Patent Publication Number: US-3874644-A

Title: Rabble cleaning device

Description:
United States Patent Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-Kasper T. Serijan; Eugene J. Kalil Grimes, decreased 5] Apr. 1, 1975 [54] RABBLE CLEANING DEVICE [57] ABSTRACT Inventor: George Grimes, decreased, l of The combination of a rabble arm and a rabble arm u g m M ry Grlmes, cleaning device is provided comprising a rabble arm executrix extending radially outward from a vertically disposed 73 A I A l N N rotatable shaft for moving said rabble arm in a circular isslgnee max nc ew York Y path. The rabble arm has blades (or rakes) which ex- Flled! Mar. 7, 1974 tend downwardly therefrom for contacting and raking particulate metalliferous material in a roasting hearth.  
 [2]] Appl 448842 The rabble arm cleaning device which is cooperably associated with said rabble arm comprises a hammer [52] US. Cl 266/20, 432/75, 432/139 assembly pivotally mounted on said rabble arm, the  
 [51] Int. Cl. F27b 9/18 pivotally mounted assembly having a weighted longitu- Field of Search dinal member disposed below the pivot and extending 266/2 24 longitudinally of said rabble arm in gravity contact with said blades, a cam-reacting member being dis- [56] References Cited posed above said pivot with its free end extending UNITED STATES PATENTS above said rabble arm for making contact with a sta- 1.s3e 002 12/193! Balz 432/75 tionary Cam disPOsed in the Path of travel Said reacting member, said cam-reacting member and said weighted member forming a coacting couple about said pivot.  
 4 Claims, 7 Drawing Figures RAW so, GAS JULFIDE 012E W l 114C... 23 z/ I FEED SEAL CALL INE DISCHARGE WENTEDAPR 3 ,874,644  
 SHKU 1 OF 5 RAW 30 6/15 sumus 012E FEED SEAL CA L C I N E DISCHARGE FIG! PATENTED 1 Salli? 2 OF 5 FIG. 2  
 PATENTED APR 1 9 5 saaznaufs PATEHTED 1 l975 sum u o 5 ATENTEQ APR 1 I95 SHEET 5 BF 5 RABBLE CLEANING DEVICE This invention relates to a rabble arm cleaning device for use in combination with rabble arms in roasting furnaces. such as the multiple hearth Herreshoff roaster.  
 STATE OF THE ART It is well known to convert sulfur-containing metalliferous materials, c.g., copper sulfide concentrates, molybdenum sulfide concentrates, and the like, to their corresponding oxides by roasting in a furnace hearth. For example, the conversion of molybdenum to molybdenum oxide is carried out in a multiple hearth furnace of the type variously referred to as Herreshoff, Nichols, Nichols-Herreshoff, Wedge, Skinner and other types of roasting furnaces.  
  The roasting of sulfide concentrates involves exothermic reaction which generates a great deal of heat. In order to insure uniform oxidation of the concentrate, it is continually rabbled using rabble arms which move in a circular path through the particulate charge, the rabble arms having spaced blades or rakes which work their way through the bed of the charge to assure continuous exposure of the charge to&#39;the oxidizing atmosphere. As the sulfide charge converts to the oxide, there is a tendency for the product to adhere to the blades. The action is progressive and eventually closes the space between the blades to the degree that they no longer function adequately.  
  Presently. the rabbles are cleaned manually by an operator using a long bar to bump each blade as the rabble arms pass a door opening. Depending upon the hearth and the operating conditions, the rabbles are cleaned from one to several times each shift. Thus, the continuous cycle of roasting varies from clean rabbles on the one hand to obstructed rabbles on the other, etc.. which can adversely affect the product between cleaning cycles.  
  As manual cleaning is quite time-consuming, the operator work load increases to an objectionable degree as production is increased to higher levels and/or as the number of rabble arms is increased from two to four on each hearth.  
 OBJECTS OF THE INVENTION It is thus an object of this invention to provide a rabble arm cleaning device which continually cleans the rabbles during the roasting cycle.  
