Abstract:
Reactor for enzymatic hydrolysis of a raw material comprising in sequence: i)—a first heat exchanger adapted to heat the raw material supplied to the reactor to a temperature within a range that favours enzymatic hydrolysis, ii)—a reactor comprising plural in reactor chambers connected in series, separated by closable valves, iii)—a second heat exchanger adapted to heat the reaction mixture to a temperature higher than the temperature range favouring enzymatic hydrolysis, the reactor being formed with inclined tubular reactor chambers assembled to form a reactor with vertical axis, the first reactor chamber being the vertically uppermost chamber of the reactor, while at least one reactor chamber is adapted to be stirred with a through-flowing inert gas.

Description:
BACKGROUND 
       [0001]    The disclosure concerns a reactor for enzymatic treatment. 
         [0002]    During enzymatic treatment of organic materials for the sake of hydrolysis (decomposition), a control of the temperature in the material and the duration of the exposure of the material for the enzymes (contact time) is a prerequisite for successful result. Too long or too short contact time will both be negative for the product of the process and can cause problems for further processing of the material and/ or be a negative for the quality of the finished product from a manufacturing process. Proper contact time is thus a central issue here. 
         [0003]    When using industrial enzymes for hydrolysing or another form of enzymatic process, the appropriate enzymes are added to a raw material. After the enzymes have been added and distributed in the raw material, it is important that the mixture is stirred constantly to ensure good contact between enzyme and raw material. As mentioned it is also important that the enzymes are in contact with the raw material for a certain time interval. When this time interval is reached, it is thus important that the enzymatic degradation ceases quickly so that the process does not go too far. This is typically ensured by heating the mixture of raw material and enzymes to a temperature at which the enzymes are destroyed (inactivated). 
         [0004]    A similar challenge applies to a number of other chemical processes where it is important with a homogeneous blend of the components included as well as a controlled reaction time which can neither be significantly shorter or considerably longer than the optimal one if the desired quality of the final product to be obtained. 
         [0005]    The easiest way to achieve proper contact time is to use reactors based on “batch” principle. By batch execution a defined volume (tank or the like) is kept at certain conditions for a certain time, before the process is stopped. For enzymatic processes, as mentioned, additional heating is used to inactivate the enzyme. In an industrial production large volumes are processed, and these large volumes are difficult to heat quickly enough if run as batch. An alternative is to use a plural of small batch volumes, but this will lead to disproportionately high costs in terms of technology. 
         [0006]    There are also other disadvantages of batch processes compared with continuous processes regardless of whether the processes involve enzymatic treatment. One such disadvantage is far more frequent starting and stopping of processes. This is labouring intensive and more difficult to automatize than continuous processes. Moreover, operating conditions during start and stop tend to vary more than what is desirable. 
         [0007]    The goal is to have a continuous through-put of homogeneously mixed raw material which process is inactivated at a given time interval. To allow a continuous flow of raw materials to go through a large “complete mix” container is not a good solution because the contact time between the individual components will then be very difficult to control. 
         [0008]    A reactor for the enzymatic treatment of the raw material is known from Norwegian patent no. 322 996 (WO 2006 126891). The treatment takes place in a substantially vertically arranged reactor with separate reactor chambers where the material in each chamber is mixed mechanically with a stirrer and transferred to an adjacent chamber below by utilizing gravitational forces. The reactor will ensure consistent retention time and consistent conditions for all material processed. 
         [0009]    For the treatment especially of marine raw material, it is important that the on-board processing takes place as soon as possible after harvesting. It is thus important that this can take place in a facility that is compact and which has such properties that is not severely affected by waves that can make a vessel heel. 
       SUMMARY 
       [0010]    The disclosure provides a system and/ or a reactor for the hydrolysis of raw material which is able to produce consistent reaction conditions for all material that is supplied, regardless of changes in external conditions. 
         [0011]    The disclosed reactor provides advantages associated with both batch processes and continuous processes when the contact time between the components included in the process is a critical parameter for product quality. 
