INDUSTRIAL AND ENGINEERING CHEMISTRY
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VOl. 19, No. 7
The Reactivity of Coke’ By S. W. Parr and W. D. Staley UNIVERSITY OF ILLINOIS, URBANA, ILL.
HE term “reactivity” as applied to coke does not
T
have a very definite meaning. With one group of investigators it is measured by the decomposition effect on carbon dioxide a t high temperatures. Here there would seem to be involved a number of factors beside the simple one of reactivity of the coke. Even so the data obtained are doubtless of value to any industry making use of those conditions. Another group may be interested in catalytic or compositional effects, including combustion. It is this phase of reactivity which has been the basis of the studies here reported. Experimental
Figure 1-Original Apparatus
Carbon begins to react with oxygen a t a definite temperature. With an increase of temperature the reaction is modified as to rate but not as to character. When the temperature at which activity begins is attained there is an increase of temperature which automatically increases the rate and the reaction proceeds autogenously. It is evident that some temperature near the point where the reaction begins may very properly be taken as a starting point which may be used for an index of the relative reactivities of various forms of free or elemental carbon.
It follows, therefore, that the methods employed for determining the ignition temperature for coals might also be applied directly to coke. The first apparatus used in this study, therefore, was that described by Parr and Coons2 in their article on the critical oxidation temperature of coal. The principle involved is illustrated in Figure 1, where the central thermometer is embedded in the coal and the companion thermometer is located in the oven space a t one side of the coal container. The oven is electrically heated and by suitable resistance can be held at any desired temperature. 02ygen from a pressure tank is passed through the coal. The results obtained by this equipment were exceedingly consistent, but the range of temperatures possible with mercurial thermometers was somewhat limited, which led to the modification shown in Figure 2. Here the containers were of the same size and shape and each was filled with the same material to be tested. They were so placed in the furnace as t o receive equal heat and each had a thermocouple a t the center of the mass. Oxygen was circulated through one charge while the other remained as a blank for comparison. Discussion of Results
I n working with it a t once became a function of the This is very well 2
this apparatus on numerous types of coke, apparent that the reactivity of coke was temperature a t which it had been made. illustrated by Figures 3 to 7 , where the
THIS JOURNAL, 17, 118 (1925).
t
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20
30 TIM;
40
in
MINUTES
Figure 3
440 4.90 v)
gw 0
8 280
g 240 Em Figure 2-Modi6ed
Apparatus
CT
x I n the case of coal this point has been called by Wheeler and others the “ignition temperature,” which is only another way of designating the relative temperature of reactivity. 1 Received March 11, 1927. Presented before the Division of Gas and Fuel Chemistry at the 73rd Meeting of the American Chemical Society, Richmond, Va., April 11 to 16, 1927.
160 120
TIME I N MINUTES Figure 4
50
INDUSTRIAL; AND E,liGI;VEERI-VG CHE;MISTRY
July, 1927
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82 1 samples had been obtained by carbonizing a certain coal at five different t e m p e r a t u r e s from 500" to 900" C., with which in Figure 8 has been included a standard high-temperature coke from BiriiiiIigham, Ala. Because of its definiteness, the critical point for denoting the beginning of positive reactivity has been taken a t the crossing of the lines representing the temperatures in the two containers. This would seem to be justified since the tem-
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3
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4
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TIMCI N MINUTES Figure 5
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Figure 6
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Figure 7
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perature gradient from this point on is rapid and characteristic. I n Figure 8 for high-temperature coke the lines did not approach e a c h o t h e r within the practical working range of the apparatus, from which it is assumed that the reactivity point is above 600" C. For more convenient comparison these values are grouped in Table I.
Table I-Effect of Coking Temperature o n Reactivity COKINGTEMPERATURE REACTIVITY TEMPERATURE
c.
c,
500 600 700
144
218
800 900 1000
Above 600
O
178
314 456
Reasons for Variations i n Reactivity
MIMUTCS Figure 11
T i M f In
This behavior of carbon would seem to upset some of our previous notions concerning coke formation. Graphitiaation to a greater or less degree is sometimes suggested as an explanation for variations in the reactivity of coke made a t high temperatures and for varying lengths of time, but that theory could not be applied to coke made a t the carbonizing temperatures here illustrated.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Table 11-Effect of Previous Heating on Reactivity of Carbon Prepared f r o m Sugar by Means of Concentrated Sulfuric Acid TEMPERATURE OF REACTIVITY APPEARANCE PREVIOUS HEATINQ TEMPERATURE OF FIRE O
c.
O
500 700 900
c.
O
96 204 322
c.
200 300
...
Another theory of long standing is that coke reactivity is governed largely by the deposition of carbon upon the cell walls as a result of the decomposition of methane a t high temperatures. To test this theory amorphous carbon was prepared by the decomposition of sugar using concentrated sulfuric acid and maintaining a low temperature during the period of decomposition by the acid. After complete decomposition and many times repeating the washing and filtering process, different portions of the carbon obtained were subjected to temperatures of 500°, 700°, and 900' C. in the same manner and under the same conditions as the cokes obtained from coal as used in Figures
VOl. 19, No. 7
3 to 7. The curves obtained are shown in Figures 9, 10, and 11 and also grouped for comparison in Table 11. Conclusion The conclusion is obvious, that for each advance in temperature, carbon assumes a definite form which directly affects its reactivity. To devise a theory that shall apply to the case is not a simple matter. It is possible that the molecular acceleration produced in gases and liquids by increased temperatures may extend to solids also, even to so-called amorphous material, and that for any given temperature there is brought about a new state of aggregation or condensation with a different capacity for reactivity. But this line of hypothetical discussion would take us too far afield. The object of this investigation was merely to demonstrate the relation between reactivity in its broad and more significant aspect and the temperature employed in the preparation or production of free carbon from carbonaceous material.
Occurrence of Hydrogen Sulfide in the Lake Washington Ship Canal' By E. Victor Smith and Thomas G. Thompson UNIVERSITY OF WASHINGTON, SEATTLE,WASH.
I
N A previous article* a description was given of the
salinity conditions produced in the Lake Washington Ship Canal in Seattle by the i d o w of sea water into the fresh water system. The presence of hydrogen sulfide was noted in the deeper portions of the canal system where quantities of brackish water had accumulated. I n the fall of three consecutive years the distribution of hydrogen sulfide was studied and the present paper deals with a summary of these results.
different depths for the three stations. The concentration of hydrogen sulfide increased with the depth while that of the oxygen decreased. The graphs in Figure 1 illustrate this relation. A curve showing the oxygen content of the water taken every 10 feet (3.1 meters) to a depth of 50 feet (15.3 meters) a t station 12 in Lake Washington is given for comparison, as this lake is free of brackish waters and empties into Lake Union. Sulfide Content of t h e Waters of Lake Union October, 1924 October. 1925 STATION DEPTH TEXP.CHLORINEHzS TEMP.CHLORINEH B Feet Meters C. Mg./l. Mg./l. C. Mg./l. Mg./l. 8" 10 3.1 13.2 205 0 0 12.9 189 0.0 20 6.1 13.5 345 0 0 13.3 200 0.0 30 9 2 14.9 1860 1.5 15.1 1520 2.0 40 12.2 14.5 3520 18.1 14 4 2578 14.0 45 13.7 14.0 3525 20.2 14.9 2765 20.5 47 14.3 14.1 3655 27.4 14.3 2860 20.0 13.8 206 0.0 14.0 440 0.0 15.5 1625 2.5 15.2 2795 12.0 14.9 3385 18.0 9 10 3.1 12.8 202 0.0 13.3 181 0.0 20 6.1 12.9 340 0.7 13.1 210 30 9.2 13.8 1925 0.8 15.9 1765 ... 40 12.2 14.3 3140 12.1 14.9 2887 12.0 45 13.7 14.1 3885 20.9 14.9 3333 20.0 For location of stations in Lake Union, see map, THISJOURNAL, 17, 1084 (1925). Table I-Hydrogen
Methods of Analysis
The iodometric method, using 0.01 normal solutions, was used for the hydrogen sulfide determinations, for after a study of conditions encountered in the waters of Lake Union it was concluded that many of the objections to the method, cited by Heath and Lee,3 did not apply or else introduced errors that were negligible. Because of the pkesence of hydrogen sulfide in some of the samples, the dissolved oxygen was determined by Rideal and Stewart's4 modification of Winkler's method. Experimental
I n Table I are given data collected in October, 1924 and 1925, which show the distribution of hydrogen sulfide, the salinity, and the temperature of the waters a t the three stations in Lake Union for different depths. A more detailed study of the hydrogen sulfide distribution was made in the fall of 1926. At this time the dissolved oxygen in the water was determined simultaneously with the hydrogen sulfide. Table I1 gives the temperature, the amount of chlorine, hydrogen sulfide, and dissolved oxygen for the waters a t Received March 10, 1927. (1925); for detailed description see University of Washington Eng. Expt. Sta., Bull. 41 (June, 1927). * J . Am. Chcm. SOC.,45, 1643 (1923). 4 Am. Pub. Health Assoc., Standard Methods for Examination of Water and Sewage, 5th ed., p. 59. 1
* THISJOURNAL, 17, 1084
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Toward the end of the summer months and after the brackish waters had been at the bottom of the entire canal system except Lake Washington, small quantities of hydrogen sulfide were detected a t places other than in Lake Union. However, with the flushing action of the fresh waters flowing through the waterway from Lake Washington in the winter months, all of the hydrogen sulfide was removed from the system with the possible exception of that occurring within a few feet of the bottom of the deeper parts of Lake Union. Water taken from the lower depths of the lake in the winter months contained varying quantities of colloidal sulfur. if the water showed any degree of salinity. This was undoubtedly due to the reaction of the dissolved oxygen in
