SK58495A3 - Process for making steel and hydraulically active binders - Google Patents

Abstract

The process for making steel and hydraulically active binders uses slags rich in iron oxide, such as steel slag of amount 5 % wt. of included slags, as oxidizing agent for carbon in pig iron. The slag is reduced, yielding a type of blast furnace slag with improved hydraulic properties.

Description

Technical field

The invention relates to a process for the production of steel and hydraulically active binders, such as e.g. blast furnace slag, clinker or similar.

BACKGROUND OF THE INVENTION

Steel production results in a steel slag having a relatively high iron oxide content caused by the forging process. Conventional steel slag contains MnO and FeO in amounts up to 33% by weight.

While the blast furnace slag has favorable hydraulic properties and due to the very low amount of ferrous oxide, its recovery as a basic building material is better, the removal of the steel mill slag causes additional difficulties because the steel mill slag is not in the formed composition, i. without additional metallurgical treatment, usable for construction or similar purposes. It was proposed to pellet the steelworks slag together with the blast furnace slag and to use it as a bulk material in road construction. Relatively high CaO content in the slag of steel mills, however, only permits the use of a limited amount of slag in the steel mills.

The metallurgical treatment of the slag of steel mills to obtain a high-value product is generally associated with high energy consumption and thus becomes uneconomical.

However, slags with a relatively high iron oxide content are also formed in other metallurgical processes or in combustion methods. In particular, it is known that Cu-converter slags often have a ferrous oxide content of over 50 percent, and slags from the incineration of waste, respectively, are also known. debris having a relatively high iron oxide content.

SUMMARY OF THE INVENTION

The invention relates to the treatment of the slag of a steel plant or to a slag. slags with a relatively high iron oxide content of the kind mentioned, immediately in the steel mill, into a better valuable end product, namely converting the slags into a hydraulically active binder. It is an object of the invention that pig iron is scaled by replenishing iron oxide in an amount above 5 percent by weight containing slags, such as e.g. steelworks slag, Cu-converter slag after reaction with lead bath or oxidizing slag from waste incineration plants. This process utilizes a high iron oxide content flowing from the slag and e.g. and steelworks slags to melt the flowing iron, which has a relatively high carbon and silicon content. Basically, iron oxide reacts with carbon or carbon monoxide. with iron carbide to form iron and carbon monoxide, whereby the iron oxide of the slag together with the silicon bath of the pig iron reacts to iron and SiC. These reactions are partially exothermic so that a high degree of economy is achieved. By reducing the iron oxide content in the slag of the steelworks, a different analysis is achieved with respect to the original analysis, which results in significantly more favorable hydraulic properties. The iron oxide content is used to oxidize the pig iron bath and, for example, in the case of steel mill slag, a reduction of the iron oxide content to less than a third of the original value can be achieved, thereby increasing the amount of other components of the original steel mill slag in their share of the total slag. This results in a new slag composition, which in no way corresponds to the original slag analysis. The new slag composition has a much more favorable hydraulic module and a relatively high alite content. Although the product produced in this way, which may be referred to as cement clinker, does not correspond to standard Portland cement-clinker, a high-grade cement clinker is obtained which is suitable as a favorable base to be mixed with other hydraulic or latent hydraulic elements. The clinker produced in this way is particularly suited to a mixture with pozzolans, and a high 28-day strength can be achieved.

The analogous ideas which have been mentioned above for the slag of the steel mills apply to the Cu-converter slag or to the slag-converter slag.

other slags, and in the case of Cu-converter slag, it must naturally be taken into account that copper, as a harmful element for steel, must not enter the steel. Copper must therefore be deposited in the molten lead, whereby the copper is removed from the slag before the iron is melted. Lead itself is reduced as a result of the reaction of molten iron, whereby iron and lead can be separated in a simple manner, since copper and iron do not form a common solution. Under molten iron respectively. a lead coating is formed by the steel and is cast in these cases of steel and lead.

By the simultaneous acquisition or resp. The recovery of metal fractions also transforms the slag with the addition of lead into a high-value, re-usable product, achieves a considerable economic advantage and can remove slags for which no meaningful use has been found to enable the desired oxidation of the carbon content of the molten iron. It is preferred that the iron oxide content of the slag is chosen to be above 8% by weight, preferably above 10% by weight.

