SOLVENT EXTRACTION OF PAKISTANI COALS (ii): EXTRACTION AND CHARACTERIZATION OF METHANOL-BENZENE EXTRACTS

Structural characterization of the solvent extracts from four different Pakistani lignitic coals has been carried out by their proximate, elemental analysis and FT-Infrared and ¹H n.m.r. spectra. The yield of each extracts was greater with 1:1 benzene-methanol mixture in comparison to the total yield obtained by separate extractions with benzene and methanol. The extracts contained significantly less amount of ash and fixed carbon along with an increase in the percentage of volatile matter. The FTIR and ¹H n.m.r. spectra indicated that basically all the extracts contained less condensed aromatic rings in comparison to the coal. The FTIR spectra showed sharp well resolved peaks which have been assigned to various functional groups.

The ¹H n.m.r. spectra were used to obtain average structural parameters for all the extracts. A detailed analysis of the FTIR and n.m.r. spectra of the coal and their extracts provided an important in-sight into the differences between various extracts and also between various coals and their corresponding extracts.     

SOLVENT EXTRACTION OF PAKISTAN COALS (III) EXTRACTION AND CHARACTERIZATION OF THE EXTRACTS BY SPECTROSCOPIC TECHNIQUES

Abstract

The Makerwal coal of Pakistan gives higher extractibi1ity with Tetrahydrofuran ( THF ) as compared to Sharigh, Sor-Range and Lakhra coals. The structural characterization of Pakistan coal extracts by FT-IR spectroscopy indicates that all the extracts contained less condensed aromatic rings in comparision to their original coal.     

NUCLEAR MAGNETIC RESONANCE STUDIES OF ASPHALTENES AND COALS. A NEW APPROACH TO OBTAINING ASPHALTENE STRUCTURAL PARAMETERS WITH DIPOLAR DEPHASING

ABSTRACT

Apparent carbon aromaticities, fa, of some asphaltenes have been measured by n.m.r. in solution and compared with those obtained by the CP/MAS technique on solid samples. The aromaticities were also measured for several Alberta plains coals. From the 1H solution spectra and 13C solid nmr spectra of asphaltenes, some of their skeletal features, not obtainable from solution spectra only, have been suggested.     

EXTRACTION ENHANCEMENT OF COAL THROUGH EPOLYMERIZATION REACTION BY PRIOR ALKALINE TREATMENT

ABSTRACT

Assam coal was treated with sodium hydroxide in phenol. The alkali treated coal was depolymerized using p-toluenesulphonic acid in phenol. The quinoline extractability of depolymerized coal was found to have been enhanced as a result of alkali pretreatment over that of the depolymerized original coal. Different alkali-coal ratios were used in the alkali pretreatment of coal and their effect on the depolymerization reaction has been studied. Depolymerized coal extracts were found to contain increased amount of colloidal matter as a result of alkali pretreatment. Alkali pretreatment also reduced the degree of cross-linking in the structure of depolymerized coals as revealed by swelling studies. This was also confirmed by the IR spectra studies. Effect of alkaline degradation (treatment) on the reduction of catalyst (p-toluenesulphonic acid) amount in the depolymerization reaction has been studied. Alkali pretreatment followed by     

SOLVENT EXTRACTION OF COALS THROUGH ATD3 REACTION UNDER AMBIENT PRESSURE CONDITION

ABSTRACT

A novel reaction such as ATD³ reaction which has been recently found to be an attractive reaction for rendering more 50% coal extractable, has been tested on different bituminous coals and a lignite. The reaction has been found to be generally applicable on coals and lignite to render about 50% coal extractable. The reaction proceeds under industrially convenient conditions and involves the use of only coal or petroleum derived solvents. Reaction of % carbon, % volatile matter and atomic O/C ratio of coals with the extractability of coal through ATD³ reaction has been drawn.     

