RU2625138C1 - Dry dolomite processing line - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: dry dolomite processing line contains a receiving lump dolomite hopper equipped with a plate unloader, an intermediate belt conveyor for feeding lump dolomite into a drying drum equipped with a group of cyclones, a bag filter and a smoke pump for removing flue gases and trapping a fine-dispersed dolomite fraction, a transport chain feeding the captured fine-dispersed fraction into the storage hopper, consisting of a belt conveyor, a screw conveyor and the first bucket elevator, a local aspiration system connected to the storage hopper and transport-technological equipment, an impact crusher installed at the output of the drying drum, and the second bucket elevator. The input of the latter is connected to the output of the impact crusher, and the output is connected to the input of a two-sieve vibrating screen. The oversize output of the upper mesh of the two-sieve vibrating screen is connected to the input of the impact crusher. The oversize output of its lower mesh is connected to the input of the single-sieve vibrating screen, from the undersize output of which the sieved dolomite is poured onto the first input of the assembly conveyor feeding the sieved dolomite through the magnetic separator, the third bucket elevator and the first flow switch into one of the two silo jars. The line is further provided with the second flow switch, the input of which is connected to the undersize output of the two-sieve vibrating screen, and the first output is connected to the second input of the assembly conveyor, an intermediate hopper connected by its input to the second output of the second flow switch, a screw discharge feeder, the input of which is connected to the output of the intermediate hopper, the fourth bucket elevator connected by its input with the output of the screw discharge feeder, an adjustable aeroclassifier, the input of which is connected to the output of the fourth bucket elevator, as well as the third flow switch and the roller crusher. From the first output of the adjustable aeroclassifier, the isolated coarse dispersion fraction of the sieved dolomite is discharged to the third input of the assembly conveyor. From the second output, the isolated fine-dispersed fraction of the sieved dolomite is fed to the input of the screw conveyor. The under-crushed fraction of the sieved dolomite from the oversize output of the single-sieve vibrating screen enters the input of the third flow switch, the first output of which is connected to the input of the impact crusher, and the second output is connected to the roller crusher connected by its output to the input of the second bucket elevator.

EFFECT: increasing the efficiency of recovering the fine-dispersed fraction from crushed dolomite, used as a mineral powder.

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Description

The invention relates to dry enrichment devices for dolomite, used for the preparation of a glass mixture and asphalt mixtures, and can be used to enrich limestone and other non-metallic materials.

Dolomite is one of the main materials for the joint introduction of calcium and magnesium oxides into the glass. Ground dolomite in the form of finely ground mineral powder is used as one of the main ingredients in the production of asphalt mixes to improve the quality of road surfaces.

Dolomite flour produced in many glass factories in the raw material processing departments, produced in accordance with GOST 23672 Dolomite for the glass industry, does not fully meet the technological requirements for the operation of glass melting furnaces and glass melting. This is primarily due to the high content (up to 80%) of dust fractions in the ground dolomite and increased dusting during batching and loading of the charge into the glass melting furnace, which leads to active entrainment and deposition of dolomite dust in the nozzles of regenerators and to a reduction in the campaign of the furnace. In addition, the process of dissociation of finely dispersed dolomite (particle fractions less than 0.1 mm) during glass melting begins already in the loading pocket and to a lesser extent contributes to the subsequent processes of clarification and averaging of glass melt. Therefore, for the successful conduct of the processes of preparing the mixture and cooking high-quality glass, ground dolomite should be coarse-grained powders in which 80-90% of the material is made up of particles ranging in size from 0.1 to 2.0 mm.

But due to the fact that when crushing lumpy dolomite, depending on its hardness, from 25 to 35 percent of dust particles are formed, it is necessary to reduce this amount of finely dispersed dolomite and partially isolate it from the general mixture of finely divided and finely divided dolomite, if this material is intended for preparation glass charge. At the same time, according to the technological requirements of a number of glass factories, the particle size distribution of crushed dolomite should contain: 5-10% of particles with a size of 1.6-2 mm; 10-5% of particles with a size of 1.0-1.6 mm; 10-15% of particles with a size of 0.63-1.0 mm; 10-15% of particles 0.315-0.63 mm in size; 30-40% of particles 0.1-0.315 mm in size; and 10-20% of particles smaller than 0.1 mm. However, it should be noted that not all finely dispersed dolomite with a particle size of less than 0.315 mm must be isolated from this mixture, since particles of the fine fraction of dolomite during the preparation and wetting of the glass mixture together with particles of soda ash and other components should envelop the silica sand grains, facilitating them subsequent melting at the initial stage of glass melting.

