U.S. patent application number 10/416830 was filed with the patent office on 2004-02-12 for method for rendering inert dust residue containing silicon metal.
Invention is credited to Weber, Rainer, Werkmeister, Jorg.
Application Number | 20040025637 10/416830 |
Document ID | / |
Family ID | 7663474 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040025637 |
Kind Code |
A1 |
Werkmeister, Jorg ; et
al. |
February 12, 2004 |
Method for rendering inert dust residue containing silicon
metal
Abstract
The invention relates to a method for rendering inert dust
residue containing silicon metal, left over from trichlorosilane
synthesis. The inventive method produces valuable materials
containing silicon which can be used in metallurgical processes.
According to said method, the process of rendering the residue
inert is carried out in several steps. In a first step, 10 to 50
wt. % water, in relation to the quantity of residue, and an at
least equimolar quantity of an alkaline compound, in relation to
the chloride content of the residue, are added to the residue.
Subsequently or simultaneously, the residue is heated to a
temperature of 50 to 200.degree. C. In a further step, at least
twice the quantity of water is added to this mixture, which is
extensively liberated from dissolved salts by filtration and
subsequent washing with water.
Inventors: |
Werkmeister, Jorg;
(Freiberg, DE) ; Weber, Rainer; (Odenthal,
DE) |
Correspondence
Address: |
MCGLEW & TUTTLE, PC
SCARBOROUGH STATION
SCARBOROUGH
NY
10510
US
|
Family ID: |
7663474 |
Appl. No.: |
10/416830 |
Filed: |
May 14, 2003 |
PCT Filed: |
November 3, 2001 |
PCT NO: |
PCT/EP01/12755 |
Current U.S.
Class: |
75/444 |
Current CPC
Class: |
A62D 3/36 20130101; Y02P
10/20 20151101; C22B 7/006 20130101 |
Class at
Publication: |
75/444 |
International
Class: |
C21B 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2000 |
DE |
100 56 722.3 |
Claims
1. A method for rendering inert dust residue containing silicon
metal originating from the trichlorosilane synthesis, characterised
by the following steps: the residues are mixed with 10 to 50 weight
percent water, in relation to the quantity of residue, and an at
least equimolar quantity of an alkaline compound, in relation to
the chloride content of the residue; the mixture is heated to a
temperature ranging from 50 to 200.degree. C.; the heated mixture
is mixed with at least the double amount of water; and subsequently
the mixture is extensively liberated from dissolved salts by
filtration and subsequent washing with water.
2. A method according to claim 1, characterised in that the
alkaline compound is provided at a molar excess of 2 to 10%, in
relation to the chloride content of the residues.
3. A method according to claim 1 or 2, characterised in that the
alkaline compounds used are NaOH, Na.sub.2CO.sub.3, NaHCO.sub.3,
CaO, Ca(OH).sub.2 or cement.
4. A method according to claim 1 or 2, characterised in that the
alkaline compounds used are CaO, Na.sub.2CO.sub.3 and cement or
mixtures thereof.
5. A method according to any one of claims 1 to 4, characterised in
that in the first step the mixture is heated to a temperature
ranging from 100 to 150.degree. C., preferably 120 to 140.degree.
C.
6. A method according to any one of claims 1 to 5, characterised in
that after heating the mixture is maintained at this temperature
for a period of 10 to 60 minutes.
7. A method for the execution of a metallurgical process, in
particular for the production of an iron alloy or copper,
comprising the following steps: a) rendering inert dust residue
containing silicon metal originating from the trichlorosilane
synthesis, comprising the following steps of rendering inert: the
residues are mixed with 10 to 50 weight percent water, in relation
to the quantity of residue, and an at least equimolar quantity of
an alkaline compound, in relation to the chloride content of the
residue; the mixture is heated to a temperature ranging from 50 to
200.degree. C.; the heated mixture is mixed with at least the
double amount of water; and subsequently the mixture is extensively
liberated from dissolved salts by filtration and subsequent washing
with water; b) utilisation of these inert residues in the
subsequent metallurgical process.
Description
[0001] The invention relates to a method for rendering inert dust
residue containing silicon metal originating from the
trichlorosilane synthesis in a fluidised bed as well as the use of
such inert residues in metallurgical processes.
