DE2337957A1 - Desulphurizing liquid unrefined iron with a calcium compound - comprising fine particles of compound coated with solid hydrocarbon - Google Patents

Abstract

Unrefined molten iron is desulphurized according to the method of DT 2301987 by adding a desulphurizing agent which comprises fine chalk particles each coated with a layer of solid hydrocarbon to the molten metal bath. Pref. the coated particles may be obtained by high-speed mixing of the ingredients in a turbomixer. Alternatively low speed mixing can be used provided the hydrocarbin is softened by applying heat. In this method a tubular mill can be employed, which also reduces the size of the chalk particles, after which the coated particles are cooled. The non-explosive easily handleable properties of the desulphurizing agent used in 2301987 are retained and a more homogeneous desulphurization of the iron is achieved.

Description

Polysius AG, Neubeckum

Process for the desulphurization of liquid pig iron

The invention relates to a method for desulfurization of liquid pig iron, being used as a desulfurizing agent Calcium compounds and hydrocarbons, both in Form of solids into which pig iron is introduced, according to P 23 01 987.6.

It is already known to blow lime into the pig iron bath with the aid of gaseous hydrocarbons (e.g. methane). However, if air gets into the pipe system with this known method, an ignitable Form a gas-air mixture. In order to avoid this, the pipe system must be filled with nitrogen before and after the injection processes and there are also special monitoring devices caution required.

A method is also known in which one works with calcium carbide, whereby the individual particles wetted with liquid hydrocarbons (e.g. oil) and the desulfurizing agent thus obtained is introduced into the pig iron bath. In this context, so-called paraffin waxes have already been used in place of oil, but these are used for Impregnating the calcium carbide particles are first converted into a liquid phase and after this treatment need to be dried again. The main disadvantage of this process is that calcium carbide is relatively expensive and is not available wherever iron and steel are produced, and that storage, transport and the Handling calcium carbide is relatively dangerous,

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there is a general aversion to this remedy half in smelting works.

It was therefore the task of the main registration to avoid the cited disadvantages of the known method to develop a method for desulfurizing pig iron, the is characterized by its simplicity and harmlessness in handling and introducing the desulfurizing agent.

In the main application, this is essentially achieved in that the calcium compounds, in particular Peinkalk, and hydrocarbons are introduced into the pig iron bath in the form of solids.

Since in the method according to the main application thus Hydrocarbons used in a physically solid state are a priori all safety measures superfluous, which are absolutely necessary when using liquid or gaseous hydrocarbons. That Desulphurising agents composed in this way from fine lime and solid hydrocarbons leads to a extremely safe and greatly simplified handling of the desulfurizing agent. The ones used in this procedure Desulfurizing agent components can be mixed with one another without difficulty, both at the point of use as well as already at the lime supplier, whereby this can also be used for storage and transport Desulphurizing agents consisting of solids cannot cause any demixing or explosion hazards.

The object of the present invention is to improve the method according to the main application to the effect that in particular the solid components used are brought to an even more homogeneous desulfurizing agent.

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This object is achieved according to the invention in that the fine lime particles are coated with the hydrocarbons will. If in this way the individual limestone particles form an outer layer of solid Obtained hydrocarbons, the result is a desulphurizing agent, in which the individual solid components are homogeneously distributed in an almost ideal way. this will lead to a further improvement of the desulphurisation effect in the pig iron bath.

Just as with the main application procedure, Also in this process according to the invention, the desulfurizing agent from fine lime and solid hydrocarbons both in the Area of the place of use as well as already at the KaIklM " put together without any problems, i.e. the pesticide components can be put into can be put together in the desired ratio. If the desulfurizing agent is produced in the process according to the invention Way (by coating the fine lime particles with the solid hydrocarbons), so is when properly stored and Conveying this desulfurizing agent prepared according to the invention practically runs the risk of segregation completely excluded. Safety-related measures, such as are sometimes used in the known methods mentioned at the beginning are required, can be omitted in the production of this desulfurizing agent.

The solid hydrocarbons used for this purpose, which come under the general chemical formula CH " ₊ ", are obtained as by-products in the processing of crude oil or in the coking of coal. The best components for pig iron desulphurizing agents are hydrocarbons with a straight chain arrangement. Furthermore, since fine lime is significantly cheaper compared to calcium carbide, the result is a desulphurizing agent overall

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of relatively low cost.

According to the invention, the desulfurizing agent is advantageously produced by adding the fine lime particles in a mixing device with a relatively high rotational speed are enveloped with the solid hydrocarbons. As a mixed . facility, so-called turbo mixers can be used, such as those used in the plastics industry for mixing be used by substances that are difficult to mix. Because of the high speed of rotation of such a mixing device are the solid hydrocarbons used here in space common brought at least to a partial melting, so that by the actual mixing process the individual Fine lime particles extremely evenly with the hydrocarbons be enveloped. The degree of melting of the solid hydrocarbons can also be adjusted by an appropriate one Choice of the rotational speed of the mixing device can be controlled.

