WO2002070423A1

WO2002070423A1 - Method of producing an additive for mixed cements and device for carrying out said method

Info

Publication number: WO2002070423A1
Application number: PCT/AT2002/000043
Authority: WO
Inventors: Alfred Edlinger
Original assignee: Tribovent Verfahrensentwicklung Gmbh
Priority date: 2001-02-06
Filing date: 2002-02-06
Publication date: 2002-09-12
Also published as: EP1360158A1; AT409860B; ATA1862001A

Abstract

The invention relates to a method of producing an additive for mixed cements that have good early strength. To this end, raw material is selected from the group comprising building rubble, waste glass, argil, marl, waste fireproof material, flue ash from power stations, waste pyrolysates, slags from non-ferrous industry and steel production, asbestos cement or asbestos sheets or fibers, harbor sludge, excavated material from mines, alkali-containing clinker furnace bypass dusts and/or washing sludge from gravel extraction are melted in a melting cyclone and are then subjected to granulation, thereby producing a vitreous product.

Description

Process for producing an admixture for mixed cements and device for carrying out this process

The invention relates to a method for producing an admixture for mixed cements with good early strength and to an apparatus for performing this method.

Debris, building rubble and, in particular, components containing asbestos fibers that occur during the demolition of buildings have so far generally been used. Attempts to process such materials in a rotary kiln during clinker production mostly fail because extremely fine-grained or dust-like components cannot be incorporated, but rather pass through a rotary kiln with the burner exhaust gases unhindered. This applies in particular to Eternit waste or crushed demolition material that contained asbestos fibers as a coating or as plates.

The invention now aims to bring such construction demolition material and large quantities of washing sludge from gravel extraction and in particular also old refractory material to an economical use and aims in particular to create an admixture for mixed cements, which can also be used when large amounts of such Admixtures result in advantageous product properties and in particular an improved early strength.

To solve this problem, he method according to the invention consists essentially in that raw material selected from the group of rubble, waste glass, clay, marl, waste material, power plant fly ash, waste pyrolyzates, slags from non-ferrous metallurgy and steel production, Eternit or asbestos panels or -fibers, harbor sludge, mining abrau, alkali-containing clinker furnace bypass dusts and / or washing sludge from the gravel extraction are melted in a melting cyclone and then subjected to granulation to form a glassy product. The use of a melting Cyclones also allow extremely fine-grained and dusty constituents to be incorporated directly into the melt, in particular asbestos waste being rapidly adsorbed on the sticky surface of the melt particles and thus being able to be safely removed from the exhaust gas stream of the melt cyclone. Dust-like and very fine-grained particles can thus be incorporated and used in the melt in a melt cyclone of this type, comparable to a wet dust wash. In contrast, the use of such fine dust in the clinker furnace would lead to an excessive load on the burner exhaust gases from the clinker furnace. Because the melted particles are now subjected to granulation to form a glassy product, a glassy binder with a glass content of over 95% by weight can surprisingly be obtained, the use of which as an admixture in composite cements or mixed cements also in amounts of up to 50% by weight surprisingly gives early strength values which are significantly higher than comparison values with good blast furnace slag. Already the melted rubble fraction results in an excellent synthetic pozzolana, low in heavy metals, which can be activated very well. With a fineness of 4900 m ^ / g according to Blaine, in a mixture of 22% by weight pozzolana, 42% by weight of the admixture that can be produced according to the invention, 2% by weight of gypsum and residual clinker, compressive strength values of 6 N / m ^ after 2 days , after 7 days of 18 N / mm2 and after 28 days of 46 N / mm ^. Instead of puzzolans, ground waste glass could also be used. Such high early strength values are surprising compared to other admixtures, such as blast furnace slag, whereby the process according to the invention is characterized by particularly low specific CO 2 emissions due to the considerably lower calcination effort and low heat consumption, since the exothermic enthalpy of fusion, ie the heat of neutralization of CaO and SiO 2 can be used and a surprisingly good grindability after the glazing could be determined during the granulation with little energy expenditure. The raw material melt is produced from a mixture whose basicity (CaO / Siθ2) is between 0.3 and 1.2, the Al2O3 content to 2 to 11% by weight, the total a2θ + K2O to 0.5 to 3% by weight , the MgO content was set at 3 to 15% by weight and the Fe 2 O 3 content was set at 1 to 4.5% by weight, such a mixture being able to be obtained either by suitable selection from the proposed raw materials, or directly, for example, in the composition corresponds to usual washing sludge from gravel extraction.

