REPURPOSED WASTE PRODUCT

Technical Field

[0001] This technical solution relates to a method for repurposing of the waste product from the production of heat or electricity from solid fuels, which comprises slag, bottom ash and fly ash. This technical solution also relates to a method of use of this repurposed waste product.

Background Art

[0002] Waste products, which are residues in the form of slag, bottom ash, fly ash and boiler dust, are formed in the production of heat or electricity from solid fuels, i.e. in the combustion of solid fuel in heating plants or thermal power plants.

[0003] Hot fly ash, which is captured by filters, slag and other waste products from burning of solid fuels are stored in silos, or they are mixed with water directly in the dredging station to form pumpable suspension - hydro- mixture. Hydro-mixture is transported by pipelines to ash pond (wet disposal of ash). Hydro-mixture freely sediments at the ash pond - water is allowed to drain. Water separated from the hydro-mixture by

sedimentation is returned by pipelines back to heating plant where it is reused for wet disposal of ash. Such ash ponds generally present long- term environmental burden.

[0004] Contact of hot residues from combustion with water causes a change in their physical and chemical properties. By applying water on hot residues, zeolitization occurs - an alteration of fly ash to phillipsite-like new zeolite mineral formation that has high sorption properties, often 2 to 2,5 times higher than natural zeolite mineral - phillipsite. Zeolitized residues have such advantage that they can be used as a sorbent of all cations and anions having a smaller ionic radius (e.g. ionic radius Ca, Mg, Pb, NH ₄ ). Despite their gained unique properties, zeolitized residues cannot be used as such for reclamation works because they themselves contain neither organic carbon nor humic substances and have unsuitable physical properties.

[0005] Object of this technical solution is to provide a method for repurposing the waste product from the production of heat or electricity from solid fuels and also a method of use of this repurposed waste product, which would substantially eliminate current problems lying especially in negatives presented by landfilling of said waste product in ash ponds.

Disclosure of Invention

[0006] Said object is achieved by the method for repurposing the waste product from the production of heat or electricity from solid fuels and the method of use of this repurposed waste product.

[0007] The method for repurposing the waste product from the production of heat or electricity from solid fuels according to this technical solution is characterized in that, it comprises a step of mixing the waste product with water and producing pumpable hydro-mixture, a step of mixing the hydro- mixture with the admixture with content of organic matter necessary for plant growth in amount of 5 to 85% related to the weight of dry matter contained in the hydro-mixture and producing the mixture with content of organic matter necessary for plant growth, and a step of safe landfilling, repurposing and/or use of produced mixture with content of organic matter necessary for plant growth.

[0008] The admixture with content of organic matter necessary for plant growth can be e.g. topsoil, peat, compost, humic substances, sludge from municipal wastewater treatment, sludge from paper industry,

diatomaceous earth slurry from the filtration of beer, and the like.

[0009] Preferably, the step of mixing the hydro-mixture with the admixture with content of organic matter necessary for plant growth comprises or is followed by a step of mixing the mixture with content of organic matter necessary for plant growth with flocculating agent.

[0010] The method for repurposing the waste product from the production of heat or electricity from solid fuels according to this technical solution is also characterized in that, it comprises a step of mixing the waste product with water and producing pumpable hydro-mixture, a step of mixing the hydro- mixture with the admixture with content of inorganic matter in amount of 5 to 85% related to weight of dry matter contained in the hydro-mixture and producing the mixture with content of inorganic matter, a step of mixing the mixture with solidifying agent and a step of safe landfilling, or use of produced mixture with content of in organic matter.

[0011] The admixture with content of inorganic matter can be e.g. filter dust, waste lime, red mud from aluminum production, drilling muds, abrasive dust, ink sludges, paints and pigments, a sludge from the bottom of a reservoir, used filter clay, used activated carbon, and the like.

[0012] Preferably, the step of mixing the hydro-mixture with the admixture with content of inorganic matter is followed by the step of mixing the mixture with content of inorganic matter with a flocculating agent.

