Combustible Recovery Values Research Articles

An Investigation into the Enrichment of Coal Wastes of Western Lignite Company (WLC) by Physical and Physico-Chemical Methods

Mechanical excavation and the successive processes coal production are the main reason for the occurrence of fine waste coals. These wastes are normally discharged without being processed from coal washing plants. Therefore, it causes not only economic loses but also severe environmental problems. It was attempted to enrich waste coals of WLC by using physical and physico-chemical methods and the results were compared.
 From the tests the optimum carbon content and the combustible recovery values were obtained as 85% and 97%, respectively, when heavy media and the coarse particle size group were chosen. From the tests with the medium particle size group using spiral and Knelson separators, combustible recovery of up to 90% was reached together with a carbon content of 80%. Moreover, a carbon content of 86.5% with a combustible recovery of 56.6% was obtained by using MGS. In the fine particle size group, the highest combustible recovery was obtained by using spiral and Knelson separators. The highest carbon content in the fine particle size group was obtained through MGS and Jameson Cell.

The application of combined lignite cleaning processes, bacterial leaching and flotation, for reducing higher ash and sulfur contents

ABSTRACT In this study, biological and physicochemical processes were combined to decrease the ash and sulfur contents of finely ground coal. Firstly, biodesulphurization experiments of lignites with high ash and sulfur contents were carried out with air-supply fiberglass bioreactor using Acidithiobacillus ferrooxidans. At the end of the 12-hour bacterial desulfurization experiments; ash content, sulfur content, calorific value, sulfur emission value, recovery of calorific value, and combustible recovery values were 33.88%, 3.97%, 3982 kcal/kg, 0.24% 91.22%, and 89.74%, respectively. Afterward, in the second stage experiments, flotation method was used to beneficiation Can/Canakkale lignites by physicochemical methods. In flotation experiments, the effects of collector (Fuel oil; 0–900 g/t) and frother (MIBC; 0–300 g/t) dosages on flotation were investigated. Optimum collector and frother dosages were determined as 750 g/t and 250 g/t in flotation experiments, respectively. In flotation experiments under optimum conditions ash content, sulfur content, calorific value, sulfur emission value, recovery of calorific value and combustible recovery values were 16.38%, 0.75%, 5166 kcal/kg, 0.03% 98.60%, and 96.11%, respectively. As a result of all experiments, ash and sulfur removal efficiencies were carried out 65.12% and 86.93% in Can/Canakkale lignites, respectively.

Effect of Temperature on Coal Flotation with Waste Vegetable Oil as Collector

ABSTRACTIn this study, the effect of pulp temperature on coal flotation was investigated. Waste vegetable oil was used as collector. Experiments were carried out at different temperatures (5, 25, 50, and 75°C) and the pros and cons of each temperature for flotation performance were revealed. While flotation performance was lower in higher pulp temperatures (50 and 75°C), flotation performance was found higher in lower pulp temperatures (5 and 25°C). Highest combustible recovery values were obtained at 25°C pulp temperature, and the lowest ash product was obtained at 75°C. However, the lowest combustible recovery value was obtained in flotation at 75°C.

A Study of Kinetics on Oily-Bubble Flotation for a Low-Rank Coal

ABSTRACTThe flotation performance and kinetics for a low-rank coal were investigated using air bubbles and oily bubbles. Five flotation kinetic models were applied to the test data to estimate the relationships between the flotation rate constant, the maximum recovery, and the collector dosage. The results showed that the oily-bubble flotation (OBF) obtained lower ash content and higher combustible recovery with less collector dosage than the air-bubble flotation (ABF). But this advantage of OBF gradually diminished with the collector dosage. It was found that the flotation of a low-rank coal in ABF and OBF can be best described with the second-order kinetic model and classical first-order model, respectively. The OBF had higher maximum combustible recovery values and lower maximum ash recovery values. The flotation rate constants of OBF were higher in all the models except the fully mixed reactor model. Furthermore, the effect of collector dosage on the low-rank coal flotation kinetics was evaluated. It was indicated that the maximum recovery values and modified rate constants increased with the collector dosage. The similar trend was observed in the flotation rate constants for all of the models except the fully mixed reactor model.

Pilot-scale Studies of Ash and Sulfur Removal from Fine Coal by Using the Cylojet Flotation Cell

This 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.

