WO2017121694A1 - Method of utilizing a steelworks slag, slag foam and use of a slag foam - Google Patents

Abstract

The present invention relates to a method of utilizing a steelworks slag (1). The method comprises introducing liquid steelworks slag (1) into a reaction vessel (2), moving an introduction device into the steelworks slag (1) present in the reaction vessel (2) such that an exit orifice (4, 4', 4'') of the introduction device (3) is within the steelworks slag (1), and treating the slag by introducing CO2 from the exit orifice (4, 4', 4'') into the liquid steelworks slag (1) by means of the introduction device (3) for provision for a chemical reaction with CaO present in the steelworks slag (1) to give calcium carbonate CaCO3 as a reaction product which forms at least partly in porous, foam-like consistency as slag foam in a slag mixture that forms in the reaction vessel. The method further comprises allowing the slag mixture to cool for conversion to a solid state after the slag treatment has ended. The invention further relates to a slag foam and to a use.

Description

 Method for utilization of a steelworks slag, slag foam and use of a slag foam

The invention relates to a method for utilization of a steelworks slag. Furthermore, the invention relates to a slag foam and a use of a slag foam. Steel mill slag, for example LD slag from the Linz-Donawitz process, is a by-product which inevitably results from steelmaking. Due to its nature, especially with regard to its physical properties, steel mill slag is well suited as a mineral substitute building material and is used in particular in road and earthworks. For example, LD slag is used as an admixture to aggregates for

Surface layers or base courses used in road construction as well as in unbound road construction. Other uses, such as the use of steelworks slags as

Fertilizers or as a water building block, are well known. Such uses are useful and resource-friendly, since a use of industrially produced rocks, such as LD slags, as a building material reduces the need for landfill of considerable masses of steelworks slags and beyond the commercial use of

 Steelworks slags also contribute to the economy of steel production. Despite the large number of currently known and commonly used uses, however, there is still a not insignificant proportion of production-related costs

Steel mill slag not used for further use. This affects in particular LD slags, which are not suitable for use in the construction sector due, among other things, to their lack of volume stability. This leads to a still significant need for capacity for landfill.

The invention is therefore based on the object to develop further ways of harnessing steel mill slag and to provide a corresponding method for harnessing steel mill slag.

The object is achieved by a method for utilization of a steelworks slag having the features of claim 1. Furthermore, the object is achieved with a slag foam according to claim 15. Another aspect of the invention comprises the features of claim 16. Advantageous developments of the invention will become apparent from the dependent claims. The invention relates to a method for utilization of a steelworks slag. The following steps are carried out: Liquid steelworks slag is filled into a reaction vessel. A

 Injection device is moved into the steelworks slag contained in the reaction vessel, so that an outlet opening of the introduction device in the

 Steel mill slag is located. Slag treatment is carried out by means of the introduction device from the outlet opening out C02 in the liquid

 Steelwork slag is introduced into it. The introduction of the C02 into the

 Steelworks slag results in providing the CO 2 for a chemical reaction with CaO contained in the steel mill slag to the calcium carbonate CaCO 3 as a reaction product that forms in a slag mixture forming in the reaction vessel at least partially in a porous, foamy consistency as slagstock.

After completion of the slag treatment, the slag mixture is allowed to cool to a solid state.

The liquid steelworks slag is introduced into the reaction vessel to the

Steel slag to have largely separated from liquid steel components. As a result, the desired slag treatment is only possible because that from the

Outlet opening into the molten steel slag initiated C02, also referred to as carbon dioxide, completely or at least substantially completely for reactions with in the

Steel slag is made available to existing reactants and does not undergo reactions with constituents of steel.

