Abstract:
A method for converting a biomass to a bio-oil includes providing a four-stroke internal combustion engine having at least one cylinder, at least one piston, and a crankshaft coupled to each of the at least one piston. The method also includes coupling a power source to the crankshaft in a manner such that the power source drives rotation of the crankshaft. The method also includes injecting a first mixture including a biomass and a non-oxidizing compression gas into one of the cylinders. The method also includes compressing and heating the first mixture during a compression stroke of the pistons. The compression and heating of the first mixture pyrolizes the biomass to produce a second mixture including a bio-oil and the compression gas. The method also includes decompressing and cooling the second mixture during an expansion stroke of the pistons. The decompression and cooling of the second mixture quenches secondary pyrolysis.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a Section 111(a) application relating to and claiming the benefit of commonly owned, co-pending U.S. Provisional Patent Application No. 62/013,750, titled “RECIPROCATING BIOMASS CONVERSION SCHEME,” having a filing date of Jun. 18, 2014, which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The exemplary embodiments relate to conversion reactors and, more particularly, to conversion reactors for the conversion of biomass to bioenergy and biochemicals. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fast pyrolysis, also referred to as flash pyrolysis, is a process whereby biomass is decomposed in an environment without an oxidizing agent at temperatures of approximately 500° C. for short times (e.g., on the order of less than five seconds). Thermo-chemical biomass conversion by fast pyrolysis to bio-oil, bio-char, and bio-gas is a part of a path to an alternative energy source because of the upgrade in heating value and density such that it may be easily transported as part of a new distribution network. Effective methods of biomass conversion to bio-oil are of interest because bio-oil represents a deployable energy carrier with favorable source characteristics (e.g., it can be produced in situ and is carbon-neutral). In fast pyrolysis, biomass is pulverized, pyrolyzed, and the bio-products are recovered. Bio-oil can be used directly in boilers (e.g., for heating or electricity), or upgraded for use as a fuel. 
         [0004]    There are a number of reactor types for the fast pyrolysis of biomass: entrained flow reactor, wire mesh reactor, vacuum furnace reactor, vortex reactor, rotating reactor, microwave reactor, fluidized-bed reactor, and the circulating fluidized-bed reactor. These reactors are complicated and require a large external energy source for operation. The fluidized-bed reactor (“FBR”) is representative of the current state of the art. The FBR requires a condenser to cool the bio-products to quench the secondary pyrolysis reactions. The condenser is an active cooling component that can lead to heat loss and system inefficiency. Primary pyrolysis reactions create the pyrolysis vapor which condenses to bio-oil, whereas secondary pyrolysis reactions adversely affect the bio-oil quality and should be avoided. Thus, improvement of thermal efficiency and control over the primary and secondary pyrolysis reactions are an objective of this invention. 
       SUMMARY OF THE INVENTION 
       [0005]    In an embodiment, a method for converting a biomass to a bio-oil includes providing a four-stroke internal combustion engine having at least one cylinder, at least one piston, each of the at least one piston disposed within a corresponding one of the at least one cylinder, and a crankshaft coupled to each of the at least one piston. The method also includes coupling a power source to the crankshaft in a manner such that the power source drives rotation of the crankshaft. The method also includes, during an intake stroke of at least one of the at least one piston, injecting a first mixture including the biomass and a non-oxidizing compression gas into at least one of the at least one cylinder corresponding to the at least one of the at least one piston. The method also includes, during a compression stroke of the at least one of the at least one piston, compressing and heating the first mixture. The compression and heating of the first mixture pyrolizes the biomass to produce a second mixture including a bio-oil and the compression gas. The method also includes, during an expansion stroke of the at least one of the at least one piston, decompressing and cooling the second mixture. The decompression and cooling of the second mixture quenches secondary pyrolysis of the bio-oil. 
