D.K. Sharma

Studies on stepwise coal conversion

ABSTRACT A two step process of organorefining (successive solvolytic extractions) using anthracene oi1-ethylenediamine-liquid paraffin followed by steam carbonization of coal afforded clean fuels from coal with higher heating values. Effect of heating rate and final temperature of pyrolysis on the pyrolysis of residual coal obtained after organorefining was studied. More than 60% coal was recovered as clean fuels by this process. Pretreatments such as reduction, depolymerization and reductive-depolymerization enhance the devoiati1ization yield through steam pyrolysis. The use of steam in pyrolysis inhibited condensation reactions and promoted the cracking of phenolic and condensed polycyclic aromatic ring structures. Dynamics of the two stage process has been studied. The observation that coal consists of 5 different types of molecules has been supported by the evidence. Behaviour of different types of coal molecules in the stepwise coal conversion is explained. Successive extraction by selected solvents ...

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.

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

ABSTRACT 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 anthr...

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 ...

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 fin...

SOLVOLYTIC EXTRACTION OF ASSAM COAL IN DIFFERENT ALKENES UNDER AMBIENT PRESSURE CONDITIONS

ABSTRACT Assam coal has been extracted with octene-1, decene-1. dodecene-1, tetradecene-1 and cetene-1 respectively-at. their boiling points. More than 50% coal was extracted using cetene-1 as a solvent and the residual coal obtained was rendered further extractable in quinoline up to 39% extent. Thus, more than 707% coal was rendered extractable in cetene-1 followed by quinoline extraction. This was more than that observed through the successive extractions in anthracene as followed by quinoline extraction (60%). These studies showed alkenes to be very promising for the extraction of coal for industrial operations, as these are coal and petroleum derived solvents.

EXTRACTION ENHANCEMENT OF COAL THROUGH CHEMICAL REACTIONS WITH CETENE AND CETANOL IN THE ANTHRACENE OIL UNDER ATMOSPHERIC PRESSURE CONDITIONS

ABSTRACT Assam coal has been reacted with cetene or cetanol in anthracene oil. These reactions were attempted to alkylate the coal in the absence of a catalyst under the conditions of extractive disintegration of coal. Coal derived chemicals were used in the reactions as far as possible. The reactions resulted in enhancing the extractability of coal in quinoline by more than 70–90%. These reactions resulted in the alkylation of coal and increase of carbon contents in coal along with the addition of nitrogenous bases from anthracene oil to coal.

Extraction enhancement of coal through depolymerization reaction by prior alkaline treatment

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 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.

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 obt...