FI94859B - Apparatus for making compost - Google Patents

Description

! 94859

Apparatus for making compost

The invention relates to an apparatus for producing compost from waste material, the apparatus comprising a shallow, mainly rectangular silo adapted to contain a mattress of compostable material, one end of which is fed with new material and from the other end of which the composted material is removed, and compost-forming mixing elements. during operation pass through the mattress and which are accessible and controllable by means of means above the mattress so that each part of the mattress can be modified. The invention also relates to a method for forming compost using such a device.

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The increase in sludge due to sewage treatment has now shifted the focus to the further treatment of sludge. The better the cleaning result for water bodies, the higher the amount of problematic sludge. The disposal of sludge has become a problem when field application as such or lime-stabilized has become strongly opposed for environmental reasons. About 80% of all sludge has so far gone to recovery, the majority to fields and a smaller part to green-25 fielding. Odor nuisances and other environmental problems make this procedure largely unworkable in the future.

In large units, hitherto the treatment of sludge has generally been solved by digestion of concentrated raw sludge, open composting of digested and dried sludge and possible mixing. The advantage of the method is that the process is known and easy to maintain. On the other hand, the high purchase price of the plant and the need for further treatment of the digested sludge-35 must be considered a disadvantage, so this procedure does not solve the reported environmental problems.

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A third possible and commonly used procedure is the drying and open composting of raw sludge using different supports. The advantage of this is simplicity. The problem, on the other hand, is the large need for transport of support and litter materials, the large 5 space requirement and the environmental disadvantages that also appear in open composting.

Efforts have also been made to mechanize composting and thus eliminate environmental damage. For example, conventional structures known in the art, such as drum furnaces and belt conveyors, have been adapted to be used for this purpose. Such a device is disclosed, for example, in Finnish patent application 891265. However, since the value of the material to be treated in composting per unit volume is very small, such devices become at least disproportionately expensive for this use, so they are not widespread.

Patent publication FI 56370 clearly describes a mechanical composting device that differs from the previous 20. It uses helical mixing members that rotate in the compostable pulp and move it further from the feed end of the pulp to its discharge end. In the opposite direction, the mixing members are moved by turning them approximately horizontally, so that they 25 can be moved above the pulp mattress from the pulp discharge end to its feed end. In general, this type of plant can be low enough in construction costs to make composting sensible. However, there are technical problems with the proposed structure that make implementation 30 questionable. First, the helical agitator tends to clog quite rapidly as it rotates in the pulp, • thus completely losing its agitation power. The cleaning of a clogged mixing member to restore its effectiveness must be done either by hand, which is slow and unpleasant, or by an automatic and of course complex and expensive device of jol-35 law. Second, the mass transfer effect of the helical mixing member is small in magnitude and unreasonably variable. Finally, in this procedure too, the transport of the 3 94859 supports requires a considerable amount of transport capacity.

It is known to try to reduce the need for supports by rotating a small portion of the finished burnt compost back into the feed of compostable material. The aim has been either to increase the efficiency of the start-up of the composting process (patent application FI-891265) or to bring the dry matter content of the compostable pulp to the desired relatively high value (BioCycle, May-June 1986: Evaluating The In-Vessel Composting Option, pp. 34-39). Alternatives to recycling and aeration have also been discussed elsewhere, but in particular it has been found that standard mechanical mixing cannot be considered a useful procedure for such pulp mixtures 15 (R. T. Haug - Compost Engineering Principles and Practice, 1980).

GB 1066158 also describes an apparatus for producing compost. However, the mixers 20 described in this publication operate only as mixers and not as compost-carrying elements, neither vertically nor horizontally. The wings are specifically constructed so that no such vertical movement would occur. The mixers are not arranged in pairs for the horizontal transport of the pulp 25, but are arranged in a row parallel to the direction of transport of the pulp. Thus, the mixers are not able to provide any mass transport in the horizontal direction. 1 2 3 4 5 6

The object of the invention is thus to provide a mechanical composting device in which continuous mixing 3 * of the mass to be composted is possible, preferably without time interruptions and in which the mixing element 4 »5 does not tend to become clogged. The device should also be affordable in terms of price and operating costs.

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A further object is a composting device with which the need for support materials can be minimized. In particular, it is an object of the invention to provide a device in which composting is carried out quickly and efficiently and in which obtaining this result is not sensitive to the type of starting materials and e.g. to the moisture of the compostable mass. Of course, the aim is also to minimize environmental problems.

The disadvantages described above can be eliminated and the objectives defined above are achieved with the device according to the invention.

The features of the invention appear from claim 1.

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The most important advantages of the invention are that the device has quite different types of pulps that can be composted mechanically due to good mixing and aeration capacity and that the reliability of the device, such as non-clogging, and the horizontal transport of the pulp are very good. A further advantage is that this method allows a low need for support and litter materials and thus low transport costs. The final product obtained according to the invention is rapidly stable for end use.

