Feb., 1912
T H E J O C R X A L OF I S D I T S T R I A L AiYD E.YGI.\-EERI.YG
in the cooled liquid before again heating the liquid to boiling. The bumping is caused, the authors believe, primarily b y uneven and irregular heating. Once bubbling has started, if i t does not cease b y reason of varying and disturbing external heat conditions, alwa3-s t o be considered in connection with an exposed or a gas-heated flask, or by reason of a diminution of the vacuum when one is used, the boiling will continue quietly. With the residual heavy tars and asphaltums, the internal coils are a source of annoyance in cleaning the apparatus. When oils contain emulsified water, it is advisable during the early stages of the distillation with all forms of stills to slowly pass a dry inert gas, such as CO,, through the still contents, b y means of a capillary tube extending nearly t o the bottom of the distilling flask, until the water is entirely removed. In such case i t is difficult to insert the two internal conductors, a capillary . t u b e and a thermometer through one stopper in the narrow neck of the ordinary distilling flask. To fuse the conductors through the bottom of the flask, though possible, is difficult and hardly practicable for general laboratory usage. I n short, the externally heated still described above is adapted to most, if not all, classes of laboratory work. I n modified form i t may be used for a great variety of heating (devices. The authors rwommend i t to those interested.
CHEMISTRY.
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in a hundred of the managers, superintendents and engineers of power plants know the true composition of the coal they are using. Not in one plant in a hundred are the products of combustion systematically sampled and analyzed. While i t is undoubtedly true that the majority of power plant managers are aware of the fact that the boiler house is the place where very substantial economies should be realizable, they cannot get themselves to tackle the problem from the chemical side. Yet in the analyses of the flue gas lies the key to fuel economy. Engineers as a class incline to solve their problems b y mechanical means. They prefer t o have something they can get a t with a hammer and cold chisel and monkey wrench. Hence coal weighing machines and water meters, or water weighers, are more readily adopted than CO, recorders.
THE CARBON D I O X I D E R E C O R D E R AS A FACTOR IN FUEL ECONOMY.’ By E. A. UEHLING. Received Dec. 19, 1 9 1 1 .
Vast improvements have been made in power plant equipment during the past quarter century. All these improvements have been along mechanical and physical lines, consequently in the utilization of the steam, which is primarily a mechanical and physical problem, is where the great economies have been achieved. The consumption of steam per h. p. hour has been reduced from that of 2 0 - 3 0 lbs. per h. p., hour less than a generation ago t o 10-15 lbs. a t the present time, whereas in the generation of the steam which is fundamentally a chemical problem, 30-40 per cent. of the heat contained in the fuel continues to go t o waste precisely as i t did 2 5 - 3 0 years ago. The mechanical devices, such as automatic stokers, coal elevators, ash conveyors, forced draft, etc., t o be found in every large and modem boiler house, accomplish a good purpose in so f a r as they increase the capacity and save labor, but do not insure, or even tend to improsre, combustion efficiency. That so little has been accomplished in the reduction of waste in the process of steam generation is due to the fact t h a t the chemist has not been called in t o assist in solving the problem. I t is undoubtedly stating i t very conservatively if we say t h a t not one 1
Abstracted by the author from an address before the Joint Meeting
of A . C . S., S. C . I. and A . E. S . , Xew T o r k , November 10,1911.
Fig. 2 .
Fig
1.
Coal and ‘water weighing machines are a good thing t o have inasmuch as they give definite information as to water evaporated per pound of coal burned. These apparatus are also useful if not absolutely necessary in testing the value of one kind of fuel against another, etc. But since you cannot solve a chemical problem b y mechanical means, coal and water weighers can be of practically no assistance in attaining and maintaining boiler efficiency, which is primarily a chemical problem. Of the heat generated from the coal burned in the average steam plant less then 7 0 per cent., and in
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T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y .
many cases not even 60 per cent., is transmitted to the water in the boiler; the bulk of the balance is carried off by the products of combustion. To reduce this loss to a minimum we must know its cause, a n d this can be determined only by having a complete knowledge of the chemical composition as well as the physical character of the fuel used, and by keeping a continuous control over the process of combustion. I lay special stress on the continuity of control over the process of combustion, because the conditions are continually changing, not only from day to day, and from hour to hour, but from minute to minute. Changes in atmospheric condition as to pressure, temperature and humidity; changes in the physical structure of the coal as to preponderance of lumps or fines; changes in the condition of the fire, due to accumulation of ashes, formation of clinker, etc., and last, but not least, changes in the rate of combustion necessary because of variable steam consumption. The best results are obtained in any given boiler b y securing complete combustion with a minimum excess of air, and since there is a true relation between the per cent of CO, in the flue gas to the excess of air supplied, we have in this constituent an index to efficient firing. If, therefore, the per cent. of CO, be continuously revealed to the fireman it will serve as a guide and enable him to control his fire so as t o obtain the most economical results. No sane manager of a steam power plant would expect his fireman to keep up a steady pressure witho u t the aid of the steam gauge to guide him. Every fireman knows that his job depends on his ability to keep up the required steam pressure, and he does it. The question whether i t is done wastefully or economically, although lately receiving some attention, has not been attacked b y power plant managers with the vigor that its importance merits, nor from the side that promises the best results. Fuel economy is primarily a chemical proposition a n d should be attacked from the chemical side. Combustion efficiency depends on so many variable conditions that a continuous control is necessary to secure the best results. Since no one would expect a fireman to maintain a steady steam pressure without a gauge to guide him, he should not be expected to maintain economical combustion without some means of knowing where he is at. The per cent. of CO, in the flue gas answers the requirement, and should be before the fireman as prominently ,and continuously as the steam pressure. The Uehling CO, recorder fulfils this requirement. 1t.consists of three principal parts: Fig. I , the regulator or analyzer, which may be located a t any con-
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Feb., 1 9 1 2
venient point within reasonable distance of the boiler, preferably in the engine room. Fig. 2, the recorder which is preferably placed adjacent t o the regulator but may be put in the engineer’s office if conveniently located. Fig. 3, the indicator which should be placed on or near the boiler front in plain view of the fireman. This apparatus is of very substantial construction and contains no moving parts. The gas is continuously drawn through by a steam aspirator, the CO, is continuously absorbed, and the volume per cent. of the gas passing through is continuously
Fig. 4.
Fig. 3.
indicated ‘and recorded. The absorbent consists of a specially prepared dry caustic soda, furnished in cartons which last about one week, and can be readily renewed in a few minutes. These instruments are made in single, double, treble and quadruple sets either plain or in combination with pyrometers which indicate and record the stack temperature, simultaneously with the CO,. Fig. 4 shows a double combined CO, and temperature recording gauge and indicator accompanying each unit.
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