         [0006]    In an embodiment, the method also includes, during an exhaust stroke of the at least one of the at least one piston, expelling the second mixture from the at least one of the at least one cylinder. In an embodiment, the compression gas includes one or more of argon, nitrogen, carbon dioxide, carbon monoxide, and air. In an embodiment, the biomass includes one or more of corn stover, municipal waste, and agricultural waste. In an embodiment, the method also includes separating the bio-oil from the compression gas. 
         [0007]    In an embodiment, the second mixture also includes one or more of bio-char and bio-gas. In an embodiment, the method also includes recycling the one or more of bio-char and bio-gas as biomass. In an embodiment, the at least one cylinder includes at least two cylinders and the at least one piston includes at least two pistons. The four-stroke internal combustion engine is arranged such that the compression stroke of one of the at least two pistons is synchronized with the expansion stroke of the other of the at least two pistons. In an embodiment, the four-stroke internal combustion engine includes a diesel engine. 
         [0008]    In an embodiment, the method also includes upgrading the bio-oil for use as a fuel. In an embodiment, the method also includes providing the bio-oil for use in a boiler. In an embodiment, the biomass is pulverized. In an embodiment, the pulverized biomass includes a plurality of particles of the biomass. In an embodiment, the particles have an average diameter in a range of about 25 microns to about 200 microns. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0009]    For a more complete understanding of the present invention, reference is made to the following detailed description of an exemplary embodiment considered in conjunction with the accompanying drawings, in which: 
           [0010]      FIG. 1  is a schematic illustration of a technique for converting biomass into bio-products; 
           [0011]      FIG. 2  is a schematic illustration of a pyrolysis process that forms a portion of the overall technique of  FIG. 1 ; 
           [0012]      FIG. 3  is a conceptual illustration of a cylinder that is used in the pyrolysis process of  FIG. 2 ; 
           [0013]      FIG. 4  is an ideal plot of pressure against volume for a cycle of the cylinder of  FIG. 3 ; 
           [0014]      FIG. 5  is an ideal temperature-state plot for a cycle of the cylinder of  FIG. 3 ; 
           [0015]      FIG. 6  is a plot of temperature and pressure against time for an analysis of a model of the cylinder of  FIG. 3 ; 
           [0016]      FIG. 7  is a plot of ideal and analyzed pressure against volume for the cylinder of  FIG. 3 ; and 
           [0017]      FIG. 8  is a plot of weight fractions of biomass and various bio-products for an analysis of a model of the cylinder of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The exemplary embodiments relate to a reciprocating biomass conversion scheme for production of bio-oil by fast-pyrolysis using a re-purposed 4-cycle internal combustion engine (“ICE”). The cycle includes the steps of intake, compression/heating, expansion, and exhaust. An inert gas and a small volume-fraction of pulverized biomass are input into the ICE intake, and the crankshaft is cycled by an external energy source to supply process heat to the cylinders. The biomass is converted during the compression/heating stroke, and then the bio-products are expelled during the exhaust stroke. The benefits of the reciprocating biomass conversion scheme of the exemplary embodiments relative to the state of the art are:
       1. Increased efficiency: the reciprocating biomass conversion scheme requires less energy per unit mass of biomass than does a fluidized bed reactor of comparable footprint. The impact is that operation costs could be reduced.   2. Increased throughput: the biomass feed-rate (mass per unit time) is higher for the reciprocating biomass conversion scheme than for a fluidized bed reactor of comparable footprint. The impact is decreased costs of biomass to biofuel conversion.   3. Improved bio-oil quality: the quality of the bio-oil produced by the reciprocating biomass conversion scheme is of higher quality than the state of the art. The impact of higher quality bio-oil is reduced cost of bio-oil to biofuel upgrading.       
 
