Ash Viscosity

HIGH TEMPERATURE
ASH VISCOSITY ANALYSIS

SGS can assist you in understanding the slag flow characteristics of your ash. Many of the T250 calculations used today were developed using eastern US and English coals. These calculated values may not apply to coals being used today.

Ash viscometer testing allows direct measurement of the temperature–viscosity relationship of your fuels and fuel blends. The high temperature ash viscometer generates a curve showing the temperature-viscosity relationship, as shown here.

Several important characteristics are indicated. According to J.D. Watt, (1969), “Tcv is the temperature at which, on cooling, crystallisation of the slag is first likely to interfere with its flow properties”. The temperature of critical viscosity (Tcv) is determined by the dogleg portion of the T-V relationship. The T250 temperature, (the temperature at which the slag has a viscosity at 250 poise) can also be determined

Test Description
The ash viscometer uses laboratory prepared ash or ash/slag from a boiler. Seventy grams of ash sample is pressed into a pellet and fed to the preheated (2700O) ceramic crucible. A ceramic bob is lowered into the molten ash. The liquid is cooled at 6o/min. while the Rheometer measures the torque. The temperature is simultaneously measured. The test is concluded when the bob is no longer able to rotate in the solidifying slag. This data is plotted producing a chart, similar to the one shown in above.