WO2015104333A1

WO2015104333A1 - Gas treatment device

Info

Publication number: WO2015104333A1
Application number: PCT/EP2015/050256
Authority: WO
Inventors: Petrus Leonardus Verbraak; Shishir SABLE
Original assignee: Danieli Corus B.V.
Priority date: 2014-01-10
Filing date: 2015-01-08
Publication date: 2015-07-16
Also published as: AR099064A1; TW201536404A

Abstract

Gas treatment device for treating a gas flow, comprising a vessel ( 2, 72} with: • a first compartment (3, 73) comprising an inlet for the gas flow to be treated and a stack of granulate beds (23, 77) holding a granulate material; • a second compartment (4, 74) for the discharge of clean gas; • a third compartment (5, 75) for the supply of a purging gas, The second and third compartments are at opposite sides of the first compartment. The granulate beds (23, 77) comprise a gas permeable top surface (33) supporting the granulate material and a clean gas collection box (31) below the gas permeable top surface having one or more clean gas exit openings (34) connecting to the second compartment.

Description

GAS TREATMENT DEVICE

The present invention relates to a gas treatment device, in particular a device for filtering or cleaning a gas stream, more particular a waste gas stream such as exhaust gas from a blast furnace .

Exhaust gas from blast furnaces leaves the blast furnace under high pressures and high temperatures. The pressures are

typically as high as 1,5 - 5 bar but can be as high as 30 bar or even higher for specific applications. The blast furnace gas contains dust particles, which need to be removed before the hot gas can be used, e.g., in a turbine. Hitherto, blast furnace gas is cleaned by water scrubbing or by filter bags. Water scrubbing has the disadvantage that it cools the gas flow, making it less suitable for use with a turbine. It also requires a water treatment plant to separate dust from the used water. Filter bags on the other hand can be used within a limited temperature range and are sensitive to sparks. Filter bags need to be replaced on a regular basis.

Filtering installations with inclined granulate beds filled with catalytic materials have been proposed for cleaning waste gas, for instance in US 2012/0282146. However, these cannot be used under medium to high pressures typically occurring with blast furnace gases.

The obj ect of the invention is to provide a filter system enabling effective cleaning of a hot gas flow under high

pressure, reducing loss of temperature or pressure of the gas. It is a further object of the invention to provide a filter configuration enabling a compact construction. The object of the invention is achieved with a gas treatment device Gas treatment device for treating a gas flow, comprising a vessel with:

• a first compartment comprising an inlet for the gas flow to be treated and a stack of granulate beds holding a granulate material;

• a second compartment for the discharge of clean gas;

• a third compartment with one or more inlets for a

purging gas .

The second and third compartments are at opposite sides of the first compartment. The granulate beds comprise a gas permeable top surface supporting the granulate material and a clean gas collection box below the gas permeable top surface having one or more clean gas exit openings connecting to the second

compartment, and one or more purging gas inlet openings

connecting to the third compartment. The gas treatment device further comprises a control unit for selectively switching between a first condition with the clean gas exit openings being opened while the purging gas inlet openings are closed, and a second condition with the purging gas inlet openings being opened while the clean gas outlet openings are closed to allow the purging gas to flow into the first compartment via the collection box to lift and remove the granulate material from the permeable top surface.

These measures result in a compact and robust configuration and enables to design installations particularly useful for the treatment of gases in a broad range of operating pressures, in particular medium to high pressures.

The granulate material can for example be a filter material and/or a reactive cleaning material.

A more specific embodiment of the gas treatment device,

particularly suitable for fast and easy replacement of used granulate material, may comprise a fourth compartment, extending between two opposite ends of the second and third compartments, a rear wall of the first compartment separating the first and fourth compartments, the granulate beds being inclined having an upper edge connected to the rear wall, the rear wall being provided with an opening along the entire width of the upper edge of each granulate bed. The fourth compartment can be filled with a stock of granulate material, which can flow to the granulate beds via the openings in the rear wall.

The granulate bed can for example be inclined under an angle corresponding to the angle of repose of the granulate material. When the granulate material flows from the fourth compartment to the granulate bed, it will cover the grit or sieve surface with a layer of uniform thickness. The thickness of the layer of granulate material is determined by the height of the rim or skirt at the lower front edge of the granulate bed.

