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 ment of this same piece of material would indicate the difficulty of converting the 5Ca0.3A1203 into tricalcic aluminate, even in the presence of a large excess of CaO. Tri-calcic aluminate seems t o be best formed when the 5Ca0.3A1203 is held for a very long time in contact with CaO a t a temperature just above the melting point of t h e eutectic solution of CaO (139g’), b u t below t h e melting point of the pure 5Ca0.3A1203 (1455’). Under these conditions, if tri-calcic aluminate is either a metastable saturated solid solution of CaO in gCa0.3A1203 or is gCa0.3Al2O3 with four molecules of CaO of crystallization, it would gradually form and separate or crystallize from t h e still fluid solution until in time saturation of t h e whole of t h e gCa0.3Al203 had taken place. The entire mass would thus be converted into tri-calcic aluminate, unless there were present a n amount of CaO in excess of what would be required t o form tri-calcic aluminate with all of t h e Alz03. If t h e problem is considered as a simple study of t h e solubility of CaO in gCa0.3A1203 we would then regard a mixture having t h e empirical formula 4CaO A1203 a t 1600’ as a saturated fluid solution of CaO in 5CaO.3Al2O3 with some undissolved crystals or grains of CaO in suspension. On cooling such a solution a t the rate of 25’ per hour, since t h e solubility of the CaO in gCa0.3Al203 is a function of the temperature, t h e grains or crystals of CaO in suspension would gradually grow a t t h e expense of t h e dissolved CaO, so t h a t a t any time during t h e cooling period down t o the solidifying point of the eutectic solution the mass would consist of crystals or grains of CaO in a matrix made up of a solution of CaO in gCa0.3A1203 saturated a t t h e temperature a t which the material is held. Since t h e separation of tri-calcic aluminate seems t o require t h a t the solution of CaO in gCa0.3AlzO3 be slightly supersaturated and held a t a constant temperature for a very long time, and since t h e “ G - I ” and “G-3” mixtures were in a supersaturated state below the melting point of tri-calcic aluminate for three hours only, comparatively little tri-calcic aluminate would separate. Three hours compared with twenty-one days is a short time, but even in three hours some tri-calcic aluminate might be expected t o be found if a careful petrographic examination of the material were made. The composition of t h e liquid drawn off from “G-3” a t temperatures between 1438 and 1446’ agrees, as closely as experimental work could be expected, with t h a t of a solution having t h e same melting point as shown in t h e diagram in Plate I.
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Vol. 9, No.
IO
LOW TEMPERATURE DISTILLATION OF LIGNITE COAL By H. K. BENSONAND L. L. DAVIS Received August 6, 1917
The use of lignite coal for t h e production of paraffin and illuminating oils by destructive distillation has been developed t o a considerable extent in the SaxoniaThuringia lignite belt of Germany.l For this purpose soft, friable “wax coals” were distilled a t about 200’ C. under a slight vacuum for 24 hours, yielding the following products: tar, 6 t o 8 per cent; coke, 3 2 t o 36 per cent; t a r water, 46 t o 5 0 per cent; and gas, I O t o 1 2 per cent. From t h e distillation and refining of t h e crude oils were obtained a light lignite oil (“benzin”), distilling under 150’ C., with a specific gravity of 0.780 t o 0.810 and a flash point of 2 5 t o 30’ C . ; a burning oil (“solarol”), boiling below 250’ C., with a specific gravity of 0.825 t o 0.830 and a flash point of 50’ C.; a solvent oil (“putzol”) boiling up t o 280’ C., with a specific gravity 0.850 t o 0.860 and flash point, 100’ C.; together with paraffin oil, soft and hard paraffin and creosote oil. Ammonia may be recovered from t h e t a r water, though it is generally used directly as a fertilizer. The coke does not “cake” as does t h a t of ordinary coking coals, but shrinks slightly during distillation and is generally briquetted for use as a fuel. I n 1908, 1 2 factories, employing 1 2 2 1 workmen, were engaged in refining lignite oils.2 Inasmuch as a large portion of the coals of Washington and of t h e West‘in general are of a lignite character a study of a representative Washington lignite coal was made t o determine t h e yield of oil from the coal and t h e relation of t h e temperature of distillation t o t h e nature of t h e products obtained. DESCRIPTION
OF THE SAMPLE
The coal used was a representative sample of black lignite from t h e Hannaford No. I Mine, Tono, Washington. It is black in color, with a brown streak, is slightly banded in structure and breaks with a conchoidal fracture. The coal slacks on exposure t o air, but may be shipped some distance without weathering if placed in closed cars. The only use made of t h e coal a t t h e present time is as a steam coal in specially designed locomotives. The proximate analysis of the coal is given in Table I : TABLS~-PERCENTAGE COMPOSITION OF TONO LIGNITE CAR SAMPLE LABORATORY 474, 75) SAMPLE PERCENTAGES: As Received Air Dry Pure Coal Air Dry Moisture.. ............ 2 0 . 2 14.5 . . . . . . 12.3 Volatiles. 31.5 33.5 44.0 40.8
(U.5‘. Geol. Survey, Bull.
