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    • 专利摘要:
    A method of making soil from sulphides or sulphide silt, comprising the following steps: a) adding lime and rock or soil material to a sulphide clay or sulphide silt so that a starting composition is obtained, the average grain size of the rock or soil material being greater than for said sulphides or sulphide silt, b) mixing the starting composition to obtain a mixed composition, c) storing the mixed composition in the presence of oxygen until it has a pH according to ISO 103902005 of 5 - 8, such as 6 - 8, such as 6 - 7, and d ) adding organic material to the stored composition from step c) to produce topsoil with the desired composition.
    公开号:SE1750692A1
    申请号:SE1750692
    申请日:2017-06-01
    公开日:2017-12-02
    发明作者:Hans Wanman；Jonas Jonsson
    申请人:Klabboele Konsult Ab；Km I Umeaa Ab；Mikael Sundberg；Strinnholm Leif；
    IPC主号:
    专利说明:

    TECHNICAL FIELD The invention relates to the handling of sulphide or sulphide silt.
    BACKGROUND Sulfidlera and sulphide silt are common soils that are mainly found along the Bothnian Sea and the coast of the Gulf of Bothnia in Sweden and Finland, but also occur in the Mälardalen area in Sweden. The sulphide clay and sulphide silt were formed about 3000-6000 years ago as a bottom sediment in the then so-called Litorina Sea. Under oxygen-free conditions, FeS (iron monosulfide) and FeS2 (iron disulfide) were formed.
    Sulphide fibers and sulphide silt have low bearing capacity, which means that in connection with the construction of infrastructure or buildings, there is a need to replace such masses with more bearing material. When the masses of sulphides and sulphide silt are excavated and exposed to oxygen, an oxidation process begins. The following formula shows this oxidation process where iron disulphide is converted to sulphate 4 FeS2 + 15O2 + 14 H2O -> 4 Fe (OH) 3 + 8 SO4- + 16 H +.
    This oxidation process (and also the oxidation of iron monosulfide) results in a very low pH value, often just below 3. Such acid conditions lead to metals going into solution and accompanying an eventual leachate. The released metals and the acidic leachate have a negative impact on the local environment.
    Sulphide-containing material is classified as waste since 2014 according to a ruling from the Swedish Land and Environmental Court with case no. M 6273-13. The only known method of handling sulphide or sulphide silt is to deposit the specially made landfills where oxygen-free conditions are achieved and the above-mentioned oxidation process is severely limited.
    SUMMARY However, the present inventors have realized that the sulfide moiety or sulfide siltane can be used to produce valuable topsoil instead of being deposited in oxygen-free conditions.
    An object of the present invention is therefore to provide an alternative way of handling sulphide salts and sulphide silt.
    The invention is a method of making soil from sulphide or sulphide silt, comprising the steps of: a) adding lime, organic material and rock or soil material to monosulphide or sulphide silt so as to obtain a starting composition, the average grain size of the rock or soil material being greater than for said sulphide or sulphide silt, b) mixing the starting composition so as to obtain a mixed composition and c) storing the mixed composition in the presence of oxygen, preferably until it has a pH according to ISO 1o39o: 2oo5 in the range 5 - 8.
    "Sulphide or sulphide silt" according to the present invention comprises what is sometimes called "silty sulphide sieve" and "muddy sulphide silt" and in terms of grain size lies between sulphide sills or sulphide silt.
    By "sulphide" and "sulphide silt" is meant not only non-oxidised sulphide and sulphide silt, but also sulphide and sulphide silt where the sulphide has been oxidised to sulphate to varying degrees. For example, it is common for a pulp of sulfide or sulfide silt to have an outer layer that is relatively oxidized while an internal amount is oxidized to a much lesser extent. However, the "sulphide" and "sulphide silt" of the present invention always have a sulfur content of at least 600 mg / kg dry matter. According to one embodiment, the sulphide clay and the sulphide silt have a sulfur content of 1-20 g / kg dry matter.
    The lime used in the present invention may be, for example, limestone, dolomite, slaked lime or mesa lime.
