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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
t h e sugar season, they devote the rest of the year t o t h e various subjects outlined in their courses. The fourth and fifth years of the sugar school, therefore, are quite special in their nature and are open t o graduates and senior students of standard schools of .engineering. The student of the graduate type is classed according t o his preliminary training and allowed t o elect such subjects as he may be able t o carry out profitably, t h e utmost latitude being given him, The Audubon Sugar School is now twenty-five years old. The number of students during t h e past five years has been 124,94, 6 5 , 7 0 , 7 j . The School graduates each year from I O t o 2 5 students. These young men have made good without exception. They are scattered all over t h e sugar world and occupy many of t h e most important positions in t h e sugar industry, which facts are taken t o indicate t h a t t h e school is founded upon correct pedagogic principles. CODE OF ETHICS
Just one thing more might be mentioned in closing.
It is somewhat difficult t o discuss this and yet its extreme importance is beyond question. From t h e time a student enters t h e Audubon Sugar School until he leaves, it is t h e writer’s custom t o call frequent attention t o t h e fact t h a t no student can hope t o learn much chemistry or mechanics or anything else of t h a t sort a t college. He merely learns where t h e Iiterature is, what t h e problems are and how t o study them for himself personally. One thing, however, he can learn a t college and t h a t is t h e standard of character necessary for success in Chemical Engineering. These men are not expected t o stay engineers or chemists; such positions are only stepping-stones. Each man should hope t o be, a t some time, a superintendent or administrator and if positions of this type are t o be won by merit, t h a t merit must include absolute personal integrity, Any lapse from t h e highest possible code of honor will destroy t h e usefulness of a chemist or a superintendent. Absolute truthfulness in work and in reports, loyalty, willingness t o cooperate-these things are essential t o t h e highest success in the sugar business. This is ‘the code of t h e students in the Sugar School, insisted upon by themselves from the time they enter the university. Lapses are treated with the rude but efficient justice of student self-government and, by t h e time a man graduates, these standards are ground into him and are a part of his professional character. It is a matter of record in t h e Sugar School t h a t in all t h e years of its history, there has not yet been one of its alumni t o prove recreant t o its personal standards, during t h e after years of his actual contact with t h e business world. The graduates of t h e Sugar School are more or less well-trained in t h e sugar industry, fair scientists or excellent as the case may be, but in all instances they are honorable men, trustworthy and loyal. They have had this record for a quarter of a century without a break. This is t h e one point in which t h e Audubon Sugar School feels it has a right t o be proud. AUDUBONSUGAR SCHOOL LOUISIANASTATE UNIVERSITY BATONROUGE
Vol. 9 , No. 4
THE CONCENTRATION OF SULFURIC ACID B y E. H. ARMSTRONG Received December 26, 1916
Owing t o the unusual demand for munitions and a s sulfuric acid is largely used in t h e manufacture of these products. there has been created a great demand for high strength sulfuric acid running from 93 t o 97 per cent HzS04. I n the old days t h e high strength sulfuric acid required was made very largely in iron and platinum stills. There are a number of other methods used for concentrating sulfuric acid b u t as all these give a small output and a s the demand for t h e last year required a large tonnage, t h e tower method, in a large number of cases, has been resorted t o by a great many chemical companies; in other cases t h e acid is first passed down a tower where it gets a preliminary concentration, bringing it up t o 62 t o 6 3 ’ BC. and thence through cast-iron pans t h a t set in a furnace, one above t h e other; by t h e time it gets t o t h e last pan, which is directly over the fire, it has attained t h e concentration of from 9 3 per cent t o 98 per cent H2S04. In this case t h e gases of combustion from t h e furnaces pass under t h e pans t o t h e tower, a t which point t h e y become mixed with t h e vapors from t h e p a n ; t h e mixed gases pass through t h e tower and thence through a system of scrubbers t o t h e atmosphere. There is quite a difference in t h e methods pursued in building t h e towers, a n d also t h e arrangements of the scrubbers for t h e recovery of t h e distillates. But the principle of concentrating in towers is t h e same, as practically all t h e engineers engaged in constructing t h e plants use quartz for t h e packing and an oil flame for generating the heat. The writer has had considerable experience recently in supervising t h e operation of some concentrators. There was very little known in t h e South, previous t o t h e last year, about concentrating acid t o such high strength; this being true, it was largely a question of experimenting t o find t h e best method of operating CHEMICAL
