WO2022084588A1

WO2022084588A1 - Method for the treatment of waste material, arrangement and consolidating binder

Info

Publication number: WO2022084588A1
Application number: PCT/FI2021/050708
Authority: WO
Inventors: Juha LEPPÄNEN; Mirja PIISPANEN; Ari Laitinen; Jenni Kiventerä; Kari Ylitalo; Maria Korppi
Original assignee: Betolar Oy
Priority date: 2020-10-21
Filing date: 2021-10-21
Publication date: 2022-04-28
Also published as: FI129403B; CA3193891A1; FI20206042A1; CL2023001156A1; CN116157371A; EP4232418A1; AU2021365401A1

Abstract

A method and an arrangement for treating waste material of a mine and for converting it to a consolidating binder and for utilizing the consolidating binder. In the method, waste material formed in an extraction process is heat-treated and its conversion to a reactive hardenable material is provided. Consolidating binder may be prepared from this material and it may be used for hardening and stabilizing waste material to be disposed of in the mine area or it may also be utilized in other construction applications.

Description

Method for the treatment of waste material , arrangement and consolidating binder

Background of the invention

The invention relates to a new solution for treatment and utili zation of waste material .

More specifically, the invention relates to a method and an arrangement for treating waste waters , sludges and precipitates in a mine area and to a binder prepared from waste material .

The obj ect of the invention is described in more detail in the preambles of independent claims of the application .

For example the mining industry, metal recovery and extraction produce massive amounts of metal containing waste waters , sludges and precipitates , the treatment of which requires large ponds and is difficult in many ways . Indeed, it has been found that various deficiencies exist in the water treatment of mines and associated recovery and extraction plants .

Brief description of the invention

The idea of the invention is to provide a new and improved method and arrangement for treatment of waste material . Further, it is an obj ect to provide a new and improved binder .

The characteristic features of the method according to the invention are set forth in the characteri zing part of the first independent claim .

The characteristic features of the arrangement according to the invention are set forth in the characteri zing part of the second independent claim .

The characteristic features of the binder according to the invention are set forth in the characteri zing part of the third independent claim . The idea of the proposed solution is to heat waste material formed in an extraction process of a mine and convert it by means of the heating to a reactive consolidating material . Said waste material may be waste water, sludge or underf low . Said heating is a heat treatment step in which the waste material is caused to become reactive .

An advantage of the proposed solution is that the fractions and precipitates formed in the treatment of waste waters can be hardened as described in this application in a simple and cost-efficient way . A further advantage is that the hardened materials may be disposed of in heaps and clamps . The use of such above-ground stores and disposal sites is signif icantly more advantageous than placing liquids in ponds . As the number and size of different types of ponds may be decreased in the operated area, great savings in space and costs will also be achieved .

Further, the storage , treatment and disposal of solid and hardened waste is significantly safer than the storage of waste waters and other liquids . The risks of overflowing caused by rain waters and breakage of the pond structures may be reduced in the storage and disposal of solid material .

The idea of one embodiment is that waste material as described in this document may also refer to a side stream material , or by-product , or co-product .

The idea of one embodiment is that gypsum containing waste material formed in an extraction process is heat- treated to form a binder . The gypsum containing waste material may be neutrali zed waste material .

The idea of one embodiment is that at least 25 % of the dry matter of the abovementioned gypsum containing waste material is gypsum .

The idea of one embodiment is that sulphate containing waste material formed in an extraction process is heat-treated to form a binder . The idea of one embodiment is that waste material formed in a bioleaching process is heat-treated to form a binder .

The idea of one embodiment is that waste material formed in an iron precipitation process is heat-treated to form a binder . In other words , the extraction process is an iron precipitation process , and the waste material formed in the process is heat-treated to form the binder .

The idea of one embodiment is that waste material formed in an ore flotation process is heat-treated to form a binder . In other words , the extraction process is an ore flotation process , and the waste material formed in the process is heat-treated to form the binder .

The idea of one embodiment is that at least one admixture is added to the prepared binder, which admixture forms , together with the binder, a consolidating structure .

The idea of one embodiment is that the abovementioned admixture is slag from metal industry or a side stream material from metal industry . One possible admixture is ash formed in a power plant . It is al so possible to use different combinations of said admixtures . In some case , one possible admixture or admixture component may be cement or a cementitious binder .

The idea of one embodiment is that the conversion of waste material to a reactive material is performed by means of heating only, without any external additives or binders . As external materials are not needed, the solution is good for logistics and cost-efficiency .

The idea of one embodiment is that the waste material is mixed with at least one admixture or additive before the heating and the mixture of the waste material and at least one admixture or additive is heated to form a binder .

The idea of one embodiment is that water is removed from the waste material by subj ecting the waste material to a first heating . The thermal drying is further followed by heat treatment in which the dried waste material is activated into the reactive consolidating material . Before the drying, the solid matter content of the waste material being treated may be increased by different types of filtration techniques and other solid-liquid separation apparatuses .

The idea of one embodiment is that the waste material being treated is metal sulphate containing waste water, precipitate , underflow or sludge . Thus , in the solution, metal sulphate containing waste material is heated such that it is converted to a reactive and consolidating binder with water and hydroxides . It should be mentioned that extraction from sulphide ore is typical in the mining industry, as many metals are bound in sulphide minerals . The proposed solution is suitable for use in connection with several different metal extraction processes .

The idea of one embodiment is that metal containing waste material formed in an extraction process is heated at a temperature of 30 - 300 ° C and under the influence of oxygen .

The idea of one embodiment is that neutrali zed waste material formed in an extraction process is heated at a temperature of 30 - 300 ° C . The heating may be performed under the influence of oxygen . Alternatively, the heat treatment may be performed in oxygen-free conditions or substantially without the presence of oxygen, for example in a nitrogen-filled oven, by means of a heat transfer fluid or by means of a heat transfer gas or by some other means .

The idea of one embodiment is that gypsum containing waste material formed in an extraction process is heated at a temperature of 60 - 600 ° C to activate the treated material into a binder .

The idea of one embodiment is that waste material formed in an extraction process is heated at a temperature of 60 - 1500 ° C to activate the treated material into a binder . The idea of one embodiment is that waste material comprising calcium sulphate CaSCg is treated, whereby calcium sulphate i s converted under heating to anhydrite that is a consolidating material .

