DE3150419A1 - Process for treating pulverulent, sludgy or dissolved materials, in particular environmental poisons or wastes containing other environmental pollutants, for transport and also subsequent recycling or long-term storage - Google Patents

Abstract

Process for treating sludgy, pulverulent or dissolved materials, in particular environmental poisons and wastes containing other environmental pollutants, for transport and subsequent recycling or long-term storage by binding the wastes with cement, and/or bentonite or with quicklime or its hydrated products. The materials are processed with the binders to give pellets having an ideal particle size distribution, the pellets being produced in different particle sizes on separate pelleting discs and being subsequently gently mixed, or being produced in the target mixture directly in a plough mixer.

Description

The invention relates to a method for processing powdery, muddy or dissolved materials, in particular waste containing environmental toxins and other environmentally harmful substances for transport, recycling or long-term storage by bonding with cement and / or bentonite or with calcium oxide or its hydrated successor products.

The processing of the environmental toxins that occur in large quantities or other powdery or dusty, liquid or suspended waste materials, in particular containing radioactive pollutants, is still a problem that has not been adequately solved. The deposit of such waste for interim storage or long-term storage has so far been carried out in such a way that the waste material is stored in special containers on landfill or is cast in blocks or pellets using cement, bitumen, synthetic resin or as glass, whereupon the blocks or pellets are packed in containers and the Containers are brought to the landfill intended for temporary or long-term storage. The disadvantage of this procedure is, in particular, that the actual deposition material provided packaging means or transport containers themselves take up a considerable part of the only limited available and therefore valuable storage space, which is therefore not available for the storage of the actually to be stored material. In addition, the transport and storage require considerable technical and organizational effort due to the necessity of multiple reloading onto the means of transport and from the means of transport to the storage area, whereby in the case of deep storage in mountain ranges the need to create the necessary technical facilities for the transport in addition, the planning and installation of which also require considerable effort.

For the long-term storage of such waste, especially radioactive waste, the most suitable solution is currently the deep storage in natural or artificial caverns of mountain domes, in particular salt domes, which are free of the circulation of liquid or gas allowing fissures and a sufficient geological Have stability, so that there is no risk of the environment being endangered by waste deposited there on the way of leaching and return to the bio-cycle.

The aim of the present invention is to create a method for the treatment of environmental pollutants, in particular waste materials containing radioactive substances for transport and disposal storage and the invention consists in the fact that the waste in powdery, sludge-like or dissolved form, optionally with the addition of liquid and / or binding agent, is pelletized to a heap of spherical bodies of a particle size range matched in such a way that the spherical bodies of the smaller classification are those of the spherical bodies of the larger Fill in the classifying spaces.

The invention creates a method with the help of which waste materials containing harmful substances can be processed in such a way that they are transported in containers or directly, ie without containers, for example by means of closed pipelines, with optimal use of space, and fed to other recycling or direct in-situ solidification can be.

For the production of transport chutes, pellets of two coordinated classifications are expediently used in such a way that the pellets of the smaller size classification have a diameter of 20 to 25%, preferably 22.5% of the diameter of the pellets of the larger classification and a proportion of the total mass of 0.5 to 0.7% by weight, preferably 0.6% by weight. With a grain spectrum of the pellets that is matched to one another in terms of size and weight, an optimal filling of the means of transport, storage or cavern space of approx. 61.0% is achieved. However, very good results are also achieved when using pellets of three size classifications, of which the pellets of the middle class have a diameter of 35 to 45%, preferably 41.5%, and a proportion of 6 to 7.5, preferably 6.8% by weight and the pellets of the small classification a diameter of 6 to 10%, preferably 8.5% of the diameter of the pellets of the largest classification with a proportion of 0, 3 to 0.5, preferably 0.4% by weight. In this way, too, excellent storage levels of up to 56%, which are significantly improved compared to the previous mode of operation, are achieved. Correspondingly good results are achieved with a pile of pellets in which the proportions belonging to the individual grain size classes are grouped in the specified ratios. Control of the pelletization in this way is possible without difficulty, all that is required is the screening of oversized and undersized particles and their return after the comminution.

