Patent Grant
9845992
The present subject matter relates to fluidized feed bin systems for use with particulate feed materials. The system described herein could be applied in fields such as flash smelting, pharmaceuticals, or any other field where uniformity of feed flow in time, space and particle size distribution (PSD) is important.
There are numerous fields in which a particulate feed material must be uniformly distributed and introduced into a device, with respect to both time and space, while maintaining a well-mixed and steady particle size distribution within the feed stream.
A group of such applications concerns the delivery of particulate materials such as pulverized coal, dust or combustible ores to a combustion system, such as may be found in burners for heat generation, insufflation or smelting.
One such application that requires uniformity of feed flow is flash smelting for sulphide concentrates, such as may be encountered in the production of copper, nickel, lead or zinc. A flash smelting furnace typically includes an elevated reaction shaft at the top of which is positioned a burner or multiple burners where particulate feed material and reaction gas are brought together. In the case of copper smelting, the feed material is typically an ore concentrate containing both copper and iron sulfide minerals. The concentrate is usually mixed with a silica flux and combusted with pre-heated air or oxygen-enriched air. Molten droplets are formed in the reaction shaft and fall to the hearth, forming a copper-rich matte and an iron-rich slag layer.
A conventional burner for a flash smelter includes an injector having a water-cooled sleeve and an internal central lance, a windbox, and a cooling block that integrates with the roof of the furnace reaction shaft. The lower portion of the injector sleeve and the inner edge of the cooling block create an annular channel. Oxygen enriched combustion air enters the windbox and is discharged to the reaction shaft through this annular channel. The water-cooled sleeve and the internal lance of the injector also create an annular channel within the combustion air flow annulus. The feed material is introduced from above and descends through the injector sleeve into the reaction shaft through this internal annulus. Deflection of the feed material into the reaction gas is promoted by a bell-shaped tip at the lower end of the central lance. In addition, the tip includes multiple perforation jets that direct compressed air outwardly to disperse the feed material in an umbrella-shaped reaction zone. Such a burner for a flash smelting furnace is disclosed in U.S. Pat. No. 6,238,457.
The material feed supply equipment is typically comprised of bins and hoppers, mechanical feeders, conveyors, splitter boxes, manifold connectors, and feed pipes located above the injector. Typical feeders and conveyors include screw-feeders, table feeders, drag-chain conveyors and air slides. Some feed systems also combine feed streams of different particle density, shape, and size upstream of the burner.
Known feed systems of this type are associated with disadvantages that can adversely affect the burner performance and cause problems, such as: poor oxygen efficiency; variable furnace metallurgy and matte grade; increased copper losses to slag; increased elutriation of dust to the off-gas handling equipment, etc. These problems result from a failure to achieve uniformity of the feed material both spatially and in time on the appropriate scales, as well as causing segregation of the individual feed components with respect to particle size, density and/or shape.
For example, it is well documented that known mechanical feed systems, such as drag chains, screw conveyors and table feeders deliver the feed in discrete packets of material, resulting in low-frequency feed pulsations in the delivery of feed material to the burner, causing incomplete combustion. Such a system and the associated problem is described in Suenaga et al., “High-Performing Flash Smelting Furnace at Saganoseki Smelter & Refinery”, Second International Conference on Processing Materials for Properties, The Minerals, Metals & Materials Society, 2000, pages 879-884.
It is also well documented that known feed systems suffer from periodic flow instabilities associated with uncontrollable partial fluidization of the charge in the feed bins. This normally occurs during the charging cycle of the bin, and results in uncontrolled delivery of feed material to the burner, typically lasting between one and several minutes. This has negative consequences on all aspects of the combustion process.
While air-slides and alternative bin designs have been proposed to address the above issues, these approaches suffer from serious drawbacks: Air-slides are incapable of eliminating low-frequency feed pulsations, serving instead to transmit them to the burner. Alternative bin designs, typically with a mass-flow hopper, can reduce the severity of the flushing phenomenon, but are typically large, or severely decrease the capacity of the bin for a given bin height or footprint. This makes retrofit of the alternative bins into existing feed systems costly and impractical.