DISINTEGRATION
OF
QUARTZ
PACKING
One of t h e first conditions t h a t t h e writer observed was t h a t an apparent obstruction would develop in the towers after a week t o ten days’ operation. necessitating shutting the plant down and washing t h e tower, after which t h e plant would usually run very satisfactorily for another week or so. During t h e abovementioned washouts, the writer observed a very heavy non-gritty substance coming from t h e tower. It was then concluded t h a t this substance must be silica and as silica could only come from a chemical disintegration of the quartz in t h e tower packing, t h e writer became convinced t h a t t h e quartz was undergoing a chemical disintegration, most especially as there was a considerable quantity of aluminum in t h e acid passing over t h e tower. This was finally proven t o my entire satisfaction by t h e fact t h a t after some weeks’ operation, t h e plant would show all symptoms of t h e tower being too open and: in one case, it was found t h a t more t h a n one-half of t h e quartz originally in t h e tower had gone in solution and passed out. I n others i t was found t h a t chan-
Apr., 1917
T H E J O U R N A L OF I N D U S T R I A L A N D ENGIMEERING C H E M I S T R Y
nels had formed through t h e packing, owing t o t h e dissolution of t h e quartz. I n view of t h e above, there can hardly be a n y disputing t h e fact t h a t under t h e conditions prevailing in t h e concentrating tower there is a chemical disintegration of t h e packing. Before t h e writer had acquired t h e above-mentioned evidence, t h e question was taken up with a number of very able men. but in no case did they subscribe t o t h e theory t h a t there could be a chemical disintegration of t h e packing. On three different occasions one of our towers became so open t h a t i t would not concentrate beyond 63' BC. and in each case t h e tower was got back t o as good condition or better t h a n i t was when first built, a n d in one special instance t h e plant was brought up from 9 tons of 6 6 " Be. in 24 hrs. t o 29.9 tons in 24 hrs The actual time t h e plant was stopped t o make t h e above stated change did not extend over z1/2 hrs. The condition was remedied by simply removing t h e lute on t o p of tower a n d introducing a piece of ordinary light cast-iron drain pipe through t h e opening in tower t o p and passing small pieces of broken quartz through t h e pipe into tower. T h e end of t h e pipe was moved about as desired, thereby making i t possible t o place t h e quartz in a n y p a r t of t h e tower. During a period of several months there was p u t into this tower as much quartz as was originally used t o pack i t , yet a t t h e end of this period t h e tower did not contain any more quartz t h a n it did when i t was first started. As there was no quartz removed from t h e tower a t any time i t is quite evident t h a t t h e packing was being removed by t h e action of heat a n d acid At one time, after t h e tower had been cooled off, a n examination by means of a n electric light let down in t h e tower showed t h a t on one side t h e packing was gone until there was very little left over t h e arches. On t h a t particular occasion i t took 40 kegs of broken quartz t o fill in t h e crevices in t h e tower so as t o bring t h a t side of t h e packing u p level with t h e rest. One party, who was operating a plant built similar t o ours, advised t h a t he usually washed his tower out with water about four times, after which he had t o shut it down and repack t h e tower. This man's experience bears out t h e theory advanced by t h e writer, t h a t there was a chemical disintegration of t h e packing under t h e conditions prevailing in t h e concentrating tower PLAS
AND
OPERATION
OF A
TOWER
CONCLNTRATIXG
PLANT
There is a series of symptoms present t h a t if properly followed out will generally lead one t o a proper understanding of t h e trouble. I n order t o make this plain, I will briefly describe a general lay-out of a tower concentrating plant. There is a small brick furnace into which t h e oil is sprayed b y steam From this furnace there is a flue leading into t h e side of concentrathg tower This tower has a brick lining a n d brick arches a n d is packed with about 4 f t . of small quartz, leaving about 5 f t . of space between t o p of tower and t o p of packing. The acid is fed t o t h e tower by a syphon-andboot arrangement so t h a t there is about l / * cu. ft. sprayed over t h e packing about once every 50 seconds. After t h e boot has become nearly e m p t y t h e syphon
