Patent CA-2420002-A1 (CA)
Title: F.o.g. (solid/semid solid fats, oil & grease) liquid separator system
Inventor: MCLEAN CID P
IPC: C02F1/40
Filed: 2003-02-19
Abstract: The present invention relates to an improved process and apparatus for separating floatable, solid and/or semi-solid Fat, Oil and Grease (F.O.G.) from a liquid source. In a typical Wastewater Plant, F.O.G. is first trapped on the surface of the primary tankage and then skimmed off to a holding tank for ultimate disposal. Several methods of disposal are currently in use. The F.O.G. can be sucked into a septic truck provided enough water is added to break up the mat of F.O.G. that typically forms in the holding tank. However, this amount of water adds significantly to the hauling costs, is detrimental to a landfill and, under upcoming rules, could soon be classified as a special waste, incurring additional costs for its disposal. Another industry method to dispose of F.O.G. is to pass it over a rotating bar screen, though typically the energy to heat the wash water renders this system very expensive. Other methods of dealing with F.O.G. often require some way, often scrapers, of mechanically lifting it up and out of the liquid if floats on. These methods are all very labour intensive as F.O.G. readily adheres to all surfaces and must be physically removed before all water drainage channels are plugged and the unit's efficiency as a F.O.G.-water separator is impaired. The above methods of F.OG.  capture must also contend with all manner of floatables that are also trapped in the primary tankage. These items may include many small plastic pieces and bags that may impair the efficiency of conventional units.   We have found that these disadvantages can be overcome by the use of our Low Angle, Slow- Speed, Enclosed Solid- Shaft Auger. Unlike other F.O.G. and liquid separators, the efficiency of our system does not deteriorate as F.O.G. clings to all surfaces. In fact, optimal efficiency only occurs a$er the enclosed auger is fully charged with F.O.G. It is at this point that the water entrained in the F.O.G. is churned out of the auger intake as the water/grease combination does not have the internal cohesion to push the grease up the auger. Nor do the floatables pose any difficulties for this system, as the eight inch auger is capable of passing a three inch piece, such a piece being much larger than that capable of passing through a typical Headworks solids removal system. The end product of this F.O.G. separator is dry enough that it can be bagged and added to the Headworks screenings, which are considered general waste. Reducing the water content of the product to this degree also reduces the shipping costs and produces a more environmentally sound substance to landfill. This concept has proven to require few man-hours to maintain and consumes much less energy than other systems needing a hot water backwash cycle.     In a drawing which illustrates the embodiments of the invention, Figure 1 is a side view. The F.O.G. is skimmed off the primary tankage and is put in a circular holding tank 4. The process comprises a slowly rotating eight inch auger 1, which is suspended in the F.O.G./water interface, with an adjustable jack 2 that allows the auger angle to be changed. The fog is directed into the half-pipe auger inlet 6 by a series of spray bars 3 that impart a rotational energy to the F.O.G. that drives it into the auger inlet. The auger, as it pushes the F.O.G. up, drives out the entrained water and deposits in a bin 5, the lard-like grease end product.