  Another object is to provide a rabble arm cleaning device in the form of an assembly coupled to a rabble arm, such that as the rabble arm continually moves through the bed ofthe charge. the assembly coacts with cam means in the hearth to effect cleaning of the rakes on the rabble arm.  
  These and other objects will more clearly appear from the following disclosure and the accompanying drawings. wherein:  
  FIG. 1 is a vertical section ofa typical multiple hearth furnace showing rabble arms in each of the hearths;  
  FIG. 2 is a partial section of several hearths showing the rabble arms more clearly;  
 FIG. 3 is a top view of FIG. 2 taken along line 3-3;  
  FIGS. 4, 5 and 6 are front elevation, plan and side elevational views. respectively, of a fragment of arabble arm showing a pivotally mounted hammer assembly for use in cleaning the rabble arm blades or rakes; and  
  FIG. 7 is a perspective of a rabble arm fragment showing more clearly the hammer assembly mounted to the back thereof.  
 THE INVENTION In its broad aspects, the invention is directed to the combination of a rabble arm and a rabble arm cleaning device comprising a rabble arm extending radially outward from a vertically disposed rotatable shaft for moving said rabble arm in a circular path about said shaft, the rabble arm having blades extending downwardly therefrom for contacting and raking particulate metalliferous material in a roasting hearth, and a rabble arm cleaning device cooperably associated with said rabble arm comprising a hammer assembly pivotally mounted to said rabble arm.  
  The hammer assembly has a weighted longitudinal member disposed below the pivot and extends longitudinally of said rabble arm in gravity contact with said blades and a cam-reacting member disposed above said pivot with a free end thereof extending above the rabble arm. The cam-reacting member and the weighted member form a coacting couple about the pivot; that is to say, as the cam-reacting member is caused to pivot by contacting cam means in the hearth, the weight member is lifted away from the blades in an arcuate path due to the coacting couple effect, such that when the cam-reacting means is disengaged from the hearth cam means during rotary movement of the rabble arm, the weighted member drops by gravity along said arcuate path and strikes the blades to dislodge any particulate material adhering thereto.  
  As stated hereinbefore, the problem of cleaning rabble arms arises in multiple hearth roasting furnaces of the Herreshoff type illustrated in FIG. 1. The furnace 10 illustrated for use in roasting molybdenum sulfide ore is comprised of an outer shell 11 of suitable heat resistant material supported on legs 12, the furnace having a plurality of multi-level hearths 13, each having a centrally located axial opening through which a hollow shaft 14 passes and is rotatably supported by a base 15. The hollow shaft is provided with a bevelled gear 16 which is driven by drive gear 17 mounted on motor 18 which is supported on pillow block 19. The hollow shaft is provided with an air feed opening 20 through which air is fed, the hollow shaft having air exit openings at each hearth level through which the air flows into the rabble arms at each hearth level while circulating from the bottom to the top of the furnace. Gas is fed by means (not shown), the gas conventionally circulating as shown by the arrows. However, certain of the hearths may have outlet flues to promote cross flow (note FIG. 2). The air flow serves a two-fold purpose: it helps to keep the furnace from overheating, otherwise the calcined material tends to stick together and, secondly, it provides the necessary oxidizing atmosphere for roasting the ore. Each hearth has associated with it rabble arms 21 which project radially outward from the shaft. Thus, as the shaft rotates, the sulfide concentrate is fed from the top of the furnace and falls from hearth to hearth as the concentrate is being rabbled. If the concentrate clogs the blades by sticking, then uniform feeding is adversely affected. The rabbling is such that, on one hearth, the particulate material is rabbled outwardly and deposits on the next hearth below, the rabble arms on the next hearth being adapted to move the concentrate radially inwardly until it deposits on the next succeeding hearth below it, and so on. As the concentrate or particulate material courses its way downward, it is converted to an oxide and is discharged as calcine at the bottom at 22. As the S forms, it leaves with the flue gas at the top through flue exit 23.  
  Generally speaking, under ordinary roasting conditions, the temperature profile may reach a steady state. The temperature appears to be highest at hearths No. 2 to No. 4, the temperature falling within the range of about l,200 to l,350F. The temperature on these hearths is frequently above the control temperature, while the temperature at the lower hearths is generally controlled under conventional practice. Sticking of the calcine can be a problem at the higher temperature.  
