DD158227A5 - PROCESS FOR THE PREPARATION OF CALCIUM CARBIDE - Google Patents

Abstract

1. Process for making calcium carbide from lime and a carbon carrier in a closed electrothermal furnace with a power of more than 20 megawatts, in which the electrodes are arranged symmetrically in the corners of an equilateral triangle, which comprises : using at least 40% of the total carbon component in the furnace burden in the form of a carbon carrier consisting of anthracite, petroleum coke and/or lean coal, the carbon carrier with an initial content of volatile constituents of more than 5.0% having been subjected to thermal pretreatment at increased temperature for as long as necessary to establish a residual content of volatile constituents of less than 5.0% and having been separated into a fraction consisting of particles with a size of 3 to 10 mm and into a fraction consisting of particles with a size of more than 10 up to 25 mm ; the fraction of smaller particles being introduced into a central region inside the furnace lying between the electrodes, and the fraction of larger particles being introduced into a peripheral region of the burden surface area inside the furnace which lies outside the triangle formed by the electrodes.

Description

Berlin, the 4,8,1981

AP C Ol B / 229 085/4 58 932/12

Process for the preparation of calcium carbide Areas of application of the invention

The present invention relates to a process for the production of calcium carbide from lime (also called white material) and a carbon support (also referred to as black material) in a closed electrothermal furnace with a power of more than 20 MW, whose electrodes are symmetrical at the corners of an equilateral triangle are arranged.

CHARACTERI stik the bekan nth technical Eras Ungen

Electrothermal furnaces have been in operation for many decades. The electrothermal industry started with the production of the Ca-carbide. For many decades kilns of smaller power were operated; Resulting gases burned on the surface of the Möller, reaction and Möller were in constant visual control, manual interventions to ) correction of irregularities were immediately possible during the operation, so that no very strict yardsticks had to be applied to the condition of the Möllerkomponenten.

For about 25 years, ovens have been developed that are completely closed for reasons of environmental protection and can accommodate a much higher output for economic reasons. So today it is quite possible to operate closed furnaces with a capacity of up to 75 MlV.

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The development of these modern large ovens was associated with some difficulties. Since direct exposure to the furnace during operation was no longer possible, especially higher demands on the Möllerzusammensetzung had to be made. This had to be such that at least a few days of uninterrupted operation was possible, before mechanical interventions eliminated caking, slag, etc. All this was made even more difficult because the considerable increase in power consumption had increased the sensitivity to unsuitable Möller.

As the size of the electroreduction furnaces becomes larger, the gas permeability of the coking layer covering the reaction vessels and the heat exchange of the gas with the coiler become increasingly a criterion for the successful operation of these furnaces. In the event of uneven degassing of these boilers, intermittently very hot furnace gases are emitted, which leads to damage to the furnace hood, electrode sockets and possibly electrostatic filter dedusting.

It has also been found that these difficulties are exacerbated when, instead of the normal Hüttenkokssorten poorly reactive carbon support, as are usually anthracite, petroleum coke and / or charcoal are used.

To improve the gas permeability of the Möllers and thus the heat exchange between gas and Möller so far the smallest possible grain spectrum of the Möllers with a certain minimum grain size, in particular the carbon support was sought.

The carbon support was therefore used mainly in the grain size 10 to 20 mm. Dust content, d. H. Granulations smaller than 6 mm had to be screened out of the Möller beforehand (Ulimanns Enzyklopädie der technischen Chemie, 5th volume, 3rd edition (1954) Urban and Schwarzenberg, Munich-Berlin, pages 30 to 33).

For this reason, attempts have been made to use the finely divided Möllerbestandteile hollow electrodes in electrothermal processes (US-PS 2,996,360).

However, the amount of finely divided material that can be used in this way is limited, because initially with increasing solids introduction through the hollow electrodes, advantages for the furnace operation (reduction of the electrode burnup per unit time, electrodes immersed deep into the hole) arise, but it leads from a certain point a further increase of this solids input to a radical deterioration of the furnace condition.

With respect to the chemical composition was to the black material u. a. demanded that it should be virtually free of volatiles. For practical use, therefore, used in closed large ovens predominantly coke.

Of course, one has already tried to use other black materials than coke, especially anthracite and petroleum coke. The practical operation of closed large furnaces has shown, however, that the use of these materials because of the proportion of volatile hydrocarbons, but also because of other properties, considerable difficulties. It has

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It is therefore believed by experts that in these cases only a small proportion of anthracite, petroleum coke or charcoal can be added to the Möller (up to a maximum of about 25 % of the black material, with the percentages always being percentages by mass, as in the following understand), if you did not want to disrupt the operation sustainable. Even this was only possible with well-running stoves. The addition of anthracite, petroleum coke or charcoal was stopped immediately when difficulties arose.

