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Conclusions Anthmcite is the principal smokeless fuel. During the past ten years the quantity of anthracite used for heating homes and commercial buildings approximately equaled, in net heating value, the combined sales in the United States of domestic coke, light and heavy heating oils, and natural and manufactured gas used for domestic and house-heating purposes. Anthracite is the only natural fuel which is smokeless under all conditions of use. It is the most concentrated, strongest, and cleanest of all solid fuels, and is available in a wide range of st’andard sizes. It can be ignited readily, burned a t the desired rating Tyith little attention, and banked for long periods. It is safe to store in any quantity. Since anthracite is closely sized, noncaking, and nonclinkering under normal conditions of household use, ideal fuel-bed conditions can be readily maintained, and it is equally well adapted to automatic (stoker) firing, magazine feed, or hand firing. This combination of properties explains why anthracite has long been the standard domestic fuel with which other fuels are compared. Yearly all of the true anthracite ( 2 to 8 per cent volatile matter) produced in the United States is mined in northeastern Penneylvania. It is used principally in the Xorth Atlantic states, which explains why that densely populated sect’ion has never had a smoke problem comparable with .many cities in other sections of the country. The present
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average production is about 50 million tons annually, which could be promptly increased by many millions of tons, even under present emergency conditions. This could be done without the need for additional capital investment simply by working the collieries a greater number of days per month. Semianthracite (8 to 14 per cent volatile matter) is produced to the extent of a few hundred thousand tons per year in Pennsylvania, Virginia, and Arkansas. Small amounts of anthracitic coals are also mined in Colorado, Tew Mexico, Washington.
Literature Cited Am. SOC. Testing Materials, Standard Specifications for Classification of Coals by Rank, Designation D-3S8-38 (1938). Ashley, G. H., Trans. 1st Ann. Anthracite Conf. Lehigh Unia., 1938, 11-24. Duim, Gano, Steel, 108, No. 9, 21-2 (1941). Mellon Inst., Bd2. MA-1, M-2 (1938), and M-3 (1939). Mellon Inst., “How t o Imyrove Your Lawn and Garden w i t h Pennsylvania Anthracite Ash”, 1939. Rose, H. J., T r a n s . 1st Ann. Anthracite COILE. L e h i y h Urkh, 1938, 25-38. Ibid., 2nd Conf., 1939, 27-44. Rose, H. J., and Laaseter, F.P., Trans. Am. SOC.Heating Vent i l a t h g Engrs., 45, 329-38 (1939) : Heating, P i p i n g , A i r Conditioning. 11, 119-22 (1939). Turner, H. G., T r a n s . Am. Inst. M i n i n g Met. Engrs., 108, 33043 (1934). U. S. Bur. Mines, Mineral Yearbook. 1938, 1939, 1940. U. S.Bur. Mines, Repl. Investigation 3283 (1935). COITRIBGTION from the Anthracite Industries Fellowship, Mellon Infitiruti.
M.D. CURRAN Coal Carbonizing Company, S t . Louis, $10.
T
HIS process v a s developed primarily for producing smokeless fuel from feebly coking Illinois coals to provide St. Louis with a means by which it could eliminate the smoke nuisance. Previous efforts, in which many millions of dollars were employed, met with failure because the coke produced could not be burned satisfactorily in existing stoves and furnaces, and the cost was so high that i t could not
compete with the cheap low-grade coal. From a technical viewpoint it was necesfary to produce a coke substance which would be sufficiently reactive to give full heat a t fuel bed temperatures below the fusion temperature of the ash, and from a n economic viewpoint the manufacturing cost must be such that the fuel consumers in St. Louis could get their heat at substantially the same annual cost.
July, 1941
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The success attained from the operations of CurranKnowles plants a t West Frankfort and Millstadt, Ill., during 1934-39, inclusive, provided St. Louis with necessary assurances that a suitable smokeless fuel could be had from the local coal. Accordingly, a smoke ordinance was passed early in 1940 and made effective in June of the same year.
handling the ovens which is not possible where silica brick comprises the major part of the structure. The CurranKnowles oven can be heated and cooled without serious damage to the structure. This is a valuable asset with which to meet any condition requiring temporary cessation of operations.