A finely divided product with a particle size of less than 0.315 mm, isolated partially from this mixture of crushed dolomite, can be used in various industries, including the production of asphalt mixes as a mineral filler.

The known line [1] of dry enrichment of materials of the calcareous group (limestone, dolomite, chalk, barite), containing a jaw crusher intended for preliminary grinding of lump dolomite, a drying drum, a hammer mill or a ball mill of fine grinding, equipment for sieving the ground dolomite into fractions and magnetic separator. This line of dry enrichment of dolomite is most often used in departments for the processing of raw materials of composite workshops of glass factories. The disadvantages of such a line are the one-stage separation of enriched dolomite, which allows separating only unrefined material from crushed material, and the fact that dust trapped and precipitated in cyclones and filters is returned to enriched dolomite, and is not used as a by-product (mineral powder) for the production of asphalt concrete.

Also known is a production line [2] for dry processing of inorganic raw materials to produce multifunctional micro- and nanopowders. The line includes a technological chain, which can conditionally be divided into three functional blocks (a drying unit, a grinding and classification unit, a deep processing unit) connected by transporting mechanisms. The drying unit comprises a drying chamber and an aspiration system. The grinding and classification unit consists of a centrifugal mill, two classifiers, a bag filter and a cyclone. A deep processing unit includes a microclassification unit and an ultrafine grinding unit. The line provides the possibility of processing mineral raw materials with various physical and mechanical characteristics and allows to obtain powder products of a narrow class with homogeneous mineral and chemical compositions. However, due to the increased degree of grinding of the processed material, which can also be used as dolomite, it is problematic to obtain the required particle size distribution of ground dolomite used for glass melting. This is due to the fact that there are no technological operations in the line that allow optimizing the ratio of fine and coarse fractions in crushed dolomite.

The closest technical solution is the dolomite dry concentration processing line, implemented at CJSC Kovrovsky Dolomite Hamlet Plant in the Vladimir Region [3]. The line contains: lump dolomite receiving hopper equipped with a plate feeder; a dryer drum equipped with a smoke exhauster, a group of cyclones and a bag filter; suction system; impact crusher; two-screen vibrating screen; single-screen vibrating screen; assembly line; magnetic separator; finely dispersed storage hopper; silo cans of finished products, as well as transporting mechanisms connecting this equipment to each other. The line allows you to partially separate the fine fraction from the crushed dolomite and to obtain a polydisperse particle size distribution of the enriched material. The disadvantage of this line is the small amount of finely dispersed fraction emitted only from the suction air and exhaust flue gases of the drying drum. This does not allow to achieve the desired particle size distribution of ground dolomite used for glass melting, and limits the volume of the obtained fine fraction used as a by-product for the production of asphalt mixtures. Also, there are no technological mechanisms in the line that allow changing the ratio of fine and coarse fractions in enriched dolomite.

The problem to be solved is the reduction in the amount of the finely dispersed fraction of the material and the relative increase in the coarse fraction in the enriched dolomite used for the glass industry, as well as the possibility of a controlled change in the amount of the finely dispersed fraction used for the production of asphalt mixtures.