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In the following, the invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows a top view of 25 plants applying the method and apparatus of the invention.

Figure 2 is a side view of the plant of Figure 1.

Figure 3 shows the plant of Figures 1 and 2 from the end.

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Fig. 4 shows the mixing elements according to the invention in the longitudinal direction of the silo and in the direction I of Fig. 5.

Fig. 5 shows the mixing members of Fig. 4 in the transverse direction of the silo and in the direction II of Fig. 4.

Figure 6 shows the mixing elements of Figures 4 and 5 seen from above in the direction III.

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Figure 7 shows the mixing members of Figures 4-6 in an axonometric view.

Figures 1-3 show the plant according to the invention schematically from different directions. The plant comprises a shallow silo 1 with an inlet end 3a and an outlet side 3b of compostable material and filled with a compostable material mattress 2. The actual composting takes place in this silo 1 and the material slowly moves from the feed end 3a to the outlet end 3b. The new material 7 to be composted, which is fed to the feed end 3a of the silo, is formed by premixing in a premixer 18. The mixing means are driven by a rail-operated drive device 6 above the silo, which can be of any type known per se, so it will not be described in more detail here. However, it is essential that the drive device 6 is able to move the mixing members 5 from end to end of the silo and, if necessary, in the transverse direction of the silo. In addition to this, the figures show a conveyor 19, by means of which part of the pre-composted material 20 to be removed from the silo and recycled to the silo is recycled back to the premixer 18 and thus recycled back to the composting process.

Figures 4-7 show a mixing element structure according to the invention used in the described composting plant.

The mixing member according to the invention is self-cleaning, which together through the air blowing according to the invention through both the mixing members and the silo bottom 16 enables efficient and continuous mechanical composting of pulps of very different types and, according to the prevailing information, difficult to handle. By continuous composting is meant here the mixing of the pulp site which takes place considerably more often than that which occurs in the open composting. In general, in this method according to the invention, each pulp point 35 is mixed several times a day, preferably the mixing interval is from half an hour to a few hours.

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The mixing member structure according to the invention comprises a pair 10 of two mixing members 5a and 5b. Each mixing member 5a, 5b has a stem part 8 rotatable per se by a drive device 6 and blades 9 projecting from the stem part 5, which are preferably but not necessarily extending along the length L against the length of the stem in a direction perpendicular to the outside. The vanes 9 are thus of the typical wing type, which extends in a direction perpendicular to the length of the arm part only to a small part-10 for the K-dimension of the entire circumferential angle, thus deviating completely from the helical structure. The arm parts 8 are parallel and the distance S of the arm parts is preferably slightly larger than the combined lengths H1 and H2 of the corresponding wings 9 ', 9' 'in the different arm parts of the pair of mixing members.

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The figures show the structure of the mixing members 5a, 5b and the pair 10 formed by them, which is believed to be particularly advantageous and simple in structure. In the illustrated embodiment, all the wings 9 are of equal length to each other, i.e. H1 = H2, and the wings are located in each mixing element in four directions U1-U4 which are perpendicular to each other. In addition, the vanes 9 in each projecting direction U1-U4 are arranged to be spaced at regular intervals in the longitudinal direction L of the mixing member, forming rows 11, 12, 13, 14 in each of the mixing members 5a and 5b. in the longitudinal direction with respect to each other and preferably so that one row of wings 11 or 12 or 13 or 14 has shifted by a quarter, i.e. generally by a dimension D, from the mutual distance P of the wings 30 with respect to each other. In general, if there are a number of wing strings other than 4. · the strings have shifted in the longitudinal direction L of the stem relative to each other by a fraction indicated by the number of wing strings from the distance P between the wings. The result of such a division 35 is that their circumferential angles K, the wings have uniformly encountered a cross-section drawn through the length L of the stem portion they encounter.

