Agitator, in particular for an anaerobic digester, maintenance device for said agitator and process for maintaining said agitator

Abstract

Agitator, in particular for an anaerobic digester (100), of the type comprising a digestion tank (101), covered by a cover base (103). The agitator (1) is provided with a support body (2), mounted on the cover base (103) of the anaerobic digester (100), and with a rotation shaft (3), which is rotatable around a vertical rotation axis (R), is partially housed within the internal volume (V) of the digestion tank (101) and is movable in rotation by means of actuation means. In addition, on the support body (2), two insertion openings (4) are attained that are transverse with respect to the rotation axis (R) of the rotation shaft (3), and on the latter a safety plate (5) is fixed, transverse with respect to the rotation axis (R) and placed at a height higher than or equal to the height at which the insertion openings (4) are placed. The agitator (1) can be equipped with a maintenance device (10) comprising two safety rods (6), intended to be inserted through the insertion openings (4) of the support body (2), and each of which comprises at least one main portion (61) and a projecting portion (62), extended projecting from said main portion (61) and intended to be placed below the safety plate (5) of the agitator (1). In addition, the maintenance device (10) comprises rotation means (7), actuatable to rotate the safety rods (6) and lift the rotation shaft (3) of the agitator (1), by acting thrustingly with the projecting portions (62) against the safety plate (5).

Description

Field of application

[0001] The present invention regards an agitator, in particular for an anaerobic digester, a maintenance device for the aforesaid agitator and a process for maintaining the aforesaid agitator according to the preamble of the respective independent claims.

[0002] The present agitator, maintenance device and maintenance process are advantageously intended to be employed for ensuring the correct and efficient operation of anaerobic digesters, in particular thermophilic anaerobic digesters, or of any other plant that requires a type of analogous agitation.

[0003] Therefore, the present invention is inserted in the industrial field of production of plants for the disposal of organic waste and the purifying of waters by means of anaerobic digestion and in the field of management of the organic waste and of the purifying of waters. In addition, the present invention is inserted in the industrial field of production and of maintenance of agitators for any other purpose, in particular for the agitation of large masses of liquid or semiliquid material in large-size plants.State of the art

[0004] In the field of treating organic waste or purifying waste waters, in particular biomass contents or organic pollutant compounds (in the jargon also termed "organic load"), plants are known for treatment which are mainly divided into two categories: aerobic and anaerobic. In general, the organic waste treated in such plants can comprise biomasses deriving from organic fraction from urban solid waste (in the jargon identified with the acronym "FORSU" in Italy), from livestock waste (sewage, livestock manure, poultry manure), from animal slaughter discards, from agricultural or industrial organic discards, from plants (silage or by-products), from beached organic material (algae), etc.

[0005] Both aerobic and anaerobic plants are arranged for degrading the biomasses or the organic pollutant compounds contained in the waste or in the waste waters, i.e. transform the chemical structure thereof into a less complex one by means of oxidation in order to render them less harmful and / or simpler to separate, as well as in order to enhance the discards, obtaining composts, fertilizers or fuels. In this manner, in the case of treatment of the waste waters, such plants are aimed to reduce the quantity of pollutant organic compound at their interior so as to render the waters suitable for once again being employed for various purposes, e.g. in agriculture, or for being released into the environment, for example in waterways or in the sea, without contaminations. In the case of treatment of organic waste, such plants are generally aimed for transforming the biomasses into compost (if aerobic processes are employed) or biogases (if anaerobic processes are employed).

[0006] With particular reference to anaerobic plants, the latter provide for a specific anaerobic digestion section, in which a degradation process occurs that is operated by microorganisms in anaerobiosis conditions. Such section of anaerobic digestion comprises an anaerobic digester, which contains anaerobic bacteria, acting on the biomasses in order to transform the latter into biogas (mainly comprising carbon dioxide and methane) and a substantially liquid digestate. The anaerobic plants can also comprise an electrical energy generator, which produces electrical energy by means of the combustion of the methane contained in the biogas, or biogas treatment unit for purifying the methane, removing carbon dioxide.

[0007] The most common anaerobic digesters of such anaerobic plants continuously operate, i.e. by maintaining the quantity of biomass at their interior nearly constant. In other words, the massive flow of biomass entering is equal to the massive flow of the products, i.e. biogas and digestate, exiting.