         [0022]      FIG. 1  illustrates a schematic representation of an exemplary conversion scheme  100 . As a raw material, the conversion scheme  100  uses biomass  110 . As described herein, biomass  100  may include virgin cellulose, corn stover, municipal waste, agricultural waste, or any other appropriate biomass. As a first step in the conversion scheme  100 , the biomass  110  is pulverized  120  through any means known in the art to form small particles of the biomass  110 . The pulverization  120  may result in small particles of the biomass  110  in a range of about 25 μm to about 200 μm in diameter. The efficacy of the exemplary embodiments will be discussed hereinafter with reference to pulverization resulting in the biomass  110  forming spherical particles 50 μm in diameter, but those of skill in the art will understand that this is only one exemplary result of the pulverization  120  and any pulverization  120  to form suitably small particles may suffice. 
         [0023]    After the pulverization  120  has been performed, fast pyrolysis  130  is performed on the pulverized biomass  110 . An exemplary mechanism for the fast pyrolysis  130  will be discussed in further detail hereinafter with reference to  FIG. 2 . The product of the fast pyrolysis  130  is recovery products  140 . The recovery products  140  may include bio-oil  142 , bio-gas  144 , and bio-char  146 . In an embodiment, the recovery products  140  may include about 70% bio-oil  142 , about 15% bio-char  144 , and about 15% bio-gas  146 . The bio-char  144  and the bio-gas  146  may be separated from the bio-oil  142  using any suitable technique, and may be recycled  150  and used again as inputs for the fast pyrolysis  130 . In an embodiment, the bio-oil  142  produced by the fast pyrolysis  130  may be used as-is, such as in a boiler  160  (e.g., for heating or electricity). In an embodiment, the bio-oil  142  produced by the fast pyrolysis  130  may be upgraded through a process of fuel upgrading  170  (e.g., for auto fuel, aviation fuel, etc.). 
         [0024]      FIG. 2  illustrates a schematic representation of a system  200  that may perform the fast pyrolysis  130  described above with reference to  FIG. 1 . The system  200  includes a four-stroke internal combustion engine (“ICE”)  210 , which will be referred to hereinafter as “engine  210 ” for brevity. The engine  210  includes a plurality of cylinders including a first cylinder  212 , a second cylinder  214 , and an n-th cylinder  216 , each of which includes a corresponding piston  222 ,  224 ,  226 . It will be apparent to those of skill in the art that the engine  210  may include any number of cylinders n depending on factors such as the space available, the purpose for which it is to be used, etc. The engine  210  also includes a crankshaft  218 . It will be apparent to those of skill in the art that, under the normal operation of an ICE such as the engine  210 , the crankshaft  218  would serve to provide output power generated by the operation of the engine  210 . However, in the exemplary system  200 , the crankshaft  218  is driven by an external power source  230  in order to power operation of the engine  210  as will be described hereinafter. 
         [0025]    Pulverized biomass  240  (e.g., as produced through pulverization  120 ) is injected into each of the cylinders  212 ,  214 ,  216  of the engine  210 . A non-oxidizing compression gas  250  is also injected into each of the cylinders  212 ,  214 ,  216  of the engine  210 . In an embodiment, the compression gas  250  is argon. In an embodiment, the compression gas  250  is nitrogen. In an embodiment, the compression gas  250  is a mixture of carbon dioxide and carbon monoxide. The ratio of the pulverized biomass  240  to the compression gas  250  is such that the pulverized biomass  240  comprises a small volume fraction of the mixture thereof. 
         [0026]    The performance of the exemplary engine  210  will be described hereinafter with specific reference to the cylinder  212 . It will be apparent to those of skill in the art that the same disclosure may be equally applicable to the cylinders  214 ,  216 . The mixture of the pulverized biomass  240  and the compression gas  250  is injected into the cylinder  212  during an intake stroke of the piston  222 , such that the volume within the cylinder  212  is substantially at its maximum after the injection. The external power source  230  drives the crankshaft  218  and thereby drives a compression stroke of the piston  222 , decreasing the volume within the cylinder  212 . The decrease of volume within the cylinder  212  correspondingly compresses and heats the mixture of the pulverized biomass  240  and the compression gas  250 . In an embodiment, the heating rate during the compression stroke of the piston  222  exceeds 2000° C./s. 
