US3607121A - Rotary furnace having recycle provision - Google Patents

Rotary furnace having recycle provision Download PDF

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US3607121A
US3607121A US886613A US3607121DA US3607121A US 3607121 A US3607121 A US 3607121A US 886613 A US886613 A US 886613A US 3607121D A US3607121D A US 3607121DA US 3607121 A US3607121 A US 3607121A
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Prior art keywords
furnace shell
furnace
recycling
shell
screw
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US886613A
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William E Watson
Richard P Troeger
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Allied Corp
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Allied Chemical Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B7/00—Rotary-drum furnaces, i.e. horizontal or slightly inclined
    • F27B7/14—Rotary-drum furnaces, i.e. horizontal or slightly inclined with means for agitating or moving the charge
    • 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
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/18—Stationary reactors having moving elements inside
    • B01J19/20—Stationary reactors having moving elements inside in the form of helices, e.g. screw reactors
    • 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
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/28—Moving reactors, e.g. rotary drums
    • 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
    • B01J6/00—Heat treatments such as Calcining; Fusing ; Pyrolysis
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00—Halogens; Halogen acids
    • C01B7/19—Fluorine; Hydrogen fluoride
    • C01B7/191—Hydrogen fluoride
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00—Halogens; Halogen acids
    • C01B7/19—Fluorine; Hydrogen fluoride
    • C01B7/191—Hydrogen fluoride
    • C01B7/192—Preparation from fluorspar
    • 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
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00051—Controlling the temperature
    • B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
    • B01J2219/00087—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements outside the reactor
    • B01J2219/00094—Jackets
    • 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
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00162—Controlling or regulating processes controlling the pressure

Definitions

  • a rotary furnace apparatus especially useful for carrying out a reaction of fluorspar and sulfuric acid, is provided with a mechanical recycling means within the furnace itself.
  • the recycling means is fixed to an inner shell portion of the furnace so that it rotates with rotational movements applied to the furnace shell by a single driving means.
  • the recycling means is in the form of a screw conveying device having a cylindrical tube mounted coaxially within the furnace shell, and with two spiral paths defined within the cylindrical tube for receiving and conveying residue material from a downstream area within the furnace shell to an upstream area near the inlet end of the furnace.
  • the screw conveyor is provided with a pair of scoops to pick up residue material and to deposit the material in controlled quantities into the two spiral paths defined in the conveyor.
  • the recycling means is in the form of an openended helical passageway which follows the inner cylindrical wall of the furnace shell from an area of residue pick up to the inlet end of the furnace.
  • a third type of furnace includes the use of heavy duty premixers which premix the calcium fluoride and sulfuric acid, either or both of which are usually preheated to attain partial reaction in the mixer, to insure that the feed to the furnace will not incrust the furnace wall. This arrangement does protect the furnace and eliminates the need for scraping devices, but the most corrosive part of the reaction is thereby transferred to the costly premixer.
  • the fourth type of furnace is the one used to form a portion of the required sulfuric acid by reacting steam and sulfur trioxide within the furnace.
  • Sulfuric acid in vapor phase S0 will not react with fluorspar, but by showering the reaction mass through the sulfuric vapor, condensation and reaction are attained. While this system eliminates the problem of heat transfer through the furnace wall, it is relatively expensive to operate because of the cost of the sulfur trioxide, and the necessity for con structing the furnace shell of costly corrosion resistant alloys to resist the effect of the presence of sulfuric and hydrofluoric acid mixtures.
  • the essential feature of that invention involves the use of more than 3 parts of calcium sulfate per part of byproduct calcium sulfate produced in the reaction mixture of fluorspar and sulfuric acid in the production of hydrofluoric acid and which is effectively achieved without any of the prior art difficulties.
  • the effectiveness of this method of operation is surprising and unexpected since the furnace used may operate without any scrapers, knockers, or other means conventionally employed in removing incrustation from the shell. In operation, the mass within the furnace is substantially a free-flowing solid, and the walls are never exposed to the action of the highly corrosive liquid sulfuric acid.