The essence of the basic reactions mentioned in the introduction of how these proceed in molten iron is to maintain a relatively high temperature. Despite a partially exothermic reaction, the desired temperature may decrease due to heat losses, and heat losses can be replaced in a particularly simple manner by means of solution electrodes. Due to its chemical composition, the melt bath can be used in a particularly simple manner as an electrical resistance and an iron melt as a counter electrode. In all cases, for a particularly economical embodiment of the inventive process, and in particular for the desired reactions to take place within a reasonable time to finish, it is desirable that the flowing slag of the steelworks be charged at temperatures above 1550 ° C, preferably 1600 ° C and flowing pig iron 1450 to 1550 ° C, preferably the liquid phases are held together for 3 to 8 hours, especially about 6 hours, at temperatures above 1550 ° C, preferably 1660 ° C to 1800 ° C. The upper limit of 1800 ° C is chosen here with regard to the alite stability upper limit. Pig iron, added as a reducing agent, must be heated to at least 1350 ° C to even allow the formation of alite. The preferred process here assumes the charging of the slag at a steel mill at temperatures above 1550 ° C to ensure optimal phase formation for further use of the slag.

Reducing the iron melt will decrease the iron oxide content in the slag e.g. to about 5% by weight, the process preferably being such that the slag is converted to a clinker phase consisting of 15 to 20% by weight of the liquid phase (aluminates and ferrites) and the clinker phase (minerals, alite belite).

The desired overheating, which results in part from the exothermic reactions of the slag with the pig iron, can be carried out by external heating, the process being preferably conducted such that an electrically heated tipping converter is used as a mixing vessel. A further possibility of providing, in addition to the relatively high iron oxide content in the slag also with an appropriate temperature, is that the slag is kept at a superheat temperature by blowing in or blowing oxygen. In particular, when the slag by blowing oxygen is to be kept at a superheat temperature, the slag melt for reaction with pig iron is preferably between 2 and 8 cm, preferably 2 to 6 cm, ensuring that the slag is free. scaled with oxygen, but not under the liquid iron.

The clinker phase is deposited on the liquid iron, whereby reduced iron droplets from the slag or slag. from the clinker phase, sediment in liquid iron. Since there is a high sedimentation resistance in the clinker phase, it is again advantageous, as mentioned above, to limit the layer thickness to 2 to 6 cm, whereby the metallic iron can be almost completely removed from the slag at a residence time of between 3 and 8 hours.

A further possibility of adjusting the desired slag parameters is to add basic weak ores to the slag to increase the iron oxide content to more than 8% by weight.

Preferably also added CaCO ^, ^ Al ₂ O and / or SiO ₂ as additives. Especially when using such other additives, the waste heat of the process, although sensible also as chemical heat, can serve to preheat the raw material.

In addition to the recovery of copper by means of a lead melt, it is naturally also possible to recover zinc, which is preferably carried out in such a way that, when introducing Cu-converter slags, lead is recovered under the steel melt and zinc condensed from the gas phase.

To supplement the heat loss, an electrically heated rotary converter is preferably used as a mixing vessel.

The iron oxide slag content is reduced correspondingly to the ratio of the amounts of slag to pig iron, while naturally only equilibrium reactions are achieved, so that a complete conversion of the iron oxide content is not conceivable without further. A particularly economical and handy method is obtained when the liquid pig iron is added to the liquid slag phase in a weight ratio ranging from 1: 2 to 1: 3.

The sintered cement clinker can be further processed by conventional technology. Preferably, the reduced slag is fed to a clinker cooling device and a granulating device, the clinker being air cooled in a particularly simple manner in a direct manner.

The forged liquid pig iron, which already corresponds to the composition of the steel, can also be further processed according to known methods.

The invention will be explained in more detail by the following examples.

EXAMPLES

Example 1

0.5 parts by weight of liquid pig iron were added to a portion of the slag of the steel mills while the two phases were kept together at 1660 ° C. The conversion produced 35 g of carbon monoxide corresponding to 28 normoliters per kg of melt. Steel slag has the following composition:

SiO ₂ ^A1 2 8 3 ⁷ °

CaO 45

MgO 5

MnO + FeO 30.5

TiO ₂ 1

Pig iron has the following composition:

Si 4

C 5

Fe 91

After a 6-hour reaction, the analysis of slag and pig iron changed as follows:

Slag analysis (%):

sio ₂ 13 ^A1 ° 2 8.9 CaO 60 MgO 6.4 MnO + FeO 10.5 T10 ₂ 1.3

Steel analysis (%):

Si 0 C 2 Fe 97

The evaluation of slag, which was used as cement clinker, was followed by a common cement-technological evaluation, which had the following values. The following table also lists the typical areas for Portland clinker because of the need for 733 g of pig iron, creating 950 g of steel and 60 g of CO, respectively. 48 normoliters of CO are released. Additionally, 225 g of quartz sand was added to produce the aforementioned target slag. The composition of pig iron and steel is given in the following table:

% pig iron steel

Si 4 0

C 5 1,5

Fe 91 98

The melting point is about 1600 ° C, and a reduction-oxidation time of about 4.5 hours was maintained. The blast furnace slag formed is perfectly usable as a hydraulically active binder. The relevant characteristics were as follows:

Hydraulic index (wedge) = 92% (very good)

Pozzolan (ASTM C 618) = 118% (excellent)

Example 3

When using Cu-slag from the converter, the resulting slag was used with the following chemical analysis:

Major Share (%) Components (%) of component components

sieve ₂ 28 Sat ₃ 0.5 ^A1 ° 2 6 K ₂ 0 0.13 Fe ₂ ° 3 53 At ₂ 0 0.64 CaO 8 tío ₂ 0.36 MgO 2 ^Cr 2 ° 3 1.4 ^ ^η 2θ3 0.35 ^P 2 ° 5 0.27 C-F 1

comparison.

criterion

Value typical area (Portland clinker)

hydraulic module 1.85 1.7-2.3 silicate module 0.67 1,8-3,2 module of acid silicic 1.46 2.5-3.5 clay modulus 0.85 1.5-2.5 lime standard 1, 12 0.8-0.95

Alite content (C ^ S) 70,

Overall, a high-grade alite clinker was achieved. 28-day y

strength according to DIN 1164 is 62 N / mm, which can be classified extremely high. It is, of course, not a standard Portland cement clinker. clay to increase the content of SiO2 and Al2O3.

Example 2

Unlike Example 1, the target slag, which could be labeled as blast furnace slag, should have the following composition:

% target slag

sieve ₂ 36 ^A1 ° 2 8 CaO 48 MgO 5 MnO + FeO 0 tío ₂ 1

reduces the original slag of the steelworks. Each kg of steelwork debris

Non-ferrous metal Share (ppm) Cu II / oOO Pb O / 800 Zn 3/760

The high copper content in the slag hurt copper was removed by a lead bath in front of an iron bath. As a result of lead reduced, taking iron and lead together to no solution, so that under the iron or. formed a lead layer. Steel and lead separately separated.

As a result of the inclusion of this was not responding steel could be

The relatively high proportion of zinc in the slag was reduced by an iron bath and condensed in the gas phase.

The remaining heavy metal concentration was found in the area of raw cement clinker material. Following reduction of the slag with the carbon dissolved in the iron melt, the following analysis was obtained:

Components

Percentage (%)

S1O2 60

A1 ₂ O ₃ 12

Fe ₂ O ₃ 0.5

CaO 17

MgO 4

The slag was cooled in a water bath and has excellent pozzolanic properties. Simultaneously with the recovery of the zinc metal fraction from the gas phase by condensation and recovery of copper as well as the recovery of the lead bath, a hydraulically active material is obtained which, due to its good pozzolanic properties, has high final strength, low hydration heat and high chemical resistance.

Example 4

Copper was removed from the liquid oxidized waste slag by the reduction-oxidation reaction described in Example 3 at a reaction time of 3.5 hours and a melting point of 1500 ° C.

The starting slag has the following composition:

Components share (%) Non-ferrous metals Percentage (%) ^Si0 2 42 Cu 1.2 Α '· 2θ3 8 Pb 0.25 ^Fe 2 ° 3 28 Zn 0.3 CaO 11 sn 0.1 MgO 2 N i 0.1 k ₂ o 1 At ₂ 0 3 τιο ₂ 1 ^P 2 ° 5 0.1 On activity copper v lead bath 30-40% and the thickness of the slag 3.5 cm e Value equilibrium concentration copper in the slag 200 ppm.

Furthermore, the remaining heavy metals from the copper-free liquid slag were lead, zinc, tin, nickel and iron reduced and eliminated.

The separation of the two iron / lead metal phases ensured the recovery of high-value, virtually copper-free, pig iron with the following analysis:

Non-ferrous metals Share (%)

Ni 0.34

Sn 0.13

Cu 0.07

Cooling, granulation and grinding of heavy metal-enriched liquid slags yielded the slag product pozzolan, which has the following analysis:

Components

Percentage (%)

Sio ₂ 59 ^A1 ° 2 12 Fe ₂ ° 3 0.5 CaO 16 MgO 2.5 k ₂ o 1.5 At ₂ 0 4.5 tío ₂ 1.5 ^P 2 ° 5 0.2

Due to the relatively high content of Al 2 O 3, the pozzolanic cement has a high early strength. His wedge index lies. at 95%.

The addition of S1O2 and Al2O3 carriers such as clay, quartz sand and bauxite can produce optimal blast furnace slags, while the melt viscosity decreases considerably. In reducing such melts, the steel droplets can be more easily separated by sedimentation, so that the free iron content of the hydraulic binder can be considerably lower.