The idea of one embodiment is that waste material comprising metal sulphate as well as calcium sulphate CaSCt and slaked lime Ca (OH) 2 is treated . Thus , the metal sulphate containing waste material is converted to a material that is consolidating and reactive with water and hydroxides in the heat treatment , and further, calcium sulphate CaSCg produced in neutrali zation is converted in the heat treatment to anhydrite that is also a consolidating reactive material . Thus , the end product of the heat treatment may be a material comprising a component caused to become reactive in two or more different ways . Typically, the metal containing waste waters formed in bioleaching are neutrali zed by means of milk of lime made from calcium oxide CaO, i . e . slaked lime Ca (OH) 2 , whereby the case according to this embodiment of causing reactivity is suitable for use in many cases .

The idea of one embodiment is that after the heating treatment , the solid material caused to become reactive is ground to a fine powder that is suitable for use as a hardenable binder . The grinding may even further improve the reactivity of the material . Powder is also easy to transport , treat and mix into a material to be hardened .

The idea of one embodiment is that underflow produced in waste water treatment of a bioleaching process of a mine is treated by mixing it with a binder from the water containing waste material produced in the bioleaching process of the mine in some abovementioned way . Thus , the binder mixed into the underflow hardens the underflow to a hardness of at least 500 kPa . It is not possible to achieve such hardness without adding binder . For example , the strength of a solid matter cake formed by filtering only is , at the highest , j ust a few hundred kPa . The idea of one embodiment is that a binder is prepared from waste material of an extraction process of a mine by means of a heat treatment and the prepared binder is used for hardening a different waste fraction or the same waste fraction produced in the same extraction process . The binder may be made from waste water, precipitate , underflow or sludge , and it may be used for hardening waste water , precipitate , underflow, sludge or other waste fraction or material containing water and solid matter particles .

The idea of one embodiment is that the hardenable binder is prepared from some of the following waste materials : preneutrali zation underflow, final neutrali zation underflow (LoNe ) , metal recovery underflow ( iron precipitate , RaSa) or underflow from a mine water treatment plant . Correspondingly, the binder prepared by means of the heat treatment is used for hardening some of the abovementioned underflows .

The idea of one embodiment is that the consolidating material and binder as described in this document are prepared in a mine area .

The idea of one embodiment is that the consolidating material and binder as described in this document are used in a mine area .

The idea of one embodiment is that the solution relates to an arrangement for disposal of waste material in a mine area . In the arrangement , a binder is prepared from waste material formed in an extraction process of the mine , which binder is converted to a reactive hardenable material by means of a heat treatment . The raw material in the preparation of the binder is thus waste water, sludge or underflow related to and formed in metal extraction and associated processes . In the arrangement , the binder is mixed into waste material to be disposed of , whereby the waste material of the mine may be disposed of as a hardened structure or material in the mine area . The hardened disposal material is solid and non-flowable material , whereby its treatment and storage is significantly easier and safer than with a liquid or other flowable material . The waste material to be disposed of may be waste material from a bioleaching process or other extraction process .

The idea of one embodiment is that the hardenable mixture is used as building material of a construction in the mine area, whereby the formed construction is at the same time a waste material disposal site .

The idea of one embodiment is that an upwardly rising rigid and autonomous construction is formed from the hardened waste material or waste material is hardened by means of the binder into such upwardly rising structure .

According to one embodiment the abovementioned construction is some of the following : heap, clamp, raised area, hill , artificial rock, barrier, protective barrier, wall or a corresponding stable and self-supporting construction .

According to one embodiment the construction is founded directly on a flat field of the mine area . The construction does therefore not necessarily need to be formed in a space surrounded by any protective structure , such as for example a protective basin .

According to one embodiment the construction comprises surfaces having an angle of repose , i . e . a slope angle , larger than 2 . 5 % .

According to one embodiment the construction comprises surfaces positioned upright or at a steep angle of inclination .

According to one embodiment the height difference between the highest point of the construction and the surface surrounding the construction is at least 10 m .

According to one embodiment the largest dimension of the base surface area of the construction is smaller than the greatest height of the construction . According to one embodiment the greatest height of the construction relative to the surrounding surface is at least 20 m .

According to one embodiment the greatest height of the construction relative to the surrounding surface is at least 30 m .

According to one embodiment the greatest height of the construction relative to the surrounding surface is at least 40 m .

According to one embodiment the greatest height of the construction relative to the surrounding surface is at least 50 m .

According to one embodiment the greatest height of the construction relative to the surrounding surface is at least 60 m .

According to one embodiment the greatest height of the construction relative to the surrounding surface is 70 - 120 m .

According to one embodiment the extent of the base surface area of the construction is less than 1 hectare .

According to one embodiment the extent of the base surface area of the construction is 1 hectare or larger .

According to one embodiment the construction is cast from the hardenable waste material by mould casting, slip forming or 3D casting .

According to one embodiment an artificial rock or boulders are cast from the hardenable waste material , which are crushed and a construction as necessary is assembled from the crushed material by earth construction methods and devices .

According to one embodiment , infrastructure to be used in basic production of the mine is built from the hardenable waste material .

According to one embodiment , one or more stiffeners are arranged in the structure , such as for example rebars , meshes , rods , wires , fibres , etc . According to one embodiment the construction formed from hardened waste material is used as a foundation of an energy production apparatus . The construction may function as a base of for example a solar power plant or a wind power plant .

The idea of one embodiment is that the hardenable waste material is used as earth construction material in the mine area .

According to one embodiment the hardenable waste material is used as surface material for a mine road or field . The hardenable waste material may function for example as a replacement for asphalt or a surface layer formed from compacted crushed natural stone . This replacement surface material may also be used outside the mine area, for example in the maintenance , fundamental improvement and building of roads leading to the mine area and other roads in the surrounding area .

According to one embodiment the hardenable waste material is used in structural layers underneath the surface of a mine road or field . The structural layers may be frost- protected and protected from runoff waters . This replacement material may also be used in road structures outs ide the mine area, for example in the maintenance , fundamental improvement and building of roads leading to the mine area and other roads in the surrounding area .

According to one embodiment the hardenable waste material or binder prepared from it is used for stabili zation of soil in the mine area .

According to one embodiment the binder prepared for example in a powdery form is transported to other sites , whereby it may also be used for stabili zation of moist and poorly load-bearing soil in other places than the mine area .

According to one embodiment the hardenable waste material or binder prepared from the waste material is used for filling mineshafts , tunnels , open-pit mines or other spaces formed in the removal of rock material with the hardenable waste material either entirely or at least partly .

