Technical Field

The invention concerns method and apparatus for hydrothermal treatment and/or extraction of plant material, especially lignocellulosic material, such as straw, bagasse and corn stover. The current invention provides an apparatus and method for hydrothermal treatment and/or extraction of particulate plant material comprising a pressure-proof cylindric reactor with a lid in one end for loading and unloading of particulate plant material, and with inlet and outlet sockets for liquid and/or steam, outlet socket for air, wherein:

The reactor is equipped with a piston with a perforated piston head.

The invention can be used as bench scale equipment for pretreatment of lignocellulosic material, and as production equipment for extraction and pre-treatment of smaller amounts of plant material, e.g for extracting herbs, perfumes, tea, pharmaceutical products and pharmanutricals .

Background

Large research and development efforts are being made in order to develop feasible methods for conversion of lignocellulosic materials to useful products , primarily fuel ethanol.

Large scale pilots plants are essential to develop industrial methods for the conversion of lignocellulosic materials. However large scale pilot plants are expensive to operate, and it is very costly if the effect of many different process conditions and feedstock compositions has to be investigated, in order to optimise the conversion processes. Therefore small pilot plants or bench scale equipment, which can achieve results that are similar to the results from the large scale plants, would be very useful to accelerate the development of optimal conversion methods for different lignocellulosic products. Most conversion methods comprise a hydrothermal pre-treatment, carried out at elevated temperature and pressure. The most promising conversion methods can work continuously, under pressure, with high dry matter and large particles, where the lignocellulosic material is conveyed from one set of conditions (dry matter concentration, temperature, pH, pressure, residence time) to the next set of conditions. An example is the conversion method described in WO2007009463, Holm Christensen, by which hydrothermal pre-treatment of lignocellulosic material, such as straw, corn stover and bagasse is conducted with at least one soaking/pressing operation, to achieve rapid reaction and effective removal of the solubilised constituents from the fibre fraction and ensure high dry matter content of the fibre fraction before enzymatic hydrolysation.

Another promising method has been developed by Enerkem Technologies, Canada, and is known as the "FIRST" pre-treatment method, wherein the feedstock is impregnated with acid followed by rapid steam treatment. This method can also operate with high solid to liquid ratio.

There are different approaches to what the composition of the liquid should be. One approach is using the liquid fraction from an upstream process step, taking advantage of the generated acetic acid; another approach is to add acid to the make-up water. An entirely different approach is the methods using organic solvents , such as WO 2010/060183 (Hallberg) .

The soaking/pressing operation makes it possible to conduct the hydrothermal pre- treatment without the presence of a free liquid phase, which reduces the energy consumption and leads to a high concentration of acetic acid in the lignocellulosic fibres. The high concentration of acetic acid means that addition of external acid is not necessary.

The absence of a liquid phase and the presence of large particles mean that standard stirred reactors cannot be used for neither the full scale continuous process, nor to simulate it in smaller scale.

Some of the proposed pre-treatment methods include special processing steps in order to reduce the amount of fermentation inhibitors such as furfural, hydroxymethylfurfural and acetic acid in the fermentation feedstock.

The fermentation inhibitors are produced inside the cells and capillaries of the lignocellulosic material, when the combined effect of low pH, high temperature and residence time passes a certain severity, and therefore some methods extract a substantial part of the inhibitors together with other dissolved material, creating a liquid fraction. This approach is e.g. seen in WO 2007/009463 A2 (Holm Christensen) and described in NREL Research Brief "Continual Shrinking-Bed Reactor Boosts Biomass Ethanol" (NREL/BR-420-21221, April 1997) .

Many processes for conversion of lignocellulosic material discharge the material from pre-treatment by steam explosion. Some scientists believe that the steam explosion contributes to breaking the bonds between lignin, hemicelluloses and cellulose, and others believe that the effect, if any, is not sufficient to justify the extra costs.

Reactors for continuous hydrothermal treatment have approximately the same temperature at the wall and at the interior as opposed to batch reactors, where the wall usually has ambient temperature when the process begins.

