Composition for purifying flue gas

Abstract

The present invention relates to a composition for purifying flue gases comprising from 1% to 99% by weight of a powder of a sodium carbonate salt and from 1% to 99% by weight of a powder of an absorbent material wherein the specific pore volume of the powder of the absorbent material is equal to or greater than 0.1 cm3 / g. The invention also relates to a method for purifying dry flue gas and to the use of an absorbent material for improving the flowability and / or storability and / or HF absorbency of sodium carbonate salts.

Description

[0001] This application is a divisional application of application number 2016800775604, filed on December 27, 2016, entitled "Composition for Purifying Flue Gas". Technical Field

[0002] This invention relates to compositions for purifying dry flue gas, methods for manufacturing said compositions, and uses of said compositions for purifying dry flue gas. The invention also relates to methods for purifying dry flue gas and the use of absorbent materials for improving the flowability and / or storage properties and / or HF absorbency of sodium carbonate. Background Technology

[0003] Flue gas is generated in many industrial processes. For example, the combustion of fossil fuels, such as in coal-fired power plants, produces large amounts of flue gas. Waste incineration also generates significant amounts of flue gas.

[0004] Flue gas typically contains harmful or even toxic pollutants, such as sulfur oxides, like sulfur dioxide (SO2) or sulfur trioxide (SO3), and / or hydrogen halides, like hydrogen fluoride (HF) and / or hydrogen chloride (HCl).

[0005] Attempts have been made to reduce the levels of pollutants in the air. In particular, processes have been designed to purify flue gas to reduce, for example, the amount of pollutants emitted from waste incineration plants and power plants that incinerate fossil fuels. These processes typically involve contacting the flue gas with an absorbent (also known as an adsorbent).

[0006] Different processes have been designed for flue gas purification, also known as flue gas scrubbing. In wet scrubbing, an alkaline absorbent (such as limestone or lime-based materials) typically comes into contact with the flue gas as a slurry in water. Disadvantages of wet scrubbing include equipment corrosion and the need to treat or reuse wastewater.

[0007] In dry scrubbing (also known as dry flue gas purification or dry absorbent injection), the absorbent is typically brought into contact with the flue gas in a dry state. After absorption, the dried reaction products are usually collected downstream of a dust collection unit, typically equipped with a fabric filter or an electrostatic filter. A major advantage of dry flue gas purification is the simplicity of the equipment required to purify dry flue gas.

[0008] Typically, lime-based materials (such as slaked lime (Ca(OH)2)) or alkali metal carbonates (such as sodium bicarbonate (NaHCO3)) or sesquicarbonates (such as natural soda (Na2CO3*NaHCO3*2H2O)) are used as absorbents for purifying dry flue gas.

[0009] Some have suggested using sodium bicarbonate and quicklime to purify flue gas. JP H11-165036A describes a method for purifying flue gas by simultaneously injecting sodium bicarbonate and quicklime into the flue gas flow through two independent injection systems. However, these two independent injection systems increase the cost of the flue gas purification system.

[0010] In addition, improved absorbents, particularly improved calcium hydroxide granules, have been reported.

[0011] For example, EP 0 861 209 B1 describes calcium hydroxide particles for trapping acidic gases, having a particle size of at least 0.1 cm. 3 / g total pore volume. Calcium hydroxide granules were prepared by slaking quicklime (CaO) particles with sufficient water at a reaction rate of 30°C / min to obtain calcium hydroxide with a residual moisture content of 15% to 30% by weight, followed by drying and grinding. These granules have been reported to be more effective at capturing sulfur dioxide and hydrogen chloride compared to standard calcium hydroxide granules.

[0012] WO 2007000433 A2 describes a powdered quicklime containing up to 3.5% by weight of alkali metals and having a 25m... 2 / g or greater of a specific BET surface area and 0.1cm 3 / g total BJH pore volume. Slaked lime is prepared by slaking quicklime. Alkali metals are introduced into the slaked lime via alkali metal salts, which are advantageously added to the slaking water of the quicklime. Slaked lime has been reported to be more effective at capturing sulfur dioxide and hydrogen chloride compared to other slaked lime absorbents.

[0013] Typically, to increase the absorption rate of absorbents, they are ground into fine powders with small particle sizes. The smaller the particle size of the absorbent, the larger the surface area of ​​the particles that can react with pollutants in the flue gas. As a characteristic value of powder particle size, the so-called d0 is usually provided. 50 Value. d of powder particles 50 The value is typically determined by the particle size distribution of the powder. The theoretical aperture size of 50% by weight of the powder that passes through the sieve, determined from the particle size distribution, is usually referred to as d. 50 Value. Typically, the absorbent needs to have a dm of less than 40 μm, or even less than 20 μm. 50 value.

[0014] It is difficult to maintain low d in sodium carbonate salts (especially natural soda and sodium bicarbonate) powders. 50 .

[0015] Although d can be prepared by grinding 50Sodium carbonate powders, especially sodium bicarbonate powders, with particle sizes smaller than 40 μm or even smaller than 20 μm are preferred, but the resulting fine powders cannot be stored for extended periods. Typically, after a few days or even a day, the particles in the sodium carbonate powder, especially sodium bicarbonate powder, begin to re-aggregate, forming larger aggregates. Powders containing large aggregates are undesirable due to the reduced surface area. Therefore, sodium carbonate, especially sodium bicarbonate, is usually ground on-site immediately before use. This necessitates the use of mills for sodium carbonate, which increases the cost of flue gas purification systems, and their maintenance costs must also be considered. Therefore, powders with low d... 50 The storage of sodium carbonate salts, especially natural soda ash or sodium bicarbonate powder, is difficult.

[0016] In addition to their surface area, particles can also contain porosity, typically specified as the specific pore volume of a material. If the pores forming the porosity allow access from the outside of the particle, this usually also increases the particle's surface area. Therefore, if the material under study has a high specific pore volume, it usually also has a high specific surface area. However, this is not always the case. For example, calcined silica (sometimes also called pyrolytic silica) has a surface area of ​​50 to 600 μm. 2 / g specific surface area of ​​particulate material, wherein the particles are non-porous.

[0017] Another problem with sodium carbonate, especially sodium bicarbonate powder, is its flowability. When stored, for example, in silos, sodium carbonate powder tends to become more compact, likely due to gravity. During this process, the powder loses its flowability, making it difficult to remove from the silo. To obtain the powder, it is necessary to agitate it, for example, using compressed air to restore its flowability.

