AU704350B2 - A process for producing agglomerates - Google Patents
A process for producing agglomerates Download PDFInfo
- Publication number
- AU704350B2 AU704350B2 AU20621/95A AU2062195A AU704350B2 AU 704350 B2 AU704350 B2 AU 704350B2 AU 20621/95 A AU20621/95 A AU 20621/95A AU 2062195 A AU2062195 A AU 2062195A AU 704350 B2 AU704350 B2 AU 704350B2
- Authority
- AU
- Australia
- Prior art keywords
- agglomerates
- fluidised bed
- mineral
- process defined
- particle size
- 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.)
- Ceased
Links
- 238000000034 method Methods 0.000 title claims description 28
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 44
- 239000011707 mineral Substances 0.000 claims description 44
- 239000002245 particle Substances 0.000 claims description 41
- 239000012141 concentrate Substances 0.000 claims description 31
- 238000009826 distribution Methods 0.000 claims description 28
- 238000002485 combustion reaction Methods 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 12
- 239000005083 Zinc sulfide Substances 0.000 claims description 11
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 claims description 11
- 238000011085 pressure filtration Methods 0.000 claims description 8
- 239000002002 slurry Substances 0.000 claims description 8
- 238000001354 calcination Methods 0.000 claims description 7
- 238000005056 compaction Methods 0.000 claims description 6
- 238000000227 grinding Methods 0.000 claims description 6
- 230000015556 catabolic process Effects 0.000 claims description 5
- 238000003860 storage Methods 0.000 claims description 3
- 239000011230 binding agent Substances 0.000 claims description 2
- 241000894007 species Species 0.000 claims 2
- 241001415395 Spea Species 0.000 claims 1
- 238000009291 froth flotation Methods 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 238000005054 agglomeration Methods 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical group [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000011021 bench scale process Methods 0.000 description 1
- -1 by way of example Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000007602 hot air drying Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 239000011147 inorganic material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Landscapes
- Manufacture And Refinement Of Metals (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Description
WO 95/25585 PCT/AU95/00156 -1- A PROCESS FOR PRODUCING AGGLOMERATES BACKGROUND OF THE INVENTION The present invention relates to a process for producing agglomerates of a feed material for a fluidised bed roaster or a fluidised bed combustion furnace.
A particular, although by no means exclusive, application of the process of the invention that is of interest to the applicant is in the field of calcining mineral concentrates, such as zinc sulphide concentrates, in a fluidised bed roaster.
The prior art belief is that optimum performance of a fluidised bed roaster depends on, amongst other factors, the mineral concentrate feed to the fluidised bed roaster having a preferred particle size distribution.
Specifically, the prior art belief is that: i. particles of the mineral concentrate feed that are below a lower limit of -a preferred particle size distribution tend to be entrained in the waste gas stream from the fluidised bed roaster; and ii. particles of the mineral concentrate feed that are above an upper limit of the preferred particle size distribution tend to remain in the bed and may lead to defluidisation of the bed.
The prior art belief is that the preferred particle size distribution for fluidised bed roasters varies with the type of fluidised bed roaster. For WO 95/25585 PCT/AU95/00156 2 example, 0.1 to 2mm is the preferred particle size distribution for a known type of Lurgi fluidised bed roaster which operates with superficial gas velocities in the bed of approximately 0.67 m/sec at a temperature of 975 0 C and approximately 0.4 m/sec in the freeboards.
The preparation of a mineral concentrate feed for fluid bed roasting is normally done by a process of grinding and froth flotation of an ore containing the mineral.
Grinding is necessary to enable liberation of the mineral particles to allow separation of the valuable mineral components of the ore from the other components by froth flotation to form the mineral concentrate.
However, grinding often results in a substantial proportion of fines which are considerably smaller in size than a lower limit of a preferred particle size distribution for a fluidised bed roaster.
Moreover, froth flotation invariably results in the mineral concentrate being produced as a slurry and, in this form, the mineral concentrate cannot be transported by shipping or handled or stored using conventional solid handling systems, and the mineral concentrate is not a suitable feed for a Lurgi-type fluidised bed roaster.