Impregnation of the pretreated material with enzymes may be improved by pressing the warm material prior to soaking it in a colder enzyme solution, which will then be pulled into the cavities of the lignocellulosic material, because most of the steam in the cavities will condense, and create a vacuum. The enzymes will adhere to the lignocellulosic material, and therefore the surplus liquid can be pressed off providing a high dry matter feedstock for hydrolysation/fermentation.

It is not yet established what the optimal process configurations are - in fact, they may differ in different markets and with different feedstock. In this context process configuration means the sequence of process steps defined by the process equipment. It is possible to change process conditions like e.g temperature, pressure, pH to a certain degree in continuous equipment, but it is very expensive, to systematically test different configurations when equipment has to be changed. The process conditions are of course intimately linked to the process configuration. This means that it is vital for improvement of process efficiency, both in relation to environmental an economic sustainability, to test both process configurations and process conditions realistically and cost-efficient. Therefore there is a need for small scale equipment, which can be used to simulate the processes outlined above, and which can test several process configurations as well as different process conditions. There are no fixed boundaries between lab scale, bench scale, pilot scale, demo scale and industrial scale, and the terms overlap. By processing of lignocellulosic materials lab scale is usually referred to when the amounts of raw material per trial are between a few grams and a kilo, bench scale is usually referred to when the amounts of raw material per trial or per hour are between 100 grams and 10 kg, pilot scale is usually referred to when the amounts per trial or per hour are between 10 kg and 1000 kg, continuous demo scale is usually referred to when the amounts per hour are between 500 kg and 5 tons, continuous industrial scale is usually referred to when the amounts per hour are larger than 2 tons.

The small scale equipment according to the invention will typically be designed for 1 to 10 kg per trial or per hour.

A very disturbing problem by existing lab and bench scale equipment is that the equipment cannot operate with large particles and high solids concentrations.

Prior art

A continuous pilot plant is described in Applied Biochemistry and Biotechnology, Volumes 105, Number 1 - 3 Spring 2003. The pilot plant can treat approx. 32 kg (dry basis)/h

The material essentially moves by plug gravity flow from the top of the reactor to the reactor discharge port at the bottom of the reactor. A rotating scraper on the bottom of the reactor facilitates movement of material to the discharge port. This pilot plant can only work with one set of conditions and it is not possible to change the process configuration .

US5705369 describes a laboratory scale reactor, but it can only work with small particles and with one set of conditions and it is not possible to change the process configuration.

The most common laboratory equipment for pressurized treatment of lignocellulosic material seems to be the so called Parr reactors from Parr Instrument Company. The largest Parr reactor presently available is a 5 gallon reactor. The Parr reactors can be heated and stirred, and monitoring devices can be installed in them, but they are not sufficiently suited for testing of different process configurations with high dry matter content. The Parr reactors are batch reactors, and cannot be stirred at high concentration of solids.

US6022419 (Torget) describes a shrinking bed reactor system, and also a laboratory scale shrinking bed reactor. The concept is that the volume of the reactor decreases as the lignocellulosic material is solubilised in order to press out the solubilised substances before they are converted to inhibitory substances . The reduction of reactor volume can be achieved in various ways, and both continuous and batch systems are proposed. The bed is shrinking, and cannot be used for subsequent soaking operations.

None of the prior art methods can work at elevated pressure with high concentration of solids and large particles and subject the raw material to different process configurations as well as different process conditions and perform extraction. As explained in more detail previously, the large scale processes which the small scale equipment must be able to simulate are:

^■ Operating continuous

^■ Operating at elevated temperatures and pressures

■ Conducting separation and extraction processes

^■ Operating with high solid concentration, usually without a liquid phase

^■ Operating with large particles

^■ Operating with or without steam explosion There are several serious problems by simulating large scale continuous equipment with small scale continuous equipment.

Continuous small scale equipment will be limited in the number of process configurations which can be tested. Although pilot plants are usually more flexible than industrial scale plants, the possibilities to change the process configuration are very limited, since there must be one piece of equipment for each process step. This is a very serious drawback

In industrial scale continuous equipment, separation and extraction processes will usually be carried out when the lignocellulose is transferred from one set of process conditions to another set of process conditions , and can e.g be carried out in a screw press or a belt press. This is however not a feasible solution for small scale equipment. The equipment will be too expensive, and in some cases problems will occur, which do not occur in industrial scale equipment (downscale problems) .