         [0027]    Process heat due to the compression of the pulverized biomass  240  and the compression gas  250  is transferred from the compression gas  250  to the pulverized biomass  240 . In an embodiment, the maximum temperature of the pulverized biomass  240  is over 500° C. Heating of the pulverized biomass  240  induces fast pyrolysis, which thermo-chemically converts the pulverized biomass  240  to bio-products  260  (e.g., bio-oil  142 , bio-gas  144 , and bio-char  146 , as described above with reference to  FIG. 1 ). In an embodiment, fast pyrolysis may occur under the Diebold mechanism. As a result of this conversion, the mixture within the cylinder  212  becomes a mixture of the compression gas  250  and the bio-products  260 . The continued work applied by the external power source  230  in driving the crankshaft  218 , together with the increased pressure within the cylinder  212 , now drives the expansion stroke of the piston  222 , increasing the volume within the cylinder  212 . It will be apparent to those of skill in the art that the engine  210  may be arranged such that cylinders thereof may be in opposition; for example, the crankshaft may simultaneously increase the volume within cylinder  212  while decreasing the volume within cylinder  214 , and vice versa. 
         [0028]    The increase of the volume within the cylinder  212  caused by the expansion stroke of the piston  222  rapidly decreases the temperature and pressure of the mixture of the compression gas  250  and the bio-products  260 . In an embodiment, the cooling rate within the cylinder  212  during the expansion stroke of the piston  222  is over minus-5000° C./s. The rapid cooling rate of the bio-products  260  during the expansion stroke of the piston  222  quenches undesirable secondary pyrolysis reactions of the bio-products  260 . An exhaust stroke of the piston  222  forces the bio-products  260  and the compression gas  250  from the cylinder  212 . Because the compression gas  250  is a non-oxidizing gas, it is substantially unaltered by the pyrolysis described above. Recovered compression gas  270  is separated from the bio-products  260  and may be recycled within the system  200  as compression gas  250 . The bio-products  260  may be separated out as described above (e.g., yielding about 70% bio-oil  142 , about 15% bio-char  144 , and about 15% bio-gas  146 ), with the bio-oil  142  being suitable for purposes as described above and the bio-char  144  and bio-gas  146  suitable for recycling within the system  200  as pulverized biomass  240 . 
         [0029]      FIG. 3  illustrates a more detailed conceptual view of a cylinder  300  (e.g., the cylinder  212  and the piston  222  described above with reference to  FIG. 2 ) that will be used hereinafter to analyze the energy balance within a control volume. The cylinder  212  contains a well-mixed, evenly-distributed mixture of the biomass  240  and the compression gas  250 ; in the illustration of  FIG. 3 , the biomass  240  and compression gas are shown separated for clarity to indicate the energy flow therebetween. In  FIG. 3 , Q represents the energy that is transferred into a control volume by heat transfer, W represents the energy that is transferred out of a control volume by work, and ΔH P  is the change in enthalpy required to pyrolyze the biomass  240 . The subscripts b, g, and w represent the biomass  240 , the compression gas  250 , and the wall of the cylinder  212 , respectively. Two subscripts in succession indicate “from a to b,” e.g., Q gb  is the energy transferred from the compression gas  250  to the biomass  240  by heat transfer. Additionally, it may be assumed that the pressure of the compression gas  250  and the biomass  240  are equal, i.e., P g =P b =P. 
         [0030]    The change in internal energy for the compression gas  250  may be represented according to the expression ΔU g =c vg n g ΔT g  and the work performed by the compression gas  250  on the wall of the cylinder  212  may be expressed as W gw =PΔV g . Here, c vg , n g , ΔT g , and V g  are the constant-volume molar specific heat, number of moles, change in temperature, and volume of the compression gas  250 , respectively. The first law for the control volume of the compression gas  250  may be written as: 
         [0000]      Δ U   g   =Q   g   −W   g   =−Q   gb   +Q   wg   −W   gw  
 
