Micro-Bac International, Inc.
Sludge Removal From 10,000-barrel Fixed Roof Storage Tank
Application Tank Bottom Cleaning.
Project The 10,000 BBL fixed roof storage tank needed sludge removed from bottom and internals cleaned to allow floor, wall, and roof to be inspected and coated. The objective was to reduce the hazard of removing gas entrained sludge plus reduce the hazard of explosive atmosphere within the tank during the sludge handling operation.
Method The tank was pumped out and both tank man-ways were opened. The heavy black sludge level in the tank was more than 2 feet deep. (approximately 600 BBLS). One barrel of Para-BacŪ was injected into the tank. In addition, approximately 50 BBLS of basin hydrocarbon skimmings, 75 BBLS of lean oil, and 175 BBLS of Pentane Plus were added to the tank. After allowing the tank to sit overnight, a circulation pump was started to circulate the bacteria/condensate within the tank. The fluid circulated was across the tank between the man-ways and in part back through the BS&W line, the center sump in the tank. This circulation took place daily for 4 to 6 hours, for a total of 18 days. The fluid was pumped from the tank and water was allowed to separate out. Approximately 200 BBLS water and 600 BBLS of condensate (Pentane+) were removed from the tank.
Results Upon opening the man-ways on the southwest and northeast sides of tank, it was observed that sludge reduction had taken place to the highest degree directly between the man-ways. The fluid was removed through the BS&W line from a sump in the center of the tank floor. It was also observed that the sludge that was still up on the walls 90 degrees to the man-ways would sluff down and turn liquid overnight and was pumped off. Furthermore, the remaining sludge could be freely removed using the vacuum truck and that the gas release from agitating the sludge was within allowable limits (less than .1% explosive mixture) allowing sludge removal within minimal exposure to explosive limits.
Conclusion It was estimated that without taking labor costs into consideration (with the bacteria treatment being considerably less expensive due to volume and degassed sludge), bacteria treatment cost was one third the cost or $74,000 less expensive.