METHOD AND SYSTEM FOR TREATING BIOMASS

Abstract

Method for treating biomass, comprising compressing and dewatering (62) the biomass to a dry solid content of DS1% by weight; feeding (63) compressed biomass to a treatment vessel; adding (64) a treatment liquid to said treatment vessel; discharging (65) treated biomass; compressing and dewatering (66) discharged biomass to a dry solid content of DS2% by weight, and treating (68) the compressed and dewatered biomass in a hydrolysis reactor, wherein 1%<DS1−DS2<6%.

Claims

1. A method for treating biomass, comprising: compressing and dewatering the biomass to a dry solid content of DS1% by weight; feeding compressed biomass to a treatment vessel; adding a treatment liquid to said treatment vessel; discharging treated biomass; compressing and dewatering discharged biomass to a dry solid content of DS2% by weight, and treating the compressed and dewatered biomass in a hydrolysis reactor, wherein 1%<DS1−DS2<6%.

2. The method according to claim 1, wherein 2%<DS1−DS2<5%.

3. The method according to claim 2, wherein 35%<DS1<60%.

4. The method according to claim 1, wherein said treatment vessel is an impregnator, and said treatment liquid is a liquid comprising chemicals selected from a group consisting of an acid, a catalyst or mixtures thereof.

5. The method according to claim 4, wherein said impregnator is a substantially vertical impregnator being filled with said treatment liquid up to a predetermined fill level, said biomass being fed to the treatment vessel at a position below the predetermined fill level, said method further comprising: controlling the fill level by adding treatment liquid to the vessel, and conveying the biomass through the treatment vessel, wherein said discharging comprises discharging treated biomass in an upper part, above said fill level, of the treatment vessel.

6. The method according to claim 1, wherein said compressing and dewatering the biomass is performed at least in part using a first plug screw device, and wherein said compressing and dewatering discharged biomass is performed at least in part using a second plug screw device.

7. The method according to claim 6, wherein said first plug screw device is configured and/or controlled to provide higher compression and/or dewatering than the second plug screw device.

8. The method according to claim 1, further comprising, after said compressing and dewatering discharged biomass, feeding the biomass to a buffer bin.

9. A system for treating biomass, comprising: a first compression device having an inlet and an outlet, said compression device being configured to compress and dewater biomass received at said inlet; a treatment vessel comprising an inlet and an outlet; injection means arranged to add a treatment liquid to said treatment vessel; wherein the first compression device comprises, or is connected to, feeding means arranged to feed biomass from its outlet to the inlet of said treatment vessel; a second compression device having an inlet and an outlet, wherein said second compression device comprises, or is connected to, feeding means arranged to feed biomass from the outlet of the treatment vessel to said second compression device, said second compression device being configured to compress and dewater biomass received at its inlet, wherein the first compression device is configured to dewater the biomass received at its inlet to a higher solid content, as measured in weight %, compared to the second compression device, wherein said first compression device comprises a first plug screw device, and wherein said second compression device comprises a second plug screw device, wherein said first plug screw device is provided with a different screw geometry and/or a different hole geometry than the second plug screw device, such that the first plug screw provides a higher compression ratio and dewatering than the second plug screw.

10. The system according to claim 9, wherein said treatment vessel is an impregnator and said treatment liquid is a liquid comprising chemicals selected from a group consisting of an acid, a catalyst or mixtures thereof.

11. The system according to claim 10, wherein said impregnator is a substantially vertically arranged impregnator being adapted to be filled with said treatment liquid up to a predetermined fill level, said vertical impregnator comprising an inlet at a lower portion thereof and an outlet at an upper portion thereof, said vertical impregnator being provided with level control means configured to continuously control the fill level by adding treatment liquid to the impregnator, said vertical impregnator comprising conveying means arranged to convey biomass upwards through the treatment vessel.

12. The system according to claim 9, wherein said first and second plug screw devices are provided with plug pipes, which the biomass passes through before discharging from the plug screw device, wherein the plug pipe of said first plug screw device is provided with dewatering holes to provide greater dewatering than the second plug screw device.