[0013] Preferably, a step of dewatering the mixture is carried out before the step of mixing the mixture with solidifying agent.

[0014] A method for use of the waste product repurposed by the method

according to this technical solution is characterized in that the hydro- mixture, and/or the mixture with content of organic matter necessary for plant growth, and/or the mixture with content of inorganic matter is disposed to the ash pond, and/or is filled to geotextile bags that are laid in the ash pond, and/or on the surface of the ash pond, and/or at different location and/or area.

[0015] Preferably, filled geotextile bags are laid upon each other in layers.

Brief Description of Drawings

[0016] The technical solution is explained more in detail on attached drawings, where,

[0017] Fig. 1 shows a scheme of the method according to this technical solution for processing with the admixture with content of organic matter necessary for plant growth,

[0018] Fig. 2 shows a scheme of the method according to this technical solution for processing with the admixture with content of inorganic matter, and [0019] Fig. 3 schematically shows the method of use of the repurposed waste product, particularly for increasing the capacity and/or closing and/or reclamation of the ash pond.

Mode(s) for Carrying Out the Invention

[0020] In one example of embodiment, with reference to Fig. 1 , hot slag, bottom ash, fly ash, boiler dust, as waste products in the production of heat or electricity from solid fuels, are mixed with water in the first step 1

Specifically, according to Fig. 1 , this is carried out by supplying the waste product from slag and dust silo 9, fly ash silo 10, and technological water from technological water tank 1_1_, to the dredging station 12 with a pump, where said components are mixed and pumpable hydro-mixture is produced. This pumpable hydro-mixture is then further transported by the pipeline 8 that typically ends at the ash pond 34.

[0021] In the next step 2, the hydro-mixture is mixed with the admixture with

content of organic matter necessary for plant growth in amount of 5 to 85% related to the weight of dry matter contained in the hydro-mixture. The admixture with content of organic matter necessary for plant growth can be e.g. topsoil, peat, compost, humic substances, sludge from municipal wastewater treatment, sludge from paper industry, diatomaceous earth slurry from the filtration of beer, and the like. Specifically, according to Fig.

1 , this is carried out by supplying the hydro-mixture from the pipeline 8 and the admixture with content of organic matter necessary for plant growth, to the mixing chamber 19. The mixture is then transported by the pump 20 from the mixing chamber 19 to the pipeline 8 and to the ash pond 34 for sedimentation. This represents the step 6 of safe landfilling or use of the produced mixture, as sedimented mixture, after the ash pond 34 capacity is reached, provides nutritive substrate suitable for the growth of vegetation, which as a result creates safe, compact surface of the ash pond 34, thus practically preventing sediment wash-off in rainfall and so. The ash pond 34 is thereby reclaimed. The sedimented mixture can also be excavated from the ash pond 34 and can be used at different location, except agricultural and forest areas, e.g. for landscaping, reclamation of other areas and so. An increase in ash pond capacity is thereby achieved, as a space is freed by excavation of the sedimented mixture in the ash pond 34. The water 26 drained during sedimentation is preferably returned to the process as technological water.

[0022] In regard to the content of zeolitized residues, which are formed in contact of hot residues from combustion with water, moreover, the resulting product has enhanced sorption properties.

[0023] In case the admixture does not have suitable consistency, therefore it cannot be pumped, this admixture is pretreated such that it is mixed with the technological water to such consistency to form homogenous pumpable suspension suitable for mixing it into the hydro-mixture.

Specifically, according to Fig. 1 , this is carried out by supplying the admixture with content of organic matter necessary for plant growth from the admixture tank 13 and the technological water from the reservoir 14 to the mixing tank 15. Pumpable admixture is transported by the pump 16 from the mixing tank 15 to the storage tank 17, where the admixture is maintained by continuous stirring in homogenous state, floating in the water, until it is mixed in with the hydro-mixture. The admixture is then supplied from the storage tank 17 to the mixing chamber 19.