Another example of a typical feed problem faced by concentrate burners is poor distribution of feed around the circumference of the burner. Feed systems usually contain one or more feed pipes that interface with the injector and attempt to utilize splitter boxes, guides and diverter chutes to distribute feed evenly around the circumference. Such systems tend to cause the feed to gather at corners/edges of the chute walls and fins, forming dense, “ropes” of feed within the plume. This lack of spatial uniformity results in poor ignition characteristics, non-uniformity of the combustion plume and reduced oxygen efficiency.
Pneumatic conveying systems have been proposed in an attempt to resolve both the pulsation problems, but these require a large investment of capital for new equipment, as well as substantial modifications to existing building layouts to accommodate the system. These systems do not, however, eliminate the problem of non-uniform circumferential distribution of the feed at the burner inlet, because they feed through intermediate, feed chutes, splitters or other equipment, and deliver the feed through discrete points around the circumference of the burner, necessarily leading to a lack of uniformity.
The process disturbances caused by temporally and spatially non-uniform delivery of the feed to flash smelting burners represent a significant loss of economic value to the flash smelter operator. None of the existing technologies adequately solves the problem of feed delivery. There thus remains a need for feed systems for flash smelting furnaces, or other applications using a particulate feed material, which provide uniform flow, both spatially and in time, around an inlet annulus with minimum particle segregation effects and in which the feed rate can be accurately controlled.
The following summary is intended to introduce the reader to the more detailed description that follows, and not to define or limit the claimed subject matter.
In some examples, there is provided a feed charging device, comprising: (a) a holding vessel having an interior chamber for holding a reserve of a solid particulate feed material in a fluidized state, wherein the feed material is held in said fluidized state in a lower zone of the interior chamber; (b) at least one inlet opening through which the feed material is supplied to the interior chamber; (c) at least one outlet opening through which the feed material is discharged from the interior chamber, wherein said at least one outlet opening is in flow communication with the lower zone of the interior chamber; (d) gas supply means for supplying a fluidizing gas to the lower zone of the interior chamber; (e) an outlet conduit in flow communication with the at least one outlet opening for receiving said feed material discharged from the interior chamber.
In some examples, the feed charging device further comprises a bottom partition having a plurality of apertures, wherein the gas supply means comprises a gas distribution chamber which is separated from the interior chamber of the holding vessel by said bottom partition, wherein the gas distribution chamber has an inlet for receiving said fluidizing gas, and wherein an interior of the gas distribution chamber is in flow communication with the interior chamber of the holding vessel through the plurality of apertures in the bottom partition.
In some examples, the gas distribution chamber is enclosed within a windbox, and wherein the bottom partition forms a top wall of the windbox. The gas distribution chamber may comprise a plurality of compartments, each of said compartments being in flow communication with a portion of the interior chamber of the holding vessel through a subset of the plurality of apertures in the bottom partition.
In some examples, the feed charging device further comprises a baffle plate located inside the interior chamber in close proximity to the at least one inlet opening, wherein the baffle plate is mounted to the bottom partition to permit pneumatic elevation of the particulate feed material from bottom to top.
In some examples, the gas supply means is selected from the group consisting of tuyeres, porous pads and porous membranes. For example, the gas supply means may comprise a plurality of said tuyeres which are received in said bottom partition in spaced relation to one another, and wherein the apertures are defined by said tuyeres. Alternatively, the bottom partition may comprise one or more of said porous pads or porous membranes, and wherein the apertures are defined by said porous pads or porous membranes.
In some examples, the lower zone of the holding vessel defines an area to be occupied by a fluidized bed of said particulate feed material, and wherein the interior chamber also includes an upper zone which comprises a gas space above said fluidized bed. For example, the at least one inlet opening is provided in the lower zone of the interior chamber, and is located below a bed level of the fluidized bed to allow introduction of the particulate feed material into the fluidized bed below the bed level.
In some examples, the feed charging device further comprises at least one off-gas outlet opening provided in the interior chamber of the holding vessel, in communication with the upper zone of the interior chamber. For example, the feed charging device may further comprise at least one deflector plate, at least a portion of which is located in the upper zone of the interior chamber, between the at least one inlet opening of the holding vessel and the at least one off-gas outlet opening. The at least one deflector plate may be oriented substantially vertically and has a lower end which extends into the lower zone. The at least one deflector plate may be oriented substantially vertically and has a lower end which is spaced above the lower zone.
