The invention relates to a reactor for manufacturing biogas from organic raw material using anaerobic digestion, the reactor including a tubular reaction chamber composed of a bottom, walls, and a ceiling for processing the raw material into end products, and agitation and transfer equipment arranged in the reaction chamber.
Publication WO/075298 A1 represents prior art proposing a reactor for manufacturing biogas from biowaste. The reaction chamber of the reactor is a tubular structure composed of walls, a floor, and a ceiling.
In small reactors, the hydrostatic pressure remains fairly low, and the reaction chamber can be manufactured as a fairly thin steel construction with the wall thickness of 100-150 mm.
However, a problem in a construction according to the aforementioned publication is that as the reactor size increases, the height of the raw material mattress in the reaction chamber also increases and thereby, the hydrostatic pressure exerted on the walls of the reaction chamber increases. To be able to make the reaction chamber sufficiently strong to resist stresses acting on it, the thickness of the walls of the reaction chamber must be increased proportionally to the increase of the reactor height. It is not reasonable to increase the width of prior art reactors, since then the floor area they require at production plants would increase, raising the need of covered space in the production plant and thereby investment costs. In turn, increasing the thickness of reaction chamber walls raises raw material costs, complicates the handling of the reaction chamber, and causes high costs when the reaction chamber is transported as a whole from the place of manufacture to the application site.
The object of the invention is to provide a reactor for manufacturing biogas from organic raw material using anaerobic digestion that is more advantageous for its manufacturing and transport costs than prior art reactors. The characteristic features of this invention are set forth in the appended claim 1.
By a housing structure assembled from shell elements and its reinforcement by concreting is provided a structure that is structurally optimized, cost-efficient and easily transported to its installation site, the structure being concreted after installation to provide a final robust structure. The reaction chamber is constructed from shell elements manufactured separately for this purpose which form a housing structure. After the installation of the shell elements, the housing is filled with concrete, whereupon the reaction chamber resists the hydrostatic pressure exerted on it from the inside, generated by biowaste with a high liquid content during the slow anaerobic digestion reaction. As the external support frame structure is arranged on the outer surface included in the reaction chamber, this stiffens and supports the shell element structure of the reaction chamber of even a large reactor externally during installation and concreting, as well as against forces generated by the raw material when the reactor is in use. By this structure is then achieved in a novel and inventive manner the aforementioned advantages, enabling, for example, the manufacture of reaction chambers of varied sizes using shell elements as much the same size as possible and elements to be used in the support frame structure.
In a reactor according to a preferred embodiment of the invention, the sandwich elements forming the reaction chamber walls supported by an external support frame structure can be manufactured quite lightweight and from steel even less than 4 mm thick. This reduces the material and transport costs of the reaction chamber of the reactor. Further, the external support frame structure can be made, for example, of tubular beams by assembling to an extremely rigid, yet fairly lightweight structure, which supports the shell elements during installation and concreting, as well as the reaction chamber from the outside during use. The installation of a reaction chamber according to the invention is initiated by assembling the external support frame to support the outermost shell elements of the housing structure. After installation of the outermost shell elements, possible remaining concrete reinforcements are installed and, after this, the inner shell elements. The external support frame structure enables in an inventive manner the use of quite lightweight shell elements and, further, with the external frame structure, a counterforce is created for the force generated by the hydrostatic pressure inside the reaction chamber. Instead of concrete or additionally, it is possible to use some other filling substance to stiffen and reinforce the shell structure.
The reactor is advantageously a plug-flow reactor. In this case, the process can be continuously operating.
Advantageously, agitation and transfer equipment is supported to the external support frame structure. With agitation and transfer equipment, raw material can be mixed to optimize the biological action, as well as moved ahead in the reaction chamber for promoting anaerobic digestion. Supporting the agitation and transfer equipment to the external support frame structure enables, in turn, the lightweight structure of the reaction chamber, as the loads of the agitation and transfer equipment are not exerted on the reaction chamber walls, but instead on the external support frame structure.
The reactor advantageously also includes heating, reject recirculation, automation and gas recovery equipment similar to that of prior art. With the heating equipment, the reaction chamber temperature is kept sufficiently high for anaerobic digestion. In turn, digestate is advantageously recirculated always to the previous agitation zone for transferring a microbial strain. An automation system is used to control the agitation and transfer equipment, heating equipment and reject recirculation equipment for maintaining anaerobic digestion in a preferably continuous process. The aforementioned components can be similar to those proposed in the prior art publication WO 2015/075298 A1.