[0008] In addition, depending on the anaerobic bacteria used in the process, the anaerobic digesters can work at different temperature conditions. In particular, with mesophilic bacteria the temperatures are comprised between 20 and 45 °C, while with thermophilic bacteria the optimal operating conditions involve temperatures that are even higher than 55 °C.

[0009] Structurally, the anaerobic digesters, in particular thermophilic, generally comprise a digestion tank, comprising a bottom wall and a perimeter wall, extended from the bottom wall and defining an internal volume closed on the upper part by a cover base. The latter allows preventing the outflow of the biogas produced, as well as maintaining the temperature controlled within the anaerobic digester.

[0010] In addition, on the cover base, agitation means are generally mounted that are adapted to mix the biomass to be treated and comprising at least one agitator provided with a rotation shaft with vertical axis, which is extended through the cover base up to the interior of the digestion tank and carries an impeller mounted thereon.

[0011] Generally, in addition, the rotation shaft is supported by a bearing and is actuatable in rotation by a motor, it too mounted on the cover base.

[0012] The thermophilic anaerobic digesters also comprise heating means for increasing the temperature at their internal volume, in the event in which the biochemical reactions involved during fermentation by the thermophilic anaerobic bacteria are not sufficiently exothermal to maintain the temperature suitably high.

[0013] The anaerobic digesters, in particular thermophilic, of known type described up to now have in practice shown that they do not lack drawbacks.

[0014] A first drawback lies in the fact that, when such anaerobic digesters must be subjected to maintenance, requiring long and complex passages in order to place the intervention zone of the plant under safe conditions and make it accessible before proceeding with the specific interventions. For example, in the event in which there is a breakage or a malfunctioning of the bearing that supports the rotation shaft of the agitator, it is first necessary to fully empty the digestion tank, in order to then remove the rotation shaft and the impeller.

[0015] A further drawback is given by the fact that the maintenance of the above-described anaerobic digesters almost always requires the use of bulky machinery and specialized personnel, since the rotation shaft has considerable size and weight and requires being moved with a mechanical lift.

[0016] A further drawback lies in the fact that in order to carry out the substitution of the bearing in case of breakage, the entire removal of of the rotation shaft is required, hence using a long and laborious process.

[0017] All of the abovementioned aspects lead to the increase of plant block times, of the complexity of the operations to be executed and of the maintenance costs.

[0018] In the field of small-size agitators, agitators are known that are provided with safety means, like that described for example in the patent FR 2803774. Such agitator is provided with a plurality of holes made on a support wall of the agitator and through a plurality of support rods are insertable that are placed in radial directions with respect to the rotation shaft. In particular, such support rods are selectively placed with a free end thereof against the rotation shaft.

[0019] In addition, the rotation shaft comprises an annular projection which can abut against the ends of the support rods during maintenance in order to prevent the fall of the free.

[0020] Also such solution has in practice shown that it does not lack drawbacks, such such safety means are not at all suitable for large-size agitators, such as those employed in anaerobic digesters.

[0021] In addition, such safety means only allow retaining the rotation shaft in an abutted manner, but it is still necessary to arrange other suitable means for lifting it, in case of maintenance of the bearing.Presentation of the invention

[0022] In this situation, the problem underlying the present invention is therefore that of eliminating the problems of the abovementioned prior art, by providing an agitator, in particular for an anaerobic digester, a maintenance device for the aforesaid agitator and a process for maintaining the aforesaid agitator, which allow executing maintenance interventions without emptying the anaerobic digester.

[0023] A further object of the present invention is to supply an agitator, a maintenance device and a maintenance process, which allow executing maintenance interventions in quick times.

[0024] A further object of the present invention is to supply an agitator, a maintenance device and a maintenance process, which allow executing maintenance interventions without completely removing bulky components that do not require being substituted.

[0025] A further object of the present invention is to supply an agitator, a maintenance device and a maintenance process, which allow executing maintenance interventions without requiring the use of large-size mechanically apparatuses.

[0026] A further object of the present invention is to provide an agitator, a maintenance device and a maintenance process, which are safe and entirely reliable in operation.