The specified technical result is achieved by the fact that the production line of dry enrichment of dolomite contains: a receiving hopper of lump dolomite equipped with a plate discharge feeder; an intermediate belt conveyor for supplying lump dolomite to a drying drum equipped with a group of cyclones, a bag filter and a smoke exhauster designed to remove flue gases and trap finely dispersed dolomite fractions; the transport chain for feeding the captured fine fraction into the storage hopper, consisting of a belt conveyor, a screw conveyor and a first bucket elevator; local aspiration system connected to the storage hopper and transport and technological equipment; impact mill installed at the outlet of the dryer drum; the second bucket elevator, the input of which is connected to the output of the impact crusher, and the output is connected to the input of a two-sieve vibrating screen. Moreover, the oversize exit of the upper mesh of a two-sieve vibrating screen is connected to the input of the impact crusher, and the oversize output of its lower mesh is connected to the input of a single-sieve vibrating screen, from the sieve of which the sifted dolomite is poured onto the first input of the assembly conveyor, which feeds the sifted dolomite through a magnetic separator, the third elevator and first flow switch to one of two silo cans. Additionally, the line is equipped with: a second flow switch, the input of which is connected to the sub-sieve output of a two-sieve vibrating screen, and the first output is connected to the second input of the assembly line; an intermediate hopper connected by its input to the second output of the second flow switch; screw discharge feeder, the input of which is connected to the output of the intermediate hopper; the fourth bucket elevator connected by its input to the output of the screw discharge feeder; adjustable air classifier, the input of which is connected to the output of the fourth bucket elevator; as well as a third flow switch and roller mill. At the same time, from the first output of the adjustable air classifier, the separated coarse fraction of sifted dolomite is discharged to the third input of the assembly conveyor, and from the second output, the separated fine fraction of sifted dolomite is fed to the input of the screw conveyor, and the undersized fraction of sifted dolomite from the over-sieve output of the one-sieve single-sieve vibrator flow, the first output of which is connected to the input of the impact crusher, and the second output is connected to the roll howling crusher connected to its output to the input of the second bucket elevator.

The advantage of the proposed line for dry enrichment of dolomite is a more efficient separation of the finely divided fraction of the material from dolomite intended for the glass industry. In this method, finely divided crushed dolomite is added to dusty material obtained from aspiration air and exhaust drying gases after its aeroclassification.

Another advantage is the ability to control and change the total amount of the finely divided fraction of crushed dolomite depending on technological parameters (for example, the hardness of dolomite can be taken into account) and seasonal demand for mineral powders (in winter, finely divided mineral powder based on crushed dolomite is not used for the preparation of asphalt mixtures) . The change in the amount of the finely dispersed fraction of dolomite is achieved both due to different methods of regrinding of unmilled dolomite, carried out either by crushing in a roll crusher, or by impact in a hammer crusher, and by adjusting the air classification modes. Moreover, in some cases, when a smaller amount of fine fractions is formed when dolomite is crushed with increased hardness, the airclassification mode can be turned off.

Another advantage is the possibility of obtaining a polydisperse particle size distribution of crushed dolomite, in which the content of coarse particles is increased (particle size greater than 0.315 mm and less than 2.0 mm) and the concentration of fine fractions is reduced. This result is achieved through a three-stage separation, the second stage of which is carried out using adjustable aeroclassification, and the first and third stages - with the help of vibrating screens. In this case, part of the fine particles is separated from the mixture of coarse and fine fractions and coarse material is added to the mixture after aeroclassification. All this also improves the flow properties of the material and accelerates its subsequent loading and unloading operations from bunkers and various vehicles.

The principle of operation is illustrated by the drawing, which shows the production line of dry enrichment of dolomite, including: receiving hopper 1 of lump dolomite; plate feeder 2 installed at the output of the receiving hopper 1; an intermediate belt conveyor 3 for feeding lump dolomite to the dryer drum 4; a group of cyclones 5, intended for the deposition of finely dispersed fractions of dolomite from exhaust drying gases; bag dust filter 6; smoke exhaust 7 with a chimney 8; belt conveyor 9; screw conveyor 10; first bucket elevator 11; local suction system 12; storage hopper 13; impact crusher 14; second bucket elevator 15; two-screen vibrating screen 16; single-sieve vibrating screen 17; assembly line 18; magnetic separator 19; third bucket elevator 20; a first flow switch 21; two silo banks 22, 23; second stream switch 24; an intermediate hopper 25 equipped with a screw discharge feeder 26; fourth bucket elevator 27; adjustable air classifier 28; a third flow switch 29 and a roll crusher 30.

The technological line of enrichment of dry dolomite works as follows. The feedstock in the form of pieces of 20-40 mm in size and with a moisture content of up to 8% is loaded by automobile transport into the receiving hopper 1 of lump dolomite. From this hopper, lumpy dolomite is fed with a plate feeder 2 and an intermediate belt conveyor 3 to a drying drum 4, in which the moisture content of the enriched material is reduced to 0.2-0.5%. In this case, flue gas exhaust gases exhausted from the dryer drum saturated with evaporated moisture and a finely divided dolomite fraction pass through a group of cyclones 5 and a bag filter 6, where they are cleaned and emitted through a chimney 7 through the chimney 8 into the atmosphere.

