EP3060845A1

EP3060845A1 - Velocity control shroud for burner

Info

Publication number: EP3060845A1
Application number: EP14856263.0A
Authority: EP
Inventors: Alexandre Lamoureux; Ivan MARINCIC; Maciej Jastrzebski
Original assignee: Hatch Ltd
Current assignee: Hatch Ltd
Priority date: 2013-10-21
Filing date: 2014-10-21
Publication date: 2016-08-31
Also published as: WO2015058283A1; EP3060845A4

Abstract

A burner for a pulverous feed material, such as for a flash smelting furnace. The burner has a burner block that integrates with the roof of the furnace and has an opening therethrough to communicate with the reaction shaft of the furnace. A wind box is mounted over the block and supplies reaction gas to the reaction shaft through a nozzle which extends through the block opening. The burner additionally has a velocity control shroud that is capable of distributing the reaction gas flow between two concentric annular flow areas to modify the flow profile of the reaction gas. The velocity control shroud can be used with auxiliary inserts to modify the velocity, direction, swirl, turbulence and stroke or other characteristics of the reaction gas flow.

Description

VELOCITY CONTROL SHROUD FOR BURNER

TECHNICAL FIELD

[0001] The present subject matter relates to burners for use with pulverous feed materials, such as burners used, for example, on flash smelting furnaces. BACKGROUND

[0002] Flash smelting is a pyrometallurgical process in which a finely ground feed material is combusted with a reaction gas. A flash smelting furnace typically includes an elevated reaction shaft at the top of which is positioned a burner where pulverous feed material and reaction gas are brought together. In the case of copper smelting, the feed material is typically ore concentrates containing both copper and iron sulfide minerals. The concentrates are 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. Much of the sulfur in the concentrates combines with oxygen to produce sulfur dioxide which can be exhausted from the furnace as a gas and further treated to produce sulfuric acid.

[0003] A conventional burner for a flash smelter includes an injector having a water-cooled sleeve and an internal central lance, a wind box, 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. The feed material is introduced from above and descends through the injector sleeve into the reaction shaft. Oxygen enriched combustion air enters the wind box and is discharged to the reaction shaft through the annular channel. 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. A contoured adjustment ring is mounted around the lower portion of the injector sleeve within the annular channel, and can slide along the vertical axis. The velocity of the reaction gas can be controlled to respond to different flow rates by raising and lowering the adjustment ring with control rods that extend upwardly through the wind box to increase or reduce the cross-sectional flow area in the annular channel. Such a burner for a flash smelting furnace is disclosed in U.S. patent no. 6,238,457.

[0004] The presence of the adjustment ring precludes the possibility of mounting additional devices which can further adjustably modify the gas flow characteristics independently of velocity. Devices such as adjustable swirl generating inserts, turbulence generating inserts, shrouds, etc. cannot be incorporated into a conventional design. These devices are known from other combustion fields, and are known to improve mixing and plume characteristics, improving combustion. Additionally, the presence of the adjustment ring necessitates that the combustion gas flow does not exit the nozzle vertically, but is instead forced to converge towards the centre of the reaction shaft.

[0005] Computational Fluid Dynamic (CFD) analysis was used to investigate a benchmark reaction shaft and burner to understand the effects of swirl intensity, turbulence intensity and injection angle within a smelting furnace. The results, as shown in Table 1 , indicate that increased swirl intensity and turbulence intensity within the reaction shaft can lead to improved combustion. The CFD analysis also showed that deviation of the gas injection angle from the vertical, either towards the centerline or away from the centerline of the burner results in reduced combustion efficiency, and should be avoided.

[0006] It is a goal of the inventors to provide an improved burner for a flash smelting furnace or other applications using a pulverous feed material that provides better mixing, more optimal oxygen efficiency, and improved control.

[0007] Table 1

SUMMARY OF THE DISCLOSURE

[0008] 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.

[0009] According to one aspect, a burner is provided for a pulverous feed material. The burner has a structure that integrates the burner with a reaction vessel, and has an opening that communicates with the interior of the reaction vessel. The burner also has a gas supply channel to supply reaction gas through the opening into the reaction vessel, and a feed supply for delivering pulverous material to the reaction vessel. The burner additionally has a velocity control shroud that is capable of distributing the reaction gas flow between two concentric, annular flow areas to modify the flow profile of the reaction gas.

