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

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.     

CLEAN FUELS FROM LOW GRADE COALS FOR THERMAL POWER STATIONS THROUGH BATCH AND SEMICONTINUOUS SOLVENT REFINING TECHNIQUE USING COAL DERIVED SOLVENTS UNDER AMBIENT PRESSURE CONDITIONS AND COMBUSTION (FIRING) CHARACTERISTICS OF SOLVENT REFINED COAL AND OF RESIDUAL COAL

ABSTRACT

Availability of good quality coals is declining. Firing of low grade coals with frequent variation of quality in thermal power stations is problematic and involves environmental pollution hazards. Low grade coals can be refined through solvent extraction. Solvent refined coal obtained through solvent extraction is a clean and high calorific value coal with a uniform quality. This has good flammability characteristics because of its high volatile matter contents and low ash contents. Batch extraction of low grade coal earn Dies obtained from two different thermal cower stations in new Delhi, in anthracene oil (a coal derived solvent) has been reported. Semi-continuous extraction of these coals by successive extraction techniques using anthracene oil (AO) followed by liquid paraffin (LP) solvents haB also been carried out and reported. Kinetic studies of the extraction of coal in AO has been performed. About 35% coal was rendered extractable through semicoatinuous extraction. The residual coals obtained after solvent refining were found to be free flawing and contained sufficient volatile matter for making these suitable for firing in fluidized bed combuators for integrated combined cycle power generation.     

SOLVENT DEASHING OF COAL TO GET AN ENVIRONMENTALLY CLEAN AND HIGH CALORIFTC VALUE FUEL BY BATCH EXTRACTIVE REFINING TECHNIQUE UNDER ABIDENT CONDITIONS

Extraction of Samla, Assam and Godavari coal (bituminous coals) and Neyveli lignite in anthracene oil has been studied. About 4 to 36% coal was rendered extractable; the residual coals showed further extractability in quinoline indicating some depolymerization of coal caused by the anthracene oil extraction. The mechanism of the extraction of coal by anthracene oil has been studied by using phenanthrene and carbazole separately as solvents for extraction. Phenanthrene was found to be a better solvent for extraction and depolymerization. Cetene was also found to be a good solvent for extraction of coal. The residual coals obtained after cetene extraction showed enhanced extraction in quinoline, indicating that coal becomes labile and is depolymerized. The extraction of coal in anthracene oil is due to co-solvency effect of phenanthrene and carbazole and other aromatic and heteroatomic solvents in anthracene oil. Cetene extraction appeared to be controlled by mass transfer effects. Cetene and anthracene oil were found to be good solvents for solvent deashing of coal and offer a means of producing environmentally clean and high calorific value fuels.     

STUDIES ON SUCCESSIVE EXTRACTION OF COAL IN COAL DERIVED SOLVENTS UNDER AMBIENT CONDITIONS TO RECOVER VOLATILE MATTER (VOLATILIZABLE COMPONENTS) FROM COAL AND TO GET PARTIALLY DEVOLATILIZED RESIDUAL COAL AND SOLVENT REFINED COAL AS CLEAN AND DETOXIFIED FUELS

ABSTRACt

Effect of anthrecene oil, quinoline and liquid paraffin extraction on the swelling of Assam coal has been studied to find out the degree of cross-linking in the pretreated coals, and to assess the molecular effect of the these solvents in the solid mass of coal, on the flexibility of coal macromolecular aggregation and molecular dynamism. Effect of successive extractions using anthracene oil-quinoline-liquid paraffin sequence, on the extraction of volatilizable components i.e. volatile matter (VM) contents and removal of toxic mineral matter contents of Assam coal has been studied. A relation of C % and VM % in coal with extraction yields through this successive extraction of different coals has been suggested. About 50 - 76% of the total VM present in the original coal can be extracted by the successive solvent extractive disintegration of coal, which was more than that through pyrolysis of coal at 600°C. Recovery of VM renders the combustion of residual coal free of pollution. The solvent refined coal is also obtained as a clean fuel. Thus, the process affords the segregation of toxic mineral matter microconstituents. Solvent extraction should be introduced as the essential coal preparation step to remove the premium organic products from coal before firing it in boilers.     

