US3497321A - Aggregating fine-granular mineral salt materials - Google Patents

Aggregating fine-granular mineral salt materials Download PDF

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Publication number
US3497321A
US3497321A US548910A US3497321DA US3497321A US 3497321 A US3497321 A US 3497321A US 548910 A US548910 A US 548910A US 3497321D A US3497321D A US 3497321DA US 3497321 A US3497321 A US 3497321A
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gap
rolling mill
rollers
densified
roller
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US548910A
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English (en)
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Hanns Decker
Heinz Meder
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Kloeckner Humboldt Deutz AG
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Kloeckner Humboldt Deutz AG
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/22—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by pressing in moulds or between rollers

Definitions

  • Our invention relates to a method and machinery for pressing and aggregating mineral salts, particularly potassium salts and/or sodium salts, in a rolling mill.
  • the more or less finegranular material is passed through a rolling mill equipped with conventional smooth rollers between which the salt material is compressed and shaped into slabs which are subjected to comminution by means of spiked rollers and thus converted to the coarse-granular or aggregate size more advantageous for fertilizing purposes and for easier manipulation.
  • this method may encounter difficulties on account of air being included in the fine-granular salt, particularly potassium salt.
  • the air cannot be sufficiently removed by shaking of the salt in the feed hopper or feed gap of the mill, but enters into the pressure gap between the rollers of the mill together with the salt.
  • This has caused the phenomenon that the salt slabs resulting from the conventional rolling mill operation become striated transversely to the direction of roller rotation, the striations being formed alternately of hard zones and very soft zones.
  • the striation effect can be explained by the theory that the air inducted with the material will partly escape upwardly each time a zone of high densification is being pressed and then loosens the material directly above the narrowest spot of the pressure gap. In consequence, the material drawn into the narrowest spot of the compression gap during the next following compres sion phase is less compact and hence is pressed to a slab zone of lesser densification and strength.
  • the invention is predicated upon a surprising effect observed as soon as the width of the pressure gap in the rolling mill exceeds a given threshold value.
  • this threshold value When this threshold value is exceeded, the material no longer issues from the mill as a coherent slab extending over the entire width of the rolling mill but forms individual strips of highly densified material extending longitudinally, namely in the peripheral direction of the rollers, with non-densified fine-granular material issuing between the densified strips.
  • the width of the highly densified strips depends upon the rotational speed of the rollers and is approximately about 10 cm. or more.
  • the threshold width of the gap depends upon the size of the roller diameter and upon the constitution of the material to be densified in the rolling mill, but in each case the threshold width can be readily determined by a test run. As a rule, this width is approximately 0.6 to 0.7% of the roller diameter or more but, as a rule, does not exceed about 1% of the roller diameter.
  • the threshold phenomenon is as follows: Due to the larger width of the gap between the rollers, the quantity of air drawn into the gap together with the fine-granular mineral material is so large that it can escape only toward the sides. Consequently the escaping air loosens the material on both sides of each strip of highly densified material to such a great extent that the formation of pressed slabs in the intermediate zones is completely prevented.
  • the fine material passing through the roller gap between the strips of highly densified material is separated from the densified material by classification and may be recycled back to the rolling mill.
  • Such separation of the fines may take place immediately following the pressing operation in the rolling mill.
  • the entire output of the rolling mill, namely the densified strips as well as the fines may be entered into the comminuting machinery.
  • the minimum gap width of the rolling mill at which the highly densified longitudinal strips with intermediate non-densified areas of fine material will occur is at about 0.6 to 0.7% or more of the roller diameter.
  • the upper limit of the gap width cannot be determined with equal definiteness because the width of the longitudinal strips of highly densified material decreases gradually with increasing width of the gap.
  • Such rolling mills afford operating with gap widths of higher absolute values than mills with smaller roller diameters and can also be run at higher roller peripheral speeds thus delivering a considerably larger output quantity.
  • the threshold value of gap width also depends upon the constitution of the material. With certain types of salt, the threshold width is rather large so that it may not always be reliably certain that the densified strips have the mechanical strength required for the intended use of the granular product to be produced. It will be desirable in such cases to provide the possibility of operating with a smaller gap width of the rolling mill, while nevertheless securing the high strength of the densi fied strips produced.
  • the supply of material may be locally reduced or braked in this manner by mounting the obstacle members above the narrowest part of the roller gap.
  • a smaller quantity of material will be drawn into the gap at the localities of the obstacle members, so that these members determine from the outset respective zones in which the air, drawn elsewhere with the material into the gap, can issue out of the gap.
  • the longitudinal strips remaining beside these zones then exhibit the desired high densification and mechanical strength.
  • the above-mentioned obstacle members are formed by elongated rods or tubes which protrude from above into the region of the roller gap.