[00010] According to another aspect, a burner is provided for a flash smelting furnace. The burner includes a burner block, a nozzle, a wind box, an injector, and a velocity control shroud. The block integrates with the roof of the furnace, and has an opening therethrough to communicate with the reaction shaft of the furnace. The wind box is mounted over the block and supplies reaction gas to the reaction shaft through the nozzle which extends through the block opening. The injector has a sleeve for delivering pulverous feed material to the furnace and a central lance within the sleeve to supply compressed air for dispersing the pulverous feed material in the reaction shaft. The injector is mounted within the wind box so as to extend through the nozzle, defining therewith an annular channel through which reaction gas from the wind box flows into the reaction shaft. The velocity control shroud is positioned concentrically outside of the injector, and defines two flow areas: a small inner annular area and a larger outer annular area. The velocity control shroud can be used with a series of auxiliary inserts positioned in the inner annular area to modify the velocity, direction, swirl, turbulence and/or other characteristics of the reaction gas flow.

[00011] In some examples, the vertical position of the velocity control shroud can be controlled to modify the relative size of the inner and outer annular areas. Lowering the shroud decreases the size of the outer annular area. This modifies the proportion of reaction gas flowing through the outer annular flow area created between the shroud and the nozzle, and the inner annular flow area created between the velocity control shroud and the injector. By lowering the velocity control shroud into the nozzle, a larger portion of the reaction gas is forced to flow through the inner annular flow area, increasing the average velocity of the total reaction gas exiting the burner. By raising the velocity control shroud, less reaction gas flows through the velocity control shroud as more reaction gas can bypass the velocity control shroud through the outer annular area, thereby reducing the average velocity of the reaction gas exiting the burner. It should be clear to those skilled in the art that the maximum velocity which can be achieved through a nozzle controlled by the velocity control shroud is governed by the size of the inner annular area. The highest outlet velocity is achieved when the shroud is in its lowest position and substantially all of the reaction gas is forced through the inner annular area. [00012] In some examples, a nesting insert with helical swirl generating vanes is inserted into the velocity control shroud to add a tangential flow component to the reaction gas exiting the burner and thereby induce swirling within the reaction shaft. In some examples, the pitch and width of the vanes of the swirler insert can be adjusted to achieve different maximum swirl intensities.

[00013] In some examples, a nesting insert containing a series of radial fins or helical vanes or other deflectors on the outside of the insert that are angled from the longitudinal axis is inserted into the velocity control shroud to modify the turbulence of the reaction gas exiting the burner. In some examples, the angle and width of the deflectors of the turbulence generating insert can be adjusted to achieve different maximum turbulence intensity. [00014] In some examples, the velocity control shroud is an externally controlled component that can be moved vertically to control the exit velocity of the reaction gas.

[00015] In some examples, the insert is an externally controlled component that can be moved vertically to control the swirling or turbulence of the reaction gas. [00016] In some examples, the velocity control shroud and insert can be independently controlled to decouple the flow velocity, and the turbulence or swirl component.

[00017] In some examples, the cross-sectional area of the velocity control shroud can be adjusted to achieve different maximum outlet velocities. BRIEF DESCRIPTION OF THE DRAWINGS

[00018] In order that the claimed subject matter may be more fully understood, reference will be made to the accompanying drawings, in which:

[00019] Fig. 1 is a cross-sectional view of a burner for a flash smelting furnace according to one embodiment containing only the velocity control shroud. [00020] Fig. 2 is a cross-sectional view of a burner for a flash smelting furnace according to a second embodiment containing the velocity control shroud and swirler insert.

[00021] Fig. 3 is a cross-sectional view of a burner for a flash smelting furnace according to a third embodiment containing the velocity control shroud and turbulence generating insert. [00022] Fig. 4 is an isometric view of a velocity control shroud shown in the three embodiments.

[00023] Fig. 5 is an isometric view of a swirler insert shown in the second embodiment. [00024] Fig. 6 is an isometric view of a turbulence generating insert shown in the third embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[00025] 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.