[0018] Another problem observed when grinding sodium carbonate salts, especially sodium bicarbonate, is that the ground material adheres to the grinding equipment (e.g., the walls of the mill). This adhesion effect necessitates regular mill maintenance. Some attempts to overcome this adhesion effect include adding stearic acid, calcium stearate, trimethylolpropane, or glycol specifically to the sodium bicarbonate during the grinding process. While this helps reduce the adhesion effect, these other additives increase the cost of the process.

[0019] In addition to compositions consisting primarily of one absorbent, mixtures of absorbents are also known.

[0020] WO 2007031552 A1 describes an absorbent composition for SO3-containing flue gas, comprising an additive and a sodium absorbent, such as mechanically refined natural alkali or sodium bicarbonate. The additive is selected from magnesium carbonate, calcium carbonate, magnesium hydroxide, calcium hydroxide, and mixtures thereof, and the amount of the additive in the mixture is preferably from 0.1% to 5% by weight, and most preferably from 0.5% to 2% by weight of the sodium absorbent.

[0021] DE 202 10 008U1 discloses a composition based on quicklime (CaO) for purifying flue gas. This composition may additionally contain calcium hydroxide and sodium bicarbonate. Compositions primarily containing quicklime are preferred.

[0022] US 4,859,438 discloses a method for removing harmful substances from flue gas using a mixture of dry absorbents based on hydrated oxides, hydroxides, or oxides. The dry absorbent may include sodium bicarbonate and one or more of NH4HCO, Al(OH)3, silica gel, calcium hydroxide, and salts having water of crystallization (such as CaCl2 or Al2O3). It has been reported that this composition can improve the removal of harmful substances from flue gas.

[0023] EP 1 004 345 A2 discloses a treatment agent for removing acidic components from gas. This treatment agent preferably contains at least 70% by weight of sodium bicarbonate and may contain another component, such as potassium bicarbonate, quicklime, calcium carbonate, zeolite, activated carbon, or silica or diatomaceous earth. To prevent agglomeration, the treatment agent may contain silica powder, calcined silica, silica fume, basic magnesium carbonate, calcium carbonate, or diatomaceous earth. The composition of EP 1 004 345 A2 can effectively remove acidic components from flue gas.

[0024] Examples of compositions from the prior art described above still do not mention the porosity of the absorbent and / or the beneficial effects therefrom.

[0025] Despite progress in maintaining storability, there is still a need to help maintain particle size distribution, especially the d of powders. 50 A valuable solution. Furthermore, absorbent compositions exhibiting good absorption of sulfur oxides and / or hydrogen halides are desirable. Additionally, compositions with good flowability, particularly those retaining good flowability after some storage time, are desirable. Summary of the Invention

[0026] Therefore, the object of the present invention is to provide a composition having good flowability, good storage properties, and / or good absorption of contaminants (such as sulfur oxides and / or hydrogen halides). In particular, the object of the present invention is to provide a composition having the highest possible flowability, especially good flowability after a period of storage, while simultaneously having good sulfur oxide absorption. Since compounds known to have good absorption of sulfur oxides (e.g., sodium bicarbonate) have limited flowability, especially after some storage time, the combination of good sulfur oxide absorption and the highest possible flowability is difficult to achieve.

[0027] Some or all of these objectives can be achieved by using the present invention. Specifically, some or all of these objectives can be achieved by the composition of claim 1, the method of claim 10, the composition of claim 15, the method of claim 16, the use of claim 17, and the use of claim 18.

[0028] Further embodiments are described in the dependent claims and will be discussed below.

[0029] This invention provides a composition for purifying flue gas, wherein, in each case, based on the total weight of the composition, the composition comprises:

[0030] a. 1% to 99% by weight of sodium carbonate powder; and

[0031] b. 1% to 99% by weight of absorbent material powder;

[0032] The specific pore volume of the powder of the absorbent material is equal to or greater than 0.1 cm³. 3 / g.

[0033] Unexpectedly, it was discovered that due to the unique combination of 1% to 99% by weight of sodium carbonate powder and 1% to 99% by weight of absorbent material powder, wherein the absorbent material powder has a particle size equal to or greater than 0.1 cm, 3 A specific pore volume of / g was obtained, thus yielding compositions for purifying flue gas that can be well stored and / or have good flowability and / or good absorption of contaminants (e.g., sulfur oxides and / or hydrogen halides). In particular, it was found that powders containing sodium carbonate have a specific pore volume equal to or greater than 0.1 cm³, especially compared to pure powders of alkali metal carbonates. 3 The composition of absorbent material powder at / g showed significantly improved flowability and good sulfur oxide absorption.

[0034] Without being bound by scientific theories, it seems that the high specific porosity of absorbent material powders can contribute to the storage of the composition and / or maintain good flowability by trapping moisture and / or liquid within the absorbent material particles. In this way, the surface of the particles can be kept unchanged. This can help prevent aggregation. It can also help maintain flowability.

[0035] Surprisingly, it was also found that when the above composition was used in flue gas purification, the peak concentration of hydrogen fluoride did not lead to very high consumption of the composition.

[0036] Furthermore, it has been found that the use of sodium carbonate is particularly effective in improving the sulfur oxide absorption of the resulting compositions. Compositions containing sodium carbonate have also proven to be more cost-effective than those containing other alkali metal carbonates.

[0037] The absorption rate of an absorbent (or absorbent composition) specifically describes its ability to retain pollutants, particularly sulfur oxides and / or hydrogen halides. The absorption rate can be expressed, for example, in absolute terms, as the absolute amount of pollutants absorbed by the absorbent (or absorbent composition), or in a relative manner, as the amount of pollutants absorbed by the absorbent (or absorbent composition) relative to a reference absorbent (or absorbent composition).

[0038] The flowability of loose materials, especially powders, relates to their availability from storage containers. Good flowability is generally attributed to the fact that loose materials, especially powders, readily flow out of storage containers (e.g., silos) due to gravity. In particular, for loose materials with good flowability, no further flow-promoting effects are required. Loose materials, especially powders, can generally be said to have poor flowability, for example, by forming solidified "bridges" (e.g., through droplets) between particles that impede flow out of silos. The flowability of loose materials, especially powders, can be described, for example, using the FFC value. A higher FFC value indicates better flowability.

