On December 29, 1972 one the Nation’s worst airline accidents occurred as Eastern Air Lines Flight 401 crashed into the Florida Everglades killing 101 of the passengers and crew. A National Transportation Safety Board (NTSB) investigation attributed the cause of the crash to crew distraction. While on approach, the crew noted that a landing gear indicator light was not functioning. While the entire crew was preoccupied with troubleshooting the burnt-out landing gear indicator light, they failed to notice that the autopilot had inadvertently been disconnected and, as a result, the aircraft gradually lost altitude and ultimately crashed.
All too often when attempting to solve a problem we suffer from tunnel vision.
A probable root cause to the problem is suggested and we spend all of energy and resources attempting to fix the suggested root cause while ignoring the indications that the actual root cause is something else or that more serious problems are occurring.
Finding and eliminating chloride contamination in refinery streams is becoming increasingly common in many of today’s refineries operations. These chlorides often react with other compounds to form insoluble salts that foul equipment or are converted to HCl and corrode refinery equipment. In the case of certain grades of stainless steel, the presence of chlorides can result in stress corrosion cracking of the metal, resulting in some cases catastrophic failure of the equipment.
A recent investigation where a team of our process experts investigated and addressed a severe case of chloride contamination in Naphtha Hydrotreater (NHT) feed illustrates how focusing on a suggested source of chlorides can distract one from looking at the bigger picture and identifying the actual root causes.
This particular refinery had been suffering for some time with high levels of organic chlorides in the naphtha feed to the NHT. The chloride level was so high and highly corrosive that the available wash water rate was insufficient to avoid severe exchanger fouling.
Chloride levels in the naphtha varied considerably. Organic chloride would occasionally spike to as high 80 ppm or drop to near zero. This lack of consistency led the refinery to believe that the source of the feed chlorides was related specifically to organic chlorides in the crude sources.
As a significant portion of the refinery crude supply was from local sources, this was not an unreasonable assumption. Producers have been known to dispose of chlorinated solvents with their crude. The refinery promptly began an investigation to determine the ultimate culprit. However, unraveling the crude supply and analyzing numerous samples of crude proved to be complex and the effort began to get bogged down. Despite months of determined efforts, the source of the chloride contamination remained a mystery.
The Becht Review
Becht’s Process expert team reviewed the past work conducted on finding the source of contaminated crude. But rather than continuing to focus solely on the crude supply the team decide to start with a fresh look at the naphtha going to the NHT. Becht then generated a cause map for potential sources of chlorides. The organic chlorides were also speciated to identify what organic chlorides compounds were present.
With fresh eyes, the Process team removed the tunnel through which, until then, everyone was looking at the problem.
Using this approach, the team determined that, while it was likely that some chlorides were present in the crude supply, there were other sources of chlorides from within the refinery. The Platformer chloride absorbers, for instance, had been long spent (a fact not realized as the test used to monitor for chloride breakthrough was not effective). Organic chlorides were being generated from these spent absorbers and migrated through the refinery systems and ultimately ended up in the slop oil system. As these oils were re-charged to the crude unit, the organic chlorides ended in the NHT feed. With this knowledge, the refinery immediately changed their chloride guard media and instigated different procedures to test for chloride breakthrough.
While efforts to continue to eliminate the remaining sources of chloride contamination continue, one source of chloride contamination was eliminated successfully.
The investigation also revealed several other issues in the refinery operation, such as:
- Low platformer catalyst activity;
- Slop handling;
- Wash water practices; and
- Lack of PSA absorbent activity due to contamination.
Crude oil containing chloride, as originally identified, continues to be a possible problem as well.
While the chloride levels are not yet where they need to be, the organic chlorides are continuing to trend downward as additional analysis and actions are taken on identified issues.
Unlike the Eastern Airlines Flight incident, the Becht team resisted the temptation to focus on a single issue. Instead they used a freshly structured holistic and logical approach to address the more significant underlying problems.
Recently, in almost every refinery I have visited, there is an issue with chloride contamination. In most cases is it is not as bad as in this case. But, in many cases, the focus is on a single issue that is often not the ultimate root cause – and this effort is squandering the refinery’s limited technical resources. Worse yet, it is allowing the problem to continue to plague the refinery.
Ask yourself, are you looking for your chlorides in the right place or are you focusing on a burnt-out light bulb as your aircraft approaches the ground?
Better yet, ask Becht Engineering to assist you with a fresh set of eyes to identify your uncovered issues.
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or Call Eric at (908) 842-0171