Another serious problem by construction of continuous small scale reactors, which can operate at elevated pressure and perform soaking/pressing, is that small continuous loading and unloading devices are difficult and expensive to construct, and it can be difficult to achieve safety approval.

Further it can be difficult to establish exact mass balances in continuous equipment.

Using traditional batch equipment as e.g. autoclaves or Parr reactors as previously described is not a feasible solution. The possible process configurations which can be simulated are not sufficient, and the most promising process configurations cannot be simulated realistically. It is especially difficult to simulate process sequences, where several process steps are carried out subsequently without pressure release between each step. Small scale batch equipment often uses stirring as the means to secure contact between feedstock and reactant. Stirring works best with higher water content than what can be accepted in industrial scale processes. Therefore it is often seen that results from batch equipment cannot be reproduced in continuous equipment, and it will seem self- contradictory to those skilled in the art to use batch equipment in the attempt to improve simulation of continuous equipment.

Summary of the invention It is, however, the goal of the invention to provide small scale equipment with the capacity to simulate industrial scale, continuous, hydrothermal, pressurised pre- treatment of lignocellulosic materials.

It is a further goal, that the small scale equipment can simulate different process configurations.

It is a further goal of the invention, that the equipment can be used to carry out solid bed extraction. It is a further goal of the invention to provide bench scale equipment, which can perform multi stage processes. By multistage processes is meant processes, where at least one of the process conditions, such as pressure, temperature, pH, dry matter content, are changed at least once.

It is a further goal of the invention that the equipment is so cost-efficient both regarding capital and operational costs that it is realistic to employ the equipment in many places worldwide and numerous tests can be carried out at each facility.

It is a further goal, that the pilot scale batch equipment has the capacity to simulate industrial scale continuous pre-treatment of lignocelluloses without the presence of a liquid phase.

It is a further goal of the invention to provide bench scale equipment, which can operate with large particles. It is a further goal of the invention to provide bench scale equipment which can simulate the development of temperature in the material related to time, from industrial scale continuous equipment.

It is a further goal of the invention, that the equipment can be used to transfer enzymes from a solution to a fibre fraction.

It is a further goal of the invention to provide bench scale equipment which can simulate steam explosion inside the reactor. It is a further goal of the invention that the batch equipment can be used as production equipment for speciality products from plant material.

It is a further goal of the invention, that the equipment can be used to simulate counter current cascade processes.

In order to achieve the goals of the invention, the small scale equipment must be able to subject the plant material to the same impacts as the large scale continuous equipment. The impacts that the equipment must be able to carry out are: ■ move liquid into and out of the cavities of the material

^■ Soaking the plant material in liquids, which are obtained from previously treated plant material, where composition and dry matter content depend on: ^■ The number of times the liquid has previously been used for treatment of plant material

^■ The temperature, pressure, retention time and dry matter content of previous treatments

■ The intensity of previous pressing operations

^■ Contacting plant material and liquids in a sequence which provides a counter current cascade process

^■ Separation of liquid and solids

^■ Extraction of dissolved dry matter

Surprisingly all of these goals can be achieved by an apparatus as stated in claim 1. The solid material is kept stationary throughout the whole process. By introducing a piston equipped with a perforated piston head, into a reactor equipped with in- and outlet devices for liquid and steam, movement of liquid into the cavities of the material can be carried out by soaking or steaming of the material and an movement out of the cavities can be carried out by pressing with the perforated piston head. By transferring the press juice to different holding tanks and reintroducing the liquid, to a new portion of material, processed subsequently, counter- current cascade processes can be simulated. Extraction or separation processes can be carried out by performing pressing with the perforated piston head, optionally with preceding soaking.

In this way, a hybrid between continuous and batch equipment is provided, and it is made possible to simulate industrial scale continuous processes realistically, without the described problems of providing small scale loading and unloading equipment. This means that the equipment will be substantially more cost effective than continuous equipment, and it will be easier to achieve safety approval, because there is no risk of a blow out through loading or unloading equipment. Furthermore, it will be easier to establish reliable mass balances than by continuous operation, because it is possible to determine the exact amounts and composition of material and liquid and exactly what treatment they have received at any time during the process. This is very difficult by continuous equipment. Brief description of the drawings

Fig. 1 shows an embodiment of the reactor in four different situations. 1A: Loading, IB retention time, 1C pressing, ID unloading.

