Abstract:
Improved, fuel-efficient systems are provided for the processing of biomass, such as wood or crop residues, food waste or animal waste in order to selectively obtain torrefied and/or carbonized final products. In general, the processes involve thermally drying incoming biomass using a dryer employing the hot gas output of a fuel-operated burner. Next, the dried product is torrefied in an indirect torrefaction reactor so as to evolve light volatile organic compounds which are used as a gaseous fuel source for the burner. The torrefied product can be recovered, or some or all of the torrefied product may be directed to a carbonization reactor coupled with a reactor burner. Carbonization serves to remove most of the remaining VOCs which are used as a gaseous fuel input to the dryer. In certain instances, portions of the dried biomass are directed to the burners, as an additional source of fuel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with methods and apparatus used in the processing of biomass to yield torrefied and/or carbonized (i.e., charcoal) biomass. More particularly, the invention is concerned with such methods and apparatus whereby starting biomass is initially dried and then torrefied in a specialized torrefaction reactor, with the combustible gases evolved from the biomass during torrefaction being used as a source of fuel for the initial biomass drying step. In other forms of the invention, at least a portion of the torrefied product may be carbonized in a separate carbonization reactor, with the combustible gases evolved from carbonization also being used as a source of fuel. The processes of the invention are characterized by high energy efficiency, and in some forms the entire thermal energy required for steady-state processing is derived from the evolved combustible gases. 
     2. Description of the Prior Art 
     Biomass as understood in the art and as used herein refers to a biological material derived from living, or recently living organisms. In the context of biomass for energy, this is often used to mean plant-based materials, but biomass can equally apply to both animal and vegetable-derived materials. Biomass is carbon-based and is composed of a mixture of organic molecules containing hydrogen, usually including atoms of oxygen, and often with other atoms, including alkali, alkaline earth, and heavy metals. Plant-based biomass is normally lignocellulo sic in nature and can be derived from a variety of sources: wood, such as forest waste, arboricultural activities, and wood processing; agricultural residues, such as corn stover and rice straw; grasses, such as switchgrass and miscanthus. Other biomass sources include food waste from food and drink manufacture, preparation, and processing, or industrial waste, municipal solid waste, and animal waste. Biomass as-received generally has a moisture content of 5-80% by weight. 
     Techniques have been developed in the past for processing biomass to obtain useful fuels. Generally, the native biomass is preliminarily pre-sized, dried and sized, and is thereafter thermally treated to obtain various end products, including torrefied biomass and carbonized (charcoal) biomass. Torrefaction involves thermal processing to evolve combustible organic gases, particularly volatile organic compounds (VOCs). However, the torrefied product still contains heavy VOCs and, if used as a fuel, will have a tendency to “smoke.” Carbonization removes most of the remaining VOCs in the torrefied biomass, leaving a residue which is essentially free of smoke-producing compounds and is composed essentially of fixed carbon. 
     Generally, attempts have been made to carry out many or all stages of the biomass processing in a direct-fired single reactor. This has proved to be problematical because of low production rates and the fact that a single reactor cannot provide the optimum conditions for drying, torrefaction, and carbonization. Moreover, the throughput of single-reactor systems is relatively low, given that most single carbonization systems are batch systems. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above and provides improved processes and equipment for the torrefaction and/or carbonization of a starting biomass. In general, the processes of the invention comprise first thermally drying the untreated, pre-sized biomass to a reduced moisture content in a dryer using the hot gas output of a fuel-operated burner assembly. Normally, the untreated biomass is reduced to a relatively uniform size (e.g., a maximum cross-sectional dimension of from about 0.125-0.75 in.) using a hammermill or other size-reduction equipment, prior to drying. Advantageously, the drying step is carried out in a rotary dryer using an incoming hot drying gas at a temperature of from about 400-1000° F., more preferably from about 600-800° F. Where the preferred dryer is employed, the drying drum would be rotated at a speed of from about 5-10 rpm. The residence time in the dryer can range from 5 seconds to 8 minutes, depending upon the particle size of the incoming biomass. In the drying step, the moisture content is reduced to a level of from about 2-15% by weight, and more preferably from about 2-4% by weight. 
