PROCEDE DE PRODUCTION D'AGGLOMERES GRAPHITIQUES ET PRODUITS AINSI OBTENUS

PROCESS FOR PRODUCING GRAPHITIC AGGLOMERATES, AND PRODUCTS OBTAINED BY IT

Abrégé anglais

Abstract of the Disclosure
A process for producing graphic agglomerates, comprising the
steps of: mixing together in a suitable mixer a very fine graphitic powder,
a coal such as, anthracite, pit-coal, coke etc., and a binder such as coal tar
pitch, starch, lignin and its derivatives such as lignin-sulphonates etc.,
thermoplastic and thermosetting resins; heating this mixture to about the
melting temperature of the binder; and feeding the amalgamated mixture into a
moulding press in which it is solidified into ovoid shapes, briquets and the
like, or feeding it into a pelletizing plant. These agglomerates find use in
metallurgical and siderurgical processes.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for producing graphitic agglomerates from very fine
graphitic powders of a size generally less than 1mm, which comprises the
steps of mixing in a suitable mixer the graphitic powder, together with a
coal selected from anthracite, pit-coal and coke, and a binder chosen from coal
tar pitch, starch, lignin, lignin derivatives, thermoplastic resins, and
thermosetting resins; heating the thus obtained mixture to about the melting
temperature of the binder; and feeding the thus obtained mixture to either
a molding press or a pelletizing plant, the mixture comprising from 10% to
50% by weight of graphitic powder, from 80% to 28% by weight of coal, and
from 10% to 22% by weight of the binder.
2. A process according to claim 1 wherein the coal is anthracite.
3. A process according to claim 1 wherein the binder is coal tar pitch.
4. A process according to claim 1 wherein the coal is anthracite and
the binder is coal tar pitch.
5. A graphitic agglomerate obtained by mixing in a suitable mixer the
graphitic powder, together with a coal selected from anthracite, coke and pit-
coal, and a binder chosen from coal tar pitch, starch, lignin, lignin
derivatives, thermoplastic resins, and thermosetting resins; heating the thus
obtained mixture to about the melting temperature of the binder; and feeding
the thus obtained mixture to either a molding press or a pelletizing plant,
the mixture comprising from 10% to 50% by weight of graphitic powder, from
80% to 28% by weight of coal, and from 10% to 22% by weight of the binder.
6. An agglomerate according to claim 5 wherein the coal is anthracite.
7. An agglomerate according to claim 6 wherein the binder is coal tar
pitch.

8. An agglomerate according to claim 7 wherein the coal is anthracite
and the binder is coal tar pitch.

Description

10~311418
This inVention relates to the production of graphitic agglo-
merates to be used in the protuction of steel in open-hearth furnaces and
in arc and intuction furnaces as well as in the production of cast iron in
arc and induction furnaces und in rotary and reverberatory furnaces.
The utilisation of coal dusts, which are collected in the various
production steps of graphite electrodes, electrode pastes, graphite anotes
etc., or which are formed by milling scraps of these products, and which
are generally of a particle size below 1 mm, is a question hitherto not
solved. Indeet these very fine graphitic dusts or powders are not utiliz-
able in practice in the form of powter, on one hand, ant it is very diffi-
cult to agglomerate them, on the other hand, as they are notoriously try
lubricants, so that hitherto their agglomeration to utilizable products has
never been successful.
Consequently, up to now sait very fine graphitic powders were
tumpet into large pits, which were then coveret with earth; this expetient,
; besides causing an economic waste, also raises ecological problems.
Considering that sait very fine graphitic powders have a carbon content from
65% to 100% ant furthermore that this carbon is in the allotropic form of
graphite, it is clear that a general economic atvantage might be obtained
by a successful agglomeration of these powders into products of an effective
;~ and easy use in metallurgic furnaces in orter to increase the carbon content
of steels ant cast irons. The ecological atvantage so reachet is eq~lally
apparent, since such an agglomerate is not only free of tust, but on the
contrary very compact.
Several attempts have been made to solve the very difficult
question of the agglomeration of this very fine graphitic powder by using
coal tar pitch, but this requiret at least 30% pitch, so that the agglome~
i
rate could contain at the most 70% graphitic powders. Such high pitch per-
centages yielded a very hard product, whose absorption by the melting bath
was tifficult ant which gave a low yielt in dissolved carbon. Therefore
this protuct was unsuitable for the intentet purpose.
- 1 -
~`

: ' `` 1~418
This invention solves the aforesaid problems by means of a process
permitting the agglomeration of said very fine graphitic powders into suitable
products for metallurgical and siderurgical use.
The invention is based on the agglomeration of said very fine
graphitic powders by using suitable tar pitch percentages and adding other
coals (anthracites, pit-coals, coke etc.); previously many prolonged attempts
were made to bond together very fine graphitic powders by means of various
types of binder but with unsatisfying results, because too high percentages
of binder were requlred to obtain a well compacted product, which was also
expensive and not free from harmful components. The addition of said carbons,
though not necessary to successfully agglomerate very fine graphitic powders,
is indispensable in order to reduce these very high percentages of the binder.
According to the prescnt invention there is provided a process for
producing graphitic agglomerates from very fine graphitic powders of a size
generally less than lmm, which comprises the steps of mixing in a suitable
mixer the graphitic powter, together with a coal selectet from anthracite, pit-
coal and coke, and a binder chosen rom coal tar pitch, starch, lignin, lignin
derivatives, thermoplastic resins, and thermosetting resins; heating the thus
obtainet mixture to about the melting temperature of the binder; and feeding
~ 20 the thus obtained mixture to either a molding press or a pelletizing plant,
- the mixture comprising from 10% to 50% by weight-of graphitic powder, from
80% to 28% by weight of coal, and from 10% to 22% by weight o the binder.
As a binder, in addition So coal tar pitch, also other materials
are adopted, provited they are not detrimental to the good characteristics of
the steel and are economically acceptablej examples of these materials are:
starch, lignin and its derivatives (lignin-sulphonates etc.), thermoplastic
, .
and thermosetting resins.
The various component percentages may range within wide limits,
since they are variable as a function of the graphite contents in said powder
~- 30 as well as of the type of coal. However, limit percentages of the components
of an exemplifying mixture are:

~(~g1418
- very fine graphitic powder with 70% graphite: 10 - 50%
- English anthracite in sizes of 0-10 ~m: 80 - 28%
- tar pitch, KS 70C: 10 - 22%
An indicative mean composition is the following:
- very fine graphitic powder, 80% graphite 35%
- English anthracite in sizes of 0-10 mm: 50%
- tar pîch, KS 70C: 15%
The present invention also includes all the various products ob-
tained with the above explained process.