CA1329046C

CA1329046C - Delignification of non-woody biomass

Info

Publication number: CA1329046C
Application number: CA000595499A
Authority: CA
Inventors: George J. Tyson
Original assignee: Xylan Inc
Current assignee: Xylan Inc
Priority date: 1988-04-05
Filing date: 1989-04-03
Publication date: 1994-05-03
Anticipated expiration: 2011-05-03
Also published as: DE68911525D1; BR8907356A; US4842877A; AU3535989A; EP0415959A1; DE68911525T2; WO1989009547A1; EP0415959B1

Abstract

DELIGNIFICATION OF NON-WOODY BIOMASS

Abstract of the Disclosure A non-woody biomass is delignified through extrusion technology, utilizing hydrogen peroxide and an alkali agent, to break down complex biomass materials. The process is useful in forming a highly absorbant fiber material for use as a dietary fiber or an absorbant fiber.
Alternatively, the process is useful for preparing dietary feeds for ruminant animals, as well as produce a broad range of alcohols or polymers from the non-woody ligno-cellulosic substrate.

Description

t 32904h ; DELIG~IFICATION OF NON-WOODY BIOMASS

Field o the Invention The present invention is directed to a process and apparatus for the delignification oE non-woody biomass through extru~ion technology to break down complex biomass ~, material~. Speci~ic~lly, the present invention iB
directed to ~he delignification of non-woody agricultural biomass wastes through extrusion technology, utilizing hydrogen peroxide and an alkali. The invention is parti~ularly directed to the formation of specific chemicals and dietary fiber for use in food products. The ~ prasent ;nvention is also directed to a process and i~ apparatu~ for preparing useful dietary feeds for ruminant ~ animals.
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Back~round of the Invention Description of the Prior Art . , ~
; The importance o dietary fiber for use in the human and non-human system cannot be overemphasized. Dietary .~ ~

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- 2 _ 1 32904 6 fiber plays a major role in health and disease resistance, physiological metabolism, and in preventative medicine.
There has been considerable effort in the development of fiber-containing foods in order to benefit from the advantages of dietary fiber in the system.
Further, many of these materials can be u~ed as an effective carbohydrate and energy source in ruminant feeds. ~owever~ in order to benefit from these advantages, the lignocellulosic materials in the residues ~u~t be converted into materials which can be metabolized by the animal. 5pecifically, the polysaccharide portion of the~e agricultural re~idue~ have to be converted into monomeric sugars.
In order to accomplish this, i~ is important to break down the lignin in the residues to release the beneficial polysaccharides in the plant cell wall.
Originally, the delignification process used sulfuric acid and chlorine as the main agents. However, due to environmental control process problems, sulfuric acid is now being replaced with ~odium hydroxide and o~ygen.
As an example in woody fibers, U.S. patent 4,459,174 to Papa~eorges, et al. discloses a process for the delignification and bleaching of chlemical and semi-chemical cellulosic pulps in which the pulp is subjected to a treatment with oxygen and ~ubsequent treatment with peroxide. ~he effluent from the treatment with peroxide is at least partially recyclea to the treatment with oxyyen.
U.S. patent 4,451,332 to Annergren, et al. i5 directed to a method for the delignification of lignocellulose containing fiber material comprising mixing an oxygen-containing gas with the cellulose fiber material in order to atomize the gas and form a foam of the gas and the cellulose fiber material. This process provides a bleached, delignified cellulose fiber without bleaching the lignin substance extracted from the material.
U.S. patent ~,372,812 to Phillips, et al. is directed to a chlorine-free bleaching proces~ for lignooellulosic .

- 3 - ' ~ 329 0 46 pulp. This process is characterized by a series of bleaching stages comprising in sequence a peroxide bleaching stage, and at least one 020ne bleaching stage.
U.S. patent 4,311,553 to Akerlund, et al. is directed to a method of producing peroxide bleached pulp by impregnating lignocellulose fiber material with an aqueous silicate solution containing a sequestering agent. The fiber material is preheated with saturated steam and defibrated between two grinding disks in an atmosphere of saturated steam a~ a temperature of 100-170C.
U.S. patent 4,298,425 to Ranzen, et al. is directed to a method and apparatus for producing fiber pulp of improved paper-forming charact:eristics from ligno-cellulose-containing material such as wood chips and the like.
U.S. patent 4,214,947 to Berger is directed to the treatment of a cellulosic material in the form of wood chips to produce at least partial deligni~ication without mechanical grinding. The material is brought into contact with a reagent, e.g., steam or a chemical reagent, and is subjected to alternate increases and decreases in pres sure .
U.S. patent 4,187,141 to Ahrel i8 directed to a method of producing mechanical pulp of improved brightness and light-scattering properties from wood chips, which are ground between a pair of disks. l~e chips are impregnated with a solution of allcali and introduced into a pressure vessel which iB in communication with the grinding zone.
U.S. patent 4,444,621 to I ndahl i3 directed to a process and apparatus for the deresination and brightness improvement of cellulose pulp, by adding an alkali to the pulp~ along with a sufficient oxidizing bleaching agent.
While the above processes are mainly directed to the delignification of woody-like materials, there are other processes known to the art which disclose the delignification of non-woody biomasses to produce food fit - for human and animal consumption. For example, U.S.
peeent 4,136,207 to Bender disclose~ ~ proceRs for the :`
`, - 4 - ' ~ 329 0 4 6 delignification and fractionation of non-woody substrates using a reactor and acid hydrolysis. This process uses a pH of 1.5 as the first step with h~at and pressure and a residen~e time of 6-13 minutes. Hemicellulose is extracted from the residues, and the residues are subjected to hydrolysis for further fermentation to ethanol, bu'canol, acetic acid, furfural, and xylitol. The cellulose and lignin ar~ then treated with an alkaline solution and separated for independent uses.
V.S. patent 4,649,113 to Gould discloses a batch process for the delignification of agricultural residues to produce cattle feeds, chemical feeds or aietary fibers through the separation of the~e components. The agricultural crop residues and other non-woody lignocellulosic plant substrates are treated with hydrogen peroxide at a controlled pH within the range of about 11.2 to ll.R. The substrates are partially delignified. This process does not use a reactor or ~echanical shear and compression device, but utilizes pHs within the range of about 11.2 to 11.8 with hydrogen peroxide in the liquid.
The cell walls are fractured in approximately 4 to 6 hours. The product can be used for animal feeds. It is also possible to separate the liquid from the cell walls if die~ary fiber as a product is desired.
While there are processes and apparatuses available which delignify both woody and non-woody cellulosic materials, these processes have inherent deficiencies.
For example, with the process as disclosed in the '113 patent to Gould, maximum delignification of biomass or non-woody lignocellulosic materials is achieved by the use of substantial amounts of hydrogen peroxide in an aqueous solution at a pH of about 11.5 in stored tanks for 4 to 6 hours at temperatures between approximately 50 and 120F. With this process, a substantial amount of chemicals must be utilized in order to effect the required delignification of the Eiber.