[0039] Methods for determining FFC values ​​are known to those skilled in the art and are also described, for example, in Dietmar Schulze's article "Zur See “von Schüttgütern – Definition und Meβverfahren”, an article in the journal “Chemie Ingenieur Technik”, Volume 67, Issue 1, pp. 60-68, published by Wiley VCH in 1995, or “Powders and Bulk Solids – Behavior, Characterization, Storage and” by Dietmar Schulze, Springer-Verlag Berlin Heidelberg, 2008. In the article "Flow", for example, the FFC value can be determined by a uniaxial compression test. In a uniaxial compression test, a hollow cylinder (ideally with smooth walls) is typically filled with the loose material to be studied, particularly powder, and a stress S1, i.e., the consolidation stress, is applied in the vertical direction in the first step. The stress S1 can also be referred to as sigma 1, σ1. Subsequently, the consolidation stress S1 of the sample is released, and the hollow cylinder is removed. Then, an increased vertical compressive stress is applied to the consolidated cylindrical loose material sample, particularly the consolidated powder sample, until the cylindrical sample breaks (or collapses) at a stress Sc. The stress Sc can be referred to as the compressive strength or unconstrained yield strength, and is sometimes also called sigma c, σc. The collapse of the consolidated cylindrical sample when stress Sc is applied indicates the initial flow of the consolidated loose material, particularly the consolidated powder. The FFC value can then be determined as the ratio FFC = S1 / Sc.

[0040] The flowability of loose materials, especially powders, can also be determined using a Jenike shear tester. In this case, the test method used to determine the FFC value typically requires determining the so-called yield strength or yield trajectory diagram, from which S1 and Sc can be determined, thus obtaining the FFC value. The determination of the yield trajectory diagram is described in the aforementioned reference by Dietmar Schulze and typically requires pre-treating the sample (shearing the sample to a constant shear stress while applying an initial consolidation force), followed by measurement (shearing the sample until the maximum shear stress at which the particles begin to move relative to each other, while applying a lower consolidation force than during the pre-shear treatment). For each point on the yield strength diagram, a new sample is required, which must undergo the same pre-treating. From the resulting yield strength diagram, S1 and Sc can be determined, thus determining the FFC value.

[0041] Alternatively, a ring shear tester, such as the RST-XS type ring shear tester, can be used to generally describe and / or determine flowability. In a ring shear tester, the sample (loose material, especially powder) is typically filled into the ring shear unit of the tester. A cap is typically placed on top of the sample and secured with a crossbeam. A normal stress S is then typically applied through the cap of the shear unit. During the test, the shear unit typically rotates slowly, while the cap and crossbeam are prevented from rotating by two tie rods connected from both sides of the crossbeam. The bottom of the shear unit and the underside of the cap are typically roughened, so that the rotation of the shear unit induces shear stress, which can be determined by the force acting on the two tie rods. The test procedure is similar to the previously described procedure, but the entire yield trajectory diagram can be determined using a single sample. From the resulting yield limit diagram, S1 and Sc can be determined, thereby determining the FFC value.

[0042] According to embodiments of the present invention, the composition has a flow value of 0.2 or more, particularly 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more, or 0.8 or more, or 0.9 or more, or 1.0 or more, or 1.1 or more, or 1.2 or more, or 1.3 or more, particularly an FFC value, especially an FFC value measured using an RST-XS circumferential shear tester.

[0043] According to an embodiment of the invention, based on the total weight of the composition, the composition comprises 1% to 70% by weight, preferably 1% to 50% by weight, or 1% to 30% by weight, or 5% to 30% by weight, or 10% to 30% by weight, or 13% to 30% by weight, or 13% to 20% by weight, or 13% to 18% by weight, or 5% to 99% by weight, or 10% to 99% by weight, or 15% to 99% by weight, or 15% by weight. Sodium carbonate powder, ranging from 90% to 15% to 80% by weight, or from 15% to 75% by weight, or from 15% to 70% by weight, or from 15% to 65% by weight, or from 15% to 60% by weight, or from 15% to 50% by weight, or from 15% to 45% by weight, or from 15% to 40% by weight, or from 15% to 30% by weight, or from 15% to 25% by weight, or from 15% to 20% by weight, or from 15% to 18% by weight. Compositions containing sodium carbonate powder within these ranges have been found to have particularly good flowability, especially after a period of storage. It has also been found that sulfur dioxide absorption is improved within these ranges. Furthermore, it has been found that compositions with particularly good balance properties can be obtained if the sodium carbonate content, based on the total weight of the composition, is about 10% to 25% by weight, particularly 15% to 25% by weight.

[0044] According to another embodiment of the invention, based on the total weight of the composition, the composition comprises 30% to 99% by weight, preferably 50% to 99% by weight, or 70% to 99% by weight, or 70% to 95% by weight, or 70% to 90% by weight, or 70% to 87% by weight, or 80% to 87% by weight, or 82% to 87% by weight, or 1% to 95% by weight, or 1% to 90% by weight, or 1% to 85% by weight. Or 10% to 85% by weight, or 20% to 85% by weight, or 25% to 85% by weight, or 30% to 85% by weight, or 35% to 85% by weight, or 40% to 85% by weight, or 50% to 85% by weight, or 55% to 85% by weight, or 60% to 85% by weight, or 70% to 85% by weight, or 75% to 85% by weight, or 80% to 85% by weight, or 82% to 85% by weight of absorbent material powder. It has been found that compositions with these amounts of absorbent material have particularly good flowability. It has been found that if the content of absorbent material is about 75% to 90% by weight, particularly 75% to 85% by weight, based on the total weight of the composition, a composition with particularly good balance properties can be obtained.

[0045] Sodium carbonate powder particles can have various sizes. Very small particles are advantageous. Therefore, according to another embodiment of the invention, the particle size d of the sodium carbonate powder... 50 The particle size is less than 50 μm, particularly less than 45 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 12 μm. Particularly preferred is the particle size d of the sodium carbonate powder. 50 The particle size is less than 20 μm, more preferably less than 15 μm or less than 12 μm. Preferably, the particle size d of the sodium carbonate powder is... 97 Smaller than 180 μm, especially smaller than 170 μm, 160 μm, 150 μm, 140 μm, or 125 μm. It has been found that sodium carbonate powder with the aforementioned particle size absorbs pollutants more effectively.

[0046] To obtain an effective composition for purifying flue gas, different sodium carbonate salts can be used. Preferably, the sodium carbonate salt is selected from the group consisting of sodium bicarbonate, sodium carbonate, sodium sesquicarbonate, and mixtures thereof. Even more preferably, the sodium carbonate salt is sodium bicarbonate and / or sodium sesquicarbonate. It has been found that the absorption rate, especially the sulfur dioxide absorption rate, is very good when using the above-mentioned sodium carbonate salts.

