WO2024260895A1

WO2024260895A1 - A horizontal fermenter

Info

Publication number: WO2024260895A1
Application number: PCT/EP2024/066732
Authority: WO
Inventors: Ahti KOIVUNEN
Original assignee: Fimuskraft Oy
Current assignee: Fimuskraft Oy
Priority date: 2023-06-21
Filing date: 2024-06-17
Publication date: 2024-12-26
Anticipated expiration: 2025-12-21
Also published as: FI20235714A1

Abstract

A horizontal fermenter for a continuous fermentation process comprises a horizontally elongated fermenter tank (101), an agitator (109) for mixing biomass in the fermenter tank, and conduits (104-108) for conducting temperature control fluid to control temperature of the biomass in the fermenter tank The fermenter tank comprises an inlet (102) for receiving biomass and an outlet (103) for removing the biomass flowed horizontally through the fermenter tank. The agitator comprises a rotatable shaft (110) parallel with the longitudinal direction of the fermenter tank and agitator arms arranged radially on the shaft. The conduits constitute departments (114, 115) each having an inlet (116) for receiving temperature control fluid and an outlet (117) for removing the temperature control fluid. The departments are separate from each other and successively in the longitudinal direction (z) of the fermenter tank to enable separate temperature controls on longitudinally successive zones (148-151) of the fermenter tank.

Description

A horizontal fermenter

Technical field

The disclosure relates to a horizontal fermenter for a continuous fermentation process of biomass.

Background

A continuously processing fermenter is a device where biomass flows at a rate determined by a natural fermentation process. The biomass may contain for example pig, cow, or chicken manure, vegetable waste, kitchen waste, human excrement, energy crop, fish processing waste, pest-plants of watercourses, and/or other suitable biomass of animal or vegetable origin. A continuously processing fermenter is advantageously a horizontal fermenter that comprises a fermenter tank that has an elongated shape in a horizontal direction. The horizontal fermenter comprises an inlet at a first end of the fermenter tank for receiving biomass and an outlet at a second end of the fermenter tank for removing biomass that has undergone a fermentation process while flowing from the first end to the second end. Therefore, the fermentation process is akin a continuous first-in-first-out “FIFO” process. In many cases, the biomass removed via the outlet can be used for example as fertilizer or as raw material of a process for producing fertilizer. Biogases which are produced in the fermentation process can be collected with a gas collector when the biogases are being produced. The biogases can be used for example as fuel or as raw material of a process for producing fuel. The fermentation process can be a thermophilic fermentation process, or a mesophilic fermentation process, or a combination of them. The horizontal fermenter typically comprises an agitator for mixing the biomass while the biomass flows from the first end to the second end in the fermenter tank. In a continuous fermentation process of the kind described above, the dry-matter content can be relatively high, 20 % - 35 %. This homogenizes the process, facilitates the control of the process, and saves energy.

A horizontal fermenter of the kind described above is presented for example in US20080138888. The horizontal fermenter described in US20080138888 comprises an agitator including a shaft passing horizontally through the fermenter tank in the longitudinal direction of the fermenter tank. The shaft is rotatably supported at the ends of the fermenter tank. The agitator comprises a plurality of agitator arms arranged radially on the shaft and suitable for mixing the biomass when the agitator is rotating. A horizontal fermenter of the kind described above is however not free from challenges. One of the challenges is related to a need to control temperature of the biomass to obtain an effective fermentation process.

Summary

The following presents a simplified summary to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying and non-limiting embodiments.

In this document, the word “geometric” when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional.

In accordance with the invention, there is provided a new horizontal fermenter for a continuous fermentation process of biomass. The biomass can contain biomass of animal origin and/or biomass of vegetable origin. A horizontal fermenter according to the invention comprises:

- a fermenter tank having a horizontally elongated shape, the fermenter tank comprising an inlet at a first end of the fermenter tank for receiving biomass and an outlet at a second end of the fermenter tank for removing the biomass flowed from the first end to the second end, conduits configured to conduct temperature control fluid, e.g. water, to control temperature of the biomass contained by the fermenter tank, and - an agitator comprising a shaft parallel with a longitudinal direction of the fermenter tank and a plurality of agitator arms arranged radially on the shaft and configured to mix the biomass when the agitator is rotating, the shaft being rotatably supported with respect to the fermenter tank.