Although anthracite and petroleum coke have long been calcined for the production of electrode materials; but this calcined material is unsuitable for use in electric red reduction furnace, even because of the high electrical conductivity "But also the reactivity of these calcinates is reduced, thereby increasing the temperatures in the furnace. The resulting side reactions cause a rapid slagging of the Möllers.

Object of the invention

The object of the invention is to provide an improved process for the production of calcium carbide, in closed electrothermal furnaces with a power of more than 20 MW, whose electrodes are arranged symmetrically at the corners of an equilateral triangle, where it is possible to large extent Anthracite, petcoke used individually or mixed with each other.

Explanation of the essence of the invention

The invention has for its object to find technological conditions, among which a flawless

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Operation of closed electrothermal furnaces with a capacity of more than 20 MlV is also ensured when using anthracite and petroleum coke.

According to the invention, at least 40% of the total carbon component used in the kiln-oiler can be used in the form of a carbon support consisting of anthracite, petroleum coke and / or charcoal, if this (') carbon support with an original volatiles content of more than 5.0 %. at elevated

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Temperatures has been thermally pretreated until it has a residual volatile content of less than 5.0 %, preferably 1 to 3 % , and then this carbon support in particle size fractions of 3 to 10 mm on the one hand and greater than 10 to 25 On the other hand divides with the fraction of smaller grain sizes, the central region lying between the electrodes and the fraction of the larger grain sizes the outer region of the Mölleroberfläche in the furnace, which lies outside the triangle formed by the .. electrodes.

The thermal pretreatment is preferably carried out at temperatures below 1000 ° C., in particular at temperatures between 600 and 800 ° C., the treatment times being known to be shorter, the higher the temperature, and conversely correspondingly longer, the lower the temperature is.

It has also proved to be advantageous if the furnace is simultaneously supplied with up to 25 % of the total carbon component used in the kiln furnace in the form of coke dust by means of hollow electrodes, wherein the coke dust can contain up to 50 % anthracite dust.

Further embodiments of the method according to the invention are that in the Möller total one carbon component used, which contains up to 60 % coke in addition to the inventively pretreated carbon support, or that in the Möller total a carbon component used in addition to the present invention pretreated carbon support up contains 60 % of a mixture consisting of coke on the one hand and untreated anthracite, petroleum coke and / or charcoal on the other hand in the ratio 1: 1.

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Furthermore, it is also possible to use in the Möller total a carbon component, which contains up to 30 % untreated anthracite, petroleum coke and / or charcoal in addition to the inventively pretreated carbon support, or that even such a carbon component is used, which consists of 100 % consists of the pretreated carbon support according to the invention

/ '^ \ Conveniently, the mass ratio of black / Vy

White material throughout the Möller adjusted to about 1: 1.5 to 1.6, so that a carbide is obtained, which provides on reaction with water 280 to 300 1 acetylene / kg. But other ways of operating the stove are possible.

Working Example

The following examples are intended to explain the new process in more detail without wishing to limit the invention to the content of these examples.

example 1

Anthracite of the following analysis

Grain size 6 - 30 mm

Water 6.3 %

Ash 12.4 %

volatile

Hydrocarbons 9.8 %

electr »resistance ₇

at 20 C 10 Xl cm

is heated in a tubular oven with indirect heating with the exclusion of air for about 1/2 hour at 850 ⁰ C. Thereafter, the dry anthracite still has a content of 1.9% of volatile hydrocarbons and an electric

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Resistance of 0.8 χ 10 _ücm. From this material, the 2 fractions of grain size 3 - 10 mm and 10 - 22 mm are then screened out.

With these two .Fraktionen is a Carbidofen closed design with a power consumption of max. 55 MW, namely the finer grain size in the central area of the furnace between the electrodes, and the coarser grain size in the outer (peripheral) area. The mixture with lime is everywhere uniformly in proportion 1 part of anthracite: about 1.6 parts of lime set.

The carbide furnace is equipped with hollow electrodes. Through this a mixture of normal coke breeze (grain 0-6 mm) and fine lime in the ratio 1: 1.6 injected, which makes up about 15% of the total Möllers. The oven can be operated properly.

A balance of 8 hours of operation had the following '. Result:

Consumption: 351,000 kWh (<v0 44 MWh / h) 56 t anthracite 10 t coke breeze

90 t lump lime

15 t fine lime production: 110 t carbide with 293 1 C ₂ H ₂ / kg.

