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EP0066392A2 - Zerkleinungsverfahren - Google Patents

Zerkleinungsverfahren Download PDF

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Publication number
EP0066392A2
EP0066392A2 EP82302460A EP82302460A EP0066392A2 EP 0066392 A2 EP0066392 A2 EP 0066392A2 EP 82302460 A EP82302460 A EP 82302460A EP 82302460 A EP82302460 A EP 82302460A EP 0066392 A2 EP0066392 A2 EP 0066392A2
Authority
EP
European Patent Office
Prior art keywords
mill
mixture
liquid
solid
coal
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.)
Withdrawn
Application number
EP82302460A
Other languages
English (en)
French (fr)
Other versions
EP0066392A3 (de
Inventor
Eduardo Angel Jose Gandolfi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GENERAL COMMINUTION Inc
Original Assignee
GENERAL COMMINUTION Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by GENERAL COMMINUTION Inc filed Critical GENERAL COMMINUTION Inc
Publication of EP0066392A2 publication Critical patent/EP0066392A2/de
Publication of EP0066392A3 publication Critical patent/EP0066392A3/de
Withdrawn legal-status Critical Current

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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
    • B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
    • B02C23/06—Selection or use of additives to aid disintegrating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C19/00—Other disintegrating devices or methods
    • B02C19/0056—Other disintegrating devices or methods specially adapted for specific materials not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C25/00—Control arrangements specially adapted for crushing or disintegrating