Features of t h e Process
Advantages
The process is based on the use of the sole-flue oven where The Curran-Knowles process opens up several new fields coal is carbonized by spreading a relatively thin layer on in carbonization. The plants now operating on Illinois coal a horizontal hearth and heating it from beneath. The fundaa t West Frankfort and Millstadt are coking a material which mental coking reaction taking place under these conditions heretofore has not produced merchantable domestic coke in is very different from that which occurs when coal is treated other known processes. The application of heat to the a t the same temperatures in the vertical-slot-type coking underside of the coal charge, with corresponding flow of chamber or the Eommon gas gases upward through the retort. Of considerable imcoal, develops a cementing portance is the fact that a part action not otherwise possible, of the gases distilled from the so that feebly coking coals The Curran-Knowles sole-flue coke oven for coal pass up through the coal are converted into strong coke producing smokeless domestic and induslayer and preheat the coal, substance. with the result that much faster The plant operating a t Owen trial fuel and some installations of this type coking speeds are developed. Sound, Ontario, C a n a d a , of oven are described-in particular, the This reaction is also accomdemonstrates the applicability installation at Millstadt, Ill. The coal is panied by less than the usual of this process to the gas incarbonized in a layer approximately one amount of cracking of the tarry dustry where experience shows foot thicli in a rectangular oven in which gases, with higher yields of that small-sized screenings tar and less graphitic carbon from gas coals can be carbonthe heat is applied to the charge from comdeposit on the coke substance. ized to produce a high-quality bustion flues in the oven floor. The gas produced is richer in domestic coke and a uniform heat units and the volume is quality of gas. The use of such small-sized screenings reduced accordingly. The primary objective in the permits a substantial saving in development of this process was the manufacture of a more the cost of coal; a t the same time the improved quality ofthe highly reactive coke than had heretofore been possible with coke creates a greater revenue from coke sales. The comthe usual types of coking equipment. This is accomplished bination of these two sources of economy materially reduces by reducing the pressure on the coal during the liquid the cost of gas. Further savings are due t o the production of stage while it is being converted from coal to coke and a t a large quantity of high-grade tar. the same time setting up conditions which eliminate a subThe breeze normally produced in coking plants and sold a t stantial part of the graphitic carbon deposit on the coke a depressed price can be mixed with the coal and recoked substance. without impairing the quality of the coke because of the exA superior quality of metallurgical coke is produced in this ceptional cementing action developed. Wet coals can be process from either high- or low-volatile coals, or mixtures coked as efficiently as low-moisture coals because the hot of them, by controlling the oven operation to reduce the gases passing up through the coal remove all free water as volatile matter in the coke to approximately one per cent. steam and do so without absorbing heat from the heating The increased reactivity of the coke produced makes possible surface of the oven. The plant a t Millstadt has been carimproved operating practice in many metallurgical operations, bonizing coal containing 15 to 20 per cent moisture with including electric furnace reduction, where an increased elecalmost the same heating efficiency as obtained in other trical resistivity of the coke is a desirable characteristic. plants using low moisture coals. I n the production of domestic coke, the oven operations Expanding coals can be coked as easily as shrinking coals. are controlled to produce a coke substance containing about Expansion takes place vertically without placing any strain 3 per cent volatile matter. The physical texture of the coke on the brickwork, and coals expanding 40 per cent of their produced is such that it is more highly reactive with air, and volume have given perfect operating practice. It is imporaccordingly has ignition and combustion qualities better tant to note that coals richest in fixed carbon (the lom-volatile suited to the requirements of the household furnace. It is or smokeless coals) are as a class highly expanding. In other easily kindled and will sustain combustion a t very low temwords, when coals of this class are coked, they swell and, peratures. These qualities permit the domestic user to dewhen coked in a confined space such as is provided in the velop full heat more quickly and to maintain his fire with ordinary vertical-slot oven, the force of the expansion is so ease during the mild-weather heating periods in the spring and great as t o seriously damage the oven structure. These coals fall. Of considerable importance also is the fact that there are known to have a higher coking index than any other class is practically no loss of unburned coke with the ashes. The of coking coals, but their use has been restricted on account coke burns completely in the firebox. of their expansion characteristic. Most by-product coking The design and construction of the oven has been so worked plants operating today use from 15 to 25 per cent of lomout as to permit the use of fire-clay brick throughout, except volatile coal in their mixture to improve coke quality. With in the floor and sole flues, where silica brick is used to permit Curran-Knowles ovens we are able to use these lowvolatile operation a t standard high temperatures. The greater part coals exclusively; we thus have the full advantage of their of the brickwork is composed of standard si5e bricks, which excellent coking properties and a t the same time develop eliminates costly shapes commonly employed by others. an operation with a higher coke yield than has heretofore been Furthermore, the use of fireclay brick provides a flexibility in possible.