[0002] Trichlorosilane is produced in the technical scope in
accordance with the "Studies in Organic Chemistry 49; Catalyzed
Direct Reactions of Silicon", Elsevier, 1993, p. 445 to 457 by
reacting metallurgical silicon with hydrogen chloride or by
reacting silicon with tetrachlorosilane and hydrogen. As a rule,
such processes are carried out in fluidised-bed reactors adding
catalysts, like e.g. copper or copper compounds, as well as without
adding any catalyst.
[0003] All such processes have in common that the
trichlorosilane-containi- ng gaseous product mixture that leaves
the fluidised bed is contaminated by solid dust containing silicon
and, if any, catalyst. The removal of such dust is achieved by
separation in a cyclone or in several cyclones which are connected
in series or by hot-gas filtration with ceramic or sintered metal
candles. Any dust residue remaining in the
trichlorosilane-containing gaseous product mixture is subsequently
removed by washing with liquid chlorosilanes.
[0004] Alternatively, procedures are known, wherein the dust is
removed from the trichlorosilane-containing product mixture
exclusively by washing with liquid chlorosilanes or by total
condensation of the product mixture and subsequent distillation
without previous separation by means of cyclones or hot-gas
filters. The suspensions containing chlorosilanes or dust which
occur in this process are usually processed to regain
chlorosilanes.
[0005] According to the methods specified in DE 36 42 285 C1, DE 37
09 577 A1, DE39 41 825 A1, DE39 41 827 A1, DE41 16 925 A1, DE41 30
880 A1, DE41 30 881 A1, DE42 43 223 C1, EP0 201 200 A1, EP 0521309
A1, U.S. Pat. No. 4,690,810 they can be processed by distillation,
wherein a distillation bottom product occurs containing silicon,
metal chlorides and, if any, catalyst, which needs to be disposed
of after rendering inert by alkali or by a treatment with water
vapour. A use of the mixtures of hydrolysed metal chlorides and
hydrolysed chlorosilanes occurring in such process, e.g. in
metallurgical processes, is not economic because of the high
contents of chloride and the low contents of valuable metals,
particularly silicon metal. In order to obtain a valuable product,
it is therefore advantageous, to extensively separate the solid
dust compounds of the trichlorosilane-containing product mixture
originating from the trichlorosilane synthesis prior to the gas
washing or the total condensation and to process them
separately.
[0006] The dust occurring in the cyclones and/or the hot-gas filter
can be composed differently depending on the operating conditions
in the fluidised-bed reaction, the composition of the metallurgical
silicon used and the application of catalyst. It consists
essentially of non-reacted residues of the metallurgical silicon
used, chlorides like FeCl.sub.2 and CaCl.sub.2, and catalyst and/or
a catalyst compound, if any. Such dust material is highly reactive
and must be rendered inert prior to its use. Inerting in this sense
means that the reactivity of the dust material is reduced and its
handleability is improved.
[0007] According to EP-A1-0 201 200 inerting can be achieved by
mixing the dust material with water and granulation of such
mixture. The product occurring is now rendered inert, but cannot be
used directly as a raw material in metallurgical processes,
however, because of its high chloride contents and low pH-value,
combined with the easy elutability of metal ions, requiring a
reprocessing of the product.
[0008] DE-C1-195 07 602 specifies another possibility of rendering
inert, wherein the dust material is reacted in hydrous suspension
with alkaline compounds, such as e.g. NaOH, CaO, Na.sub.2CO.sub.3,
NaHCO.sub.3 or cement, and subsequently filtered. Inerting is
achieved also in this procedure, but the suspensions occurring are
often difficultly filterable, resulting in filter cake with a high
water and chloride content. Also such products cannot be used
directly as raw material in metallurgical processes and must be
reprocessed in expensive aftertreatment.
[0009] EP 0 416 584 A1 discloses the use of a heatable solids mixer
as well as a heatable plough blade mixer within the scope of
processes of chemical engineering.
[0010] EP 0 428 338 A2 discloses a method of rendering inert
metallic silicon containing residues that originate during the
generation of organic halogenide silane compounds. Water and an
alkali compound are added to these residues. In the process, the
residues are added to an aqueous basic solution, which has been
heated to 50 to 100.degree. C., and then filtered.
[0011] EP 0 433 600 A2 describes a method of processing silicon
containing residues by reaction with calcium bases or calcium
carbonate.