Definitions

  • the invention relates to a process for comminuting a solid in a mill.
  • the solid may for example be coal, which needs to be comminuted before being fed into a steam boiler.
  • the mixture When a liquid such as water is added to a solid such as coal, the mixture has a consistency, when comminuted, that depends not only on the size and shape of the solid particles, but also on the quantity of added liquid.
  • the mixture flows easily like a powder when poured or otherwise allowed to fall; when very wet, again the mixture flows easily, being predominantly liquid, Most mixtures have an intermediate stage at which the mixture substantially does not have the property of being able to flow freely.
  • the particles in the mixture adhere to each other, or agglomerate; the mixture is pasty, in that it is like a solid to the extent that it is capable of holding itself in a shape, though like a liquid to the extent that it has virtually no structural strength.
  • Such a mixture is a mixture of sand and water of a consistency suitable for the building of sand-castles.
  • the particles of solid are said to cohere with each other in such a mixture, and the mixture itself to be cohesive.
  • the time it spends in the mill is usually an important factor in determining how finely it is comminuted. If the mixture is such that it flows, then gravity is what determines how quickly the mixture goes through the mill. If the mixture is cohesive on the other hand, then if the mill is provided with channels that move as the mill is operated, the residence time that the mixture spends in the mill can be altered. By a careful selection of the speeds of the mill, and size and rate of movement of the channel, a cohesive mixture can be caused to remain indefinitely in the mill, or to feed upwards through the mill against gravity, or to feed downwards at a rate greater than that due purely to gravity. In a mill without such channels, even a cohesive mixture travels through the mill under the action only of gravity, and of whatever frictional or viscuous resistances to motion may be present.
  • a mill that has such a movable channel, so that it is capable of transporting cohesive mixtures, is said to have a transport capability. If the channels are arranged to transport the mixture in a direction to assist gravity, or whatever other agency feeds the mixture into and out of the mill, to urge the mixture through the mill, the transport is termed positive. If the channels are arranged to transport the mixture against gravity, on the other hand, the transport capability is a negative transport capability.
  • a mill with a positive transport capability allows cohesive mixtures to be milled economically. Without positive transport, such mixtures tend to remain in the mill because the particles of solid tend to cohere not only to each other but to the mill itself. Some mixtures however, such as some foodstuffs, have in the past had to be milled at a very sticky consistency, and it has been necessary in such cases, in order for the mixture to pass through the mill, to provide for a positive feed capacity-for the mill.
  • a positive feed capacity is one in which a pressure is exerted on the mixture to push it, or even to suck it, through the mill from inlet to outlet, in the event that gravity is ineffective to do this.
  • the provision of such a pressure carries with it the requirement that the mill remains full, for no voids can appear in the mixture if it is to be fed under pressure. Whilst it is possible, and economical, to comminute in that way some mixtures such as food substances (e.g. chocolate), other mixtures (such as coal and oil) are so stiff when cohesive that the power consumption needed to operate a mill that is full of that mixture would be wastefully large.
  • the positive transport capability allows the mill to be used on mixtures that are so cohesive that they would not otherwise move through the mill unless pressurized, yet the positive transport capability allows the mill to transport such mixtures without the mill needing to be full of the mixture.
  • batch comminution needs no transport, and no feed, capability in the mill, so that again the mill need not be full during comminution.
  • Batch comminution is however much less economical than continuous comminution, to which the invention is mainly applicable.
  • the efficiency of comminution depends upon the amount of liquid that has been added to the solid to form the mixture. According to the invention, it is preferred that the comminution is carried out using a mixture having the liquid content that maximizes the comminution efficiency.
  • the efficiency of comminution that is referred to should be understood as being not confined to any particular measure of efficiency. What is most efficient usually is dependent on what is most economical, which can depend on a variety of factors.
  • the miller has in mind a criterion by which the efficiency or economy of the comminution in that case is to be measured.
  • the criterion of economy will be the compromise between the fineness of the comminuted powder and the power consumption of the mill Ond such a compromise will differ in dependence on the change in price of electricity from area to area); sometimes, as another example, the criterion of economy will be the fineness of the powder as compromised by the capital cost of the mill required to produce that degree of fineness in a given throughput rate of the solid.
  • the invention provides that experiments are carried out to measure how economical (according to that criterion) the comminution is at varying added liquid throughputs. If the experiments show that there is a liquid throughput that gives a maximum level of economy (according to that criterion), then that throughput is used when comminuting the solid under the particular conditions of the case.