In some examples, the outlet conduit may pass through the lower and upper zones of the interior chamber, and wherein the at least one off-gas outlet opening is provided in a conduit wall of the outlet conduit.
In some examples, the outlet conduit has a conduit wall in which said at least one outlet opening is formed. For example, the outlet conduit may extend substantially vertically through said interior chamber, and wherein said gas supply means are radially dispersed around the outlet conduit. The at least one outlet opening may be arranged to receive said feed material from a plurality of radial directions. The conduit wall of the outlet conduit may have an outer perimeter, and wherein said at least one outlet opening is open to the lower zone of the interior chamber along substantially the entire outer perimeter of the conduit wall. For example, the at least one outlet opening may comprise a plurality of openings spaced apart along substantially the entire outer perimeter of the conduit wall; or the at least one outlet opening may comprise a horizontal slit extending throughout substantially the entire outer perimeter of the conduit wall.
In some examples, the at least one outlet opening is separated from a bottom of said interior chamber by a baffle ring having a height sufficient to prevent coarse particles within said particulate feed material from blocking said at least one outlet opening.
In some examples, an area of the at least one outlet opening is adjustable.
In some examples, the outlet conduit includes a slidable or rotatable cover member adapted to be moved steplessly or in discrete steps from a first position in which the area of the at least one outlet opening is at a maximum, to a second position in which the area of the at least one outlet opening is at a minimum.
In some examples, the feed charging device further comprises an actuation mechanism for controlling the movement of the cover member between said first position and said second position. For example, the at least one outlet opening may comprise a horizontal slit extending throughout substantially the entire outer perimeter of the conduit wall, and wherein the cover member comprises a sleeve which is slidable longitudinally along a surface of the outlet conduit between said first position and said second position, and wherein the horizontal slit has a greater height with the sleeve in the first position than in the second position.
In some examples, the feed charging device further comprises a plurality of sensors to measure a pressure drop of the particulate feed material in the interior chamber of the holding vessel.
In some examples, the feed charging device further comprises multiple actuated valves mounted externally of the holding vessel, a pressure sensor located in the lower zone and an electronic feedback controller for controlling the valves, so as to control a volumetric flow rate of the fluidizing gas into the interior chamber and maintain a required fluidization velocity using feedback from the pressure sensor, wherein the flow rate of the fluidizing gas is optionally used to control a discharge rate of the particulate feed material.
In some examples, the at least one outlet opening is provided in a side wall of the holding vessel.
In some examples, the side wall in which the at least one outlet opening is provided is distal to the at least one inlet opening. For example, the at least one outlet opening may be open to the lower zone of the interior chamber. The at least one outlet opening may comprise one or more openings located along a base of the side wall. The at least one outlet opening may comprise a horizontal slit extending along the base of the side wall. The at least one outlet opening may be spaced from a bottom of said interior chamber by a height sufficient to prevent coarse particles within said particulate feed material from blocking said at least one outlet opening. The area of the at least one outlet opening may be adjustable.
In some examples, the at least one outlet opening includes a slidable or rotatable cover member adapted to be moved steplessly or in discrete steps from a first position in which the area of the at least one outlet opening is at a maximum, to a second position in which the area of the at least one outlet opening is at a minimum. The feed charging device may further comprise an actuation mechanism for controlling the movement of the cover member between said first position and said second position. The at least one outlet opening may comprise a horizontal slit, and wherein the cover member comprises a valve member which is rotatable between said first position and said second position, and wherein the horizontal slit has a greater height with the sleeve in the first position than in the second position.
In some examples, an area of the at least one outlet opening is adjustable, and wherein the feed charging device further comprises: at least one sensor for measuring, directly or indirectly, a quantity of said particulate feed material inside the interior chamber; and means for controlling the area of the at least one outlet opening in response to changes in the quantity of said particulate feed material inside the interior chamber.
In some examples, said means for controlling the area of the at least one outlet opening comprises a slidable or rotatable cover member adapted to be moved steplessly or in discrete steps from a first position in which the area of the at least one outlet opening is at a maximum, to a second position in which the area of the at least one outlet opening is at a minimum.
