Kelley Green Biofuel showcases biodiesel ingenuity at CBC event
Small-scale biodiesel producers have long been a source of process innovation and ingenuity, and the minds behind Kelley Green Biofuel simply confirm this assertion. Kristopher Kelley and Link Shumaker presented Kelley Green Biofuel’s approach to biodiesel production and methanol recovery at the 2014 Collective Biodiesel Conference this month in Pittsboro, N.C.
Kelley Green Biofuel is an RFS2-registered small-scale facility based in Kentucky that can produce 70,000 to 100,000 gallons of biodiesel per year. The farm-based plant uses repurposed propane and milk tanks to make biodiesel. While the milk tanks were designed for cooling with Freon, they were plumbed with steam to heat rather than cool, which “works just fine,” Kelley said.
The process heat and steam come from an Ag Solutions low-pressure steam boiler that has been tweaked to burn what Kelley and Shumaker call “g.esters”—or a mixed stream of glycerin and high-FFA out-of-spec fuel from the glycerin bottoms. A 15-gallon-per-minute (gpm) Alfa Laval centrifuge is used to save residence time in the soap-settling tank, which also allows water-free washing with resin columns and moves batch-processing further along in less time. A positive displacement meter is used to measure yield, for RIN recording.
Kelley Green performs the 27/3 test for glycerin and uses Eurofins QTA on demand program for other testing parameters. What’s lacking at this point for testing, they said, is an in-process test for total glycerin.
The process features vapor recovery to keep methanol vapors down with a venting system connected to any tank in which the volatile alcohol is introduced. They ground and bond across metal components when using plastic because plastic could build up a static charge, and use an explosion-proof motor on the variable frequency drive.
Biodiesel exits the reactor containing about 4 to 6 percent methanol by volume, and enters a flash drum pulling 27 to 28 inches of mercury. Using steam the mixture temperature is raised to about 185 F, requiring about 42,000 Btu. A 5.5 gpm shell-and-tube heat exchanger is used. About 365 gallons of methanol-laden (4-6 percent) fuel is sent into the flash drum and through the methanol recovery system they reclaim about 13 gallons of methanol with 2 to 3 percent moisture. When choosing a pump for a methanol recovery system, they recommended one with a net positive suction head.
Kelley and Shumaker said developing a safe and reliable methanol recovery system proved much more complicated than developing the biodiesel reaction process.