  • the mill 10 shown in Figs. 1 and 2 comprises a housing 12 having an inner cylindrical surface 14.
  • the housing 12 is part of the fixed frame (not shown) of the mill 10.
  • a rotary assembly 16 is located inside the housing 12.
  • a shaft 18 is driven by a motor (not shown), and runs in bearing 20 housed in the fixed frame.
  • Keyed to the shaft 18 are drive plates 22.
  • Mounted between the drive plates 22 are three rollers 24, which can rotate freely with respect to the plates 22 about axes parallel to the shaft 18.
  • the mill 10 is mounted with the shaft 18 vertical, and the solid to be milled is fed into the top of the mill, onto the upper one 22A of the drive plates 22, from a vibratory hopper (not shown) or other suitable feed device.
  • the liquid is conveyed through a pipe (not shown) also into the top of the mill.
  • the mixture falls down into the annular gap 28 between the plate 22A and the surface 14; is milled by the rollers 24 against the surface 14 as it passes down through the mill; and finally passes out through a corresponding gap between the bottom plate 22B and the surface 14.
  • the milled mixture is collected in a hopper (not shown) or other suitable collecting means placed below the mill.
  • the mill has a positive transport facility, as called for in the invention, in that the rollers 24 are each formed with a helical groove 30, comprising a transport channel.
  • the grooves 30 will tend to transport the substance in the mill either up or down depending on the direction of rotation of the assembly 16. A number of factors influence the extent to which the grooves impose this transport effect on the substance.
  • the first factor is the consistency of the substance. Both gravity, and the grooves can have an effect on the transport rate of the mixture through the mill. If the mixture is very dry, then most mixtures tend to pass through the mill under gravity, the grooves having only a comparatively slight effect. This is particularly the case with dense materials, such as metals and ores. With light, fluffy, materials, such as pieces of paper, the grooves can significantly affect the transport rate even though the material is dry. Equally, if the mixture is very wet, in that it is of a very thin and runny consistency, then again the substance tends to fall through the mill under the action substantially only of gravity. When, on the other hand, the mixture is a thick, pasty, sticky, cohesive mixture, the mixture can support itself to a certain degree, and the grooves can now be extremely effective in setting the residence time that the mixture spends in the mill.
  • the residence time is also affected by the other factors, which include the configuration of the grooves, the number of starts, the lead and pitch of the helix, the flank angle of the sides of the grooves, the diameters of the rollers and of the housing, and the speeds of rotation of the rollers and shaft.
  • the grooves do create the positive transport effect, they do not become clogged.
  • the rotary speed of the rollers should be high enough that centrifugal_force flings the material out of the groove, to empty the groove at least partially.
  • the material in the groove is constantly changing.
  • the mixture is extremely cohesive, it may be that the groove is so arranged that it cannot be emptied at all: when the groove on the roller rolls over a point on the wall on the housing the mixture is packed so tightly into the groove that it is not flung out by centrigual force.
  • Such a fault is not cured by increasing the speed of the mill, since that causes the mixture to be packed even tighter. It is necessary in such an event to increase the size of the groove, or to provide the sides of the grooves with a flank angle.
  • the positive transport feature in the kind of mill illustrated in Figs. 1 and 2 may be regarded as an axial screw conveying capability. In other mills, the positive transport feature may be provided somewhat differently, but essentially it requires the presence in the mill of a channel which travels, when the mill is operating, in a direction to hold the mixture in the mill for a longer or shorter time than it would remain in the absence of the traveling channel.
  • Figs. 3 and 4 are graphs showing the results of these experiments, which in this example were carried out on a mixture of coal and water.
  • the quantity of coal fed through the mill was the same throughout the experiments, and was 720 kg/hr.
  • the shaft was driven at a speed of 1250 rpm.
  • the vertical scale is the proportion, expressed as a percentage, of the 720 kg/hr. throughput of coal that was milled finely enough to pass through a mesh of a predetermined size, which in the case of curve A was a 100 mesh; curve B, 200 mesh; and curve C, 325 mesh.
  • the vertical scale is the measured power consumption of the electric motor driving the shaft.
  • Such a graph as Fig. 3 naturally may be drawn for any mixtures of solids and liquids. It is recognized in the invention that if the graph exemplified by Fig. 3 should display such a maximum as is displayed by Fig. 3., then that maximum is useful in determining what the consistency of the mixture should be to provide the most efficient milling; the most efficient, that is, as determined by the prevailing fineness of a given throughput.
  • Fig. 3 shows the corresponding graph to Fig. 3 for the mixture of limestone and water, from which it can be seen that the position of the maximum, and the profile of the graph at the maximum, may even vary with the level of fineness that was chosen as a measure.
