AU615693B2 - System for conveying bulk materials - Google Patents

Description

FAML PI DATE 01/06/89 U WE] AOJP DATE 06/07/89 J Tr' 1. 'T 0. A C A r APPLN. I D 26154 88 PCT NUMBER PCT/A188/00091 114 r I CiSN 1-'L IJ INILL r X iNVLL. 11-~ INTERNATIONALE ZUSAMMENARBEIT AUF DEM GEBIET DES PATENTWESENS (PCT) (51) Internationale Patentklassifikation 4: (11) Internationale Verdffentlichungsnummer: WO 89/ 04445 F16K 3/02, C21B 53/46 Al (43) Internationales F16K 13/214 l 50 Verdffentlichungsdatum: 18. Mai 1989 (18.05.89) (21) Internationales tA-ktenzeichen: PCT/AT88/00091 (74) Anwalt: WOLFRAM, Gustav; Schwindgasse 7, P.O.

(22) Internationales Anmieldedatun: Bx25 -01We

A)

7. November 1988 (07.11.88) (81)-Bestimmungsstaaten: AU, JP, KR, SU.

(31) Prioritiitsaktenzcichen: A 299 1/87 Veroffentlicht (32) Prioritlitsdatum: 12. November 1987 (12.11.87) Mit internationalem..Recherchelbericht.

Vor Ablauf derfilr Anderungen der A nspruiche zugelas- (33) Prioritiitsland: AT senen Frist. Verdffentlich zng wird wiederh alt falls Anderungen eintreffen.

(71) Anmelder: VOEST-ALPINE INDUSTRIEANLA- GENBAU [AT/ATl; Gesel'schaft Turmstra~e 44, A-4020 Linz (AT).

(72) Erfinder: STASTNY, Wilhelm Berbersdorf 15, A-4211I Alberndorf RINNER, Bernhard Gabesstra~e 61, A-4030 Linz (AT).

(54) Title: SYSTEMA FOR CONVEYING BULK MATERIALS (54) Bezeichnui t EINRICHTUNG ZUM FORDERN VON SCHClTTGUT (57) Abstract In a system for conveying bulk materials (11) form the first con- 692 tamner into a second container arranged below the latter, the two con- 3Q\65 a-7 12 tainers being connected by a conveyor channel first slide and a sec- 12 ond slide arranged downstream in the direction of conveying ran each 70 3 'SN1 be moved from an inlet position (A or to a closed position (B or and 68 1 0 vice and versa perpendicular to the conveyor channel. To obtain a simple 28 A62 ~~7 reliable metering device which is adequately sealed from adjacent spaces, 423 51 metered conveying of the bulk materials is effected by dividing the convey- 22 16 or channel (10) into two parts. The first part (14) of the conveyor channel 4 51 62 opens into a lateraly offset metering chamber which opens the sec- 3 <~6 ond part (18) of the conveyor channel First slide is arranged at the57:564 junction of the first part (14) of the conveyor channel (10) within the ing chamber (16) and the second slide is arranged at the junction of the me- 12 tering chamber (16) within the second part (18) of the conveyor channel (57) Zitsamnmenfassung Die Erfindung betrifft eine Einrichtung zum F76rdern von Schfittgut (11) von einem ersten Behdlter in einen darunter angeordneten zweiten Behfllter, welche Behdlter mittels eines F6rderkanales (10) verbunden sind, wobei emn erster Schieber und emn in F6rderrichtung (12) nachgeordneter zweiter Schieber jeweils aus einer Einlagposition (A bzw.

in eine Schliellposition (B bzw. und umgekehrt quer zumn F6rderkanal bewegbar sind. Um eine Dosiereinrichtung in einfacher Bauweise, mit holier Betriebssicherheit und ausreichender Dichtheit gegeniiber angrenzenden Rdumen zu schaffen, ist zum dosierten Fi~rdern des Schiittgutes der F6rderkanal (10) zweigeteilt ausgebildet und miindet der erste Teil (14) des F6rderkanales. (10) in eine zu ihm seitlich versetzt angeordnete Dosierkammer von der der zweite Teil (18) des F6rderkaniales (10) ausgeht, wobei der erste Schieber an der Einmiindlung des ersten Teiles (14) des F6rderkanales (10) in die Dosierkammer (16) und der zweite Schieber an der Miindung der Dosierkamnmer (16) in den zweiten Teil (18) des F~rderkanales (10) vorgesehen ist.

