86
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 15, No. 1
Trend of Modern Fertilizer Plant Construction' By Peter S. Gilchrist CHARLOTTE, N. C .
A
M O D E R N facROCK STORAGE There is a great tendency to get away from the time-honored tory should meet fertilizer buildings, brought about by the disculfy of getting s u s There should be one or two the following princient labor f or short seasons, high-wage schedule, and heavy insurance, concrete or steel silos of amcipal requirements: and thefaci that manufacturers are beginning to realize that they will ple capacity, located conven1-Be a s u b s t a n t i a l have to operate on a closer margin of profit. In this paper we have iently so that cars can disstructure and of such matepointed out the requirements for consfruction of a modern fertilizer charge the phosphate rock rials and construction as to plant, together with a description of present practice in manipulainto silo elevator, or be unentail the minimum upkeep tion of equipment and handling of materials. loaded from cars by autoand obtain the lowest rate of matic shovel into elevator, insurance. as the case may be. If rock is 2-Be so designed that the minimum amount of labor shall coarse a crusher is used through which the rock passes on its way be required for operation, and that the fertilizers are produced to the elevator, so that the greater part of the rock can run from in the best chemical and mechanical conditions. the silos directly into the grinding mill, arrangements being made 3-Have printing press for bags. SO that the balance of the rock in the silos can be transferred 4-Have ample trackage. mechanically to the mills. 5-Make provision for condensing noxious vapors. GRINDING AND ACIDULATING 6-Locate office and bag shed convenient, to factory. 7-Provide ample fire protection. Many different mills are used for grinding the rock, the type 8-Be equipped with mechanical labor-saving devices when they can show a definite return upon the investment after de- being determined by capacity. repairs, and depreciation and power consumed. Some mills give a finished product, but ducting wear, tear, and depreciation. it is generally advantageous to use air separators through which 9-Be so designed that the materials are handled as little as possible, and the manufacture may be as nearly continuous as the partially ground rock is passed, or to maintain a strong suction on the mill and pass the air and finely ground rock through practicable. 10-The grinding material should be carefully selected so that air separators. Considerable difference exists as to how fine the the rock is of correct fineness to obtain the best mechanical rock should be ground. Many superintendents look upon reactions with sulfuric acid, thereby producing a high available capacity as the goal, and are content with 96 per cent through with low insoluble and with a negligible percentage of free acid. 60 mesh in place of thinking in units of available Pa05 in the acid 11-Acid phosphate, when cured, should be of the lowest phosphate. Modern plants require a 98 per cent product through 80 mesh as a minimum, while some aim for 96 per cent moisture content and in good mechanical condition. 12-Sufficient equipment should be installed so that all ferti- through 100 mesh. Fine grinding enables a minimum amount of sulfuric acid to be lizer materials are ground to sufficient fineness before manipulatused, the reaction is quicker and more intense, with the result ing, and the manipulating should take place considerably in advance of the shipping, as the fertilizer should be shipped as dry that the greater heat dries off more of the moisture, all of which as possible so that it will be in good mechanical condition for tends to dryer acid phosphate and low insoluble. Acid phosphate dens are of various designs, the great essendrilling. Furthermore, it should be of sufficient dryness so that tials being solidity, ease of discharging, and a product as dry as the weights will be accurate, 13-Provisions for filling and weighing the bags and moving possible and in a fine mechanical condition. Hand labor in dens is very objectionable and difficult to handle, apart from the them to the cars with the least possible delay in handling. cost of same. There have been developed other devices for disLOCATION OF PLANT charging the dens-an electric shovel is used in some instances Care should be taken to get the local advantages of the site where a clam-shell or orange-peel bucket operated by an overwith relation to wharf, railroad connections, and contour, as head crane is used. Mechanical discharging dens are used, well as the receiving of the various raw materials and shipping such as the Svenska and the Forbis. Several of each are in operation in this country. of the finished fertilizer. The mechanical discharging den is receiving the most consideraBUILDINGS tion to-day. The grab-bucket operation, while giving a large The buildings should be of concrete base with steel frame and tonnage, does not have the acid phosphate in as good mechanical hollow tile walls with noncombustible roof of tile, cement, or condition as it might be, and the compression the phosphate gypsum, the idea being to make the structure as near fireproof as receives is apt to be detrimental to the PeOs solubility. In mechanical discharging dens it is most important that as little mapossible, and to reduce the upkeep and repairs to the minimum. Light and ventilation are now considered absolutely essen- chinery be used as possible, for the free phosphoric acid and the tial to economical operation, as it means less waste of ma- corrosive action of the gases act rapidly on iron, and this natuterials, and labor gives a higher efficiency when operating in a rally entails a heavy upkeep. The Forbis den, in the writer's opinion, comes nearer givhg well-lighted and ventilated building. The loading platform should be housed in, with continuous an ideal equipment. It consists of a circular concrete den, sliding doors for protection from the rain and severe cold weather. hollow in the center, operated on a single circular track, making The floors for this platform and for the main buildings should a complete revolution in about 12 hrs. and requiring not over 3 h. p. to revolve it when loaded. Above the den is a solid be of hard-surfaced concrete. stationary platform with a cover for the den suspended from it. 1 Presented before the Division of Fertilizer Chemistry at the 64th On the platform is the mixer with weighing hopper and acid Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 boots, the excavator for the acid phosphate, the fume pipe, to 8, 1922.
