Patent Publication Number: US-3880306-A

Title: Method of charging a shaft furnace

Description:
United States Patent [1 1 Grewer et al.  
 [ Apr. 29, 1975 1 1 METHOD OF CHARGING A SHAFT FURNACE [75] Inventors: Rudolf Grewer; Herbert Hickmann; Wolfgang Welke, all of Oberhausen, Germany {73] Assignee: Thyssen Niederrhein AG Hutten-und Walzwerke, Oberhausen, Germany 122] Filed: Oct. 16, 1973 [21] Appl. N0.: 406,785  
  Related US. Application Data [62] Division of Sci. N0. 324,132,1an. 16, 1973, Pat. No.  
 Primary Examiner-Robert G. Sheridan Attorney, A gent. or F irm-Karl F. Ross, Herbert Dubno Controller -To cylinder 22 [57] ABSTRACT A housing on top of a shaft-type furnace, e.g. for the direct reduction of iron ore with a reducing gas preferably consisting in major part-of carbon monoxide and hydrogen, has a laterally opening inlet and a downwardly opening outlet. Green pellets, e.g. of iron ore, are charged into the housing through the inlet and pass with a minimum free fall into a bucket which is lowered linearly in the housing as a pile of pellets is formed in the bucket so that the top of the pile remains substantially at the same level, adjacent the discharge end of the loading device. Once the bucket has been displaced linearly downwardly to its lowermost position, the pellet feed is stopped and the input is blocked by a pivotal bell. The bottom of the bucket, which is formed by another linearly displaceable but pivotally suspended bell, is then displaced downwardly away from the sidesof the bucket and a bell temporarily blocking the outlet is also moved downwardly to allow the mass of pellets in the bucket to spill out and down into the furnace. The bells thus form alternately effective inlet and outlet gates sealing the head of the furnace against the escape of gas.  
 1 Claim, 5 Drawing Figures PAYENIEUAPMQIQB SHEET 1 BF 2 -To cylinder 22 Controller FIG. I  
  METHOD OF CHARGING A SHAFT FURNACE This is a division of application Ser. No. 324,132, filed Jan. 16, 1973, now U.S. Pat No. 3,827,584.  
 FIELD OF THE INVENTION The present invention relates to a method of charging a shaft-type furnace. More specifically, this invention concerns a gas lock type arrangement for feeding socalled green or soft ore pellets into the head of such a furnace.  
 BACKGROUND OF THE INVENTION The use of green pellets of ore, e.g. iron ore agglomerated with or without binders in the presence of moisture on pelletizing trays, in an unfired and therefore generally soft, abrasion-sensitive and low-compressivestrength state, in shaft-type direct-reduction furnace has found increasing acceptance in recent years, particularly with the advent of systems for upgrading such ores. However, because of the low cohesiveness and compressive strength, such pellets tend to crumble into powder which may block or render nonuniform the flow of gases through the furnace charge. The furnaces preferably make use of reducing gases consisting in major part of carbon monoxide and hydrogen.  
  The problem of charging such furnaces without causing breakdown of the pellets is greatly complicated by the necessity of providing at the head of the furnace a gas lock through which the pellets must be fed into the mouth of the furnace. Various solutions have been attempted, including the use of sliding-plate closures, tilting buckets and clamshell arrangements without complete success.  
 OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved system for charging green ore pellets into a shaft-type furnace whereby the aforementioned disadvantages can be obviated, i.e. the pellets can be charged into the furnace without damage while a gas-tight seal of the furnace mouth is maintained.  
  Another object is the provision of a method that serves to eliminate most of the free fall of the green pellets so that they do not break up.  