The running time of the furnace from one necessary control to the next under the given conditions is about the same as with the usual driving with coke

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- ar

Example 2

The fine material O - 3 rome obtained in the processing of the anthracite into the two grain fractions is added to the coke breeze for the hollow electrode. It falls in this work-up about as much fine anthracite, that with complete processing of this material, the black component of the hollow electrode consists of a mixture of about 1 part of coke breeze and 1 part of anthracite.

Otherwise, the procedure is as in Example 1.

The result obtained is within the limits of error the same as in Example 1.

Example 3

The procedure is basically as in Example 1, except that the anthracite after degassing untreated anthracite is added in such an amount that the mixture contains about 30 % crude anthracite. Admittedly, however, before cooling the anthracite, so that the water of the untreated anthracite can evaporate, but not the hydrocarbons.

The consumption in this experiment are also within the error limit same as in Example 1. Only the liter number of carbide produced is only 285 1 C ₂ H ₂ / kg.

However, the oven has a much stronger tendency to form slag at the surface of the Möllers. This makes a somewhat more frequent control

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Lieren and correcting the Ofenganges necessary. The frequency of the associated business interruption is just so high in this driving style that can be spoken of a still acceptable operation. 5

Example 4

Petroleum coke of grain size 6 - 35 mm and a content of volatile hydrocarbons of 9.7 %, 6 % HpO and ash less than 1 % is heated in the same oven as described in Example 1, but to a temperature of 750 C and a residence time of about 2 hours. Thereafter, the coke still contains 2.8% of volatile hydrocarbon material ^p and the electrical resistance is 1.6 χ 10 _flcm. The coke is then worked up as in Example 1, used in the carbide furnace, the coke is also described as in Example 1. Only the ratio of coke: lime is adjusted to 1 part of coke to 1.5 parts of lime. The hollow electrode is charged with normal coke breeze.

Result of an 8 hour balance:

Consumption: 438 000 kWh (-0 55 MWh / h) 115 t petroleum coke

20 t coke breeze 77.t lump lime 13 t fine lime

Production: 145 t carbide with 298 1 C ₂ H ₂ / kg. 30

The kiln operation is normal, controls are not "more often necessary than the usual operation with metallurgical coke.

Claims (8)

1 A process for the production of calcium carbide from lime and a carbon support in a closed electrothermal furnace with a power of more than 20 MlV, whose electrodes are arranged symmetrically at the corners of an equilateral triangle, characterized in that at least 40 % of the total in Ofenmoller used carbon component in the form of a carbon support, consisting of anthracite, petroleum coke and / or charcoal, is used after this carbon support with an original content of volatile constituents of more than 5.0 % at elevated temperatures has been thermally pretreated until he has a residual volatile content of less than 5.0 % , then this carbon carrier in grain size fractions of 3 to 10 mm on the one hand and greater than 10 to 25 mm on the other hand divides and with the fraction of smaller grain sizes the central, lying between the electrodes area and m it the fraction of the larger grain sizes, the outer portion of Mölleroberfläche charged in the oven, which is outside the triangle formed by the electrodes. 2. The method according to item 1, characterized in that the carbon carrier at temperatures between 60O ^- and 800 C thermally pretreated. 3 * Process according to item 1 or 2 ", characterized in that the carbon carrier is thermally pretreated until it has a residual volatile content of 1 to 3 % * 2290 8 5 A .. «. 4 »method according to one of the items 1 to 3, characterized in that at the same time up to 25 % of the total Kohlenmoller used in the carbon component feeds the furnace in the form of coke dust by hollow electrodes, wherein the coke dust may contain up to 50 % anthracite dust. 08/04/1981 AP C Ol B / 229 085/4 58 932/12 4 * 8.1981 ο η η η Q CI ^{ΑΡ c 01 Β / 229 085/4} LL Ό U Ö D 4 - * / - 58 932/12 invention claim 5 »method according to one of the items 1 to 4, characterized in that in the Möller total of a carbon component used, which contains up to 60 % coke in addition to the inventively pretreated carbon support, 6 # Method according to one of items 1 to 4, characterized in that in the Möller a total of a carbon component is used, which contains up to 60 % of a mixture in addition to the inventively pretreated carbon support of a coke on the one hand and untreated anthracite, petroleum coke and / or lean coal, on the other hand, in the ratio 1: 1. 7, Method according to one of the items 1 to 4, characterized in that in the Möller total a carbon component is used, which contains up to 30 % untreated anthracite, petroleum coke and / or charcoal in addition to the inventively pretreated carbon support. 8, Method according to one of the items 1 to 3, characterized in that one uses in the Möller a carbon component which consists of 100 % of the inventively pretreated carbon support.