  The rabble arms are shown in more detail in FIGS. 2 and 3.  
  FIG. 2 is a fragmented section in elevation of a multihearth roasting furnace of the type shown in FIG. 1, FIG. 3 being a plan view taken along line 33 of FIG.  
 2. Using the same numerals of FIG. 1, a fragment of the vertically disposed hollow shaft 14 is shown passing centrally through hearths 13A, 13B, 13C and 13D which extend radially inward from shell 11. For clarity, only one set of rabble arms 21 is shown. In the case of top hearth 13A, the rabble arms (not shown) move the material being roasted inwardly towards the hollow shaft where it drops off of hearth 13A onto hearth 13B, where it is rabbled outwardly (towards the furnace wall or shell) by rabble arms (not shown) where the material drops through openings 13B-1 onto the next succeeding hearth 13C, the material then being rabbled inwardly by arms 21, the material dropping off of hearth 13C onto hearth 13D below, and so on. In the case of sulfur-containing ore or concentrate, the byproduct sulfur dioxide is exhausted through flue 23.  
  The shell 11 is normally provided with door openings 30 at each hearth level for entrance with a bar for striking the rabbles to dislodge calcine sticking to blades 31.  
  The combination of the rabble arm and rabble arm cleaning assembly is shown in detail in FIGS. 4 to 7.  
  Thus, the front elevational view of FIG. 4 and the plan view of FIG. show a fragment of a rabble arm 21 having a plurality of spaced blades 31 depending downwardly therefrom, said blades being freely supported by means of a dove-tail coupling 32 (note FIG. 6) via a mating slot 33 running longitudinally along the bottom of the rabble arm. The rabble arm is supported by a vertically disposed rotatable shaft (not shown) in FIGS. 4 to 7, reference in this connection being made to FIGS. 1 to 3. The rabble arms comprise two or more for each hearth.  
  The hammer assembly is pivotally supported by the rabble arm, the assembly being attached to the back of the rabble arm (note FIGS. 6 and 7). Thus, in FIG. 7 the hammer assembly is designated generally by the numeral 34.  
  The hammer assembly is comprised of a shaft 35 to which is rigidly attached at one end thereof a camreacting member 36 in the form of a crank arm comprising spaced arms 36A 36B rigidly fixed to shaft 35, the free end of the arms having a roller 37 supported therebetween for making contact with a fixed cam surface 38 attached to hearth 39 shown fragmentarily in FIG. 4.  
  Shaft 35 rests in two or more brackets 40 cast as an integral part ofthe rabble arm (note FIG. 7). As will be noted, the brackets have U-shaped slots 40A therein for receiving and supporting shaft 35. Depending downwardly from shaft 35 and rigidly attached thereto are a series of spaced crank arms 41 for supporting a weight member 42 in the form of a bar in gravity contact with each of the blades 31 of the rabble arm. That is to say, bar 42 traverses and contacts all of the blades so that when the bar is allowed to drop (as will be described later), it strikes all of the blades to dislodge adhering particulate material therefrom.  
  As the rabble arms rotate counterclockwise around the hearth, cam-reacting roller 37 contacts stationary cam 38 which, in FIG. 6, causes cam-reacting member 36 to move along a counterclockwise are as shown by the arrows. This results in a coating couple vis-a-vis crank arms 41 which similarly move in a counterclockwise arc as shown causing weight member or bar 42 to move to a vertical height H above its original position. Thus, when roller 37 of cam-reacting member 36 has moved to the end of the stationary cam 38, it is freely released to return to its original position as the weight member or bar 42 drops by gravity to strike across blades 31. The impact dislodges material which may have accumulated on or against the rabble blades in the interval between the cam positions (38) around the.  
 hearth.  
  As has been stated hereinabove, the moving parts of the hammer assembly are carried by each rabble arm. Thus, there is no problem of synchronizing the motion of the bar 42 with the motion of the rabble blades.  