Fig. 2 shows an embodiment of the apparatus of the invention, fig 2A shows plan projection and 2B shows front projection.

Fig. l

1A loading

The removable inner cylinder 1.2 has been filled with lignocellulosic biomass, and is lowered into the reactor 1.1. The perforated cylinder lid 1.4 is fastened to the cylinder wall 1.3, which makes it possible to lower the cylinder 1.2 by means of the grip 1.5 of the lid 1.4. The bottom of the cylinder is a perforated piston head 1.6, which in the centre is equipped with a fastening device 1.7 for a shaft 1.9, which is equipped with fastening device 1.8 which fits with the fastening device 1.7. The fastening devices may be joined by rotating the cylinder 1.2. The shaft 1.9 can perform reciprocating movements and is pressure tightly sealed 1.10 towards the surroundings.

The reactor 1.1 is equipped with an inlet and outlet for liquid 1.11 , which is situated at the bottom of the reactor 1.1. The reactor lid 1.12 is equipped with a 3 way socket 1.13 with valves.

The reactor wall and the lid is equipped with a heating device 1.14, which enables heating of the reactor wall, in order to simulate continuous operation, where the reactor wall will usually have the same temperature as the content in the reactor. The reactor and the heating device are surrounded by insulation 1.15.

IB Retention time

The cylinder 1.2 is in place in the reactor 1.1. The perforated piston head 1.6 placed in the bottom of the cylinder 1.2 is connected to the shaft 1.9 by means of the fastening devices 1.7 and 1.8. The reactor lid 1.12 is closed and locked to the reactor 1.1 in a manner which can withstand the combined mechanical forces and vapour pressure pressing against the lid. Liquid or vapour with a pre-selected temperature and pressure is led into the reactor 1.1 through the inlet/outlet 1.11. Air which is driven out by the liquid or vapour can escape through the valve 1.13a. Downstream of the valve 1.13a, a condenser 1.17 is provided in an outlet line 1.18 from the valve 1.13a. Preferably, the outlet line is a flexible line and is detachably connected to a valve. The valve 1.13b is a safety valve and valve 1.13c can be used as inlet for liquid and vapour. Alternatively or additionally, a vapour inlet 1.16 can be provided in the bottom of the reactor.

When the retention time is over, any liquid in the bottom of the reactor 1.1 may be drained out through the inlet/ outlet 1.11.

1C Pressing

The perforated piston head 1.6 is moved upwards, towards the lids 1.4 and 1.12, by means of the shaft 1.9. The lignocellulosic biomass is compressed, and liquid will be pressed out of the cavities between and inside the particles . The liquid, the so called press juice, will be led out through the inlet/outlet 1.11.

ID Unloading

The reactor lid 1.12 is opened and the inner cylinder is either pushed upwards by means of the shaft 1.9 or pulled upwards by means of the grip 1.5. The shaftl.9 will be detached from the perforated piston head 1.6 and the cylinder can be removed and emptied.

Fig. 2

2 A is a plan projection of an embodiment of the invention. 2.1 is the reactor. 2.2, 2.3, 2.4 and 2.5 are holding tanks. Each holding tank contains liquid with different temperature and dry matter content, as described in Example 1. The holding tanks are connected to the reactor by piping 2.6

2B is a front projection of an embodiment of the invention. Two holding tanks are hidden. 2.12 is the reactor lid. The reversible pump 2.7 can transfer liquid from any of the holding tanks to the reactor, and from the reactor to any of the holding tanks. In order to control to and from which holding tank the liquid is led, each holding tank is equipped with a valve 2.8. Detailed description of the Invention

The reactor is a pressure tight vessel, equipped with a piston, with a perforated piston head, which can be moved from one end of the reactor towards the other. By moving the piston in one direction, a pressing operation is carried out, and by moving it in the opposite direction, a soaking operation can be carried out by introducing steam or liquid. The reactor is equipped with an inlet and outlet for liquid. It can either be one inlet and one outlet or it can be the same socket functioning as both inlet and outlet. The outlet must be placed in the bottom of the reactor. If there is a separate inlet it will often be an advantage if it is placed in the top of the reactor, where it can be combined with inlet for steam, outlet for confined air and safety valve. If vacuum operation is desired, the outlet for confined air can be equipped with a vacuum pump , or the reactor can be equipped with a dedicated valve for the vacuum pump.

