Method for the production of graphite bodies

Abstract

The present invention relates to a method for production of graphite bodies. Carbon bodies are formed from a mixture of electric calcined coke particles calcined at a temperature between 1200 and 3000 C. and a binder where the coke particles have sulphur-and nitrogen content varying between 0 and 1.5% by weight and where the coke particles have an average sulphur content less than 0.6% by weight and a nitrogen content of less than 0.6% by weight, baking of the carbon bodies at a temperature between 700 and 1400 C. and graphitizing of the baked carbon bodies at a temperature above 2300 C.

Claims

1. Method for production of graphite bodies, comprising: selecting electric calcined coke particles calcined in an electric calcining furnace at a non-uniform temperature between 1200 and 3000 C.; the selected electric calcined coke particles comprising individual coke particles vary from each other in sulfur content and in nitrogen content, the varying content of sulfur of the individual coke particles varying between 0 and 1.5% by weight, the varying content of nitrogen of the individual coke particles varying between 0 and 1.5% by weight; forming a mixture from the selected electric calcined coke particles, the mixture having an average sulfur content less than 0.6% by weight and an average nitrogen content of less than 0.6% by weight; forming carbon bodies from the mixture of the selected electric calcined coke particles and a binder; baking the carbon bodies at a temperature between 700 and 1400 C.; and graphitizing the baked carbon bodies at a temperature above 2300 C.

2. Method according to claim 1, wherein the mixture of coke particles and binder consist of 70-90% by weight of coke particles and 10-30% by weight of binder.

3. Method according to claim 2, wherein the mixture of coke particles and hinder consist of 80-87% by weight of coke particles and 13-20% by weight of binder.

4. Method according to claim 1, wherein the binder is tar pitch, petrol pitch or a resin based binder.

5. Method according to claim 4, wherein the resin based hinder is selected among phenolic resin, furan resin and furfuryl alcohol.

6. Method according to claim 1, wherein the baking of the carbon bodies is carried out at a temperature between 700 and 900 C.

7. Method according to claim 1, wherein the graphitizing of the baked carbon bodies are carried out at a temperature above 2300 C.

8. Method according to claim 1, wherein the electric calcined coke particles have an average sulfur content of less than 0.3% by weight.

9. Method according to claim 1, wherein the electric calcined coke particles have an average nitrogen content of less than 0.3% by weight.

10. Method according to claim 1, wherein the electric calcined coke particles are selected among petrol coke, pitch coke, needle coke and anthracite.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows appearant/geometric density for six commercial qualities of graphite is marked A-F while the density for graphite bodies produced according to the invention are shown by a dotted horizontal line. For quality A and B the density is shown both for unimpregnated graphite and for the same graphite impregnated once (I). For quality C and D it is shown density for graphite impregnated once (1) and for the same graphite impregnated twice (2).

(2) FIG. 2 shows similar diagram as shown in FIG. 1 for porosity for graphite bodies produced according to the invention (horizontal line) compared with the same six commercial graphite bodies A-F as shown in FIG. 1.

(3) FIG. 3 shows similar diagram as shown in FIG. 1 for electric resistivity for graphite bodies produced according to the invention (horizontal dotted line) compared with the same six commercial graphite bodies A-F as shown in FIG. 1.

(4) FIG. 4 shows similar diagram as shown in FIG. 1 for air permeability for graphite bodies produced according to the present invention (horizontal line) compared with the same six commercial graphite bodies A-F as shown in FIG. 1.

EXAMPLE

(5) Production of Graphite Bodies

(6) Electric calcined petrol coke calcined at a temperature between 1200 and 3000 C. having a sulphur content of 0.3% by weight was mixed with 20% by weight of tar pitch. The mixture contained 80% by weight of electric calcined petrol coke and 20% by weight of tar pitch.

(7) The mixture was formed to a rectangular body by vibration and thereafter baked at 950 C.

(8) The baked carbon body was thereafter graphitized in a standard graphitizing furnace at a temperature of 2300-3000 C.

(9) Samples of the graphite body were tested for density, porosity, electric resistivity and air permeability. Electric resistivity and air permeability are dependant on the direction and values for respectively parallel and perpendicular direction of the grains were measured. The results are shown in Table 1.

(10) TABLE-US-00001 TABLE 1 Parallell to Perpendicular to grain the grain Property Unit direction direction Appearant density: g/cm.sup.3 1.734 Open porosity: % 14.3 Electric resistivity: m 7.7 9.0 Air permeability: nPm 2.8 0.8

(11) The results in Table 1 show that graphite bodies produced by the method according to the present invention have properties that are substantially better than for the commercial graphite bodies produced without impregnation, baking and a second graphitization after the first graphitization step.

(12) The graphite bodies produced according to the present invention have a substantially higher density than unimpregnated the commercial graphite bodies A, B and E shown in FIG. 1 and as high or higher density then the commercial graphite body A, B, C, D and F which have been impregnated once. Only the commercial graphite bodies C and D which have been impregnated twice have a significant higher density than the graphite bodies produced according to the present invention. Two times impregnation followed by baking and graphitizing have however a significant higher production costs.

(13) FIG. 2 shows that the graphite bodies according to the invention have a substantially lower porosity than the commercial graphite bodies A, B and E without impregnation, and as low or lower that the graphite bodies A, D and F which have been impregnated once. Only when having been impregnated twice commercial graphite bodies C and D show a porosity that is significantly better than the graphite bodies according to the invention.

(14) FIG. 3 shows that the graphite bodies according to the invention have a substantially low resistivity than all the unimpregnated commercial graphite bodies A, D, C, E and F. Only commercial graphite body D which has been impregnated once and twice has a lower electric resisitivity than the graphite bodies according to the present invention.

(15) FIG. 4 shows that the air permeability for the graphite bodies according to the invention is substantially lower than for the unimpregnated commercial graphite bodies B and E.