The conduits for the temperature control fluid are configured to constitute departments each having an inlet for receiving the temperature control fluid and an outlet for removing the temperature control fluid from the department. The departments are separate from each other and successively in the longitudinal direction of the fermenter tank to enable separate temperature controls on longitudinally successive zones of the fermenter tank. This makes it possible to have different temperatures on different ones of the longitudinally successive zones for example so that some of the zones have a temperature advantageous for the mesophilic fermentation whereas some other of the zones have a temperature advantageous for the thermophilic fermentation.

A horizontal fermenter according to an advantageous and non-limiting embodiment has a modular structure so that the horizontal fermenter comprises fermenter modules attached to each other to be successive in the longitudinal direction of the fermenter tank.

Exemplifying and non-limiting embodiments are described in accompanied dependent claims.

Exemplifying and non-limiting embodiments both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in conjunction with the accompanying drawings.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features.

The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

Brief description of figures

Exemplifying and non-limiting embodiments and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which: figures 1 a, 1 b, and 1c illustrate a horizontal fermenter according to an exemplifying and non-limiting embodiment.

Description of exemplifying and non-limiting embodiments

The specific examples provided in the description below should not be construed as limiting the scope and/or the applicability of the accompanied claims. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated.

Figures 1 a and 1 b show schematic section views of a horizontal fermenter according to an exemplifying and non-limiting embodiment. The section shown in figure 1 a is taken along a geometric line A1 -A1 shown in figure 1 b, and the section shown in figure 1 b is taken along a geometric line A2-A2 shown in figure 1 a. The geometric section plane related to figure 1 a is parallel with the yz-plane of a coordinate system 199, and the geometric section plane related to figure 1 b is parallel with the xy-plane of the coordinate system 199.

The horizontal fermenter comprises a fermenter tank 101 that has a horizontally elongated shape. In figures 1 a and 1 b, the horizontal direction that is the longitudinal direction of the fermenter tank 101 is parallel with the z-axis of the coordinate system 199. The fermenter tank 101 comprises an inlet 102 at a first end of the fermenter tank 101 for receiving biomass 139 and an outlet 103 at a second end of the fermenter tank 101 for removing biomass that has undergone a fermentation process while flowing from the first end of the fermenter tank 101 to the second end of the fermenter tank 101 . Therefore, the fermentation process is akin a continuous first-in-first-out “FIFO” process. In this exemplifying case, the horizontal fermenter comprises a screw-conveyor 133 for removing the biomass 139 from the fermenter tank 101 via the outlet 103. The biomass can contain for example pig, cow, or chicken manure, vegetable waste, kitchen waste, human excrement, energy crop, fish processing waste, pest-plants of watercourses, and/or other suitable biomass of animal or vegetable origin. In many cases, the biomass removed via the outlet 103 can be used for example as fertilizer or as raw material of a process for producing fertilizer. Biogases which are produced in the fermentation process are collected with a gas collector 138 as when the biogases are being produced. The biogases can be used for example as fuel or as raw material of a process for producing fuel. The fermentation process can be a thermophilic fermentation process, or a mesophilic fermentation process, or a combination of them. The drymatter content of the biomass supplied to the fermenter tank 101 can be relatively high, 20 % - 35 %.