.............
Fixed . . . . . . . .......... Ash., . . . . . . . . . . 3 89 . 94 Sulfur. . . . . . . . . . . . . . . . . 0 . 5 2 Nitrogen.. . . . . . . . . . . . 1.06 B t. u . . . . . . . . . . . . . . . . 9.280
4 93 ..095 0.56 1.14 9,940
5. 6. ..0. . . 0.73 -1.49 13,000
3 79 . 81 0.3 1.60 9,650
CONCLUSIONS
I-A binary system of CaO and A1203 containing more t h a n 4 7 . 8 per cent ca0 should be regarded as a study in solubility of CaO in gCa0.3A1203. 11-Tri-calcic aluminate should be regarded either as a metastable saturated solid solution of CaO in jCa0.3A1203, or as gCa0.3A1203 with four molecules of CaO of crystallization, rather t h a n as a stable phase in t h e strict sense of the word. UNIVERSITY
OF
MICHIGAN,ANN ARBOR
APPARATUS U S E D
The retort used in distilling t h e coal was constructed as in Fig. I. A piece of standard black 3-in. pipe ( A ) 18 in. long was closed a t one end with a cap and a t the other with a companion flange and blind flange. The blind flange was bolted t o the face with t w o 1 Dammer, “Handbuch, der Chemiscben Technologie,” 4, 135-148; Ludwig Medicus, “Lehrbuch der Chemischen Technologie,” 965-977; Fischer, “Handbuch der Chemischen Technologie.” 141-153. 2 Z. angew. Chem., 1909, 2072.
OCt., 1917
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
S/4-in. bolts, t h e companion flange being threaded t o receive t h e bolts. The face plate was turned smooth in a lathe t o obtain a tight fit. T h e flange was made perfectly air-tight by means of a n asbestos gasket, well rubbed with flake graphite and oil. T h e face plate was tapped for t h e outlet pipe ( F ) a n d a pyrometer‘ socket (P). A ’/B-in. pipe ( M ) was tapped in t h e cap a t t h e back of t h e retort a n d connected t o a manometer for measuring t h e pressure in t h e retort. The heating element was of nichrome wire f / G
1
r2 1
.*.
c-“
I
_I
1,.
$
$
R
947
lasted 24 hours, during which time t h e temperature was held constant and t h e p u m p so regulated t h a t t h e pressure within t h e retort was atmospheric. At t h e completion of a run t h e hot coke was drawn out and placed in a n air-tight can t o cool. The wash bottles were removed a n d clean bottles p u t in their places and a new charge of coal placed in t h e retort. Gas samples were drawn from t h e system a t intervals and analyzed. The coal was prepared for distillation by passing through a jaw crusher. The coal which passed through a 4-mesh a n d remained on a 40-mesh sieve was used.
c =
YIELD O F RAW PRODUCTS
The yields of raw products a t different temperatures are recorded in Table 11.
w
I
The pipe was first insulated with two layers of miconite ( B ) :40 f t . of KO.14 nichrome wire ( N ) was then wound on, t h e individual turns being separated with asbestos cord ( I ) . T h e heating unit was then covered with alundum cement ( C ) . T h e retort was then placed in a metal lined box, on fire-brick supports (S) and was packed with powdered diatomaceous earth (D) as a heat insulator. T h e nichrome wire was brought out in leads through porcelain tubes ( t ) and was connected t o t h e I Io-volt alternating current lighting circuit. T h e temperature was controlled b y means of a resistance rheostat ( R ) having a capacity of 50 amperes. A copper advance couple and millivoltmeter was used for temperature measurements.
