Method for increasing the accessibility of cellulose in lignocellulosic materials, particularly hardwoods agricultural residues and the like
First Claim
1. An improved method for increasing the accessibility of cellulose in lignocellulosic materials, such as hardwoods, bagasse and the like, to rumen bacteria, enzymes, microorganisms and the like, characterized by an optimization of a range of cooking times (tc) which will respond to the actual pressure conditions in the reactor as they may change over time during a given cooking run and render the cellulose most open for attack by said microorganisms or enzymes, as measured by the rate or extent of their reaction, said method comprising the steps of:
- (a) feeding lignocellulosic material, in a divided form, into a pressure reactor vessel; and
(b) introducing pressurized steam into the vessel during a pressurization time phase so as to reach reactor pressures of between 250 and 1000 psig wherein said reactor pressures does follow a given time profile; and
(c) cooking by maintaining the lignocellulosic material at said time variable pressures between 250 and 1000 psig for a total period of time (tc) in seconds, which includes the pressurization phase, wherein t3 ≦
tc ≦
t4 and the given reactor pressure time profile is used to determine t3 and t4 for that given cook run since t3 is defined implicitly by ##EQU11## and t4 and defined implicitly by ##EQU12## wherein Ts is the temperature (°
C.) of saturated steam, at the indicated reactor pressures and corresponds to the saturated steam temperature values along the indicated reactor pressure time profile, thereby also making Ts a given function of time (t); and
(d) decompressing the cooked lignocellulosic material down to substantially atmospheric pressure at the end of said cooking time, tc.
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Abstract
This invention comprises a method for increasing the accessibility of cellulose in lignocellulosic materials to chemical or biochemical reagents. The material is steam cooked for a predetermined time, then rapidly depressurized. A venting sequence is used to remove volatiles from the reactor. Optimal cooking times for normal and acid catalyzed cooking are disclosed, according to the discovery of a novel set of governing equations, wherein optimum cooking times can be determined as a time integration of reactor pressure.
265 Citations
38 Claims
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1. An improved method for increasing the accessibility of cellulose in lignocellulosic materials, such as hardwoods, bagasse and the like, to rumen bacteria, enzymes, microorganisms and the like, characterized by an optimization of a range of cooking times (tc) which will respond to the actual pressure conditions in the reactor as they may change over time during a given cooking run and render the cellulose most open for attack by said microorganisms or enzymes, as measured by the rate or extent of their reaction, said method comprising the steps of:
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(a) feeding lignocellulosic material, in a divided form, into a pressure reactor vessel; and (b) introducing pressurized steam into the vessel during a pressurization time phase so as to reach reactor pressures of between 250 and 1000 psig wherein said reactor pressures does follow a given time profile; and (c) cooking by maintaining the lignocellulosic material at said time variable pressures between 250 and 1000 psig for a total period of time (tc) in seconds, which includes the pressurization phase, wherein t3 ≦
tc ≦
t4 and the given reactor pressure time profile is used to determine t3 and t4 for that given cook run since t3 is defined implicitly by ##EQU11## and t4 and defined implicitly by ##EQU12## wherein Ts is the temperature (°
C.) of saturated steam, at the indicated reactor pressures and corresponds to the saturated steam temperature values along the indicated reactor pressure time profile, thereby also making Ts a given function of time (t); and(d) decompressing the cooked lignocellulosic material down to substantially atmospheric pressure at the end of said cooking time, tc. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 17, 32)
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9. An improved method for increasing the accessibility of cellulose in lignocellulosic materials, such as hardwoods, bagasse and the like, to rumen bacteria, enzymes, microorganisms and the like, while reducing pentose sugar losses, characterized by an optimization of a range of cooking times (tc) which will respond to the actual pressure conditions in the reactor as they may change over time during a given cooking run and render the cellulose most open for attack by said microorganisms or enzymes, as measured by the rate or extent of their reaction, said method comprising the steps of:
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(a) feeding lignocellulosic material in a divided form into a pressure reactor vessel; and (b) introducing pressurized steam into the vessel during a pressurization time phase so as to reach reactor pressures of between 250 and 1000 psig wherein said reactor pressures does follow a given time profile; and (c) cooking by maintaining the lignocellulosic material at said time variable pressures between 250 and 1000 psig for a total period of time (tc) in seconds, which includes the pressurization and purging phase, wherein t3 ≦