_ 5 - ~ ~29 046 Summary of the Invention In accordance with this invention, lt is an object to provide a delignification process which permits the effi~ient utilization of non-woody agricultural residues.
It is also an object of the present invention to provide a process for the deligniication of waste or very low value agricultural biomass or industrial waste to produce value-added foods, solvents, or polymers.
It is al30 an object of t'he present invention to provide a nontoxic nutritional ruminant feea source at a cost less than traditional energy foods.
It is also an object of the present invention to develop a process w'hich may produce a broad range of alcohols or polymers, ~uch as ethanol, butanol, butanediol, 2-3-L glycerol, acetic acid, furfural, xylitol or single cell protein6.
It is als~ an object of the present invention to provide graln and seed proce~sors with a new use for their non-woody agricuLtural residue waste hulls, shell~ or other wa~te portions of t'heir processin~ systems.
It i~ also an object of the present invention to produce a non-toxic material whic'h produces at least 80%
cellulose in a food grade dietary fiber that will be FDA
approved~
~ hese and other objects are met by the present invention which discloses a method for continuously treating a non-woody lignocellulosic substrate comprising reacting the substrate in a reactior. medium containing an aqueous solution of a strong alkali at a pH in the range of about 10.5 and 12.5. This is followed by adding a chelating agent to the substrate in an amount effective to chelate the metal ions in the substrate. The substrate is then continuously fed into a pre3surized extruder reactor conducted in an o~ygen atmosphere at a temperature between about 150 and 315F and at a pressure between about 250 and 450 p8i. Tbe reactor i9 operated in the preeence of ~' '~

- 6 - ~ 329 0 46 hydrogen peroxide, which is added to the extruder at a rate of between about 20 to 40 pounds of hydrogen peroxide per ton of suhstrate on a dry matter basis.
The process provides a mechanical extrusion ~ystem to mix, grind and sterilize non-woody agricultural substrates while mixing them with sodium hydroxide, potassium hydroxide or other buffering agents in the presence of heat, pressure, and hydrogen peroxide. Following the extruder reaction process, the substrate can be passed to a cooling drum for bagging or truck loading, or passed into enzyme and fermentation tanks for production of ethanol, acetic acid or ferm0lltation to 2, 3-butanediol or glycerol, or the substrate can be further processed to produce a high quality dietary fiber.
The proces~ allow~ the mixture of grains, vegetables and fruits or portions of thess plants to be processed together, a~ well as aeparately to achieve the proper proportions of non-digestible or soluble dietary ~iber.
Without wishing to be limited to one explanation, it is believed that the process of the present invention di~rupts the lignin and cellulose comprising the e~sential par~ of the ce]l walls of the plants allowing oxygen to escape. Thi~ happens a~ the bonds between the hydrogen and oxygen erupt. The water and oxygen leave in the form of steam. Hydrogen oxidizes and is eliminated as the pressure is raleased and as the water hydrolize~
hemicellulose, or other polysaccharides, and lignin into the desired proportions to customize the fiber, based on itB usage. The biomass may be treated with less hydrogen pero~ide and correspondingly less alkali buffering agents, such as sodium hydroxide or potassium hydroxide in order to maintain an adjusted pH of approximately 11.5 and to eliminate the need to handle and dispose of the liquid waste stream.
The dietary fooa fiber may be produced from any of a number of non-woody biomass sources by use o an extruder, by injecting chemicals into the barrel, at specific points, to custom produce a substrate which can then ~ 7 ' 13290~6 hydrolized and/or bleached and separated into the ratios desired to meet the exactin~ specifications of the baking and food preparation industry~
By the use of non-corrosive extruders, the substrates can be ground and mixed utilizing less chemicals than the prior inventions. Fox example, the process of the present invention is advantageous over the '113 patent to Gould in that instead of 200 pounds of hydrogen peroxide per ton of dry biomass, the process of the present inven~ion only requires between 20 and 40 pounds of hydrogen peroxide and a corresponding lesser amount of sodium hydroxide or other buffering agents for a ten-fold advantage in chemical cost to give a superior delignification effect. The process is expected to allow fermentation of, or aigestion of, 85 to 90% of the sugars, calories, xylose or glucose.
The process uti~izes no harsh toxin forming acids and uses a natural com~ination of chemicals which dis~ipate under heat and pressures o~ approximately 280F and up to 400 pounds of pressure in less than two minutes. The resulting substrates contain no inhibitors to prevent enzymes or yeaæt from fermenting the cellulose and hemicellulose to energy for ru~inant feed stocks or for use as chemical feed stocXs to procluce chemicals such as ethanol or acetic acid or butanediol.
Further, the txeatment of the substrate under the conditions of the present invention increases, ~n situ, the normal digestibility of the material to nearly 90% on a dry matter basis.
Further still, the continuous process of the present invention increases product recovery as opposed to a batch process which must be shut down on occasion in order to recover the batch product.
Further still, the process of the present invention requires no presoaking of the raw material for any period longer than the pre-mix time at the front end of the extruder. The temperature range in the extruder is also effective in sterili~ing the biomass substrate by Xilling all bacteria, such as ~almonella.

