Oil Blending Systems
The aim of a blender installation is to produce a controlled blend of two different oil products in line. This is done by bringing together a flow of low- and high viscosity medium in a known relation (flow ratio) and thereafter creating a turbulent flow in a static mixer. This mixer will create a homogeneous mix of both products, thus creating an oil product with a lower viscosity grade than the initial heavy product due to accurate viscosity control.
Basic construction of a modern in-line blender system is that both flows are measured with a flowmeter fitted with a pulse transmitter. The flow of the high-viscous product (HFO) is optionally regulated by a frequency controlled pump to a fixed set-point calculated from the desired flow in the outlet. To this product, a flow of MDO is added, controlled by means of a 4-20 mA signal to the frequency control of the MDO-pump or to a control valve. Adjusting the blend ratio by proportional integral control of the MDO-flow gives a changing viscosity grade of the resulting product (blend). To adjust the blend, the viscosity of the blended product is measured in the outgoing line with a ViscoSense viscosity sensor. Together with the measured temperature this viscosity is used to calculate the viscosity at 50°C, at which it is compared with the desired setpoint. Depending on the difference with the setpoint, the ratio between heavy and light product is changed by a ‘proportional integral’ blend control monitor. The use of a viscosity sensor ensures a constant quality over the batch, even if the quality of the HFO is not stable throughout the batch, as the MDO ratio will be adjusted continuously. The latter will result in a cost effective operation, since the optimum amount of MDO is used.
A blender unit can, depending on its execution, also be used for straight run delivery of MDO or HFO, or can be used for batch applications. For this application also the Blender Control Monitor can be used to control the valves.
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