DD265084A1 - METHOD OF GRINDING CELLULAR PROPERTIES, PRIMARY PLATED ISOTROPERS AND ANISOTROPIC MATERIALS - Google Patents

Abstract

The invention relates to a method for grinding kaelteversproedeter, primarily platy isotropic and anisotropic materials. It is applicable for the preparation of different materials such as pre-shredded tires, electronic scrap and the like. a. m. The objectives of the invention are the improvement of energy utilization, the reduction of the number of process stages and more favorable Koernungsverteilungen for subsequent processing. The object is achieved in accordance with the invention by exposing the kaelteversproedete material in the narrowing grinding gap of a Waelzmuehle as quasi einkornschicht one up to a maximum value, which is dependent on the Sproedbruchdruckfestigkeit of reprocessing isotropic or anisotropic material, increasing pressure load with subsequent pressure drop and superimposed Reibbespruchung so is that the resulting cracks disassemble the material after one or more rolling over more or less completely. Fig. 1

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to a method for the grinding of cold-brittle, primarily platy materials.

It is used in the mechanical treatment of käiteversprödbaren secondary raw materials, especially vorzerkleinerto scrap tires, electronic waste u.a. m.

This creates conditions for better exploitation of the energies used, reduces the number of otherwise required process stages and achieves the better adaptability of the grain distributions to the technological conditions of further processing.

Characteristic of the known state of the art

A general overview of the problems of cryogenic treatment has been given by N. R. Braton (1). It is known that in the processing of secondary raw materials such as used tires or electronic scrap, the cold embrittlement of the materials is applied before their comminution. Some of the pre-shredding processes that are still working at normal temperature are used and combined with subsequent sub-cooling (DE-PS 2549752, DE-OS 2636805). Multistage cooling processes and systems are used (eg, AT-PS 363303, DE-AS 1778659, DE-AS 2311933, DE-OS 2223769, DE-OS 2630805, DE-PS 2651871, DE-OS 3018774, DE-OS. AS 2312753, DE-PS 2516764, DD-WP 102 344) or cold-insulated grinding plants used, for. B. DE-OS 2630803. There were systems with other refrigerants than liquid nitrogen, z. B. liquefied natural gas from DE-AS 2529382 or with indirect cooling of the feedstock (DE-OS 2743766) proposed. Likewise, in addition to the use of cutting tools (eg DE-PS 2516764) in pin mills, the use of impact crushing effects for surface enlargement (DE-AS 1955206, DE-AS 2061184, DE-OS 2334822) Use of chemical additives (DE-OS 3510266) or more particularly, for. B. ionized Mahlraumatmosphären (DE-AS 22 35986) or the addition of non-stick agents before cooling and further processing (DE-OS 2648301) known. The most important crumbling equipment used in (1) was the impact crusher type hammer or grinder mill. There are modifications like

-2- 264 084

- Use of additional crushing plates in the task bark,

- Use of sieve grates for the fines discharge

- Kreisluufführung cooled air in the mill u. a.

but all of them are basically the nightmare of bouncing shreds

- wear-intensive shredding tools and

- Generating a wide grain spectrum (with a relatively small proportion of fines - 0.316 mm and - 1.0 mm) in the finished product

do not cancel and necessarily require the construction of elaborate forming and classifying the finished product (2,3). An important effect of cold embrittlement, the different cold toughness of various substances at low temperatures, make use of the selectively operating methods and / or devices (eg CH-PS 604899, OE-OS 2803869, OE-PS 3027262). Further effects such as a classification process superimposed on the comminution use suggestions from DE-OS 2344582. Likewise, the combination of cold shock and subsequent pressure comminution was recommended (DE-OS 2803859). In (1), p. 86, reference is made in this connection to the use of pressure-sensitive pressure plates and fallblinds. Breaking and bending stress after cold embrittlement has also been proposed (eg DE-OS 2145728). Roller mills of a known type have the advantage of being able to apply the large comminution forces required for the comminution of brittle or embrittled materials. For example, it has been proposed in US Pat. No. 4,638,768 to provide the drive and bearing area of the full plate of a roller mill with a separate cooling system. The use of roller mills for the selective treatment of pre-shredded waste tires was provided in the DD-WP 2928230, while the DD-WP 224807 and 225390 view the roller mill as Feinmahl- and Piastifizierungsaggregat of pure rubber. Roller mills with separate application of locally large comminution forces with relief of the storage and drive system were proposed in DD-WP 126241, while the individually driven grinding media are included in DD-WP 127122. Wälzmahlanlagen with external classification (DD-WP 142426) or with gravity discharge on the Mahltellerrand (DD-WP 214302) have been developed as well as Mahltrocknungsschaltungen with Wälzmühlen (eg DD-WP 239131) for special treatment tasks.

