DE2419971A1 - METHOD OF COMPRESSING POROESE CARBON MATERIAL - Google Patents

Description

CRASEMANN & RAFFAY

2 HAMBURG 7O

SOHLOSSTRASSEQ PATENTANWÄLTE

DIPL-INQ. JCIRQEN CRASEMANN 23 April I974 DlPL ₁ -ING. VINCENCE V. RAFFAY

PATENT and LAWYER DIPL-ΙΝΘ. DR. JUR. QERT HELDT

REF: 1140/10

Commonwealth Scientific and Industrial Research Organization Limestone Avenue,

Campbell, Australian Capital Territory, Commonwealth of Australia

Process for densifying porous carbon material.

The invention relates to a method for compacting porous Carbon material in which pyrolytic carbon is in porous grains of coal is deposited in order to increase the density and / or to change the reactivity. In particular the invention is directed to a method for the production of carbon for electrodes, for example in the production of aluminum be used.

Electrodes of this type are heretofore made by connecting petroleum coke made with pitch, the electrodes made of this material in the desired shape by the action of pressure and then be carbonized. In such electrodes it is necessary that the carbon material (Petroleum coke) is dense, solid and durable and has a low ash content, especially a low iron content. This material is not only expensive, but due to the changes in oil refining, this material will be used in the future are no longer readily available.

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The invention is therefore fundamentally based on the object of creating a method of the type mentioned at the beginning that solid and dense coal products are made from low-ash lignite or low-ash coke.

Another object of the invention is to provide a method for compacting porous coal grains and / or to reduce reactivity by depositing pyrolytic carbon within the pores between the Grains.

Numerous attempts to find a substitute for petroleum coke have been made, with the most promising attempt consisted in removing the bound salts of the lignite with sulfuric acid and then breaking it perform. This was followed by compaction with a pitch binder and sintering or baking to create a build-up that is suitable for the production of electrodes. However, the required density and strength for the electrodes was not achieved ^ and in a corresponding article from 1969 it was recommended to use such material for electrodes create pyrolytic deposition of carbon in the pores,

The deposition of carbon in the pores of carbon bodies is known. For example, Vohler, Reiser and Sperk in an article in the magazine "Carbon" Ur. 6, pages 397 to 403 from 1968 the protection of nuclear graphite by cracking methane at 1100 ° C. It was recognized that low deposition temperatures and low gas pressures are advantageous here, which makes it clear that there is only one interest in the deposition of carbon on the surface and existed in the outer pores and that one looks at the deposition in the pores between the grains (intergranular) and not focused on the deposition in the grains themselves (intragranular). The co-published photographs become It is clear that there is only a carbon layer in the graphite

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until the pores are closed at their entrances, so that any increase in density at such a Procedure is limited.

Another article in the same magazine "Carbon" No. 6, by Bochirol, Ortega and Teoule, pages 649 to 660, 1968, describes the change in the pore size spectrum when carbon in the pores corresponds to industrial nuclear graphite Quality is deposited by cracking natural gas at 125 ° C over a period of 80 hours. It it is noted that larger pores are preferred for deposition, but with a substantial increase in density as they are for Electrode carbon material is required is not achieved is because again there is no deposit in the smaller pores in the grains of the graphite body itself.

In U.S. Patent 3,284,334 there are fluid carbon electrodes and reference is made to a deposit in the pores of the coal using a fluid bed is used to produce a relatively non-porous, very hard and very dense material for electrode production. The substrate, however, is a petroleum coke whose strength far exceeds that of lignite carbonization, and the pyrolysis is carried out at a relatively high temperature. This US patent can therefore be understood by a person skilled in the art does not lead to the assumption that this deposition of carbon in the pores of the brown coal at temperatures below of 1100 ° C is practically possible.

