Separation of Different Products
Distillation products are often mixed with other substances of varying density and consistency. In the separating tank, for example, water is separated from the hydrocarbons and collected at the bottom of the tank. To determine the exact proportion of each substance, an interface measurement is necessary. Previously used displacer systems have several disadvantages: they can only detect the interface if the densities of the products remain constant, and they cannot measure the total level or the top surface of the upper material.
New Measurement Technology for Interface Detection – VEGAFLEX 67
Because microwaves radiate freely through non-conductive substances, such as hydrocarbons, interface measurement is also possible in addition to pure level measurement. The two measured substances must simply have different dielectric constants. The classic interface application – water and oil product – yields a strong reflection at the interface due to the very large difference in DK values (oil DK = 2, water DK = 80). Interestingly, the total level can also be measured at the same time with one sensor. The signals from the two measured value outputs are then transmitted either digitally via HART or as 4…20 mA signal via the signal conditioning instrument.
