Part 31

But the start has been made. The point of the wedge has already found entrance. The discovery of radium, and the study of its decompositions, has opened wide our field of vision. The problem must yield, as the blows of chemical investigation fall upon the wedge and drive it home.

Chemistry has always been a utilitarian science. Its results have always been at the service of humanity. And if we can judge the future by the past, even discounting for the enthusiasm of the chemist, we can forsee improved processes which will reduce our present wasteful 351 methods; we can see new processes making for us such things as india rubber from starch, for which we must now depend upon the bounty of nature; and we can dimly see the time when we shall be able to utilize some of that energy which is hidden away in the recesses of matter, and whose vastness we have just begun to appreciate.

THE CLOSE RELATION OF THE PRODUCER-GAS POWER PLANT TO THE CONSERVATION 352 OF OUR FUEL RESOURCES.

BY ROBERT HEYWOOD FERNALD.

Official reports show that the coal placed on the market amounts annually to between 450,000,000 and 500,000,000 short tons in the United States alone. These figures, however, are somewhat misleading as they do not in any way show the tremendous wastes that are going on due to our present methods of mining and restrictions in qualities of coal that can be transported and placed on the market at a reasonable profit. Careful investigation has shown that the coal wasted or left in the mines in such form as to be inaccessible to future generations amounts each year to practically 100 per cent of that placed on the market, or in other words, at the present time some 450,000,000 tons are annually lost as far as commercial value is concerned.

If this condition is allowed to continue it is estimated by the United States Geological Survey that our available supply of bituminous coal will be exhausted within the next two hundred years.

A realization of the seriousness of this situation has led to a careful and systematic study of the present lack of efficiency in the utilization of fuels for both power and metallurgical purposes, to investigations into more efficient use of the present marketable grades of fuel, and to a consideration of methods of using the so-called low-grade fuels, lignites and peats.

The United States Geological Survey has for several years been investigating the economic value of coals and lignites as gas-producer fuel. This work, begun with tests of coal and lignite at the 353 coal-testing plant erected at the Louisiana Purchase Exposition, St. Louis, Mo., in 1904, was continued at St. Louis and at Norfolk, Va., and is now being carried on by the Survey at the fuel-testing plant in Pittsburg, Pa. The tests were undertaken because it was evidently desirable to determine the value of the gas producer as a means of increasing efficiency in the use of the coal supplies of the United States. The early tests proved decidedly encouraging, demonstrating that many coals now wasted or not mined because they are not satisfactory fuel for steam-power plants can, by conversion into producer-gas, be made to do from two to three times as much work as can be done by the best grades of steam coal burned in a boiler plant. In consequence, the making of producer-gas tests and the study of the processes that take place within the gas producer now form an essential part of the fuel investigations conducted at the Pittsburg plant under the provisions made by Congress for the analyzing and testing of mineral fuels.

Rapid Development of the Gas Engine.

It was not until late in the nineteenth century that the gas engine came into common use, and although many types have been devised within the last twenty or thirty years it is only within eight or nine years that large gas engines have been constructed. This development started eleven or twelve years ago in Germany, Belgium, and England, but marked progress has been limited to the last eight years.

For a long time the natural fuel of these internal-combustion engines was city gas, but this was too expensive except for engines of small capacity. It was seldom found economical to operate units of more than 75 horsepower with this fuel. Cheap gas was essential for the development of the gas engine, but the early attempts to produce cheap gas were somewhat discouraging, and for a time it seemed very 354 unlikely that the gas engine would encroach to any extent on the field occupied by the steam engine. The theoretical possibilities of the internal-combustion engine operating with cheap fuel promised so much, however, that the practical difficulties were rapidly overcome, with the result that the internal-combustion engine has become a serious rival of the steam engine in many of its applications.

The development of the large gas engine within the last few years has been exceedingly rapid. It was only ten years ago that a 600-horsepower engine exhibited at the Paris Exposition was regarded as a wonder, but today four-cycle, twin-tandem, double-acting engines of 2,000 to 3,500 horsepower can be found in nearly all up-to-date steel plants, and there are installations in this country containing several units rated at 5,400 horsepower each.

Development of the Gas Producer for Power Purposes.

The rapid advance of the large gas engine was made possible by improvements in the production of cheap gas directly from fuel by means of the gas producer. An early form of producer introduced in Europe, and now in general use both abroad and in the United States, is known as the suction producer, a name suggested by the fact that the engine develops its charge of gas in the producer by means of its own suction stroke. Although many producers of this type are now used, most of them are small, seldom exceeding 200 horsepower. A serious limitation to the utility of the suction producer has been the fact that, owing to the manner of generating the gas, no tarry fuels could be used, a restriction that prevented the use of bituminous coals, lignites, peats, and other like fuels. The fuels in most common use for producers of this type are charcoal, coke, and anthracite coal, although attempts are being made so to construct plants that they can be operated with bituminous or tarry coals.

