Patent Description:
Various industries, such as the paper and textile industries, make use of natural fibres. The natural fibres, which are derived from natural sources such as, but not limited to, trees or other plants, may be treated after they have been separated from their originating structure to form a fibrous material in order to improve the suitability of the fibres for particular applications.

In known processes, the fibrous material may be added in batches to a tank to which various reagents may be added for a desired period of time under required processing conditions, such as controlled temperature and pressure, before unused reagents and/or waste products are removed. For each step in a process, different reagents may be added to or removed from the tank to perform multiple steps to a batch of material in a single tank or each step in a process may be performed in a different tank, with the batch of fibrous material transported between tanks for each step to be performed.

However, processing material in batches may be inefficient and may result in variations of quality and/or material properties between batches.

<CIT> discloses biomass pretreatment technology via a controlled feeding system of fibrous biomass into a continuous high-pressure reactor. <CIT> discloses a double-screw inclined screw conveyor. <CIT> discloses a drainer for continuously draining a liquid from a slurried thermally treated lignocellulosic biomass stream.

The present invention aims to at least partly solve the above-mentioned problems.

According to an aspect of the present invention, there is provided a reaction chamber as defined in appended claim <NUM>.

In an arrangement, the transporter comprises a second screw, arranged parallel to the first screw and extending along the elongate cavity from the input section to the output section.

In an arrangement, the transporter is configured such that the first and second screws rotate in the same direction to drive fibrous material from the first end to the second end of the elongate cavity.

In an arrangement, the reaction chamber further comprises a gearbox configured to drive both screws from an input of motive force from a single motor.

In an arrangement, the reaction chamber is configured such that the elongate cavity can be maintained at a pressure that is different from the atmospheric pressure, optionally greater than atmospheric pressure.

In an arrangement, the difference in pressure between the elongate cavity and atmosphere can be maintained at greater than <NUM> bar, optionally greater than <NUM> bar, optionally greater than <NUM> bar and optionally up to <NUM> bar.

In an arrangement, the input section is configured to feed fibrous material into the first end of the elongate cavity while maintaining the pressure difference between the elongate cavity and atmosphere.

In an arrangement, the output section is configured to output fibrous material from the second end of the elongate cavity while maintaining the pressure difference between the elongate cavity and the atmosphere.

In an arrangement, the elongate cavity is positioned such that the second end is higher than the first end.

In an arrangement, the reaction chamber further comprises at least one reagent port in fluid communication with the input section, output section or the elongate cavity and that is configured to supply a chemical reagent into the elongate cavity.

In an arrangement, the reaction chamber further comprises at least one reagent port in fluid communication with the input section, output section or the elongate cavity and that is configured to remove unused chemical reagents and/or waste products from the elongate cavity.

In an arrangement, a screw within the transporter comprises an interior cavity extending along its length and a plurality of perforations that provide fluid communication between the interior cavity of the screw and the elongate cavity of the reaction chamber around the screw; and
the interior cavity of the screw is in fluid communication with at least one reagent port configured to supply chemical reagent to the interior cavity or to remove from the interior cavity unused chemical reagents and/or waste products.

In an arrangement, within at least one region the screw comprises said perforations; and within at least one other region the screw does not have said perforations.

In an arrangement, the reaction chamber further comprises a temperature controller, configured to control the temperature of the contents of the elongate cavity.

In an arrangement, at least one region is associated with a temperature controller configured to control the temperature of the contents of the elongate cavity in that region alone.

According to an aspect of the present invention, there is provided a processing system for continuous chemical processing of fibrous material, comprising at least one reaction chamber as above.

In an arrangement, a plurality of reaction chambers as above may be arranged to process fibrous material successively.

In an arrangement, at least two reaction chambers are configured differently from each other.

In an arrangement, a single unit functions as the output section of a first reaction chamber and the input section of a second reaction chamber.

According to an aspect of the present invention, there is provided a method of continuous chemical processing of fibrous material as defined in appended claim <NUM>.

In an arrangement, the chemical processing is performed using a reaction chamber as above.

The invention will now be described by way of example only with reference to the accompanying figures, in which:.