         [0000]      Δ Ug=C   vg   n   g   ΔT   g   =−Q   gb   +Q   wg   −PΔV   g  
 
         [0031]    The change in enthalpy of the biomass  240 , ΔH b , includes the change in sensible enthalpy, ΔH S , and enthalpy of the pyrolysis reactions, ΔH P , as: 
         [0000]      Δ H   b   =ΔH   S   +ΔHP=ΔU   b +Δ( PV   b ).
 
         [0032]    It may be assumed that there is no volumetric change of the biomass  240 . The change in enthalpy due to pyrolysis of the biomass  240  is ΔH P =m P Δh P , and the change in sensible enthalpy is ΔHS=m b c b ΔTb. Here, m P , Δh P , m b , c b , and ΔT b  are the pyrolyzed mass, mass-specific enthalpy of the pyrolysis, the mass of the biomass  240 , the specific heat of the biomass  240 , and the change in temperature of the biomass  240 , respectively. The first law for the control volume for the biomass can be written as: 
         [0000]      Δ U   b   =Q   b   −W   b   =Q   gb   +Q   wb   −W   b  
 
         [0000]      Δ U   b   =m   b   c   b ΔT b   +m   P   Δh   P   −V   b   ΔP=Q   gb   +Q   wb  
 
         [0033]    Based on the above, a model of decomposition of the biomass  240  in the system  200  may be created. In this model, heat transfer to the walls of the cylinders  212 ,  214 ,  216  is not considered (i.e., Q wb =Q wg =0), it is assumed that all of the biomass  240  is pyrolized (i.e., m P =m b ), and the change in pressure term is assumed to be small for the biomass  240  (i.e., V b ΔP          m b c b ΔT b , and V b ΔP          m P Δh P ). Based on these assumptions, the first law equations expressed above can be rewritten as: 
         [0000]    
       
         
           
             
               
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         [0034]      FIGS. 4 and 5  illustrate a pressure-volume space  400  and a temperature-state space  500 , respectively, of the compression gas  250  of the system  200 . More particularly,  FIGS. 4 and 5  present an ideal analysis of the system  200 . In  FIG. 4 , which illustrates a pressure-volume space  400  of a cycle of the system  200  in a counterclockwise direction, the pressure within a cylinder (e.g., cylinder  212 ) is plotted against the volume within the cylinder. In  FIG. 5 , temperatures are plotted against state; plot  550  illustrates the temperature of the compression gas  250  and plot  560  illustrates the pressure of the biomass  240 . In  FIGS. 4 and 5 , states  410 ,  420 ,  430  and  440  correspond to states  510 ,  520 ,  530  and  540 , respectively, and phases  415 ,  425 ,  435  and  445  correspond to phases  515 ,  525 ,  535  and  545 , respectively. 
         [0035]    In phase  415 ,  515 , work W in  is applied by the piston  222  to compress the compression gas  250  in an isentropic manner. The compression occurs quickly relative to any heat transfer, so it may be assumed that Qg b =ΔT b =0. In phase  425 ,  525 , isobaric heat transfer Q gb  from the compression gas  250  to the biomass  240  occurs. The biomass  240  undergoes complete conversion (based on the assumption noted above that the entire biomass  240  is pyrolized) at a temperature that is typical of fast pyrolysis, converting biomass  240  into bio-products  260 . In phase  435 ,  535 , isentropic expansion of the compression gas  250  occurs, with work W out  being applied to the piston  222 . The expansion occurs quickly relative to any heat transfer, so it may be assumed that Qg b =ΔT b =0. In phase  445 ,  545 , isochoric heat transfer Q gb  occurs from the bio-products  260  to the compression gas  250 . As noted above, this heat transfer quenches undesirable secondary pyrolysis. It will be apparent to those of skill in the art that the cycle described with reference to  FIGS. 4 and 5  represents two strokes of the exemplary four-stroke engine  210 , with the exhaust and injection strokes being extraneous to the cycle described above. 
         [0036]    The following adapts the ideal model described above with reference to  FIGS. 3-5  into a detailed model, to enable comparison to other biomass conversion schemes, by formulating the first law expressions above as differential equations. The time-rate form of the first law expression for the compression gas  250  may be expressed as: 
         [0000]    
       
         
           
             
               
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         [0037]    Based on the above, it may be inferred that the time-rate of change of temperature is increased by decrease in the volume of the cylinder  212  and decreased by outward heat transfer; the term dV g /dt may be prescribed by the kinematic motion of the piston  222 . 
         [0038]    The analysis assumes that the biomass  240  includes a collection of independent spheres acting as a lumped mass m b  with a constant volume and specific heat c b . However, individual fractions of the mass m b  may evolve as computed by the first order kinetics mechanism of the Diebold model of pyrolysis. The model may also consider the rate of energy loss due to pyrolysis, Δ{dot over (H)} P ={dot over (m)} P Δh P . The time-rate form of the first law expression for the biomass  240  may then be expressed as: 
         [0000]    
       
         
           
             
               
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         [0039]    In the above, the dP/dt term can be related to the time rate of change of the temperature of the compression gas  250  and to the change of the volume within the cylinder  212  through the differentiation of the logarithm of the ideal gas law, as shown: 
         [0000]    
       
         
           
             
               