In many cases there can be one or more pre-processing units for treating the biomass prior to supplying the biomass into the fermenter tank 101 . The one or more pre-processing units may comprise for example a water removal unit to increase the dry-matter content of the biomass to the level of 20 % - 35 %. The water removal unit is not shown in figure 1 a. Furthermore, the one or more pre-processing units may comprise a hyginesation unit for treating the biomass in high temperature, e.g. 100°C. The hyginesation unit can be needed for example when the biomass contains animal waste and/or human excrement. The hyginesation unit is not shown in figure 1 a. The one or more pre-processing units may also comprise a shredder unit for cutting solid pieces contained by the biomass into particles small enough, e.g. into particles of 1 cm³ or smaller. The shredder unit is not shown in figure 1 a. Furthermore, the horizontal fermenter may comprise a supply unit comprising for example a screw-conveyor for supplying the biomass into the fermenter tank 101. The supply unit is not shown in figure 1 a. The entire system can be controlled with a controller unit and several sensors such as e.g. one or more temperature sensors, one or more pressure sensors, and/or one or more methane concentration sensors. The sensors can be communicatively connected to the controller unit where dedicated software is installed for automatic process control. The controller unit and the sensors are not shown in figure 1 a. The horizontal fermenter comprises an agitator 109 for mixing the biomass 139 while the biomass flows from the first end to the second end in the fermenter tank 101. The agitator 109 comprises a shaft 110 that is parallel with the longitudinal direction of the fermenter tank 101 and rotatably supported with respect to the fermenter tank 101 . The agitator 109 comprises a plurality of agitator arms arranged radially on the shaft 110 and suitable for mixing the biomass when the agitator 109 is rotating. Figure 1 c shows a part of the agitator 109. In figure 1 c, three of the agitator arms are denoted with references 111 , 112, and 113. As shown in figure 1 c, the agitator arms are shaped to constitute blades that are angled with respect to the longitudinal direction of the fermenter tank 101 . Therefore, the agitator arms are capable of acting as propeller blades for conveying the biomass in the longitudinal direction of the fermenter tank 101 when the agitator 109 is rotating. In a horizontal fermenter according to an exemplifying and non-limiting embodiment, all agitator arms are configured to act as propeller blades. In a horizontal fermenter according to another exemplifying and non-limiting embodiment, the agitator comprises arms configured to act as propeller blades and other arms that that are not configured to act as propeller blades. As the biomass can be kept in a continuous movement having a suitable speed, the fermentation process can be effective, the need for physical space is smaller, and the residence time of the biomass can be significantly shorter than e.g. when using a batch-process fermenter. Energy is saved because the movement of the biomass is continuous, i.e. there is no need to stop the material flow, to store the biomass as non-moving, and to start again to move the biomass.

In the exemplifying horizontal fermenter illustrated in figures 1 a-1 c, the agitator comprises support rings which are connected to the ends of the agitator arms, and which are concentric with the shaft 110. In figure 1 c, one of the support rings is denoted with a reference 131. The support rings improve the mechanical strength of the agitator 109. In the exemplifying horizontal fermenter illustrated in figures l ai c, the agitator comprises auxiliary arms extending from the above-mentioned agitator arms in the longitudinal direction of the fermenter tank. In figure 1 c, one of the auxiliary arms are denoted with a reference 132. The auxiliary arms intensify the mixing effect. The horizontal fermenter comprises conduits configured to conduct temperature control fluid, such as water, to control temperature of the biomass contained by the fermenter tank 101. In figure 1 a, two of the conduits are denoted with references 104 and 105. In figure 1 b, three of the conduits are denoted with references 106, 107, and 108. The conduits are configured to constitute departments each having an inlet for receiving the temperature control fluid and an outlet for removing the temperature control fluid from the department under consideration. The departments are separate from each other and successively in the longitudinal direction of the fermenter tank 101 to enable separate temperature controls on longitudinally successive zones of the fermenter tank 101. In figure 1 a, two of the departments are depicted with references 114 and 115 and the longitudinally successive zones are denoted with references 148, 149, 150, and 151. Each of the departments is provided with a temperature control system independent of corresponding temperature control systems of the other departments. In figure 1 a, the temperature control systems are denoted with references 134, 135, 136, and 137. The inlet and the outlet of the department 114 are denoted with references 116 and 117. The fermentation process can be a thermophilic fermentation process where the advantageous temperature range is from 55°C to 58°C, or a mesophilic fermentation process where the advantageous temperature range is from 37°C to 38°C, or a combination of them. The independent temperature control systems make it possible to have different temperatures on different ones of the zones 148- 151 for example so that some of the zones have a temperature advantageous for the mesophilic fermentation whereas some other of the zones have a temperature advantageous for the thermophilic fermentation. In a horizontal fermenter according to an exemplifying and non-limiting embodiment, the control systems are configured to keep a temperature in the zone 148 that is first in the flowing direction of the biomass lower than a temperature in the zone 151 that is last in the flowing direction of the biomass.