<FIG> schematically depicts an arrangement of a reaction chamber <NUM> for continuous chemical processing of fibrous material. In an example, the reaction chamber may be used for processing fibrous material derived from biomass, including for example cellulosic substances. Examples of biomass substances that may be processed in the reaction chamber <NUM> include fibrous material derived from wood, straw, grass, seeds and similar materials. The fibrous material may be in an intermediate fibrous form such that one or more initial processes have been performed to separate the fibres from an originating structure in which the fibres were formed.

One or more of a variety of treatment steps may be performed on the fibrous material, namely the free-moving fibres separated from any originating structure in which the fibres were originally formed. The treatment steps may include delignification of the fibres, for example. The lignin present in plant cell walls lends rigidity to the original natural material, and may need to be removed to produce the desired properties in the processed fibres. Other processes performed on the fibrous material may include or facilitate processes such as digestion, degumming, bleaching and other similar common refinery process steps. Alternatively or additionally, the processes may be selected to at least one of remove hemicellulose, modify the surface energy of the fibres, de-bundling of fibres (for example into elementary fibres), modify fibril structures and/or add functional groups to the fibres. It should be appreciated that other processes may be performed on fibrous material within a reaction chamber <NUM>.

The reaction chamber <NUM> includes an elongate cavity <NUM> having first and second ends <NUM>, <NUM>. First and section ends, <NUM>, <NUM> are arranged at opposite ends of the elongate cavity <NUM> with respect to the elongate direction. The elongate cavity <NUM> may be defined by an outer wall <NUM> such that the elongate cavity can contain fibrous material added to it and any reagents used for chemical processing.

At the first end <NUM> of the elongate cavity, an input section <NUM> is provided that is configured to feed fibrous material into the first end <NUM> of the elongate cavity <NUM>. At the second end <NUM> of the elongate cavity <NUM> an output section is provided that is configured to output fibrous material from the second end <NUM> of the elongate cavity.

The reaction chamber <NUM> further includes a transporter that, in use drives the fibrous material from the first end <NUM> to the second end <NUM> of the elongate cavity. In such an arrangement, the fibrous material may be continuously processed as it is transported through the reaction chamber without the need to provide separate process tanks for processing of the fibrous material in batches or separate transportation systems to transfer the material between tanks.

The transporter includes a screw <NUM> that is rotated in order to drive the fibrous material from the first end <NUM> to the second end of the elongate cavity <NUM>. Such a screw <NUM> is provided within the elongate cavity <NUM> and the outer wall <NUM> defining the elongate cavity <NUM> may be positioned closely to the edges of the screw <NUM>. Such an arrangement may minimise reverse flow of material between the edges of the screw <NUM> and the wall <NUM>. In some arrangements, the separation between the edge of the screw <NUM> and the wall <NUM> may be selected such little or no fibrous material flows in the reverse direction (namely from the second end <NUM> towards the first end <NUM>) but such that liquid can flow in this direction.

As shown in <FIG> which shows an arrangement of a transporter <NUM>, the transporter <NUM> may include first and second screws, <NUM>, <NUM>. The two screws <NUM>, <NUM> may be arranged parallel to each other and such that the central axis of rotation of the two screws, <NUM>, <NUM> is parallel to the elongate direction of the elongate cavity <NUM>.

In a particular arrangement, the transporter <NUM> may be configured such that, in use, the first and second screws, <NUM>, <NUM> rotate in the same direction as each other in order to drive fibrous material from the first end <NUM> to the second end <NUM> of the elongate cavity <NUM>. Such an arrangement, which may be referred to as having co-rotating screws, may be particularly beneficial for driving fibrous material along the elongate cavity <NUM>. This is because the fibrous material with a tangle of free-moving fibres may be difficult to handle in a transporter. The use of co-rotating screws may provide a self-cleaning function, reducing the likelihood of fibrous material being retained within the elongate cavity <NUM> of the reaction chamber <NUM> for longer than is desired. The use of co-rotating screws may also provide improved mixing in the processing of fibrous material. In other arrangements, counter-rotating screws may be used.

In an arrangement as depicted in <FIG>, a single gearbox <NUM> may be provided that drives both screws <NUM>, <NUM>. A motor, for example and electric motor <NUM> may be provided to drive the gear box <NUM>. Such an arrangement may be beneficial because it may simplify the control system for the reaction chamber <NUM> as only a single motor needs to be controlled.

