CA1115677A - Grinding method - Google Patents
Grinding methodInfo
- Publication number
- CA1115677A CA1115677A CA297,812A CA297812A CA1115677A CA 1115677 A CA1115677 A CA 1115677A CA 297812 A CA297812 A CA 297812A CA 1115677 A CA1115677 A CA 1115677A
- Authority
- CA
- Canada
- Prior art keywords
- particle size
- fraction
- mill
- grinding
- crushed
- 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
- 238000000227 grinding Methods 0.000 title claims abstract description 57
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000000463 material Substances 0.000 claims abstract description 57
- 239000002245 particle Substances 0.000 claims abstract description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 239000011435 rock Substances 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 238000001238 wet grinding Methods 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 239000000727 fraction Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000011144 upstream manufacturing Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000033558 biomineral tissue development Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000010423 industrial mineral Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
- B02C17/002—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls with rotary cutting or beating elements
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Crushing And Grinding (AREA)
Abstract
A B S T R A C T OF T H E D I S C L O S U R E
A GRINDING METHOD
There is provided a method of disintegrating pre-crushed lump material, in which, for obtaining a high and uniform throughput, the lump material is divided into a coarse and a finer fraction, and in which the coarse fraction is charged directly to a primary drum mill whilst the finer fraction is charged to a crusher and is crushed therein to a largest particle size which is at most one third of the smallest particle size of the coarse fraction, and is thereafter directly charged to the primary drum mill and ground therein whilst using the said coarse fraction as grinding bodies.
A GRINDING METHOD
There is provided a method of disintegrating pre-crushed lump material, in which, for obtaining a high and uniform throughput, the lump material is divided into a coarse and a finer fraction, and in which the coarse fraction is charged directly to a primary drum mill whilst the finer fraction is charged to a crusher and is crushed therein to a largest particle size which is at most one third of the smallest particle size of the coarse fraction, and is thereafter directly charged to the primary drum mill and ground therein whilst using the said coarse fraction as grinding bodies.
Description
The present invention relates to a method of disintegrating pre-crushed lump material, preferably ore and other mineral material, with the aid of a crushing device and a primary auto-genous or semi-autogenous drum-type grinding mill.
When processing ore to recover therefrom one or more of its constituents, such as metal minerals, industrial minerals etc., the ore is normally mechanically dislntegrated in a first operation.
The main purpose of this mechanical disintegration of the ore is to render the valuable cons~tuents accessible in a subsequent sepa-10 ration process, in which minerals present in the ore can be sepa-rated in dependence upon their difference in colour, shape or density, or in dependence upon differences in surface activity, ;
.
magnetic properties or other properties.
The mechanical disintegration of the ore normally takes place initially in the mine, when the ore is blasted from solid ` rock, and is then conti`nued progressively in the form of a series ; of crushing and grinding operations, which may take different forms.
The ore is normally crushed in a plurality of successive stages ~ .
using jaw crushers or cone crushers, whereafter the thus disinte-grated ore has been ground in rotary drums containing grinding bodies, such as balls or rods, which are normally made of steel.
Because of the hardness of the rock, however, the grinding bodies are subjected to intensive wear, which results in considerable cost. In an effort to avoid this, a technique has been developed in which the mineralization or ore itself forms the grinding bodies, i,e. the so-called autogenous grinding technique.
The autogenous grinding technique has found wide use and is employed to a large extent throughout the world and enables the pre-crushing of the rock to be limited to the crushing of only large pieces of rock and boulders to a maximum particle size acceptable from the transport aspect. The investment costs and operation costs of the crushing plant is therefore relatively low.
: . ' ~.:
~ :~15677 The absence of artificial grinding bodies of high specific weight in comparison with the material being ground, necessitates, how-ever, mills of large diameter in order that the requisite impact energy is obtained in the grinding charge, which increases the investment cost and operation cost of the mill. If grinding bodies -are -to be formed to a satisfactory extent, the material being ground must have a high mechanical strength. If this is not so, there is a risk that pieces of material of so-called critical size will accumulate in the mill, it being meant by pieces of critical size such pieces which do not exert any appreciable grinding action and which are not appreciably-affected by the grindlng bodies.
