12 research outputs found
Pilot-scale Studies of Ash and Sulfur Removal from Fine Coal by Using the Cylojet Flotation Cell
No full textThis article presents the results of pilot-scale studies of ash and sulfur removal from a Turkish coal
by using the cyclojet flotation cell. The cyclojet cell, which was developed by H. Hacifazlioglu and I.
Toroglu in 2006, utilizes an alternative jet flotation technique. Apart from being based on the working
principle of jet flotation, the cyclojet cell incorporates centrifugal forces into the flotation process, thus
providing an excellent separation for ash and pyritic sulfur removal. The most important parameters
for the removal of ash and pyritic sulfur in the cycojet cell are the length of the conical jet, frother
type, wash water rate, and froth thickness. With decreasing the conical jet length and increasing the
wash water rate and froth thickness, there is an increase in the removal of pyritic sulfur. On the
other hand, the frothing agents MIBC produced better results in terms of pyritic sulfur removal in the
cyclojet cell. Under optimal conditions, the cyclojet cell removed 61.25% of the pyritic sulfur and
73.98% of the ash with a combustible recovery value of 71.10% without any need for a depressant
The Effects of Ash and Maceral Composition of Azdavay and Kurucasile (Turkey) Coals on Coking Properties
No full textIn this study, investigations were made as to the effect of the maceral compositions and mineral matter content of Azdavay and Kurucasile coals on the coking property. Chemical and maceral analyses and coking properties were determined for the products of the float-sink procedure. The coking properties were established on the basis of free swelling index and Ruhr dilatometer tests. Maceral analyses showed that as the ash content of a coal containing both high and medium volatile matter increases, its effective maceral proportion decreases, and the coking property is affected in an unfavorable way
The Recovery of Coal from Waste Coal Slurry by Cyclojet Flotation Cell
No full textIn this article, experiments were conducted under various working conditions in order to recover coal from waste coal slurry by cyclojet flotation. Waste coal slurry with 47.50% ash yielded products having an ash content of 7-17% with 65-80% combustible recoveries. It has been found that results of the cyclojet cell are close to the release curve, and the cyclojet cell can be substituted for the mechanically-agitated conventional cell. Moreover, the total flotation time for the cyclojet cell is 30 seconds and a cell with a capacity of 100 liters can enrich as much as 0.6 tonne of coal (for 5% solid ratio). It has other important advantages, such as having a simple structure, requiring little room, and being easy to operate
Effect of Operational Parameters on the Particle Size Distribution of Marble Wastes in Stirred Media Mill
No full textStirred mills are very effective grinders in the production of micronized materials. Stirred mills are widely used in mining, construction, chemical, plastic, food, paper, ceramics and chemistry industries because of the need for very fine materials. The paper shows the possibility to produce marble nanoparticles in a stirred media mill by appropriate milling parameters. In this study, marble wastes in the form of large pieces from Marfam Marble’s factory were crushed below -1 mm and then dry grinding of wastes were investigated in a laboratory scale pin-type vertical stirred mill. Working parameters such as stirring speed, feed rate and grinding time were found to have considerable effect on the fineness of the product. Different grinding experiments were carried out for all working parameters. Zircon beads with diameters of 3,36-2,00 mm were used as the grinding media. The effect of stirring speed during grinding was determined at different five speeds of 360, 540, 720, 1080 and 1440 rotation per minute against different times. Under the effect of five different feed rates (%60, %80, %100, %120 and %140), experiments were carried out as a function of time. Size analyses and chemical properties of micronized marble wastes were determined. The result of the experimental studies confirmed that micronized grinding of marble wastes by stirred mill could be efficient
Studying the effect of different operation parameters on the grinding energy efficiency in laboratory stirred mill
No full textAbstract In this study, considering different operational parameters for stirred media mill, change in specific energy was compared to the change in Rx values, i.e. the cumulative weight of the material undersized to a specific sieve. R values, namely R38, R75, R106, were measured before and after grinding in stirred mill. The change in Rx (ΔRx, %) values were calculated and they were used to evaluate the certain unit of effectual energy (Ecb). This abovementioned calculation is performed by proportioning the Specific Energy (SE) to ΔRx values. The effectual part of SE is considered to be the ratio of the energy needed only for size reduction in grinding and it should be related to the ΔRx. The relative Ecb ratios of different grinding conditions give the relative specific energy efficiency ratio (SEe). The relative specific energy efficiency ratio is inversely proportional to specific grinding parameters and ground product particle sizes. The relative specific energy efficiency can be considered as the relative amount of energy for various grinding conditions. The variation between relative energy amount and the previously specified particle size provides a realistic comparison of different grinding parameters. The abovementioned variation could be employed to understand the resistance particle size which is a new concept to describe the particle size at which the maximum effectual SE is directly used. In the context of this study, it was aimed to figure out the interrelation between specific energy efficiency and PSD variation along with the resistance particle size
