CA1132780A - Process and installation for the production of sintered magnesite, sintered dolomite or the like - Google Patents
Process and installation for the production of sintered magnesite, sintered dolomite or the likeInfo
- Publication number
- CA1132780A CA1132780A CA325,280A CA325280A CA1132780A CA 1132780 A CA1132780 A CA 1132780A CA 325280 A CA325280 A CA 325280A CA 1132780 A CA1132780 A CA 1132780A
- Authority
- CA
- Canada
- Prior art keywords
- receptacle
- calcined
- bars
- materials
- vibration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 5
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 title abstract description 6
- 229910000021 magnesium carbonate Inorganic materials 0.000 title abstract description 6
- 235000014380 magnesium carbonate Nutrition 0.000 title abstract description 6
- 239000001095 magnesium carbonate Substances 0.000 title abstract description 6
- 229910000514 dolomite Inorganic materials 0.000 title abstract description 4
- 239000010459 dolomite Substances 0.000 title abstract description 4
- 238000009434 installation Methods 0.000 title description 6
- 239000000463 material Substances 0.000 claims abstract description 78
- 238000010438 heat treatment Methods 0.000 claims abstract description 28
- 238000005056 compaction Methods 0.000 claims abstract description 13
- 238000005273 aeration Methods 0.000 claims abstract description 12
- 239000007789 gas Substances 0.000 claims description 20
- 238000001354 calcination Methods 0.000 claims description 17
- 239000011819 refractory material Substances 0.000 claims description 7
- 238000005245 sintering Methods 0.000 claims description 5
- 238000003860 storage Methods 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 3
- 230000000694 effects Effects 0.000 claims description 2
- 239000002912 waste gas Substances 0.000 claims description 2
- 230000004323 axial length Effects 0.000 claims 4
- 238000012432 intermediate storage Methods 0.000 abstract description 15
- 239000002994 raw material Substances 0.000 abstract description 11
- 238000007596 consolidation process Methods 0.000 abstract description 9
- 238000003825 pressing Methods 0.000 abstract description 6
- 239000000543 intermediate Substances 0.000 description 44
- 235000012054 meals Nutrition 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 239000004484 Briquette Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005549 size reduction Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2/00—Lime, magnesia or dolomite
- C04B2/10—Preheating, burning calcining or cooling
- C04B2/102—Preheating, burning calcining or cooling of magnesia, e.g. dead burning
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Processing Of Solid Wastes (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
Abstract
ABSTRACT
The invention relates to a process for the production of sintered magnesite, sintered dolomite or the like in which the raw material is size-reduced, pre-calcined in a first heat-treatment stage and then intermediately stored, de-aerated and consolidated, after which it is compacted while still hot and sintered in a second heat-treatment stage. The intermediate storage, de-aeration and consolidation of the pre-calcined material before compaction increases the compaction level and also the density and strength of the pressings obtained.
The invention relates to a process for the production of sintered magnesite, sintered dolomite or the like in which the raw material is size-reduced, pre-calcined in a first heat-treatment stage and then intermediately stored, de-aerated and consolidated, after which it is compacted while still hot and sintered in a second heat-treatment stage. The intermediate storage, de-aeration and consolidation of the pre-calcined material before compaction increases the compaction level and also the density and strength of the pressings obtained.
Description
~3Z~8(3 This invention relates to a process for the production of sintered magnesite, sintered dolomite or the like, the raw material first being size-reduced to the fineness of meal, subsequently pre-calcined in loosened form with hot gases in a first heat-treatment stage and compacted while still hot, after which the compacted material is sintered in a second heat-treatment stage. The invention also relates to an installation for carrying out this process.
Refractory bricks, monolithic mixtures etc. of sintered magnesite, sintered dolomite and the like are required in the steel industry, in the cement industry and in other branches of industry where heat treatments are carried out at relatively high temperatures (for example above 1500 C).
On account of the need for refractoriness and resistance to slag, sintered materlals of increasingly higher quality are required, the trend being towards increasingly purer materials which, unfortunately, can only be sintered at relatively high temperatures (above 1800C) and under difficult conditions.
In known processes, the raw material obtained from quarries is first size-reduced, subsequently pre-calcined in a first heat-treatment stage (so-called kauster calcination with elimination of CO~) and then at least partly cosled, ground and compacted, after which the compacted material is sintered in a second heat-treatment stage. In this two-stage process, ~haft furnaces, travelling grates or even revolving tubular kilns are normally used for the first heat-treatment stage whereas revolving tubular kilns are predominately used for the second heat-treatment stage.
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The main disadvantages of these known p~ocesses lie in the fact that only a very limited particle size range of the ra~ material can be processed in the heat exchangers used for the first heat-treatment stage, in the fact that pre-calcination and compaction have to be followed by cooling to enable grinding to be carried out and in the fact that the grinding and compaction of the cooled material involve the danger of partial hydration which adversely affects the sin~ering operation.
By contrast, in a process developed by Applicants, the raw material is size-reduced to the fineness of meal before the first heat-treatment stage, subse~uently pre-calcined in suspended or fluidised form (i.e. in loosened form with hot gases) in the first heat-treatment stage and then compacted while still hot. In this way, therefore, the raw materlal is size-reduced sufficiently finely before any heat treatment, after which the entire slze-reduced raw materlal is pre-calcined in loosened form with the hot gases which itself leads to an extremely uniform and, by comparison with the above-described processes, much more economical pre-calcination of the raw material.
Another advantage of this process lies in the fact that, before compaction, the adequately siæe-reduced and pre-calcined ra~ material is then pressed~or compacted / while still hot, i,e. without any intermediate cooling and size-reduction, which gives better pressings and higher press outputs by comparison wlth the known processes described above.
Refractory bricks, monolithic mixtures etc. of sintered magnesite, sintered dolomite and the like are required in the steel industry, in the cement industry and in other branches of industry where heat treatments are carried out at relatively high temperatures (for example above 1500 C).