Advantageously, at least the walls and the ceiling of the reaction chamber are composed of modularly dimensioned shell elements. In this case, a large-size reaction chamber is easy to transport from the place of manufacture to the application site as notably smaller elements. The use of elements is particularly advantageous with an external support frame structure, since the frame is used for supporting the wall elements during installation and concreting, and no additional support structures are required.
The height of the reactor may be in the range of 3-15 m, preferably 8-10 m. Hydrostatic pressure generated by liquid material in the reaction chamber produces extremely high forces as the reactor height increases when aiming for a higher capacity.
The modularly dimensioned shell elements in the reaction chamber walls can have a height ranging 0.5-3.6 m, preferably, 0.5-2.4 m. In this way, the elements are easier to handle than large elements and they can be tightly packed in conventional marine containers minimizing the empty space that remains in the marine container.
The modularly dimensioned shell elements in the reaction chamber walls can have a length of 6-13 m, preferably 10-12 m. In this way, the shell elements are easier to handle than large elements and they can be tightly packed in conventional marine containers minimizing the empty space that remains in the marine container. At the outer corners are high corner elements.
The reaction chamber advantageously includes sealed lead-throughs for agitation and transfer equipment for keeping liquid raw material or end products in the reaction volume. This enables a sufficiently high filling rate for the reaction chamber in order to achieve good efficiency.
Advantageously, the flanges of the shell elements serve along with the reinforcing steel bars as a stiffening structure.
Advantageously, the flanges of the shell elements have ready-made holes for the reinforcing steel bars.
Advantageously, each shell element includes seals for sealing the seams between the elements. In this way, the shell elements can be made tight avoiding discharge of hydrostatic pressure in the reaction chamber between the shell elements.
The thickness of the walls (shell) of the reaction chamber can be in the range of 200-500 mm, preferably 250-350 mm. The thickness of the shell elements is preferably 80-140 mm, whereupon the weight of the prefabricated shell elements of the reaction chamber remains moderate reducing transport costs and lowering material costs during the reactor manufacture. This also defines the maximum width of the filling space or housing.
Advantageously, the shell elements, at least their casing, can be made from carbon steel. The shell elements can also be made from stainless steel. Instead of steel, the shell elements can also be made, for example, of composite, plastic, or other similar material with sufficient rigidity.
Advantageously, into the filling space or housing remaining between the shell elements is poured concrete (and, if required, added reinforcements such as rebars), but on the other hand, instead of concrete, some other material with the required strength properties can be used.
Advantageously, the external support frame structure is composed of angle irons or tubular beams that are welded to each other. Angle irons or tubular beams are sufficiently rigid components to offer sufficient stiffness, yet notably light to save weight and material. Instead of steel, the external support frame structure can be made, for example, of composite or other similar material with sufficient rigidity.
Advantageously, the external support frame structure includes vertical columns arranged at a distance from each other in the lengthwise direction relative to the reactor on both sides of the reactor, transverse support structures for connecting the vertical columns in the transverse direction relative to the reactor and longitudinal support structures for connecting the vertical columns to each other in the lengthwise direction relative to the reactor on each side of the reactor. Such an external support frame structure is notably light and can thus also be transported from the place of manufacture to the application site with low transport costs.
Advantageously, each shell element includes an edged reinforcement arranged to circulate the element for reinforcing it. With reinforcements, it is possible to increase the stiffness and load bearing capacity of the shell elements.
Advantageously, the edged reinforcement (the flange) has holes for the reinforcing steel bars.
Advantageously, the external support frame structure includes plate stiffeners fastened against the outer surface of the reaction chamber. Due to the plate stiffeners, the external support frame structure stiffens the reaction chamber in such a way that it can be supported at selected points only and the external support frame structure can be quite sparse as to its vertical columns.
Plate stiffeners are advantageously fastened between edged reinforcements in each shell element. Thus, each shell element is sufficiently stiff to receive forces acting on it.
Advantageously, the plate stiffeners have holes for the reinforcing steel bars.
The external support frame structure is advantageously composed of hollow tubes fastened together. In this way, the weight of the external support frame structure remains moderate compared to a structure manufactured from solid iron, while, on the other hand, tubes provide sufficient structural rigidity for supporting the reaction chamber. Correspondingly, the external support frame structure can also be manufactured, for example, from composite or similar material.
