Abstract:
A biomass processing system produces charcoal briquettes in a closed loop system. The system includes a first and second torrefaction/drying augers drying green raw sawdust and providing the dried material to a carbonizing auger. Charcoal released from the carbonizing auger is formed into charcoal briquettes. Process gas created during the charcoal production is used to provide heat required by the process.

Description:
The present application is a Continuation In Part of U.S. patent application Ser. No. 14/140,766 filed Dec. 26, 2013 and U.S. patent application Ser. No. 14/140,956 filed Dec. 26, 2013 and U.S. patent application Ser. No. 14/510,298 filed Oct. 9, 2014, which applications are incorporated in their entirety herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to charcoal production and in particular to a method for converting woody biomass feed material into useful charcoal briquettes. 
     Biomass is comprised mainly of cellulose, hemi cellulose and lignin. A typical woody biomass may contain 40-50% cellulose, 25-35% hemi cellulose, and 15-18% lignin. Typical yields from a slow pyrolysis machine are 30% charcoal containing 70% plus carbon, 35% non-condensable gases containing hydrogen, methane, carbon mono oxide, carbon dioxide primarily, and 35% pyrolysis oil, also known as bio oil or bio crude, consisting tar, aldehydes, formic acid, acetic acid, water, esters, phenols, sugar derivatives, lignins. Such typical slow pyrolysis machine yields oil and charcoal in nearly equal portions. Slow pyrolysis involves heating of dried biomass (&lt;8% moisture) in an oxygen free environment at 450-500 degrees centigrade in heated auger tubes. The process involves thermo chemical conversion of solid biomass to a liquid product, bio oil, and solid material, charcoal. Non-condensable gases are utilized to heat the incoming wet biomass material, thus creating a closed loop system. 
     Convention slow pyrolysis process yields bio oil that has the following properties: 
     Chemical formula: CH 1.3 O 0.47    
     Flash point: 80 deg C. 
     pH=2.5 
     Sp Gr.=1.2 
     Moisture content: 20-25% 
     Heating value=7,522 btu/lb (17.5 mj/kg) 
     Viscosity=60-100 cp 
     and 
     Elemental analysis: 
     C=55-60% 
     H=5-8% 
     O=28-40% 
     N=0.06% 
     Rotary dryers are commonly used to dry biomass. There are several variations of rotary dryers, but the most widely-used is the directly heated single-pass rotary dryer. The directly heated single-pass rotary dryer uses hot gases contacting the biomass material inside a rotating drum. The rotation of the drum, with the aid of flights, lifts the solids in the dryer so they tumble through the hot gas, promoting better heat and mass transfer. The biomass and hot air normally flow co-currently through the dryer so the hottest gases come in contact with the wettest material. The exhaust gases leaving the dryer may pass through a cyclone, multicyclone, baghouse filter, scrubber or electrostatic precipitator (ESP) to remove any fine material entrained in the air. An ID fan may or may not be required depending on the dryer configuration. If an ID fan is needed, it is usually placed after the emissions control equipment to reduce erosion of the fan, but may also be placed before the first cyclone to provide the pressure drop through downstream equipment. The inlet gas temperature to rotary biomass dryers can vary from 450°-2,000° F. (232°-1,093° C.). Outlet temperatures from rotary dryers vary from 160° to 230° F. (71°-110° C.), with most of the dryers having outlet temperatures higher than 220° F. (104° C.) to prevent condensation of acids and resins. Retention times in the dryer can be less than a minute. While known dryers generally perform adequately, they consume significant energy increasing the cost of processing the biomass material. 
     Further, known systems have difficulty processing wet biomass material, may produce unwanted oil, exhaust process gas, and lack efficiency. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above and other needs by providing a biomass processing system which produces charcoal briquettes in a closed loop system. The system includes a first and second torrefaction/drying augers drying green raw sawdust and providing the dried material to a carbonizing auger. Charcoal released from the carbonizing auger is formed into charcoal briquettes. Process gas created during the charcoal production is used to provide heat required by the process. 
     In accordance with one aspect of the invention, there is provided a biomass processing system capable of processing wet raw biomass. A first and second torrefaction/drying augers drying green raw sawdust before providing the dried material to a carbonizing auger. 
     In accordance with another aspect of the invention, there is provided a biomass processing system having zero production of oil. Pyrolysis is done in the presence of steam and higher temperature. Partially carbonized material fed to the second torrefaction/drying auger also acts as a catalyst for the conversion of tar to gases. 