According to one embodiment the hardenable waste material i s cast inside a light mould structure , such as a geotube . Thus , the geotube or corresponding film structure is able to keep the cast hardenable waste material stable until the quickly-hardenable material reaches a suf ficient mechanical strength .

According to one embodiment a structure or material reserved for later closure and coverage of the mine area is cast from the hardenable waste material . Such solid material may be stored temporarily in a suitable place close to the site that is to be landscaped later . At the time of coverage , a covering layer may be formed from this temporarily stored material for example over gypsum precipitate ponds , gangue heaps , tailings heaps and other by-product stores and disposal sites in the mine area . Because the coverage material is solid and it has mechanical strength, it may also be easily used for forming surface shapes as desired in connection with landscaping . The material may be for example crushed material of a desired si ze , by means of which ditches and inclined surfaces may be formed as desired in the coverage layer for managing surface and rain waters . In the coverage it may be necessary, in addition to said coverage material , to form layers s lowing down the flow of water and insulating against frost over the site being covered .

According to one embodiment said activated binder powder may also be used as a material for making a structural hardenable layer over gangue and tailings heaps .

According to one embodiment a waste material heap or clamp covered or stabili zed with the binder powder prepared from the waste sludge may be covered with a waterproof coverage layer for example bentonite , roll covering arrangements and other layers slowing down the flow-through of water . According to one embodiment the hardenable structural layer made with the binder powder may be frost-protected with a thermally insulating soil layer .

The idea of one embodiment is that the proposed solution relates to a hardenable binder that is prepared from underflow formed in the treatment of wastewaters of an extraction process of a mine by heating the material to a reactive form .

The idea of one embodiment is that said binder is in a powdery form . Thus , the heat-treated material is ground after the heating to a desired particle si ze , whereby it mixes well in a mixture and its mechanical treatment and transportation are easy .

The idea of one embodiment is that the waste material formed in the abovementioned processes and s ituations may be converted in a simple and cost-efficient way to a compression-res istant bui lding, fill ing and coverage material suitable for earth construction .

The idea of one embodiment is that the waste material formed in the abovementioned processes and s ituations may be converted in a simple and cost-efficient way to a hardenable binder that may be used as a binder in the hardening of other materials suitable for earth construction . The materials to be hardened by means of the binder may include natural stone materials , crushed natural stone materials , industrial side stream materials and wastes .

The idea of one embodiment is that waste waters , precipitates or sludges comprising iron and sulphate are treated .

The idea of one embodiment is that iron sulphate containing waste waters , precipitates or sludges are treated .

The idea of one embodiment is that aluminium sulphate containing waste waters , precipitates or s ludges are treated . The idea of one embodiment is that metal sulphate and gypsum containing waste waters , precipitates or sludges are treated .

The idea of one embodiment is that metal sulphate and gypsum containing waste waters , precipitates or sludges or pastelike material are treated . In addition to calcium sulphate CaSCg , the waste waters , precipitates , sludges or pastelike waste materials may also contain slaked lime , i . e . calcium hydroxide Ca (OH) 2 -

According to one embodiment , bas ic gypsum-based precipitate formed in the treatment of metal containing water and precipitated to the bottom of a gypsum pond is treated by the solution described in this document . In a gypsum precipitate pond the solid matter, which may also be referred to as final neutrali zation underflow, in the precipitate settles to the bottom of the pond and free water forms at the surface . The precipitate in the gypsum precipitate pond has a high water content , typically 80 - 85 % .

According to one embodiment , the gypsum precipitate is transferred to a deposition area by pumping through a discharge pipe . During the trans fer, the reactive hardenable binder as described in this document is mixed into the gypsum precipitate , whereby the gypsum precipitate hardens in the deposition area .

The idea of one embodiment is that a hardenable structure may be formed by means of the hardenable material or powder as formed in this document without adding any external binder . The proposed reactive material provides as such with water a hardening reaction and a compression strength sufficient for many applications . In other words , a hardenable structure may be made from the binder and water or hydroxide as such .

According to one embodiment the hardenable material or powder as described in this document is used as a binder mixed into a material to be hardened or stabili zed at 0 . 5 - 80 % by total weight of the mas s . This provides already a compression strength of several MPa .

According to one embodiment the hardenable material or powder as described in this document is used as a binder and the material to be hardened with the binder is solid mine waste or soil material .

According to one embodiment the hardenable material or powder as described in this document is used as a binder and the material to be hardened with the binder is liquid, sludge-type or precipitate-type mine waste .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof are insoluble or substantially insoluble in water . The hardened material also binds well the heavy metals and other detrimental elements possibly found in the starting materials and thus reduces their dissolution and migration into the environment .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 0 . 5 Mpa .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 1 Mpa .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 2 Mpa .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 3 Mpa .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 4 Mpa .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 5 Mpa .

According to one embodiment the hardenable material as described in this document or the material or structure hardened by means thereof have a compression strength of at least 10 Mpa .

The idea of one embodiment is that waste heat and energy formed in a production plant located in the mine area or in the vicinity may be used for the drying by heat and for the actual heat treatment . Further, in the heating it is possible to utili ze electricity produced by wind energy, and solar energy as such focused by means of lenses , converted to electricity by means of solar cells or by means of heat produced by different types of other solar col lectors .

Heating and activation

Next , some findings wil l be presented regarding the tests performed and the effects having or assumed to have occurred in the tests .

Heat treatment of a metal sulphate containing waste material , which is produced in the neutrali zation processes of a bioleaching process , in oxygen containing conditions seems to activate the waste material and to convert it to a material that is consolidating and reactive with water or other hydroxide . It has also been observed in the tests that when the activated material is later mixed in water or a solution containing one or more hydroxides , it forms a formable and consolidating mass .

In the tests performed, said waste material has been heated at different temperatures . The temperatures of 30 - 300 ° C have been used, depending on what metal compound the waste material contained . For example , in the tests performed it was found that a suitable heating temperature for ferrous sulphate containing material is 100 - 180° C . The suitable heating temperature was also found to depend on the amount of impurities in the starting material . It was found that the treatment time may be shortened by rais ing the temperature . On the other hand, by extending the treatment time , the heat treatment may be performed at a lower temperature .

In the tests it was found that the heating should advantageously be performed on a small material thickness , such that there is a large surface area under the influence of heat and ambient oxygen . The waste material to be treated may be spread as a thin layer onto a flat surface for the oxidation treatment .