[0012] The object of the invention is therefore to provide a method
for rendering inert dust residue containing silicon metal
originating from the trichlorosilane synthesis, providing an easy
way of obtaining valuable materials containing silicon metal, which
can be used in metallurgical processes.
[0013] This object is achieved by a method for rendering inert dust
residue containing silicon metal originating from the
trichlorosilane synthesis, characterised in that the process of
rendering the residue inert is carried out in several steps. In a
first step, 10 to 50 weight percent water, in relation to the
quantity of residue, and an at least equimolar quantity of an
alkaline compound, in relation to the chloride content of the
residue, are added to the residue. Subsequently or simultaneously,
the residue is heated to a temperature of 50 to 200.degree. C. In a
further step, at least twice the quantity of water is added to this
mixture, which is extensively liberated from dissolved salts by
filtration and subsequent washing with water.
[0014] It is preferred to use the alkaline compound at a molar
excess ratio of 2 to 10%, in relation to the chloride content of
the residues. Such alkaline compounds can be, for example, NaOH,
Na.sub.2CO.sub.3, NaHCO.sub.3, CaO, Ca(OH).sub.2 or cement.
Preferred are CaO, Na.sub.2CO.sub.3 and cement or any mixtures
thereof.
[0015] In a particularly preferred modification of the inventive
method the mixture is heated to a temperature in the range from 100
to 150.degree. C., preferably 120 to 140.degree. C.
[0016] In a modification of the inventive method the mixture having
been heated to 50 to 200.degree. C. is maintained at this
temperature for a period of 10 to 60 minutes.
[0017] When the material according to the invention is applied the
products obtained have as a rule a chloride content of <1 weight
percent in relation to the dry substance and a water content of
<40 weight percent. Such products can be used in metallurgical
processes, such as e.g. the manufacture of iron alloys or the
manufacture of copper, without any further aftertreatment.
[0018] The preparation of the mixture in the first step can be
carried out in a usual heatable solids mixer. Preferably mixers
with in-built mixing tools are used, e.g. plough blade mixers.
[0019] Filtration and washing is preferably carried out in a filter
press. It showed that washing the filter cake requires only small
amounts of water in order to remove the dissolved salts
extensively. The preferred amount of water is in a range of a 1.5
to double the amount in relation to the mass of the filter
cake.
[0020] The method according to the invention will be explained in
the following by means of some examples.
[0021] The composition and the silicon corn spectrum of the samples
used in the experiments correspond to typical dust residue
containing silicon metal originating from the reaction of
metallurgical silicon with silicon tetrachloride and hydrogen to
trichlorosilane.
[0022] The samples used had the following composition:
1 Sample A Sample B Si 57.2 wt. percent Si 48.4 wt. percent Fe 4.8
wt. percent Fe 18.7 wt. percent Cu 26.0 wt. percent Cl 29.0 wt.
percent Cl 10.2 wt. percent residue 3.9 wt. percent residue 1.8 wt.
percent (Ca etc.) (Ca etc.)
[0023] The composition of Sample A corresponds to a residue
originating from a trichlorosilane synthesis which was catalysed
with CuCl and wherein metallurgical silicon with an Fe contents of
0.4 weight percent was used. The composition of Sample B
corresponds to a residue originating from a trichlorosilane
synthesis wherein metallurgical silicon with an Fe contents of 1.9
weight percent was used.
EXAMPLE 1 (COMPARATIVE EXAMPLE)
[0024] 200 g of Sample A were mixed with 20 g cement and 1000 ml
water and heated to 75.degree. C. Subsequently the pH-value was
adjusted to 8 in the suspension by 10 molar soda lye. After 60 min
the suspension was filtered over a vacuum laboratory filter and
washed on the filter with 600 ml of water. The filter cake sucked
off had a water content of 44.5 weight percent.
EXAMPLE 2 (COMPARATIVE EXAMPLE)
[0025] 200 g of Sample B were mixed with 20 g cement and 1000 ml
water and heated to 75.degree. C. Subsequently the pH-value was
adjusted to 8 in the suspension by 10 molar soda lye. After 60 min
the suspension was filtered over a vacuum laboratory filter and
washed on the filter with 600 ml of water. The filter cake sucked
off had a water content of 70 weight percent.