The device is particularly suitable for use with medium or high pressures, if the vessel is an internally compartmented

cylindrical housing or pressure vessel. In a specific

cylindrical embodiment, viewed in radial cross section the first compartment may be formed by a central square and a first cylinder segment bridging the corners of the square at a front side of the vessel. The cylindrical shell may for example join the corners of the central square to define the second, third and fourth compartment and the first cylindrical front part of the first compartment. Alternatively, to create more space for storing granulate material, the corners of the central square adjacent the fourth compartment may be at a distant from the cylindrical shell. The granulate beds are within the borders of the central square.

Instead of cylindrical vessels the gas treatment installation may use a housing or vessel with a different cross section, e.g. a polygonal, rectangular or square cross section. Whereas the cylindrical embodiment is particularly suitable for high pressure processes, such as filtering blast furnace gases, the rectangular variant may for example be used with lower or atmospheric pressure gas treatment processes. The rectangular outline makes it possible to position the vessels closely together in a compact and robust arrangement.

Raw dirty gas or blast furnace gas enters the gas inlet and penetrates through the granulate beds due to a slight under pressure. Dust particles are collected on the top layer of the granulated material. Depending on the treatment of the gas, the granulated material can be sand or ceramic material for de- dusting purposes or might be active carbon or coke or other materials to remove or react or enhance reactions, like

catalytic materials, to specific components of the gas, like sulphur oxides, nitrogen oxides, halogens, VOC's, dioxins, etc.

After buildup of dust particles, or saturation of the granulated material with specific components or loss of reactivity of the granulated material, the granulated material might be removed and replaced. The granulate material can be removed using a purge gas which enters the clean gas collection space below the grit or sieve surface of the granulate bed. The purging gas passes the grit or sieve surface and fluidizes and lifts the granulated material and increases the total height of the granulated layer. This height exceeds the rim height at the lower front edge of the granulate bed. As a result the

granulated material with possible dust particles on top will flow over the rim by gravity. The released dust and granulated material will be collected, e.g., in a hopper bottom, where it can be removed from the gas treatment device. After purging, part of the layer of granulated material falls back down on the sieve surface and the rest of the layer will automatically be replenished with fresh granulated material. The purging gas can for example be compressed air or an inert gas, such as carbon dioxide or nitrogen gas, or it can be cleaned gas, cleaned in an earlier step, e.g., cleaned blast furnace gas. The purging gas is purged under a pressure

exceeding the pressure of the blast furnace gas collected in the first compartment.

Collected dust and used and removed granulate material may be separated for storage or transport to another location. The granulate material may for example be recycled.

Exemplary embodiments of the filtering device are explained with reference to the accompanying drawings.

Figure 1: shows a perspective view of a gas treatment device with one side partly broken away;

Figure 2; shows the device of Figure 1 in front view;

Figure 3; shows a cross section along line II -^■■ II in Figure

2;

Figure 4 : schematically shows a perspective view of an

individual granulate bed of the device of Figure

1;

Figure 5: shows a longitudinal cross section of the device of Figure 1 ;

Figure 6 ; shows an installation of a plurality of gas

treatment devices in parallel arrangement;

Figure 7 ; shows in cross section an alternative embodiment of a gas treatment device;

Figure 8 ; shows the gas treatment device of Figure 7 in

longitudinal cross section;

Figure 9; shows the cross section of Figure 3 for an

alternative embodiment. Figure 1 shows a gas treatment installation 1 for processing a high pressure gas flow, in particular flue gas from a blast furnace comprising solid particles, such as fly ash. The

installation 1 comprises a vessel formed by a cylindrical compartmented pressure vessel 2,

The cross section in Figure 3 shows the various compartments: a central first compartment 3 bordered at opposite sides by a second compartment 4 and a third compartment 5 respectively, and by a rear fourth compartment 6, extending between two opposite ends of the second and third compartments 4, 5. The four compartments 3, 4, 5, 6 extend vertically and jointly have a circular outline in cross section. The first compartment 3 is formed by a central square 3A and a first cylinder segment 3B bridging the corners 8, 9 of the square 3A at a front side 11 of the vessel 2, The cylindrical shell 2 joins the corners 8, 9, 12, 13 of the central square 3A to define the second, third and fourth compartments 3, 4, 5 and the first cylindrical front part 3B of the first compartment 3.

