WO2017095042A1

WO2017095042A1 - Development of biomass pretreatment technology via controlled feeding system of fibrous biomass into continuous high-pressure reactor

Info

Publication number: WO2017095042A1
Application number: PCT/KR2016/013094
Authority: WO
Inventors: Ju-Hyun Yu; In-Yong EOM; Jong-Geon Jegal; Myung-Hoi Koo
Original assignee: Korea Research Institute Of Chemical Technology
Priority date: 2015-12-03
Filing date: 2016-11-14
Publication date: 2017-06-08

Abstract

The present disclosure relates to a high-pressure reactor for continuous hydrolysis of lignocellulosic biomass and a method for continuous high-pressure pretreatment. The present disclosure is very useful in continuous high-temperature, high-pressure steam explosion and hydrolysis of biomass because the surface area can be increased and the aspect ratio (fiber width/fiber length) can be decreased through quick hydration and abrasion and various crushed lignocellulosic biomass having different properties can be continuously injected into the high-pressure reactor, regardless of the kind of biomass.

Description

DEVELOPMENT OF BIOMASS PRETREATMENT TECHNOLOGY VIA CONTROLLED FEEDING SYSTEM OF FIBROUS BIOMASS INTO CONTINUOUS HIGH-PRESSURE REACTOR

This invention relates to the novel devices for preparing lignocellulosic biomass via continuous process of high-pressure pretreatment. Simultaneously, this invention also relates to a method development of continuous high-temperature and high-pressure pretreatment using the same devices. In addition, a continuous high-pressure reactor for lignocellulosic biomass pretreatment was also developed. These series of technology development would include; 1) biomass hydrate preparation and hydrate feeding system, producing lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio via continuous process of rapid hydration and rough grinding of lignocellulosic biomass; 2) compression process and compressed biomass hydrate feeding system, squeezing the biomass hydrate with a single-screw and conveying them to a high-pressure reaction unit; 3) a continuous process of high-pressure pretreatment and the high-pressure reactor, pretreating the compressed biomass hydrate under continuous high-pressure conditions.

When the fibrous biomass hydrate is continuously fed into a single-screw extrusion of a compressed biomass hydrate feeding system, in order to uniformly disperse and distribute fibrous biomass hydrate into a single-screw extrusion system, compressed air is periodically injected to the biomass hydrate. Then, biomass hydrate is compressed by a single-screw and conveyed to the high-pressure reactor.

The present patent application claims priority from Korean Patent Application No. 10-2015-0171193 filed on December 3, 2015 and Korean Patent Application No. 10-2016-0128976 filed on October 6, 2016 in the Republic of Korea, the disclosures of which were incorporated herein.

In general, lignocellulosic biomass refers to plant biomass on the Earth. It contains cellulose, hemicellulose and lignin as structural components as well as proteins, minerals and the more as extractable components. Among structural components, cellulose (30-55%) and hemicellulose (15-25%) are carbohydrates that can be converted to fermentable sugars, while the remaining lignin (15-35%) is as the aromatic polymer compound. Although types and availability of lignocellulosic biomass would vary greatly depending on locations, at the moment, agricultural byproducts such as corn stover, rice straw, wheat straw, empty fruit bunch of oil palm, etc., energy crops such as pampas grass, reed, switch grass, white birch, willow, etc., food industry byproducts, and industrial wastes such as waste wood are important industrial sources for lignocellulosic biomass.

In order to obtain microbial metabolites such as fermentable sugar, bio-alcohol, etc. from lignocellulosic biomass in consideration of industrial utilization, a series of physicochemical conversion processes including pretreatment, acid saccharification, and enzymatic hydrolysis of biomass are required. In particular, in terms of cost aspect, biomass pretreatment is very critical to determine the most of economic feasibility during sugar production, while sugar productivity and yields are also quite important. Until now, various methods and techniques in biomass pretreatment area have been studied. For instance, depending on solvents and catalysts used, many pretreatment methods are available such as steam explosion, acid treatment, alkali treatment, organic solvent treatment, oxidizing agent treatment, supercritical ammonia pretreatment, etc.

Among these pretreatment, the acid or alkali catalyst pretreatment is usually performed at high temperatures of 100 ℃ or higher in order to obtain high efficiency using no or a small amount of chemicals. However, in order to add heated water together as a reactant to 100 ℃ or higher, a high-pressure reaction apparatus that can endure the pressure on the vapor pressure curve of water is necessary. For example, because the vapor pressure of water at 200 ℃ is 15 atm or higher, a specialized high-pressure reactor has to be used in the pretreatment process.

The high-pressure reactors commonly used in researches are stirred batch reactors. Examples include the laboratory-scale stirred Parr reactor of Parr Instrument (Moline, IL). Although the high-pressure batch reactor can endure the water vapor pressure at 300 ℃, it cannot treat a large quantity of biomass continuously. Examples of a continuous high-pressure reactor that can be used for continuous high-pressure reactions of lignocellulosic biomass include the Carbofrac series of Biogasol (Denmark), SuPR2G of AdvanceBio (USA), etc. Carbofrac is semi-continuous in that the reactor is operated by opening and closing valves before and after a high-pressure reaction unit for intermittent injection of biomass and it is very costly because various valve technologies are employed. On the other hand, SuPR2G is a continuous high-pressure reactor in the true sense of the word because flowable compressed biomass is formed using a single screw and, thus, biomass can be injected continuously into a high-pressure cylinder without leakage of steam outside the cylinder. In addition, it is advantageous in that the machinery is relatively simple and inexpensive.

