SE541382C2 - Feeding arrangement comprising a screw feeder and method for feeding comminuted biomass material - Google Patents

Abstract

The invention relates to a feeding arrangement (1) for feeding comminuted biomass material through a treatment stage (200), which feeding arrangement comprises a screw feeder (10), which comprises an inlet (12) and an outlet (13), and a feed screw (2) for transporting the biomass material from the inlet to the outlet. The feed screw comprises at least one screw flight (2b) with a pushing flight surface (PF) and a leeside flight surface (LF). The feeding arrangement comprises a supply channel (SC) arranged to supply anti-fouling liquid from at least one liquid supply source (So, So), and a plurality of nozzles (NZ) connected to said supply channel, which are arranged to distribute said anti- fouling liquid over the leeside flight surface for establishing a liquid layer on said leeside flight surface. The invention also includes the use of said screw feeder in hydrolysis processes and method for operation of said screw feeder.

Description

FEEDING ARRANGEMENT COMPRISING A SCREW FEEDER AND METHOD FOR FEEDING COMMINUTED BIOMASS MATERIAL TECHNICAL FIELD The present invention relates to a feeding arrangement for feeding comminuted biomass material through a treatment stage. The feeding arrangement comprises a screw feeder for feeding the material trough the treatment stage, the screw feeder comprising a housing comprising an inlet and an outlet, and a feed screw extending at least partially through said housing for transporting the biomass material from the inlet to the outlet. The feed screw comprises at least one screw flight with a pushing flight surface and a leeside flight surface located on opposite sides of the screw flight.

The present invention also relates to use of said feeding arrangement in a hydrolysis process of lignocellulosic material of wood or non- wood origin.

The present invention also relates to a method for feeding comminuted biomass material through a treatment stage using the above described feeding arrangement.

BACKGROUND Feeding of comminuted cellulose material to be treated in a pressurized treatment stage may be carried out in different ways and is dependent on a number of factors such as the characteristics of the material to be fed and the possible desired action on the material besides the actual feeding thereof. Screw conveyors, in which a rotating screw transports the material forward by the continuous movement of one or more screw flights is a commonly used type of feeder.

Hydrothermal processes are common initial treatments of lignocellulosic biomass to make possible the fractionation of the biomass into its main constituents, sugars from hemicelluloses and cellulose, and lignin, by subsequent enzymatic hydrolysis. Hydrothermal pretreatment utilizes various technologies such as chemical treatment at elevated temperature to alter plant cell wall structural features so that the polysaccharide fractions become more accessible and responsive to enzymatic hydrolysis. The released mono sugars from the hydrolyzed biomass polysaccharides can be fermented or refined in chemical processes to advanced biobased transportation fuels, platform chemicals and materials. Dilute acid or autocatalyzed pretreatments, depending on the biomass raw material, have been considered to be among the leading and most promising pretreatment technologies that can enhance sugar release performance. Dilute acid pretreatment involves the treatment of biomass with a combination of an acidic solution, heat and pressure with residence times ranging from less than a minute to 1 h, which is generally carried out using 0.4-2.0 % (w/w) H2SO4at a temperature of 140-225 °C. Such processes are here referred to as “pretreatment”, “prehydrolysis” or only “hydrolysis”. Autocatalyzed prehydrolysis, or auto hydrolysis, is performed without the addition of external acid. In autohydrolysis, acetyl groups liberated from the hemicellulose in the biomass during the hydrothermal pretreatment provide the acidity that catalyzes further hydrolysis of the polysaccharides, primarily the hemicellulose fraction. By applying more severe process conditions with regard to temperature and/or time and addition of e.g., acid as a catalyst, also glucose from the cellulose can be released. The hydrothermal treatment can also be extended, e.g., by longer treatment time, to include direct continued conversion of the sugars into certain products, e.g., furfural or levulinic acid.

In processes for prehydrolysis or hydrolysis of biomass by hydrothermal treatment, feed screws or screw conveyors are often used in certain process stages where the comminuted bio material is subjected to heating and at least partial hydrolysis of the material. An advantage of screw conveyors is that the comminuted bio material may be subjected to a uniform treatment owing to a narrow residence time distribution in the treatment zone.