As an alternative to the above-described flat-bed heating, the material may be stirred during the heating . Thus , the material can be well subj ected to the oxidative effect of oxygen and heat during the heat treatment . This way it may be possible to shorten the treatment time and decrease the temperature .

As an alternative heat treatment technique there is a bubbling fluidi zed bed, circulating fluidi zed bed and fluidi zation method performed with a heat transfer gas or a heat transfer fluid .

It is possible to perform the transfer of heat to the waste material also by direct heat transfer surfaces without a requirement for the presence of a medium .

It was also found in the tests that if necessary, it is possible to do the heating in a higher ambient oxygen content than the normal oxygen content of the atmosphere to enhance the oxidation .

Furthermore , it was found in the tests that if the waste material being treated contained calcium sulphate , the heat treatment could be done in oxygen-free or low- oxygen conditions , and yet it provided a reactive material that could later be hardened when it was mixed with water or moist waste material . In this case, the activation could not be deemed as being based on oxidation, but was due to a modification in the structure of calcium sulphate caused by the heating .

Increasing the dry matter content

The idea of one embodiment is that the dry matter content of the waste water, sludge or precipitate is increased before the heat treatment . This is to increase the metal content , calcium sulphate content or both of the waste material before the heating . In addition, the actual heat treatment time may be shortened, if the starting material is well pre-dried .

The fol lowing techniques and devices , and combinations thereof , may be used for increasing the dry matter content of the waste material and for the removal of water :

- Mechanical removal of water or drying, for example by centrifuging, whereby the water is removed from the solid matter by means of the centrifugal force .

- Mechanical separation of water in which the free water is removed by vibrating, pressing or compacting .

- Devices for the mechanical removal of water include the abovementioned centri fuge and a screw press , belt filter press .

- Drying may also be performed with the following devices : a wire-type filter (belt filter) , vibrating sieve , gravity filter, pressure filter, centrifugal filter ( centrifuge filter) , reverse osmosis filter, membrane filter, pressure filter, vacuum dryer or some combination thereof .

- Removal of water by filtering by means of filter cloths or sieves of a fi lter device . The filter devices include belt filters , disc filters , drum filters plate filters and filter devices used in the paper and mining industry . The filter devices utilize a pressure difference , typically vacuum .

- Drying may also be performed by means of geotubes or geobags . Thus , the material to be treated is arranged inside the tube or the bag and liquid is gradually removed and the sol id matter remains inside .

- Separation of water may also be performed by means of ultrasound . The water and solid matter can be separated by focusing an ultrasound on the sludge or precipitate .

- Before the drying and activation performed by heating, the solid matter content may be increased by some acoustic technique . For example an acoustic resonance tank may be employed . The acoustic resonance may also be utili zed below ultrasound frequencies .

In precipitation, the solid matter in sludge is allowed to gradually settle to the bottom of a precipitation pond . Clear water remains in the surface part of the precipitation pond, from where it may be pumped to a water purification plant for further treatment . A precipitate having a higher solid matter content may be removed from the bottom or bottom part of the precipitation pond . The removal of the material may be performed for example by means of a suction apparatus . A suction dredge device designed for the treatment of shorelines may be adapted into a device suitable for this purpose .

- Removal of water may also be performed by evaporating . Evaporating is applicable particularly when large ponds or solar energy is available . In thermal drying, water is evaporated at an elevated temperature . In other words , the dry matter content of the sludge is increased by means of heat . For example vapor or flue gases may be used in the drying, if they are available in the mine area .

Grinding

In the tests performed, the solid material caused to become reactive by means of the heating treatment was ground to a fine powder .

In the tests performed it was found that the reactivity of the formed material could be further increased by means of grinding and other mechanical treatments . Mechanical treatment was found to improve the reactivity of the material itself and additionally the reactive surface area of particles of a f ine powder is large and their mixing in a mixture is efficient .

Bond formation

In the tests performed it was found that the material or powder caused to become reactive in the abovedescribed manner reacted with water and upon drying formed a strong bond . When the material processed to become reactive was mixed later in water or other solution containing one or more hydroxides , it formed a strong bond . In the tests it was found for example that a hardening reaction was provided by means of potassium hydroxide and calcium hydroxide .

Without lime

The idea of one embodiment is that by using the solution described in this document for hardening a material with a reactive material formed from metal sulphate containing waste water, it is possible to even entirely give up the lime , milk of lime or gypsum treatment of waste waters. It is clear that this allows significant cost savings .

It is typical that the metal sulphate containing waste water produced in a bioleaching process of a mine is neutralized with lime in connection with waste water treatment of the mine. Thus, calcium hydroxide Ca(OH)2, i.e. slaked lime or milk of lime is mixed into the sulphuric acid H2SO4 containing waste water produced in the bioleaching process. If the use of lime may be avoided or reduced, it provides significant logistic and economic benefits.

Use of the material caused to become reactive

The reactive material made from the mine's metal sulphate containing waste water, waste sludge, waste precipitate or waste material in clayey form may be used in the mine and the mine area in many ways. In other words, in the manner described in this document, a dif f icult-to-treat and environmentally harmful component may be converted to a less harmful form and the waste material may even be converted to useful building material for building roads, edge banks of precipitation ponds, dams, foundations of storage sites and other infrastructure of the mine.

According to one embodiment the waste material may be hardened to a coverage material that may be stored for a later need. When mining and recovery of metals in the mine area will be finished sometime later, the mine, mine constructions, mine equipment and surroundings of the mine may be covered and landscaped. The hardened material may thus be stored easily and safely for the closure of the mine.

According to one embodiment the hardenable material may be cast to form clamps or heaps, i.e. type of artificial rocks, that may be later broken and crushed to crushed material or boulders. E.g. the mine's gypsum precipitate ponds, waste water ponds, precipitation ponds and other liquid storage ponds and constructions used for precipita- tion may be covered by means of such hardened waste material . The hardened material may also be used for covering and closing storage sites of solid material in the mine area . For example gangue heaps may be covered with the material .

According to one embodiment it is also pos sible to mix the reactive material described in this document into waste water or any material containing water or one or more hydroxides and spread this hardenable pumpable mixture over the sites to be covered to a desired layer thickness . I f necessary, the processability and consolidation properties of the mixture thus prepared may be adj usted by adding slaked lime Ca (OH) 2 , gypsum CaSCg or burnt lime CaO into the admixtures . The reactive material providing the hardening may be mixed in by means of the waste water mixing device for example during or in connection with transfer pumping . The mixer apparatus may be arranged as an extension to or in connection with a discharge pipe of a precipitation pond . It i s also possible to pump waste water or the l ike from a precipitation pond to a tank vehicle , mix the reactive binder into the waste water to be transported, transport the cargo to a coverage area serving as a discharge site and pump and spread the hardenable mixture onto the coverage area as a protective layer .

