SE192590C1

SE192590C1 -

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Publication number: SE192590C1
Authority: SE
Publication date: 1964-01-01

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KLASS INTERNATIONELLSVENSK B 02 c. 50 c:17/ PATENT- OCH REGISTRERINGSVERKET Ans. 3315/1955 inkom den 4/4 1955 utlagd den 16/3 1964 METALLURGICAL PROCESSES, INC., TORONTO, CANADA Satt att reglera driften av en kvarn fir kombinerad torrkrossning och malning TJppfinnare: D Weston Prioritet begdrd Nit den 25 maj 1954 (USA) Foreliggande uppfinning hanfor sig till ett satt att reglera driften av en kvarn for kombinerad torrkrossning och -malning i avsikt att framstalla en reglerad kornstorlek hos produkten, i vilken kvarn luft anvandes som medel for utmatning av produkten och som dr forsedd med en omkring en horisontell axel roterbar trumma, vars diameter dr minst dubbel sa stor som Magda,: och vars inre periferi är forsedd med hoga utstaende krossstavar, vilka aro fordelade langs trummans insida, och i vilken kvarn beskickningsvolymen kan vara mellan c:a 24' och 32 % av totala kvarnvolymen for erhallande av maximal produktionshastighet. I det amerikaiiska patentet 2 555 171 och i det svenska patentet 172 305 beskrives en kvarn for kombinerad torrkrossning och -malning och sattet enligt foreliggande uppfinning avser att reglera driften av kvarnar av delta slag. CLASS INTERNATIONAL SWEDISH B 02 c. 50 c: 17 / PATENT AND REGISTRATION AGENCY Ans. 3315/1955 was received on 4/4 1955 laid out on 16/3 1964 METALLURGICAL PROCESSES, INC., TORONTO, CANADA Set to regulate the operation of a mill for combined dry crushing and grinding TJppfinnare: D Weston Priority requested Nit 25 May 1954 (USA) The present invention relates to a method of controlling the operation of a mill for combined dry crushing and grinding in order to produce a controlled grain size of the product, in which mill air is used as a means for discharging the product and which is provided with a horizontal axis about rotatable drum, the diameter of which is at least twice as large as the Magda, and whose inner periphery is provided with high protruding crushing rods, which are distributed along the inside of the drum, and in which mill the loading volume may be between about 24 'and 32% of total the mill volume for obtaining the maximum production speed. U.S. Pat. No. 2,555,171 and Swedish Pat.

Sasrom angives i patentet 172 305 samt i det amerikanska patentet 2 680 568 har det visat sig, att sadana kvarnars maximala kapacitet kunde uppnas genom att rotera kvarnen med en hastighet, som Egger mellan granserna 82 och 90 % av den kritiska hastigh.eten och genom att halla en beskickningsvolym i kvarnen uppga.en.cle till 24-32 % av den totala kvarnvolymen, varvid den ideala beskickningsvolymen vanligen dr av storleksordningen cirka 27 % av kvarnvolymen. Sasrom is disclosed in U.S. Patent 172,305 and U.S. Pat. No. 2,680,568. It has been found that the maximum capacity of such mills could be achieved by rotating the mill at a speed maintaining a load volume in the mill amounts to 24-32% of the total mill volume, the ideal load volume usually being of the order of about 27% of the mill volume.

Studier av det satt, pit vilket malfaktorerna i Adana kvarnar paverka:s av olika forhallanden, ha visat, att vid drivning av en kvarn av det ovan beskrivna slaget det ar mojligt att reglera kross- och malfaktorernas inbordes forhallande for att erhalla produkter, som till overvagande delen ha en i forvag bestamd och onskad kornstorleksfordelnin.g. Studies of the type in which the grinding factors in Adana mills are affected by different conditions have shown that when operating a grinder of the type described above, it is possible to regulate the inboard ratio of the crushing and grinding factors in order to obtain products which the predominant part have a predetermined and desired grain size distribution.g.

Med »krossning» avses en sonderbrytning av materialstycken genom sammantryckande krafter, under det att med »malning» avses sOnderbrytning av material genom gnidning av partikelytorna mot varandra. I kvarnen, som skall regleras enligt foreliggande uppfinning ager bade krossning och malning rum. Det finns ett antal foreteelser, som ager rum i kvarnen, vilka resultera i »mai:fling» och dessa benamnas »malfaktorer». Likaledes firms ett antal fareteelser som resultera i »krossning» och dessa benamnas »krossfaktorer». By "crushing" is meant a probe breaking of pieces of material by compressive forces, while by "grinding" is meant breaking of material by rubbing the particle surfaces against each other. In the mill, which is to be regulated according to the present invention, both crushing and grinding takes place. There are a number of phenomena which take place in the mill, which result in «mai: fling» and these are called «malfactors». There are also a number of hazards that result in "crushing" and these are called "crushing factors".

Det har visat sig, att far givna kvarnhastigheter malfaktorerna huvudsakligen aro direkt proportionella mot beskickningsvolymen i kvarnen, medan krossningsresultatet ar beroende av beskiekningsvolymen inom relativt kritiska granser och avsevart reduceras, dit beskickningsvolymen varieras i vasentlig grad i endera riktningen. Nar saledes malfaktorn har silt maximum ar krossfaktorn relativt Ii-ten, och nar krossfaktorn har silt storsta maximum liar malfaktorn ett avsevart lagre varde an sitt maximum. Genom att variera den totala kvarnbeskickningen kan kvarnskotaren avva.ga kross- och malfaktorerna i fOrhallande till varandra, varigenom saledes produkter, svarande mot specifikationer om ett start omrade, kunna frambringas. It has been found that given mill speeds the grinding factors are mainly directly proportional to the loading volume in the mill, while the crushing result depends on the loading volume within relatively critical limits and is considerably reduced, where the loading volume varies significantly in either direction. Thus, when the grinding factor has a maximum, the crushing factor is relatively small, and when the crushing factor has the largest maximum, the grinding factor is a considerable layer at its maximum. By varying the total mill load, the mill forwarder can balance the crushing and grinding factors in relation to each other, whereby thus products, corresponding to specifications of a starting area, can be produced.

