DK159818B - FLY BASKET IN STOCK FORM AND PROCEDURE FOR PREPARING SAME - Google Patents

Abstract

1. A storable granular material on the basis of fly ashes and a hydraulic mixture of a bonding agent containing cement and gypsum, mixed under admixture of water and brought into granular shape, characterized in that the fly ashes are of any origin, and that the bonding agent mixture contains carbide sludge and, optionally, additives, and in that for every 100 parts by weight of fly ashes there are 8 to 12 parts by weight of cement, 7 to 11 parts by weight of gypsum, and 6.5 to 8.5 parts by weight of calcium carbide.

Description

in

DK 159818 B

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a fly ash-based granular material and a hydraulic binder blend containing cement and gypsum, mixed with water admixed and granulated, as well as a process for making the same.

Such a material is known from DE-A-1,471,360. However, it is not calculated as the harmful substances present in the fly ash are not sufficiently bound.

As a combustion residue in cow 1 power plants, fly ash is formed, which is composed of 10 different carbon content and other chemical substances. For a long time, proposals have been made to process fly ash so that it can be used as an additive for the construction industry. It is e.g. German Patent Specification No. 859,426 is known to mix fly ash with waste lime sludge of the kind that results from the decomposition of calcium carbide d.

German Patent Specification No. 2,018,221 discloses another method for preparing a waste material 20 waste material from lignite-heated plants where a mixture of dust and additives is granulated and the granules are heated after heating. It is also known to produce a fly ash granulate to mix the dust from the dry separator in a coal-fired power plant with the dried or burned residue from the sulfur leach washer (calcium sulfate residue). The resulting granular granulate is then painted.

All known methods have at least one, mostly two disadvantages. They are too little economic to apply in 30 practices. Thus, e.g. a sintering process associated with excessive energy costs. Furthermore, the harmful substances contained in the fly ash are not bound in such a way that an environmentally friendly operation can be ensured. On the contrary, there is a danger that the harmful substances will be washed out and strain the soil. This disadvantage is also found in a deposit on depots or when used as aggregates, e.g. at street and road construction.

The object of the invention is therefore to bring the fly ash produced by the combustion of coal-fired power plants into a form which

DK 159818B

2 allows for environmentally friendly storage. A granular material of the kind specified in the introduction must be provided which can be used as an additive and filler, especially in the construction industry. In addition, a process for producing these materials must be specified.

This object is solved by the material of claim 1 and by the method of claim 9. Preferred embodiments are set forth in the subclaims.

10

It has been found that the use of fly ash together with cement, gypsum and carbide sludge leads to a fly ash finished product, which is distinguished by good coatability. The mixture with the three binders leads to a grainy material, the grain of which is distinguished by sufficient strength and resistance to leaching by water storage and groundwater contact, respectively. Nevertheless, heavy metals and other substances that affect the environment remain firmly bound. An alkaline reaction between the additives and the environment is also largely avoided.

When used as a finishing material for the construction industry, the product according to the invention is also suitable. It is distinguished by a sufficient strength and frost resistance. Furthermore, any aggressiveness to iron or steel structures lapses when used as a filler or filler.

The ratio of fly ash dust to hydraulic binder is preferably 3/4 to 1/4 based on the dry matter weights.

Particularly excellent results are obtained by adding: 8-12 parts by weight of cement, 7-11 parts by weight of gypsum and 6.5-8.5 parts by weight of calcium carbide to 100 weight parts of fly ash.

3 5

The invention further has the advantage that additional environmentally harmful substances are bound environmentally friendly. Gypsum excess

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3 is precipitated e.g. by flue gas desulphurisation. Carbide sludge is a waste product in the production of acetylene. It is preferably stored at least 14 days before it is used as a binder component.