-ii VERIFED TRANSLATION OF' z The invention relates to an arrangement for conveying bulk material from a first container into a second container arranged therebelow, which containers are interconnected by means of a conveying channel, a first slider and a second slider arranged to follow said first slider in the conveying direction each being movable transversely to the conveying channel from an opening position into a closing position and vice versa.

It has been known to use bucket wheels for conveying bulk material in doses. They are, however, of complex construction and are worn relatively quickly. Furthermore, the bucket wheels have only a low operational safety, particularly when operating at higher temperatures.

Thus, it is possible that, due to the weight of the bulk material column resting thereabove, pieces of a coarse bulk material are wedged or arrested at the entry of the supply channel into the bucket wheel region such that they block the bucket wheel. Furthermore, cakings formed at the inner wall of the bucket wheel housing when operating at higher temperatures cause the bucket wheel to get stuck due to friction.

Also pressure sluices have complex structures and become blocked frequently due to cakings formed or due to the weight of the bulk material column.

From DE-A 30 34 539 a worm conveyor arranged in a reduction shaft furnace and serving as dosing means for bulk material to be conveyed from the reduction shaft furnace into a consecutively arranged melt-down gasifier has been known. This known dosing means also has a very complex structure and is prone to operational failures due to wear and cakings formed. Furthermore, the drive motor becomes ovorloaded relatively easily. The cantilever mounting of the srew conveyor constitutes an additional failure-inducing factor.

3 hi ty' C I1 C 2 The operational failures and breakdowns occurring in the known dosing arrangements may, e.g. in a plant according to DE-A 30 34 539 lead to an interruption of the entire process, which should be avoided at all costs.

Furthermore, these dosing means often are not sufficiently sealed relative to adjacent spaces, so that a possibly desired pressure difference between these spaces cannot be maintained.

From DE-A 33 11 655 an arrangement of the initially defined kind is known which is designed as slider-bulk material lock for heterogenous solids. This known lock has at least two sliders consecutively arranged in a q conveying channel in the conveying direction, which sliders alternately close or open the conveying channel.

To prevent coarse pieces of the conveyed solids from being arrested by a slider on the side wall of the fall shaft, the first slider facing the bulk material flow leaves an opening in the fall shaft when it is in its closed position. This opening may be provided in a side chamber of the fall shaft, a locking plate serving as locking element sealing the side chamber relative to the front rim of the slider. There, this side chamber only serves for accommodating the front rim of the slider. In that case it is difficult to impart a sufficient tightness to the fall shaft closed by the first slider. Furthermore, the known arrangement is failure-prone, because upon closing of the first slider the locking plate acting as locking element becomes loaded by the material conveyed.

The invention aims at avoiding these difficulties and disadvantages and has as its object to provide a dosing arrangement of the initially defined kind that is of simple construction, has an increased operational safety and ensures a sufficient pressure loss, i.e. a sufficient throttling effect when the adjacent containers have

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3 different pressures.

According to the invention this object is achieved in that the conveying channel is designed in two parts for conveying the bulk material in doses and that the first part of the conveying channel enters into a dosing chamber arranged to be laterally offset, from which dosing chamber the second part of the conveying channel departs, the first slider being provided at the entry of the first part of the conveying channel into the dosing chamber, and the second slider being provided at the entry of the dosing chamber into the second part of the conveying channel.

When conveying bulk material from the first part of the conveying channel into the second part of the conveying channel, the first slider is in the opening position and the second slider is in the closing position so that an amount of bulk material cfined by the location of the opening position of the first slider or by the size of the dosing chamber, is conveyed into the dosing chamber and intermediately stored there. When the first slider has been shifted from the opening position into the closing position and thus the dosing chamber has been closed relative to the first part of the conveying channel, the entry of the dosing chamber into the second part of the conveying channel is freed by shifting the second slider into the opening position, and the bulk material intermediately stored in the dosing chamber is further conveyed. Thus, at least one of the two sliders is in the closing position during the entire conveying procedure, whereby the first part and the second part of the conveying channel are always sealed relative to each other and an undesired emerging of a gaseous medium from one part of the conveying channel into the other one is prevented.

4 The use of sliders as locking means ensures a high operational safety, because they are of uncomplicated construction and simple to actuate. Furthermore, blocking of the sliders due to cakings is prevented because the sliders are self-cleaning.