I en kvarn for kombinerad torrkrossning och -maltning av det ovan. beskrivna slaget, strava alla partiklarna i beskickningen morn vissa zoner att under kvarnens drift rotera kring en egen axel, som ar paraliell med kvarnens, rotationsaxel. Kvarnens malningsverkan ar huvadsakligen ett result at av, att dessa roterande partiklar 'iota pa varandra. Det har visat sig att sjalva beskickningsvolymen ãr huvudfaktorn vid reglering av krafterna mom kvarnen f8r att erhalla en onskad finhet hos det malda materialet och att em derma beskickningsvolym. Ras finfOrdelningskrafter- 2— — na okas och mangden, finmalningsarbete, som gores, okar i motsvarande utstrackning. Samtidigt minskas, am beskickningens volym iikas till ett varde, dar slag- eller krosszonen har vasentlig utstrackning bakom ett vertikalplan genom kvarnaxeln, kraftigt den grundlaggande krossningen pa grund av, att de av krosstavarna utdelade krosslagen dam-pas pa satt som beskrives i amerikanska patentet 2 680 568, och slutligen minskar aven malningsverkningsgraden, dâ partiklarna icke langre vrida sig kring sina axlar. In a mill for combined dry crushing and malting of the above. described stroke, all the particles in the mission must, in certain zones, rotate around a separate axis during the operation of the mill, which is parallel to the axis of rotation of the mill. The grinding action of the mill is mainly a result of these rotating particles superimposing on each other. It has been found that the actual loading volume is the main factor in regulating the forces at the mill in order to obtain a desired fineness of the ground material and to increase the loading volume. The grinding forces are increased and the amount of grinding work that is done increases to a corresponding extent. At the same time, if the volume of the charge is equalized to a value where the impact or crushing zone has a substantial extent behind a vertical plane through the mill axis, the fundamental crushing is greatly reduced due to the crushing strokes dispensed by the crushing rods in the manner described in U.S. Pat. 680 568, and finally the grinding efficiency also decreases, as the particles no longer rotate around their axes.

Ovanstaende iakttagelse star i direkt liontrast till den antagna teorin for vanliga kulkvarnar och liknande, enligt vilken reduktionsgraden for varje partikel huvudsakligen bestammes av grip- eller nypvinkeln mellan angransande malkroppar oberoende ay beskickningsvolymen (mellan de normala arbetsvolym.erna 35-55 % av kvarnvolymen) och kvarnens produktionshastighet bestammes huvudsakligen av beskickningsvolymen. The above observation is in direct contrast to the accepted theory of ordinary ball mills and the like, according to which the degree of reduction for each particle is mainly determined by the grip or nip angle between adjacent grinding bodies regardless of the loading volume (between the normal working volumes 35-55% of the mill volume). the production rate of the mill is mainly determined by the loading volume.

Sattet enligt uppfinningen kannetecknas i huvudsak darav, att for att erhalla en gray medelkornstorlek anyandes en beskickningsvalym, som ligger under den mot maximal produktionshastighet svarande beskickningsvolymen och for att erhalla en fin medelkornstorlek anvandes en heskickningsvolym, som ligger Over den mot maximal produktionshastighet svarande beskickningsvolymen samt att ingaende gods inmatas med en sadan hastighet, att den Onskade beskickningsvolymen halles konstant. The method according to the invention can be characterized mainly by the fact that in order to obtain a gray average grain size requiring a loading volume which is below the loading volume corresponding to the maximum production rate and in order to obtain a fine average grain size a loading volume is used which exceeds the maximum production rate. Incoming goods are fed at such a rate that the desired mission volume is kept constant.

Uppfinningen beskrives nedan narmare under hanvisning till bifogade ritningar. The invention is described in more detail below with reference to the accompanying drawings.

Fig. 1 user en schematisk tvarsektion lagd genom mittplanet i en kvarn for kombinerad torrkrossning och -malning av det slag, Yid vilken sattet enligt uppfinningen tillampas, fig. 2 en delvis schematisk vy av en typisk malkrets, innefattande den i fig. 1 visade kvarnen, fig. 3 ett diagram askadliggorande partikelstorlekens variation for olika beskickningsvolymer under ett typiskt provforsok, Oar serpentinperidodit maldes, fig. 3a ett diagram askadliggorande en malkurvas allmanna form vid en kvarn av det ovan beskrivna slaget samt fig. 4 ett blockschema, askadliggorande en lamplig regleringskrets lamplig for anvandning i samband med forfarandet enligt uppfinningen. Fig. 1 uses a schematic cross-section laid through the center plane of a mill for combined dry crushing and grinding of the kind to which the set according to the invention is applied, Fig. 2 a partial schematic view of a typical grinding circuit, comprising the mill shown in Fig. 1. Fig. 3 is a diagram showing the variation in particle size variation for different loading volumes during a typical test run. Serpentine peridodite was ground; suitable for use in connection with the method according to the invention.

