ARRANGEMENT AND METHOD FOR MIXING A PASTE AT A WASTE DISPOSAL SITE

Abstract

An arrangement and a method for mixing and handling industrial side-stream materials. The mixer (6) is arranged onto a movable work machine (5) and it is used for mixing at least two side-stream materials to form a geopolymer. The side-stream materials are processed between a waste pile (4) and a casting area (13) in the mixer (6). Cast paste is allowed to harden and after that it is crushed to obtain an earthwork material.

Claims

1. An arrangement at a factory waste disposal site, which arrangement comprises at least one waste pile of a first industrial side-stream material, wherein the arrangement further comprises: at least one movable work machine which is provided with a mixer, and wherein the work machine is arranged to take said first industrial side-stream material directly with the mixer from said waste pile for handling it by the mixer; an admixture station which comprises at least one feed device for feeding at least one admixture into the material located in the mixer of the work machine; a casting area which is arranged to receive from the mixer a geopolymeric hardenable paste formed by said side-stream material and admixtures as a result of their mixing; and in which arrangement the handled material is kept in said mixer of the work machine throughout the whole handling process from the waste pile up to the casting area.

2. The arrangement according to claim 1, wherein-the arrangement further comprises: a quarrying device for quarrying hardened paste in the casting area; a crusher device for crushing material extracted by quarrying to obtain crushed material; and a temporary storage for receiving crushed material from the crusher device.

3. The arrangement according to claim 1, wherein the factory waste disposal site is located in connection with a pulp mill; and the waste pile is green liquor precipitate, whereby the first industrial side-stream material taken from the waste pile with the mixer is green liquor precipitate.

4. A method for mixing a paste, which method comprises the mixing of at least one industrial side-stream material in the manufacture of a geopolymer; wherein the paste is mixed in a mixer arranged onto a movable work machine.

5. The method according to claim 4, wherein the mixer is forced into a waste pile by means of the work machine to load a first side-stream material into the mixer; a loaded portion of the first side-stream material is transferred in the mixer from the waste pile to an admixture station; at least one second side-stream material is added at the admixture station into the first side-stream material located in the mixer; the materials located in the mixer are mixed by means of rotary mixer elements of the mixer; the mixed paste is transferred in the mixer of the work machine to a casting area; and the mixer is unloaded onto the casting area.

6. The method according to claim 4, wherein several batches of hardenable geopolymer paste are unloaded onto the casting area from the mixer to provide a uniform casting formation; the paste is allowed to harden in the prevailing conditions; smaller blocks are quarried from the hardened casting formation; and the blocks are crushed in a crusher device to obtain a fraction which is smaller than a predetermined grain size.

7. The method according to claim 4, wherein the paste is foamed after mixing the admixtures in order to manufacture a crushed material having a porous structure.

Description

SHORT DESCRIPTION OF THE FIGURES

[0065] Some embodiments of the proposed solution are illustrated in more detail in the following figures, in which

[0066] FIG. 1 is a schematic and simplified diagram presenting admixtures of one geopolymer,

[0067] FIG. 2 is a schematic and simplified diagram presenting the manufacture of one geopolymeric earthwork material,

[0068] FIG. 3 schematically illustrates the manufacture of one geopolymer at a factory waste disposal site,

[0069] FIG. 4 schematically illustrates one mixing unit formed by a mixer and a work machine,

[0070] FIG. 5 schematically illustrates the use of one mixer in different stages of a geopolymer manufacturing process,

[0071] FIG. 6 illustrates one mixer and its rotary mixer shaft as seen from the front,

[0072] FIG. 7 schematically illustrates one mixer and its apparatuses as seen from the side; and

[0073] FIG. 8 is a schematic diagram presenting components of a mixed paste.

[0074] For clarity purposes, some embodiments of the proposed solutions are illustrated in the figures in a simplified form. In the figures, same reference numerals are used to denote the same elements and features.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0075] FIG. 1 represents a geopolymer comprising at least two side-stream materials. In some cases even more side-stream materials may be used in the formation of a hardenable paste. A common feature of these side-stream materials and their mixture is that they comprise silicon oxide SiO.sub.2 and aluminium oxide Al.sub.2O.sub.3 which react with each other and form a paste which hardens to a compression-resistant state. The compression strength achieved is at least 10 Mpa, but is generally over 40 Mpa, and sometimes even over 80 Mpa.

[0076] Industrial side-stream materials are e.g. tailings, such as red mud. Further side-stream materials are slags from the steel industry, such as blast furnace slag, steel slag and refined steel slag. Ashes from the energy industry, such as organic ashes produced in the combustion of wood as well as inorganic ashes produced in the combustion of coal, oil shale and the like are also side-stream materials. The ashes may include fly ash, grate ash or bottom ash formed in boilers. Further side-stream materials are produced in the forest industry. In the pulp industry, green liquor precipitate is formed as waste in large quantities.

[0077] Green liquor precipitate is a side-stream material formed in the wood processing industry in the manufacture of pulp, and is also called dregs. Dregs are produced in a sulphate process at a chemical recovery line. The dregs are removed from green liquor in a green liquor clarifier before conducting green liquor to causticizing, i.e. to the manufacture of cooking chemicals. Green liquor precipitate is a mixture of various green liquor insoluble substances, inorganic salts, such as oxides, carbonates and sulphides. It also contains hazardous metals in addition to the normal alkali metals and calcium and magnesium. Dregs removed from the process are washed in order to recover the sodium compounds contained in them. The washed dregs are dried before tipping in a waste disposal site, and their typical dry matter content is about 50%.