On account of the need for refractoriness and resistance to slag, sintered materlals of increasingly higher quality are required, the trend being towards increasingly purer materials which, unfortunately, can only be sintered at relatively high temperatures (above 1800C) and under difficult conditions.
In known processes, the raw material obtained from quarries is first size-reduced, subsequently pre-calcined in a first heat-treatment stage (so-called kauster calcination with elimination of CO~) and then at least partly cosled, ground and compacted, after which the compacted material is sintered in a second heat-treatment stage. In this two-stage process, ~haft furnaces, travelling grates or even revolving tubular kilns are normally used for the first heat-treatment stage whereas revolving tubular kilns are predominately used for the second heat-treatment stage.
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The main disadvantages of these known p~ocesses lie in the fact that only a very limited particle size range of the ra~ material can be processed in the heat exchangers used for the first heat-treatment stage, in the fact that pre-calcination and compaction have to be followed by cooling to enable grinding to be carried out and in the fact that the grinding and compaction of the cooled material involve the danger of partial hydration which adversely affects the sin~ering operation.
By contrast, in a process developed by Applicants, the raw material is size-reduced to the fineness of meal before the first heat-treatment stage, subse~uently pre-calcined in suspended or fluidised form (i.e. in loosened form with hot gases) in the first heat-treatment stage and then compacted while still hot. In this way, therefore, the raw materlal is size-reduced sufficiently finely before any heat treatment, after which the entire slze-reduced raw materlal is pre-calcined in loosened form with the hot gases which itself leads to an extremely uniform and, by comparison with the above-described processes, much more economical pre-calcination of the raw material.
Another advantage of this process lies in the fact that, before compaction, the adequately siæe-reduced and pre-calcined ra~ material is then pressed~or compacted / while still hot, i,e. without any intermediate cooling and size-reduction, which gives better pressings and higher press outputs by comparison wlth the known processes described above.
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The object of the present invention is to further develop the earlier process to the extent that, in particular, the compaction level and also the density and strength of the pressings obtained are further increased.
According to the invention, this object is achieved in that, before compaction, the pre-calcined material is intermediately stored, de-aerated and pre-consolidated.
In the extensive tests on which the present invention is based, it was found that, in the first heat-treatment stage, the raw material size-reduced to the fineness of meal is generally "aerated" to a considerable extent by the hot gases in which it is treated in loosened form, in other words it is heavily permeated by the hot treatment gases (for example the waste kiln gases from the second heat-treatment stagej. As a result, the pre-calcined material is loosened up to a very considerable extent, giving a weight per litre of from about 0.4 to 0~7 kg/l depending on its fineness. However, this highly loosened pre-calcined material is not conducive either to a relatively high compaction level or to relatively intense consolidation and hardening of the pressings to be formed. In these tests, it ~as found that both the compaction level and also the consolidation and hardening of the pressings bear a certain proportionality to the weight per litre of the pre-calcined material, in otherwords they decrease with decreasing welght per litre, i.e. to highly loosened ~aterial.
No~, in the process according to one aspect of the invention, the precalcined material is quite deliberately subjected to intermediate storage and, at the same time, de-aerated and pre-consolidated, de-aeration generally being understood to mean the removal of the treatment gases still
.3Z~
The object of the present invention is to further develop the earlier process to the extent that, in particular, the compaction level and also the density and strength of the pressings obtained are further increased.
According to the invention, this object is achieved in that, before compaction, the pre-calcined material is intermediately stored, de-aerated and pre-consolidated.
In the extensive tests on which the present invention is based, it was found that, in the first heat-treatment stage, the raw material size-reduced to the fineness of meal is generally "aerated" to a considerable extent by the hot gases in which it is treated in loosened form, in other words it is heavily permeated by the hot treatment gases (for example the waste kiln gases from the second heat-treatment stagej. As a result, the pre-calcined material is loosened up to a very considerable extent, giving a weight per litre of from about 0.4 to 0~7 kg/l depending on its fineness. However, this highly loosened pre-calcined material is not conducive either to a relatively high compaction level or to relatively intense consolidation and hardening of the pressings to be formed. In these tests, it ~as found that both the compaction level and also the consolidation and hardening of the pressings bear a certain proportionality to the weight per litre of the pre-calcined material, in otherwords they decrease with decreasing welght per litre, i.e. to highly loosened ~aterial.
No~, in the process according to one aspect of the invention, the precalcined material is quite deliberately subjected to intermediate storage and, at the same time, de-aerated and pre-consolidated, de-aeration generally being understood to mean the removal of the treatment gases still
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1~1L3'~7~C~
present in the ma-terial from the pre-calcination step.
Greatly increased weigh-ts per litre of the pre-calcined mater-ial are obtained by this de-aeration and pre-consolidation, thereby establishing the essential pre-requisites for increasing the compaction level and improving the density and strength of the pressings.
It has proven -to be particularly favourable to intermediately store the pre-calcined material for a period of from about 30 to 90 minutes and preferably for a period of from ~5 to 80 minutes. The intermediate storage period is essentially determined by the fineness of the material to be treated.
A particularly favourable pre-condition for the required incrqase in the compaction level is established by pre-consolidating the pre-calcined material to a powder density of from about 0.85 to 1.~5 kg/l during its intermediate storage~
In general, the pre-consolidation of the pre-calcined material during its intermediate storage~may be achieved simply by appropriate and adequate de-aeration.
However, in order to obtain particularly high throughputs, it has proved to be of particular advantage to intensify pre-consolidation of the pre-calcined material during its intermediate storage by applying vibration.