When the heterogeneous material is soaked in an excess of liquid, it will be an advantage to place the steam inlet in the bottom of the reactor, to facilitate the mixing of material and steam, and thereby facilitate the heat transfer from steam to material.

In order to simulate the temperature curve of the material in an industrial scale continuous reactor, the reactor according to the invention can be equipped with a separate external heating system, which can ensure that the inner surface of the reactor wall has a temperature equal to or higher than the material in the reactor.

The reactor is preferably insulated, in order to be able to maintain high temperatures inside the reactor, and to avoid safety problems .

The reactor is connected to at least two holding tanks , which can withstand the same pressure or vacuum as the reactor. Simulation of counter- current operation can be established by soaking the batch of solid material in the reactor with at least two different liquids , where at least one liquid has previously been used to treat at least one batch of plant material, and where the liquid with the highest content of dissolved plant material is used for the first soaking operation, and the liquid with the lowest content of dissolved plant material is used for the last soaking operation.

The removal of liquid after a soaking step can be carried out in two steps . First the solid material can be drained, which in this context means that the liquid is extracted from the bottom of the reactor, without pressing by the perforated piston head. This will mainly remove liquid between the particles which have not been in close contact with the huge inner surface of the solid material, and which has a relative modest increase in dry matter content. This liquid is referred to as drained extract. The subsequent pressing will remove some of the liquid from the cavities inside the particles , which has been in closer contact with the huge inner surface of the solid material, and therefore has a larger increase in dry matter content than the drained extract. The liquid which is removed by pressing will be referred to as press juice. The drained extract and the press juice can be transferred to different holding tanks. Typically the drained extract will be returned to the holding tank where it came from, and the press juice will be transferred to a holding tank for liquid with a higher dry matter content than the holding tank from which it came.

The depressurization can be carried out by releasing all of the steam at once, which will simulate steam explosion, or it can be carried out more slowly, by introduction of cold liquid.

In order to improve the possibility to make closed mass balances, the gas outlet by a preferred embodiment of the invention is equipped with a condenser. Thereby condensable gasses created in the reactor during the process can be characterized, and the amounts produced can be established.

Adhesion of enzymes to the pre-treated plant material can be conducted in the following way. After the material has been pressed, and optionally washed and subsequently pressed, it is soaked in an enzyme solution. The enzymes will adhere to the cellulose fibre and surplus liquid can be removed by pressing without removing too much of the enzymes.

The conditions inside the reactor can be changed as many times as desired without removing the solid material: ■ The temperature can be changed by introducing steam or liquid and by regulating the heating in lid and mantel. The temperature range used in the reactor will most often be between 10 and 220 C

^■ The pressure can be regulated by introducing steam of various pressures and by regulation of the mantel heating and optionally a vaccum pump. The pressure range used in the reactor will most often be between 0,2 - 30 bar

^■ The dry matter content is regulated by introducing steam and/or liquid and by pressing liquid out by means of the perforated piston.

The ability to control and change dry matter content, pressure, temperature, chemical composition any desired number of times, makes it possible to test numerous different process configurations and process conditions, while the material stays in the reactor throughout the whole process. The fact that the material stays in the reactor through the whole process facilitates operation without a liquid phase and with large particles which can be up to 20-30 cm long, since transfer of solid material from one pressure to another is particularly difficult when there is no liquid phase and the particles are large. The hydrothermal treatment can be carried out with various liquids and thus simulate numerous different processes, such as steam treatment, hot water treatment, dilute acid treatment, alkaline treatment and organosolv treatment.

To increase the capacity of the reactor, it can be equipped with at least two removable inner cylinders with perforated lids of which one containing a portion of raw material is under treatment inside the reactor, while another is being loaded with raw material outside the reactor.

Removing one cylinder after treatment and placing another in the reactor is conducted by a lifting device.

