WO2010015724A1 - Composition of a material having a porous structure, composition preparation method and use of composition - Google Patents

Abstract

The invention relates to the preparation of novel materials having a porous structure and containing calcium carbonate of mineral origin or originating from algae mainly formed by this salt together with bentonite-type clays. The invention also relates to the industrial use of said materials in the elimination of acid fumes and gases and as agricultural fertilisers. These materials are characterised in that they take the form of straight or curved, smooth or ribbed hollow pipe-type cylinders which can be cut in an irregular or regular manner in any shape or size and in that they have noticeable textural features.

Description

 COMPOSITION OF A MATERIAL WITH POROUS STRUCTURE, PROCEDURE TO PREPARE A COMPOSITION AND USE OF

A COMPOSITION

SECTOR OF THE TECHNIQUE

The invention relates to new materials with porous structure and their industrial use in the elimination of acid gases and vapors and their use in agriculture as soil fertilizers.

STATE OF THE TECHNIQUE

The elimination of undesirable compounds present in industrial effluents has been the subject of numerous studies and technological developments in order to avoid their emission into the atmosphere.

The sulphurous anhydride and nitrogen oxides, which are the compounds together with the ammonia that contribute most to the formation of acid rain, are generated mainly in the units that incinerate fossil fuels or their derivatives.

Among the technologies developed for the elimination of gases and acid vapors, the treatment with aqueous suspensions of carbonates, hydroxides and oxide of alkaline and alkaline earth elements or their mixtures is the process used in most desulfurization facilities.

In these processes the SO2 is absorbed in water and the acid formed must be neutralized in order to continue the absorption of _SO2. The speed at which this neutralization occurs determines the speed with which SO ₂ is absorbed in the liquid. Generally, this process uses calcium carbonate. The low solubility of this compound limits the concentration of calcium cations in the water and, thus, the neutralization rate of the absorbed SO2; consequently this reaction is the stage of control of the global process. In these processes, by wet route, it is necessary to use high liquid / solid ratios, long contact times and the possible addition of additives to maintain the pH of the system.

Despite its extensive implementation, this wet technology presents important technological problems. The undesirable fixing of solids in the walls of the tanks or tubes and the frequent clogging of the pipes and ducts are especially serious; Both undesirable phenomena are caused by the transformation of calcium sulphite into calcium sulfate (gypsum) by the action of oxygen present in the gases to be treated. Thus, the construction materials of these units are exposed to the effects of corrosion, erosion and abrasion phenomena, especially in areas of contact with the suspensions, sludge or pastes used in the process.

Other additional difficulties are the management and treatment of excess sludge and water from the process, which must comply with the regulations in force in each country for discharge.

To solve these difficulties, numerous procedures have been proposed. For example, in US patents 4,690,807, US 5,362,458 and US 6,221,325 the aqueous suspensions of solid compounds are substituted by a solution of ammonium sulfate, in which the sulphite and ammonium bisulfite formed are oxidized to sulfate and ammonium bisulfate which, by treatment with ammonia, is transformed into ammonium sulfate in two reaction stages; in US 4,035,470, copper or iron compounds are used to inhibit the oxidation of sulphite to sulfate. Most of the registered proposals improve aspects of the process although, in many cases, they increase the complexity of the system and its operational difficulty.

On the other hand, certain clays are known that have plastic properties, that is, sufficiently moist, they are deformable when a slight pressure is applied while maintaining the shape, and they become rigid when dried and vitreous when subjected to high temperatures. In general they are natural phyllosilicates composed of small particles or crystals, generally of colloidal size, which give rise to materials of great surface development with capacity for both physical adsorption and chemical interaction.

Most plastic clays can incorporate other materials in powder form as fillers. For example, Larsson B. K. et al. (J. Amer, OiI Chem. Soc. 64365-70, 1987) describe the preparation of mixtures of calcium montmorillonite with activated carbon for the elimination of benzopyrene present as an impurity in edible oils. With this same objective, in the US patent 5,218,112 a smectite is used that contains within its texture activated carbon formed by carbonization of previously adsorbed oil. Thus, Yates M. et al. (Studies in Surface Science and Catalysis, 160, pp. 233-240, 2007) study the incorporation of titanium dioxide in the structure of bentonite as a possible catalyst support.