Alternatively or additionally, the use of a single gearbox <NUM> that drives both screws <NUM>, <NUM> may beneficially facilitate driving the first and second screws <NUM>, <NUM> in perfect synchronism which may result in improved performance of the transporter. For example, synchronized screw motion may improve overall energy efficiency. This is because, if the screws are not in synchronism, the material distribution in between overlapping crests in the screw pitch can become too tight, leading to high packing of the fibre mass, which in turn leads to increased torque load in the drive unit.

It should be appreciated that other arrangements may also be used for driving the first and second screws <NUM>, <NUM> including, for example, the use of separate motors for driving each screw. In such an arrangement, a suitable controller may be used to drive the screws <NUM>, <NUM> in synchronism.

In an arrangement, the reaction chamber <NUM> may be configured such that the interior of the elongate cavity <NUM> can be maintained at a pressure that is different from atmospheric pressure. In an arrangement, the pressure within the elongate cavity <NUM> may be maintained at a pressure that is greater than atmospheric pressure. Alternatively or additionally, the reaction chamber <NUM> may be configured such that the elongate cavity <NUM> can be maintained at a lower than atmospheric pressure, for example a partial vacuum.

The reaction chamber <NUM> may be designed to maintain a pressure difference between the elongate cavity <NUM> and atmosphere that is a pressure greater than <NUM> bar, optionally a pressure greater than <NUM> bar, optionally a pressure greater than <NUM> bar and optionally up to a pressure difference of up to <NUM> bar. A pressure controller may be provided in order to operate the reaction chamber at a required pressure.

In order to enable continuous processing of the fibrous material within the reaction chamber <NUM> whilst maintaining a pressure difference between the elongate cavity <NUM> and atmosphere, the input section <NUM> and the output section <NUM> may be configured to feed fibrous material into the first end <NUM> of the elongate cavity and output fibrous material from the second end <NUM> of the elongate cavity <NUM>, respectively, while minimising the ingress or escape of gas, such that the desired pressure can be maintained.

The input section <NUM> and output section <NUM> may be any convenient arrangement for achieving this function. For example, a cell feeder may be used, in which a unit with a plurality of cells, separated by leaves rotates. As each cell rotates, it transfers material from a first side of a barrier to a second side of the barrier but at any instant one or more leaves are sealed against a section of the barrier to prevent a reverse flow of fluid through the barrier. Alternatively or additionally, a plug screw feeder may be used that uses a screw to drive material into the elongate cavity <NUM>. Either such an arrangement may introduce material into the cavity <NUM> against a pressure difference.

In an arrangement, the elongate cavity <NUM> may be positioned such that the second end <NUM> is at a higher elevation than the first end <NUM>. In such an arrangement, while the transporter drives the fibrous material to move from the first end <NUM> to the second end <NUM> of the elongate cavity <NUM>, liquid within the elongate cavity <NUM> may flow under the effect of gravity from the second end <NUM> to the first end <NUM>. Such an arrangement may conveniently improve chemical processing. For example, a reagent may be introduced at the second end <NUM> that is gradually consumed during a chemical process. The reagent at the second end <NUM> will therefore be most concentrated at the second end <NUM> and encountering fibrous material at the second end <NUM> that is most processed and requires high concentration reagent in order to complete the chemical process. In contrast, the least processed fibrous material at the first end <NUM> encounters the lower concentration reagent. Such an arrangement may improve the efficiency of the chemical process.

In an arrangement, the reaction chamber <NUM> may include at least one reagent port <NUM> that is configured to supply a chemical reagent into the elongate cavity <NUM>. The one or more reagent ports <NUM> may supply the chemical reagent directly to the elongate cavity <NUM>, or via the input section <NUM> or the output section <NUM> or some combination thereof. A reagent port <NUM> directly in fluid communication with the elongate cavity <NUM> may be located at any location along the length of the elongate cavity <NUM>. It will be appreciated that, depending on the chemical process being performed on the fibrous material, plural reagent ports <NUM> may be provided to supply a chemical reagent at different points along the length of the elongate chamber <NUM>, corresponding to different stages in the processing of fibrous material that is driven from the first end <NUM> to the second end <NUM> of the elongate chamber <NUM>.