In some examples, said means for controlling the area of the at least one outlet opening further comprises an actuation mechanism for controlling the movement of the cover member between said first position and said second position.
In some examples, the feed charging device is for a flash smelting furnace including an elevated reaction shaft having a burner, and wherein the outlet conduit is attached to the upper end of the burner, above a reaction shaft where the particulate feed material is reacted with a reaction gas.
In some examples, there is provided method for improving the combustion performance of a flash smelting concentrate burner by improving the spatial and temporal uniformity of the feed entering the burner, the method comprising: (a) providing a holding vessel having an interior chamber, the holding vessel having an interior chamber, at least one inlet opening and at least one outlet opening; (b) feeding a solid particulate feed material into the interior chamber through said at least one inlet opening; (c) fluidizing the feed material in a lower zone of the interior chamber by injecting a fluidizing gas into the lower zone of the chamber; (d) discharging the fluidized feed material through the at least one outlet opening, wherein the at least one outlet opening is in flow communication with the lower zone of the interior chamber.
In some examples, the method further comprises: measuring, directly or indirectly, a quantity of said particulate feed material inside the interior chamber.
In some examples, the method further comprises: controlling an area of the at least one outlet opening in response to changes in the quantity of said particulate feed material inside the interior chamber.
According to another aspect, a feed flow conditioner is provided for a flash smelting concentrate burner, which integrates with a reaction shaft of a furnace. The feed flow conditioner includes a holding vessel, feed supply inlets, a discharge aperture, a fluidizing plate, a windbox, and fluidizing gas supply system. The holding vessel integrates with the burner feed chute, and has a discharge aperture there through to communicate with the feed chute of the burner via an intermediate conveying apparatus, such as a chute or air-slide. The feed supply inlets are mounted over the holding vessel and supply the feed flow conditioner with particulate feed. The discharge aperture, which is in the form of one or more openings arranged in one or more walls of the holding vessel may allow flow of the particulate feed into the conveying apparatus. The fluidizing plate, which forms the bottom of the holding vessel, contains a plurality of gas distributors such as tuyeres, porous pads, or porous membrane to supply the holding vessel with fluidizing gas, which fluidizes the particulate feed, creating a suspension of feed within the holding vessel, thereby promoting the flow of the particulate feed through the aperture and into the feed chute of the burner via the conveying apparatus. The windbox, which is mounted underneath the fluidizing plate, is fitted with a fluidizing gas supply system to deliver and distribute fluidizing gas throughout the entire windbox.
According to another aspect, a method for improving the combustion performance of a flash smelting concentrate burner is provided, which delivers feed to a flash smelting concentrate burner with low spatial non-uniformity and with greatly reduced low-frequency fluctuations, regardless of the spatial and temporal flow characteristics of the feed delivered upstream of the system. The method utilizes a fluidized holding vessel with sufficient buffer capacity to absorb any fluctuations in the incoming feed. The discharge rate of the holding vessel is controlled, in response to operator input or long-term changes in the incoming feed rate. Control of the discharge rate is achieved by manually or automatically adjusting the aperture size, the fluidizing air flow rate, or the height of the fluidized bed.
In some examples, the discharge aperture is one or more holes or slots that are arranged in one or more of the walls of the holding vessel.
In some examples, the discharge aperture opening height can be modified through the use of an adjustable gate to control the discharge rate.
In order that the claimed subject matter may be more fully understood, reference will be made to the accompanying drawings, in which:
In the following description, specific details are set out to provide examples of the claimed subject matter. However, the embodiments described below are not intended to define or limit the claimed subject matter. It will be apparent to those skilled in the art that many variations of the specific embodiments may be possible within the scope of the claimed subject matter.
The feed charging device 20 is shown as having an overall box-like shape, with the holding vessel 11 and the windbox 15 each having a side wall 22 or 24 comprising four side wall sections. In addition, the holding vessel 11 has a top wall 26 and the windbox 15 has a bottom wall 28. It will be appreciated that the box-like shape is not essential for proper operation of the feed charging device 20, and that the feed charging device may have any suitable shape, including cylindrical.