[0047] Sodium sesquicarbonate can be used, for example, in the form of naturally occurring soda ash that can be directly mined. Therefore, mined naturally occurring soda ash, whether further refined or not, can be used. Sodium bicarbonate can be used, for example, in the form of mined soda ash and / or as a product of a chemical process. Therefore, mined soda ash, whether further refined or not, can be used.

[0048] The mined natural soda ash may contain impurities such as sodium carbonate calcium ore, dolomitic shale, quartz, illite, calcite, feldspar, and / or sodium fluoride. Based on the total weight of the natural soda ash, the mined natural soda ash may contain up to 20% by weight, preferably up to 15% by weight, more preferably up to 10% by weight, more preferably up to 5% by weight, and more preferably up to 3% by weight of the aforementioned impurities.

[0049] The compositions of the present invention may contain different materials as absorbent materials. Preferably, the absorbent material is an absorbent for sulfur oxides, particularly sulfur dioxide, and / or an absorbent for hydrogen halides, particularly hydrogen chloride and / or hydrogen fluoride.

[0050] The materials included as absorbent materials in the compositions of the present invention may advantageously be calcium-containing materials, calcium- and magnesium-containing materials, and / or magnesium-containing materials. Examples of calcium-containing materials include limestone, quicklime, and slaked lime. Examples of calcium- and magnesium-containing materials include dolomite, dolomite quicklime, and dolomite slaked lime. Examples of magnesium-containing materials include magnesium carbonate, magnesium oxide, and magnesium hydroxide.

[0051] Preferably, the absorbent material included as a powder in the composition of the present invention is selected from the group consisting of limestone, quicklime, slaked lime, dolomite, dolomite quicklime, dolomite slaked lime, magnesium carbonate, magnesium oxide, magnesium hydroxide, and mixtures thereof. More preferably, the absorbent material included as a powder in the composition of the present invention is selected from the group consisting of quicklime, slaked lime, dolomite quicklime, dolomite slaked lime, magnesium oxide, magnesium hydroxide, and mixtures thereof. Most preferably, the absorbent material included as a powder in the composition of the present invention is slaked lime.

[0052] The use of the above materials, alone or in combination, has shown particular benefit to the flowability and / or absorbency of the resulting compositions, especially HF absorbency. These beneficial effects are especially evident when hydrated lime is used as the absorbent material.

[0053] The slaked lime used according to the present invention is also called quicklime and mainly contains Ca(OH)2. Preferably, based on the weight of the slaked lime in the composition, the slaked lime of the present invention contains more than 90% by weight, more preferably more than 93% by weight, more preferably more than 95% by weight, more preferably more than 97% by weight, and more preferably more than 99% by weight of Ca(OH)2. In addition to Ca(OH)2, the slaked lime may also contain impurities, particularly impurities derived from SiO2, Al2O, Al2O3, iron oxides (e.g., Fe2O3), MgO, MnO, P2O5, K2O, CaSO4, and / or SO3. Preferably, based on the weight of the slaked lime in the composition, the slaked lime of the present invention contains less than 10% by weight, more preferably less than 7% by weight, more preferably less than 5% by weight, more preferably less than 3% by weight, and more preferably less than 1% by weight of the impurities listed above.

[0054] Similarly, calcium-containing materials (especially limestone and quicklime), calcium and magnesium-containing materials (especially dolomite, dolomite quicklime and dolomite slaked lime), and magnesium-containing materials (especially magnesium carbonate, magnesium oxide and magnesium hydroxide) may contain the aforementioned impurities in the amounts described above.

[0055] In addition to the impurities in the slaked lime mentioned above, the slaked lime of the present invention may also contain calcium-containing impurities, particularly CaO and / or CaCO3. Calcium oxide impurities in the slaked lime may originate from insufficient hydration of the quicklime raw material. Calcium carbonate impurities in the slaked lime may originate from the initial limestone from which the slaked lime of the present invention is derived, or from the partial carbonation reaction of the slaked lime with air. Based on the weight of the slaked lime in the composition, the calcium oxide content in the slaked lime of the present invention is preferably less than 5% by weight, more preferably less than 3% by weight, more preferably less than 2% by weight, and even more preferably less than 1% by weight. Based on the weight of the slaked lime in the composition, the calcium carbonate content in the slaked lime of the present invention is preferably less than 15% by weight, more preferably less than 10% by weight, more preferably less than 6% by weight, and even more preferably less than 4% by weight.

[0056] The size of the absorbent material particles in the composition, especially the d of the absorbent material. 50 The value should be very small. Preferably, the particle size d of the absorbent material is... 50 The particle size d of quicklime used as the absorbent material in the composition is less than 50 μm, more preferably less than 40 μm, or less than 30 μm, or less than 20 μm, or less than 10 μm. 50 Optimal results were obtained when the particle size was less than 50 μm, preferably less than 40 μm, or less than 30 μm, or less than 20 μm, or less than 10 μm. As an absorbent material in the composition, d is particularly preferred. 50 Quicklime with a particle size less than 10 μm. Advantageously, the particle size d of absorbent materials, especially quicklime, is favorable. 97Less than 150 μm, especially less than 140 μm, or less than 130 μm, or less than 120 μm, or less than 110 μm, or less than 100 μm, or less than 90 μm.

[0057] d of powder particles 50 Values ​​(for example) can be determined by determining the particle size distribution of the powder. The theoretical aperture size of 50% by weight of the powder that passes through a sieve, determined from the particle size distribution, is generally referred to as d. 50 Value. Therefore, the theoretical aperture size of the sieve through which 97% by weight of the powder, determined from the particle size distribution, passes is usually referred to as d. 97 The value. Different methods for determining particle size distribution are known to those skilled in the art. For example, particle size distribution can be determined by sieving experiments. It can also be determined by laser diffraction, particularly according to ISO 13320:2009. When determining the particle size distribution of a powder by laser diffraction, the powder under study can be suspended in a liquid medium, such as ethanol, and the suspension can be ultrasonically treated, for example, for 120 seconds, then paused, for example, for 120 seconds. Alternatively, the suspension can be stirred, for example, at 70 rpm. The particle size distribution can then be determined by plotting the measurement results, particularly the mass percentage of the measured particle size relative to the cumulative sum of the measured particle sizes. The value d can then be determined based on the particle size distribution. 50 value and / or d 97 Value. For determining the particle size distribution and / or d of powder by laser diffraction. 50 value and / or d 97 For this purpose, a particle size analyzer, the Helos, purchased from Sympatec, can be used, which can be used with additional Sucell dispersion equipment, for example.

