SE459236B - PROCEDURE FOR TRANSFER OF SOLID WASTE INCLUDING AT LEAST 30% BY WEIGHT OF CELLULOSAMATERIAL TO SOLID, INERT MATERIAL THAT IS INSULAR IN WATER - Google Patents

Description

459 EO ES &0 236 -E _. the temperature is below 100'C, to a temperature which is at least E50'C but which is below the melting temperature of the plastic materials which may be present in the original waste mass.

The moisture content of the solids is suitably regulated to a value of 27-30 percent by weight before heat treatment.

To achieve this, both the amount of powdery mass in the waste and the amount of fillers and additives that may be mixed with the mass before it is compressed can be analyzed, with water, aqueous solutions or other aqueous media, such as aqueous slurries, being added if necessary.

In order for solid bodies to be formed, the mass is also suitably compressed under a three-phase pressure between 150 and 500 degrees.

According to a particularly suitable embodiment, the mass is compressed in the form of granulated particles consisting of cylindrical bodies with a diameter between δ and 80 mm and a length between δ and 30 mm. At least before the pulverized waste mass is compressed, according to a particular embodiment, at least one additive is incorporated therein.

As additives, for example, at least one substance selected from the following can be used: monocalcium phosphate, phosphoric acid, calcium sulfate, urea, ammonium salt, an aqueous solution of ammonia, horax, sodium bicarbonate, sodium chloride, dry extract of gelatin, root or leaf starch from cassava, sodium alginate, carboxymethyl cellulose, methyl cellulose, modified methyl cellulose, polyglycol acetate, polyglycol alcohol, melamine formaldehyde resin, phenolic resin, agent for making melamine formaldehyde resin insoluble, agent for making polyglycol alcohol insoluble, coumarone resin, urea formaldehyde resin, potassium silicate, sodium silicate, wherein the substance is in powder or liquid form or in the form of an aqueous solution or dispersion, when incorporated into the powdery waste mass.

A certain amount of quicklime in powder form may also be incorporated into the mass before it is compressed, the amount corresponding, for example, to a proportion between 0.3 and 10 2 of the powdered waste mass. The purpose of incorporating quicklime is to bring about an increase in the temperature of the waste mass to a value that is optimal for the pressing process, i.e. up to a temperature of, for example, the order of magnitude of 80°C, as a result of the reaction between quicklime and water in the waste mass. The quicklime may be incorporated into the waste mass alone or in admixture with a certain amount of at least one calcium salt, such as carbonate, for example in a weight ratio Ca₄/Ca₂O₄ of between 2:1 and 1:5.

According to a particularly suitable embodiment, during the initial heating phase, the core of the solid bodies in the waste mass is heated to a temperature between E50 and 300°C, after which they are held at this temperature for a certain time, the initial heating phase being followed by an intermediate cooling phase, during which the temperature gradually drops to a value between S0 and B0°C, and a final phase, during which the temperature is held between 50 and B0°C.

The total time for the heat treatment is suitably between 80 and 80 minutes.

Likewise, the total time for the initial heating phase suitably corresponds to approximately 1/3 of the total time for the heat treatment.

According to a particularly suitable embodiment, the heat treatment is carried out by moving the granulated particles at a constant speed from a first heating zone, in which the temperature is between E50 and 300'C, to a final heating zone, in which the temperature is between 80 and B00'C, whereby the particles pass through an intermediate zone, in which there is a temperature gradient which corresponds to the temperature gradually changing in the direction of movement of the granulated particles between the temperature in the first heating zone and the final heating zone, whereby the granulated particles are introduced at the beginning of the first heating zone at the same time as quicklime in powder form or a powdery mixture of quicklime and at least one calcium salt in a solid, finely divided state.

The calcium salt is suitably calcium carbonate.

Just before the granulated particles are subjected to heat treatment, a proportion of quicklime or a mixture of quicklime and at least one calcium salt is added, which suitably corresponds to 0.3-0.5 weight percent Ca and 0.3-0.5 weight percent calcium salt.