However, a high degree of skill is required to continuously inject biomass into a high-pressure cylinder using a plug screw feeder consisting of a single screw and plug pipe, as in SuPR2G, and even a skilled engineer often experiences problems that make continuous pretreatment impossible, such as leaking of steam out of the high-pressure cylinder or bursting of hydrate when lignocellulosic biomasses with different properties such as wood chip, etc. are continuously injected into the high-pressure cylinder, stoppage of the single screw as due to excessive torque applied to a single screw driving motor when the biomass is not stably injected into the high-pressure cylinder, etc.

The inventors of the present disclosure have found out, after carrying out many researches on continuous and effective injection of various lignocellulosic biomasses such as empty fruit bunch of oil palm, miscanthus, reed, acacia wood, white birch, etc. into a continuous high-pressure reactor equipped with a plug screw feeder consisting of a single screw in order to inject the biomass into a high-pressure cylinder, that by preparing a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio (fiber width/fiber length) through quick hydration and abrasive grinding and supplying the same in the form of a compressed biomass hydrate by compressing with a screw or supplying the same onto a single screw in the form of a wet powder. Compressed air was periodically injected to the biomass hydrate so as to uniformly disperse and redistribute it on a single screw, when the biomass hydrate was supplied with a plug screw feeder consisting of the single screw to a high-pressure reaction unit in the form of a compressed biomass hydrate. Finally, continuous high-pressure pretreatment of the lignocellulosic biomass becomes possible because the biomass can be stably supplied into the high-pressure reactor and have completed the present disclosure.

The present disclosure is directed to providing a continuous high-pressure reactor for pretreatment of a lignocellulosic biomass with an improved raw material supply unit such that various lignocellulosic biomasses having different properties can be continuously and stably supplied into the high-pressure reactor in order to improve the disadvantage of a continuous high-pressure reactor having a single screw type biomass injector that a high degree of skill is required and various kinds of biomasses cannot be used and a method for continuous high-pressure pretreatment using the same.

In one aspect of the present disclosure, there is provided a continuous high-pressure reactor wherein a biomass hydrate preparation and supply unit which is capable of saturating the inside pore of biomass with water and increasing the surface area of and decreasing the aspect ratio (fiber width/fiber length) of the ground biomass by applying mechanical abrasion to hydrate crushed lignocellulosic biomass with water; and a compressed biomass hydrate supply unit which forms a compressed biomass hydrate by compressing the supplied biomass hydrate with a screw and supplies the same to a high-pressure cylinder are equipped in front of the continuous high-pressure reactor which hydrolyzes the lignocellulosic biomass, so that continuous biomass injection is possible regardless of the kind of the lignocellulosic biomass, and a method for continuous high-pressure pretreatment of a lignocellulosic biomass using the same.

In another aspect of the present disclosure, there is provided a continuous high-pressure reactor wherein a biomass hydrate preparation and supply unit which is capable of saturating the inside pore of biomass with water and increasing the surface area of and decreasing the aspect ratio (fiber width/fiber length) of the ground biomass by applying mechanical abrasion to hydrate crushed lignocellulosic biomass with water; a device which uniformly disperses and redistribute the supplied biomass hydrate on a single screw by periodically injecting compressed air to the biomass hydrate and a compressed biomass hydrate supply unit which forms a compressed biomass hydrate by compressing the supplied biomass hydrate with a screw and supplies the same to a high-pressure cylinder are equipped in front of the continuous high-pressure reactor which hydrolyzes the lignocellulosic biomass, so that continuous biomass injection is possible regardless of the kind of the lignocellulosic biomass, and a method for continuous high-pressure pretreatment of a lignocellulosic biomass using the same.

More specifically, the present disclosure provides a continuous high-pressure reactor for pretreatment of a lignocellulosic biomass, including: a biomass hydrate preparation and supply unit which prepares and supplies a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of a continuously supplied lignocellulosic biomass; a compressed biomass hydrate supply unit which is connected to the biomass hydrate preparation and supply unit, forms a compressed biomass hydrate by compressing the supplied biomass hydrate with a screw and supplies the same to a high-pressure reaction unit; and the high-pressure reaction unit which is connected to the compressed biomass hydrate supply unit and performs pretreatment using the supplied compressed biomass hydrate.

Also, the present disclosure provides a continuous high-pressure reactor for pretreatment of a lignocellulosic biomass, including: a biomass hydrate preparation and supply unit which prepares and supplies a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of a continuously supplied lignocellulosic biomass; a compressed biomass hydrate supply unit which is connected to the biomass hydrate preparation and supply unit, forms a compressed biomass hydrate by compressing the supplied biomass hydrate with a screw and supplies the same to a high-pressure reaction unit; a biomass hydrate redisposition unit which is located between the biomass hydrate preparation and supply unit and the compressed biomass hydrate supply unit and on top of the screw of the compressed biomass hydrate supply unit and includes a plurality of compressed air injection nozzles which periodically inject compressed air toward the screw; and the high-pressure reaction unit which is connected to the compressed biomass hydrate supply unit and performs pretreatment using the supplied compressed biomass hydrate.

The compressed biomass hydrate supply unit may supply the compressed biomass hydrate continuously while the high pressure of the high-pressure reaction unit is maintained by the compressed biomass hydrate compressed by the single screw.

The biomass hydrate preparation and supply unit may be a twin screw extruder or a disc type grinder. The twin screw extruder may include a pair of mixing screws having a screw profile consisting of a forward conveying screw element, a forward kneading block and a reverse kneading block.

The biomass hydrate redisposition unit which uniformly disperses and distributes the biomass hydrate on the single screw by periodically injecting compressed air to the hydrate may be configured by equipping a nozzle for injecting compressed air in one or more compartment wherein the biomass hydrate is filled by the single screw which rotates and compresses the biomass hydrate in order to convey it to the high-pressure reaction unit and further equipping an air pump and a controller for periodically supplying compressed air to the nozzle outside thereof.