tc ≦
t4 and the given reactor pressure time profile is used to determine t3 and t4 for that given cook run since t3 is defined implicitly by;
##EQU14## and t4 is defined implicitly by;
##EQU15## and wherein Ts is the temperature (°
C.) of saturated steam, at the indicated reactor pressures and corresponds to the saturated steam values along the indicated reactor pressure time profile, thereby also making Ts a given function of time; and(d) removing volatile degradation products from the pressure reactor vessel by purging gases from the reactor so as to reduce the pressure by at least 100 psig; and
then(e) suddenly decompressing the cooked lignocellulosic material by ejection through an outlet portion of the pressure reactor vessel in an explosive manner. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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18. An improved method for increasing the accessibility of cellulose in lignocellulosic materials, such as hardwoods, bagasse and the like, to rumen bacteria, enzymes, microorganisms and the like, while reducing pentose sugar losses, characterized by an optimization of a range of cooking times (tc) which will respond to the actual pressure conditions in the reactor as they may change over time during a given cooking run and render the cellulose most open for attack by said microorganisms or enzymes, as measured by the rate or extent of their reaction, said method comprising the steps of:
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(a) feeding a lignocellulosic feedstock material in a loose, divided form, which contains an added acid level that is equivalent to between 0.01 and 1% by weight of sulphuric acid, into a pressure reactor vessel; and (b) introducing pressurized steam into the vessel during a pressurization time phase so as to reach reactor pressures of between 250 and 1000 psig wherein said reactor pressures does follow a given time profile; and (c) cooking by maintaining the lignocellulosic material at said time variable pressures between 250 and 1000 psig for a total period of time (tc) in seconds, including the pressurization phase, which is chosen so that t1 ≦
tc ≦
t2 and the given reactor pressure time profile is used to determine t2 for that given cook run since t2 is defined implicitly by ##EQU17## and t1 is defined implicitly by ##EQU18## where R is a constant that is chosen between 2 and 80, and where Ts is the temperature (°
C.) of saturated steam at the indicated reactor pressures and corresponds to the saturated steam temperature values along the indicated reactor pressure time profile, thereby also making Ts a given function of time (t), and AC represents the added acid concentration to the lignocellulosic feedstock stated as an equivalent acid concentration in percent by weight of sulphuric acid; and(d) decompressing the cooked lignocellulosic material down to substantially atmospheric pressure, at the end of said cooking time, tc. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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19. An improved method for increasing the accessibility of cellulose in lignocellulosic materials, such as hardwoods, bagasse and the like, to rumen bacteria, enzymes, microorganisms and the like, while reducing pentose sugar losses, characterized by an optimization of a range of cooking times (tc) which will respond to the actual pressure conditions in the reactor as they may change over time during a given cooking run and render the cellulose most open for attack by said microorganisms or enzymes, as measured by the rate or extent of their reaction, said method comprising the steps of:
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(a) feeding a lignocellulosic feedstock into a reactor vessel, wherein said material is in a loose, divided form and contains no added acid level that is equivalent to between 0.01 and 1% by weight of sulfuric acid; and (b) rapidly introducing pressurized steam into the vessel during a pressurization time phase so as to reach reactor pressure between 250 and 1000 psig wherein said reactor pressures does follow a given time profile; and (c) cooking by maintaining the lignocellulosic material at said time variable pressures between 250 and 1000 psig for a total period of time (tc) in seconds; and (d) removing volatile degradation products from the pressure reactor vessel by purging gases from the reactor so as to reduce the pressure by at least 100 psig, wherein the total cooking time (tc), including the pressurization cooking and purging, is chosen so that t1 ≦
tc ≦
t2 and the given reactor pressure time profile is used to determined t2 for that given cook run since t2 is defined implicitly by ##EQU19## and t1 is defined implicitly by ##EQU20## wherein R is a constant that is chosen to have a value between 2 and 80, Ts is the temperature (°
C.) of saturated steam temperature values along the indicated reactor pressure time profile, thereby also making Ts a given function of time (t), and AC represents the added acid concentration to the lignocellulosic feedstock stated as an equivalent acid concentration in percent by weight of sulphuric acid; and(e) suddenly decompressing the cooked lignocellulosic material substantially to atmospheric pressure by ejection through an outlet portion of the pressure reactor vessel in an explosive manner.