387
gets air, which stops it from flowing; t h e boot in t h e meantime is being refilled from a supply t a n k overhead. When t h e boot fills t o a certain point t h e syphon automatically starts emptying same, so we have a n alternating spray. This is done t o give t h e heat in the tower a chance t o recover and t h e tower is supposed t o concentrate better with this arrangement t h a n when fed continuously. The vapors and mists of acid pass from t h e tower into t h e scrubbers through a n 18-in. flue, this flue being divided so t h a t one-half of t h e gas goes into each scrubber. These scrubbers are merely enclosed tanks packed with fine gravel. The gravel packing is supported on brick a n d coke in t h e bottom of scrubbers, t h e brick being so arranged t h a t tunnels or passageways are provided for t h e gas t o pass out through a 12-in. flue in t h e bottom and thence t o t h e auxiliary scrubber packedwith coke. The draught is created i n t h e flues b y either a fan or steam jets a n d as each plant has a certain draught pressure t h a t gives t h e best results it is generally tried t o keep t h e draught as near this pressure as possible. I n t h e flue between t h e furnace a n d tower there is a pyrometer tube placed. connected b y wires t o a dial which gives a continuous record of t h e temperature of the gases entering t h e tower. I n t h e flue leaving t h e tower near t h e t o p a n ordinary glass U-tube containing water indicates t h e suction inside t h e flue. There is also placed a t this point a Fahrenheit thermometer, so t h a t by observing t h e temperature of gas entering tower a n d noticing t h e temperature and suction in t o p flue, one can get a pretty good line on t h e working of t h e plant. For instance, a tower doing proper work will usually show about 1 2 0 0 t o 1400" F. for t h e gas entering, and about 280 t o 290" F. with about 6 / ~in. suction in t h e flue leaving t h e t o p of t h e tower. When t h e tower begins t o become foul there will be observed a n increase in t h e temperature of gas entering t h e tower and a n increase in t h e suction pressure in t h e flue leaving t o p of tower. Also there will be observed a decrease in t h e temperature of t h e gas leaving t h e tower and when this temperature falls t o about 2 j 0 " F. it will be found t h a t very little 66" BE.acid is being made. This condition is corrected by shutting down t h e tower and running weak acid down same until t h e packing becomes comparatively cool, after which it should be thoroughly washed with water running over the packing for a t least 1 2 hrs. When t h e tower is again started i t will be found t h a t t h e temperature of gas entering it will be about 200" F. lower and t h e temperature of gas leaving i t will be 40 t o 50" higher with t h e suction pressure in flue reduced t o about onehalf t o five-eighths of a n inch. It is absolutely necessary t o maintain a strong suction, either b y steam jets or a fan, SO t h a t all vapor and distillates will be quickly taken from t h e tower as rapidly as formed, otherwise they would condense and dilute t h e 66" acid, thereby undoing t h e work already performed. On t h e other hand, when the tower packing becomes too open SO t h a t t h e hot gases and acid are not split up into minute quantities t h e acid will pass through
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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
without attaining a strength greater t h a n 63 t o 64' BC. and t h e gases will pass out of t h e tower entirely too hot, going as high as 350 t o 360" F.; also t h e suction of t h e flue leaving t h e tower will drop t o almost nothing, while t h e temperature of t h e gas entering t h e tower will decrease from 2 0 0 t o 300' F. The above-described conditions were t h e ones t h a t were corrected by introducing broken quartz through t h e lute a t t h e t o p of t h e tower. DIFFICULTY
WITH
AN
OPEN
BRICK
LINING BETWEEN
T H E PACKING A N D LEAD
T h e writer had a very peculiar experience on one occasion. T h e tower showed all symptoms of being too open. It was s h u t down and t h e t o p removed b u t t h e packing appeared t o be in perfect condition. However, as i t was quite evident t h a t t h e gas was passing too freely through t h e tower and as we had been unable t o get any 66" acid from this unit for several days previous, i t was decided t o remove t h e packing, not disturbing, however, t h e 18-in. brick lining between t h e packing a n d lead. After t h e packing h a d been removed and t h e tower repacked, t h e plant was started up, b u t with no better results t h a n before. It is needless t o say t h a t t h e writer was very much concerned about t h e matter, as t h e tower would not produce 66" acid a n d yet there was nothing apparently wrong with t h e packing. However, t h e t o p was removed again a n d a very