Naseer Sheikh

Desulfurization and Demineralization of Lakhra Coal by Molten Caustic Leaching

The present study describes the beneficiation of coal using oxidative caustic molten leaching technique. The crushed coal was subjected to caustic solution in a sealed stainless vessel. The demineralization degree was estimated by determining ash, sulfur, and gross calorific value of coal samples. After leaching, significant reductions in ash and sulfur were observed: ash reduced to about 85% and sulfur reduced to approximately 40%. The increase in gross calorific value was also observed in the experiments. The demineralization of Pakistan coal by oxidative process may be a viable option for coal beneficiation.

Effects of Moisture and Coal Blending on the Hardgrove Grindability Index of Pakistani Coals

The Hardgrove Grindibility Index (HGI) of coal is an indicator of its grindibility characteristics to determine the energy required for its pulverization. The present study is aimed at investigating the effect of inherent moisture and the blending behavior on HGIs of indigenous coals. Experiments were carried out using the standard Hardgrove Grindibility Machine to determine HGIs of three indigenous coals belonging to the Lakhra, Degari, and Chamalang coal deposits. In addition, the blending effect of six binary and six ternary blends of parent coals with different blending ratios were also tested for their HGIs. The Lakhra coal has shown the highest HGI value of 66 against 23% of inherent moisture, whereas the Degari and Chamalang coals respectively indicated HGI values of 53 and 32 against 10% and 6.95% of inherent moisture content. It was found that as the inherent moisture in coal increased the HGI values also increased. Lakhra coal, having the highest HGI value, was found to be easy to grind as compared to the Degari and Chamalang coals that have lower HGI values. The HGI values of the binary and ternary blends of parent coals, in various proportions, were found to be the proportionally average values of the parent coals.

Agglomeration of Makarwal coal using soybean oil as agglomerant

ABSTRACT The study was carried out for beneficiation of Makarwal coal using soybean oil as agglomerant. The effect of six parameters – pH, mesh size of coal particles, slurry ratio, stirring speed, soybean oil concentration, and time of agglomeration – was investigated to reduce ash and sulfur from Makarwal coal and to enhance the gross calorific value. In the cleaned product obtained after the agglomeration process, the gross calorific value was increased from 4900 to 7115 Kcal/kg. The ash of agglomerates was reduced from 30% to 7.5% and sulfur was reduced from 5.4% to 2.0% The optimum operating conditions were concentration of soybean oil 10 mL, pH 9, stirring speed 2800 rpm, mesh size 200, coal to water ratio of 15:450 (W/V), and time of agglomeration 20 min. Significant reduction in ash and sulfur showed the effectiveness for agglomeration of Makarwal coal using soybean oil as the agglomerant. The final product thus obtained may be used efficiently in various energy recovery schemes.

Cleaning of Pakistani low-grade coal by agglomeration

ABSTRACT This study was carried out for the beneficiation of Dukki (Pakistani) coal using agglomeration technique. The effect of six parameters, particle size, solid to liquid ratio, xylene concentration, agitation speed, agitation time, and pH, was investigated to improve the quality of coal in terms of reduced ash and sulfur content. The clean coal obtained at optimum parameters was found to have 69.25 and 26.6% reduction in ash and sulfur, respectively. The gross calorific value (GCV) increased to 6,377 kcal/kg compared with 5,300 kcal/kg in the original sample. A maximum reduction in ash and sulfur contents was achieved by the following input parameters: particle size, 100 mesh (150 µm); solid to liquid ratio, 20:80 (w/v); xylene dose, 6.8 mL; agitation time, 10 min; pH 7; and stirring speed, 2,520 rpm. Significant reduction in ash (%) and sulfur (%) showed the effectiveness for agglomeration of Dukki coal using xylene as agglomerant. The final product thus obtained may be used efficiently in various energy recovery schemes.

Agglomeration of Pakistani coal (Lakhra) using diesel oil

ABSTRACT The upgradation of a low quality coal enables it suitable for wider applications. The Lakhra coal (Pakistan) belongs to the lignite coal category. This study investigates the agglomeration technique for beneficiation of Lakhra coal using diesel oil as an agglomerant. Three parameters were investigated such as the solid–liquid ratio, residence time, and shear velocity. Characterization of the Lakhra coal before and after agglomeration was carried out in order to determine its volatile matter, fixed carbon, ash and sulfur contents, and gross calorific value. According to the results, agglomerates contained fixed carbon 35.63%, volatile matter 42.21%, gross calorific value (GCV) 5570.6 kcal/kg, ash 17.07%, and sulfur 4.03%. The ash and sulfur reductions were 42.3% and 58.4%, respectively, suggesting significant reduction in ash and sulfur compared to the original coal. The clean coal, resulting from this cleaning process, is a good grade product which may be valued as a good fuel source for any coal fired utility.