In an alternative embodiment the rear fourth compartment 6 may be enlarged by spacing the rear corners 12, 13 from the

cylindrical inner wall of the vessel 2, as is shown in Figure 9, A first flat side wall 14 separates the central first

compartment 3 from the second compartment . A second flat side wall 15 is opposite to the first side wall 14 and separates the first compartment 3 from the third compartment 5. A flat rear wall 16 separates the first and fourth compartments 3, 6.

In cross section, a first quarter circle segment 18 of the wall of the cylindrical pressure vessel 2 forms a front wall of the first compartment 3. The other quarter segments 19, 20, 21 of the pressure vessel 2 form outer walls of the second, third and fourth compartments 4, 5, 6, respectively. The central first compartment 3 encases a stack of inclined granulate beds 23, In cross section (see Figure 3) the granulate beds 23 fill up the central square 3A. Each granulate bed 23 comprises a substantially horizontal upper side 24 (see Figure 4) bordering the rear wall 16 of the first compartment 3 and two inclined side edges 26, 27 sloping down towards the front side 11. Side edge 26 joins the first side wall 14, while side edge 27 joins the second side wall 15. A continuous front space 28 extends vertically between the substantially horizontal front edges 29 of the granulate beds 23 and the front wall 18 of the first compartment 3.

Figure 4 shows schematically an individual granulate bed 23, Each granulate bed 23 comprises a box 31 and a layer 32 of substantially even thickness of a granulate filter material on top of the box 31 (not shown in Figure 4) . The granulate beds 23 have upstanding front edges 29 preventing granulate material from falling down.

The boxes 31 of the granulate beds 23 have a gas permeable top surface or grit 33 carrying the granulate material. All other walls of the box 31 are gas tight. The boxes 31 of each

granulate bed 23 comprise one or more openings 34, 35 opening into the second and third compartments 4, 5, respectively. The opening 34 to the clean gas collection compartment 4 is a wide rectangular opening. The openings 35 to the purging gas

compartment 5 include a number of smaller openings. Other configurations of openings can also be used, if so desired.

These openings 34, 35 are closeable by a programmable control unit (not shown) . The boxes 31 are closed at the front and rear sides 37, 38.

The rear wall 16 of the first compartment 3 is provided with an inlet 39 opening into the fourth compartment 6. The inlet 39 is a rectangular slit extending over the full width of the granulate bed 23. The fourth compartment 6 is configured to store a supply of granulate material to be used for the

granulate beds 23.

The vessel is capped by a dome shaped top 41 (see Figures 1, 2 and 5). The second and third compartments 4, 5 are closed off by respective top plates 42 at the top of the cylindrical part of the vessel 2. The first and fourth compartments 3, 6 continue in the dome shaped top 41 and are separated here by an inclined wall 43. At the top end the dome comprises an inlet 44 for the fourth compartment 6 allowing filling of the fourth compartment 6 with granulate material. At the front side 11 of the vessel 2, the dome 41 comprises an inlet 46 for gas to be treated.

Figure 5 shows a longitudinal cross section of the vessel 2 along a midplane parallel to the rear wall 16. The second compartment 4 is divided by a partition 48 into an upper

compartment 4A and a lower compartment 4B. Upper compartment 4A is connected to a first outlet 51 for filtered gas. Lower compartment 4B is connected to a second outlet 52 for filtered gas. Similarly, the third compartment 5 is divided by a

partition 49 into an upper compartment 5A and a lower

compartment 5B. Upper compartment 5A is connected to a first inlet 53 for purging gas. Lower compartment 5B is connected to a second inlet 54 for purging gas.

The cylindrical pressure vessel has a reverse cone shaped bottom section 56 with a central discharge opening 57 for solid waste collection.