When such accumulation takes place, the throughput falls greatly.
The fact that the material forms its own grinding bodies thus implies that the efficiency of the grinding operation is also dependent upon variations in the properties of the material being ground. Since the properties of the material of, for example, an ore deposit normally vary, autogenous grinding has been encumbered with a large number of problems, primarily when existing grinding apparatus are to be utilised effectlvely and when a constant through-put is to be obtained with the grinding operation.
If, when effecting a primary autogenous grinding operation,a constant amount of pre-crushed lump material is charged to the drum mill per unit of time, the extent to which the mill is filled will vary, as will also the power required to grind the material when the physical properties of the material or its constituents, such as its mechanical strength, hardness, toughness, elasticity etc., vary. It was discovered during tests carried out in conjunc-tion with the advent of the present invention that the size distri-bution of the lumps of material charged to the mill also greatly influences the constitution of the grinding charge formed, and therewith the grinding process. Changes in the size distribu-tion of the material charged to the mill influences the degree of fill-ing of the mill and the power requirement, as does also thephysicaI properties of the material and in practice it is con-sequently always necessary to compromise, i.e. both to over-size the mill and to vary the feed, in order to avoid excessively wide variations in the degree of fllling of the mill and in order to :
- be able to maintain a relatively uniform throughput. A uniform - throughput is d~esirable in order to~prevent disturbances in process stages preceding and fo~llowing the grinding operation. It will be understood from the~aforegoing~-that an;autogenous grinding mill is seldom operated at~opt~imum conditi~ons, i.e. at the highest possible throughput. A relatlvely~signlflca~nt reserve capacity must always be available in order to even out those variations occurring in the throughput as a r;esult of variatlons in the properties of the ~- material being ground.
r~ It is often necessary to finely grind the material prior to the~separation process, and consequently the primary autogenous -grinding stage is normally~followed~by a further stage, a so-called secondary grinding stage. This~ secondary~grinding stage in auto-genous grinding processes ofté~comprises ~a pebble~mill, in which ~; 70 pebbles screened from the grinding charge of the primary mill form r~ ~ thé grinding bodies. The material belng ground is given its final~ ;
~;~ particle size distribution in this secondary grinding stage. In ~order to~;obtain~the best~ return f~or the capital invested, the throughput must be uniform and, of course, as high~as possible I, or both grindlng stages.
The object of the present invention is to provide a novel and useful grinding method in which all the advantages afforded by the autogenous grinding technique are retained whilst, at the ' same time, substantially eliminating the aforementioned disadvan- -tages.
To this end there is proposed in accordance with the inven-tion a method of the type mentioned in the introductlon in which :: :
.....
': . , ~, , the lump material is divided into a coarse and a finer fraction in which the coarse fraction is charged to the drum mill whilst the finer fraction is charged to a crushing device and is crushed therein to a largest particle size in the order of magnitude of at most one third of the smallest particle size of the coarse fraction, and is thereafter charged directly to the drum mill and is ground therein whilst utilising the aforementioned coarse frac-tion as grinding bodies. By dividing the lump material and crush-ing the separated finer fraction to said relationship between the material fractions charged to the mill, there is obtained a uni-form and high throughput in the mill without any appreciable tendency of the pieces of material of critical size to accumulate therein and without any appreciable tendency of variations in the degree of filling of the mill whilst maintaining the amount of material charged to the mill per unit of time constant. In this way the need of substantial over-sizing the mill is obviated, with considerable saving in cost as a result thereof, at the same time , as the process apparatus arranged upstream and downstream of the mill can be dimensioned to work with substantially constant quanti-ties of material per unit of time without requiring the arrangementof storage bins etc. upstream or downstream of the mill. The material ground in the drum mill may be subjected, to advantage, to a secondary, further grinding operation in a drum-type secondary mill downstream of said drum mill.
By "largest particle size" is meant here and in the following a measurement which corresponds substantially to the smallest slit width of the crusher, and by "the smallest particle size of the coarse fraction" is meant a measurement which corresponds substan-tially to the smallest mesh size or the like of a screen device capable of being used to separate the desired coarse fraction from the remain~er of the ingoing lump material.