  • the HF produced is also of higher purity than that obtained from the types of furnaces previously discussed, because in those type furnaces the product gases contain large amounts of sulfur dioxide and elemental sulfur as a result of the reduction of sulfur acid by nascent hydrogen released during the attack or corrosion of the metal of the furnace by the acid. Elemental sulfur is particularly objectionable as it tends to deposit on heat transfer surfaces and to plug acid drip collection lines. 1
  • the present invention relates to a furnace system for the production of hydrogen fluoride which permits controlled recycling of residue within a single furnace without any requirement for external conveyors, multiple drives, or other complex and unreliable equipment.
  • the improved apparatus of this invention provides a recycle conveying system within a single rotary furnace apparatus.
  • a single drive motor can power the entire apparatus, including the internal recycle conveying system, and the recycle conveying system does not move relative to the furnace shell in which it is mounted, thereby eliminating problems of bearing supports or of erosion-accelerated corrosion between moving parts.
  • the recycling conveyor comprises a screw-conveying means in the form of a cylindrical conveyor tube having two spiral paths defined on its inner cylindrical wall.
  • the two spiral paths are offset from each other by about and are of approximately the same pitch.
  • the two paths are wound in a direction to carry residue material back towards the inlet end of the furnace apparatus when the furnace shell and the recycle conveyor are rotated in the same direction by a common drive means.
  • Each of the two spiral paths of the screw conveyor communicates with a radially extending scoop means positioned at the downstream end of the recycle conveyor.
  • the scoops are positioned to receive residue material from the reaction zone and to deposit controlled quantities of the material into their respective spiral paths with which they communicate.
  • the scoops are preferably provided with screens to sort out oversized lumps of residue material so that large, hard lumps are not introduced into the recycle conveyor.
  • the recycle conveyor is in the form of a closed tube or passageway, having open ends, and which is positioned in a helical path around the inner cylindrical wall of the reaction zone portion of the furnace apparatus. At least one such helical passageway is provided in a rotary furnace so as to extend from a residue pickup area of the furnace back to an inlet end of the furnace.
  • This embodiment is especially useful where it is desired to carry a recycle of residual calcium sulfate all the way back to the inlet end of a reaction zone which is receiving fluorspar and sulfuric acid as reactants.
  • the recycle conveyor of this embodiment functions as an effective metering device so that a desired recycle quantity can be accurately designed into the construction of a rotary furnace.
  • the recycle conveyor of this embodiment may be combined with the screw-type conveyor of the first embodiment in any given rotary furnace apparatus.
  • FIG. 1 is a side elevational view, somewhat schematic in its representation, of a rotary furnace apparatus of the type contemplated by the present invention
  • FIG. 2 is an elevational view similar to FIG. l, but on an enlarged scale and showing only a portion of the FIG. 1 apparatus with respect to a first basic embodiment of a recycling means contained within the furnace apparatus;
  • FIG. 3 is an enlarged perspective view of the downstream end of the type of recycling means used in the embodiment shown in FIG. 2;
  • FIG. 4 is an enlarged sectional view taken on lines 44 of FIG. 2;
  • FIG. 5 is a sectional view similar to FIG. 4, but viewed from lines 55 of FIG. 2;
  • FIG. 6 is an enlarged top plan view of a downstream end portion of the recycle conveyor shown in FIG. 2, as seen generally on line 6--6 but with the outside furnace jacket omitted for clarity;
  • FIG. 7 is an enlarged elevational view of a rotary furnace incorporating a second embodiment of recycling means with the first embodiment recycling means of this invention.
  • FIG. 8 is an elevational view similar to FIG. 7, showing a rotary furnace provided with recycling means in accordance with the second embodiment of the invention.
  • the rotary furnace includes an inner, cylindrical furnace shell 10 into which reactants are introduced for producing hydrogen fluoride.
  • the inner shell 10 functions as a reaction zone, and the reaction zone is preferably divided into two stages, with an upstream portion above an annular darn l2 and a downstream portion below the annular darn 12.
  • the furnace shell 10 is supported for rotation by tires 14 and trunnions 16, in a manner well known in this art.
  • a single driving means (not shown) of conventional structure is provided for rotating the furnace shell 10 through a bull or girth gear 18.
  • the illustrated apparatus is provided with a heating jacket around a major length of the furnace shell 10, and products of combustion are circulated through the heating jacket 20 by a fan means contained within a housing 22.