Sasom framgar av ritningarna, sarskilt fig. 1 och 2, kannetecknas trumman 10 av ett stort forhallande mellan diameter och langd I det att trummans diameter alltid ãr atmins- tone tva ganger 15.ngden. Samtidigt uppbar trumman vid sin hare periferi ett flertal hoga krosstavar 11, vilka aro jamnt fOrdelade och pa tillrackligt avstand fran vara.ndra, sa att det material, som reduceras i kvarnen, icke tenderar att kilas fast mellan krosstavarna och Rams med runt i trummans rotationsroraise. Dessutam kunna ett antal olika infodringselement uppbaras air trummans andvaggar, t. ex. elementen 12 (se fig. 2), for att utova yissa sarskilda funktioner. Dessa infodringselement och deras funktion beskrives mera ingaende i det amerikanska patentet 2 555 171 och I patentet 172305. As can be seen from the drawings, in particular Figures 1 and 2, the drum 10 can be characterized by a large ratio between diameter and length in that the diameter of the drum is always at least twice the length. At the same time, at its periphery, the drum carried a plurality of high crusher rods 11, which are evenly spaced and at a sufficient distance from each other, so that the material reduced in the mill does not tend to wedge between the crusher rods and . In addition, a number of different lining elements can be supported by the air drum of the air drum, e.g. elements 12 (see Fig. 2), in order to perform various functions. These liner elements and their function are described in more detail in U.S. Patent 2,555,171 and U.S. Patent 172,305.

Trumman 10 fir forsedd med centrala Oppningar 13 och 14. Material infores i kvarnen genom oppningen 13 och lamnar kvarnen genom oppningen 14, genom vilken oppning Oxen en viss mangd uttaget material med for stor kornstorlek kan aterforas till kvarnen. Over kvarnens hela driftstid suges en luftstrom medelst flakten 15 genom oppningen 13 in i kvarnen. och ut ur kvarnen genom oppningen 14. Denna luftstroms hastighet är sadan, att den rycker med sig och transporterar ut ur kvarnen partiklar av Onskad kornstorlek. Sedan luften har strommat ut ur kvarnen fores den runt ett knaror 16, dar overstora korn falla ur luftstrommen och tillbaka till en yta 17, genom Oppningen, 14 och tillbaka in i kvarnen f Or ytterligare malning, medan huvuddelen av kvarnprodukten forblir i luftstrommen och skiljes Iran denna i en cyklon 18, frail vilken den uttages genom ett roterande luftlas 19 sasom fardigmalen produkt. Luftstrommen, som fortfarande innehailer en miss indngd mycket finfordelat material, strommar vidare genom flakten 15 och atercirkuleras genom en ledning 20 till kvarnens inloppssida. For att reglera den ktercirkulerande luftens damm- och fuktighetshalt uttages en miss mangd av den medelst en flat 21 fran atercirkuleringsledningen 20 genom en dammuppsamlare 22 och slappes ut i luften, medan en tillracklig mangd frisk luft tillfores ett stalle 23 for att uppratthalla jamyikten i luftkretsen och intern (Lamm- och fuktighetsfOrhallandena i trumman 10. Denna luftcirkulationsanlaggning beskrives i patentet 181 048. Del är emellertid gird t att foreliggande uppfinning lake ãr beroende ay denna sarskilda typ ay luftcirkulationsanlaggning, vilken beskrivits endast for att askadliggiira uppfinningen. The drum 10 is provided with central openings 13 and 14. Material is introduced into the mill through the opening 13 and leaves the mill through the opening 14, through which opening Taurus a certain amount of removed material with too large grain size can be returned to the mill. During the entire operating time of the mill, an air stream is sucked through the opening 15 through the opening 13 into the mill. and out of the mill through the opening 14. The velocity of this air stream is such that it pulls with it and transports particles of the desired grain size out of the mill. After the air has flowed out of the mill, it is passed around a grinder 16, where oversized grains fall from the air stream and back to a surface 17, through the opening, 14 and back into the mill for further grinding, while the bulk of the mill product remains in the air stream and separates. Iran this in a cyclone 18, from which it is taken out by a rotating air laser 19 as a finished product. The air stream, which still contains a missile of very finely divided material, flows further through the flap 15 and is recirculated through a conduit 20 to the inlet side of the mill. To regulate the dust and moisture content of the recirculating air, a different amount of it is taken by means of a flat 21 from the recirculation line 20 through a dust collector 22 and released into the air, while a sufficient amount of fresh air is supplied to a stable 23 to maintain the humidity in the air circuit and internally (The lamb and moisture conditions in the drum 10. This air circulation system is described in patent 181 048. However, it is to be understood that the present invention depends on this particular type of air circulation system, which is described only to illustrate the invention.

Under kvarnens drift tendera i allmanhet de materialpartiklar, som underga reduktion, att folja en naturlig bana i trumman, heroende pa sin storlek. Denna tendens askadliggores i fig. 1, vilken angiver de teoretiska ha-nor, som skulle foljas ay kulor med olika diametrar under antagande av att varje kula more fri att rora sig langs den bana, som den foredrager. En liknande situation rader for partiklar i beskickningen och allmant sett strava de storsta partiklarna att samlas nara beskickningens slag- eller krosszon 30 och transporteras icke sa Mgt upp i beskickningen pa trummans uppat sig rorande sida som de mindre partiklarna. Da partiklarna bli mind-re, medforas de hogre och hOgre upp tills de,. — —a nar de ha redneerats till en storlek av cirka 25 mm, fOras ut genom beskickningsanordningens ovre arida och strava att folja en bana for fritt fall (fig. 1). Naturligtvis forhindras i verklig drift genom den mekaniska beroringen mellan partiklar av olika storlekar fullstandig uppdelning av det slag, som antytts i fig. 1 men ritningen angiver dock den tendens, som tros i nagon man forklara de Overraskancle resultat, vilka ha uppnatts vid utOvandet av forfarandet enligt foreliggande uppfinning. During the operation of the mill, the material particles which undergo reduction generally tend to follow a natural path in the drum, depending on its size. This tendency is illustrated in Fig. 1, which indicates the theoretical shapes to be followed by spheres of different diameters, assuming that each sphere is free to move along the path it prefers. A similar situation prevails for particles in the charge and generally the largest particles struggle to collect near the impact or crushing zone of the charge and are not transported as much up in the charge on the upwardly moving side of the drum as the smaller particles. As the particles become smaller, they are carried higher and higher up until they,. - —when they have been reduced to a size of about 25 mm, are carried out through the upper arid of the loading device and strained to follow a path of free fall (Fig. 1). Of course, in actual operation, the mechanical interference between particles of different sizes prevents complete division of the kind indicated in Fig. 1, but the drawing does indicate the tendency believed in any man to explain the surprising results which have been obtained in the practice of the process. according to the present invention.