In a primary autogenous grinding operation,when applying the 1~5677 method according to the invention, the smallest particle size of the coarse fraction is suitably approximately 80-150 mm, al-though this range is not critical. On the other hand, the lump material should be divided, if possible, in a manner such that the coarse fraction is substantially consumed during grinding of the finer fraction. The amount of the coarse fraction obtained ~ -`
may be sufficient, however, to form in the mill an intermediate fraction which can be screened therefrom and used as grinding bodies in a subsequent, drum-type secondary mill working in ac-10 cordance with the autogenous grinding technique. e.g. in accord-ance with the method disclosed in the U.S. Patent Specifications 3,924,814 and 3,942,727. An excessively large percentage of coarse fraction in the primary mill should be avoided, however.
The throughput will normally decrease when the coarse fraction ~;
comprises re than 40% by weight of the grinding charge. Ac-cordingly, the lump material is conveniently divided so that said ; coar~e fraction comprises approximately 0.15-0.35 times the total ~ ~
guantity of the original lump material, optimal, and therewith ~ -preferred conditions, being obtained at a value of approximately 0.2S. Should the smallest particle size of the coarse fraction have been selected such that the amount of coarse fraction is in-suffi¢ient to provide the desired grinding of the goods arriving from the crusher device, said division of the lump material may be modified in a manner such that the requisite quantity of o~se fra¢tion having a somewhat smaller least partic~e size isobtained, or further grinding bodies which consist of a forelgn material, e.g. steel, can be charged to the drum mill to the extentre~i~d.
If, in this latter case, the primary ground goods are further ground in a subsequent drum-type secondary mill, the ~rrangement des¢ribed in the aforementioned U.S. Patent Specifications 3,924,814 and 3,942,727 can be used to advantage, thereby ren-dering it unnecessary to separate the aforementioned for~ign grinding bodies from the primary ground material in a specific separating operation.
In order for the grinding bodies formed by said coarse fraction to have an optimal effect on the material obtained by crushing the aforementioned finer fraction, said material should be crushed to a largest particle size ranging from a fifth to a tenth, preferably at most approximately a sixth of the smallest particle size of the coarse fraction.
The finest particles of the finer fraction, and also those particles of small size obtained during the crushing operation, have, in some instances, a tendency to partially clog the crusher in a manner such as to considerably reduce its capacity. In order to circumvent this disadvantage, in accordance with the invention material having a maximum particle size of at most one third of the smallest particle size of the coarse fraction can be separated from the said finer fraction prior to crushing the same and charged directly to the drum mill. When grinding in the presence of water, however, it is preferred to avoid this clogging of the crushing device by charging at least a part of or the whole of the amount of water required for the wet-grinding process to the crushing device, the water being caused to accompany the crushed material to the drum mill. In -this way the crushing devic~ is flushed clean by the water charged thereto, said water forcing the material being flushed through the crushing device in a manner such as to improve the capacity of said crushing device instead. The water can also be used as a transportation medium for carrying the crushed material to the drum mill. In this latter method, there is therefore no need to separate the finest particles of the said finer material fraction in a separate screening device, whilst the arrangement provided for conveying the crushed material from the crushing device to the drum mill can be greatly simplified.
The invention will now be described in more detail with reference to a preferred plant illustrated schematically in the Ll '_ ~ ' 7 accompanying drawing.
The plant illustrated in the drawing comprises a screen 10, a crusher ll and a drum mill 12 for primary autogenous or semi-autogenous wet-grinding. ~ pre-crushed lump material, e.g. ore, is charged to the screen 10 in the manner indicated by arrow 13.
The material is divided by the screen lO into a coarse fraction, the amount of which comprises 15 to 35% by weight of the total amount of said material. ~s shSown by the arrow 14, this coarse fraction is passed directly to the mill 12, whlle the finer frac-tion passing through the screen is charged to the crusher ll, asshown by the arrow 15, in which crusher said fraction is crushed to a particle size which is at most one third of the smallest particle size of the coarse fraction. ~s indicated by the arrow 16, at least part of the water required for the wet-grinding operation is charged to the crusher 11, said water being effective to force the material through said crusher. The crushed material and water departing from the crusher are collected in a chute as shown at 17, which chute conducts said material and water directly to the mill 12, as indicated by the arrow 18, in which mill the goods are ground whilst utilising said coarse material fraction as grinding bodies, and is thereafter discharged from the mill, as indicated by the arrow 19. The mill 12 may be included as a primary grinding stage in a grinding plant of the type illustrated in US
Patent Specification 3 942 727, wherewith the discharge end may be modified to advantage in the manner illustrated in US Patent 3 924 ~14.