According to one embodiment , in some cases it may be well-founded to spread the reactive hardenable material directly into the waste water or other waste material in a pond, whereby the hardening is performed in situ in the precipitation pond or the like . Thus , the hardenable binder, for example powdery reactive material , is spread into the water in the pond and at the same time mixed by means of a mixer . I f necessary, the processability and consolidation properties of the mixture thus prepared may be adj usted by adding slaked lime Ca (OH) 2 , gypsum CaSCg or burnt lime CaO into the admixtures . In this configuration the pond becomes the disposal site of the waste water or precipitate . After the treatment the pond comprises hard solid material instead of flowable material .

According to one embodiment the hardenable activated waste material described in this document may be utili zed in so-called paste backfil l in which filler material is pumped into disused mine galleries , shafts or galleries or spaces required by the mining method to reinforce their structure . I f necessary, the processabil ity and consolidation properties of the mixture thus prepared may be adj usted by adding slaked lime Ca (OH) 2 , gypsum CaSCg or burnt lime CaO into the admixtures . Paste backfill may also be used in situations where the rock adj acent to a site to be mined next needs to be reinforced before starting the mining .

The method in said paste backfill may be combination filling utili zing mined gangue and the hardenable binder prepared from the waste sludge of a bioleaching process .

Use of the hardenable material described in thi s application as binder in the paste backfill material is advantageous as the hardening thereof may be very quick . Thus , long waiting times are avoided and mining may be continued next to the filled cavity or space after j ust a short interruption . In addition, it is an advantage that a material formed in the mining area from the mine' s own process may be used as the binder and it is not necessarily required to bring in any external components for making the backfill paste . This is logistically very efficient .

According to one embodiment it is possible to use a pumpable flowable mass or paste that is hardenable by means of the reactive material or binder as described in this document in the mine area for fabricating different types of support and protective structures by using a slip forming technique . Slip forming is enabled e . g . by fluidity of the material before hardening and quick hardening after casting . I f necessary, the processability and consolidation properties of the mixture thus prepared may be adj usted by adding slaked lime Ca (OH) 2 , gypsum CaSCg or burnt lime CaO into the admixtures . Further, the material is suitable for 3D printing of structures , for example by means of a casting head movable with a robot arm . Said slip forming and 3D printing are suitable for example for building the edge walls of precipitation and water treatment ponds . Slip forming and printing techniques may also be used when instal ling coverage structures , whereby it is possible to fabricate large continuous protective structures that are wel l protected e . g . from rain waters . A temporary support structure may be arranged over a gypsum precipitate pond or the like , from which support structure the coverage structure may be cast . Alternatively a light mobi le casting apparatus may be used for performing the casting over the pond for example by spraying or by means of conveyors .

Some examples of the tests performed

Example 1 :

Sludge settled to the bottom of a gypsum precipitate pond of a mine was taken for the test . The sludge was green in colour assumably because it contained ferrous sulphate Fe2SO4 . The sludge was heated in an oven at a temperature of 180 ° C , whereby the water was first evaporated off . The dry matter content was increased to 40 % by weight by means of the evaporation . The paste-like mass formed after the evaporation step was spread as a thin layer of approximately 10 mm into a shal low vessel , after which it was heated in an oven at a temperature of 180 ° C for 4 hours . In the heating the mass turned into a brown crumbling sheet . The colour of the mass after oxidation was the characteristic rust brown . The formed sheet of mass was crushed and ground to a fine powder in a grinder . The heat-treated and homogeni zed waste material was found to be consolidating and reactive with water and hydroxides .

Example 2 : The powder prepared in Example 1 above was mixed in pure water, whereby a hardenable mixture was provided .

Further, it was tested to mix the powder in waste water taken from the gypsum precipitate pond, which waste water could also be hardened by means of the reactive powder .

Similarly, the precipitate taken from the bottom of the gypsum precipitate pond could also be hardened by means of the powder .

It was found that already after a hardening time of half an hour, the compression strength of the hardened mass was approximately 10 Mpa . The compres sion strength did not significantly increase from this value if the hardening time was extended .

In one test , a reactive binder was prepared from metal sulphate containing waste sludge of a gypsum precipitate pond by first removing water and then by a heat treatment . When 1 /3 by volume of this prepared binder and 2 /3 of corresponding metal sulphate containing waste sludge of the gypsum precipitate pond were taken, and they were mixed with each other in said mixing ratio , the mixture could be hardened to a compression strength of 10 Mpa . Thus , in the test the binder was first made from waste sludge and then the same waste sludge was hardened with the binder . Such selfhardening was found to be a very interesting solution for the treatment of waste sludges .

Further tests were performed with several different powders that had been prepared before the heating step from starting materials having different metal sulphate contents .

The test specimens were further subj ected to solubility tests in water . The hardened test specimens were found to be insoluble or poorly soluble in water . The starting materials contained heavy metals , but they were not found to significantly dissolve in the dissolution tests . The tests show that the formed reactive powder may be used as a hardenable binder for example in the stabilization and hardening of stone material fractions . Further, the precipitates of metal refining of the waste water treatment of a mine or even the waste waters directly may be hardened by means of the powder .

Example 3

Waste sludge (precipitate ) was subj ected to moisture and pH measurement ( solid matter content 15 - 65 % by wet weight and the pH varied between 5 , 0 - 9 , 0 ) .

The waste sludge (precipitate ) was mixed with a whisk until it was smooth and was dried and heat-treated at 105 ° C ( 1 day) in the presence of an oxygen-containing gas mixture . The dried solid matter was pulveri zed and homogeni zed to a powder . This provided a binder powder that was activatable with water and waste sludge .

The test was repeated at different temperatures between 30 - 245 ° C and it was found that the required treatment time depends on the temperature used . Also , the binder properties of the powder become less advantageous if the treatment is performed at a temperature below 80 ° C or at a temperature above 200 ° C .