Som framgar av- fig. 1 finnes en zon, vilken utbildas pa beskickningens ovansida, genom vilken zon partiklar med en storlek av cirka 25 ram och mer studsa eller rulla tillbaka mot kvarnens botten ovanpa beskickningen och na botten i slag- eller krosszonen 30 av beskickningen. Samtidigt bildas omedelbart framfor d.enna bakre beskickningsdel 30 en. valk 31 av tillskottsmaterial, som standigt matas in i kvarnen och faller ned pa dennas botten. Sasom beskrives i det amerikanska patentet 2 680 568 agar den huvudsakliga krossningen i kvarnen rum i omradet for det bakre beskickningspartiet under inverkan av krosstavar 11, vilka drivas in. i det bakre beskickningspartiet, som innehaller de storsta partiklarna i beskickningen och darfor uppvisar den storsta trogheten. Krossningens verkningsgrad beror i forsta hand pa det faktum, att dessa storre partiklar och/eller kulor standigt na in i omradet for det bakre partiet av beskickningen, di de rora sig vertikalt neat mot trummans mantel och kontinuerligt traffas av stotar av krosstavarna 11. Det framgar att denna maximala krossverkan endast upptrader medan beskickningsvalken och den av tillskottsmaterial bildade valken 31 aro belagna pa Omse sidor om en vertikal line 32, genom trummans centrum. Det är avail uppenbart att laget av beskickningsvalken beror pa den totala beskickningsvolymen i kvarnen. Den ideala beskickningsvolymen for erhallande av maximal krossverkan iskadliggores allmant i diagrammet och motsvarar vanligen cirka 27 % av sjalva kvarntrummans totala volym. Om beskickningsmangden eller chargen avsevart minskas fran detta varde ror sig valken 30 at vanster och forblir valken av inmatat material emedan delta faller in i kvarnen vertikalt genom inloppet 13, i silt centrala lage och hela chargen blir mindre kompakt och den beskrivna krossverkan blir saledes mindre verksam. Om ft andra sidan beskickningsvolymen Okas va- sentligt utover den ideala, vilken represente- rar maximikapaciteten, ror sig valken 30 at hoger och smaller samman med valken 31, och materialmangden i zonen ovanpa. beskick- ningen Ras, vilket resulterar i en avsevard 6kning av det material, som rinner Over val- ken och blandar sig med materialet fran zonen for fritt fall med bildning av en kudde av relativt finkornigt material som resultat, varigenom krosstavarna 11 forhindras fran att utova slagverkan pa det grovkorndga ma- terialet i beskickningens slag- eller krosszon. Resultatet dr givetvis en avsevard minskning av verkan av de slag, som utdelas av krossta- varna. Samtidigt Ras emellertid friktions- eller notningszonens storlek och den tid, som varje separat partikel forblir i beskickningen, eftersom tiden for en partikels passerande genom en beskickning med stor volym ar langre an motsvarande tid for en liten volym. Dessutom har beskickningen blivit mera kompakt bade pa grund av den storre vikten av det dari inga.ende materialet och pa grund av en minskning av infodringselementets 12 stodverkan, vilket alstrar en »fastkilningsverkan», vilken finnes mera detaljerat beskriven i patentet 172 305. Resultatet blir att medan krossverkan har vasentligt reducerats, sjalva malarbetet aven reduceras, i det att partiklarna snarare slira an Trida sig kring sina axlar, vilket resulterar i slambildning eller finfordelning, vilket i manga fall icke as onskvart. Slutresultatet Or dels lagre kapacitet i ton per timme, dels en produkt av slamtyp och dels en okning av effektfOrbrukningen jamfort med den som forefinnes vid drivning av kvarnen med dess optimala kapacitet, da krossfaktorerna ni maximum. As can be seen from Fig. 1, there is a zone which is formed on the top of the embryo, through which zone particles with a size of about 25 frames and more bounce or roll back towards the bottom of the mill above the embryo and reach the bottom in the impact or crushing zone 30 of the embassy . At the same time an immediate rear part 30 is formed in front of it. choice 31 of additional material, which is constantly fed into the mill and falls to its bottom. As described in U.S. Pat. in the rear mission portion, which contains the largest particles in the mission and therefore exhibits the greatest inertia. The efficiency of the crushing is primarily due to the fact that these larger particles and / or spheres constantly reach the area of the rear part of the charge, in which they move vertically against the mantle of the drum and are continuously hit by impacts of the crushing rods 11. It is apparent that this maximum crushing action occurs only while the loading wall and the wall 31 formed of additional material are covered on opposite sides of a vertical line 32, through the center of the drum. It is avail obvious that the layer of the mission selection depends on the total mission volume in the mill. The ideal loading volume for obtaining maximum crushing action is generally damaged in the diagram and usually corresponds to about 27% of the total volume of the mill drum itself. If the amount of charge or charge is considerably reduced from this value, the wall 30 moves to the left and remains the wall of input material as the delta falls into the mill vertically through the inlet 13, in a silt central layer and the whole charge becomes less compact and the described crushing action thus becomes less effective. . If, on the other hand, the loading volume increases significantly beyond the ideal, which represents the maximum capacity, the roll 30 moves higher and narrower together with the roll 31, and the amount of material in the zone above. the mission Ras, which results in a considerable increase in the material flowing over the wall and mixes with the material from the zone of free fall, resulting in the formation of a cushion of relatively fine-grained material, thereby preventing the crushing rods 11 from impact on the coarse-grained material in the impact or crushing zone of the mission. The result is, of course, a considerable reduction in the effect of the blows distributed by the crushing rods. At the same time, however, the size of the friction or groove zone and the time that each separate particle remains in the charge, since the time for a particle to pass through a large volume charge is longer than the corresponding time for a small volume. In addition, the loading has become more compact both due to the greater weight of the material contained therein and due to a reduction in the support effect of the lining element 12, which produces a "wedging effect", which is described in more detail in patent 172 305. The result is that while the crushing action has been substantially reduced, the grinding work itself is also reduced, in that the particles rather slip on Trida around their shoulders, which results in sludge formation or comminution, which in many cases is not as bad. The end result Or partly lower capacity in tonnes per hour, partly a sludge-type product and partly an increase in power consumption compared to that which is present when operating the mill with its optimal capacity, as the crushing factors reach a maximum.

