DE2060675A1 - Process for reducing the reactivity and at the same time increasing the abrasion resistance of cokes - Google Patents

Description

1 · ■ 1 I P I

Note: Bergwerksverband GmbH Essen, December 5, 1970 Essen Fr / Gr

Frillendorfer Str. 551

Process for reducing the reactivity and at the same time increasing the abrasion resistance of cokes

The invention relates to a method for reducing the reactivity and at the same time increasing the abrasion resistance of cokes.

Lump coke, which has been produced in a conventional manner in a horizontal chamber furnace, has a reactivity which lies between a k value of about 0.05 and ¹ Z m

0.50 ctr / g see fluctuates. For molded coke (coked briquettes) the k value is between about 0.25 and 0.60 cm / g see. The k value is the reaction rate constant k that at 1000 ° C. gravimetrically on the piece of coke measured reaction with

The abrasion value M ₁₀ for lump cokes is usually between 5 % and 7 %, while shaped cokes often have abrasion values of 6 % to 9 % . They are determined by the so-called llicum test.

Reactivities of the cokes with a k value between However, 0.25 and 0.50 cnr / g see are for individual purposes, too high for the extraction of zinc in special blast furnaces, for example. Eei this well-known In zinc extraction, the zinc reduced in the blast furnace shaft is vaporized at high temperature with the furnace gas condenser connected to the furnace. Using

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reactive coke occurs in higher zones of the shaft furnace due to the strongly endothermal Boudouard reaction according to the equation CO ₂ + C 2 CO - 41.2 kcal a cooling of the charging column and thus a premature condensation of the zinc vapor. In addition, the lowering of the temperature causes an unfavorable shift in the equilibrium reaction according to the equation Zn + CO ZnO + C, as a result of which ZnO is formed back. The reactivity of the coke should therefore be as low as possible for use in the zinc blast furnace. Your k-value should be below 0.15 a / g. lake lie. Also for other shaft furnaces, such as cupola furnaces and lime shaft furnaces, the respective cokes are desired to have low reactivity. In view of the high stresses placed on cokes in shaft furnaces, increased abrasion resistance of the cokes is always desirable.

It has now been found, surprisingly, that there is an appropriate reduction in reactivity in the case of cokes and a simultaneous increase in abrasion resistance achieved if the cokes with a boron compound impregnated. According to a preferred embodiment, the impregnation with an approximately 5-30 ^ igen, aqueous boric acid solution carried out.

The method according to the invention is effective with blast furnace cokes, special cokes, shaped cokes, coke pellets and coke-coal briquettes with up to 15 % volatile constituents, in particular so-called hot briquettes, and also adsorption cokes including active "coals".

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The amount of degradation caused by the impregnation the reactivity increases with the amount of boron compounds absorbed, but it is not absolutely proportional. The increase in abrasion resistance also depends on the amount of boron compound absorbed away. To increase the abrasion resistance, it is understandably sufficient if the impregnation solution penetrates only into the outer edge zone of the eokse.

The amount of boron compounds absorbed during the impregnation can be due to various factors, such as in particular can be influenced by the concentration of the impregnation solution and also its temperature. Also through The amount of boric acid absorbed can be varied by changing the duration of the impregnation. Usually An impregnation time of around 20 seconds should be sufficient and a maximum of 15 minutes should not be exceeded will. Finally, the impregnation method chosen also has an influence on the amount of boron compounds absorbed. The impregnation of the coke can be done> by spraying with the impregnation solution or by Dipping (soaking) done. Larger amounts of the boron compounds are absorbed by vacuum impregnation.

According to a further inventive feature, the impregnation with aqueous solutions of a boron compound made on cokes at a temperature of around 100-300 ° C. It has been found, surprisingly, that the impregnation solution deeper into the pore system of the coke penetrates when the coke to be impregnated has a higher temperature than the impregnation solution.

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Not only aqueous solutions of boric acid, but also aqueous solutions are suitable as impregnating agents and dispersions of ammonium borates (ammonium borate, ammonium pentaborate), boron oxides and boric acid methyl and ethyl ester. According to the invention, it is also possible to use the mentioned impregnating agents according to the invention to be pollinated in solid form. The impregnated cokes should be 0.2-5%, preferably 0.5-2% by weight, of boron compounds, based on pure boron.

Another embodiment of the process according to the invention consists in adding plastic emulsions or dispersions to the impregnating solution at the same time. Suitable plastic emulsions or dispersions can be prepared, for example, from polyvinyl propionate, polyvinyl methyl ether, vinyl chloride copolymers or acrylates. Surprisingly, it is achieved that by the Z of the plastics to the boron _and the impregnation rate of the coke water-r and weather resistant is, without reducing the reactivity is impaired. This prevents the boron compounds from being washed out, for example when the coke is stored outdoors. It is generally sufficient that the proportion of the plastic emulsion or dispersion in the impregnation solution is about 2-10, preferably 3-7 % .