The pellets are advantageously produced in such a way that an aqueous solution or suspension containing the highest possible pollutant concentration is first produced and this solution or suspension is bound with an anhydrous, optionally predried, binding agent, which increases the binding force of the binding agent and thus the resulting Pellet amount is significantly reduced. Diagrams 1 and 2 below illustrate the importance of the use of dried binders on the process. Diagram 1, which shows the water-binding capacity (W / C) as a function of the water content of the binder (Tr), in the example cement, shows that the water-binding capacity decreases considerably with increasing moisture content of the binder. Correspondingly - Diagram 2 - the salt load related to the amount of cement used increases proportionally with the concentration of the solution used (curve S = f (LG)) and disproportionately when dry or pre-dried cement is used as a binding agent [curve S = f (LG, Tr [deep] 1)]. If quicklime is used, it is added, after the lime has been extinguished with water, if necessary, in an amount which results in a total water content in the final pellet product of 8-15% by weight.

The pelletization can take place in a manner known per se on granulating plates working next to one another with subsequent gentle mixing of the pellets obtained in this way, the mixing expediently in a ploughshare mixer at a rotational speed of the horizontal mixing element between 0.120 and 0.180 m / sec, preferably 0.165 m / sec during a mixing time takes between 10 and 15 minutes. The further transport of the mixture until it is finally deposited in the container or until it is suspended in a slurry is carried out in a known manner which prevents the grain sizes from segregating.

In another embodiment of the process according to the invention, the pelletization can also take place with the aid of a single pelletizing ploughshare mixer at a low speed of rotation of the ploughshare mixing elements and while maintaining a mixer temperature of 25 to 35 ° C, with a speed of between 0.65 m / sec at a low peripheral speed and 6.5 m / sec, preferably between 1.3 m / sec and 2.7 m / sec, which is roughly the speed of between 20 and 200 rpm, preferably between 40 and 80 rpm Mixer with a drum diameter of 630 mm. Here, the liquid or slurry containing the pollutants is advantageously added to the dry cement Flour in the granulating drum at the beginning of the pelletizing process slowly, ie over a period of about 3 to 5 minutes, and evenly distributed over the entire length of the mixer by spraying onto the parts of the container wall located in the direction of rotation of the ploughshare mixing elements above the material level, after which the pellets are added agglomeration in the granulating drum with stationary mixing elements for a time of 10 to 20 minutes, preferably 15 minutes, flushed with fresh air and then deposited for a time of at least 15 minutes, preferably 20 minutes on a conveyor belt, also flushed with fresh air for cement hardening. The filling quantity is expediently limited in such a way that the filling level of the finished pellet quantity in the batch is between 30 and 70%, preferably 45 to 55% of the drum volume. In this way, it is possible to work specifically on the desired grain spectrum, with the effectiveness of the rotating cutter head at a high speed of approx. U = 1500 reducing the formation of oversized grain. The processing of powdery materials is carried out in a corresponding manner by first mixing with cement or with quicklime slaked in the above manner and, if necessary, betonite, after which the mixture is processed into pellets by adding water in the manner also described above.

To ensure that the pelletizing process runs properly, it is necessary to maintain the specified, relatively narrowly limited mixer temperature and thus to ensure good heat dissipation through the container wall. For this purpose, the cement or quicklime deposits on the container wall must be carefully removed at regular intervals, for example after a throughput of 8 to 10 batches. The cleaning is expediently carried out by blasting with the aid of the classification pellets produced as blasting agents in the process

1 mm, after which the resulting mixture of blasting media and blasted drum feedstock is fed back into the pelletizing process.

The containerless transport and / or the in-situ solidification take place in such a way that the pellets are suspended in a flowable suspension of a carrier and / or binding agent, for example a cement paste, to form a pellet suspension. In this case, the suspension is advantageously produced while maintaining a negative pressure of 0.6 atm, which prevents air from being absorbed into the suspension and a high material density is achieved. The particular advantage of this procedure is that the material required to solidify the material also serves as a means of transport, which, as a further essential advantage, achieves a significantly improved utilization of the space available for long-term storage by using the previous method of operation The space required for storing the transport containers is also available for material storage. The basis for this is the division of the consolidation, which was previously seen as a uniform process. The process is divided into two independent sub-processes, one of which is only used for the preparatory preparation of the materials, the other for the final consolidation. Due to the division of the process, the heat development can also be kept within the required narrow limits of approx. 30 ° C without any problems, which, if significantly exceeded, could pose a risk in the processing of e.g. radioactive waste.