Advantageously, the shell elements forming the reaction chamber insulation or casing, or both, are sandwich elements provided with a stiffening casing structure and insulation. These are extremely lightweight structures.
Implementation of a reaction chamber of a reactor according to the invention advantageously with shell elements enables transportation of the reactor in marine containers or containers transported by road and delivery of reactors larger than before to customers located in poorly accessible regions. In turn, an external support frame structure provides the benefit that it is not necessary to increase thickness of walls (shell) of the reaction chamber even though the size of the reactor is increased, and no additional support structures are needed during installation and concreting of the shell elements. However, this does not preclude that, if required, the width of the filling space or housing (i.e. the width of the concreting) can be defined at the installation site to achieve sufficient durability. A structure supported in this manner also enables the formation of a tubular reaction chamber having a rectangular cross-section and having a large chamber in relation to the wall thickness.
The invention is described below in detail by making reference to the appended drawings that illustrate some of the embodiments of the invention, in which
A reactor 10 according to the invention comprises in all of its embodiments an external support frame structure 24 of a tubular reaction chamber 12 shown in
The reactor is meant for producing biogas via anaerobic digestion from organic raw material, such as household or agricultural waste. As a consequence of anaerobic digestion, the water content of raw material increases as digestion progresses and the water content of material in the reaction chamber is high, since the dry content of the material in the reaction chamber can preferably range between 10% and 40% by weight of dry matter. This high water content and the high filling rate of the reaction chamber result in that the material generates hydrostatic pressure that acts on the walls of the reaction chamber and tends to push the walls of the reaction chamber outwards. The filling rate of the reaction chamber is preferably such that the liquid level extends to a distance of 0.5-1.5 m from the ceiling of the reaction chamber. However, on the basis of aforementioned dry matter content, it can be stated that a reactor according to the present embodiment of the invention is a so-called dry digestion reactor. The invention is however not necessarily limited to these.
Let it be mentioned that the ceiling 18 of the reaction chamber 10 can be formed as a structure similar to the walls 16 according to the invention, but the structure of the ceiling 18 may also vary from this. The structure of the ceiling (by layers) may be, for example, as follows from the inside outwards: shell element, concreting, insulation, upper surface cast from concrete. In this case, the thickness of the upper surface is thinner than the thickness of the actual concreting, being, for example, approximately 5 cm.
An advantage of a reactor according to the invention when using this type of reaction chamber is that remarkable material savings are achieved, when the walls and the ceiling of the reaction chamber can be manufactured thinner than in prior art solutions and from thinner material thicknesses, because sufficient rigidity is assured by concreting 17a. At the same time, the shell elements 16a and 16b serve as formwork for concreting.
According to
It can be mentioned separately that the organic raw material in the reactor presented above moves substantially horizontally in the lengthwise direction relative to the reactor. The reactor can also be arranged vertically, whereupon the floor 14 (as well as the ceiling) of the embodiment presented above is a vertical wall (like other walls) and the organic raw material moves vertically or substantially vertically. The term “floor” thus does not limit its placement. In this case, the floor may be structurally similar to the walls 16.
Further, in connection with the shell elements are advantageously arranged reinforcing steel bars 16c. They are advantageously led through both the edged reinforcements 23 and the plate stiffeners 17b. For this purpose, the edged reinforcements 23 are equipped with holes 23a and the plate stiffeners 17b are equipped with holes (not shown in
With shell part, to which the structure according to the invention is adapted, is meant here at least the side and end walls 16 of the reactor 10, and possibly also the ceiling 18. It is also feasible that, instead of concrete, a structure according to the invention can also be adapted to the floor, when the reactor is arranged into an upright position.
A reactor design according to the invention implemented by using a thin reaction chamber and an external support frame structure can also be applied in other uses, wherein the reactor contains a large amount of material in a high liquid content, which generates a high hydrostatic pressure in a high reaction chamber.
Number | Date | Country | Kind |
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20215103 | Feb 2021 | FI | national |
This application is a National Phase entry of International Application No. PCT/FI2022/050057, filed Jan. 31, 2022, which claims priority to Finland Patent Application No. 20215103, filed Feb. 1, 2021, the disclosures of which are incorporated herein by reference in their entireties.
Filing Document | Filing Date | Country | Kind |
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PCT/FI2022/050057 | 1/31/2022 | WO |