A method for continuous high-pressure pretreatment of a lignocellulosic biomass according to the present disclosure may include: a biomass supply step of continuously supplying a lignocellulosic biomass; a biomass hydrate preparation and supply step of preparing and supplying a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of the supplied biomass; a compressed biomass hydrate supply step of forming and supplying a compressed biomass hydrate by compressing the biomass hydrate with a screw; and a biomass pretreatment step of pretreating the supplied compressed biomass hydrate using a high-pressure reactor.

Also, a method for continuous high-pressure pretreatment of a lignocellulosic biomass according to the present disclosure may include: a biomass supply step of continuously supplying a lignocellulosic biomass; a biomass hydrate preparation and supply step of preparing and supplying a fibrous lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of the supplied biomass; a biomass hydrate redisposition step of uniformly dispersing and distributing the supplied biomass hydrate on a single screw by periodically injecting compressed air to the hydrate; a compressed biomass hydrate supply step of forming and supplying a compressed biomass hydrate by compressing the biomass hydrate with a screw; and a biomass pretreatment step of pretreating the supplied compressed biomass hydrate using a high-pressure reactor.

In the compressed biomass hydrate supply step, the compressed biomass hydrate may be supplied continuously while the high pressure of 15 bar or higher of a high-pressure reaction unit is maintained by the compressed biomass hydrate compressed by the single screw.

In the biomass hydrate preparation and supply step, the quick hydration and abrasive grinding of the biomass may be performed using a twin screw extruder or a disc type grinder.

The lignocellulosic biomass hydrate supplied in the biomass hydrate preparation and supply step may contain 35-75 wt%, more specifically 45-65 wt%, of water. The biomass hydrate may have an aspect ratio (fiber width/fiber length) of 0.4 or smaller, more specifically 0.25 or smaller. The biomass hydrate may have a fiber width of 20-50 μm, more specifically 26-40 μm, and a fiber length of 0.1-10 mm, more specifically 0.5-5 mm.

A continuous high-pressure reactor for pretreatment of a lignocellulosic biomass with an improved raw material supply unit of the high-pressure reactor and a method for continuous high-pressure pretreatment using the same can increase surface area and decrease aspect ratio (fiber width/fiber length) through quick hydration and abrasive grinding of a lignocellulosic biomass. In addition, because a biomass hydrate with a fiber width in a specific range can be prepared and uniformly supplied to a single screw for conveying to a high-pressure reaction unit regardless of the kind of biomass, various lignocellulosic biomasses having different properties can be continuously and easily supplied into the high-pressure reactor.

FIG. 1 schematically shows a continuous high-pressure reactor for pretreatment of a lignocellulosic biomass according to an exemplary embodiment of the present disclosure.

FIG. 2 is a cross-sectional view of a twin screw extruder as a biomass hydrate preparation and supply unit according to an exemplary embodiment of the present disclosure.

FIG. 3 is a cross-sectional view of a compressed biomass hydrate supply unit according to an exemplary embodiment of the present disclosure.

FIG. 4 is a cross-sectional view showing a twin screw extruder as a biomass hydrate preparation and supply unit and a compressed biomass hydrate supply unit coupled according to an exemplary embodiment of the present disclosure.

FIG. 5 is a cross-sectional view of a disc type grinder as a biomass hydrate preparation and supply unit according to an exemplary embodiment of the present disclosure.

FIG. 6 is a cross-sectional view showing a disc type grinder as a biomass hydrate preparation and supply unit and a compressed biomass hydrate supply unit coupled according to an exemplary embodiment of the present disclosure.

FIG. 7 is a process chart of a method for continuous pretreatment of a lignocellulosic biomass according to an exemplary embodiment of the present disclosure.

FIG. 8 shows the internal pressure of a high-pressure reactor and the relative torque ratio of a hydrate compressing screw depending on operation time according to an exemplary embodiment of the present disclosure.

FIG. 9 is a schematic view of a compressed hydrate supply unit which non-uniformly supplies a biomass hydrate seen from the side.

FIG. 10 is a schematic view of a compressed hydrate supply unit which non-uniformly supplies a biomass hydrate seen from the front.

FIG. 11 is a schematic view of a compressed hydrate supply unit which non-uniformly supplies a biomass hydrate seen from above.

FIG. 12 is a cross-sectional view of a device according to an exemplary embodiment of the present disclosure wherein a biomass hydrate redisposition unit having compressed air injection nozzles is equipped on top of a compressed hydrate supply unit in order to overcome non-uniform supply of a biomass hydrate.

FIG. 13 is a lateral cross-sectional view of a device according to an exemplary embodiment of the present disclosure wherein a biomass hydrate redisposition unit having compressed air injection nozzles is equipped on top of a compressed hydrate supply unit in order to overcome non-uniform supply of a biomass hydrate.

FIG. 14 is a schematic view for explaining the operation principle of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure.

FIG. 15 is a schematic view of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure seen from above.

FIG. 16 is a schematic view seen from the side for explaining the operation principle of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure.

FIG. 17 is a schematic view seen from the front for explaining the operation principle of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure.

FIG. 18 shows a result of operating a pretreatment apparatus without using a biomass hydrate redisposition unit having compressed air injection nozzles according to an exemplary embodiment of the present disclosure.

FIG. 19 shows a result of operating a pretreatment apparatus using a biomass hydrate redisposition unit having compressed air injection nozzles according to an exemplary embodiment of the present disclosure.

FIG. 20 is a process chart of a method for continuous high-pressure pretreatment of a lignocellulosic biomass according to an exemplary embodiment of the present disclosure.

Hereinafter, the present disclosure is described in detail.