[0027] A further object of the present invention is to provide an agitator, a maintenance device and a maintenance process, which are simple and inexpensive to attain or actuate.Brief description of the drawings

[0028] The technical characteristics of the invention, according to the aforesaid objects, are clearly seen in the contents of the below-reported claims and the advantages thereof will be more evident from the following detailed description, made with reference to the enclosed drawings, which represent a merely exemplifying and non-limiting embodiment of the invention, in which: figure 1 and figure 2 show two perspective views from different angles of an agitator, in particular for an anaerobic digester and of a maintenance device for such agitator, object of the invention, in accordance with the preferred embodiment; figure 3 shows a vertical section view of the agitator of figure 1 installed in an anaerobic digester; figures 4 and 5 show two perspective views from different angles of a part of the maintenance device of figure 1; figures 6A and 6B show two enlargements of the section of figure 3 (in which a rotation bearing has been removed for greater clarity) at a safety plate of the agitator and of safety rods of the maintenance device respectively in a lowered position and in a raised position; figure 7 shows a bottom section view of the agitator and of the maintenance device of figure 1 executed along the trace VII-VII of figure 6B; figure 8 shows a side section view of a detail of the agitator and of the maintenance device of figure 1 (in which the rotation bearing has been removed for greater clarity) executed along the trace VIII-VIII of figure 6B. Detailed description of a preferred embodiment

[0029] With reference to the enclosed figures, reference number 1 overall indicates an agitator, in particular for an anaerobic digester 100 according to the present invention.

[0030] The present invention has particular application in the industrial field of production of plants for removing organic waste and purifying waters by means of anaerobic digestion and in the field of managing organic waste and purifying waters.

[0031] Advantageously, the agitator 1 is intended to be used in an anaerobic digester 100, preferably thermophilic, of the type comprising a digestion tank 101, comprising a bottom wall (not illustrated in the enclosed figures) and a perimeter wall 102, extended from the bottom wall, and defining an internal volume V. In particular, the perimeter wall 102 of the digestion tank 101 is substantially cylindrical.

[0032] Of course, the perimeter wall 102 can be of any other shape depending on the section of the digestion tank 101 and hence comprise multiple sides. For example, the digestion tank 101 can be square, rectangle, polygonal, etc.

[0033] Suitably, on the aforesaid anaerobic digester 100, one or more agitators 1 can be installed, depending on the overall plant capacity and on the dimensions of the digestion tank 101. Such agitators 1 are advantageously placed in a manner such to optimally make the agitation uniform within the internal volume V.

[0034] In addition, the anaerobic digester 100 advantageously comprises a cover base 103, supported by the perimeter wall 102 and placed to cover of the digestion tank 101. Preferably, the cover base 103 is flat, in a manner such to advantageously minimize the dispersible quantity of heat. In addition, on the cover base 103, at least one passage opening 104 is made in order to allow the passage of mechanical components through the cover base 103 itself, for example of the agitator 1 described hereinbelow. In particular, the cover base 103 has a number of passage openings 104 at least equal to the number of agitators 1 that must be installed in the anaerobic digester 100.

[0035] Advantageously, in addition, the anaerobic digester 100 comprises heating means at least partially placed within the digestion tank 101 in order to heat the biomasses to be disposed of and advantageously bring them to an optimal digestion temperature, suitable for the survival and operativity of the anaerobic bacteria, in particular thermophilic.

[0036] Of course, without departing from the protective scope of the invention, the anaerobic digester 100 can also be a mesophilic anaerobic digester and therefore provide for heating means that bring the biomasses to be disposed of to a temperature such to ensure the operativity of the mesophilic anaerobic bacteria (lower than the operating temperature of a thermophilic anaerobic digester).

[0037] The anaerobic digester 100 can have any further characteristic of the anaerobic digesters known in the reference field, relative for example to biomass loading systems, to digestate discharge systems, to biogas collection systems, or to control systems, and therefore it will not be further described hereinbelow.

[0038] Of course, the present invention also has application in the industrial field of production and of maintenance of agitators for any other purpose, in particular for the agitation of large masses of liquid or semiliquid material in large-size plants. Such plants are, analogous to the anaerobic digester, provided with tanks that contain the material to be mixed, delimited by a lateral wall and covered by a cover base.

[0039] According to the invention, the agitator 1 is provided with a substantially tubular support body 2, intended to be mounted on the cover base 103 of said anaerobic digester 100.

[0040] In particular, the support body 2 comprises a support base 21 intended to be placed in abutment against the cover base 103 and / or fixed to the latter, preferably at the passage opening 104 of the cover base 103.

[0041] For example, illustrated in figures 1, 2 and 3 is a support base 21 provided with a base plate 211 intended to be placed in abutment against, preferably fixed to, the cover base 103. Advantageously, in addition, the support base 21 comprises a first tubular portion 212 extended below the base plate 211 and in particular placed passing within the passage opening 104.

