1、DRY CLEANING OF PULVERIZED COAL USING A NOVEL ROTARY TRIBOELECTROSTATIC SEPARATOR (RTS)D. TAO 1,2 , A. SOBHY1 , Q. LI1, R. HONAKER 1 , AND Y. ZHAO21University of Kentucky, Lexington, KY, USA 2School of Chemical Engineering, China University of Mining Technology, Xuzhou, Jiangsu Province, China Coal
2、cleaning is often conducted using wet physical separation processes such as heavy medium vessels or spirals at coal prep- aration plants to remove impurities such as ash, sulfur, and mercury. However, the resultant clean coal product still contains a significant amount of impurity due to the fact th
3、at impurities are not well liber- ated from coal particles ranging from several millimeters to inches in size at which wet cleaning processes take place. A cleaner coal product can be obtained if a dry process is avaialble to further clean pulverized and thus better liberated fine coal at the power
4、plant prior to its combustion.In this study, a novel rotary triboelectrostatic separator (RTS) was investigated for its application to dry cleaning of fine coal sam- ples acquired from the power plants in the state of Illinois. The pro- prietary RTS is characterized by an innovative high-efficiency
5、rotary charger, charger electrification, laminar air flow, etc. Compared to existing triboelectrostatic separators, the RTS offers significant advantages in particle charging efficiency, solids throughput, The authors would like to sincerely acknowledge the funding of the Department of Commerce and
6、Economic Opportunity of the state of Illinois through the Office of Coal Development and the Illinois Clean Coal Institute under the project Number of 08-1= 4.1A-1, which made this work possible. Technical assistance and professional advice from the project manager Joseph Hirschi is deeply appreciat
7、ed. separation efficiency, applicable particle size range, etc. Important process parameters such as charger rotation speed, injection and co-flow rate, and feed rate were investigated for their effects on separation performance. Keywords: Fine coal; Liberation; Particle charging; Rotary charger; Tr
8、iboelectrostatic separation INTRODUCTION Coal is a major source of energy in the United States and more than 51% of the electricity used in the country is generated from coal. Numerous advanced coal-cleaning processes have been developed in recent years to reduce ash, sulfur, and mercury contents. H
9、owever, most of the processes involve the use of water as a medium and thus the clean coal products must be dewatered before they can be transported and burned at power plants. The high cost associated with fine coal dewatering makes it difficult to deploy advanced coal-cleaning processes in commer-
10、 cial applications. Dry beneficiation technique is an alternate approach to solving this problem. Recently, the literature on dry beneficiation methods for coals with specific reference to high-ash Indian coals has been summarized by Dwari and Rao 1. Triboelectrostatic process is one of the key dry
11、pro- cess techniques to separate the ash-forming inorganic minerals from coal. Electrostatic separator with tribo-charging technique has great potential for coal preparation in fine sizes. The triboelectrostatic system can be divided into two major zones: a tribocharging zone to differentially charg
12、e a mixture of particles and a separation zone to physically separate charged particles. The coal- and ash-forming minerals are charged in the tribocharger based on their rela- tive work functions. After triboelectrification, the particles entering into the electric field get attracted towards a pos
13、itive or negative electrode plate according to their charge polarity and magnitude. Several studies have shown that clean coal generally charges positively and ash-forming minerals or high-ash coals charge negatively 25. The present study was conducted to investigate the novel rotary tri- boelectros
14、tatic separator (RTS) for its application to dry cleaning of fine coal samples acquired from a power plant. The pulverized fine coal con- tains well liberated ash and pyrite minerals and is an ideal feed to the tri- boelectrostatic separator for further cleaning without the use of water or any chemi
15、cal reagents. The coal particles are positively charged while ash particles are negatively charged as a result of differential charging in the charging chamber.EXPERIMENTAL Fine Coal Sample The pulverized coal sample used in this study was acquired from a power plant that uses a wet pulverizer to reduce coal size feed to the boiler. The proximate analysis showed the coal sample had 16.32% moisture, 8.0% ash, 45.50% volatile matter, and 30.73% fixed carbon. Table 1 shows the size-by-size weight and ash distribution data of the coal sample. Approxi- mately 50.41% of the samp