Steel mill slag is the non-metallic melt produced during the production of steel and consists predominantly of different oxides of the minerals used, which are also referred to as slag formers. Large shares of

Steel mill slag consists of SiO 2, Fe 2 O 3 and CaO. Furthermore, there are several

Transition metal oxides. The CaO content in the steel mill slag is approximately 45% by mass in the example of the LD slag. The proportion of CaO, which is present in the unbound state, especially in unhydrogenated state, is also referred to as free lime or sometimes as quicklime. This free lime is often abbreviated, as in the following, with CaO free. In typical steelworks slag, as currently results from the implementation of the LD process in German steelworks, CaO-free is typically present in a mass fraction in the range 8-10% by mass. Depending on the mode of operation of the steel mill, however, up to 15% by mass of CaO-free may also be contained in the LD slag. If the formula CaO is used in the following, the proportion CaO-free should also be included. With the introduction of C02 into the steelworks slag C02 is available as a reaction partner. In particular, due to the high oxygen affinity of the calcium, a reaction takes place until a saturation threshold is reached

CaO + CO 2 CaCO 3. From lime, CaO, after the addition of CO 2, the calcium carbonate CaCO 3 is formed. Because of the CaO free present in the unbound state, a reaction of the CaO free with CO 2 to the reaction product CaCO 3 according to the above reaction equation preferably takes place. The steel mill slag which is the basis of the process and which is filled into the reaction vessel thus forms together with the CO 2 and optionally further reaction products in the

Steel mill slag existing components, especially with C02, a

carbonate-enriched, in particular caicium carbonate enriched, slag mixture. As a result of the reaction of the gaseous CO 2 with conversion into the CaCO 3, a constituent of the slag mixture with a porous, foam-like consistency develops at the degassing zone, ie the interface between the outlet opening and the slag mixture. CaCO 3 is therefore present in the slag mixture at least partially in a porous, foam-like consistency, so it is at least partially present as slag foam. This present in porous, foam-like consistency CaC03 and optionally present in porous and foamy consistency present proportions of the slag mixture thus form a total of a present in porous and foam-like consistency portion of the slag mixture; this proportion is also referred to as slag foam in the context of this invention. Of the

 Slag foam may include exclusively or almost exclusively the reaction product CaCO 3. However, the slag foam can also comprise steelworks slag enriched with the reaction product CaCO 3, carbonates enriched or chemically combined with further constituents from the steelworks slag, or else a mixture thereof. Last but not least, the slag mixture can of course also other

 Reaction products, in particular from components of steel mill slag and C02 include.

The fact that CaCo3 forms in its porous, foam-like consistency as slag foam, so that forms a slag foam, which in addition to CaCo3 also has other ingredients. The term slag foam is merely a term describing the porous, foamy consistency.

The fact that CaCO 3 forms as slag foam can be understood in one embodiment such that at least 30% by mass of the slag foam consists of CaCO 3. The fact that CaCO 3 forms as slag foam can be understood in one embodiment such that at least 50% by mass of the slag foam consists of CaCO 3.

Depending on which additional constituents of the steelworks slag or reaction products of the steelworks slag, in particular with the introduced CO 2, are likewise present in a porous, foam-like consistency, less than 30% of the slag foam may also consist of CaCO 3.

Upon completion of the introduction of CO 2 into the slag mixture, cooling of the slag mixture to ambient temperature is effected to allow the slag foam to be provided in a solid state and hence its optionally desired reuse.

As a result of the high oxygen affinity of the calcium and the unbounded presence of the CaO free with its opposite to all or - depending on the composition of

Steel mill slag - compared to a large part of the remaining components of the

Steel mill slag with a tendency to react with CO 2, the described method achieves a significant reduction of the proportion of CaO-free in the treated steelworks slag compared to its original composition. Since CaO-free classified as a hazardous material and above certain thresholds further use of CaOfrei containing materials for reasons of environmental protection and / or health protection may be difficult or prohibited, this reduction in the proportion of CaOfrei represents a further advantage of the development described The reduction in the proportion of CaO free as a result of the reaction with CO 2 is the avoidance of volume shrinkage that occurs with CaO free as a result of hydration and therefore CaO free containing substances (eg LD slag) for many applications, for example in the construction sector , are unsuitable. The resulting slag foam, however, has a very good volume stability, which is very advantageous for use, for example, in the higher-quality construction sector.