A preferred embodiment is characterised in that the second part of the conveying channel is laterally offset relative to the first part of the conveying channel in the same direction as the dosing chamber.

A particularly suitable embodiment is characterised in that the conveying channel parts are arranged to be approximately vertical and at least the first slider is inclined to the axis of the conveying channel parts.

Thus, the bulk material is conveyed by means of gravity and the load on the first slider caused by the weight of the bulk material is reduced.

An embodiment which is particularly suited for high operational temperatures is characterised in that the sliders are arranged to be parallel to each other and the first slider is guided on the second slider, whereas the second slider is guided on a stationary guide. Thus, no expansion problems occur when the dosing means heats up and only slight stresses or bending moments occur at the sliders.

An embodiment with particularly good sealing properties is characterised in that the first slider has a recess at its free end at its upper side facing the first part of the conveying channel. When closing the first slider, a conical pile forms in the recess, sealing the dosing chamber relative to the first part of the conveying channel. Furthermore, the recess substantially reduces the friction occurring, upon closing the first slider,

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between the first slider or the bulk material resting thereon and a corresponding sealing edge or sealing surface at the wall of the dosing chamber in the region of entry into the dosing chamber.

A further preferred embodiment is characterised in that the first slider has a front face conveying the bulk material and directed approximately perpendicular to the slider movement, whereby a particularly high filling degree of the dosing chamber can be achieved.

Advantageously, the first slider has a sealing surface abutting, in the closing position, a wall at the entry 4 to the dosing chamber, which makes the dosing chamber particularly tight.

Suitably, each slider is provided with a separate actuating means which can be activated independently )f the actuating means of the other slider.

The dosing means according to the invention is particularly well suited for a plant with a shaft furnace serving for the direct reduction of iron ore and a melt-down gasifier arranged therebelow, the shaft furnace being in flowconnection with the melt-down gasifier via several dosing means arranged at the periphery of the shaft furnace. Due to the throttling effect of the dosing means, the construction height of the shaft furnace can be reduced as compared to the shaft furnaces provided in known plants.

In the following the invention will be described in more detail and with reference to the exemplary embodiments illustrated in the drawing, wherein Fig. 1 shows a section through a part of a metallurgical vessel, with a dosing means illustrated in section.

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6 Fig. 2 represents a section along line II-II of Fig. 1, and Fig. 3 shows a detail of a further embodiment, also in section.

Fig. 4 shows a schematically illustrated plant, provided with dosing means, with a shaft furnace and a melt-down gasifier.

According to Fig. 1, in the lower region 1 of a first metallurgical container 2 a dosing means 3 is a arranged.

The chamfered bottom 4 and the cylindrical shell 5 of the first container 2 have a lining 6, 7 surrounded by a metal outer shell 8, 9. In the outer peripheral region of the bottom 4, several vertically directed conveying channels 10 are provided one of them being illustrated in Fig. 1 in section for conveying bulk material 11 stored in the first container 2 in the conveying direction illustrated by arrows 12 into a second metallurgical container arranged therebelow and not illustrated.

An upper opening provided in the transition region between shell 5 and bottom 4 of the first container 2 and tangent to the inner side 13 of the shell lining 7 forms a first part 14 of the conveying channel viewed in the conveying direction 12. This first part 14 of the conveying channel 10 enters into a dosing chamber 16 arranged below the first part 14 and laterally offset thereto towards the middle axis 15 of the vessel, which dosing chamber is provided in the lining 7 of the bottom 4 of the first container 2. In the entry region of the first part 14 of the conveying channel 10, the lining 7 of the first container 2 forms a sealing edge 17. Below the dosing chamber 16, a vertically directed pipe 18 follows which forms the second part of the conveying channel 10 and preferably has a circular cross-section, which pipe 18 is connected to the bottom of the first C7 container 2. The pipe 18 has a lining 20 surrounded by a metal shell 19 and forms the flow connection with the second container (not illustrated) A socket 21 projecting beyond the cylindrical shell and directed obliquely upwards enters in the transition range between the cylindrical shell 5 and the bottom 4 of the first container 2. The socket 21 has a lining 23 enclosing its inner space 22 and a cylindrical metal shell 24 surrounding the lining 23. The cylindrical metal shell 24 is closed by a metal front plate 25 at its end side, in which an opening 26 corresponding with the inner space 22 of the socket 21 is provided.