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(upward), and the raw coal therefore receives considerable preheating. Since the gases escape from the coal charge without the usual amount of cracking, there is a substantial increase in the amount of tar produced per ton of coal. At the same time the heat required for carbonization is reduced by that amount of heat which would ordinarily be absorbed in cracking the tarry gases into carbon and hydrogen. The simplicity of design incorporated in the CurranKnowles process affords a substantial saving in plant costs. I n other words, the investment cost per ton of capacity is considerably less than has generally prevailed with other byproduct coke oven plants. Carbonization is therefore made economically possible in plants of moderately small capacity because of the lower investment and operating cost. The rugged design of the ovens and equipment and the simplicity of operation permits the installation of this process in connection with mining operations where a substantial increase in revenue may be had by converting the dust and smallsized screenings to a high-grade domestic smokeless fuel.
The plant now operating a t Michel, British Columbia, on low-volatile expanding coal demonstrates the usefulness of the Curran-Knondes oven for handling expanding coals. The coke produced a t this plant from low-volatile coals has the same high degree of reactivity as the cokes produced from the high-volatile coals mentioned previously. The Michel coke is giving excellent results in metallurgical operations as well as in the domestic field. I t s high degree of reactivity permits blast furnace and foundry operators t o develop a greater useful heat value in the melting zones of their respective furnaces than they have heretofore secured from the standard cokes available in the market area tributary to the Michel plant. The carbonizing of coal in a thin horizontal layer with application of the heat on the underside of the coal charge substantially increases coking speed. I n some cases the rate of coking is practically double that developed in the verticalslot oven. The flow of the products of distillation is in the same direction as the flow of heat through the coal charge
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W. L. JONES
F. E. VANDAVEER
The St. Louis County Gas Company, Webster Groves, Mo.
American Gas Association Testing Laboratoriess,Cleveland, Ohio
ENSE concentrations of industry and population make of smoke a nuisance long incontrolled but accepted as a by-product of industrial virility and modern urban life. Smoke pouring from factory stacks, a symbol of throbbing machinery, smoke wisping from workers’ homes, promising warmth and security, becomes, when its sources are multiplied a thousand fold, a vicious destroyer of civic beauty, public health, and property. Smoke rising from a hundred towers of inefficiency and waste merges over a community to strike again a t the citizensz purses, and to undermine their mental and physical well-being. The smoke problem is a real one. Probably its worst aspect is its effect on health. This relation is difficult t o evaluate. As in other crusades, the evils of this public problem have in many instances been overstressed. I n order to discuss with reasonable accuracy the effect of smoke on health, it is first necessary that the true nature of the former be well understood. Smoke is popularly supposed to be nothing more or less than particles of carbon and other tarry substances. This is a natural conclusion, since these constituents of smoke render i t visible. Such carbon particles are produced by inefficient combustion of bituminous coal. These wasteful methods can be corrected by proper firing, and this aspectthe liberation of visible “dirty” smoke-can be eliminated without conversion to more refined fuels. But smoke is not a simple substance. Bituminous coal generally has an appreciable sulfur content. A reasonable average value may be taken as 2 per cent. Thus, a ton of coal when burned will produce some 60 pounds of sulfur oxides which, since they are liberated in gaseous form, occupy a volume of nearly 700
cubic feet. This invisible, and possibly one of the most vicious elements of smoke, is seldom considered. Yet in 1930 sixty-five people were killed in the Upper Meuse district of Belgium by ‘6smokes’from factory stacks (S), the fatal gas being identified as a sulfur compound. Conditions for this disaster represented a unique combination of barometric pressureJ wind, temperature, fog, and topographical surroundings which may never again be duplicated. However, i t graphically illustrates an acute case of conditions normally and continually surrounding every industrial center. Another nearly invisible constituent of smoke is silica, the deadly and widely publicized killer in certain mining and industrial operations. Adso may be mentioned the presence of arsenic, manganese, iron, and other allotropic and polyvalent substances resulting from industrial processes, all of which may have a deleterious effect directly or through catalytic action (11). Smoke must therefore be considered in its true light as a complex heterogeneous mixture containing more than one substance harmful to health. It is no wonder, then, that estimates of the baneful influence of smoke on human life by responsible physicians and health officers vary so widely. It has been said that a prolonged smoke fog lasting several days will kill more people than automobiles do in that area in many months. Correlation of smoke and high incidence of pneumonia seems to have been clearly established. More conservative experts point out that such relations between cause and effect have not yet been irrefutably established, largely because of lack of fundamental data on physiological reactions to the substances involved. However, boundless