Furthermore, the slag foam produced in the solid state can be further

Be used for purposes. As a volume-stable solid with a porous structure, slag foam can be used not only for traditional transport infrastructure but also for use as an innovative building material, in particular as a building material with a heat-insulating function, ie as a filler or insulating material, the latter also referred to as an insulating material, or as an aggregate for concrete , This aspect of the further utilization of the original LD steel mill slag is particularly advantageous with regard to a cost-effectiveness of the method. Another advantageous aspect is that over the above Reaction C02 in a solid, namely in particular the solid state in the solidified CaC03, is bound in the slag mixture. In a

theoretical calculation shows that 44.01 g CO 2 / (mol CaCO 3) can be bound; 1000 kg of CaCO 3 thus allow a binding of about 440 kg CO 2. In other

Processes, for example in the steel production, freed C02 can thus be bound by means of the described method for slag treatment. This has the advantage that CO 2 is removed from the atmosphere. Regardless of its further use, the advantage for the C02 content of the atmosphere is that industrial CO 2 releases are compensated for because the bond of CO 2 is present in the solid state

Slag foam can be done in a lasting and safer way. This type of C02 definition can thus be used, for example, to support the efforts of the steel industry

Support decarbonization and thus be an important contribution to climate protection. A product resulting from the slag treatment, in particular the volume-stable or substantially volume-stable, CaC03-containing slag foam, can be used, for example, in the construction sector. With further use of the slag foam, for example in the above-mentioned use as a building material, the binding of the C02 is an additional advantage, with appropriate marketing, especially against the background of

In Germany, the control of C02 emissions by means of correspondingly obtained C02 allowances will advantageously contribute in addition to the economy of steel production.

According to an advantageous embodiment of the method can be provided that the introduction device has a refractory lance, with the C02 is introduced in the immersion lance method in the liquid steel mill slag. The use of the refractory lance has the advantage that such are readily available due to the customary use of refractory lances in steelmaking. For the same reason, there is a great deal of experience in the use of a refractory lance, which can be used.

According to a development of the method, it is provided that the outlet opening of the introduction device is positioned in a lower third of the reaction container and / or that the introduction device has a plurality of outlet openings, which are arranged offset from each other locally over a cross section of the reaction container. The

Positioning the outlet opening in the lower third of the reaction vessel has the advantageous effect that the CO2 introduced into the steelworks slag in the form of a gas caused by its upward movement is supplied to a large part of the CaO contained in the steelworks slag as a potential reactant. The Such an embodiment that a plurality of outlet openings is provided on the introduction device has the advantage that a more homogeneous distribution of the CO 2 takes place for the provision as a reaction partner, in particular for the CaO contained in the steelworks slag. As appropriate, for example, over the cross section of

Reaction vessel made locally offset arrangement of

 To see outlet openings. Thus, for example, a ring tube may be provided, which is arranged at one end of the introducer and the distributed along its circumference provides outlet openings.

To further homogenize the local distribution of a reaction of C02 with

To achieve constituents of the steelworks slag, in particular with CaO present in the steelworks slag, can be provided in an advantageous development of the invention that the outlet opening is moved during the slag treatment. Preferably, the movement takes place along closed loops, which have both a vertical and a horizontal component of movement. Additionally or alternatively, it can be provided that a stirrer is arranged in the reaction vessel.

As an alternative or additional measure for promoting the maximum possible supply of CO 2 to suitable reactants present in the steel mill slag, according to a further development of the method it can be provided that a flux is supplied to the steelworks slag before the slag treatment and / or during the slag treatment. The flux reduces the viscosity of the steelworks slag and promotes diffusion of CO 2 through the steelworks slag, making it easier to obtain more reaction sites for the CO 2. As a flux, for example, fluorspar can be provided.

In one embodiment of the invention it can be provided that during the

Slag treatment is carried out an active cooling of the slag mixture to dissipate heat of reaction. Since the formation of CaCO 3 from the reaction of CaO with CO 2 takes place in an exothermic reaction, the removal of heat of reaction is advantageous in order to accomplish a controlled procedure of the process.

