Spray granulation of silicon dioxide in the preparation of quartz glass

Patent metadata

Field	Value
Publication number	US-11053152-B2
Application number	US-201616062366-A
Country	US
Kind code	B2
Filing date	Dec 16, 2016
Priority date	Dec 18, 2015
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate, making a glass melt out of the silicon dioxide granulate, and making a quartz glass body out of at least a part of the glass melt. In one aspect, providing a silicon dioxide granulate includes providing of a silicon dioxide powder and processing of the powder to obtain a silicon dioxide granulate including the spray drying of a silicon dioxide slurry using a nozzle. The nozzle has a contact surface to the slurry made of glass, plastic or a combination thereof. Furthermore, one aspect relates to a quartz glass body obtainable by this process. Furthermore, one aspect relates to the preparation of a silicon dioxide granulate. One aspect also relates to a light guide, an illuminant, and a formed body, made from processing of the quartz glass body.

First claim

The invention claimed is:

1. A process for the preparation of a quartz glass body comprising:
providing a silicon dioxide granulate comprising the following:
providing a silicon dioxide powder;
processing the silicon dioxide powder to obtain a silicon dioxide granulate, wherein the processing comprises:
providing a liquid;
mixing the silicon dioxide powder with the liquid to obtain a slurry;
spray drying the slurry to obtain a silicon dioxide granulate,
wherein the spraying of the slurry is done through a nozzle,
wherein the nozzle has a contact surface with the slurry during spraying,
wherein the contact surface comprises a glass;

making a glass melt out of the silicon dioxide granulate; and
making a quartz glass body out of at least part of the glass melt.

2. The process according to claim 1 , wherein the glass is a quartz glass.

3. The process according to claim 1 , wherein more than 70 wt % of the nozzle is made of an element selected from the group comprising glass, plastic, a combination of glass and plastic, the wt % being based on the total weight of the nozzle.

4. The process according to claim 1 , wherein the nozzle contains a nozzle plate and optionally a screw twister, wherein the screw twister and the nozzle plate, each independent of the other, are made of glass.

5. The process according to claim 1 , wherein the contact surface contains no metal.

6. The process according to claim 1 , wherein the spray drying comprises at least one of the following features:
spray granulation in a spray tower;
the presence of a pressure of the slurry at the nozzle of not more than 40 bar, wherein the pressure is given in absolute terms (relative to p=0 hPa);
a temperature of the droplets upon entering into the spray tower in a range from 10 to 50° C.;
a temperature at the side of the nozzle directed towards the spray tower in a range from 100 to 450° C.;
a throughput of slurry through the nozzle in a range from 0.05 to 1 m 3 /h;
a solids content of the slurry of at least 40 wt. %, based on the total weight of the slurry;
a gas inflow into the spray tower in a range from 10 to 100 kg/min;
a temperature of the gas flow upon entering into the spray tower in a range from 100 to 450° C.;
a temperature of the gas flow at the exit out of the spray tower of less than 170° C.;
the gas is selected from the group consisting of air, nitrogen and helium, or a combination of two or more thereof;
a residual moisture content of the granulate on removal out of the spray tower of less than 5 wt.-%, based on the total weight of the silicon dioxide granulate produced in the spray drying;
at least 50 wt.-% of the spray granulate, based on the total weight of the silicon dioxide granulate created in the spray drying, completes a flight time in a range from 1 to 100 s;
at least 50 wt.-% of the spray granulate, based on the total weight of the silicon dioxide granulate created in the spray drying, covers a flight path of more than 20 m;
the spray tower has a cylindrical geometry;
a height of the spray tower of more than 10 m;
screening out of particles with a size of less than 90 μm before the removal of the granulate from the spray tower;
sieving out of particles with a size of more than 500 μm after the removal of the granulate from the spray tower; and
The exit of the droplets of the slurry out of the nozzle occurs at an angle of 30 to 60 degrees from vertical.

7. The process according to claim 1 , wherein the silicon dioxide granulate comprises the following:
an angle of repose in a range from 23 to 26°.