         [0012]    The disclosed embodiments provide the above benefits by means that are convenient and inexpensive in industrial scale. 
         [0013]    Particularly, the disclosure provides a reactor for the hydrolysis of marine raw material on board a vessel with limited space, which is able to provide consistent reaction conditions under varying wind and wave conditions. 
         [0014]    The material to be treated in the reactor is partly referred to as “the raw material”, partly as “the material”. 
         [0015]    The disclosed reactor can be manufactured compact in that the reactor externally can have the form of a standing cylinder where the reactor chambers are located with a given inclination relative to the horizontal plane, while the reactor as a whole has a generally vertical orientation. The reactor chambers are tubular and preferably have a circular cross section with the exceptions indicated by the enclosed drawings and the discussions of same. The inclination of each chamber may vary, but is preferably at least 1/10 (vertically/ horizontally) [5.7 degrees]. For some embodiments the inclination can be ⅕ [11.3 degrees]. 
         [0016]    Required heat exchange can be realized concentrically with and within this vertical coil of reactor chambers. Stirring takes place by means of supplied inert gas being bubbled through the reactor chambers. Valves between all reactor chambers ensure uniform residence time in each reactor chamber and therefore uniform total residence time in the reactor. Transportation of partially treated material from one reactor compartment to the next can be performed by supplying an excess of pressure of the inert gas used for stirring while the upstream valve is closed and the downstream valve an open in the reactor chamber in question. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention is below described in further detail with reference to the accompanying drawings, where: 
           [0018]      FIG. 1  shows in perspective a first embodiment of the reactor according to the disclosure. 
           [0019]      FIG. 2  is a schematic view of one reactor chamber according to an embodiment. 
           [0020]      FIG. 3  is a schematic sectional view of certain details of the embodiment of  FIG. 1 . 
           [0021]      FIG. 4  is a schematic view showing further details of the embodiment of  FIG. 1 . 
           [0022]      FIG. 5  is a schematic view of a flow sheet over a process utilizing the reactor according to the disclosure. 
           [0023]      FIG. 6  is a schematic and simplified top view of the reactor shown in  FIG. 1 . 
           [0024]      FIG. 7  is a schematic and simplified top view of a reactor according to the disclosure which constitutes a variant to the one shown in  FIG. 1 . 
           [0025]      FIG. 8  is a side view of a further embodiment of the reactor according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]      FIG. 1  generally shows an embodiment of a reactor of the disclosure. A number of reactor chambers R 1 -R 6  are coiled up helically downwards into the reactor which as a whole can be said to have a vertical orientation or a vertical axis. An arbitrary reactor chamber can be termed Ri where i is to be viewed as an index. Each reactor chamber R covers circumferentially close to 360 degrees, that is, a full circle. Each reactor chamber Ri is followed by a valve Vi, where i is to be viewed as an index, separating it from the next chamber. Reactor chamber R 1  is thus followed by the valve V 1 . The valves V 1 -V 5  which separates the chambers from each other, is in the shown embodiment aligned over one another. This is for convenience and is not an essential feature of the reactor. Below the reactor chambers there are three pasteurizing chambers P 1 -P 3  in the illustrated embodiment, having substantially the same shape and size as the reactor chambers. These are also separated by valves, numbered as VP 1  and VP 2 . The exact number of reactor chambers and pasteurizing chambers may vary. 
         [0027]      FIG. 1  also shows the supply conduit  01  for raw material, discharge conduit  02  for processed material. Also shown are a pressure tank  13  for inert gas, a number of pipes  10  for inert gas to each of the reactor chambers and pasteurizing chambers, a manifold  11  for used inert gas and a return conduit  14  for recycling the used inert gas to the container  13 , via a compressor  12 . The inert gas is discharged from reactor chambers via valves generally designated RV 1  (where i is to be viewed as an index). Three of these are shown with numbers in  FIG. 1 , RV 1 -RV 3 . 