According to a particularly suitable embodiment, the heat treatment is carried out by causing the granulated particles to pass through a rotating tunnel kiln, the axis of which is arranged in a practically horizontal position and provided with an internal helical ramp which enables the bodies to be transported at a constant speed from one end of the kiln to the other.

The materials that can be subjected to the process according to the invention can have very varying origins and compositions.

For example, this can include both household waste and waste or residual products from industry.

In view of the nature of the materials, which in practice consist of mixtures of products of varying origin, it is obvious that the composition may vary to a certain extent, the variation being more or less random. In general, however, it is particularly suitable that the average composition of the treated material lies within the following limits (expressed in weight percent): cellulosic material: 50-50 2 starchy materials (such as leaf and root starch); S-7 2 plastic materials (resins of synthetic polymers) 6-7 2 silicon-containing materials: 3-Q 2 Before the process is used, the garbage and waste collected at the collection site are subjected to sorting and screening in the usual manner, in order to separate the objects that can possibly be recycled and/or recycled, such as particularly large pieces of metal. ' The production of the waste mass in the form of a homogeneous powdery mixture that is essentially free of metallic material, particularly iron, can be carried out by grinding and mixing, which can be carried out simultaneously or separately and combined with one or more sorting processes, which are intended to separate the metal pieces, particularly pieces of iron-based material.

Hassan can, for example, be subjected to a first coarse grinding to an average coarseness of the pieces of about 50 mm, whereby the grinding is carried out before or after a magnetic separation, which is to remove iron particles and other ferromagnetic material, which separation is followed by a second grinding which is carried out, for example, by means of a rotating hammer mill, whereby the size of the particles in the mass is reduced so that it does not exceed 5-B mm.

A supplementary filler may optionally be added to the waste mass, preferably after the powdery mixture has been prepared, so that the overall composition of the mass is changed, whereby in particular the composition and properties of the end product are affected and, for example, the desired density is achieved. The addition of the supplementary filler may either be before the binder is incorporated into the ground waste mass or at the same time as this occurs. As a constituent of the supplementary inorganic filler, for example, one or more materials selected from the following can be used: potassium carbonate, gypsum, burnt gypsum, blast furnace fly ash, magnesium oxide, barium sulfate, lithopone, dolomite, clay material, coal powder.

The total proportion of material of which the supplementary filler consists is then that it constitutes ED-H0 weight percent of the total amount of mixture of waste pulp and filler.

The additive is suitably incorporated into the ground waste mass, which optionally includes supplementary fillers, in a mixing apparatus (e.g. a vertical mixing device), after which it is for a time in another mixing apparatus (e.g. a horizontal mixing device), in which the waste mass is further impregnated by the additive for, for example, a time of the order of 15-80 minutes, so that a homogeneous mixture, in which the additive completely impregnates the ground material, is produced from the ground material and the additive.

As additives, any material in the form of powder, liquid or paste can be used which can be incorporated intimately and homogeneously into the ground material and provide such properties, especially in terms of plasticity and flowability, that it will later be possible to bring the mixture into the form of solid bodies which can maintain their cohesion during the final thermochemical treatment.

As an additive, for example, a substance can be used which is prepared by heating at least one of the following substances in water at a temperature exceeding 50°C (preferably in the proportion given below in weight percent in relation to the amount of water used): monocalcium phosphate: 0.2-1.5% phosphoric acid: 0.8-1.5% calcium sulfate: 2.5-7.5% urea: 0.5-1% ammonium salt: 1.0-3.0% aqueous solution of ammonia at 30°C: 1.0-3.0% borax (e.g. the product known under the commercial name "nöbore"): 0.3-8.0% sodium bicarbonate or sodium chloride: 0.3-1.5% dry extract of gelatin (e.g. bengalatin): 1.8-3.0% root starch from cassava: 2.0-8.0 Z leaf starch from cassava; ¶.0-12.0 2 sodium alginate: 8.0-8.0 2 carboxymethylcellulose: 1.5-%.0 2 methylcellulose: 1.0-3.0 2 modified methylcellulose (e.g. the product known under the commercial name "Iglose"): 1.5-5.0 2 plasticized polyglycol acetate: 2.0-8.0 2 polyglycol alcohol: 2.5-8.0 2 urea formaldehyde resin: 0.5-3.0 2 phenol resin: 1.0-8.0 2 polyglycol alcohol s agents for making polyglycol alcohol insoluble, agents for making melamine formaldehyde resin insoluble coumarone resin silicate of potassium or sodium, etc.

