EP0699736A1 - Binder for cold briquetting of fuel fines, briquetted products and process of their manufacturing - Google Patents

Abstract

Binding agent for the cold agglomeration of solid fuel fines, comprises at least one amyl-acetate, a clay and calcium aluminate. Also claimed, are the agglomerates formed and the process for their manufacture.

Description

The present invention relates to the agglomeration of fuel fines.

The agglomeration of powders, fines or granules is a technique allowing or facilitating their use or recycling.

Among the fuel fines, there are more particularly the anthracite, vegetable coal and petroleum coke fines agglomerated, alone or in combination.

Numerous agglomeration processes are known which allow the formation of balls, briquettes, granules, pellets or other agglomerates and which use binders. The invention particularly relates to cold agglomeration by compression or agitation.

Many binders have already been proposed for the implementation of an agglomeration process under good conditions.

These good conditions relate to the economic cost of implementing the process, that is to say the cost of the various components required and of the energy supply that it involves. They relate to the quality of the agglomerates, determined by their green cohesion, that is to say immediately after their manufacture, their mechanical strength, that is to say their cohesion over time, their resistance to compression and their water resistance, that is to say their good weather resistance, even after a relatively short drying time.

For the agglomeration of coal fines, thermoplastic compounds have been used, such as coal pitches, petroleum bitumens, etc. These binders contain volatile materials, generating fumes when using the coal as fuel. This is the reason why the agglomerates thus obtained are generally subjected to a smoke extraction operation, in an oxidizing atmosphere, the objective of which is to remove volatile materials. However, this operation is costly and, moreover, deteriorates the mechanical properties of the agglomerates.

The use has also been proposed, as a binder, of lignosulphite detergents, starches, molasses, sodium hydroxide, hydraulic binders, clays (for example bentonites).

Each of these binders has drawbacks. Thermoplastic binders require large expenditure of thermal energy, binders based on molasses and lignosulphite detergent also involve a significant energy expenditure for obtaining agglomerates having good water resistance, mineral binders cannot confer good mechanical resistance to the agglomerates that after a relatively long maturing time, the starches give the agglomerates good cohesion during demolding, but are poorly resistant to humidity.

The objective of the invention is therefore to provide a binder simultaneously giving the agglomerates good mechanical demolding behavior, good crushing resistance, good weather resistance and an implementation of the agglomeration process in good conditions. economic conditions and making it possible to obtain agglomerates having a completely ecological character. Neither the products used nor the process should present polluting risks.

To this end, the invention relates to a binder for cold agglomeration of fuel fines which comprises at least one starchy and at least one calcium aluminate.

• l'amylacé peut être un amidon prégel ou un amidon natif;
• le liant comporte un agent hydrofugeant;
• le liant comporte un agent biocide;
• le liant comporte au moins une argile;
• l'argile est de la bentonite.

According to different embodiments, each presenting their own advantages, this binder has the following characteristics, possibly taken in combination:

• the starch can be a pregel starch or a native starch;
• the binder comprises a water-repellent agent;
• the binder comprises a biocidal agent;
• the binder comprises at least one clay;
• the clay is bentonite.

The invention also relates to an agglomerate comprising a binder itself comprising at least one starchy and at least one calcium aluminate.

Such an agglomerate preferably comprises 0.5 to 5% of starchy products and 0.5 to 5% of calcium aluminate.

As a variant, the agglomerate can also comprise at least one clay. Preferably, the agglomerate comprises from 0.5 to 5% of clay.

The invention also relates to a method for manufacturing agglomerates of cold fuel fines from said fuel fines with a binder comprising at least one starchy and at least one calcium aluminate.

According to this process, the fuel fines are treated so as to give them a water content of between 6 and 15% when they are mixed with the binder.
Furthermore, one can add to the components of the binder, a water-repellent agent. This agent not only improves water resistance, and at the same time prevents water retention.