Den variation av produktens kornstorlek, som framkallas av variationer i beskickningsvolymen, iskadliggeres tydligt i fig. 3, vilken visar ett diagram Over ett prov med en kvarn av det beskrivna slaget, som hade en nominell diameter av 5,5 m och en nominal! langd av 1,6 m och i vilken serpentinperidotit frail en gruva i ostra delen av provinsen Quebec Kanada krossades och maldes. The variation in the grain size of the product, which is caused by variations in the loading volume, is clearly damaged in Fig. 3, which shows a diagram of a sample with a mill of the type described, which had a nominal diameter of 5.5 m and a nominal! length of 1.6 m and in which serpentine peridotite frail a mine in the eastern part of the province of Quebec Canada was crushed and ground.

Under loppet av d.etta fors& drevs kvarnen med elektronisk reglering, vilket mojliggjorde uppratthillandet av vilka som heist onskade driftsvillkor, och experimentdata fOr ett arttal forsok tabulerades och anvandes for uppstallande av diagramkurvorna A, B och C i fig. 3. LuftstrOmmens hastighet genom kvarnen Mils konstant under alla proven. During this process, the mill was operated with electronic control, which made it possible to maintain the desired operating conditions, and experimental data for a number of experiments were tabulated and used to plot the diagram curves A, B and C in Fig. 3. The velocity of the air flow through the mill Miles constantly during all tests.

Kurvan A askadliggar kvarnkapaciteten i ton per timme i beroende av av kvarnmotorn forbrukad effekt uttryckt i hk. Det framgar att kurvan A, som nedan kallas kapacitetskurvan, nar silt maximum vid cirka 330 hk, och darefter faller i det narmaste linj art med 6kande effekttal, tills den i omradet 520-530 hk faller snabbt. Kapacitetskurvans maximipunkt M representerar den maximala kapaciteten for kvarnen och den maximala krosseffekt, vid vilken forhallandena Mom kvarnen kunna askadliggoras i stern drag i fig. 1. Den snabba kapacitetsminskning som infra-der ungefar vid punkten P pi kapacitetskurvan, ar resultatet av att beskickningen i kvarnen blivit sO. stor, att krossfaktorerna har allvarligt forsamrats och sjalva beskickningen 4— — i sin helhet borjar oscillera sã att den viii rora sig uppat mot den uppatgaende kvarnvaggen till en ViSS punkt och sedan viii glida tillbaka. Curve A ash damages the mill capacity in tonnes per hour depending on the power consumed by the mill engine expressed in hp. It appears that curve A, which is hereinafter referred to as the capacity curve, reaches the silt maximum at about 330 hp, and then falls in the nearest line species with 6th power figures, until it falls rapidly in the range 520-530 hp. The maximum point M of the capacity curve represents the maximum capacity of the mill and the maximum crushing effect, at which the conditions of the mill can be substantially damaged in Fig. 1. The rapid decrease in capacity which occurs approximately at point P in the capacity curve is the result of the loading in the mill become sO. large, that the crushing factors have been seriously assembled and the mission itself 4— - in its entirety begins to oscillate so that it viii moves upwards towards the ascending mill wall to a ViSS point and then viii slide back.

For jamforelses skull visas en kurva A' (streckad linje), vilken askadliggor en typisk kapacitetskurva for en vanlig kulkvarn, i vilken kapaciteten vid samma siktanalys for det malda materialet gradvis okar till ett maximum, efter vilket maximum kapaciteten snabbt faller. For comparison, a curve A '(dashed line) is shown, which represents a typical capacity curve for an ordinary ball mill, in which the capacity in the same sieve analysis for the ground material gradually increases to a maximum, after which the maximum capacity drops rapidly.

B och C are kurvor for procenthalt av en viss erhallen partikelstorlek i beroende air effektfOrbrukningen. Kurva B askadliggor procenthalt erhalIen produkt med en kornstorlek mindre an 0,84 mm och kurva C askadliggor procenthalt erhallen produkt med en kornstorlek storre an 4,76 mm. Det framgar att ,dessa tva kurvor korsa varandra vid en effekt av 340 hk och att vid en hogre effektforbrukning procenthalten material mindre an 0,84 mm okar, medan procenthalt al; material storre an 4,76 mm minskar tills vid cirka 480 hk vasentligen hela produkten är mindre an 4,76 mm. B and C are curves for the percentage of a certain obtained particle size in dependent air power consumption. Curve B ash content percentage obtained product with a grain size less than 0.84 mm and curve C ash content percentage obtained product with a grain size larger than 4.76 mm. It appears that these two curves intersect at a power of 340 hp and that at a higher power consumption the percentage of material less than 0.84 mm increases, while the percentage of al; material larger than 4.76 mm decreases until at about 480 hp essentially the entire product is smaller than 4.76 mm.