As an additive, a powdery product can be used in particular, which is a mixture, in which the weight ratio is between 1:8 and 8:1, comprising a first powder of 0.3-1.2 parts by weight of potassium sulfate, 0.3-1.8 parts by weight of monopotassium phosphate, 0.5-E parts by weight of borax, 0.5-E parts by weight of urea, 0.5-3 parts by weight of gelatin, 0.1-1 parts by weight of carboxymethylcellulose, 50 parts by weight of calcium carbonate and a second powder which is prepared by drying cassava flour which has been caused to swell by heating to the boiling point in an aqueous medium comprising formaldehyde and ammonia (whereby, for example, 0.5-E parts of formaldehyde and 0.5-E parts of ammonia at &O' Baumä are used per 10-50 parts by weight of cassava flour). The amount of additive may, for example, be between 0.5 and 5 percent by weight relative to the weight of the homogeneous waste mass. The mixture of waste mass (possibly containing supplementary fillers and additives and, where applicable, quicklime or a mixture of quicklime and at least one potassium salt) may be pressed in a manner known per se depending on the shape desired for the material constituting the end product in the desired conversion. In order to produce a granulated material, for example in the form of small cylinders with a length of 5-30 mm and a diameter of 0-80 mm, an industrial-grade granulation apparatus is suitably used, which allows granulation to take place under a pressure of 150-500 bar.

The mixture of waste mass and additives and/or inorganic fillers can also be pressed into shaped pieces with a size of several centimeters, which can serve as structural elements in walls or for road paving or be in the form of plates or sheets which can, for example, serve as revetment elements for walls. The proportion of quicklime or mixture of quicklime and calcium carbonate is suitably 0.3-0.5 weight percent Ca and 0.3-0.5 weight percent calcium carbonate in relation to the solid bodies subjected to the heat treatment. The total heating time is suitably between 0 and 35 minutes, the first heating phase suitably corresponding to 1/3 of the total heating time.

According to an embodiment particularly suitable for the method, the heat treatment is carried out by moving the solid bodies to be treated at a constant speed from a first heating zone with a temperature between E50 and 300°C to a final heating zone with a temperature between 50 and 80°C, whereby they pass through an intermediate heating zone, in which there is a temperature gradient corresponding to the temperature gradually changing in the direction of movement for the solid bodies between the temperature in the first heating zone and the final heating zone, whereby the solid bodies to be subjected to the heat treatment are introduced at the beginning of the first heating zone at the same time as quicklime or a mixture of quicklime and calcium salt, for example by sprinkling the solid bodies with quicklime in powder form or the powdery mixture of quicklime and calcium salt just before the bodies is introduced into the first heating zone.

To carry out the heat treatment, a tubular rotary kiln with a shaft arranged in a substantially horizontal position is suitably used, the material to be heat treated being introduced at the end of the kiln corresponding to the first heating zone and the material having undergone the heat treatment exiting the kiln near the opposite end. The final product is in the form of inert and insoluble pieces, e.g. non-cylindrical granulated material consisting almost exclusively of inorganic material and having a limestone-like structure. This product can be used in many ways, in particular as building elements, for revetment or deposition in the building industry and engineering.