TABLE11-YIELDS OF DISTILLATIONP R O D U C T S Total Dry Aqueous COKE Distillate Tar Solution Per Per cent Per cent Per cent cent 87 7 12.3 12.3 77.3 22.1 22.1 ... 63.8 21.3 24.9 3.6 3 .5 63.8 21.7 25.2 22.2 56.0 4.9 27.1 57.2 21.9 4.9 26.8 54.2 21.4 5.4 27,3 22.0 53.8 5.1 27.1 54.4 22. 1 5.4 27.4 53.9 22.1 4.6 26.7 21.8 53.7 4.4 26.2 52.6 21.4 4.2 25.6 52.6 21.6 4.2 25.8 51.2 20.9 4.1 25.0 .... ... .... 51.4 25.2 4.0 21.2 51.1 24.9 3.8 21.1 50.1 25.0 3.9 21.1 49.8 24.6 3.4 21.2 48.8 24.4 3.5 20.9 48.9
Temp.
c.
100 200 250 250 330 330 380 3 80 380 415 415 450 450 490 49 0 490
550 550 600 600
GAS c u . ft. per ton
....
200 1900 1700 3800 4000 4400 4200 4400 6100 5800 7500 7800 8700
....
8COO 9600 9800 9800 9700
GAS
The washed gas was measured in a Sargent wet test meter. T h e yields are indicated by Fig. 111. The gases were sampled and analyzed in a Moorehead gas apparatus a n d t h e percentage compositions are given in Table 111. TABLE111-PERCENTAGE
FIG. LT
C.
COz 82.4 52.1 38.2 14.6 10.2 4.8 4.4 3.6 3.0
Ill. 0.0 0.0 0.0 0.8 0.8 1.0 0.8 1.2 1.6
Oz 0.0 1.2 1.8 1.1 3.2 0.8 ,1.4 1.6 2.2
COYPOSITIONS CO Hz 12.2 0.0 0,0 13.4 14.0 8.2 13.1 18.1 20.0 13.2 32.6 15.6 34.8 15.4 35.2 17.2 19.6 35,4
OF
GASES CHI 0.0 0.0 1.4 17.2 17.0 21.3 23.9 24.2 24.4
Kz 5.4 33.3 36.4 35.1 35.6 23.9 19.3 17.0 14.8
T h e calorific values calculated b y Lunge’s method‘ are plotted against t h e temperature of distillation in Fig. IV. Fig. I1 gives a diagrammatical sketch of t h e set-up. T h e distillation gases passed from t h e retort ( R ) t o t h e t a r extractor ( T ) , thence through t h e Liebig condensers ( L ) t o t h e wash bottles ( A ) , (C) a n d (0),a n d finally through t h e gas meter ( M ) t o t h e exhaust pump. T h e t a r extractors a n d washers consisted of 16-02. wide-mouth bottles. T h e first washer ( A ) was for ammonia and contained slightly acidified water, t h e second (C) was for cyanides a n d contained a suspension of ferrous carbonate in water. T h e third washer f 0 ) was a n oil scrubber a n d was filled with a high flash lubricating oil. T h e retort was heated t o t h e desired temperature a n d weighed wash bottles were p u t in place. One kilogram of coal was t h e n placed in t h e retort, t h e apparatus closed, and t h e exhauster started. A run
LIGNITE RESIDUE O N COKE
T h e coke or residue differs from t h a t obtained from coking coals. It is dull black in color and retains t h e size a n d shape of t h e original particles. I t s composition is given in Table IV, showing t h e yields per t o n of coal and Fig. V shows t h e increase in calorific value with increase of temperature. TABLE IV-YIELDS Temp. 0
c.