As shown in the cross-sectional view of
As shown in
The holding vessel 11 further comprises at least one feed inlet opening 7, through which the feed material is supplied to the interior chamber 30 of the feed flow conditioner 20, for example from a particulate feed duct 40 through which the feed material is fed by gravity to the holding vessel 11. For purposes of illustration, the feed charging device 20 is shown in
The feed charging device 20 further comprises at least one outlet opening 2 through which the feed material is discharged from the interior chamber 30 of the holding vessel 11. The at least one outlet opening 2 is formed in the wall of an outlet conduit 5, sometimes referred to in this description as “discharge pipe 5”. The outlet conduit 5 extends through the bottom partition 13 of the holding vessel 11 and extends into the interior chamber 30 thereof. In the illustrated embodiment, the outlet conduit 5 passes through the lower and upper zones 36, 38 of the interior chamber 30 and extends through a wall of the holding vessel 11 in the upper zone 38 of the interior chamber 30. For example, where the outlet conduit 5 is substantially vertically oriented, it extends vertically through the entire height of the holding vessel 11 and extends through an aperture 42 provided in the top wall 26 of the holding vessel 11, with the conduit 5 being sealed to the inner peripheral edge of the aperture 42 in the top wall 26.
Where the feed charging device 20 includes a windbox 15, the outlet conduit 5 also extends through an aperture 44 in the bottom wall 28 of the windbox 15 and through the gas distribution chamber 32. The outlet conduit 5 therefore provides a flow passage through which the particulate feed material in the fluidized bed 9 is discharged from the device 20.
In the illustrated embodiment, the bottom partition 13 comprises a rigid plate which may be substantially flat and horizontally oriented, also sometimes referred to herein as a “fluidizing plate 13”. However, it will be appreciated that the bottom partition 13 is not necessarily flat and horizontal. Rather, the bottom partition 13 may be sloped and/or may have a dished or conical shape. The outlet conduit 5 is shown in the drawings as being centered within the feed charging device 20 around the discharge pipe 5. It can be appreciated that the outlet conduit 5 does not necessarily need to be centered within the feed charging device 20. For example, the position of outlet conduit 5 may be biased such that it is further away from the at least one inlet opening 7. Typically the outlet conduit 5 will be spaced from the side wall 22 of holding vessel 11 such that it is surrounded on all sides by the fluidized bed 9 of particulate feed material in the lower zone 36 of the interior chamber 30.
The interior chamber 30 of the holding vessel 11 communicates with the discharge pipe 5 through the at least one outlet opening 2 and is in flow communication with the fluidized bed 9 of particulate feed material in the lower zone 36. In the illustrated feed charging device 20 shown in
Although the at least one outlet opening 2 is shown as comprising a single, continuous aperture slit, it will be appreciated that other configurations are possible. For example, the at least one outlet opening 2 may comprise a plurality of openings or slits which are spaced apart along substantially the entire outer perimeter of the conduit wall 46, such that the at least one outlet opening 2 is open to the lower zone 36 of the interior chamber 30, and the fluidized bed 9 located therein, along substantially the entire outer perimeter of the conduit wall 46. Where the at least one outlet opening 2 comprises a plurality of openings or slits, they are separated by webs which may be integral with the wall 46 of the outlet conduit 5.
The holding vessel 11 is designed to provide adequate capacity to allow some self-regulation of the fluidized bed 9 level movement. In other words, if the feed rate from the feed inlet 7 is increased, the fluidized bed 9 level will rise, which will increase the discharge flow of particulate feed through the at least one outlet opening 2, without a requiring a change to any other operating parameters.
The at least one outlet opening 2 is located in close proximity to the bottom partition 13, and a bottom threshold of the at least one outlet opening 2 is formed by a replaceable baffle ring 17, which prevents coarse particles within the fluidized bed 9 of particulate feed material from partially or completely blocking the at least one outlet opening 2. The baffle ring 17 also reduces local effects of the fluidizing gas on the discharge path created by the at least one aperture 34.