Advantageously, the inventive method is performed so that the melt is melted under pressure seal and is blown into the melting cyclone hot blast at temperatures of between 600 ° C and 1200 ° C, wherein slag temperatures are achieved in the order of about 1450 ^q C before the granulation.

In order to enable a quick and safe melting using the exothermic enthalpy of fusion, the procedure is advantageously that the raw material is used comminuted to a maximum grain size of d _a χ = 2 mm. The melt can be granulated in any manner, with fine porous material having excellent grindability being obtained when using boiling water granulation. However, the molten material can also be granulated, for example, with 2.5 Nm.3 air per kg of melt, the material being obtained in both cases due to the low basicity when using washing sludge from the gravel extraction, X-ray amorphous and practically 100% glazed. In the case of a basicity C / S of> 0.7, however, air granulation is not suitable in order to achieve the desired fineness and grain size.

The process is advantageously carried out in such a way that the melt from the melting cyclone into a slag tundish or

Introduced beforehand and fed to the granulation from this, in such a slag tundish or forehearth if necessary, correction substances can be added and further material with a lower melting point can be melted.

The device according to the invention for carrying out this method is essentially a melting cyclone or a suspended gas melter, the head of which is pressure-tightly connected to a cyclone separator via a suspended gas heat exchanger or a fluidized bed reactor and its discharge opening for the melt, with the melting cyclone or Floating-gas melter lines for blowing in granular raw material and hot wind are connected. The melting cyclone or floating gas melter allows the safe incorporation of very fine dust or materials that can be easily conveyed in the gas flow, whereby the use of a floating gas heat exchanger at the top of the melting cyclone further increases the proportion of solids that is actually melted in the melting cyclone. The arrangement of a suspended gas heat exchanger or a fluidized bed reactor also enables the waste heat of the process to be used further, the total heat balance being able to be improved by supplying combustion air into the riser pipe of the suspended gas heat exchanger or into the fluidized bed of the fluidized bed reactor. For example, the fine fraction of building rubble (d <8 mm) contains up to 18% of combustible constituents, so that there is optimal burnout in the fluidized bed. In this case, the coarse fraction of the rubble can be used as a substitute for gravel in the concrete.

With a corresponding maximum grain size of about 2 mm, the feed material can be blown into the melting cyclone in a simple manner, wherein temperatures of about 1500 ° C. can be achieved in the melting cyclone. The additional use of a cyclone separator allows oversize particles to be circulated, the design advantageously being such that the cyclone separator opens a discharge lock for coarse particles. points, which is connected to the melting cyclone via a recirculation line. The amount of gas drawn off from the cyclone separator can advantageously be cleaned in a simple manner, the device according to the invention advantageously being developed in such a way that the gas space of the cyclone separator is connected to a fine dust filter and that the fine dust separated in the fine dust filter is connected to the hot wind pipe of the Melt cyclone connectable discharge line is connected. The material accumulating in the fine dust filter can, with appropriate dimensioning of the suspended gas heat exchanger and design of the cyclone separator depending on the selected feedstocks, result in fine dust, which is composed to a large extent of chlorides or sulfur compounds, so that it is possible to provide a corresponding bypass and to oversupply them Remove materials from the circuit. In principle, the fine dust from the fine dust filter can also be returned to the melting cyclone together with the hot wind, so that the solids can be almost completely recycled and a safe exhaust gas is formed.