The invention is explained below with reference to the accompanying drawing and a few examples. Show it

1 shows a schematic representation of an alternative to a desired spherical packing of the pellets

2 shows a further alternative of a possible spherical packing of the pellets.

The method according to the invention is based on the principle that by mixing specifically selected grain size fractions that fill the filling space with the greatest possible precision, mutual support of the grains of the fractions occurs and this prevents large-scale displacements, so that not only optimal use of space is achieved but also separation of the chute or the Suspension is prevented.

If one assumes a uniform classification of pebbles, a theoretical space filling of 52.4% results in the closest packing of the spheres. Fig. 1 in conjunction with Table 1 shows a schematic representation of the deposition of an inventive Matched heap on the basis of pellets of two grain size classes, the pellets denoted by 1 in FIG. The drawing shows that when coordinated in this way, the pellets of the larger grain size class are deposited in layers in the spaces between the pellets of the underlying layer and the pellets of the smaller size class fill the remaining - relatively small - spaces. The degrees of filling that can be achieved in this way are shown in Table 3.This shows that, in this embodiment of a suspension according to the invention, the pellets 1 of size class d'1 - regardless of their actual dimensions in detail - 60.445% and the pellets of size class d'2 0.415% fill in the available space. Practical testing shows that if the classification is adhered to within the specified limits, a segregation-free deposit occurs according to the scheme shown in the drawing and room filling degrees of over 60% - compared to approx. 52% when using unclassified pebbles.

Fig. 2 shows, in conjunction with Table 2, also a schematic representation of the deposition of the pellets from a pile formed according to alternative 2 from three coordinated size classes. In this case, the pellets 3 with the diameter d [deep] 1 are "supported" by the pellets 4 with the diameter d [deep] 2 in such a position that the spheres lie vertically one above the other in layers. The balls 5 with the diameter d [deep] 3 fill the remaining intermediate rooms. Table 3 shows that with such a sorting, a space filling of 56.46% is theoretically achieved. Tests have surprisingly shown that the deposition of the heap sorted in this way actually follows the scheme shown and degrees of space filling of around 55% are achieved. Surprisingly, it has also been shown that the results given are also achieved with heaps of mixed sorting in such a way that they partially add up in groups to form mixtures of the given ratios. Such a mixture results from what follows, for example.

example 1

140 kg of cement (fresh mass) and 10 kg of dry concrete are poured into a pelletizing ploughshare mixer with a drum diameter of 630 mm via a weighing device and mixed for about 5 minutes, whereupon at a speed of the horizontal plowshare mixing element of n = 52 and the cutter head of n = 1,500 is sprayed in at a temperature of about 30 ° C in a period of 3 to 5 minutes, 35.0 kg of an aqueous solution containing concentrated pollutants or toxins. The temperature is kept at approx. 30 ° C. by intensive cooling. After about 20 minutes of work, calculated from the beginning of the injection time of the solution, the mixing operation is ended, whereupon the contents of the mixer are flushed with fresh air for 10 to 15 minutes.

With the horizontal mixing element switched on, the pellets are brought onto a conveyor belt, where the pellet mass cools down to room temperature for 20 minutes before sieving.

The sieve analysis (after the oversized and undersized grains had been screened off) with a maximum grain size of 5mm in accordance with the specifications gave the following grain groups of spherical pellets on the test sieve (grain groups are grain sizes between the closest test sieves)

- Grit group 4.5 mm 100 kg

- grain group 2.5 mm 100 kg

- Grit group 1.25 mm 100.6 kg

- Grain group 0.625 mm 100.6 kg

- Grain group 0.300 mm 0.6 kg

- Grain group 0.150 mm 0.6 kg

Of the grain size classes listed above, ideally 100 kg of the 5.0 mm grain group fill with 0.6 kg of the 1.25 grain group, the remaining 100 kg of the 1.25 mm group with the 0.300 mm grain group. The grain group 2.5 mm is still ideally filled with 0.6 kg of the grain group 0.625 mm, the last grain group remains 100 kg, which in turn is ideally filled with the grain group 0.150 mm.

