Gas sintered carbon block and method

• US 7,022,274 B2
• Filed: 11/25/2003
• Issued: 04/04/2006
• Est. Priority Date: 11/25/2003
• Status: Expired due to Fees

• Current Assignee: Graver Technologies Incorporated (Berkshire Hathaway Incorporated)
• Original Assignee: Graver Technologies Llc (Berkshire Hathaway Incorporated)
• Inventors: Harris, S. Dyer, LeSieur, John K., Shertok, Joel T.
• Primary Examiner(s): Lechert, Jr., Stephen J.
• Application Number:
  US10/722,882
• Publication Number:
  US 20050110178A1
• Time in Patent Office: 861 Days
• Field of Search: 264109-128, 264/29.1, 264/29.6, 264/29.7, 264/653
• US Class Current: 264/126
• CPC Class Codes: C04B 2235/658 Atmosphere during thermal treatment
• CPC Class Codes: C04B 2235/6583 Oxygen containing atmosphere, e.g. with changing oxygen pressures
• CPC Class Codes: C04B 35/52 based on carbon, e.g. graphite
• CPC Class Codes: C04B 35/532 containing a carbonisable binder
• CPC Class Codes: C04B 35/64 Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F

Abstract

The present invention relates to an effective and rapid method and apparatus for sintering carbon filter blocks having a polymeric binder. The method employs direct contact heat transfer by gas molecule to powder particle, as opposed to conduction heat transfer from an external heating source, using commercially available sintered porous metal sheets and cylinders to form the mold and confine the powder, while allowing heated gas to pass uniformly through the mixture.

Claims

1. A method for producing a sintered carbon block by direct heat transfer, the method comprising:

a) selecting a mixture comprising least one polymer and carbon particles;

b) providing a mold defined by interior and exterior walls, wherein at least one interior wall and at least one exterior wall is permeable to a heated gas;

c) introducing said mixture into said mold between said interior and exterior walls;

b) providing a gas;

c) heating said gas to an elevated temperature, said temperature being determined by the composition of the polymer and carbon mixture whereby the polymer softens without melting;

d) introducing said heated gas into the mold;

e) passing said heated gas through said mixture between said interior and exterior walls; and

d) heating said mixture by direct heat transfer at said temperature for a predetermined time period sufficient to allow said mixture to sinter,

whereby a sintered carbon block is formed.

2. The method of claim 1, wherein the method further comprises the step of compressing the gas prior to heating the gas.

3. The method of claim 1, wherein the gas is chemically non-reactive with said polymer and carbon mixture.

4. The method of claim 1, wherein the gas is selected from the group comprising carbon dioxide (CO₂), nitrogen (N₂), helium, or air.

5. The method of claim 1, wherein the heated gas passes through at least one permeable interior wall of said mold, through said polymer and carbon mixture, and out through at least one permeable exterior wall.

6. The method of claim 1, wherein said gas is recovered and recycled upon passing through said mixture.

7. The method of claim 1, further comprising the step of cooling said sintered carbon block, wherein a gas is cooled, introduced into the mold by way of at least one permeable interior wall, passes through said sintered carbon block and is exhausted by way of at least one permeable exterior wall.

8. The method of claim 1, wherein the mold is formed of a porous and sintered metal.

9. The method of claim 1 wherein the amount of time the mixture is sintered, in the absence of heat loss, is governed by the equation:

t=M_bC_bΔ

T_b/q_aC_aΔ

T_a, wherein

M_b is the mass of the block powder mixture;

C_b is the effective specific heat of the block powder mixture;

q_a is the mass rate of flow of the heating gas; and

C_a is the specific heat of the heated gas.

10. The method of claim 1 wherein the gas is heated to a temperature from approximately 275°

F. to approximately 400°

F.