[0042] More in detail, in the support base 21, in particular within the first tubular portion 212, a valve can be mounted (not illustrated in the figures) capable of preventing the outflow of gas (including biogas) present within the digestion tank 101.

[0043] Advantageously, in addition the support base 21 comprises a second tubular portion 213, e.g. cylindrical, extended above the base plate 211 and in particular provided with an end flange 214, in order to allow the connection with other components of the support body 2.

[0044] In accordance with the preferred embodiment of the invention, the support body 2 also comprises a cover element 22, in particular with tubular form, e.g. cylindrical, preferably mounted indirectly on the support base 21. In order to simplify the connection of the cover element 22 to the other components, the cover element 22 has a lower flange 221.

[0045] In particular, an upper opening 222 is made on the cover element 22.

[0046] Advantageously, in addition, the support body 2 comprises a safety element 23, preferably with tubular form, e.g. cylindrical, whose function will be described more in detail hereinbelow, preferably mounted directly on the support base 2. In particular, the safety element 23 is interposed between the support base 21 and the cover element 22.

[0047] In order to be connected to the support base 21 and preferably also to the cover element 22, the safety element 23 is advantageously attained in the form of a tube with flange, in particular provided with two opposite flanges 231, each of which respectively connected to the end flange 214 of the support base 21 and advantageously to the lower flange 221 of the cover element 22.

[0048] Advantageously, the support body 2 comprises a lateral wall 20, in particular divided into multiple sections, each corresponding to a perimeter wall of the second tubular portion 213 of the support base 21, of the cover element 22 and / or of the safety element 23.

[0049] Of course, without departing from the protective scope of the invention, the components of the support body can have different forms, e.g. tubular with square section or polygonal section, and they can be connected in a different manner (e.g. welded, as well as provided with further intermediate connection elements) or made in a single body. In the latter case (not represented), the lateral wall 20 is continuous, i.e. it is not divided into sections, and defined by the overall perimeter wall of the entire support body.

[0050] According to the invention, the agitator 1 comprises at least one rotation bearing C, mounted on the support body 2, in particular within the cover element 22. For example, the support body 2, preferably the cover element 22, can provide - in a per se known manner - a suitable seat where the aforesaid rotation bearing C is placed.

[0051] The agitator 1 also comprises a rotation shaft 3, which is mechanically supported at least partially by the rotation bearing C and rotatable around a vertical rotation axis R.

[0052] Preferably, the rotation shaft 3 is completely supported by the rotation bearing C. In particular, the rotation shaft 3 is of "suspended" type.

[0053] In particular, the rotation shaft 3 is extended through the support body 2 and preferably also through the cover base 103 of the anaerobic digester 100, and is partially housed within the internal volume V of the digestion tank 101.

[0054] Given the generally large dimensions of the rotation shaft 3, the latter can be made in a known manner, in multiple sections that are connected to each other.

[0055] Advantageously, on the rotation shaft 3, suitable mixing blades are fixed (not illustrated in the enclosed figures), placed within the internal volume V of the digestion tank 101 and integral in rotation with the rotation shaft 3.

[0056] According to the invention, the agitator 1 also comprises actuation means (not illustrated), mechanically connected to the rotation shaft 3 in order to rotate it around the rotation axis R.

[0057] For example, the actuation means comprise a motor, advantageously mounted outside the support body 2, preferably above the cover element 22, coaxial with the rotation shaft 3. In particular, an upper end 31 of the rotation shaft 3 exits from the upper opening 222 of the cover element 22 in order to allow the connection with the motor.

[0058] Alternatively, the motor can also be placed within the support body 2, or as another alternative it can be mounted on the cover base 103 of the anaerobic digester 100 alongside the support body 2 (hence not coaxial with the rotation shaft 3) and be mechanically connected to the rotation shaft 3 itself by means of suitable transmission means.

[0059] Advantageously, the actuation means also have the function of maintaining the rotation shaft 3 aligned, since as stated above the latter is preferably substantially supported only by the rotation bearing C.

[0060] In accordance with the idea underlying the present invention on the support body 2, at least two insertion openings 4 are made, extended transverse with respect to the rotation axis R of the rotation shaft 3. In particular, the insertion openings 4 are extended along the opening directions D, which advantageously lie on a plane perpendicular to the aforesaid rotation axis R. In addition, the rotation shaft 3 is advantageously interposed between the two opening directions D, i.e. in a manner such that the latter are not incident with the rotation shaft 3 and that such opening directions D are not both situated on the same side with respect to the rotation shaft 3.