    Furthermore, the sulphide clay or sulphide silt treated according to the present invention may from the outset contain up to 30% (based on dry weight) of organic material. According to embodiments of the present invention, the sulfide moiety or sulfide silt initially contains a maximum of 20, 15 or 10% (based on dry weight) of organic material. Around Umeå in Sweden, for example, the content of organic material is about 4-5%. The content of organic material can, for example, be estimated with an emission loss measurement (see Earth structure: Proposals for geotechnical laboratory instructions, part 3 (1974), Roland Pusch, in collaboration with SGF's laboratory committee, Byggforskningens informationsblad B14: 1974, Statens institut för byggforskning, Stockholm).
    The additions of the organic material and the rock or soil material make the mixed composition more airy, which accelerates the oxidations of sulphide. The acid formed during the oxidations is then neutralized by the lime added so that a pH suitable for topsoil is obtained. In addition to accelerating the oxidation, the added organic material causes an increased soil content in the soil. The rock or soil material also improves the quality of the topsoil.
    According to one embodiment, in a first step, only lime and rock or earth material are added to the sulphide clay or sulphide silt, after which it is mixed and stored in the presence of oxygen until it has a pH value in the range 5 - 8. The organic material is advantageously added only when preparing it. the final product, and the amount and type of organic material can then be adapted to the desired quality of the topsoil to be produced. This embodiment is suitable when the demand for topsoil is less, and the mixture of sulphide clay or sulphide silt, lime and rock or soil material becomes long-lasting, eg over the winter or longer.
    BRIEF DESCRIPTION OF THE FIGURE Figure 1 shows a grain size distribution diagram with a so-called sieve curve (in fact the area between two lines) for a preferred embodiment of the starting composition according to the present invention. The following sieves have been used to produce the curve: 20 mm, 2 mm, 0.63 mm, 0.2 mm, 0.063 mm, 0.02 mm and 0.002 mm.
    Figure 2 shows the development of pH in a sample of untreated sulphide clay during 10 leaching steps; and Fig. 3 shows the development of pH during 10 leaching steps in a sample of sulphide with the addition of lime according to an embodiment of the invention.
    DESCRIPTION OF THE INVENTION The present invention thus provides a method of making topsoil from sulphide or sulphide silt. A general aspect of the invention is a method of making topsoil from sulphide or sulphide silt, comprising mixing lime, rock or soil material, and organic material into a sulphide or sulphide silt, the average grain size of the rock or soil material being greater than that of said sulphide or sulphide silt; and storing the presence of oxygen until the mixture has a pH value according to ISO 10390: 2005 of 5 - 8, such as 6 - 8, such as 6 - 7.
    A preferred aspect of the invention is a method of making topsoil from sulphide or sulphide silt, comprising the steps of: a) adding lime and rock or soil material to a sulphide clay or sulphide silt so that a starting composition is obtained, the average grain size of the rock or soil material being greater than for said sulphides or sulphide silt, b) mixing the starting composition so that a mixed composition is maintained, c) storing the mixed composition in the presence of oxygen until it has a pH value according to ISO 10390: 2005 of 5 - 8, such as 6 - 8, such as 6 - 7, and d) adding organic material to the stored composition from step c) to produce topsoil with the desired composition. The average grain size of the rock or soil material is larger than said sulphide or sulphide silt. Preferably, the amount and grain size distribution of the rock or soil material is selected so that a sieve curve according to Table 1 is obtained for the starting composition. In sieve analysis, a number of sieves, so-called sieves, are used of wire mesh with square holes where the side of the holes, the mesh width, is determined. A series of sieves should consist of mesh sizes that connect to the grain fraction limits and standard; 0.063, 0.2, 0.63, 2.0, 6.3 and 20 mm free mesh width (Swedish Geotechnical Association, 1981, rev. 2004). A soil sample is placed in the top sieve that has the coarsest mesh and is vibrated so that the grains fall down as far in the series as the mesh width allows. The person skilled in the art is well acquainted with sight analysis and sight curves.
    Table 1. Screening curve indicating the proportion of% by weight%) of a material that passes a series of sieves Sieve (mm) 0.002 0.02 0.063 0.2 0.63 2 20Max (weight%) 15 20 40 65 100 - -Min (wt.%) 5 5 15 40 60 80 100 The sieve curve is also illustrated in figure 1. To obtain this sieve curve, the kanberg or soil material, for example, include intermediate sand, coarse sand, finger gravel or a mixture thereof. Preferably, the rock or soil material comprises coarse sand. As can be seen from Figure 1, the grain sizes for medium sand, coarse sand and finger gravel are 0.2 - 0.63 mm, 0.63 - 2 mm and 2 - 6.3 mm, respectively.
