DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTJS SMITH, DIRECTOR 382 THE EFFECT OF OXYGEN IN COAL BY DAVID WHITE WASHINGTON GOVERNMENT FEINTING OFFICE 1909 CONTENTS. Page. Introduction.............................................................. 5 Deoxygenation in the formation of coal..................................... 6 Initial controlling factors............................................... 6 Stages of formation.................................................... 6 Deoxygenation.......................................................... 7 Oxygen rind ash as impurities.............................................. 8 Evic ence of their nearly equal value................................... 8 Calorimeter tests................................................... 8 Ultimate analyses................................................. 9 Arrangement of analyses............................................ 19 Fuels high in oxygen or ash........................................ 19 .Fuels of lower' ash and oxygen..................................... 20 Belation to calorific value.........................'................ 21 Cur\ e platted from C : (0+ash) ratios and efficiencies.................... 22 Determination of curve............................................. 22 Detailed study of a curve segment................................... 22 Variations from the curve.......................................... 23 Comparison with calculated thermal units........................... 24 Forecast of fuel efficiency from ratios............................... 24 Relations in moisture-free coals........................................ 25 Recalculation of analyses........................................... 25 Compensated calorific values....................................... 34 Value of moisture-free data.....................:.................... 35 Relative negative value of ash and oxygen............................... 36 Relative effect of the oxygen of moisture................................ 37 Estimate of the empirical anticalorific value of oxygen................... 39 Negative value of oxygen and ash.................................... 39 Application of the curve........................................... 39 Fluctuation in effects of changes.............'....................... 40 Estimate applied to the analyses................................... 40 Causes of variance from the curve...................................... 41 General statement.................................................. 41 Causes not shown by ultimate analyses.............................. 41 ' Causes recognizable in analyses...................................... 42 Varying available hydrogen.................................... 43 Sulphur....................................................... 44 Nitrogen............'.......................................... 46 Anthracitization............................................... 46 Weathering................................................... 48 Quantitative relation of oxygen to coking.................................... 48 Supposed algal ingredients in coals..............................:....... 48 i'5ource and chemical effects........................................ 48 Characteristics of algal coals......................................... 50 Possible connection with coking quality............................ 50 3 4 CONTENTS. Quantitative relation of oxygen to coking Continued. Page. Hydrogen-oxygen ratios of coking coals................................. 51 Description of diagram in Plate III.......................:.......... 51. Indications of ratio limits........................................... 52 Application to algal hypothesis..................................... 53 Coking of high fixed carbon coals....................................... 53 Volatile-carbon ratios.............................................. 53 Consultation of efficiency errors..................................... 54 Hydrogen and oxygen losses in the progressive development of coal....... 54 Available hydrogen as index of coking coals.............................. 55 Hydrogen-oxygen ratio the best index............................;...... 56 Status of algal hypothesis.............................................. 56 Mixture of coals for coking.............................................. 57 General observations on the tabulated coals.................................. 58 Range of the samples................................................... 58 Rank of peats and lignites............................................. 58 Explanation of high oxygen............................................. 59 Quantitative relation of volatile carbon and hydrogen..................... 59 Loss of volatile matter.................................................. 60 Relation of stage of coal formation to classification ........................... 60 Like analyses for coals of different origin.................'................ 60 Distinct categories impossible.......................................... 61 Comparison of types.................................................... 61 Obliteration of distinctions as a result of regional metamorphism.......... 62 Oxygenation and weathering of coals........................................ 63 Changes in low-grade coals.............................................. 63 Efficiency losses in weathering.......................................... 63 Losses shown by analyses and ratio-efficiency curve...................... 64 Losses shown by H : 0 and VC : C ratios................................. 65 Underground weathering................................................ 67 Losses by weathering in shipment...................................... 69 Summary.................................................................. 70 Partial bibliography....................................................... 73 Index.................................................................... 75 ILLUSTRATIONS. Fage. PLATE I. Ratio-efficiency curve of coals tabulated..........................'. 22 II. Segment of ratio-efficiency curve................................... 22 III. Diagram showing hydrogen-oxygen ratios of coals................... 52 THE EFFECT OF OXYGEN IN COAL. By DAVID WHITE. INTRODUCTION. This paper is the result of a comparative study of ultimate coal analyses made and published by the United States Geological Survey. This study, at first casually undertaken to devise an acceptable classification of coals based on chemical analyses, was continued in connection with a microscopic examination of a number of the coals. The initial comparisons, made from a relatively small number of analyses, not only confirmed a previous conviction that the elimina­ tion of oxygen incident to the development of a coal is economically far more important than has been generally suspected, but also showed that oxygen is very nearly as harmful as ash in coal. The immediate purposes of the present study were: (a) To deter­ mine more definitely, from a comparative examination of a large number of ultimate analyses, the relative importance of oxygen as an impurity in various coals; (&) to illustrate the transition between various grades of coal of similar origin transition mainly due to progressive devolatilization, brought about more or less directly by dynamic influences; (c) to ascertain the relative proportions of oxygen, hydrogen, and carbon in coking coals, especially with refer­ ence to a theory tentatively framed to explain the coking quality; and (d) to forecast the probabilities of successfully treating a large number of coals so as to render them amenable, in a softened condition, to satisfactory study under the microscope. Although the hypothesis as to coking quality finds but partial support in the chemical analyses, its consideration has led to a method of predicting from an analysis with a fair degree of certainty whether any given coal will coke by the ordinary process. The unbroken transition between coals originally similar but now classed in widely different groups, whether of the same age or of different ages, as a result of dynamochemical action, appears demonstrated by the analyses as well as by field observation. This subject will not be 5 6 THE EFFECT OF OXYGEN IN COAL. specially discussed in this paper, though the tables offer forcible, if not convincing, evidence concerning it. The great number of ultimate analyses published by the Survey, covering samples of coals of so many sorts collected throughout the wide range of American coal fields, furnishes an unrivaled wealth of analytical data concerning the fuels of the country; and the fact that all are made under one highly expert direction, and are standard­ ized, renders them especially valuable for comparative study. The discussion of chemical changes that have occurred in the coals and of the nature of the compounds now existing in them is left to the professional chemist, who is familiar with the great mass of litera­ ture concerning the chemistry of coals. Acknowledgments are gratefully tendered to Messrs. M. R. Camp­ bell and J. S. Burrows for placing at my disposal many of their recalculations of the analyses from the "as received'' to the "air- dried" basis and thus greatly lightening the labors of computation; also to Mr. Burrows for annotations as to the coking qualities of the coals. Thanks are also due to Mr. Wirt Tassin, of the National Museum, for frequent and generous gifts of information and counsel. DEOXYGENATION IN THE FORMATION OF COAL. INITIAL