Recently, a good customer of ours sent us a bid request on a project they inherited from a consultant who worked for the same client. The Corrective Action Plan (CAP) for the project, which specified the equipment to be used, had already been approved by the state. For reasons that may become apparent later in this post, their client decided to change horses in midstream and have our customer handle the remediation system build and install.
Upon reviewing the specified equipment for the project we noticed a few interesting design features of the system:
- An oil sealed liquid ring pump(LRP) specified for an application where 20 inches of mercury vacuum (INHG) was needed at 300 cubic feet per minute (CFM). The system included a knockout tank with a transfer pump and an electric solenoid. The solenoid was activated to release vacuum when the tank level reached the HHL float. The system was designed to continue operating during this process. The hydrocarbon concentrations were about 12000 PPM.
- A 100 CFM electric catalytic oxidizer being fed by a 300 CFM (cubic feet per minute) oil sealed liquid ring pump
- The LRP knockout tank fed an oil water separator (flow not specified) which fed a 10 gallon per minute (GPM) air stripper
- A 30 GPM transfer pump (at 50ft of head) on the air stripper fed to an open top equalization tank about 5 feet from the air stripper and at the same elevation
- Air Stripper exhaust of at least 200 CFM fed directly to two 55 gallon drums of GAC in series with listed concentrations of aromatic hydrocarbons in the range of 10,000 ppm
And the controls, electrical and plumbing? Well, we’ll skip most of those to keep this blog post short.
So What is Wrong With This?
In the first bullet we have a LRP which is used for high vacuum applications (greater than 15 INHG) and is not suitable for low vacuum applications because it will exhaust oil mist. The solenoid valve will cause the LRP to lose a great deal of vacuum and produce oil mist.
In our second bullet, we have 300 CFM of possible oil mist filled air going into a 100 CFM rated oxidizer. Aside from the obvious flow issue, and the high hydrocarbon loading rate at triple the design flow, the $5000 catalyst in this oxidizer will be fouled in no time by this mist and have to be replaced (numerous warnings on manufactures website and literature). That is assuming it will even run.
Third and fourth bullets, we have a flow not specified and a pump too large for the application specified. And last, of the few things mentioned, we have a high concentration effluent going into 55 gallon drums of GAC (about 160Lbs in each). First, the carbon may last a day before it has to be replaced. Second, the flow is at the design maximum of 200 CFM for the drums and the effluent from the stripper will have high humidity which will lessen the efficiency of the GAC.
So do we bid to build it as specified, then catch hell when it doesn’t work? We report, you decide!
Brian E Chew Sr. P.G.