scope:

This method determines the gross (or high) heating value of black liquor, containing up to 55% by mass of water, derived from sodium-based kraft pulping¹.

The products of combustion in the recovery furnace are different from the bomb calorimeter products because of the reducing atmosphere which exists in the hearth zone of the furnace. A "heat of reaction correction" based on an elemental analysis of the waste liquor sample should be used to account for this difference. It is described in a TAPPI Steam and Power Committee Technical Information Sheet for calculation of recovery unit performance (TIP 0416-01 "Recovery Boiler Performance Calculation - Short Form").

¹Can also be used on spent liquors from NSSC and sodium sulfite pulping processes.