A proposal is made in DE-AS 2315687, over which the Wälzzerkleinerung takes place in the narrowing grinding gap, which comes close to a friction comminution, wherein the Mahlkörperumlauf changing gap between a housing and a pipe for the rubber preparation is used.

In addition to the above-mentioned disadvantages of impact crushing for brittle-embrittled materials is to be noted that the production of very fine-grained products as a prerequisite for the complex material use of scrap tires and other Kältversprödbaren secondary raw materials requires the establishment of multi-stage systems (4), but this is the fundamental deficiency of the impact - And steel crushing, at relatively low solids concentration in the stress zone only small crushing success with a corresponding increase in surface to achieve, not compensated. A substantial increase in the fine grain content can be achieved in the known technical state only by further cooling and / or Feinmahlstufen, the overall economy is significantly influenced by the refrigerant consumption.

As well-known advantages of Wälzmerkleinerung as high energy density in the crushing zone and relatively low specific energy consumption for crushing (5) can be used tollweise when grinding kSlteversprödeter, primarily plattigyr materials, because known mill types especially the formation of a stable, repeatedly rolled Mahlgutbettes presuppose on the grinding table of the mill. The grinding of refrigerated brittle particles Jadoch runs for reasons of refrigeration economy and because of the comparison of granular mineral materials Einzugr.bedlängungen on the Zerkibinerungswerkzeugzeugen the Wälzmühle on a single grain or quasi Einkornsohicht comminution process without the formation of a special Mahlgutbettes addition. It can even be assumed that, after a maximum of three roll-overs, even the largest charged particle is no longer in the kite-evolved state, and therefore the grinding of such materials, which have to be well crushed by pressure and friction, must take place even at high grinding-plate speeds To compensate for deteriorating grindability as well as centrifugal force discharge effects on the Mahltellerrand to Aufgabo the Austragsgutes on the way of gravity or in conveying gas streams to use.

This is to be kept in mind that the previously milled on roller mills feed materials have a granular structure with consistent bulk properties and also have a variety also at normal temperature become effective fracture-promoting structural defects and microcracks.

Object of the invention

The object of the invention is to provide a method of grinding cold-embrittled, predominantly flattened materials by combined compressive and frictional loading to obtain better energy production conditions, a reduction in the number of otherwise required process steps, and favorable grain size distributions adapted to the further processing conditions.

Explanation of the essence of the invention

The invention has for its object to provide a method for the olehlversprödeter materials by combined pressure and friction stress such that using the known per se, adapted to the intended purpose mechanical engineering construction solution of the roller mill in the feed to be crushed by targeted rapid pressure increase and superimposed frictional stress in the Zerklingorungszone the technological required particle size reduction is achieved.

According to the invention, this object is achieved in that in de'i kältevesprödeten, primarily platy task particles in the process of drawing in the tapered gap between the Zei kleinungswerkzeugen an increasing number of microcracks under the effect of pressure builds up that üie microcracks expand with further pressure increase in that the maximum pressure is set by known structural measures so as to run most of the previously generated cracks through the feedstock particles or up to an in-particle boundary with dab crack propagating properties and that the subsequent slow pressure drop on the overrolled feedstock particles contributes with the superimposed Reibbeanspruchung for further Gutzerkleinerung, in particular for fines formation. This is a highly productive and crushing energy saving process for the preparation of different, primarily plate-like materials such as pre-shredded scrap tires, electronic waste u.a.m. created.

The fact that different known discharge, classifying and / or sorting systems can be connected to the shredding system requires no further explanation. Decisive for the solution according to the invention is that the state of embrittlement and thus the particularly good pressure crushing ability of the feed material remains as long as possible or the stressing process for the individual feed piece has already been completed when the embrittlement state is completed. This can lead to variable cooling conditions for different feed materials, may require adjustability of crushing conditions such as pressures, gap widths, and orbital tool rotational speeds, and may also cause different pulping results for different materials.

Based on the need to subject each (larger) feedstock particle in the embrittled state of stress to the pressure in the narrowing gap, the pieces to be crushed must be directly and individually aufgegebun in front of the crushing tools. The formation of a bed of good, within which a further particle stress takes place, is useful only under the grinding body in engagement. Upon completion of the first overrun of the embrittled particle trapped by the grinding media at a certain point on the grinding table, the increase in surface area of the milling products is so great that brittleness due to heat of the pipe is expected to result from relatively rapid loss due to heat and conduction and efficacy is to be expected and the effectiveness of a we'teren overrun of the fragments with the aim of further comminution is called into question. The one or more times practice, particles should be discharged from the field of crushing tools, classified and / or destroyed and, if necessary, after renewed cold embrittlement of the roller mill to be abandoned. It depends on the formation of a quasi Einkornschicht to let the defined Druckzerkleinorungsbeanspruchung take effect.