Vid vanliga torrmalningskyarnar skulle mot kurvorna B och C och med kurva A' beslaktade kurvor vara vasentligen parallella och horisontella, da kornstorleksfordelningen i produkten Iran sadana kvarnar huvudsakligen beror pa den typ av malkroppar, som anvandes och icke pa beskickningsvolymen, sasom her visats vara fallet med sadana kvarnar for kombinerad torrkrossning och torrmalning, som avses i f8religgande uppfinning. Uppskattning air de faktorer, som deltaga md reglering ay malningen i sadana kombinerade kvarnar som beskrivits har varit mojlig endast efter utvecklandet av effektiva regleringsorgan for uppratthallandet av vasentligen konstanta beskickningsvolymer i kvarnen. I kvarnar av detta slag fir vanligen den forsta krossningsverkan mycket snabb, och varje minskning eller &fling av den hastighet, med vilken material inmatas i kvarnen, resulterar snabht i en okning eller minskning av beskickningsvolymen i kvarnen. Manuella regleringsmetoder giva en jamfOrelsevis stor variation air beskickningsvolymen, vilket gör en uppskattning av hur produktens partikelstorlek varierar med beskickningsvolymens variation oerhort sva'r. Ehuru misstankar hade funnits, att en del air variationen i produkten fran en kvarn for kombinerad torrkrossning och -malning av det beskrivna slaget stod i samband med beskickningsvolymen, her det icke forran effektiva regleringsranordningar av det i patentet 176 095 beskrivna slaget utvecklats varit mojligt att bestamma, att det fanns ett direkt funktionssamband mellan kornstorleken for den produkt, som erholls frail sa.dana kvarnar, och beskickningsvolymen under kvarnarnas drift. Med hjalp av dessa regleringsanordningar, som Ora det mojligt att uppratthalla en given beskicknin:gsvolym aven da man arbetar med en storre beskickningsvolym an den, som giver maximal kapacitet, (beskickningsvolymen är alltsa tankt sasom en funktion am kvarnmotorns hk-tal) liar det kunnat visas, att det ar mojligt att driva en kvarn av detta slag pa ett sadant satt, all produkter, svarande mot produktspecifikationer inom ett relativt vitt omrade, kunna erhallas helt enkelt genom att under drift halla en beskickningsvolym mom kvarnen, vilken star i ett visst i fOrvag bestamt volymforhallande till kvarntrummans totala volym. In the case of ordinary dry grinding clouds, the curves B and C and curved with curve A 'would be substantially parallel and horizontal, as the grain size distribution in the product such mills depends mainly on the type of grinding bodies used and not on the loading volume, as shown here. such mills for combined dry crushing and dry grinding as contemplated in the present invention. Estimation of the factors involved in regulating the grinding in such combined mills as described has been possible only after the development of effective control means for maintaining substantially constant loading volumes in the mill. In mills of this kind, the first crushing action usually proceeds very rapidly, and any decrease or fling of the rate at which material is fed into the mill, quickly results in an increase or decrease in the loading volume of the mill. Manual control methods give a comparatively large variation in the loading volume, which makes an estimate of how the particle size of the product varies with the variation of the loading volume extremely difficult. Although there had been suspicions that some air variation in the product from a mill for combined dry crushing and grinding of the type described was related to the loading volume, it was not possible to determine previously ineffective control devices of the type described in patent 176,095. , that there was a direct functional relationship between the grain size of the product obtained from such mills and the loading volume during the operation of the mills. With the help of these control devices, which make it possible to maintain a given load volume even when working with a larger load volume than that which gives maximum capacity, (the load volume is thus intended as a function of the mill engine hk number) it has been possible shows that it is possible to operate a mill of this kind in such a way that all products, corresponding to product specifications within a relatively wide range, can be obtained simply by maintaining a loading volume between the mill during operation, which is in a certain FOrvag determined volume ratio to the total volume of the mill drum.

Det ãr givet att det i allmanhet icke vid drift enligt sattet enligt uppfinningen Kr utforbart att direkt mata den verkliga beskickningsvolymen i kvarnen, och det ar dad& bekvamt att uppratta onskade forhallanden med hjalp av malkurvan, pa vilken varje punkt representerar kNarnens arbete med en. speeiell heskiekningsvolym. En typisk malkurva for en kvarn air det ovan beskrivna slaget med kombinerad torrkrossning och -malning visas i fig. 3A, vilken erhallits genom att pricka in kapaciteten i ton per timme i beroende av beskickningsvolymen. Ay fig. 3A framgar, att malkurvan nar silt maximum vid punkten X, vilken representerar den beskickningsvolym, vid vilken kvarnen her sin storsta kapacitet. Vid punkten till vans-ter om punkten X pa malkurvan Ms i allmanhet gravre kornstorlekar, medan punkter till hOger om punkten X representera forhallanden, liar avsevart mera finmalningsarbete gores i kvarnen. Det framgar, att om man vet pa vilken sida om punkten X de onskade driftvillkoren falla, den erforderliga effekten i hk for att driva kvarnen vid den onskade punkten kan bestammas, och det ar mojligt att stalla den onskade kornstorleksfordelningen i direkt samband med av motorn fOrbrukad effekt i hk. It is a given that in operation according to the method of the invention it is generally not feasible to directly feed the actual load volume in the mill, and it is convenient to establish desired conditions with the aid of the grinding curve, at which each point represents the work of the grinder with one. speeiell heskiekningsvolym. A typical grinding curve for a mill of the type described above with combined dry crushing and grinding is shown in Fig. 3A, which is obtained by plotting the capacity in tons per hour depending on the loading volume. Fig. 3A shows that the grinding curve reaches a silt maximum at point X, which represents the loading volume at which the mill has its largest capacity. At the point to the left of point X on the grinding curve Ms, in general, heavier grain sizes, while points to the right of point X represent ratios, considerably more fine grinding work is done in the mill. It appears that if one knows on which side of the point X the desired operating conditions fall, the required power in hp to drive the mill at the desired point can be determined, and it is possible to set the desired particle size distribution in direct connection with the engine consumed power in hp.