In the following, the invention is explained in more detail with the help of non-limiting examples: Example 1 Municipal waste, which essentially consists of household waste, is received directly into a receiving hopper which continuously feeds at a constant speed a primary waste grinder provided with a ballistic, 5 meter high chimney, which makes it possible to throw out the solid material objects that may be present in the waste, in particular pieces of scrap iron with a mass between 50 g and 3 kg, and an explosion-proof device (armor plate). waste When the waste comes out of the waste grinder, it passes through a screening drum which allows objects with a maximum size of 8 µm to be separated, the remainder being led to the primary receiving pocket. The waste thus separated is led onto a roller conveyor connected to a magnetic iron removal device and a magnetic block fitted at the beginning of the conveyor, so that any particles of ferromagnetic material which may have remained in the waste coming from the primary waste grinder can be withdrawn. The waste thus treated then falls back into a secondary waste grinder, where it is possible to reduce the average particle size to E-30 mm. The ground waste mass was then added to a belt mixer, in which a binder is added, which binder is prepared by mixing 10 parts by weight of cassava flour and 1.5 parts by weight of aqueous sodium hydroxide solution at 32' Baumä and 8.5 parts by weight of aqueous hydrochloric acid solution at 32' Baumä with 100 parts by weight of water, after which heating is carried out to 50'C for 15 minutes and the mixture is finally dried so that a practically dry powdery product is formed. A homogeneous, powdery mixture is thus obtained, which mixture is introduced into a rotary granulator, in which non-cylindrical granulated particles are formed by compressing the mixture under a pressure of 500 bar, the particles having a diameter of 5 mm and a length of 15 mm. The granulated particles thus obtained contain about 30 percent by weight of moisture.

Both the granular particles and a mixture of quicklime and calcium carbonate in an amount corresponding to 0.35 2 finely powdered quicklime (average grain size = 50-100 gm) and 0.35 2 technical potassium carbonate in powder form (average grain size: 00-150 gm) containing at least 00 weight percent calcium were continuously added to the entrance of a tubular rotary kiln with a diameter of 1 m and a length of 8 m, in which the rotation speed is regulated so that the passage time of the treated material in the kiln is of the order of 0 minutes.

The tubular furnace is heated by a gas burner arranged at the end through which the granulated particles and the mixture of quicklime and potassium carbonate are introduced into the furnace. The granulated particles are gradually introduced into the furnace by means of a helical screw arranged therein and exit at the end opposite to that through which they were introduced, the granulated particles being in the furnace for a total of 10 minutes. When the granulated particles are in the oven, they pass successively into a first heating zone, where they are for 15 minutes at a temperature between 200°C and 500°C, after which they are for 15 minutes in an intermediate zone, where the temperature drops almost linearly from 250°C to 500°C, after which they are finally for 10 minutes in a final heating zone, where they are kept between 80°C and 500°C.

Example Q 459 236 _ m _ Same procedure as in example 1 except that at the same time as the binder, a quantity of gypsum waste is incorporated into the ground waste mass, which quantity is such that the proportion of gypsum is 30 percent by weight in relation to the total quantity of waste and supplementary gypsum, which consists of gypsum.

Claims (15)