First, in the present disclosure, a lignocellulosic biomass which is desired to be continuously injected to a continuous high-pressure reactor refers to most of terrestrial plants containing cellulose, hemicellulose and lignin as structural components. Examples include agricultural byproducts such as corn stover, rice straw, wheat straw, empty fruit bunch of oil palm, etc., energy crops such as miscanthus, reed, switch grass, white birch, willow, etc., waste wood, etc., which are drawing attentions as industrial raw materials at present. In the present disclosure, these lignocellulosic biomasses may be used as raw materials regardless of whether they are dried or contain water.

In the present disclosure, the continuous high-pressure reactor which is used for continuous high-pressure hydrolysis of a lignocellulosic biomass refers to a device which forms a compressed hydrate that can endure high pressure by compressing a raw material ground at normal temperature and normal pressure with a single screw and continuously injects the same to a high-pressure reaction unit. Examples include SuPR2G of AdvanceBio (USA).

In the present disclosure, an apparatus which is further equipped in front of a raw material injection inlet of the continuous high-pressure reactor to allow for easy injection regardless of the kind of biomass is an apparatus which is capable of saturating the inside pore of biomass with water and at the same time decreasing aspect ratio (fiber width/fiber length) and increasing surface area of the crushed lignocellulosic biomass through quick hydration and abrasive grinding and is capable of preparing a biomass hydrate with a fiber width in a specific range regardless of the kind of the biomass. Examples of currently available products include a twin screw extruder formed of mixing screws, a disc type grinder designed for refining, etc. The twin screw extruder or the disc type grinder as the device which makes the supply of a raw material into the continuous high-pressure reactor of the present disclosure may be any one that can be attached in front of the high-pressure reactor as long as it is effective in increasing the surface area and decreasing the aspect ratio (fiber width/fiber length) through quick hydration and abrasive grinding of the lignocellulosic biomass. Also, additional devices may be added to exert such function. For example, when the twin screw extruder or the disc type grinder is equipped in front of the continuous high-pressure reactor, a continuous screw press or a continuous centrifuge may be added between it and the continuous high-pressure reactor in order to remove excess water or recover extractable components.

The twin screw extruder equipped to provide the continuous high-pressure reactor with an improved raw material supply function of the present disclosure should be equipped with a quantitative water supplier in order to supply water for mechanical abrasion of the raw material and should have enough number of mixing screws in order to ensure violent abrasion and conveying of the raw material. It is desired that a forward or reverse kneading block commonly used in polymer extrusion is used as the mixing screw. The number of the kneading blocks may be varied depending on the raw material in order to control the aspect ratio (fiber width/fiber length) and surface area of the ground biomass hydrate. If the number of the kneading blocks is insufficient, the effect of decreasing the aspect ratio (fiber width/fiber length) and the increasing the surface area of the ground biomass hydrate is slight and a continued operation under such a condition may cause a durability problem due to excessive friction inside the barrel and between the screws of the twin screw extruder because of insufficient grinding of the biomass. On the contrary, if the number of the kneading blocks is excessive, the amount that can be ground per unit time and treatment efficiency are decreased and the grinding efficiency may be negatively affected because continuous supply becomes difficult due to backflow of water to the raw material supply unit. Accordingly, it is desired that the biomass such as miscanthus, reed, wood chip, etc. is ground by adequately arranging kneading blocks corresponding to about 10-30% of the total screws together with a forward conveying screw. For such raw materials as empty fruit bunch of oil palm, sunflower, corn stover, etc., 20-40% is desired.

And, the disc type grinder equipped to provide the continuous high-pressure reactor with an improved raw material supply function of the present disclosure should also be equipped with a mixer capable of uniformly wetting the ground biomass with water before the injection of the raw material or a quantitative water supplier in order to supply water for mechanical abrasion of the raw material. The type and spacing of the discs should be selected such that violent abrasion occurs mainly and the generation of fines with a fiber length of 200 μm or smaller is minimized while the aspect ratio (fiber width/fiber length) of the ground biomass is decreased and its surface area is increased.

Because of the twin screw extruder or the disc type grinder, the continuous high-pressure reactor with an improved raw material supply function of the present disclosure can form a compressed hydrate which is solid and has appropriate fluidity by controlling the degree of grinding aspect ratio, surface area and water content of the biomass in advance and can safely convey the same to the high-pressure reaction unit. The ground biomass hydrate has a water content of 35-75%, more specifically 45-65%, by weight before being conveyed to the single screw for formation of the compressed hydrate. Most importantly, the supplied biomass hydrate has an aspect ratio (fiber width/fiber length) of specifically 0.4 or smaller, more specifically 0.25, a fiber width of specifically 20-50 μm, more specifically 26-40 μm, and a fiber length of specifically 0.1-10 mm, more specifically 0.5-5 mm. When the biomass hydrate satisfies this condition, the compressed biomass hydrate can be formed easily by the single screw.

However, the prepared biomass hydrate may form a plug when it is dropped conveyed to a compressed hydrate supply unit of a continuous high-pressure pretreatment apparatus by gravitation due to adhesion between the fine particles constituting the biomass hydrate. Because the plug tends to be hardly fluid (channeling) rather than uniformly disperse and settle in screw grooves, the compressed hydrate is not smoothly conveyed to the high-pressure reaction unit. Also, even when the plug can be conveyed as they are broken up and settled in the grooves of the screw, it may aggregate again or form a channel due to adhesion of the fine particles.

FIG. 9 is a schematic view of a compressed hydrate supply unit which non-uniformly supplies a biomass hydrate seen from the side, FIG. 10 is a schematic view of the compressed hydrate supply unit which non-uniformly supplies a biomass hydrate seen from the front and FIG. 11 is a schematic view of the compressed hydrate supply unit which non-uniformly supplies a biomass hydrate seen from above.