The potential major problem during prehydrolysis or hydrothermal pretreament processes is the formation of sticky reaction products that form deposits on the equipment surfaces and that even may clog the equipment, which causes frequent stops and need for subsequent cleaning, for example, by high pressure water jets. A particularly problematic type of substance is socalled pseudolignin, which actually contains no or very little lignin, but is formed through condensation and oxidative polymerization of reaction products originating in degraded sugars. In some prehydrolysis processes, e.g., acid-catalyzed hydrolysis of softwoods, the equipment may be blocked by deposits even after only 24-72 hours of operation after which the process needs to be shut down for emptying and cleaning of the equipment.

Hydrothermal treatments or hydrolysis processes may comprise only one steam heated reactor, where the material may be at least partially hydrolyzed, or two or more reactors in series where continued hydrolysis take place. Each of these steps may be implemented in horizontal or inclined tube reactors equipped with internal feed screws for the transport of the biomass through the reactors. The problem with sticky deposits may occur in all steps but to different extent. The problem to be solved in hydrothermal hydrolysis processes is to avoid buildup of deposits on the equipment and thereby eliminate or significantly reduce the need for shut-downs for cleaning of the process equipment.

In numerous pilot-scale tests in horizontal hydrolysis reactors with internal feed screws, it has been observed that application of typical prehydrolysis conditions on common types of lignocellulosic biomass raw materials, e.g., dilute acid catalyzed hydrolysis of softwood sawdust, can cause very rapid buildup of sticky deposits that accumulate on the leeside of the screw flights and ultimately block the screw entirely.

There is thus a need for an improved feeding arrangement for feeding comminuted cellulosic material through a treatment process, and especially a treatment process where at least partial hydrolysis is performed and there is a high risk that sticky deposits are formed during the treatment stage.

SUMMARY OF THE INVENTION In the present context, a screw flight is a helical ridge that extends one or more turns along a screw shaft to ensure that biomass material will be conveyed along the length of the screw shaft when the screw shaft is rotated about its longitudinal center axis. Each screw flight has a pushing flight surface and a leeside flight surface located on opposite side of the screw flight.

The object of the invention is achieved in accordance with the invention as initially described and characterized in that the feeding arrangement comprises a supply channel arranged to supply anti-fouling liquid from at least one liquid supply source, and a plurality of nozzles connected to said supply channel, which nozzles are arranged to distribute said anti-fouling liquid over the leeside flight surface for establishing a liquid layer on said leeside flight surface.

The liquid layer will flush away sticky particles and any precursors that may form deposits on the leeside flight surface. Furthermore, by distributing an alkaline liquid, the alkaline boundary layer formed will counteract formation of deposits by keeping solubilized the hydrolysis reaction products, dissolved substances from the biomass and possible precursors that are prone to form deposits.

The nozzles are arranged at the leeside flight surface, which in this context means that they are located on the leeside of the screw flight and within 0-10 mm from the actual leeside flight surface.

Advantageously, the nozzles are arranged so that the liquid jets emanating from the nozzles first meet the leeside flight surface before any other surface of the screw feeder. This solution optimizes the effect of the added anti-fouling liquid to the location where present sticky compounds typically will accumulate, and the dilution of the material fed by the screw is minimized, i.e., the desired hydrolysis conditions will be maintained in the bulk volume of the biomass material.

An anti-fouling liquid is in this context a liquid that is either neutral or alkaline. Examples of suitable anti-fouling liquids are neutral or alkaline solutions, liquid surfactants, solvents, water and mixtures thereof. In a preferred embodiment, the anti-fouling liquid is alkaline, advantageously with a pH above 8 and even more preferably above 9. An alkaline boundary layer is advantageous in that it will counteract formation of deposits by keeping solubilized the hydrolysis reaction products, dissolved substances from the biomass and possible precursors that are prone to form deposits.

In a preferred embodiment, the anti- fouling liquid used is any of alkali, SO2, sulfite or bisulfite solution, water, or mixtures thereof. Alkali usage has the positive effect of dissolving acidic sticky compounds and keeping them solubilized, and when the alkaline solution is applied as a layer on the leeside flight surface, the hydrolysis of the bulk part of the biomass material volume will not be impeded. Applying a sulfite solution resulting in sulfonation of certain compounds, e.g., aromatic moieties from lignin, is known to make them more soluble and thus less prone to precipitate under hydrolysis conditions. Water may also be used, especially if a continuous flushing flow is applied, i.e., mechanical removal of sticky reaction products from the surface of the screw flight. Hence, the liquid may be any mixture of alkali, SO2/sulfite/bisulfite and water.