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,, 8 ~ 3 2 9 0 4 6 The process of the present invention has several uses. First, as a food processing plant, the present invention effectively processes products that are generally discarded, such as hulls, skins, and the pulp of vegetables, grains and fruits, into animal feeds, dietary fibers, absorbent materials, or chemical feed stocks for new industries.
Of major importance, the process of the present ; invention effectively produces a very light colored dietary fiber from grain hulls or vege~able matter, which can be so customized to alter the soluble portions versus the insoluble. The process o~ the present invention produces a high percentage dietary fiber in the form of a non-toxic, non-woody, nearly white, fluffy, cellulose material that can be ground to a 120 mesh particle size which is highly water soluble and non-gritty to t~a taste~ Grinding of this fiber can be accomplished with about one-third of the horsepower that is required by the ~3ame substrate prior to processing~ due to lignin removal. Further, there is considerably less wear on the apparatus.
The dietary fiber produced from the present invention ha~ been found to contain only 24 c-alories per hundred grams and can be used as an ef~ective replacement or sub~3titute for some of the ingredients in foods such as mashed potatoe~, cakes, pasta, cookies, donuts, pancakes, breads, meat loaves, pi~a, and gravie~. For example, dietary fiber produced by the present invention can be sub~titu~ed for up to 33% of the white flour in white bread and 40% in caXes and cookies.
Further, the process of the present invention produces a highly ab~30rbent fiber of light manilla color for food / additives or pharmaceutical use.
i Further still, the process of the present invention advantageously produces a light, fluffy, water absorbent fiber for absorbing body fluid~ in products such a~ baby diaper~, sanitary napkins, linen~ and kitty litter.

' - 9 - ~ 1 3~ 6 The process of the pre~ent invention also can be utilized to produce a pre-processed compost for greenhouses or mushroom bed material, which allows accelerated growth of any horticultuYe species, and allows for rapid micelial growth in a sterile environment with all nematodes or bacteria killed during the process. The compost material can be bagged after cooling.
Further still, the process of the present invention can be utilized a~ a portable waste-processing system used by the fruit or vegetable industry in reducing its disposal costs in many agricultural operations and turning otherwise costly waste products into new sources of fermentable sugar strains for the production of dietary fiber products, chemicals such as acetic acid and ethanol, cattle feeds, and compost material.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawing.

Brie~_Description of the Drawing The drawing is a schematic plan view of the process of the present invention.

~ LbL~2~31E~n of the Invention The process is directed to a continuous treatment of biomass to produce dietary fiher and other desirable products in a convenient and efficient way. By the use of a pressuri~ed extruder, the non-woody biomass substrate can be conveniently converted into the desirable product in a fa~t and efficient manner while substantially reducing the amount of necessary chemicals used to de~ignify the biomass products. For purpoæes o~ the present invention, the term "non-woody" is meant to include oryanic plant material comprising no more than about 20% lignin.

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~ ~2qo~6 By the term non-woody lisnocellulosic Rubstrate or bioma~s, it is meant that the present invention can treat any non-woody materials including tree fruits, such as apples, apricots, cherries, peaches, pears, and plums;
citrus fruits such as lemon, lime, oranges and grapefruits; and bushberries ~uch as blackberries, raspberries, strawberries, and blueberries. Further, cereal grains such as barley, corn, oats, rice, rye, and wheat, as well as the waste material left after the processing of these materials, can be used. In other words, agricultural residues such as corn stalks, wheat straw, prairie grass, hulls of grains and brans, etc., are within the scope of the substrates utili~ed in the present invention.
Reference iæ now made to the drawing which illustrates in schematic form the process of the present invention.
The biomass substrate, which is preferably chopped or reduced in size to particles not more than one-half inch in length, is fed to a prehydrolysis tank 10 in order to soften and solubilize the biomass. The prehydrolysis tank 10 includes a reaction medium comprising a strong alkali which softens the biomass at a pH between 10.5 and 1~.5 and a temperature between 130 and 160F. Preferably, the prehydrolysis tank 10 is an agitator tank. The preferred alkali in the reaction medium is either sodium hydroxide or potassium hydroxide. In some cases it may be preferred to ~eep the levels of sodium reduced, especially for food grade applications. Sodium levels may be kept reduced by the use of potassiu~ hydroxide instead of sodium hyaroxide. The levels of potassium hydroxide may additionally be reduced by the hydrolyzation of the prehydrolysis tank reaction me!dium in a subsequent phase and the recycling of a portion of that efflu~nt, containing potassium hydroxide, back to prehydrolysis tank 10. This recycling process may be conducted as many as 7 to 10 times before the buffer loses its effectiveness.
The biomass ~ubstrate is preferably allowed to remain in the prehydrolysis tank 10 for a period of at least 20 .

