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perature is borne out in actual practice, could probably be determined by temperature measurements at different heights of the section, but it is claimed that the efficiency of the descending flow section is materially less than the efficiency of the ascending flow section. If this be so, it would seem to me to be in part accounted for by the fact that the tars precipitated in the process of quick temperature equilibrium at the top of the section, must continue their way downward in company with the liquor and gas and naturally the liquor and tars would come into temperature equilibrium in this descent. In the ascending section, however, any such tars will immediately drop back at the temperature of precipitation, hence the liquor above such point is not affected by them.
As compared with the process of dry, or merely surface condensation, Mr. Blauvelt's suggestion that the precipitated tar globules are enveloped at once in a film of liquor, and are thus substantially removed from contact with the gas, is at least a very plausible and interesting theory. It would, however, seemingly be of a lesser importance in apparatus of the counter current principle, but, on the contrary, of considerable moment in apparatus wherein the gas should at any stage of cooling be made to descend through the scrubbing grids with the liquor.
Incidentally, Mr. Blauvelt's experience appears to give the most positive proof we save yet had of the correctness of the theory of the fractional removal of the tars.
The results detailed by him are particularly gratifying to me as confirming the opinion which I have long held that the present forms of vertical tubular condensers are about the worst possible apparatus in which gas could be condensed. It seems to me that it has been completely proven by the work of the last few years that the so-called critical point for the removal of tars is in reality not in the neighborhood of 100° Fahr. as has been popularly supposed, but begins at the highest point at which any of them will liquefy, in other words, practically at the dip pipe. Sufficient proof of this might be found in the difference of quality observable where the dip pipes in the hydraulic seal into tar as against liquor. The action of the ordinary condenser with the gas entering at the top, the condensed tars agglomerating on the verti
cal tubes and flowing downwardly on these tubes, transferring their excess temperature to the cooling water as they descend, and requiring the gas therefore to be cooled through the medium of a cooling tar surface, presents about the worst possible condition. Further, as Mr. Blauvelt points out, the investment in equipment per unit of capacity is immensely in excess.
I think the most valuable result of Mr. Blauvelt's paper is its conclusive demonstration of the superiority of the direct cooling system and in apparatus of large size, it is probable that it would be difficult to surpass the Doherty application of this principle. In small or moderate sized apparatus, I am of opinion that there is a different method of applying the direct cooling principle which might prove more simple in such operations, and be made to have certain reserve qualities not possible in the Doherty application.
If the unquestionable success of this system inculcates one lesson more strongly than another, it seems to me it is the value to any business of men who conceive entirely unconventional means and apply them to their own needs in an admittedly unperfected form and of those others who, deducing the possibilities from such an application turn to and employ it on a scale so large and so vital in their operations.
Alva F. Traver, Denver:
Mr. Blauvelt's paper, reporting further progress in the development of the Washer-Cooler is extremely interesting to me. I do not, however, believe that we have reached anything like the limit of the possibilities of this scheme. If, however, as stated in the paper, we are able to obtain the same results with this apparatus with one-fifteenth the amount of cooling surface and have reduced the ground area 25% under that necessary in the ordinary condensing systems, it shows at least that we are working along the right lines.
I regret exceedingly that since the last report on this subject to this Association, I have been unable to do further experimental work on this type of apparatus, and am therefore unable to give any definite results. There are, however, a few points brought out in the paper with which I do not agree, and some of the actual results are not reported, which would help us in the further development of the apparatus.
On the second page of Mr. Blauvelt's paper, he states that from theoretical considerations, four or more stages of condensation are preferable. It is my belief that with this type of apparatus cooling with condensed liquor, the rapidity of cooling has no appreciable effect on the quality of the gas. The mere rapid cooling of the gas can not in itself do harm unless some of the constituents are condensed out and carried away. With this system of cooling, as we do only with the condensed liquors, which are thoroughly saturated, I do not believe it possible to cool too rapidly. Experiments that I have made along this line have seemed to bear out this contention. The only limit, as far as I can see, depends on our ability to sub-divide the cooling water into fine enough streams so that it will effectively cool the gas quickly. However, no experiments ,as far as I know, have been reported along this line, that is the determination of the most efficient apparatus for the dividing of the streams of water and the amount of circulating liquor actually necessary.
I would like to ask Mr. Blauvelt, however, whether or not he has tried to do all his cooling in one of his shells by pumping all of his circulating liquor through that shell and if so what resuts he has obtained.
No figures are given in the paper to show the actual efficiency of the cooling coils as heat transfering agents. Perhaps Mr. Blauvelt can tell us what is the actual rate of heat transfer per square foot of surface per degree difference in temperature per hour; also which form of cooling coil has been found the more efficient.
In order to balance the initial cost and the operating cost of this apparatus against the ordinary forms it would be well to know the rate at which cooling circulating liquor is pumped, the total head pumped against, the loss in head through the coils and the loss in head in the distributing sprays at the top of the scrubber. This will allow us to figure the cost of pumping. I would also like to know what form of pump is now used for handling this circulating liquor and what efficiency is obtained from it.
As I understand Mr. Blauvelt's arrangement, no tar extractor, other than the Washer-Cooler, is used anywhere in the system the gas entering the shells of the cooler immediately after leaving the hydraulic and going from the cooler direct to the ammonia washing apparatus. My experience along this line has been that scrubber shells with trays arranged as in this one will not effectively remove all the tar, some of it being carried forward into the other apparatus. If Mr. Blauvelt has succeeded in eliminating all his tar with scrubber shells I would like to know the arrangement.
The entire scheme as shown by Mr. Blauvelt is slightly different than the arrangement which was originally proposed; that is, that the apparatus act not only as a condenser but also as a scrubber. I believe, however, that Mr. Blauvelt is working along the right lines and that the condensing or cooling system should be entirely separate from the scrubbing system.
I trust that further work along this line will be done by the members of the Association during the coming year, and as I expect to have some definite data from an installation I am now putting in in Denver, I trust another paper on this subject will be presented to the Association next year.
John Batten, Detroit :
The old statement that practically no progress has been made in any part of the manufacture of gas is probably substantiated better in no department than that of gas condensing. The normal and practically the only method in use from the earliest days of the gas business up until the last few years has been that of transferring the heat of the gas to water by the medium of thin tubes. In the paper that was presented by Mr. Seymour, three years ago, a description was given of the work which had been done at Grand Rapids, and it embodied with the possible exception of some work that had been done at Denver, the only work done in connection with the operation of the Doherty Washer-Cooler, as a gas condenser in coal gas operation that I know of. The ability to transfer heat from gas to water by actual contact of the gas with the water, and the efficiency of such a method has been known for a long time, but it appears as though the ordinary gas man must have considered it a more or less immoral operation, which would have resulted in some dire and mysterious effects on the quality of the gas. However, Mr. Blauvelt has described his method which appears to be an extremely effective one in getting rid of any deleterious effect on the gas by virtue of this actual contact. As a result of his passing the gas and the water always in opposite directions, tar is deposited from the gas and passes from contact with it at a constantly increasing temperature, thus making it absolutely impossible for the tar to carry down illuminants.
The virtue of this installation over the one at Grand Rapids from the standpoint of cooling only is shown in the increased efficiency due to passage of the gas invariably in an opposite direction to the water. It seems to me that the value of this new type of condenser will be found more particularly in the possibility which it opens up to the perplexed gas engineer of increasing the capacity of his plant with practically a small increase in cost, with no increase in ground area required and by the utilization of his present outgrown apparatus. This method of condensing and scrubbing has been tried now on coal gas in Grand Rapids and on coke oven gas by Mr. Blauvelt in Detroit; but I believe that it has never been used on water gas. Mr. Dewey in Detroit has committed himself to an installation of this kind, with the object of cooling and condensing the water gas made at the Station A plant of the Detroit company.
For the installation of a new 2,200,000-foot water gas machine it became necessary to abandon the old 500,000-foot per day hand stoked retort house with accompanying condensers and scrubbers. It also became necessary to largely increase the condensing capacity of the water gas plant. Moreover, the regular water gas scrubber filled with grids rapidly became clogged with a deposit of lamp-black and carbon with accompanying high backpressure on the machines, as a result of which they are at present permanently by-passed. Part of the condensing plant discarded consisted of a tubular box condenser size: 30x14x5, of an ancient pattern, designed and capable of cooling 500,000 cu.ft. of gas per day from 120 deg. F. to 90 deg. F. The tubes and crown sheets were ripped out and their place taken by three stacks of