The nature of the removal of the comminuted particles from the crushing area is enforced by the technological task. The coarse grain digestion for the separation of grain constituents having properties other than that of the embrittled base material is expediently carried out with the known expressed classification and an embrittlement device lying outside the comminution machine, e.g. a combined with liquid nitrogen cooling drum combined. For the fine grinding of elastic materials that can be cooled by cold, such as old tire pieces, granulated plastic waste, etc. m. will be contrast to the well-known roller mill with integrated sifter and inner circuit of coarse grain to be oriented, being used as the medium vaporized nitrogen with zusiitzlicher addition of liquid nitrogen on the Sichteraustrag o.a. is usable. The logical demand for the use of grinding tools and construction materials with sufficient brittle-resistance of the o. G. Quasi single-grained crushing must circumferential speeds of the circumferential grinding gap 0.5m / s and contact pressures brittle fracture resistance of the material; be guaranteed. Then it is possible to make better use of the energies used, to reduce the number of process stages and to better adapt the possible grain size estimations to the technological requirements of the downstream processing industry.

embodiment The invention will be explained in more detail with reference to two embodiments. The corresponding representations zeigon Fig. 1: the scheme of a cold grinding plant with working in the outer circuit known per se roller mill at gravity discharge,

2 shows the diagram of a cold grinding plant with internal circulation and pneumatic discharge; and FIG. 3 shows the range of grain size distribution achievable with rolling mills in the coldmilling of rubber in relation to other known Zakleinerungsmeschinen operating under comparable conditions.

In Kaltmahlanlage of Fig. 1 verkälteversprödete pre-shredded parts of used tires are processed. The material to be crushed is from the feed hopper 1 together with the cooling medium 2.1 from the coolant tank 2 of the cooling section 3, which as a cooling drum, cooling screw o. A. can be constructed, supplied.

The embrittled, cooled to temperatures -80 ° C Augabegut 3.1 enters the cold insulated mounted mill 4 and is directly in front of the grinding table 4.4. abandoned in portions or portions. The crushing conditions should be adjusted so that maximum contact pressures 15-16Mpa, no grinding gap 4.3 between grinding plate 4.4 and pressed Mahlkörper 4.2 in the idle state is measured and peripheral speeds of the sand-less Mahltellers 4.4 0.5-1.0m / s can be achieved. The overrun and thus shredded pieces of scrap tire are dropped over the grinding table edge 4.5 of the mill 4 and ice mill discharge 4.1 supplied via a vertical conveyor 5 in the separator 6.

From the classifier feed stream 5.1, a coarse grain fraction + 1 mm is separated and fed again as coarse grain return 6.1 of the cooling section 3. The finer fractions 6.7 were pneumatically fed by means of a conveyor fan 7 ale cyclone 7.1 to the cyclone separator 8 and subsequently to the filter 9, where the Fertiggutausträge 8.1.9.1 together or (not shown in Fig. 1) get separated for further processing. It is to be assumed for the Altreifenaufbereitung that the Fertiggutaustrag 8.1 of the cyclone has a fineness + 0.315mm, while in the fines 8.2 from the filter fraction -0.315mm outweighs.

The accumulating exhaust air 9.2 goes away over pressure, so that a clear separation between unterkühltom coarse grain + 1 mm and working at normal temperature fine grain range -1 mm is achieved in working with gravity discharge Wälzmühle4.

The Kaltmahlanlage shown in Figure 2 uses a conventional Wälzmühlenkostruktion 4 with integrated, z. The feed stream 1.1 from the hopper 1 and the cooling medium 2.1 from the coolant tank 2 are abandoned together the cooling section and thus arrive as a cooled feed stream 3.1 in the mill 4. Under the same conditions as in the embodiment of FIG the comminution, the removal of the ground material is carried out pneumatically by the induced draft 7, wherein the classifier is adjusted so that only finished -1 mm flows as a mill discharge 4.1 the cyclone separator 8. The separation of both the grain fractions -0.315 mm and +0.315 mm from the Sichterfeingut 6.2 is analogous to FIG. 1. However, important are the work of the entire system in the supercooled area and the return of the exhaust gas 9.2 to the cooling section 3, where the second use for the Jacket cooling takes place. Subsequently, the exhaust gas is added via the cooling gas recirculation 3.2 ale conveying air and cooling gas in the mill 4, wherein if necessary. Not shown in Fig. 2 addition of coolant 2.1 for Sicliorstellung of mill inlet temperatures in the range of -2O ⁰ C and below is necessary. In addition, it should be noted that for balance reasons, a partial flow can be repelled as exhaust 9.2 '.

