Standard Test Method for On-Line Colorimetric Measurement of Silica

Importancia y uso:

5.1 Silicon (Si), a metalloid, is the second most abundant element in the earth’s crust. Various forms of silica (silicon dioxide SiO₂) are found in quartz, sand, and rocks. The degradation of these rocks results in silica found in natural waters. Silica in natural waters can be found as ionic silica, silicates, colloidal or suspended particles.

5.2 Elevated temperatures and pressure can cause silica in water to vaporize and form deposits or scale. Scale deposits of silica will coat boilers and turbine blades used in power plants. The presence of silica scale affects the ability of metals to transfer heat. Silica needs to be removed when deionized water is used as a rinse for manufacturing wafers in the semiconductor industry.

5.3 Silica is commonly removed by demineralization using anion exchange resins, distillation, reverse osmosis or precipitation in a lime softening process. The on-line measurement of silica is the preferred method to laboratory analyses for industries trying to obtain and monitor ultra-pure water. Since silica is one of the first species to breakthrough anion exchange resins, on-line silica monitoring is frequently used to determine the need for regeneration of an anion or mixed resin bed.

Subcomité:

D19.03

Volúmen:

11.01

Número ICS:

13.060.50 (Examination of water for chemical substances)

Palabras clave:

colorimetric; on-line; process measurement; silica;