5

In yet another embodiment of the invention, it is found to be advantageous when at least one additive such as a curing accelerator, a retarding agent, a pore former, a pelleting aid or a mixture of two or more of these agents is added. Any known means could be used. Preferably, as the accelerator, sulfate accelerators such as alum, sodium hydrogen sulfate, as retarding agent, phosphates such as sodium phosphate, or Na , preferably an acrylic homo or copolymer added with acidic groups such as carboxyl groups. The proportion of such additives is approx. 1.5 to approx. 2 parts by weight on 100 parts fly ash. The cure accelerator causes the granules to decompose within a relatively short time and harden, in which connection it must be taken into account that the plaster already added also serves as the cure accelerator. A delay means contributes to the unbinding process running uniformly throughout the mass.

The pore former promotes water withdrawal, and the pelleting aid mediates the emergence of most regular pellets.

In the preparation of the product, preparation water is added. The amount of preparation water, of course, depends on the moisture content of the materials used, namely whether the fly ash is dry or damp and the electro-filter plaster appears dry or as sludge. According to one embodiment of the invention, between 100% and 32% of preparation water is used for 100% fly ash, binder mixture and additives.

35

According to a further embodiment of the invention, the fly ash body can be powdered with fly ash dust. The pudding causes it

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4 available surface moisture is largely bonded. In this way, the drying of the surface is ensured and a granulation of the granules in the further processing is almost excluded. In addition, during the winter months, freezing 5 of the non-bound surface water to ice is prevented. Preferably, an amount of fly ash dust is added which approximately binds 8-14% surface moisture.

According to the invention, a process for producing fly ash finished products 10 of the kind described above comprises fly ash dust and hydraulic binder first premixed. Only afterwards will cooking water and any additives be added. In a special compulsive mixer, the mixture is brought into granular form. The pre-mixing time 15 is approx. 30 seconds. However, it depends on the consistency of the individual substances as well as their moisture content. Preferably, a mixer is used which, in addition to a stirrer, has a swirl device which ensures the production of a homogeneous granular substance. In the mixing process, it is essential that the mass be homogeneously mixed. In order to achieve this purpose, it is essential to have the exact water addition as well as the speed of rotation of the agitator and swirl device.

The additional additives, such as cure accelerators and / or pore formers, are preferably inserted in liquid form, namely in that they are introduced into the inlet water. In this way, a premix of the additives with the water can be obtained.

30

Above, it has been explained that it is extremely advantageous to powder the fresh granules. In this connection, in yet another embodiment of the invention, the granular material approximately uniformly distributed from low drop height 35 can be discharged onto a conveyor belt and in a powder station fly ash can be blown beyond the width of the conveyor belt. The placement of the granules on the conveyor belt must be done so that

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5 so that they are not destroyed. The width and speed of the conveyor belt are chosen such that the granules are placed flat in gt on the conveyor belt so that regular pudding can take place in the powder station.

5

Although the surface residual moisture of the granules is bound by the dusting with fly ash dust, there is still a risk of clumping or baking when the granules are soaked up cone shaped. Therefore, an embodiment of the invention ensures that the granular material is uniformly distributed. This can be achieved with the aid of a very wide belt conveyor or by means of a commuting conveyor belt in a so-called round-bearings.

It is further found to be useful when the granular material according to a further embodiment of the invention after a storage period is screened for grain sizes. The fineness screen is preferably provided with vibration means to prevent adhesion of the screen. In this context, according to a further embodiment of the invention, during the sieving process, a post-dusting with fly ash dust may take place. Especially in cold weather, the baking of the granules is thereby prevented.

After a further storage time, e.g. 5 days, the granules then achieve a sufficient transport strength or building strength respectively. The granules then have the opportunity, during and after the installation time, to harden further, as is the case with concrete and other aggregates with hydraulic binders. With a deposition deposit, as in other use cases, it is ensured that the bound heavy metal is not washed out by storage in water or by contact with groundwater, respectively. Furthermore, it is ensured that the combustible components do not exceed the standards applicable to silicon and sand. Adequate alkaline resistance is also ensured, and thus utility in the construction industry or environmentally friendly storage at a unloading location.