SOLVENT EXTRACTION OF PAKISTAN COALS (III) EXTRACTION AND CHARACTERIZATION OF THE EXTRACTS BY SPECTROSCOPIC TECHNIQUES

The Makerwal coal of Pakistan gives higher extractibi1ity with Tetrahydrofuran ( THF ) as compared to Sharigh, Sor-Range and Lakhra coals. The structural characterization of Pakistan coal extracts by FT-IR spectroscopy indicates that all the extracts contained less condensed aromatic rings in comparision to their original coal.     

SUPERCRITICAL EXTRACTION OF ORGANOSULFUR FROM COAL USING ACETONE-VATER MIXTURES

Abstract

Binary mixtures of acetone and water at their supercritical conditions have been investigated for their ability to remove organic sulfur from high sulfur Midwestern coals. The reduction of organic sulfur from Ohio 5/6 and Indiana 5 coals has been as high as 61% (based on a BTU basis) The experiments have been carried out following a statistical experimental design and the optimal process conditions and discerning characteristics of the process have been identified. The solvent composition and the extraction conditions can be tailored in such a way as to selectively remove sulfur and further increase the calorific value of the treated coal.     

GAS CHROMATOGRAPHIC AND IR SPECTRAL STUDIES OF THE PRODUCTS OBTAINED FROM EXTRACTIVE DISINTEGRATION OF COAL

ABSTRACT

Assam coal was extracted in anthracene oil, in quinoline and in liquid paraffin. The gases evolved during the extraction/reaction of Assam coal in anthracene oil and in liquid paraffin, were analyzed using a gas chromatograph. The IR spectra of residual coals were compared with the IR spectrum of original Assam coal. An increase in absorption at 710 cm^?1, decrease in 2940-2860 cm^?1 and increase in nitrogen contents of residual coal was observed in the residual coal obtained from the extractive disintegration.     

PERCHL0R0ETHYLENE EXTRACTION DESULFURIZATION OF WEATHERED COALS

Abstract

The perchloroethylene extraction process has proven to be an effective pre- combustion coal desulfurization process which offers a complete process package including wet grinding, organic sulfur removal, pyrite and mineral matter separation, solvent recovery, and byproducts and sulfur recovery. In this paper, coal weatherability was investigated for various Midwestern and Eastern U.S. coals, and its effect on organosulfur extractability by the perchloroethylene process was identified. Both “natural” and “artificial” weathering of these coals were experimentally investigated. A statistically significant difference in the extraction efficiency between fresh and weathered coals vas observed. A strong relation between the extractability and degree of weathering of the coal was established. The results provide a valuable insight into the process engineering of this process.     

STATISTICAL ANALYSIS OF ORGANOSULFUR EXTRACTION DATA OF OHIO 5/6 COAL USING THE PERCHLOROETHYLENE COAL CLEANING PROCESS

ABSTRACT

The perchloroethylene coal cleaning process removes both organic and pyritic forms of sulfur using perchloroethylene as the solvent medium. The effect of process variables including temperature, extraction time, solvent to coal ratio and particle size of coal has been studied by a systematic 2⁴ full factorial experimental design with a single replicate. The process was found to be strongly dependent on the type of coal. Hence, this variable was controlled by choosing one single type of coal, i.e., Ohio 5/6 (1:1 mixture of Ohio 5 and Ohio 6 coals) throughout this entire investigation. The significant effects and interactions have been quantified by F-tests. The estimates of significant effects have been obtained by Yates algorithm. Residual probability and normal probability plots have been obtained to test model adequacy. Finally, a computational model has been developed to predict the organosulfur extraction efficiency of this coal at various values of process variables. The parity plots conclude that the model has a good interpolational predictive capability.     

PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF LOW SULFATE COALS

ABSTRACT

The perchloroethylene coal refining process utilizes perchloroethylene (PCE) as its solvent in all phases of the precombustion desulfurization process, including wet grinding, organic sulfur removal, gravitational separation of pyrites and mineral matter, and recovery of elemental sulfur (S₈). The Process is capable of producing compliance coal which emits less than 1.2?lb SO_X/MBTU when burnt, starting from 5 mass percent sulfur Midwestern and Eastern U.S. coals. However, the process efficiency was found to be very strongly dependent upon the degree of weathering or the level of coal oxidation. In this paper, perchloroethylene extraction data of fresh, low-sulfate coals are summarized and critically assessed. The extraction efficiency of the organic sulfur removal ranged from 5 to 30 percent for fresh coals, while that for weathered coals ranged from 30 to 60 percent. This study provides a valuable insight into the chemical reaction mechanism of perchloroethylene desulfurization process.     