In yet a preferred embodiment, a number of nozzles are arranged at different radial distances from a center axis of the feed screw. This may establish a layer closer to the screw shaft, and as the layer progresses radially outwards it may be replenished with more anti-fouling liquid. These holes may differ in size depending on their radial position, with larger holes located closer to the center axis of the feed screw and smaller holes located farther out for replenishing anti- fouling liquid for maintaining the liquid layer as the surface to be covered increases.

Advantageously, at least one nozzle comprises a hole in the leeside flight surface connected to the supply channel by means of a branch channel that extends through the screw flight. This arrangement ensures that the anti-fouling liquid is applied directly onto the leeside flight surface.

A plurality of nozzles may be connected to the supply channel by a single branch channel. The branch channel may comprise a bore that extends through a main body of the screw flight. Alternatively, the screw flight comprises a wall member attached to the main body of the screw flight, which wall member defines the leeside flight surface, and wherein at least a portion of said branch channel extends between the wall member and the main body. Preferably, the wall member is a thin sheet or plate of metal and the nozzles may be formed by pressing out dimples from said thin sheet or plate. This embodiment is advantageously used in an upgrade of existing feed screws, where the wall member can be welded to the screw flight, forming the branch channel. The wall member also makes it easy to implement as many nozzles as needed, and these nozzles may be integrated in the wall member by simple pressing action, forming outlets like a cheese grater, and with nozzle outlets directed in either radial or rotational direction of the screw.

The feed screw may comprise a screw shaft and said supply channel may be a central hole running longitudinally through at least a portion of the screw shaft. In an alternative embodiment, the supply channel may be a pipe wound over the screw shaft, preferably along the innermost root of the leeside flight surface. In this embodiment, the nozzles may be radially directed holes in a pipe wall of a pipe arranged parallel to the leeside flight surface. This arrangement is advantageous in that it will enable a low-cost installation without changing the physical integrity of the screw feeder, and may be installed if functionality of the anti-fouling system is challenged and/or if the anti-fouling system should be readily removed at low cost. The last-mentioned alternative for implementation may be selected according to customer requests, as different objectives, such as costs versus function, may apply for the operator of the hydrolysis process.

In a preferred embodiment, a control member is used for regulating the flow of the anti- fouling liquid in said supply channel. This control member may be intermittently operated such that the anti-fouling liquid is supplied for at least a part-time of the operation of the screw feeder, with varying lengths of on-off cycles adaptable to the propensity for formation of sticky deposits. Hence, starting with a continuous supply of anti-fouling liquid it may be interrupted in periods of increasing length until deposits start to occur, which will set the lower limit for operation. Assuming a treatment time (average residence time for the biomass) of 10 min in a continuous prehydrolysis reactor, a first step from continuous supply of anti-fouling liquid could be to stop the supply one minute every 10 minutes and the amount of sticky deposits on the conveyor screw observed after 24 h of operation. The length of the periods of interrupted supply could be increased in steps of 1 minute per 10-minute period for each operation period of 24 h after wich the conveoyor screw is observed and from which observations it can be concluded what cycle times represents the lower limit for the supply of anti-fouling liquid.

Further, the supply channel may be connected to at least two liquid supply sources with different anti- fouling liquids and the control member may be used to alternate between said liquid supply sources. For example, one cycle with supply of water (neutral pH) may be activated for each 2to 5thsupply cycles with alkaline anti-fouling liquid. The length of a supply cycle corresponds to the average trement or residence time of the biomass in the reactor. By this method of alternating supply sources, the alkali addition to an otherwise acidic hydrolysis process may be minimized.

The rate of formation of sticky deposits during hydrolysis depends on the biomass raw material, its physical form and size and the severity of the hydrolysis process. Normally, acid-catalyzed hydrolysis of softwood sawdust forms larger amounts of buildups on the equipment and more rapidly than what occurs, for instance, during auto hydro lysis of wheat straw under milder hydrolysis conditions. Thus, the anti-fouling liquid application frequency must be adapted to each material being hydrolyzed and its proneness for forming sticky deposits.

