Lessons Learned from Activated Carbon Odor Control Systems

As consultants, owners, operators, and vendors we feel good about extolling our successful and award-winning projects. It is our human nature to congratulate ourselves on the good things we do. I do not take issue with or dispute this practice. But, I do question those projects that do not go according to plan - that did not quite work out, did not meet expectations, and/or failed miserably. Do we as an industry encourage everyone to capture the miscues and then educate others on how not to do something the next time around, or do we simply bury these projects and that knowledge by sweeping them under the rug so that they can occur over and over again because we are too embarrassed by the outcome? We can all learn from our past mistakes, if only we were willing to admit them, and then educate others before they suffer from the same miscues.This paper presents the top twelve lessons learned associated with the design and operation of activated carbon odor control systems gathered from miscues experienced over the past nearly thirty years. Activated carbon, of course, has been a key player in the odor control arena for a long time. It has changed with the times to improve required performance; witness the growth from virgin, to impregnated, to catalytic carbon varieties and, has found its place as a single stage technology or as a second stage polishing step. No one questions its proven track record and its effectiveness in the right application. Nevertheless, its relatively simple layout, nonmechanically intensive design, lack of continuous by-product disposal, generally can provide a false sense of security unless we have paid attention to and understood many of the potential pratfalls of the activated carbon odor control system. Many of these pratfalls initially were not intuitively obvious to either the designer or operator of the technology. However, through practical experience gained over the years, these lessons learned can be shared. The top twelve lessons learned from designing and operating activated carbon systems are:#12. Install sample taps at three different levels of the activated carbon media bed.#11. Install differential pressure monitors across the activated carbon media bed.#10. Design for independently supported beds, particularly in dual bed vessels.#9. Design a bottom drain for the vessel instead of a side drain.#8. Avoid designing an exhaust stack with a hat.#7. Provide sample taps on the inlet and outlet (both outlets if it is a dual bed unit) air flows to allow for the monitoring of carbon performance.#6. Ensure that the carbon specifications are satisfied and monitor how it is loaded into the vessel (avoid fines in the carbon delivered and from being created, based on how they load the vessel).#5. A good practice is to place bed limiters on the top and bottom of your carbon media bed(s).#4. Carefully design the inlet air connection in a dual bed orientation to avoid shortcircuiting, furrowing and fluidizing surface carbon.#3. Install pre-filters in front of the activated carbon vessel to avoid potential blinding of the carbon.#2. Do not allow water to accumulate in the bottom of a carbon vessel, particularly in a dual bed orientation.#1. Carbon fires can occur! Know the limitations of the activated carbon being used.Each of these two twelve lessons learned will be discussed in detail with anecdotal references to real life situations. The reader/attendee will walk away with a more thorough understanding of how to more effectively design/operate an activated carbon odor control system.