Method of reducing redox ratio of molten glass and the glass made thereby
View Patent ↗A soda-lime-silica glass for solar collector cover plates and solar mirrors has less than 0.010 weight percent total iron as Fe 2 O 3 , a redox ratio of less than 0.350, less than 0.0025 weight percent CeO 2 , and spectral properties that include a visible transmission, and a total solar infrared transmittance, of greater than 90% at a thickness of 5.5 millimeters, and reduced solarization. In one non-limiting embodiment of invention, the glass is made by heating a pool of molten soda-lime-silica with a mixture of combustion air and fuel gas having an air firing ratio of greater than 11, or an oxygen firing ratio of greater than 2.31. In another non-limiting embodiment of the invention, streams of oxygen bubbles are moved through a pool of molten glass. In both embodiments, the oxygen oxidizes ferrous iron to ferric iron to reduce the redox ratio.
1. A soda-lime-silica glass, comprising:
SiO 2
65-75
weight percent
Na 2 O
10-20
weight percent
CaO
5-15
weight percent
MgO
0-5
weight percent
Al 2 O 3
0-5
weight percent
K 2 O
0-5
weight percent
SO 3
0-0.30
weight percent
and a colorant portion consisting essentially of:
Total iron as Fe 2 O 3
0.005-0.120 weight percent
Redox ratio
in the range of 0.15-0.286
CeO 2
less than 0.0025 weight percent
ZrO 2
less than 0.01 weight percent and
TiO 2
less than 0.01 weight percent, and
wherein spectral properties of the glass measured at a thickness 5.5 millimeters comprises:
a visible transmission of greater than 85% measured using C.I.E. standard illuminant “A” with a 2° observer over a wavelength range of 380 to 770 nanometers;
a total solar infrared transmittance of greater than 87% measured over a wavelength range of 775 to 2125 nanometers, and
a total solar energy transmittance of greater than 90% measured over a wavelength range of 300 to 2500 nanometers, wherein the total solar infrared transmittance and the total solar energy transmittance are calculated using Parry Moon air mass 2.0 direct solar irradiance data and ASTM air mass 1.5 global solar irradiance data respectively, and integrated using the Rectangular Rule and Trapezoidal Rule, respectively.
2. The glass according to claim 1 wherein the spectral properties comprise:
the visible transmission is greater than 87%, and
the total solar infrared transmittance of greater than 89%.
3. The glass according to claim 1 wherein the spectral properties comprise:
the visible transmission is greater than 90%, and
the total solar infrared transmittance of greater than 90%.
4. The glass according to claim 1 wherein weight percent of ingredients that oxidize Fe ++ to Fe +++ other than those listed in claim 1 is less than 0.0025 weight percent.
5. The glass according to claim wherein the redox ratio is in the range of 0.15-0.27.
6. The glass according to claim 1 wherein the redox ratio is in the range of 0.15-0.19.
7. A soda-lime-silica glass, comprising:
SiO 2
65-75
weight percent
Na 2 O
10-20
weight percent
CaO
5-15
weight percent
MgO
0-5
weight percent
Al 2 O 3
0-5
weight percent
K 2 O
0-5
weight percent
SO 3
0-0.30
weight percent
and a colorant portion consisting essentially of:
Total iron as Fe 2 O 3
0.005-0.025 weight percent,
Redox ratio
less than 0.350,
CeO 2
less than 0.0025 weight percent,
ZrO 2
less than 0.01 weight percent and
TiO 2
less than 0.01 weight percent, and
wherein spectral properties of the glass measured at a thickness 5.5 millimeters comprises:
a visible transmission of greater than 90% measured using C.I.E. standard illuminant “A” with a 2° observer over a wavelength range of 380 to 770 nanometers;
a total solar infrared transmittance of greater than 90% measured over a wavelength range of 775 to 2125 nanometers, and
a total solar energy transmittance of greater than 90% measured over a wavelength range Of 300 to 2500 nanometers, wherein the total solar infrared transmittance and the total solar energy transmittance are calculated using Parry Moon air mass 2.0 direct solar irradiance data and ASTM air mass 1.5 global solar irradiance data respectively, and integrated using the Rectangular Rule and Trapezoidal Rule, respectively.