Bentonite is a very fine grain clay of the montmorillonite type and has a chemical structure and composition that confers a high specific surface area, high cation exchange capacity, great plasticity and ease of molding. The bentonite shaped material may incorporate as a load significant amounts of different materials, including calcium carbonates or magnesium; This fact is a way of great interest for the preparation of adsorbent / reactive compounds of acid gases with geometry suitable for industrial use.

Bentonite is used in numerous products and processes (Kendall,

T., 1996 Industrial Minerals, May, pp. 25-37); Its use is known for the improvement of sandy or acidic soils whose effect could be enhanced by the incorporation into its structure of compounds that not only contain elements of interest in soil preparation but also introduce macroporosity, unlike conventional solid fertilizers. necessary to facilitate desirable biological processes, as is the case with most algae.

DESCRIPTION OF THE INVENTION

The present invention relates to new materials, with porous structure, preferably formed as hollow cylinders, their industrial use in the elimination of acid gases and vapors and their use in agriculture as soil fertilizers.

The present invention relates to a composition of adsorbent / reagent material characterized in that it includes bentonite together with carbonates of alkaline earth elements of mineral or organic origin, in this case from calcareous algae.

For the preparation of the materials object of this invention, bentonite powders and selected carbonates are mixed dry and homogeneously; subsequently, the mixture is kneaded with water in a high shear kneader. When the bentonite particles are adequately kneaded in an aqueous medium (or in any other polar solvent), a pseudoplastic mass is produced that easily incorporates the carbonate particles. The mass obtained after kneading is molded or extruded to obtain the desired shape and then preferably dried at room temperature for at least 2 hours and at 80-150 ° C for at least four hours; subsequently the material is heat treated between 300 ° C and 900 ° C for at least 2 hours in air.

When the wet mass obtained with these materials is formed in hollow cylinder structures of suitable dimensions, adsorbent materials can be obtained with important operational advantages for the purification of fluids in dynamic regime or for incorporation into the soil as a fertilizer or fertilizer potentializer of conventional fertilizers.

These hollow cylinders can be of the "macaroni" type smooth, striated, straight, curved, regular or irregular cut, of any shape and size. In its application for the elimination of acid gases and vapors, the passage of the fluid to be purified through the adsorbent material arranged in this geometric form, gives rise to a fluid dynamic that combines a turbulent regime caused by the flow that passes between the cylinders with a laminar regime that takes place in the passage of the fluid inside the hollow cylinders. This situation gives rise to a unique behavior that significantly improves the effectiveness of the adsorption phenomenon when compared to the units formed in a hive where the fluid passes through it according to a laminar regime. In its application as a fertilizer, the material offers greater contact area per unit volume than systems containing pellets or solid materials and its macroporous structure provides adequate space for a better development of desirable biological processes.

The present invention further relates to a process for preparing the compositions indicated above. According to a preferred embodiment of the process, this includes the following steps:

a) mix bentonite and calcium carbonate powders until a homogeneous powder mixture, b) kneading the homogeneous powder mixture obtained with the addition of water to obtain a wet paste, c) forming the wet paste in the form of hollow cylinders, d) drying the shaped pieces in the air and at room temperature for at least during 2 hours and between 80 and 15O ⁰ C for at least 4 hours, preferably for 24 hours. e) heat treating the parts at temperatures between 65O ⁰ C and 900 ⁰ C, preferably between 700 ⁰ C and 800 ⁰ C, for at least 2 hours, preferably for at least 4 hours.

According to this embodiment and, preferably in step a), bentonite and calcium carbonate are mixed exclusively with a proportion of bentonite between 20 and 30% by weight.