The finely dispersed pulverulent fraction of dolomite precipitated in the group of cyclones 5 and the bag filter 6 is discharged from these units to the belt conveyor 9 and then, using the screw conveyor 10 and the first bucket elevator 11, is loaded into the storage hopper 13, the filling of which is controlled by a tensometric weighing system (not shown ) The finely dispersed fraction of dolomite from the suction system 12, which purifies the air with dust emissions generated on the conveyor belt 9 and vibration screens 16, 17, is also unloaded into the same storage hopper 13.

The dried lump dolomite from the dryer drum enters the inlet of the impact mill 14 (rotor or hammer mill), where it is intensively crushed. Crushed to particles of different sizes, dolomite is lifted by the second bucket elevator 15 and sent to the upper grid of a two-sieve vibrating screen 16.

Oversize product from this mesh, having a mesh size of 7 × 7 mm, is discharged into the impact crusher 14 and recirculates until it is crushed to a smaller size. The remaining crushed dolomite particles fall through the upper grid and fall on the lower grid with a mesh size of 2 × 2 mm. At the same time, about half of the crushed material that has fallen through the upper grid is sieved through the lower grid of a two-sieve vibrating screen 16, and the second half, not having time to sift, is sent to the input of a single-sieve vibrating screen 17, the grid of which also has a mesh size of 2 × 2 mm.

Particles of dolomite having a size larger than 2 × 2 mm are screened out by a single-sieve vibrating screen 17 and through the third flow switch 29 are discharged for regrinding either into the roll crusher 20 or into the impact crusher 14. The smaller particles fall through the grid and fall onto the first entrance of the assembly line 18, the third entrance of which is also discharged coarse fraction of dolomite after the aeroclassification operation.

Aeroclassification, in which a finely dispersed (less than 0.315 mm) and coarse (with a size greater than 0.315, but less than 2.0 mm) fractions of crushed dolomite are distinguished from the sublattice product of the lower mesh of a two-sieve vibrating screen 16; The sublattice product from the bottom grid of the two-screen vibrating screen 16 through the second flow switch 24 enters the intermediate hopper 25, from which it is sent to the input of the adjustable air classifier 28 with the help of the screw feeder 26 and the fourth bucket elevator 27. The air classification of the crushed dolomite is carried out according to the principle of aerodynamic separation of particles, having different weights in a swirling high-speed air stream created by a turbine installed inside the air classifier. By changing the amount of material supplied from the screw feeder 26 and changing the speed of the turbine (adjustment is carried out by frequency converters (not shown)), it is possible to adjust the degree of separation of fractions according to particle size.

The fine fraction of crushed dolomite after an adjustable air classifier is fed to the inlet of the screw conveyor 10 and, together with the fine dust deposited in the group of cyclones 5 and the bag filter 6, is loaded into the storage hopper 13, which also receives dust from the aspiration system 12. As it accumulates in hopper 13 finely dispersed fraction of dolomite in the form of a mineral powder is shipped to the respective consumers.

From the second output of the adjustable air classifier 27, the separated coarse fraction of crushed dolomite is discharged to the third input of the assembly conveyor 18, into which the sublattice product is also unloaded from the single-sieve vibrating screen 17 during the separation process. It should be noted that this sublattice product contains significantly less fine fraction than the sublattice product the lower grid of the two-screen vibrating screen 16, since the main volume of small particles falls through the lower screen of the screen 16 and the post falls on aeroclassification. Therefore, an optimal mixture of particles with a main size of more than 0.315 mm and less than 2.0 mm is formed on the assembly line 18, although this mixture also partially contains a finely dispersed fraction, which in small quantities is necessary for the preparation of a glass charge.

Next, the mixture with a reduced content of the finely divided fraction of crushed dolomite passes through a magnetic separator 19 that separates the ferromagnetic inclusions, and with the help of the third bucket elevator 20 and the first flow switch 21 is sent to one of the silo cans 22, 23 for storage and subsequent shipment to glass plants.