  • the upper curve A is that for 100 mesh, or 150 microns
  • the middle, B is that for 200 mesh, or 75 microns
  • the lower C is that for 325 mesh, or 45 microns.
  • Figs. 9 and-10 are the corresponding graphs to Figs. 3 and 5, when the feed rate of the coal is increased to 1200 kg/hr. through the mill. The size and positions of the various peaks can be seen to have altered, indicating again the potential importance of factors other than the liquid content on the efficiency.
  • the graph of the electric power used by the mill also displays a maximum, in dependence on the quantity of added liquid. Again, from the experiments, the maximum power was associated with the maximum cohesiveness of the mixture.
  • the width of the maximum on the graph of power against added liquid content is less than the width of the maximum on the graph of fineness against added liquid content.
  • the power peak of Fig. 4 is narrower than the fineness peak of Fig. 3.
  • the efficiency of milling to be measured in terms of the fineness of a given throughput, but it should also be measured in terms of the quantity of energy consumed in producing that degree of fineness. It is recognized in the invention that because of the difference in widths of the peaks, it is worthwhile to move slightly away from the peaks: this will produce a large reduction in the amount of energy consumed, but only a small reduction in the degree of fineness produced.
  • the graph of Fig. 5 illustrates this effect.
  • the graph is a derivation from Figs. 3 and 4; a point on the Fig. 5 graph was found by dividing the values at the liquid content on the Fig. 3 graph from the corresponding values from the Fig. 4 graph.
  • a peak on this derived graph therefore represents an effective compromise between power consumption and fineness, insofar as these things depend upon the consistency of the mixture.
  • the graph of Fig. 5 has two peaks.
  • the mixture strength is preferable to set the mixture strength to that of the right hand peak of the two peaks, not only because that peak is highest (for that may not be the case for all mixtures and conditions) but also because the right hand peak is wider, and the wider the peak the more flexible the control means can be for keeping the liquid content at a value that gives the peak efficiency. Furthermore, even though the peak of Fig. 5 occurs at a mixture strength of about 50% added water throughput, it will be noted that the efficiency falls only very slowly as the water content is increased. There is an advantage in increasing the liquid content in that the grooves in the mill tend to empty themselves more easily the wetter the mixture.
  • the water may have to be dried off before the coal is fed into the boiler, or will evaporate in the boiler, the mixture should not be too wet. It was found that beyond about a 70% mixture strength, the benefits of increasing the water content still further were not worth the expense of the extra drying difficulties, particularly as the efficiency at strengths above 70% is starting to be significantly less than that at 50%. If the grooves are big, and thus especially not prone to clogging, the water content may be as low as 40%. Below that, the efficiency enters the trough on the Fig. 5 curve, and comminution becomes uneconomical. Further experiments have indicated that the corresponding range in the coal/oil mixture, that gives a corresponding maximum efficiency, is the range from 30% to 60% added liquid.
  • Figs. 7 and 8 are examples that show the power and derived graphs, corresponding to Figs. 4 and 5 respectively, for the limestone/water mixture illustrated in Fig. 6.
  • the liquid and solid that make up the mixture that is to be comminuted may or may not be pre-mixed before being fed into the mill. If the solid has a powder or dust content even before comminution, as coal often has, it may be preferable to add some if not all of liquid to control the dust (especially if the dust is explosive) before feeding the solid to the mill. However, the more cohesive the mixture, the more it tends to clog the conveyors and conduits, so it is usually preferable to feed dry solid and pure liquid separately into the mill, and thus to let all the mixing take place actually in the mill.
  • the material may actually be pumped into the mill, if appropriate, though the mixtures with which the invention is mainly concerned are often too cohesive to be pumped easily. Mixtures of coal and water, or coal ; and oil, may be pumped at all but the most cohesive consistencies. :
  • the quantity of added liquid throughput that gives the maximum efficiency can be determined from the graphs, either in terms of the fineness of the comminuted solid, or in terms of that fineness as compromised by the power needed to produce it or in terms of whatever other measure of efficiency is appropriate in the particular case.
  • production-scale comminution can then be proceeded with, manual or automatic controls being set up to keep the quantity constant.
  • the nature of the liquid can have an effect on the maximum, both on the "peakiness" of the maximum, and on its position.
  • oil tends to soak into the pores of coal to a less extent than does water. Therefore, less oil need be added to the coal than water to produce - the maximum.
  • the other carbon products such as coke, graphite, and carbon black, tend to display corresponding differences.
  • This carbonaceous material may also be comminuted in low molecular weight alcohols such as methanol and ethanol or in any mixture of oil, water, and alcohol.
  • Some mixtures have rheological non-linearities, such as the tendency to become psuedoplastic, dilatent, or thixotropic, which can affect the peakiness and position of the maximum.