EXAMPLE 3 (COMPARATIVE EXAMPLE)
[0026] 100 g of Sample B were mixed with 45.5 g Na.sub.2CO.sub.3
(equivalent to 1.05 mol pro mol chloride), 5 g cement and 289 ml
water. This adjusted a temperature of 35.degree. C. After 45
minutes the suspension was filtered over a vacuum laboratory filter
and washed on the filter with 250 ml of water. The filter cake
sucked off had a water content of 45.1 weight percent and a
chloride content of 0.24 weight percent based on dry substance.
EXAMPLE 4 (COMPARATIVE EXAMPLE)
[0027] 100 g of Sample A were mixed with 16 g Na.sub.2CO.sub.3
(equivalent to 1.05 mol pro mol chloride), 5 g cement and 14 ml
water. This adjusted a temperature of 52.degree. C. After 45
minutes the mixture was mixed with 250 ml water and filtered over a
laboratory pressure filter at a filtration pressure of 2.5 bar and
subsequently washed on the pressure filter with 250 ml water. The
filter cake had a water content of 26 weight percent and a chloride
content of 1.2 weight percent based on dry substance.
EXAMPLE 5 (COMPARATIVE EXAMPLE)
[0028] 100 g of Sample B were mixed with 45.5 g Na.sub.2CO.sub.3
(equivalent to 1.05 mol pro mol chloride), 5 g cement and 39 ml
water. This adjusted a temperature of 53.degree. C. After 45
minutes the mixture was mixed with 250 ml water and filtered over a
laboratory pressure filter at a filtration pressure of 2.5 bar and
subsequently washed on the pressure filter with 250 ml water. The
filter cake had a water content of 40.3 weight percent and a
chloride content of 1.4 weight percent based on dry substance.
EXAMPLE 6 (ACCORDING TO THE INVENTION)
[0029] 100 g of Sample A were mixed with 16 g Na.sub.2CO.sub.3
(equivalent to 1.05 mol pro mol chloride) and 14 ml water and
heated to 130.degree. C. After 45 minutes the mixture was mixed
with 250 ml water and filtered over a laboratory pressure filter at
a filtration pressure of 2.5 bar and subsequently washed on the
pressure filter with 250 ml water. The filter cake had a water
content of 23.4 weight percent and a chloride content of 0.27
weight percent based on dry substance.
EXAMPLE 7 (ACCORDING TO THE INVENTION)
[0030] 100 g of Sample A were mixed with 16 g Na.sub.2CO.sub.3
(equivalent to 1.65 mol pro mol chloride), 5 g cement and 14 ml
water and heated to 130.degree. C. After 45 minutes the mixture was
mixed with 250 ml water and filtered over a laboratory pressure
filter at a filtration pressure of 2.5 bar and subsequently washed
on the pressure filter with 250 ml water. The filter cake had a
water content of 25.5 weight percent and a chloride content of 0.7
weight percent based on dry substance.
EXAMPLE 8 (ACCORDING TO THE INVENTION)
[0031] 100 g of Sample B were mixed with 45.5 g Na.sub.2CO.sub.3
(equivalent to 1.05 mol pro mol chloride) and 39 ml water and
heated to 130.degree. C. After 45 minutes the mixture was mixed
with 250 ml water and filtered over a laboratory pressure filter at
a filtration pressure of 2.5 bar and subsequently washed on the
pressure filter with 250 ml water. The filter cake had a water
content of 32 weight percent and a chloride content of 0.24 weight
percent based on dry substance.
EXAMPLE 9 (ACCORDING TO THE INVENTION)
[0032] 100 g of Sample B were mixed with 45.5 g Na.sub.2CO.sub.3
(equivalent to 1.05 mol pro mol chloride), 5 g cement and 39 ml
water and heated to 130.degree. C. After 45 minutes the mixture was
mixed with 250 ml water and filtered over a laboratory pressure
filter at a filtration pressure of 2.5 bar and subsequently washed
on the pressure filter with 250 ml water. The filter cake had a
water content of 37 weight percent and a chloride content of 0.38
weight percent based on dry substance.
[0033] As can be seen from the examples, the method according to
the invention provides products with water contents below 40 weight
percent and chloride contents below 1 weight percent (in relation
to the dry substance). Therefore these products are particularly
suitable for a utilisation in metallurgical processes.
* * * * *