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6

In principle, there are three different forms regarding the structure of the fly ash according to the invention:

Granules, 5 pellets, gravel.

The granules are readily obtained in the appropriate form by means of the aforementioned forced mixer / plate mixer. It is also possible to insert granules according to the invention as filling material in street, dike and road foundations. Continuous grain build-up ensures favorable compression. Cracks during and after installation are largely excluded. It is possible to keep the non-frost resistant components below 10%.

Alternatively, can. pellets are produced. For this purpose, the fresh granules coming out of the forced mixer are fed to a pelletizing plate. The converted granules b 1 in -20 ver by continuous application of a mixture of fly ash dust, cement, gypsum, carbide sludge and preparation water via spray nozzles in known manner pel leter. Depending on the setting of the mixing plate, the size of the pellets is determined. With regard to the frost resistance of such pellets, the requirements of DIN 4226 can be met.

Finally, fly ash can also produce gravel. For this purpose, the mixing time in the forced mixer is extended by about 40 seconds. This results in relatively large granules, which are otherwise processed further in the manner described above. For larger piles, the heat occurring in the pile significantly accelerates the hydraulic curing process and a disproportionately firm concrete is formed. Due to the inevitable lump formation, the material is then preferably subsequently fed to a jaw or centrifugal crusher. The crushed grain material can then be screened again and arranged according to grain sizes and added to the single fractions. Also in the case of gravel can the requirements

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7 concrete and for use in street building is fulfilled, whereby the non-frost resistant components here can also be kept below 4%.

With the invention or with the method according to the invention, for the first time, it is shown how fly ash can be made stock or how it can be used in the construction industry. The cost of producing the fly ash according to the invention is relatively small and, above all, the energy consumption is small and is limited to the thrust energy.

10

The invention will now be explained in more detail by way of example and with reference to the accompanying drawings, in which: FIG. 1 schematically shows the process according to the invention for the production of fly ash granules; FIG. 2 is a schematic representation of the fly ash pellets; and FIG. 3 schematically the production of fly ash gravel.

Before going into the details shown in the drawing, it should be noted that each of the features described or shown individually or in connection with the features of the claims is of substantial inventive importance.

25

Reference numerals 1-4 denote a silo group in which fly ash in silo 1 and in silos 2-4 hydraulic binders. Via a raw material weight 5, the substances from silos 1-4 are introduced dosed into the mixing granulator 6, which contains a stirrer 30 and a swirl device. In the reservoirs 8-10 are stored additives which are introduced into the water supply 7 to the mixing granulator 6 and thus are already premixed.

The freshly formed granules from the granulator 6 are discharged onto a conveyor belt 11 and uniformly powdered in a powder egg.

35 From the powder in place 12, the powdered granules reach via a conveyor belt 13 to a circular storage facility. A conveyor belt 15 carries the cured granules from

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8 to a sieving system 16, in which a classification is made in grain sizes between 0 and 32 mm. During the screening, further dusting with fly ash dust may occur, which is not shown here. From the sieve system 16, 5 reaches the sieved material via a conveyor belt 17 to a circular bearing 18, from which it can be driven to landfill or to another storage location by means of a wheel-loaded loader and a truck.

10 During the screening, flour which is raised by means of a return line is transported back to the granulator 6.

FIG. 2 is substantially similar to FIG. 1, and the same parts are provided with the same reference numerals. In FIG. 2 is also shown a pelletizing plate 11a, which is arranged after the granulator 6. Water, as indicated by a dotted line, is also supplied with water.

ISLAND

FIG. 3 again shows a plant similar to FIG. 1. Therefore, again 20 same parts are provided with the same reference numerals. Since, with the system of FIG. 3 to produce gravel, a crushing device 17b is arranged on the conveyor belt 15 which disintegrates the relatively large and hard fly ash lumps.