[0061] In particular, the insertion openings 4 comprise at least four support holes 40 made on the lateral wall 20 of the support body 2, preferably at the safety element 23, and aligned two-by-two along the corresponding opening directions D, transverse with respect to the rotation axis R of the rotation shaft 3. More in detail, the support holes 40 have substantially circular form and advantageously placed substantially circumferentially spaced along the lateral wall 20.

[0062] Advantageously, the insertion openings 4 of the support body 2, and in particular the support holes 40, are provided with edge portions 41, preferably intended to abuttingly receive suitable rodlike safety supports (e.g. safety rods 6 that will be described hereinbelow).

[0063] According to the invention, on the rotation shaft 3, a safety plate 5 is fixed, which is extended at least partially transverse with respect to the rotation axis R of the rotation shaft 3 and is placed at a height higher than or equal to the height at which the insertion openings 4 are placed. In particular, the safety plate 5 lies on a plane perpendicular to the aforesaid rotation axis R, i.e. advantageously parallel to the plane on which the opening directions D lie.

[0064] Advantageously, the safety plate 5 is provided with a lower face 51, directed towards the digestion tank 101 of the anaerobic digester 100, and an opposite upper face 52.

[0065] Advantageously, in addition, the safety plate 5 has discoidal form.

[0066] By means of the presence of the insertion openings 4 and of the safety plate 5, it is possible to secure the agitator 1 and more particularly the rotation shaft 3, for example in case of breakage of the rotation bearing C, in a simple, quick, effective and inexpensive manner.

[0067] In operation, it is in fact possible to insert any one rodlike support within the insertion openings 4, in a manner such that the safety plate 5 at most abuts against such rodlike supports.

[0068] As will be described hereinbelow, the shape of the agitator 1 according to the invention is particularly adapted to being coupled to a maintenance device 10 which is also capable of lifting the rotation shaft 3, if it is necessary to execute maintenance and / or substitute the rotation bearing C.

[0069] Therefore, also forming the object of the present invention is a maintenance device 10 for an agitator 1 of the type described above, regarding which the same reference numbers will be maintained for improved description clarity.

[0070] The present maintenance device 10 is particularly adapted to being used in order to execute the maintenance of the aforesaid agitator 1, in particular for the substitution of mechanical components such as bearings or parts of the motor and more generally in order to ensure the correct and efficient operation of anaerobic digesters, in particular thermophilic anaerobic digesters. The maintenance device 10 thus has particular application in the industrial field of production of devices for the maintenance of machinery for moving biomasses in the anaerobic digesters.

[0071] The maintenance device 10 according to the invention comprises at least two safety rods 6, intended to be inserted through the insertion openings 4 of the support body 2 of the agitator 1.

[0072] Each safety rod 6 comprises at least one main portion 61, extended along a corresponding main extension direction S1, and at least one projecting portion 62, extended projecting from the main portion 61 with respect to the main extension direction S1.

[0073] In accordance with the preferred embodiment, illustrated in the enclosed figures, each safety rod 6 comprises two main portions 61, intended to be placed in abutment against corresponding edge portions 41 of the insertion openings 4 of the support body 2 of the agitator 1. In addition, each projecting portion 62 is advantageously interposed between the two main portions 61 (of the respective safety rod 6) and is intended to be placed within the support body 2.

[0074] Advantageously, in addition, the projecting portion 61 is rectilinear and is extended along a secondary extension direction S2, parallel to and offset with respect to the main extension direction S1. Advantageously, the projecting portion 62 is connected to the main portions 61 by means of respective connector portions 63.

[0075] In operation, when the safety rods 6 are inserted within the insertion openings 4 of the support body 2, they are placed with their main extension directions S1 parallel to the corresponding opening directions D of the insertion openings 4, and preferably substantially coinciding therewith.

[0076] According to the invention, the projecting portion 62 is intended to be placed below the safety plate 5 of the agitator 1. In this manner, by means of the rotation of the safety rod 6 with a suitable force, the projecting portion 62 is capable of applying a lifting thrust to the safety plate 5, in particular on its lower face 51, and hence of lifting the rotation shaft 3, in particular in order to allow maintenance operations.

[0077] Therefore, according to the invention, the maintenance device 10 comprises rotation means 7, mechanically connected to the safety rods 6 and actuatable to rotate the safety rods 6 around the main extension direction S1 at least between a lowered position and a raised position. In particular, in the lowered position each projecting portion 62 is released from the safety plate 5. In addition, in the raised position, each projecting portion 62 acts thrustingly against the safety plate 5 in order to lift the rotation shaft 3 of the agitator 1.