         [0028]      FIG. 1  furthermore shows a supply conduit  03  for air to at least one heat exchanger and outlet  04  for air from a heat exchanger, designated HEX 2 . In practice, two heat exchangers will typically be used as explained later. 
         [0029]      FIG. 1  also shows a conduit  17  for the processed material from the reactor chamber R 6  to the heat exchanger HEX 2 . Also shown is a conduit  16  from the upper part of the heat exchanger HEX 2  to the inlet of pasteurizing chamber P 1 .  FIG. 1  also shows a portion of a conduit  18  which brings the heat exchanged feedstock into reactor chamber R 1 . 
         [0030]      FIG. 2  shows a cross-section of a single reactor chamber, here chamber  3  has randomly been chosen. A difference from the embodiment shown in  FIG. 1  is that this reactor chamber for simplicity is shown as a straight chamber. It is also possible to realize the present reactor with straight chambers. The material inlet to the reactor chamber R 3  is through the valve V 2  to the right in the figure while the outlet is via valve V 3  to the left in the figure. Due to the inclination of the reactor chamber, the material flow is assisted by gravity. In  FIG. 2 , the inclination of the reactor chamber is about 1/10. This is often sufficient in practice, but can in some cases be larger, such as ⅕. Inert gas, typically nitrogen, is introduced via the supply conduit  10  near the downstream end of the reactor chamber and discharged through the discharge stub  21  near the upstream end of the reactor chamber. During treatment both valves V 2  and V 3  are closed, so that the material for a limited period of time remains stationary in the reactor chamber. As the arrows indicate, the transportation of inert gas through the chamber causes a circulation of the material in the chamber. The inert gas is thus used to efficiently agitate the mass being processed. There is a feed valve IV 3  on the supply conduit  10  into the reactor chamber and there is also a return valve RV 3  on the discharge stub  21  for gas to the manifold  14 . 
         [0031]    When reactor chamber  3  is to be emptied, valve RV 3  is closed and a selected overpressure is applied to the reactor. It is essential that both valves V 2  and V 3  are also closed. It is assumed that the adjacent downstream reactor chamber R 4  have been previously emptied of material and released from any overpressure. Then valve V 3  is opened and a rapid pressure release will take place as gas and material are blown into reactor chamber R 4 , also assisted by gravity. While the gas will be distributed between the two chambers, virtually all solid and liquid materials will end up in reactor chamber  4  for further processing there. 
         [0032]    It is to be understood that reactor chamber R 3  has only been chosen as an arbitrary example; essentially the same type of treatment takes place in all reactor chambers, and the main reason for using so many separate chambers is to ensure uniform residence time for the entire mass to be treated, the flow of material from the outside behaving approximately as an ideal plug flow from the inlet of reactor chamber R 1  to the outlet from reactor chamber R 6 . The discharge from the reactor chamber R 6  is slightly different because the flow of material does not go directly to a below located chamber, but to a heat exchanger for further heating to thereby interrupt the hydrolysis reaction. The temperature of the pulp after this heat exchange may typically be 90° C. or more. 
         [0033]    The skilled artisan will understand that from a situation where all reactor chambers are filled with material for processing, the material in reactor chamber R 6  must be emptied before any other chamber, then reactor chamber R 5  before reactor chamber R 4  etc. However, to make room for the material to be evacuated from reactor chamber R 6 , it will be necessary to make room by means of a similar procedure for the pasteurizing chambers P 1 -P 3  that is by discharge of the chambers P 3 , P 2  and P 1  in this order. 
         [0034]    The heat exchange in the reactor is basically classical and can be performed the same way and in the same type of equipment as in prior art processes. It is advantageous, however, both in view of space and other considerations that it is performed in a heat exchanger which is coaxial with the reactor chambers when these are arranged so that they together form a helix. 