In operation the openings 35 between the boxes 31 and the third compartments 5 are closed, while the opening 34 between the boxes 31 and the second compartment 4 are open. The gas inlet 46 at the dome shaped top 41 is opened. Gas flows down into the continuous front space 28 of the first compartment 3. Gas from blast furnaces is very hot and highly pressurized. The gas is distributed over the various granulate beds 23 where it crosses the layers 32 of granulate material to enter the respective boxes 31. The filtered gas leaves the boxes 31 via the openings 34 to the second compartment 4 where the clean filtered gas is collected for discharge via the outlets 51, 52, e.g., to a turbine .

After a use period the granulate filter material 32 is clogged with residue dust material which hinders effective filtering. To clean the granulate beds 23, opening 34 is closed and opening 35 is opened via an automated control system. Ά purging gas is purged through the boxes 31 to lift the layers 32 of granulate material, which falls down via the front part 28 of the first compartment 3 to be collected in the reverse cone shaped bottom section 56.

Simultaneous purging of the complete stack of all granulate beds 23 would be impeded by back pressure by the blast furnace gas in the first compartment 3. To coop with this the upper and lower halves of the stack are purged alternately. First the openings 34 between the boxes 31 and the upper second compartment 4A are closed, while the openings 35 between the upper third

compartment 5A and the boxes 31 are opened. Purging gas is blown from the upper third compartment 5A into the respective boxes 31 to lift the granulate filter material 32. As a result the granulate bed material flows down via the continuous front space 28 of the first compartment 3 to the reverse cone shaped bottom section 56 where it is collected for discharge.

After removal of the granulate bed material 32 in the upper half of the stack, the supply of purging gas is stopped by closing the openings 35 to the upper third compartment 5A. As the angle of inclination of the granulate bed 23 corresponds to the angle of repose of the granulate material, fresh granulate material flows from the fourth compartment 6 into the first compartment 3 to cover the gas permeable top surfaces 33 of the respective boxes 31. A stable layer 32 of essentially uniform thickness is formed on the boxes 31 of the granulate beds 23. After the granulate beds 23 have been replenished, the openings 39 in the rear wall 16 are closed off and the openings 34 leading to the upper second compartment 4A are re-opened. In a next step, the granulate beds 23 of the lower half of the stack can be purged in the same manner, the purging gas being supplied by the lower purging gas inlet 54 via the lower third compartment 5B. During these purging cycles the inlet 46 for raw gas remains opened.

The cylindrical configuration is particularly useful for high pressure gas treatment processes, such as filtration cleaning of blast furnace gases. The closing mechanisms for the openings 34, 35, 39 are not shown by the drawings but can be realized in a conventional manner known to the average person skilled in the art, e.g., by means of valves at the purging gas inlets, the clean gas outlets and the inlet for fresh granulate.

The gas treatment installation 60 may comprise a plurality of gas treatment devices 1 in parallel arrangement, as for example is shown in Figure 6. The installation 60 in Figure 6 has a central supply line 61 transporting gas to be treated to the various gas treatment devices 1 and discharge lines 63 for collecting treated clean gas. Purging gas may be taken from gas storage cylinders or directly from clean gas lines 62, if clean gas is used for purging. A pressure booster can be used to increase the pressure of clean gas for purging. Clean gas is collected from the vessels 1 via the clean gas outlets. Solid waste from the gas treatment devices 1 contains granulate material and dust. These two materials can be separated

mechanically, e.g., by sieving. Subsequently, the granulate material can be recycled to the gas treatment devices 1.

Instead of cylindrical vessels the gas treatment installation may use a vessel with a different cross section, e.g. a

rectangular or square cross section, as is shown in Figure 7. Apart from the rectangular cross section the configuration and the way of functioning are the same. Whereas the cylindrical embodiment is particularly suitable for high pressure processes, such as filtering blast furnace gases, the rectangular variant may for example be used with lower or atmospheric pressure gas treatment processes.