The 1ntermediate storage of the pre-calcined material affords the possibility of another significant process advantage which lies in the fact that the decomposition temperature in the first heat-treatment stage can be kept at a ~z~
lower level than would be possible without intermediate storage or with excessively brief or unsuitable intermediate storage. Thus, whereas in known processes, calcination is carried out either a-t extremely high temperatures (for example above 1100C), which in many cases adversely affects the pre-calcined material, or at relatively low temperatures (for example 850 to 900C), at which the specific throughput is reduced and residual ignition losses have to be accepted, the raw material in the process according to the invention is pre-calcined at a temperature of from about 850 to 1000C and preferably at a temperature in the range from about 900 to 950C in the first heat-treatment stage. As already mentioned, however, pre-calcination at these temperatures is onIy possible if the pre-calcined material is intermediately stored in accordance with the invention. During this pre-calcination, the temperature is kept above the theoretical decomposition temperature of the particular material being treated, but distinctly below the temperature level at whch the pre-calcined material (so-called kauster) would undergo negative property changes such as, for example, impaired sinterability, delayed ~uenching etc. Although this pre~calcination at the rela tively low temperatures in question is accompanied by certain residual ignition losses, such residual ignition losses as ... .
occur can be recouped by the intermediate storage according ~
.
to the invention. During this intermediate storage, the gaseous decomposition products are quickly removed (b~ the de-aeration).
According to the present invention, then, there is provided a process for the production of re~ractory ~L~L3Z7'8~
materials from feedstock including the steps of size-reducing the feedstock into a fine grained material, calcina-ting the fine grained materials with hot gases, storing the calcinated materials to effect the de-aeration and settling thereof, subsequently compacting the material while still hot, and sintering the compacted materials.
An installation for carrying out the process according to the invention contains at least one size-reducing unit, a hot-gas heat-exchanger unit as the first heat-treatment stage for pre-calcin~ing the size-reduced raw material, a compacting unit, an insulated intermediate vessel arranged between the hot-gas heat-exchanger unit and the compacting unit and a revolving tubular kiln following the compacting unit as the second heat-treatment stage.
According to ~he invention, the intermediate vessel is designed for intermediately storing, de-aerating and pre-consolidating t~e pre-calcined material.
According to a preferred embodiment of the invention, an intermediate vessel of the type in question may have a straight, preferably cyIindrical upper part and a funnel-shaped lower part.
In the tests on which the invention is based, it was also found that the intermediate vessel provides for particularly effective de-aeration and pre-consolidation of the pre-calcined material during its intermediate storage providing its straight upper part has a height of less than about 2.5 metres, preferably less than about 1~5 metres, the height of the straight part of the intermediate vessel being essentially determined by the fineness of the pre-calcined ~' ~3278~
material. This height of the straight upper part is gauged in such a way that, in the intermediate vessel the gas trapped in the hot material is ab]e to escape upwards, even from the lower parts of the material, without being impeded in any way by the pressure of the overlying materal.
In order to accelerate de-aeration and pre-consolidation during intermediate storage, particularly in the case of high-throughput installations, it has also proved to be of advantage to associate a vibration unit with the intermed-iate vessel. Providing the vibration unit is suitably designed and arranged, the height of the straight upper part of the intermediate vessel discussed in the preceding paragraph may even considerably exceed 2.5 metres.
According to a further aspect of the present invention, then, there is also provided an apparatus for producing refractory materials from feedstock comprising size reducing means to grind the feedstock into a fine grained material, heating means for calcinating the fine grained material with hot gases, insulating receptacle means to temporarily ~
store the calcined material, compacting means for subsequently ;;
compacting the stored material, and means to sinter the compacted material to form the refractory materials, wherein the calcined materials are allowed to settle and de-aerate during the temporary storage thereof.
According to yet another aspect of the present invention, there is also provided an insulating receptacle ~or use with apparatus for producing refractory materials from feedstock including size reducing means to grind the feedstock into a fine-grained material, heating means for calcinating the -~ ;r ~ 7 -.
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fine-grained material, compacting means and sintering means, the receptacle comprising a substantially cylindrical upper portion adjoining a lower, funnel-shaped portion to define a hopper-shaped vessel for receiving and temporarily storing the calcined material to allow for the de-aeration and settling thereof prior to compaction.
Embodiments of the invention are described by way of the example in the following with reference to the accompanying drawings, wherein:
Yigure 1 is a diagrammatic general view of an installation for carrying out the process according to the invention.
Figure 2 is a simplified vertical section through an intermediate vessel provided in accordance with the invention.
Figures 3 and 5 are partial elevations of various embodiments of vibration bars which may be axranged in the intermediate vessel.
Figure 6 is a vertical section through another embodiment of an intermediate vessel (with a vibration cage) provided in accordance with the invention.
Figure 7 is a partial cross-section on the line VII-VII through the intermediate vessel shown in Figure 6.
Looking in the direction of movement of the~
material to be treated, the installation for carrying out the process according to the invention which is illustrated in Figure 1 includes a preliminary crusher 1, a fine-grinding unit, for example in the form of a ball mill 2, following the preliminary crusher 1 and connected thereto by means of a ~ . .
~3~1!30 valve 6 and conduit 7, a conduit 8 leading to a hot-gas heat-exchanger unit 3 (as the first heat-treatment stage), a compacting unit formed for example by a briquetting press 5 of known type and a revolving tubular kiln 4 following the briquet-ting press 5 as the second heat-treatment stage. Tubular kiln 4 is supported by a stationary housing 9 which includes an inclined chute (not shown) ~or the supply of material. Between the hot-gas heat-exchanger unit 3 and the briquetting press 5 there is an insulated intermediate vessel 20 which is designed for intermediately storing, de-aerating and pre-consolidating the material pre-calcined in the heat-exchanger unit 3, as will be explained in detail hereinafter.
So far as the hot-gas heat-exchanger unit 3 is concerned, it is pointed out that, according to the invention, it may with advantage be formed either by a multistage cyclone heat exchanger or by a fluidised-bed heat exchanger, in either case of known type. The heat exchanger in question should in particular be designed in such a way that the raw material size-reduced to the fineness of meal which is delivered to it can be pre-calcined in loosened form with the hot waste gases from the revolving tubular kiln (arrow 13) which are carried from the revolving tubular kiln 4 to the lower end of the hot-gas heat exchan~er unit 3 by a pipe 21. The path followed by the material to be treated is indicated by the arrow 12.
In this embodiment of the invention, particular significance is attributed to the design and function of the intermediate vessel 20 arranged between the hot-gas heat g _ .