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minutes at temperatures between about 130 and 160F, which time has been shown to be an effective time to produce a sufficiently softened and solubilized hiomass for the next step. If desired, the temperature of the reaction medium may be reduced to ambient temperature:
however the reaction time will be correspondingly increased.
After the biomass has been sufficiently processed in the prehydrolysis tank 10, the substrate is passed through line 12 and filtered via filter 20. The filter 20 may be any of a number of filters known to the art for removing a reaction medium from a substrate. A preferrea filter is a vibrating screen filter. The purpose of the filter 20 is to remove the reaction medium from the prehydrolysis tank 10 for recycling, via line 22, back to the prehydrolysis tank 10. I necessary, the solution which is recycled back to the prehydrolysis tank 10 may be p~l corrected by the addition of sodium hydroxide or other buffering material via line 24 from storage container 26.
Additionally, it may be necessary to correct the temperature of the recycled solution to be within the preferred 130 to 160F temperature prior to entering the prehydrolysis tank 10. The reaction medium may be continuously recycled back to the prehydrolysis tank 10 until the liquid becomes too densely contaminated. The contaminanted reaction medium is then replaced with fresh medium.
After a sufficient amount of the solution from the prehydrolysis tank 10 has been removed by means of the filter 20, the biomass substrate is then transferred via line 28 to a mixer 30. The purpose of the mixer 30 is to remoisten the substrate to a desired moisture percentage, normally 30% to 50~ moisture and to add a sufficient amount, preferably between about 2.5% and 4% v/v, o~ a chelating agent, such as sodium silicate, which will be effective to chelate the metal ions in the solution and coat any meta1s in the apparatus.

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- 12 - ~ ~29 0 ~ 6 The addition of sodium silicate or other chelating agents is necessary in order to prevent unwanted precipitation of insoluble deposits, such as metals or metal ions. These insoluble deposits may tend to form deposits on any of the downstream components of the apparatus of the present invention. The subsequent peroxide bleaching can then be carried out with fully satisfactory re~ults. The addition of a chelating agent to the substrate also tie~ up the metal ions in the substrate and watsr preventing unnece~sary oxidation of the hydrogen peroxide by the metal contact. This in turn reduces any premature oxidation of the hydrogen peroxide, reduces the amount of hydrogen peroxide needed by at least 10 to 20~ and helps in the bleaching proce~s of the substrate which iæ very important in producing near white cellulose useful for dietary fibers or ahsorbancy products. Additionally, the c~elating agent coats any knives or discs in the downstream extruder barrel to avoid product burn on or adherence buildup on the surfaces.
The substrate from line 28 is generally processed through the mixer 30 for a time bet:ween approximately 2 and 5 minutes at a pressure between approximately 300 to 400 p9i and a temperature between lgO and 280F. If necessary, sodium hydroxide or other alkali chemicals may be added from the buffer solution storage tank 26 vi~ line 32 in order to adjust the pH to between about 11.2 and 12.~. If the hemicellulose i8 to be retained as in the case of dietary fiber preparation, the pH should be ad~u3ted to between 11.4 and 11.8. The chelating agent is added ~rom the storage tank 34 via line 36. The chelating agent can be added concurrently with the buffering agent ` prior to leaving the mixer 30.
s After a sufficient amount of chelating agent and buffering agent nave been added to the substrate, the substrate is then passed vla line 38 to the extruder reactor 40. The extruder reactor 40 allows for the effectiYe treatment of the substrate with hydrogen peroxide at higher solid~ levels. This eliminates a `: :