Cleaning of Dukki (Baluchistan) coal by oil agglomeration process

Cleaning of coal fines by oil agglomeration is an efficient technique by which an appreciable recovery of combustible matter and significant reduction in ash forming minerals are possible. In this study, oil agglomeration process has been employed to clean indigenous coal under the influence of parameters such as oil type, particle size and the pH value of aqueous medium. As agglomerant, castor oil, canola oil proved to be successful, giving 75% and 64% yields of agglomerates, respectively. The gross calorific value increased from 4,903 Kcal/Kg to 6,257 Kcal/Kg while using canola oil whereas the reduction in ash content was found to be 66%. Consequently the agglomeration process was found to be quite effective for Dukki coal in enhancing its gross calorific value and reducing its ash content. (Received: November 11, 2013; Accepted: April 3, 2014)

Identification of Macerals in Lakhra and Chamalang Coals in Pakistan

Microscopic examination of thin sections of coal under reflected lights was undertaken in this study to identify the macerals in Lakhra and Chamalang coals. The golden yellow luster in Lakhra coal reflected the presence of sporinite maceral. The presence of sporinite is useful for gasification and liquefaction processes. The telinite maceral was dominant in Chamalang coal, which is a leading subgroup of vitrinite. Chamalang coal is being blended with imported coal at Pak Steel, Karachi to produce good quality coke for furnace operations.

Co-pyrolysis and hyrdogenation of waste tires and thar coal blends

ABSTRACT This study was carried out to investigate the direct co-pyrolysis of blends comprising lignite coal and waste tires. The effects of various parameters that include coal to waste tires ratio, temperature, pressure, hydrogen donor concentration, and retention time were investigated. From the results, an optimum oil yield obtained with 50:50 coals to waste tires ratio was found to be 36% with maximum gross calorific values of 5501 Kcal/kg. Fourier transform infrared resonance spectra (FTIR) suggested the presence of aromatic and aliphatic linkages along with hydroxyl group and carbonyl functional groups. According to nuclear magnetic resonance analysis (NMR), the aromatic and aliphatic fractions were found to be 65% and 35%, respectively, with 50:50, coal to waste tires blend. The presence of carbon fractions from C16 to C36 was found in liquid oil through gas chromatograph mass spectroscopic analysis (GC-MS). The results of study could be applied to the commercial production of pyrolysis oil through pyrolysis of waste tires and coal largely available in Pakistan.

Oxidative desulfurization of Chakwal coal using potassium permanganate, ferric sulfate, and sodium hypochlorite

ABSTRACT This study investigates the desulfurization of Chakwal coal (Punjab, Pakistan) using three oxidants, namely KMnO4, Fe2(SO4)3, and NaOCl. Operational parameters were concentration, particle size, and pH. According to the results, KMnO4 removed 95% sulfur from coal. Similarly, Fe2(SO4)3 removed 71% and NaOCl removed 50% sulfur. NaOCl was found to be less efficient compared to other two oxidants. Fe2(SO4)3 and KMnO4 both removed sulfur significantly. Fe2(SO4)3 could be considered for cleaning of low grade coals since it is cheaper and very effective in removing sulfur from coal. The cleaned Chakwal coal can be used in different energy recovery schemes.

Production of ethanol and bio-chars from Pakistani ligno-cellulosic biomasses

ABSTRACT The objective of this study was the production of ethanol from two locally available lingo-cellulosic biomasses: rice hulls and wheat straw. Both biomasses were ground to a particle size of 2 mm and pretreated with 2.5% solution of NaOH and the dried masses were individually subjected to enzymatic hydrolysis using cellulase enzyme in buffer solutions. Fermentation of the hydrolyzed products was carried out by using saccharomyces cervices under anaerobic conditions at 35°C for three days of incubation period. The rice hulls and wheat straw produced 15.22 mg/ml and 25.02 mg/ml ethanol, respectively, (on the last day) with appreciable yields. The two bio fermentation residues were used for the production of bio using fixed-bed pyrolysis. At the optimum temperature of chars 600°C, the bio-char products from rice hulls contained 56.15% fixed carbon and 40.88% volatile matter (VM) with a gross calorific value of 7513 Kcal/Kg, whereas bio-chars from wheat straws contained 53.69% fixed carbon, 45.19% VM, and a gross calorific value of 7123 Kcal/Kg. Both bio-chars appear to be good value added products for fuel applications, activated carbon production, and carbon dioxide sequestration.