The obtained grain spectrum thus fulfills the conditions for optimal space filling in the sense of the deposition picture shown in Fig. 1, in which the larger pellets 1 each lie in the gap between four pellets 2 of the underlying layer and pellets 3 of the smaller classification each lie between the three large ones Fill in the space formed by pellets. The determined value for the pore volume is 42.8% in the example given, which corresponds to a space filling of 57.2%. The theoretical table possible maximum value would be 60.85%. A filling or a suspension delimited by walls is filled in by gentle mixing in the production stage or during filling in a period of 10 to 15 minutes with a circulation speed of the mixing element of between 0.120 m / sec and 0.180 m / sec spread over the entire mass , preferably 0.165 m / sec for the suspension in the absence of air, d. H. under a vacuum of at least 0.6 atmospheres at room temperature. The filling quantities or suspensions obtained in this way, without the use of mechanical force, show no segregation and very stable degrees of filling, which are at least 7.8% to 16.4% above the values achieved with spherical pellets of the same diameter or non-spherical (three-dimensional) granules.

A sufficiently good space filling is also achieved when working on a grain size spectrum corresponding to FIG. 2 with pellets of three size classes, of which the pellets 4 of the middle classification have a diameter of 35% to 45%, preferably 41.5% and the pellets 5 of the smaller ones Classification have a diameter of 6% to 10%, preferably 8.5% of the diameter of the pellets 6 of the largest classification. This is based on a deposition scheme in which the middle pellets 4 are deposited in the space between four pellets of the large classification and thus force them into a position in which the connecting lines 7 between their centers lie on a straight line, while the pellets of the small Classification fill the remaining spaces between the large and medium pellets. The arithmetically maximum degree of space filling is in this case 56.46%.

Increasing the speed of rotation of the ploughshare mixing element with otherwise unchanged operating conditions results in larger pellets.

Then the inner wall of the pelletizer with pellets becomes a grain size of

1 mm blasted to clean the walls from the wall attachment. The wall attachment and the cleaning pellets are used as input material and processed into pellets that meet the specifications.

The pellets obtained in this way can now be suspended in a cement slurry in the manner described and brought to the deposition site in this form by means of a pipeline.

Example 2

100 kg of quicklime are introduced into a pelletizing plowshare mixer with a drum diameter of 630 mm via a weighing device and extinguished with 25 kg of water under intense heat, or dry calcium hydroxide from aretylene production from carbide in an amount of 1.5 kg is placed in the pelletizing mixer. You now put 200 kg of fly ash, fly ash or 150 kg of waste sand or 150 kg of dust from sintering plants into the mixer.

Now, according to example 2, about 30.0 kg of water are added and the mixture is processed into pellets.

The results are exactly as in Example 1, only the oversize fraction was 1.1% by weight and the undersize fraction was 1.85% by weight.

Example 3

70 kg of cement, 105 kg of fly ash and 10 kg of bentonite are introduced into a pelletizing plowshare mixer with a drum diameter of 630 mm via a screw metering device. After intensive mixing, 20 kg of water are then added in portions with cooling and the mixture is processed into pellets according to Example 2.

Here, too, the results are exactly as in Examples 1 and 2. The oversize fraction is 0.45% by weight and the undersize fraction is 2.15% by weight.

With the same result, different types of pulverulent waste materials, such as waste sand, sintered dust or the like, can also be processed, for which purpose the following mixtures can be produced, for example, in the process sequence described above.

A: cement 80 kg B: cement 55 kg

Waste sand 160 kg sintered dust 200 kg

Bentonite 10 kg Bentonite 12 kg

Water 37 kg water 40 kg

_____________________ ______________________

287 kg 307 kg

Table 3: Degree of filling

Comments / a) Values rounded up

b) Data listed with index relate to alternative 1, without

Index alternative 2

Table 1: Grain size (micrometers) Alt. 1

d'1 d'2

_________________________

500 110

250 55

------------------------------------------

150 33.0

120 26.4

100 22.0

80 17.6

60 13.2

40 8.8

20 4.4

_________________________

Table 2: Grain size (micrometers) alt. 2

d1 d2 d3

____________________________________

500 207.1 42.9

250 103.55 21.45

-------------------------------------------

150 (= 0.150 mm) 62.13 12.87

120 49.70 10.30

100 41.42 8.58

80 33.14 6.86

60 24.85 5.15

40 16.57 3.43

20 8.28 1.72

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Claims (19)

