Neles E6-series ceramic ball valve after 1 year in FCCU severe bottom slurry service.
The FCC unit, which converts heavy gas oils (HGO) into several light hydrocarbon constituents, is one of the most profitable operations in any refinery. The FCC process involves blowing catalyst into the reactor and recycling it from the regenerator to enhance the “cracking” of the heavy hydrocarbon molecules. The unit typically operates for five years between turnarounds. For the first few years, valve erosion was minimal and had little if any effect on performance. However, during the final two years, the pace of erosion and damage to valves and piping became severe.
The typical valves used by the refinery in the bottoms circuit were stellated control valves.
During the final two years of the cracking unit’s run, these valves were failing at six-month intervals. Due to the remote and challenging location of the valves the refinery put off replacing them as long as it reasonably could. Unfortunately this meant that operating safely with marginally effective valves required the unit to reduce production rates.
Costs associated with valve replacement in a FCC unit are particularly high. In this case, it cost the refinery USD 8,000 for new valve package hardware, USD 5,000 for labor and thousands upon thousands of dollars in lost production. These costs were incurred at six-month intervals during the final two years of the run.
As a test case, Neles proposed replacing the existing 6″ valve with a full ceramic lugged ball valve, actuator, and positioner at the 3.5-year point in the turnaround cycle. Neles ceramic E6-series ball control valves are designed to meet the most severe erosive service requirements with improved process safety and efficiency. The E-series valves use a new generation ceramic material to line the flow path and trim parts. As a result, the valves are suitable for highly abrasive rotary control applications, where metallic coatings like Stellite do not last. This coating can also withstand the thermal shock produced by the FCC bottoms circuit’s widely fluctuating temperatures.
This proposal was implemented and after one year of service, the valve was inspected for wear. They discovered no discernible erosion to the ball or seating surfaces. Plant management was pleased with both the elimination of subsequent valve replacement costs and the dramatic improvements in FCC unit uptime and process throughput— all of which went directly to the unit’s bottom line.
The refinery has since purchased additional E6 valve packages that will be used to replace other critical valves within the FCC unit.
Written by Sari Aronen.
This blog post has been up-dated in July 2020, due to company name change to Neles.