     In the next step, at least a portion of the dried biomass is thermally torrefied in an indirect torrefaction reactor different than the dryer using the hot gas output of the fuel-operated burner assembly to generate: (1) a first solid product output stream comprising torrefied biomass; (2) a first burnable gaseous output stream comprising burnable organic constituents evolved from the torrefaction of the biomass; and (3) a first residual gas stream from the torrefaction reactor comprising the gas used to indirectly torrefy the dried biomass. Importantly, at least a portion of the first burnable gaseous output stream is used as at least a part of the fuel to operate the burner assembly. Preferably, the first residual gas stream is also used as a source of heat for the biomass dryer. 
     In the torrefaction process, the temperature within the reactor should be from about 350-650° F., and more preferably from about 400-600° F. The indirect heating gases to the reactor preferably have a temperature of from about 400-800° F., more preferably from about 500-750° F. The residence time within the torrefaction reactor generally ranges from about 5-25 minutes, and more preferably from about 8-20 minutes. The oxygen content with the torrefaction reactor should be less than about 8% by weight, and more preferably less than about 6% by weight. Where the preferred torrefaction reactor is employed, the shell thereof should be rotated at a rate of from about 0.5-5 rpm, more preferably from about 1-3 rpm. As used herein, “torrefied biomass” refers to a treated biomass product having moisture content of up to about 4% by weight, a reduced volatiles content of from about 10-30% of the volatiles content of the dried, pre-torrefied feedstock, and a fixed carbon content of up to about 35% by weight. 
     The first solid product output stream from the torrefaction reactor may be wholly recovered as a torrefied product. More commonly, however, at least a portion of this solid product output stream is directed to an indirectly heated carbonizing reactor different than the torrefaction reactor, in order to carbonize the torrefied biomass with the hot gas output of the burner assembly to generate: (1) a second solid product output stream comprising carbonized biomass; (2) a second burnable gaseous output stream comprising burnable organic constituents evolved from the carbonization of the torrefied biomass; and (3) a second residual gas stream from the carbonization reactor comprising the gas used to indirectly carbonize the torrefied biomass. As in the case of the torrefaction reactor, at least a portion of the second burnable gaseous output stream is used to operate the burner assembly. Similarly, it is preferred to use the second residual gas stream as a source of heat for the dryer. 
     During carbonization, the temperature within the reactor will range from about 600-1100° F., more preferably from about 700-800° F. The gases used to indirectly heat the carbonization reactor will be at a temperature of from about 700-1200° F., and more preferably from about 800-1000° F. The VOC-laden output gases from the carbonization reactor recycled to the reactor burner as fuel should have a temperature of from about 600-1000° F., more preferably from about 700-900° F. The residence time of the material within the carbonization reactor will range from about 5-30 minutes, more preferably from about 8-20 minutes. The oxygen content within the carbonization reactor should be less than about 8% by weight, more preferably less than about 4% by weight. Where the preferred carbonization reactor is employed, the shell thereof should be rotated at a rate of from about 0.5-5 rpm, more preferably from about 1-3 rpm. As used herein, “carbonized biomass” or “charcoal” refers to a treated biomass product having moisture content of up to about 4% by weight, a VOC content of up to about 35% by weight and fixed carbon content of up to about 60% by weight. 
     Preferably, the burner assembly comprises separate dryer and reactor burners respectively operably coupled with the biomass dryer and the torrefaction reactor; and where a carbonization reactor is employed, the reactor burner is also coupled with this reactor. Also, when it is desired to produce only a torrefied biomass or both torrefied and carbonized biomass, a portion of the dried, pre-torrefied solid product output stream from the dryer is directed to the burner assembly as a part of the fuel for the operation thereof. 