The gas treatment device 70 of Figure 7 comprises a vessel 72 with a rectangular outline vessel with a first compartment 73 comprising an inlet 78 for the gas flow to be treated and a stack of granulate beds 77 holding a filtering granulate filter material. At one side of the first compartment 73 is a second compartment 74 connected to an upper and a lower clean gas outlet 81, 82 (see Figure 8). At the opposite side is a third compartment 75 connected to an upper and a lower purging gas inlet 83, 84. At the rear side of the first compartment is a fourth compartment 76 for the storage of fresh granulate filter material. The second, third and fourth compartments 74, 75, 76 are in communication with the first compartment 73 via closeable openings, in the same manner as described above for the

installation of Figures 1 - 6. Also the granulate beds 77 and the process of operation are the same as described above, except for that lower pressures are to be used.

The foregoing description is provided for the purpose of

explanation and is not to be construed as limiting the

invention. While various embodiments have been described it is understood that the words which have been used herein are words of description and illustration, rather than words of

limitation. Although the embodiments have been described herein with reference to particular structures and methods, the invention is not intended to be limited to the particulars disclosed herein. Structures and methods described in

association with one embodiment are equally applicable to all other embodiments described herein unless otherwise indicated. Those skilled in the relevant art, having the benefit of the teachings of this specification, may effect modifications to the invention as described herein, and changes may be made without departing from the spirit and scope of the invention, for instance as set forth by the appended claims.

Claims

Gas treatment device for treating a gas flow,

comprising a vessel (2, 72) with:

• a first compartment (3, 73) comprising an inlet (46, 78) for the gas flow to be treated and a stack of granulate beds (23, 77) holding a granulate material;

• a second compartment (4, 74) for the discharge of

clean gas;

• a third compartment (5, 75) with one or more inlets (53, 54; 83, 84) for a purging gas;

wherein the second and third compartments are at opposite sides of the first compartment,

wherein the granulate beds (23, 77) comprise a gas

permeable top surface (33) supporting the granulate material and a clean gas collection box (31) below the gas permeable top surface having one or more clean gas exit openings (34) connecting to the second

compartment, and one or more purging gas inlet openings (35) connecting to the third compartment,

wherein the gas treatment device comprises a control unit for selectively switching between a first condition with the clean gas exit openings being opened while the purging gas inlet openings are closed, and a second condition with the purging gas inlet openings being opened while the clean gas outlet openings are closed to allow the purging gas to flow into the first compartment via the collection box to lift and remove the granulate material from the permeable top surface .

Gas treatment device according to claim 1, comprising a fourth compartment (6, 76), extending between two opposite ends of the second and third compartments (4, 5; 74, 75), a rear wall (16) of the first compartment separating the first and fourth compartments, the granulate beds (23) being inclined having an upper edge (24) connected to the rear wall, the rear wall being provided with an opening (39) at the upper edge (24) of each granulate bed.

Gas treatment device according to claim 2 wherein the granulate bed (23) is inclined under an angle

corresponding to the angle of repose of the granulate material .

Gas treatment device according to anyone of the

preceding claims, wherein the vessel (2) is a

cylindrical pressure vessel.

Gas treatment device according to claim 4, wherein the vessel (2) has a cylindrical shell which, viewed in cross section, is compartmented with the first

compartment (3) being formed by a central square ( 3A) and a first cylinder section (18) bridging the corners

(8, 9) of the square at a front side of the vessel, wherein the cylindrical shell joins the corners (8, 9, 12, 13) of the central square to define the second, third and fourth compartment (4, 5, 6) and the first cylindrical front section (3B) of the first compartment

(3) .

Gas treatment device according to one of claims 1 - 4, wherein the vessel is rectangular in top view.

Method of purging a gas treatment device according to any one of the preceding claims, wherein a purging gas is blown from the third compartment into the clean gas collection boxes of at least a part of the stack of granulate beds (23) . 8, Method according to claim 7 wherein different groups of granulate beds (23) are purged alternately.

9. Method according to claim 8, wherein the upper half and the lower half of the stack of granulate beds (23) are purged alternately.

10. Method according to any one of claims 7 - 9, wherein removed granulate material is cleaned and subsequently recycled to the fourth compartment.

11. Method according to claim 10, wherein the removed

granulate material is cleaned by mechanical separation of dust from the granulate material.