[0024] In order to accelerate separation of water from the mixture, flocculating agents can be added in the next step 3 after the step 2 of mixing the hydro-mixture with the admixture. Addition of the flocculating agents can also be carried out in the step 2. Products known e.g. under trade names Superfloe, Sokoflok, Magnafloc can be used as the flocculating agents. Specifically, according to Fig. 1 , this is carried out by supplying the flocculants from the tank 21 of the flocculants through the pump 22 to the mixing chamber 23. The mixture formed in this step 3 is then transported to the pipeline 8 by the feed pump 24.

[0025] In another example of embodiment, with reference to Fig. 2, slag, bottom ash, fly ash, boiler dust, as waste products in the production of heat or electricity from solid fuels, are mixed with water in the first step 1

Specifically, according to Fig. 1 , this is carried out by supplying the waste product from slag and dust silo 9, fly ash silo 10, and technological water from technological water tank to the dredging station 12 with a pump, where said components are mixed and pumpable hydro-mixture is produced. This pumpable hydro-mixture is then further transported by the pipeline 8 that typically ends at the ash pond 34.

[0026] In the next step 2, the hydro-mixture is mixed with the admixture with

content of inorganic matter in amount of 5 to 85% related to the weight of dry matter contained in the hydro-mixture. The admixture with content of inorganic matter can be e.g. filter dust, waste lime, red mud from aluminum production, drilling muds, abrasive dust, ink sludges, paints and pigments, a sludge from the bottom of a reservoir, used filter clay, used activated carbon, waste from beer filtration and the like. Specifically, according to Fig. 2, this is carried out by supplying the hydro-mixture from the pipeline 8 and the admixture with content of inorganic matter to the mixing chamber 19. The mixture is then transported by the pump 20 from the mixing chamber 19 to the pipeline 8.

[0027] In the next step 5, the mixture is mixed with solidifying agent. Water

solutions with reagents e.g. Na2Si03, or K2S1O3, or NaOH, or Na2C03, or KOH, or K2CO3 can be used as the solidification agents. Specifically, according to Fig. 2, this is carried out by supplying the solidifying agents from the tank 28 of the solidifying agents through the feed pump 30 to the mixing tank 31 The mixture formed in the previous step 2 is being fed by the pipeline 8 through the feed pump 27 to the mixing tank 31 The mixture formed in this step 5 is then transported by the dredging pump 32 to the pipeline 8 and to the ash pond 34 for sedimentation. This represents the step 6 of safe landfilling or use of the product produced from mixture, as sedimented mixture, after the ash pond 34 capacity is reached, solidifies over time while forming safe, compacted surface of the ash pond 34, thus practically preventing sediment wash-off in rainfall and so. The ash pond 34 is thus practically closed. This sedimented mixture - the product can also be excavated from the ash pond 34 as the solidification does not occur quickly, and can be used at different location, e.g. for landscaping and so. An increase in ash pond capacity is thereby achieved, as a space is freed by excavation of the sedimented mixture in the ash pond 34. The water 26 drained during sedimentation is preferably returned to the process as technological water. It is also possible to use the mixture already solidified, however, it is then necessary to disintegrate the solidified mixture before its use for its further handling, whereby such mixture can be used e.g. as a backfill.

[0028] Said product possess new physical and chemical properties, for example strength, chemical immobilization of heavy metals, reduced radioactivity, lower filtration coefficient (depending on added agents).

[0029] In regard to the content of zeolitized residues, which are formed in contact of hot residues from combustion with water, moreover, the resulting product has enhanced sorption properties.

[0030] In case the admixture does not have suitable consistency, therefore it cannot be pumped, this admixture is pretreated such that it is mixed with the technological water to such consistency to form homogenous pumpable suspension suitable for mixing it into the hydro-mixture.

Specifically, according to Fig. 2, this is carried out by supplying the admixture with content of inorganic matter from the admixture tank 13 and the technological water from the reservoir 14 to the mixing tank 15.