Heat treatments of the material prepared with bentonite and calcium carbonate at temperatures below 400 ⁰ C give rise to pieces that are too sensitive to abrasion and the collapse of the physical structure due to water. These limitations practically disappear when the material is treated for times greater than 2 hours at temperatures between 500 ⁰ C and 800 ⁰ C. From 600 ⁰ C, the carbonate is transformed into calcium oxide with CO2 evolution. At temperatures of 700 ⁰ C for a time not less than 2 hours, all carbonates break down.

The pieces formed and thermally stabilized at 700 ⁰ C have a high content of new macropores, mainly caused by the gaps or spaces that are caused by the evolution of carbon dioxide. Consequently, an increase in the value of the total pore volume is observed with the temperature and the treatment time; for the initial composition calcium carbonate / bentonite of 70:30, the pieces treated at 600 ° C / 2 h have a total pore volume of 0.27 ml g ^{~ 1} , for 700 ° C / 2 h the value increases to 0.76 mi g ^"1 , and for 800 ° C / 2h it goes to 0.79 mi g ^{" 1} .

The present invention also relates to the use of a composition made as described above, as an adsorbent / reagent material for the elimination of acid gases and vapors in a dynamic regime. When gases contaminated with sulfur dioxides, hydrochloric acid or hydrofluoric acid or mixtures thereof are passed through this material in the form of a hollow cylinder, the reaction of these acid gases with the calcium oxide it contains occurs, effectively forming extraordinary sulfite, sulfate, chlorides and calcium fluorides that are deposited filling the pores of the material. The saturated material, arranged in a moving bed, can easily be replaced (for example, by a pneumatic system) by the fresh material without problems of corrosion, deposits, or sludge treatment.

The calcium carbonate used may be of mineral origin or high-calcareous algae can also be used in said salt with similar yields.

Thus, when these materials are treated in stage e) at temperatures between 500 ⁰ C and 600 ⁰ C for at least 2 hours, they can be used as neutralizing or remineralizing agents for water treatment, lowering their CO ₂ content and providing the necessary carbonate and bicarbonate ions.

According to another particular preferred embodiment of the process, this includes the following steps:

a) mixing bentonite and calcareous algae powders until a homogeneous powder mixture is obtained, b) kneading the homogeneous powder mixture obtained with the addition of water to obtain a wet paste, c) form the wet paste in the form of hollow cylinders, d) dry the shaped parts in air and at room temperature for at least 2 hours and between 80 and ¹⁵ ° C at least for 4 hours, preferably for 24 hours, e) heat treating the parts at temperatures between 300 ⁰ C and 600 ⁰ C, preferably between 400 ⁰ C and 500 ⁰ C, for at least 2 hours, preferably for at least 4 hours in air.

According to this embodiment and, preferably in step a), bentonite and calcareous algae are mixed with a proportion of bentonite of 10 and 15% by weight.

The material prepared with bentonite and calcareous algae with a 10% bentonite content and treated at 500 ⁰ C for 4 hours in air has a specific surface area of 7 m ² g ^"1 and a total pore volume of 0.28 mi g ^{" 1} .

The present invention also relates to the use of a composition made as described above, as a fertilizer and acidic or sandy soil improvement material, introducing the numerous nutrient elements present in the calcareous algae and offering a hollow cylinder shape with walls. macroporous that favor in an extraordinary way the biological phenomena that take part in the growth of the plants.

In another application, the cylinders prepared in this way are used as beds (temporary covering of the soil) in poultry farms that improve the health of the installation, favor the fattening of the animals and increase the quality of the product.

The bentonite used as raw material in this invention was supplied by Tolsa SA under the name Atox, with a surface BET specific of 130 m ² g ^"1 and a particle size of 75% less than 45 μm. Thus, a natural bentonite supplied by Oil-Dry Corporation called Bentonite of Paraná with a specific BET surface of 95 m ^{2 was used} g ^"1 and a particle size of 82% less than 44 μm.

The precipitated calcium carbonate used in this invention called SOCAL P2V was supplied by the Solvay Group with a purity of 98.8%, an average particle size of 1.5 μm and a specific surface area of 7 m ² g ^"1 .