10 15 BO 25 30 35 Q0 459 236 _ 'I _ PRTENTKRHU A process for transferring solid waste comprising at least 30% by weight of cellulosic material to East, inert material which is insoluble in water, characterized in that the metal objects which may be present in the waste are removed, after which the waste is ground and homogenized so that a homogeneous, powdery mass is formed which is pressed in the form of a plurality of solid bodies, after which the bodies in the presence of quicklime are finally subjected to a heat treatment which comprises an initial heating phase which provides a rapid heating of the core of the bodies from an initial temperature below 100 'C to a temperature which is at least E50 ° C but which is less than the pgrolg temperature of the plastic materials which may be present in the original waste mass. E. 2. A method according to claim 1, characterized in that the moisture content in the solids is regulated to a value of 27-30% by weight before the heat treatment. Method according to claim 1 or E, except that the mass is compressed under a pressure between 150 and 900 bar. ä. 4. A method according to any one of claims 1-3, characterized in that the mass is pressed in the form of cylindrical bodies with a diameter between ä and EO mm and a length between E and 30 mm. A method according to any one of claims 1-E, wherein the falling mass is compressed, means. 5. A process according to claim 5, characterized in that at least before the powdery substance is incorporated therein at least one additive characterized in that at least one substance selected from the following is used as additive: monocalcium phosphate , phosphorus gray, potassium sulphate, urea, ammonium salt, aqueous solution of ammonia, borax, sodium bicarbonate, sodium chloride, dry extract of gelatin, root or leaf starch of manioc, sodium alginate, carboxymetho-gloellulose, methglcellulose , resin insoluble, polygwing alcohol solubilizer Insoluble, potassium silicate, polygwing acetate, phenolic resin, melamine formaldehyde resin coumarone resin, urea formaldehyde resin, sodium 459 10 15 20 ES 30 35 QO 236 _. silicate, the substance being in the form of a powder, aqueous solution or dispersion, when incorporated into the pulverulent waste mass. A method according to any one of claims 1-E, characterized in that a supplementary Egl agent consisting of at least one inorganic material is incorporated in the waste mass. , B. Process according to Claim 7, characterized in that the inorganic material is chosen from the following materials: potassium carbonate, gypsum, burnt gypsum, blast gas from blast furnaces, magnesium oxide, harium sulphate, lithopone, dolomite, clay material and carbon powder. S. 9. A method according to claims 7 and 8, characterized in that the proportion of supplementary Egll means is such that the filler constitutes 20- & 0% by weight of the total amount of mixture of waste pulp and supplementary Egller. 10. A method according to any one of claims 5-8, characterized in that an amount of quicklime between 0.3 and 10 2 is incorporated into the powdery waste mass before it is compressed. 11. ll. Process according to any one of claims 1-10, characterized in that during the initial heating phase a heating of the core in the solid bodies is effected to a temperature between E50 and 300 ° C, after which the bodies are kept at this temperature for a certain time. , and that this initial heating phase is followed by an intermediate cooling phase, during which the temperature gradually drops to a value between 60 and 80 ° E, and a final phase when the temperature is kept between 50 and B0'C. 12. A method according to claim 1 or claim 11, characterized in that the total time for the heat treatment is between 20 and ES minutes. A method according to any one of claims 1, 11 or 18, characterized in that the total time for the initial heating phase corresponds to about 1/3 of the total time for the heating operation. leeward. 14. A method according to any one of claims 1-13, characterized in that the heat treatment is performed by moving the solids from a first heating zone at a constant speed with a temperature between E50 and 300 ° C at a constant speed. 236 -Ia _. to a final heating zone with a temperature between S0 and 80 ° C, passing through an intermediate zone, wherein there is a temperature gradient corresponding to the temperature gradually changing in the direction of movement of the solids between the temperature in the first heating zone and the temperature in the final heating zone, wherein the solids are introduced into the bed of the first heating zone at the same time as quicklime or a mixture of quicklime and at least one calcium salt. A process according to claim 1%, in that the potassium salt is potassium carbonate. A method according to any one of claims 1 to 15, characterized in that the proportion of quicklime or mixture of quicklime and at least one calcium salt brought into contact with the solids immediately before the heat treatment corresponds to 0. , 3-0.5% by weight of Caü and 0.3-0.5% by weight of calcium salt in relation to the weight of the solids. A method according to any one of claims 1-15, characterized in that the heat treatment is performed by passing the solids through a rotating tunnel furnace, wherein the axis of rotation is arranged in a practically horizontal position and the furnace is provided with an internal, helical ramp that makes it possible to transport the bodies at a constant speed from one end of the oven to the other. 15. A method according to any one of claims 1, E or 5-10, characterized in that the homogeneous, powdery waste mass is pressed into a brick shape or in the form of tiles. k ä n n e t e c k n a t