Pumpable admixture is transported by the pump 16 from the mixing tank 15 to the storage tank 17, where the admixture is maintained by continuous stirring in homogenous state, floating in the water, until it is mixed in with the hydro-mixture. The admixture is then supplied from the storage tank 17 to the mixing chamber 19.

[0031] In order to accelerate separation of water from the mixture, flocculating agents can be added in the next step 3 after the step 2 of mixing the hydro-mixture with the admixture. Addition of the flocculating agents can also be carried out in the step 2. Products known e.g. under trade names Superfloe, Sokoflok, Magnafloc can be used as the flocculating agents. Specifically, according to Fig. 2, this is carried out by supplying the flocculants from the tank 21 of the flocculants through the pump 22 to the mixing chamber 23, into which the mixture from the mixing chamber 19 in the previous step 2 is fed by the dredging pump 20 through the pipeline 8. The mixture formed in this step 3 is then transported by the feed pump 24 to the pipeline 8. [0032] In order to increase solidification efficiency of the mixture, the step 4 of dewatering the mixture is preferably carried out between the step 3 of adding the flocculation agents and the step 5 of adding the solidification agents. Specifically, according to Fig. 2, this is carried out by feeding the mixture the dewatering device 25, where significant part of the water is removed that as separated water 26 is preferably returned to the process as technological water. The mixture is dewatered to such degree only, to be still transportable by pumps.

[0033] In the above-mentioned examples, existing equipment of heat plants or thermal power plants is used for the preparation of the hydro-mixture, i.e. pumpable mixture of the waste product from the production of heat or electricity from solid fuels and water. This existing equipment typically includes waste product silos 9, 10, technological water tank 1_1_ and dredging station 12. The hydro-mixture is then transported from this dredging station 12 through the pipeline 8 to the ash pond 34. Within the scope of this technical solution it is however possible to produce the hydro-mixture separately, that is without the use of existing equipment and pipelines of heat plants or thermal power plants. In this case, for the method according to this technical solution, it is directly obtained as dry waste product, or it is obtained from the ash pond. The hydro-mixture is then produced in separate equipment and it is subsequently processed similarly as described in the above-mentioned examples. Then, also particular existing pipeline 8 of heat plants or thermal power plants is not used, and an ash pond, or disposal area for processed product can also be in different location as the ash pond 34.

[0034] Following examples of embodiments according to Fig. 3 relates to the method of use of the waste product repurposed by the method according to this technical solution, particularly to increasing the capacity and/or closing and/or reclamation of the ash ponds 34.

[0035] In one example, it is possible to take the waste product repurposed by the method according to this technical solution form the pipeline 8 and fill it into geotextile bags 35. When the ash pond 34 capacity is reached, the bags 35 are laid on the surface of the ash pond 34. Preferably, the bags 35 are filled successively from the farthest part of the ash pond 34. The mixture in the bag 35 settles and water drains from the bag 35, whereby a space is freed in the bag 35 for further filling the mixture. After the bag 35 is filled with sedimented mixture, filling of the next bag 35 continues. If one bag 35 capacity is reached during its filling, that is the water does not drain sufficiently fast, it is possible to continue with filling the next bag 35, while the previous bag 35 can be filled up after the water has drained from it. Bags 35 can also be placed one upon another in layers, thus after completing one layer of bags 35 with sedimented mixture, it is possible to continue laying and filling the bags 35 in the next layer. Also, other options of laying and filling the bags 35 are possible based on a project

requirements or layout of specific ash pond 34.

[0036] Geotextile bags, in general, are available on the market, e.g. under

trademarks Geotube®, Geobag®, Geocontainer®, WaterStructures® and AquaDam®. Geotextile bags are manufactured directly in required dimensions. Typically, they have the width from 4,57 to 18,29 m (the width according to requirements) and the length 61 m. These bags can be placed either individually or can be arranged into various bodies (dams, fields). Bags are used in various building constructions. Application of the bags is usually divided to construction applications and dewatering applications. In the field of construction applications, geotextile bags are used as embankments or dams to prevent erosion and also as static protection. Bags can also be used for slope protection. Construction bags are usually designed to resist short-term and also long-term exposure to environment.