[0058] It has been found that absorbent materials with a high surface area are advantageous. Specifically, materials with a surface area equal to or greater than 20 m² are found to be... 2 / g, preferably equal to or greater than 30m 2 / g, or equal to or greater than 40m 2 / g, or equal to or greater than 45m 2 Compositions of absorbent materials with a surface area of ​​ / g are particularly effective in flue gas purification. When used as the absorbent material in the composition, a surface area equal to or greater than 20m² is preferred. 2 / g, preferably equal to or greater than 30m 2 / g, or equal to or greater than 40m 2 / g, or equal to or greater than 45m 2 When the concentration of quicklime is / g, it can achieve particularly good results in flue gas purification.

[0059] The surface area of ​​materials described herein, particularly the surface area of ​​absorbent materials, specifically refers to the specific surface area, and more specifically, the BET (Brunauer, Emmett, Teller) specific surface area. Methods for determining the specific surface area of ​​materials are known to those skilled in the art. For example, according to the BET multi-point method, the specific surface area can be determined by measuring the nitrogen absorption of a preferably dry and evacuated sample at 77 K. For this purpose, for example, an apparatus of the Micromeritics ASAP 2010 type can be used. In particular, the BET specific surface area can be determined according to DIN ISO 9277, and especially according to ISO 9277:2014-01, particularly using static volume determination methods and, in particular, multi-point analysis methods.

[0060] The absorbent material preferably has a high specific pore volume. This is particularly useful for obtaining a composition with good sulfur oxide absorption and / or good flowability. Additionally, it is beneficial to the absorbency of the composition. Therefore, the composition preferably contains an absorbent material with a specific pore volume equal to or greater than 0.11 cm³. 3 / g or equal to or greater than 0.12cm 3 / g or equal to or greater than 0.13cm 3 / g or equal to or greater than 0.14cm 3 / g or equal to or greater than 0.15cm 3 / g or equal to or greater than 0.16cm 3 / g or equal to or greater than 0.17cm 3 / g or equal to or greater than 0.18cm 3 / g or equal to or greater than 0.19cm 3 / g or equal to or greater than 0.2cm 3 / g. When used as an absorbent material in a composition, the best results are obtained with slaked lime having a specific pore volume equal to or greater than 0.11 cm³. 3 / g or equal to or greater than 0.12cm 3 / g or equal to or greater than 0.13cm 3 / g or equal to or greater than 0.14cm 3 / g or equal to or greater than 0.15cm 3 / g or equal to or greater than 0.16cm 3 / g or equal to or greater than 0.17cm 3 / g or equal to or greater than 0.18cm 3 / g or equal to or greater than 0.19cm 3 / g or equal to or greater than 0.2cm 3 / g. It has been found that compositions containing absorbent materials with high pore volumes, particularly those with pore volumes as described above, exhibit improved properties, especially regarding their flowability values, and more specifically, their FFC values.

[0061] The specific pore volume described herein specifically refers to the total specific pore volume of pores with a preferred diameter of less than 100 nm, as determined by BJH (Barrett, Joyner, Halenda), i.e., assuming a cylindrical pore geometry. Advantageously, in the specific pore volume of absorbent materials, particularly in the specific pore volume determined according to BJH, the portion of the pore volume with a diameter of 10 to 40 nm, as determined by BJH, can account for more than 50% by volume, preferably more than 55% by volume, more preferably more than 60% by volume. Methods for determining the specific pore volume of a material are known to those skilled in the art. For example, the specific pore volume can be determined by nitrogen desorption measurements on a preferably dry and evacuated sample at 77 K. Data obtained in this way can preferably be analyzed according to the BJH method, i.e., assuming a cylindrical pore geometry. For this purpose, for example, an apparatus of the Micromeritics ASAP 2010 type can be used. Specifically, the specific pore volume determined according to BJH can be determined according to DIN 66134, particularly according to DIN 66134:1998-02, especially using a volumetric method.

[0062] Methods for manufacturing the quicklime that can be used in this invention are known to those skilled in the art. For example, WO97 / 14650A1 describes a method for manufacturing quicklime that can be used in this invention.

[0063] In another embodiment of the invention, the composition contains up to 30% by weight of clay and / or activated carbon and / or zeolite, based on the total weight of the composition. This is particularly helpful in obtaining compositions effective in flue gas purification, especially flue gas that also contains heavy metals and / or organic pollutants (such as dioxins).

[0064] In addition to the composition, the present invention also provides a method for manufacturing a composition for purifying flue gas.

[0065] The method for manufacturing the composition of the present invention for purifying flue gas essentially comprises the following steps:

[0066] a. A composition, in each case based on the total weight, comprising:

[0067] -1% to 99% by weight of sodium carbonate powder; and

[0068] -1% by weight to 99% by weight of absorbent material powder; and

[0069] b. Applying mechanical energy and / or thermal energy to the composition;

[0070] The specific pore volume of the powder of the absorbent material is equal to or greater than 0.1 cm³. 3 / g.

[0071] These steps can be performed in any desired order. Preferably, they are performed in the order shown above.

[0072] According to one embodiment of the manufacturing method of the present invention, based on the total weight of the composition, the composition in step a comprises 1% to 70% by weight, preferably 1% to 50% by weight, or 1% to 30% by weight, or 5% to 30% by weight, or 10% to 30% by weight, or 13% to 30% by weight, or 13% to 20% by weight, or 13% to 18% by weight, or 5% to 99% by weight, or 10% to 99% by weight, or 15% to 99% by weight. Powder of sodium carbonate salts in the range of 15% to 90% by weight, 15% to 80% by weight, 15% to 75% by weight, 15% to 70% by weight, 15% to 65% by weight, 15% to 60% by weight, 15% to 50% by weight, 15% to 45% by weight, 15% to 40% by weight, 15% to 30% by weight, 15% to 25% by weight, 15% to 20% by weight, or 15% to 18% by weight.