As a consequence, invariably, dewatering and agglomeration of a mineral concentrate are necessary to produce a mineral concentrate in a form that can be readily handled, transported, and stored, and subsequently calcined under optimum operating conditions for a fluidised bed roaster.
An object of the present invention is to provide an improved process for producing agglomerates of a mineral WO 95/25585 PCT/AU95/00156 3 concentrate, particularly a finely-ground mineral concentrate.
SUMMARY OF THE INVENTION According to the present invention there is provided a process for producing agglomerates comprising the following steps: grinding an input feed which includes the feed material into a particle size distribution which comprises at least a significant proportion of fines; and compacting the ground input feed to form agglomerates.
It is preferred that the agglomerates be suitable for use as a feed material for a fluidised bed roaster or a fluidised bed combustion furnace. In this context, the process may include the addition of water to the agglomerates.
It is preferred that the compaction step (b) forms agglomerates that are relatively dense with a sufficient "green" strength to enable handling, transportation, and storage without significant breakdown of the agglomerates.
The term "relatively dense" is understood herein to mean that the agglomerates be sufficiently compact to withstand handling without degradation to an unsatisfactory size range.
It is preferred particularly that the compaction step forms relatively dense agglomerates and/or that the moisture content of the agglomerates be selected so WO 95/25585 PCT/AU95/00156 4 that, when the agglomerates are fed into a fluidised bed roaster or a fluidised bed combustion furnace and are subjected to elevated temperatures, the agglomerates break down into smaller-sized agglomerates that can be processed more efficiently in the fluidised bed roaster or the fluidised combustion furnace.
The present invention is based on the realisation that: by appropriate selection of the particle size of the input feed and the compaction of the input feed in step it is possible to form agglomerates having a preferred pore size; and (ii) by appropriate selection of the moisture content of the agglomerates; when the agglomerates are fed into a fluidised bed roaster or a fluidised bed combustion furnace and are subjected to elevated temperatures, the agglomerates break down into smaller-sized agglomerates that can be processed more efficiently in the fluidised bed roaster or the fluidised combustion furnace.
The feed material may be any material.
The feed material may be an organic material, such as coal washery slimes.
The feed material may also be an inorganic material, such as a mineral or a mineral concentrate.
By way of example, in one particular application of interest to the applicants, it is preferred that the feed material be a zinc sulphide concentrate for calcining WO 95/25585 PCT/AU95/00156 in a fluidised bed roaster.
In situations where the feed material is a mineral concentrate, it is preferred that the input feed for step comprises an ore containing the mineral.
In that event, it is preferred that the process further comprises an additional step of treating the ground mineral-containing ore to separate the mineral from other components of the ore and to form a slurry of the mineral.
It is preferred that the particle size distribution of the ground mineral-containing ore produced in step be 100% less than 100 micron.
It is preferred particularly that the particle size of the ground mineral-containing ore produced in step be less than 40 micron.
It is preferred more particularly that the particle size of the ground mineral-containing ore produced in step comprises at least 50% of the particles being less than 10 micron.
It is preferred more particularly that the particle size of the ground mineral-containing ore produced in step comprises at least 10% of the particles being less than 2 micron.
It is preferred that the size of the agglomerates produced in step be 1 to It is particularly preferred that size of the agglomerates produced in step be 4.5 to 15 mm.
It is preferred that the moisture content of the agglomerates produced in step be less than 15% at the
~I
WO 95/25585 PCT/AU9/00156 6 time the agglomerates are fed to a fluidised bed roaster or a fluidised bed combustion furnace.
It is particularly preferred that the moisture content of the agglomerates produced in step be less than 13% at the time the agglomerates are fed to a fluidised bed roaster or a fluidised bed combustion furnace.
It is preferred that the moisture content of the agglomerates produced in step be greater than 1% at the time the agglomerates are fed to a fluidised bed roaster or a fluidised bed combustion furnace.