100 200 250 330 380 415 450 490 550 600 1
Coke
Lbs. 1754 1546 1276 1120 1092 1078 1052 1024 1002 976
AND
Voletiles Per cent 46.6 34.3 26.5 16.2 14.0 12.9 10.8 8.4 6.4 3.9
COMPOSITIONS OB LIGNITE COKE Ash Nitrogen Per cent B. t. u. Per cent 1.8 11,000 8.1 9.2 1.4 11,800 0.8 12,200 11.1 0.5 12,570 12.7 0.5 12.710 13.0 0.3 12,740 13.1 0.3 12,750 13.5 13.8 0.3 12.760 0.2 12,810 14.1 0.2 12.850 14.5
“Technical Methods of Chemical Analysis.” Vol. 11, P a r t 1. p. 694
948
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
AMMONIACAL
LIQUOR
T h e aqueous distillate was tested for ammonia a n d cyanides. T h e latter were present only in traces at t h e higher temperatures b u t t h e yield of ammonia in lbs. per t o n is given in Fig. VI. L I G N I T E OILS
The oily portion of t h e crude distillate was extracted with ether a n d t h e latter distilled off a t 50' C. T h e TABLEOMPOSI POSITION OF LIGNITE OIL Coke GAS Light Oil Medium Oil Paraffin Oil Temp. 4.0 2.9 28.6 41.1 25OOC. 23.4 2.0 41.4 4.4 28.4 330 23.8 4.2 2.0 27.4 42.4 380 23.9 6.2 2.4 27.5 41.3 415 22.5 33.3 28.8 6.1 2.5 450 24.4 2.0 20.9 26.7(a) 26.4 490 24.2 31.8 1.8 28.2 18.8 550 19.0 24.5 18.2 36.1 2.2 600 19.2 ( a ) At 490° thecharacter of the t a r so changed t h a t a crystalline paraffin mass could not be obtained by-distillation and the residue resembled ordinary coal-tar pitch. TABLEVI-YIELD Temp. 250° C.
330 380 415 450 490 550 600
Raw T a r 72 98 108 92 84 82 76 68
OF OILS IN POUNDS PER TONOF COAL Light Oil Medium Oil Paraffin Paraffin Oil 16.8 20.6 3.8 25.8 23.3 27.6 5.6 34.9 25.8 29.3 6.9 38.9 20 7 25.3 5.5 32.5 24.1 28.0 3.5 20.6 19.9 21.7 17.2 ... 14.3 14.4 21.5 ... 12.4 13.0 16.7
IO
distilled in small glass retorts and t h e percentage yields are given in Table V. I n Table VI t h e yields per t o n of coal are given, including also t h e paraffin separated b y Eisenlohr's method.' CHEMICAL P R O P E R T I E S O F L I G N I T E OILS
T h e light oils were washed with sodium hydroxide and sulfuric acid, 3 2 per cent being soluble in alkali. The washed oils were treated with concentrated nitric and sulfuric acids in a reflux condenser b u t no evidence of t h e formation of nitro derivatives was obtained. The cresols obtained from t h e alkali washings were tested with bromine waterbut no phenols were isolated. The specific gravities of t h e oils were obtained by means of a pipette pycnometer, made by blowing a small bulb in a capillary tube. The gravities of t h e various fractions are given in Table V I I . TABLEVII-SPECIFIC TemD. 2500 330 380 415 450 490 550 600
...
crude oil t h u s resulting was dark brown in color and was solid at ordinary temperatures. I t s specific gravity at 15' C. was 0 . 9 8 5 t o 0 . 9 9 5 . At 550' C. t h e oil was black with a gravity of 1.000and at 600' C. it was slightly heavier t h a n water. T h e oils were
Vol. 9 , No.
c.
Linht Oil
GRAVITIES OF LIQNITE OILS Medium Oil Paraffin Oil
0.876 0.870 0.868 0.864 CONCLUSIONS
I-The maxiinum yield of lignite oils is obtained by distilling at 380' C. 1
Z. angew. Chem., 1897, 300-326, 332-336.
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
OCt., 1917
11-About j . 5 per cent of t h e coal may be obtained as raw oils. 111-These raw oils are more similar t o petroleum a n d shale oil t h a n t o coal t a r , there being no benzol or benzol derivatives present. IV-Lignite raw oils will give valuable solvents, burning oils, engine fuel oils, and lubricating oils. V-About seven pounds of paraffin wax per t o n of coal may be obtained. VI-The gas resulting from t h e low temperature distillation of lignites is of low heat value a n d is small in volume. VII-Small quantities of ammonia can be obtained from lignite t a r water. VIII-The residue from lignite distillation is a valuable fuel having a calorific value of over 12,000 B. t. u. per lb. IX-Due t o t h e small unit used i t is impossible to determine t h e commercial feasibility of lignite distillation, b u t sufficient d a t a have been obtained t o warrant a semi-commercial test t o be made upon t h e Tono lignites. LABORATORY OF
INDUSTRIAL CHEMISTRY UNIVERSITY O F WASHINGTON
SEATTLE. WASHINGTON
THE DETERMINATION OF SULFUR DIOXIDE By 0.