[0078] In operation, the lifting of the rotation shaft 3 is substantially executed by translating the rotation shaft 3 upward along the same rotation axis R thereof.

[0079] In accordance with the preferred embodiment of the invention illustrated in the enclosed figures, the rotation means 7 are removably connected to the safety rods 6.

[0080] More in detail, the rotation means 7 comprise at least one rotation lever 8, extended along a direction transverse with respect to the main extension direction S1 (of at least one of the safety rods 6), between a first end 81, connected to and integral with one of the safety rods 6, and a second end 82, opposite the first end 81.

[0081] In addition, the rotation means 7 advantageously comprise at least one lifting mechanism 9, mechanically connected to the second end 82 of the rotation lever 8 and configured to lift or lower the second end 82, rotating the safety rod 6.

[0082] Preferably, the rotation means comprise two rotation levers 8, each connected to a respective safety rod 6, and two corresponding lifting mechanisms 9, each connected to the respective rotation lever 8.

[0083] As anticipated above, each rotation lever 8 is removably connected with the first end 81 thereof to the safety rod 6. For example, the rotation lever 8 comprises, fixed at its first end 81, a grooved bushing and the safety rod has one end processed with knurling, i.e. in a manner counter-shaped with respect to the grooved bushing. In this manner, each safety rod 6 and the respective rotation lever 8 can be easily coupled together and uncoupled from each other.

[0084] Of course, without departing from the protective scope of the present invention, the safety rod 6 and the rotation lever 8 are couplable in any other suitable mode, for example any one stable shape coupling.

[0085] More in detail, the lifting mechanism 9 comprises a support base 91, susceptible of being placed in abutment for example against the cover base 103 of the anaerobic digester 100. Such support base 91 can be positioned directly on the cover base 103, or abut against the support body, e.g. on the base plate 211, as illustrated in figure 3.

[0086] Advantageously, the lifting mechanism 9 also comprises a worm screw 92, rotatably mounted on the support base 91 and extended along a lifting direction L, transverse with respect to the main extension direction S1 of at least one safety rod 6.

[0087] In addition, the lifting mechanism 9 advantageously comprises a slider 93, which is mechanically connected to the second end 82 of the rotation lever 8, is mounted on the worm screw 92 and configured for sliding along the lifting direction L when the worm screw 92 is actuated in rotation. For example, the slider 93 comprises a tubular body, internally threaded, fit on the worm screw 92. In particular, therefore, the relative rotation of the worm screw 92 with respect to the tubular body, determines the sliding of the latter. Such tubular body is advantageously hinged to the second end 82 of the rotation lever 8, such to be able to vary the angle between the slider 93 and the rotation lever 8 itself, so as to transform the sliding of the slider 93 in a rotation movement of the rotation lever 8.

[0088] In order to more easily rotate the worm screw 92, the lifting mechanism 9 also advantageously comprises an actuation crank 94, mechanically connected to the worm screw 92 in order to rotate it.

[0089] The lifting mechanism 9 thus constituted, in combination with the rotation lever 8, allows suitably rotating, in a facilitated manner, the corresponding safety rod 6 and thus easily lifting the rotation shaft 3.

[0090] Of course, without departing from the protective scope of the present invention, it is possible to use any other lifting mechanism 9 capable of rotating the rotation lever 8 (or both rotation levers 8 simultaneously) in a simple and quick manner.

[0091] The maintenance device 10 thus advantageously allows securing the agitator 1, preventing the fall of the rotation shaft 3, and subsequently facilitating the maintenance of the agitator without removing the rotation shaft 3 and thus without the use of complex and expensive machinery. In addition, by not removing the rotation shaft 3, it is not even necessary to empty the digestion tank 101 of the anaerobic digester 100. Such aspect allows executing the entire maintenance of the agitator 1 completely outside, reducing to a minimum also the risks of injury for operators.

[0092] Therefore, also forming the object of the present invention is an assembly comprising the agitator 1 for an anaerobic digester 100 and the maintenance device 10 for the aforesaid agitator 1, previously described, regarding which the same reference numbers will be maintained for improved description clarity.

[0093] Such agitator 1 and such maintenance device 10 can suitably have any above-described characteristic and therefore they will not be described more in detail hereinbelow.