In the process of separation of crushed dolomite, including aeroclassification of the material, a control system (not shown) controls the filling rate of the storage hopper 13 with a finely divided fraction. If the filling of the storage hopper 13 occurs with lower productivity than is required (an increased amount of mineral powder for the production of asphalt is necessary in the summer), then the regrinding of large particles of dolomite, screened by a single-sieve vibrating screen 17, must be carried out in a crusher 14, which, when crushed, gives a significant amount of fine dust particles. To this end, the third flow switch 29 switches to the corresponding position and connects the material flow from the over-screening output of the screen 17 to the input of the impact crusher 14. In this case, the finer fraction is formed more and more precipitated by the aspiration system 12 and is separated by the adjustable air classifier 28. In addition to the seasonal increased demand for an increased amount of finely divided fraction of crushed dolomite, the need to increase the amount of finely dispersed material obtained occurs when crushing dolomite of increased hardness, which gives less dust and which, due to increased hardness (4-4.5 units on the Mohs scale), is better to grind in a hammer or rotary crusher.

If in the process of crushing dolomite excess fine particles are formed, which can be when crushing a relatively soft dolomite (2-2.5 units on the Mohs scale) or when the demand for mineral powder decreases in winter, regrinding of large particles screened by a single-sieve vibrating screen 17, it is advisable to perform using a roller crusher 30. The reduction in the number of small particles during crushing screenings in the roller crusher is due to the crushing of crushed particles between the shafts, which allows to obtain less dust than impact crushing. To provide such a mode of regrinding, the third flow switch 29 is switched to a position in which the material flow from the over-sieve outlet of the single-sieve vibrating screen 17 is directed to the roller crusher 30 and then to the input of the second bucket elevator 15 for re-separation.

When crushing and separating relatively hard batches of dolomite (the hardness of dolomite even in one deposit may depend on the depth of various layers), a situation is possible where, with reduced demand for mineral powders and with a small amount of the finely divided dolomite fraction, it is inappropriate to carry out aeroclassification at the second separation stage. In this case, the second flow switch 24 switches to the position in which the sublattice product from the lower grid of the two-sieve vibrating screen 16 is sent to the second input of the assembly conveyor 18, where it is mixed with the sublattice product of the one-sieve vibration screen 17. The resulting mixture is further through the magnetic separator 19, the third bucket elevator 20 and the first flow switch 21 is likewise sent to one of the silo cans 22, 23. The presence of the first flow switch 21 allows separate storage of one of the cans lchenny dolomite with a high content of fine material fractions and in the other bank - with a lower concentration of fine dust particles of crushed dolomite. This possibility of separate receipt and storage of crushed dolomite having a different fractional composition is caused by different technological requirements of various glass factories for this product.

The operation of the dolomite dry concentration processing line is also illustrated by examples.

Example No. 1.

The production line capacity is 50 t / h. The line operates without aeroclassification, and the grinding of unrefined dolomite with a hardness of 2.0-2.5 units is carried out using a crusher 14 impact. The amount of fine fraction (particle size less than 0.315 mm) captured by the aspiration system 12 is 5 t / h. The distribution of particles by fractions in the mixture of ground material collected on the assembly line 18 in the amount of 45 t / h, the following is obtained: (1.0-2.0) mm - 2%; (0.63-1.0) mm - 8%; (0.315-0.63) mm - 20%; (0.1-0.315) mm - 35,%; (less than 0.1) mm - 35%. Obviously, when a relatively soft dolomite is crushed, a significant amount of a finely divided fraction is undesirable for glass melting. The amount of the finely dispersed fraction extracted using the suction system 12 is small (only 10%) and cannot provide the requirements for this product to third-party consumers.

Example No. 2.

The production line capacity is 50 t / h. The amount caught by the dust aspiration system is 5 t / h. The line operates with aeroclassification, and the grinding of unrefined dolomite with a hardness of 2.0–2.5 units is carried out using a impact mill 14. The air classifier 28 additionally emits 3-4 tons / hour. fine fraction with a particle size of less than 0.1 mm Moreover, the distribution of particles by fractions in the mixture of ground dolomite collected on the assembly line 18 in an amount of 41-42 t / h, has the following form: (1.0-2.0) mm - 2.2%; (0.63-1.0) mm - 8.8%; (0.315-0.63) mm - 22%; (0.1-0.315) mm - 38.4%; (less than 0.1) mm - 28.6%. The total amount of the separated fine fraction used as a mineral powder increased to 8–9 t / h, but an increased content of fine particles is still present in the mixture of the fine and coarse fractions of crushed dolomite collected on the assembly line 18. Therefore, with a relatively soft dolomite, it is advisable to finish it up in a roll crusher 30.