To allow control of the discharge rate, the area of the at least one outlet opening 2 is adjustable. For the example shown in
For example, in the embodiment shown in
As can be seen from the above description, the variable aperture slit 1 allows the axisymmetric and spatially uniform discharge feed rate to be controlled, and can be increased in height and area to increase the discharge rate (up to a maximum area equal to that of the at least one outlet opening 2), or reduced to decrease the discharge rate by moving the cylindrical sliding sleeve 4. The movement of the cylindrical sliding sleeve 4 is controlled by an actuation mechanism 6 for moving the sliding sleeve 4 between the first and second positions. In the illustrated embodiment, the actuation mechanism 6 is located above the feed flow conditioner 20 and comprises a power screw, which converts the rotational motion of the motor to the vertical motion required of the cylindrical sliding sleeve 4 in this embodiment. It can be appreciated that any actuation mechanism 6, positioned at any location, can be used to adjust the outlet opening area.
Where the gas supply means of the feed charging device 20 includes a windbox 15, the windbox 15 may be supplied with the fluidizing gas through a fluidizing gas inlet nozzle 14, and is separated from the holding vessel 11 by the bottom partition 13, which may be in the form of a fluidizing plate. The fluidizing plate 13 contains a plurality of apertures 34, which may be defined by a plurality of high precision tuyeres 12, which allow the fluidizing gas to enter the holding vessel 11, as shown in
Instead of tuyeres 12, it will be appreciated that the bottom partition 13 may be partially or entirely comprised of one or more porous pads or porous membranes, and wherein the apertures 34 of bottom partition 13 are defined by the porous pads or porous membranes.
The holding vessel 11 further includes at least one off-gas outlet opening 10, which is provided in the conduit wall of the outlet conduit 5, and allows the fluidizing gas to be discharged from the device 20. The at least one off-gas outlet opening 10 is located above the height of the fluidized bed 9 of particulate feed, in communication with the upper zone 38 of interior chamber 30. This allows the collecting of elutriated fines that are carried with the off-gas from the fluidized bed 9, which will be discharged downwards through the discharge pipe 5, with the rest of the particulate feed.
Inside the holding vessel 11, a deflector plate 8 is positioned in the upper zone 38 of interior chamber 30 between the feed inlet opening 7 and the off-gas outlet opening 10. The deflector plate 8 eliminates short circuiting of fines from the feed inlet 7 to the at least one off-gas outlet opening 10. The deflector plate 8 may be oriented substantially vertically and the lower edge of the deflector plate 8 may be submerged into the fluidized bed 9, as shown in
Multiple actuated valves (not shown) mounted externally to the feed charging device 20 are governed by a PLC (programmable logic control) or other mechanical or electronic feedback controller and control the volumetric flow rate of the fluidizing gas, maintaining a required fluidization velocity in the bed 9 using feedback from a pressure sensor (not shown) positioned within the bottom zone 36 of the fluidized bed 9 immediately above the fluidizing plate 13. If required the flow rate of the fluidizing gas can be used to control the discharge rate of the particulate feed into the outlet conduit 5, along with the adjustment of the area of outlet opening 2.
Pressure sensors (not shown) are also located in the holding vessel 11, in the freeboard above the fluidized bed 9 level of particulate feed, as well as at the bottom of the fluidized bed 9, immediately above the bottom partition 13. This arrangement measures the pressure drop through the fluidized bed 9 and provides feedback to the PLC. This data is used to monitor the weight of the particulate feed within the feed flow conditioner 20, as well as the level of fluidized bed 9. The PLC can adjust the outlet opening 2 by, for example, changing the height of the variable aperture slit 1, or flow rate of the fluidizing gas, to control the discharge rate of the particulate feed through the outlet conduit 5.
Load cells 16 are placed at the bottom of the feed flow conditioner to support and accurately measure the weight of the feed flow conditioner 20 and its contents. The load cells 16 can be used to accurately measure/calibrate the mass flow rate of the particulate feed through the feed flow conditioner 20, by deliberately stopping the flow of particulate feed to the inlets 7 for a short period of time and measuring the rate of weight loss. In addition, the load cells 16 can effectively monitor the fluidized bed 9 level.