The invention, however, is not limited to use in conjunction with the illustrated and described plant. Thus, as indicated by means of the arrow 20, water and/or a given quantity of foreign grinding bodies may be charged directly to the mill 12. Further, as indicated by means of dash-lines 21, the screen 10 may be arranged to separate from the said finer fraction small particles ` ` 1115677 capable of passlng through the crusher 11 without being crushed therein. As indicated by means of the arrow 22, these finer particles in the illustrated embodiment are charged directly to the chute 17, to which water can be charged, as shown at 22, to convey these particles into the mill 12.
~2,
When processing ore to recover therefrom one or more of its constituents, such as metal minerals, industrial minerals etc., the ore is normally mechanically dislntegrated in a first operation.
The main purpose of this mechanical disintegration of the ore is to render the valuable cons~tuents accessible in a subsequent sepa-10 ration process, in which minerals present in the ore can be sepa-rated in dependence upon their difference in colour, shape or density, or in dependence upon differences in surface activity, ;
.
magnetic properties or other properties.
The mechanical disintegration of the ore normally takes place initially in the mine, when the ore is blasted from solid ` rock, and is then conti`nued progressively in the form of a series ; of crushing and grinding operations, which may take different forms.
The ore is normally crushed in a plurality of successive stages ~ .
using jaw crushers or cone crushers, whereafter the thus disinte-grated ore has been ground in rotary drums containing grinding bodies, such as balls or rods, which are normally made of steel.
Because of the hardness of the rock, however, the grinding bodies are subjected to intensive wear, which results in considerable cost. In an effort to avoid this, a technique has been developed in which the mineralization or ore itself forms the grinding bodies, i,e. the so-called autogenous grinding technique.
The autogenous grinding technique has found wide use and is employed to a large extent throughout the world and enables the pre-crushing of the rock to be limited to the crushing of only large pieces of rock and boulders to a maximum particle size acceptable from the transport aspect. The investment costs and operation costs of the crushing plant is therefore relatively low.
: . ' ~.:
~ :~15677 The absence of artificial grinding bodies of high specific weight in comparison with the material being ground, necessitates, how-ever, mills of large diameter in order that the requisite impact energy is obtained in the grinding charge, which increases the investment cost and operation cost of the mill. If grinding bodies -are -to be formed to a satisfactory extent, the material being ground must have a high mechanical strength. If this is not so, there is a risk that pieces of material of so-called critical size will accumulate in the mill, it being meant by pieces of critical size such pieces which do not exert any appreciable grinding action and which are not appreciably-affected by the grindlng bodies.
When such accumulation takes place, the throughput falls greatly.
The fact that the material forms its own grinding bodies thus implies that the efficiency of the grinding operation is also dependent upon variations in the properties of the material being ground. Since the properties of the material of, for example, an ore deposit normally vary, autogenous grinding has been encumbered with a large number of problems, primarily when existing grinding apparatus are to be utilised effectlvely and when a constant through-put is to be obtained with the grinding operation.
If, when effecting a primary autogenous grinding operation,a constant amount of pre-crushed lump material is charged to the drum mill per unit of time, the extent to which the mill is filled will vary, as will also the power required to grind the material when the physical properties of the material or its constituents, such as its mechanical strength, hardness, toughness, elasticity etc., vary. It was discovered during tests carried out in conjunc-tion with the advent of the present invention that the size distri-bution of the lumps of material charged to the mill also greatly influences the constitution of the grinding charge formed, and therewith the grinding process. Changes in the size distribu-tion of the material charged to the mill influences the degree of fill-ing of the mill and the power requirement, as does also thephysicaI properties of the material and in practice it is con-sequently always necessary to compromise, i.e. both to over-size the mill and to vary the feed, in order to avoid excessively wide variations in the degree of fllling of the mill and in order to :
- be able to maintain a relatively uniform throughput. A uniform - throughput is d~esirable in order to~prevent disturbances in process stages preceding and fo~llowing the grinding operation. It will be understood from the~aforegoing~-that an;autogenous grinding mill is seldom operated at~opt~imum conditi~ons, i.e. at the highest possible throughput. A relatlvely~signlflca~nt reserve capacity must always be available in order to even out those variations occurring in the throughput as a r;esult of variatlons in the properties of the ~- material being ground.