• on utilise un liant comportant également au moins une argile;
• les composants du liant sont prémélangés avant leur mélange avec les fines de combustible;
• les composants du liant sont ajoutés séparément aux fines de combustible;
• les amylacés peuvent être prégélatinisés ou les amylacés sont natifs ;
• l'éclatement des amylacés est fait après leur mélange avec les fines de combustible;
• l'éclatement des amylacés est fait avant leur mélange avec les fines de combustible;
• l'éclatement de l'amidon est réalisé à la chaleur,
• l'éclatement de l'amidon est réalisé avec un additif.

In different preferred embodiments:

• using a binder also comprising at least one clay;
• the binder components are premixed before mixing with the fuel fines;
• the binder components are added separately to the fuel fines;
• starches can be pregelatinized or starches are native;
• the starch bursting is done after mixing with the fuel fines;
• the starch bursting is done before mixing with the fuel fines;
• the starch bursts with heat,
• the starch is burst with an additive.

The starch products used in the composition of the binder of the invention can belong to any one of the various known families. It could be:
* native starches, such as cereal starches (wheat, corn, rice ...), tuber starches, in particular potato, cassava starch ...

In this case, the starchy products can be burst by cooking with live steam in an autoclave according to the so-called "jet cooker" process. This makes it possible to obtain a viscous liquid which is then incorporated into a mixer with the others. components of the binder and the fines to be treated.

• * de produits amylacés transformés, tels que les dextrines, les produits oxydés ou chlorés, les produits hydrolysés et estérifiés et les produits éthérifiés.
• * de produits prégélatinisés, encore appelés amidons prégels, produits précuits ou amidons gonflants qui sont obtenus à partir de produits natifs ou hydrolysés cuits en phase aqueuse sur un cylindre sécheur, avec ou sans réactif chimique. Ils se présentent alors sous forme de petites paillettes qui, par dispersion dans l'eau froide, sous agitation, donnent des colles.

The bursting can also be carried out in situ after the native starch products have been mixed with the fines to be treated and the components of the binder.

• * of processed starch products, such as dextrins, oxidized or chlorinated products, hydrolysed and esterified products and etherified products.
• * of pregelatinized products, also called pregel starches, precooked products or swelling starches which are obtained from native or hydrolysed products cooked in aqueous phase on a drying cylinder, with or without chemical reagent. They then take the form of small flakes which, by dispersion in cold water, with stirring, give adhesives.

The calcium aluminates are supplied in the form of calcium aluminate cements, sometimes called simply aluminous cements, which are products obtained by fine grinding of clinker of calcium aluminates. The calcium aluminate clinker is a product consisting mainly of calcium aluminates obtained either by fusion of limestone and bauxite, or by sintering lime (CaO) and alumina (Al2 O3). Calcium aluminates set faster than, for example, Portland cement.

Various adjuvants can also be added to the calcium aluminates, in order to facilitate their use and to optimize the setting conditions.

Use is preferably made here of an aluminate cement containing from 30 to 80% of alumina, advantageously from 40 to 70% and, for example, from 50 to 60%.

The invention relates to the agglomeration of fuel fines with a binary starch / aluminate mixture. Thus, the binder used for this purpose generally comprises one or two starch products and one or two calcium aluminates. However, there are applications where at least one clay is added to the binder.

Different clays can be used as components of the binder of the invention. It is advantageous to use clays of the smectite family, in particular bentonites natural or activated sodium or calcium. Good results have been obtained with bentonites which are a particular type of clay and which form a gel with water.

However, the addition or not of clays to the binder has an influence on the simplicity of the manufacture of the agglomerates and also on the rate of ash during the combustion of the latter. When the addition of clays is abandoned, the production of agglomerates is simplified and the ash rate is reduced.

Furthermore, a binary binder according to the invention contains more starchy products than a ternary binder according to the invention.

Agglomeration processes often involve heating the agglomerates after they have been removed from the mold. The processes which do not include such heating are called cold agglomeration processes here.

• la Figure 1 est une représentation schématique d'une installation pour la mise en oeuvre du procédé de l'invention ;
• les Figures 2 et 3 sont des représentations schématiques indiquant la forme des agglomérés utilisés lors des essais donnés en exemples;

An embodiment is described below in detail, with reference to the examples and the appended drawings in which:

• Figure 1 is a schematic representation of an installation for implementing the method of the invention;
• Figures 2 and 3 are schematic representations indicating the shape of the agglomerates used during the tests given in examples;

The process for manufacturing agglomerates of cold fuel fines of the invention is more particularly described with reference to FIG. 1.