The current invention provides an apparatus and method for hydrothermal treatment and/or extraction of particulate plant material comprising a pressure-proof cylindric reactor with a lid in one end for loading and unloading of particulate plant material, and with inlet and outlet sockets for liquid and/or steam, outlet socket for air, wherein:

The reactor is equipped with a piston with a perforated piston head.

In a preferred embodiment the reactor is equipped with a second circular perforated plate fitting within the reactor and fixed in short distance from the reactor lid.

In a preferred embodiment of the invention, the reactor according to the invention is equipped with sockets for temperature and pressure monitoring.

In a preferred embodiment of the invention, the reactor is equipped with thermal insulation towards the surroundings.

The method for hydrothermal treatment and/ or fractionation of plant material according to the invention comprises that: a. The plant material stays in one reactor throughout the entire processing period, and b. At least one pressing operation is carried out in the reactor, by means of a piston with a perforated piston head

An embodiment of the method according the invention comprises that at least one soaking operation followed by at least one pressing operation is carried out in the reactor

By another embodiment of the method according to the invention the liquid content of the plant material is so high, that liquid can be pressed off by means of the perforated piston head.

A further embodiment of the method according to the invention comprises that the reactor wall is preheated to at least the desired operating temperature, prior to loading of the material into the reactor. A further embodiment of the method according the invention comprises that a. the plant material is subjected to at least two sets of process conditions of which at least one process parameter (e.g. temperature, pressure, chemical composition of the liquid, residence time) is changed

b. the plant material is pressed after it has been subjected to each set of process conditions

c. the extract from the first set of process condition is led to one holding tank, the extract from the next set of process conditions is led to another holding tank and so forth.

A further embodiment of the method according the invention comprises that a liquid can be used to soak several batches of plant material

A further embodiment of the method according the invention comprises that the removal of liquid after a process step is carried out in the following way: a. Liquid is drained off, by opening the liquid outlet. The perforated piston head is in the same position as it was during the process step. This drained off extract is led to one holding tank

b. Subsequently the perforated piston head is moved in the direction of the lignocellulosic material, which will press out additional liquid. This press juice is led to a different holding tank than the drained off extract. A further embodiment of the method according the invention comprises that the lignocellulosic material is: a. loaded into the reactor

b. soaked in an extract from a first holding tank 2.3. This extract has previously been used for extraction of 2 batches of lignocellulosic material. The temperature of this extract is between 60C and lOOC , more peferred between 85C and 95C c. drained through the liquid outlet. The drained off extract is returned to the first holding tank 2.3.

d. pressed. The press juice is transferred to a second holding tank 2.2 for final extract

e. soaked in extract from a third holding tank 2.4. This extract has previously been used for extraction of one batch of lignocellulosic material. The temperature of this extract is between HOC and 170C more preferred between 130C and 150C . f. drained through the liquid outlet. The drained off extract is returned to the third holding tank 2.4.

g. pressed. The press juice is transferred to the first holding tank

h. soaked in liquid from a fourth holding tank 2.5. This liquid has previously been used for washing of hydrothermally treated lignocellulosic material. The temperature of this water is between 160C and 220C more preferred between 185C and l95C

i. drained through the liquid outlet. The drained off extract is returned to the fourth holding tank 2.5.

j . pressed. The press juice is transferred to the third holding tank 2.4

k. cooled by flashing off steam and washing with make up water

1. pressed. The press juice is transferred to the fourth holding tank 2.5.

m. unloaded from the reactor A further embodiment of the method according the invention comprises that the reactor wall and lid is heated prior to the loading of the plant material.

A further embodiment of the method according the invention comprises that the temperature of the reactor wall is equal to or higher than the temperature of the reactor content during the whole process. A further embodiment of the method according the invention comprises that the make up water is replaced with an ethanol solution with an ethanol concentration between 25 and 65% more preferred between 40 and 50%. A further embodiment of the method according the invention comprises that a. the pre-treated, pressed lignocellulosic material is soaked in an enzyme solution. b. the temperature of the enzyme solution is lower than the optimum temperature for the enzymes

c. the temperature of the lignocellulosic material is higher than the optimum temperature for the enzymes

d. the moisture content of the lignocellulosic material is adjusted by pressing to the optimal level for enzymatic liquefaction, hydrolysation and fermentation.