Example 4

A solid piece was made from binder powder prepared from one sample batch of waste sludge by adding water at appr . 18 ° C ( 2 parts powder and 1 part water) . With thi s mixing ratio the processing time upon casting into a prismpress piece mould was found to be 2 minutes as measured from the time of addition of the water . The mass made from the binder powder and water warmed up considerably during the initial consolidation . As measured from the prism-press test piece , the compression strength was 6 , 86 MPa (measured from the press test piece at an age of 28 days ) . When the test was repeated with binder powder prepared from the same sample batch of waste sludge and with the same powder-water ratio , the processing time varied between 1 - 4 minutes depending on the temperature of the components being mixed (between 0 ° C - 60 ° C) , the vibration strength and the mixing homogeneity .

When the test was repeated with binder powders prepared from different sample batches of waste sludge and with water, the proces sing time upon casting into a prism-press piece mould varied between 30 seconds - 60 minutes depending on the vibration strength, the powder-water ratio , the temperatures of the admixtures ( 0 ° C - 60 ° C) and the mixing homogeneity . The compression strength results from the prism-test pieces at an age of 28 days have been measured to be between 0 , 5 - 10 MPa depending on the recipe . The processing time and the final strength were found to depend on the chemical composition of the waste sludge sample used in the preparation of the powder .

Example 5

From waste sludge , a hardenable powder was also prepared from sludge concentrated to a nearly or fully clayey form ( i . e . having a higher solid matter content than the waste sludge sample ) . The concentration, i . e . increase of the solid matter content , was performed by gravity and pressure filtration . The filtration was boosted with acoustic resonance and mechanical vibration of the filtrate cake . The concentrated sludge was subj ected to a heat treatment of 1 day at a temperature of 105 ° C in the presence of an oxygen-containing gas mixture . The waste material activated with the heat treatment was pulveri zed and ground mechani cally to a homogeneous powder and similar consolidation and processability properties were obtained with the powder thus prepared as with the abovementioned mere thermal drying and heat treatment . Example 6

A solid piece was made from a powder prepared from one sample batch of waste sludge by adding a sludge sample representing the same waste sludge used in the preparation of the powder at a temperature of 18 ° C ( 1 part powder and 2 parts sludge at a solid matter content of 20 % ) . With this mixing ratio the processing time upon casting into a prismpress piece mould was found to be 3 minutes from the start of mixing of the waste sludge and powder . The mass made from the binder powder and waste sludge warmed up considerably during the initial consolidation . As measured from the prism-type 40 x 40 x 100 mm press test piece , the compression strength was 1 , 61 MPa (measured from the press test piece at an age of 28 days ) .

When the test was repeated with powder prepared from the same sample batch of waste sludge and with the same powder-waste liquor ratio , the proces sing time varied between 1 - 10 minutes depending on the temperature of the components being mixed (between 0 ° C - 60 ° C) , the vibration strength and the mixing homogeneity .

When the test was repeated with powders prepared from different sample batches of waste sludge and with untreated waste sludge , the proces sing time varied between 30 seconds - 60 minutes depending on the vibration strength, the powder-waste sludge ratio , the solid matter content of the waste sludge , the temperatures of the admixtures ( 0 °C 60 ° C) and the mixing homogeneity . The compression strength results from the prism-test pieces at an age of 28 days have been measured to be between 0 , 5 - 5 MPa depending on the recipe . The processing time and the final strength were found to depend on the chemical composition of the waste sludge sample added to the powder when making the test casting mass and in the preparation of the powder and on the solid matter content of the waste sludge .

Example 7 A solid piece was made from powder and precipitate sludge by adding concentrated precipitate sludge ( in a clayey form) at a solid matter content above 40 % to the powder in a mixing ratio of 1 part powder and 5 parts concentrated sludge ) . Similar processability and consolidation properties were achieved with the piece made this way as with powder and untreated sludge . The mass made from the binder powder and concentrated waste sludge warmed up considerably during the initial consolidation .

When the test was repeated with the same powder - concentrated waste liquor ratio , the processing time varied between 1 - 10 minutes depending on the temperature of the components being mixed (between 0 ° C - 60 ° C) , the vibration strength and the mixing homogeneity .

When the test was repeated with powders prepared from different sample batches of waste sludge and with concentrated waste sludge , the proces sing time varied between 30 seconds - 60 minutes depending on the vibration strength, the powder-waste sludge ratio , the solid matter content of the waste sludge , the temperatures of the admixtures ( 0 °C 99 ° C) and the mixing homogeneity . The compression strength results from the prism-test pieces at an age of 28 days have been measured to be between 0 , 5 - 5 MPa depending on the recipe . The processing time and the final strength were found to depend on the chemical composition of the waste sludge sample added to the powder when making the test casting mass and in the preparation of the powder and on the solid matter content of the concentrated waste sludge .

Example 8

When testing the binder properties of the heat- treated powder prepared from waste sludge in soil stabilization, it was found that for example dredged materials , peats , silts , clays , crushed stones and gravel can be stabili zed in the same way as with commercially available binders used in soil stabili zation . Example 9

When testing the binder properties of the heat- treated powder prepared from waste sludge , it was found that also the bottom ash of a waste incineration plant , mining industry tailings and gangue fractions can be stabili zed .

Example 10

In one water permeability test the water permeability k2o°c of a test specimen made from binder powder, which was prepared from waste sludge , and from water was 10 ^A - 6 , 7 m/s .

Example 11

In one free zing-melting test it was found that the duration of a test made from binder powder, which was prepared from waste sludge , and from water was 12 freezingmelting cycles before the specimen was broken .

Definitions of some terms

The following should be mentioned about the terms used in this document :

- Waste water is disused water used as a liquid with a detrimental amount of foreign substances . In this application, waste water refers specifically to industrial waste waters and mine waters . In mining, water is used in excavation, ore grinding and refining and possible further processing . The mine waters include process water circulating in the mine proces ses , water being removed from the mine and runoff waters of the mine area .

- Precipitate is an impurity deposited to the bottom of a liquid . - Sludge is a mixture of a liquid and a solid, fine material mixed therein in a high concentration .

- Underflow is a solid matter containing material separated from a liquid by filtration, precipitation or other separation method .

Bioleaching

The proposed solution may be used for the treatment of waste waters formed in bioleaching and of the precipitates settling from the waste waters .

Bioleaching is an extraction method in which metals are separated from ore by means of microbes . In the bioleaching process , optimal conditions are created for microbes existing naturally in the soil , whereby the microbial activity catalyses oxidation reactions of metal sulphides .

Bioleaching may be bioheap leaching, but the proposed solution is al so suitable for use in connection with mines utili zing other bioleaching processes .