r~ It is often necessary to finely grind the material prior to the~separation process, and consequently the primary autogenous -grinding stage is normally~followed~by a further stage, a so-called secondary grinding stage. This~ secondary~grinding stage in auto-genous grinding processes ofté~comprises ~a pebble~mill, in which ~; 70 pebbles screened from the grinding charge of the primary mill form r~ ~ thé grinding bodies. The material belng ground is given its final~ ;
~;~ particle size distribution in this secondary grinding stage. In ~order to~;obtain~the best~ return f~or the capital invested, the throughput must be uniform and, of course, as high~as possible I, or both grindlng stages.
The object of the present invention is to provide a novel and useful grinding method in which all the advantages afforded by the autogenous grinding technique are retained whilst, at the ' same time, substantially eliminating the aforementioned disadvan- -tages.
To this end there is proposed in accordance with the inven-tion a method of the type mentioned in the introductlon in which :: :
.....
': . , ~, , the lump material is divided into a coarse and a finer fraction in which the coarse fraction is charged to the drum mill whilst the finer fraction is charged to a crushing device and is crushed therein to a largest particle size in the order of magnitude of at most one third of the smallest particle size of the coarse fraction, and is thereafter charged directly to the drum mill and is ground therein whilst utilising the aforementioned coarse frac-tion as grinding bodies. By dividing the lump material and crush-ing the separated finer fraction to said relationship between the material fractions charged to the mill, there is obtained a uni-form and high throughput in the mill without any appreciable tendency of the pieces of material of critical size to accumulate therein and without any appreciable tendency of variations in the degree of filling of the mill whilst maintaining the amount of material charged to the mill per unit of time constant. In this way the need of substantial over-sizing the mill is obviated, with considerable saving in cost as a result thereof, at the same time , as the process apparatus arranged upstream and downstream of the mill can be dimensioned to work with substantially constant quanti-ties of material per unit of time without requiring the arrangementof storage bins etc. upstream or downstream of the mill. The material ground in the drum mill may be subjected, to advantage, to a secondary, further grinding operation in a drum-type secondary mill downstream of said drum mill.
By "largest particle size" is meant here and in the following a measurement which corresponds substantially to the smallest slit width of the crusher, and by "the smallest particle size of the coarse fraction" is meant a measurement which corresponds substan-tially to the smallest mesh size or the like of a screen device capable of being used to separate the desired coarse fraction from the remain~er of the ingoing lump material.
In a primary autogenous grinding operation,when applying the 1~5677 method according to the invention, the smallest particle size of the coarse fraction is suitably approximately 80-150 mm, al-though this range is not critical. On the other hand, the lump material should be divided, if possible, in a manner such that the coarse fraction is substantially consumed during grinding of the finer fraction. The amount of the coarse fraction obtained ~ -`
may be sufficient, however, to form in the mill an intermediate fraction which can be screened therefrom and used as grinding bodies in a subsequent, drum-type secondary mill working in ac-10 cordance with the autogenous grinding technique. e.g. in accord-ance with the method disclosed in the U.S. Patent Specifications 3,924,814 and 3,942,727. An excessively large percentage of coarse fraction in the primary mill should be avoided, however.
