February, 1925
INDVSTRIAL AND ENGINEERINQ CIIEMISTRY
Figure 5 , giving the weight of carbon dioxide evolved at the four temperatures studied, shows the behavior of the coal for these temperatures and obviously the values could he interpolated for all intervening temperatures. Charts showing the behavior of air instead of oxygen, on the same coal a t the same temperatures, have been plotted with similar results, excepting that the time is increased to approximately twice that for corresponding values with oxygen. Interpretation of Results The coals studied show an increase in weight throughout the period, seemingly approaching a saturation point at ahout 8 per cent of the original weight. The coals studied were all from Illinoiu. Moisture equivalent to from 4 to 8 per cent of the weight of the sample is evolved, varying in amount with the temperat.ure. The carbon dioxide evolved is equivalent to from 2 to Bper cent of the sample. Carbon monoxide, where determined, is present but in very small percentages, not exceeding 1 per cent a t 110” C . The preliminary stage of heating in nitrogen shows a small generation of both water and carbon dioxide, with a slight accession of weight by the coal, probably due to a small absorption of nitrogen. In the case of the water and carbon dioxide these would naturally result from the breaking down of the oxygen compounds of the coal. Bynotingthedischargeof oneconstituent, ascarbon dioxide, for the different temperatures employed, it is evident that the amount increases directly with the increase of temperature (Figure 5). Attention is specifically called to the fact that at ordinary atmospheric temperatures this value is very low hut consistent. The values for the other temperatures increase in an accelerated ratio with the increase in temperature. The loss of heat values is of especial interest. After 50 days a t 100’ C. the loss is of the order of 1200in 14,700B.t. u., or approximately 8 per cent, while a t 150’ C. the drop is 3700 units, or 25 per cent, while for a continuous normal temperature the drop is insignificant, being substantially only that which would he indicated by an increase in weight due to the ahsorption of oxygen. The meaning of these facts from the standpoint of coal storage may he more concisely shown by a hypothetical graph based on these results and shown as Figure 6. Finally, there seems to he ground for the conclusion that oxygen is taken into the coal texture primarily in an adsorbed or surface condensation form. In this stage its presence is indicated by an increase in weight of the mass, and the loss in heat units corresponds to this weight increment; hence the heat loss is apparent and not real. But a t slightly elevated temperatures the adsorbed oxygen goes over into actual cbemical combination, with the evolution of water and carbon dioxide. Here there is an actual loss of heat, practically equip-alcnt in amount to the heat of combustion represented by the weight of carbon and hydrogen in the water and carbon dioxide evolved. These conclusions, if correct, will aid materially in explaining some of the wide discrepancies encountered, both in fuel literature and in practical experience, as to the lossor absence of loss in the heating value of stored coal. New Scientific Journal-The Rockeieller Foundation of New York has appropriated S50,OOO to finance a new scientific periodical, to be known as Inkrnalional Biological ifbslracls. It will give in condensed form a monthly summary of all nublicacover scientific territory- which at present ‘is neglected
117
Oxidation of Sulfur as a Factor in Coal Storage’ By S . W. Parr and E. R. Hilgard UNIYHBSmTY 011
IrLxnors, uaa*x*. ILL
ROM the investigations on coal oxidation of which this study is a part, the question is continually being raised-what are the conditions which furnish the initial incremenk of heat, assuming now the absence of extraneous sources, such as hot walls, steam pipes, sun’s rays, etc.? Obviously,under certain circumstances heat is generated within the coal mass independently of any external influence. The earlier references in the literature stress the presence of sulfur, whereas later investigations discredit that idea. Abundant proof is at hand showing that oxygen is
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Marcasite Crystals
Concretion from Coal Showing Surlace Cryat&
of Marcasite
absorbed by coal and euters into heat-producing reactions at comparatively low temperatures, but this does not furnish evidence as to the source of the initial heat for starting the process. As studies proceed connected with the sulfur in coal, its distribution and forms, both with reference to crystallization and size of aggregates, it is evident that its possible role in the oxidation processes must he given further consideration. I
Reccived August 8,1924.