According to another feature of the invention, the mixing process can also be carried out in a mixing device with lower Speed can be made, then to soften the waxy solid hydrocarbons inherent in the device Heat or external heat can be exploited. A so-called tube mill is particularly suitable for this process, in which the calcium compound can be crushed and mixed with solid hydrocarbon at the same time, because the resulting frictional heat can be used in an advantageous manner.

It should also be mentioned in this context that at least the fine lime particles are expediently as possible have the same grain size, the grain size preferably being less than 1 mm. Here it is also

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moderate, the grain size of the solid hydrocarbons on the grain size of the fine particles, whereby Care should be taken that the grain size of the solid hydrocarbons such a melting allows that the desired uniform coating of the individual pale lime particles is ensured.

As mentioned earlier, various solid hydrocarbons can be used as the desulfurizing agent component be used. Depending on the type of hydrocarbons used, it can happen that the finished desulfurizing agent after the coating of the limestone particles, that is to say after the treatment in the mixing device, for Tends to form lumps. In such cases, it can be used to avoid this

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be expedient, the desulfurizing agent, so the fine lime particles coated with hydrocarbons, after Envelop to cool.

In the experiments on which the main application is based, it has been found that an addition of about 5% solid hydrocarbons to the desulfurizing agent is sufficient, the remainder being fine lime; however, this desulfurizing agent can also contain up to 20% solid hydrocarbons. Desulfurization of pig iron results in what is known as desulfurization slag, which is generally difficult to handle. The combination of the desulfurizing agent in the mixing device now offers the possibility of adding another component to the desulfurizing agent for treating the pig iron bath. This further component can be a flux by means of which the desulphurisation slag that is produced is converted into a crumbly state, so that the consistency of the desulphurisation slag is thus influenced in a favorable manner. Fluorspar, for example, could be added to the defrosting agent as a flux.

Introducing the desulfurizing agent made from solids into the pig iron bath is preferably carried out with the aid of a pneumatic conveyor system. Here can For example, the so-called immersion lance method is used, in which a immersion lance with its mouth into the Pig iron bath is introduced so that the desulfurizing agent (if necessary with additional flux) with the help of a Pressurized or carrier gas is blown into the liquid pig iron at a desired immersion depth. As a print or Carrier gas can be air or - if a reducing atmosphere is to be created in the pig iron bath - one containing carbon monoxide Gas can be used. However, there is also the

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Possibility of using the desulphurisation agent by mechanical means to be introduced into the pig iron bath.

By introducing the desulfurizing agent under the bath surface, the thermally induced Conversion of solid hydrocarbons into their gaseous form . '"i old products in the pig iron bath a strong movement obtained by the formation of carbon monoxide (during the reaction of desulphurizing agent with liquid pig iron) is reinforced. The stronger this bath movement, the more intensive the mixing of liquid pig iron becomes and desulphurising agents, which in turn become an extremely good desulfurization of the pig iron leads.

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Claims (9)

-t- claims 1. Process for the desulfurization of liquid pig iron, with calcium compounds as desulfurizing agents, in particular fine lime and hydrocarbons, both in the form of solids, are introduced into the pig iron bath are, according to P 23 01 987.6, characterized in that the fine lime particles be enveloped with the solid hydrocarbons. 2. The method according to claim 1, characterized in that the fine lime particles in a mixing device with relative high rotational speed are enveloped with the solid hydrocarbons. 3. The method according to claim 1, characterized in that the coating of the fine lime particles with the solid hydrocarbons is carried out in a mixing device using the device's own frictional heat. 4. The method according to claim 1, characterized in that the coating of the fine lime particles with the solid hydrocarbons in a mixing device when they are supplied is carried out by additional external heat. 5. The method according to claims 3 and 4, characterized in that the fine lime particles in a tube mill mixed and coated, in which the potassium compounds are crushed at the same time. 6. The method according to claims 1 to 4, characterized in that the coated with the hydrocarbons Fine lime particles are cooled after being coated. 409886/0799 7. The method according to claims 2 to ^, characterized in that that the desulfurizing agent in the mixing device still has a further component for treatment of the pig iron bath is added. 8. The method according to claim 7> characterized in that as a further component, the resulting development '
Sulphurizing slag is mixed into a crumbly state converting flux. 9. The method according to claim 8, characterized in that the desulfurizing agent as a further component fluorspar is admitted. 409886/0799