A cylindrizal pipe piece 28 is flanged to the front plate 25 so as to extend the socket 21 in the direction of its longitudinal axis 27 directed obliquely upwards, which pipe piece 28 is provided with a lid 30 at its free end 29, the inner space 22 of the !.cket 21 thus being sealed towards outside. In the cross-section, the inner space 22 of the socket 21 is laterally delimited by circular-arc-shaped inner walls 31, 32, and in the upper anC lower regions by plane and parallel inner walls 33, 34 of the lining 23.

The plane inner wall 33 extending parallel to the longitudinal axis 27 of the socket 21 in the lower region thus forms a supporting surface for a ground plate 35 stationarily arranged in the inner space 22.

The ground plate 35 forms a guide rail 39 of U-shaped cross-section together with guide ledges 37, 38 fastened to its upper side 36 and also extending in the direction of the longitudinal axis 27 of the socket 21 parallel to I each other, which guide rail extends approximately from the outer, front-side end 40 of the sock?' 21 into the dosing chamber 16 as far as into the second part 18 of S8 the conveying channel O10, where its free end.41 abuts a supporting surface 42 provided in the lining 7. In the region extending over the second part 18 of the conveying channel 10, a passage opening 43 is provided in the ground plate 35, for the bulk material 11 to be conveyed.

In the inner space 22 of the socket 21, above the guide rail 39, two immediately superposed sliders 44, 45 are mounted, both being shiftable in the direction of the longitudinal axis 27 of the socket 21, the slider plates 46 of the upper, first slider 44 being arranged at the entry 48 of the first part 14 of the conveying channel into the dosing chamber 16, and the slider plate 47 of the second slider 45 provided therebelow being arranged at the entry 49 of the dosing chamber 16 into the second part 18 of the conveying channel IThe guide rail 39 serves for guiding the slider plate 47 of the lower, second slider 45, which slider plate, on its lower side 50, is provided with guiding grooves 51 corresponding to the guiding ledges 37, 38.

The slider plate 47 of the second slider 45 has an upper side roof--shaped in cross-section, with guiding surfaces 52 arranged at an oblique angle to each other, which form a prism guide 54 for the lower side of the slider plate 46 of the first slider 44, which has corresponding sliding surfaces 53. The upper side 55 of the slider plate 47 of the second slider 45 extends approximately parallel to the upper inner wall 34 of the socket 21.

The slider plate 46 of the first slider 44 has a recess 57 at its free end 56 facing the conveying channel on its upper side 58 facing the first part 14 of the conveying channel. At the free end 56 of the slider plate 46 of the first slider 44 a front face 59 conveying C 9 9 the bulk material l is furthermore provided which is directed approximately at a right angle to the longitudinal axis 27 of the socket 21, i.e. to the shifting direction.

The slider plate 47 of the second slider 45 has a sloping 62 on its free end 60, on its upper side 61 facing the dosing chamber. On each of the slider plates 46, 47 of the first and second sliders 44 and 45, respectively, at the outer ends 63, 64 thereof, i.e. facing away from the conveying channel O10, an actuation rod 65, 66 extending parallel to the longitudinal axis 27 of the socket 21 is arranged, which each is followed by a piston rod 67, 68 of a pressure medium cylinders 69, 70 extending the actuating rod 65, 66. The piston rods 67, 68 penetrate the lid 30 of the pipe piece 28 and are each guided in a cylinder housing 69', 70' of the first and second pressure medium cylinder 69, 70, respectively, fastened to the lid 30 of the cylindrical pipe piece 28.

The first slider 44 is movable by actuating the first pressure medium cylinder 69 from an opening position A clearing the entry 48 of the first part 14 of the conveying channel 10 into the dosing chamber 16 and illustrated in the drawing in full lines into a closing position B locking off the first part 14 of the conveying chaniial 10 and illustrated in dot-and-dash lines (in which the first slider 44 reaches into the dosing chamber 16 with its free end 56), and vice versa. Analogously, the second pressure medium cylinder 70 serves for shifting the second slider 45 from a closing position B' locking off the entry 49 of the dosing chamber 16 into the second part 18 of the conveying channel 10 and illustrated in full lines, into an opening position A' clearing the entry 49 and illustrated in dot-and-dash lines, and in the opposite direction, FThe manner in which the arrangement functions will be ~w O, L _i .3D explained in more detail below: The bulk material 11 to be conveyed from the first container 2 into the second container arranged therebelow gets via the first part 14 of the conveying channel 10 into the dosing chamber 16 that is closed relative to the second part 18 of the conveying channel 10 by means of the second slider The amount of bulk material 11 to be conveyed or the filling degree of the dosing chamber 16, respectively, can be dosed by the opening position A of the first slider 44, by which the entry 48 of the first part 14 of the conveying channel 10 can be opened to a greater or lesser degree. Subsequently, by actuating the first pressure medium cylinder 69 the first slider 44 is moved into the closing position B, in which the slider plate 46 extends into the dosing chamber 16 with its free end 56.

