DD285335A5 - METHOD AND DEVICE FOR PREPARING MOISTURE FINE-COATED SMOKE GAS - Google Patents

Abstract

The invention relates to a method and a device for the treatment of moist feinkoernigem flue gas gypsum. The method is based on dividing the flue gas gypsum from a Foerderstrom into individual bodies, which are umhuellt with a crust of a preferably hydraulic erhhaertenden binder. The device consists of a hopper, a Teilungsflaeche and arranged below this Schneckenfoerderer. With the solution according to the invention it is possible to make flue gas gypsum technologically manageable with very low equipment and energy expenditure. Fig. 1 {processing; Device; synthetic gypsum; flue gas desulfurization; Flue gas gypsum; Foerderstrom; Teilungsflaeche; hydraulic binder; screw conveyor; Hopper}

Description

For this 2 pages drawings

Field of application of the invention

The present invention relates to the treatment of fine-grained moist accumulating or subsequently moistened synthetic gypsum, as obtained mainly in the flue gas desulfurization, but also in the production of hydrofluoric acid and other chemical processes.

Applications exist in other areas everywhere, where the task is to transfer fine-grained substances in a coarse-grained good.

Cha-akterlstlk of known technical solutions

With the increasing requirements for keeping the air clean, the desulphurization of flue gases from the combustion of fossil fuels gains importance. The methods used today produce considerable quantities of gypsum, which must be reused. In some applications, it has been possible to design processes such that flue gas gypsum replaces natural gypsum. Thus, flue gas gypsum is converted into calcium sulfate hemihydrate by autoclaving and used for the production of molded bodies (DE 3711367). Also gypsum fiber boards are produced from flue gas with fibrous aggregates, which solidify after shaping by a pressure and temperature treatment (DE 3419559).

There are proposals to produce building materials from mixtures in which flue gas gypsum has a significant proportion (DE 3639841, DE 3529823, DE 3205147). They are mainly intended for applications with heavy use and low strength requirements.

A large part of the flue gas gypsum is not used for technical purposes and must be landfilled.

At the same time, natural gypsum is mined on a large scale for industrial purposes. The cause is partly the poor handling of the bunkers and chutes strongly prone to bridging flue gas gypsum. The substitution of natural gypsum by flue gas gypsum as setting regulator has hitherto only been carried out to a limited extent in cement (for example DE 201667), because prior to use in the existing cement plants a treatment is required whose costs, however, generally exceed the recovery costs for natural gypsum.

It is known to reduce the moisture by admixing a dry fine-pored material, preferably fly ash, whereby the low moisture results from the simple mixing rule (DF 3620778). However, such treatment is insufficient for many applications. It comes then, for example, in plants on which otherwise Anhydritschotter is processed, to permanent disturbances in the flow of material.

For briquetting without additives, the previous drying to <1 wt .-% moisture is necessary (DE 3201853). The drying is mechanically not possible due to the high fineness. Therefore, an energy-intensive thermal process with high operational costs is required.

The briquetting itself is done with high electrical drive power of the machine at high wear.

This also applies to another method in which the material is processed with a Koller extruder.

The problem is the guarantee of a high dimensional stability of flue gas gypsum briquettes, especially under subsequent exposure to moisture. Described is the increase in shelf life, abrasion resistance and compressive strength of the briquettes by mixing with a binder before briquetting, in particular with the known hydraulically setting materials cement or REA gypsum building materials of gypsum phases α- and ß-hemihydrate and anhydrite II with 3 to 40Gew.- % (DE 3501 238).

The use of binders incurs additional costs for expensive briquette production.

Also very aui agile is a method in which the briquetting of the flue gas gypsum is partially calcined by being dried at relatively high temperatures, ie exhaust gas temperatures of 120 ⁰ C to 15O ⁰ C (DE 3 626912).

From other fields of technology apparatuses are known, with which moist fine-grained materials are granulated. Thus, there are various rotor granulators in which a drum provided with holes, which receives the material and pressure rollers or mats are mutually offset in rotating relative motion, whereby the material is printed through the holes (DD 243170, DE 3615677). Similarly, a device for passing, in particular granulation and / or sieving a good, consisting of a vertical rotationally symmetric container with a conical bottom, in which the conical surface is formed by a sieve and a circulating in the container Streichwendel the good through the sieve pushes (DE 3617175).

These solutions have in common that the material is pressed by mechanical pressure through the openings.

Depending on the applied pressure, a relatively high energy consumption, wear and maintenance costs arise. Gypsum agglomerates made with these apparatus would have a low dimensional stability because of the residual moisture and they could not be transported away from the place of shaping without a large part of the flue gas gypsum being present again as a shapeless mass.

Object of the invention

The aim of the invention is the treatment of moist fine-grained flue gas gypsum at low cost, to allow the economic use of large quantities of flue gas gypsum, especially in the building materials industry, as a secondary raw material.

Explanation of the essence of the invention

The invention has for its object to transfer wet and fine-grained flue gas plaster cost in a coarse-grained material to make it manageable on existing industrial equipment for such material the task.

According to the invention, the flue gas gypsum to be treated is divided into individual bodies, which are enveloped with a crust of a, preferably hydraulically, hardening binder. By bypassing the process steps of drying and pressing and containing the gypsum bodies in the interior flue gas gypsum in the initial state, an energetic advantage over methods is achieved in which the entire amount of substance is subjected to a conversion. It eliminates the use of heat energy and the high drive power for press tools.