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- ]3 -~ ~3~9046 substantial amount of the necessary liquid stream and improves the recovery of carbohydrate products as in the case of animal feeds. The effect of friction and pressure in the extruder is to accelerate the reaction and to reduce the amount of hydrogen peroxide used while maintaining the pH of the substrate at levela between about 11.2 and about 12.2, preferably between 11.4 and 11O8. Ideally, the extruder reactor will process approximately 6,000 lbs. of substrate per hour continuously. The advantage to the use of an extruder reactor is that it replaces steam cooking in a batch process thus maXing the entire process more efficient.
The extruder reactor i8 formed of a stainless steel or other noncorrosive material and is modified to cram feed chopped biomass at a 40 to 50% moisture level into a compres ion chamber with water containing a 4% solution of chelating agent. The solutioll i8 pH modified with either the addition of ~odium hydroxide, potassium hydroxide, or other buffering agent. The reaction takes place within approximately 1.5 to 5 minutes at a pressure of between approximately 250 and 450 psi, preferably 300 and 400 p5i, and a temperature between approximately 150 and 315F, preferably 190 and 280F, and most preferably 215 to 275F. Advantageously, the substrate passing through the extruder 40 may be delignified with as little as 20 to 40 lbs., preferably 25 lbs. of hydrogen peroxide per ton of substrate on a dry matter basis.
Although the extruder reactor may be of twin-screw variety, it i~ preferably a single screw stainless s~ael barrel with a steam jacket, capable of food grade operation. The orifice i8 hydraulically operated to control the temperature and time of the process.
Preferred extruders for purposes of the present invention are the Wenger TX-138, X-175, X-185 or X-200 continuous extrusion cookers, which operate at 150-250 horsepower for high capacity industrial applications. These extruders have a feeder device which provides a uniform and controllable ~eed rate to the extruder.
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1 3 2 9 ~ 4 6 Pressure gauges are strategically placed to indica~e pressure and heat of ths substrate throughout the extruder process. As indicated above, the material of the reactor should be stainless steel or a similar corrosion- free material. I'he reactor may be driven with a variable speed or similar-type speed reduction motor. It will become apparent from the following description of the extruder that the extruder 40 will need several port entries to allow high pressure pumps to introduce water in alkaline form, hydrogen peroxide, sodium silicate or other chelating agent at any point desirable in the process.
The pH of the extruder 40 should be maintained at between 11.2 to 11.8 if hemicellulose is to be retained.
If the pH exceeds 11.8, degeneration of the hemicellulose will be enhanced to a point where almost all of the hemicellulose is reduced by hydroly~ation. Therefore, the solubility of the fiber will be reduced. If the hemicellulos~ retention is desired, the pH must be kept as near to 11.4 as po~sible. PH monitoring devices will be incorporated into the reactor and subsequent hydrolyzing tanks. Preferably, they will be computerized in order to control the level of operation of the extruder 40.
In operation, the extruder is preferably equipped with a cram feeder to forcefeed the biomass substrate into the throat of the e~truder barrel. During the extrusion process, sodium silicate or other chelating agents may be injected, along with buff~ring agents, oxygen or a suitable gas, and hydrogen peroxide. The biomass enters the extruder 40 as a 35-45% solid subqtrate.
Oxygen iB added to the extruder from an oxygen producing unit 42 via line ~4. Oxygen is induced into the extruder in order to help reduce the amount of hydrogen peroxide needed to cause a delignification reaction on the cell wall~. Further, the addition of oxygen aids in the initiation and acceleration o-f the activation of the hydrogen peroxide. A preferred oxygen producing tank is a Prism~ Alpha-Controlled Atmosphere System. The purpose of the Prism~ alpha-system is to generate nitrogen ir. order ~ 1S ~ 1 329 ~ 4 6 to extend the storage life of food products. However~ a biproduct of the sy~tem is oxygen which i9 used in the present invention. ~f course, other oxygen producing systems may be incorporated into the process of the present invention.
Following the introduction of oxygen, hydrogen peroxide from storage tank 46 is added via line 48.
Hydrogen peroxide causes a reaction on the cell walls ~o allow the hemicellulose and lignin to solubilize and be removed through a subsequent hydrolyzing process.
Approximately 20 to 40 lbs. of hydrogen peroxide i8 all that is neces~ary to effectively process a ton of substrate through the extruder 40. The hydrogen peroxide i9 injected approximately 1/3 of the way into the reactor 40 system following the introduction of oxygen. Hydrogen peroxide is generally diluted to a 10% or less concentration to prevent accidents in transfer. Adequate moisture is needed during this proce~s to prevent too much heat from forming which will cause charring of the material. The induction port 49 for the hydrogen peroxide may be adjusted so that most of the hydrogen peroxide has decomposed by the time the biomass emerges from the reactor 40. The hydrogen peroxide stream preferably passes through a precious metal gauze screen under pressure to immediately initiate the activation of the hydrogen peroxide. Preferred precious metals include platinum and palladium with palladium being most preferreA.
It is a substantial benefit of the present invention that the amount of hydrogen peroxide used in the present ~nvention has been reduced from other prior art processes. The reasons for this are several. First, the material is processed in the extruder 40 under elevated temperatures and pressure. Actditionally, the material i5 prevented from contacting surfaces with a sequestering agent, which would cause the premature degeneration of the hydrogen peroxide. Further still, all exposed surfaces of the components of the present invention are of stainless steel or other noncorrosive material.

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1 3~9~46 Advantageously, all hydrogen peroxide i5 dissipated from the sample collected within 24 hours of the treatment. This is important as levels allowable under FDA will at all times need to he below 3 ppm for GRAS
affirmation. Human usage is esp~cially important when it comes to these levels.
The extruder 40 itself may be divided into as many as eight ~ections, each of which being separated by a steam lock. The first section, or cram feeder iB designed to grab and feed the material into the compres~ion zones.
This section operates at a speed of 300 RPM with a single screw against a shear block to pressuri~e. The next section is designed to reabsorb the oxidizing agent, hydrogen peroxide, that has been catalyzed by the metal acetate half way down the reactor. This allows a nscessary time for the oxidation process to occur. The final section is an ancular die which extends 2 to 3 inches past the last steam lock.
A preferred extruder reactor include~ a single ~crew stainless steel barrel approximately 5 inches to 16 inches, preferably 5 inches to 5 1/2 inches, in diameter and 6 to 8 ~eet in length. The extruder barrel should be made of a high carbon alloy or stainless steel and having the strength to withstand pre~sure~ up to 500 psi and temperatureæ exceeding 260F. A typical power source for the extruder i8 a 200 horsepowex, 3-phase electric motor located near the entrance of the extruder. A 6:1 gear reducer reduces the 1800 RPM drive to a 300 RPM extruder speed. A cram feeder hopper powered by a variable speed hydraulic motor feeas the materia~s, which may have a variable consistency, into the throat of the extruder barrel. A second hopper or mixing pump combines a diluted solution of an alkali agent, such as sodium hydroxidP or potassium hydroxide, into the substrate mass in the extruder barrel. Hydrogen peroxide, in diluted form i8 then injected into the ~ubstrate. The developing vapors are withdrawn by exhaust fans. The process material is then augered either to a cooling drum for bagging, to an 1 32qo46 enzyme or fermentation tank, or to an acid ba~h for further procesling to a dietary or absorban~ fiber.
Remotely located safety sensing devices register both temperature and pressure at the highest point in the extruder barrel. Both ~anual and automatic shutdown devices are located throughout the system. As a safety measure, a shroud, generally formed of stainless steel, surrounds the extruder. The shroud includes devices which continuously moniter the toxicity level of the emitted vapors. Thiæ ~afety aspect of the sys~em is able to signal and/or shut down the machine without clo~ing off the vapor exhaustion system until the toxicity leYel is brought under control.
The biomass leaving the extruder should have a moisture level between approximately 30 and 50~, preerably 40~ moisture. The temperature of the biomass at this point would generally be in the range o 195 to 200F. As mentioned previously, all hydrogen peroxide should have been decomposed by the time the bioma~s leaves the extruder. Additionally, the pH o the biomass at this point wlll be in the area of 11.5.
Following reaction in the extruder 40, the substrate may be passed via line 50 to cooling drum 52 where the substrate may be cooled and dried. The product 54 may be utilized to feed ruminant livestock, Ruch as cattle and sheep. AlternatiYely, the product 54 may be converted in~o a chemical eedstock 58 by the addition of appropriate fungal cellulose enzyme complexes, such as Trichederma reesei, which is native to the ruminant's :
digestive systemO The addition of such enzymes converts the cellulose and hemicellulose to glucose and xylose for the production of ethanol, acetic acid, butanol and other chemical derivatives.
Alternatively, the extrudate from the reactor 40 may be processed through a hydrolyzer 60, i.e., an agitated water tank having a temperature of at leaqt 140F. The purpose of the hydrolyrer 60 i~ to wesh out hemicellulo~e.

