Methods for producing solid ceramic particles using a microwave firing process

Patent metadata

Field	Value
Publication number	US-9670401-B2
Application number	US-201514831249-A
Country	US
Kind code	B2
Filing date	Aug 20, 2015
Priority date	Sep 5, 2014
Publication date	Jun 6, 2017
Grant date	Jun 6, 2017

Abstract

Methods for producing solid, substantially round, spherical and sintered particles from a slurry of a raw material having an alumina content of greater than about 40 weight percent. The slurry is processed to prepare green pellets which are sintered in a furnace with microwave energy at a temperature of 1480 to 1520° C. to produce solid, substantially round, spherical and sintered particles having an average particle size greater than about 200 microns, a bulk density of greater than about 1.35 g/cm 3 , and an apparent specific gravity of greater than about 2.60.

First claim

What is claimed is:

1. A method for forming sintered substantially round and spherical pellets, comprising:
forming substantially round and spherical green pellets from raw materials comprising water and kaolin clay; and
sintering the green pellets in a microwave furnace at a temperature of from about 1480° C. to about 1520° C. for a time at peak temperature of from about 20 to about 45 minutes, to form a proppant having a bulk density of from about 1.35 to about 1.60 g/cm 3 and a crush percent at 7500 psi of from about 1.5 to about 3.5;
wherein the proppant has a bulk density and a crush percent at 7500 psi that is less than that of proppant made from the green pellets and sintered in a gas-fired rotary kiln.

2. The method of claim 1 , wherein the proppant has an apparent specific gravity of about 2.6 to about 2.8.

3. The method of claim 1 , wherein the green pellets have a moisture content of at least about 25% by weight.

4. The method of claim 1 , wherein the green pellets have a size of from 16 to 80 U.S. mesh.

5. The method of claim 1 , wherein the green pellets are sintered in the microwave furnace for about 50 to about 200 minutes.

6. The method of claim 1 , wherein the substantially round and spherical green pellets are prepared from a slurry having a solids content of from about 40 to about 60% by weight and having an alumina content in a range of from about 40 to about 55% by weight.

7. A method for producing sintered particles comprising:
preparing a slurry having a solids content of from about 40 to about 60% by weight, and comprising water and a raw material having an alumina content in a range of from about 40 to about 55% by weight;
atomizing the slurry into droplets;
coating seeds comprising alumina with the droplets to form green particles; and
sintering the green particles in a microwave furnace at a temperature of from about 1480° C. to about 1520° C. for a time at peak temperature of from about 20 to about 45 minutes, to form a proppant having a bulk density of from about 1.35 to about 1.60 g/cm 3 and a crush percent at 7500 psi of from about 1.5 to about 3.5;
wherein the proppant has a bulk density and a crush percent at 7500 psi that is less than that of proppant made from the green particles and sintered in a gas-fired rotary kiln.

8. The method of claim 7 , wherein the green particles are sintered for about 50 to about 200 minutes.

9. The method of claim 7 , further comprising adding to the slurry at least one of a pH adjusting reagent, a dispersant and a defoamer before atomizing the slurry.

10. The method of claim 7 , wherein atomizing the slurry comprises feeding the slurry to a fluidizer operable to atomize the slurry into droplets; and wherein the seeds are positioned in a particle bed in the fluidizer.

11. The method of claim 7 , further comprising drying the green particles before sintering.

Assignees

• Carbo Ceramics Inc

Inventors

• Cannan Chad
• Wilson Brett A
• Eldred Benjamin T

Classifications

• C04B2235/667

  Sintering using wave energy, e.g. microwave sintering · CPC title

• C09K8/80

  Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open · CPC title

• F26B3/347

  Electromagnetic heating, e.g. induction heating or heating using microwave energy · CPC title

• H05B2206/046

  Microwave drying of wood, ink, food, ceramic, sintering of ceramic, clothes, hair · CPC title

• H05B6/80

  Apparatus for specific applications (stoves or ranges F24C7/02) · CPC title