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(4A) Gillespie, L. J., and Gerry, H. T., Phys. Rev., 40, 269 (1932) : Gillespie, L. J., and Fraser, L. H. D., J . Am. Chem. SOC.,58,
Keer.an, J. H., and Keyes, F. G., “Thermodynamic Properties of Steam”, New York, John Wiley & Sons, 1936. 2260 (1936). (14) Keyes, F. G., J . Applied Mechanics, 7, 22 (1940). Goff, J. A., and Bates, A. C., H a t i n g , pi pi^, Air c o ~ i t i o n ~ n g , (15) Osborne, N. S., Stimson, H. F., and Ginnings, D. C., J . Reseorch 13,442 (1941). Natl. Bur. Standards, 23, 197 (1939). Gaff, J. A., and Hunter, J. B.1 J . Applied Mechanics, 9, No. 1 1 (16) Partington, J. R.,and Soper, W. E., Phil. Mag., 7, 209 (1929). 21 (1942). (17) Pearce, J. N., and Hopson, H., J . Phys. Chem., 41,535 (1937). G‘ggenheim* E* “Modern Thermodynamics by the Methods (18) Pollitzer, F., and Strebel, F., 2. physik. Chem., 110, 768 (1924). of Willard Gibbs”, p. 35, London, Methuen and Co., 1932. (19) Rossini, F. D., Bur. Standards J . Research, 6 , 791 (1931). Ibid., p. 38. (20) Smith, A. W., Phys. Rev., 25, 145 (1907): 33, 173 (1911). Ibid., p. 66. (21) VrevsW M. S., et al., J . Russ. P ~ w .Chem. SOC.,59, 69, 77 Harrison, w.R., and perman,E. p., TraGs,Faraday sot., 23, 1 (1927); Z. physik. Chcamm., 144,359, 385 (1929). (1927). “Heating. Ventilating- and Air Conditioning Guide”, Chap. I (1941c
Hillebrand, W. F., and Lundell, G. E. F,, ,‘Applied Analysis”, New York, John Wiley & Sons, 1930.
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B A ~onDa dissertation presented by J. B. Hunter to the Graduate School, University of Pennsylvania, in partial fulfillment of the requirements for the degree of doctor of philosophy.
Heating Value of Natural Gas DETERMINATION OF TOTAL AND NET VALUES WITH A WATER-FLOW GAS CALORIMETER A. J. W. HEADLEE AND JAMES L. HALL’ West Virginia Geological Survey, Morgantown, W . Vu. portional to the heating value The total and net heating values of natural gas are related H E heatsof combustion so that NHV could be calby the empirical equation: of several thousandsamculated from THV, and vice ples of natural gas have 34 0.34 I THV 1.072 NHV versa. The equation derived been determined in this laboby the usual algebraic proratory during the past eight, This equation is used to check the accuracy of the correccedures from data given in years. These data are of tions for the water of combustion of a water-flow gas the Table I for the relavalue in the operation of a calorimeter. The net heating value can be calculated tion between THV and NHV water-flow gas calorimeter from the total heating value by this expression, and vice of each of the first six and also agree with a n versa. The suggested calorimeter practice will shorten saturated normal hydrocarempirical relation between the number of man-hours per test, increase the accuracy, bons is: the total and net heating and decrease the size of the test sample. value of saturated hydroTHV - 1.072NHV = 34 (1) carbons. Nitrogen and other inerts affect the value of the constant 34 in The heating value (a) is the number of B.t.u. produced by the Equation 1. The equation, correcting for inerts, is: c-onstant-pressure combustion of 1 cubic foot of gas with air when the inlet and outlet gases are a t the same temperature. The cubic THV - 1.072 NHV = 34 0.34 Z (2) foot of gas is measured at 60’ F. saturated with water vapor, where I = inerts, % and under a total pressure of 30 inches of mercury a t 32” F. It is to be noted that 9% inerts affects the constant by only 3. under standard gravitational force. When the heating value is Equations 1 and 2 hold for natural gas within the limits of deviacalculated as if the water formed by combustion is in the liquid tion of the gas from the law of partial pressures. state, it, is known as the total heating value, THV; when in the vapor state it is known as the net heating value, NHV. HEATING VALUE TESTS A water-flow gas calorimeter condenses out a portion of the water vapor of combustion so that the observed heating value, Recommendations of the National Bureau of Standards (1, 4) OHV, is between THV and NHV, and both are calculated from for the operation of water-flow calorimeters were followed, includOHV. Corrections for the water of combustion that is carried out in the vapor state with the flue gases, TABLE I. PROPERTIES OF GASES heat of condensation heat of condensation Conditions specified in definition of THV and NHV; column 2 calculated THV + OHV NHV from data of Rossini (3)at 25’ C. 2 3 4 5 6 7 8 of combustion water of condensed water 1 Heat of leaving calorimeter as Condensavapor tion of Water of NHV, are necwsctry in calculating THV, and corrections for the water CombusCol. Col. Col. Sp. Gr. HydroWater, tion, Col. 2 5 X 2 (Air that condenses out are necessary for calculating NHV. The carbon THV Grams 3 X 2.337 Col. 4 1.072 Col.6 = 1) latter correctioqs are much greater in magnitude than those for 996 42.48 99 897 96 34 0.5544 CHI 1612 1728 34 1.0492 CzHs 1762 64.33 150 THV. If the fuel gas consists of a homologous series such as the CaHs 2546 87.1 204 2342 2511 35 1.6623 n-CdHio 3313 109.3 255 3058 3278 35 2.067 saturated paraffin hydrocarbons in natural gas, the quantity of n-CsHiz 4080 131.4 307 3773 4045 35 2 . 6 7 water formed by complete combustion should be sufficiently pron-CsHir 4850 153.2 358 4492 4816 34 3 . 0 8
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On leave of absence with the Armed Forces.
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ing till the sugges:ted calibrations and correetions. Complete lowtemperature fractional distillation analyses, using a Podhielniak :ipparatus with liquid nitrogen as a refrigerant, and specific gravity tests were made on most of the samples whose heating values iTere determined. The accuracy of the heating value dererminations were checked with these data. Heating values of natural gases containing methane as the only hydrocarbon checked, within less than 2 H.t.u., the value obtained by Hossini fnr methane..
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correct; the negative scale represents higher experimental than calculated iYHV's because insufficient water was collected, arid the positive scale iepresents lower XHV's because more water was collected than was produced by the burning of the test sample. The positive and negative portions of curve 1 are similar, 60 that the median value, -0.5 I%.t.u.,may be considered a measure of the amount of excess air beyond the 40% limit; the spread is due to fluctuations in runoff and errors of measurement. CALORIMETER PERFORMANCE
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WARMIKG-UP PERIOD.At the beginning of a group of testh the calorimeter was operated for 40 minutes so that operating contiitions would be in equilibrium before an actual test was made. Curve 2 of Figure 2 shows that the water of combustion was not properly accounted for in about 45% of these first tests. Insufficient condensate water was collected during 40% of the first tests, while too much was recovered in 5%. The condensate water alternately holds hack and floods out before it reaches a steady uniform runoff.
Figure 1. THV us. NHV Curve through \lethalie arid Ethane Points a t a Burner Pressure of 0.11 Inch o f Mercury plus Atmosphere
C$%en a group of saniples was used, they were arranged in order of increasing specific gravity, and the tests were made in this order; the next group of samples was run with the highest specific: gravity first, the others following in order of decreasing specific gravity; the next group, in order of increasing specific gravity, et,c. This reduced errors due to purging, variations in soluhility of the gar in water, etcv., and permitted uniform operation of the calorirn. et,er. The Sargent automat,ic calorimeter was operated with the damper closed, under a constant pressure of 1.5 inches of water on t,he meter, and with the stopcork on the burner wide open a t a gas mte of 3300 l3.t.u. per hour. The damper was fairly t,ight fitting and had two l/e-inch holes. The water condensed from t,he combustion of 0.4 cuhic foot of gas was collected and measured after t'he preliminary hurning of 0.4 cubic foot or more of the sample. Experimental THV and XHV were plotted (Figure 1) in order t o compare them with theoretical Equation 1. A11 first tests after t,he caforimeter had been idle a few hours were excluded from this curve. The experiment,al values were calculated to the inert-free basis. The curve was drawn through the points for pure methane and ethane. This figure indicates that the empirical equation holds for natural gas, so t,hat any variation between THV or NHV as calculated from this equation and as experimentally determined is a measure of the correctness of part, of the operating procedure. Of twenty-nine samples tiaviiig inert contents between 4 and 2778, fifteen showed higher calculated than experimental NHV and fourteen showed lower. When properly adjusted for an average natural gas, the calorimeter operates without further adjustments a t the correct excess air rate, independent of the inert or hydrocarbon content. Equation 1 was solved for 197 tests, and the difference between calculated and experimental NHV was plotted cumulatively (Figure 2, curve 1). The calculated values were assumed t,o be
CALCULATED NHV-EXPERIMENTAL
NHV
Figure 2. Cumulative Frequency Curves of the DitTerence between Calculated and Experimental NHV Curve 1. Gas pressure, 0.11 inch mercury; 197 teats Curve 2. First run of a group; gas pressure, 0.10-0.12 inch mercury; 98 tests Curve 3. G a s presaure, 0.07 inch mercury; 73 tests
The warming-up period for two samples of natural gas was studied to determine the rharacteristics of the condensate Tvater runoff. The condensate water from previous runs had evaporated from the condenser tubes, so that they were dry a t the start of these tests. THV and NHV were calculated from the data for each 0.1 cubic foot of gas burned in order that the fluctuation< would not be partially ironed out by too long a test period. Thesr tests were plotted in the order made to show the progressive changes in the determined values (Figure 3). The test number scale is also a time scale; each test number represents the time necessary for one revolution of the meter (100 seconds). THV becomes steady in ten revolutions of the meter, equivalent to 17 minutes; NHV becomes steady after 40 minutes. The low point5 in the NHV curves are condensate floods. Two floods occurred during one of the tests before the condensate runoff became steady. NHV fluctuates much more than THV, even after the calorimeter is operating a t its maximum steady state because of pulsating condensate-water drainage.
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40% excess air (but always more than enouglt for complete combustion) passes through the calorimeter, then the experimental NHV will be less than that calculated by Equation 1. Performance curves (Figures 2 and 3) should be madr Eoi, each calorimeter and occasionnlly’checked. They give the uniformity of operation of the calorinet,er and the condensate water holdup and runoff. Test, period?.,of even shorter duration than 0.1 cubic foot should also be cha:.t>ed. The chart of each reading of the outlet thermometer will frequently show fluctuations from the normal due to differential friction in the shaft of the wet test meter. This is especially true of new or reconditioned meters. The number of man-hours per test can be shortened by making such curves for a day’s run of tests. The accuracy of the test will be increased and the sample size will be materially reduced. The calorimeter should be operated for a t least one hour before a test is made in order t o ensure uniform runoff of condensate water after the calorimeter has been idle a few hours. Accurate THV can be obtained after a shorter warming-up period because the rate of runoff of the condensate water does not influence it. A calorimeter with accurately uniform condensate-water runoff would produce NHV’s that could be used to advantage in crtlculating accurate THV’s for natural gas and thus eliminate t,he necessit,y for humidity corrections.
Figlire 3. Calorimeter Performance Vhile 4ttaining Equilihrium
O p E R A w o N ABOVE 40% Excess AIR. Several tests were made with only 0.07 inch of mercury pressure on the meter at a gas rate of 2500 B. t.u. per hour. Wide variations were obtained between calculated and experimental XHV as indicated by curve 3 of Figure 2. The calorimeter was operating considerably above the 40% excess air limit, and the tables for calculating THV canriot be used with accuracy although the error involved was no more than 5 B.t.u. The condensate water runoff was pulsating even more than that shown in curve 2. These pulsations may have been partly due to ,the design of the collecting pan (shield) at the base of the calorimeter. If accurately uniform water runoff could be obtained, then accurate NHV tests could be made with any quantity of excess air, provided it remained uniform during a test. Atmospheric humidity and excess air would not be important factors so long as they remained uniform during a test, because Equation 1 could be used to calculate THV.
SUGGESTED CALORIMETER PRACTICE
h simple empirical relation (Equation 2) exists between the total and net heating value of natural gas. This relation can be used to check the operation of a water-flow calorimeter with respect to the water of combustion. It can be used t,o calculate NHV more accurately than it can be determined, provided THV is accurate t,o *I I3.t.u. The fact that, det,erminetl ‘1’HV and XHV fit, Eqriat,ion 9 does not necessarily mean that they are the cvrrect heat,ing value for t,hat gas; it indicates only that the water accounted for by the humidity and condensed water c:orrect,ionswas equal to t,he water formed by the combust,ion of the gas. THV and NHV may be high or low because of other errors. If the NHV calculated from Equation 1 is consistently lower than the experimental value, then the Calorimeter is being operated above the 40% excess air limit, and the experimental THI’ is too low by an amount equal to the heat of vaporization of the water vapor going out, with the excess air, provided t,he proper amount of condensate was collected. If t,he drainage of condendate is less t h m that condensing out in the calorimeter, then the correct,ion for condensat,e will be low and thus give too high an NHV. One or both causes may account. for tshehigh experimental NHV values as compared with those calculated from Equation 1. If too much condensate drains from the calorimeter or if less than
LITERATURE CITED (1) Natl. Bur. of Standards, Circ. 48 (1916); 65 (1917); 405 (1934); C417 (1938). (2) Zbid., 405, p. 3 (1934). (3) Rossini, F. D., BUT.Standards J. Research, 13, 21-35 (1934). (4) Waidner, C. W., and Mueller, E. F., Bur. Standards, Tech. Paper 36 (1914). PREUENTEV before the Division of Gas and Fuel Chemistry at the 105th CHEMICAL SOCIETY, Detroit, Mich. Published by Meeting of the AMERICAN permission of the State Geologist.
Process for Aminoguanidine (Correspondence) SIX My attention has been attracted to the following staternent in the article by R. 2;. Shreve and R. P. Carter (line 12, column I , page 423, May, 1944): “Wyler (2.9) in 1935 was granted ti patent using zinc acetate indead of acetic acid with zinc dust, with yields claimed to be 90Tc. R‘e were unable to obtain better than 50%.” In the patent t o which they refer, U. S. Patent 1,990,511 (1935), it is stated: “By my process I obtain a yield of aminoguanidine bicarbonate, for example, equivalent to 90% or more of the weight of the nitroguanidine used. , This means that I claimed yields of a t least 104 X 0.9 or 93.6 grams of aminoguanidine bicarbonate for 104 grams of nitroguanidine starting material, or about 7170 of theory. Actuallj we obtain plant yields of more than 85% of theory under carefully controlled conditions and technique.
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JOSEPH A. WYLE.H THOJAN P O W D E R (“(OMI‘4N) ALLENTOWN. PA.
SIR:Mr. Wyler is correct in that our article should have carried his claim of 71% yield rather than 90% as stated. It is true, however, that we got only 50%, but the reduction is not simple and we plan now to repeat. the work in an effort to get up to 76 or 80% yield. Nothing would suit us better than to do this. R. NORRESHREVC: I’URUUE UNIVERUITY LAFAYETTE,I N V