In a preferred embodiment, a plurality of nozzles are arranged at a respective innermost radial position of the leeside flight surface and each directed along a respective axis that deviates less than 10 degrees from the leeside flight surface and less than 10 degrees from a radial direction. The formed liquid layer should have a flow direction in radial direction, but as the passing biomass material may deflect the layer somewhat the radial direction of the liquid jet from the nozzle may be inclined less than 10 degrees from the strict radial direction, and preferably inclined against the rotational direction of the screw flight. By this implementation the liquid layer may be formed evenly as the screw rotates and is not impeded by material flowing over the screw flight and against any liquid flow ejected from the nozzles.

The invention also relates to use of a feeding arrangement as described above, wherein the feeding arrangement is used in a hydrolysis process of lignocellulosic material of wood or nonwood origin, wherein the feeding arrangement is used in a hot process stage at temperatures above 100 °C, either in pure steam heating or assisted with hydrolysis promoting agents, wherein sticky deposits are formed during the hydrolysis process.

The invention also relates to a method for feeding comminuted biomass material through a treatment stage using a feeding arrangement comprising a screw feeder for feeding the material through the treatment stage, the screw feeder comprising a housing comprising an inlet and an outlet, and a feed screw extending at least partially through said housing for transporting the biomass material from the inlet to the outlet, which feed screw comprises at least one screw flight with a pushing flight surface and a leeside flight surface located on opposite sides of the screw flight. The method comprises the step of applying anti-fouling liquid from at least one liquid supply source directly on the leeside flight surface during at least a part of the run time of the screw feeder, establishing a liquid layer on said leeside flight surface for flushing away, dissolving and/or preventing sticky deposits from adhering to said leeside flight surface.

By application of the liquid layer directly on the leeside flight surface, and by adapting the pH of the alkaline anti-fouling liquid and the volume of the liquid relative to the mass of the biomass material, the acidic conditions in the bulk volume of biomass material subjected to the hydrolysis stage will not be altered to any significant extent. The continual splitting off and release of acetyl groups in the biomass into the bound and the free present liquid will buffer the bulk volume of the biomass material and keep the pH in the bulk of the biomass at a level low enough to promote the desired hydrolysis reactions of the polysaccharides.

In a preferred application, the feeding arrangement according to the invention is used in a hydrolysis process of lignocellulosic material of wood or non-wood origin, wherein the feeding arrangement is used in a hot pressurized process stage at temperatures above 100 °C, either in pure steam heating or assisted with hydrolysis promoting agents, wherein reaction products and products of further degradation are potentially sticky and may form deposits on the feed screw and/or the surfaces of the reactor vessel which may hinder or obstruct the feeding of the biomass through the reactor vessel.

For the purpose of this disclosure, the term comminuted bio material includes wood material as well as non-wood plant material. The invention is especially suitable for softwoods and hardwoods and bark as well as bulky non-wood material from plants, such as straw, bagasse, bran and grain material of cereals. Peat material and empty fruit bunches of oil palm are also encompassed by the term. In short, the term non- wood plant material is used for all kinds of plant/plant part containing material not being defined as wood. The particle dimensions of the comminuted cellulose material may be in the range of 5 to 70 mm when feeding wood chips (dimension in the longest direction), sawdust typically contains particles less than 5 mm, and in case of straw material the length of chopped straw may lie in the range from very short, a few millimeters up to lengths of 250 mm.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with further objects and advantages thereof, may best be understood by reference to the following description and appended drawings, in which: Fig. 1 shows a schematic set-up of a typical hydrolysis treatment stage; Fig. 2 shows the same set-up as that in Fig. 1, but with an added system for supply of antifouling liquid; Figs. 3a and 3b show a first implementation of the inventive feeding arrangement, where Fig. 3b is a side view of the feed screw and Fig. 3a is a cross section trough the feed screw; Figs. 4a-4d show a second implementation of the inventive feeding arrangement, where Fig. 4b shows the feed screw in axial direction with a full flight turn, Fig. 4a shows a cross section through the feed screw and Figs. 4c and 4d show two orthogonal cross sections through a nozzle; Figs. 5a and 5b show a third implementation of the inventive feeding arrangement, where Fig. 5a is a side view of the feed screw and Fig. 5b is a cross section trough the feed screw shaft with a full flight turn; Figs. 6a and 6b show a fourth implementation of the inventive anti- fouling liquid distribution, where Fig. 6a is a side view of the feed screw and Fig. 6b is a cross section through the feed screw with a full flight turn.

DETAILED DESCRIPTION In Figs. 1-6, similar or corresponding elements are denoted by the same reference numbers.