The calcareous algae was supplied by Algarea Mineragáo Industria e Comercio Ltda. (Brazil) and corresponds particularly to the species Lithothamnium spp. The average value of its weight composition is 90.9% calcium carbonate, 3% magnesium as Mg and 0.75 silica as SiO ₂ . The rest corresponds to compounds of more than 20 existing elements in small quantities. 90% of the disintegrated particles of this dry material are less than 5.2 μm in size. The porous texture of this material has an average specific surface area of 6 m ² g ^"1 with textural development centered on macroporosity (pores with a diameter of 50-10,000 nm) and absence of micropores.

EXAMPLES OF EMBODIMENT OF THE INVENTION

The following non-limiting examples further illustrate the present invention.

Example 1

As raw materials, Socal P2V calcium carbonate supplied by Solvay and Bentonite del Paraná supplied by Oil-Dry Corporation is used; both materials in powder form. 332.6 g are mixed. of bentonite, with a humidity of 7%, with 705 g. of calcium carbonate, with a humidity of 0.7%. After obtaining a homogeneous mixture, it is taken to a double sigma kneader and kneading is started by slowly adding deionized water; once the addition of water is finished, kneading is maintained for 4 hours. The mass thus obtained is formed by an extruder obtaining hollow cylinders 10 mm long, 4.5 mm outside diameter and 2.5 mm inside diameter. Shaped parts, air dried at room temperature for 24 hours and subsequently treated at 15O ⁰ C for 24 hours in air and 700 ⁰ C for 2 hours in air.

The hollow cylinders thus obtained have a specific surface area of 30 m ² g ^"1 , a negligible micropore volume, a mesopore volume of 0.08 cm ³ g ^{" 1} and a macropore volume of 0.68 cm ³ g ^"1 . The mechanical properties of the cylinders obtained are suitable for industrial use; thus, its structure proved to be perfectly stable to water or water vapor.

Example 2

The material prepared in the previous example is tested to determine its adsorption capacity in a dynamic regime. The tests are carried out at temperatures of 20-24 ⁰ C and a pressure close to atmospheric. The air to be treated contains 4% molar volume of water and 700 ppm of SO2. It operates at a spatial velocity of 2014 h ^"1 (CN.) And at a linear velocity of passage of gases through the bed of 0.2 Nrrrs ^"1; The adsorption of SO ₂ is measured to a concentration at the output of 50 ppm.

After the adsorption test, the material used increases its weight by 46% and its resistance to compression increases from 1.0 to 2.2 kg ^' cm ^"1 . Example 3

Following the procedure set forth in Example 1, hollow, fluted cylinders 10 mm long, 5 mm outside diameter and 3 mm inside diameter are prepared, using as raw materials bentonite supplied by Tolsa, SA (Spain) with the designation Atox and calcareous algae supplied by Algarea Mineragáo Industria e Comercio Ltda. (Brazil). The weight ratio bentonite / seaweed is 20:80. In this example, the thermal treatment of shaped depressions and dried cylinders is carried out at 500 ⁰ C for 4 hours in air.

The product obtained has a BET surface of 15 m ^z g ^"1 and a total pore volume of 0.20 cm ^3- g ^{" 1} of which 0.15 cm ^3- g ^"1 corresponds to the volume occupied by the macropores. The filling density of the product is 0.58 g cm ³ and its water adsorption capacity is 0.18 g of water per gram of product.

Example 4

A first product in accordance with what is described in Example 3, which is a heat treatment at temperature of 500 ⁰ C for four hours in air is prepared. Thus, a second product similar to that described in Example 3 is prepared, although the heat treatment is carried out at 400 ⁰ C for 4 hours. Finally, a third product is prepared with thermal treatment at 300 ⁰ C for 4 hours. The products are mixed in the ratio 1: 1: 1 by weight for use as fertilizer in a soybean plantation in the proportion of 300-350 Kg / Ha. obtaining an average productivity, measured in Tm / Ha. greater than 10% by weight with respect to the planting area used as a reference.