[0037] In order to increase the capacity and/or to close and/or to reclaim the ash pond 34 regarding the composition of layers of bags 35, it is possible to apply various approaches, where some of them are presented below as illustrative examples. In this case, other options are also possible based on given project requirements for increasing of capacity and/or closing and/or reclamation of the ash pond 34.

[0038] In one example, in order to increase the capacity of the ash pond 34

above the level of its designed maximum capacity and for its reclamation, it is possible to lay bags 35 on its surface or within its banks, in one or several layers and fill them with the waste product repurposed by the method according to this technical solution that comprises the admixture with content of organic matter necessary for plant growth. The bags 35, after sedimentation, can be disintegrated and the substrate can be levelled and prepared for planting of vegetation.

[0039] In another example, in order to increase the capacity of the ash pond 34 above the level of its designed maximum capacity and for its closing, it is possible to lay bags 35 on its surface or within its banks, in one or several layers and fill them with the waste product repurposed by the method according to this technical solution that comprises the admixture with content of inorganic matter and solidifying agent. The mixture in bags 35 is allowed to sediment and solidify. Optionally, if reclamation of the pond is requested, it is possible to form the outer layer of bags 35 filled with the waste product repurposed by the method according to this technical solution that comprises the admixture with content of organic matter necessary for plant growth. The bags 35, after sedimentation, can be disintegrated and the substrate can be levelled and prepared for planting of vegetation.

[0040] In another example, in order to increase the capacity of the ash pond 34 above the level of its designed maximum capacity and for its closing and/or reclamation, it is possible to build a layer or several layers of bags 35 that are filled directly with the hydro-mixture, i.e. the mixture of the waste product from the production of heat or electricity from solid fuels, and water, before building a layer of bags 35 with the mixture comprising organic matter necessary for plant growth and/or with the mixture comprising inorganic matter and solidifying agent. This can provide an advantage of saving the admixtures and agents when significant increase in capacity of the ash pond 34 is required.

[0041] As already mentioned above, the waste product repurposed by the method according to this technical solution can be obtained directly from the pipeline 8. In another example, it is possible to install a dredging pump at the ash pond 34, which will pump the liquid mixture from the ash pond 34, while freeing a space for the mixture flowing of the pipeline 8.

[0042] The above-mentioned example of use of the waste product repurposed by the method according to this technical solution was related to already existing ash pond 34. Repurposed waste product can also be placed, pumped, as well as filled to the bags 35 also at other suitable locations or areas, where, after dewatering, it can be further transported for other uses as mentioned below in the industrial applicability of this technical solution.

[0043] The examples described above are for illustrative purposes and do not exhaust all possibilities of embodiments of methods according to this technical solution that are possible within the scope of the claims.

Industrial Applicability

[0044] Disclosed technical solution has wide application. It can be used directly in companies involved in production of heat or electricity form solid fuels, as well as in waste processing companies. Waste product repurposed by the method according to this technical solution can be used as a material - product, for carrying out technical works in building industry, such as for the production of building products and materials, for carrying out technical works in building industry related to, for example, closing and reclamation of landfills, quarries, erosion furrows, empty mines, ash ponds and ash sediment landfills (ash, slag, fly ash and filter dust), reconstruction, modification and raising the height of dams, embankments, increasing the capacity of landfills, borrow pits, settling basins (also above the crest of dam, or above the maximum water level), landscaping, for prevention and stabilization of landslides, reclamation and recovery of excavated abandoned spaces and areas, waste banks, settling ponds (also above the crest of dam, or above the maximum water level), quarries, surface mines. Also, it can be used in building industry for various landscaping such as pit filling, retaining walls, construction and reinforcement of slopes and so.