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                 P 
               
               
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         [0040]    More detailed consideration of the rate of heat loss from the pyrolysis reactions requires a calculation of the rate at which the biomass  240  is decomposed during the pyrolysis. The following will be based on pyrolysis predicted by the Diebold model. The first-order kinetic rates of Arrhenius form are tabulated from each component in the Diebold model. The kinetic rates can be expressed as: 
         [0000]        k   i   =A   i  exp( E   i /( R   u   T   b )) 
         [0041]    The Diebold model considers six components: virgin cellulose (“VC”), active cellulose (“AC”), char and water (“CW”), primary vapors (“PV”), secondary gas (“SG”), and secondary tar (“ST”). Under the Diebold model, VC is converted to AC and CW. The kinetic rate of conversion from VC to AC is referred to as k CC ; the kinetic rate of conversion from VC to AC is referred to as k CA . AC is converted to CW, PV, and SG. The kinetic rate of conversion from AC to CW is referred to as k AC ; the kinetic rate of conversion from AC to PV is referred to as k AV ; the kinetic rate of conversion from AC to SG is referred to as k AG . PV is converted to SG and ST. The kinetic rate of conversion from PV to SG is referred to as k VG ; the kinetic rate of conversion from PV to ST is referred to as k VT . Thus, the rate of mass production of each component can be expressed as: 
         [0000]    
       
      
       {dot over (m)} 
       VC 
       =−k 
       CA 
       m 
       VC 
       −k 
       CC 
       m 
       VC  
      
     
         [0000]    
       
      
       {dot over (m)} 
       CW 
       =k 
       CC 
       m 
       VC 
       +k 
       AC 
       m 
       AC  
      
     
         [0000]    
       
      
       {dot over (m)} 
       AC 
       =k 
       CA 
       m 
       VC 
       −k 
       AC 
       m 
       AC 
       −k 
       AG 
       m 
       AC 
       −k 
       AV 
       m 
       AC  
      
     
         [0000]    
       
      
       {dot over (m)} 
       PV 
       =k 
       AV 
       m 
       AC 
       −k 
       VG 
       m 
       PV 
       −k 
       VT 
       m 
       PV  
      
     
         [0000]    
       
      
       {dot over (m)} 
       SG 
       =k 
       AG 
       m 
       AC 
       +k 
       VG 
       m 
       PV  
      
     
         [0000]      {dot over (m)} ST =k VT m PV    
         [0042]    The mass-specific heat of the pyrolysis reaction may be expressed as Δh P =538 kJ/kg. The overall mass-conversion rate due to pyrolysis, {dot over (m)} P , may be considered to be the rate at which VC and AC are decomposed; therefore, the rate of change in enthalpy due to pyrolysis may be expressed as: 
         [0000]      Δ {dot over (H)}   P   ={dot over (m)}   P   Δh   P =( k   CC   m   VC   +k   AC   m   AC   +k   AG   m   AC   +k   AV   m   AC )Δ h   P  
 