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exchanger unit 3 and the briquetting press 5, As will be explained hereinafter with reference to Figures 2 and 6, this intermediate vessel 20 has a straight upper part and a funnel-shaped lower part. The straight upper part of the intermediate vessel 20 is preferably cylindrical.
With relatively low throughputs of material to be treated, it is sufficient for the straight upper part of the intermediate vessel to have a height of less than about 2.5 metres and preferably less than 1.5 metres. With this construction and also with the relatively low throughput referred to, the gas trapped in the hot material in lower parts of the intermediate vessel is also able to escape upwards so that adequate de-aeration and extremely effective pre-consolidation of the pre-calcined material are achieved during its intermediate storage. However, this does presuppose a reasonable residence time in the intermediate vessel of, for example, up to one hour or even up to 1.5 hours, depending on the fineness of the material. In this case, there is no need for other measures (particularly fittings) to be taken in the intermediate vessel apart from adequate insulation.
In order to obtain higher throughputs, however, it is best to associate a vibration unit with the intermediate vessel.
Fîgure 2 shows a first embodiment of an intermediate vessel 20 which on its outside has an adequate insulation 23 by which losses of heat are largely avoided. This ;~
intermediate vessel 20 has a straight, cylindrical upper part 22a, a funnel-shaped lower part 22b (with a taper .
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angle ~ at its lower end of preferably - 50 ) and a cover 22c. The cover of the intermediate vessel is provided with an inlet 24 for the introduction of pre-calcined raw material (arrow 12) from the first heat-treatment stage and, optionally, with a second inlet 25 for return material from the briquetting press, whereas at the lower end of the lower part 22b there is an outlet 26 from which the pre-consolidated material is delivered to the briquetting press tnot shown in Figure 2).
A vibration unit 27 is associated with the intermediate vessel 20. In this case, the vibration unit 27 contains a plurality of vibration bars 28 projecting into the interior 22d of the intermediate vessel. As can clearly be seen from Figure 2, the vibration bars 28 are preferably straight and project into the interior of the intermediate vessel substantially perpendicularly from above (through the cover 22c), being uniformly distributed over the entire cross section of the intermediate vessel. Accordingly, the vibration bars 28 are more or less long corresponding to their associated vessel section, as also clearly shown in Figure 2. All the vibration bars 28 may with advantage be held by a vibration frame 29 arranged over the cover 22c of the intermediate vessel and may be vibrated by a common vibration drive 30.
The vibration bars 28 themselves may be designed in different ways. For relatlvely gentle vibration of the material intermediately stored in the intermediate vessel 20, it may be sufficient to provide completely smooth bars.
For intense vibration, however, it is preferred to provide ~3~
the vibration bars with corresponding projections. For example, the vibration bars 28 are provided over at least part of their length and preferably over their entire length with a number of pin-like pro~ections 28a, as also shown in an enlarged view in Figure 3. These pin-like projections 28a are preferably arranged and designed as projections protruding substantially radially from the particular vibration bar 28.
Figure 4 shows another type of vibration bar 28' which, over at least part of its length, comprises continuous vanes 28a' on the lines of a conveying screw vane.
Figure 5 shows a somewhat modified embodiment (i.e.
in relation to Figure 4) of a vibration bar 28" which may again be provided over at least part of its length with vanes 28a" on the lines of conveying screw vanes. In this case, however, the individual vanes 28a" may be spaced apart from one another.
Both the vanes 28a' shown in Figure 4 and also the ~0 vanes 28a" shown in Figure 5 may be made of solid material or even of perforated material, depending on the particular application in question.
Figures 6 and 7 show a somewhat modified embodiment of an intermediate vessel 20l. In Figures 6 and 7, the design of the actual intermediate vessel 20' is identical with that of the intermediate vessel 20 shown in Figure 2, so t~at the same elements have ~een denoted by the same reference numerals accompanied by an apostrophe. The main difference between t~ese two embodiments (Figure 2 on the one hand and Figures 6 and 7 on the other hand) lies in the construction of the vibration unit 27'.
~7 ~ .
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The vibration unit provided in the embodiment shown in Figures 6 and 7 essentially comprises a cage-like vibration assembly 41 which projects into the interior ~2d' of the intermediate vessel from above (through the cover 22c') and which is supported by a vibration frame 27' provided over the cover 22c' and carrying a vibration drive 30'.
The cage-like vibration assembly 41 essentially consists of several rings 45 of different diameter arranged concentrically to the central axis 44 of the intermediate vessel and of a number of bars 46 which are arranged sloping downwards towards the central axis 44 of the vessel, the bars 46 being arranged in stages in such a way that their upper ends are supported by a ring 45 of relatively large diameter and their lower ends by a ring of smaller diameter.
In this way, the vibration assembly 41 tapers conically towards the outlet end of the vessel.
In order further to illustrate the process according to the invention, some test results are set out in the following Table. These tests were carried out with finely ground spathic magnesite, the raw material being pre-calcined in a first heat treatment stage in the form of a multistage cyclone heat-exchanger unit, intermediately stored, de-aerated and pre-consolidated in an intermediate vessel according to the invention and then compacted in a briquetting press.
As can be seen from the following TabIe, the tests were carried out with two different raw meal finenesses which were subsequently consolidated during intermediate storage on the one hand with vibration and on the other hand without vibration, the influence of the vibration bars on the different , .
1~3Z780 ra~ meal finenesses also being apparent. It can also be seen that, where vibration bars are used, the residence time in the intermediate vessel can also be considerably shortened (greater throughput). In this connection, it is also mentioned that, where vibration bars are used, the height of the straight part of the intermediate vessel may even amount to more than 2.50 metres.