As seen from FIGS. 9-11, the hydrate is retained at a specific portion of the inner wall of the supply unit as the screw rotates. As a result, the biomass hydrate is non-uniformly conveyed to the high-pressure reaction unit and formation of a compressed hydrate with enough solidity is hindered. The loosely formed compressed hydrate may burst without enduring the steam pressure inside the high-pressure reaction unit and may flow backward in the high-pressure reaction unit together with steam. This may result in the stoppage of the operation of the pretreatment apparatus. As seen from FIG. 18, which shows a result of operating the pretreatment apparatus without using the biomass hydrate redisposition unit having compressed air injection nozzles according to an exemplary embodiment of the present disclosure, abnormal stoppage of operation may occur due to the bursting of the compressed hydrate or the backflow of steam in the high-pressure reaction unit.

Therefore, in the present disclosure, a compressed air injection system equipped on top of the single screw was developed to stably convey the biomass hydrate introduced into the compressed hydrate supply unit to the high-pressure reaction unit.

FIG. 12 is a cross-sectional view of a device according to an exemplary embodiment of the present disclosure wherein a biomass hydrate redisposition unit having compressed

air injection nozzles

1, 2 is equipped on top of a compressed hydrate supply unit in order to overcome non-uniform supply of a biomass hydrate and FIG. 13 is a lateral cross-sectional view.

FIG. 14 is a schematic view for explaining the operation principle of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure and FIG. 15 is a schematic view of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure seen from above.

In the present disclosure, three or four nozzles injecting compressed air are equipped at four corners in front of or above a biomass hydrate supply unit 21 such that the flow of a dropping hydrate is not interrupted by the compressed air system, as shown in FIG. 14 and FIG. 15. Compressed

air injection nozzles

1, 2, 3, 4 may be equipped at four corners in the compressed hydrate supply unit. The

nozzles

1, 2 and 3 are compulsory but the nozzle 4 is optional. The compressed air injection time and order of each nozzle may be set differently depending on the speed of the sample dropped and conveyed from the biomass hydrate supply unit 21 and the rotation speed of the screw of the compressed hydrate supply unit. Specifically, the

nozzles

2 and 3 may operate at the same time a few seconds after the operation of the nozzle 1 has been completed, such that the nozzle 1 does not operate simultaneously with the

nozzles

2 and 3. The pressure of the compressed air may be set differently depending on the apparent specific gravity of the hydrate. The pressure may be set such that the dropped and conveyed biomass hydrate can be broken up and disperse and settle uniformly in screw grooves. For example, when the apparent specific gravity of the biomass hydrate is 100-200 kg/m³, the pressure of the compressed air may be 7-9 MPa.

Hereinafter, the present disclosure is described in detail through examples. The following examples are for illustrative purpose only and the scope of the present disclosure is not limited by the examples.

Apparatus 1: Continuous high-pressure reactor with twin screw extrusion function

FIG. 2 is a cross-sectional view of a twin screw extruder 10 as a biomass hydrate preparation and supply unit according to an exemplary embodiment of the present disclosure.

The twin screw extruder 10 includes a pair of mixing screws 14 having a screw profile consisting of a forward kneading block 11 and a forward conveying screw element 12 and a reverse kneading block 13 having different pitches. A lignocellulosic biomass is supplied through a biomass supply unit 15 and an adequate amount of water is supplied by a water supplier (not shown). A lignocellulosic biomass hydrate is prepared by the pair of mixing screws 14 through quick hydration and abrasive grinding and supplied to a compressed biomass hydrate supply unit 20 shown in FIG. 3 through a biomass hydrate outlet 16.

FIG. 3 is a cross-sectional view of a compressed biomass hydrate supply unit 20 according to an exemplary embodiment of the present disclosure.

The compressed biomass hydrate supply unit 20 is supplied with the lignocellulosic biomass hydrate with increased surface area and decreased aspect ratio through the biomass hydrate outlet 16 of the twin screw extruder 10 shown in FIG. 2, through a biomass hydrate supply unit 21. The compressed biomass hydrate supply unit 20 forms a compressed hydrate that can endure high pressure by conveying and compressing the biomass hydrate with a single screw 22 and continuously conveys the same to a high-pressure reaction unit 30. Various forms of pretreatment processes may be applied to the conveyed compressed hydrate in the high-pressure reaction unit 30.

Apparatus 2: Continuous high-pressure reactor with mechanical refining function

FIG. 5 is a cross-sectional view of a disc type grinder 40 as a biomass hydrate preparation and supply unit according to an exemplary embodiment of the present disclosure.

The disc type grinder consists of a rotor 41, a driving motor 42, a biomass supply unit 43, grinding units 44 and a biomass hydrate outlet 45. A lignocellulosic biomass is supplied through the biomass supply unit 43 and an adequate amount of water is supplied by a water supplier (not shown). By a pair of the grinding units 44 rotating in opposite directions, a lignocellulosic biomass hydrate is prepared through quick hydration and abrasive grinding and then supplied to a compressed biomass hydrate supply unit 20 shown in FIG. 6 through the biomass hydrate outlet 45.

The compressed biomass hydrate supply unit is the same as described above referring to FIG. 4 and FIG. 6 is a cross-sectional view showing a disc type grinder as a biomass hydrate preparation and supply unit and a compressed biomass hydrate supply unit coupled according to an exemplary embodiment of the present disclosure.

Apparatus 3: Continuous high-pressure reactor with compressed air injection system

Compressed air injection nozzles were equipped at an upper part inside a compressed hydrate supply unit of the continuous high-pressure reactor SuPR2G as shown in FIG. 12 and FIG. 13. An air compressor for supplying compressed air and a controller for sequentially supplying the compressed air to the four nozzles were equipped outside the apparatus.