     The preferred torrefaction and carbonization reactors of the invention are substantially identical, save for the materials used in the construction thereof. Thus, these reactors comprise an elongated, axially rotatable shell having a biomass input adjacent one end thereof and a treated biomass output adjacent the other end thereof, with a housing in surrounding relationship to the shell and defining with the shell an indirect heating zone, and including a hot gas inlet operable to receive hot gas for indirectly thermally treating biomass within the shell, and a gas outlet. The outlet includes a frustoconical wall with internal spiral fighting along the length thereof, with the wall secured to the shell and rotatable therewith. The spiral flighting is preferably in the form of a number of individual spiral walls circumferentially spaced from one another around the frustoconical wall. Further, it is preferred to employ a series of internal flights along the length of the shell and each including a first segment secured to the internal surface of the shell, and a second segment oriented at an angle relative to the first segment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic flow diagram illustrating the important components and operation of the preferred biomass conversion system of the invention, for the production of a charcoal end product; 
         FIG. 1B  is a schematic flow diagram illustrating the important components and operation of the preferred biomass conversion system of the invention, for the production of torrefied end product; 
         FIG. 1C  is a schematic flow diagram illustrating the important components and operation of the preferred biomass conversion system of the invention, for the production of both torrefied and charcoal end products; 
         FIG. 2  is a front perspective view of the rotary torrefaction reactor forming a part of the systems of  FIGS. 1A-1C ; 
         FIG. 3  is a front elevation of the reactor illustrated in  FIG. 2 , with parts broken away to reveal the construction thereof; 
         FIG. 4  is a rear elevational view of the reactor of  FIG. 2 ; 
         FIG. 5  is a vertical sectional view of the reactor illustrated in  FIG. 2 ; 
         FIG. 6  is an enlarged, fragmentary sectional view illustrating the details of construction of the front input end of the reactor of  FIG. 2 ; 
         FIG. 7  is an enlarged, fragmentary sectional view illustrating the details of construction of the rear output end of the reactor of  FIG. 2 ; and 
         FIG. 8  is a vertical view taken along line  8 - 8  of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, and particularly  FIGS. 1A-1C , biomass conversion systems  10 A,  10 B, and  10 C are schematically illustrated. The system  10 A is designed to convert starting biomass from a variety of sources into a carbonized or charcoal product; system  10 B is designed to convert the biomass to a torrefied product; and system  10 C is designed to simultaneously produce both charcoal and torrefied products. As explained below, all of the systems  10 A- 10 C further produce gaseous (VOC) fuel streams and hot gas output streams to provide a substantial fraction of thermal energy requirement for the equilibrated, steady state operation of the systems, and, in the cases of systems  10 B and  10 C, dried solid biomass fuel streams. A prime goal of the invention is to operate the systems  10 A- 10 C so as to thereby supply a substantial fraction (preferably at least about 80% thereof, more preferably at least about 90% thereof, and most preferably substantially all) of the thermal energy needed in the steady state operation of the systems. 
     System  10 A for the Production of Charcoal Products ( FIG. 1A ) 
     The principal components of the charcoal system  10 A are a conventional rotary drum dryer  12 , a rotary torrefaction reactor  14 , a rotary carbonization reactor  16 , a conventional dryer burner  18 , a conventional reactor burner  20 , and a conduit assembly  22  which operably interconnects the foregoing components. 
     The rotary drum dyer  12  is preferably of the type described in U.S. Pat. No. 7,155,841, incorporated by reference herein in its entirety. The dryer  12  includes an elongated, circular in cross-section, axially rotatable dryer shell  24  with an input  26  and an output  28 . Internally, the dryer  12  has axially spaced apart first and second drying sections each equipped with a turbulator and a downstream serpentine flow section (not shown). The turbulators are designed to divert portions of a product/air stream in different directions respectively to achieve intense mixing within the shell  24 . 
     The torrefaction reactor  14  is illustrated in detail in  FIGS. 2-8  and broadly includes an elongated, horizontally extending, generally circular in cross-section rotatable metallic (carbon steel) shell  30  with an input assembly  32 , and opposed output assembly  34 , and a multiple-piece insulative housing  36  surrounding the shell  30 . Internally, the shell  30  is equipped with an input flight assembly  38 , an output flight assembly  40 , and a frustoconical, spiral outlet  42 . A lowermost frame assembly  43  supports the shell  30  and housing  36 , and the related equipment described below. 
     The shell  30  includes a cylindrical main body  44  with an input end wall  46  and an output end wall  48 . The wall  46  includes a central projection  50  defining a tubular inlet  52 , whereas the wall  48  likewise has a central projection  54  defining an outlet opening  56 . The shell  30  is designed to rotate during operation of the reactor  14  and, to this end, the input and output ends of the reactor are provided with conventional trunnion assemblies  58  and  60 . In addition, the input end of the shell  30  is equipped with a circular drive sprocket  62 , as well as a drive motor  64 ; a drive chain  66  is operatively coupled between the output  64   a  of motor  64  and the drive sprocket  62  so as to effect rotation of the shell  30  at a desired rotational speed ( FIGS. 2 and 3 ). 