" , -- 18 - ~ 3~ 0 4 6 The product of the hydrolyzer 60 i5 then transferred via line 62 to a filter 64 which filters out the hydrolyzer solution. The filter 64 acts in a similar fashion to the filter 20, previou~ly described. The product of the filter 64 can then be transferred via line 66 to a conversion tank 68 in order to convert the product to xylose or other chemical feed stocks in a manner similar to that previously described with respect to ~he cooling drum 52.
Alternatively, the product of filter 64 should be washed at least once and preferably at least two times in an acid bath 70. Purpose of the acid bath is to wash out substantial amounts of the lignin and hemicellulose remaining in the substra~e. 'rhe pM of the acid bath is reduced to .5 to 3 by adding hydrochloric acid from ~torage tank 72 via line 74. Advantageously, the acid bath acts to further bleach the cellulose fiber in the substrate in order to make the final product brighter and w~iter. Following multiple washin~s in the acid bath 70, the substrate i~ transferred via line 76 to filter 78 which removes a substantial amount of the acid wash solution~ Thi~ 2cid wash solution may be recycled back to acid hath 70 via line 80.
The substrate is then transferred via line 82 to a ~ubsequent washing area 84, having a pH o 6.5 to 7Ø
The p~ is corrected by the addition of bufEering agents, such as calcium ~arbonate or bi~arbonate of soda from storage tank 86 via line 88. This washing process a~fords a final removal of the bleaching or extraction solution~
and solubliæed compounds therein from the pulp prior to recovery.
Following the p~ correction process, the substrate is transferred via line 90 to ~ilter press 9~. Filter press 92 i8 pre~erably a hydraulic lilter press, which reduces the moisture of the substrate to a 55 to 65~ moisture level. The liquid which is extracted from the substrate may then be recycled via line 94 back to washer 84 in order to reduce t~e cost of calcium carbonate and b~carbon~ts of soda.

The compressed substrate from filter press 92 is then transferred via line 96 to Eluffer 100, which acts to breaX apart the condensed hard packed substrate. The material is then transferred via line 102 to dryer 110, a fluid bed dryer, which dries the fluffed material to a moisture content of approximately 3 to 8%. The temperature in the ~luid hed clryer 110 should not exceed 180F in order ~o obtain the best coloring for the fiber sub6trate.
Following drying, the substrate is passed via line 112 to a cutting mill 120, which grounds the substrate fiber through preferably a 60 mesh screen with a cutting mill.
Although other cutters, such as hammer or ball mill types may be used, cutting mills are preferred~ This i~ because hammer and ball mills tend to compress the fluffy cellulose and diminish the puffing or absorbing qualities of the fiber.
The final product leaving the cutting mill 120 via line 122 enters a powder tank 130 in preparation to be bagged at 132.
The entire system of the present invention may be hydraulically controlled to maintain certain pre~sure~, temperatures and retention times, depending upon the substrate used, the amount of water used and the amount of delignification desired. The whole system can of course be computerized and controlled by pressures, heat or end result~ ana the capacity desired. The apparatus may be powered by diesel power with water circulation through the diesel engine block used as a boiler, along with the function which would provide heat for cooking in the extruder. Excess hot water would then be recycled to the water jacketed pre-pulper tanX and then back to the diesel motor block. Diesel would power the extruder ana hydraulic systems to control the orifice on the extruder.
The final product of ~he present invention preferably has a particle size small enough to pass through a 100 mesh screen. Such a particle is acceptable as a food grade material for total dietary fiber. Additionally, 1 3290~6 this fiber has a brightness reading of over 80 GE units as measured by a General Electric brightness meter. The dietary fiber is also a food product acceptable to the FDA
residue requirementsO
Thus, the need for a nearly white, high percentage dietary fiber can be met by applying the process of the present invention which simultaneously delignifies, bleaches, shears, sterilizes and liquifies the substrate cau~ing both the lignin and hemicellulose to be removed, leaving 80~ or more cellulose in the final productO The final product is a non-toxic, non-woody white flufy cellulose material which can be to a 120 mesh particle size anA which is highly soluble and non-gritty to the taste.
It is within the scope of the present invention to cu~tomize the apparatus to leave in more lignin and hemicellulose vr take out more by qimply changing the pH
level during the process. Additionally, the process may be mobilized as a portable unit, which would effect tremendous ~avings on the cost of transporting the substrate for livestock feeding.
The following examples are given to illustrate certain preferred embodiments of the process o~ the present invention.

Example l Example l is designed to illustrate the delignifica-tion of a non-woody lignocellulose biomass substrate to a feed suitable for ruminant dige~tion. The biomass substrate is chopped to a size not exceeding l/~ inch and ~orwarded to a prehydraulysis tank containing water as a reaction medium. Potassium hydroxide is added to the water to raise the pH to 11,5. The temperature of t~e water is approximately 130F. The substrate is allowed to react in this mixture for approximately 20 minutes. The substrate is then pumped through a filter extractor to remove the lignin. The reaction fluid is then recycled back to the prehydraulysis tank and the substrate is conveyed to a .