The feed flow conditioner can utilize expansion joints 18 that isolate the feed flow conditioner 20 from the burner downstream (below device 20), as well as the off-gas equipment upstream (above device 20). The expansion joints 18 isolate the feed flow conditioner 20 from the rest of the system and allow the weight of the feed flow conditioner 20 and its contents to be accurately weighed by the load cells 16. The expansion joints 18 also allow thermal expansion of the feed flow conditioner 20 and are connected to the feed flow conditioner 20 other equipment such as a burner, feed and off-gas ducts.
Both the windbox 15 and holding vessel 11 contain multiple access ports for inspection, cleaning and adjustment of the internals, the ports being covered by plates 47 when the device 20 is in use.
It will be appreciated by those skilled in the art that many variations are possible within the scope of the claimed subject matter. The embodiment shown in
To illustrate some of the variations possible,
In the embodiment shown in
The windbox 15 is separated from the holding vessel 11 by the bottom partition 13, which is in the form of two fluidizing plates that sandwich a porous membrane 51 in between. The bottom partition 13 contains a plurality of apertures 34, in both plates, which allow the fluidizing gas to enter the holding vessel 11 through the porous membrane 51. However, it will be appreciated that the bottom partition 13 may instead comprise a single apertured plate 34 with tuyeres 12, as in the first embodiment.
The windbox 15 consists of separate compartments, which are separated and sealed by a divider plate 49. Each of the compartments is supplied with fluidizing gas from separate fluidizing gas inlet nozzles 14.
A permanent baffle plate 48 is positioned on the top surface of the fluidizing plate 13 and protrudes into the fluidized bed 9. The position and shape of the baffle plate 48 can be modified to optimize the feed distribution from the feed inlet 40 along the holding vessel 11 to achieve uniform residence time for the particulate in the holding vessel 11. In the embodiment shown in
It can be seen that the baffle plate 48 and the windbox divider plate 49 at least partially define a feed inlet zone 53 within the chamber 30 of vessel 11, and that the separation of the windbox 15 into separate compartments allows different amounts of fluidizing gas to be supplied to the fluidized bed within the feed inlet zone 53. This arrangement allows the particulate feed entering at the feed inlet 7 to be pneumatically elevated, minimizing elutriation of dust in the freeboard due to the freefall of particulate material through the feed inlet 7. This also minimizes fluidizing gas percolation into the feed inlet 7. The feed inlet zone 53 functions as a check on the flow of feed into the fluidized bed 9. By connecting feed inlet 7 directly to a feed bin, and varying the flow of air to the windbox compartment 32 in this arrangement, the feed flow conditioner 20 can also be used as a feeder.
A deflector plate 52 is positioned in the upper zone 38 of interior chamber 30 between the feed inlet opening 7 and the off-gas outlet opening 10. The deflector plate 52 extends downwardly from top wall 26 and is positioned with its lower edge located above the fluidized bed 9 and above the upper edge of baffle plate 48 to provide a passage for flow of gas and particulates out of the feed inlet zone 53 and into the main portion of chamber 30. The position and shape of deflector plate can be modified to minimize the amount of dust that enters the holding vessel 11 or the off-gas vents 10 from the feed inlet opening 7.
In the embodiment shown in
The sliding outlet conduit 50 passes through the lower and upper zones 36, 38 of the interior chamber 30, extends vertically through the entire height of the holding vessel 11, and extends through an aperture 42 provided in the top wall 26 of the holding vessel 11, with the sliding outlet conduit 50 being sealed to the inner peripheral edge of the aperture 42 in the top wall 26. The sliding outlet conduit 50 extends downwards through the baffle ring 17, and may extend downwardly through the bottom partition 13, the sliding conduit 50 being sealed to the inner peripheral surface of the baffle ring 17.
The sliding outlet conduit 50 is positioned such that the outlet openings 2 are located in close proximity to the bottom partition 13, and the replaceable baffle ring 17. By varying the vertical position of the sliding outlet conduit 50, the outlet openings 2 can be movable from a first position away from the baffle ring 17 in which the area of the outlet openings 2 is open and at a maximum, to a second position in which the area of the at least one outlet opening 2 is constricted by the baffle ring 17 to a minimum. The sliding outlet conduit 5, together with baffle ring 17, thus define a variable aperture 1. For example,
The movement of the sliding outlet conduit 50 is controlled by an actuation mechanism 6 which may be the same as the actuation mechanism 6 described above.
