the stream  28 ,  29  changes back to the first direction  28 , which is opposite to that of the second direction  29  of the stream  28 ,  29  through the inner pyrolysis chamber  35 . 
         [0037]    Continuing with  FIG. 2 , in addition to heat radiating from the flow of the heated gas stream  28 ,  29  through the pyrolysis unit  30 , heat from the heated gas stream  28 ,  29  is also conducted among the three generally concentric chambers  31 ,  35 ,  39  through the common walls  33 ,  37  of the three chambers  31 ,  35 ,  39 . In this way, the chambers  31 ,  35 ,  39  operate as a countercurrent flow heat exchanger. Note that the temperature of the combustion chamber  31  during operation of the system  10  is typically in excess of six-hundred-fifty degrees Celsius. 
         [0038]    Referring now to  FIGS. 1 and 2 , biomass  12  (see  FIG. 1 ) is fed from the biomass feed bin  20  (see  FIG. 1 ) by the auger  68  (see  FIG. 1 ) attached to the lower portion  22  (see  FIG. 1 ) of the biomass feed bin  20 . The auger  68  conveys the biomass  12  out of the feed bin  20  and into a proximate rotary air lock  70  (see  FIG. 1 ). The rotary air lock  70 , in turn, introduces the biomass  12  into the pyrolysis unit  30  at the distal end  32  (see  FIG. 2 ) of the combustion chamber  31 , where the combustion chamber  31  is in communication with the proximate end  36  (see  FIG. 2 ) of the inner pyrolysis chamber  35 . 
         [0039]    Continuing with  FIGS. 1 and 2 , the continuous heated gas stream  28 ,  29  (shown as arrows in  FIG. 2 ) captures the biomass  12  in its flow and carries the biomass  12  along through the inner pyrolysis chamber  35  toward the distal end  36  (see  FIG. 2 ) of the inner pyrolysis chamber  35 , opposite the proximate end  36  of the inner pyrolysis chamber  35  where the biomass  12  entered. As the heated gas stream  28 ,  29  moves the biomass  12  along, heat radiating from the stream  28 ,  29  fast pyrolysizes the biomass  12 . (Optimally, pyrolysis of a particle of biomass  12  takes no more than two seconds.) Exhaust  18  (shown as an arrow) resulting from the pyrolytic reaction comprises primarily non-condensing gases (not shown), bio-oil vapor (bio-oil not shown in vapor form), and entrained char  14  (see  FIG. 1 ). Note that the non-condensing gases are substantially made up of carbon dioxide, carbon monoxide, and nitrogen. Note also that the entrained char  14  might include excess, non-combusted char  14  from the char-air  14 ,  16  mixture (see  FIG. 1 ) that was introduced into the burn enclosure  44 , as described above with reference to  FIG. 1 . Note further that in alternate embodiments, various forms of inert material might be employed to assist in the transfer of heat to biomass that is to be pyrolysized. 
         [0040]    Still referring to  FIGS. 1 and 2 , the exhaust  18  from the pyrolytic reaction, along with any remaining non-pyrolysized biomass  12 , reaches the distal end  36  of the inner pyrolysis chamber  35 , where the inner pyrolysis chamber  35  communicates with the proximate end  40  (see  FIG. 2 ) of the outer pyrolysis chamber  39 . As the exhaust  18  and remaining biomass  12  enter the outer pyrolysis chamber  39 , the exhaust  18  and remaining biomass  12  change from flowing in the second direction  29  (see  FIG. 2 ) to flowing in the first direction  28  (see  FIG. 2 ) opposite to that of the second direction  29 . As the remaining non-pyrolysized biomass  12  is swept through the outer pyrolysis chamber  39 , the remaining biomass  12  is fast pyrolysized by heat from the gas stream  28 ,  29 . Exhaust  18  from this pyrolytic reaction combines with the existing exhaust  18  in the outer pyrolysis chamber  39 . Note that in some instances it is possible that a small quantity of oxygen will remain in one or both of the pyrolysis chambers  35 ,  39  at the time of pyrolysis. In this event, a small amount of the biomass  12  will react with the oxygen and combust rather than pyrolysize. This limited amount of combustion does not present a significant problem, although it might reduce the efficiency or yield of the pyrolysis unit  30  somewhat. 