The granulation itself can be carried out by any known method, and in addition to boiling water granulation and granulation with cold air, granulation with steam or cold water can also be carried out here in order to ensure correspondingly high glazing.

The invention is explained in more detail below using a process example.

Washing sludge from the gravel extraction was dried, calcined and slagged directly without further additives. The 1450 ° C hot slag was quenched in a boiling water granulation to fine porous material with excellent grindability. Another portion of the molten hot slag was granulated with 2.5 Nm ^ air per kg of melt. The chemical composition of the slag showed the following directional analysis:

Due to the low C / S basicity, the material solidified in both cases, X-ray amorphous and practically 100% glass-like.

Composite cements were subsequently produced with the product obtained, which was ground to a Blaine fineness of 4900 cm / g, for which 38 KWh / t were used, ie mixtures of the material obtained, pozzolans and / or ground waste glass, clinker and Plaster. The samples for the strength tests were produced according to EN 196-1 with a water / cement ratio of 0.5. The composition examined had a content of 22% by weight pozzolana, 42% by weight of the vitrified process product, 2% by weight of gypsum and the rest of the clinker. With such a composite cement was after 2 days a compressive strength of 6 N / mm ² after 7 days 18 N / mm ² after 28 days and 46 N / mm ² measured, and it was therefore found a high early strength.

The product of the process reacted both pozzolanically and hydraulically, with sulfate excitation with higher gypsum proportions also being possible with AI2O3 contents of over 5% by weight, whereby the clinker proportion can be further reduced. The invention is further explained below with reference to an example of a device suitable for carrying out the method according to the invention, which is shown schematically in the drawing. 1 shows a first embodiment of the device according to the invention and FIG. 2 shows a detail of FIG. 1 in a modified embodiment.

In Fig. 1, 1 denotes a melting cyclone onto which raw material is charged via lines 2 and 3, respectively. ^■ on the line 4, and fuel delivery air is supplied, the supply of the raw material in the head 5 of the melting cyclone 1, or can be done in a processor coupled to the head 5 suspended gas heat exchanger 6 according to the type of the raw material. The maximum grain size of the raw material is 2 mm.

A cyclone separator 7 connects to the suspended gas heat exchanger 6, from which oversize particles can be discharged via line 9 via a lock 8 and introduced into a hot wind line 10. The hot wind line for the hot wind with temperatures between 600 ° and 1200 ° C is in turn connected to the head region 5 of the melting cyclone 1, hot wind being used as a transport medium for the coarse particles fed via the line 9.

From., The cyclone separator 11 gas is discharged via a line and fed to a fine dust filter 12. The cleaned exhaust gas can be withdrawn via line 13 at temperatures of approximately 300 ° C. Dust is discharged from the fine dust filter via the lock 14 into a line 15, which in turn can be connected to the hot wind line 10. If large amounts of chloride-containing or sulfur-containing material are obtained, the possibility can additionally be provided of a corresponding bypass, for which purpose a line 16 is arranged for the discharge of such excess amounts into a collecting container 17. The melt of the melting cyclone passes into a tundish 18, the mouth of the melting cyclone opening below the bath surface 19 of the melt in the tundish 18, so that a pressure-tight closure is ensured. The discharge opening for the melt 20 can be closed with a conventional stopper 21, which can be moved vertically in the direction of the double arrow 22, and opens into a granulator, indicated schematically by 23. An air granulator, for example that from Austrian application A403 / 2001, can advantageously also be used as the granulator, in which case the hot air can be recirculated as combustion air. The granulate can be discharged from the granulator via a chute 24 into a corresponding collecting container 25. The slag tundish can be heated in any way and used as a forehearth. The granulator 23 can be designed in any way, and in addition to boiling water granulation or cold water granulation, it can also be granulated with cold air or steam. The material drawn off via the chute 24 has a glass content of over 95% by weight. When using washing sludge from the gravel extraction, a specific heat consumption of approx. 2.7 MJ / kg granulate was determined.