The raw product 1, stored in the hopper 2, is transmitted by the conveyor belt 3 to the dryer 4. After drying, the fuel fines are transmitted by the screw 5 with a screen 7. The screw 5 is also supplied with the products recovered by the air filtration system 6 and by the residues discharged by the screening belt 22, the role of which will be indicated below.

The grinder 8 and the screen 7 make it possible to control the particle size of the products transmitted by the screw 9 and by the elevator 10 to the storage hopper 11. Furthermore, the hoppers 12, 13 and 14 respectively contain clay, starches and calcium aluminate intended for the production of binders.

The conveyor 15 supplies these products, together with the fuel fines, carried by the conveyor 16 in the continuous mixer 17. In this mixer, water is also supplied by the circulation 18 and steam by the circulation 19.

The assembly is then supplied to a press with tangential wheels 20, subjected to a screening belt 21, possibly recycled by the conveyor 21, and then feeds the conveyor 23 which constitutes the stock of agglomerated products 24.

Thus, the moisture content of the fuel fines 1 is adjusted and controlled by the dryer 4. These products are duly fragmented by the crusher 8 and, after sieving, are mixed by the mixer 17 with the various components of the binder. The water supply 18 ensures a water content of the fuel fines of between 6 and 15%, and the steam supply 19 allows the native starch to burst. In the event that, upon storage, the fuel fines have the desired humidity level, the drying step can be omitted.

The tangent wheel press 20 performs cold agglomeration. The screen conveyor 16 allows the recovery of product waste during agglomeration and its recycling in the process.

The mat 23 allows the evacuation of the agglomerates and their storage 24.

The following examples illustrate the invention. The tests described were carried out on anthracite fines included in the particle size range from 0 to 3 mm.

The balls have the shapes shown, respectively in Figures 2 and 3. In these Figures, 30 and 33 represent the front views, 31 and 34 the side views, 32 and 35 the top views.

The ball of about 28 cm3, shown in Figure 2, has a thickness of about 56 mm, a height of about 36 mm, a width of about 24 mm.

The ball of about 10 cm3, shown in Figure 3, has a thickness of about 27 mm, a height of about 34 mm, a width of about 18 mm.

The agglomerated balls corresponding to those of Figure 2 have a weight of 32 g and are obtained on a KOMAREK tangent wheel press (registered trademark) type DH 400.

The agglomerated balls corresponding to those of Figure 3 have a weight of 9 g and are obtained on a KOMAREK tangent wheel press (registered trademark) type B100.

EXAMPLE 1

The measurements are carried out according to the following protocols on 9 g balls (Figure 3).

The humidity percentage is determined by thermopesée, for example, measured by a Sartorius (Registered trademark) moisture meter on paste, before passing through the press.

The fall tests are carried out as follows: 5 balls are launched from a height of 2 meters on a sheet metal plate, 4 consecutive times. We give the number of intact balls after 4 falls.

The compressive strengths R are given at t = 0, at t = 24 hours and at t = 7 days. The resistances are expressed in kg. The chipboard is placed between two plates. The lower plate on which the ball rests, rises at constant speed to a predefined height. Resistance is the force opposed by the ball to its crushing.

• mesure de R, résistance à la compression après une durée déterminée de maturation Tm à l'air ;
• immersion du boulet dans de l'eau pendant 7 jours;
• après sept jours d'immersion, mesure de la résistance à la compression r;

The good water resistance of the ball is measured by a particularly demanding immersion / compression test, the protocol of which is as follows:

• measurement of R, resistance to compression after a determined duration of maturation Tm in air;
• immersion of the ball in water for 7 days;
• after seven days of immersion, measurement of the compressive strength r;

The results given in Table 1 were obtained with compositions I to III which are embodiments of the invention. Compositions IV to VII are comparative tests.