         [0041]    Continuing with  FIGS. 1 and 2 , an exhaust duct  54  is fitted to the pyrolysis unit  30  proximate the distal end  40  (see  FIG. 2 ) of the outer pyrolysis chamber  39 , opposite the proximate end  40  of the outer pyrolysis chamber  39  where the outer pyrolysis chamber  39  communicates with the inner pyrolysis chamber  35 . The exhaust  18  exits the outer pyrolysis chamber  39  and rises along the exhaust duct  54 . The exhaust duct  54  leads from the pyrolysis unit  30  and attaches to the cyclone separator  80  (see  FIG. 1 ), as described below with reference to  FIG. 4 . 
         [0042]    Referring now to  FIG. 4 , the cyclone separator  80  comprises a body  84  with a collection cone portion  86 , a central exhaust pipe  81 , an inflow pipe  82 , and the cooling duct  83 . The collection cone portion  86  is in the general shape of a cone having an upwardly facing mouth  87  and an opposing open end  88  for collecting and distributing char  14  separated from the exhaust  18  (shown as an arrow) of pyrolysis reactions. The exhaust pipe  81  resides in the approximate center of the body  84  with the collection cone portion  86  located beneath a lower end of the exhaust pipe  81 . The exhaust pipe  81  is used for carrying the exhaust  18  out of the cyclone separator  80  following separation of the entrained char  14  from the exhaust  18 . The inflow pipe  82  and cooling duct  83  are aligned parallel with each other and share a common wall  85 , with the inflow pipe  82  located inwardly of the cooling duct  83 . The common wall  85  promotes heat transfer from the exhaust  18  in the inflow pipe  82  to the cooler air  16  in the cooling duct  83 . The inflow pipe  82  and cooling duct  83  spiral downwardly together around the central exhaust pipe  81 , beginning near an upper portion  89  of the exhaust pipe  81  and descending to a point just above the mouth  87  of the collection cone portion  86 . 
         [0043]    Continuing with  FIG. 4 , the exhaust duct  54  (see  FIG. 1 ) connects to an end of the inflow pipe  82  that is near the upper portion  89  of the central exhaust pipe  81 . The cyclone separator  80  draws the exhaust  18  downwardly through the inflow pipe  82  toward the mouth  87  of the collection cone portion  86 . A blower  66  (see  FIG. 1 ) is attached to an end of the cooling duct  83  that is near the mouth  87  of the collection cone portion  86 . The blower  66  forces outside air  16  (shown as an arrow) upwardly through the cooling duct  83 . The cooler outside air  16  inside the cooling duct  83  absorbs some of the heat of the hotter exhaust  18  inside the inflow pipe  82  through the common wall  85  between the inflow pipe  82  and the cooling duct  83 , thereby heating the air  16  and cooling the exhaust  18 . The char-air input duct  78  (see  FIG. 1 ) connects to an opposing end of the cooling duct  83  that is near the upper portion  89  of the exhaust pipe  81 . The now-heated air  16  flows through the char-air input duct  78  until the air  16  is eventually vented into the burn enclosure  44  along with the char  14  to be combusted, as described above with reference to  FIG. 1 . Note that in alternate embodiments, preheated air  16  from a cooling duct  83  is routed to a fuel-air input duct  74  or to both a char-air input duct  78  and a fuel-air input duct  74 . 
         [0044]    Still referring to  FIG. 4 , as the exhaust  18  spirals downwardly through the inflow pipe  82  toward the mouth  87  of the collection cone portion  86 , centrifugal force drives the particles of char  14  entrained within the exhaust  18  toward the common wall  85  between the inflow pipe  82  and the cooling duct  83 . As the particles of char  14  exit the end of the inflow pipe  82 , the char  14  falls into the mouth  87  of the collection cone portion  86  and exits the open end  88  of the collection cone portion  86 . Connected to the open end  88  is a rotary air lock  70  (see  FIG. 1 ). The rotary air lock  70  feeds the char  14  into the char bin  24  (see  FIG. 1 ). 