Thus, on the one hand, a failure of the reaction vessel can be avoided. Furthermore, an optimum reaction temperature can also be set. It does not have to be

necessarily be provided that the active cooling takes place during the entire process of introduction of CO 2, but it can also be done only temporarily during the introduction of CO 2, the active cooling. For the already mentioned active cooling of the slag mixture, heat of reaction is preferably removed by means of a heat exchanger arranged on the reaction vessel wall. For example, the reaction container wall can be double-walled and have a cavity in which a heat exchanger arrangement is arranged. The heat exchanger can be used advantageously for heat recovery.

For active control of the method sequence, it can be provided according to an exemplary development that the method is regulated with a CO 2 flow rate as a manipulated variable. In particular, the CO 2 flow can be regulated by the entirety of the outlet openings of the introduction device. The C02 flow can be used in a particularly advantageous manner as a manipulated variable, since the provision of C02 for in the

 Slag mixture reactions react largely directly to changes in the CO 2 flow. On the other hand, other possible manipulated variables, such as

Changing a heat removal rate or the change of the slag mixture, provided with higher inertia in the change of the corresponding control variables, but this does not speak against their alternative or additional use with a suitable design.

In one embodiment of the method, a temperature of the slag mixture may be a

Be controlled variable. In particular, it can be provided that the control takes place with a setpoint for the temperature, wherein the setpoint for the temperature is in the range between 500 and 900 degrees Celsius. Preferably, the set point for the temperature is in the range between 600 degrees Celsius and 800 degrees Celsius. Particularly preferably, the desired value for the

 Temperature in the range between 650 degrees Celsius and 750 degrees Celsius. The setpoint for the temperature in the range between 650 degrees Celsius and 750 degrees Celsius represents a particularly advantageous compromise between the highest possible C02 determination, which takes place at about 650 degrees Celsius, and sufficiently low viscosity of the

Steel mill slag, which is at about 750 degrees Celsius. With decreasing temperature, the viscosity of the steel mill slag increases with the side effect that an efficient supply of CO 2 for the reaction with constituents of the slag, in particular CaO, increasingly difficult. As the temperature continues to fall, there is the danger of reaching a threshold value at which the slag mixture or at least constituents and in particular already formed CaCO 3 convert into their solid state, which would make it impossible to further react and carry out the process without increasing the temperature of the slag mixture. This threshold is around 500 degrees Celsius. At temperatures above 850 degrees Celsius, the carbonates formed, or in any case present in the slag mixture, in particular calcium carbonates, are increasingly dissolved and it becomes CO 2 submit. At too high a temperature, in particular above 900 degrees Celsius, the chemical stability of CaC03 decreases, before a further increase in temperature reaches a threshold at which no new formation of CaCO3 takes place or even a dissolution of CaCO3 occurs. A rapid cooling to a temperature below 600 degrees Celsius after C02 treatment supports sustainable fixation in the slag matrix. The use of set points located in the abovementioned temperature ranges leads to avoidance of these explained effects and consequently results in a particularly advantageous implementation of the described method.

In a development of the method it can be provided that a viscosity of the

Slag mixture is a controlled variable. With the use of the viscosity as a controlled variable, a process control within parameters can be achieved directly, which were already explained in connection with the use of temperature as a control variable. The value of the viscosity actually used as a controlled variable is empirically in knowledge of the given framework conditions, in particular the composition of the used

Steelworks slag, to be determined before carrying out the process.

Furthermore, a multi-dimensional control, in particular using at least two controlled variables and / or at least two manipulated variables can be provided.