MECHANISM AND MOLECULAR DYNAMICS OF SUCCESSIVE SOLVOLYTIC EXTRACTION IN SIMPLE AND THERMOCHEMICAL DISSOCIATIVE SEQUENTIAL EXTRACTIONS UNDER AMBIENT PRESSURE CONDITIONS AND ROLE OF MOLECULAR ENTANGLEMENTS AND DISAGGREGATIONS

ABSTRACT

Assam coal was subjected to solvent extraction studies using 40 solvents belonging to different class, group and functionality. Boiling point of a solvent was found to have no relation with extractability of coal at atmospheric pressure, excepting within the same class, group and functionality of solvents. Boiling point should not be used for classifying the coal extractability, rather chemical nature of solvent should be used. Cetene (high boiling α-olefin), anthracene oil, liquid paraffin (through thermochemical dissociative extraction) and ethylenediaraine (simple extraction) were found to give good extraction yields from Assam coal. Successive extraction of coal was possible only using anthracene oil or ethylenediaraine. Chemical interaction of these solvents with coal which renders the enhanced amount of coal extractable through stepwise extractions has been discussed. Mechanism and molecular dynamics of solvent extraction of coal in AO, α-olefins etc. has been explained. This is a novel finding in coal chemistry. Stepwise extraction could cut short the total extraction time in anthracene oil. Anthracene oil and high boiling α-olefins extractions result in molecular fluidization of coal macromolecules under ambient pressure. Successive extractions of coal in low boiling solvents ( < 250°C) did not modify on the highest extraction yield of coal in the solvent used in the sequence, whereas in case of successuve chemical dissociative extractions it did.     

DIFFERENTIAL THERMAL ANALYSIS OF COAL IN NON-FLOWING AIR

ABSTRACT

The DTA studies in air are reported on some Indian coals and a lignite. Extraction of coal in quinoline or in liquid paraffin was found to result in the coal residues having higher ignition temperature than that of the original coal. However, extraction of coal in anthracene oil or successive extractive disintegration of coal in anthracene oil, in quinoline and in liquid paraffin was found to yield residual coals having higher reactivities towards oxygen in air as understood from the fact that the ignition temperature of these residues was lower than that of the original coal. DTA studies also supported the degradation of coal as a result of acidic depolymerization reaction.     

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.     

CLEAN FUELS FROM LOW GRADE COALS FOR THERMAL POWER STATIONS THROUGH BATCH AND SEMICONTINUOUS SOLVENT REFINING TECHNIQUE USING COAL DERIVED SOLVENTS UNDER AMBIENT PRESSURE CONDITIONS AND COMBUSTION (FIRING) CHARACTERISTICS OF SOLVENT REFINED COAL AND OF RESIDUAL COAL

Availability of good quality coals is declining. Firing of low grade coals with frequent variation of quality in thermal power stations is problematic and involves environmental pollution hazards. Low grade coals can be refined through solvent extraction. Solvent refined coal obtained through solvent extraction is a clean and high calorific value coal with a uniform quality. This has good flammability characteristics because of its high volatile matter contents and low ash contents. Batch extraction of low grade coal earn Dies obtained from two different thermal cower stations in new Delhi, in anthracene oil (a coal derived solvent) has been reported. Semi-continuous extraction of these coals by successive extraction techniques using anthracene oil (AO) followed by liquid paraffin (LP) solvents haB also been carried out and reported. Kinetic studies of the extraction of coal in AO has been performed. About 35% coal was rendered extractable through semicoatinuous extraction. The residual coals obtained after solvent refining were found to be free flawing and contained sufficient volatile matter for making these suitable for firing in fluidized bed combuators for integrated combined cycle power generation.     

SHORI COAL LIQUEFACTION AND ITS CO-PROCESSING WITH PETROLEUM RESIDUE

ABSTRACT

Shori coal from China shows an excellent applicability to liquefaction. The reactivity to liquefaction of Shori coal is proved to show higher temperature-dependence than those of Wandoan coal and Battle River coal. Anthracene oil has an excellent solvent effect as a vehicle oil. However, Shori petroleum residue shows a comparable effect as a vehicle oil to anthracene oil at 450°c. Hydrogen contents in the hexane-soluble fraction produced from co-processing with Shori petroleum residue are higher than the hydrogen contents in the hexane-soluble fraction produced when anthracene oil was used. Shori petroleum residue seems to be associated with the lowering of the nitrogen content and oxygen content in the hexane-soluble fraction. But the sulfur in Shori petroleum residue was transferred to the hexane-soluble fraction.     