  The cams 38 are rigidly attached to the stationary walls of the hearth, preferably at door openings 30, to allow for access during maintenance. The number of hammer strikes or impacts per revolution of center shaft is determined by the number of cams installed on each hearth. Simultaneous operation of the assembly on all hearths is avoided by indexing the position of the fixed cams around the roaster so that impacts are substantially staggered rather than simultaneous.  
  The shaft 35 is subjected to torsional loads and exposed to temperatures in the neighborhood of about l,000 to 1,400F range. The properties of HK Alloy (also referred to as AMS 5365) appear to offer adequate tensile strength,elastic modulus and creep resistance for this application. This alloy contains by weight 24 to 28 percent chromium, 18 to 22 percent nickel, 2 percent maximum silicon, 0.2 to 0.6 percent carbon and the balance iron. The same material with an inner core of carbon steel may be used as the impact bar. For the impact bar, the outer sheath of HK Alloy provides rigidity and protection against the furnace atmosphere. The carbon steel adds mass and provides the desired ductility.  
  The magnitude of impact on the rabble blades is governed by the mass of the weighted member or impact bar, the center line distance between shaft 35 and impact bar 42, and by the are through which roller 37 moves. This are is governed by the dimensions of fixed cam 38. The crank arm may be made of heat resistant material well known in the art.  
  Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.  
 What is claimed is:  
 l. The combination of a rabble arm and a rabble arm cleaning device comprising,  
 a rabble arm extending radially outward from a vertically disposed rotatable shaft for moving said rabble arm in a circular path, said rabble arm having blades extending downwardly therefrom for contacting and raking particulate metalliferous material in a roasting hearth,  
 and a rabble arm cleaning device cooperably associated with said rabble arm comprising a hammer assembly pivotally mounted to said rabble arm, said pivotally mounted hammer assembly having a weighted longitudinal member disposed below the pivot and extending longitudinally of said rabble arm in gravity contact with said blades, and a cam-reacting member disposed above said pivot with a free end extending above said rabble arm,  
 said cam-reacting member and said weighted member forming a coacting couple about said pivot,  
 such that during rotary movement of said rabble arm in a hearth, said cam-reacting member is caused to strike a stationary cam disposed in the path of travel of said cam-reacting member, whereby said cam-reacting member is caused to rock about the pivot to raise and release said weighted member which strikes said blades to dislodge any particulate material adhering thereto.  
 2. The cleaning device of claim 1, wherein said hammer assembly comprises a shaft pivotally mounted to and along said rabble arm, wherein said cam-reacting member is rigidly integral with said shaft and extends upwardly therefrom. and wherein said weighted member is a bar supported below said shaft by at least two spaced crank arms rigidly coupled to said shaft and extending downwardly therefrom.  
  3. The cleaning device of claim 2, wherein the said shalt is pivotally supported by spaced brackets integral with said rabble arm.  
 4. The combination of a rabble arm and a rabble arm cleaning device comprising,  
 a rabble arm extending radially outward from a vertically disposed rotatable shaft for moving said rabble arm in a circular path, said rabble arm having blades extending downwardly therefrom for contacting and raking particulate metalliferous material in a roasting hearth, and a rabble arm cleaning device cooperably associated with said rabble arm comprising a hammer assembly pivotally mounted to said rabble arm, said hammer assembly comprising bracket means integral with said rabble arm, a rotatable shaft supported by said bracket means and running longitudinally of said rabble arm, said shaft serving as a pivot means, a cam-reacting member rigidly coupled to said rotatable shaft and disposed upwardly thereof with a cam-actuating free end extending above said rabble arm. at least a pair of spaced crank arms rigidly coupled to said rotatable shaft and extending downwardly therefrom, and a weighted member in the form of a bar rigidly coupled to said crank arms, said bar extending longitudinally of said rabble arm in gravity contact with said blades, said cam-reacting member and said crank arms with the weighted bar forming a coacting couple about said pivot means,  
 such that during rotary movement of said rabble arm in a hearth, the free end of said cam-reacting member is caused to strike a stationary cam disposed in the path of travel of said cam-reacting member, whereby said member is caused to rock about said pivot means and raise and release said weighted bar which strikes said blades to dislodge any particulate material adhering thereto.