For the production of gypsum bodies, the thixotropic properties of the moist flue gas gypsum can be used.

After passing from a delivery stream into the area above an apertured dividing surface, fluidity is increased by induced vibration so that it pauses the openings and the tearing strands

n. I form the nodular gypsum bodies. As soon as the gypsum comes out of the field of action of the vibration, the water is partially withdrawn from the near-surface areas of the tubers, as the capillary structure disturbed during the vibration absorbs the water again. At the same time this improves the conditions for the subsequent encrustation in connection with the binder.

In particular, in the case of low initial moistures of the flue gas gypsum, another variant of the division into individual gypsum bodies can be applied by mechanically pushing the flue gas gypsum on the dividing surface so as to prevent bridging over the apertures, whereby according to the invention the flow is achieved without pressure application

Because of the low strength of the plaster tubers must be gently collected. For a good bed of the binder or the crust-building substance mixture is suitable. This is moved below the dividing surface along with a conveyor, which causes a gentle circulation of the good bed during the conveying process, at the same time ensuring the all-round encrustation of the plaster body with binder. The fatigue strength of the encrustation does not become established until after the solidification reaction of the binder has ended.

In order to support the use of binders or solidification, the binder may be at least pre-mixed with a substance which is present as a solid in granulations of preferably <10 mm and / or in the strength-promoting chemical Reactio ι with the binder occurs.

The invention was qleichzeitig the technical problem of proposing a device for carrying out the method.

According to the invention the object is achieved by a arranged below a hopper dividing surface, coupled with a known auger. In the division surface are openings for the divided material passage due to gravity. To prevent bridge formation, the division surface operates in vibration or in an alternating movement. The auger below the dividing surface exercises in one of the functions feeding the binder, gentle collection of the gypsum in the binder bed and circulation of gypsum bodies in the binder. To avoid bridge formation, the dividing surface of the device can also be designed as a trough, in which the thrust members rotate in the form of a helix or of revolving plates.

embodiments

example 1

From a flue gas gypsum with a moisture content of 30% stored for several months, nodular bodies were prepared according to the described method with a volume of 5 to 10 cm ³ . The binder used was ZZ1 / 25 slag cement. The cement input was 10% by weight to the total.

The substances are characterized by the following analytical values:

Part / characteristic Share in weight ZZ1 / 25 Flue gas gypsum Loss of ignition at 0.16 100OX 23.9 24.13 SiO ₂ 1.1 7.14 Al ₂ O ₃ 0.4 1.61 Fe ₂ O ₃ 0.5 53.77 CaO 33.2 4.98 MgO 0.9 3.68 SO ₃ 43.3 0.89 K ₂ O 0.04 0.30 Na ₂ O 0.01 2.1 > 90μηι 0 6.7 > 63μσι 0.7 21.7 > 40μιη 3.0

After a storage period of one month, the test material was in coarse-grained form without fines.

Example 2

FIG. 1; FIG. 2

The device shown in Figures 1 and 2 consists of a flat dividing surface 2 with circular holes on which a hopper 1 is fixedly mounted. To create the vibration, the division surface is equipped with external vibrators (f = 2625min " ¹ ).

From the binder feed point 4, a screw conveyor 5 leads below the dividing surface 2 along to the discharge 6.

The device can be arranged both stationary and on a chassis of a vehicle.

Example 3

Figur3; Figur4; Figur5

The device shown has, in contrast to the aforementioned embodiment 2, a trough-shaped dividing surface 2, which consists of a basket formed of welded round steel. In this basket, a spiral screw 7 (Fig. 4) or rotating Umwälzbleche 8 (Fig. 5) are arranged.

Claims (5)

A process for the treatment of wet fine-grained flue gas gypsum with the addition of a hardening binder to obtain a coarse-grained lump, characterized in that flue gas gypsum is divided from a flow by passing an apertured division surface (2) without external pressure application due to gravity, according to which the falling in falling gypsum strands in a bed of self-hardening or hydraulic binder, which is guided along by a conveyor under the dividing surface, collected and the gypsum bodies are wrapped on all sides with binder during the common further promotion with gentle circulation. 2. The method according to claim 1, characterized in that the passage of the flue gas gypsum is supported by the dividing surface (2) by vibration and / or circulation on the dividing surface. 3. The method according to claim 1, characterized by the premixing of the binder with at least one substance which promotes the hardening of the crusts by the binder by being present as solids in grain sizes of preferably <10mm and / or in the strength-promoting chemical reaction with the binder occurs. 4. An apparatus for the treatment of wet fine-grained flue gas gypsum, characterized by a dividing surface (2) in which openings for the divided material passage are due to gravity and which operates in vibration or an alternating movement and is located under a hopper (1) , coupled with a below the dividing surface (2) along, known per se screw conveyor (5), which here in one of the functions supplying the binder, gently collecting the gypsum in the binder bed and circulation of the gypsum body in the binder exerts. 5. The device according to claim 4, characterized in that the dividing surface (2) is formed as a trough in which rotate about an axis a screw helix (7) or Umwälzbleche (8) as thrust members, which circulate the goods on the division surface (2) , wherein the openings are present in so large a number and such geometry that everything passes without solidification through the openings and the Schuljorgane are designed so that no material pressures occur in the material to be treated.