  • the products of combustion are generated in a combustion chamber 24 in which fuel gas or oil is burned with a controlled amount of air.
  • Known means are provided for controlling the introduction of fuel and air into the combustion chamber 24.
  • combustion gases are generated at temperatures below 1300 F. at their point of admission 26 to the heating jacket 20. Due to the volume of combustion gas which can be circulated by the fan 22, there is a temperature drop from the point of admission 26 to the exits 28 from the jacket of approximately 300 F.
  • Dampers 30 are provided in return pipes 32 to regulate the flow of hot gases to each end of the heating jacket 20.
  • the pressure of gases within the heating jacket 20 is controlled to be maintained at essentially atmospheric pressure to avoid excessive hot gas loss or cold air in-leakage across crude seals 34 provided at each end of the jacket.
  • the furnace shell 10 in which reaction takes place is provided with end walls at each end so that it is a substantially closed furnace.
  • the entire furnace assembly, including the furnace shell 10, is canted slightly so that its inlet end A is slightly higher than its outlet end B. This provides for a movement of reactants from the inlet end to the outlet end while the furnace is being rotated.
  • FIG. 2 illustrates additional details of the inlet end of the furnace apparatus.
  • the end is closed and sealed by an upright wall or head 40 which is secured to the cylindrical furnace shell 10 so as to rotate therewith.
  • the end wall 40 is preferably recessed into the furnace shell 10 for a sufficient distance to be included in the area of the furnace shell 10 which is surrounded and heated by the heating jacket 20. Since a tire 14 is provided for mounting the inlet end of the furnace on a trunnion 16, it is not possible to extend the heating jacket all the way to the very end of the furnace shell 10. Accordingly, it is preferred to define the inlet end of the reaction zone by an upright wall 40 which positions the reaction zone completely within a heated area of the furnace shell 10.
  • Reactants are introduced into the reaction zone through the upright wall 40.
  • the means for introducing reactants are conventional and include a screw feeder 42 for feeding fluorspar into the reaction zone together with an acid pipe 44 for feeding sulfuric acid into the reaction zone. There is no premixing of the fluorspar and acid prior to being mixed with recycled residue within the reaction zone, thereby avoiding the formation of a sticky mass at the inlet end of the furnace.
  • the screw feeder and pipe are mounted in a stationary housing 46 which is provided with a seal at 48. A rotating portion 50 of the housing is secured to the end wall 40 and is sealed in its movement relative to the stationary housing 46.
  • Hydrogen fluoride gas is removed from the system through the wall 40 and the stationary housing 46 by way of a flue 52.
  • This general arrangement for feeding reactants into a reaction zone and removing I-IF gas therefrom are generally known in this art and do not constitute a separate part of the present invention.
  • the downstream end of the furnace shell 10 is provided with internal lifters 54 which lift and dump calcium sulfate residue material from the end of the final reaction zone into a stationary chute 56.
  • the stationary chute 56 is provided with a conventional sealing device which has a rotating star valve 58 to prevent loss of HF gas out of the furnace through the stationary chute. Also, the valve 58 prevents an excess of air from being sucked into the furnace, although the furnace reaction area is maintained at nearly atmospheric, or slightly below atmospheric, pressure during operation.
  • At least one recycling means is positioned within the furnace shell 10 to pick up a portion of residue material from a downstream reaction area of the furnace and to return the material back to the inlet end of the furnace.
  • the recycling means is positioned to pick up residue material from the downstream end of the initial reaction zone defined above the annular dam 12 so that a preferred ratio of residue is recycled back to the inlet end of the furnace prior to final reaction of the mixture in the second reaction zone below the annular dam 12.
  • a preferred process for reacting fluorspar with sulfuric acid provides for a recycling in excess of three parts of residue material for every part of calcium sulfate produced in the reaction. The residue material not recycled is moved over the annular dam l2 and passed into the discharge end of the reaction zone.
  • FIGS. 1-6 relate to constructional features of a first basic embodiment of a recycling means in accordance with the present invention
  • FIG. 8 represents the second basic embodiment
  • FIG. 7 illustrates a preferred arrangement wherein the first embodiment of recycling means is combined with the second embodiment of recycling means.
