Investigation of Dissolved Gases in Smelt, 2010 TAPPI/PAPTAC International Chemical Recovery Conference

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The flow of smelt from a recovery boiler is important for safe and reliable operation. Previous studies have focused on the influence of smelt composition and temperature as a means of explaining the increase in smelt viscosity and a lack of fluidity. However, smelt composition and temperature would only seem to explain an increase in viscosity to something like a light oil, which is still free-flowing. Mills with multiple boilers that burn the same liquor and have similar smelt temperatures produce smelt with vastly different flow properties.

In the study of magma, dissolved gases are known to increase its magma by orders of magnitude. A review of the literature showed that gases such as carbon monoxide and carbon dioxide are soluable in molten sodium and potassium carbonate in a ratio up to about 30:1 by volume. Measurements of the smelt from one recovery boiler indicated that it contained about 10 ft³ of carbon dioxide and carbon monoxide per cubic foot of smelt.

Many of the details that control how gases are dissolved in smelt, and how it influences smelt fluidity, need to be expanded on. However, this may be the key to overcoming problems with poor smelt fluidity.