 SUMMARY OF THE INVENTION These objects are attained according to the present invention in an apparatus comprising at the head or mouth of the furnace for the direct reduction of iron ore with a gas consisting in major part of carbon monoxide and hydrogen, a gas lock housing having an upper inlet gate opening to the exterior and a lower outlet gate opening into the throat of the furnace. A  
 &#39; vertically linearly displaceable vessel or bucket is provided in this housing with an openable bottom. The apparatus is operated as follows:  
  The outlet gate, forming a gas-tight seal, is held closed and the inlet gate open, and the vessel or bucket is lifted to an uppermost position with its bottom closed (advantageously by a downwardly diverging conical bell). The pellets are then charged into this upwardly open bucket through the open inlet gate and the bucket is lowered onto the outlet gate as the bucket is filled, so that the top of the pile of pellets in the bucket remains substantially at the level of the inlet. Once the bucket (in a filled state) reaches a bottom position the pellet feed is stopped and the input gate is closed, then the bottom of the bucket and the outlet gate are opened by lowering them, to spill the charge of pellets into the furnace.  
  In such a system the free fall of the pellets is reduced to a minimum and the abrasive rubbing of the pellets against the inner walls of the housing is also minimized. The pellets are spilled out the short distance from the outlet gate to the top of the descending charge column in the furnace.  
  According to another feature of the invention, the gates are bells of generally conical configuration which fit into seats at the inlet and outlet of the apparatus housing. Another generally conical bell forms the bottom of the bucket, this bell being vertically linearly displaceable. The sides of the bucket are formed by a sleeve which is vertically linearly displaceable, as previously described, between an upper position adjacent the laterally opening inlet and a lower position. The bell forming the bottom of the bucket is displaceable downwardly away from the sleeve in its lower position along with the outlet gate to spill the contents of the bucket into the furnace on top of the charge therein. The outward and downward divergence of the bottomforming and outlet-closing bells distributes the fresh charge substantially uniformly. In accordance with yeat another feature of this invention, the pellets are charged into the housing by a transport band whose discharge end extends into the housing during charging but is withdrawn when the inlet gate is closed during emptying of the charge into the furnace.  
 DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the invention will become apparent from the following description, reference being made to the accompanying drawing in which:  
  FIG. 1 is a vertical section through the apparatus, according to the present invention;  
  FIG. 2 is a view in enlarged scale and taken in the direction of arrow II of FIG. 1 of a detail of the apparatus; and  
  FIGS. 3A, 3B and 3C are schematic views illustrating the operation of the apparatus of FIGS. 1 and 2.  
 SPECIFIC DESCRIPTION As shown in FIGS. 1 and 2, mounted on the top or head of a shaft-type furnace l for the direct reduction of iron ore is a housing 5 having an inlet opening 8 and an outlet opening 23. The inlet 8 opens laterally into the housing and is offset from the vertical axis thereof; the inlet 8 can be closed by a generally conical bell 3 which is swingable about a horizontal axis A on an arm 24 provided with a pin 25 having a ball end on which the bell 3 can rock slightly so that a tight fit is ensured against the inside of inlet 8.  
  The rocking motion allows the bell to be selfcentering in its seat. A hydraulic cylinder 22 connected to a controller 21 opens and closes the inlet 8.  
  Green (unfired) iron ore pellets P are fed into the housing 5 by means of a transport belt 2 whose one end roll 26 can be displaced horizontally linearly into and out of the housing through inlet 8 by another cylinder 9, also controlled by the unit 21.  
  Below the inlet 8, the housing 5 is formed with a cylindrical well 18 extending downwardly into the housing and having a cross-sectional area that is a fraction, here about one-sixth, of that of the cylindrical lower portion of the housing 5, the-lower edge of well 18 forming a seat for another bell 7, as described in greater detail hereinafter.  
  The outlet 23 is closed by another conical bell 4 which is vertically linearly reciprocable along an axis A by means of two cylinders 27 whose piston rods 14 pass through stuffing boxes 28 into the furnace 1 where they are connected to a traverse 13 provided at its center with an upstanding pin 29, like the pin 25, whose ball end 15 is fitted into a semispherical recess in the back of the bell 4. These cylinders 27 are also connected to the controller 21 so that they can displace the bell 4 up and down along the axis A to empty the housing 5. The inner edge of the outlet 23 is provided with an inwardly projecting seal 16 which ensures a leakproof fit of the self-centering bell 4 in this opening.  
