Large-capacity nozzle centrifuge for starch applications Merco CH-36B GOF Alfa Laval separator centrifuges for the starch industry are available in many different sizes and confi gurations, each one designed and adapted for dealing with the widely varying separation tasks required. The Merco CH-36B GOF is a dedicated starch centrifuge, designed for several applications in the maize wet milling process. Applications The Merco CH-36B GOF is a nozzle centrifuge designed for continuous discharge of solids. It is used for classifying, concentrating and washing solids, and for clarifying liquids that contain relatively high solids concentrations. The Merco CH-36B GOF is widely used in the maize starch industry for processes that include primary starch separation, gluten thickening, millstream thickening and middling concentration. Standard design Separation takes place in the bowl, which is mounted on a vertical spindle. The vertically mounted motor drives the spindle near the top via two bound V-belts. All metallic parts that come in contact with the process liquid are made of high-grade stainless steel. Thirty nozzles are placed in the bowl periphery at a narrow angle from the tangent, in order to recover energy from the material being discharged through the nozzles. The nozzles are made of tungsten carbide, suitable for abrasive solids. The centrifuge is equipped with sensors for monitoring the bowl speed, vibration and bearing temperature. The inlet and outlet devices are equipped with fl anges. Circulating oil ensures that the bearings are lubricated. An external pump maintains the necessary pressure. Special features The Merco CH-36B GOF employs a special recirculation system that provides highly effi cient separation. Solids can be recirculated to the nozzles at the same time as wash water is added. Working with the underfl ow draw-off valve, the return fl ow system provides a unique means of controlling the separation process. It allows the operator to control and optimize the separation process by determining how much underfl ow is to be removed, how much is to be recycled back to the rotor and how much wash water is to be added. This makes it possible to use nozzles with a large diameter, which allows variations in feed concentration and prevents blockages. The centrifuge thus becomes more versatile, and can be easily adapted to changes in procedure. The Merco CH-36B Fig. 1 Merco CH-36B GOF with motor GOF has a built-in hydraulic hoist that eliminates the need for an external lifting device, and thus reduces the downtime required for servicing the centrifuge. Basic equipment The centrifuge is equipped with a motor, a self-cleaning strainer for the feed, speed and vibration sensors, oil temperature sensors for the spindle bearings and the motor winding, a hydraulic power unit for the lifting hoist, a set of special tools and a standard set of spare parts. Options Control-torque motors of two different power ratings are available. Frequency drive is also possible. The centrifuge bowl is available in classifi er (PS) or clarifi er (GT, MST, CL) execution, with different disc spacings. A double underfl ow outlet is available for the MST version.

Operating principles The feed consisting of both liquid and solids is introduced into the rotating centrifuge bowl (fi g. 2) from the top via a stationary inlet (1) and is accelerated in a distributor (2) before entering the disc stack (3). Separation takes place between the discs. The liquid phase moves through the disc stack towards the centre of the bowl and is discharged to the overfl ow by gravity, via power a ring (4). The heavy solids are collected at the bowl periphery and continuously discharged to the underfl ow by gravity, through the nozzles (5). Part of the concentrated solids discharged...