careful examination was made t o determine, if possible, how t h e gas was slipping through t h e tower with so little resistance. It was observed t h a t t h e brick wall between packing a n d lead was very open, there being spaces of from to in. between t h e bricks a n d as t h e bricks had been laid dry. with t h e exception of about 3 in. on t h e edge of t h e wall, it was decided t h a t t h e heat was evidently coming u p through t h e wall a n d not through t h e packing, as i t should. T h e wall was taken down t o t h e level of t h e packing (about 5 ft. from t o p of tower) a n d acid-proof cement, consisting of silicate of soda a n d silax, was poured down through crevices in t h e wall a n d a small amount of i t appeared under t h e arches, proving t h a t t h e theory of t h e heat going u p through t h e wall was a correct one. The wall was then laid from t h e t o p of t h e packing up in mortar made from silicate of soda a n d silax. This mortar was used very liberally, making t h e bricks tight with it, just as would be done in building a n ordinary brick wall. When this work had been finished t h e t o p was replaced a n d plant started u p ; i t worked beautifully, even better t h a n i t h a d ever worked before. LOSSES OF ACID I N T H E COKCENTRATOR AKD REGULATION OF DRAUGHT
I n regard t o losses of acid in t h e concentrator under normal conditions, when t h e tower was being fed with 60,000 lbs. of 60' acid in 24 hrs., t h e losses would amount t o from 2 , 0 0 0 t o 4,000 lbs. of 60' BC. acid per d a y of 24 hrs. and there would be recovered as 66" B&. acid about 39,000 lbs., equivalent t o 46,792 lbs. of 60" B4, acid and t h e balance, or 9,208 lbs., would be recovered in t h e distillates from scrubbers. This scrubber acid runs about 46' BC. It is
Vol. 9, No. 4
pumped over t o t h e sulfuric acid plant and sent down t h e Glover tower, where i t is brought up t o 60" BC. along with t h e other acid passing over a Glover tower, after which i t is returned t o t h e concentrating plant again. T h e losses varied greatly, according t o t h e amount of draught t h a t was used. When a very strong draught was being used i t was found t h a t t h e loss of H2S04 was very much greater t h a n was sustained when only a moderate draught was being used on plant. W e , therefore, tried t o get t h e happy medium of using just enough draught t o take t h e distillate from t h e top of t h e tower and at same time not t o have too great a loss at t h e exit stack. I n connection with t h e above, i t was found t h a t when using Lunge's method, namely, I O cc. of iV/ro caustic soda solution a n d aspirating gas through t h e same t h a t t h e loss of SOs would r u n from 0 . 2 5 t o 0 . j per cent. This test was made twice daily on each plant and was depended upon t o a certain extent t o determine t h e amount of draught which should be used, but as t h e tower very rapidly became choked, necessitating a constant increase of draught, t h e testing of t h e gases was of very small benefit in regulating t h e plant. However, if i t were possible t o get a tower packing t h a t would not disintegrate, so t h a t t h e opening would s t a y uniform, t h e testing of t h e exit gases could be used t o a great advantage as a method of control. SOUTHERN FERTILIZER A N D CHEMICAL COMPANY SAVANNAH, GEORGIA
PRINTING PLATES FROM PHENOL RESIN COMPOUNDS By I,. V. REDMAN, A. J, WEITH,F. P. BROCK Received January 26, 1917
T h e growth of syndicate work in illustrated advertising, comic supplement a n d "filler" for our 30,000 American Newspapers, has created a need for a material which will lend itself t o t h e rapid production of printing plates in manifold. T h e plate requires t o be produced rapidly a n d inexpensively a n d must be of such quality as will print clearly on t h e cheap sheet used by daily papers. Such a plate is in no way intended t o take t h e place of copper, zinc, stone or wood cuts where there is needed only one cut or a t most a very few cuts of any one subject, such as in t h e printing of magazines, books, and catalogs. T h e new plate is designed t o fill t h e need of thousands of daily papers which require t h e same news t o print at t h e same time, either advertising, comic supplement, news of general interest t o t h e country or "filler" for dailies or weeklies. Printing plates for this work have been made from celluloid compounds a n d shellac by pressing t h e celluloid or shellac plastic into t h e original papier m$chC mat which had previously received an impression from t h e zinc etching. T h e celluloid plate is used extensively. T h e shellac plate does not seem t o h a v e made its way t o a commercial success. T h e shellac a n d celluloid plates will not stand t h e heat, pressure a n d moisture required for making t h e papier miich6 mat for stereotype machines. Also t h e "dots" making u p t h e screen in half-tones of celluloid are not full