COAL SWELLING AND CO-PROCESSING

ABSTRACT

Herrin No. 6 coal and the filter cake cleaned product from Pittsburgh No. 8 coal were co-processed with a liquid produced from the mild gasification of Wyodak coal. The co-processing studies were conducted in tubing bomb reactors and in a batch autoclave under hydrogen pressure. The reactants were thermally pretreated under helium to induce coal swelling and promote catalyst dispersion. Ferrocene and iron pentacarbonyl were used as catalyst precursors for these studies and were sulfided in situ to generate the active forms of the iron catalyst. Iron pentacarbonyl was found to form the better catalyst for conversion of these coals. Conversion of the filter cake product was found to be enhanced by pretreatment with the mild gasification liquid, because this treatment caused the coal to swell and promoted uniform dispersion of the catalyst. Higher coal conversion was observed from co-processing Herrin No. 6 coal compared to the filter cake product. This indicates the Herrin No. 6 coal would be the preferred coal to use in a commercial process. There was improvement in the quality of the oil product from co-processing Herrin No. 6 coal compared to the mild-gasification liquid.     

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.     

EFFECTS OF COAL SURFACE CHARGE ON THE ADSORPTION AND GASIFICATION ACTIVITIES OF CALCIUM AND POTASSIUM

ABSTRACT

The electrokinetic properties of lignite, subbituminous and bituminous coal particles and their demineralized derivatives have been measured as a function of pH. Compared to the raw coals, demineTalization generally increased the net negative surface charge densities on the coals. Calcium or potassium adsorption (by ion-exchange) onto the demineralized coals was strongly dependent on pH and the surface charge properties of the coals. Metals uptake was very low (0,1-0.4% wt.) in strongly acidic media (～pHl) but increased dramatically as the net negative charge on the coals was increased by increasing the pHs of the coal suspensions to pH 6 or 10. The reactivities of the calcium- ot potassium-loaded chars in carbon dioxide at 800^°C were similarly dependent upon the pHs at which the catalysts were ion-exchanged onto the coals. For the calcium-containing chars, the reactivities increased in the order: pH 6 > “pH 10 > pH 1 while the variation of the gasification rates with potassium loading pH was: pH 6 ～ pH 10 ? pH I. These findings are attributed to differences in the extent of electrostatic interaction between the calcium or potassium ions and the charged coal surface during catalyst loading from solution.     

GASIFICATION KINETICS OF RESIDUAL COAL PRODUCED FROM SOLVENT EXTRACTION WITH N - METHYLPYRROLIDONE

Abstract

A low-temperature, coal-extraction technique utilizing the solvent N-methyl-2-pyrrolidone has been shown to enhance significantly the rate of gasification of the residual, unextracted portion of the coal as compared to that of the ray coal. Five coal/residue pairs were subjected to gasification in a carbon dioxide atmosphere at temperatures of 1200-1500'K and atmospheric pressure. In all cases, the activation energy (as described by an Arrhenius-type relationship) of the residue was found to be lower than that of the raw coal. In addition, over the temperature range studied, the residues exhibited rate constants as much as four times larger than those for the raw coals. A trend vas found to exist between the extent of extraction and the ratio of the activation energies of the residue and raw coal. It is postulated that this behavior is a manifestation of a complex combination of catalytic and surface area effects. The technique of solvent extraction followed by gasification of the residue may constitute an attractive option for the production of clean fuels from coal.     

COMBUSTION CHARACTERISTICS OF EXTRACTIVELY DISINTEGRATED COAL OBTAINED AFTER RECOVERY OF SUPER CLEAN COAL BY ORGANOSOLVO- REFINING AND CHEMICALLY DEPOLYMERIZED COALS AND UNTREATED COALS BY THERMOGRAVIMETRIC ANALYSIS IN OXIDIZING ATMOSPHERE