Fig. 1 shows a schematic set-up of a typical hydrolysis or treatment stage 200 with a feeding arrangement 1 in the form of a single horizontal tube reactor provided with an internal feed screw 2. The comminuted biomass material Bio is fed into a chute by a rotating pocket feeder or a plug screw feeder, which forms a steam-tight plug at a discharge end of the plug screw feeder. The biomass material may be preimpregnated by water or by chemicals Ch, e.g., organic or mineral acids for catalysis of the hydrolysis reactions. Addition of acid or other catalyzing chemicals may also be added in the chute. The biomass falls through the chute by gravity into the reactor. Steam St for heating can be added in the chute and through headers along the horizontal reactor. The operating temperature in the reactor 1 is typically in the range 140-225 °C and the corresponding pressure 2.6-25 bar(g).

The feed screw 2 comprises a screw shaft 2a provided with a screw flight 2b (schematically shown) and is driven by a motor M1for the transport of said biomass material through the reactor and for control of the retention time of the biomass material in the reactor. The main part of the hydrolysis reactions take place in the reactor. At a discharge end of the reactor, the biomass material can be discharged directly through an orifice or a blow valve. By discharge of the biomass material to atmospheric pressure, the sudden drop in pressure will cause a steam explosion effect, which will disintegrate the treated biomass material into smaller particles. Alternatively, the treated biomass material can drop into a discharge unit where the temperature can be decreased to below 100 °C by addition of cold dilution liquor. No or very limited steam explosion effect will then occur when the biomass material meets atmospheric pressure. Depending on the feed rate and target severity factor of the hydrolysis process, two or more reactors can be connected in series.

Fig. 2 shows the same set-up as in Fig. 1, but with an added system 20 for supplying anti- fouling liquid. In this embodiment the treatment stage 200, the hydrolysis stage, is such that an antifouling liquid may be added from a first and a second liquid supply source So1and/or So2, and fed to a supply channel SC in the screw shaft 2a of the feed screw 2 and from there to nozzles (shown in detail in Fig. 3a, 3b, 4a - 4d, 5a, 5b, 6a, and 6b) in the screw flight 2b. The number of liquid supply sources may be one, two or even more, selected from any of neutral or alkaline solutions of different concentrations, water or mixtures thereof. The important feature is to establish a neutral or alkaline liquid boundary layer that keeps potentially sticky compounds in solution and thereby blocks the sticky compounds from attaching to the surfaces of the screw flight 2b. In parallel there may be a cleaning action from the flow of liquid over the screw flight 2b. The actual liquid supply source to be used may be selected by a control member CM for opening and regulating the volumetric flow of the anti-fouling liquid in said supply channel SC.

The anti-fouling liquid may be supplied during a predetermined period of time and thereafter stopped and then supplied again. In hydrolysis processes where sticky deposits are formed slowly, i.e., to a low extent, alkaline liquid may be supplied, for instance, 5 minutes per 10-minute period (50% of the time). While in hydrolysis processes where the combination of biomass raw material and process conditions leads to rapid formation of sticky compounds and to a high extent, (e.g., acid-catalyzed hydrolysis of softwood sawdust) alkaline liquid may be added during 8-9 minutes per 10-minute period. In the most severe cases with formation of substances prone to adhere and form deposits on the feed screw 2 and reactor surfaces, antifouing liquid may be added continuously.