Example 1: Operation of continuous high-pressure reactor using apparatus 1

After installing a 10-mm screen on a plastic grinder (Korea Pulverizing Machinery, Incheon, Korea), samples were prepared by crushing empty fruit bunch of oil palm (Indonesian), miscanthus (Korean), acacia chip (Vietnamese) and corn stover (Korean) as lignocellulosic biomasses.

While continuously supplying 4 kg of the crushed empty fruit bunch of oil palm and 6 L of deionized water per hour through the raw material injection inlet of the high-pressure reactor of the apparatus 1, a biomass hydrate was formed by operating a twin screw extruder wherein about 10-40% of a forward kneading block of total screws is arranged adequately together with a forward conveying screw element at 100 rpm. At the same time, a high-temperature, high-pressure reaction was performed continuously at 200 ℃ and 15.55 bar while injecting the raw material into the high-pressure reactor through the single screw type compressed hydrate supply unit and it was investigated whether the pressure was maintained normally. The result is shown in Table 1 and FIG. 8. During this procedure, some of the biomass hydrate was taken and the mean aspect ratio (fiber width/fiber length) of the ground fiber was measured in an aqueous solution with a concentration of less than 1% using the L&W fiber tester plus+ (Lorentzen & Wettre, Sweden). In addition, standard freeness as the measure of the freeness of the fiber in the biomass hydrate and water retention as the measure of free water present inside and between fibers were measured according to TAPPI T-227 and J.TAPPI No. 26, respectively.

This procedure was repeated for the pampas grass, empty fruit bunch of oil palm, acacia and corn stover samples. The result is shown in Table 1, Table 2 and FIG. 8.

Example 2: Operation of continuous high-pressure reactor using compressed air injection system

FIG. 16 is a schematic view seen from the side for explaining the operation principle of compressed air injection nozzles and a compressed hydrate supply unit according to an exemplary embodiment of the present disclosure and FIG. 17 is a schematic view seen from the front. While supplying a biomass hydrate to the apparatus 3 of the present disclosure, compressed air was injected through a nozzle 1 when the hydrate was retained on the inner wall of the supply unit and a channel resisting the movement of a screw was about to be formed, in order to break up the hydrate retained on the inner wall of the supply unit and disperse it toward the advancing direction of the screw. Although an empty space was formed instantly around the inner wall of the supply unit in the advancing direction of the screw, the screw was rotated continuously and the hydrate was quickly conveyed to the empty space by injecting compressed air from

nozzles

2 and 3 so as to form a compressed hydrate without formation of an additional channel.

The injection of compressed air from the

nozzles

2 and 3 shown in FIG. 17 can be explained with a cross-sectional view of the hydrate supply unit seen from the front. The channel observed at the front is caused by the retention of the hydrate on the inner wall of the supply unit in the advancing direction of the screw and the hydrate dispersed by the injection of compressed air from the nozzle 1, likewise the one formed at the side. Compressed air is injected simultaneously from the

nozzles

2 and 3 in order to destroy the channel. The empty space formed at the injection location is quickly filled by the hydrate owing to the rotating screw and the injection from the nozzle 1 and the hydrate for forming the compressed hydrate can be supplied without formation of a channel.

Comparative Example 1: Continuous high-pressure reaction for various biomasses

Biomass was ground to a particle size similar to that of the biomass hydrate of Example 1 using cutting mills of a plastic grinder (Korea Pulverizing Machinery, Incheon, Korea) and a food grinder (Daehwa Precision, Daegu). 4 kg of the ground biomass was added to a 100-L rubber bucket. After adding 6 L of water, water was absorbed into the ground biomass by stirring for 3 minutes with 30-minute intervals, for a total of 6 hours. During this procedure, some of the biomass hydrate was taken and the mean aspect ratio (fiber width/fiber length) of the ground fiber was measured in an aqueous solution with a concentration of less than 1% using the L&W fiber tester plus+ (Lorentzen & Wettre, Sweden). In addition, Canadian standard freeness (CSF) as the measure of the freeness of the fiber in the biomass hydrate and water retention as the measure of free water present inside and between fibers were measured according to TAPPI T-227 and J.TAPPI No. 26, respectively.

A high-pressure reaction was performed by supplying the sample directly into a continuous high-pressure reactor SuPR2G operated by a single screw and it was investigated whether the high-pressure reaction proceeded normally. The result is shown in Table 1, Table 2 and FIG. 8.

	Biomass	Standard freeness(mL)	Water retention (%)	Mean fiber width(μm)	Applicable high-pressure reactor internal pressure (bar)
Example 1	Twin ground pampas grass	548	109	32.7±14.7	~15.6
	Twin ground empty fruit bunch of oil palm	588	148	26.8±12.2	~15.6
	Twin ground acacia	528	107	28.3±12.1	~15.6
	Twin ground corn stover	508	212	35.0±16.6	~15.6
Comparative Example 1	Cutting ground pampas grass	660	107	36.0±15.7	~4
	Cutting ground empty fruit bunch of oil palm	568	120	37.0±17.0	~10
	Cutting ground acacia	619	87	31.9±14.1	~2
	Cutting ground corn stover	670	213	42.3±16.3	~10

The standard freeness (CSF, mL) and water retention (%) of biomass hydrates are indicative of the freeness of the fiber in the biomass hydrate and free water present inside and between fibers, respectively. A smaller standard freeness value means improved freeness and a higher water retention value means more free water present inside and between fibers.

To compare the result for the twin ground (ground by the twin screw extruder) biomass hydrates of Example 1 with that for the cutting ground biomass hydrates of Comparative Example 1, it can be seen that the standard freeness and water retention of the twin ground biomass hydrates were improved by up to 20%. This means that the continuous preparation of a biomass hydrate using a twin screw extruder according to the present disclosure is useful in that the freeness of the fiber in the biomass hydrate is improved and the biomass can be sufficiently hydrated even inside the fibers.