         [0035]      FIG. 3  shows a vertical cross-section of a system for heat exchange which may be included as an integral part of the reactor. The reactor chambers R 1 -R 6  are shown in the figure as are also the pasteurizing chambers P 1 -P 3 . Coaxially with these and with the vertical axis of the reactor, the superposed two heat exchangers HEX 1  and HEX 2  are arranged, which may also be perceived as one two-stage heat exchanger. The purpose of the lower heat exchanger HEX 1  (or lower stage of the heat exchanger) is to heat the material to a temperature that supports the enzymatic hydrolysis, typically a temperature of about 50° C. This is performed with the flow of material supplied to the reactor through the supply conduit  01  ( FIG. 1 ) before the material enters reactor chamber R 1 . The material flow supplied to the heat exchanger HEX 1  via supply conduit  01  passes, in the illustrated embodiment, upwards through the heat exchanger HEX 1  in a helically arranged conduit coil  33  near the outer wall of the heat exchanger. Heat is supplied the heat exchanger to heat exchange device  31 . The heat exchanger HEX 1  is generally filled with a liquid, preferably an aqueous liquid. In the illustrated embodiment, moreover, air is supplied to the heat exchanger from air supply  03  via a manifold  35 . The air helps to circulate water upwards near the centre of the heat exchanger while the water circulates down again along the periphery of the heat exchanger where the helical conduit coil  33  is located, so that the heat exchange in relation to the conduit coil  33  essentially has the character of counter-current heat exchange. 
         [0036]    We now refer to  FIG. 4  as well as to  FIG. 3 . The outlet of the conduit coil  33  is connected to conduit  18  ( FIG. 4 ) which brings the heated raw material to reactor R 1 . Typical temperature of the material mixture into R 1  is 50° C., but it may vary a few degrees up or down. The actual, measured real time temperature of the material in the reactor R 1  or out of the conduit coil  33  may be used to control the gate opening of the heat exchange unit  31 . 
         [0037]    Heat exchanger (or heat exchange step) HEX  2  has the same general construction as heat exchanger HEX 1 . Material treated in the reactors R 1 -R 6  is supplied to a heat exchanger HEX 2  in a helically upward conduit coil  34  which is located near the wall of the heat exchanger, via a conduit  17 . A heat exchanger unit  32  supplies necessary heat to the heat exchanger HEX 2  so that the material passing through the conduit coil  34  is heated to a temperature high enough to terminate the enzymatic hydrolysis. A suitable temperature can be ca. 90° C. or more. The actual, measured real time temperature of the material out of the conduit coil  34  can be used to control the gate opening on the heat exchanger unit  32 . The material leaving the heat exchanger HEX 2  is fed to the first pasteurizing chamber P 1  via a conduit  16 . 
         [0038]      FIG. 4  shows parts of the reactor  1  stripped for reactor chambers and pasteurizing chambers, for more clearly to show the outer conduit connections. This being conduit  01  for material supply, conduit  02  for processed material, conduit  03  and  04  for air to and from heat exchanger respectively, conduit  17  for transfer of material from reactor chamber R 6  ( FIG. 1 ) to second heat exchanger HEX 2 , conduit  18  for transfer of material from the first heat exchanger HEX 1  to first reactor chamber R 1  ( FIG. 1 ), and conduit  16  for transfer of material from second heat exchanger HEX 2  to first pasteurizing chamber P 1  ( FIG. 1 ). 
         [0039]    It should be emphasized that the heat exchangers described herein only represent an example of a suitable layout of the heat exchangers and that any heat exchanger which makes it possible to heat the raw material to a temperature which supports enzymatic hydrolysis and any heat exchanger which makes it possible to heat the treated material to a higher temperature to stop the enzymatic hydrolysis of the material, can be used. It is preferred, however, to use the available volume along the axis of the vertical reactor to the heat exchange, and the shown principle of helical material loop and bubbling of air through the heat exchangers, is convenient because it provides a good temperature distribution in the heat exchangers and in practice a substantially counter-current heat exchange, due to the fact that air pulls the liquid upwards near the vertical axis of the heat exchangers, while the liquid circulated down again near the periphery of the heat exchangers. 