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In the mixing member pair 10, the mixing members are arranged at such an angle to each other that in the area between their arms 8 the wing 9 'of the first mixing member 5a and the corresponding wing 9' 'of the second mixing member 5b are aligned, as shown in the figures. Thus, the wing string 11 of the mixing member 5a is always opposite the wing string 11 of the second mixing member 5b, and likewise the second wing strings 12, the third wing strings 13 and the fourth wing strings 14 of these mixing members are opposite each other. Thus, in general, in the case where the wings in the mixing members 5a and 5b protrude other than in the four directions described above and the wings are arranged other than in the described rows, the wings protrude symmetrically from the shank portions 8 of the mixing member pair. In this case, when the mixing members 5a and 5b 15 rotate in opposite directions at the same speed, the wings 9 'of the first mixing member always form the counter-wing of the wing 9' 'of the second mixing member and point towards each other in the area between the arm parts. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Thus, in the structure described above, the wings 9 'and 9' 'in the mixing member pair 10a, 5b in the different mixing members 10 are thus not 3 interleaved in the area between the shaft parts 8, but are as shown in Fig. 4, so that the combined length of the wings corresponds to the distance S In this case, the pair of mixing members 10 produces a transverse force perpendicular to the plane 7 connecting the arm parts 8, which is caused by a circumferential tangent T perpendicular to this plane. When this direction T is aligned in the silo from its feed end 3a to its outlet end 3b and the pair of mixing members 10 or 11 pairs of members rotate and move as described during operation 12 in the compostable mattress 2, the agitator 13 gradually moves the material from end to end of the silo, although the agitating members 5a, 5b remain in the mattress 2 at all times. up to mix mass. The mixing member pair can be programmed to move different paths in the longitudinal and transverse direction of the silo. The non-clogging or self-cleaning of the mixing members is achieved by the fact that the wings with different projections β 94859 U1-U4 do not interleave in the direction of the circumferential angle K, so that the substance to be mixed can flow further between the trailing and vertical wings.

This is facilitated and enhanced by the fact that the wings 9 5 form a substantial angle α with respect to the direction L of the arm parts 8. This angle α is preferably between approximately 30-50 ° either upwards or downwards. This means that the vanes 9, when rotating, shape the mass either upwards or downwards. It is obviously preferred that in the mixing member the wings 10 are all angled in the same direction, but it is possible to arrange them in some way alternately.

In the embodiments described above, the vanes 9 are arranged at regular intervals both in the longitudinal direction L and in the direction of the circumferential angle K of the mixing member 5a, 5b, i.e. at regular intervals P and the rectifier U1-U4. Of course, there can in principle be only one direction of projection, but for the sake of uniformity of load, there should probably be at least two. There is no fundamental upper limit to the number of wing strings, as long as adjacent wings differing in the direction of protrusion-20 do not overlap, at least substantially in the direction of the circumferential angle. Also, the vanes in the mixing member do not necessarily have to be in rows, but may be arranged in the form of single- or multi-headed spirals or otherwise, as long as one wing 9 '25 in the first mixing member always corresponds to one wing 9' 'in the second mixing member. In principle, it would also be conceivable for the wings in the different mixing members 5a and 5b to interleave in the area between the shaft parts 8 as not shown in the figures, whereby the distance S between the shaft parts is less than 30 times the total length H1 + H2 of the wings. . the force decreases. In the embodiments described above, all the wings 9 are of the same length, but in practice the wings can also be of different lengths, as long as the mating wings 35 9 ', 9' 'are arranged so that the second wing is shorter and the other wing is shorter, so that their total length corresponds to the distance between the stem parts.

• · il »U I 1-1 1. 1-44 * · 1 9 94859

In addition to the wing structure described above, heavier-than-usual compostable materials can be treated with the equipment according to the invention with the associated air blowing solutions. According to the invention, air is controlled in the compostable mattress pu-5 through both the mixing elements and the bottom 16 of the silo. For this purpose, the bottom 16 of the silo is formed as not shown in the figures from a perforated plate or the like for supplying air to the compostable mattress 2 from below. For the same purpose, the arm part 8 10 of the mixing member is also hollow and its lower end 15, which comes close to the bottom 16 of the silo, has holes 17 for supplying air to the material mattress and in particular to its lower part. With this arrangement, large amounts of air can be distributed and finely divided and evenly in the material mattress, whereby the material of the material mattress does not have as many requirements as have traditionally been set, as will be described below.

With the equipment described above, it is possible to compost, in particular, the raw sludge from the treatment plants, which has a dry matter content of approximately 15-25%, using only very small amounts of supports or litter. The primary purpose of the support material is to reduce toughness, i.e. dough-like, and the primary purpose of the bedding material would be to increase the dry matter content. Normally, crude-25 sludge contains enough carbonaceous substances, so • it is usually not necessary to add them for this reason. In the preferred case, the use of these supports and bedding materials can be completely avoided. To achieve this, 20-60% of the total amount of recycle 4 with a dry matter content in the range of 50-70%, preferably approximately 60%, is mixed into the slurry. In this way, composting is obtained. the dry matter content of the van mixture is preferably in the range * · about 30-50% and preferably about 40%. Theoretically, the bacterial activity in composting could be rapid in a well-moist pulp, i.e. a pulp with a dry matter content well below 30% due to the rapid growth and movement of bacteria. On the other hand, an adequate supply of oxygen to such a moist mass is difficult or impossible in prior art processes. For this reason, i.e. due to the sufficient airiness of the pulp, relatively dry pulp has been recommended in the prior art to keep the process aerobic as required. The device of the invention has a very efficient supply of air to the pulp, as a result of which very moist pulps, even pulps with a dry matter content of less than 30%, can also be treated, while keeping the process safely aerobic. However, as the processing time increases, it is generally appropriate to use more conventional dry matter contents as defined above. Thus, composting with the device of the invention takes place in a technically flawless manner at dry matter contents of the cage of less than 30%, but such treatment is often not the most economically advantageous.

