1、1 英文翻译原文Effect of pH, air velocity and frother concentration on combustible recovery, ash and sulphur rejection using column flotationJorge Pieres , Juan BarrazaEscuela de Ingeniera Qumica, Ciudadela Universitaria de Melndez, Universidad del Valle, A.A. 25360, Cali, ColombiaAbstract:This study shows
2、 the effect of pH, air velocity (Jg) and frother concentration (FC) on combustible recovery, ash and sulphur rejection for four Colombian bituminous coals: Cerrejn (Guajira), Nech (Antioquia), Jagua (Cesar) and Guachinte (Valle del Cauca) using column flotation. For the experimental development a 23
3、 factorial central composite experimental design was used. The coal samples were processed in a pH range of 4 to 10, Jg in the range of 0.7 to 2.1 cm/s and FC in the range 2.1 to 6.3 kg/t. Results showed that Cerrejn and Jagua coal presented combustible recovery higher than 50%, (57.6% and 54.7% res
4、pectively), at acidic pH (pH 5), with Jg of 1 cm/s and 3.2 to 4.2 kg/t of FC, respectively, while Guachinte coal presented a maximum combustible recovery of 56.4% at alkali pH (pH 9), Jg of 1 cm/s and 3.2 kg/t of FC and Nech coal obtained the highest combustible recovery (46.8%) at pH 7 with 2.1 kg/
5、t of FC and Jg of 1.4 cm/s. For Guachinte and Nech coal ash and sulphur rejection were high (90.3% and 88.5%) and (71.3% and 73.8%) respectively at acidic conditions (pH 4 and 5) with Jg in the range of 1.4 to 1.8 cm/s, whereas Cerrejn and Jagua coals exhibited high values of ash (85.4% and 94.7%) a
6、nd sulphur rejection (81.1% and 85.1%) at alkali conditions (pH 9 and 10) with Jg in the range of 1.0 to 1.4 cm/s. In general, it was observed that Cerrejn and Jagua coals presented higher values of combustible recovery under acidic conditions than Nech coal and Guachinte coal.Keywords:Column otatio
7、n; Combustible recovery; Experimental design1.IntroductionCoal is a complex mixture of organic and inorganic materials. The inorganic fraction is mainly composed of mineral matter, while the organic matter is related to maceral groups. The mineral matter occurs in coals in different amounts and type
8、s, and it represents the main problem in coal separation process. The efficient use of coal as a fuel requires extensive cleaning for the rejection of mineral matter such as pyrite, clays and other. Different cleaning processes such as heavy media separation, washing cyclones, shaking tables, among
9、others, have been used for coarse particle sizes, most have shown a significant success, in any case this success is limited only by the small scale operations conducted in the laboratory, also, some of these techniques present difficulties to scale up the process for industrial use, especially when
10、 operating with small particle sizes. In the case of cleaning fine coal particle, the most adequate process is column flotation, especially due to its high efficiency. High amount of clean coal can be obtained in a wide range of operation conditions using froth flotation. Froth flotation can be an e
11、ffective and easy method for the production of clean coal type premium, especially for small particle sizes costs associated with flotation system can be offset by the increase in the price of these clean coal type premium, could be sold in a number of different markets at prices that are substantia
12、lly higher than that obtained in the usual steam and metallurgical markets. During the flotation, hydrophobic particles (organic matter) adhere to air bubbles and they are taken in the froth, while hydrophili particles (mineral matter) are obtained in tailing of flotation column.The efficient separa
13、tion of the mineral matter in coal is determined by the hydrophobicity of coal and minerals. To improve the separation, coal surface needs to be appropriately modified, increasing the hydrophobicity of coals and also increasing hydrophilicity of mineral matter. The pH is a parameter commonly used to
14、 modify surface properties of coal 1,2.Pierre Boutin, Remy Tremblay and Don Wheeler introduced the concept of flotation column in the early years of the 1960s with the objective to process fine mineral, offering a solution to problems encountered in conventional flotation 3,4. The flotation column d
15、iffers dramatically from conventional mechanical flotation machines, both in design and operating philosophy. The column flotation produces better separations mainly with fine particles, since it eliminates the problem of hydraulic entrainment. Column flotation creates a more quiescent environment f
16、or particlebubble aggregates, generates small bubbles and eliminates the need for banks of conventional me-chanical flotation machines 5. This increase in popularity is attributed to the progress made in developing the design, scaling and operating procedures 3.Some works studied the effect of pH on the mineral species in Pittsburgh 8 coal in a flotation system 1,2. Other authors studied the effect of different reagents on lignite flotation 6, Naik