In the exemplifying horizontal fermenter illustrated in figures 1a-1 c, the bottom portion of the fermenter tank 101 has a curved shape. As shown in figure 1 b, a geometric section line between the bottom portion of the fermenter tank and a geometric plane perpendicular to the longitudinal direction of the fermenter tank constitutes an arc of a geometric circle 198 whose center coincides with a geometric center line of the shaft 110 of the agitator 109. The bottom portion of the fermenter tank 101 has the curved shape to avoid pocket areas in which the biomass is not affected by the agitator 109 and thereby conditions for proliferation of harmful bacteria could develop, such as e.g. bacteria which produce undesired hydrogen sulfide H2S. In this exemplifying case, the bottom portion and side walls of the fermenter tank 101 constitute a U-shape when seen along the longitudinal direction. Thus, the fermenter tank has a room 122 above an operating area of the agitator 109. As shown in figure 1 b, the conduits for the temperature control fluid have curved walls coinciding with the curved bottom portion of the fermenter tank 101 to maximize heat transfer between the temperature control fluid and the biomass. As shown in figure 1 b, each of the conduits for the temperature control fluid is wider in a circumferential direction of the geometric circle 198 than in a radial direction of the geometric circle 198.

As illustrated in figure 1 b, the fermenter tank 101 comprises a sheet of material 123 constituting an inner wall of the fermenter tank, a thermal insulator 124 surrounding the inner wall of the fermenter tank, and a frame structure 125 outside the thermal insulator 124. The sheet of material 123 can be for example a sheet of stainless steel or other metal resistive against chemical effects caused by the biomass, or a sheet of metal provided with a coating resistive against chemical effects caused by the biomass, or a sheet of some other suitable material which provides a sufficiently slippery surface to which the biomass does not stick. The thermal insulator 124 may comprise for example polyurethane or some other suitable insulator material. The frame structure 125 may comprise for example steel enforced concrete. As illustrated in figure 1 b, the conduits for the temperature control fluid are between the sheet of material 123 and the thermal insulator 124 to minimize heat leak from the temperature control fluid to the frame structure 125.

The exemplifying horizontal fermenter illustrated in figures 1a-1 c comprises advantageously a recycling system configured to recycle a part of the biomass from the outlet 103 of the fermenter tank 101 back to the inlet 102 of the fermenter tank 101. The recycled amount can be for example from 20 % to 35 % of the total output coming through the outlet 103 of the fermenter tank 101. The recycling makes it easier to achieve a desired spatial distribution of bacteria within the biomass inside the fermenter tank 101. In figure 1a, the recycling system is schematically depicted with the line 130. A practical implementation of the recycling system may comprise e.g. a screw conveyor and/or a belt conveyor and/or other elements for transferring biomass from the outlet 103 to the inlet 102.

The exemplifying horizontal fermenter illustrated in figures 1a-1c has a modular structure so that the horizontal fermenter comprises fermenter modules attached to each other to be successive in the longitudinal direction of the fermenter tank 101 . In figure 1a, the modules are denoted with references 126, 127, 128, and 129. In this exemplifying case, there are four modules. It is also possible that the number of modules differs from four. The length of each module can be for example about 12 meters which is the length of a standardized large shipping container.