From the mean fiber width measurement result shown in Table 1, it can be seen that the mean width of the twin ground biomass hydrates is 20-40 μm, decreased by up to 27% as compared to the cutting ground biomass hydrates.

The result of performing the high-pressure reaction using SuPR2G for the biomass hydrates of Example 1 and Comparative Example 1 was as follows. When the twin ground biomass hydrates were used as raw materials, the compressed biomass hydrate was continuously conveyed into the reactor without any problem even when the internal pressure of the high-pressure reactor was increased to 15.6 bar, regardless of the kind of the biomass. At this time, the temperature inside the reactor was 200 ℃. In contrast, when the cutting ground biomass hydrates were used as raw materials, the pressure could be increased to 10 bar only for particular samples and the continuous high-pressure pretreatment was impossible because of such problems as stoppage of sample supply due to overload of the single screw supplying the compressed hydrate, leaking of steam out of the high-pressure reactor or bursting of the hydrate.

Accordingly, it was confirmed that the twin ground hydrates have improved standard freeness and water retention as compared to the cutting ground biomass hydrates and the decrease in aspect ratio allows for higher pressure inside the high-pressure reactor because a solid and tight compressed biomass hydrate can be formed by the single screw.

The mean aspect ratio (fiber width/fiber length) of the ground biomass hydrates for different particle sizes is shown in Table 2. The biomass hydrate has a spherical or square shape as the value is closer to 1 and has a long and thin shape as the value is closer to 0.

	Biomass	Mean aspect ratio
	Biomass	[a,b)	[b,c)	[c,d)	[d,e)	[e,f)	[f,g)	[g,h)
Example 1	Twin ground pampas grass	0.23(±0.11)	0.14(±0.07)	0.10(±0.04)	0.07(±0.03)	0.06(±0.02)	0.06(±0.02)	0.05(±0.02)
	Twin ground empty fruit bunch of oil palm	0.19(±0.09)	0.11(±0.05)	0.07(±0.03)	0.06(±0.02)	0.05(±0.02)	0.04(±0.02)	0.04(±0.02)
	Twin ground acacia	0.19(±0.08)	0.13(±0.05)	0.10(±0.04)	0.08(±0.03)	0.07(±0.03)	0.07(±0.02)	0.05(±0.02)
	Twin ground corn stover	0.24(±0.11)	0.16(±0.08)	0.12(±0.06)	0.08(±0.04)	0.07(±0.03)	0.06(±0.03)	0.05(±0.02)
Comparative Example 1	Cutting ground pampas grass	0.25(±0.11)	0.17(±0.07)	0.12(±0.05)	0.09(±0.04)	0.07(±0.03)	0.07(±0.03)	0.06(±0.03)
	Cutting ground empty fruit bunch of oil palm	0.26(±0.12)	0.16(±0.08)	0.11(±0.05)	0.08(±0.04)	0.07(±0.03)	0.06(±0.03)	0.05(±0.02)
	Cutting ground acacia	0.21(±0.09)	0.15(±0.06)	0.12(±0.05)	0.10(±0.03)	0.08(±0.03)	0.07(±0.03)	0.07(±0.02)
	Cutting ground corn stover	0.29(±0.11)	0.19(±0.08)	0.13(±0.05)	0.11(±0.04)	0.09(±0.03)	0.08(±0.03)	0.06(±0.02)

It can be seen that, for the samples with small particle sizes, the mean aspect ratio of the twin ground biomass hydrates was decreased by up to 25% as compared to the cutting ground biomass hydrates, regardless of the kind of biomass. This means that the twin ground biomass hydrate is formed of a fiber having a long and thin shape like a needle. The mean aspect ratio of the twin ground biomass hydrate having a similar fiber length as the cutting ground hydrate has decreased because it has a decreased fiber width. The formation of the biomass hydrate having a long and thin shape greatly affects the fiber flexibility, which is favorable for the formation of the solid and tight compressed hydrate. This results correspond to those of Table 1.

FIG. 8 shows the internal pressure of the high-pressure reactor and the relative torque ratio of the hydrate compressing screw depending on operation time according to an exemplary embodiment of the present disclosure. When the high-pressure reaction was performed using SuPR2G for the biomass hydrate prepared using the apparatus 1 in Example 1, the compressed biomass hydrate could be continuously conveyed from the single screw supplying the compressed hydrate into the high-pressure reactor as the internal pressure of the high-pressure reactor was increased to 15.6 bar. This means that the tight compressed hydrate acts as a valve which prevents leaking of steam out of the high-pressure reactor and, at the same time, it is continuously supplied into the reactor.

FIG. 18 shows a result of operating the pretreatment apparatus without using a biomass hydrate redisposition unit having compressed air injection nozzles according to an exemplary embodiment of the present disclosure and FIG. 19 shows a result of operating the pretreatment apparatus using the biomass hydrate redisposition unit having compressed air injection nozzles according to an exemplary embodiment of the present disclosure.

As seen from FIG. 19, when the pretreatment apparatus was operated using the compressed air injection system, the torque applied to the single screw of the compressed hydrate supply unit and the pressure inside the high-pressure reaction unit are almost constant without large variation. This means that the hydrate is supplied uniformly to the compressed hydrate supply unit without formation of a plug or a channel and a rigid and tight compressed hydrate is formed continuously. In contrast, as seen from FIG. 18, when the pretreatment apparatus was operated without using the compressed air injection system, the torque applied to the single screw of the compressed hydrate supply unit decreased gradually as the pressure inside the high-pressure reaction unit was increased. This result means that a compressed hydrate that can endure the pressure inside the high-pressure reaction unit is not formed because the hydrate is not smoothly conveyed to the compressed hydrate supply unit. If the pretreatment apparatus is operated in this state, the loose compressed hydrate is destroyed and flows backward in the high-pressure reaction unit together with steam, leading to stoppage of the operation. This problem can be solved by the compressed air injection system equipped inside the compressed hydrate supply unit, which allows for stable conveying of the hydrate by the single screw without formation of a hydrate plug or a channel, formation of a rigid and tight compressed hydrate and long-term operation of the pretreatment apparatus at constant pressure.