EXAMPLES Example 1

Combined solid bed extraction and hydrothermal pre-treatment of wheat straw, corn stover or bagasse in a 50 1 vertical reactor with the lid at the top.

3 kg of chopped straw is loaded into the innerl.2 cylinder with the perforated piston head 1.6 as bottom, and closed with the perforated lid 1.4 and placed at the top of the reactor 1.1, where the free end of the shaftl .9 is in the high position. The movable perforated piston head 1.6 at the bottom of the inner cylinder 1.2 is locked to the fastening device of the shaft 1.8, The shaft 1.9 is then withdrawn to the low position, bringing the inner cylinderl .2 in place inside the reactor 1.1 after that, the reactor lid 1.12 is closed and locked. Extract at about 90C is transferred from the tank 2.3 to the reactor by the pump 2.7, driving off the air confined inside and between the straw particles. The extract in tank 2.3 has been used for extraction of two preceding batches of straw. After a certain soaking time, the extract is drained off and returned to the tank 2.3. Subsequently the perforated piston head 1.6 is moved upwards by the shaft 1.9, pressing off additional liquid. The press juice is transferred to the storage tank 2.2 which is the tank for the so called Liquid Fraction. Hereafter extract at 140C from the tank 2.4 is transferred to the reactor 2.1. The extract in the tank 2.4 has been used for extraction of one preceding batch of straw. After a certain soaking time, the drained off extract is returned to the tank 2.4 and the pressed off extract is transferred to the tank 2.3.

Finally liquid at 190C from the tank 2.5 is transferred to the reactor 2.1 and after a certain soaking time, the drained off extract is returned to the tank 2.5 and the pressed off extract is returned to the tank 2.4.

The press cake is cooled by flashing off steam and by washing with water which is pressed off and transferred to the tank 2.5 and the inner cylinder with the press cake is removed from the reactor.

Most of the alkali chlorides and a substantial part of the hemicellulose are solubilized and removed with the press juice. The rest of the hemicellulose, the cellulose and the lignin remain in the press cake.

Example 2

Combined steam treatment and solid bed extraction of wheat straw and/or corn stover in a 50 1 vertical reactor, with a lid at the top.

Loading of the reactor and extraction with a liquid at about 90C is conducted as in Example 1.

Hereafter steam is introduced to the pressed plant material in the reactor, increasing the temperature to about 190C . After a certain retention time, the press cake is cooled by flashing off steam and by washing with water, which is pressed off and transferred to the holding tank for liquid at 90 C .

Subsequently, the inner cylinder with the press cake is removed from the reactor.

Example 3

Hydrothermal treatment and fractionation of lignocellulose with a mixture of water and ethanol. The processing steps in example 3 are conducted in the same way as in example 1 with almost the same temperatures but with a higher pressure in the reactor because of the presence of ethanol. In Example 1 most of the alkali chlorides and a substantial part of the hemicellulose are solubilized and removed with the press juice, whereas the cellulose and the lignin remain in the press cake.

In example 3 the mixture of water and ethanol (around 55% water and 45% ethanol) will solubilize most of the alkali chlorides , hemicellulose and lignin, leaving a press cake with a very high concentration of cellulose. This means that the press cake will be very a good feedstock for production of cellulosic ethanol by enzymatic liquefaction followed by fermentation. Alternatively it can be used as feedstock for the paper industry. Example 4

Enzymatic hydrolysis of hydrothermally pre-treated lignocellulosic material.

After a hydrothermal treatment as e.g. the treatment described in Example 1 , the lignocellulosic material can after washing-pressing have a temperature of 60 -80° C .

The press cake is soaked in an enzyme solution with a temperature of around 30° C and a relatively low enzyme concentration. The enzyme solution will cool the lignocellulosic material to 50-60° C , and condense the vapour inside the cavities and the capillaries of the material, and thereby enhance the absorption of the enzyme solution into the cavities and capillaries . Most of the enzymes will adhere to the cellulose fibres , from which lignin and hemicellulose has been displaced by the pre-treatment.

Subsequent to the absorption of the enzyme solution and adhesion of the enzymes , a pressing operation can be carried out, to remove surplus liquid from the enzyme solution.