In bioheap leaching, conditions that are conductive to bacterial activity are provided in leaching heaps by irrigating the heaps and blowing air therein . The heaps are thus aerated and irrigated with an acidic (pH 1 , 5-3 ) solution by means of irrigation pipes from the top of the heap, such that the bacterial activity can be accelerated . The bacteria separate the metals from the ore by catalysing the oxidation of iron and sulphur contained by the ore in order to obtain energy for their growth .

The main processes of the production process are : mining, crushing, agglomeration, bioheap leaching and recovery of metals .

After agglomeration, the ore is collected into heaps having a height of 6- 12 meters and is leached in the heaps for 1 -3 years . In bioleaching, the metal sulphides contained in the ore are oxidi zed to soluble compounds via microbial activity . The main reaction in the recovery of metals is : Metal sulphate (MeSCy ) + hydrogen sulphide (H2S ) Sulfuric acid (H2SO4 ) + Metal sulphide (MeS )

In an iron precipitation step, the pH of the solution is raised by means of limestone sludge . The precipitation of a final neutrali zation step is performed by raising the pH of the solution to a clearly basic level (pH=10 ) with milk of lime (Ca (OH) 2 ) , which enables the precipitation of residual and other metals as hydroxide . The underflows from the thickeners are pumped to a gypsum pond where gypsum precipitate settles and clear solution is pumped in time back to the leaching heaps via solution purification .

Underflow from the final neutrali zation may be conveyed to the gypsum precipitate pond .

The main reaction of final neutrali zation (LoNe ) is :

Metal sulphate (MeSCg ) + milk of lime (Ca (OH) 2 ) Gypsum precipitate (CaSCg x H2O) +metal hydroxide Me (OH) ₂

The proposed solution may be used for treating pro- cess-derived metal containing waste waters , waste liquors and precipitates produced in bioleaching .

The above-described embodiments and their features may be combined to provide desired configurations .

Brief description of the figures

Some embodiments of the proposed solution are illustrated in more detail in the following figures , in which Fig . 1 is a schematic and simplified diagram illustrating one arrangement for treatment of waste material produced in an extraction process ,

Fig . 2 is a schematic and simplified diagram illustrating a heat treatment of one waste material , Fig . 3 is a schematic and simplified diagram illustrating preparation of a binder from one waste material and use of the binder,

Fig . 4 schematically illustrates some constructions and applications made from hardenable material in a mine area,

Fig . 5 schematically illustrates a cover structure formed over a pond from hardenable material ,

Fig . 6 schematically illustrates one configuration in which a mixer apparatus is arranged in connection with a waste water discharge pipe for mixing in a binder and in which, after additive supplementation, the waste material is conveyed to a pond for hardening;

Fig . 7 schematically illustrates a side view of one very high construction in which hardened waste material may be arranged for disposal , and

Fig . 8 is a simple diagram illustrating some extraction processes and some waste materials formed therein .

For the purpose of clarity, some embodiments of the proposed solutions are illustrated in the figures in a simplified form . The same reference numerals are used in the figures to refer to the same elements and features .

Detailed description of some embodiments

Fig . 1 illustrates steps for converting moist waste material formed in extraction to a binder and how the prepared binder may be utili zed in a mine area . The waste material 1 may be pretreated 2 to increase its dry matter content by using different types of filters , separation apparatuses and thermal dryers . Activation of the waste material to reactive material is carried out by means of a heat treatment 3 . In the heat treatment , the waste material is heated in an oven or a corresponding heating device . After heating and activation, the hardened material may be ground 4 to fine powder . The prepared powder may be used as a binder 5 , by means of which the waste materials formed in the mine area and possible other components may be hardened . The binder may be mixed into water containing waste material in a suitable ratio , whereby the water of the waste material activates the reactive binder and causes the hardening of the waste material . Due to the hardening, the waste material may be used as building material , i . e . the problematic waste material can be disposed of 6 in the mine area as a hardened useful structure . It may be used for building mine infrastructure 7 , upwardly rising hardened structures 8 and different types of protective structures 9 .

Fig . 2 illustrates the heat treatment 3 of the waste material 1 . The treated waste material 1 may be metal containing, whereby it may undergo activation of metal sulphate 10 , when the heating is performed in an oxygen containing space 11 . I f the treated waste material 1 comprises gypsum it may undergo , during the heating, conversion of calcium sulphate 12 to material that is consolidating and reactive with water or other hydroxides . During the heating there may also occur one or more other reactions providing or facilitating formation of reactive hardenable material 13 . In any case , practical experiments have shown that for example from waste material formed in bioleaching it is pos sible to prepare material 13 that is consolidating and reactive with water or other hydroxides by means of the heat treatment .

In Fig . 3 it is illustrated that the waste material 1 may be used, by means of preparing the binder 14 , for forming a hardenable binder that may be used for hardening waste material 15 corresponding to or differing from that from which the binder itself is prepared . Further, the binder may be used for hardening of any natural soil material 16 .

Fig . 4 illustrates some applications . The hardenable material may be used for fabricating a bank 17 or a barrier that may be used for example as an edge of a pond or as a protective structure . I f necessary, the processability and strength properties may be adj usted by additive supplementation, for example with gypsum CaSCg , slaked lime Ca (OH) 2 or burnt lime CaO . Further, the hardenable material may be used for casting an upwardly extending uniform hill or heap 18 that remains firmly in place and standing without external structures . Further, it is possible to form the heap from crushed material or boulders that are formed by first casting a hard structure , for example an artificial rock, and by crushing it after final hardening to crushed material or boulders . By utili zing different types of casting techniques , walls 19 and other support and foundation structures may also be formed from the hardenable material . It is possible to reinforce the soil by using the hardenable materials described in this document for soil stabili zation 20 . The described hardenable material may also be used as a surface 21 and surface layers for roads and fields of the mine and its surroundings .

It can further be seen from Fig . 4 that the upwardly directed structures 17 , 18 and 19 may be founded directly on a flat surface 22 .

Fig . 5 illustrates a pond 23 that may be for example a gypsum precipitate pond . At the edges of the pond 23 there are banks 17 that may be formed from the described hardenable material . The final coverage of the pond 23 may be performed by casting a cover 24 from the hardenable material over the pond .