The Benefication of Ultrafine Coal by Using the LM, Modified LM, and Conventional Flotation Cell
No full textThis article describes modification of the LM cell developed by Cheng Xinghua and using it to clean ultrafine coal. The major modifications involve replacing the column in a standard LM cell with a hydrocyclone and giving air into the system through a porous material. Thus, centrifugal forces are also incorporated into the system and a higher coal recovery is obtained. In addition, such important design and operating parameters as the apex diameter, gas flow rate, wash water rate, reagent dosage, and solid ratio were optimized, which affect the performance of the modified LM cell. Next, flotation experiments were carried out using the standard LM cell and conventional mechanical cell and the results were compared with those obtained from the flotation with the modified LM cell. It was established that the modified LM cell is an effective one for cleaning ultrafine coal and has a considerably high capacity. In fact, following the flotation of merely 60 sec, coals with an ash content of 46% yielded clean coals having a 10-15% ash content with 70-75% combustible recovery. The conventional flotation cell, on the other hand, produced a poor selectivity and lower coal yield. The separation efficiency of the modified LM cell was in the 55-60% range, whereas that of the conventional cell varied between 50-55%
Coal Calorific Value after Physical and Chemical Cleaning
No full textAbstract In this study a total of 12 coal sample was collected. 7 of these samples are local coal samples and 5 of them is exported coals. These coals samples were fractionated into two size groups, i.e. -10+3.15, -3.15+05. Float and sink analysis was performed on this two size groups of samples with Ca(NO3)2 medium at the density of 1.50 g/cm3. Latter within the scope of this study, chemical cleaning was employed on this samples. Chemical cleaning on coal samples was carried out with acids (HF and HNO3) at specific conditions. Samples have different calorific values after physical and chemical cleaning. Although some impurities have been removed with both cleaning methods, physical cleaning resulted in higher ash content coals at the end while with chemical cleaning almost no ash content coals were obtained. However, it was observed the fact that chemical cleaning resulted lower calorific values of samples. This might be because of chemical cleaning results in the decomposition of the coal matrix structure.</jats:p
An Evaluation of the Impact Strength Index as a Criterion of Grindability
No full textAbstract In this study, Hargrove Grindability Index and Impact Strength Index values of coals collected from 17 coal seams in the Zonguldak Hardcoal Basin were determined. Then, the effect of the Impact Strength Index test on grindability was examined by investigating the relationship between Hargrove Grindability Index and Impact Strength Index values. The results indicated that the best relationship between Hargrove Grindability Index and Impact Strength Index values was found to be in the form of a parabolic function, i.e., coals with high values of Hargrove Grindability Index and low values of Impact Strength Index are much easier to grind. Furthermore, investigations have been conducted as to the effect of volatile matter and carbon contents as well as the rank and maceral composition of the samples on Hargrove Grindability Index and Impact Strength Index values. As a result, it has been proven that Impact Strength Index values can be assessed as a criterion of grindability
Size-Related Evaluation of Unburned Carbon
No full textABSTRACTThe unburned carbon (UBC) content of ash from coal-fired thermal power stations and plants that use massive amount of coal can sometimes be 6–7% or more; this simply means loss of carbon and decrease in efficiency. Carbon loss not only causes a decrease in efficiency but is also an economical issue. Decreasing the carbon content would provide the usage of ash from thermal power stations as cement additives. Many factors cause low combustion efficiency and a high amount of UBC. In the course of this study, fly ash and bottom ash were divided into size fractions and accumulation of UBC at coarser size fractions was observed. In this study, a ground coal sample from a mill was sieved, and the accumulation of UBC at coarser size fractions was associated to a lack of grinding of pulverized coal. Ground coal has a size distribution where 54.45% was below 75 µm, and 45.55% was still over this critical size. A significant amount (35.48%) of the UBC accumulated in the size fraction over 75 µm in fly ash, w..
Open and closed circuit dry grinding of cement mill rejects in a pilot scale vertical stirred mill
No full textAbstract In this study, separator rejects of a closed circuit cement tube milling were dry ground in a 10-l pilot scale vertical stirred mill. Tests were done as open and closed circuit. The results were evaluated by size distributions, Blaine surface area of the products and the specific energy consumed during the tests. Mill capacity and the stirring speeds were the investigated parameters for the open circuit tests, whereas closed circuit tests were carried out at a constant stirring speed but variable discharge rate. Five speed levels used in the open circuit grinding tests are 200, 400, 600, 800 and 1000 rpm. The capacities were determined to obtain product Blaine surface areas in the limits between 2000 and 5000 cm2/g. Closed circuit tests have resulted in 87%, 182% and 452% circulating loads