  Inside the housing there is provided a bucket 6 having cylindrical side walls 30 with an inwardly and downwardly tapering apron at 31 to form a mouth 32 which is plugged during charging by another conical selfcentering bell 7 suspended via links 33 from the piston rod 11 of another cylinder also controlled by the controller 21. The bucket 6 rides on ribs 34 formed on the inside of the housing 5 and in its lower position illustrated in FIG. 1 rests on several supports or stops 12 which extend from the walls of the housing 5 and abut the wall 31. The lower edge of the inwardly tapered wall section 31 is formed with an outwardly flared lip 17 adapted to lie flatty on the surface of the bell 7 when this element is in or between its upper position and its central position. It should be clear that the cylinder 10 serves to raise the bucket 6 by means of the hell 7. The underside of the bell 7 is conically concave and shaped to conform to the top of the larger bell 4. The weight of a charge in the bucket, applied to the apron 31, holds the bucket sealingly against bell 7 until the bucket comes to rest on stops 12. The bell 7 can thus perform lost motion with respect to the bucket.  
  With reference to FIGS. 3A-3C, the above-described device function as follows:  
 The bells 4 and 7 are lifted all the way up so as to sealingly block the outlet 23 and lift the basket 6 to its uppermost position, as shown in FIG. 3A. In addition, in this position the bell 7 effectively sealingly blocks the bottom of sleeve 18. The cylinder 9 is actuated to introduce the end 20 of the belt 2 in through the open inlet 8 and above the shaft 18, and this belt is advanced by a motor 36 to form a pile 19 of green pellets in the shaft 18. During this operation, of course, the gate 3 is open.  
  Once the level of pellets rises above the upper end of the shaft 18, a sensor 35 actuates the controller to start slowly lowering the bell 17 so as to maintain the pile just below the level of the sensor. Lowering of the bell 7 causes the pile 19 to spill out into the bucket 6 to form a mass 20 therein, the pellets P merely moving as a mass with virtually no free fall. The bucket 6 is lowered until the bell 7 rests on top of the bell 4, as shown in FIG. 3B. In this fully lowered position the level of the topof the charge in the housing 5 is again detected and when it reaches the top of the shaft 18 the motor 36 is stopped, the cylinder 9 is retracted to pull back the belt 2, and cylinder 22 (FIG. 2) is actuated to close the gate 3. Of course the weight of the charge may be used to lower the bucket against a counteracting force of cylinder 10 to maintain the top of the pile at the level of the belt 2.  
  Thereafter, as shown in FIG. 3C, the bells 7 and 4 are lowered together to spill the mass 20 out through the outlet 23 into the interior of the furnace 1. Once the bell 7 is lowered below the position shown in FIG. 38, it moves away from the bucket 6 which remains in its lower position resting on the supports 12 so as to open up the bottom of this bucket.  
  Due to the generally conical shapes of the bells 4 and 7 the pellets P flow down over and around them smoothly so that they do not fracture and crumble. Since the top of the pile 18 is maintained just below the discharge end 20 of the belt 2, these pellets do not fall far enough to break at any time. Since the inlet and outlet bells are operated alternately, the system is effectively sealed against the escape of gas.  
 I claim:  
  1. A method of charging a shaft furnace which comprises:  
 a housing disposed above the furnace;  
 an inlet formed in said housing;  
 a gate for closing said inlet externally of said housing;  
 an outlet between said housing and said furnace below said inlet;  
 an upwardly convex outlet bell for closing said outlet;  
 an upwardly open bucket between said inlet and said outlet in said housing; and  
 a further bell engageable with the bottom of said bucket to close the latter, said method comprising the steps of: i  
 a raising said further bell against the bottom of said bucket and said bucket toward said inlet to close said inlet within said housing with said further bell;  
 b. charging pellets through said inlet into said housing and into said bucket onto said further bell while closing said outlet with said outlet bell;  
 c. linearly lowering said bucket with said further bell closed thereagainst while continuing to charge pellets into said bucket at a rate such that the top of the pile of pellets in said bucket remains at a substantially constant level adjacent said inlet and until said further bell come to rest upon said outlet bell;  
 d. closing said gate; and  
 e. retaining said bucket against further downward movement while lowering both said bells simultaneously to open said outlet and spill the pellets in said bucket into said furnace through said outlet.