13. The system according to claim 9, further comprising a hydrolysis reactor, wherein an outlet of the second compression device is connected to an inlet of said hydrolysis reactor.

14. The system according to claim 13, further comprising a buffer bin connected between said second compression device and said hydrolysis reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Above discussed and other aspects of the present invention will now be described in more detail using the appended drawings, which show presently preferred embodiments of the invention, wherein:

[0025] FIG. 1 shows an embodiment of a system according to the second aspect of the invention;

[0026] FIG. 2 shows another embodiment of a system according to the second aspect of the invention;

[0027] FIG. 3 shows yet another embodiment of a system according to the second aspect of the invention;

[0028] FIG. 4 shows yet another embodiment of a system according to the second aspect of the invention;

[0029] FIG. 5a-b show two examples of plug screw devices which may be part of the embodiments shown in FIGS. 1-4, and

[0030] FIG. 6 shows a flow chart illustrating an embodiment of a method according to the first aspect of the invention.

DETAILED DESCRIPTION

[0031] FIG. 1 shows an embodiment of a system according to the second aspect of the invention. The system 1 for treating biomass comprises first and second compression devices 2, 6 in the form of plug screw devices, a treatment vessel 3 being a vertical impregnator adapted to be filled with treatment liquid up to a predetermined fill level 7, the vertical impregnator having conveying means in the form of a vertical conveyor screw 4 arranged to convey the biomass vertically upwards in the vessel. The system further comprises injection devices 5a, 5b arranged to inject treatment liquid into the vessel at two positions below the fill level 7, as shown in the figure. In other embodiments, further injection devices may be provided, which may be distributed in the vertical and/or circumferential directions of the treatment vessel. The vertical impregnator is further provided with level control means comprising a level sensor, for instance a float sensor (not shown), and a control unit (not shown) configured to continuously control the fill level by injecting treatment liquid using the injection devices 5a, 5b when necessary to maintain the fill level 7. The first plug screw device 2 is configured to receive biomass through an inlet (shown as an arrow at an upper portion thereof), and to output compressed and dewatered biomass at an outlet coupled to an inlet of the treatment vessel at a lower portion thereof, as shown in FIG. 1. Liquid which has been dewatered from the biomass is outputted at the bottom of the plug screw device (shown as an outgoing arrow in the figure). Impregnated biomass which has been conveyed through the impregnator is discharged at an upper portion thereof, above the fill level 7, and is received at an inlet of the second plug screw device 6.

[0032] The first plug screw device 2 is configured to dewater the biomass received at its inlet to a higher solid content, as measured in weight %, compared to the second plug screw device 6. This is achieved by providing the first plug screw device with a plug pipe with dewatering holes, but not the second plug screw device, as shown in FIG. 5a-b. Alternatively, the different solid content may be achieved by providing the first plug screw device 2 with a different hole geometry and/or a different compression ratio than the second plug screw device. The treatment liquid is a liquid comprising chemicals selected from a group consisting of an acid, a catalyst or mixtures thereof. The treatment vessel 3 is optionally provided with counter threads (not shown) at the uppermost portion thereof to co-operate with the threads of the conveyor screw 4.

[0033] FIG. 2 shows another embodiment of a system according to the second aspect of the invention. The first and second plug screw devices 12, 16 correspond to plug screw devices 2, 6 in FIG. 1. This embodiment differs from FIG. 1 however in that the treatment vessel is of a different type, being a soaking bin 13a provided with injection devices 15a, 15b for injecting soaking liquid into the soaking bin 13a at two positions as seen in the figure. An outlet at a bottom portion of the soaking bin 13a is connected to an inclined drainage screw 13b being provided with a screw conveyor 14 configured to convey the biomass while draining excess soaking liquid from the biomass. The outlet of the drainage screw is connected to the second plug screw device 16. The soaking liquid is a liquid comprising chemicals selected from a group consisting of an acid, a catalyst or mixtures thereof.