The thickness of the slider plate 46 of the first slider 44 is somewhat less than the clearance of the entry 48, whereby a gap 71 is formed between the slider plate 46 and the sealing edge 17 in the lining 7. When closing the first part 14 of the conveying channel 10 a conical pile of bulk material forms in the recess 57 at the free end 56 of the slider plate 46, which, commonly with the gap 71, forms a dynamic gas seal and ensures a sufficient tightness of the dosing chamber 16 relative to the first part 14 of the conveying channel 10. Furthermore, due to the recess 57 the friction between the bulk material 11 and the sealing edge 17 is kept low, so that also abrasive bulk material does not cause an excessive abrasion and the actuating force required for closing the first slider 44 is kept low. It is, however, also possible to design the slider plate 46 without such a recess, the thickness of the slider plate 46 being selected such that the upper side of the slider plate 46 sealingly contacts the sealing edge 17 in the closing 11 position B. During the closing procedure, the front face 59 provided on the free end 56 of the first slider 44 conveys further bulk material 11 into the dosing chamber 16 in addition to the bulk material 11 that has automatically flowed into the dosing chamber 16, whereby the dosing chamber 16 can be filled more or less completely, depending on the distance passed by the first slider 44, which means, also the right hand upper region 72 of the dosing chamber 16 in Fig. 1.

When the entry 48 of the first part 14 of the conveying channel 10 into the dosing chamber 16 has been closed by the first slider 44, the second slider 45 is moved into F the opening position A' by actuating the second pressure medium cylinder 70 in the opposite direction, and the entry of the dosing chamber 16 into the pipe 18 forming the second part of the conveying channel 10 is cleared.

The bulk material 11 drops through the pipe 18 arranged at the lower side of the first container 2 into the container therebelow (not illustrated).

When the dosing chamber 16 has been emptied, the entry 49 of the dosing chamber 16 into the second part 18 of the conveying channel 10 is closed by actuating the second pressure medium cylinder 70 and shifting the second slider 45 into the closing position Subsequently, the entry 48 of the first part 14 of the conveying channel 10 into the dosing chamber 16 is cleared again by shifting the first slider 44 into the opening position A, and a further charge of the bulk material 11 to be conveyed gets into the dosing chamber 16.

During the entire conveying procedure at least one of the two sliders 44 or 45, respectively, is in the closed position B or respectively, whereby the first part 14 and the second part 18 of the conveying channel 12 are always sufficiently sealed relative to each other and an undesired escape of a gaseous medium is prevented.

A further advantage of the arrangement is that the sliders 44, 45 are self-cleaning, cakings thus being avoided.

Due to the slanted position of the first slider 44, only little force is required for actuating the first slider 44, because the bulk material 11 to be conveyed,due to gravity largely gets automatically into the dosing chamber 16 when opening the entry 48. Since the two sliders 44, 45 are guided parallel to each other and the first slider 44 is guided on the second slider 45, no expansion problems occur when the dosing means 3 heats up, so that the dosing means is ready for use also at high temperatures. Furthermore, loads or bending moments acting on the sliders 44, 45 themselves thus kept low.

Acr-rdCing to the embodiment illustrated in Fig. 3, the slider plate 46' of the first slider 44 has a sealing surface 74 directed parallel to the vertical wall 73 of the first part 14 of the conveying channel 10, which sealingly abuts that wall 73 in the closing position B of the first slider 44. This embodiment ensures a particularly good tightness.

