CA1082422A - Process for the production of silicon carbide - Google Patents
Process for the production of silicon carbideInfo
- Publication number
- CA1082422A CA1082422A CA251,448A CA251448A CA1082422A CA 1082422 A CA1082422 A CA 1082422A CA 251448 A CA251448 A CA 251448A CA 1082422 A CA1082422 A CA 1082422A
- Authority
- CA
- Canada
- Prior art keywords
- silicon carbide
- production
- rectifier
- electric resistance
- resistance furnace
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/0019—Circuit arrangements
- H05B3/0023—Circuit arrangements for heating by passing the current directly across the material to be heated
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/956—Silicon carbide
- C01B32/963—Preparation from compounds containing silicon
- C01B32/97—Preparation from SiO or SiO2
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Carbon And Carbon Compounds (AREA)
- Ceramic Products (AREA)
- Furnace Details (AREA)
- Resistance Heating (AREA)
Abstract
Title of the Invention PROCESS FOR THE PRODUCTION OF SILICON CARBIDE
Abstract of the Disclosure A process for the production of silicon carbide by con-version of quartz sand and coke, preferably in the presence of common salt and sawdust, in an electric resistance furnace. The conversion is conducted in an electric resistance furnace which has a heating core which is connected to a DC current source.
Preferably the DC current device is connected to a heating core by means of a movable rectifier-transformer unit.
Abstract of the Disclosure A process for the production of silicon carbide by con-version of quartz sand and coke, preferably in the presence of common salt and sawdust, in an electric resistance furnace. The conversion is conducted in an electric resistance furnace which has a heating core which is connected to a DC current source.
Preferably the DC current device is connected to a heating core by means of a movable rectifier-transformer unit.
Description
, 108;~422 ¦I Background of the Invention ! 1. Field of This Invention Il .
This invention relates to a process for the production ~! of silicon carbide using an electrical resistance furnace.
,2. Prior Art i Silicon carbide has been produced on an industrial l scale using the electrical resistance furnace according to the ! process developed by Acheson at the end of the l9th Century. An electrical resistance furnace consists of two stationary fire resis-l tant walls, opposite one another, through which the electrodes i projecting into the furnace are inserted. AC current is applied to i the electrodes. The fire resistant lateral walls can be disassem~
bled and are removed after completion of the burning process in order to clear away the charge. The summation equation of the production of silicon carbide is:
SiO2 + 3 C ~ SiC + 2 CO (-1120 Kcal) . . '.
The crude mixture consists of granular quartz and coke, advantage-ously mixed with sawdust and common salt. The protion of the main components in the crude mixture corresponds to the stoichiometric ' ratio with a slight excess of coke.
First the furnace is filled up to the level of the elec-trodes with the crude mixture. Subsequently the electrode blocks , are contacted or connected with a heating conductor (nerve) con-sisting of a coke-graphite mixture an~ the remaining crude mixture, is charged. The conversion process is completed after 25 to 36 hou~s~ The cooling time is several days. The lateral walls of the furnace are dismantled and the cylindrical crust, which has formed, is separated from the unconverted portion of the crude mixture.
This invention relates to a process for the production ~! of silicon carbide using an electrical resistance furnace.
,2. Prior Art i Silicon carbide has been produced on an industrial l scale using the electrical resistance furnace according to the ! process developed by Acheson at the end of the l9th Century. An electrical resistance furnace consists of two stationary fire resis-l tant walls, opposite one another, through which the electrodes i projecting into the furnace are inserted. AC current is applied to i the electrodes. The fire resistant lateral walls can be disassem~
bled and are removed after completion of the burning process in order to clear away the charge. The summation equation of the production of silicon carbide is:
SiO2 + 3 C ~ SiC + 2 CO (-1120 Kcal) . . '.
The crude mixture consists of granular quartz and coke, advantage-ously mixed with sawdust and common salt. The protion of the main components in the crude mixture corresponds to the stoichiometric ' ratio with a slight excess of coke.
First the furnace is filled up to the level of the elec-trodes with the crude mixture. Subsequently the electrode blocks , are contacted or connected with a heating conductor (nerve) con-sisting of a coke-graphite mixture an~ the remaining crude mixture, is charged. The conversion process is completed after 25 to 36 hou~s~ The cooling time is several days. The lateral walls of the furnace are dismantled and the cylindrical crust, which has formed, is separated from the unconverted portion of the crude mixture.