[0034] FIG. 3 shows another embodiment of a system according to the second aspect of the invention. The first and second plug screw devices 22, 26 correspond to plug screw devices 2, 6 in FIG. 1. This embodiment differs from FIG. 1 however in that the treatment vessel is of a different type, being a mixing screw device 23 provided with injection devices 25a, 25b for injecting mixing liquid into the mixing screw at two positions, the first one being below the inlet of the compressed/dewatered biomass from the first plug screw device 22 and the second one being an intermediate position as seen in the lengthwise direction of the treatment vessel. The mixing screw device is provided with a screw conveyor 24 arranged to convey the biomass forwards, in the right direction as seen in the figure, to an outlet, to which the second plug screw 26 device is connected to received treated/mixed biomass. The treatment liquid is a liquid comprising chemicals selected from a group consisting of an acid, a catalyst or mixtures thereof.

[0035] FIG. 4 shows yet another embodiment of a system according to the second aspect of the invention. The first and second plug screw devices 32, 36 correspond to plug screw devices 2, 6 in FIG. 1, and the vertical impregnator 33 with conveyor screw 34, injection devices 35a, 35b and fill level 37 correspond to impregnator 3, screw 4, injection devices 5a, 5b and fill level 7 in FIG. 1. This embodiment is however provided with further devices. A buffer bin 310 is provided after the second plug screw 36. As explained in the summary above, impregnation may continue in the buffer bin, the addition of which thus may lead to improved impregnation. Furthermore, a hydrolysis reactor 311 is shown in the figure, to which the biomass is conveyed from the buffer bin 310. The treatment liquid injected by injection devices 35a, 35b is received via control valve 39 to which a source of fresh impregnation liquid is connected as well as a tank 38 of recycled impregnation liquid being discharged pressate from the second plug screw device 36, as indicated by the arrows in FIG. 4. The fresh impregnation liquid may also be contained in a tank (not shown in the figure). In other embodiments, the system may furthermore be provided with an additional dewatering step before the first and/or second plug screw devices 32, 36, for instance a drainage screw as shown in FIG. 2. The treatment vessel 33 is optionally provided with counter threads (not shown) at the uppermost portion thereof to co-operate with the threads of the conveyor screw 34.

[0036] FIG. 5a-b show two examples of plug screw devices which may be part of the embodiments shown in FIGS. 1-4. FIG. 5a shows a plug screw device 42 comprising a bearing house 410 in which the screw axle (extending to the left of the bearing house, and connectable to a motor) is rotatably arranged. An inlet 411 and a conical throat 412 are provided, followed by a plug pipe 49 of constant diameter in which a plug of compressed biomass material is formed. In FIG. 5a, the plug pipe 48 is formed with dewatering holes 49, i.e. perforated walls, to provide further dewatering after the conical portion 412. FIG. 5b shows a plug screw device 56 which is identical to that in FIG. 5a, except that the plug pipe 58 is not provided with dewatering holes. The plug screw 42 in FIG. 5a is thus suitable as the first plug screw device in FIG. 1-4, whereas the plug screw 56 in FIG. 5b is suitable as the second plug screw device.

[0037] FIG. 6 shows a flow chart illustrating an embodiment of a method according to the first aspect of the invention. The method for treating biomass comprises supplying 61 biomass material, compressing and dewatering 62 the biomass to a dry solid content of DS1% by weight, feeding 63 compressed biomass to a treatment vessel, adding 64 a treatment liquid to said treatment vessel, discharging 65 treated biomass, compressing and dewatering 66 discharged biomass to a dry solid content of DS2% by weight, wherein DS2<DS1, feeding (67) the biomass to a buffer bin for further impregnation while stored therein, and feeding the biomass to a hydrolysis reactor for acid hydrolysis (68) of the biomass.

[0038] The description above and the appended drawings are to be considered as non-limiting examples of the invention. The person skilled in the art realizes that several changes and modifications may be made within the scope of the invention. For example, the first and/or second plug screw device may be replaced with other types of compressing and dewatering devices, for instance screw presses, twin-roll presses or any other type of devices suitable for the described purpose. Furthermore, one or more conveying devices may be arranged between the described devices, for instance between a plug screw device and the treatment vessel. Furthermore, there may be fewer or further injection devices for injection of treatment liquid.