[00026] As shown in Fig. 1 , a burner 13 is positioned above the reaction shaft of a flash smelting furnace. The base of the burner 13 is provided by a block 11 which integrates into the roof of the reaction shaft of the furnace and a nozzle 14 which extends through the block 1 1. A wind box 15 is mounted above the nozzle 14 and an injector 16 having a sleeve 17 (which may be water-cooled) and a central lance 18 extends through the wind box 15 and through an opening 19 in the nozzle 14. Above the wind box 15 is the material feed equipment, comprising air slides, splitter boxes, manifold connectors, feed pipes, and a distributor which communicates with the sleeve 17 of the injector 16. The central lance 18 of the injector 16 extends upwardly beyond the sleeve 17 through the top of the distributor to a lance head section. Radiating guide wings 12 help to keep the central lance 18 centered within the sleeve 17. The sleeve 17 may also have similarly radiating vanes (not shown) to help to keep the sleeve 17 centered within the opening 19 of the nozzle 14.

[00027] The burner is mounted on the furnace support structure and the nozzle 14 extends through the burner block 1 1 which provides the main seal between the reaction shaft of the furnace and the burner 13. The block 11 is water-cooled and has multiple ports for access and cleaning of the burner components that are located below the block 11. The injector sleeve 17 extends down into the upper portion of the reaction shaft of the furnace. The central lance 18 has a tip 28 at its lower end which extends below the sleeve 17. The lower, inside rim of the sleeve 17 diverges towards the bottom opening and the lance tip 28 has a frustoconical shape and together they direct the feed material outwardly. The lance 18 carries compressed air which is directed horizontally from the tip 28. The compressed air further disperses the feed material in an umbrella pattern through the reaction shaft of the furnace.

[00028] Inside the burner 13 is a velocity control shroud 22, which is positioned concentrically with the sleeve 17 of the injector 16. The velocity control shroud 22, as shown in Fig. 4, is of generally conical shape, and is larger than the lower nozzle opening 19a. The opening 19 of the nozzle 14 and the outer surface of the velocity control shroud 22 define an outer annular channel 20, while the inner surface of the velocity control shroud 22 and the sleeve 17 define an inner annular channel 21 , through which the reaction gas passes from the wind box 15 to the reaction shaft. [00029] A shroud actuator, which may be hydraulic, pneumatic, or a mechanical screw jack, (not shown) mounted externally to the burner is governed by a PLC (programmable logic control) to adjust the vertical position of the velocity control shroud 22. Adjusting the vertical position of the velocity control shroud 22 changes the size of the outer annular area. This allows the proportion of reaction gas that flows through the outer annular channel 20 and that flows through the inner annular channel 21 to be manipulated. When the velocity control shroud 22 is in a high position it has little effect on the velocity of the reaction gas that flows through the burner 13. In this case the velocity is governed by the opening 19 formed by the nozzle 14. If the velocity control shroud 22 is lowered along the sleeve 17 of the injector 16, the portion of reaction gas entering the velocity control shroud 22 and flowing through the inner annular channel 21 increases, while the portion of reaction gas flowing through the outer annular channel 21 decreases. When the velocity control shroud 22 is at its lowest position, which brings it into contact with the nozzle 14, the full flow of reaction gas is forced through the inner annular channel 21 , which decreases the cross-sectional exit area of the reaction gas flow, thereby maximizing the exit velocity. The effect of the shroud position on the outlet velocity for the high and low positions was simulated using CFD, and is shown in Table 2. [00030] Turning to Fig. 2, a second embodiment is shown. Similar components are given like names and like reference numbers, and their description will not be repeated.

[00031] In this embodiment, a swirler insert 23 resides in the inner annular channel 21 defined by the inner surface of the velocity control shroud 22 and the sleeve 17, and manipulates the passing reaction gas flow velocity profile. The swirler insert 23, as shown in Fig. 5, contains a plurality of vanes 25, which impart a tangential velocity to the passing fluid, thereby inducing an overall swirling motion of the fluid flowing into the reaction shaft. The swirler insert 23 partitions the inner annular channel 21 and creates a swirling annular channel 24 of flow within.

[00032] The swirler insert 23 can be raised and lowered with an insert actuator, which may be hydraulic, pneumatic or a mechnical screw jack (not shown), to manipulate the amount of swirl induced in the reaction gas, controlling the overall burner plume shape as well as the mixing characteristics within the reaction shaft. When the swirler insert 23 is in the highest position the amount of reaction gas that is forced into the the swirl annular channel 24 is minimized. When the swirler insert 23 is progressively lowered along the sleeve 17, the amount of reaction gas that is forced through the swirl annular channel 24 increases. The amount of swirl imparted to the flow is maximized when the swirler insert 23 is in its lowest position and in contact with the velocity control shroud 22. The total tangential (swirling) velocity of the gas jet emerging from the nozzle of the burner can be manipulated by varying the position of the swirler insert, as indicated in the CFD modeling results shown in Table 2.

