Aug., 1 9 2 0
T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
783
then pulverized t o 60 mesh and the residual moisture I-Freezing-point determinations were made on determined by heating a one-gram sample for one three sets of mixtures of sulfuric and nitric acids, having hour at 10.5' C.l Experiments made by t h e Bureau2 total acidities of 100,95, and 103 per cent, respectively, have shown t h a t total moisture in coke can be determined with adequate accuracy ( * 0 . 5 per cent) for and nitric contents varying from zero t o 5 0 per cent. a-The freezing-point curve for the IOO per cent most purposes by simply heating t o constant weight acidity mixtures was found t o reach a minimum when a large sample of lump coke, in any convenient oven, the nitric acid content was 5.4 per cent. The maxi- or on a stove, hot plate, or steam coil, a t a temperature mum was attained with a nitric acid content of 10.8 of 105'to zooo C. per cent. The curve showed a marked resemblance The standard methods of analyzing coke as given to t h a t of sulfuric acid and water. by the American Society for Testing Materials8 state 3-It seemed probable t h a t the composition, a t the t h a t t h e total moisture shall be determined by drying above maximum, represented a definite chemical t h e entire sample received at t h e laboratory without compound between sulfuric and nitric acids, t h e acids any preliminary crushing t o constant weight at a at t h a t point being present in t h e proportion 5H2SO4- temperature of not less than 104' or more than zooo "01. C., and t h a t t h e loss in weight is to be calculated as 4-The freezing-point curves for t h e 9 j and 103 per percentage of moisture which shall constitute t h e total cent mixtures were complicated by t h e presence of a moisture in the coke as received in the laboratory. third constituent. No attempt, therefore, was made The sample for analysis crushed to a fineness of 60 t o explain them. mesh is prepared from t h e dried coke without any regard t o changes in moisture content. Moisture is then determined on the 60-mesh material by heating HYGROSCOPICITY OF BY-PRODUCT COKE' a one-gram sample of the coke for one hour in a suitBy W. A. Selvig and B. B. Kaplan able oven at a temperature of 104' t o 110' C. The FUELSCHEMICAI, LABORATORY, PITTSBURGH EXPERIMENT STATION, PA. BUREAUOF MINES, PITTSBURGH, moisture obtained on the 60-mesh material is used Received April 9, 1920 simply to calculate t h e determinations made on this The experiments described i n this paper were under- material t o a dry basis. The total moisture as detertaken. in order t o obtain data as t o t h e amount of mined on t h e lump size sample is taken as t h e total moisture absorbed by dry pulverized coke on exposure moisture content of the coke, and the air-dry figures, t o air of varying humidity in connection with methods2 are then calculated t o the "as received'' condition. used in many commercial laboratories for t h e analysis OUTLINE O F E X P E R I N E N T S of coke. Four samples of coke were selected for the tests, I n these methods t h e sample for total moisture one sample of beehive coke and three samples of bydetermination is taken from t h e regular sample for product coke. These samples had been previously analysis by reserving one or more rejected quarters air-dried and crushed t o pass through a 60-mesh sieve. after t h e sample has been crushed t o half-inch size. The analysis and origin of these samples are given in Moisture is determined in I O lbs. or more by drying t o Table I. approximately constant weight at a temperature of TABLEI-AIR-DRIED 60-MESH COKE SAMPLES USED IN TESTS 105' C. The laboratory sample for analysis is prePER CENT pared by crushing and reducing t h e regular sample ORIGINOF Mois- Volatile Fixed No. SAMPLE ture Matter Carbon Ash Sulfur until about one pound of 40-mesh material remains. 31177 Connellsville 72-hour beehive A sufficient amount of this 40-mesh material is transfoundry c o k e . . . . . . . . . . . . 0 . 1 5 1.56 89.09 9.20 0 . 7 8 31075 By-product furnace coke from ferred t o a bottle and dried for one hour a t 105' C. Franklin County, Ill., coal 0 . 9 8 2 . 5 3 83.79 12.70 0 . 8 8 33754 By-product domestic size coke No moisture determination is made in the laboratory (source of coal unknown). 0 . 5 0 1.98 85.79 11.73 0 . 8 2 31677 By-product domestic size coke on t h e dried material, i t being assumed t h a t t h e coke frornPittsburghbedcoa1.. 0.56 2 . 8 0 79.46 17.18 0 . 8 9 will not absorb appreciable amounts of moisture from the air. It is evident t h a t , if t h e pulverized sample One-gram samples of the 60-mesh coke were weighed of coke did absorb appreciable amounts of moisture i n duplicate into porcelain capsules, dried i n an oven between t h e time of drying and the weighing of t h e for one hour at 105' C., cooled over sulfuric acid i n various portions for analysis, t h e analysis would be in desiccators, and weighed, t h e loss i n weight being error corresponding t o t h e amount of moisture absorbed. recorded as moisture. I n order t o prevent any changes The volatile matter determination, especially, would in moisture during t h e weighing of the samples, all be too high. weighings throughout the test were made by placing STANDARD MOISTURE DETERMINATION METHODS t h e porcelain capsules containing the samples in glass When a high degree of accuracy is desired, the weighing dishes provided with tightly fitting ground moisture in coke is determined in two stages. The caps. coke is crushed t o one-half or one-quarter inch size The uncovered crucibles and contents were placed and air-dried t o approximately constant weight at a in one-quart Mason jars containing mixtures of sultemperature of 30' t o 35' C. The air-dry sample is SUMMARY
Published by permission of the Director of the Bureau of Mines. * United States Steel Corporation, "Methods for the Commercial Sampling and Analysis of Coal, Coke, and By-products," 1916, p. 18. 1
1 F. M. Stanton and A. C. Fieldner. Bureau of Mines, TechnicaE Pager 8 (1913), 7. 2 A C. Fieldner and W. A. Selvig, Ibid., 148 (1617), 14. 8 Am. SOC.Test. Mat. Standards. 1919, 711.
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
784 TABLE11-PER
No. 31177 31075 33754 31677
CENT
MOISTURE ABSORBED BY I-G. COKE
SAMPLES AFTER DRYING AT PER CBNT HUMIDITY AT
Per cent Moisture on 1-G. Sample Heated Hours 1 Hr at of SOURCE O F COKE 105O C. Exposure 1 0.15 Connellsville 72-hr. beehive foundry coke 6 18 1 By-product furnace coke from Franklin Co., Ill., coal.. 0 . 9 8 6 18 1 By-product domestic size coke (source of coal unknown) 0 . 5 0 6 18 1 By-product domestic size coke from Pittsburgh bed coal 0 . 5 6 6 18
. . . . . .. . . . . .
.
furic acid and water t o give a range of humidity in the air above the acid of 25, 50, and 80 per cent a t 28' C. The acid was placed in the jars t o a depth of about 2 in. and the porcelain capsules were supported by glass triangles in the air above the acid. The jars containing t h e acid were completely submerged in a water bath provided with a thermostat which maintained a temperature of 28' C. ( * o o . 2 ' C.) throughout the test. After the jars and contents had been submerged in the water for a sufficient time t o come t o the temperature of the bath, the porcelain capsules containing t h e dried coke samples were heated in an air oven t o approximately 40' C., and quickly placed in the jars above the acid. This preliminary heating t o 40° C. was made t o prevent any condensation of moisture on the capsules or contents which might result if the capsules and contents were a t a lower temperature than the air in the jars. The various coke samples placed in the jars giving humidities of 25, 50, and 80 per cent a t 28' C. were allowed t o remain for periods of I , 6, and 24 hrs. a t each of these humidities. At the end of these periods the capsules containing the samples were quickly removed, placed in covered weighing dishes, allowed t o come t o room temperature, and weighed. The results of these tests are given in Table 11. Tests were also made on one-gram samples of t h e same cokes weighed in porcelain capsules, dried for one hour a t 105' C., and allowed t o stand exposed t o the air in the laboratory, weighings being made a t intervals covering periods of 24 hrs. Temperature a n d humidity readings were made a t the time of the different weighings. The results of these tests are given in Table 111. TABLE111-PER CENT MOISTURE ABSORBED BY I-G. COKE SAMPLES AFTER DRYINGAT 105O C. FOR 1 HR., WHEN EXPOSED TO AIR O F LABORATORY Per cent Moisture Average on I-G. RelaUndried tive Coke Aver- Hu(Heated age midity Per cent Moisture Absorbed by Dry Coke 1 Hr. at Tzrnp. Per , -Hours of Exposure No. 105' C.) C. cent 1 1.5 2 3 4 5 7 24 31177 0.15 22 20 0 . 0 6 0 . 0 8 0 . 0 9 0.10 0.10 0 . 1 1 0 . 1 4 0 . 1 1 31075 0.98 24 27 0.33 0.41 0.47 0.49 0 . 4 9 0 . 5 4 0.54 0 . 5 0 25 0.18 0 . 2 2 0.22 0.23 0.25 0.25 0.29 0.37 33754 0.50 23 23 26 0.17 0 . 1 8 0 . 2 2 0 . 2 6 0 . 2 6 0 . 3 0 0.35 0 . 4 6 31677 0.56
105' c. FOR 1 HR., WHEN 28' C.
