Gas Liquid Mass Transfer in Laboratory Oxygen Delignification Reactors, 2004 Engineering, Pulping, and PCE&I Conference

The objective of the present study was to measure the liquid phase mass transfer coefficients in two laboratory reactors that have been widely used to estimate kinetic data for the oxygen delignification process. The liquid phase mass transfer coefficients (kla) were determined by using a variant of the sulfite oxidation method. The total pressure in the reactor was monitored as a function of time and used to estimate the liquid phase mass transfer coefficients in the reactor. The mass transfer coefficients in the laboratory reactors were determined as a function of consistency, stirring speed and pulp suspension mass. Values for the volumetric mass transfer coefficients (kla) were determined to range between about 0.001 and 0.01 sec-1 depending upon the reactor geometry and process conditions. A new mass transfer term named as “specific mass transfer coefficient” is introduced in the current study. The specific mass transfer coefficient was calculated based on the oxygen transfer rate per unit mass of the pulp and was used to compare mass transfer rates in the laboratory reactors with that of industrial towers. A pseudo steady state analysis was derived to check whether the oxygen delignification experiments previously reported (Agarwal, 1998) were mass transfer limited.