         [0040]      FIG. 5  schematically shows the process flow for a process utilizing the apparatus as shown in the embodiment of  FIGS. 1-5 . To the far left a supply of raw material  51  to a feed tank  52  is shown, furthermore a mill  53  for convenient subdivision of the raw material and a pump  54  for feeding the material into the reactor. The pump  54  also sucks in a desired amount of enzyme from enzyme container  55 , where the enzyme can be suitably diluted. The components  52  to  55  do not constitute part of the reactor of the present invention and may include any suitable tanks, mills or pumps. In addition to the material flow,  FIG. 6  shows also how the inert gas circulates from container  13 , via the various reactor chambers and back to container  13  via manifold  11  and compressor  12 . A container  56  for the finished treated material is also shown. 
         [0041]      FIG. 5  also schematically shows the flow of inert gas (g) from a container  13  through the reactor and back to container  13  via a manifold  11 , optionally a not illustrated return conduit  14 , and a compressor  12 . 
         [0042]      FIG. 6  shows schematically and simplified a top view of the reactor shown in  FIG. 1 , with the reactor chamber R 1  coiled around the heat exchanger HEX 2 , valve V 1  (and below this, the valves V 2 , V 3 , etc.). Conduit  18  for supplying raw material is indicated, while the flow of inert gas in the system is omitted. 
         [0043]      FIG. 7  shows a view of an alternative embodiment relative to that shown in  FIG. 1 , where the reactor chambers R 1  ‘to R 4 ’ are straight. It is not apparent from  FIG. 8  that also in this case the reactor chambers are arranged with inclination. Additional reactor chambers can be provided below the illustrated ones; as an example a reactor chamber R 5 ′ below reactor chamber R 1 ′, a reactor chamber R 6 ′ below reactor chamber R 2 ′ etc. 
         [0044]      FIG. 8  shows an alternative embodiment of that illustrated in the preceding figures. 
         [0045]    Details shown in  FIG. 8  have numbers in the same series as in  FIG. 1 , with an addition of 100. 
         [0046]    There are two main differences between these embodiments, one consisting in that the reactor chambers R 101 -R 107  and pasteurizing chambers P 101 -P 103  are not tubular, but having the form of more regular tanks, preferably without sharp corners where material undesirably may collect. The other difference is that the reactor system is arranged so that it occupies less space in height and more space in the form of the floor area, specifically that the heat exchangers HEX 101  and HEX 102  are located beside each other, not superposed, and that the pasteurizing chambers are not positioned below the reactor chambers, but laterally adjacent to the reactor chambers. 
         [0047]    The local space conditions are thus an important factor with regard to which embodiment is most favourable; if one has more space in the form of floor area than height, the variant of  FIG. 8  being the most preferable one. Moreover, the system as illustrated still comprises a first heat exchanger HEX 101  intended to heat supplied material to a temperature which supports enzymatic hydrolysis while heat exchanger HEX 102  is arranged to heat the material mixture received to a higher temperature than temperatures supporting enzymatic hydrolysis. 
         [0048]    Furthermore there are seven reactor chambers R 101 -R 107  which are all stirred by means of inert gas and wherein the material transportation from reactor chamber R 101  to R 107 , step by step (five steps) takes place to lower vertical levels so that the transfer is supported by gravity. Discharge of the system can also take place in the same manner as described above, using supply of gas at elevated pressure. 
         [0049]    The system of  FIG. 8  further includes three pasteurizing tanks which can have the same regular shape as reactor chambers R 101 -R 107 . In this embodiment, it is less important than in the embodiment shown in  FIG. 1  that the pasteurizing chambers have the same shape and the same size as the reactor chambers, but it is still a natural choice that they are substantially equal, specifically because it is easier and more efficient to produce chambers of uniform size and shape. 
         [0050]      FIG. 8  shows supply of raw material  101 , discharge of processed material  102 , conduit  118  for material transportation from the first heat exchanger to the first reactor chamber, conduit  117  from the last reactor chamber to the second heat exchanger, conduit  116  from second heat exchanger to the first pasteurizing chamber, supply conduit  110  for inert gas and manifold  111  for used inert gas to be used again. 