Fig . 6 illustrates an arrangement in which a mixing apparatus 27 is arranged in a discharge pipe 26 for waste water or corresponding waste material of a bioleaching process or metal recovery unit 25 . By means of the mixing apparatus 27 , hardenable binder is mixed into the waste material transferred in the discharge pipe 26 by means of a feeding device 28 , whereby a hardening reaction starts in the waste material . The waste material may be conveyed into the pond 23 or other location where it is controllable while still in a flowable state . However, the hardening occurs quite quickly . Hardenable waste material may be sprayed or spread by means of suitable nozzles 29 as a thin layer over the whole location . The location may be a disposal site or alternatively, the hardened solid material 30 may later be broken and crushed for example to crushed material and transported for use as an earth construction or coverage material in the mine area or its surroundings . Thus , the same pond 23 or corresponding location may be reused as a reception site of hardenable waste material after removal of the solid material .

Fig . 7 illustrates a mountain 31 , heap or simi lar very high construction formed from hardenable waste material . The height h of this hardened structure from the surrounding surface is several ten meters . The height is thus at least 20 m, but preferably it has a height of at least 50 m and even 100 m, or more . Due to the hardened material , large amounts of waste material can be stored or disposed of in this type of very high construction compared to the current depositions . The sides of the construction may be terraced 32 , observing the working safety and technical aspects of deposition . In the case of disposal , the structure may be covered with soil , bentonite , different types of films , meshes , roll coverings and geotextiles , the purpose of which may be to participate in landscaping of the construction, prevention of weathering, directing of waters or other purposes . These abovementioned materials and components may be combined into a suitable coverage layer 33 in a desired manner . The abovementioned terracing 32 may also participate in and facilitate the installation and maintenance in place of the coverage layer .

It is noted that in Fig . 7 the proportions of the dimensions of the structure relative to each other are not necessarily illustrated to the actual scale .

Fig . 8 further illustrates some mine extraction processes producing waste material for the treatment of which the solution described in this document has at least been found to be suitable . In addition, the figure illustrates some waste materials which are formed in the extraction processes and in the treatment of which the proposed solution may be applied . These include for example sulphate containing waste and gypsum containing waste that may be for example waste neutrali zed with calcium hydroxide .

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

Claims

1. A method for treating waste material, which method comprises treating waste material which is formed in an extraction process of a mine and which is waste water, sludge or underflow, and heating the waste material to convert it to a reactive consolidating material, cha ra ct e r i z ed in that a binder is prepared from said waste material of an extraction process of a mine by means of a heat treatment.

2. The method according to claim 1, c h a r a c t e r i z e d in that gypsum containing waste material formed in the extraction process is heat-treated to form the binder.

3. The method according to claim 1 or 2, c h a r a c t e r i z e d in that sulphate containing waste material formed in the extraction process is heat-treated to form the binder.

4. The method according to any of the preceding claims 1-3, c h a r a c t e r i z e d in that waste material formed in a bioleaching process is heat-treated to form the binder.

5. The method according to any of the preceding claims 1-3, c h a r a c t e r i z e d in that waste material formed in an iron precipitation process is heat-treated to form the binder.

6. The method according to any of the preceding claims 1-3, c h a r a c t e r i z e d in that waste material formed in an ore flotation process is heat-treated to form the binder.

7. The method according to any of the preceding claims 1-6, c h a r a c t e r i z e d in that the prepared binder is used for hardening a different waste fraction or the same waste fraction produced in the same extraction process.

8. The method according to any of the preceding claims 1-7, c h a r a c t e r i z e d in that at least one admixture is added to the prepared binder, which admixture forms, together with the binder, a consolidating structure.

9. The method according to claim 1, c h a r a c t e r i z e d in that the conversion of waste material to a reactive material is performed by means of heating only, without any external additives.

10. The method according to any of the preceding claims 1-9, c h a r a c t e r i z e d in that a first heating of the waste material is performed to remove water from the waste material; and after drying, the heat treatment is continued to activate the dried waste material to the reactive consolidating material.

11. The method according to any of the preceding claims 1-10, c h a r a c t e r i z e d in that metal sulphate containing waste material is heat- treated such that the metal sulphate compounds contained therein are activated to a material that is consolidating and reactive with water and hydroxides.

12. The method according to any of the preceding claims 1-11, c h a r a c t e r i z e d in that metal sulphate containing waste material is heated at a temperature of 30 - 300° C and under the influence of oxygen .

13. The method according to any of the preceding claims 1-12, c h a r a c t e r i z e d in that waste material that contains metal sulphates and calcium sulphate CaSCg is treated, whereby calcium sulphate is converted under heating to anhydrite that is a hardenable material .

14. The method according to any of the preceding claims 1-13, c h a r a c t e r i z e d in that after the heating treatment, the solid material activated with the heat treatment is ground to a fine powder suitable for use as a consolidating binder.

15. The method according to any of the preceding claims 1-14, c h a r a c t e r i z e d in that underflow produced in the treatment of waste waters of an extraction process of a mine is treated by mixing it with the binder prepared according to any of the preceding claims 1-14, whereby the binder hardens said underflow to a hardness of at least 500 kPa.

16. An arrangement for disposal of waste material in a mine area, cha ra ct e r i z ed in that a binder is prepared from waste material which is formed in an extraction process of the mine and which is waste water, sludge or underflow, which binder is converted to reactive hardenable material by means of a heat treatment ; the binder is mixed into the waste material to be disposed of; and the waste material of the mine is disposed of as a hardened structure or material in the mine area, and wherein said waste material to be disposed of is the same waste material formed in the extraction process of the mine from which said hardenable binder is prepared.

17. The arrangement according to claim 16, c h a r a c t e r i z e d in that the hardenable mixture is used as building material of a construction in the mine area, whereby the formed construction is at the same time the disposal site of the waste material.

18. The arrangement according to claim 16 or 17, c h a r a c t e r i z e d in that an upwardly rising rigid and autonomous structure is formed from the hardenable waste material.

19. The arrangement according to any of the preceding claims 16-18, c h a r a c t e r i z e d in that the hardenable waste material is used as earth construction material in the mine area.

20. A consolidating binder that is formed from waste material ; cha ra ct e r i z ed in that the binder is prepared from underflow or a filtrate cake formed in the treatment of waste waters of an extraction process of a mine by heating the material to a reactive form.

21. The binder according to claim 20, c h a r a c t e r i z e d in that the treated material is ground after the heating, whereby the binder is present in a powdery form.

22. The binder according to claim 20-21, c h a r a c t e r i z e d in that the binder is configured to react when mixed in water or other OH group liquid and to provide a hardening reaction.