  • these members of tubes are preferablysupplied with compressed air issuing from the lower end of each tubular member. This permits providing a larger distance between the lower ends of the tubes and the narrowest spot of the roller gap, although in this manner a larger width of the non-densified zones will also result so that the delivering efliciency of the pressing operation in the rolling mill is slightly reduced.
  • the formation of alternately highly densified and non-densified strips parallel to respective rotational planes of the rollers is secured by giving the rolling-mill from the outset such a design that in predetermined zones a high densification of the material being pressed is prevented.
  • This is done, for example, by providing the peripheral surface of one or both rollers with peripheral grooves at these localities so that at these peripheral localities no appreciable densifying pressure is exerted upon the material passing through the mill. If both rollers are provided with peripheral grooves, the grooves in both rollers are preferably equally spaced and the respective grooves in one roller preferably register with those of the other.
  • FIG. 1 is a schematic lateral view of the rolling mill partly in section
  • FIG. 2 is a section along the line II--II in FIG. 1.
  • FIG. 3 is a view according to FIG. 1 showing the relative dimensions of the rollers and the gap, and tubes for the supply of compressed air;
  • FIG. 4 is a flow diagram of the method of the invention.
  • the rolling mill exemplified on the drawing comprises two pressure rollers 1, 2 with smooth peripheral surfaces.
  • the diameter of each roller is 900 mm. for example.
  • a hopper chute 3 for supplying the material to be aggregated is mounted above the rollers.
  • a roofshaped support 6 is mounted between the lateral wa ls 4 of the chute 3 at a locality perpendicularly above the gap 5 formed between the two rollers.
  • Fastened to the support 6 are a number of downwardly extending rods or tubes 7 which, relative to the axial direction of the rollers, are regularly spaced from each other, for example 140 mm.
  • the lower ends of the rod-shaped members 7 terminate above the narrowest spot 8 of the roller gap 5.
  • a sufiicient vertical spacing must remain between the lower end of each member 7 and the narrowest spot 8 of the gap. If the spacing is excessively reduced, the rods may be pulled by the entering material into the roller gap and become damaged or torn off. On the other hand, the vertical spacing of the rods 7 from the narrowest spot 8 of the roller gap must not be too large because then the desired efiect cannot be obtained. The proper spacing depends largely upon the feed conditions of the particular rolling mill. In each case, however, the spacing may remain within a conveniently wide range.
  • the obstacle rods may be given a diameter of A"; and, when operating the rolling mill with a narrowest gap width of 7 mm., the spacing between the bottom end of the rods 7 and the narrowest spot 8 of the roller gap may amount to approximately mm.
  • each rod is supplied from above with compressed air to issue from the bottom opening.
  • the carrier 6 is preferably designed as a horizontal manifold pipe 6' which communicates with the vertical tubular rods 7' and is to be connected with a supply of compressed air.
  • the obstacle rods or tubes reduce the amount of material passing through the gap at the localities where these members are situated. It can be achieved in this manner that the formation of the densified longitudinal strips takes place already at gap widths at which, without these obstacle members, there would still issue a coherent slab having the above-mentioned undesired transverse striation.
  • At least one of the rollers 1, 2 may be provided on its peripheral surface with peripheral grooves spaced from each other in the axial direction; this likewise,
  • the entire output delivery of the rolling mill was supplied to a screen-type classifier 9 in which the fines were separated from the potassium-salt strip or plate material.
  • the fines were returned into the supply chute of the rolling mill by means of a pocket conveyor not shown in the flow diagram.
  • the potassium salt strips or pieces were subsequently comminuted in an impact mill 10 and the comminuted material then classified by a screen 11 for separation of grain sizes from 0.6 to 3.5 mm.
  • the fine fraction was recycled back to the rolling mill.
  • the coarse fraction, having grain sizes larger than 3.5 mm., was recycled back into the impact mill.
  • the output delivery of granules in the desired size range of 0.6 to 3.5 amounted up to about 86% of the input supplied to the impact mill. Relative to this quantity of granulated material, the power requirement for the pressing operation, inclusive of the lifting work for recycling the fines passing through the rolling mill without being pressed, amounted to about 10 to 10.2 kwh. per metric ton of the aggregated product.
  • a rolling mill for producing agglomerated potassium, sodium and similar mineral salt material comprising two opposingly rotating rollers forming a gap between each other, means for supplying fine-granular salt material to the gap, and obstacle members mounted at said gap on the supply side of said rollers, said obstacle members having free end portions, respectively, extending into said gap but terminating short of the narrowest part of said gap, said members being fixedly spaced from each other at respective localities along said gap for minimizing the densification of the material at said localities, said gap having a width of about 0.6 to about 1% the diameter of said rollers so as to produce highly densified material in the form of longitudinal strips spaced from one another over the width of said rollers with substantially non-densified fine-granular material disposed therebetween at said localities.
  • said supply means forming a chute above said gap, and said members being mounted in the bottom portion of said chute above the narrowest part of said gap.
  • rodshaped members being tubular, open at the lower end, and forming part of means for issuing air under pressure from said open ends.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crushing And Grinding (AREA)
  • Glanulating (AREA)
  • Metal Rolling (AREA)
  • Battery Electrode And Active Subsutance (AREA)
US548910A 1965-05-22 1966-05-10 Aggregating fine-granular mineral salt materials Expired - Lifetime US3497321A (en)