- 21 ~ 32904 6 mixer where the pH is converted to 11.5 and a chelating agent iB added at a 2.5 to 4% v/v level. The substrate i~
procPssed through the mixer for approximately 2 1/2 minutes at a pressure between approximately 300 and 400 psi and a temperature of about 190.
The ~ubstrate is then Eed to an extruder re~ctor, and oxygen i5 then introduced to create an oxygen atmosp~ere.
Suh~equen~ly, a 10% solution of hydrogen peroxide is in~roduced through a high pressure orifice through a palladium gauze and into the reactor. The hydrogen peroxide is added at a rate of 25 lbs. of hydrogen peroxide per ton of substrate on a dry matter basis.
After reacting for approximately 45 to 60 seconds, the substrate emerge~ through a hydraulically controlled valve in the extruder reactor. At ~hi 9 point, the temperature of the substrate environment is between approxi~ately 200 to 265F.
The sub~trate is then conveyed to a cooling drum where j the substrate i8 cooled and dried. The product of the cooling drum may then be utilized to feed ruminant feed stock. Alternatively, the product can be converted into a chemical feed stock by the subsequent addition of appropriate enzyme~.

E~ample 2 ;

Example 2 illu trates a preferred process for producing a dietary fiber. The proces6 according to Example 1 is followea through the extruder reactor.
Rather than forwarding the sub~trate to a cooling drum, the substrate is hydrolyzed in an agitated vat in a pH
approximately 11.4 to 11.8 for approximately 30 minutes.
The ~ubstrate i8 then passed through a vibrating filter to ~eparate the substrate from the reaction fluid. The fluid may then be pumped back to a recycle 3ilo to concentrate the sugars and hemicellulose. ~e substrate is then washed through an acid bath at a pH of 1.5. After the acid bath~ the acid i3 wa~hed off and the pH of the substrate 1s converted to et leest 6Ø The acid bath may - 22 ~ l 329 0 4 6 be recycled back to the supply tank for further use~ The product i~ then hydraulically pressed to decrease the total moisture content to the low 70%, followed by fluffing and drying in a fluid vat dryer to bring the moisture to no more than 8%, preferably 4~. The product is then forwarded to a cutting mill to cut the fibers to a 70 to 120 mesh size. The prepared dietary fiber may then be bagged for transport~

Exam~le 3 Example 3 illustrates the process for the production of an ab~orbant fiber for industrial purposes. The process of Example 2 is followed wi~h the exception that the substrate leaving the extruder reactor i~ hydroly~ed in an agitated vat having a pH between 11.8 and 12.2. At this pH, most of the hemicellulose is removed and only the cellulose remains in the substrate.
It is under3tood that the invention is not confined to the particular construction and arrangement of parts herein illustrated and described, but embraces such modi~ied forms thereof as come within the scope o~ the fol l ow i ng c l ~ ims .

Claims

1. A process for continuously treating a non-woody lignocellulosic substrate comprising:
a) reacting the substrate in a reaction medium including an aqueous solution of a strong alkali at a pH
in the range of about 10.5 and 12.5;
b) reacting an effective amount of a chelating agent with the substrate;
c) continuously feeding the product of step b) to an aqueous solution in a pressurized extruder reactor in an oxygen atmosphere at a temperature between about 150° and 315°F and at a pressure between about 250 and 450 psi, and in the presence of hydrogen peroxide wherein the hydrogen peroxide is added to the extruder at a rate of between about 20 and 40 pounds of hydrogen peroxide per ton of substrate.

2. The process of Claim 1 wherein the substrate is selected from the group comprising tree fruits, citrus fruits, bushberries, cereal grains and agricultural residues.

3. The process of Claim 1 wherein the substrate is reduced in size to a particle not more than one-half inch in length prior to reacting in the reaction medium.

4. The process of Claim 1 wherein the substrate is reacted in a reaction medium in a prehydrolysis tank, wherein the substrate is softened in the reaction medium at a temperature between 130° and 160°F.

5. The process of Claim 4 wherein the prehydrolysis tank is an agitator tank.

6. The process of Claim 1 wherein the alkali is selected from the group consisting of sodium hydroxide and potassium hydroxide.

7. The process of Claim 1 wherein the alkali is potassium hydroxide.

8. The process of Claim 1 wherein the substrate is reacted in the reaction medium of step a) for a period of at least 20 minutes.

9. The process according to Claim 1 wherein the reaction medium is removed from the substrate prior to feeding the substrate to a pressurized extruder reactor.

10. The process of Claim 9 wherein the reaction medium is filtered from the substrate.

11. The process of Claim 10 wherein the filtered reaction medium is recycled back to the prehydrolysis tank.

12. The process of Claim 1 wherein the chelating agent is added in an amount between about 2.5% and 4.0%
v/v.

13. The process of Claim 12 wherein the chelating agent is sodium silicate.

14. The process of Claim 1 wherein the chelating agent is added in an amount sufficient to reduce the amount of hydrogen peroxide necessary by approximately 10 to 20%.

15. The process of Claim 1 wherein the chelating agent is reacted with the substrate for a time between approximately 2 and 5 minutes and at a pressure between approximately 300 and 400 psi, a temperature between 190°
and 280°F and a pH of approximately 11.4.

16. The process of Claim 1 wherein the extruder reactor is formed of a noncorrosive material and is modified to cram feed the substrate at a 40 to 50%
moisture level.

17. The process of Claim 1 wherein the substrate is reacted in the extruder reactor at a pH between about 11.2 and about 11.8.

18. The process of Claim 1 wherein the substrate is reacted in the extruder reactor at a pH of about 11.5.

19. The process of Claim 1 further comprising adding chelating agents and buffering agents to the aqueous solution of the extruder reactor.

