Slop Oil Disposal Investigation: Lessons Learned

by Onochie Okonkwo, PhD student, Washington University (St. Louis)

Process engineers in various facilities are bedeviled by many technical challenges. Some of these challenges we eventually solve; others we learn to manage safely instead. This article shares some of the lessons I learned in my first project exploring a solution to an LNG plant’s slop oil disposal problem.

BACKGROUND

The process facility’s slop oil tank was overflowing and damaging the local environment. The original facility design called for slop oil incineration, but the incinerator was not functional. Hence, the slop oil was trucked to a nearby crude oil loading facility. This method was unreliable and resulted in tank overflows.

EXPLORING SOLUTIONS

In a meeting with the operations team, the idea of spiking slop oil into condensate was raised as an alternative disposal method that would be reliable and safe. The engineer proposing this solution knew this approach was used in a similar facility he had operated.

LESSON 1: Before spending time to engineer solutions to technical problems, find out if such problems have occurred in the past or in similar process facilities and how they were solved. Adapting solution from past experience is faster and easier than engineering new solutions (Ensure that the adaptation meets present day regulatory and operational specifications).

Spiking slop oil into condensate could also generate additional revenue as it could then be sold at the price of condensate. The team decided to explore this alternative and I volunteered to determine how much slop oil we could add without affecting the condensate sales specifications.

LESSON 2: Good candidates for adoption are solutions that reliably and safely solve the problem either at the least cost or by generating the highest revenue or cost savings. Therefore, you should seek to optimize cost while engineering solutions to technical problems.

I estimated the total annual amount of slop oil generated and condensate produced by the facility. I then estimated the concentration of the slop oil in condensate when all the slop is added. This was the maximum slop oil concentration. I worked with the lab personnel to obtain samples and run different tests on varying concentrations of slop oil in condensate. It turned out that we could spike all the slop oil into the condensate and still meet all the condensate sales specifications.

LESSON 3: Technical challenges in process plants are often solved by an interdisciplinary approach. Process engineers have to work in multidisciplinary teams that require us to have good working relationships with other disciplines, to expedite the problem solving process and develop more robust solutions.

I was excited with the results. I returned to my boss with a report. He decided that we should share our findings with the facility’s sales team to get their opinion. The sales team opined that there were more concerns than meeting the formal condensate specifications since the condensate was usually sold to refineries and chemical plants that use it to produce precursors for plastics production. The trace heavy metals contaminants from the lube oil could, over time, poison the catalysts and cold-box heat exchangers of the crackers. While a few cargos might be sold because condensate specifications are technically met, the long-term relationship with buyers would likely be compromised, and this should avoided.

LESSON 4: Good technical solutions are those solutions that not only mitigate the present challenge but do not create worse problems when implemented. Process engineers must be careful to look beyond the present problem and engineer solutions that do not create unforeseen problems.

I was disappointed when I realized the proposal would not fly. However, my boss clarified my thoughts. He did not consider the proposal a failure. Before we did not know if it was feasible, but now we are sure it is not feasible in our facility. A report on this investigation would be kept and it would preclude a repeat investigation in the future, saving the organization time and effort.

LESSON 5: No technical investigation to solve a problem is a failure. Process engineers must learn from solutions that are feasible and solutions that are not. Documentation of the non-feasible proposals is equally important to save time and effort on repeat investigations.

I was still bothered that the original problem had not been solved. If everything stayed the same, the slop oil tank would overflow again. I returned to the problem definition and discovered that the real problem was not the slop oil tank overflowing, but the unreliability of the slop oil evacuation. I dug even further to discover the problem’s root causes included inadequate communication and scheduling with the crude oil facility receiving the slop oil.

LESSON 6: Before attempting to solve any technical problem, process engineers must first know the problem and its root causes.

CONCLUSION

I recommended improving communication between our facility and the crude oil facility to improve evacuation process reliability. I also recommended our facility not spike slop oil into condensate. I prepared my report and properly closed out the technical investigation. The slop oil tank did not overflow again while I was with the organization.

These are some of the most valuable lessons I learned on my first project as a process engineer. I continue to use them as a guide as I delve into more complex problems today.