2 shows a melting cyclone 1, on which raw material is charged via lines 2 and 3. Fuel and hot wind are also supplied via line 3, depending on the nature of the raw material, the raw material can be fed into the melting cyclone 1 or into a fluidized bed reactor 26 connected to the top of the melting cyclone 1. A line 27 for the supply of combustion air is connected to the fluidized bed reactor 26, so that the overall heat balance can be improved by burning the combustible components contained in the raw material. A cyclone separator 7 in turn connects to the fluidized bed reactor 26, from which oversize particles are discharged via line 9 via a lock 8 and can be fed to the fluidized bed reactor 26 or the melting cyclone 1. Analogously to the design according to FIG. 1, gas can be discharged from the cyclone separator via a line 11 and fed to a further filtering.

If steel slag is used for C / S correction, the Cr (chromium) contained in it can be incorporated in the spinel ("magnetite") formed by an oxidation process in the slag tundish so that it is resistant to leaching. However, the magnetite can also be magnetically removed from the slag dust after the slag grinding process or micro-granulation.

The waste heat from the hot gases can, if desired, be recovered, and the energy consumption can be reduced if asphalt from road demolition material is used. The asphalt can advantageously be introduced as fuel into the fluidized bed. In this case it is also possible to mix asphalt with waste oils, waste solvents, heavy and medium-sized heating oil derivatives or oil refinery residues from petroleum distillation. The asphalt can, however, also be introduced into a gasifying fluidized bed, producing hot exhaust gas which is rich in H2 / CO and which can be partly supplied to the melting cyclone as fuel. The excess energy can be used for drying or preheating the raw material.

Claims

claims:

1. A process for producing an admixture for mixed cements with good early strength, characterized in that raw material selected from the group of rubble, waste glass, clay, marl, refractory material, power plant fly ash, waste pyrolyzates, slags from non-ferrous metallurgy and steel production, Eternit- or Asbestos slabs or fibers, harbor sludge, mine spoil, alkali-containing clinker furnace bypass dusts and / or washing sludge from the gravel extraction are melted in a melting cyclone, the raw material melt being produced from a mixture whose basicity (CaO / Si02) is between 0.3 and 1,2, the Al2θ3 content to 2 to 11% by weight, the total Na2θ + K2O to 0.5 to 3% by weight, the MgO content to 3 to 15% by weight and the Fe2θ3 ~ content to 1 to 4.5% by weight were set and that the raw material melt is then subjected to granulation to form a glassy product.

2. The method according to claim 1, characterized in that the melt is melted under pressure closure and is blown into the melting cyclone hot wind at temperatures between 600 ° C and 1200 ° C.

3. The method according to claim 1 or 2, characterized in that the raw material is crushed to a maximum grain size of d _m ax = 2mm.

4. The method according to any one of claims 1, 2 or 3, characterized in that the melt from the melting cyclone in one

Slag tundish or forehearth is introduced and from this is fed to the granulation.

5. Device for performing the method according to one of claims 1 to 4, characterized "by a melting cyclone or a suspended gas melter (1), the head (5) of a suspended gas heat exchanger (6) or a fluidized bed reactor with a cyclone separator (7) and its discharge opening for the melt (20) with a tundish (18) or forehearth is connected pressure-tight, with lines (2, 3, 4) for the Blowing in granular raw material and hot wind are connected.

6. The device according to claim 5, characterized in that the cyclone separator (7) has a discharge lock (8) for coarse grain, which is connected via a recirculation line (10) with the melting cyclone (1).

7. Device according to one of claims 1 to 6, characterized in that the gas space of the cyclone separator (7) is connected to a fine dust filter (12) and that the fine dust separated in the fine dust filter (12) with a with the hot wind pipe (10) of the discharge line (15) which can be connected to the melting cyclone (1).