Similarly, one or more reagent ports <NUM> may be provided that are configured to remove unused chemical reagents and/or waste products resulting from the chemical process from the elongate cavity <NUM>. As with the reagent ports <NUM> used to supply chemical reagents to the elongate cavity <NUM>, the reagent ports <NUM> used to remove chemical reagents and/or chemical waste products may be in fluid communication with the input section <NUM>, the output section <NUM> or directly with the elongate cavity <NUM> or any combination thereof. Furthermore, reagent ports <NUM> used to remove the unused chemical reagents and/or waste products from the elongate cavity <NUM> may be provided at plural locations along the elongate cavity <NUM> in order to remove chemical reagents and/or waste products at corresponding stages within the chemical process that is being performed on the fibrous material that is driven from the first end <NUM> to the second end <NUM> of the elongate cavity <NUM>.

By means of the supply and/or removal of chemical reagents and/or waste products at different locations along the length of the elongate cavity <NUM>, the conditions may be different for different regions of the elongate cavity <NUM>, enabling different processes to be performed on the fibrous material in the different regions. It will be appreciated that the different regions, which in some contexts may be referred to as zones, may all be the same size or some or all of the regions may be different sizes.

In an arrangement in which the transporter includes one or more screws <NUM>, <NUM>, one of both screws <NUM>, <NUM> may have an interior cavity extending along some or all of its length and perforations to enable fluid to pass between the interior cavity of the screw <NUM>, <NUM> and the elongate cavity <NUM> of the reaction chamber <NUM> that is around the screw <NUM>, <NUM>. In such an arrangement, the interior cavity, <NUM>, <NUM> may be in fluid communication with a reagent port <NUM>, <NUM>, in order to supply a chemical reagent to the interior cavity and then to the elongate cavity <NUM> or to remove from the interior cavity of the screw <NUM>, <NUM> unused chemical reagents and/or waste products that have drained from the elongate cavity <NUM> of the reaction chamber <NUM> into the interior cavity of the screw <NUM>, <NUM>.

The elongate cavity <NUM> is divided into plural regions. In such an arrangement, the perforations between the interior cavity of the screw <NUM>, <NUM> and the elongate cavity <NUM> around the screw <NUM>, <NUM> may be provided in one or more regions and not provided in one or more different regions. As with the positioning of the reagent ports <NUM>, <NUM> this may enable the control of the position along the length of the elongate cavity <NUM> at which reagents are provided to and/or reagents and/or waste products, are removed from the elongate cavity <NUM>.

Other differences in processing conditions may also be provided between different regions of the elongate cavity <NUM>. For example, <FIG> depicts a screw <NUM> that may be used within a transporter within the elongate cavity <NUM> having <NUM> regions, <NUM>, <NUM>, <NUM>. Comparing the first and second regions <NUM>, <NUM>, it will be seen that the pitch of the thread of the screw <NUM> is greater in the second region <NUM> than in the first region <NUM> such that the screw has variable pitch along its length. With such an arrangement, for a given speed of rotation of the screw <NUM>, the fibrous material will move more slowly in the elongate direction of the elongate cavity <NUM>, namely from the first end <NUM> to the second end <NUM>, within the first region <NUM> in comparison to that within the second region <NUM>. Accordingly the variable pitch of the screw may be used to control the conveying velocity.

Such an arrangement may be used to retain fibrous material within the first region <NUM> for a relatively longer time period and to relatively quickly move the fibrous material through the second region <NUM>. By selection of appropriate pitch of the thread of the screw <NUM> within each region one may therefore control the relative time that the fibrous material spends within each region and is therefore subject to the processing conditions within that region.

Comparing the second region <NUM> to the third region <NUM> shown in <FIG>, it will be seen that, while the pitch remains constant, the distance between the central core <NUM> of the screw <NUM> and the outer edge <NUM> of the thread of the screw <NUM> is reduced in the third region <NUM> in comparison to that of the second region <NUM>. This may be referred to as a screw with variable pitch line. The effect of this is to compress the fibrous material as it transfers from the second region <NUM> to the third region <NUM>. This compression may, for example, be used to squeeze liquid from the bulk of the fibrous material, for example, to remove chemical reagents and/or waste products which, as discussed above may be removed from the elongate cavity <NUM>, for example through one or more reagent ports <NUM>.

It will therefore be understood that by selecting the design of the screw <NUM> in different regions of an elongate cavity <NUM>, additional control of the movement of the fibrous material may be provided in addition to merely driving it from the first end <NUM> to the second end <NUM> of the elongate chamber.