20. A product prepared by the process of Claim 1.

21. The process of Claim 1 further comprising washing the substrate in an aqueous wash solution to remove the hemicellulose from the substrate.

22. The process of Claim 21 wherein the substrate is washed in an agitated water tank at a temperature of at least 140°F.

23. The process of Claim 21 further comprising removing the aqueous wash solution.

24. A product prepared by the process of Claim 23.

25. The process of Claim 21 further comprising washing the substrate in an acid bath including an aqueous acid bath solution having a pH between about .5 and 3.0, followed by washing the substrate in an aqueous pH
correction solution, where a buffering agent is added to the aqueous pH correction solution to adjust the pH to between about 6.5 and 7Ø

26. The process of Claim 25 wherein the acid in the acid bath solution is hydrochloric acid and the buffering agent in the pH correction solution is selected from the group consisting of calcium chloride and bicarbonate of soda.

27. The process of Claim 25 further comprising subsequently reducing the moisture content of the substrate.

28. The process of Claim 25 further comprising the following steps in sequence:
a) subsequently reducing the moisture content of the substrate to a moisture level between about 55 and 65%;
b) fluffing the substrate; and c) drying the substrate at a temperature no greater than about 180°F.

29. A product prepared by the process of Claim 25.

30. A product prepared by the process of Claim 28.

31. A delignified dietary fiber source suitable for food grade consumption, containing at least 80% cellulose prepared by the process of Claim 28.

32. A highly absorbant fiber prepared according to the process of Claim 27.

33. A highly absorbant fiber prepared according to the process of Claim 28.

34. A process for continuously preparing a nearly white, non-woody, delignified dietary fiber suitable for food grade consumption, wherein the fiber contains at least 80% cellulose, the process comprising the following steps in sequence:

a) reacting a non-woody lignocellulosic substrate in a reaction medium including an aqueous solution of a strong alkali at a pH in the range of about 10.5 and 11.8;
b) reacting an effective amount of a chelating agent with the substrate;
c) continuously feeding the substrate to an aqueous solution in a pressurized extruder reactor in an oxygen atmosphere at a temperature between about 150° and 315°F and at a pressure between about 250 and 450 psi, and in the presence of hydrogen peroxide wherein the hydrogen peroxide is added to the extruder at a rate of between about 20 and 40 lbs. of hydrogen peroxide per ton of substrate;
d) washing the substrate in an aqueous wash solution to remove the hemicellulose and lignin from the substrate;
e) washing the substrate in an acid bath including an aqueous acid bath solution having a pH
between about .5 and 3.0;
f) washing the substrate in an aqueous pH
correction solution, wherein a buffering agent is added to the aqueous pH correction solution to adjust the pH to between about 6.5 and 7.0;
g) reducing the moisture content of the substrate to a moisture level between about 55% and 65%;
h) fluffing the substrate; and i) drying the substrate at a temperature no greater than about 180°F.

35. The process of Claim 34 wherein the substrate is selected from the group comprising tree fruits, vegetables, citrus fruits, bushberries, cereal grains and agricultural residues.

36. The process of Claim 34 wherein the substrate is reacted in a reaction medium in a prehydrolysis tank, wherein the substrate is softened in the reaction medium at a temperature between 130° and 160°F.

37. The process of Claim 34 wherein the chelating agent is added in an amount between about 2.5% and 4.0 v/v.

38. The process of Claim 34 wherein the chelating agent is reacted with the substrate for a time between approximately 2 and 5 minutes and at a pressure between approximately 300 and 400 psi, a temperature between 190°
and 280°F and a pH of approximately 11.4.

39. The process of Claim 34 further comprising removing the hemicellulose and lignin from the substrate in an agitated water tank at a temperature of at least 140°F.

40. A dietary food fiber source prepared according to the process of Claim 34.

41. A process for preparing a ruminant feed source comprising the following steps in sequence:
reacting a non-woody lignocellulosic substrate in a reaction medium including an aqueous solution of a strong alkali at a pH in the range of about 10.5 and 12.5.
b) reacting an effective amount of a chelating agent with the substrate;
c) continuously feeding the substrate to an aqueous solution in a pressurized extruder reactor in an oxygen atmosphere at a temperature between about 150° and 315°F and at a pressure between about 250 and 450 psi, and in the presence of hydrogen peroxide wherein the hydrogen peroxide is added to the extruder at a rate of between about 20 and 40 lbs. of hydrogen peroxide per ton of substrate; and d) cooling the substrate.

42. A process for preparing a highly absorbant fiber source comprising the following steps in sequence:

a) reacting a non-woody lignocellulosic substrate in a reaction medium including an aqueous solution of a strong alkali at a pH in the range of about 10.5 and 12.5;
b) reacting an effective amount of a chelating agent with the substrate;
c) continuously feeding the substrate to an aqueous solution in a pressurized extruder reactor in an oxygen atmosphere at a temperature between about 150° and 315°F and at a pressure between about 250 and 450 psi, and in the presence of hydrogen peroxide wherein the hydrogen peroxide is added to the extruder at a rate of between about 20 and 40 lbs. of hydrogen peroxide per ton of substrate;
d) washing the substrate in an aqueous wash solution to remove the hemicellulose and lignin from the substrate;
e) washing the substrate in an acid bath including an aqueous acid bath solution having a pH
between about .5 and 3.0;
f) washing the substrate in an aqueous pH
correction solution, wherein a buffering agent is added to the aqueous pH correction solution to adjust the pH to between about 6.5 and 7.0;
g) reducing the moisture content of the substrate to a moisture level between about 55% and 65%;
h) fluffing the substrate; and i) drying the substrate at a temperature no greater than about 180°F.