     The input assembly  32  of the shell  30  includes an elongated, tubular auger assembly  68  having a casing  70 , an internal conveying auger  72  driven by motor  74 , and an inlet opening  76 . As will be appreciated, rotation of auger  72  serves to convey material to be processed into the interior of shell  30 . 
     The output assembly  34  includes a stationary outer housing  78  having an upper gaseous outlet  80 , a lower solids output  81 , an airlock  82  in communication with output  81 , and a central access door  84 . The airlock  82  includes a rotary airlock permitting flow of solids from output  81 , and moreover serves to prevent the escape of VOC&#39;s. The rear wall of the housing  78  further has a circular flange  86  which is in alignment with outlet opening  56 , and a housing input aperture  88 . A circular, circumferentially extending seal connector  90  extends around the projection  54  of output end wall  48  and the flange  86 , and serves to operably interconnect the shell  30  and housing  78 . 
     The input flight assembly  38  ( FIG. 6 ) includes a plurality of circumferentially spaced apart, spirally oriented flights  92  which extend from the inner surface of input end wall  46 . The assembly  38  further has a series of equally circumferentially spaced apart angular flights  94  which extend from the flights  92  along a majority of the length of the shell  30 . Each flight  94  includes an inwardly projecting segment  96  welded to the inner surface of shell  30 , and an oblique segment  98  extending from the inboard end of the segment  92  ( FIG. 8 ). 
     The output flight assembly  40  includes a series equally circumferentially spaced apart, radially inwardly extending rectilinear flights  100 , which are located substantially equidistantly between the upstream angular flights  94 . The flights  100  extend from the ends of the angular flights  94  up to the spiral outlet  42  ( FIG. 5 ). 
     The spiral outlet  42  includes an open-ended frustoconical wall  102  which is secured to the inner surface of shell  30  and to the inner edge of the outlet opening  56  ( FIG. 7 ) in order to rotate with the shell  30 . The output end of the wall  102  includes a short cylindrical section  104  which extends into the output aperture  88 . Internally, the wall  102  is equipped with a series of four equally circumferentially spaced apart spiral flights  106 ,  108 ,  110 ,  112 . 
     The insulated housing  36  includes a lower section  114  having a bottom wall  116 , upstanding, opposed sidewalls  118 ,  120 , and opposed end walls  122 ,  124 , and a series of lower hot gas inputs (not shown). As best seen in  FIG. 8 , the sidewalls  118 ,  120  extend upwardly approximately to the rotational axis of shell  30 , and the walls  116 - 124  are equipped with an inner layer of refractory thermal insulation  126 . The housing  36  also has an upper arcuate section  128 , including an elongated, sectionalized primary wall section  130  with end-to-end interconnected sections  132 ,  134 , and  136 , and input and output end walls  138 ,  140 , respectively extending from the sections  132  and  136 . The section  128  covers the upper half of the shell  30  and is secured to lower section  114 . As best seen in  FIGS. 6 and 7 , the end walls  138 ,  140  extend into close proximity with the rotatable shell  30 , and corresponding seals  138   a ,  140   a  provide a sealing engagement with the shell  30 . In this fashion, the sections  114  and  128 , cooperatively define an enclosed, indirect heating zone  142  around shell  30 . The upper section walls  132 - 136  also have an internal layer of refractory thermal insulation  144 . 
     Each of the sections  132 - 136  has an upstanding port  146 ,  148 , and  150 , and a shiftable slide gate  152 ,  154 , and  156 , allowing selective opening and closing of the associated ports  146 - 150 . The ports  146 - 150  serve as output ports for the introduction of hot gas to the dryer  12 . 
     The frame assembly  43  includes fore and aft extending primary rails  158  on opposite sides of the housing  36 , with cross-rails  160  extending and interconnected to the rails  158  along the lengths thereof. Additionally, upstanding struts  162  are provided adjacent the housing  78  in order to support the latter, along with an inverted, U-shaped support  164  coupled with auger assembly  32 . 
     The carbonization reactor  16  is essentially identical with the torrefaction reactor  14 , except that the metallic components thereof are formed of a high temperature alloy in lieu of carbon steel. Moreover, insulative housing of the reactor  16  is equipped with castable refractory, which can withstand temperatures up to 2200-2500° F., similar to the refractory material used in the torrefaction reactor  14 . Accordingly, the same reference numerals are used in describing and depicting the carbonization reactor. 