It can be provided according to an advantageous development of the method, that a monitoring of a prevailing in the reaction vessel pressure takes place, and that takes place when reaching a limit pressure, an automatic shutdown of the introduction of C02 in the steel mill slag inside. In particular, monitoring of an absolute pressure above the surface of the slag mixture can be provided. Monitoring the pressure leads to the advantage that failure of the protective housing is avoided. A further advantage is that an uncontrolled escape of CO 2 from the reaction vessel due to the shutdown of the introduction of CO 2 is effectively avoided. Furthermore, the increase in absolute pressure indicates increasing CO 2 saturation of the slag mixture with the benefit of further control and the ability to control and / or regulate the introduction of CO 2 into the steelworks slag. In order to avoid an uncontrolled escape of CO 2 outside of the steelworks slag or outside of the slag mixture during extension and retraction of the lance, it may further be provided that after moving the introducer into the steelworks slag into a rinsing of

Einleitevorrichtung with a, preferably inert, purge gas, such as nitrogen, takes place. For an optimization of the throughput of the transformation of steel mill slag into reaction products, in particular in CaC03, can according to another advantageous

Be provided design that the reaction vessel is a first of two

Reaction vessels is that already during the slag treatment the second

Reaction vessel is filled with steel mill slag, and that a second introduction device is moved into the steelworks slag contained in the second reaction vessel to a slag treatment in the second during or immediately after the slag treatment of the steelworks slag located in the first reaction vessel

Reaction vessel slag to begin. In particular, an LD slag can be used as the steelworks slag. Due to the predominant application of the LD process for steelmaking LD slag is produced in large quantities, which on the one hand, the need for re-use of LD slag is given, which on the other can also be expected to have particularly positive effects on the economics of the described method. Because of the comparatively high proportion of CaO-free on the LD slag of up to about 15% by mass, the method explained is particularly suitable with regard to the desired formation of CaCO 3 and the associated permanent bonding of CO 2.

A further aspect of the invention relates to solid state slag foam, which is prepared by the method described, and which is claimed separately as such. A further aspect of the invention relates to a use of the solid state slag foam, which is produced according to the described method as a filling material,

Concrete aggregate and / or insulating material. Generally, a use can be provided as a diverse building material.

In the following, a concrete embodiment of the invention will be explained in more detail with reference to the figure. The figure and accompanying description of the resulting features are not intended to be limiting to the particular embodiment, but serve to illustrate an example embodiment. Furthermore, the respective features may be used among each other as well as with features of the above description for possible further developments and improvements of the invention, especially in additional embodiments, which are not shown.

It shows Fig. 1: An exemplary arrangement of a device by means of which an implementation of the method according to the invention can be carried out and will be explained below.

FIG. 1 shows a reaction vessel 2 in which a steel mill slag 1 has already been filled. In the steelworks slag 2 is a refractory lance 5 is located, which is part of an introduction device 3. The refractory lance 5 is connected via a gas line 6 to a C02 container 10. The refractory lance 5, in addition to an outlet 4 still the

In the embodiment shown, each of the outlet openings 4, 4 ', 4 "is positioned in a lower third of the reaction vessel 2. At a filling level of the filling container 2, which corresponds to the maximum filling level, this ensures that, when CO 2 is introduced from the outlet openings 4, 4 ', 4 ", a high proportion of the steelworks slag contained in the reaction container 2 acts as a reaction partner for the CO 2 In the embodiment shown, the outlet openings 4 'and 4 "are concentrically positioned about the longitudinal axis of the refractory lance 5, so that in the positioning of the refractory lance 5 shown a distribution of the outlet openings 4, 4', 4" in spatial offset from each other over the Cross section of the reaction vessel 2 is present

Reaction vessel is housed in a protective housing 9, to escape from

Reaction products and / or C02 in the environment to avoid. In this constellation, in addition to a desired protection of the environment, including surrounding living beings, it is also possible to monitor a pressure in the protective housing 9. Thus, it is provided that a switch-off of the introduction of CO 2 into the steelworks slag takes place by means of a pressure gauge when a threshold value critical for the integrity of the protective housing 9 is exceeded. For the replacement of degraded due to their heavy load refractory lances Wechsellanzen 7 are available, against which the previously used refractory lance 5 by means of a changing device 8 is replaceable if necessary.