The specific examples provided in the description given above should not be construed as limiting the applicability and/or interpretation of the appended claims. It is to be noted that lists and groups of examples given in this document are non- exhaustive lists and groups unless otherwise explicitly stated.

Claims

What is claimed is:

1 . A horizontal fermenter comprising:

- a fermenter tank (101 ) having a horizontally elongated shape, the fermenter tank comprising an inlet (102) at a first end of the fermenter tank for receiving biomass and an outlet (103) at a second end of the fermenter tank for removing the biomass flowed from the first end to the second end,

- conduits (104-108) configured to conduct temperature control fluid to control temperature of the biomass contained by the fermenter tank, and

- an agitator (109) comprising a shaft (110) parallel with a longitudinal direction (z) of the fermenter tank and a plurality of agitator arms (111-113) arranged radially on the shaft and configured to mix the biomass when the agitator is rotating, the shaft being rotatably supported with respect to the fermenter tank, characterized in that the conduits for the temperature control fluid are configured to constitute departments (114, 115) each having an inlet (116) for receiving the temperature control fluid and an outlet (117) for removing the temperature control fluid from the department, the departments being separate from each other and successively in the longitudinal direction (z) of the fermenter tank to enable separate temperature controls on longitudinally successive zones (148-151 ) of the fermenter tank.

2. A horizontal fermenter according to claim 1 , wherein each of the departments is provided with a temperature control system (134-137) independent of temperature control systems of other ones of the departments.

3. A horizontal fermenter according to claim 1 or 2, wherein a bottom portion of the fermenter tank has a curved shape so that a geometric section line between the bottom portion of the fermenter tank and a geometric plane perpendicular to the longitudinal direction of the fermenter tank constitutes an arc of a geometric circle (198) whose center coincides with a geometric center line of the shaft (110) of the agitator, and the conduits (104-108) for the temperature control fluid have curved walls coinciding with the curved bottom portion of the fermenter tank.

4. A horizontal fermenter according to claim 3, wherein each of the conduits for the temperature control fluid is wider in a circumferential direction of the geometric circle than in a radial direction of the geometric circle.

5. A horizontal fermenter according to claim 3 or 4, wherein the fermenter tank has a room (122) above an operating area of the agitator.

6. A horizontal fermenter according to claim 5, wherein the bottom portion and side walls of the fermenter tank (101 ) constitute a U-shape when seen as a crosssection perpendicular to the longitudinal direction of the fermenter tank.

7. A horizontal fermenter according to any one of claims 1 -6, wherein the fermenter tank comprises a sheet of material (123) constituting an inner wall of the fermenter tank, a thermal insulator (124) surrounding the inner wall of the fermenter tank, and a frame structure (125) outside the thermal insulator, the conduits for the temperature control fluid being between the sheet of material and the thermal insulator.

8. A horizontal fermenter according to any one of claims 1 -7, wherein the horizontal fermenter comprises a recycling system (130) configured to recycle a part of the biomass from the outlet of the fermenter tank back to the inlet of the fermenter tank.

9. A horizontal fermenter according to any one of claims 1 -8, wherein at least some of the agitator arms (111-113) are shaped to constitute blades angled with respect to the longitudinal direction of the fermenter tank for moving the material in the longitudinal direction of the fermenter tank when the agitator is rotating.

10. A horizontal fermenter according to any one of claims 1 -9, wherein the agitator comprises support rings (131 ) connected to ends of the agitator arms and concentric with the shaft.

11. A horizontal fermenter according to any one of claims 1 -10, wherein the agitator comprises auxiliary arms (132) extending from the agitator arms in the longitudinal direction of the fermenter tank.

12. A horizontal fermenter according to any one of claims 1 -11 , wherein the horizontal fermenter comprises a screw-conveyor (133) for removing the biomass from the fermenter tank via the outlet.

13. A horizontal fermenter according to any one of claims 1 -12, wherein the horizontal fermenter comprises fermenter modules (126-129) attached to each other to be successive in the longitudinal direction of the fermenter tank.