     The conduit assembly  22  interconnects the above-described components to form a complete, operative system. The assembly  22  includes a gaseous fuel input conduit  166  with a blower  166   a , and a combustion air input conduit  170  with a blower  170   a ; both of the conduits  166  and  170  are coupled with dryer burner  18 . An output conduit  174  extends from the output of dryer burner  18  to the input assembly  26  of drum dryer  12 , in order to deliver hot combustion gas to the latter for initial drying of incoming biomass. A biomass input conduit  175  is also coupled with input assembly  26  to provide incoming biomass to the system  10 A. 
     A solids/gas output conduit  176  is provided between the output  28  of drum dryer  12  and the input of a conventional cyclone separator  178 , which serves to separate the solid and gaseous fractions received from the output  28  of drum dryer  12 . A gaseous output conduit  180  provided with a blower  180   a  extends from the upper gaseous output of cyclone  178  to an atmospheric vent. A solids output conduit  182  extends from the lower solids output of cyclone  178  to the input assembly  32  of torrefaction reactor  14 . 
     A hot gas input conduit  184  from the output of reactor burner  20  extends to one of the ports  146 - 150  of the shell  36  of reactor  14  in order to supply the indirect heat necessary to torrefy the incoming solids from cyclone separator  178 . A separate conduit  185  with blower  185   a  provides combustion air to the burner  20 . A conduit  186  equipped with a blower  186   a  is coupled between another of the ports  146 - 150  of the shell  36  and conduit  174 , for delivery of additional drying hot gas to the dryer  12 . The hot VOC-laden gas recovered in the output assembly of the torrefaction reactor is conveyed by line  166  equipped with blower  166   a  to the input of burner  18 . 
     A torrefied solids output conduit  188  extends from the airlock  82  to convey the torrefied product to the input assembly  32  of carbonization reactor  16 . The dried and torrefied product from reactor  14  is then subjected to a further carbonization reaction within the reactor  16 . To this end, a hot gas input conduit  190  extends from burner  20  to the input ports along the lower half of shell  36  of reactor  16 , and a residual hot gas output conduit  192  extends from the ports  146 - 150  to conduit  186 , thereby providing another source of drying gas for use in drum dryer  12 . The hot VOC-laden gas recovered in output assembly  34  of reactor  16  is conveyed by line  194  equipped with blower  194   a  to the input of burner  20 . The final charcoal output from the system  10 A is conveyed via conduit  196  from output assembly  34  of reactor  16  via airlock  82  for cooling and collection thereof. 
     As will be appreciated from the foregoing description, the overall system  10  is designed to serially process incoming biomass to initially dry the biomass in dryer  12 , to thereupon torrefy the dried biomass in reactor  14 , followed by final carbonization in reactor  16 . Importantly, once the system  10 A reaches an equilibrated, steady-state operation, all of the thermal energy requirements required for the operation of the system are provided in the form of gaseous VOC-laden byproducts generated by the reactors  14  and  16 . 
     EXAMPLE 1 
     This is a hypothetical, computer-based example using system  10 A for the conversion of a typical wood chip biomass into charcoal product, and production of all of the thermal energy used in the operation of the system, once the process has achieved steady state operation. 
     Referring to  FIG. 1A , locations A-O are indicated throughout the system  10 A. The following legend sets forth the mass-energy balance for the process at these respective locations. 
                                                         A - dryer burner operation                   500 BTU/lb                   435 lb/hr VOCs                   0.22 MMBtu/hr                   B - combustion air to dryer burner                   2,327 SCFM                   32° F.                   40% excess air                   C - biomass infeed to dryer                   4,300 lb/hr total                   2,365 lb/hr solids                   1,935 lb/hr water                   D - hot gases to dryer                   11,164 ACFM                   21,647 lb/hr                   2.21 MMBtu/hr                   770° F.                   E - dryer output                   2,438 lb/hr total                   2,365 lb/hr solids                   73 lb/hr water                   110° F.                   F - vented exhaust gases                   8,000 ACFM                   230° F.                   G - torrefaction reactor input                   2,438 lb/hr total                   2,365 lb/hr solids                   73 lb/hr water                   H - exhaust to atmosphere                   4,194 ACFM                   8,132 lb/hr                   2.75 MMBtu/hr                   1500° F.                   I - reactor burner                   7,300 BTU/lb                   1,309 BTU/hr VOC                   9.56 MMBtu/hr                   J - VOCs to dryer burner                   402 lb/hr                   33 lb/hr water                   K - combustion air to reactor burner                   6,790 SCFM                   32° F.                   40% excess air                   L - VOCs to reactor burner                   1,276 lb/hr                   33 lb/hr water                   M - torrefied biomass from torrefaction reactor                   2,003 lb/hr total                   2% water                   450° F.                   N - carbonized output from carbonization reactor                   694 lb/hr total                   1% water                   600° F.                   O - cooled carbonized output                   694 lb/hr total                   1% water                   270° F.                        
