Major components

The GF-MDL-VI/VII Installation major components

The primary supply included with the GFSE MDL-VI Plant is an 8-g elliptical screen separator where coarse particles and floating debris are separated before being fed to the primary separation equipment. GFSE applies 2-phase decanters to handle any load of solids normally associated with oily waste. This plant is designed to handle solid contaminates from any range up to 40% in the feed without affecting performance. The job assigned to the 2-phase decanter is to remove the majority of solids from the screened effluent. Following the 2-phase decanter the GFSE system is designed to raise the decanter effluent temperature to >95°C, apply the proper mix of treating chemicals in the API oil phase collection tank (to insure minimization yet performance optimization of treating chemicals) and then to feed directly into the 3-phase disc stack centrifuge to separate the water and any remaining sediments from the oil phase for the purpose of achieving the highest quality treated oil.

The Plant in the photo is specifically designed for the treatment of a wide variety of oily waste classifications from fresh slop oils stored in tanks to mixtures of weathered oily waste held in pits, lagoons and lakes. Its capacity is determined mainly by the viscosity of the feed. For example waste oils with a viscosity in the range of Cst30 at 50°C can be treated at 7,5 m3/hr whereas those having a Cst600 at 50°C can be treated at 2 m3/hr. We therefore recommend treating at a temperature of 95°C to maximize the plant capacity and to improve the overall separation performance thereby producing the highest quality oil. A major variable in treating slops are the concentrations of common contaminates, water & solids as well as emulsions. This plant can handle solids up to 40% in the feed and any combined ratio of oil & water. The plant comes with a variety of options to choose from that include: plant heat (hot water boiler or steam converter), buffer tanks for receiving oily waste and tanks for clean oil and clean water. Other important features are also included or quoted as options to the MDL-VI. This include heat exchangers, treating chemical dosing systems, sludge solids thickeners, pit excavation assemblies, cabins for storage of tools and spare parts, site laboratory, and site office.

Separation of two liquids, with or without simultaneous separation of a solids phas

The 3-phase disc-stack centrifuge used by GFSE is unique for the treatment of difficult to separate oily waste. This is especially evident when compared to 3-phase horizontal 3000-g range decanters, in that 3-phase decanters are more sensitive to changes in oil and water feed ratios typical of oily waste thereby resulting in off-spec oil and water. Typically 3-phase decanters, with their low g-force (3000-g compared to 6,000-g) require pre-treatment in special residence tanks for batch feed preparation all of which consumes time and personnel. The GFSE system eliminates the requirement of batch blending residence tanks and as a result produces a consistent higher quality treated oil phase.

A special design feature of the MDL-VI is the interconnecting pipe & pump works (what we call the logic box) where all plant components centrally flange thereby minimizing space requirements, making installation and commissioning a quick, simple and easy task and providing excellent operations logic and safety monitoring as required for the treatment of the various classifications of oily waste. This allows the plant operator total flexibility when routing and treating the various oily waste streams.


When separating two liquids, the heavier phase is collected at the periphery of the bowl and the lighter phase near the centre. Any solids will separate out at the periphery of the bowl. Each liquid leaves the separator through its own outlet, that of the heavier phase being located at a somewhat greater radius than the lighter liquid outlet. The more or less cylindrical division between the two liquids is known as the interface. The location of the interface is fixed by using gravity discs of different diameters located in the heavy liquid outlet. The degree of separation obtained is dependent on the diameter of the gravity disc. Where the interface is considerably extended, the lighter liquid occupies the disc-stack and is therefore purified best. The result is a pure light phase and a heavy phase which contains a certain amount of the lighter.

This is known as purification.

The separation of water from oil is an example of purification. The oil (the light phase) is to be purified while the water (the heavy phase) may contain small quantities of oil.


If the interface is located closer to the axis of rotation, the heavy liquid (water) will have a greater chance of being purified. In this case, the result is that the heavier liquid is purified while the lighter liquid will contain small quantities of the heavier liquid. This is known as concentration. An example of concentration is the removal of oil from water for the purpose of obtaining an “oil free” water. The feed is introduced at or close to the interface so that neither of the liquids are disturbed during the process of separation. This is usually achieved by means of distribution holes in the disc stack.