[0073] According to another embodiment of the manufacturing method of the present invention, based on the total weight of the composition, the composition in step a comprises 30% to 99% by weight, preferably 50% to 99% by weight, or 70% to 99% by weight, or 70% to 95% by weight, or 70% to 90% by weight, or 70% to 87% by weight, or 80% to 87% by weight, or 82% to 87% by weight, or 1% to 95% by weight, or 1% to 90% by weight, or 1% to 85% by weight. Powder of absorbent material in the range of 10% to 85% by weight, 20% to 85% by weight, 25% to 85% by weight, 30% to 85% by weight, 35% to 85% by weight, 40% to 85% by weight, 50% to 85% by weight, 55% to 85% by weight, 60% to 85% by weight, 70% to 85% by weight, 75% to 85% by weight, 80% to 85% by weight, or 82% to 85% by weight.

[0074] For the sodium carbonate salt and / or absorbent material manufactured according to the method of the present invention, the above-described provisions concerning the sodium carbonate salt and / or the absorbent material shall apply respectively. In particular, the provisions described above regarding the type and / or particle size of the material used for the sodium carbonate salt, and / or regarding the type, particle size, surface area, and / or pore volume of the absorbent material used, shall apply. Furthermore, the provisions regarding the flowability values ​​of the above-described compositions, particularly the FFC value, shall apply.

[0075] According to one embodiment of the manufacturing method of the present invention, thermal and / or mechanical energy is applied to the powder of sodium carbonate and / or the powder of the absorbent material. This provides greater flexibility in preparing the compositions according to the present invention.

[0076] For example, heat energy can be applied by heating the powder and / or composition, such as by heating (e.g., in an oven) or by irradiating the powder and / or composition with a suitable radiation source (e.g., a radiation heater).

[0077] Mechanical energy can be applied to powders and / or compositions in various forms. For example, mechanical energy can be applied by crushing, grinding, and / or milling. Suitable apparatus, such as ball mills, jet mills, roller mills, pin mills, or roller mills, can be advantageously used for this purpose. However, mechanical energy can also be applied to powders and / or compositions by mixing them using a mixer. Suitable mixers can include plow mixers, rotor mixers, paddle mixers, screw mixers, jet mixers, and / or spiral mixers. The application of mechanical energy can also involve several steps, such as a primary crushing, grinding, and / or milling step followed by a secondary mixing step.

[0078] In another embodiment of the manufacturing method according to the invention, step b includes a mixing and / or grinding step. This minimizes the adhesion of the sodium carbonate salt to the grinding equipment. Furthermore, a very homogeneous composition can be obtained.

[0079] The manufacturing method according to the invention achieves optimal results when step b includes a grinding step in which the composition is ground to a particle size d. 50 The particle size is equal to or less than 50 μm, particularly less than 45 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 12 μm. Advantageously, the composition is ground to a particle size d. 97 Smaller than 180 μm, particularly smaller than 170 μm, 160 μm, 150 μm, 140 μm, or 125 μm. This allows for the direct provision of readily available compositions that can be stored. It may also help reduce abrasive adhesion in grinding equipment.

[0080] In addition, the present invention also provides a method for purifying flue gas. In the method for purifying flue gas of the present invention, the flue gas is brought into contact with the composition of the present invention.

[0081] The compositions according to the invention can be used for various purposes. Ideally, the compositions according to the invention are used for the purification of flue gas, preferably for the purification of flue gas containing HF.

[0082] Furthermore, the present invention provides a specific pore volume equal to or greater than 0.1 cm³. 3 / g of absorbent material powder improves particle size d 50 Uses of powders containing sodium carbonate salts with a particle size less than 50 μm, particularly less than 45 or less than 40 μm, for their flowability (especially after a period of storage), storage properties, and / or HF absorbability. Preferably, the sodium carbonate salt is sodium bicarbonate and / or sodium sesquicarbonate.

[0083] According to embodiments of the use of the absorbent material powder of the present invention, the amount of absorbent material powder used, based on the total weight of the composition, is from 1 wt% to 99 wt%, particularly 30 wt% to 99 wt%, preferably 50 wt% to 99 wt%, or 70 wt% to 99 wt%, or 70 wt% to 95 wt%, or 70 wt% to 90 wt%, or 70 wt% to 87 wt%, or 80 wt% to 87 wt%, or 82 wt% to 87 wt%, or 1 wt% to 95 wt%, or 1 wt%. Up to 90% by weight or 1% by weight to 85% by weight or 10% by weight to 85% by weight or 20% by weight to 85% by weight or 25% by weight to 85% by weight or 30% by weight to 85% by weight or 35% by weight to 85% by weight or 40% by weight to 85% by weight or 50% by weight to 85% by weight or 55% by weight to 85% by weight or 60% by weight to 85% by weight or 70% by weight to 85% by weight or 75% by weight to 85% by weight or 80% by weight to 85% by weight or 82% by weight to 85% by weight.

[0084] For the use of the absorbent material powder of the present invention as an absorbent material, the above-mentioned provisions regarding absorbent materials shall apply. Specifically, the provisions regarding the type of material used in the absorbent material, the particle size, surface area, and / or pore volume of the absorbent material shall apply. Attached Figure Description

[0085] Figure 1 The relationship between relative SO2 absorption rate % (so-called SO2 emission reduction rate) and the proportion of ground sodium bicarbonate in different absorbent compositions with different contents of sodium bicarbonate and quicklime is shown.

[0086] Figure 2The dependence of the FFC values ​​of fresh samples and 18-hour old samples of the absorbent composition on different ratios of sodium bicarbonate and quicklime is shown. Detailed Implementation

[0087] In the following description, the invention will be further explained by means of illustrative embodiments only, and not in any way construed as limiting.

[0088] Materials used

[0089] Sodium bicarbonate, NaHCO3 (Bicarb, Solvay); slaked lime, Ca(OH)2 (Sorbacal SP, Lhoist). Sorbacal SP has approximately 40m 2 The specific surface area of ​​BET per g is approximately 0.2 cm². 3 / g BJH specific pore volume and approximately 6μm particle size d 50 .

[0090] Example 1: Preparation of a composition for purifying flue gas

[0091] Sodium bicarbonate was ground into d using a needle mill. 50 The powder with a value of 28.9 μm, this d 50 The values ​​were determined using a Helos particle size analyzer from Sympatec in an ethanol suspension via laser scattering. The particle size analyzer, equipped with a Sucell device, subjected the sample to 120 seconds of ultrasonic treatment followed by a 120-second pause, while the suspension was stirred at 70 rpm. Subsequently, ground sodium bicarbonate was uniformly mixed with slaked lime in the proportions shown in Table 1 to obtain the composition for purifying flue gas. The powder was mixed using a rotor mixer.