Embodiments 1Alternative In Figs. 3a and 3b, a first implementation of the inventive feeding arrangement is disclosed. Fig. 3b shows a side view of the feed screw 2 and Fig. 3a shows a cross section trough the screw shaft 2a and the screw flight 2b. The anti- fouling liquid is supplied to nozzles NZ via the supply channel SC in the form of a central bore running along a center axis CC of the screw shaft 2a. As disclosed in Fig. 3b, the screw shaft 2a is equipped with a screw flight 2b, and as the screw shaft 2a rotates in the direction ROT and subjects the biomass material to axial movement in the direction TF, the screw flight 2b will have a pushing flight surface PF and a leeside flight surface LF on opposite sides of the screw flight. The anti- fouling liquid is distributed from the supply channel SC through a radially extending branch channel BC to said plurality of nozzles NZ in the form of holes in the leeside flight surface LF. In this simplest embodiment the nozzles NZ are holes in the leeside flight surface LF and distribute the anti-fouling liquid over the leeside flight surface LF. 2Alternative In Figs. 4a-4c a second implementation of the inventive feeding arrangement is disclosed. Fig. 4b shows a feed screw 2 in axial direction with a full flight turn, Fig. 4a shows a cross section through the feed screw 2 and Figs. 4c and 4d show two orthogonal cross sections through the nozzle NZ shown in Fig. 4a. The nozzles NZ in Fig. 4b are placed in three different radial positions: closest to the center of the screw shaft, in an intermediate position and in an outermost position, and in each radial position with four nozzles NZ evenly distributed over the circumference. The nozzles NZ are here all directed essentially in parallel to the leeside surface LF and generally against the rotational direction ROT of the screw flight. As shown in Fig. 4a, the branch channel BC is a common chamber between a thin wall member 40 that defines the leeside flight surface LF and a main body of the screw flight 2b. The nozzles NZ are formed by pressing out dimples from said wall member 40, which is shown in detail in Figs. 4c and 4d. Hence, the liquid layer is formed after the downstream end (as seen in the direction of rotation) behind each dimple, and the form of the dimple prevents ingress of material into the nozzle NZ. 3Alternative In Figs. 5a and 5b, a third implementation of the inventive feeding arrangement is disclosed; Fig. 5a shows a side view of a feed screw 2 and Fig. 5b shows a cross section through a screw shaft 2a and a full screw flight 2b tum. The rotation ROT and axial movement of the screw flight 2b are opposite to that shown in Fig. 3b, and hence the leeside flight surface LF is the opposite side to that in Fig. 3b. The supply channel SC is a central bore running along the center axis CC of the screw shaft with branch channels BC running radially from the supply channel SC and ending in nozzles NZ at the outer periphery of the screw shaft 2a at the leeside flight surface 2b of the screw flight 2b, as shown in Fig. 5a. As shown in Fig. 5b, a number of branch channels BC are arranged on a full screw flight 2b turn, i.e., in different axial positions along the screw shaft 2a. 4thAlternative In Figs. 6a and 6b a fourth implementation of the inventive anti-fouling liquid distribution is disclosed. Fig. 6a shows a side view of the feed screw 2 and Fig. 6b shows a cross section trough the screw shaft 2a with a full screw flight 2b turn. In this embodiment the supply channel SC is in the form of a pipe 60 helically wound on the screw shaft 2a, preferably welded in its position, along the leeside flight surface LF of the screw flight 2b. The pipe 60 is a wound along the radial innermost root of the screw flight 2b and radially directed nozzles NZ parallel to the leeside flight surface LF are formed by holes in the wall of the pipe 60. Here the nozzles NZ may be simple drilled holes in the wall of the pipe 60 and oriented such that the flow of antifouling liquid is pumped parallel to the leeside flight surface LF and oriented generally in the radial direction. As shown in Fig. 6b, eight nozzles NZ could be arranged in the pipe for each turn of the screw flight, but the number of nozzles NZ may be higher than that.

Method The method according to the invention will now be described with reference to Figs. 2, 3a and 3b.

The comminuted bio material Bio is fed through the feeding arrangement 1 comprising a screw feeder 10. The screw feeder 10 comprises a feed screw 2 with a screw flight 2b with a pushing flight surface PF and a leeside flight surface LF on opposite sides of the screw flight 2b, and a corresponding housing 11 (i.e., reactor vessel) with an inlet 12 at one end and an outlet 13 at the other end, which housing 11 surrounds a central portion of the feed screw 2.

The method comprises the step of supplying anti- fouling liquid from at least one liquid supply source So1, So2to said nozzles NZ via said supply channel SC and applying said anti- fouling liquid directly on the leeside flight surface LF during at least a part of the run time of the screw feeder 10, establishing a liquid layer on said leeside flight surface LF dissolving or preventing sticky deposits from adhering to said leeside flight surface LF.

Although the invention has been described with reference to specific illustrated embodiments, it is emphasized that it also covers equivalents to the disclosed features, as well as changes and variants obvious to a person skilled in the art, and the scope of the invention is only limited by the appended claims. For example, the following alterations may be made: - Using nozzles with flat fan-shaped outlets, said flat shape being parallel to the leeside flight surface; - Using multiple supply channels, each suppling its own anti-fouling or cleaning liquid and connected to dedicated nozzles; - Using the inventive concept in two or more hydrolysis reactors in series; and - Using a feeding arrangement with a single liquid supply source.