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TABLE
Example 1 Example 2 without with without with vibration bars vibration bars .... _ , ~
Fineness of the 20 %>0.09 mm l %>0.09 mm raw magnesite Temperature (C) in the reaction part of the first heat-treatment stage 920 910 Residence time in the intermediate vessel (mins.) 60 45 80 55 Residual ignition loss (%) before the intermediate vessel3.30 2.90 1.95 2.03 after the intermediate vessel 0.33 0.41 0.72 0.33 Powder density (kg/l) before the intermediate vessel0.70 0.65 0.58 0.53 after the intermediate vessel 1.03 1.08 0.88 1.02 (measured hot) Temperature (C) at the :
outlet end of the vessel685 735 665755 Briquetting press Efficiency *) 185 % 275 % 150 %220 %
Proportion of briquettes > 10 mm ~~65 %75 % 55 ~78 %
Compressive strength of the briquettes (kg/briquette) 18 25 16 23 :~
Dropping resistance of the briquettes ~ 1.25m 1.50m 1.00m1.25m *) Operation without intermediate storage = 100 %, ~ -for a briquette-yield~with 45 % > 10 mm, compressive strength 8 - 12 kg/briquette, dropping resistance 0.40 m.
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1~1L3'~7~C~
present in the ma-terial from the pre-calcination step.
Greatly increased weigh-ts per litre of the pre-calcined mater-ial are obtained by this de-aeration and pre-consolidation, thereby establishing the essential pre-requisites for increasing the compaction level and improving the density and strength of the pressings.
It has proven -to be particularly favourable to intermediately store the pre-calcined material for a period of from about 30 to 90 minutes and preferably for a period of from ~5 to 80 minutes. The intermediate storage period is essentially determined by the fineness of the material to be treated.
A particularly favourable pre-condition for the required incrqase in the compaction level is established by pre-consolidating the pre-calcined material to a powder density of from about 0.85 to 1.~5 kg/l during its intermediate storage~
In general, the pre-consolidation of the pre-calcined material during its intermediate storage~may be achieved simply by appropriate and adequate de-aeration.
However, in order to obtain particularly high throughputs, it has proved to be of particular advantage to intensify pre-consolidation of the pre-calcined material during its intermediate storage by applying vibration.
The 1ntermediate storage of the pre-calcined material affords the possibility of another significant process advantage which lies in the fact that the decomposition temperature in the first heat-treatment stage can be kept at a ~z~
lower level than would be possible without intermediate storage or with excessively brief or unsuitable intermediate storage. Thus, whereas in known processes, calcination is carried out either a-t extremely high temperatures (for example above 1100C), which in many cases adversely affects the pre-calcined material, or at relatively low temperatures (for example 850 to 900C), at which the specific throughput is reduced and residual ignition losses have to be accepted, the raw material in the process according to the invention is pre-calcined at a temperature of from about 850 to 1000C and preferably at a temperature in the range from about 900 to 950C in the first heat-treatment stage. As already mentioned, however, pre-calcination at these temperatures is onIy possible if the pre-calcined material is intermediately stored in accordance with the invention. During this pre-calcination, the temperature is kept above the theoretical decomposition temperature of the particular material being treated, but distinctly below the temperature level at whch the pre-calcined material (so-called kauster) would undergo negative property changes such as, for example, impaired sinterability, delayed ~uenching etc. Although this pre~calcination at the rela tively low temperatures in question is accompanied by certain residual ignition losses, such residual ignition losses as ... .
occur can be recouped by the intermediate storage according ~
.
to the invention. During this intermediate storage, the gaseous decomposition products are quickly removed (b~ the de-aeration).
According to the present invention, then, there is provided a process for the production of re~ractory ~L~L3Z7'8~
materials from feedstock including the steps of size-reducing the feedstock into a fine grained material, calcina-ting the fine grained materials with hot gases, storing the calcinated materials to effect the de-aeration and settling thereof, subsequently compacting the material while still hot, and sintering the compacted materials.
An installation for carrying out the process according to the invention contains at least one size-reducing unit, a hot-gas heat-exchanger unit as the first heat-treatment stage for pre-calcin~ing the size-reduced raw material, a compacting unit, an insulated intermediate vessel arranged between the hot-gas heat-exchanger unit and the compacting unit and a revolving tubular kiln following the compacting unit as the second heat-treatment stage.
According to ~he invention, the intermediate vessel is designed for intermediately storing, de-aerating and pre-consolidating t~e pre-calcined material.
According to a preferred embodiment of the invention, an intermediate vessel of the type in question may have a straight, preferably cyIindrical upper part and a funnel-shaped lower part.
In the tests on which the invention is based, it was also found that the intermediate vessel provides for particularly effective de-aeration and pre-consolidation of the pre-calcined material during its intermediate storage providing its straight upper part has a height of less than about 2.5 metres, preferably less than about 1~5 metres, the height of the straight part of the intermediate vessel being essentially determined by the fineness of the pre-calcined ~' ~3278~
material. This height of the straight upper part is gauged in such a way that, in the intermediate vessel the gas trapped in the hot material is ab]e to escape upwards, even from the lower parts of the material, without being impeded in any way by the pressure of the overlying materal.
In order to accelerate de-aeration and pre-consolidation during intermediate storage, particularly in the case of high-throughput installations, it has also proved to be of advantage to associate a vibration unit with the intermed-iate vessel. Providing the vibration unit is suitably designed and arranged, the height of the straight upper part of the intermediate vessel discussed in the preceding paragraph may even considerably exceed 2.5 metres.
According to a further aspect of the present invention, then, there is also provided an apparatus for producing refractory materials from feedstock comprising size reducing means to grind the feedstock into a fine grained material, heating means for calcinating the fine grained material with hot gases, insulating receptacle means to temporarily ~
store the calcined material, compacting means for subsequently ;;
compacting the stored material, and means to sinter the compacted material to form the refractory materials, wherein the calcined materials are allowed to settle and de-aerate during the temporary storage thereof.
According to yet another aspect of the present invention, there is also provided an insulating receptacle ~or use with apparatus for producing refractory materials from feedstock including size reducing means to grind the feedstock into a fine-grained material, heating means for calcinating the -~ ;r ~ 7 -.
