In pulp and paper mills, there are many hazardous, corrosive and reactive chemicals used in the chemical pulping process. This particularly hostile atmosphere demands properly engineered automated valve systems and ruggedized valve actuators, spring units, and positioners.
In the early stage of paper production, during the separation of pulp from wood chips, digesters combine high heat and a strong alkaline liquid called “white liquor” to turn wood chips into pulp. The white liquor breaks down the lignin in wood chips and mixes with the white liquor to form a by-product referred to as “black liquor”. Another by-product of this process is hydrogen sulfide, a poisonous, corrosive, and flammable gas.
Later in the paper production process, the pulp is washed, screened and bleached. During this phase, valve actuators are exposed to atmospheres containing many other aggressive compounds such as oxygen chlorine, hydrogen peroxide, and ozone.
Proper selection of valves and actuators is critical for worker safety, plant safety, and for the quality of the paper production. All components – valves, actuators, spring units, and positioners – need to be carefully selected to provide safe operation, redundancy, optimum control, and optimal service life.