The reboiler temperature controls the concentration of the water in the lean glycol. The higher the temperature the higher the concentration, as shown in Figure 8-11. Reboiler temperatures for triethylene glycol are limited to 400°F, which limits the maximum lean glycol concentration without stripping gas. It is good practice to limit reboiler temperatures to between 370°F and 390°F to minimize degradation of the glycol. This effectively limits the lean glycol concentration to between 98.5% and 98.9%.
When higher lean glycol concentrations are required, stripping gas can be added to the reboiler, or the reboiler and still column can be operated at a vacuum.