The throughput will normally decrease when the coarse fraction ~;
comprises re than 40% by weight of the grinding charge. Ac-cordingly, the lump material is conveniently divided so that said ; coar~e fraction comprises approximately 0.15-0.35 times the total ~ ~
guantity of the original lump material, optimal, and therewith ~ -preferred conditions, being obtained at a value of approximately 0.2S. Should the smallest particle size of the coarse fraction have been selected such that the amount of coarse fraction is in-suffi¢ient to provide the desired grinding of the goods arriving from the crusher device, said division of the lump material may be modified in a manner such that the requisite quantity of o~se fra¢tion having a somewhat smaller least partic~e size isobtained, or further grinding bodies which consist of a forelgn material, e.g. steel, can be charged to the drum mill to the extentre~i~d.
If, in this latter case, the primary ground goods are further ground in a subsequent drum-type secondary mill, the ~rrangement des¢ribed in the aforementioned U.S. Patent Specifications 3,924,814 and 3,942,727 can be used to advantage, thereby ren-dering it unnecessary to separate the aforementioned for~ign grinding bodies from the primary ground material in a specific separating operation.
In order for the grinding bodies formed by said coarse fraction to have an optimal effect on the material obtained by crushing the aforementioned finer fraction, said material should be crushed to a largest particle size ranging from a fifth to a tenth, preferably at most approximately a sixth of the smallest particle size of the coarse fraction.
The finest particles of the finer fraction, and also those particles of small size obtained during the crushing operation, have, in some instances, a tendency to partially clog the crusher in a manner such as to considerably reduce its capacity. In order to circumvent this disadvantage, in accordance with the invention material having a maximum particle size of at most one third of the smallest particle size of the coarse fraction can be separated from the said finer fraction prior to crushing the same and charged directly to the drum mill. When grinding in the presence of water, however, it is preferred to avoid this clogging of the crushing device by charging at least a part of or the whole of the amount of water required for the wet-grinding process to the crushing device, the water being caused to accompany the crushed material to the drum mill. In -this way the crushing devic~ is flushed clean by the water charged thereto, said water forcing the material being flushed through the crushing device in a manner such as to improve the capacity of said crushing device instead. The water can also be used as a transportation medium for carrying the crushed material to the drum mill. In this latter method, there is therefore no need to separate the finest particles of the said finer material fraction in a separate screening device, whilst the arrangement provided for conveying the crushed material from the crushing device to the drum mill can be greatly simplified.
The invention will now be described in more detail with reference to a preferred plant illustrated schematically in the Ll '_ ~ ' 7 accompanying drawing.
The plant illustrated in the drawing comprises a screen 10, a crusher ll and a drum mill 12 for primary autogenous or semi-autogenous wet-grinding. ~ pre-crushed lump material, e.g. ore, is charged to the screen 10 in the manner indicated by arrow 13.
The material is divided by the screen lO into a coarse fraction, the amount of which comprises 15 to 35% by weight of the total amount of said material. ~s shSown by the arrow 14, this coarse fraction is passed directly to the mill 12, whlle the finer frac-tion passing through the screen is charged to the crusher ll, asshown by the arrow 15, in which crusher said fraction is crushed to a particle size which is at most one third of the smallest particle size of the coarse fraction. ~s indicated by the arrow 16, at least part of the water required for the wet-grinding operation is charged to the crusher 11, said water being effective to force the material through said crusher. The crushed material and water departing from the crusher are collected in a chute as shown at 17, which chute conducts said material and water directly to the mill 12, as indicated by the arrow 18, in which mill the goods are ground whilst utilising said coarse material fraction as grinding bodies, and is thereafter discharged from the mill, as indicated by the arrow 19. The mill 12 may be included as a primary grinding stage in a grinding plant of the type illustrated in US
Patent Specification 3 942 727, wherewith the discharge end may be modified to advantage in the manner illustrated in US Patent 3 924 ~14.
The invention, however, is not limited to use in conjunction with the illustrated and described plant. Thus, as indicated by means of the arrow 20, water and/or a given quantity of foreign grinding bodies may be charged directly to the mill 12. Further, as indicated by means of dash-lines 21, the screen 10 may be arranged to separate from the said finer fraction small particles ` ` 1115677 capable of passlng through the crusher 11 without being crushed therein. As indicated by means of the arrow 22, these finer particles in the illustrated embodiment are charged directly to the chute 17, to which water can be charged, as shown at 22, to convey these particles into the mill 12.