[0092] Table 1: Proportions of the Composition Used for Purifying Flue Gas

[0093]

[0094] Example 2: Determination of SO2 absorption rate.

[0095] The main description is found on pages 10-12 of WO 2007 / 000433 A2. Figure 2 The SO2 absorption rates of compositions 3, 4, and 5 were determined in a flue gas treatment test apparatus. The compositions were injected in a co-current manner to purify model flue gas with the following gas conditions:

[0096] Temperature 220℃

[0097] SO2 inlet concentration 1500 mg / Nm 3 ,

[0098] H2O content 10%

[0099] CO2 concentration 9%,

[0100] The average stoichiometry of the absorbent composition relative to SO2 (expressed relative to the inlet) is 2.5.

[0101] The results of the SO2 absorption test are summarized in Table 2, and are compared with... Figure 1 The results for hydrated lime, used as a comparative example, are shown together.

[0102] Table 2:

[0103]

[0104] No blockage or abnormal clogging of the feeding equipment was observed during the experiment. Therefore, the feeding equipment was unaffected by the presence of ground sodium bicarbonate. This may indicate that quicklime has a beneficial effect on the ground sodium bicarbonate.

[0105] Furthermore, compositions 3, 4, and 5 exhibit significantly higher SO2 absorption rates than hydrated lime.

[0106] Example 3: Flowability of the composition

[0107] For compositions 1 to 5 and hydrated lime as a comparative example, their flowability was studied by determining their FFC values ​​using an RST-XS ring shear tester. The results showed... Figure 2 In this study, rhombuses were used as the FFC values ​​for samples of freshly prepared compositions, while squares were used as the FFC values ​​for samples measured 18 hours after composition preparation.

[0108] from Figure 2It can be seen that the mixture of quicklime and sodium bicarbonate powder has a beneficial effect on flowability after a period of storage. For freshly prepared compositions, the FFC value of compositions with low quicklime content is higher than that of compositions with high quicklime content. However, after 18 hours, the FFC value of compositions with low quicklime content is lower than that of compositions with high quicklime content. In particular, for compositions containing more than 70 wt% quicklime, the FFC value remains above 1 even after 18 hours. Furthermore, for compositions 4 and 5 containing 50 wt% and 25 wt% quicklime respectively, the reduction in FFC value is greater than that of compositions 1 to 3 containing 95 wt%, 90 wt%, and 75 wt% quicklime respectively. This indicates that the decrease in flowability over time depends on the quicklime:sodium bicarbonate ratio. If the sodium bicarbonate content is about 10 wt% to 25 wt%, especially about 15 wt% to 25 wt%, the FFC value is about 1 or greater, and improved sulfur dioxide absorption is achieved, resulting in a particularly well-balanced performance characteristic. As mentioned earlier, a higher FFC value indicates better liquidity.

[0109] Importantly, it was also observed that compositions containing more than 25% by weight of quicklime could be stored, at least temporarily, without exhibiting the poor handling properties of pure ground sodium bicarbonate.

Claims

1. A composition for purifying flue gas, wherein, in each case, based on the total weight of the composition, the composition comprises: a. 1% to 99% by weight of sodium carbonate powder; and b. 1% to 99% by weight of absorbent material powder; The specific pore volume of the powder of the absorbent material is equal to or greater than 0.1 cm³. 3 / g.

2. The composition of claim 1, wherein, based on the total weight of the composition, the composition comprises 1% to 70% by weight, particularly 1% to 50% by weight, or 1% to 30% by weight, or 5% to 30% by weight, or 10% to 30% by weight, or 13% to 30% by weight, or 13% to 20% by weight, or 13% to 18% by weight, or 5% to 99% by weight, or 10% to 99% by weight, or 15% to 99% by weight. The sodium carbonate salt of the above amount % or 15 wt% to 90 wt% or 15 wt% to 80 wt% or 15 wt% to 75 wt% or 15 wt% to 70 wt% or 15 wt% to 65 wt% or 15 wt% to 60 wt% or 15 wt% to 50 wt% or 15 wt% to 45 wt% or 15 wt% to 40 wt% or 15 wt% to 30 wt% or 15 wt% to 25 wt% or 15 wt% to 20 wt% or 15 wt% to 18 wt% The powder; and / or wherein, based on the total weight of the composition, the composition comprises 30% to 99% by weight, particularly 50% to 99% by weight, or 70% to 99% by weight, or 70% to 95% by weight, or 70% to 90% by weight, or 70% to 87% by weight, or 80% to 87% by weight, or 82% to 87% by weight, or 1% to 95% by weight, or 1% to 90% by weight, or 1% to 85% by weight, or 10% by weight. The powder of the absorbent material in the range of % to 85% by weight, or 20% to 85% by weight, or 25% to 85% by weight, or 30% to 85% by weight, or 35% to 85% by weight, or 40% to 85% by weight, or 50% to 85% by weight, or 55% to 85% by weight, or 60% to 85% by weight, or 70% to 85% by weight, or 75% to 85% by weight, or 80% to 85% by weight, or 82% to 85% by weight.

3. The composition according to claim 1 or 2, wherein the particle size d of the sodium carbonate powder is... 50 Less than 50 μm, particularly less than 45 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 12 μm; and / or the particle size d of the powder of said sodium carbonate salt. 97 Less than 180 μm, especially less than 170 μm, less than 160 μm, less than 150 μm, less than 140 μm, or less than 125 μm.

4. The composition according to any one of the preceding claims, wherein the sodium carbonate salt is selected from the group consisting of sodium bicarbonate, sodium carbonate, sodium sesquicarbonate and mixtures thereof.

5. The composition according to any one of the preceding claims, wherein the sodium carbonate salt is sodium bicarbonate and / or sodium sesquicarbonate.

6. The composition according to any one of the preceding claims, wherein the absorbent material is selected from the group consisting of limestone, quicklime, hydrated lime, dolomite, dolomite quicklime, dolomite hydrated lime, magnesium carbonate, magnesium oxide, magnesium hydroxide, and mixtures thereof.

