H-factor is a kinetic model for the rate of delignification in kraft pulping. It is a single variable model combining temperature (T) and time (t) and assuming that the delignification is one single reaction.

H = ∫ 0 t exp ⁡ ( 43.2 − 16115 / T ) d t {\displaystyle H=\int _{0}^{t}\exp \left(43.2-16115/T\right)\,dt\,}