Example No. 3.

The production line capacity is 50 t / h. The amount caught by the dust aspiration system is 5 t / h (this amount of dust is mainly captured by cyclones 5 and bag filter 6 during the drying of lump dolomite). The line works with an air classifier, and the grinding of unrefined dolomite is made on a roll crusher 30. The air classifier additionally emits 3-4 t / h of finely dispersed fraction. The distribution of particles by fractions in the mixture of ground dolomite collected on the assembly line 18 in an amount of 41-42 t / h, the following: (1.0-2.0) mm - 8%; (0.63-1.0) mm - 15%; (0.315-0.63) mm - 26%; (0.1-0.315) mm - 34%; (less than 0.1) mm - 17%. The total number of fractions less than 0.315 mm decreased by 6% compared with example No. 2, but the number of particles less than 0.1 mm in size significantly decreased, which, when using such dolomite for the production of a glass charge, favorably affects the glass melting process.

If you use a more rigid (4-4.5 units of hardness on the Mohs scale) lumpy dolomite, then after crushing, the crushed dolomite will have a fractional composition close to optimal.

Thus, the use of the proposed dolomite dry enrichment production line allows increasing the amount of emitted fine fraction used as a mineral powder in the production of asphalt mixes, and optimizes the particle size distribution of dolomite used to prepare the glass mixture. Moreover, the granulometric composition of the content of fine and coarse fractions can vary depending on the hardness of dolomite and the technological requirements of glass plants that produce various glass products.

Information sources

1. Sivko A.P. Technology of electric lamp glass, - Saransk. Mordovian University Press. 2015 - 190 s.

2. Beach A.V. et al. Processing line for dry processing of inorganic raw materials to produce multifunctional micro- and nanopowders. RF patent for utility model No. 10711. Publ. 08/31/2011.

3. Efremenkov VV An integrated approach to the design and construction of enterprises for the processing of raw materials for a glass charge. Glass containers, No. 11, 2011, with. 6-9.

Claims (1)

Dolomite dry concentration processing line containing a lump dolomite receiving hopper equipped with a plate discharge feeder, an intermediate belt conveyor for feeding lump dolomite to a drying drum equipped with a group of cyclones, a bag filter and a smoke exhauster designed to remove flue gases and to capture the finely dispersed dolomite feed fraction, transport captured fine fraction into the storage hopper, consisting of a belt conveyor, a screw conveyor and a first bucket a new elevator, a local aspiration system connected to a storage hopper and transport and technological equipment, a impact crusher installed at the outlet of the dryer drum, a second bucket elevator, the input of which is connected to the output of the impact crusher, and the output is connected to the input of a two-screen vibrating screen, the oversize exit of the upper mesh of a two-sieve vibrating screen is connected to the input of the impact crusher, and the oversize output of its lower mesh is connected to the input of single sieves vibrating screen, from which the sieved dolomite is poured from the under-sieve to the first input of the assembly conveyor, which feeds the sieved dolomite through a magnetic separator, the third bucket elevator and the first flow switch into one of two silo cans, characterized in that it is additionally equipped with a second flow switch, input which is connected to the sub-sieve output of a two-sieve vibrating screen, and the first output is connected to the second input of the assembly line, an intermediate hopper connected by its input about the second output of the second flow switch, a screw discharge feeder, the input of which is connected to the output of the intermediate hopper, a fourth bucket elevator, connected by its input to the output of the screw discharge feeder, regulated by an air classifier, the input of which is connected to the output of the fourth bucket elevator, as well as a third flow switch and roller crusher, while the selected coarse fraction of sifted dolomite is discharged to the third input from the first output of the adjustable air classifier full-time conveyor, and from the second output, the separated fine fraction of sifted dolomite is fed to the input of the screw conveyor, and the unmilled fraction of sifted dolomite from the sieve output of a single-sieve vibrating screen goes to the input of the third flow switch, the first output of which is connected to the input of the impact crusher, and the second output is connected with a roll crusher connected by its outlet to the inlet of the second bucket elevator.

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