Screenbowl centrifuges have shown excellent results for Ruhrkohle
In view of the fact that separating the water mechanically is less expensive and less complicated than thermal drying, RAG decided to install additional mechanical dewatering devices. Screenbowl centrifuges consist of a two-stage screw conveyor centrifuge, which combines a solid bowl with a screenbowl-type machine. The slurry is introduced through the feed pipe and subsequently goes through two stages. During the first stage, within the solid-bowl section, solids are deposited by the effects of centrifugal force. Effluent leaves the machine over the overflow weir. Pre-thickened flotation concentrate is then pushed by the screw conveyor into the second stage, the screenbowl. Centrifuged cake is further dewatered and then discharged. Effluent leaving the screenbowl is returned to the feed. The first centrifuge used on an industrial scale by Ruhrkohle was the KHD Humboldt Wedag type SVS 900 by 1800 model. This centrifuge had a rotor diameter of 900 millimeters (36 inches) and a rotor length of 1800 millimeters (72 inches). Its optimum feed rate was 10 tons per hour. The unit was run continuously for seven months without any failure or noticeable wear. Now after more than two years of continuous operation of screenbowl centrifuges in three RAG coal preparation plants, the following conclusions can be made: (1) steady and uncomplicated operation of these machines is impressive. Centrifuges are run without flocculant; they require only starting and stopping with the desired feed rate being controlled as a function of power consumption; (2) screenbowl centrifuges discharge a product of good flow properties, with good handling characteristics; (3) in cases that have a high proportion of fine particles in the feed or high throughput rates, combined operation of rotary vacuum filters with screenbowl centrifuges or the use of compartment-type presses with screenbowl centrifuges is advisable for dewatering effluent.
- OSTI ID:
- 5009127
- Journal Information:
- World Coal; (United States), Vol. 8:3
- Country of Publication:
- United States
- Language:
- English
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