ABSTRACT

ABSTRACT Indian coals and lignite were subjected to TGA studies in an oxidizing atmosphere (natural flow of air) as well as in a nitrogen atmosphere. The catalytic effect of mineral matter on the combustion of coals was more predominant in bituminous coals containing 36 to 42 % volatile matter (VM) than of VM and oxygen contents of the coals. In comparison to the original coal, the depolymerized coal and the residue obtained from extractive disintegration or organosolvo-rafining of coal under ambient pressure conditions showed higher rates of combustion at relatively lower temperatures. The depolymerization reaction enhanced the devolati1ization of coal in an inert atmosphere, whereas the organosolvo-refining of coal decreased the same. The reasons for the enhancement in the reactivity for combustion of chemically and solvent pretreated coals are discussed. The process of recovery of solvent refined coal through extractive disintegration or depolymerization affords a super clean fuel having high calorific value and renders the combustion of the residual coal pollution free by recircu1atory fluidized bed combustion. Several value added uses for super clean coal hava been suggested.     

DIFFERENTIAL THERMAL ANALYSIS OF COAL IN NON-FLOWING AIR

The DTA studies in air are reported on some Indian coals and a lignite. Extraction of coal in quinoline or in liquid paraffin was found to result in the coal residues having higher ignition temperature than that of the original coal. However, extraction of coal in anthracene oil or successive extractive disintegration of coal in anthracene oil, in quinoline and in liquid paraffin was found to yield residual coals having higher reactivities towards oxygen in air as understood from the fact that the ignition temperature of these residues was lower than that of the original coal. DTA studies also supported the degradation of coal as a result of acidic depolymerization reaction.     

STUDY ON CHEMICAL STABILITY OF ORGANIC SULFUR IN COAL AND ITS STRUCTURE*

ABSTRACT

In this paper, two high-sulfur coals were selected from Yazhou and Donglin mines of China. Inorganic sulfur was completely removed first, then the tested samples were experimented under various conditions: hydrolysis, oxidation, reduction, and supercritical extraction with methanol. The change in organic sulfur was investigated. It was found that approximately 40-60% organic sulfur in coal was released at the temperature of 350°C. The removed organic sulfur was thioalcohol and thioether, while the remaining part in coal was thiophenic sulfur.     

SOLID STATE 13C NMR STUDY OF THERMALLY UPGRADED LOW RANK COALS

ABSTRACT

The results of solid-state ¹³C NMR study aimed at evaluating the chemical changes and extent of upgrading achieved in the thermal treatment of two western Canadian low rank coals are discussed. The coals were thermally treated at varying temperatures (200 - 500°C) using different process media (nitrogen, steam and products of combustion)

Apparent aromaticity of the two coals was increased after the thermal treatment and increased with treatment temperature. Significant chemical changes, such as loss of the protonated aromatic carbons, quaternary carbons in alkylated rings and aliphatic ethers, were observed at 400°C and above. Condensation and polymerization of the chemical components were also evident. The effect of process medium was found to depend on the coal feed and the treatment temperature.     

STUDIES ON SUCCESSIVE EXTRACTION OF COAL IN COAL DERIVED SOLVENTS UNDER AMBIENT CONDITIONS TO RECOVER VOLATILE MATTER (VOLATILIZABLE COMPONENTS) FROM COAL AND TO GET PARTIALLY DEVOLATILIZED RESIDUAL COAL AND SOLVENT REFINED COAL AS CLEAN AND DETOXIFIED FUELS

Effect of anthrecene oil, quinoline and liquid paraffin extraction on the swelling of Assam coal has been studied to find out the degree of cross-linking in the pretreated coals, and to assess the molecular effect of the these solvents in the solid mass of coal, on the flexibility of coal macromolecular aggregation and molecular dynamism. Effect of successive extractions using anthracene oil-quinoline-liquid paraffin sequence, on the extraction of volatilizable components i.e. volatile matter (VM) contents and removal of toxic mineral matter contents of Assam coal has been studied. A relation of C % and VM % in coal with extraction yields through this successive extraction of different coals has been suggested. About 50 - 76% of the total VM present in the original coal can be extracted by the successive solvent extractive disintegration of coal, which was more than that through pyrolysis of coal at 600°C. Recovery of VM renders the combustion of residual coal free of pollution. The solvent refined coal is also obtained as a clean fuel. Thus, the process affords the segregation of toxic mineral matter microconstituents. Solvent extraction should be introduced as the essential coal preparation step to remove the premium organic products from coal before firing it in boilers.     

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

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.