3;~
fine-grained material, compacting means and sintering means, the receptacle comprising a substantially cylindrical upper portion adjoining a lower, funnel-shaped portion to define a hopper-shaped vessel for receiving and temporarily storing the calcined material to allow for the de-aeration and settling thereof prior to compaction.
Embodiments of the invention are described by way of the example in the following with reference to the accompanying drawings, wherein:
Yigure 1 is a diagrammatic general view of an installation for carrying out the process according to the invention.
Figure 2 is a simplified vertical section through an intermediate vessel provided in accordance with the invention.
Figures 3 and 5 are partial elevations of various embodiments of vibration bars which may be axranged in the intermediate vessel.
Figure 6 is a vertical section through another embodiment of an intermediate vessel (with a vibration cage) provided in accordance with the invention.
Figure 7 is a partial cross-section on the line VII-VII through the intermediate vessel shown in Figure 6.
Looking in the direction of movement of the~
material to be treated, the installation for carrying out the process according to the invention which is illustrated in Figure 1 includes a preliminary crusher 1, a fine-grinding unit, for example in the form of a ball mill 2, following the preliminary crusher 1 and connected thereto by means of a ~ . .
~3~1!30 valve 6 and conduit 7, a conduit 8 leading to a hot-gas heat-exchanger unit 3 (as the first heat-treatment stage), a compacting unit formed for example by a briquetting press 5 of known type and a revolving tubular kiln 4 following the briquet-ting press 5 as the second heat-treatment stage. Tubular kiln 4 is supported by a stationary housing 9 which includes an inclined chute (not shown) ~or the supply of material. Between the hot-gas heat-exchanger unit 3 and the briquetting press 5 there is an insulated intermediate vessel 20 which is designed for intermediately storing, de-aerating and pre-consolidating the material pre-calcined in the heat-exchanger unit 3, as will be explained in detail hereinafter.
So far as the hot-gas heat-exchanger unit 3 is concerned, it is pointed out that, according to the invention, it may with advantage be formed either by a multistage cyclone heat exchanger or by a fluidised-bed heat exchanger, in either case of known type. The heat exchanger in question should in particular be designed in such a way that the raw material size-reduced to the fineness of meal which is delivered to it can be pre-calcined in loosened form with the hot waste gases from the revolving tubular kiln (arrow 13) which are carried from the revolving tubular kiln 4 to the lower end of the hot-gas heat exchan~er unit 3 by a pipe 21. The path followed by the material to be treated is indicated by the arrow 12.
In this embodiment of the invention, particular significance is attributed to the design and function of the intermediate vessel 20 arranged between the hot-gas heat g _ .
~z~
exchanger unit 3 and the briquetting press 5, As will be explained hereinafter with reference to Figures 2 and 6, this intermediate vessel 20 has a straight upper part and a funnel-shaped lower part. The straight upper part of the intermediate vessel 20 is preferably cylindrical.
With relatively low throughputs of material to be treated, it is sufficient for the straight upper part of the intermediate vessel to have a height of less than about 2.5 metres and preferably less than 1.5 metres. With this construction and also with the relatively low throughput referred to, the gas trapped in the hot material in lower parts of the intermediate vessel is also able to escape upwards so that adequate de-aeration and extremely effective pre-consolidation of the pre-calcined material are achieved during its intermediate storage. However, this does presuppose a reasonable residence time in the intermediate vessel of, for example, up to one hour or even up to 1.5 hours, depending on the fineness of the material. In this case, there is no need for other measures (particularly fittings) to be taken in the intermediate vessel apart from adequate insulation.
In order to obtain higher throughputs, however, it is best to associate a vibration unit with the intermediate vessel.
Fîgure 2 shows a first embodiment of an intermediate vessel 20 which on its outside has an adequate insulation 23 by which losses of heat are largely avoided. This ;~
intermediate vessel 20 has a straight, cylindrical upper part 22a, a funnel-shaped lower part 22b (with a taper .
~3Z~7~3~
angle ~ at its lower end of preferably - 50 ) and a cover 22c. The cover of the intermediate vessel is provided with an inlet 24 for the introduction of pre-calcined raw material (arrow 12) from the first heat-treatment stage and, optionally, with a second inlet 25 for return material from the briquetting press, whereas at the lower end of the lower part 22b there is an outlet 26 from which the pre-consolidated material is delivered to the briquetting press tnot shown in Figure 2).
A vibration unit 27 is associated with the intermediate vessel 20. In this case, the vibration unit 27 contains a plurality of vibration bars 28 projecting into the interior 22d of the intermediate vessel. As can clearly be seen from Figure 2, the vibration bars 28 are preferably straight and project into the interior of the intermediate vessel substantially perpendicularly from above (through the cover 22c), being uniformly distributed over the entire cross section of the intermediate vessel. Accordingly, the vibration bars 28 are more or less long corresponding to their associated vessel section, as also clearly shown in Figure 2. All the vibration bars 28 may with advantage be held by a vibration frame 29 arranged over the cover 22c of the intermediate vessel and may be vibrated by a common vibration drive 30.
The vibration bars 28 themselves may be designed in different ways. For relatlvely gentle vibration of the material intermediately stored in the intermediate vessel 20, it may be sufficient to provide completely smooth bars.
For intense vibration, however, it is preferred to provide ~3~
the vibration bars with corresponding projections. For example, the vibration bars 28 are provided over at least part of their length and preferably over their entire length with a number of pin-like pro~ections 28a, as also shown in an enlarged view in Figure 3. These pin-like projections 28a are preferably arranged and designed as projections protruding substantially radially from the particular vibration bar 28.
Figure 4 shows another type of vibration bar 28' which, over at least part of its length, comprises continuous vanes 28a' on the lines of a conveying screw vane.
Figure 5 shows a somewhat modified embodiment (i.e.
in relation to Figure 4) of a vibration bar 28" which may again be provided over at least part of its length with vanes 28a" on the lines of conveying screw vanes. In this case, however, the individual vanes 28a" may be spaced apart from one another.
Both the vanes 28a' shown in Figure 4 and also the ~0 vanes 28a" shown in Figure 5 may be made of solid material or even of perforated material, depending on the particular application in question.