Whether the coke immediately after impregnation has no effect on the reduction in reactivity still dripping wet, after slow drying at normal temperature or after a quick drying at z. B. 100 ° C is fed to a reaction. The one with the descent

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Setting of the reactivity occurring at the same time However, an increase in abrasion resistance can only take effect after the impregnated coke has dried When coke is used in a Zn blast furnace, such drying takes place inevitably in that the Coke, before being fed into the shaft furnace with the help of superheated Gases is preheated to approx. 800 ° C.

example 1

Formed coke mil: a temperature of 300 ° C by hot briquetting a coke-coal mixture and coking the briquettes at about 850 ° C, is by means of a sieve-like conveyor belt through a with a 5 ^ igen Boric acid solution filled immersion bath heated to 55 ° C. The residence time of the farm coke in the immersion bath is about 20 seconds.

During the immersion, the molded coke absorbed 0.7 % boric acid, based on its initial weight. A piece of molded coke removed from the conveyor belt before the immersion bath has a reactivity k of 0.24 cm / g seawater and an abrasion of 9.2%; for a piece of molded coke removed after the immersion bath, the corresponding values are 0.18 ciir / g see or 7.1 %. This corresponds to a reduction in reactivity to 75 % and abrasion to 77 % of the original value.

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Example 2

Molded coke according to Example 1 was impregnated by spraying with a 10% boric acid solution. The molded coke absorbs 1.2% boric acid. A shaped coke piece removed after the immersion bath has a reactivity of k _m = 0.11 cnr / g see "and an abrasion of 6.3 %. This corresponds to a reduction in reactivity to 46 % and abrasion to 68.5 % of the original value .

Example 3

Coke pellets with a porosity of 50 % and a piece weight of about 12 g, made from 40 % fatty coal and 60 % fluidized bed coke by pelletizing the mixture and coking the green pellets at 750 ° C, are impregnated by spraying with a 10 Joigen boric acid solution. The coked pellets absorb 1.5 % boric acid. The reactivity of a pellet before immersion is 0.63 cnr / g see, its abrasion

is 8.7%> after the immersion the k value is • 7 m

0.35 cm / g see. This corresponds to a reduction in reactivity to 55 % and abrasion to 67 % of the original value.

Example 4

A 30/40 mm blast furnace coke with a porosity of 49 %, produced from a medium fatty coal at a coking temperature of 1050 ° C, is with a temperature

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at a temperature of about 20 ° C through a 10 % ± ße boric acid solution at about 55 ° C. During the 20 sea immersion, the lump coke absorbs 0.4 % boric acid. A piece of coke removed before the immersion bath has a reactivity of 0.23 cm / g sec and an abrasion of 4.3 %; after impregnation, the k value is 0.13 cm / g see and the abrasion is 2.9 %. This corresponds to a reduction in the reactivity to 56 % and the abrasion to 67 % of the original value.

Example 5

Blast furnace coke according to Example 4 is passed through at a temperature of about 300 ° C. by means of a sieve-like conveyor belt an immersion bath heated to 55 ° C with a 10 Joigen Ammonium pentaborate solution led. The dwell time of the coke in the immersion bath is about 20 seconds.

When immersed, the coke absorbs 11% ammonium pentaborate solution. A coke impregnated in this way has a reactivity of Is ^ = 0.10 cnr / g see and an abrasion of 6 %.

Example 6

Hot briquettes produced by the briquetting _t a mixture of 75% coke breeze and 25% fine coal at 420 ° C are sprayed, after cooling to 200 ° C with a mixture '20% Borsäuretrilnethylester and 80% water.

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The hot briquettes have 7 % volatile components and before the treatment a reactivity of k = 0.28 cur / gs ^{ec and} an abrasion of 7.4%. After the treatment the reactivity is k _m = 0.17 cnr / gsec and der Abrasion 4.9 %.

This result corresponds to a reduction in reactivity to 61% and a reduction in abrasion to 66% of the original value.

Example 7

According to Example 1, molded coke is passed through an immersion bath containing a 10 % boric acid solution which has been neutralized with technical ammonia solution and mixed with 5% of a 50% aqueous polyvinyl propionant emulsion.

The impregnated shaped coke pieces are sprinkled with water under a shower for a quarter of an hour. For a non-irrigated sample, the reactivity results in k = 0.11 cm / g sea and for the irrigated sample k = 0.12 cm / g sea. As a result of the sprinkling, the reduction in reactivity achieved by the impregnation is only reduced by about 5 %. The coke has an abrasion of 5.4%, corresponding to 58.6 % of the original value. Mold coke not impregnated with the plastic emulsion loses 50 % of the reduction in reactivity and 65 % of the increase in abrasion resistance when it is sprinkled.

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Claims (5)

Claims Π j) Process for reducing the reactivity and at the same time increasing the abrasion resistance of cokes, characterized in that the cokes are impregnated with aqueous solutions of boron compounds. 2) Method according to claim 1, characterized in that the impregnation with an approximately 5 ~ 30%, aqueous Boric acid solution. 3) Process according to claims 1 and 2, characterized in that the impregnation with an approximately 100 300 ° C makes a hot piece of coke. 4) Process according to claims 1 to 3, characterized in that plastic emulsions or dispersions are added to the impregnating solution. 5) cokes characterized by impregnation according to the method according to claims 1-4. 109883/1060