It is preferred that the moisture content of the agglomerates produced in step be greater than 5% at the time the agglomerates are fed to a fluidised bed roaster or a fluidised bed combustion furnace.
It is preferred that the compaction step be carried out in a high pressure filtration apparatus.
According to the present invention there is also provided a process for producing agglomerates of a mineral concentrate comprising the following steps: grinding an ore containing the mineral into a particle size distribution which comprises at least a significant proportion of fines; treating the ground ore to separate the mineral from other components of the ore and to form a slurry of the mineral; and dewatering and compacting the slurry of the mineral to form relatively dense WO 95/25585 PCT/AU95/00156 7 agglomerates of the mineral concentrate that have a particle size distribution and/or a moisture content which are selected so that, when the agglomerates are fed into a fluidised bed roaster or a fluidised bed combustion furnace and are subjected to elevated temperatures, the agglomerates break down into smaller-sized agglomerates that can be processed more efficiently in the fluidised bed roaster or the combustion furnace.
According to the present invention there is also provided a process for calcining a mineral concentrate comprising, feeding agglomerates of the mineral concentrate formed by the process described in the preceding paragraphs into a fluidised bed roaster or a fluidised bed combustion furnace, and calcining the agglomerates therein.
PREFERRED EMBODIMENT OF THE INVENTION The present invention is described further by way of example in relation to experimental work carried out by the applicants on zinc sulphide concentrate from the Century deposit in North Queensland, Australia.
The results of the experimental work are summarised in part in the accompanying figure and also in the following discussion.
The figure is a graph which illustrates the particle size distribution of calcine produced from zinc sulphide concentrate in fluidised bed reactors from agglomerates formed by a range of different compaction processes, as summarised below.
Sample a high pressure filtration in a Denver WO 95/25585 PCT/AU95/00156 8 tube press to form agglomerates which were dried to a moisture content of 1% and prepared with a particle size distribution of 9.5 to 16mm.
Sample b i.
high pressure filtration in a Denver tube press to form agglomerates having a moisture content of 12% and a particle size distribution of 9.5 to 16mm; and Sample c ii. high pressure filtration in a Denver tube press to form agglomerates having a moisture content of 12%, drying the agglomerates to a moisture content of re-wetting the agglomerates to a moisture content of 12% and a particle size distribution of 9.5 to 16mm; low pressure filtration and mixing in an Eirich agglomerator to form agglomerates having a moisture content of 11% and a particle size distribution of less than 2mm.
low pressure filtration and thereafter hot air drying in a rotary drier to form agglomerates having a moisture content of 11% and a particle size distribution of less than Sample d Sample e shredding a cake produced in a Denver WO 95/25585 PCT/AU95/00156 9 tube press and thereafter reagglomerating the shredded cake in an Eirich agglomerator to form agglomerates having a moisture content of 11% and a particle size distribution of 0.1 to 1mm.
The grain size distribution of the unagglomerated concentrate used to produce the samples was as follows: 98% 20 micron 85% 10 micron 63% 5 micron 2 micron The samples were calcined in either a 300mm diameter pilot plant fluidised bed roaster or a diameter bench scale fluidised bed roaster.
The fluidised bed roasters were found by the applicants to have similar fluidising conditions to the commercial Lurgi-type fluidised bed roasters discussed above and thus the results of the experimental work are indicative of the results that would be achieved in those Lurgi-type fluidised bed roasters.
With reference to the figure, the particle size distribution for samples b, c, and d and, to a lesser extent, sample e, are within the preferred particle size distribution of 0.1 to 2mm for optimum operation of a Lurgi-type fluidised bed roaster.
This is a significant and, in many respects, an unexpected outcome, because the input feed which produced the samples comprised agglomerates which were formed, without added binder, from slurries of finely ground zinc sulphide concentrate and, on the basis of known prior art, WO 95/25585 PCT/AU95/00156 10 it was expected that such agglomerates, i.e. agglomerates formed from fines, would disintegrate quickly into fines of less than 0.1mm in the fluidised bed roasters and would be blown from the fluidised bed roasters.