Figures 6 and 7 show a somewhat modified embodiment of an intermediate vessel 20l. In Figures 6 and 7, the design of the actual intermediate vessel 20' is identical with that of the intermediate vessel 20 shown in Figure 2, so t~at the same elements have ~een denoted by the same reference numerals accompanied by an apostrophe. The main difference between t~ese two embodiments (Figure 2 on the one hand and Figures 6 and 7 on the other hand) lies in the construction of the vibration unit 27'.
~7 ~ .
~3~
The vibration unit provided in the embodiment shown in Figures 6 and 7 essentially comprises a cage-like vibration assembly 41 which projects into the interior ~2d' of the intermediate vessel from above (through the cover 22c') and which is supported by a vibration frame 27' provided over the cover 22c' and carrying a vibration drive 30'.
The cage-like vibration assembly 41 essentially consists of several rings 45 of different diameter arranged concentrically to the central axis 44 of the intermediate vessel and of a number of bars 46 which are arranged sloping downwards towards the central axis 44 of the vessel, the bars 46 being arranged in stages in such a way that their upper ends are supported by a ring 45 of relatively large diameter and their lower ends by a ring of smaller diameter.
In this way, the vibration assembly 41 tapers conically towards the outlet end of the vessel.
In order further to illustrate the process according to the invention, some test results are set out in the following Table. These tests were carried out with finely ground spathic magnesite, the raw material being pre-calcined in a first heat treatment stage in the form of a multistage cyclone heat-exchanger unit, intermediately stored, de-aerated and pre-consolidated in an intermediate vessel according to the invention and then compacted in a briquetting press.
As can be seen from the following TabIe, the tests were carried out with two different raw meal finenesses which were subsequently consolidated during intermediate storage on the one hand with vibration and on the other hand without vibration, the influence of the vibration bars on the different , .
1~3Z780 ra~ meal finenesses also being apparent. It can also be seen that, where vibration bars are used, the residence time in the intermediate vessel can also be considerably shortened (greater throughput). In this connection, it is also mentioned that, where vibration bars are used, the height of the straight part of the intermediate vessel may even amount to more than 2.50 metres.
. - 14 -~ J
-~ ~
7E~(~
TABLE
Example 1 Example 2 without with without with vibration bars vibration bars .... _ , ~
Fineness of the 20 %>0.09 mm l %>0.09 mm raw magnesite Temperature (C) in the reaction part of the first heat-treatment stage 920 910 Residence time in the intermediate vessel (mins.) 60 45 80 55 Residual ignition loss (%) before the intermediate vessel3.30 2.90 1.95 2.03 after the intermediate vessel 0.33 0.41 0.72 0.33 Powder density (kg/l) before the intermediate vessel0.70 0.65 0.58 0.53 after the intermediate vessel 1.03 1.08 0.88 1.02 (measured hot) Temperature (C) at the :
outlet end of the vessel685 735 665755 Briquetting press Efficiency *) 185 % 275 % 150 %220 %
Proportion of briquettes > 10 mm ~~65 %75 % 55 ~78 %
Compressive strength of the briquettes (kg/briquette) 18 25 16 23 :~
Dropping resistance of the briquettes ~ 1.25m 1.50m 1.00m1.25m *) Operation without intermediate storage = 100 %, ~ -for a briquette-yield~with 45 % > 10 mm, compressive strength 8 - 12 kg/briquette, dropping resistance 0.40 m.
`
.
` :
Claims (32)
1. A process for the production of refractory mater-ials from feedstock including the steps of:
size-reducing the feedstock into a fine grained material;
calcinating said fine grained materials with hot gases;
storing said calcinated materials to effect the de-aeration and settling thereof;
subsequently compacting said material while still hot;
and sintering said compacted materials.
size-reducing the feedstock into a fine grained material;
calcinating said fine grained materials with hot gases;
storing said calcinated materials to effect the de-aeration and settling thereof;
subsequently compacting said material while still hot;
and sintering said compacted materials.
2. A process as claimed in claim 1, wherein said calcined material is stored for 30 to 90 minutes.
3. A process as claimed in claim 1, wherein said calcined material is stored for a period of 45 to 80 minutes.
4. A process as claimed in claim 1, wherein said calcined material settles to attain a powder density ranging between 0.85 to 1.25 kilograms per litre during the storage thereof.
5. A process as claimed in claim 1, wherein said settling of the calcined material during the storage thereof is intensified by vibration.
6. A process as claimed in claim 1, wherein said fine grained material is de-acidified to a residual CO2 content of less than 2% at a calcinating temperature ranging between 850 to 1000°C.
7. A process as claimed in claim 1, wherein said fine-grained material is de-acidified to a residual CO2 content of less than 0.8% at a calcinating temperature ranging from 900 to 950°C.
8. A process as claimed in claims 5, 6 or 7 wherein the hot waste gases from said sintering step are used for calcinating said fine grained material.
9. An apparatus for producing refractory materials from feedstock comprising:
size reducing means to grind said feedstock into a fine grained material;
heating means for calcinating said fine grained mater-ial with hot gases;
insulating receptacle means to temporarily store said calcined material;
compacting means for subsequently compacting said stored material; and means to sinter said compacted material to form said refractory materials, wherein said calcined materials are allowed to settle and de-aerate during said temporary storage thereof.
size reducing means to grind said feedstock into a fine grained material;
heating means for calcinating said fine grained mater-ial with hot gases;
insulating receptacle means to temporarily store said calcined material;
compacting means for subsequently compacting said stored material; and means to sinter said compacted material to form said refractory materials, wherein said calcined materials are allowed to settle and de-aerate during said temporary storage thereof.
10. The apparatus of claim 9 wherein said receptacle means comprise a substantially cylindrical upper portion adjoin-ing a funnel-shaped lower portion to define a hopper-shaped vessel.
