April, 1923
I N D UXTRIAL A N D ENGINEERIXG CHEMISTRY
best carried out by the use of a regenerative checkerwork system after the completion of the reduction reaction. TABLE I1 TEMPERATURES
Run 8 c (Final) 5 (Middle)
7(First) (Middle) (Final)
Final Sample Gas Analysis Point COa 0 2 CO " C . 12.3 2 . 0 1 0 . 4 895 10.2 0.6 9 . 4 865 10.4 4.1 12.5 1 . 2 , , , ,
Run 8c 5(Middle) :(First) , (Middle)
.
,
,
6.5 8.3 ,
..
900
Entering Point OC. 495 775
690
Mols Air per Hr. 0.670 0.577
Lbs. Coal Burned per Hr. 1.96 1.84
0.485
1.16
TABLE I11 C v . FT. OF COMBUSTION SPACE PER LB. OF COALPER H R . Calculated Observed 0.7 1.2 1.0 1.0 0.8 0.9 1.5 0.9 Average.
Air Preheated All Less than one-half Less than one-half
Ratio of Observed to Calculated 1.72 1.0 1.12 1.67 . . 1.38
. ... .. . . .
RESULTS Table I1 illustrates the type of results obtained with two different coals. I n Run 7 the temperature fell from 1300" C. a t the combustion chamber to 900" C. at the point where the final sample was taken. These runs, as well as the others, showed conclusively that a gas richer in CO was obtained the higher the temperature of the entering air. However, it is to be noted that in the case where all the air was preheated, an air temperature of only 495" C. was obtained, whereas 1000" C. was desired. A comparison (Table 111) is given between aalculated and observed reduction rates by integrating Equation 2 between the limits zero per cent CO and the per cent
357
CO formed in the run, upon introducing the proper fraction of COn initially formed in the run. The difference beween the calculated and observed capacities may be due to the coal not being a t 900' C. (the temperature used for calculation) throughout the run or by incomplete mixing of the coal and flue gas. Although the design of the furnace was changed several times, great difficulty was encountered in maintaining a uniform mixture of coal and gas. Coal dust had a tendency to settle out and the gas stream became stratified. I n a number of runs incompletely consumed coal was carried out of the furnace by the gas stream. CONCLUSIONS 1-It is much more difficult to generate producer gas from powdered coal than the literature would lead one to suspect. However, the problem does not seem hopeless and in view of the possibilities of obtaining cheap power additional work should be carried out. 2-The difficulties seem to be the production of a sufficiently high temperature in the reacting zone, and the maintenance of the necessary intimacy of mixing between the powdered coal and reacting gas. 3-With each increase in the temperature of the incoming air, better results were obtained. It seems desirable to preheat the air to about 1000" C. 4-The maximum amount of CO obtained in any reliable run was 10.4 per cent, although for short periods 12 to 13 per cent was reached. &-For the condition of the experiments the observed size of combustion space required for reduction of COZ to CO by the powdered coal was 1.38 times that calculated by Equation 3.
Note on the Use of Phosphorus in Gas Analysis' By August Holmes 47 N. 1 6 T ~ST.,
Pyrogallic acid, widely used for the determination of oxygen in gas, has several disadvantages. It will absorb carbon dioxide if present; if not properly prepared it is liable to give off carbon monoxide; it exhausts its absorbing power for oxygen so gradually that it is difficult to determine when absorption is complete. It has the advantage, however, of being rapid, accurate when freshly prepared, and uninfluenced by traces of illuminants. It has been the writer's experience that phosphorus is a better reagent for oxygen because, although a little slow, it is never exhausted as long as there is any present. By observing a few points it is quite rapid, and complete oxygen absorption is easily determined by the disappearance of the white fumes. To remove the last traces the sample should be replaced in the measuring pipet, mixed, returned to the phosphorus pipet, and allowed to stand until the disappearance of the white fumes. After the gas has passed through the bromine water and absorbed the illurninants, the oxygen is easily absorbed by the phosphorus. This is also true for flue gases from boilers and burners, but not for the exhaust from a gas engine, nor the residue from the explosion in a gas analysis. Frequently, the oxygen in these cases is not easily acted upon by the phosphorus, which leads to the conclusion that there is no excess oxygen present. By passing such gases through bromine 1 Received
February 16, 1923.
EASTORANGE,N. J.
water, although there will be no change in reading after absorbing the bromine in the caustic potash, it will be found that the oxygen has been activated and is easily absorbed. It is not necessary, however, to pass the entire sample through the bromine water but merely to inoculate it with bromine by passing 2 to 3 cc. into the bromine pipet and then directly to the phosphorus pipet. A rapid absorption of the oxygen takes place at once. This bromine inoculation has been found advantageous for sluggish oxygen absorption. It is not necessary to pass the gas, after this treatment, through the caustic, since no change in reading takes place. If the room is cold, inoculation assists the absorption. I n case the phosphorus has become contaminated by the illuminants or, more likely, by the cuprous chloride, the black spots may be removed by displacing the water on the phosphorus with concentrated nitric acid or, if the spots are very bad, with concentrated nitric acid to which a little concentrated hydrochloric acid has been added. The acid should, of course, be removed with clean water. The phosphorus will be light in appearance, and very active for some time. The time required for a complete analysis of illuminating gas for carbon dioxide, illuminants, oxygen, carbon monoxide, explosions for hydrogen and paraffins, and absorption of the excess oxygen is about 20 min. with phosphorus, which is not very long.