  • the first embodiment will be referred to hereafter as a screw-type-recycling means
  • the second embodiment will be referred to as a worm-typerecycling means in the form of an open-ended, closed helical passageway formed about the inner cylindrical wall of the furnace shell.
  • a furnace system will combine both of the two types of recycling means into a single construction, but for purposes of clarity of description, the two recycling means will be described below separately.
  • Screw-Type-Recycling MEANS Referring to FIGS. 1 and 2, a screw-type-recycling means 60 is shown as being mounted in a fixed position within the furnace shell so that the entire recycling means rotates with rotational movements applied to the furnace shell 10 and without any requirement for separate driving arrangements.
  • the screw-recycling means 60 includes a cylindrical conveyor tube 62 mounted coaxially within the furnace shell 10, and the conveyor tube 62 contains two spiral or helical paths defined on its inner cylindrical wall surface. The spiral paths are,
  • the screw-recycling means is constructed to function something like an Archimedes screw conveyor for carrying residue material from a downstream area within the furnace to an upstream area within the furnace.
  • the cylindrical conveyor tube 62 is mounted within the furnace by any suitable means, such as by posts 66 positioned about its external surface, Thus, when material is deposited into the two spiral paths of the rotating-screw-recycling means 60, it is carried back towards the inlet end of the furnace, where it is dropped from an open end 68 of the conveyor tube 62. It is desirable to place the open end 68 of the recycling means as close as possible to the inlet end of the reaction zone so that reactants are mixed with recycled residue. However, it can be seen that the end of the conveyor tube 68 cannot interfere with apparatus used for the introduction of reactants into the inlet end of the reaction zone, and therefore, there is a practical limit, in the illustrated equipment, to the length of the cylindrical conveyor tube 62 that can be used.
  • the invention provides for a pair of scoop means 70 mounted at the downstream end of the screw-conveying tube 62 for picking up residue material and for depositing controlled quantities of the material into the two spiral paths defined within the screw-conveying means.
  • the pair of scoop means 70 are generally in the form of radially extending boxlike structures displaced form one another by 180 to provide a communication between the downstream end of the screw-conveying tube 62 and the inner wall surfaces of the furnace shell 10.
  • each of the scoop means 70 is in the general fonn of a boxlike structure having an open inlet end 72.
  • the open inlet of each scoop means is directed transversely across the furnace shell so that residue material being moved along within the shell can be received into the inlets 72 as the shell and recycling means 60 are rotated.
  • FIG. 2 shows the inlet ends 72 as viewed transversely across the furnace apparatus.
  • Each of the inlets 72 may be provided with screening means 74 in the form of a plurality of rods for screening out oversized lumps of residue. This prevents a scooping up and depositing of oversize lumps into the screw flights. of the conveying means.
  • the screening means 74 can be omitted, and the scoop means can be provided with completely open inlets 72.
  • the screening means 74 may be set at an oblique angle relative to the longitudinal axis of the furnace, as shown in the FIG. 6 view.
  • one scoop means functions to pick up residue material from the bottom of the furnace shell, at a given time during rotation of the shell and the recycling means, while the other scoop means deposits its load of residue material into the downstream end of the conveying tube 62.
  • the two scoop means function to alternately plow through the bed of residue material and to pick up a quantity of material for dumping into the screw-conveying means 60.
  • the annular dam 12 functions to cause a sufficient buildup of residue bed within the furnace to allow the scoop means 70 to receive desired quantities for recycle.
  • Each scoop means 70 is provided with an inclined slide 74 for depositing its load of residue into the end of the conveyor tube 62, and the relationships of the two inclined slides 74 to the end of the conveyor tube 62 are important to a successful operation of the recycling means.
  • the general relationship of each inclined surface 74 to the end of the conveyor tube 62 is shown in FIG. 2.
  • Each of the inclined surfaces 74 communicates with one of the spiral paths defined within the conveyor tube 62, although an overflow provision is made so that the quantity of material deposited into each spiral path can be controlled.
  • FIG. 3 further illustrates the positions of the inclined slides 74 as related to the end of the conveyor tube 62.
  • the slides 74 define a closed end to the conveyor tube 62 so that there is a path of communication with the inlet opening 72 of each scoop means 70.
