Water Technology, July/August 2019

JULY AUGUST 2019 watertechonline com 13 separate the solids from liquids coming from a DAF unit The solids were sent to a raw bin and the leftover water and oil mixture was then run through a disc stack separator which separated the oil and the water Two machines required twice the labor and twice the maintenance so these systems required optimization The solution The company installed a Flottweg Tricanter a centrifuge system that can handle the work of both of the previous two machines saving time space energy maintenance and costs The DAF sludge is typically 10 fat 10 solids and 80 water The Tricanter can extract the 10 fat and use it for biodiesel fuel the solids are separated via the same machine and sent to the rendering plant for pet food and the water remains inside the system for further processing Rather than sending material to land applications which requires special equipment the material is processed How it works In three phase separation two liquid phases can be separated from one solid phase at the same time The Tricanter can separate these three phases The different densities of the immiscible liquids and the solids means that all three phases can be discharged simultaneously To ensure the separation process can take place the solid phase must be the heaviest phase and the liquid phases must have different densities Otherwise the scroll of the decanter will not transport the solid at all or only inadequately which affects the separation result The structure and function of the Tricanter are similar to those of a decanter two phase separation The decisive difference between the two machines is the way the liquid is discharged There are two liquid phases in a Tricanter a heavy liquid phase higher density and discharged under pressure and a light liquid phase lower density and discharged without pressure An adjustable impeller discharges the heavy liquid phase The operator can use the adjustable impeller to adjust the pond depth of the heavy liquid without difficulty during ongoing operation An adjustment mechanism causes the position of the impeller to change thereby changing the separation line of the liquids The process results can be influenced to achieve the required separation result Most three phase separation machines require disassembly to change the weir ring which sets the separation line This makes optimization of the separation between the two liquids cumbersome The adjustable impeller on the machine is a unique feature that allows clean oil to be extracted with one pass Other applications This type of three phase separation can be used in other industries as well For example peanut oil can be recycled from plants that cook potato chips in peanut oil Other examples include used cooking iznashih iStock Figure 2 Tricanter sectional view along with the three phases that can be discharged simultaneously Figure 3 In contrast to a two phase process product can be separated into water oil and grease with one machine