7. The composition according to any one of the preceding claims, wherein the absorbent material is slaked lime.

8. The composition according to any one of the preceding claims, wherein the absorbent material, in particular the quicklime, has a particle size d. 50 Less than 50 μm, especially less than 40 μm, or less than 30 μm, or less than 20 μm, or less than 10 μm; and / or the particle size d of said absorbent material, especially said quicklime. 97 Less than 150 μm, particularly less than 140 μm, or less than 130 μm, or less than 120 μm, or less than 110 μm, or less than 100 μm, or less than 90 μm; and / or the surface area of ​​said absorbent material, particularly said quicklime, is equal to or greater than 20 m². 2 / g, especially equal to or greater than 30mg 2 / g, or equal to or greater than 40m 2 / g, or equal to or greater than 45m 2 / g; and / or the specific pore volume of said absorbent material, particularly said quicklime, is equal to or greater than 0.11 cm³. 3 / g or equal to or greater than 0.12cm 3 / g or equal to or greater than 0.13cm 3 / g or equal to or greater than 0.14cm 3 / g or equal to or greater than 0.15cm 3 / g or equal to or greater than 0.16cm 3 / g or equal to or greater than 0.17cm 3 / g or equal to or greater than 0.18cm 3 / g or equal to or greater than 0.19cm 3 / g or equal to or greater than 0.2cm 3 / g.

9. The composition according to any one of the preceding claims, wherein the composition contains up to 30% by weight of clay and / or activated carbon and / or zeolite based on the total weight of the composition.

10. The composition according to any one of the preceding claims, wherein the composition has a flow value of 0.2 or more, particularly 0.3 or more, or 0.4 or more, or 0.5 or more, or 0.6 or more, or 0.7 or more, or 0.8 or more, or 0.9 or more, or 1.0 or more, or 1.1 or more, or 1.2 or more, or 1.3 or more, particularly an FFC value, particularly an FFC value measured using an RST-XS circumferential shear tester.

11. A method for manufacturing the composition for purifying flue gas according to claims 1 to 10, the method comprising: a. A composition is provided, in each case based on the total weight of the composition, the composition comprising: -1% to 99% by weight of sodium carbonate powder; and -1% by weight to 99% by weight of absorbent material powder; and b. Applying mechanical energy and / or thermal energy to the composition; The specific pore volume of the powder of the absorbent material is equal to or greater than 0.1 cm³. 3 / g.

12. The method of claim 11, wherein, based on the total weight of the composition, the composition in step a comprises 1% to 70% by weight, particularly 1% to 50% by weight, or 1% to 30% by weight, or 5% to 30% by weight, or 10% to 30% by weight, or 13% to 30% by weight, or 13% to 20% by weight, or 13% to 18% by weight, or 5% to 99% by weight, or 10% to 99% by weight, or 15% by weight. Sodium carbonate of the stated amounts: up to 99 wt% or 15 wt% or 90 wt% or 15 wt% or 80 wt% or 15 wt% or 75 wt% or 15 wt% or 70 wt% or 15 wt% or 65 wt% or 15 wt% or 60 wt% or 15 wt% or 50 wt% or 15 wt% or 45 wt% or 15 wt% or 40 wt% or 15 wt% or 30 wt% or 15 wt% or 25 wt% or 15 wt% or 20 wt% or 15 wt% or 15 wt% or 18 wt% The salt powder; and / or, based on the total weight of the composition, the composition in step a comprises 30% to 99% by weight, particularly 50% to 99% by weight, or 70% to 99% by weight, or 70% to 95% by weight, or 70% to 90% by weight, or 70% to 87% by weight, or 80% to 87% by weight, or 82% to 87% by weight, or 1% to 95% by weight, or 1% to 90% by weight, or 1% to 85% by weight, or The powder of the absorbent material is 10% to 85% by weight, or 20% to 85% by weight, or 25% to 85% by weight, or 30% to 85% by weight, or 35% to 85% by weight, or 40% to 85% by weight, or 50% to 85% by weight, or 55% to 85% by weight, or 60% to 85% by weight, or 70% to 85% by weight, or 75% to 85% by weight, or 80% to 85% by weight, or 82% to 85% by weight.

13. The method according to any one of claims 11 or 12, wherein the sodium carbonate salt is as defined in any one of claims 3 to 5, and / or the powder of the absorbent material is as defined in any one of claims 6 to 8.

14. The method according to any one of claims 11 to 13, wherein thermal energy and / or mechanical energy are applied to the powder of sodium carbonate and / or the powder of absorbent material.

15. The method according to any one of claims 11 to 14, wherein step b comprises a mixing and / or grinding step, and optionally, wherein in said grinding step, the composition is ground to a particle size d. 50 The particle size is equal to or less than 50 μm, particularly less than 45 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 12 μm; and / or wherein the composition is ground to a particle size d. 97 Less than 180 μm, especially less than 170 μm, less than 160 μm, less than 150 μm, less than 140 μm, or less than 125 μm.

16. A composition for purifying flue gas that can be obtained by the method according to any one of claims 11 to 15.

17. A method for purifying flue gas, wherein the flue gas is contacted with a composition according to any one of claims 1 to 10 or 16.

18. Use of the composition according to any one of claims 1 to 10 or 16 for purifying flue gas, particularly for purifying flue gas containing HF.

19. The specific pore volume is equal to or greater than 0.1 cm³. 3 / g of absorbent material powder improves particle size d 50 Use of powders of sodium carbonate with a particle size of less than 50 μm, particularly less than 45 μm or less than 40 μm, for their flowability, and / or storage properties, and / or HF absorption properties, wherein the flowability is particularly after a period of storage.

20. The use according to claim 19, wherein, based on the total weight of the composition, the amount of the powder of the absorbent material is from 1 wt% to 99 wt%, particularly 30 wt% to 99 wt%, or 50 wt% to 99 wt%, or 70 wt% to 99 wt%, or 70 wt% to 95 wt%, or 70 wt% to 90 wt%, or 70 wt% to 87 wt%, or 80 wt% to 87 wt%, or 82 wt% to 87 wt%, or 1 wt% to 95 wt%, or 1 wt% to 90 wt%, or 1 wt% to 85 wt%, or 10 wt% to 85 wt%. % or 20 wt% to 85 wt% or 25 wt% to 85 wt% or 30 wt% to 85 wt% or 35 wt% to 85 wt% or 40 wt% to 85 wt% 50 wt% to 85 wt% or 55 wt% to 85 wt% or 60 wt% to 85 wt% or 70 wt% to 85 wt% or 75 wt% to 85 wt% or 80 wt% to 85 wt% or 82 wt% to 85 wt%; and / or the powder of said absorbent material is as defined in any one of claims 6 to 8; and / or said sodium carbonate salt is sodium bicarbonate and / or sodium sesquicarbonate.

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