The hot gas input in line  174  was 623° F., and the dryer  12  operated at a power of 2.42 MMBtu/hr in order to evaporate 1862 lb/hr of water from the biomass infeed. The hot gas input in conduit  184  was 713° F., and the torrefaction reactor  14  operated a power of 3.09 Btu/hr to evolve VOC&#39;s from the dried biomass to generate the torrefied output product. The hot gas in line  190  was 854° F., and the reactor  16  operated at a power of 1.51 MMBtu/hr.
 
     Considering an 8000 hr/yr operation of system  10 A the annual output of the carbonized charcoal final product would be 2776 tons with 6.20 tons of starting biomass yielding 1 ton of the final product. 
     System  10 B for the Production of Torrefied Products ( FIG. 1B ) 
     Referring to  FIG. 1B , the system  10 B employs many of the components of system  10   a , and accordingly where appropriate the same reference numerals and foregoing descriptions will be used. Given that the system  10 B produces only torrefied products, it does not employ the secondary carbonization reactor  16  and related components. Moreover, the solids from cyclone  178  are split, with a fraction delivered to reactor  14 , and another fraction delivered to burner  18  and burner  20  as a source of fuel. 
     In detail, the solids output from conduit  182  from cyclone  178  is split using a conduit  198  to deliver a fraction thereof to the input assembly  32  of reactor  14  to yield torrefied product, and the remainder thereof is conveyed by conduit  100 ; this solids fraction is again split using conduits  102  and  104 , for delivery of solid product to the burners  18  and  20  respectively, to provide fuel therefor. The torrefied product from reactor  14  is delivered by line  106  for cooling and recovery thereof. 
     The system  10 B thus sequentially dries and torrefies incoming biomass, and produces both gaseous VOC and solid dried biomass fuel streams which provide a substantial amount of the thermal energy used in the process at steady-state operating conditions. 
     EXAMPLE 2 
     This is a hypothetical, computer-based example using system  10 B for the conversion of a typical wood chip biomass into torrefied product, and production of thermal energy used in the operation of the system, once the process has achieved steady state operation. 
     Referring to  FIG. 1B , locations A′-M′ are indicated throughout the system  10 . The following legend sets forth the mass-energy balance for the process at these respective locations. 
                                                         A′ - dryer burner operation                   8,000 BTU/lb dried biomass                   362 lb/hr dried biomass                   2.90 MMBtu/hr                   B′ - combustion air to dryer burner                   1,223 SCFM                   32° F.                   175% excess air                   C′ - biomass infeed to dryer                   4,300 lb/hr total                   2,365 lb/hr solids                   1,935 lb/hr water                   D′ - hot gases to dryer                   2,122 ACFM                   5,885 lb/hr                   0.50 MMBtu/hr                   400° F.                   E′ - dryer output                   2,438 lb/hr total                   2,365 lb/hr solids                   73 lb/hr water                   110° F.                   F′ - vented exhaust gases                   8,000 ACFM                   230° F.                   G′ - torrefaction reactor input                   1,909 lb/hr total                   1,852 lb/hr solids                   57 lb/hr water                   H′ - Mass loss of VOC&#39;s                   315 lb/hr                   26 lb/hr water                   I′ - reactor burner operation                   7,300 BTU/lb                   1,309 BTU/hr VOC                   9.56 MMBtu/hr                   J′ - Combustion air to reactor burner                   565 SCFM                   32° F.                   175% excess air                   K′ - Torrefied product                   1568 lb/hor total                   2% water                   450° F.                   L′ - Cooled torrefied product                   1568 lb/hr total                   2% water                   270° F.                   M′ - Dried biomass fuel to dryer and reactor burners                   529 lb/hr                   3% water                   ambient temperature                        
The hot gas input in line  174  was 622° F., and the dryer  12  operated at a power of 2.90 MMBtu/hr in order evaporate 1862 lb/hr of water from the biomass infeed. The hot gas input in conduit  184  was 725° F., and the torrefaction reactor  14  operated at a power of 3.09 Btu/hr to evolve VOC&#39;s from the dried biomass to generate the torrefied output product.