Per 25 Per cent -Humidity1 2 Av. 0 . 1 5 0.15 0 . 1 5 0.19 0.17 0 . 1 8 0 . 1 6 0.15 0 . 1 6 0.39 0.43 0.41 0.53 0.54 0.54 0.52 0.56 0.54 0.26 0.26 0.26 0.41 0.41 0.41 0 . 4 0 0.41 0 . 4 0 0.19 0.19 0.19 0.52 0.55 0 . 5 4 0.50 0.52 0.51
Vol.
12,
EXPOSED TO AIR O F 25, 50,
No. 8 AND
80
cent Moisture Absorbed 50 Per cent 80 Per cent -Humidity-Humidity1 2 Av. 1 2 Av. 0.21 0.21 0.21 0.53 0.52 0 . 5 2 0.42 0 . 4 3 0.42 0.68 0.67 0.68 0.44 0.45 0.44 0.70 0.67 0 . 6 8 1.12 1.05 1.08 1 . 5 4 1.63 1.58 1.77 1 . 7 3 1 . 7 5 2.25 2.32 2.28 1 . 7 7 1 . 7 5 1.76 2.28 2.35 2.32 0 . 7 5 0 . 7 5 0.75 1 . 4 9 1 . 4 3 1.46 0 . 9 8 1 . 0 8 1.03 1.76 1 . 7 8 1.77 1.22 1.14 1.18 1.82 1.79 1.80 1 . 0 0 1 . 0 2 1.01 1 . 3 0 1.18 1 . 2 4 1.15 1 . 1 1 1.13 1.54 1 . 5 2 1 . 5 3 1 . 2 8 1 . 3 5 1.32 1.56 1 . 5 4 1 . 5 5
t h e winter months when t h e temperature of the laboratory air is considerably higher t h a n t h a t of the outdoor air, a relatively low humidity is likely t o prevail. Such conditions prevailed a t the time of making the tests, the laboratory air having a humidity of about 25 per cent. During the summer months when t h e temperature of t h e laboratory air and the out-door air is about the same, a relatively high humidity may prevail, and conditions comparable t o the 50 and 80 per cent humidity of Table I1 would result. As shown in Tables I1 and 111, the hygroscopicity of each coke was different. The three samples of byproduct coke absorbed moisture much more readily t h a n the sample of beehive coke. The cokes varied as t o t h e rapidity with which they absorbed moisture and as t o the amounts absorbed when they reached equilibrium with respect t o the moisture in the surrounding air. At 50 per cent humidity two of t h e byproduct cokes absorbed I per cent moisture in one hour. The gain in moisture between the 6- and 18hr. intervals was small, showing t h a t under the conditions of the test the cokes had practically come t o an equilibrium with the moisture in the air in less t h a n 6 hrs. Under these conditions the beehive coke had absorbed 0.4 per cent moisture, and one of the byproduct cokes had absorbed 1 . 7 per cent moisture. CONCLUSIONS
The tests show t h a t dry pulverized by-product coke rapidly absorbs moisture in appreciable amounts and t h a t different cokes vary considerably in hygroscopicity. T h e by-product cokes tested were more hygroscopic t h a n the beehive coke. This absorption may, under humidity conditions such as exist in the average laboratory, be sufficient t o cause appreciable errors in the analysis unless i t is determined and accounted for. The greatest error would occur in the volatile matter determination, as any absorbed moisture would be directly included in this determination. A safe procedure is t o make a moisture determination on the laboratory sample and take this result into consideration in calculating the analysis t o the dry coke basis. ACKNOWLEDGMENT
D I S C U S S I O N O F RESULTS
The range of humidity from 2 5 t o 80 per cent, as shown in Table 11, covers conditions t h a t may occur in the average laboratory during the year. During
Acknowledgment is made t o Mr. A. C. Fieldner, supervising chemist of the Pittsburgh Station of the Bureau of Mines, for helpftll suggestions as t o the method of making the hygroscopicity tests.