The size classification - micro, meso and macro - used in this document is the one adopted by the IUPAC "Manual of Symbols and Terminology of Physicochemical Quantities and Units "E. Butterworths. London (1972). The values of the pore volumes and specific surface area of the materials were determined by mercury intrusion and by nitrogen adsorption following the BET procedure.

Use of the new product technology (macaroni), in the preparation of the floor covering (beds), of the poultry breeding farms.

Currently, poultry producers use wood clippings

(wood shavings) for the realization of floor covering of breeding farms. The purpose of this coating use is to avoid direct contact of the birds with the ground and absorb moisture from the floor and the feces of the birds during the growth period.

The movement of the birds on the moistened sawdust during the period of growth, provides the compaction of the coating. Due to this alteration, the coating is left with a harder consistency, forcing the birds to walk with their legs extended.

Normally, the wet sawdust provides the environment suitable for the proliferation of microorganisms such as bacteria, fungi and mites that negatively interfere with the health of the birds.

The new technology developed consists of replacing the coatings made with sawdust by the use of a product with a "macaroni" format, produced by the extrusion of natural mineral products.

The use of this new technology avoids the direct contact of the birds with the ground and also provides the contact of the legs of the birds with a softer consistency floor that naturally modifies the bird movement characteristic.

Contrary to the situation described above, in which the birds walk with the legs extended, the use of the macaroni facilitates movement, since the birds use the legs, fingers and nails more evenly.

The nails of the legs develop much more since the animal has a tendency to dig in the hard soil and at this time the friction of the nails in the macaroni absorbs a very important amount of calcium carbonate and minerals, for this reason, the fingers they develop much more due to the size of the nails and the calcification of the entire structure of the animal's legs.

The use of macaroni as an embodiment of the floor covering of farms, directly provides the following benefits for birds:

1. Mineralization of nails and spikes; 2. Better calcification of the skeleton;

3. Increase in the dimensions of the nails with the consequent increase in the dimensions of the fingers, spurs and tibiae;

4. Increase in the proportion of the chest, due to the ease of movement.

5. Alteration in the consistency of the meat of the birds, generating a more tender and tasty meat; Y

6. Reduction of breeding time.

In addition, during the growth period, the birds feed on the macaroni that carries carbonates and minerals in its composition. Additionally, during the growth period, the birds tend to bite and ingest the macaroni that, due to its composition in carbonates and minerals, accelerate the activation of the stomach of the animal, reducing the ammonia content that at the same time modifies the composition of the waste and decreasing their liquid content. This complementary feeding activity will cause the significant decrease in the ammonium content that is generated in the digestion process to occur in the stomach of birds. This reduction of the ammonium content takes place due to the neutralization of the ammonium with the carbonates and minerals present in the macaroni, which favors the digestion process and modifies the composition of the feces, making them drier.

The reduction of the moisture content in the feces of the birds contributes directly to the reduction of the humidity of the farm floor.

The humidity of the farm floor is also reduced due to the absorption of this moisture by the macaroni formation structure. At the same time, thermophilic reactions that occur inside the macaroni transform the ammonia present in the environment into ammonium carbonate, which is a natural sanitation agent.

The generation of ammonium carbonate together with the reduction of moisture content in the farm floor are conditions that do not favor the growth of bacteria, fungi and mites, providing a healthier environment for the growth of birds. The properties of the materials according to the invention are mentioned: Contribution of Ca-Mineralization NH ₃ adsorbents and water Odor adsorbents Relative humidity regulators

Lifetime exceeds the materials used today. The effects on the growth and development of the species can be summarized as follows:

Increase:

Postural disposition of the birds that allows a greater development of the fingers and legs by direct contact. Bone mineralization

.Increase the absorption of nutrients by ingestion.

Developing:

.Permanent increase in mass in the legs and chest

Reinforcement of the skeleton. Reinforcement of the eggshell

.Reduction of the concentration of ammonia in the feces

.Reduction of eye and respiratory problems

.Improvement of air quality

.Improved bird appearance. Benefits:

.Increased molecular mass in less time

.Reduction of the fattening period

.Reduction of infectious diseases

.Increase in productivity. Longer bed time

.After application of the material -> agricultural fertilizer.