A preferred field of application of the dosing means is its use for a plant for producing steel according to Fig. 4 comprising a shaft furnace 75 for the direct reduction of iron ore and a melt-down gasifier 76 arranged therebelow. The shaft furnace 75 comprises several dosing means 3 provided in its lower region and is connected with the melt-down gasifier 76 via conveying ducts 77 connected to the dosing means 3. The throttling effect of the dosing means 3 makes it possible to 613 maintain the pressure difference prevailing between the shaft furnace 75 and the melt-down gasifier 76 also while the bulk material is conveyed into the melt-down gasifier 76, i.e. only very slight amounts of gas forming in the melt-down gasitier 76 can escape via the conveying channels of the dosing means 3 into the inner space of the shaft furnace The good tightness of the dosing means thus also leads to a reduction of the shaft height as compared to known shaft furnaces, considerably lowering the construction costs of the plant. The particularly simple construction of the dosing means according to the invention are r additionally cost-saving. The extremely high operational safety of the dosing means furthermore ensures lower operational and maintenance costs.

The invention is not restricted to the exemplary embodiments illustrated in the drawing, but may be modified in varisous respects. Thus other actuation means, eog. adjustment spindles, may be provided instead of the pressure medium cylinders for shifting the sliders.

Furthermore it is possible to arrange only the first slider slanted and to arrange the second slider horizontally.

According to a further embodiment, both sliders may be arranged horizontally, wherein it is possible to guide the first slider on a separate guide rail fastened to a stationary plate provided above the second slider. The first part and the second part of the conveying channel can also be arranged in alignment with each other. For particularly hot bulk material it may be suitable to provide the slider plates with a water cooling, in particular in their front end regions.

Claims (7)

1. 2. An arrangement according to claim i, characterized in that the second part (18) of the conveying channel is laterally offset relative to the first part (14) of the conveying channel (10) in the same direction as the dosing chamber (16).
2. 3. An arrangement according to claim 1 or 2, characterized in that the conveying channel parts (14, i- i i i o 15 18) are arranged to be approximately vertical and at least the first slider (44) is inclined to the axis of the conveying channel parts (14, 18).
3. 4. An arrangement according to one or several of claims 1 to 3, characterised in that the sliders (44, 45) are arranged to be parallel to each other and the first slider (44) is guided on the second slider whereas the second slider (45) is guided on a stationary guide (39). An arrangement according to one or several of claims 1 to 4, characterlsed in that the first slider (44) has a recess (57) at its free end (56) on its upper side (58) facing the first part of the conveying channel.
4. 6. An arrangement according to one or several of claims 1 to 5, characterised in that the first slider (44) has a front face (59) conveying the bulk material (11) and directed approximately perpendicular to the slider movement.
5. 7. An arrangement according to one or several of claims 1 to 6, characterised in that the first slider (44) has a sealing surface (74) abutting, in the closing position a wall (73) at the entry (48) to the dosing chamber (16) (Fig 3).
6. 8. An arrangement according to one or several of claims 1 to 7, characterised in that each slider (44, 5) is provided with a separate actuating means (69, 70) which can be activated independently of the actuating means (69, 70) of the other slider (44,
7. 9. A plant comprising a shaft furnace (75) for the direct reduction of iron ore and a melt-down gasifier a II- I 16 (76) arranged therebelow, characterised in that the shaft furnace (75) is in flow-connection with the melt-down gasifier (76) via several of the arrangements (3) according to any one or more of claims 1 to 8 arranged at the periphery of the shaft furnace. DATED THIS 19TH DAY OF JULY 1991 VOEST-ALPINE INDUSTRIEANLAGENBAU GESELLSCHAFT m.b.H. By its Patent Attorneys: GRIFFITH HACK CO Fellows Institute of Patent Attorneys of Australia *ee• *go a a. a 17 Abstract: An Arrangement for Conveying Bulk Material The invention relates to an arrangement for conveying bulk material (11) from a first container into a second container arranged therebelow, which containers are interconnected by means of a conveying channel a first slider and a second slider arranged to follow the first slider in the conveying direction (12) each being movable transversely to the conveying channel from an opening position (A and respectively) into a closing position (B and respectively), and vice versa. To 'Provide a dosing means of simple construction, great operational safety and sufficient tightness relative to adjacent spaces, the conveying channel (10) is designed I in two parts for conveying the bulk material in doses, and the firt part (14) of the conveying channel enters into a dosing chamber (16) laterally offset thereto, from which the second part (18) of the conveying channel departs, the first slider being provided at the entry of the first part (14) of the conveying channel (10) into the dosing chamber and the second slider being provided at the entry of the dosing chamber (16) into the second part (18) of the conveying channel (Fig. 1). f. jL* T A4