However, it has been found that when using brown coal particles as a feed to a combined moving bed entrainment reactor as described in "Industrial Research News" No. 81, May 1970, the carbon in is deposited in the internal voids of the extremely porous particles of the granular charge. Not just the density of the Lignite increases significantly, but so does carbon deposition creates a particularly strong product. This is especially

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This is especially the case with lignite, which was produced by carbonizing a demineralized raw lignite by a technique as described in Australian patent 56 889/73. The same effect occurs with low-ash Coke and coal.

It has also been found that when the process is carried out in two steps, first at relative low temperature in order to achieve maximum deposition in the pores of pyrolytic carbon and then at relatively high temperature in order to increase the order of the carbon taken up by the pores in order to continue the filling to improve the pores with pyrolytic charcoal and to influence the surface arrangement of the charcoal on the grains, whereby - as far as the manufacture of electrodes is concerned - an improved product is achieved.

Therefore, according to the inventive method, the densification of porous, granular coal, a combined Bewegungsbettmitführungsreaktor is charged with the material which is maintained at a temperature of 650-1100 ⁰ C, wherein a cracking of the hydrocarbon gases takes place in the reactor. The porous coal is, for example, low-ash brown coal or low-ash coke, the two-stage treatment mentioned above being carried out. Very fine (ultra-fine) pores in the granular feed to the reactor can be opened by activation which is carried out before the carbon is deposited in the pores.

As already mentioned, there is a corresponding combined moving bed entrainment reactor known from the article mentioned. Basically, a bed that moves downwards occurs hot, granular feed material (carbonized lignite or coke) to hydrocarbon gases that are in the opposite direction Move direction. Hydrocarbon gases are at the

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Feed material cracked and deposited in the pores. the Pores are essentially filled as the cracking proceeds. If the cracking reaction is heat consuming, the temperature of the feed will drop. Particles from the bottom of the bed are carried along by hot gases from a burner and carried up the bed.

To make the best carbon product for electrodes, a certain amount of charge material becomes essentially a fill pyrolytic charcoal is used at a temperature in the range of 650 to 850 ° C. The temperature of the hot entrainment gases is then increased until the particles re-enter the reactor at a temperature of 1100 ° C, causing another cracking of hydrocarbon takes place at a temperature in the range from 850 to 1100 ° C. At these higher temperatures there is an increased order of the carbon stored in the pores, an additional filling and a deposit on the surface.

It is clear to one skilled in the art that the deposit allows only partial filling of the pores of the granular charge for a shorter period of time. This enables the reactivity of the carbonized lignite or coke to be reduced to the required level (by reducing their surface area), while at the same time solidifying by increasing the carbon content. In those cases where maximum density is required, the porous carbon can be subjected to an activation process using known techniques to open up the very fine pores before carbon is deposited. The very fine pores make up about 20 % of the pores in a porous carbon material, and the opening of the pores ensures that they are also filled by pyrolytic charcoal and not blocked _{by carbon which is deposited at the inlet openings of the pores 9.}

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Claims (6)

Claims 1. Process for compressing porous coal, in which a combined Moving bed entrainment reactor with the material that forms the bed, is charged, characterized in, that the material is kept at a temperature in the range between 650 and 1100 ° C and that the hydrocarbon gases in the bed of the reactor are cracked. 2. The method according to claim 1, characterized in that the porous carbon is selected from a group which carbonized Contains lignite, low-ash coke and fine coke. 3. The method according to claim 1 or 2, characterized in that the cracking of the hydrocarbon gases first at a ! Temperature in the range of 650 to 850 ° C and then at a Temperature in the range of 850 to 1100 ° C is carried out. 4. The method according to any one of the preceding claims, characterized in, that the porous carbon undergoes an activation treatment before cracking is subjected to the very fine (ultra-fine) pores within the porous material to open. 5. The method according to any one of the preceding claims, characterized in, that the cracking is completed before the pores of the carbon material are essentially pyrolytic Carbon of the crack are filled in order to thereby ensure the necessary deactivation of the carbon material. 6. Charcoal object characterized by the manufacture according to the method according to one or more of the preceding claims. 409846/0833