Det framgar av det oven sagda att den onskade driftpunkten for erhallande ay en viss produkt maste bestammas experimentellt for varje sarskild malgodstyp, som skall finfordelas. Harfor maste man forst bestamma pa vilken sida om punkten X ph malkurvan, som den onskade punkten ar belagen, marcher belagenheten pa malkurvan ay den punkt, som svarar mot den onskade speciella produkten, skall bestammas. Det ar emellertid givet, att med beskaffenheten av variationen ay produktens kornstorlek med beskickningsvolymen i minne det ar en enkel sak att i varje sfirskilt fall bestamma den onskade driftpunkt, vilken maste uppratthallas far att erhalla den onskade produkten. Det fir sarskilt viktigt att observera den reglering av slam, som kan utforas enligt uppfinningen. Genom att arbeta till vanster om punkten X i fig. 3a kan en produkt innehallande mycket litet eller inlet slam erhallas, medan mid — — arbete till hOger om punkten X pa malkurvan slampartiklar erhallas i en reglerad utstrackfling, sa att da man onskar en produkt med hog slammhalt detta kan forverkligas helt enkelt genom att valj a en lamplig arbetspunkt till linger om punkten X pa malkurvan. It appears from the above that the desired operating point for obtaining a certain product must be determined experimentally for each particular type of mold, which is to be finely divided. Therefore, it must first be determined on which side of the point X ph the grinding curve, in which the desired point is located, the location on the grinding curve at the point corresponding to the desired particular product is to be determined. However, given the nature of the variation in the grain size of the product with the loading volume in mind, it is a simple matter to determine in each particular case the desired operating point which must be maintained in order to obtain the desired product. It is particularly important to observe the control of sludge which can be carried out according to the invention. By working to the left of point X in Fig. 3a, a product containing very little or no sludge can be obtained, while mid - - work to the right of point X of the grinding curve sludge particles are obtained in a regulated extent, so that when a product with high sludge content this can be realized simply by selecting an appropriate working point at points X on the grinding curve.

Sasom forut namnts finnas lampliga regleringsanlaggningar for hallande av beskickningen i en kvarn vid den anskade volymen beskrivna i patentet 176 095. Sarskilt lampligt Sr att anvanda en regleringsanordning av det slag, som beskrives i sistnamnda patent. Denna regleringsanordning styr matningen till kvarnen i beroende av en differenssignal, som erhallits genom att jamfora en. regleringssignal, som Sr beroende av ett driftsforhallande i kvarnen med en referenssignal, vilken svarar mot ett anskat tillstand for detta driftforhallande i kvarnen. As previously mentioned, suitable control devices for holding the charge in a mill at the claimed volume are described in patent 176 095. Particularly suitable is to use a control device of the type described in the latter patent. This control device controls the supply to the mill in dependence on a difference signal obtained by comparing one. control signal, which Sr depends on an operating condition in the mill with a reference signal, which corresponds to a required state for this operating condition in the mill.

En forenklad sehematisk bild av en sadan regleringsanlaggning visas i fig. 4. Regleringssignalen alstras i organ, vilka representeras av organet 40, medan referenssignalen alstras separat for sig av organ 41. De tva. signalerna jamforas i en komparator 42 och differenssignalen Iran denna anvandes, sedan den forstarkts i en forstarkare 43 for reglering av en proportionerande matare 44, som matar in material i kvarnen 45 med en hastighet, som alias eller minskas i beroende av den i komparatorn 42 alstrade differenssignalens riktning och styrka. A simplified sehematic view of such a control system is shown in Fig. 4. The control signal is generated in means, which are represented by the means 40, while the reference signal is generated separately by means 41. The two. the signals are compared in a comparator 42 and the difference signal Iran is used, after being amplified in an amplifier 43 for controlling a proportioning feeder 44, which feeds material into the mill 45 at a rate which is aliased or reduced depending on the generated in the comparator 42. the direction and strength of the difference signal.

Regleringssignalen kan alstras antingen av kvarnljudet medelst en dynamisk mikrofonpickupanlaggning eller den kan alstras av den av kvarnmotorn forbruka:de effekten medelst I. ex. en elektronisk wattmatare. I stallet far att anvanda ljud som kalla for regleringssignalen kan vibration anvandas, och i Edda fallen kan det vara anskvart att anvanda endast ett utvalt frekvensomrade far att eliminera icke direkt till den i kvarntrumman pagaende malningen horande vibrationer och ljud. I stort sett foredrager man att alstra en regleringssignal pa ett sadant satt att den star i funktionssamband med det frail kvarnen liarrörande ljud, som liar en frekvens av Over 2000 p/s, vilket slags ljud liar visat sig i hog grad tillfredsstallande for att representera verkliga forhallanden inom trumman. The control signal can be generated either by the mill sound by means of a dynamic microphone pickup system or it can be generated by the power consumed by the mill motor by means of I. ex. an electronic watt feeder. Instead of using sound as a cold for the control signal, vibration can be used, and in Edda cases it may be appropriate to use only a selected frequency range father to eliminate vibrations and sounds not directly related to the milling in the mill drum. In general, it is preferred to generate a control signal in such a way that it is in functional relationship with the frail mill sounding sound, which has a frequency of Over 2000 p / s, which kind of sound has been found to be highly satisfactory to represent real conditions within the drum.