2-,; i1 ~ .
!l ,i In the case of such process, well-developed SiC crystals ¦are achieved at a temperature of about 2000~ to about 2300C.
! Above approximately 2300C., the SiC is decomposed. The silicon developing during the decomposition evaporates and is deposited in i colder zones; the relatively pure graphite which remains behind ¦ contaminates the silicon carbide.
¦ In the case of direct resistance heating, the voltage is ¦applied directly to the heating conductor. In the regular case, Ithe voltages here are low and currents are very high. If one wants Ito achieve a uniform heating, and that is always sought, then the resistance of the heating material must be uniform over the entire path of the current (cross section) - therefore, any uneveness in l the cross section must not be present. Both assumptions (presupp-! ositions) are difficult to fulfill. The question of contract alsooffers considerable difficulty. Not only is a very good contact required, with the least possible transmission resistance, but also again a uniform transmission of the current is required. In the case of a high current intensity of a few thousand ampere, even a transition resistance of a fraction of an ohm will lead to con-siderable development of heat. Such heat must then be eliminated by particular (selective) cooling of the place of contact and constltutes a loss in the power balance. In the case of the use of AC current for heating, and practically only this comes into question, since it alone will permit withdrawal of the high current in a simple manner from the main system, the reaction of the strong ¦ magnetic fields must also be taken into consideration [Ullmann, I Vol. I, (1951), page 191].
The achievement of a good yield of heat and thus of a ~29 high energy yield presupposes as small as possible idle (reactive) ':
~ -3-1i1 i lOB;~422 power (Cos ~). However, this supposition in the case of the known SiC resistance furnaces has been fulfilled very poorly and imperfectly. In order to keep this idle power as small as possible, capacitors are connected in series in a known manner. However, even in the case of series connected capacitors, there are certain limits to the furnaces with regard to cross section and length. For example, in the case of enlargement of the cross section and length, the idle power is greatly increased.
In most cases, three such furnaces are switched in parallel in order to achieve a balanced load of the generator and of the main system.
.~
`
¦I Description of This Invention Il , An object of this invention is to provide a process il that eliminates the enumerated disadvantages of the prior art.
Another object of this invention is to provide a process that has an increased power yield and uniform furnace run. Other objects and advantages of tnis process are set forth herein or are obvious herefrom to one ordinarily skilled in the art.
The objects and advantages of this process are ¦ achieved by the process of this invention.
! This involves a process for the production of silicon carbide by conversion of quartz sand and coke, preferably in the presence of common salt and sawdust, in an electric resistance furnace. The conversion is conducted in an electric resistance ' -furnace which has a heating core which is connected to a DC current source. Preferably the DC current source is connected to the ¦ heating core by means of a movable rectifier-transformer unit.
Preferably such rectifier/transformer unit is pre-programmable.
This invention achieves a uniform run of the electricall resistance furnace and in increased power yield (small idle power) even in the case of large dimensioned furnaces, whenever such electrical resistance furnaces are operated with DC current (i.e., the heating core is attached to a DC current source).
The process of this invention for the production of silicon carbide from quartz sand, coa~ sawdust and common salt is characterized in that the conversion is carried out in an electric resistance furnace which has a heating core which is attached to a DC current.
Preferably a Si-rectifier/transformer, most preferably 29 a movable Si-rectifier/transformer, is inserted between the main .
system and the furnace. By this arrangement, a three-phase current ¦¦(all three phases) can be rectified. As a result of the rectifier/
,transformer unit being movable, such unit can be moved directly up jto the furnace. The losses resulting from long supply lines are ¦eliminated. A unilateral load of the main system is omitted.
¦ A further advantage of this invention is that this arrangement can be more easily regulated and thus fewer losses of power develop.
Il The rectifier/transformer unit is preferably pre-pro-llgrammable, whereby the predetermined program corresponds to the ~-¦pertinent power (energy) absorption of the furnace.
Electrical resistance furnaces operated according to this invention are operated with abut 80 KA. The performance amounts to 350 to 400 kW per meter of length of furnace. The achievable yield amounts to about 40 kg of well-crystallized SiC
per meter of length of furnace per hour.
!l ,i In the case of such process, well-developed SiC crystals ¦are achieved at a temperature of about 2000~ to about 2300C.