[00033] Table 2

[00034] The vertical position of the swirler insert 23 controls the degree of swirling independently of the axial velocity of the fluid, which is controlled by the velocity control shroud 22.

[00035] Controlling the plume shape also allows control of the temperature and wear of the reaction shaft refractory lining.

[00036] Turning to Fig. 3, a further embodiment is shown. Similar components are given like names and like reference numbers, and their description will not be repeated.

[00037] In this embodiment, a turbulence generating insert 26 resides in the inner annular channel 21 defined by the inner surface of the velocity control shroud

22 and the sleeve 17, and manipulates the passing reaction gas flow profile. The turbulence generating insert 26, as shown in Fig. 6, contains a plurality of fins 27, which are situated in pairs around the full circumference of the turbulence generating insert 26 and fixed at an angle normal to the curved surface of the ring. Each pair of fins 27 has an angle of attack with respect to the direction of the fluid flow. The angle of attack and fin spacing is selected to produce the desired turbulence structure generated by the turbulence generating insert 26.

[00038] As the reaction gas from the wind box 15 passes each pair of fins 27, counter-rotating eddies are formed through the the inner annular channel 21 defined by the opening 19 of the nozzle 14 and the sleeve 17, thereby increasing the turbulence of the reaction gas entering the reaction shaft. This increases the degree of mixing of the reaction gas and feed, thereby promoting better combustion.

[00039] The turbulence generating insert 26 can be raised and lowered with an insert actuator, which may be hydraulic, pneumatic or a mechnical screw jack (not shown), to provide the optimal degree of turbulent mixing required depending on the incoming reaction gas flow rate and composition.

[00040] The vertical position of the turbulence generating insert 26, hence the turbulence intensity of the reaction gas, is controlled independently of the axial velocity of the reaction gas, which is controlled by the velocity control shroud 22. [00041] It will be appreciated by those skilled in the art that many variations are possible within the scope of the claimed subject matter. The embodiments that have been described above are intended to be illustrative and not defining or limiting. For example, there are possible methods of vertically positioning the velocity control shroud and inserts using feedback control. [00042] In some cases, the turbulence generating insert may be fitted with vanes of a helical geometry, or other insert geometries, in lieu of the angled fins, to provide alternative gas flow patterns and mixing characteristics within the reaction shaft.

[00043] 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 pulverous feed materials, such as burners for furnaces that are fueled by pulverous coal.

Claims

What is claimed is:

1. A burner for use with a pulverous feed material, comprising: a burner structure that integrates with a reaction vessel, and that has an opening therethrough to communicate with the interior of the reaction vessel; a gas supply channel to supply reaction gas into the reaction vessel through the opening; a feed supply for delivering pulverous material into the reaction vessel; a velocity control shroud that is capable of distributing the reaction gas flow between two concentric annular flow areas to modify the flow profile of the reaction gas; and a shroud actuator by which the vertical position of the shroud can be varied such that the ratio between the inner and outer annular areas can be varied.

2. The burner of claim 1 , for use on a flash smelting furnace, wherein: the burner structure integrates with the roof of the furnace, having a nozzle that defines an opening therethrough to communicate with the reaction shaft of the furnace; the gas supply channel supplies the reaction gas to the reaction shaft through the nozzle; the shroud divides the outlet of the burner into an inner annular area and an outer annular area; and further comprising: an injector having a sleeve for delivering the pulverous feed material into the furnace, the injector extending through the nozzle, defining therewith an annular channel through which the reaction gas flows into the reaction shaft.

3. A burner according to any one of the above claims which includes a swirl inducing insert with guide vanes revolved around the nozzle to induce swirling of the flow of the reaction gas.

4. A burner according to claim 3 where the swirl inducing insert can be moved vertically by an insert actuator.

5. A burner according to any one of the above claims which includes a turbulence generating insert fitted with a plurality of deflectors around the nozzle to induce turbulence of the flow of the reaction gas independently of the port fluid streams.

6. A burner according to claim 5 where the turbulence generating insert can be moved vertically by an insert actuator.

7. The burner of any one of claims 5 or 6 wherein the deflectors are fins.

8. The burner of any one of claims 5 or 6 wherein the deflectors are helical vanes.

9. The burner of any one of the above claims wherein the shroud is generally conical.