The process according to the invention can be easily transferred to a steel plant. Assuming an hourly slag production of about 15 t, a converter of about 125 t active weight, resp. 35 m ^J active volume so that • 2 t can mix 90 tons of slag at the same time. about 30 ms near about 34 tons of crude iron (about 5 m). The clinker phase is tapped separately from the steel and in the vessel where it will be finished. Into this container, e.g. adding ingredients such as e.g. clays, and further reduction leads to upgrading to Portland cement clinker. Ultimately, however, the slag turnover can be compensated first in such a device.

The clinker cooling and granulating apparatus may be air-cooled by a direct process. In these cases, the air at 20 ° C is heated to about 1100 ° C and the clinker is cooled from about 1600 ° C to 250 ° C.

The amount of CO generated is another source of energy. CO is formed at temperatures of about 1600 ° C and contains not only latent chemical thermal energy but also sensible heat. When a correspondingly well insulated metallurgical tank is assumed to have a maximum heat loss of 30%, this means that the inventive process could be concerned with the production of steel and clinker exothermically, whereby the combustible gases produced could be optimally evaluated.

The process can be used to convert the hardly recoverable slag of steel mills into a cement clinker in a particularly simple manner, while at the same time a forging operation is achieved. The process in question also allows for the use of large amounts of heat, which are not appreciated in conventional processes without further intervention, thereby reducing gas emissions, in particular co ₂ .

Within the present process, decisive reactions are also found at the melt boundary surfaces and the process can take place! in an agglomeration furnace. The degassed carbon monoxide from the boundary surface reduces dissolved iron oxide in the slag bath layer, while naturally the proportion of CO ₂ reducing gas in the slag layer increases. From a volume fraction of about 15 vol. % C0 ₂ gas is lost by reduction with, and is yet still at least partially removed by further use of energy, for such gases on the surface of the slag layer can be ventilated if necessary. oxygen or a mixture of oxygen and air burned. The heat transfer to the slag and iron phases takes place almost exclusively through the radiation processes.

The generated waste heat can be! used to preheat the ingredients, wherein the drifted clinker phase can be separately removed. The heat conduit of the invention is set to a stable region of alite, resulting in the desired overheating. The formed alite clinker can be frozen by a conventional clinker cooling technique, the main aim being to minimize the free lime content.

The desired carbon supply to control the temperature of the iron melt and the reduction potential can be achieved by saturating the bath with carbon, for example, by immersion or a similar process. The carbon supply may be assumed to be countercurrent or direct current at multiple locations. Here, the iron bath not only fulfills the role of the wearer of the reducing agents, but also the role of the transport medium for the slag or slag. clinker phases, whereby particularly simple open furnaces can be used.

Claims (14)

PATENT REQUIREMENTS OF ACTIVE BINDERS OF AND IN WHICH THE POTENTIAL OF FERROUS in a number of shavings such as e.g. Slags after reaction of slags from the apparatusThe steel and hydraulic slag process, characterized by high iron, is slagged by the addition of two more than 5% by weight of the slags of the steelworks, Cu-converters with lead bath or oxidized to waste incineration. Method according to claim 1, characterized in that the iron oxide content of the slag is selected above 8% by weight, preferably above 10% by weight. Method according to claim 1 or 2, characterized in that liquid slag of the steel mills at temperatures above 1550 ° C, in particular above 1600 ° C, and liquid pig iron at temperatures from 1450 ° C to 1550 ° C are charged. The process according to claim 1, 2 or 3, characterized in that the liquid pig iron is added to the liquid slag phase in an amount of from 1: 2 to 1: 3. The method according to claims 1 to 4, characterized in that the liquid phases are held together for 3 to 8 hours, preferably about 6 hours at temperatures above 1550 ° C, preferably from 1660 ° C to 1800 ° C. Method according to one of Claims 1 to 5, characterized in that an electrically heated tipping converter is used as the mixing vessel. Method according to one of Claims 1 to 6, characterized in that the slags are maintained at a superheat temperature by blowing in or blowing oxygen. Method according to one of Claims 1 to 7, characterized in that basic light ores are added to the slag to increase the iron oxide content above 8% by weight. Method according to one of Claims 1 to 8, characterized in that in the batch of C'u-converter slags lead is poured from underneath the steel bath and the zinc is condensed from the gas phase. Method according to one of Claims 1 to 9, characterized in that the height of the slag bath for the reaction with pig iron is 2 to 8 cm, preferably 2 to 6 cm. Method according to one of Claims 1 to 10, characterized in that the slag is converted into a clinker phase consisting of 15 to 25% by weight of a liquid phase (aluminates, ferrites) and a clinker phase (minerals, alite, belite) . 12. The method according to one of the claims, which is charged as additives. of claims 1 to 11 that CaCO2, Al2O3 and / or S1O2 are Method according to one of Claims 1 to 12, characterized in that the reduced slag or clinker phase is fed to the clinker cooling device and the granulating device. Method according to one of Claims 1 to 13, characterized in that the clinker is a direct process.