  • the scoop means 70 are further provided with wall sections 80, 82, and 84 (see FIG. 4) to form closed boxlike structures within the furnace shell 10. These wall sections are affixed to a section 86 of the inner surface of the furnace shell to enclose the scoop means, except for their inlets 72 and their points of entry into the conveyor tube 62.
  • the screening section of each inlet may be closed off by a plate section 87 at its connection to an extended part of the cylindrical tube 62, however, the plate 87 can be omitted if desired.
  • FIG. 4 is a view from the inlet end of the furnace shell 10, showing the downstream end of the recycling means 60 at its point of communication with the scoop means 70.
  • each of the two elongated flight elements 64 which together make up the two spiral screw paths defined within the conveyor tube 62, originates along a diameter 88 of the conveyor tube.
  • the line of origination of the two elements 64 is defined by the line of juncture between the two inclined slides 74 of the scoop means 70.
  • each of the two separate spiral paths defined by the flight members 64 has an origination line which is aligned with an inclined surface 74 of one of the scoop means 70. This arrangement is quite important to a recycling means incorporating two spiral paths and utilizing two scoop means of the type disclosed in this specification.
  • FIG. 4 also illustrates the paths of movement followed by residue material within the recycling means when the furnace shell 10 and the recycling means 60 are rotated in the direction of the arrow.
  • material is picked up through the inlet 72 of the scoop means. Then, as the shell, and the recycling means therein, continue to rotate, the picked-up material falls back into a closed section of the scoop means from where it can drop down onto its associated inclined slide 74 for being deposited into the conveyor tube 62.
  • FIG. 4 shows an arrow pointing downwardly in the interior of the upper scoop means 70 to represent the fall of material down towards the upper inclined slide 74.
  • each scoop means 70 communicates with the conveyor tube 62 only for the width of its wall section 80, the remainder of the scoop means (mainly, the triangular inlet portion which includes the screening bars 72) is closed off from the conveyor tube 62 be extended portions of the conveyor tube itself (see FIG. 3).
  • residue material descends into the end of the screw-conveying means along the left half of the upper inclined slide when the scoop means is in the position shown in FIG. 4.
  • FIG. 4 also shows two separate arrows extending downwardly over the inclined slide 74 which is associated with the upper scoop means 70.
  • the left arrow illustrates the flow of material onto a flight element 64 which is generally aligned with the upper inclined slide 74.
  • a portion of the downward flow falls into one of the two spiral paths defined in the conveyor tube 62.
  • the flight element 64 the left-hand element of FIG. 4 when the scoops are in the positions indicated
  • each complete rotation advances residue material for one pitch in the tube 62 so that an empty pocket in the spiral path is presented to each scoop means when it rotates to the top position.
  • the scoop means 70 are designed to always pick up an amount of material which exceeds the quantity necessary to feed the screw flights to full capacity. This allows a complete filling of the recycle conveyor, with an overflowing of excess material into an opposed scoop. The overflow material is then deposited in the screw conveyor in the next one-half cycle.
  • the structural elements which make up the recycle means are fabricated from known materials which can resist the corrosive environment of the furnace, and all elements are assembled together by known techniques.
  • the individual spiral flight elements 64 can be welded into position within the conveyor tube 62, and their end portions at 90 can be welded along the juncture line 88 of the two inclined slides 74.
  • FIGS. 7 and 8 illustrate a second embodiment of the recycling means of this invention.
  • FIG. 7 shows the second embodiment recycling means combined with the first embodiment recycling means in a preferred arrangement for a hydrogen flouride-process furnace.
  • FIG. 8 illustrates a furnace structure utilizing only the second embodiment type of recycling means.
  • FIGS. 7 and 8 The basic furnace arrangement shown in FIGS. 7 and 8 is the same as that previously described with reference to FIGS. I and 2 above.
  • the second embodiment of this invention comprises a recycling means which may be considered a worm type of recycle conveyor having at least one helical passageway 100 formed about the inner cylindrical wall of the furnace shell 10.
  • the helical passageway is open-ended at its inlet end I02 and at its outlet end 104, but the remainder of the passageway is closed off from the interior of the furnace shell 10.
  • the helical passageway 100 may be formed around the inner cylindrical wall of the furnace shell in any suitable manner.
  • a semicircular tunnel element may be welded, or otherwise secured, about the inner furnace wall so as to provide the type of configuration illustrated in FIGS. 7 and 8.