11. The apparatus of claim 10 wherein the axial length of said cylindrical portion is less than 2.5 meters.
12. The apparatus of claim 10 wherein the axial length of said cylindrical portion is less than 1.5 meters.
13. The apparatus of claim 12 wherein said receptacle means include vibrating means to facilitate the settling of said calcined materials.
14. The apparatus of claim 13 wherein said vibrating means include a plurality of vibration bars which project into and are uniformly distributed about the interior of said recep-tacle.
15. The apparatus of claim 14 wherein said vibration bars are substantially straight and project downwardly into said receptacle means to be uniformly distributed about the interior thereof.
16. The apparatus of claim 15 wherein said vibration bars are smooth.
17. The apparatus of claim 15 wherein said vibrating bars have affixed thereto a plurality of radially extending pin members formed at spaced intervals along at least a portion of the length of said bars.
18. The apparatus of claim 15 wherein said vibrating bars have affixed thereto a plurality of spaced apart, radially extending vane members arranged along at least a portion of the length of said bars.
19. The apparatus of claim 15 wherein said vibration bars have affixed thereto vane members wound helically there-about.
20. The apparatus of claims 18 or 19 wherein said vane members are perforated.
21. The apparatus of claim 13 wherein said vibrating means include a cage-like assembly of elements projecting down-wardly into said receptacle and drive means for vibrating said elements.
22. The apparatus of claim 21 wherein said assembly tapers downwardly towards said funnel-shaped portion.
23. An insulating receptacle for use with apparatus for producing refractory materials from feedstock including size reducing means to grind said feedstock into a fine-grained mater-ial, heating means for calcinating said fine-grained material, compacting means and sintering means, said receptacle comprising:
a substantially cylindrical upper portion adjoining a lower, funnel-shaped portion to define a hopper-shaped vessel for receiving and temporarily storing said calcined material to allow for the de-aeration and settling thereof prior to compac-tion.
a substantially cylindrical upper portion adjoining a lower, funnel-shaped portion to define a hopper-shaped vessel for receiving and temporarily storing said calcined material to allow for the de-aeration and settling thereof prior to compac-tion.
24. The receptacle of claim 23 wherein the axial length of said cylindrical portion is less than 2.5 meters.
25. The receptacle of claim 23 wherein the axial length of said cylindrical portion is less than 1.5 meters.
26. The receptacle of claim 25 including vibrating means to facilitate the settling of said calcined materials.
27. The receptacle of claim 26 wherein said vibrating means include a plurality of uniformly spaced rod members pro-jecting downwardly into said receptacle and drive means to cause said rod members to vibrate.
28. The receptacle of claim 27 wherein said rod members have affixed thereto a plurality of spaced apart out-wardly projecting pin members arranged along at least a portion of the length of said rods.
29. The receptacle of claim 27 wherein said rod mem-bers have affixed thereto a plurality of spaced apart, outwardly extending vane members arranged along at least a portion of the length of said rods.
30. The receptacle of claim 27 wherein said rod mem-bers have affixed thereto vane members wound helically there-about.
31. The receptacle of claim 26 wherein said vibrating means include a cage-like assembly of elements projecting down-wardly into said receptacle and drive means for causing said assembly to vibrate.
32. The receptacle of claim 31 wherein said assembly tapers downwardly towards said funnel-shaped portion of said receptacle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2819038.7 | 1978-04-29 | ||
| DE2819038A DE2819038C2 (en) | 1978-04-29 | 1978-04-29 | Process and plant for the production of sintered magnesite and sintered dolomite |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132780A true CA1132780A (en) | 1982-10-05 |
Family
ID=6038395
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA325,280A Expired CA1132780A (en) | 1978-04-29 | 1979-04-10 | Process and installation for the production of sintered magnesite, sintered dolomite or the like |
Country Status (8)
| Country | Link |
|---|---|
| AT (1) | AT375901B (en) |
| BR (1) | BR7902604A (en) |
| CA (1) | CA1132780A (en) |
| DE (1) | DE2819038C2 (en) |
| ES (1) | ES8204400A1 (en) |
| GR (1) | GR65663B (en) |
| IT (1) | IT1112806B (en) |
| MX (1) | MX151776A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5246648A (en) * | 1988-08-26 | 1993-09-21 | Dolomitwerke Gmbh | Production of sintered dolomite in a rotary kiln |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3020881C2 (en) * | 1980-06-02 | 1984-08-09 | Krupp Polysius Ag, 4720 Beckum | Process and plant for the production of sintered magnesite from magnesium hydroxide |
| DE3925474A1 (en) * | 1989-08-01 | 1991-02-07 | Krupp Polysius Ag | Roasting fine grained limestone to produce roasted lime - by hot compacting roasted fine grains before tempering to complete roasting |
-
1978
- 1978-04-29 DE DE2819038A patent/DE2819038C2/en not_active Expired
-
1979
- 1979-04-10 CA CA325,280A patent/CA1132780A/en not_active Expired
- 1979-04-14 GR GR58899A patent/GR65663B/en unknown
- 1979-04-25 AT AT0310879A patent/AT375901B/en not_active IP Right Cessation
- 1979-04-27 BR BR7902604A patent/BR7902604A/en unknown
- 1979-04-27 IT IT22234/79A patent/IT1112806B/en active
- 1979-04-27 MX MX177469A patent/MX151776A/en unknown
- 1979-04-27 ES ES480054A patent/ES8204400A1/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5246648A (en) * | 1988-08-26 | 1993-09-21 | Dolomitwerke Gmbh | Production of sintered dolomite in a rotary kiln |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1112806B (en) | 1986-01-20 |
| ES480054A0 (en) | 1982-05-01 |
| ATA310879A (en) | 1984-02-15 |
| AT375901B (en) | 1984-09-25 |
| MX151776A (en) | 1985-03-08 |
| DE2819038A1 (en) | 1979-11-08 |
| DE2819038C2 (en) | 1986-07-17 |
| ES8204400A1 (en) | 1982-05-01 |
| BR7902604A (en) | 1979-11-20 |
| GR65663B (en) | 1980-10-16 |
| IT7922234A0 (en) | 1979-04-27 |
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