[0078] Further, one or more activators may be added to the mixture formed by the side-stream materials, or in some cases the activator is not needed but the side-stream materials react with each other. Or, they may react after water has been added to the mixture.

[0079] The method and solution proposed in this document may be used in a versatile way for the manufacture of products comprising various industrial side-stream materials.

[0080] Further, it is stated that in some cases only one side-stream material may be used in the manufacture of a geopolymer. In that case, other admixtures are mixed with the side-stream material in a mixer.

[0081] FIG. 2 is a diagram presenting an earthwork material manufacturing process as described in this application. The steps and features presented in the diagram have been described in detail already hereinabove, and are also disclosed in the description of FIG. 3.

[0082] In FIG. 3 an industrial plant or a factory 1 produces a first side-stream material 2 which is tipped in a waste pile 4 at a factory waste disposal site 3. The waste pile 4 may be a mound-like formation, a heap or a clamp. It may also be a previously deposited formation.

[0083] A work machine 5 has a mixer 6 by which the side-stream material 2 is taken from the waste pile 4. A mass of the loaded material and possibly other properties may be measured and the measurement results are sent to a control unit CU of an admixture station 7. The combination of the work machine 5 and the mixer 6, i.e. a mixing unit 8, transfers to the admixture station 7 where a second side-stream material may be fed into the mixer 6 from a second feed device 9. Activators may be fed from a third feed device 10 and a fourth feed device 11. Further, water may be fed from a fifth feed device 12 if necessary. The feed devices 9-12 may comprise upper containers or hoppers below which the mixer 6 may be positioned for admixing. In some cases the second side-stream material is not fed into the paste.

[0084] The materials fed into the mixer 6 are mixed during their transfer, and finally the formed paste is unloaded onto a casting area 13. A uniform larger formation may be formed from the paste, for example a type of artificial rock 14. The material is allowed to harden at least to a partial hardness. Blocks 16 may be quarried from the artificial rock 14 for example with a hydraulic impact hammer 15 as small-batch quarrying, with wedges or some other quarrying method. When quarrying is carried out before reaching the final hardness, it may be performed even with a bucket of an excavator or a rock tine mounted to it. The extracted blocks 16 may be fed into a feed opening of a crusher device 17 and crushed into crushed material 18 of a desired grain size. The crushed material 18 may be stored temporarily 19 and transferred to a site of usage by road transport.

[0085] The crusher device 17 may be for example a jaw crusher, an impact crusher or a cone crusher.

[0086] If necessary, the quarrying and crushing may also be performed after a longer time, whereby the quarrying and crushing equipment is selected according to the situation.

[0087] FIG. 4 illustrates a situation where the work machine 5 pushes the mixer 6 into the waste pile 4 and thereby loads the first side-stream material 2. In FIG. 4 it is shown that the mixer 6 may comprise two horizontal mixer shafts 20a, 20b which are provided with mixer elements and which may be rotated.

[0088] In FIG. 5 it is shown that the mixer 5 may be tilted to a desired position about a pivot joint 21 and introduced at the admixture station 7 under the feed device 9 for feeding the admixtures. The top of the mixer 5 is open, for receiving the admixtures. Further, the mixer 5 may be kept in a desired tilt position during the mixing. The mixing may be carried out by the rotary mixer shafts 20a, 20b during the transfer. When the paste has been mixed, it may be foamed before unloading, if desired. Foaming devices may be arranged in connection with the mixer 5. At the unloading site the mixer 5 may be tilted in a downward direction about the pivot joint 21, and the unloading may further be facilitated by means of the mixer devices.

[0089] The unloading may be carried out by way of batch casting into a casting pile. In this process a large quantity of smaller batches 22 form a larger formation.

[0090] In FIG. 6 it is illustrated that the rotary mixer shaft 20 of the mixer 5 may comprise a large number or arms 23 which are provided with mixing surfaces 24. In a mixer device 26 there may be one, two or even more of such parallel mixer shafts 20 provided with mixer blades 28. Alternatively the mixer shafts may comprise screw-type mixing surfaces.

[0091] In FIG. 7 it is illustrated that the mixer shafts 20a, 20b of the mixer device 26 of the mixer 5 may rotate in opposite directions. A rotation motor M for rotating the shafts 20 is located outside the bucket part 27. Further, the mixer 5 comprises a connecting device 25 for connecting it to the work machine. The mixer 5 may also be provided with a sensor S1 for determining a mass of the material located in the mixer, as well as with a sensor S2 for determining moisture or other property of the material. A vibrator T may also be arranged with the mixer to provide vibration facilitating the unloading and mixing.

[0092] FIG. 7 additionally illustrates a sensor S3 or a corresponding measuring device by which a resistance to rotation caused by the paste being mixed may be determined by monitoring the motor M. The resistance to rotation may manifest as an increased need for rotation torque, rotating force, drive energy or the like, or alternatively for example from a change in the rotation speed. The resistance to rotation may provide information on the plasticity and also moisture of the paste. Further, there may be one or more cameras K in connection with the mixer to produce visual data which may be transmitted to an operator for making sensory observations on the paste being mixed. A skilled operator may see the plasticity of the paste from a video camera picture.

[0093] FIG. 8 presents possible components of a geopolymer comprising a side-stream material from the pulp industry.

[0094] The figures and their description are only intended to illustrate the inventive idea. However, the scope of protection of the invention is defined in the claims of the application.