         [0045]    Continuing with  FIG. 4 , a given amount of the char  14  from the char bin  24  will be fed into the burn enclosure  44 , as described above with reference to  FIG. 1 . Since the char bin  24  is continually filling with char  14  from the cyclone separator  80 , it is possible that some amount of the char  14  will also need to be removed from the char bin  24  to keep the char bin  24  from overflowing. This excess char  14  is removed as an end product of the system  10 . 
         [0046]    Still referring to  FIG. 4 , at this point substantially all of the char  14  will have been removed from the exhaust  18 . The substantially char-free exhaust  18  now principally comprises non-condensing gases (not shown) and bio-oil vapor (bio-oil not shown in vapor form). This generally char-free exhaust  18  flowing from the end of the inflow pipe  82  rises and exits the cyclone separator  80  through an end of the upper portion  89  of the central exhaust pipe  81  and enters a second exhaust duct  56  (see  FIG. 1 ) attached to the end of the upper portion  89 . 
         [0047]    Referring now to  FIG. 1 , the exhaust duct  56  transports the exhaust  18  (shown as an arrow) through a bio-oil condensing system  62  that cools the exhaust  18  to a temperature of below one-hundred degrees Celsius. At this temperature, substantially all of the bio-oil vapor (bio-oil not shown in vapor form) condenses out of the exhaust  18  while the non-condensing gases (not shown) in the exhaust  18  remain in a gaseous state. The exhaust duct  56  leads from the bio-oil condensing system  62  to a bio-oil storage tank  52 . The now-liquid bio-oil  15  and the bio-oil-free exhaust  18  empty into the bio-oil storage tank  52 . The liquid bio-oil  15  collects in the storage tank  52  and is dispensed from the tank  52  as an end product of the system  10 . 
         [0048]    Continuing with  FIG. 1 , a third exhaust duct  58  leads from the bio-oil storage tank  52  to the biomass feed bin  20 . The biomass feed bin  20  is generally enclosed to provide greater control over the channeling of the exhaust  18  fed into the feed bin  20 , as described above with reference to  FIG. 1 . The exhaust  18  leaves the third exhaust duct  58  and passes through the biomass feed bin  20 . The biomass  12  in the feed bin  20  acts as a filter for the exhaust  18 , filtering out of the exhaust  18  any liquid or solid matter still entrained. The non-condensing gases of the exhaust  18  then exit the biomass feed bin  20  through an exhaust vent  60  leading to the outer environment. Note that in alternate embodiments, an exhaust vent  60  is attached to a char-air input duct  78  to channel a portion of the cleansed non-condensing gases exiting a biomass feed bin  20  into a burn enclosure  44  to join char  14  that is to be combusted, as described above with reference to  FIG. 1 . 
         [0049]      FIG. 5  depicts a second preferred embodiment of a concentric-chambered pyrolysis system, designated generally by reference numeral  110 , in accordance with the present invention. In the present embodiment, substantially an entire amount of char  14  produced from pyrolytic reactions in a pyrolysis unit  30  is fed back into the system  110  to help fuel further pyrolytic reactions. 
         [0050]    Referring now to  FIG. 5 , as particles of char  14  (see  FIG. 4 ) exit an open end  88  of a collection cone portion  86  of a cyclone separator  80 , the char  14  enters a rotary air lock  70  attached to the open end  88 . The rotary air lock  70  feeds the char  14  directly into a char feed duct  123 . The char feed duct  123  leads to a char-air input duct  78 . The char-air input duct  78 , in turn, leads to a burn enclosure  44  of a pyrolysis unit  30 . In this way, virtually all of the char  14  produced from pyrolysized biomass  12  is fed back into the system  110  and used to power further fast pyrolytic reactions. Additional fuel  17  (shown as an arrow), such as fuel oil or bio-oil  15 , is added to the burn enclosure  44  as needed to ensure the system  110  continues to effect efficient fast pyrolytic reactions. 
         [0051]    Regarding  FIG. 5 , note that unlike the concentric-chambered pyrolysis system  10  of the first preferred embodiment (see  FIGS. 1-4 ), the system  110  of the present embodiment does not require a char bin  24  or augers  68  to convey char  14  from the char bin  24  to the char-air input duct  78 . 
         [0052]    While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, that the appended claims cover all such modifications and changes as fall within the true spirit and scope of the invention.