The result of sample b is particularly significant, and unexpected, because the particle size distribution of the input feed of agglomerates was in the range of 9.5 to 16mm, which is considerably larger than the upper limit of the preferred prior art particle size distribution for Lurgi-type fluidised bed roasters, and it was expected that, under normal circumstances, such largesized agglomerates would not be fluidised and hence render the roasters inoperable.
It is believed by the applicants that the unexpected result with sample b is due to the agglomerates being relatively dense. Whilst not wishing to be limited to a particular theory, it is thought by the applicants that when the relatively dense agglomerates were subjected to elevated temperatures in the fluidised bed roaster: there was a sudden increase in pressure within the pores of the agglomerates due to the evolution of steam and, (ii) as a consequence of the relatively small pore size, the agglomerates were not able to accommodate the increased internal pressure and therefore fractured into smaller components.
The sample e was prepared in view of concern that agglomerates of zinc sulphide concentrate may break-down into fines during transportation from an ore resource to a commercial fluidised bed roaster. The result for sample e shows that re-agglomeration of shredded agglomerates WO 95/25585 PCT/AU95/00156 11 produced agglomerates that had a satisfactory particle size distribution when calcined in a fluidised bed roaster.
The result for sample b ii also illustrates the effect of moisture content on the agglomerates.
Specifically, as is noted above, sample b ii was formed by re-wetting the dried agglomerate which had been used to produce sample a and thereafter re-forming this agglomerate to a moisture content of 12%. The results for sample b ii were the same as for sample b i and indicate that agglomerates can be re-wetted without loss of performance should the agglomerates be over-dried.
The experimental work carried out by the applicants has also shown that, above a critical value of (and up to 25mm), the lump size of agglomerates produced by high pressure filtration, as described for sample b i above, did not affect significantly the particle size distribution of the calcined product of the fluidised bed roasters. Thus, the top size of the agglomerates is not a significant factor since agglomerates up to 25mm will break-down in fluidised bed roasters into smaller components having a particle size distribution predominantly in the range of 0.1 to 2mm.
In summary, the experimental work established that it is possible to form agglomerates from fine ground zinc sulphide concentrate which have a "green" strength that should withstand handling, transportation and storage and calcining in a fluidised bed roaster. As a consequence, it is possible to obtain the benefits of finegrinding zinc bearing ore, such as liberating impurities in such ores, in producing zinc sulphide concentrates without having an adverse effect on subsequent calcining of the zinc sulphide concentrate. A particular outcome of the experimental work is that relatively dense agglomerates having a relatively large particle size distribution, i.e.
WO 95/25585 PCT/AU95/00156 12 in excess of 4mm, were broken-down into smaller agglomerates when subjected to elevated temperatures in a fluidised bed roaster and the smaller agglomerates were in the preferred particle size distribution for optimum performance of a Lurgi-type fluidised bed roaster.
Many modifications may be made to the process of the invention as described with reference to the experimental work carried out by the applicants without departing from the spirit and scope of the invention.
In particular, whilst the experimental work relates to zinc sulphide concentrate, it can readily be appreciated that the invention is not so limited and extends to any suitable material such as, by way of example, coal washery slimes.
Claims (12)
1. A process for producing agglomerates of a mineral for use as a feed material for a fluidised bed roaster comprising the following steps: grinding an ore containing the mineral to form a ground ore having a particle size of less than 100 micron; treating the ground ore to separate the mineral from other components of the ore and to form a slurry of the mineral; and dewatering the slurry and compacting the mineral to form agglomerates that are relatively dense and have a moisture content of at least 1 wt.% which, when the agglomerates are fed into a fluidised bed 20 roaster and are subjected to elevated temperatures, break down into smaller-sized agglomerates that are within an optimum size distribution for the fluidised bed roaster. 0. 06
2. The process defined in claim 1 comprising compacting the ground input feed in step to form agglomerates that are relatively dense with a sufficient S' "green" strength to enable handling, transportation, and storage without significant breakdown of the agglomerates.