By utilizing the internal heat and the pressure in the circular storage, the bonding process is accelerated and smaller pits are formed, which after a crushing process are available as gravel.

The following is an example of a recipe based on 30 dry binder additives: 35

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9

Range Preferred compositions

Fly ash 75-80 wt% 77.5 wt% 77.5 wt%

Cement 6.5-10 wt% 8 wt% 7 wt% 5 Plaster filler 5.5-9 wt% 7 wt% 7 wt%

Carbide sludge 5-7 wt% 6 wt% 7 wt%

Additives 0-2.5 wt% 1.5 wt% 1.5 wt% 100.0 wt% 100.0 wt% 10

Preparation water according to the moisture content of the additives 10-32%.

Following examples for adverse conditions: 15 1. Poor frost resistance (in principle at high lime content) 20 Fly ash 60% Fly ash 70%

Cement, PZ351) 10% Cement, PZ351) 2%

Carbide 20% Carbide 20%

Gypsum filler 10% Carbohydrate 7%

No additives Quick-cure 1% 25 2. Poor strength (in principle at higher water additions, ie above 30% cooking water) 30

Fly ash 70% Fly ash 70%

Cement, PZ351) 2% Cement, PZ351) 3%

Fine sand 18% Carbide 7%

Carbide 10% Carbohydrate 10% Fine sand 10%

Cement, PZ35 means Portland cement with a compressive strength of 35 kN.

Claims (14)

1. Aggregated granular material based on fly ash and a hydraulic binder mixture containing cement and gypsum, mixed under admixture of water and granulated, characterized in that the fly ash is of any origin and the binder mixture contains carbide sludge and any additives, and that to 100 parts by weight of fly-10 ash are added 8-12 parts by weight of cement, 7-11 parts by weight of gypsum and 6.5-8.5 parts by weight of about 1 cum carbide. 2. A granular material according to claim 1, characterized in that the hydraulic binders in the binder mixture are present with approximately the same proportions. Storage grained material according to claim 1 or 2, characterized in that the ratio of fly ash to binder mixture is approximately 3/4 to 1/4, calculated on the dry solids weights. Storage composite grain according to one or more of claims 1 to 3, characterized in that it contains as an additive a curing accelerator, a retarding agent, a pore former, a pelletizing aid or a mixture of two or more of these agents. 5. A granular material according to claim 4, characterized in that it contains as a curing accelerator a sulfate, as a retarding agent, a phosphate which pores a saponified crosslinked resin, and as a pelleting aid, an acrylic homo or copolymer containing acidic groups. Stored grainy material according to one or more of claims 1-5, characterized in that between 10% and 32% of preparation water is used for the bonding of 100% dry starting materials. DK 159818B u Storage computed grainy material according to one or more of claims 1-6, characterized in that the fly ash grains are powdered with fly ash dust. A composite grained material according to claim 7, characterized by a quantity of fly ash dust which binds approximately 8-14% surface moisture. A process for producing a composite granular material according to one or more of claims 1-8, first mixing (6) the fly ash (1) and the hydraulic binder mixture (2-4) and then adding cooking water only (7), characterized in that the premixing time is approx. 30 seconds and optionally adding one or more additives (8-10) to the cooking water (7) and in a forced mixer (6) bring the mixture into granular form. Process according to claim 9, characterized in that curing accelerators and / or pore formers are used in 20 liquid form (8-10), which are introduced into the preparation for the preparation water. Process according to claim 9 or 10, characterized in that the granulate-like material 25 is regularly distributed and after a storage period (16) the granular material is screened according to grain sizes. A method according to claim 11, characterized in that during the screening (16) a post-dusting with 30 fly ash dust is made. Process according to one of claims 9-12, characterized in that the fresh, yet unbound granular-like material is pelleted (11a, Fig. 2). 35 14. A process according to claim 13, which is known to pellet the newly formed granules by continuously adding fly ash dust and preparation water (11a, Fig. 2). 5 10 15 20 25 30 35