118
Vol. 17, No. 2
INDUSTRIAL A N D ENGI MEERING CHEMISTRY
I n this connection the ostimate of Parr and Kressmad as t o the m o u n t of heat evoked in the oxidation of pyriticsulfuris of interest, in view of the bearing small increments of heat may have as a booster for further oxidation activities, both of the hydrocarbons and of the sulfur constituents. According to those calculations, 0.1 per cent of sulfur in the pyritic form upon oxidation will raise the mass through a temperature of 14.5" C.; hence the oxidation of so small an amount as 0.5 @am of sulfur would result in a heat rise of 71.5" C.-a really dangerous boost. The purpose of this paper is merely to point out that sulfur may he the initial source of heat after all, and that we need to suspend judgment in the matter until further evidence is in hand. The workof Yancey3shows the distribution of pyritic sulfur in microscopic form to be quite as common as in the massive fonn. Some work along this line in the writers' laboratory shorvs that mother of coal frequently hss a very high sulfur content. If it is also in the finely divided form, it is in an especially advantageous condition for starting oxidation. But
Carbon Dioxide as an Index of the Critical Oxidation Temperature for Coal in Storage' By S. W. Parr and C. C. Coons UNIYBRSlrY 01 ILLINOII. U R B I N A .
ILL
ROM the accompanying studies it is evident that coal is continuously reactive with oxygen to a greater or less degree, depending upon various factors, hut chiefly upon temperature. The two products most in evidence are, first, water and then carbon dioxide. An a p paratus that would give the initial appearance of these products of oxidation would be of both practical and scientific interest. The difficulties attending the indication for the appearance of water are far greater than those for carbon dioxide; hence it is the latter that will be considered a t this time. Apparatus and Procedure The apparatus devised for this purpose uses a solution of barium hydroxide as the indicating medium, while temperature control is obtained by an electric resistance coil so placed that the rise in temperature can he maintained evenly and a t any desired point. The mechanism for indicating the appearance of carbon dioxide is shown in Figure 1. Figure 2 is a photograph of the apparatus. In this apparatus, which embodies a number of features suggested by the investigations of FrancisZand also of Whceler,a there is a resistance furnace with a rheostat controlling the rise in temperature to about Lena of Pyrite from C u d Showing Sulfate Oxidation. VermUlon 10" C. per minute. Immediately below the furnace is the C w n f y Coal carbon dioxide detection assembly, as shown in Figure 1. The of especial interest is the fact that a study of the forms of other accessories are crystallization in the Illmois coal measures shows marcasite to for washing the gases he almost always present, if indeed it does not predominate used in the tests. Oxyover the usually assigned pyritic form of crystallization. gen thus purilied is led Even so, it is not clear from experiments in this laboratory into the upper part of that marcasitic sulfur is necessarily more susceptible to ox- the furnace and after idation than the pyritic form, when both arc in a fine state of passing through the coal is delivered below division. This point offers a field for investigation. A few illustrations are of interest in showing the presence of into the dioxide detectmarcasitic sulfur in pyritic masses in certain of the Illinois ing tube, through a 1-mm. capillary. This coal deposits. capillary is so placed Univcrsityof Illinois, Ens. Expt.Sta.. Bull. I6 (IOIO). that the gas from the 1 Tars Joumar,IS,501 (1924). coal impinges upon a drop of bafium hydroxNew Canadian Publication ide suspended from a The Canadian Department of Mines has issued a 310-page solid rod having a publication on "The Development of Chemical, Metallurgical, flat, ground tip. The and Allied Industries in Canada in Relation to the Mineral barium hydroxide soluIndustry," which sets a high standard in government publications tion is contained in a and presents in concise form much information of value to the chemical industry. The publication is provided with a number of separatory funnel hav- o r _ useful tables, such BS one upon the principal chemicals used in ing a tube filled with 1 industry, trade statistics of chemicals and allied products, and lime fitted into F i ~ u r el-Carbon Diorfde Detectloo Tubs charts which give in concise form information pertaining to "da the top of it in order electro products and some of their uses, the alkali industry, the to remove the carbon dioxide and moisture from the air as the industrial applicationsof lime, some of the many uses of alcohol, and products derived from coal. The discussion of primary solution is removed from the fnnnel. The barium hydroxide inorganic products contains information worthy to class this solution can he conducted to the lower end of the drip rod by publication as a source of reference reading, while primary or- a rubber and a glass tube, the latter being drawn out to a ganic products are treated in the same thoroughgoing manner. The parts devoted to manufacturing treat explosive mannfac- narrow tip which is placed so that it just touches the drip ture, the fertilizer, ceramic, and glass industries, besides a num- rod. In this way a h e r adjustment of the harinm hydroxber of those classed as miscetlaneaus and minor, so far as Canada ide can be obtained. The acid tube is placed directly.above is concerned. The metallurgical industries are treated in another part, as are food products and general manufacturing. The publication is recommended to those who find interest in such general as well as specific information which finds a proper place in a well-indexed government publication of this character.
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I I
Rmived AvgUst 8. 1924. Parr and Frsnds, Univvsiiy of Illinois, Eng. Expt. Sta., Bull. %I
(1808). s J . Chcnr. Soc (Landon),11% 945 (1918).