3. The process defined in claim 1 or claim 2 comprising compacting the ground input feed in step to form relatively dense agglomerates which are selected so that, when the agglomerates are fed into a fluidised bed 35 roaster or a fluidised bed combustion furnace and are subjected to elevated temperatures, the agglomerates break down into smaller-sized agglomerates that can be processed H:\pau1ad\Keep\speci\TRPL INDIA 315CAL95 CLAIM 1-ngm.doc 11/02/99 14 more efficiently in the fluidised bed roaster or the fluidised bed combustion furnace.
4. The process defined in any one of the preceding claims wherein the feed material comprises a zinc sulphide concentrate for calcining in the fluidised bed roaster. The process defined in any one of the preceding claims wherein the particle size of the ground mineral-containing ore produced in step is less than micron.
6. The process defined in any one of the preceding claims wherein the particle size of the ground mineral-containing ore produced in step comprises at least 50% of the particles less than 10 micron.
7. The process defined in claim 6 wherein the S. 20 particle size of the ground mineral-containing ore produced in step comprises at least 10% of the particles less than 2 micron. *oo
8. The process defined in anyone of the preceding claims wherein the size of the agglomerates produced in step is 1 to
9. The process defined in claim 8 wherein the size of the agglomerates produced in step is 4.5 to S The process defined on any one of the preceding claims wherein the moisture content of the agglomerates is less than
11. The process defined in claim 10 wherein the moisture content of the agglomerates is less than 13%. H:\pau ad\Keep\spea±\TRpL INDIA 315CAL95 CLAIM I-nqr.doc 11/02/99 15
12. The process defined in any one of the preceding claims wherein the moisture content of the agglomerates is greater than
13. The process defined in claim 1 wherein the compaction step is carried out in a high pressure filtration apparatus.
14. The process defined in any one of the preceding claims comprising compacting the slurry of the mineral without the addition of a binder. S S *e S 5* S H: \pau1ad\Keep\speci\TRPL INDIA 315CAL95 CLAIM l-ngm.doa 11/02/99
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU20621/95A AU704350B2 (en) | 1994-03-21 | 1995-03-21 | A process for producing agglomerates |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPM4609 | 1994-03-21 | ||
| AUPM4609A AUPM460994A0 (en) | 1994-03-21 | 1994-03-21 | A process for producing agglomerates |
| PCT/AU1995/000156 WO1995025585A1 (en) | 1994-03-21 | 1995-03-21 | A process for producing agglomerates |
| AU20621/95A AU704350B2 (en) | 1994-03-21 | 1995-03-21 | A process for producing agglomerates |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU2062195A AU2062195A (en) | 1995-10-09 |
| AU704350B2 true AU704350B2 (en) | 1999-04-22 |
Family
ID=25617947
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU20621/95A Ceased AU704350B2 (en) | 1994-03-21 | 1995-03-21 | A process for producing agglomerates |
Country Status (1)
| Country | Link |
|---|---|
| AU (1) | AU704350B2 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1514963A1 (en) * | 1961-06-12 | 1969-09-04 | Atomic Energy Authority Uk | Process for the production of spheroids from a powder, in particular from nuclear fuel |
| US3738785A (en) * | 1968-11-08 | 1973-06-12 | Degussa | Apparatus for processing of finely divided particulate materials |
| DE3734760A1 (en) * | 1987-10-14 | 1989-05-03 | Kloeckner Humboldt Deutz Ag | Method and installation for compacting fine-grained material with pelletising |
-
1995
- 1995-03-21 AU AU20621/95A patent/AU704350B2/en not_active Ceased
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1514963A1 (en) * | 1961-06-12 | 1969-09-04 | Atomic Energy Authority Uk | Process for the production of spheroids from a powder, in particular from nuclear fuel |
| US3738785A (en) * | 1968-11-08 | 1973-06-12 | Degussa | Apparatus for processing of finely divided particulate materials |
| DE3734760A1 (en) * | 1987-10-14 | 1989-05-03 | Kloeckner Humboldt Deutz Ag | Method and installation for compacting fine-grained material with pelletising |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2062195A (en) | 1995-10-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |