The Spontaneous Combustion of Charcoal - Industrial & Engineering


The Spontaneous Combustion of Charcoal. Ind. Eng. Chem. , 1912, 4 (7), pp 541–542. DOI: 10.1021/ie50043a034. Publication Date: July 1912. ACS Legacy...
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July, 1912

T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y .

At the present time, two classes of oil-engines are in use, wz.: light-oil engines, which use fuel capable of forming explosive mixtures a t ordinary temperatures and possessing a density of 0.68-0.72; and heavy-oil engines, which use fuel requiring high temperatures or mechanical “pulverization” for the formation of explosive mixtures, and possessing a specific gravity of 0.80.9. Of the heavy-oil class, the Diesel engine, which has received much space lately in the technical press, is the most important type. In it the compression occurs entirely on a charge of air, into which the fuel is afterwards injected, so that there is no danger of pre-ignition, and compression pressures up t o 450--500lbs. per sq. in. can be used. It is, in fact, in its high compression t h a t the great efficiency of the Diesel engine lays. I n the semi-Diesel type of engine, in iyhich, after compression of air, the fuel is injected into a hot bulb, there is no danger of pre-ignition, but compressions up to about zoo lbs. per sq. in. are usually found to be sufficient to ensure ignition. In the Diesel engine admission occurs a t constant pressure and exhaust a t constant volume, as compared with the gasengine and petrol-engine, in which admission takes place a t constant volume. This difference gives the Diesel engine a n advantage, since there is a greater difference between the upper portions of the actual and theoretical diagrams in the two cases. The economy of the Diesel engine is also largely accounted for by the high compressions, up to from 4jo-joo lbs. per sq. in., which can be used. The temperature reached in the cylinder of a Diesel engine is usually about 1 2 0 0 ~F. With a 2-stroke cycle gas-engine there is danger that some of the new working charge may be blown out of the exhaust by the scavenging air, but in a Diesel engine this can not happen, so that the Diesel may be regarded as essentially a n-stroke engine. According to Industrial Engineering, 11, 401,the thermal or indicated efficiency of the Diesel engine of to-day reaches 48 per cent., while the effective or brake efficiency reaches, in some cases, 3.j per ccnt. of the heat value of the fuel. This engine converts the heat of the natural fuel into work in the cylinder itself, without any previous transforming process. Allner (1. Gasbel., 54, 321) reported that tests on a IOO h. p. Diesel motor showed vertical-oven tar was a very satisfactory fuel for this type of engine; later (Progressive .4ge, 29, 481) it was pointed out that tar fuel was the least expensive for Diesel engines and t h a t lvith slight changes in the engine, no difficulty was experiencecl in using i t ; and Allner has more Gasbel., 54, 1025) that the present recently pointed out (1. practice in using tar is to assist ignition by spurting into the cylinder about j per cent. of gas oil just ahead of the tar. Recently, however, i t has been found possible t o operate on tar oil and avoid the use of even this small amount of gas oil, and quite lately it has been ascertained t h a t a 40 h. p. Diesel engine may be operated by the use of raw tar itself, using both vertical oven tar and certain kinds of retort oven tar, and wholly avoiding any use of ignition oil.

THE CLASSIFICATION OF SOAPS. With the object of classifying different soaps on a commercial scale, the Commission appointed by the Italian Union of Soap Makers has proposed to divide them in the order of their requirements. Gianoli reports as follows concerning the rec50,, 465 ommendations of the Commission [Chent. Trade I. (1912)l: I. PCRE SOAPS OF THE FINEST QUALITY.

( a ) Boded Soaps.-Hard, soft, floating, white and dyed, scented or unscented; not liable to change color or to become rancid; completely soluble in water and in alcohol; and constituted by a combination of soda and fatty acids when this is insoluble in sodium chloride solutions a t 1 5 O Be., i. e . , free from oxy-fatty acids, and in which the total percentage of hydrated fatty acids., non-siccative, is not less than 60 per cent.

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Free from unsaponified glycerides, hydrocarbons, wax, alkaline and metallic soaps; not more than 0.3 per cent. free sodium hydroxide; not more than I j per cent. total mineral matter, not more than 2 per cent. foreign organic matter (coloring matter, perfume, or fatty acids of low- molecular weight). (b) Resin Soaps.-Boiled with not more than I j per cent. of colophony, and otherwise corresponding to the requirements assigned t o the preceding. (c) ;Mottled and Marbled Soaps, in which the proportion of hydrated fatty acids is not less than 55 per cent., and the total free alkalies, carbonates, sulphates, and alkaline silicates do not exceed 3.5 per cent. 2.

CURREST SOAPS OF INFERIOR QUALITY.

Hard or soft, plain or marbled, containing, or not containing, alkaline mineral detergents, organic or mineral fillings in quantities greater than 3.j per cent. when the soaps contain 33 per cent. humidity-namely, soaps containing carbonates and alkaline silicates, talc, kaolin, asbestine, fossil flour, or sugar, starch, fecula, hydrocarbons, etc. Soaps manufactured cold or hot with f a t t y acid or glycerides of any nature, with or without resin. 3. DRY SOAPS. Soaps which do not give more than 2 0 per cent. of water when exposed for 3 hours t o a temperature of Ioj-110~C. after being pulverized with I O times their weight of powdered glass. The soap classifications hitherto published have been generally based on the methods of manufacture. The above classification seemed to the Italian Commission to more nearly meet the requirements of the analyst and consumer. What the latter desires to know is the peculiar charac.ter of the soap he is buying, and not how it is made. Consequently, to satisfy the trade, the limits within which the composition may vary must be specified.

THE SPONTANEOUS COMBUSTION OF CHARCOAL. I n 1911,there were 64 reported fires in the transportation of charcoal in the United States, and of these 63 were evidently caused by spontaneous combustion. During 19I I, experiments on the spontaneous heating and ignition of hardwood charcoal were started a t Straight, Pa., and a t Westline, Pa., by the Bureau for the Safe Transportation of Explosives and other Dangerous Articles. The charcoal, after varying treatment as to cooling and air exposure, was loaded into box cars, and the temperature of the interior of these cars was observed a t intervals to detect any increase in temperature. From the incomplete series of experiments performed, i t was reported (Bureau of Explosives, Report No. 5, February, 1912,p. 47) that “no conclusions can be drawn as to the relative efficiency of various periods of cooling and airing. In no case was there any ignition or a n increase of temperature approaching ignition. In every case but one there was a noticeable rise of temperature, which can be ascribed only to the action of air on the cold charcoal, and not to any residual sparks or fire.” The figures obtained so far have not shown t h a t wetting the charcoal increases the heating effects, although it is the general belief t h a t heating more frequently occurs in damp weather. “To attain absolute security from fires of spontaneous origin it is necessary to store the charcoal in the open till such time as i t attains its equilibrium with regard t o absorption of air”-an impracticable procedure, so “the logical alternative is to supplement the best present practice of cooling, airing and storing in open cars for 24 hours prior to shipment by a safe method of ventilation of cars during shipment.” The experiments on the spontaneous combustion of charcoal recently published by the National Physical Laboratory (Report for 1910,85; 1911,86) were conducted in an electrically heated oven, in which I cu. f t . of the charcoal was exposed to a uniform temperature (constant within I C.),measured by

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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y .

means of thermocouples. The charcoal was surrounded by an air space about 3 inches wide, and the oven could be closed airtight or a current of air of any desired velocity passed through it. Experiments with flake charcoal showed t h a t with air currents ranging from 5-62 cu. f t . per minute for I cu. f t . of charcoal, spontaneous combustion occurred at temperatures of from 96-11o0 C., while a t lower temperatures no signs of spontaneous heating could be observed. Additional experiments showed that in a current of air containing 5 per cent. sulphur dioxide, spontaneous combustion of the charcoal took place after some hours; therefore, there is risk of danger in using sulphur dioxide for disinfecting rooms, etc., where charcoal is present in the walls. It is reported t h a t decayed wood appears to be much less inflammable than charcoal.

ARTIFICIAL RUBBER FROM SEAWEED. A product, now being marketed under the name “Seagumite,” said to be non-inflammable, damp-proof, and unaffected by heat or cold, and to be expected to provide a substitute for rubber and leather, is the subject of a patent recently issued t o J. S. Campbell, of London (English Patent 5395, 1911). His invention relates to improvements in the production of a substance having the characteristics of rubber and capable of vulcanization. It had previously been proposed t o treat marine plants, lixiviated by acidulated water, with alkalies such as ammonia; and it is said that the material thus produced has, after impregnation with siccative oil or dissolved india-rubber, been found suitable for use in the whalebone industry. The Campbell process consists in boiling washed and crushed seaweed in steam-jacketed pans with ammonia for about 45 hours, I gallon of ammonia (specific gravity, 0.88) being used for 5 cwts. of seaweed; drying in an agitating apparatus, t o which heat is applied, and during agitation adding I gallon of a mineral or vegetable oil, as rosin oil; adding next a vulcanizing substance, such as sulphur, and subsequently mixing the whole mass with 25 per cent. by weight of a glutinous or resilient binder, as pontianac gum, jelutong, gutta-percha, or reclaimed rubber waste. The whole is then heated for I hour and finally dried in a vacuum pan or press. Prior to removing and drying, a preservative, as wood or bark extract, may be added to the amount of 0.85 per cent. by weight of the seaweed used. The Campbell process seems to be primarily dependent upon the formation of ammonium alginate. Algin in its soluble forms is recognized as having probable value as a n agglutinant, and a substance resembling gutta-percha may be prepared from the alkaline alginates and shellac.‘

J u l y , 1912

inferior in cutting value. The sharp cutting implements were therefore the result of Nature’s handiwork, and it is indeed very questionable whether these people possessed the sec e t of tempering.

THE PURIFICATION OF AIR BY OZONE. Nature, 89, 304, states that the system of ozone production and distributing plant installed for air purification and ventilation on the Central London Railway is a plenum one, and consists of Sirocco fans placed a t each of the underground stations, except that at Shepherd’s Bush. The total air supplied to the tubes is about 80,000,000 cu. ft. per day. Each fan draws its air through a filter screen, and works in conjunction with a n ozone-generating plant. The latter consists of mica sheets with metallic gauze on each side, stacked side by side, and energized by alternating current at about 5,000 volts, in such connection t h a t a silent discharge passes between the various plates, so that air passing between them is ozonized. The ozone generator is supplied with a small transformer, which in turn is supplied with 380 volts alternating current from a small rotary converter. The converter is connected on its directcurrent side t o the 5go-volt lighting circuit of the railway. THE USE OF COKE-OVEN GAS. Cooper (/. Gas 1-tg., 118, 107) states that in Germany the towns of Waldenburg, Altwasser, Salzbrunn, Essen, Dortmund, and Mhlheim have been supplied for some time with gas from the neighboring coke-oven plants. The entire supply of gas for Mulheim-on-the-Ruhr and for Barmen is obtained from two coke-ovcn plants. The installation consists of 50 Koppers’ horizontal regenerator ovens, each of which is capable of taking a charge of 8-10 tons of coal; the period of carbonization is 2 4 hours and only the richer portion of the gas (that evolved from the second to the twelfth hour, representing 50 per cent. of the yield) is used for distribution. During this time one oven will produce 70,600 cu. f t . of gas possessing a calorific value well over 600 B. t. u. per cu. ft. and costing $0.17per 1,000cu. ft The gas is purified from hydrogen sulphide by the town authorities and distributed.

THE PRESERVATION OF WOOD WITH “BELLIT.” I n order to increase the preservative effect of sodium fluoride on wood, it is now being mixed with nitro-phenols. According to Nowotny (Oesterr. Chem. Ztg., 15, 100;cf. Idem, Ij, SI),one of these mixtures, “Bellit,” consists of 90 parts of 90-95 per cent. sodium fluoride and IO parts of dinitrophenolaniline. The latter compound is used because it does not, like free dinitrophenol, act upon the iron vessels in which the timber is impregnated; it is also active as an antiseptic. The selective “TEMPERED COPPER” TOOLS. According to The Engzneeiing and Mimtzg , J o u r m l , gj, No. phenomena observed when treating timber with mixtures of zinc fluoride and hydrochloric acid are reproduced in the 20, 986,the copper-cutting instruments of the Tarascans, found “Bellit” treatment. in the Balsas River ruins in Guerrero, are so hard that they would turn the edge of a modern knife, and it has been claimed CHROME-NICKEL BRONZE. t h a t these people, along with the Aztecs and Toltecs, possessed Chrome-nickel bronze is now being manufactured by a Philathe secret of tempering copper. On the other hand, copper knives and axes, found a t Atcopotzalco, are so soft t h a t they delphia company, the product being known as “Chromax can be cut with a n ordinary pocket knife. Analysis showed Bronze.” The proportions of metal in the alloy are said to be t h a t in all three localities the copper implements were of the as follows: Copper, 66.66 per cent.; zinc, 12.13 per cent.; same composition as the copper ores found therein. The nickel, I 5 . I j per cent. : chromium, 3 03 per cent. : and aluminum, blades from Guerrero, which are hard and apparently tempered, 3.03 per cent. The tensile strength of the alloy is said to be we-e made from the natural ore carrying nickel and cobalt, 79,000 lbs. per sq. in.; the color is white, and i t takes a fine, thus rendering the smelted alloy steel-like in hardness. Thus, silvery polish: the fracture is fine and dense, particularly after the natural product gave a n alloy of great hardness when heated being remelted; and the alloy, owing to its high melting point, and sharpened, while the other ores of practically pure copper, has a denser structure and greater compressive strength than when smelted, resulted in implements whi h “ere soft and manganese bronze. It can be rolled into sheets and wire.