    The amount of rock or soil material added in step a) may, for example, be such that the dry weight ratio between added coarse-grained rock or soil material and sulphide clay or sulphide silt in the starting composition is in the range 1: 4 to 2: 1. It is preferred that the dry weight ratio be in the range of 1: 3 to 1.5: 1. Most preferred is a dry weight ratio in the range of 1: 2 to 1.5: 1 or 1.5: 1 to 1: 1.5. If sulphides are used, the ratio is typically in the range 1: 2 to 2: 1. If sulphide silt is used, the ratio is typically in the range 1: 4 to 1.5: 1.
    The additives according to step a) can be made into a mass of sulphide or sulphide salt which is stored outdoors. In that case, step b) can, for example, take place with the aid of a single-load machine equipped with a bucket or a rotating unit. According to one embodiment, the same type of loader is used for the additives according to step a) and the mixture according to step b).
    Alternatively, the additives according to a) can be made to a vessel, a pocket or a compartment. The components (ie sulphide or sulphide silt, lime and organic material) can then be emptied in the right proportions in the vessel, pocket or compartment. For example, conveyor belts can be used in step a) to feed said sulfide or sulfide silt and said rock or soil material in proper proportions to the vessel, pocket or compartment. The organic material and / or board lime can also be added in the correct proportion (s) using one or more conveyor belts. The organic material and / or said lime can, however, be added in another way when sulphide or sulphide silt and the rock or soil material are added with conveyor belts.
    The above-mentioned vessel, pocket or compartment may be provided with a mixing means which can be used for step b). The mixing means may, for example, be a stirrer. Alternatively, or as a complement, the pre-starting composition is further passed to a mixing unit, which may for example comprise a sieve.
    According to one embodiment, step b) comprises mixing in a drum mixer. A drum mixer may be particularly suitable if the starting composition is present in a relatively small amount.
    The amount of lime added in step a) can be adapted to the sulfur content of the sulphide or sulphide silt. At a sulfur content of 0.5% by weight, a calculation requires a theoretical amount of lime of approximately 15 kg / m3 to neutralize. However, the inventors have found that it is advantageous to add more than the theoretical amount, such as for example at least 1.5 times the theoretical amount, preferably at least 2 times the theoretical amount. Accordingly, it is preferable to add at least 30 kg / m 3 of lime when the sulfur content is 0.5%. It is particularly advantageous to add a theoretical excess of lime when mixing in step b) is less efficient, such as when it is done by means of a loader.
    Since the density of sulphide clay or sulphide silt is typically about 1.6 tonnes / m3, it follows from the above that the weight ratio of added lime to sulfur is the sulphide sulfur or sulphide silt is preferably at least 2: 1. More preferred is a ratio of at least 3: 1, such as at least 3.5: 1, such as at least 4: 1. To avoid adding too much lime, an upper limit of the ratio can be 15: 1, 1o: 1 or 8: 1.
    It follows from the above that according to an embodiment of the method, step a) is preceded by the step of measuring the sulfur content of the sulphide clay or sulphide silt. Such a measurement can be made, for example, by means of mass spectrometry with inductive coupling plasma (ICP analysis).
    The organic material added in step a) can be, for example, manure, peat, sawdust, bark, ice, digestate, digestate or compost. The organic material may also be a combination of at least two of these. According to one embodiment, at least two of the above-mentioned organic materials are premixed before being added in step a).
    The amount of organic material added in step a) is preferably such that the dry weight ratio of added organic material to sulphide or other sulphide silt in the starting composition is in the range of 1: 100 to 30: 100. It is preferred that the dry weight ratio is in the range of 2: 100 to 20: 100. Most preferred is a dry weight ratio in the range of 2: 100 to 15: 100. In one embodiment, the dry weight ratio is in the range of 5: 100 to 15: 100. In another embodiment, the dry weight ratio is in the range of 2: 100 to 100 μl.
    The method of the present invention further comprises the step of c) storing the mixed composition in the presence of oxygen, for example oxygen in air. In contrast to previously known technology for handling sulphide clays and sulphide silt, an oxygen-containing environment (eg the presence of air) is not undesirable. On the contrary, access to oxygen is necessary for the method to work.
    Preferably the storage takes place until the mixed composition has reached a pH value according to ISO 103902005 of 5-8, preferably 6-8. Most preferred is a pH of 6-7. During storage, the pH can be measured once or twice. The re-measurement (s) show that the pH remains too low or approaches the desired range (eg pH 6-7) too slowly, extra mixing can be performed. As an alternative or complement to mixing, additional lime can be added in such a case.
    How long the storage time is needed depends, among other things, on how efficient the mixture in step b) has been. In most cases, however, at least 2 weeks of storage time is required. Preferably, the shelf life is at least 4 weeks, such as at least 6 weeks, such as at least 8 weeks, such as at least 10 weeks, such as at least 12 weeks, such as 3-12 months, such as 3-8 months.
    The organic material is advantageously added only in the preparation of the final product, and the amount and type of organic material can then be adapted to the desired quality of the topsoil to be produced. This embodiment is suitable when the demand for topsoil is less, and the storage of the mixture of sulphides or sulphide silt , lime and rock or soil material become long-lasting, eg over the winter or longer. A later addition of the organic material makes it possible to optimize the consistency and nutritional value of the final product. In cases where the sulphide clay or sulphide silt itself contains organic material, the term "addition of organic material" refers to the additional addition of organic material in addition to that already contained in the sulphide clay or sulphide silt.
    The mixed composition from step b) can be laid in stacks, piles or strands before storage according to step c). The mixed composition from step b) can also be spread evenly on the ground. In order to avoid the formation of significant oxygen-free zones in the mixed composition, it is stored according to an embodiment in such a way that the distance to the nearest surface to air is nowhere in the stored mass more than 2 meters. According to one embodiment, this distance is not more than 1.5 meters. At least some of the deposition takes place preferably outdoors. As large quantities of material are often involved, indoor storage is unnecessarily expensive. In addition, the outdoor environment is advantageous due to the large supply of air and thus oxygen. According to one embodiment, the mixed composition is stored outdoors for at least 50%, such as at least 75%, of the time that step c) is in progress.
    The outdoor stored mixed composition is preferably protected from rain. Rain protection can be obtained, for example, by covering the masses stored outdoors, for example with tarpaulins.
    An alternative to rain protection may be to store the mixed composition outdoors in such a way that the leachate that can be formed during rain can be collected. EXAMPLES The inventors have carried out pilot experiments where naturally occurring sulphides or sulphide silt have been collected, and mixed with lime, rock or soil material and organic material. according to the present invention. The results show that the samples have stabilized. Compared with untreated sulphide clay or sulphide silt, the leaching of metals can be significantly reduced. Methods The leaching test was carried out by MRM Konsult AB according to a method described in principle in Advice and recommendations for handling sulphide soils (Pousette 2007). The leaching test was performed in two parts. On the one hand, an anaerobic leaching step was performed on fresh sample material to assess in-phone conditions, and on the other hand, aerobic leaching was performed in fl your steps (usually 10 steps). At each leach step the pH and conductivity were measured and between the leach steps the samples were dried in an oven at 10 ° C.
    Sulphide soils that are laid aerobically above the groundwater surface will be subjected to pre-drying, causing drying cracks. During precipitation, water will flow down into the cracks and drain from the soil. To some extent, commercial precipitation must be infiltrated into the underlying material or taken up by the dehydrated soil. The current leaching experiment was designed to mimic this natural process and to assess the soil's acidification potential and acidification effect.
    In addition to the leaching, the water ratio and loss of annealing of the samples were also determined, the samples were assessed visually and a dried partial sample was sent to an accredited laboratory for analysis of iron and sulfur content.
    Lime was added to 3 samples, of which one sample, designated A1, is the same soil as the reference. The lime was added in the form of magnesium carbonate obtained in the form of ordinary liming agent (Granngården, Luleå). The lime addition was calculated based on the sulfur content of the samples and for the current samples was between 659 and 673 grams of lime per 25 kg TS. In order to be able to use even numbers and compensate for heterogeneity, lime addition was rounded off to 1 kg lime / 25 kg TS.
    Result The annealing loss was approx. 3.4% for the reference sample, and between 2.9 - 3.9 for the tested samples A1, A2, A3.
    Initial Fe / S ratio and pH were measured before the leaching experiments. When anaerobalking sulphide soils that are not affected by oxygen, the pH value is normally between 6.5 and just over 8. The current tests showed pH values between 7.9 - 8.6, which indicates that the acidification process was counteracted by the lime addition.