Landscapes

  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Crushing And Grinding (AREA)
  • Disintegrating Or Milling (AREA)
  • Detergent Compositions (AREA)
EP82302460A 1981-06-02 1982-05-14 Zerkleinungsverfahren Withdrawn EP0066392A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA378877 1981-06-02
CA378877 1981-06-02

Publications (2)

Publication Number Publication Date
EP0066392A2 true EP0066392A2 (de) 1982-12-08
EP0066392A3 EP0066392A3 (de) 1984-07-18

Family

ID=4120123

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82302460A Withdrawn EP0066392A3 (de) 1981-06-02 1982-05-14 Zerkleinungsverfahren

Country Status (7)

Country Link
EP (1) EP0066392A3 (de)
JP (1) JPS5817851A (de)
AU (1) AU8382582A (de)
BR (1) BR8203258A (de)
ES (1) ES512694A0 (de)
FI (1) FI821671A7 (de)
ZA (1) ZA823402B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0238432A3 (en) * 1986-02-14 1988-07-06 Rexnord Inc. Method and apparatus for energy efficient comminution
EP0549136A3 (en) * 1991-12-23 1993-11-03 Smidth & Co As F L Method for grinding particulate material in a roller press and apparatus for carrying out the method
EP0749782A1 (de) * 1995-06-20 1996-12-27 Krupp Polysius Ag Verfahren zur Zerkleinerung von sprödem Mahlgut, insbesondere Hüttensand
WO2015091133A1 (fr) * 2013-12-18 2015-06-25 Societe Industrielle Liegeoise Des Oxydes Sa Composition d'additif de vulcanisation

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6376311A (ja) * 1986-09-17 1988-04-06 松下電器産業株式会社 金属化フイルムコンデンサの製造方法
JP2004000905A (ja) * 2002-02-07 2004-01-08 Toray Ind Inc ペーストおよびその製造方法ならびにプラズマディスプレイパネル用部材の製造方法
KR100616606B1 (ko) 2006-04-13 2006-08-25 대금환경개발 주식회사 폐콘크리트 파쇄용 수직형 임팩트 밀의 고무캡

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1685115A (en) * 1928-09-25 Apparatus for making colloidal fttel
FR603729A (fr) * 1924-10-02 1926-04-22 Broyeur mélangeur
US2999649A (en) * 1956-03-01 1961-09-12 Conct Corp Apparatus for continuously crushing and selectively discharging solid materials
FR1444809A (fr) * 1965-05-24 1966-07-08 Stein & Roubaix Perfectionnements aux broyeurs à pendulaires
US3960330A (en) * 1974-06-21 1976-06-01 Henson Howard K Method for maximizing throughput in an ore grinding system
GB1522813A (en) * 1975-09-18 1978-08-31 Gen Communication Inc Material processing apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0238432A3 (en) * 1986-02-14 1988-07-06 Rexnord Inc. Method and apparatus for energy efficient comminution
EP0549136A3 (en) * 1991-12-23 1993-11-03 Smidth & Co As F L Method for grinding particulate material in a roller press and apparatus for carrying out the method
EP0749782A1 (de) * 1995-06-20 1996-12-27 Krupp Polysius Ag Verfahren zur Zerkleinerung von sprödem Mahlgut, insbesondere Hüttensand
WO2015091133A1 (fr) * 2013-12-18 2015-06-25 Societe Industrielle Liegeoise Des Oxydes Sa Composition d'additif de vulcanisation
BE1021762B1 (fr) * 2013-12-18 2016-01-15 Societe Industrielle Liegeoise Des Oxydes Sa Composition d'additif de vulcanisation

Also Published As

Publication number Publication date
ZA823402B (en) 1983-06-29
EP0066392A3 (de) 1984-07-18
FI821671A7 (fi) 1982-12-03
ES8308715A1 (es) 1983-10-16
FI821671A0 (fi) 1982-05-12
ES512694A0 (es) 1983-10-16
JPS5817851A (ja) 1983-02-02
BR8203258A (pt) 1983-05-24
AU8382582A (en) 1982-12-09

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Inventor name: GANDOLFI, EDUARDO ANGEL JOSE