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Application Number Priority Date Filing Date Title
DEK0056188 1965-05-22

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DE (1) DE1567974A1 (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838958A (en) * 1972-10-30 1974-10-01 Mallory & Co Inc P R Multi layer capacitor and apparatus for making same with screen vibrating means
US3869240A (en) * 1972-11-07 1975-03-04 Mackie & Sons Ltd J Plastic films
US3888635A (en) * 1973-09-26 1975-06-10 Ozark Mahoning Co Agglomerating sodium sulfate
DE2605099A1 (de) * 1975-02-27 1976-09-02 Freunt Ind Co Ltd Pulver-verdichtungsmaschine
WO1988008330A1 (en) * 1987-04-28 1988-11-03 Nittetsu Mining Co., Ltd. Roll crusher and method of crushing using the same
US4925382A (en) * 1988-01-26 1990-05-15 Maschinenfabrik Koppern Gmbh & Co. Kg Roller press for compacting fine-grained salts into sheets
US5362471A (en) * 1991-09-27 1994-11-08 Air Products And Chemicals, Inc. Process for producing gypsum flake from flue gas desulfurization
US20110139913A1 (en) * 2009-12-11 2011-06-16 Flsmidth A/S Milling device
US10710089B2 (en) * 2014-09-11 2020-07-14 Henry Johnson System and method for the comminution and harvesting of trees and brush type vegetation

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1459082A (en) * 1922-04-08 1923-06-19 Continental Salt And Chemical Process for preparing salt and the like
US2922189A (en) * 1957-03-05 1960-01-26 Int Nickel Co Apparatus for the production of metal strip from metal powder
US3029723A (en) * 1960-07-26 1962-04-17 Allis Chalmers Mfg Co Compacting device
US3145418A (en) * 1960-11-12 1964-08-25 Kuesters Eduard Maschf Apparatus for drawing out foils from plastic material
US3223026A (en) * 1962-05-22 1965-12-14 Weyerhaeuser Co Compacter de-aerator
US3282199A (en) * 1965-05-28 1966-11-01 French Oil Mill Machinery Flaking or crushing rolls

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1459082A (en) * 1922-04-08 1923-06-19 Continental Salt And Chemical Process for preparing salt and the like
US2922189A (en) * 1957-03-05 1960-01-26 Int Nickel Co Apparatus for the production of metal strip from metal powder
US3029723A (en) * 1960-07-26 1962-04-17 Allis Chalmers Mfg Co Compacting device
US3145418A (en) * 1960-11-12 1964-08-25 Kuesters Eduard Maschf Apparatus for drawing out foils from plastic material
US3223026A (en) * 1962-05-22 1965-12-14 Weyerhaeuser Co Compacter de-aerator
US3282199A (en) * 1965-05-28 1966-11-01 French Oil Mill Machinery Flaking or crushing rolls

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838958A (en) * 1972-10-30 1974-10-01 Mallory & Co Inc P R Multi layer capacitor and apparatus for making same with screen vibrating means
US3869240A (en) * 1972-11-07 1975-03-04 Mackie & Sons Ltd J Plastic films
US3888635A (en) * 1973-09-26 1975-06-10 Ozark Mahoning Co Agglomerating sodium sulfate
DE2605099A1 (de) * 1975-02-27 1976-09-02 Freunt Ind Co Ltd Pulver-verdichtungsmaschine
US4111626A (en) * 1975-02-27 1978-09-05 Takeda Chemical Industries, Ltd. Powder compacting machine
AU632621B2 (en) * 1987-04-28 1993-01-07 Nittetsu Mining Co. Limited Roll crusher and crushing method in use for the roll crusher
WO1988008330A1 (en) * 1987-04-28 1988-11-03 Nittetsu Mining Co., Ltd. Roll crusher and method of crushing using the same
US5088651A (en) * 1987-04-28 1992-02-18 Nittetsu Mining Co., Ltd. Roll crusher and crushing method in use for the roll crusher
US4925382A (en) * 1988-01-26 1990-05-15 Maschinenfabrik Koppern Gmbh & Co. Kg Roller press for compacting fine-grained salts into sheets
US5362471A (en) * 1991-09-27 1994-11-08 Air Products And Chemicals, Inc. Process for producing gypsum flake from flue gas desulfurization
US20110139913A1 (en) * 2009-12-11 2011-06-16 Flsmidth A/S Milling device
US8091817B2 (en) 2009-12-11 2012-01-10 Flsmidth A/S Milling device
US10710089B2 (en) * 2014-09-11 2020-07-14 Henry Johnson System and method for the comminution and harvesting of trees and brush type vegetation

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Publication number Publication date
DE1567974A1 (de) 1970-10-22
DE1567974B2 (de) 1973-09-13

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