! Above approximately 2300C., the SiC is decomposed. The silicon developing during the decomposition evaporates and is deposited in i colder zones; the relatively pure graphite which remains behind ¦ contaminates the silicon carbide.
¦ In the case of direct resistance heating, the voltage is ¦applied directly to the heating conductor. In the regular case, Ithe voltages here are low and currents are very high. If one wants Ito achieve a uniform heating, and that is always sought, then the resistance of the heating material must be uniform over the entire path of the current (cross section) - therefore, any uneveness in l the cross section must not be present. Both assumptions (presupp-! ositions) are difficult to fulfill. The question of contract alsooffers considerable difficulty. Not only is a very good contact required, with the least possible transmission resistance, but also again a uniform transmission of the current is required. In the case of a high current intensity of a few thousand ampere, even a transition resistance of a fraction of an ohm will lead to con-siderable development of heat. Such heat must then be eliminated by particular (selective) cooling of the place of contact and constltutes a loss in the power balance. In the case of the use of AC current for heating, and practically only this comes into question, since it alone will permit withdrawal of the high current in a simple manner from the main system, the reaction of the strong ¦ magnetic fields must also be taken into consideration [Ullmann, I Vol. I, (1951), page 191].
The achievement of a good yield of heat and thus of a ~29 high energy yield presupposes as small as possible idle (reactive) ':
~ -3-1i1 i lOB;~422 power (Cos ~). However, this supposition in the case of the known SiC resistance furnaces has been fulfilled very poorly and imperfectly. In order to keep this idle power as small as possible, capacitors are connected in series in a known manner. However, even in the case of series connected capacitors, there are certain limits to the furnaces with regard to cross section and length. For example, in the case of enlargement of the cross section and length, the idle power is greatly increased.
In most cases, three such furnaces are switched in parallel in order to achieve a balanced load of the generator and of the main system.
.~
`
¦I Description of This Invention Il , An object of this invention is to provide a process il that eliminates the enumerated disadvantages of the prior art.
Another object of this invention is to provide a process that has an increased power yield and uniform furnace run. Other objects and advantages of tnis process are set forth herein or are obvious herefrom to one ordinarily skilled in the art.
The objects and advantages of this process are ¦ achieved by the process of this invention.
! This involves a process for the production of silicon carbide by conversion of quartz sand and coke, preferably in the presence of common salt and sawdust, in an electric resistance furnace. The conversion is conducted in an electric resistance ' -furnace which has a heating core which is connected to a DC current source. Preferably the DC current source is connected to the ¦ heating core by means of a movable rectifier-transformer unit.
Preferably such rectifier/transformer unit is pre-programmable.
This invention achieves a uniform run of the electricall resistance furnace and in increased power yield (small idle power) even in the case of large dimensioned furnaces, whenever such electrical resistance furnaces are operated with DC current (i.e., the heating core is attached to a DC current source).
The process of this invention for the production of silicon carbide from quartz sand, coa~ sawdust and common salt is characterized in that the conversion is carried out in an electric resistance furnace which has a heating core which is attached to a DC current.
Preferably a Si-rectifier/transformer, most preferably 29 a movable Si-rectifier/transformer, is inserted between the main .
system and the furnace. By this arrangement, a three-phase current ¦¦(all three phases) can be rectified. As a result of the rectifier/
,transformer unit being movable, such unit can be moved directly up jto the furnace. The losses resulting from long supply lines are ¦eliminated. A unilateral load of the main system is omitted.
¦ A further advantage of this invention is that this arrangement can be more easily regulated and thus fewer losses of power develop.
Il The rectifier/transformer unit is preferably pre-pro-llgrammable, whereby the predetermined program corresponds to the ~-¦pertinent power (energy) absorption of the furnace.
Electrical resistance furnaces operated according to this invention are operated with abut 80 KA. The performance amounts to 350 to 400 kW per meter of length of furnace. The achievable yield amounts to about 40 kg of well-crystallized SiC
per meter of length of furnace per hour.
Claims (6)
1. In a process for the production of silicon carbide by conversion of quartz and coke in an electric resistance furnace, the improvement characterized in that the conversion is conducted in an electric resistance furnace which has a heating core which is connected to a DC current source.