  • the recycling means 100 is combined with the screw type of recycling means 60 discussed above.
  • Such a combination is particularly advantageous because the screw-type-recycling means 60 can handle larger quantities of recycle material to bring the recycle ratio up to a desired level whereas the worm-type-recycling means 100 can introduce recycle material to the extreme end of the reaction zone at the very point of introduction of reactants into the furnace shell.
  • the recycling means 60 cannot extend far enough towards the end wall 40 of the furnace shell to dump recycle material at the introduction point of reactants, and therefore, the second embodiment of recycling means assists in preventing a formation of a sticky, corrosive mass at the inlet end of the furnace by depositing recycle residue through its outlet 104 at the extreme end of the reaction zone.
  • Another advantage of the recycling means 100 of this embodiment is that it deposits recycle material back into the charge end of a reaction zone without dropping the recycle material through the furnace atmosphere within the furnace shell 10.
  • a dropping of material through the atmosphere of the reaction zone, especially adjacent to the point at which I-IF gas is to be withdrawn, can create a dust problem in the takeoff ducting for the HF gas.
  • the recycling means 60 of the first embodiment cannot deposit recycle calcium sulfate as close to the inlet end of a furnace as can the second embodiment recycling means 100.
  • the recycling means 100 functions by receiving a quantity of residue material into its inlet end 102 as it rotates with rotational movements of the furnace shell 10. Continued rotation of the shell and of the recycling means causes the received residue material to be carried back towards the inlet end of the furnace until it is discharged from the end 104.
  • FIG. 8 illustrates an arrangement wherein two separate recycling means 100 are formed around the inner cylindrical wall of a furnace shell so as to deposit recycle residue material from positions at the inlet end of the furnace.
  • Each of the two recycling means 100 are of the same pitch and direction so that they follow each other around the inner wall of the furnace shell 10 in a parallel relationship to each other.
  • Both of the recycling means 100 receive residue material at their open inlet ends 102 as their respective inlet ends plow through an accumulation of residue material upstream of the annular dam 12. This initiates recycling of the residue material back towards the inlet end of the furnace.
  • the recycling means 100 can function as an effective metering device to control the quantity of recycle material.
  • the dimensions of the recycling means 100 can be set to return desired portions of residue to the inlet end of the furnace.
  • a rotary furnace apparatus for carrying out a reaction of fluorspar and sulfuric acid to produce hydrogen fluoride
  • the combination comprising: a cylindrical furnace shell for receiving and reacting the fluorspar with sulfuric acid, said furnace shell having end walls and said shell being mounted with its axis slightly inclined so that reactants will move from the first end to a second end of the furnace shell; means for rotating and heating said furnace shell; inlet means for introducing reactants into said first end of the furnace shell; outlet means for removing hydrogen fluoride from the reaction zone and separate outlet means at said second end for removing final reaction residue from the furnace shell; and internal recycling means for picking up and recycling a portion of residue material from a point within the furnace shell back to the area of said first end, said recycling means comprising screw-conveying means which comprises a cylindrical conveyor tube mounted coaxially within said furnace shell, said conveyor tube containing two spiral paths defined on its inner cylindrical wall, said spiral paths being offset from each other by 180 and of the same pitch, and said spiral paths being wound in a direction to carry residue material
  • said furnace shell generally includes a first reaction zone which is upstream of a second reaction zone, and wherein said recycling means is positioned to pick up residue material from the downstream end of said first reaction zone for recycling back to the upstream end of the same reaction zone.
  • recycling means contained within a furnace shell portion of said apparatus for picking up a portion of residue material from a downstream area of the shell and returning the residue material to an upstream area of the shell, said recycling means being fixed in its position relative to the furnace shell so that it will rotate with rotational move- 5 ments, of the furnace shell, and said recycling means being in the form of a screw-conveying means having a cylindrical conveying tube mounted coaxially within said furnace shell, said conveyor tube containing two spiral paths defined on its inner cylindrical wall, said spiral paths being ofiset from each other by 180 and of the same pitch, and said spiral paths being wound in a direction to carry residue material back towards the inlet end of the furnace shell when the furnace shell and the screw-conveying means are rotated in the same direction, and including scoop means at the downstream end of said screw-conveying means to pick up residue material and for depositing controlled quantities of material into said two spiral paths of said screw-conveying means.