In an arrangement, a temperature controller <NUM> may be provided to control the temperature of the contents of part, parts or all of the elongate cavity <NUM>. Such an arrangement is schematically depicted in <FIG>, in which a heating system <NUM> is provided around one region or plural regions of the elongate cavity <NUM>. It should be appreciated that such a heating system <NUM> may utilise one or more known arrangements, for example, providing liquid or gas through a conduit provided in or around the elongate cavity <NUM>, an electric heater provided in or around the elongate cavity and/or by provision of a combustion system in or around the elongate cavity <NUM>. It should also be appreciate that a temperature controller may alternatively or additionally include a refrigeration system.

Furthermore, it should be appreciated that the temperature controller may include a sensor for determining, directly or indirectly, the temperature of the contents of the elongate cavity <NUM> in the region of the temperature controller such that the heating and/or refrigeration can be controlled within that region, or within plural regions, to achieve a desired temperature.

The temperature controller may be used in order to assist in the control of or promotion of the chemical processing of the fibrous material. In arrangements in which it is desirable for the chemical processing to vary along the length of the elongate cavity <NUM>, separate temperature controllers may be provided to one or more regions along the length of the elongate cavity such that distinct temperature zones can be provided in different regions of the elongate cavity <NUM>.

As discussed above, in an arrangement, plural different processing conditions can be provided along the length of an elongate cavity <NUM> within a reaction chamber in order to provide varying conditions under which the fibrous material is processed.

For instance, as discussed above, the elongate cavity <NUM> is divided into plural regions, wherein different regions of the elongate cavity may have different processing conditions. The processing conditions that are varied between different ones of the plural regions may be, for instance, one or more of: the type and/or amount of chemical reagent supplied to the elongate cavity in each region; the type and/or amount of unused chemical reagent and/or waste products removed from the elongate cavity in each region; flow/movement characteristics (e.g. velocity and/or compression) of fibrous material in each region; and process temperature in each region. The division of an elongate cavity into plural regions with different processing conditions may enhance process control in the processing of fibrous material. This is because such processes may comprise multiple phases, in which the required or optimum process conditions vary from one phase to the next. The inclusion of plural regions as discussed above enables different process phases to be carried out in a single reaction chamber, thus enabling each phase of the process to be individually optimised. This provides an improvement in process efficiency compared with, for instance, an arrangement in which material is processed through a series of distinct reactors having different process conditions, or an arrangement in which material is processed in batches with varying conditions between each batch.

Alternatively or additionally, plural reaction chambers <NUM>, <NUM>, <NUM> may be joined in sequence, as depicted in <FIG>, such that the output of a first reaction chamber <NUM> is input into a second input chamber <NUM> and the output of the second reaction chamber <NUM> is output into a third reaction chamber <NUM>.

It will be appreciated that any number of reaction chambers may be joined together in such a way in a processing system. It should also be appreciated that the reaction chambers <NUM>, <NUM>, <NUM> need not be directly joined. For example, between two reaction chambers a storage vessel could be provided to temporarily store an intermediate product.

It should also be appreciated that, in a processing system having plural reaction chambers as discussed above, two or more or all of the reaction chambers may be configured differently from each other, for example varying by any or all of the variations discussed above.

Claim 1:
A reaction chamber (<NUM>) for continuous chemical processing of fibrous material, comprising:
an elongate cavity (<NUM>) having first (<NUM>) and second (<NUM>) ends at opposite ends of the elongate cavity and configured to contain the fibrous material and any reagents added to it for chemical processing;
an input section (<NUM>) at the first end of the elongate cavity, configured to feed fibrous material into the first end of the elongate cavity;
an output section (<NUM>) at the second end of the elongate cavity, configured to output fibrous material from the second end of the elongate cavity; and
a transporter (<NUM>) configured to drive fibrous material from the first end to the second end of the elongate cavity,
wherein the transporter comprises a screw (<NUM>) extending along the elongate cavity from the input section to the output section, and
wherein the elongate cavity comprises plural regions (<NUM>, <NUM>, <NUM>), and at least one of the pitch of the screw or screws and the separation between the central core (<NUM>) of the screw or screws and the edge (<NUM>) of the screw or screws is different in one region of the elongate cavity from that of another region.