     In accordance with yet another aspect of the invention, there is provided a biomass processing system providing a complete closed loop system. Process gas is rerouted to supply process heat, water produced is neutralized and utilized to make briquettes, charcoal is sold as product. 
     In accordance with still another aspect of the invention, there is provided a biomass processing system providing a small foot print. The system does not require an external dryer thus reducing the foot print of the plant. 
     In accordance with another aspect of the invention, there is provided a biomass processing system providing higher process efficiency. A heat recovery system optimizes the process heat demand. Stack gases exit to a heat recovery box, steam exits to an air heater, hot water return is used to heat the binder solution. Cracking of tar provides higher gas yields. Two step pyrolysis provides higher charcoal yields. 
     In accordance with yet another aspect of the invention, there is provided a biomass processing system providing environmentally superior performance. The only emission point is the stack gases. Utilization of process gas to provide heat provides lower NOx and particle emissions. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1  is a biomass processing system for producing charcoal briquettes according to the present invention. 
         FIG. 2  is a pyrolysis system according to the present invention. 
         FIG. 3  is a bulk packaging system according to the present invention. 
         FIG. 4  is a condensables processing system according to the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
     Where the terms “about” or “generally” are associated with an element of the invention, it is intended to describe a feature&#39;s appearance to the human eye or human perception, and not a precise measurement. 
     A biomass processing system  100  according to the present invention is shown in  FIG. 1 . The biomass processing system  100  includes two pyrolysis systems  10   a  and  10   b , both fed green raw sawdust  19  stored in a bin  17 . The pyrolysis systems  10   a  and  10   b  further receive ambient air  28 , cooling water  63 , and process gas  72 . Prior to entering the heat exchangers  24 , the air  28  may be pre heated by steam captured from the condensers  38  and advanced by a fan. The pyrolysis systems  10   a  and  10   b  produce heated water  32 , liquid/gas mixture bio oil  50 , solids  51 , heated air  52 , and charcoal  53 . The solids  51 , heated air  52 , and charcoal  53  of the pyrolysis systems  10   a  and  10   b  are depicted provided to multiple instances of bulk packaging  80  for convenience, and only one bulk packaging  80  is necessarily present in the biomass processing system  100 . 
     The liquid/gas mixture bio oil  50  is provided to separator vessels  48   a  and  48   b . The separator vessels  48   a  and  48   b  separate the liquid/gas mixture bio oil  50  into non-condensable gases  76  and condensed liquids  74 . The liquid  74  is provided to condensables processing  90 . Non-condensable gases  76  from the separator vessels  48   a  and  48   b  are provided to non-condensable gases vessel  49  and on to condensable gases compressor  56  where the non-condensable gases  76  is compressed to preferably 8 inches of Water Column (WC) pressure and resulting compressed gases  57  are discharged to compressed gases vessel  58  to remove trapped moisture. Gas  68  from the vessel  58  is then provided to final moisture catch vessel  70  to create process gas  72 , and process gas  72  to process gas burners  23   b  (see  FIG. 2 ). Excess gas from the vessel  58  is provided to flare  60  through back pressure regulator  59 . 
     The pyrolysis systems  10   a  and  10   b  are described in  FIG. 2 . The pyrolysis systems  10   a  and  10   b  each contain a pyrolysis chamber  10 ′ containing three sealed augers  16   a ,  16   b , and  16   c , a top air heater  24 , and two burners  23   a  and  23   b . A bottom charcoal discharge auger  16   d  resides under the pyrolysis chamber  10 ′. Auger speed is preferably about 1 RPM. A typical auger is between 20 and 24 inches in diameter and about 20 ft. long. The green raw sawdust  19  is fed through first air lock  15   a  into first sealed auger  16   a  rotated by first auger motor  18   a . The feed rate into the pyrolysis systems  10   a  and  10   b  is preferably 6 tons per hour of green raw sawdust  19 . 
     In the top sealed auger  16   a , the green raw sawdust material  19  is partially carbonized and dried to about 16% moisture content providing a partially carbonized material  19   a . The dried, partially carbonized material  19   a  is released through second air lock  15   b  to the second sealed auger  16   b  rotated by second auger motor  18   b  and dried additionally to produce additionally carbonized material  19   b . The additionally carbonized material  19   b  is finally released through air lock  15   c  into the bottom charcoal discharge (or pyrolysis) auger  16   c , where temperature again is maintained at 500-600 degrees Centigrade. Material in the bottom charcoal discharge auger  16   c  then begins to pyrolysis and volatiles are removed from the additionally carbonized material  19   b  to produce charcoal output  53  with almost 80% carbon content. 
