Mobilization of Sludge & Blending of Tank Contents
Side-entering mixers installed in oil storage tanks are required to perform two main tasks: mobilization of sludge and blending of the contents.
The Problem: An Owner/Operator in central Texas, with a 114 ft diameter crude oil tank storing WTS, had been struggling for several years with mixing equipment that needed replacing. The tank had been gauged and it was determined that tank bottom amounted to 18” to 48” in peaks and valleys across the floor. This translated to 5,781 bbls of deposition.
The Solution: The patented Advance Pitch Propeller has been developed to generate a collimated flow to maximize the velocity across the floor of the vessel, which mobilizes the sludge. This maximizes the velocity of the vertical flow up the opposite wall of the tank and impinges on the interface between the oil’s heavy and light components.
Challenge: Like much of the equipment installed throughout oil storage tank sites today, the original tank equipment is obsolete, and ineffective. The obsolete equipment left the tank site Owner/Operator blind to the build up of the hard pan. The result was a potential loss of over $275,000. They needed a mixer that would better mobilize the sludge and effectively blend the heavy and light components.
PMSL’S Solution: Working with the Owner/Operator, a new tank mixer was purchased to assist with deposition suspension. The equipment selected was a Philadelphia Mixing Solution Swivel-Angle, BSER-28P-SA-25hp. The mixer was operated through its seven angles for 3 months, with each angle being held for 2 days. Several sweeps of the tank floor were made. After 3 months the deposition had dropped by 3,007 bbls, leaving 2,774 bbls of “hard pan”.
The tank mixer was able to suspend the “soft pan” bottom but not the “hard pan”. Hydrocarbon Solutions’ Tank Bottom Cleaner was added at the rate of 4 bbls chemical / 1000 bbls of deposition. The Philadelphia tank mixer was able to suspend the “soft pan” bottoms and the chemical liquified the “hard pan” and was also homogenized. After adding the Tank Bottom Cleaner, a small amount of fresh oil was added sufficient to operate the tank mixer. After 1 month, the tank was filled and the contents homogenized and shipped via pipeline to the main terminal. The 2,774 bbls of “hard pan” were gone!
Benefit to the Customer: This customer was looking at a large loss. PMSL was able to recover that 5,781 bbls of deposition, based upon a hydrocarbon content of 90% that realized a value of $286,159 (@ $55.00/bbl August 2005). Furthermore, API 653’s were undertaken in less time.