Process for the processing of powdery, sludgy or dissolved materials, in particular waste containing environmental toxins and other environmentally harmful substances, for transport and subsequent recycling or long-term storage by binding the waste with cement and / or betonite or with calcium oxide (quicklime) or its hydrated secondary products , characterized in that the waste is pelletized in powdery, sludge or water-dissolved form, optionally with the addition of water and / or binding agent, to form a heap of spherical bodies of a grain spectrum coordinated in such a way that the spherical bodies (2, 4, 5) of the smaller classifications are those of ideally fill the spaces formed by the spherical bodies (1, 3) of the larger classification. 2. The method according to claim 1, characterized in that the binders, for example cement and betonite, are dried before they are added. 3. The method according to claim 1 or 2, characterized in that the pellets (1, 2) are produced in two coordinated classifications such that the pellets (2) of the smaller size classification have a diameter of 20 to 25%, preferably 22% of the Diameter of the pellets (1) of the larger classification and a proportion of the total mass of 0.5 to 0.7% by weight, preferably 0.6% by weight. 4. The method according to claim 1 or 2, characterized in that the pellets are produced in three coordinated size classifications such that the pellets (4) of the middle class (4) have a diameter of 35 to 45%, preferably 41.5 % and a proportion of 5.5 to 7.5%, preferably 6.8% by weight, and the pellets (5) of the small classification have a diameter of 6 to 10%, preferably 8.5% of the diameter of the pellets
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of the largest classification and a proportion of 0.2 to 1.2%, preferably 0.4% by weight. 5. The method according to claim 4 or 5, characterized in that heaps of pellets are represented in which the proportions belonging to the individual grain size classes are partially added in groups to form mixtures of the specified size and quantitative ratios. 6. The method according to any one of claims 1 to 5, characterized in that the pelletization takes place on granulating plates. 7. The method according to claim 6, characterized in that the pelletization takes place on granulating plates working next to one another and the pellets obtained are then gently mixed. 8. The method according to claim 7, characterized in that the mixing takes place in a ploughshare mixer at a speed of rotation of the horizontal mixing element between 0.120 and 0.180 m / sec, preferably 0.165 m / sec during a mixing time between 10 and 15 minutes. 9. The method according to claim 1, characterized in that the pelletization takes place in a per se known pelletizing ploughshare mixer at a low speed of rotation of the ploughshare mixing elements and while maintaining a mixer temperature of 25 to 35 ° C, preferably 30 ° C. 10. The method according to claim 9, characterized in that the pelletizing at a peripheral speed of the horizontal mixing element between 0.65 m / sec and 6.5 m / sec, preferably between 1.3 m / sec and 2.7 m / sec The cutter head rotates at 1500 rpm. 11. The method according to claim 9 or 10, characterized in that the aqueous solution, liquid or slurry is sprayed onto the dry cement powder or quicklime in the granulating drum at the beginning of the pelletizing process for a period of 3 to 5 minutes the parts of the container wall located above the material level in the direction of rotation of the ploughshare mixing elements are added. 12. The method according to claim 9 or 10, characterized in that the powdery material is first mixed with the dry cement flour or quicklime in the granulating drum and the mixture is then pelletized with the addition of water. 13. The method according to claim 9, 10 or 12, characterized in that the quicklime used is extinguished with an amount of water before being added to the drum, which corresponds to a total water content of 8-15% by weight of the resulting granulated material. 14. The method according to any one of claims 10 to 13, characterized in that the degree of filling of the mixer, based on the finished quantity of pellets in a batch, is 30 to 70%, preferably 45 to 55%. 15. The method according to claim 9 or 10, characterized in that the pellets after agglomeration in the granulating drum with stationary mixing elements for a time of 10 to 20 minutes, preferably 15 minutes with fresh air and then for a time of at least 15 minutes, preferably 20 minutes outside the granulating drum, for example on a conveyor belt, which is also flushed with fresh air. 16. The method according to any one of claims 9 to 15, characterized in that the granulating drum is cleaned at regular intervals of deposits attached to the container wall. 17. The method according to claim 16, characterized in that the cleaning is carried out by blasting with the aid of the classification pellets produced in the process and used as blasting agents 1 mm takes place. 18. The method according to any one of claims 1 to 17, characterized in that the pellets in a flowable slurry of a binding agent, for example in a cement slurry to form a pellet suspension and transported in this form by means of pipelines for the purpose of deposition. 19. The method according to claim 18, characterized in that the production of the pellet suspension takes place at room temperature under a negative pressure of at least 0.6 at.