Development process and future outlook of the coal dewatering centrifuges

Coal dewatering is an indispensable link in the process of wet cleaning of coal, and what are commonly used for this purpose are centrifuges. The paper presents an introduction to the categories of centrifuges, particularly the course of development of the vertical scraper discharge, horizontal vibrational discharge, horizontal scraper discharge, and screen-bowl versions. The vertical scraper discharge centrifuge with its basket up to 1400 mm in diameter right now is principally suitable for dewatering of 13～0.5 mm small coal and < 3 mm coarse-grained slime. This version remains the coal preparation plant′s first choice for its special features of high adaptability to variation of coal properties, good working performance and reliability. The shortcomings of the centrifuge is short service life for its use of a number of quick-wear parts. The research work that has been made in recent years is focused on the method for extending the service life of wear parts, reduction of operating cost and realization of intelligent monitoring and control. The horizontal vibrational discharge centrifuge is mainly used for dewatering of the 50～0.5 mm coarse coal. The maximum diameter of the basket of the largest version is 1600 mm. It features the use of few wear parts and is high in both capacity and reliability. Through incessant development, this type of centrifuge has shifted from a single-mass to a double-mass vibration mode, and the troubles of leak of oil and cracking of supports have been thoroughly eliminated. The horizontal vibrational discharge centrifuge can work with an intelligent monitoring and control system which is capable of performing real-time monitoring of operating state of the centrifuge and issuing early warning of fault. The horizontal scraper discharge centrifuge is mainly used for dewatering of < 3 mm coarse slime.The WLL1300 centrifuge, the largest of its kind, is developed. The centrifuge features a novel structural design which facilitates replacement of wear parts and smooth discharge, making it possible to dramatically increase the capacity of the centrifuge. The horizontal screen-bowl centrifuge is mostly used for dewatering of < 0.5 mm fine coal. The WLG1600×2400 version is now the largest one in terms of capacity. Through improvement of structure of its discharge systems, the trouble of blocking of discharge chute is eliminated, the service life of screw conveyor and screen mesh is extended, and the reliability of different motor mechanism is enhanced. Lastly, the co-authors look ahead to the future development of China-made centrifuges, and points out that large-size and high-capacity horizontal vibrational discharge and vertical scraper discharge centrifuges should be developed to meet the needs of the coal preparation plants which are growing increasingly large in scale; efforts need to be made to the development of vertical scraper discharge centrifuge and to increase its capacity and operating reliability; special endeavors ought to be directed to the development of the screen-bowl centrifuge and addressing of the difficulties in replacement of worn-out parts and maintenance; and the intelligent level of centrifuges needs to be enhanced for enabling them to operate in an unattended manner.