Recovery of Coal from Cyclone Overflow Waste Coals by Using a Combination of Jameson and Column Flotation

In this study, combustible matters are recovered from high-ash waste coal separately, first by Jameson flotation and then column flotation. Although high combustible recovery can be obtained from waste coal by Jameson cell, low-ash coals could not be obtained due to low froth height. High froth depth in column flotation has increased the probability of particles dropping back from froth to pulp and very low-ash products have been obtained. However, column flotation has been relatively less successful compared to Jameson flotation in terms of coal recovery. Therefore, both cells have been combined in a common circuit system and low-ash products have been achieved with high combustible recovery values. As a result, clean coals with 7.12% ash were recovered from waste coal having 48.80% ash with 73.60% combustible recovery in the common circuit system. However, in a similar circuit system only with column flotation, coals with 7.04% ash were recovered with 67.85% combustible recovery value. On the other hand, only with Jameson cell, coals with 10.40% ash were recovered with 74.50% combustible recovery.

A Study of Rotary Tribo-Electrostatic Separation of South African Fine Coal

This article presents an experimental study of rotary tribo-electrostatic separation (RTS) as an alternative approach for beneficiating steam coal mainly used in South African power plants. An RTS with an octagonal charger developed at the University of Kentucky, USA has been used in beneficiating two types of South African coals containing nearly 37% and 32% ash, respectively. System parameters, such as applied charger potential, separation chamber voltage, rotation speed of the copper-plated rotor, and splitter distances were investigated for their effects on the separation performance. It was found that better separation was observed at 5000 rpm rotation speed, no applied potential to the charger, and 25 KV separation voltage. The RTS process reduced the ash content of the −177 µm coal fraction by nearly 14.9% for the Klipfontein coal and 12.2% for the Liketh Townlands coal, with corresponding combustible recovery values of 10.7% and 8.9%, respectively. Total sulphur content was also reduced from 2.1% to 0.9% for the Klipfontein coal and from 2.8% to 0.4% for the Liketh Townlands coal at corresponding combustible recovery values of 5.7% and 8.9%, respectively. The x-ray diffraction analysis of the cleaned-coal samples confirmed a reduction in the mineral content with an improvement in the organic composition for both coal samples.

Optimization of design and operating parameters in a pilot scale Jameson cell for slime coal cleaning

The Jameson flotation cell has been commonly used to treat a variety of ores (lead, zinc, copper etc.), coal and industrial minerals at commercial scale since 1989. It is especially known to be highly efficient at fine and ultrafine coal recovery. However, although the Jameson cell has quite a simple structure, it may be largely inefficient if the design and operating parameters chosen are not appropriate. In this study, the design and operating parameters of a pilot scale Jameson cell were optimized to obtain a desired metallurgical performance in the slime coal flotation. The optimized design parameters are the nozzle type, the height of the nozzle above the pulp level, the downcomer diameter and the immersion depth of the downcomer. Among the operating parameters optimized are the collector dosage, the frother dosage, the percentage of solids and the froth height. In the optimum conditions, a clean coal with an ash content of 14.90% was obtained from the sample slime having 45.30% ash with a combustible recovery of 74.20%. In addition, a new type nozzle was developed for the Jameson cell, which led to an increase of about 9% in the combustible recovery value.

In-plant optimization of a full-scale Jameson flotation cell

An optimization study has been conducted to obtain the desired separation performance and the maximum throughput capacity from a 5-meter diameter Jameson Cell operating in a coal preparation plant in the Eastern United States. The results indicate that nearly 0.8 tonne/hr-m 2 of clean coal is achievable while reducing the ash content from nearly 30% to 6% for a fine coal having a d 90 particle size of approximately 45 μm. The test data indicate that a significant improvement in the combustible recovery value is achievable with the increased amount of tailings recirculation although at the cost of concentrate throughput capacity. Based on empirical models developed for the plant process responses such as clean coal tonnage, product ash and product total sulfur contents, an appropriate set of operating parameter values was determined to produce a target set of separation performance and throughput capacity.

Evaluation of the Altair Centrifugal Jig for Fine Coal Separation

A significant effort has been made during the past decade to develop gravity separators for treating fine particles. As a result, several enhanced gravity separators have been developed and commercialized. The Altair Centrifugal Jig is an enhanced gravity separator that provides relatively efficient separations on +25 μm size fractions. An experimental program conducted on −600 μm coal found that the Altair Jig reduced the ash content of the 600×44 urn material from about 30% to 10% with an 86% combustible recovery value. The pulse water pressure, feed volumetric rate and ragging volume were found to be the key operating parameters affecting the separation performance indices obtained from the process. A low density cut point of 1.55 with a probable error value of 0.09 was indicative of the high process efficiency values achievable by the Altair Jig.