Claims (13)

1. A feeding arrangement (1) for feeding comminuted biomass material (Bio) through a treatment stage (200), said feeding arrangement (1) comprising a screw feeder (10) for feeding the biomass material (Bio) through the treatment stage (200), the screw feeder (10) comprising a housing (11), which comprises an inlet (12) and an outlet (13), and a feed screw (2) extending at least partially through said housing (11) for transporting the biomass material (Bio) from the inlet (12) to the outlet (13), which feed screw (2) comprises at least one screw flight (2b) with a pushing flight surface (PF) and a leeside flight surface (LF) located on opposite sides of the screw flight (2b), characterized in that said feeding arrangement (1) comprises a supply channel (SC) arranged to supply anti- fouling liquid from at least one liquid supply source (So1, So2), and a plurality of nozzles (NZ) connected to said supply channel (SC) and arranged at the leeside flight surface (LF), which nozzles (NZ) are arranged to distribute said anti- fouling liquid over the leeside flight surface (LF) for establishing a liquid layer on said leeside flight surface (LF).

2. A feeding arrangement (1) according to claim 1, wherein the anti- fouling liquid used is chosen from neutral or alkaline solutions, liquid surfactants, solvents, water or mixtures thereof

3. A feeding arrangement (1) according to claim 1 or 2, wherein a number of nozzles (NZ) are arranged at different radial distances from a center axis (CC) of the feed screw (2).

4. A feeding arrangement (1) according to any of the preceding claims, wherein at least one nozzle (NZ) comprises a hole in the leeside flight surface (LF) connected to the supply channel by means of a branch channel (BC) that extends through said screw flight (2b).

5. A feeding arrangement (1) according to claim 4, wherein said screw flight (2b) comprises a main body and a wall member (40) attached to said main body, which wall member (40) defines the leeside flight surface (LF), and wherein at least a portion of said branch channel (BC) extends between said wall member (40) and said main body.

6. A feeding arrangement (1) according to any of the preceding claims, wherein said feed screw (2) comprises a screw shaft (2a) and wherein said supply channel (SC) is a central hole running longitudinally through at least a portion of said screw shaft (SC).

7. A feeding arrangement (1) according to any of claims 1-5, wherein said supply channel (SC) is a pipe (60) wound around the screw shaft (2a).

8. A feeding arrangement (1) according to any of the preceding claims, said feeding arrangement (1) comprising a control member (CM) for regulating the flow of the anti- fouling liquid in said supply channel (SC).

9. A feeding arrangement (1) according to claim 8, wherein the supply channel (SC) is connected to at least two different liquid supply sources (So1, So2) with different anti- fouling liquids and the control member (CM) is used to alternate between said liquid supply sources (So1, So2).

10. A feeding arrangement (1) according to any of the preceding claims, wherein a plurality of nozzles (NZ) are arranged at a respective innermost radial position of the leeside flight surface (LF) and each directed along a respective axis that deviates less than 10 degrees from the leeside flight surface (LF) and less than 10 degrees from a radial direction.

11. A feeding arrangement (1) according to claim 10, wherein said axes are inclined against the rotational direction (ROT) of the screw flight (2b).

12. Use of a feeding arrangement (1) according to any of claims 1-11, wherein the feeding arrangement (1) is used in a hydrolysis process of lignocellulosic material of wood or non- wood origin, wherein the feeding arrangement (1) is used in a hot process stage at temperatures above 100 °C, either in pure steam heating or assisted with hydrolysis promoting agents, wherein sticky deposits are formed during the hydrolysis process.

13. A method for feeding comminuted biomass material through a treatment stage (200) using a feeding arrangement (1) comprising a screw feeder (10) for feeding the biomass material (Bio) through the treatment stage (200), said screw feeder (10) comprising a housing (11), which comprises an inlet (12) and an outlet (13), and a feed screw (2) extending at least partially through said housing (11) for transporting the biomass material (Bio) from the inlet (12) to the outlet (13), which feed screw (2) comprises at least one screw flight (2b) with a pushing flight surface (PF) and a leeside flight surface (LF) located on opposite sides of the screw flight (2b), characterized in that said method comprises the step of applying anti-fouling liquid from at least one liquid supply source connected to a supply channel (SC) connected to a plurality of nozzles (NZ) arranged at the leeside flight surface (LF) directly on the leeside flight surface (LF) during at least a part of the run time of the screw feeder (10), establishing a liquid layer on said leeside flight surface (LF).