In this case, the paste-transformed material due to the adsorption of the droppings and footsteps of the birds has a high content of N, P, K, carbonates, trace elements and organic matter and thus becomes a nutrient contribution for soils in agriculture as fertilizer.

Claims

1. Composition of a material with porous structure characterized in that it includes bentonite together with carbonates of alkaline earth elements. 2. Composition of a material with porous structure according to claim 1, characterized in that the carbonates of alkaline earth elements can be of mineral origin or come from algae containing said carbonates. 3. Composition of a material with porous structure according to claims 1 and 2, characterized in that said composition is shaped as hollow cylinders. 4. Composition of a material with porous structure according to claims 1 to 3, characterized in that said hollow cylinders are selected from smooth cylinders of regular or irregular cut, fluted cylinders of regular or irregular cut, straight cylinders of regular or irregular cut and curved cylinders of regular or irregular cut, whose preferred dimensions are 10 mm long, 5 mm outside diameter and 3 mm inside diameter. 5. Composition according to claims 1 to 4 characterized in that it includes bentonite and calcium carbonate of mineral or organic origin, with bentonite contents of 20-30% by weight, or the derivatives obtained by treating these materials formed at temperatures equal to or greater than 65O ⁰ C and equal to and less than 900 ⁰ C for at least 2 h in air. 6. Procedure for preparing the composition according to claims 1 to 5, characterized in that it includes the following steps: a) mixing bentonite and calcium carbonate powders of mineral origin or organic until obtaining a homogeneous powder mixture, b) kneading the homogeneous powder mixture obtained with the addition of water to obtain a wet paste, c) forming the wet paste in the form of hollow cylinders, d) drying the shaped parts in air and at temperature ambient for at least 2 hours and between 80 and 15O ⁰ C for at least 4 hours, preferably for 24 hours, e) heat treat the parts at temperatures between 65O ⁰ C and 900 ⁰ C, preferably between 700 ⁰ C and 800 ⁰ C, for at least 2 hours, preferably for 4 hours, since according to the preferred embodiment of the process, the composition has a specific surface area between 15 and 30 m ^z g ^"1 and a total pore volume between 0.7 and 0, 8 7. Composition according to claims 1 and 4, characterized in that it includes bentonite and calcareous algae with bentonite contents of 10-15% by weight or the derivatives obtained by treating these shaped materials at temperatures greater than or equal to 300 ⁰ C and less than or equal to 600 ⁰ C for at least 2 hours in air. 8. Method for preparing a composition according to claims 1 to 4 and 7, characterized in that it includes the following steps: a) mixing bentonite powders and calcareous algae until a homogeneous powder mixture is obtained, b) kneading the homogeneous mixture of powders obtained with the addition of water to obtain a wet paste, c) forming the wet paste in the form of hollow cylinders, d) drying the shaped pieces in the air and at room temperature for at least 2 hours and between 80 and ¹⁵ ° C at least during 4 hours, preferably for 24 hours, e) heat treat the parts at temperatures between 300 ⁰ C and 600 ° C, preferably between 400 ⁰ C and 500 ⁰ C, for at least 2 hours, preferably for 4 hours in air, since according to the preferred embodiment of the process, the composition has a specific surface area between 7 and 15 m ^z g ^"1 and a total pore volume between 0.2 and θ, 3 m ^| -g ^{" 1} . 9. Use of a composition according to claims 1 to 6, which refer to products prepared from bentonite and calcium carbonate of mineral or organic origin, characterized in that it is used as a dynamic adsorbent material of gases and acid vapors . 10. Use of a composition according to claims 1, 2, 3, 4, 7 and 8 which refer to products prepared from bentonite and calcareous algae, characterized in that it is used as a soil fertilizer. 11. Use of a composition according to claims 1, 2, 3, 4, 7 and 8 which refer to products prepared from bentonite and calcareous algae, characterized in that it is used for the preparation of the floor covering (beds) ) of poultry breeding farms.