EFFECT OF SOLVOLYTIC EXTRACTION AND PYROLYSIS PRETREATMENTS ON THE TOEMPRATURE STEAM GASIFICATION REACTTVITY OF COAL AND REDUCTION OF TAR FORMATION IN PRODUCT GASES

ABSTRACT

Pre-extraction of Talcher coal ( a bituminous coal) in anthracene oil was found to be a beneficial treatment for enhancing the reactivity for steam gasification of coal. Similarly, anthracene oil followed by liquid paraffin extraction of coal was also found to be a-better pretreatment for the steam gasification of coal. Anthracene oil extraction at 270°Cand steaming of coal at 650°C had almost equal effect on steam gasification of coal. Pyrolysis in steam of pre-extracted coals was found to further enhance the reactivity of coal for steam gasification. The studies were further confirmed by carrying out thermogravimetric analysis of pretreated coals in steam atmosphere. Degree of cross-linking in pretreated coals was studied by measurement of swelling of coal in quinoline. The formation of tar in gaseous product was reduced as a result of pre-extraction and steam pyrolysis of coal prior to their gasification in steam.     

COBENEFICIATION OF COALS IN PERCHLOROCTHYLENE EXTRACTION DESULFURIZATION

ABSTRACT

The perchloroethylene (PCE) coal refining process has been investigated for its process feasibility, operational reproducibility, organic sulfur selectivity, process efficiency, minimization of residual chlorine by steam stripping and process optimization. It was found that some coals result in a better organosulfur extraction than others. It was also confirmed that the PCE extraction process was a hybrid system of chemical reaction and physical solvation. It was further established that the coals giving a higher organosulfur extraction contain some naturally available ingredients, which promote the extraction process. Coals giving a much lower organosulfur extraction lack these species. This paper focuses on demonstration of the process feasibility of cobeneficiating both types of coals, together. In this novel process, both types of coal are blended together in fixed proportions and subjected to the PCE process. This process of cobeneficiating coals is industrially significant because of its cost effectiveness. It not only removes the organosulfur from one type of coal, but also significantly improves the organosulfur extraction from the other.     

EXTRACTION KINETICS OF COALS AT SUBCRITICAL AND SUPERCRITICAL CONDITIONS

ABSTRACT

The extraction kinetics of two lignites and one bituminous coal with benzene, toluene and pyridine were studied at both sub and supercritical conditions in a batch reactor equipped with a coal basket. The time-extract yield data of lignites at supercritical conditions could'nt be treated due to severe thermal decomposition and heating-up effects. The data for Zonguidak coal and those for subcritical extraction of Cizre lignite could be fitted into a first order rate equation with the rate constants changing 0·02-0·05 min^?1 range.     

REACTOR MODELING AND SIMULATION OF PERCHLOROETHYLENE EXTRACTION DESULFURIZATION OF COAL

ABSTRACT

Desulfurization of coal by perchloroethylene extraction is based on a complex and hybrid system of chemical reaction and solvent extraction. Batcb kinetic studies have shown that the reaction follows a pseudo-first order rate kinetics. The batch kinetic data have been used to estimate first order rate parameters. In this paper, these parameters have been used to develop models for batch, plug-flow (PFR), single and continuous stirred tank reactor (CSTR). Simulation studies have been conducted to obtain exit concentrations of these reactors. A new parameter, called "Performance Index", has been developed in order to compare the performances of various reactors. In order to arrive at relevant conclusions, simulation studies have been conducted on three different types of coals. It was found from the simulation results that the batch reactor performance coincided with the experimental data, indicating a good predictive capability of the model. It was also found that coals of different types differed in their kinetic behavior, and thus, the reactor design to achieve optimal conversion is a strong function of the type of coal. Finally, given the kinetic data for a specific type of coal, the "Residence Time Curves" for CSTR determine the most optimal reactor design. This investigation is very significant from the point of reactor design and perchloroethylene coal cleaning process development.     