         [0043]    The above expressions include radiation and convection in their heat transfer terms, and heat transfer coefficients are modified to account for transpiration effects where appropriate. The above expression may be analyzed based on the assumptions that the walls of the cylinder  212  have the properties of steel and the biomass  240  has the thermo-physical properties of corn stover. Convection to the walls of the cylinder  212  and to the biomass  240  are assumed to be steady. Thermo-physical properties for the compression gas  250  may be modeled using chemical kinetics software such as Cantera. The system expressed by the above equations may be integrated in time to calculate the evolution of pressure within the cylinder  212 , temperature of the biomass  240 , temperature of the compression gas  250 , and conversion fractions during the compression and expansion strokes of the piston  222 , as illustrated in  FIGS. 4 and 5 . The modeling may use the initial conditions that the biomass  240  consists entirely of VC, the biomass  240  and compression gas  250  begin at temperature T b =T g =22° C., and the mass m b  and radius r b  of the biomass are specified. Modeling may be performed using computing software such as MATLAB, developed by The MathWorks, Inc., of Natick, Mass. 
         [0044]    In an embodiment, the system  200  may be implemented with a 7.3 liter, 8-cylinder, 4-stroke diesel engine adapted from an intended use in a truck. Such an exemplary engine may have a bore of 106 mm and a stroke of 104 mm. The exemplary engine may be cycled at 100 rpm. The exemplary engine may have a volumetric compression ratio of 22.4, and it may be assumed that the dynamic compression ratio is 75% of the dynamic compression ratio. In an embodiment, argon may be used as the compression gas, and spherical biomass particles having a diameter of about 50 μm and the thermo-physical properties may be used as the biomass. 
         [0045]      FIGS. 6-8  present the results of the analysis of the detailed model described above.  FIG. 6  illustrates a chart  600  showing time histories of pressure  620  and temperature  630  along a vertical axis, against time  610  along a horizontal axis. The chart  600  includes a plot  640  of pressure P within cylinder  212 , a plot  650  of the temperature T g  of the compression gas  250 , and a plot  660  of the temperature T b  of the biomass  240  (or the bio-products  260  into which the biomass is converted), all of which may be determined based on the above. It may be seen that the maximum temperature of the biomass  240  is over 500° C. and that the heating rate exceeds 5000° C./s during the compression stroke. The maximum temperature and heating rate are appropriate for fast pyrolysis. It may further be seen that the cooling rate of the bio-products  260  is over −5000° C./s during the expansion stroke, which is sufficient to quench the undesirable secondary pyrolysis reactions. 
         [0046]      FIG. 7  illustrates a chart  700  showing pressure  720  along a vertical axis against volume  710  along a horizontal axis. The chart  700  includes a plot  730  of a detailed model of a cycle as predicted by the differential equations above, as compared to a plot  740  for an ideal cycle of the system  200 . The ideal plot  740  may reach a higher pressure because it ignores heat transfer to the biomass  240  and the wall of the cylinder  212  during the compression stroke. 
         [0047]      FIG. 8  illustrates a chart  800  showing weight fractions during the conversion of biomass  240  to bio-products  260 . In the chart  800 , weight fractions  820  are plotted against a time axis  810 . The chart  800  includes a plot  830  for virgin cellulose, a plot  840  for active cellulose, a plot  850  for pyrolysis vapor, a plot  860  for char and water, a plot  870  for secondary gas, and a plot  880  for secondary tar. As noted above, the weight fractions shown in the chart  800  may be calculated according to the Diebold model for pyrolysis. It may be observed that the virgin cellulose and active cellulose are degraded primarily between 0.2-0.3 s. This phenomena manifests itself in the calculated temperature of the biomass  240 , as shown in  FIG. 6  as a slight change in heating rate; this is because appreciable amounts of energy are utilized for the heat of pyrolysis during that time. At the end of the expansion stroke, 70% (by weight) of the biomass is converted to pyrolysis vapor, as indicated by plot  850 . Little undesirable secondary gas and tar are produced because the rapid expansion quenches all reactions within cylinder  212 , as indicated by plots  870  and  880 . 
         [0048]    The following table compares the exemplary system  200  based on a 7.3 liter diesel engine, as described above, to a small fluidized bed reactor. These represent an appropriate comparison because they have roughly the same footprint, and therefore may be assumed to have roughly similar capital costs. For the fluidized bed reactor, the input energy per unit of biomass includes input energy required to heat the biomass. The calculations described above predict that significantly less input energy is required per unit of biomass, with a significantly increased biomass feed rate. In the table below, the power ratio refers to the ratio of power available from bio-oil output to power required to operate the reactor. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                   
                 Mass flow 
                   
               
               
                   
                   
                 Input energy per 
                 rate 
                 Power 
               
               
                 Type 
                 Gas flow rate 
                 unit of biomass 
                 of biomass 
                 ratio 
               
               
                   
               
             
             
               
                 Exemplary 
                 38 kg/hr (Ar) 
                 1.8 MJ/kg 
                 4.3 kg/hr 
                 7.6 
               
               
                 system 
               
               
                 Fluidized bed 
                 4.8 kg/hr (N 2 ) 
                 3.5 MJ/kg 
                 2.2 kg/hr 
                 3.5 
               
               
                 reactor 
               
               
                   
               
             
          
         
       
     
         [0049]    Therefore, it may be seen that the exemplary embodiments may provide a system that increases biomass throughput by roughly 100% while decreasing the mass-specific energy requirement by roughly 50% as compared to the state of the art (i.e., the fluidized bed reactor. 
         [0050]    In an embodiment, the reciprocating biomass conversion scheme is intended to pyrolyze biomass to bio-oil, bio-char, and bio-gas. In an embodiment, this is achieved with an inert compression gas, however, biomass gasification can be achieved by injecting the pulverized biomass with ambient air. Other feedstocks are also appropriate for fast pyrolysis or gasification according to the present invention. Alternative feedstocks include municipal and agricultural waste streams and other feedstocks known in the art. 
         [0051]    It should be understood that the embodiments described herein are merely exemplary in nature and that a person skilled in the art may make many variations and modifications thereto without departing from the scope of the present invention. All such variations and modifications, including those discussed above, are intended to be included within the scope of the invention.