  • each of said recycling means being fixed in its position relative to the furnace shell so that it rotates with rotational movements of the furnace shell.
  • said first recycling means comprises a screw-conveying means defined within a cylindrical conveying tube mounted coaxially within said furnace shell, said conveying tube containing two spiral paths defined on its inner cylindrical wall, said spiral paths being offset from each other by 180 and of the same pitch, and said spiral paths being wound in a direction to carry residue material back towards the inlet end of the furnace shell when the furnace shell and the screw conveying means are rotated in the same direction, and including scoop means at the downstream end of said screw-conveying meansto pick up residue material and for depositing controlled quantities of material into said two spiral paths of said screw-conveying means.
  • said second recycling means comprises at least one open-ended, closed, helical passageway formed around the inner cylindrical wall of said furnace shell.
  • a rotary furnace apparatus for carrying out a reaction of fluorspar and sulfuric acid to produce hydrogen fluoride
  • the combination comprising: a cylindrical furnace shell for receiving and reacting fluorspar with sulfuric acid, said furnace shell having end walls and said shell being mounted with its axes slightly inclined so that the reactants will move from a 55 first end to a second end on the furnace shell; means for rotating and heating said furnace shell; inlet means for introducing reactants into said first end of the furnace shell; outlet means for removing hydrogen fluoride from the reaction zone and separate outlet means at said second end for removing final reaction residue from the furnace shell; and internal recycling means for picking up and recycling a portion of residue material from a point within the furnace shell back to the area of said first end, said recycling means comprising two openended CLOSED, helical passageways formed about the inner cylindrical walls of said furnace shell along a path which is displaced 180 from the path of the other helical passageway and extending from an area of residue pickup to said first end of the furnace.
  • a rotary furnace apparatus which is especially useful '70 for carrying out a reaction of fluorspar and sulfuric acid the improvement comprising: internal recycling means contained within a furnace shell portion of said apparatus for picking up residue material from a downstream area of the furnace shell and returning the residue material to an upstream area of the furnace shell, said recycling means being fixed in its position which is displaced 180 from the path of the other helical passageway and extending from an area of residue pickup to said first end of the furnace.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
  • Processing Of Solid Wastes (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US886613A 1969-12-19 1969-12-19 Rotary furnace having recycle provision Expired - Lifetime US3607121A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US88661369A 1969-12-19 1969-12-19
CH165271A CH548003A (de) 1969-12-19 1971-02-04 Drehofen.

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US3607121A true US3607121A (en) 1971-09-21

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US886613A Expired - Lifetime US3607121A (en) 1969-12-19 1969-12-19 Rotary furnace having recycle provision

Country Status (7)

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US (1) US3607121A (de)
CA (1) CA951091A (de)
CH (1) CH548003A (de)
DE (1) DE2048226C3 (de)
FR (1) FR2072724A5 (de)
GB (2) GB1304783A (de)
NL (1) NL7017062A (de)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3741717A (en) * 1971-12-27 1973-06-26 L Triplett Grain treating apparatuses and processes of operation thereof
US3805406A (en) * 1971-09-03 1974-04-23 A Castonoli Interchangeable path drying apparatus
US3809528A (en) * 1973-09-04 1974-05-07 Fuller Co Apparatus for cooling solid particulate material