Claims

claims Method for utilization of a steelworks slag (1), characterized in that liquid steelworks slag (1) is filled into a reaction vessel (2), an introduction device is moved into the steelworks slag (1) located in the reaction vessel (2), so that an outlet opening ( 4, 4 ', 4 ") of the introduction device (3) in the steel mill slag (1) is located, and that a slag treatment takes place by means of the introduction device (3) from the outlet opening (4, 4', 4") out C02 in the molten steelworks slag (1) is introduced into the calcium carbonate CaCO 3 to provide a chemical reaction with CaO contained in the steel mill slag (1) as a reaction product which is at least partially porous in a slag mixture forming in the reaction vessel (2); foam-like consistency forms as slag foam, and that after completion of the slag treatment, the slag mixture for conversion i n is allowed to cool a solid state. A method according to claim 1, characterized in that the introduction device (3) comprises a refractory lance (5), with which the CO 2 is introduced by immersion lancing method in the liquid steel mill slag (1). A method according to claim 2, characterized in that the outlet opening (4, 4 ', 4 ") of the introducer (3) is positioned in a lower third of the reaction container (2) and / or that the introducer (3) has a plurality of  Outlet openings (4, 4 ', 4 "), which are arranged over a cross section of the reaction vessel (2) locally offset from each other. Method according to one of the preceding claims, characterized in that the outlet opening during the slag treatment is moved to homogenize the reaction of CO 2 with CaO contained in the steel mill slag (1), preferably the movement takes place along closed loops, both vertical and vertical have horizontal movement component. 5. The method according to any one of the preceding claims, characterized in that the steelworks slag (1) before the slag treatment and / or during Schlackebenhandlung a flux, such as fluorspar, is supplied to reduce the viscosity and to promote a diffusion of C02 by the  Steel mill slag (1) to facilitate the achievement of reaction sites. 6. The method according to any one of the preceding claims, characterized in that takes place during the slag treatment for dissipating the reaction heat, an active cooling of the slag mixture. 7. The method according to claim 6, characterized in that for active cooling  Heat of reaction by means of a arranged on the reaction vessel wall  Heat exchanger is discharged. 8. The method according to any one of the preceding claims, characterized in that the method is controlled with a CO 2 flow as a manipulated variable. 9. The method according to claim 8, characterized in that a temperature of  Slag mixture is a controlled variable, which is controlled to a target value for the temperature, wherein the target value for the temperature in the range between 500 degrees Celsius and 900 degrees Celsius, preferably between 600 degrees Celsius and 800 degrees Celsius, more preferably between 650 degrees Celsius and 750 degrees Celsius. 10. The method according to claim 8 or claim 9, characterized in that a viscosity of the slag mixture is a controlled variable. 11. The method according to any one of the preceding claims, characterized in that a monitoring in the reaction vessel (2) prevailing pressure takes place and that upon reaching a limit pressure, an automatic shutdown of the introduction of C02 in the steel mill slag (1) takes place. 12. The method according to any one of the preceding claims, characterized in that prior to moving the introducer (3) into the steelworks slag (1) into a rinsing of the introducer (3) is carried out with a purge gas. 13. The method according to any one of the preceding claims, characterized in that the reaction vessel (2) is a first reaction vessel of at least two Reaction vessels is, and that already during the slag treatment in the first reaction vessel (2) located steel mill slag a second reaction vessel with steel mill slag (1) is filled, and that a second  Introduction device (3) is moved into the steelworks slag (1) located in the second reaction vessel, in order to still during or immediately after the  Slag treatment located in the first reaction vessel  Steelwork slag (1) with a slag treatment in the second  Reaction vessel slag to begin. Method according to one of the preceding claims, characterized in that the steel mill slag (1) is an LD slag. Slack foam present in the solid state, produced by a process according to one of Claims 1 to 14. 16. Use of a solid state slag foam, prepared by a method according to one of claims 1 to 14, as a filler, concrete aggregate and / or insulating material.