DESCRIPTION
Kraft paper pulping, strong black liquor was sprayed onto buildings and equipment.
INCIDENT OVERVIEW
Erosion of a stainless steel pressure piping elbow located on top of a black liquor storage tank resulted in strong black liquor being sprayed onto buildings, equipment, and the and surrounding area.
INVESTIGATION CONCLUSIONS
Black liquor is the by-product of the Kraft pulping process when digesting pulpwood into paper pulp removing lignin’s and other extractives from the wood to free the cellulose fibers.
The organic matter in the black liquor is made up of water/alkali-soluble degradation components from the wood.
Black liquor is corrosive and exposure may be through inhalation, ingestion, eye, or skin contact.
During the Kraft process, strong black liquor (75 percent solids) is fed from a concentrator vessel to a liquor storage tank which is several stories high. The black liquor is pumped to the top of the tank at 293°F and under pressure.
The process is normally contained in the vessels and stainless steel pressure piping.