Vol. 19, No. 1
INDUSTRIAL A N D ENGINEERING CHEMISTRY
144
Table 11-Experimental
0.366
Lbs. steam per lb. coal Coal used B. t. u. per cu. f t . , gross, 30 in. Hg, 60' F., Hz0 saturated Cold gas efficiency, per cent K, (COn)(Hz) (CO)(HiO) 'k (reaction) Per cent H i 0 decomposed Lbs. coal per sq. ft. per hr. Cu. f t . gas per lb. coal Cu. f t . air per Ib. coal Actual depth, f t . T o p bed temperature, F. Primary reducing zone depth (in.) Primary reducing zone temperature, F. Oxidation zone thickness (in.)
E 107.4 67.4 1.112 3.69 80.4 40.6 76.0 56.8 2.88 1450 7.0 2200 2.0
stant. The decrease in the reaction constant explains the decrease in the percentage steam decomposed in the bed (Figures 3 and 4). Table 111-Previous
WORKERS Bone and Wheelero Clementsb Clementsb Osannc
Results
RATEOF STEAM-COAL RATIOFOR MAX. FUELBED FIRING COLDGASEFFICIENCY Ft. Lbs. coal/sq. ft./hr. Lbs. steam/lb. coal DEFTH O F
7.0 5.0 3.5 2.5
20.6 16.8 15.5 16.7
0.4 0.35 0.4 0.4
J . Iron Steel Insl. (London), 73, 126 (1907).
* I b i d . , 107, 97 (1923).
Siahl Eisen, 46, 1566 (1925).
I n these runs, as in the previous ones, the steam goes through the oxidation zone unchanged. I t s decomposition does not start until it reaches the primary reduction zone. The thickness of the primary reduction zone, as well as the thickness of the oxidation zone, is constant and is not affected by the amount of steam passing through. The apparent equilibrium constant,
remains substantially constant. This is in accord with previous w ~ r kbecause , ~ ~ ~the depth of the fuel bed has been kept constant in these runs so that the equilibrium constant, 4
Haslam, THIS JOURNAL, 16,782 (1924)
Data
Run4
Run 201
0.378 C 104.8 65.2 0.72 4.34 73.4 38.3 77.4 59.0 3.20 1450 5.8 2200 2.5
Run203
Run 204
0.577
0.624
106.8 69.5 0.921 2.09 68.3 38.6 78.3 56.7 3.08 1260 9.0 1900 4.0
115.2 75.6 1.980 2.05 80.2 39.0 79.5 54.5 3.12 1200 11.0 1800 3.0
E
E
Run 105 0.679 D
116.8
73.0 0.839 1.43 69.0 39.8 76.2 52.2 3.12 1100 13.0 1900 3.0
Run 202
R u n 103
0.896 E 118.8 71.0 0.921 1.21 58.7 36.3 79.1 54.2 3.00 1400 10.0 1950 3.0
1.03 C 114.4 74.1 0.765 1.96 59.1 36.1 80.1 52.8 2.88 1300 7.5 1900 4.5
which was found to be a function of the fuel bed depth, varies only to the extent of 12 per cent average deviation, leaving out run 204. Conclusions 1-The optimum value of steam-coal ratio for efficient producer operation at 40 pounds of coal per square foot per hour lies between 0.7 and 0.8 pound of steam per pound of coal. 2-This optimum value is a function of rate of firing, increasing with increased rates of firing, it being possible to decompose more steam with the excess heat evolved a t high rates. 3-It appears that the most desirable method of operation of a gas producer is a t high rates of firing with thick fuel beds and with steam-coal ratios that increase as the rate of firing increases. 4-The thickness of the oxidation zone and the thickness of the primary reduction zone are constant. 5-The reaction rate constant, k', decreases with increasing amounts of steam in the air blast. 6-The average temperature of the primary reduction zone decreases with increasing steam-coal ratio. Acknowledgment The authors wish to express their sincere thanks to W. H. Emerson, J. T. McCoy, and John Buss for their helpfulness in the experimental work.
Volumetric Determination of Alumina in Aluminum Salts' By Frederick G. Germuth DEPARTMENT OF PUBLIC W O R K S , BUREAUOF
T
HE method described herein is as accurate as the gravimetric method so universally employed, and has the advantage of requiring less time to accomplish. Method
Dissolve a 1-gram sample of the aluminum salt in 100 cc. of distilled water contained in a 250-cc. beaker. This process is hastened by gentle heating over a Bunsen burner. After dissolution is complete add several drops of methyl red indicator, concentrated ammonium hydroxide (sp. gr. 0.90), and finally 10 per cent ammonium hydroxide as the indicator shows a tendency to change color. Heat the solution containing the precipitated aluminum hydroxide slowly on the hot plate until the excess ammonia is removed, as indicated by the change of color of the methyl red to a faint 1
Received October 27, 1926.