 
     Considering a 8000 hr/yr operation of system  10 B, the annual output of the carbonized charcoal final product would be 6273 tons. 
     System  10 C for the Production of Both Torrefied and Charcoal Products ( FIG. 1C ) 
     The system  10 C is designed to simultaneously produce torrefied and carbonized final products. The system has many of the components of the previously described system  10 A, and certain components from the system  10 B. Accordingly, like reference numerals in  FIGS. 1A and 1B  will be used throughout the ensuing discussion. There are two principal differences between systems  10 A and  10 C. The first is provision of apparatus for recovering a portion of the torrefied product, with the remaining portion being directed to carbonization reactor  16  via conduit legs  188   a  and  188   b . The second difference is the use of a portion of the solid product derived from the output of cyclone  178  as a source of solid fuel to the dryer and reactor burners  18 ,  20 , via conduits  100 ,  102 , and  104 . 
     EXAMPLE 3 
     This is a hypothetical, computer-based example using system  10 C for the simultaneous conversion of a typical wood chip biomass into torrefied and charcoal products, and production of a substantial part of the thermal energy used in the operation of the system, once the process has achieved steady state operation. 
     Referring to  FIG. 1C , locations A″-Q″ are indicated throughout the system  10 C. The following legend sets forth the mass-energy balance for the process at these respective locations. 
                                                         A″ - dryer burner - wood/VOC burner                   8,000 BTU/lb wood                   232 lb/hr wood                   1.86 MMBTU/hr                   B″ - combustion air                   713 SCFM                   32° F.                   150% excess air                   C″ - biomass infeed to dryer                   4,300 lb/hr total                   2,365 lb/hr solids                   1,935 lb/hr water                   D″ - hot gases to dryer                   4,371 ACFM                   8,476 lb/hr                   1.36 MMBTU/hr                   770° F.                   E″ - dryer output                   2,438 lb/hr total                   2,365 lb/hr solids                   73 lb/hr water                   3% moisture                   110° F.                   F″ - vented exhaust gases                   8,000 ACFM                   230° F.                   G″ - torrefaction reactor input                   2,201 lb/hr total                   3% water                   110° F.                   I″ - reactor burner - wood/VOC burner                   7,300 BTU/lb VOC                   591 lb/hr VOC                   8,000 BTU/lb wood                   5 lb/hr wood                   4.33 MMBTU/hr                   J″ - VOCs to dryer burner                   363 lb/hr                   30 lb/hr water                   K″ - combustion air to reactor burner                   3,065 SCFM                   32° F.                   80% excess air                   L″ - VOCs to reactor burner                   576 lb/hr                   15 lb/hr water                   O″ - wood fuel to burners                   237 lb/hr total                   0% water                   ambient temperature                   P″ - torrefied product output                   1,808 lb/hr total                   2% water                   450° F.                   Q″ - recovered torrefied product                   904 lb/hr total                   2% water                   270° F.                   M″ - carbonized biomass output                   313 lb/hr total                   1% water                   600° F.                   N″ - cooled carbonized output                   313 lb/hr total                   1% water                   270° F.                        
The hot gas input to dryer  12  in line  174  was 621° F., and the dryer  12  operated at a power of 3.22 MMBtu/hr in order evaporate 1862 lb/hr of water from the biomass infeed. The hot gas input in conduit  184  was 758° F., and the torrefaction reactor  14  operated a power of 2.85 Btu/hr to evolve VOC&#39;s from the dried biomass to generate the torrefied output product. The hot gas in line  190  was 838° F., and the reactor  16  operated at a power of 1.40 MMBtu/hr.
 
     Considering an 8000 hr/yr operation of system  10 C the annual output of the torrefied product would be 3617 tons, and the output of the carbonized product would be 1253 tons.