     Charcoal output  53  from the charcoal discharge auger  16   c  is discharged to the charcoal cooler auger  16   d  rotated by fourth auger motor  18   d . The charcoal output  53  is cooled in the cooler auger  16   d  by the cooled water  63  to about 80 degrees Fahrenheit and discharged to bucket elevator  54  and carried to bulk packaging  80 . 
     Pyrolysis gases  11  from the pyrolysis systems  10   a  and  10   b  collected from the charcoal discharge auger  16   c  by auger condensers  38   c  are carried to a cyclones  47 . The cyclones  47  are preferably about 20 inches in size. Gases  36  exit the cyclones  47  and go to doubled walled condensers  38   d  where the gases  36  are cooled by cooling water  63 . The cooling process condenses all condensables in the gases  36  (water, acetic acid, and formic acid primarily). The liquid-gas mixture  50  is then provided to the separator vessels  48   a  and  48   b  (see  FIG. 1 ). 
     Solids  51  collected by the cyclones  47  fall through air locks  15   c  into cyclone discharge cooler auger  16   e  and are cooled by cooling water  63  and discharged to the bulk packaging  80 . 
     Steam  27  is collected by condensers  38   a  and  38   b  from the augers  16   a  and  16   b  respectively is collected in a common manifold  30  and is pulled by an exhaust fans  31  (see  FIG. 1 ) and is exhausted into the atmosphere. 
     The pyrolysis systems  10   a  and  10   b  further includes a heat exchanger  24  residing above the auger  16   a  and where air blown through the heat exchangers  24  by fan  13  is heated to about 180 degrees Fahrenheit and provided to the bulk packaging  80  (see  FIG. 3 ) to dry the charcoal briquettes. 
     The heated water  32  is collected from the condensers  38 , the charcoal cooler auger  16   d , and cyclone discharge cooler augers  16   e . The heated water  32  is first routed to heat exchanger  61  where heat is transferred to the charcoal binder  81  (see  FIGS. 3 and 4 ) used to form for briquettes. After the heat exchanger  61 , the heated water  32  (now somewhat cooled) is pumped by pump  66  through a cooling tower  62  where it is cooled from about 150 degrees Fahrenheit to about 65 degrees Fahrenheit, and into a cooling water tank  64  for storage. The cooled water  63  from the cooling water tank  64  is then cycled back to the pyrolysis systems  10   a  and  10   b.    
     The pyrolysis systems  10   a  and  10   b  are heated to a process temperature Tp between 500 and 600 degrees Centigrade. Upon startup, the pyrolysis systems  10   a  and  10   b  are heated by propane burners  23   a . Once the pyrolysis systems  10   a  and  10   b  reach the process temperature Tp, the pyrolysis systems  10   a  and  10   b  produce process gas, the startup burners  23   a  are turned off and process heat is provided by the burners  23   b  burning the process gas  72  produced by the pyrolysis systems  10   a  and  10   b . The burners  23   a  and  23   b  are rated at 2.5 mmbtu/hr each. 
     Bulk packaging  80  is described in  FIG. 3 . The solids  51  and charcoal  53  are provided to a surge bin  83 . Charcoal  82  from the surge bin  83  is provided to two briquette machines  89   a  and  89   b  through augers  84   a  and  84   b . A charcoal binder solution  81  (see  FIG. 4 ) is injected into the augers  89   a  and  89   b . Extruder type machines  85   a  and  85   b  apply pressure to the charcoal and binder and push the charcoal and binder through a tapered screw to produce hexagonal briquettes that can be 1 inch to 4 inches long, 1 inch in diameter with a 1/16th inch hole in the middle. The briquettes at this point contain about 30% moisture and need to be dried. The wet briquettes are then provided to the belt dryer  86  where hot air  52  is blown from underneath the belt to dry the charcoal to about 8% moisture content. Dried charcoal is then provided to packaging section  87 . 
     Binder production  90  is described in  FIG. 4 . A concentrated binder  73  contained in binder vessel  92  is pumped by pump  93  and mixed with condensed liquids  74  in mixing vessels  91   a  and  91   b . A mixed binder  75  is pumped by pump  94  to mixing vessels  98   a  and  98   b  and the binder solution is then pumped by pump  99  to be heated in the heat exchanger  61  by the hot water  32 . Reservoir vessel  95  and pump  96  maintain a flow of the mixed binder to the mixing vessels  98   a  and  98   b.    
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.