A new approach for the prediction of ash fusion temperatures: A case study using Turkish lignites

Prediction of ash fusion temperatures by using the chemical composition of the ash has previously been conducted only with linear correlations. In this study, a new technique is presented for predicting the fusibility temperatures of ash. Non-linear correlations are developed by using the chemical composition of ash (eight oxides) and coal parameters (ash content, specific gravity, Hardgrove index and mineral matter content). Regression analyses are conducted using information for Turkish lignites. Regression coefficients and variances of non-linear and linear correlations are compared. The results show that the non-linear correlations are superior to linear correlations for estimating ash fusion temperatures

Removal of hazardous air pollutants based on commercial coal preparation plant data

This paper investigates the concentration, distribution, and rejection of hazardous air pollutants, specifically identified by the US Clean Air Act Amendments of 1990, based on commercial coal preparation plant data obtained on-site. The samples were collected from the products of the different cleaning circuits of the operating plant. The concentrations of twelve potentially hazardous trace elements, including As, Cd, Co, Cr, Hg, Mn, Ni, Pb, Se, Th and U in those samples were determined. Compared with the average concentration of the trace elements in Turkish coals, the run-of-mine coal fed to the existing plant appears to contain higher concentrations of Cd, Hg, Mn, Th and V. However, the concentrations of As, Cd, Cr, Mn, Se, Th, U and V of the run-of-mine coal are above the world averages. Cd, Cr, Hg, Mn, Pb and Th concentrations of run-of-mine coal were easily removed at commercial coal preparation plant refuse in the range of 51.8% to 77.4 %, while only a small reduction was achieved for U and V as they were concentrated in clean coals. The present study reveals that conventional coal preparation technologies could significantly reduce hazardous air pollutants concentrations in coal

Environmentally sound coal-derived binder for coal briquetting

Conventional coal binders such as coal tar pitch and petroleum refinery residue provide agglomerates of satisfactory quality. However, their use has been banned for a quarter century due to their hazardous effect on human health and their contribution to air pollution. On the other hand, environmentally sound binders such as molasses, dextrin, etc. provide poor water-resistant agglomerates. In this research, coal-derived humic acid was used as coal binder. It was extracted from Afsin-Elbistan lignite by nitric acid oxidation and ammoniation processes. During briquetting, the effect of heat treatment, amount of binder added, particle size, pressure, and moisture content of the briquetting charge on the quality of the briquette have been investigated. The briquette produced at 165°C for 1 h heat treatment by adding 5% humic acid and 10.50% moisture showed that the radial compressive strength was 80 kg/briquette and abrasion resistance was 87.03%, with no water disintegration. Copyright © 2002 Taylor & Francis

SUPER-CLEAN COAL PRODUCTION FROM TURKISH BITUMINOUS COAL

The possibility of producing super-clean coal from Zonguldak bituminous coal by heavy medium separation and flotation techniques was investigated. The coal sample used was a - 50 mm + 18 mm size jig concentrate from the Central Washery of Zonguldak. It was composed of 12.11% ash and 0.41 % total sulfur. The vitrain band of the same coal contained 3.28% ash and 0.22% total sulfur. By applying a two-step heavy medium separation, it was possible to reduce the ash content from 12.11% to 4.00%. Additional cleaning to less than 3.0% ash was carried out by flotation. To determine the optimum flotation conditions required for the production of super-clean coal, the effects of different types of frothers, pH and collector dosage were studied. The optimum result was obtained using 170 g/t kerosene and 160 g/t MIBC. The investigation showed that it was possible to produce a coal containing 2.16% ash and 0.42% total sulfur from Zonguldak bituminous coals

Production of ammonium nitrohumate from Elbistan lignite and its use as a coal binder

The conversion of Elbistan lignite into nitrogen-rich, alkali-soluble humic acid (ammonium nitrohumate) and its use as a coal binder were investigated. The optimum conditions for nitric acid oxidation and ammoniation were determined. The optimum HNO3 concentration was determined as 4.87 wt%. As a result, a humic acid solution containing 10.75 wt% nitrogen was obtained with 88.2 wt% recovery from Elbistan lignite. Coal-derived humic acid was used as a binder in briquetting of Tuncbilek lignite fines. It was possible to produce water-resistant and durable briquettes. (C) 1997 Elsevier Science Ltd

Briquetting of ulexite fines

Turkey is the main boron minerals producing country in the world. The most important boron minerals are tincal, colemanite and ulexite. All mining, beneficiation and handling operations generate fines which cause ecological and economical problems. Utilization of this accumulated material requires both upgrading and agglomeration. The aim of this research was to exploit the ulexite fines by improving their grade and size. Attrition-scrubbing followed by washing and screening was employed for upgrading the fines. It was found that the grade can be increased from 23-25% B2O3 to 29% B2O3 with 73% recovery. Briquetting was applied as the size enlargement process. During the briquetting, the effect of moisture content, pressure, amount and type of binder, and dryin g on the quality of briquettes were investigated. The tests showed the possibility of production of strong briquettes by adding water alone, but the briquettes had no resistance to abrasion and water. Binders, namely boric acid and borax have been added to improve the properties of briquettes. The results showed that the compressive strengths and abrasive resistances of briquettes obtained with both binders were acceptable. However, the briquettes have no water resistance properties

Briquetting of tuncbilek lignite fines by using ammonium nitrohumate as a binder

Results of experiments on the briquetting of Tuncbilek lignite fines using ammonium nitrohumate (anh), a low calorific value, young lignite-derived humic acid salt solution, are reported. The paniculate material was blended with ammonium nitrohumate serving as the binder. In the briquetting tests, the effects of moisture content, pressure, binder content, nitrogen content and heat treatment were investigated. Durable briquettes, in terms of mechanical strength and water resistance, were produced with a 7% binder content at 10.5% moisture, following pressing at 1280 kg/cm2 and drying at 165°C for 1 h. The briquettes produced with ammonium nitrohumate had better combustion properties than run-of-mine samples; the contribution of the binder to smoke and sulphur emissions was very low, and fine dust particles were negligible.© 2004 Io M Communications Ltd

ELECTROKINETICS OF OXIDIZED COAL

Electrokinetic measurements were carried out in order to determine the properties of oxidized coal surfaces over a wide pH range both in the presence and absence of various metal ions and flotation collectors. It was found that polyvalent cations, such as Fe++, Fe+++ and Al+++ decreased the zeta potential to zero and then reversed the charge. In the presence of cationic collectors, the negative value of zeta potential of oxidized coal was driven positive, below 9.3 to 10.9 depending on the type and concentration of collector used. The infrared spectra of oxidized coal did not indicate any characteristic bands for amine at any pH. These studies demonstrated that amines are not chemically adborbed on oxidized coal surfaces