Ppg Industries, Inc.

William C Harrell

John F Krumwiede

William G Hilliard

James E Harris

Leonard A Knavish

Premature dissociation of fining agent is avoided in a glass melting operation while controlling the final redox state of the product glass by initiating the melting process under relatively oxidizing conditions and subsequently altering the redox conditions to make the glass more reducing. A glass that is more reduced than usual can thereby be produced without sacrificing the ability to adequately fine the glass. For a given redox level, less fining agent need be used, thereby lowering emissions from the melting operation, because dissociation of the fining agent is delayed until a later stage of the process where the redox conditions are changed.

Melting glass with oxidation control and lowered emissions

In a glass melting furnace, the beneficial effects of passing molten glass streams through the intensified heating at the surface of the 'spring zone' are enhanced by the use of bubblers. In one aspect, the rate of bubbling is greater near a side wall of the furnace than in the center immediately upstream of the spring zone so as to direct side portions of the throughput stream into the spring zone. In another aspect of the invention, the rising currents of the spring zone are enhanced by bubbling a stream entering the spring zone at a first elevation and then bubbling the same stream portion at a higher elevation.

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Buffalo Township, Butler County, PA, United States of America

William C Harrell