IND USTRlAL AND ENGINEERING CHEMISTRY
August, 1924
847
A Furnace for t h e Determination of t h e Fusing Point of Coal Ash' By B. B. Kaplan WEST VIRGINIA GEOLOGICAL SURVEY, MORGAKTOWN, W. Va.
N WORK on the fusibility of coal ash it is desirable to have a gas and air furnace which will attain a maximum temperature of 3000" F. The No. 3 melter's furnace, modified as recommeiided by the U. S. Bureau of Mines,2 attains a maximum teniperature of 2700" F. There is a gas pressure of about 6 ounces and an air pressure which a t the nozzle is between 4 and 6 pounds. By increasing the insulation of the melter's furnace and the wall thickness of the crucible which corresponds to the Type Kof theDenver Fire Clay Company, a temperature of 3050 " F. can be attained. EXPERIMESTAL
I
After trying various refractory mixtures it was found that 5 parts of alundum cement mixed with 3 parts of kaolin yield a mixture of the desired plasticity, which burns to a buff color and withstands high temperatures. This clay was worked up into a paste, and the bottom compartment of the inch of the No. 3 melter's furnace was filled to within burners. The bottom of a Denver Fire Clay Company's Type K crucible was pressed into the center of the mixture for about half an inch. This facilitated placing the crucible into exactly the same position during the various runs. The crucible was removed and the clay was permitted to air-dry overnight. It was then heated elowly so that a t the end of 6 hours it reached a temperature of 1800" F. An iron cylinder 14 inches in diameter, 7 inches tall, and inch 1hick was constructed. I n the bottom of the cylin1 2
Received April 23, 1024. Bur. Mines, Bull. 129 (1918).
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E
FIG.I-MOLD FOR REFRACTORY CRUCIBLE A , the inner cone fits into groove D and is held in place by an iron rod, C,which is riveted t o the bottom of the cone on one end, and to strip S at the other. B is theouter cone which fits into groove E and is held in place by the screws G and G.'
der was cut a hole 11 inches in diameter. This cylinder was then slipped over the middle cylinder of the No. 3 melter's. The observation hole and the thermocouple hole were cut in the outside cylinder to correspond with that of the inner one, and the observation tube and thermocouple tube were put in place. Five parts of alundum cement and 3 parts of kaolin were mixed with water and worked until a smooth, thick paste was obtained, which was used to fill the space between the two cylinders. The cylinder was air-dried for 24 hours. The furnace was then heated slowly so that a t the end of 8 hours its temperature was about 1200' F. It was cooled overnight. During the next S hours the temperature was allowed to rise to 2200" F. The furnace was now ready for a regular run. At 2850 " F. the fire clay crucible melted. Further heating wasimp o s s i b l e , since the "melt" blocked up the burners. S i n c e negotiations for making a refractory crucible of the desired thickness were unsuccessful, it was accordingly decided to make FIG. 2 - o B S E R V A T I O N A N D THERMOCOUPLE some crucibles. The HOLESCUT I N S T R I P OF LEAD mold was made as in Fig. 1. Great care was taken to have the surfaces that come in contact with the clay very smooth. Five parts of alundum cement and 3 parts kaolin were well mixed and worked up with water until the mixture was so dry that it almost crumbled. It was then hammered into the mold. Part B was tapped gently and it came off. Then A was inverted, lightly tapped, and the crucible slipped off. With a strip of lead as a guide (Fig. 2 ) the observation and the thermocouple holes were cut, in the crucible while it was still wet. The crucible was then allowed to air-dry overnight. The foregoing requires a little experience, and the novice can hardly expect to get a perfect crucible the first time. The mold must be very smooth and well greased. The clay must be neither too wet nor too dry. Should the clay appear too wet after part B of the mold has been removed, it will do no good to let the clay dry on part A , because it will crack while drying. It is best to use a dryer mixture a t once. A cover for the crucible is easily made without a mold. It was made 3/q inch thick. A solid cylinder shaped to fit the crucible and tall enough to reach to the bottom of the observation hole was also made out of the same mixture. After air-drying overnight, the crucible, cover, and cylinder were all dried on a hot plate for several hours, after which they were placed in the furnace and baked very slowly for a day. The mahimum temperature reached was 1800" F. They were allowed to cool slowly and the temperature reached this time was 2500" F. a t the end of 8 hours. The next day a run was made as specified in the Tentative Method for the Determination of the Fusing Point of Coal
I N D USTRIAL A N D ENGINEBRING CHEMISTRY
848
Ash.3 Readings in degrees Fahrenheit taken every 5 minutes were as follows: 1482,1608,1716, 1806, 1878, 1950,'2022,2094, 2146, 2198, 2250, 2300, 2354, 2410, 2458, 2510, 2562, 2615, 2666, 2725, 2770, 2828, 2880, 2935, 2990,3015,3045
The temperature measurements were made with a Leeds & L~~~ No. 4391 ; Telescope No. Northrup 63,359; Ammeter No. 66,693; it was standardized by the U. S. Bureau of Standards, Washington, D. C. (B. S. Test No. Ttp-33,767), on April 4, 1922. It was rechecked on 8
Proc. Am. SOC.Testing Materials, 20, 796 (1920).
Vol. 16, No. 8
April 15,1924, by checking the fusing points of samples of coal ash, the fusing points of which were determined by the s' Bureau Of Mines author a t the laboratories Of the through the courtesy of A. C. Fieldner, superintendent of the Pittsburgh Station. The same batch of cones was used and the results checked within 20' F. a t 2900" F. The rise in temperature is surprisingly uniform and a reducing temperature can be maintained through the entire run. The most pleasing feature of this experiment is the durability of the crucible. Seventy-five runs have already been made with it, and it shows no signs of wear. It promises to be good for another fifty runs.
Preparation of Guanidinium Salts from Calcium Cyanamide' By J. S. Blair and J. M.Braham FIXEDNITROGEN RESSARCHLABORATORY, WASHINGTON, D. C.
HILE guanidinIt is believed, however, Guanidinium salts can be advantageously produced only from ium salts havenot that the method described cyanamide or its derivatives. The methods heretofore deoeloped for as yet become inin the present paper, involvits production have entailed either the ammonation, in nonaqueous dustrially important, there ing as it does the utilization solution, of cyanamide itself, or the ammonation or hydrolysis of appear to be a number of of neutralized aqueous exdicyanodiamide. The use of cyanamide in its most readily and uses to which they may be tracts of calcium cyanamcheaply available form-i. e., in the aqueous solution in which it may devoted when they become ide, offers important adbe obtained by extraition of crude calcium cyanamide with water-has cheaply available in large vantages over any methods apparently not hitherto been considered practicable. The presquantity. Nitroguanidine, using d i c y a n o d i a m i d e, ent paper describes the conditions under which about 80 per cent of for example, seems to give since, as will later be shown, the cyanamide contained in such solutions may be convetted to considerable promise as an it gives a better yield, a guanidinium salts by heating under pressure with ammonium salts. explosives i n g r e d i e n t . purer product, and constiGuanidinium hydroxide is tutes a more direct process. an unusually strong organic base,2 and guanidinium carbonEXPERIMENTAL PROCEDURE ate, which can be prepared in a very pure state, has been Solutions of free cyanamide, HsCNZ, were' obtained as suggested as a standard in alkalimetry.* Crude calcium cyanamide was gradually added to follows: In the early methods for the preparation of guanidinium salts, by the fusion of ammonium thiocyanate,4 cyanamide is about five times its weight of cold water, and after vigorous thought to be formed as an intermediate. These methods are mechanical agitation for 2 hours the insoluble material much inferior to the processes that have been devised since was filtered off and washed; the filtrate was immediately the development of the cyanamide process of nitrogen fixa- neutralized accurately with sulfuric acid, the calcium sulfate tion, which gives a more direct and much cheaper source of filtrated off and washed, and the neutral solution concentrated the cyanamide. The methods described in the literature for to about 375 grams cyanamide per liter at a temperature not synthesis of guanidinium salts from cyanamide itself6 in- exceeding 80" C. This was accomplished by heating in a volve the isolation of solid cyanamide ina relatively pure state, large dish on a steam bath and passing a blast of air over the a step which it would be advantageous to avoid. The use of surface. The precise cyanamide content of this solution was cyanamide in aqueous solutions such as are readily obtained then determined by analysis, and measured quantities of from calcium cyanamide has not heretofore been considered ammonium salt and water were added to give the solution the practicable, apparently because of an insufficient understand- composition desired for heating. The solution was then anaing of the conditions governing the stability of cyanamide lyzed for total nitrogen, cyanamide, ammonia, dicyanodiamide, solutions. For this reason, the more recently developed and urea. The two last-named compounds were always presmethods have involved the utilization of dicyanodiamide, ent in very small amounts. I n all but a few preliminary experiments 100 cc. of solufrom which guanidine can be produced either by hydrolysis6 tion were used, the heating being performed in small steel or by ammonation.? autoclaves with enameled interior surfaces, heated by means of Received March 18, 1924. oil baths. The temperatures and pressures inside the autoOstwald, J . p r a k t . Chem., 121 88, 367 (1888). claves were measured in some cases. d Dodd, J . SOC. Chem. I n d . , 40, 89T (1921). In most of the experiments ammonium nitrate was used, 4 Delitsch, J . prakl. Chem., [21 9, 1 (1874). 5 Erlenmeyer, AWL, 146, 259 (1868). Bannow, Bey., 4, 161 (1871); because guanidinium nitrate is only moderately soluble in Volhard, J . prakl. Chem., [2] 9 15 (1871); Ewan and Young J . Soc Chcm. water and is hence more easily recovered from solution in a Ind., 40,189 (1921). (Volhard did not use aqueous solutions as stated by pure state than are the other common guanidinium salts, Ewan and Young but fused together solid cyanamide andsn ammonium salt.) which are extremely soluble. The method is otherwise not Ulpiani, D. R. Patent 209,431 (October 16, 1907). Stolle and Rrauch, B e . , 46, 2337 (1913); Levene and Senior, J . B i d . Chem., 25, 623 (1916); restricted to the use of any particular ammonium salt, Davis, J . A m . Chem. Soc., 48, 669 (1921). however. 7 Spandau Stickstoffwerke, D. R . Patent 222,552 (October 30, 1908); The contents of the autoclaves after beating consisted of Werner and Bell, J . Chem. SOC.( L o n d o n ) , 4 8 ,669 (1921); Ewan and Young, yellow solutions of disagreeable odor. Small quantities of bc. dl.; Davis, J . A m . Chem. SOC.,48, 2234 (1921).
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