To meet the demand for the concentration of power in large units, 355 instead of operating a large number of separate installations of small power capacity, the pressure producer was devised. This producer develops its gas under a slight pressure due to the introduction of an air and steam blast, and the gas is stored in a holder until it is required by the engine. As the gas may thus be stored before passing to the engine, and as its generation does not depend on the suction stroke of the engine, tar and other impurities may be removed from it by suitable devices, and the use of bituminous coal, lignite, and peat thus permitted.

The pressure producer was closely followed in the course of development by the down-draft producer, which fixes the tar as a permanent gas and therefore completely uses the volatile hydrocarbons in bituminous coal, lignite, and peat.

A few scattered producer-gas plants were installed for power purposes in the United States before 1900, but the application of this type of power in any general sense has been developed since that date. During the first few years of this period of development anthracite coal, coke, and charcoal were used almost exclusively, although occasionally pressure and down-draft plants ventured to use a well-tried bituminous coal known to be especially free from sulphur and caking difficulties and low in both ash and tar making compounds. The rapid development of the anthracite plant was to be expected, but it remained for the United States Geological Survey in its testing plants at St. Louis and Norfolk to demonstrate the possibility of using in such plants practically all grades of fuel of any commercial value, without reference to the amount of sulphur or tarry matter which they contain. Figures 1 and 2 illustrate the very rapid increase in the number of installations and in the total horsepower of the plants operating with bituminous coal and lignite since the beginning of these 356 investigations by the Geological Survey in 1904.

Owing to the fact that the dates of installation of many plants are not ascertainable, it is impossible to present the exact growth either in number of installations or in horsepower. The relative rate is, however, approximately shown by Figures 1 and 2, the data for which were secured from 375 installations. The points for the year 1909 are estimated from the returns for the first five months. These points have been checked by two or three methods and indicate only the normal increase established by the rate of development before the business depression of 1908. It is probable that the actual figures for the entire year may exceed those indicated.

Relative Results of Steam and Producer-Gas Tests.

In considering the relation between the economic results of plants of the two types under discussion, namely steam and producer-gas, the fact should be remembered that today, in the ordinary manufacturing plant operated by steam power, less than 5 per cent of the total energy in the fuel consumed is available for useful work at the machine.

In this connection it is of interest and value to glance at the possibilities of the best-designed and most skilfully operated commercial plant now in use. The data concerning the steam plant selected for this determination are derived from a table prepared by Mr. Stott, superintendent of motive power, Interborough Rapid Transit Company, New York City, which, as Mr. Stott says, shows “the losses found in a year’s operation of what is probably one of the most efficient plants in existence today, and, therefore, typical of the present state of the art.”

Average losses in steam plant of the Interborough Company in 359 converting 1 pound of coal, containing 12,500 British thermal units, into electricity.

======================================+==========+========== | British | | thermal | Per cent. | units. | --------------------------------------+----------+---------- Loss by friction | 138 | 1.1 Loss in exhaust | 7,513 | 60.1 Loss in pipes and auxiliaries | 275 | 2.2 Loss in boiler | 1,000 | 8.0 Loss in stack | 1,987 | 15.9 Loss in ashes | 300 | 2.4 +----------+---------- Total losses | 11,213 | 89.7 Energy utilized | 1,287 | 10.3 +----------+---------- | 12,500 | 100.0 --------------------------------------+----------+----------

Mr. Stott further presents a table showing the thermal efficiency of producer-gas plants, concerning which he says:

The following heat balance is believed to represent the best results obtained in Europe and the United States up to date in the formation and utilization of producer gas.

Average losses in a producer-gas plant in the conversion of 1 pound of coal, containing 12,500 British thermal units, into electricity.

======================================+==========+========== | British | | thermal | Per cent. | units. | --------------------------------------+----------+---------- Loss in gas producer and auxiliaries | 2,500 | 20.0 Loss in cooling water in jackets | 2,375 | 19.0 Loss in exhaust gases | 3,750 | 30.0 Loss in engine friction | 813 | 6.5 Loss in electric generator | 62 | .5 +----------+---------- Total losses | 9,500 | 76.0 Converted into electric energy | 3,000 | 24.0 +----------+---------- | 12,500 | 100.0 --------------------------------------+----------+----------

The thermal efficiency of such plants, as given by different writers, runs as high as 33, 36, and 38.5 per cent, and for some plants figures as extravagant as “above 40” are boldly published. Although the present aim has been to give the figures for a producer-gas plant that may compare favorably with those of the steam plant of the Interborough Company, an effort has been made to keep well within obtainable efficiencies. Attention is also directed to the fact that 360 the producer-gas plant considered should be large enough to compare favorably with the steam plant. This precludes comparisons with suction plants, which are relatively small but give higher proportional efficiencies than the larger pressure and down-draft plants, for these require more or less auxiliary apparatus.