SOME REMARKS ON SURFACE FREE ENERGY OF POLISH COALS

ABSTRACT

On the basis of the studies concerning the determination of the surface free energy of Polish coals published earlier analyses of the equilibrium state of three-phase system were carried out. The three-phase systems were:

1) coal - liquid drop - air, 2) coal - water drop -air, 3) coal - water drop - hydrocarbon, 4) coal -hydrocarbon drop - water and 5) coal - air bubble -water.

Analysing the measured values of the contact angles in the systems studied the occurrence of a liquid film on the coal surface was taken into account. The surface free energy. of Polish coals results from both dispersion (T_s ^d) and nondispersion (T_s ⁿ) intermolecular interaction. A distinct relationship was found between the dispersion components of the surface free energy and coal ranks.     

STRUCTURAL STUDIES OF PINSHUO COAL EXTRACTS USING 1H- AND 13C-NMR SPECTROSCOPY

ABSTRACT

The pyridine extracts of Pingshuo coal were fractionated by silica gel chromatography. Several fractions have been characterized in terms of their average molecular structures using a combination of ¹H- and ¹³C-NMR spectroscopy. The ¹H- and ¹³C-NMR spectra of the fractions revealed distributions of hydrogen as well as carbon in the fractions. From the NMR data, average molecular weight and elemental analysis of the fractions, the average molecular structure parameters were calculated, and their structure models were represented based on these average parameters. Some significant structural differences were found which have provided reliable information in detail for Pingshuo coal bulk structure.     

MINERALOGICAL COMPOSITION OF NIGERIAN COALS

ABSTRACT

The results of a study aimed at evaluating the mineral constituents of four Nigerian coals (a Iignite, a subbituminous and two high volatile bituminous coals) are reported in this paper. The low temperature ash (LTA) obtained from the coals was analyzed using scanning electron microscopy (SEM) and x-ray diffraction (XRD).

X-ray fluorescence spectra obtained from SEM showed the presence of silica, alumina, iron- and titanium-containing minerals in smaller amounts, and exchangeable cations (Ca, K, Na) in the four coals. The concentration of exchangeable cations and alumina was found to increase with increase in coal rank. X-ray diffraction results indicated the presence of quartz, kaolinite and pyrite in all four coals; calcite and marcasite only in the lignite; and anorthite only in the bituminous coal; albite and gypsum in all except lignite; and montmorillonite in the low rank coals only.     

STRUCTURAL CHARACTERIZATION OF PANERO CRUDE OIL BY FT-INFRARED AND 1H N.M.R. SPECTROSCOPY

ABSTRACT

The Panero crude oil from the Badin block of Sind Province in Pakistan was separated into four fractions, i.e., naphtha, kerosine, diesel oil and the residue. Each fraction has been characterized by FT-Infrared and 1H n.m.r. spectroscopy. The infrared spectroscopy has provided important insight into the functional groups present in each fraction, while the ¹H n.m.r. data was used to obtain average structural parameters.     

CATALYTIC HYDROPYROLYSIS OF WESTERN CANADIAN COAL COMBINED WITH CRITICAL GAS EXTRACTION

ABSTRACT

Experimental results of catalytic hydropyrolysis combined with solvent extraction near critical conditions of an Alberta subbituminus coal indicated a conversion of 40 wt% of coal to hydrocarbon products. The effects of catalyst and solvent on the structural parameters of the extracts were evaluated from the modified Brown-Ladner's equation. Both alcoholic and aromatic solvents and Lewis acids (ZnCl₂ and SnCl₂ 2HO₂) showed Increased yields of hydrocarbon products, but the presence of hydrogen was necessary to improve this yield.