A major disadvantage of this technical variant is the high internal material circulation in the mill 4 between classifier 6 and comminution zone. It has been found in studies on rolling mills 5 that he can exceed the task stream 1.1 times' multiple times. The large inner Gutkreislauf restricts the possibilities of effective Wälzmahlung thereby, that on the one hand, the defined Mahlgutaufgabe as quasi- einkornschicht is practically unattainable and that, secondly, the necessary Kälteversprödung the return material requires large amounts of cooling medium 2.1 directly into the mill. As a result, the technological capacity of the mill 4 is restricted with high contact pressures given a mill design and a fixed material use.

The grain spectra of cold-spattered old tire rubber processed in different crushers, taken from (2), p. 521 and supplemented by own results, show:

- The crushing machines previously used in grinding plants for refrigerated embrittled waste rubber such as cutting mill, shredder, hammer mill with two rotors and impact mill are not able to produce high levels of fine grain -1 mm. The proportion of ultrafine grain -0.315 mm is negligible.

- With the help of deep-frozen fine grinding, which is constructed in two stages from baffle or hammer mill and schneilaufender granulator, succeeds with a specific energy consumption of about 100KWh / t, the production of finished goods with a fine grain content -1 mm up to 100% and a Feinstkornanteil -0.315mm to about 75% sieve passage.

- With Hi Ife Wälzmahlung shredded cold rubber embrittled old rubber pieces of tires have been processed so far in a single-stage plant structure that partly the results of frozen fine grinding were outbid, but in any case significantly better Mahlgutfeinheiten be achieved as in other single-stage plants.

Overall, it can be estimated that it succeeds with the help of Wälzmahlung with targeted variation used Beanspriichungsbedingungen any required for known Welterverarbeitungsverfnhren digestion of the kaltvorsprödbaren material to be ground. In this case, compared to known methods low investment, lower specific electrical energy consumption and based on the Herstellungsautwand, higher intricacies of the finished goods secured. It goes without saying that in this way higher yields or better qualities of the products produced become transparent in subsequent processing stages. This also applies to isotropic materials, such as rubber with a desired high fineness of the finished good as well as anisotropic Materialleo, in which by exposing the material structures z. B. the separation conditions for built-in metals are improved in electronic waste.

Claims (4)

1. A process for the grinding of kaltversprödeter, primarily platy isotropic or anisotropic materials, characterized in that the aufzufenden Aufgabegutteilchen (3.1) individually or as a quasi Einkornschicht before the grinding media (4.2) of a known cold-insulated and constructively designed for the required low-temperature load roller mill (4) fed, retracted in narrowing grinding gap (4.3) between grinding media (4.2) and grinding plate (4.4) and by the loading conditions with Mahlbahngeschwindigkeiten greater or equal '. 0.5 m / s, with contact pressures above the Brödbruchdruckbelastbarkeit of the feed (3.1) and with a to the required digestion or minimum grain size of the finished good (6.2) tuned closest Mahlspalt (4.3) are loaded so that under the effect of up to a machine-technically adjustable and for different task materials (1.1) variable Druckmaximussich increasing stress on the Aufgabegutteilchen (3.1) and the subsequent pressure relief with superimposed Reibbeanspruchung in pressure and friction loaded Aufgabegutteilchen (3.1) forms an ever-increasing number of cracks, passes through it that the feedstock particle (3.1) after passing through the grinding gap (4.3) either completely disassembled or changed so far in the structure of the structure that the next rollover leads to dissolution of the composite material. 2. The method according to claim 1, characterized in that the Kälteversprödung on the grain size of the feed material (1.1) and the stress rate in the grinding gap (4.3) is tuned so that after a maximum of two to three overrolling of the feed material (1.1) dependent embrittlement temperature is exceeded , 3. The method according to claim 1 and 2, characterized in that the feed material (1.1) after exceeding the embrittlement temperature limit and mono- or Mehrmahliger.jedoch to a maximum of three limited roll over the adjustable between zero and a constructive maximum value in a conventional manner Staurand (4.5) of the grinding table is discarded and fed in a known manner subsequent classification and / or sorting device. 4. The method according to claim 1 to 3, characterized in that the feed stream (1.1) of the roller mill used (4) is composed of the coarse grain return (6.1) of the classifying and / or sorting facilities and off to a preferred piece size with less than or equal to 30 mm pre-shredded material (1.1).