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The material mixture 7 fed to the composting is formed by mixing the starting material in a separate premixer 18. In addition to the sludge and the recycle, 0-30% of the total amount of undried chips or 20 corresponding fibrous supports can be mixed into this premix. It is estimated that the most preferred compostable pulp would contain 40% feedstock, 40% recycled material and 20% support material, with ranges in all of the order of ± 5%. Such a support generally has a dry matter content in the range of 50-85% and typically about 70%, which not only increases the dry matter content of the compostable mixture 2, but above all reduces its tendency to stickiness and makes it granular and increases air permeability. The premixed material mixture 7 to be fed to the composting can be fed as a continuous process 30 to the silo 1 or, preferably, intermittently, the entire amount of premixed material at a time immediately after the mixing is completed.

· This will start composting. With the device according to the invention, a large amount of air is distributed evenly in the compostable material mixture 2, whereby the composting is fast and complete and the dehumidification takes place efficiently.

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Claims (7)

An apparatus for producing compost from waste material, the apparatus comprising a low-angle substantially rectangular silo (1) adapted to contain a mattress (2) of compostable material, at one end (3a) of which a new substance (7) can be fed and at one end (3b) 4) are removable, and composting elements (5a, 5b) containing rotating parts which form the compost, the mixing elements (5a, 5b) being arranged to run in the mattress during work and 10 being accessible and controllable by means (6) above the mattress so that each part of the mattress can be modified, and each individual mixing member (5a and 5b) has a rotating arm part (8) known per se and only a part of the wings 15 (9) projecting from the entire circumferential angle (K) / which form several different wings along the length (L) of the arm part queues located at different heights, characterized in that - the mixing elements (5a, 5b) are arranged in pairs (10), the plane of which is formed by substantially vertical and parallel shank portions 20 (8) perpendicular to the direction of travel of the mattress, the mixing member pair (10) having wings arranged so that each wing (9 ') in the first mixing member (5a) corresponds to one wing ( 9 '') in the second mixing member (5b), and that the mixing members (5a, 5b) are arranged to rotate in opposite directions and such that, in said pairs, the circumferential tangent (T) perpendicular to the plane connecting their arm parts (8) is directed towards the outlet end (3b) of the silo (1), and - the distance (S) between the shank parts of the mixing member pair (10) is greater than 30 μs than the combined length (H1 and H2) of the respective wings in the different shank parts and the different projections (U1-U4), * adjacent wings (9) do not overlap in the direction of the circumferential angle (K). Device according to Claim 1, characterized in that in each mixing element (5a, 5b) the wings (9) project in at least two circumferential angles and preferably in at least three directions, and in that the mixing elements 12 94859 of the mixing element are arranged to rotate relative to each other. said counter-wings (9 ', 9' ') always point approximately towards each other when in the area between the arm parts (8). 5 Device according to Claim 2, characterized in that the mixing element (5a, 5b) has a plurality of vanes (9) projecting in each projection direction (U1, U2, U3, U4) and the vanes projecting in a certain direction are located in the arm part (8) of the mixing element. as a parallel row (11, 12, 13, 14) and that the wings with different projections are interleaved at different points in the direction (L) of the arm part. Device according to Claim 2 or 3, characterized in that the wings which always project in a certain direction are located at least approximately evenly spaced along the length (L) of the arm part (8). Device according to Claim 3 or 4, characterized in that the different wing strings (11, 12, 13, 14) 20 in the mixing element have the same number of vanes (9) and that the approximately evenly spaced wing strings differing in the direction of projection (U1-U4) are in the direction of the arm part (L ) so displaced relative to each other such that the distance (D) between the wings of two rows of wings corresponds to a fraction of the distance (P) of the wings 25 in the direction of the stem, indicated by the number of projections. «• · Device according to one of the preceding claims, characterized in that the arm part (8) is hollow and its lower end (15), which comes close to the bottom (16) of the silo (1), has holes 30 (17) for supplying air to the compostable mattress (2). and that the bottom (16) of the silo is formed by a perforated plate or the like also for supplying air to the mattress (2) to be composted. Device according to one of the preceding claims, characterized in that the wings (9) form a substantial angle (α) with respect to the direction (L) of the arm parts (8) and that this angle is approximately between 30 and 60 ° upwards or downwards. 13 94859