         [0051]    It should be emphasized that while  FIG. 8  does not show details such as compressor for inert gas, pressure vessel for same, or supply and discharge of heat medium to the heat exchangers, the skilled person would have no difficulty in selecting the proper equipment for such items. 
         [0052]    In the following a practical example of using the reactor in a typical usage situation is provided. 
         [0053]    A partition wall may separate conduit coils  33  and  34  from the central mass of water in each of the heat exchangers HEX 1  and HEX 2 . Thereby the principle of the heat exchange having the form of counter-current heat exchange is additionally enhanced. 
         [0054]    There should be an “aperture” between the coils of the coil pipe, between the conduit coils and the outer wall, and between the conduit coils and the partition wall when such one is present. This is to achieve the best possible heat transfer. With a diameter for example of 60 mm, an aperture of e.g. 20 mm may be used. When using partition wall, this naturally ends at distance from both top and bottom of the heat exchangers to allow the water to turn down at the top and turn up again at the bottom. 
         [0055]    Heat supplied to heat exchangers units  31  and  32  may typically be in the form of hot water, steam, or a combination thereof. 
         [0056]    The product temperature is determined in practice primarily by the following variables: 
         [0057]    a—The rate of the product flow up through the conduit coil. The rate will vary over time in even transitions, controlled by a pump which typically can be a double-acting piston pump. 
         [0058]    b—The rate of the hot water counter-currently to the conduit coil can be varied in line with the product flow, by controlling the rate of feed air to manifold  35 . 
         [0059]    c—The temperature of hot water. Gate opening of steam/hot water for heat exchangers device  31  can be controlled in accordance with temperature of the residual raw material as it leaves the heat exchanger HEX 1 . 
         [0060]    Heat exchanger HEX 2  is used to pasteurize the product after hydrolysis to “kill” the enzyme activity and to prevent bacterial growth. 
         [0061]    The temperature of the raw material may have fallen approximately 3° C. during the time it takes to hydrolyse the raw material. Thereafter, it is heated in the heat exchanger HEX 2  for example to 95° C. The relationship between the height of the lower (HEX 1 ) and upper HEX 2 ) heat exchanger can be adjusted by temperature differences: 5-48° C. and 45-95° C. The air flows out into the open after having set the water in both chambers in motion. 
         [0062]    The dimensions of reactor chambers R 1 -R 6  may vary, but a typical size may be 600 mm diameter, that being whether the reactor chambers are helical or straight. The passages between individual chambers, at which the valves are arranged, may be of the order of 150 mm. All valves in the reactor, either for bulk material or inert gas etc., may advantageously be arranged to be automatically controlled. The way of controlling these does not form part of the inventive concept disclosed herein and therefore not described any further here. 
         [0063]    The processing time in each chamber can vary and can typically range from 5 to 15 minutes. The number of chambers in the reactor will naturally affect this, as well as the type of raw material used. 
         [0064]    The disclosed reactor is suitable for use on board harvesting vessels and do not need to stand vertically to function. An inclination of reactor chambers of 1:10 (vertical/horizontal) is normally enough for use even at sea. If desired to ensure functionality at more severe heel, the inclination can be increased, for example, to 1:5. 
         [0065]    Although not being s a central part of the inventive concepts of the disclosure, it is to be noted that the reactor embodiment of  FIG. 1 , with relevant dimensions of the reactor chamber and heat exchanger, can be embedding in a standard 20 feet container erected vertically; that is with a total height of about 6 meters. The reactor shown in  FIG. 8  can do with a substantially lower overall height, but does not allow being embedded in a container. 
         [0066]    The principles of the present reactor, however, can also realize whether or not such a height is available. For example, the reactor chambers can be arranged in a column while the pasteurizing chambers can be provided in a separate column disposed alongside, so that the reactor builds less in height and more in width than the one shown in the accompanying drawings.