October, 1944
INDUSTRIAL AND ENGINEERING CHEMISTRY
95s
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