Om man anvander effekten for regleringen, kan man a:nvanda en ljudsignal som Overvakare for att halla effekten pa den ratta sidan S malkurvan. Detta Sr endast onskvart nar man! efterstravar en till slam maid produkt eller ,arbetar nara kurvans topp. If you use the power for the control, you can use an audible signal as a Monitor to keep the power on the right side S of the grinding curve. This is only unfortunate when you! strives for another slam maid product or, works near the top of the curve.

Valet mellan effekt och ljud eller vibration som kalla for regleringssignalen beror vasentligen pa, p5 vilken del ax kapacitetskurvan den driftpunkt, som det Sr onskvart att uppratthalla, befinner sig. Den kvarnmotorn tillfarda effekten Sr en mera tillfredsstallande regleringssignal vid sma. beskickningsvolymer, medan ljud eller vibration i allmanhet Sr mera tillfredsstallande, nar man arbetar med starre beskickningsvolymer. Vad foreliggande uppfinning betraffar framgar det vid betraktande av kurvorna i fig. 3, att man for finmalningsarbete vanligen arbetar med en storre beskickningsvolym an den som giver maximal kapacitet, medan det far grovmalning kan vara anskvart att arbeta till vanster om punkten M pa kurvan A. I manga fall och sarskill om den onskade driftpunkten ligger i omradet for maximal effekttillforsel kan det vara onskvart att anvanda en sammansatt regleringssignal eller anvanda en regleringssignal, alstrad medelst en av de ovannamnda kallorna och styrd av en andra signal, erhallen frau den andra kallan. Anvandningen av sammansatta regleringssignaler beskrives i patentet 176 095. Oavsett vilken regleringssignal Man anvander, jamfores signalen med en referenssignal med en styrka, som representerar den anskade beskickningsvolym, vid vilken man avser att arbeta, och materialinmatningshastigheten i kvarnen varieras i beroende av den sa alstrade differenssignalens riktning och styrka. Pa detta satt kan: beskickningsvolymen i kvarnen hallas konstant inom relativt tranga gamer, varigenom det blir majligt att i averraskande stor utstr5.ckning reglera den sa. erhallna produktens kornstorlek. The choice between power and sound or vibration which is called the control signal depends essentially on which part of the capacity curve the operating point which it is difficult to maintain is located. The mill motor supply power Sr a more satisfactory control signal at small. mission volumes, while sound or vibration in general is more satisfactory when working with larger mission volumes. As far as the present invention is concerned, when looking at the curves in Fig. 3, it appears that for fine grinding work one usually works with a larger loading volume than that which gives maximum capacity, while for coarse grinding it may be difficult to work to the left of point M on curve A. In many cases and especially if the desired operating point is in the range of maximum power supply, it may be unwise to use a composite control signal or to use a control signal, generated by one of the above-mentioned sources and controlled by a second signal, obtained from the second call. The use of composite control signals is described in patent 176,095. direction and strength. In this way: the loading volume in the mill can be kept constant within relatively narrow gamers, whereby it becomes possible to regulate it so to a surprisingly large extent. obtain the grain size of the product.

Produkten frail en sadan kvarn, i vilken beskickningsmaterialet utsattes far torrkrossfling och torrmalning, som beskrivits ovan uttages i en luftstrom, och det Sr dfl.rfor givet att det Sr viktigt enligt foreliggande uppfinning att vidtaga atgarder (inom granser, som bestammas av kvarnens och luftsystemets kapacitet) for aii tillvarataga den del av produkten, sona har de onskade kornstorlekarna. Vid arbete enligt forfarandet enligt foreliggande uppfinning Sr det saledes nodvandigt att sakerstalla, att en luftstrom uppratthalles igenom kvarntrumman, vilken luftstrom liar tillrackligt hastighet och tillracklig volym for att medrycka och bortfora ur kvarnen den fardigmalda produkten. I allmanhet foredrar man att arbeta vid en nagot hogre hastighet och bortfora en viss mangd averstora korn, vilka separeras fran luftstraramen vid knararet 16 (se fig. 2) och vilka darefter falla tillbaka I kvarnen for ytterligare reduktion. The product frail such a mill, in which the loading material is subjected to dry crushing and dry grinding, as described above, is taken out in an air stream, and it is therefore given that it is important according to the present invention to take action (within limits determined by the mill and air system capacity) for aii take advantage of the part of the product, the zone has the desired grain sizes. When working according to the method of the present invention, it is thus necessary to ensure that an air stream is maintained through the mill drum, which air stream provides sufficient speed and sufficient volume to entrain and remove from the mill the finished ground product. In general, it is preferred to work at a slightly higher speed and remove a certain amount of oversized grains, which are separated from the air jet frame at the crank 16 (see Fig. 2) and which then fall back into the mill for further reduction.

Claims

Patent claim:

1. Set to control the operation of a mill for combined dry crushing and grinding in order to produce a controlled grain size of the product, in which mill air is used as a means of discharging the product and which is provided with a drum rotatable about a horizontal axis (10) , the diameter of which is at least twice as long as the length and 6 - - the inner periphery of which is provided with high protruding crushing rods (11), which are distributed Hugs the drum, inside, and in which mill the loading volume can be between about 24 and 32% of the total mill volume to obtain the maximum production rate, characterized in that in order to obtain a coarse average grain size a loading volume was used which is below the loading volume corresponding to the maximum production rate and in order to obtain a fine average grain size a loading volume above it was used. to the maximum production speed corresponding to the loading volume and that incoming goods are fed at such a speed that the desired shipment volume is constant.

2. Salt according to claim 1, characterized in that the stone or smaller loading volume is maintained by causing a signal corresponding to the sound generated by the mill or to the power consumption of the mill motor to regulate the input of goods to the mill and that the sound or the power consumption is Mlles mainly constant at a value which corresponds to the thinned mission volume. Request Publications: U.S. Patent Papers. 2 555 171, 2 674 413, 2 680 568.