8. A soda-lime-silica glass, comprising:
SiO 2
65-75
weight percent
Na 2 O
10-20
weight percent
CaO
5-15
weight percent
MgO
0-5
weight percent
Al 2 O 3
0-5
weight percent
K 2 O
0-5
weight percent
SO 3
0-0.30
weight percent
and a colorant portion consisting essentially of:
Total iron as Fe2O3
0.005-0.025 weight percent
Redox ratio
less than 0.200
CeO 2
less than 0.0025 weight percent
ZrO 2
less than 0.01 weight percent and
TiO 2
less than 0.01 weight percent, and
wherein spectral properties of the glass measured at a thickness 5.5 millimeters comprises:
a visible transmission of greater than 85% measured using C.I.E. standard illuminant “A” with a 2° observer over a wavelength range of 380 to 770 nanometers;
a total solar infrared transmittance of greater than 87% measured over a wavelength range of 775 to 2125 nanometers, and
a total solar energy transmittance of greater than 90% measured over a wavelength range of 300 to 2500 nanometers, wherein the total solar infrared transmittance and the total solar energy transmittance are calculated using Parry Moon air mass 2.0 direct solar irradiance data and ASTM air mass 1.5 global solar irradiance data respectively, and integrated using the Rectangular Rule and Trapezoidal Rule, respectively.
9. A soda-lime-silica glass, comprising:
SiO 2
65-75
weight percent
Na 2 O
10-20
weight percent
CaO
5-15
weight percent
MgO
0-5
weight percent
Al 2 O 3
0-5
weight percent
K 2 O
0-5
weight percent
SO 3
0-0.30
weight percent
and a colorant portion consisting essentially of:
Total iron as Fe2O3
equal to or less than
0.01 weight percent,
Redox ratio
less than 0.200
CeO 2
less than 0.0025 weight percent
ZrO 2
less than 0.01 weight percent and
TiO 2
less than 0.01 weight percent, and
wherein spectral properties of the glass measured at a thickness 5.5 millimeters comprises:
a visible transmission of greater than 85% measured using standard illuminant “A” with a 2° observer over a wavelength range of 380 to 770 nanometers;
a total solar infrared transmittance of greater than 87% measured over a Wavelength range of 775 to 2125 nanometers, and
a total solar energy transmittance of greater than 90% measured over a wavelength range of 300 to 2500 nanometers, wherein the total solar infrared transmittance and the total solar energy transmittance are calculated using Parry Moon air mass 2.0 direct solar irradiance data and ASTM air mass 1.5 global solar irradiance data respectively, and integrated using the Rectangular Rule and Trapezoidal Rule, respectively.
10. A soda-lime-silica glass, comprising:
SiO 2
65-75
weight percent
Na 2 O
10-20
weight percent
CaO
5-15
weight percent
MgO
0-5
weight percent
Al 2 O 3
0-5
weight percent
K 2 O
0-5
weight percent
SO 3
0-0.30
weight percent
and a colorant portion consisting essentially of:
Total iron as Fe 2 O 3
greater than 0.01 to 0.12
weight percent,
Redox ratio is
less than 0.150,
CeO 2
less than 0.0025 weight percent,
ZrO 2
less than 0.01 weight percent and
TiO 2
less than 0.01 weight percent, and
wherein spectral properties of the glass measured at a thickness 5.5 millimeters comprises:
a visible transmission of greater than 85% measured using C.I.E. standard illuminant “A” with 2° observer over a wavelength range of 380 to 770 nanometers;
a total solar infrared transmittance of greater than 87% measured over a wavelength range of 775 to 2125 nanometers, and
a total solar energy transmittance of greater than 90% measured over a wavelength range of 300 to 2500 nanometers, wherein the total solar infrared transmittance and the total solar energy transmittance are calculated using Parry Moon air mass 2.0 direct solar irradiance data and ASTM air mass 1.5 global solar irradiance data respectively and integrated using the Rectangular Rule and Trapezoidal Rule, respectively.