At 12:30 am on May 30th, 2020, failure of a 6” pressure piping elbow located on top of a storage tank resulted in black liquor being sprayed onto adjacent buildings, equipment, and ground within an approximately 50m (165′) area. The line from the liquor transfer pump into the top of the tank failed and 74% black liquor solids were released for approximately 20 minutes. A similar failure had occurred on Feb 8, 2020.
The organic matter in black liquor is made up of water/alkali-soluble degradation components from wood. Black liquor is corrosive. High solids black liquor at a temperature of approximately 140°C is transferred from a concentrator vessel to a storage tank via stainless steel piping. The piping material is made from a corrosion-resistant material. The flow of black liquor into the storage tank is controlled by a valve located immediately upstream of a 90-degree piping elbow discharging into the storage tank. The system configuration and materials are designed to be suitable for black liquor service.
Failure scenario(s) :