[0094] Also forming the object of the present invention is a process for maintaining the above-described agitator 1, by means of the maintenance device 10 also described above, regarding which the same reference numbers will be maintained for improved description clarity.

[0095] The present maintenance process is particularly suitable for being used for executing the maintenance of the aforesaid agitator 1, in particular for the substitution of mechanical components such as bearings or parts of the motor and more generally for ensuring the correct and efficient operation of anaerobic digesters, in particular thermophilic anaerobic digesters. The maintenance process therefore has particular application in the industrial field of maintenance of machinery for moving the biomasses in the anaerobic digesters.

[0096] According to the invention, the maintenance process comprises an insertion step, in which the safety rods 6 are inserted in the insertion openings 4 of said support body 2, with the respective projecting portions 62 placed below the safety plate 5 of the rotation shaft 3 of said agitator 1.

[0097] In particular, in the insertion step, the safety rods 6 are placed with their main extension directions S1 parallel to the corresponding opening directions D of the insertion openings 4, and preferably substantially coinciding therewith.

[0098] The maintenance process also comprises a lifting step, in which the safety rods 6 are rotated along a first rotation sense by means of the rotation means 7 and the projecting portions 62 of the safety rods 6 act in abutment against the safety plate 5 and lift the rotation shaft 3. In particular, the lifting step occurs by means of the rotation means 7, i.e. preferably by means of the rotation lever 8 and of the lifting mechanism 9 (e.g. by rotating the actuation crank 94).

[0099] Advantageously, the maintenance process can provide for an intermediate tensioning step, preceding the lifting step, in which the safety rods 6 are manually rotated along the first rotation sense by means of the rotation means 7 until the projecting portions 62 of the safety rods 6 come to abut against the lower face 51 of the safety plate 5, but without a lifting force being applied (generally impossible to apply manually).

[0100] At the end of the intermediate tensioning step, the rotation means 7 can therefore be suitably connected to the safety rods 6 (e.g. with the coupling of the first ends 81 of the rotation levers 8 with the corresponding rotation rods 6) in order to continue with the lifting step.

[0101] Of course, without departing from the protective scope of the present invention, the (manual) intermediate tensioning step can be omitted and the safety rods 6 can already be initially rotated with the rotation means 7.

[0102] Advantageously, the maintenance process also comprises a substitution step, subsequent to the lifting step, in which the rotation bearing C is removed from the agitator 1 and substituted with a new rotation bearing. Of course, in such substitution step it is possible to substitute any other component of the agitator 1 that requires maintenance.

[0103] Advantageously, the maintenance process also comprises a release step, in which the safety rods 6 are rotated in a second rotation sense, opposite the first rotation sense and the corresponding projecting portions 62 disengage the safety plate 5. In this manner, the rotation shaft 3 is brought back into operating position according to its correction operation.

[0104] The maintenance process according to the invention thus advantageously allows operating on the agitator in a facilitated and quick manner and without the use of heavy machinery. In addition, by not removing the rotation shaft 3, it is not even necessary to empty the digestion tank 101 of the anaerobic digester 100. Such aspect is extremely advantageous since the entire maintenance of the agitator 1 can take place completely outside, considerably reducing the risks for the operators.

[0105] Suitably, the maintenance process can further provide for operations that are known in practice, such as for example a step of uncoupling the actuation means, i.e. the motor, from the rotation shaft 3 and / or a step of removing the cover element 22 from the support body 2 (in order to expose the rotation bearing C) and / or other suitable steps.

[0106] The invention thus conceived therefore attains the pre-established objects.

Claims

1. Agitator, in particular for an anaerobic digester (100), wherein said anaerobic digester (100) is of the type comprising: - a digestion tank (101), comprising a bottom wall and a perimeter wall (102), extended from said bottom wall, and defining an internal volume (V); - a cover base (103), supported by said perimeter wall (102) and placed to cover said digestion tank (101); wherein said agitator (1) is provided with: - a substantially tubular support body (2), intended to be mounted on the cover base (103) of said anaerobic digester (100); said support body (2) comprising a lateral wall (20): - at least one rotation bearing (C), mounted on said support body (2); - a rotation shaft (3), which is mechanically supported at least partially by said rotation bearing (C) and rotatable around a vertical rotation axis (R), is extended through said support body (2) and is partially housed within the internal volume (V) of said digestion tank (101); - actuation means, mechanically connected to said rotation shaft (3) in order to rotate it around said rotation axis (R); wherein on said support body (2), at least two insertion openings (4) are attained that are extended transverse with respect to the rotation axis (R) of said rotation shaft (3); characterized in that on said rotation shaft (3), a safety plate (5) is fixed which is extended at least partially transverse with respect to the rotation axis (R) of said rotation shaft (3) and is placed at a height higher than or equal to the height at which said insertion openings (4) are placed; wherein said insertion openings (4) comprise at least four support holes (40) attained on the lateral wall (20) of said support body (2) and aligned two-by-two along corresponding opening directions (D), transverse with respect to the rotation axis (R) of said rotation shaft (3).