In some examples, the off-gas discharge opening 10 can be at the top of the holding vessel 11 and can be equipped with a bin vent dust collector (not shown). In some examples, the holding vessel 11 would contain a plurality of feed inlet openings 7 to supply particulate feed. Such a configuration would allow a feed flow conditioner 20 to be positioned on top of an existing concentrate burner, with the feed supply system interfacing with the feed inlets. This arrangement would allow a bypass valve to divert the particulate feed from the feed supply system directly through the top of the outlet conduit 5, allowing maintenance to occur on the feed flow conditioner 20 without taking it offline.
To illustrate some of the variations possible,
The embodiment of
The feed charging device 20 of
As can be seen from the above description, the variable aperture 1 allows the rectangular spatially uniform discharge feed rate to be controlled, and can be increased in height and area to increase the discharge rate by rotating the valve mechanism 500 counter clockwise, or reduced to decrease the discharge rate by rotating the valve mechanism 500 clockwise. The movement of the valve mechanism 500 is controlled by an actuation mechanism (not shown) for rotating the valve mechanism 500. It can be appreciated that valve mechanism 500 can be replaced by other known actuated valves, such as knife gates or slide gates, to form an outlet aperture 1 of any desired plane shape.
As shown in this embodiment, the windbox 15 may consist of separate compartments, with each containing a specific arrangement of tuyeres 12 in the fluidized plate 34 to allow modification of the fluidizing characteristics within the holding vessel 11.
In some examples the variable aperture slit 1 can be replaced by a series of holes or slot openings, where the adjustment of the aperture cross-sectional area can be an internal sleeve controlled either vertically or rotationally.
The embodiments specifically described below are feed charging devices for a flash smelting furnace including an elevated reaction shaft having a burner where particulate feed material and reaction gas are brought together and reacted. However, it will be appreciated that the devices described below could be adapted for use in other fields using particulate feed systems, such as in the pharmaceutical, chemical and food production and processing industries.
In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
It will be appreciated by those skilled in the art that many installation variations are possible within the scope of the claimed subject matter. The embodiment shown in
A flash smelting furnace operating with a conventional feed system was simulated using an axisymmetric transient CFD model. Details of the modeling work can be found in a paper by Lamoureux et al. entitled “Impact of Concentrate Feed Temporal Fluctuations on a Copper Flash Smelting Process”, http://onlinelibrary.wiley.com/doi/10.1002/9781118887998.ch52/summary. Three transient conditions, with identical time-averaged feed rates, were modeled: (1) ideal, temporally uniform feed; (2) intermittent feed injected with a frequency of 1 Hz, with an 80% duty cycle; and (3) intermittent feed injected with a frequency of 5 Hz, with an 80% duty cycle. The latter two cases correspond to the feed frequencies of a conventional feed system, and the modeled natural frequency of a feed flow conditioner (as described herein), respectively. Performance of the burner was evaluated on the basis of oxygen efficiency. The reported values for the intermittent feed case are relative to the oxygen efficiency of the ideal case. The simulation results shown below in Table 1 illustrate that for the same amplitude, low-frequency feed intermittency has a significant negative impact on burner oxygen efficiency, while high-frequency intermittency has a negligible impact.
Furthermore to the above results, the impact of the amplitude of the intermittency was evaluated. Two additional transient conditions were modeled: 4. Sinusoidal intermittency, at a frequency of 1 Hz with an intermittency amplitude equal to 33% of the mean, and 5. Sinusoidal intermittency, at a frequency of 1 Hz with an intermittency amplitude equal to 50% of the mean. The simulation results shown below in Table 2 illustrate that for the same frequency, increasing intermittency amplitude has a correspondingly increasing negative impact on burner oxygen efficiency.
With the above in mind, the response of the feed flow conditioner to low frequency feed intermittency at the inlet was simulated using commercial CPFD software. The results, illustrated in
While the above subject matter has been described in the context of burners for flash smelting furnaces, it will be appreciated that it may also have application to other burners for particulate feed materials, such as burners for furnaces that are fueled by particulate coal, or other equipment requiring particulate feed.
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