The present disclosure is applicable to a series of related industries, including pretreatment, acid saccharification, enzymatic hydration, etc. of biomass, for obtaining microbial metabolites for industrial use such as fermentable sugars, bioalcohols, etc. from lignocellulosic biomass.

Claims

A continuous high-pressure reactor for pretreatment of a lignocellulosic biomass, comprising:

a biomass hydrate preparation and supply unit which prepares and supplies a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of a continuously supplied lignocellulosic biomass;

a compressed biomass hydrate supply unit which is connected to the biomass hydrate preparation and supply unit, forms a compressed biomass hydrate by compressing the supplied biomass hydrate with a screw and supplies the same to a high-pressure reaction unit; and

the high-pressure reaction unit which is connected to the compressed biomass hydrate supply unit and performs pretreatment using the supplied compressed biomass hydrate.
A continuous high-pressure reactor for pretreatment of a lignocellulosic biomass, comprising:

a biomass hydrate preparation and supply unit which prepares and supplies a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of a continuously supplied lignocellulosic biomass;

a compressed biomass hydrate supply unit which is connected to the biomass hydrate preparation and supply unit, forms a compressed biomass hydrate by compressing the supplied biomass hydrate with a screw and supplies the same to a high-pressure reaction unit;

a biomass hydrate redisposition unit which is located between the biomass hydrate preparation and supply unit and the compressed biomass hydrate supply unit and on top of the screw of the compressed biomass hydrate supply unit and comprises a plurality of compressed air injection nozzles which periodically inject compressed air toward the screw; and

the high-pressure reaction unit which is connected to the compressed biomass hydrate supply unit and performs pretreatment using the supplied compressed biomass hydrate.
The continuous high-pressure reactor for pretreatment of a lignocellulosic biomass according to claim 1 or 2, wherein the compressed biomass hydrate supply unit supplies the compressed biomass hydrate continuously while the high pressure of the high-pressure reaction unit is maintained by the compressed biomass hydrate compressed by the single screw.
The continuous high-pressure reactor for pretreatment of a lignocellulosic biomass according to claim 1 or 2, wherein the biomass hydrate preparation and supply unit is a twin screw extruder or a disc type grinder.
The continuous high-pressure reactor for pretreatment of a lignocellulosic biomass according to claim 4, wherein the twin screw extruder comprises a pair of mixing screws having a screw profile consisting of a forward conveying screw element, a forward kneading block and a reverse kneading block.
A method for continuous high-pressure pretreatment of a lignocellulosic biomass, comprising:

a biomass supply step of continuously supplying a lignocellulosic biomass;

a biomass hydrate preparation and supply step of preparing and supplying a lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of the supplied biomass;

a compressed biomass hydrate supply step of forming and supplying a compressed biomass hydrate by compressing the biomass hydrate with a screw; and

a biomass pretreatment step of pretreating the supplied compressed biomass hydrate using a high-pressure reactor.
A method for continuous high-pressure pretreatment of a lignocellulosic biomass, comprising:

a biomass supply step of continuously supplying a lignocellulosic biomass;

a biomass hydrate preparation and supply step of preparing and supplying a fibrous lignocellulosic biomass hydrate with an increased surface area and a decreased aspect ratio through quick hydration and abrasive grinding of the supplied biomass;

a biomass hydrate redisposition step of resolving retention of the supplied fibrous lignocellulosic biomass hydrate by periodically injecting compressed air through some of a plurality of compressed air injection nozzles;

a biomass hydrate uniform supply step of uniformly supplying the hydrate with the retention resolved by periodically injecting compressed air through the remaining nozzles of the plurality of compressed air injection nozzles;

a compressed biomass hydrate supply step of forming and supplying a compressed biomass hydrate by compressing the uniformly supplied biomass hydrate with a screw; and

a biomass pretreatment step of pretreating the supplied compressed biomass hydrate using a high-pressure reactor.
The method for continuous high-pressure pretreatment of a lignocellulosic biomass according to claim 6 or 7, wherein, in the compressed biomass hydrate supply step, the compressed biomass hydrate is supplied continuously while the high pressure of a high-pressure reaction unit is maintained by the compressed biomass hydrate compressed by the single screw.
The method for continuous high-pressure pretreatment of a lignocellulosic biomass according to claim 6 or 7, wherein, in the biomass hydrate preparation and supply step, the quick hydration, the abrasive grinding and the supply of the biomass are performed using a twin screw extruder or a disc type grinder.
The method for continuous high-pressure pretreatment of a lignocellulosic biomass according to claim 7, wherein the biomass hydrate redisposition step and the biomass hydrate uniform supply step are repeated alternatingly and, in each step, the injection of compressed air is performed periodically.
The method for continuous high-pressure pretreatment of a lignocellulosic biomass according to claim 6 or 7, wherein the lignocellulosic biomass hydrate supplied in the biomass hydrate preparation and supply step comprises 35-75 wt% of water.
The method for continuous high-pressure pretreatment of a lignocellulosic biomass according to claim 6 or 7, wherein the lignocellulosic biomass hydrate supplied in the biomass hydrate preparation and supply step has a fiber width of 20-50 μm and a fiber length of 0.1-10 mm.
The method for continuous high-pressure pretreatment of a lignocellulosic biomass according to claim 6 or 7, wherein the lignocellulosic biomass hydrate supplied in the biomass hydrate preparation and supply step has an aspect ratio (fiber width/fiber length) of 0.4 or smaller.