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33. An improved control method for increasing the accessibility of cellulose in lignocellulosic materials, such as hardwoods, bagasse and the like, to rumen bacteria, enzymes, microorganisms and the like, while reducing pentose sugar losses, characterized by optimizing the cooking times (tc) in response to the actual pressure conditions in the reactor as they may change over time during a given cooking run, in order to render the cellulose most open for attack by said microorganisms or enzymes, as measured by the rate or extent of their reaction, said control method comprising the steps of:
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(a) feeding a lignocellulosic feedstock material in a loose, divided form, which may also contain an acid level that is equivalent to less than 1% by weight of sulphuric acid, into a pressure reactor vessel; and (b) introducing pressurized steam into the vessel during a pressurization time phase so as to reach reactor pressures of between 250 and 1000 psig and monitoring in time said reactor pressures as it follows a given time profile; and (c) cooking by maintaining the lignocellulosic material at said time variable pressures between 250 and 1000 psig for a total period of time (tc) in seconds, including the pressurization phase, which is chosen so that tc substantially is determined by the reactor pressure time profile so monitored, wherein the given reactor pressure optimum cook time profile is used to determine tc by integrating the pressure time profile over time until there is a substantial satisfaction of the mathematical relationship, as follows;
##EQU22## wherein R is a constant that is chosen as approximately 80, and wherein Ts is the temperature (°
C.) of saturated steam at the monitored reactor pressures and corresponds to the saturated steam temperature values along each point of the monitored reactor pressure time profile, thereby also making Ts a given function of time (t), and wherein AC represents any added acid concentration to the lignocellulosic feedstock stated as an equivalent acid concentration in percent by weight of sulphuric acid; and(d) decompressing the cooked lignocellulosic material down to substantially atmospheric pressure, at the end of said cooking time, tc. - View Dependent Claims (34, 35)
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36. An improved method for increasing the level of accessibility of cellulose in lignocellulosic material such as hardwoods, bagasse and the like, said method comprising the steps of:
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(a) feeding lignocellulosic material in a divided form into a pressure reactor vessel; and (b) rapidly introducing pressurized steam into the vessel so as to reach a reactor pressure of between 250 and 1000 psig; (c) Cooking by maintaining the lignocellulosic material at a pressure of between 250 and 1000 psig for a period of time tc in seconds defined by the formula ##EQU23## wherein Ts is the temperature (°
C.) of saturated steam of said reactor pressure; and(d) suddenly decompressing the cooked lignocellulosic material down to substantially atmospheric pressure at the end of said cooking time, tc. - View Dependent Claims (38)
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37. An improved method for increasing the level of accessibility of cellulose in lignocellulosic material such as hardwoods, bagasse and the like, said method comprising the steps of:
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(a) feeding lignocellulosic material in a loose divided form, which contains an added acid level equivalent to between 0.01 and 1% by weight of sulphuric acid, into a pressure reactor vessel so as to reach a pH of 4 or lower; and (b) rapidly introducing pressurized steam into the vessel so as to reach a reactor pressure of between 250 and 1000 psig; and (c) cooking by maintaining the lignocellulosic material at a pressure of between 250 and 1000 psig for a period of time tc in seconds defined by the formula ##EQU24## wherein Ts is the temperature (°
C.) of saturated steam at the reactor pressure, andAC represents the added acid concentration to the lignocellulosic material stated as an equivalent acid concentration inppercent by weight of sulphuric acid; and (d) suddenly decompressing the cooked lignocellulosic material down to substantially atmospheric pressure at the end of the said cooking, tc.
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Specification