STANDARDS,
BALTIMORE, MD
pink. Filter, while still warm, on an asbestos mat in a Gooch crucible, and wash three times with a warm 2.5per cent solution of ammonium chloride in distilled water. Discard the filtrate, add slowly to the precipitate on the filter 50 cc. of standard sulfuric acid solution (measured from a 50-cc. buret, into a 250-cc. beaker), and then heat to 80" C. After the aluminum hydroxide is dissolved, add 25 cc. of boiling distilled water. Add another 25 cc. of boiling distilled water to filter, and after this has passed into the filter flask, wash again thoroughly with hot water. Pour the filtrate from the flask into a 400-cc. beaker, add one drop of methyl orange (indicator solution), and then run in from a buret standard solution of potassium hydroxide, to determine excess of standard sulfuric acid. Deduct the number of cubic centimeters of standard sulfuric acid employed in excess of that amount required for
January, 1927
IXDUSTRIA L A N D ENGINEERING CHEMISTRY
the production of the aluminum salt from the number of cubic centimeters of standard sulfuric acid added, and multiply the remainder by the factor 0.005, or that factor determined by standardization. This figure gives the amount of aluminum oxide contained in the sample. Any iron oxide that the sample may contain is determined in a separate sample, and the iron sulfate equivalent to the iron oxide deducted. Solutions Required By placing 8.4 cc. of concentrated sulfuric acid in 1 liter of distilled water a solution is obtained of which 1 cc. is approximately equal to 0.005 gram aluminum oxide. By dissolving 31 grams of potassium hydroxide in 1 liter of distilled water, a solution is obtained which is chemically equivalent to the standard sulfuric acid solution. The relation existing between these two solutions is determined by the usual procedure (methyl orange solution being employed as indicator) and corrections are made for difference.
145
Standardization
The factor for obtaining the weight of aluminum oxide represented by 1 cc. of the sulfuric acid solution is determined by dissolving 0.1 gram of pure metallic aluminum (shavings or foil) in sufficient 25 per cent potassium hydroxide solution to effect complete dissolution. Several drops of phenolphthalein indicator solution are now added, and dilute (about 10 per cent) sulfuric acid added until the gelatinous precipitate of aluminum hydroxide is completely formed. Care must be exercised to cease adding the sulfuric acid solution a t the point where the solution becomes colorless. The precipitate is filtered off, and treated as described above. By use of the factor 1.8856, the amount of aluminum oxide corresponding to the weight of the aluminum employed, is ascertained. By dividing the number of cubic centimeters of standard sulfuric acid required, into the weight of aluminum oxide equivalent of the sample utilized, the alumina value per cubic centimeter of solution is obtained.
Measurement of Knock Characteristics of Gasoline i n Terms of a Standard Fuel’ By Graham Edgar ETHYL GASOLINECORP..YONKERS, N. Y
HERE is a t present no satisfactory method of expressing the tendency of a fuel to “knock,” or detonate, in terms which are independent of either an arbitrary non-reproducible standard or of the exact experimental technic of measurement. As the general public and producers of motor fuels are showing a great deal of interest in the relative knock characteristics of fuels, it appears highly desirable to develop a method whereby these characteristics can be expressed in terms of a definite reproducible scale, as independent as possible of the technic of measurement. Certain difficulties of this problem, and a possible solution, are here discussed.
T
Present Methods
The methods commonly employed in measuring knock characteristics will not be considered here in every detail, nor will a preference for any one of them be indicated, but i t must be pointed out that none of them give absolute data on which to base a rating of fuels. I n Ricardo’s2 method the compression ratio a t which incipient detonation occurs is measured in a variable compression engine and listed as the “highest useful compression ratio,” frequently abbreviated to “H. U. C. R.” At first sight this seems a satisfactory solution of the problem, as gasoliries might be rated in terms of their H. U. C. R.-a practice which has already been frequently adopted. Examination of the factors which play a part in determining the actual knock developed by a given fuel, however, makes it clear that the H. U. C. R. has no absolute significance. Among the factors involved are: compression ratio, fuel-air ratio, cylinder wall temperatures, timing of the spark, design of the cylinder head, and the position of the spark plug, valves, 1 Received August 28. 1926. Presented before the Division of Petroleum Chemistry at the i2nd Meeting of the American Chemical Society, Philadelphia, Pa., September 5 to 11, 1926. 2 Inst. Automotive Eng., Rept. Empire Motor Fuels Co., 18, pt. 1 (1923-24).
etc., material of cylinder and piston, cleanness of the cylinder and piston, humidity, barometric pressure, leakage a t valves, and blowby a t pistons. It might be possible to standardize a number of these factors. For example, the first, second, fourth, fifth, and sixth may be kept approximately constant. Other factors, such as the third and the last four, however, cannot always be kept uniform, owing to the number of variables involved. They will vary from day to day and even from test to test. Furthermore, the data thus obtained are not in any way translatable into performance in any other engine, except as they serve as a qualitative comparison of two fuels. The detonation characteristics of fuels have been measured in terms of the amount of spark advance which may be employed to bring about incipient detonation in a given engine a t fixed compression ratio, and the mean effective pressure developed, or the engine speed developed, has been similarly employed. These methods are affected by numerous uncontrollable variables and serve only to measure the relative effectiveness of fuels under the conditions of the particular test employed. Other investigators have adopted the method of comparing various fuels with some standard fuel to which antiknocks, such as tetraethyl lead or aniline, or non-knocking fuels, such as benzol, have been added, and rating the fuels in terms of the quantity of these substances which must be added to the standard fuel or the unknown fuels to give them the equivalent knocking characteristics. The tendency of each fuel to knock has been measured by the aid of the “bouncing pin” devised by Midgley and Boyd,3 by ear, or by the foregoing methods. These methods would be reasonably satisfactory if some reproducible standard fuel, by which the results of different investiaators could be comDared, Were available. Most laboratories have employed as standard fuel a sample of gasoline arbitrarily chosen. I n some cases gasoline 8
J . SOC.Aulomotiue Eng., 10, i (1922).