~2,
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of disintegrating pre-crushed lump material by means of a crushing device and a primary autogenous or semi-autogenous drum-type grinding mill, characterized in that the lump material is divided into a coarse and a finer fraction, the coarse fraction being charged directly to the drum mill whilst the finer fraction is charged to the crushing device and is crushed therein to a largest particle size which is at most one third of the smallest particle size of the coarse fraction, and is thereafter directly charged to the drum mill and ground therein whilst using the said coarse fraction as grinding bodies.
2. A method according to claim 1, characterized in that the lump material is divided in a manner such that said coarse fraction comprises approximately 0.15-0.35, preferably approx-imately 0.25 times the total quantity of the lump material.
3. A method according to claim 1 or 2, characterized in that grinding is effected in the presence of water and that at least part of said water is charged to the crushing device and is caused to accompany the material crushed therein to the drum mill.
4. A method according to claim 1 or 2, characterized in that material having a maximum particle size of at most one third-of the smallest particle size of the coarse fraction is separated from said finer fraction prior to said finer fraction being crushed, and is passed directly to the drum mill.
5. A method according to claim 1 or 2, characterized in that the finer fraction is crushed to a particle size in the range of one fifth to one tenth, preferably at most approximately one sixth of the smallest particle size of the coarse fraction.
6. A method according to claim 1 or 2, characterized in that further grinding bodies are charged to the drum mill to the extent necessary.
7. A method according to claim 1, characterized in that material ground in the drum mill is subjected to a secondary, additional grinding operation in a drum-type secondary mill downstream of said drum mill.
8. A method according to claim 7, characterized in that the secondary grinding operation is effected autogenously or semi-autogenously with the aid of grinding bodies taken from said drum mill.
9. A method according to claim 1 or 2, characterized in that grinding is effected in the presence of water and that at least part of said water is charged to the crushing device and is caused to accompany the material crushed therein to the drum mill, the finer fraction being crushed to a particle size in the range of one fifth to one tenth, preferably at most approximately one sixth of the smallest particle size of the coarse fraction.
10. A method according to claim 1 or 2, characterized in that material having a maximum particle size of at most one third of the smallest particle size of the coarse fraction is separated from said finer fraction prior to said finer fraction being crushed, and is passed directly to the drum mill, the finer fraction being crushed to a particle size in the range of one fifth to one tenth, preferably at most approximately one sixth of the smallest particle size of the coarse fraction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7702466-9 | 1977-03-04 | ||
| SE7702466A SE7702466L (en) | 1977-03-04 | 1977-03-04 | PAINTING PROCEDURE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1115677A true CA1115677A (en) | 1982-01-05 |
Family
ID=20330627
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA297,812A Expired CA1115677A (en) | 1977-03-04 | 1978-02-27 | Grinding method |
Country Status (5)
| Country | Link |
|---|---|
| AU (1) | AU513313B2 (en) |
| CA (1) | CA1115677A (en) |
| ES (1) | ES467529A1 (en) |
| PT (1) | PT67735A (en) |
| SE (1) | SE7702466L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5642863A (en) * | 1995-04-04 | 1997-07-01 | Krupp Polysius Ag | Method of extracting metals from ore material |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE429303B (en) * | 1981-11-27 | 1983-08-29 | Boliden Ab | METHOD OF AUTOGEN PAINTING |
-
1977
- 1977-03-04 SE SE7702466A patent/SE7702466L/en unknown
-
1978
- 1978-02-27 CA CA297,812A patent/CA1115677A/en not_active Expired
- 1978-03-02 AU AU33756/78A patent/AU513313B2/en not_active Expired
- 1978-03-03 PT PT67735A patent/PT67735A/en unknown
- 1978-03-03 ES ES467529A patent/ES467529A1/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5642863A (en) * | 1995-04-04 | 1997-07-01 | Krupp Polysius Ag | Method of extracting metals from ore material |
Also Published As
| Publication number | Publication date |
|---|---|
| SE7702466L (en) | 1978-09-05 |
| ES467529A1 (en) | 1979-06-16 |
| PT67735A (en) | 1978-04-01 |
| AU3375678A (en) | 1979-09-06 |
| AU513313B2 (en) | 1980-11-27 |
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