2. Agitator according to claim 1, characterized in that said support holes (40) are placed substantially circumferentially spaced along said lateral wall (20); wherein said support holes (40) are provided with edge portions (41) intended to abuttingly receive safety rods (6).

3. Maintenance device for an agitator (1) according to claim 1 or 2, characterized in that it comprises: - at least two safety rods (6), intended to be inserted through the insertion openings (4) of the support body (2) of said agitator (1); each said safety rod (6) comprising: - at least one main portion (61), extended along a corresponding main extension direction (S1); - at least one projecting portion (62), extended projecting from said main portion (61) with respect to said main extension direction (S1); wherein said projecting portion (62) is intended to be placed below the safety plate (5) of said agitator (1); - rotation means (7), mechanically connected to said safety rods (6) and actuatable to rotate said safety rods (6) around said main extension direction (S1) at least between a lowered position, in which each said projecting portion (62) is released from said safety plate (5), and a raised position, in which each said projecting portion (62) acts thrustingly against said safety plate (5) in order to lift the rotation shaft (3) of said agitator (1).

4. Maintenance device (10) according to claim 3, characterized in that said rotation means (7) are removably connected to said safety rods (6).

5. Maintenance device (10) according to claim 3 or 4, characterized in that said rotation means (7) comprise: - at least one rotation lever (8), extended along a direction transverse with respect to said main extension direction (S1), between a first end (81), connected to and integral with one of said safety rods (6), and a second end (82), opposite said first end (81); - at least one lifting mechanism (9), mechanically connected to the second end (82) of said rotation lever (8) and configured to lift or lower said second end (82), rotating said safety rod (6).

6. Maintenance device (10) according to claim 5, characterized in that said lifting mechanism (9) comprises: - a support base (91), susceptible of being placed in abutment against the cover base (103) of said anaerobic digester (100); - a worm screw (92), rotatably mounted on said support base (91) and extended along a lifting direction (L), transverse with respect to the main extension direction (S1) of at least one said safety rod (6); - a slider (93), which is mechanically connected to the second end (82) of said rotation lever (8), is mounted on said worm screw (92) and configured for sliding along said lifting direction (L) when said worm screw (92) is actuated in rotation; - an actuation crank (94), mechanically connected to said worm screw (92) in order to rotate it.

7. Maintenance device (10) according to any one of the preceding claims, characterized in that each safety rod (6) comprises two main portions (61), intended to be placed in abutment against corresponding edge portions (41) of the insertion openings (4) of the support body (2) of said agitator (1); and that in each said projecting portion (62), it is interposed between said two main portions (61) and is intended to be placed within said support body (2).

8. Maintenance device (10) according to claim 7, characterized in that said projecting portion (61) is rectilinear and is extended along a secondary extension direction (S2), parallel to and offset with respect to said main extension direction (S1); wherein said projecting portion (62) is connected to said main portions (61) by means of respective connector portions (63).

9. Process for maintaining an agitator (1) according to claim 1, by means of a maintenance device (10) according to any one of the claims from 2 to 8, characterized in that it comprises the following operative steps: - an insertion step, in which said safety rods (6) are inserted in the insertion openings (4) of said support body (2), with the respective projecting portions (62) placed below the safety plate (5) of the rotation shaft (3) of said agitator (1); - a lifting step, in which said safety rods (6) are rotated along a first rotation sense by means of said rotation means (7) and the projecting portions (62) of said safety rods (6) act in abutment against said safety plate (5) and lift said rotation shaft (3).

10. Maintenance process according to claim 9, characterized in that it also comprises: - a substitution step, subsequent to said lifting step, in which, with said rotation shaft (3) lifted, said rotation bearing (C) is removed from said agitator (1) and substituted with a new rotation bearing; - a release step, in which said safety rods (6) are rotated in a second rotation sense, opposite said first rotation sense and the corresponding said projecting portions (62) disengage said safety plate (5).

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