8. The process according to claim 7 , wherein the silicon dioxide granulate additionally comprises at least one of the following:
a BET surface area in a range from more than 5 to 50 m 2 /g;
a mean particle size in a range from 50 to 500 μm;
a bulk density in a range from 0.5 to 1.2 g/cm 3 ;
a carbon content of less than 10 ppm;
an aluminium content of less than 200 ppb;
a tamped density in a range from 0.7 to 1.3 g/cm 3 ;
a pore volume in a range from 0.1 to 2.5 mL/g;
a particle size distribution D 10 in a range from 50 to 150 μm;
a particle size distribution D 50 in a range from 150 to 300 μm; and
a particle size distribution D 90 in a range from 250 to 620 μm,
wherein the ppm and ppb are each based on the total weight of the silicon dioxide granulate.

9. The process according to claim 1 , wherein the slurry comprises at least one of the following:
the slurry is transported in contact with a plastic surface;
the slurry is sheared;
the slurry has a temperature of more than 0° C.;
the slurry has a zeta potential at a pH value of 7 in a range from 0 to −100 mA;
the slurry has a pH value in a range of 7 or more;
the slurry has an isoelectric point of less than 7, in a range from 1 to 5;
the slurry has a solids content of at least 40 wt.-%, in a range from 50 to 80 wt.-%, based on the total weight of the slurry;
the slurry has a viscosity according to DIN 53019-1 (5 rpm, 30 wt.-%) in a range from 500 to 1000 mPas;
the slurry has a thixotropy according to DIN SPEC 91143-2 (30 wt.-% in water, 23° C., 5 rpm/50 rpm) in the range from 3 to 6; and
the silicon dioxide particles in the slurry have in a 4 wt.-% slurry a mean particle size in suspension according to DIN ISO 13320-1 in the range from 100 to 500 nm.

10. The process according to claim 1 , wherein the silicon dioxide powder is prepared from a compound selected from a group consisting of siloxanes, silicon alkoxides and silicon halides.

11. The process according to claim 1 , comprising the following:
making a hollow body with at least one opening out of the quartz glass body.

12. A process for the preparation of a light guide comprising preparing a quartz glass body by the process of claim 1 :
wherein the quartz glass body is first processed to obtain a hollow body with at least one opening;
introducing one or multiple core rods into the hollow body through the at least one opening to obtain a precursor; and
drawing the precursor in the warm to obtain a light guide with one or multiple cores and a jacket M1.

13. A process for the preparation of an illuminant comprising preparing a quartz glass body by the process of claim 1 :
wherein the quartz glass body is first processed to obtain a hollow body with at least one opening;
optionally fitting the hollow body with electrodes; and
filling the hollow body with a gas.

14. A process for the preparation of a formed body comprising preparing a quartz glass body by the process of claim 1 :
and
forming the quartz glass body to obtain a formed body.

15. A process for preparing a silicon dioxide granulate, comprising the following:
providing a silicon dioxide powder and a liquid;
mixing the silicon dioxide powder with the liquid to obtain a slurry; and
spray drying the slurry to obtain a silicon dioxide granulate,
wherein the slurry is sprayed through a nozzle in a spray tower,
wherein the nozzle has a contact surface with the slurry during spraying,
wherein the contact surface comprises a glass.

Assignees

• Heraeus Quarzglas

Inventors

• Otter Matthias
• Wittrin Mirko
• Wilde Markus

Classifications

• C03C1/026

  Pelletisation or prereacting of powdered raw materials (apparatus or methods C03B1/02) · CPC title

• C03B19/108

  Forming porous, sintered or foamed beads (chemical aspects C03C11/00) · CPC title

• Y02P40/57

  Improving the yield, e-g- reduction of reject rates · CPC title

• C03B2201/32

  doped with aluminium (C03B2201/36 takes precedence) · CPC title

• G02B6/0238

  Longitudinal structures having higher refractive index than background material, e.g. high index solid rods · CPC title