• Un liant hydraulique classique, en l'occurrence un ciment type CPJ 45 utilisé à la place de l'aluminate de calcium dans le liant, ne donne pas une bonne résistance à l'eau : 56 % seulement de la résistance est conservée, contre au minimum 80 % avec un liant à base d'AC (composition IV).
• L'utilisation d'amidon prégel ou d'amidon natif comme co-liants donne des bons résultats dans les quatre cas.

The association of the two co-binders described in this invention and subject of compositions I and II, as well as the combination of the three co-binders described in the present invention and subject of composition III, give satisfactory results for the criteria selected: drop tests, compressive strength and resistance to the immersion.

• A conventional hydraulic binder, in this case a CPJ 45 type cement used in place of calcium aluminate in the binder, does not give good water resistance: only 56% of the resistance is retained, against minimum 80% with a binder based on AC (composition IV).
• The use of pregel starch or native starch as co-binders gives good results in all four cases.

EXAMPLE 2

This example concerns 32 g balls obtained on an industrial press (Figure 2).

The same measurement protocols are applied for the humidity percentage, the compressive strength and the good water resistance.

The humidity measured on this test is 9%; the falling tests were carried out on 5 kg of balls thrown 4 times from a height of 2 meters. The percentage of broken balls is only 4%.
Table 2 makes it possible to compare the evolution of the compressive strength after immersion as a function of the curing time, in absolute value and in relative value (that is to say relative to the resistance before immersion) of the agglomerates obtained according to this Example 2 with compositions A, B, C.

The results of the R and r measurements are indicated at 24 hours, 7 and 30 days.

Compositions A to C are embodiments of the invention. Composition D is a comparative test.

The reference signs inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter, and in no way limit their scope.

The water uptake is the percentage of humidity of the balls measured after immersion for 24 hours in water.

Claims (22)

1. Binder for cold agglomeration of fuel fines, characterized in that it comprises at least one starchy and at least one calcium aluminate. 2. Binder according to claim 1, characterized in that the starch is a pregel starch. 3. Binder according to claim 1, characterized in that the starch is a native starch. 4. Binder according to any one of claims 1 to 3, characterized in that it also comprises at least one clay. 5. Binder according to claim 4, characterized in that the clay is bentonite. 6. Binder according to any one of claims 1 to 5, characterized in that it comprises a biocidal agent. 7. Binder according to any one of claims 1 to 6, characterized in that it comprises a water-repellent agent. 8. Aggregate of fuel fines comprising a binder, characterized in that this binder comprises at least one starchy and at least one calcium aluminate. 9. Agglomerate according to claim 8, characterized in that it comprises from 0.5 to 5% of starchy products and from 0.5 to 5% of calcium aluminate. 10. Agglomerate according to one of claims 8 or 9, characterized in that the binder also comprises at least one clay. 11. Agglomerate according to claim 10, characterized in that it comprises from 0.5 to 5% of clay. 12. Agglomerate according to any one of claims 8 to 11, characterized in that the binder comprises a water-repellent agent. 13. Process for the production of agglomerated cold fuel fines from said fuel fines, characterized in that a binder comprising at least one starchy and at least one calcium aluminate is used, and that the fuel fines are treated with so as to give them a water content of between 6 and 15% when mixed with the binder. 14. The method of claim 13, characterized in that the components of the binder are premixed before mixing with the fuel fines. 15. Method according to claim 13, characterized in that the components of the binder are added separately to the fuel fines. 16. Method according to any one of claims 13 to 15, characterized in that the starches are pregelatinized. 17. Method according to any one of claims 13 to 15, characterized in that the starches are native. 18. The method of claim 17, characterized in that the starch bursting is done after mixing with the fuel fines. 19. The method of claim 17, characterized in that the starch bursting is done before mixing with the fuel fines. 20 Method according to any one of claims 17 to 19, characterized in that the bursting of the starch is carried out with heat. 21. The method of claim 20, characterized in that the bursting of the starch is carried out with an additive. 22. Method according to any one of claims 13 to 21, characterized in that a binder is also used comprising at least one clay.

Images