US4010245A (en) * 1974-07-24 1977-03-01 Bayer Aktiengesellschaft Production of hydrogen fluoride and calcium sulfate
US4031191A (en) * 1975-01-30 1977-06-21 E. I. Du Pont De Nemours And Company Process for producing hydrogen fluoride
US4288217A (en) * 1980-04-28 1981-09-08 Gte Products Corporation Rotary calciner feed spiral
US4514297A (en) * 1982-12-09 1985-04-30 A. Ahlstrom Osakeyhtio Bioreactor
US4639216A (en) * 1985-04-25 1987-01-27 Schnupp's Grain Roasting, Inc. Grain roasting machine and method
US4881947A (en) * 1988-06-28 1989-11-21 Parker Thomas H High efficiency gasifier with recycle system
US5078836A (en) * 1989-07-21 1992-01-07 Hogan Jim S Method and apparatus for retorting material
US5091157A (en) * 1990-04-30 1992-02-25 Rollins Environmental Services (Tx) Inc. Recycle conduit insulation assembly
US5217578A (en) * 1989-05-22 1993-06-08 Alberta Oil Sands Technology And Research Authority Dry thermal processor
US5851361A (en) * 1996-11-25 1998-12-22 Hogan; Jim S. Apparatus for processing an organic solid
US6841140B2 (en) 2000-07-10 2005-01-11 Daikin Industries, Ltd. Method and apparatus for producing hydrogen fluoride
US20090165231A1 (en) * 2001-07-25 2009-07-02 The Libman Company Mop with attached wringer
WO2010020662A1 (de) * 2008-08-20 2010-02-25 Universität Kassel Reaktor mit einem archimedischen schraubenförderer
CN118405661A (zh) * 2024-06-28 2024-07-30 江苏三美化工有限公司 一种无水氟化氢内返渣安全生产系统及其方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2914964A1 (de) * 1979-04-12 1980-10-16 Bayer Ag Drehrohrreaktor zum waermebehandeln von gut und verfahren unter verwendung dieses drehrohrreaktors

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2986457A (en) * 1957-11-26 1961-05-30 Arthur J Jones Iron ore reduction
US3396953A (en) * 1965-12-22 1968-08-13 United States Steel Corp Kiln

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2986457A (en) * 1957-11-26 1961-05-30 Arthur J Jones Iron ore reduction
US3396953A (en) * 1965-12-22 1968-08-13 United States Steel Corp Kiln

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3805406A (en) * 1971-09-03 1974-04-23 A Castonoli Interchangeable path drying apparatus
US3741717A (en) * 1971-12-27 1973-06-26 L Triplett Grain treating apparatuses and processes of operation thereof
US3809528A (en) * 1973-09-04 1974-05-07 Fuller Co Apparatus for cooling solid particulate material
US4010245A (en) * 1974-07-24 1977-03-01 Bayer Aktiengesellschaft Production of hydrogen fluoride and calcium sulfate
US4031191A (en) * 1975-01-30 1977-06-21 E. I. Du Pont De Nemours And Company Process for producing hydrogen fluoride
US4288217A (en) * 1980-04-28 1981-09-08 Gte Products Corporation Rotary calciner feed spiral
US4514297A (en) * 1982-12-09 1985-04-30 A. Ahlstrom Osakeyhtio Bioreactor
US4639216A (en) * 1985-04-25 1987-01-27 Schnupp's Grain Roasting, Inc. Grain roasting machine and method
US4881947A (en) * 1988-06-28 1989-11-21 Parker Thomas H High efficiency gasifier with recycle system
US5217578A (en) * 1989-05-22 1993-06-08 Alberta Oil Sands Technology And Research Authority Dry thermal processor
US5078836A (en) * 1989-07-21 1992-01-07 Hogan Jim S Method and apparatus for retorting material
US5091157A (en) * 1990-04-30 1992-02-25 Rollins Environmental Services (Tx) Inc. Recycle conduit insulation assembly
US5851361A (en) * 1996-11-25 1998-12-22 Hogan; Jim S. Apparatus for processing an organic solid
US6841140B2 (en) 2000-07-10 2005-01-11 Daikin Industries, Ltd. Method and apparatus for producing hydrogen fluoride
US20090165231A1 (en) * 2001-07-25 2009-07-02 The Libman Company Mop with attached wringer
WO2010020662A1 (de) * 2008-08-20 2010-02-25 Universität Kassel Reaktor mit einem archimedischen schraubenförderer
CN118405661A (zh) * 2024-06-28 2024-07-30 江苏三美化工有限公司 一种无水氟化氢内返渣安全生产系统及其方法

Also Published As

Publication number Publication date
CH548003A (de) 1974-04-11
DE2048226C3 (de) 1980-12-18
GB1304782A (de) 1973-01-31
DE2048226A1 (de) 1971-06-24
NL7017062A (de) 1971-06-22
FR2072724A5 (de) 1971-09-24
DE2048226B2 (de) 1980-04-30
GB1304783A (de) 1973-01-31
CA951091A (en) 1974-07-16

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