2. A process as described in Claim 1 wherein the DC current source is connected to the heating core by means of a movable rectifier-transformer unit.
3. A process as described in Claim 2 wherein the rectifier/transformer unit is pre-programmable.
4. A process as described in Claim 1 wherein common salt and sawdust are also present.
5. In a process for the production of silicon carbide by conversion of quartz sand and coke, in the presence of common salt and sawdust, in an electric resistance furnace, the improvement characterized in that the conversion is conducted in an electric resistance furnace which has a heating core which is connected to a DC current source by means of a pre-programmable movable rectifier-transformer unit.
6. A process as described in Claim 5 wherein the rectifier/transformer is a movable Si-rectifier/
transformer.
transformer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH552575A CH595283A5 (en) | 1975-04-29 | 1975-04-29 | |
| CH5525/75 | 1975-04-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1082422A true CA1082422A (en) | 1980-07-29 |
Family
ID=4295077
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,448A Expired CA1082422A (en) | 1975-04-29 | 1976-04-29 | Process for the production of silicon carbide |
Country Status (11)
| Country | Link |
|---|---|
| BE (1) | BE841291A (en) |
| CA (1) | CA1082422A (en) |
| CH (1) | CH595283A5 (en) |
| DE (1) | DE2617647A1 (en) |
| ES (1) | ES447420A1 (en) |
| FR (1) | FR2309469A1 (en) |
| GB (1) | GB1476916A (en) |
| IT (1) | IT1058237B (en) |
| NL (1) | NL182394C (en) |
| NO (1) | NO761442L (en) |
| ZA (1) | ZA762478B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0171858A3 (en) * | 1984-08-14 | 1989-06-14 | AGIP S.p.A. | Method of making silicon carbide and coatings of silicon carbide on carbonaceous substrates |
| DE4226867C1 (en) * | 1992-08-13 | 1993-11-25 | Kempten Elektroschmelz Gmbh | Resistance heated open furnace for silicon carbide prodn. - has multi-limb resistive core connected to poly phase supply |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR327189A (en) * | 1902-12-09 | 1903-06-16 | Acheson Edward Goodrich | Improved method and apparatus for reduction of compounds by electric heating |
| GB383540A (en) * | 1931-05-11 | 1932-11-17 | Aurele Louis Mingard | A process for manufacturing hard objects of carbon silicide or like substances |
| US2005956A (en) * | 1931-12-02 | 1935-06-25 | Norton Co | Method of making abrasive metal carbides and an apparatus therefor |
| FR887377A (en) * | 1941-11-26 | 1943-11-11 | Deutsche Edelstahlwerke Ag | Method and device for obtaining reactions between metal oxides or oxidic ores and coal |
-
1975
- 1975-04-29 CH CH552575A patent/CH595283A5/xx not_active IP Right Cessation
-
1976
- 1976-04-22 DE DE19762617647 patent/DE2617647A1/en not_active Ceased
- 1976-04-22 NL NLAANVRAGE7604277,A patent/NL182394C/en not_active IP Right Cessation
- 1976-04-26 ZA ZA762478A patent/ZA762478B/en unknown
- 1976-04-27 GB GB1700776A patent/GB1476916A/en not_active Expired
- 1976-04-27 IT IT49204/76A patent/IT1058237B/en active
- 1976-04-27 NO NO761442A patent/NO761442L/no unknown
- 1976-04-28 ES ES447420A patent/ES447420A1/en not_active Expired
- 1976-04-29 FR FR7612762A patent/FR2309469A1/en active Granted
- 1976-04-29 CA CA251,448A patent/CA1082422A/en not_active Expired
- 1976-04-29 BE BE166582A patent/BE841291A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| NL7604277A (en) | 1976-11-02 |
| NL182394C (en) | 1988-03-01 |
| BE841291A (en) | 1976-10-29 |
| GB1476916A (en) | 1977-06-16 |
| CH595283A5 (en) | 1978-02-15 |
| FR2309469B1 (en) | 1981-09-25 |
| ZA762478B (en) | 1977-04-27 |
| NL182394B (en) | 1987-10-01 |
| NO761442L (en) | 1976-11-01 |
| FR2309469A1 (en) | 1976-11-26 |
| ES447420A1 (en) | 1977-07-01 |
| IT1058237B (en) | 1982-04-10 |
| DE2617647A1 (en) | 1976-11-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |