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water is also used on the outside of the 3 inch pipes in the same way as in the single pipe coolers.
The cooling coils for the secondary circulation are placed directly over the primary cooling coils, thus economizing space and making possible without extra piping, the use on the primary coils of the cooling water from the secondary coils.
As temperature conditions during condensation are practically the same for both rich and lean gas, only two cooling and circulating systems are required for the four washer-coolers. A centrifugal pump is provided to maintain the circulation through each system. A third pump is installed in such a manner that it can be used to handle either the primary or secondary circulation.
The washer-coolers have been in continuous service since July, 1909. The only changes made since the original installation were the installation of a high efficiency pump, to take the place of a low efficiency pump on the primary circulation, and the addition of seven stacks of double pipe cooler. The addition to the cooling capacity was made in connection with an enlargement of plant which increased the quantity of gas to be cooled daily about 2,000,000 cubic feet.
There has been no trouble on account of napthalene stoppages in the apparatus. As naphthalene can collect in masses only on stationary surfaces, there can be no trouble from this source in an apparatus where all the surfaces are at all times covered with flowing liquor, which immediately carries away any particles of naphthalene which condense.
There is a slight accumulation of naphthalene on the walls of the cooling pipes through which the animonia liquor circulates. This is very quickly removed by steaming out the coil. In order to maintain the cooling efficiency of the pipe coils, it has been found advisable to steam them out at intervals of about three months.
So far as observed, the rapid cooling has had no ill effect upon the illuminating power of the gas. Loss of candle power in condensation is due to the absorption of illuminants by tar. Such losses increase if the tar, after condensation, is allowed to remain in contact with the gas, and especially if the temperature of the tar, after condensation, is reduced before it is separated from the gas. In the washer-cooler the tar after condensation flows down through the apparatus. As it descends with the liquor its temperature is constantly raised and its power to absorb illuminants is greatly reduced. It is somewhat of a question also whether the tar, after condensation, ever comes in contact with the gas. It is probable that each particle of tar is covered with water immediately after it has condensed.
Temperature observations made July 21, 1910, are given below:
The results of this substitution of washer-coolers for tubular condenesrs have been very satisfactory. The total condensing capacity has been increased 50% while the ground area occupied by the condensing plant, including the pumping station, has been reduced 25%. The cooling surface in the new installation per unit of condensation is less than 1-15 that provided in the old tubular condensers. The labor of cleaning the apparatus has been reduced, and naphthalene stoppages have ceased. The effective scrubbing during condensation removes practically all the condensate as soon as produced, thus delivering a much cleaner gas to the ammonia scrubbers than was obtained from the tubular condensers.
DISCUSSION. William Seymour, Grand Rapids :
Of course this paper is very interesting to me as it is descriptive of apparatus and work with which we have had much to do in the Grand Rapids' plant.
Our apparatus has been developed to practically the same stage as that used by Mr. Blauvelt, and our condensing is entirely performed by this type of apparatus.
We have obtained such good results with this system that we can substantiate all that Mr. Blauvelt says in its favor. It seems strange that it has not been more widely adopted.
Personally, and because it might serve to impress upon some the advantages of this system, I would like to see some results given of the transfer of heat units through the coils per square foot per degree difference in temperature per minute. Prof. White, Ann Arbor:
It would have been interesting if Mr. Blauvelt had given a fuller statement of the efficiency if the apparatus as a tar and ammonia scrubber. Apparently it removes a very large proportion of the tar, the statement being that practically all the condensate is removed. This is what might be expected from an efficient scrubber. It has also practically eliminated naphthalene stoppages. The reason for this is not so evident.
It was shown in a paper presented before this Association by Mr. Clary and myself five years ago that naphthalene troubles were frequently produced when the gas carrying in suspension light tar which had passed the condensers and mechanical tar separators reached the ammonia washers and scrubbers. Experiments were cited showing that these light tars high in naphthalene became supersaturated when the ammonia dissolved out from the tar some of the phenols with the result that naphthalene in the free state was returned to the gas. This evil has not happened with Mr. Blauvelt's apparatus for two reasons. In the first place all their tars, both heavy and light, are removed together so that their percentage of naphthalene is not so high as would have been the case with the light tars alone. In the second place Mr. Blauvelt circulates the same liquor continuously, not adding any fresh water. A small amount of water is constantly formed through destructive distillation of the coal but the liquor circulated may be considered as always saturated and incapable of exerting any marked solvent action on the tar. If an attempt were made to simultaneously remove tar and ammonia, naphthalene troubles might occur.
I agree with Mr. Blauvelt in his explanation of the lack of ill effect upon candle-power. I believe that the quicker and more completely the tar can be gotten rid of the better. The old ideas and forms of apparatus are largely due to the mechanical difficulties of removing the tar completely at a high temperature. It was necessary to cool the gas slowly in order that the globules of suspended fog might be large enough to permit frictional separation. If only a part of the tar was removed at high temperatures the residue could not be separated by friction alone and so passed to the ammonia scrubbers with naphthalene troubles as described above.
Samuel Ball, Saginaw:
The results obtained by Mr. Blauvelt with the WasherCooler are very interesting and it seems to me they indicate that we are tending toward a very radical change in our condensing system. Up to the present I think we have all been in the habit of cooling our gas down to normal temperature and removing the tar before bringing the gas into direct contact with crude liquor. I am very much surprised that no trouble is experienced with naphthalene. I should like to ask whether there is any appreciable difference in the per cent of naphthalene in coke oven gas as compared with ordinary coal gas. I know that if we attempt to do any considerable cooling in the ordinary washer we are quite sure to have trouble from naphthalene. For this reason it seems very remarkable that no trouble of this nature is experienced in dropping the temperature 95 degrees in two steps in the washer-cooler.
I should like to inquire as to what per cent of tar is removed in the cooler. Judging from the temperature at the outlet of the cooler it would seem that practically all the tar must be re
moved and in that case the tar extractor could be eliminated from the condensing system.
I should also like to ask whether Mr. Blauvelt has any figures on the amount of liquor pumped through the cooler per thousand of gas.
Ernest F. Lloyd :
So far as I know, the Solvay Process Co., under Mr. Blauvelt's direction is the first company to exclusively rely upon the Doherty System of cooling and scrubbing through the medium of direct contact of the liquor with the gas.
The Solvay application of this principle differs quite materially from the apparatus as originally designed and installed at Grand Rapids. This difference takes two forms; one, that of the mechanical apparatus itself, which is not so important, the other, I believe of much more consequence, viz., that whereas in the Doherty application at Grand Rapids, for, I believe, constructional reasons, the gas passes alternately up in counter current to the liquor and down in company with the liquor, in the Solvay application, the counter current application is maintained throughout. This, I believe, has a greater influence than the mere efficiency of apparatus.
The counter current principle prevents the possibility of any condensed tars coming into contact with any of the gas at a temperature lower than that at which the tar vapor has been liquefied, and it further insures the continually gradual equalization of temperature between gas and cooling liquor, hence there is no opportunity for the cooling tars to further absorb the light hydrocarbons, and there is further a distinct avoidance of any possible temperature shock.
With the alternating counter and concurrent flow of the gas and liquor the gas in the second stage is instantly brought into contact with the liquor in its coolest condition in that compartment, hence the gas must drop into almost instant temperature equilibrium with the liquor, for in its further progress downward through the section, little, if any, cooling can take place, while the cooled tars flowing downward with the gas are in contact with it. Whether this theory of the quick equilibrium of tem