    The samples were then subjected to 10 aerobic leaching steps. In normal cases, the pH value drops markedly with each leaching step, usually from a pH value of 7-8. The pH values in the untreated sample fall rapidly after the first anaerobic leaching step and fall steadily throughout the leaching process, while the pH in the samples treated according to the invention (addition of lime) drops slightly in the first leaching step, but 11 then returns to the range pH 6 - 7 and kept stable for 10 lak steps. See fi g.2 and 3.
    The results clearly show the stabilizing effect of a lime additive according to an embodiment of the invention.
    权利要求:
    Claims (13)
    [1]
    A method of making topsoil from sulphides or sulphide silt, comprising the steps of: a) adding lime and rock or soil material to a sulphide clay or sulphide silt so as to obtain a starting composition, the average grain size of the rock or soil material being greater than for said sulphides or sulphide silt , b) mixing the starting composition so that a mixed composition is maintained, c) storing the mixed composition in the presence of oxygen until it has a pH value according to ISO 10390: 2005 of 5 - 8, such as 6 - 8, such as 6 - 7, and d ) adding organic material to the stored composition from step c) to produce topsoil with the desired composition.
    [2]
    A method according to claim 1, wherein lime is added in such an amount that the weight ratio of added lime to sulfur in the sulphide clay or sulphide silt is at least 2: 1, such as at least 3: 1, such as at least 3.5: 1, such as at least 4: 1.
    [3]
    A method according to claim 1, wherein lime is added in such an amount that the weight ratio of added lime to sulfur in the sulphide clay or sulphide silt is in the range 2: 1 to 10: 1, such as 3: 1 to 8: 1, such as 3.5: 1 to 8 : 1.
    [4]
    A method according to any one of the preceding claims, wherein step a) is preceded by the step of measuring the sulfur content of the sulphide clay or sulphide silt.
    [5]
    A method according to any one of the preceding claims, wherein the mixed composition in step c) is stored for at least 2 weeks, such as at least 4 weeks, such as at least 6 weeks, such as at least 8 weeks, such as at least 10 weeks, such as at least 12 weeks, such as at least 3 weeks. to 12 months, such as at least 3 to 8 months.
    [6]
    A method according to any one of the preceding claims, wherein the mixed composition is laid in stacks, piles or strands prior to storage according to step c). 13
    [7]
    A method according to any one of the preceding claims, wherein the mixed composition is stored outdoors for at least a portion of the time that step c) is in progress, such as at least 50% of the time that step c) is in progress.
    [8]
    Method according to one of the preceding claims, wherein the organic substance is manure, peat, sawdust, bark, ice, digestate, digestate, compost or a combination of at least two of these.
    [9]
    A method according to any one of the preceding claims, wherein organic material is added in such an amount that the dry weight ratio of added organic material to sulphide or sulphide silt in the starting composition is in the range 1: 100 to 30: 100, such as 2: 100 to 20: 100, such as 2: 100 to 15: 100, such as 5: 100 to 15: 100.
    [10]
    A method according to any one of the preceding claims, wherein the coarse-grained rock or soil material is added in such an amount that the dry weight ratio of added coarse-grained rock or soil material to sulphides or sulphide silt in the starting composition is in the range 1: 4 to 2: 1, such as 1: 3 to 1.5: 1, such as 1: 2 to 1.5: 1, such as 1.5: 1 to 1: 1.5.
    [11]
    A method according to any one of the preceding claims, wherein the coarse-grained rock or soil material comprises intermediate sand, coarse sand and / or finger gravel.
    [12]
    A method according to any one of the preceding claims, wherein additional lime is added during step c).
    [13]
    A method of making soil from sulphide or sulphide silt, comprising mixing lime, rock or soil material, and organic material into a sulphide clay or sulphide silt, wherein the average grain size of the rock or soil material is greater than that of said sulphides or sulphide silt; and storing in the presence of oxygen until the mixture has a pH value according to ISO 103902005 of 5 - 8, such as 6 - 8, such as 6 - 7 »wherein the main part of the organic material is added after storage when the mixture of suliiderla or sulfisilt, lime and rock or soil material reached a pH value according to ISO 103902005 in the interval 5 - 8.
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    SE541545C2|2019-10-29|
    引用文献:
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    FI20165455A|FI127356B|2015-06-02|2016-06-01|A process for preparing a food soil from sulfuric clay or sulfide grit|
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