R . SWEENEY,
HARRYE. OUTCAULTAND
JAMES
R . WITHROW
Received May 31, 1917
The accurate determination of sulfur dioxide in gas mixtures is a matter of great importance a t the present time. T h e control of sulfuric acid plants, t h e investigation of air charged with fumes from smelters, t h e regulation of community nuisances from high pressure sulfuric acid concentration in unreasonable proximity t o residential districts, a n d t h e analysis of t h e products from t h e explosion of gunpowder are some of t h e cases where such a determination is necessary. Since t h e sulfur dioxide is nearly always accompanied by sulfur trioxide, those methods which oxidize t h e dioxide a n d weigh i t as barium sulfate are not suited t o this kind of work. The nature of such investigations generally requires a volume of determinations a n d therefore speed of method is strongly desired. T h e titration of t h e sulfur dioxide with standard iodine solution has been developed into a satisfactory method by t h e “Selby Smelter Commission” a n d is described in t h e Bureau of Mines Bull. 98. The objections t o this method are t h a t i t uses a n iodine solution which must be frequently standardized a n d is so sensitive t o t h e action of light t h a t a blank must be run during t h e determination. Potassium permanganate is known t o be a n oxidizing medium for sulfurous acid. Since its solution is more stable t h a n t h a t of iodine, a n d can be used without a n indicator, i t is a more inviting reagent t o use. I n applying permanganate, however, it was found t h a t thereaction did not give results which would beexpected if t h e sulfurous acid were oxidized completely t o sulfuric acid. There was fair agreement among t h e
949
results themselves, however. Dymond and Hughes,’ who studied this reaction exhaustively, found t h a t a part of t h e sulfurous acid was oxidized t o t h e dithionate accordingly t o t h e equation 17H2SOa 6KMn04 = 2K2S206 K t S O l + 6MnS04 6H2SOa 11H20. This explained our failure t o get results in accordance with a complete oxidation t o sulfuric acid. They also found t h a t this reaction is not modified b y t h e concentration of sulfuric acid present, t h e temperature, or b y t h e dilution of t h e solution. Our results confirmed all of this, except t h a t t h e concentration of t h e sulfuric acid must be within certain wide limits, a n d there must always be a n excess of permanganate present. A very considerable amount of. experimenting was necessary before t h e proper conditions for making titrations were obtained. It is necessary t o record here only t h e conditions which were finally found t o give proper results. It was found t h a t 0.005 N potassium permanganate was t h e best strength t o use. Under proper conditions t h e effect of one drop could be observed, a n d t h e low normality made a high degree of accuracy possible. One drop of such a solution corresponds t o 0.000009 g. SOz. Should t h e concentration of sulfur dioxide be very large a stronger solution should be used. The‘solution was prepared by diluting t h e laboratory stock solution, and, after standing for several days, was standardized. Satisfactory results were obtained b y using thiosulfate, b u t in order t o duplicate more, nearly t h e conditions of t h e actual analysis sodium sulfite was used. Both Dymond a n d Hughes, a n d t h e Selby Smelter Commission used sodium sulfite for their standard. The sodium sulfite was purified b y a series of recrystallizations from water, after which i t was dried. Weighed quantities were dissolved in water a n d definite portions were pipetted out a n d titrated. Measured volumes of pure sulfur dioxide gas were also dissolved in water and portions were titrated a n d found t o check t h e sulfite method as did other methods of standardizing. As was stated above, t h e permanganate must always be present in excess. For this reason i t was impossible t o titrate t h e sulfurous acid directly. Recourse was had t o t h e scheme of t h e Selby Smelter Commission. A certain amount of t h e permanganate was run into dilute sulfuric acid solution, and, after mixing, was divided into two equal parts. T h e sulfur dioxide was dissolved in one of t h e parts and standard permanganate was then added from a burette until t h e color again matched t h a t of t h e other portion. Of course, such a n amount of permanganate was added as would oxidize t h e sulfur dioxide a n d still be in excses. Experiments showed t h a t t h e best color t o match was produced b y adding I O cc. of approximately 0.005 N permanganate t o 490 cc. of water. It was observed t h a t after t h e permanganate was reduced, t h e color on back titration did not exactly match t h e original, b u t h a d a slightly redder tinge. If, however,
+
1J
+
. Chcm. SOC.,71, 314.
+
+