January, 1923
INDUSTRIAL AND ENGINEERING CHEMISTRY
etc. The measuring and weighing devices for the raw materials are such as to get very accurate results, this being a very important part of the manufacture. The mixing of the acid phosphate and excavating the acid phosphate go on simultaneously. The acid phosphate remains in the den 24 hrs. before it reaches the excavator. Since the construction of the den is such that it is not opened up, the phosphate retains the heat until it is cut. The cuts are about l/8 in. thick when the steam is liberated and drawn off by an exhauster. The thin layer of phosphate, as i t is cut, falls onto angle-iron trays where it is discharged to any convenient point, its condition resembling sand. The excavator is simply a two-strand elevator with links capable of withstanding the free phosphoric acid present, with angle-iron trays in place of buckets. The capacity of the den is from 100 to 150 tons per day, but if operating continuously i t is approximately 400 tons per 24 hrs. The den only revolves while the mixing is being done; when completed the den is stopped. The finished product as it leaves the den is very light and contains usually about 11 per cent moisture, with about 1 to l l / d per cent insoluble P~06,which in a short time rapidly reduces. It is equivalent to acid phosphate made three to four weeks by the other methods. There is only one man operating it-namely, the mixer-and either a crane man or car man t o take it t o storage from the den.
87
no difficulty in handling 600 lbs. to a load on a good floor, and discharging it in the car stacked, obviating stackers unless the car is to be heavily loaded. This method gives a clean bag with accurate weight. Test bags should be taken at intervals to see that the weight is correct. The complete fertilizers are delivered to a hopper in front of the bagging machine, requiring one man a t the elevator, one on the machine, one weigher, two sewers, one chute man, two or three tuckers, one tag boy, and, if stackers are used, two additional men. These easily do 200 to 225 tons per 10 hrs. A modern factory can put out fertilizer in good mechanical condition without harm to the bags, maintaining a uniform output with a very small labor charge; the overhead expenses are not excessive and the upkeep of a well-designed and well-built factory is low, enabling the manufacturer to produce his goods at the lowest possible cost and make a profit when others fail to do so. I n days of close competition the old-type factories are at a great advantage as compared with the modern factory.
Hotel Accommodations for the Spring Meeting of the A. C. S.
It is very apparent that the coming spring meeting of our SOCIETYwill be very largely attended, and i t is recommended that all who desire hotel accommodations make their reservaThis is done most economically by the electrically operated tions as early as possible-at least thirty days in advance of the grab-bucket crane of from 2- or 4-cu. yd. capacity. One crane man meeting. The hotel headquarters will be at the Hotel Taft, at one of the factories handles 6000 tons per 10 hrs. with a 2l/~-cu. and the management of this hcstelry advises that reservations for this hotel be made, if possible, ninety days in advance. In yd. bucket. No hand labor or any other mechanical device has case there is an overflow which cannot be provided for with acbeen able to come anywhere near this when labor and equipment commodations in New Haven, arrangements have been made upkeep are taken into consideration, as it not only handles the whereby guests may obtain suitable reservations in hotels of neighboring cities-namely, Hotel Stratfield in Bridgeport, material but digs it a t the same time. Conn., Hotel Winthrop in Meriden, Conn., and Hotel Elton in Waterbury, Conn. MANIPULATION OF COMPLETE FERTILIZER The committee on hotels and transportation have canvassed very carefully the hotel and apartment house situation and deAccurate weighing is absolutely essential to success. The in- sire to announce the following list of hotels, arranging them as accurate weighing of ingredients with consequent overages is nearly as possible in the order of convenient location. one of the chief sources of loss to manufacturers. NEW HAVEN HOTELS Usually, a series of hoppers is elevated so as to admit of a CAPACITY RATES wide belt being installed to carry the materials to the manipulating Single Room Double Room T a f t . . ..................... 400 $3 to $3.50 $5 to $6 or bagging machines, as the materials are discharged from the Garde.. .................... 100 $2.50 up $5 to $6 Duncan.. .................. 100 $2 t o 83 $4 t o $6 scale hoppers and located underneath the storage hopper. Bishop.. ................... 50 $3 $5 The crane or other mechanical device puts the various in- Strand ..................... 40 $1.50 to $3 $3 to $5 $2 (flat rate and for men only) Baths.. ...............l50 gredients into the hoppers, which have close cut-off gates, The Liberty Royal .................... 75 $1.50 (men only) $2 t o $3 scales have large dials so that the operator sees the weight all the time the material is on the scale and can shut off instantly OUTSIDEHOTELS when the desired weight is attained. The scale hoppers are CAPACITY RATES Sin le R o o m Double Room discharged a t a given signal, and refilled for the next batch. Stratfield Bridgeport.. ...... 100 $3.50 $5 to $6 The hopper system calls for fewer men than are generally needed. Winthrod, Meriden.. ........ 50 $2 t o $3 100 $2.50 up $5 to $8 Elton, Waterbury.. ......... The manipulated goods are taken by the crane t o storage and are finally passed through bagging machines. The Hotel Taft offers a special arrangement on the American The manipulating and bagging machines are of various types. plan : The vibrating screens are receiving much attention. Good Double room bath meals 3) $13.00 per day work has been done with the hexagonal revolving screens with Double room: bath: meals { 2 ) $11.00 per day suitable tapping devices. Rapid operation is necessary to get It is too early for the committee to make any announcement tonnage; hence, a batch mixer has to be used that will fill, possible accommodations in university dormitories. mix, and empty in a very short time. Automatic weighing regarding It can be stated, however, that the Yale dining hall will be in machines are being extensively used, and little difficulty is ex- operation during the week of the convention. The members of the hotel committee will be glad t o assist in every way possible perienced when the goods are dry. Instead of weighing the bags on the ground floor, this is in the making of early reservations. being done on an elevated platform, with an endless slat conveyor HOTEL AND TRANSPORTATION COMMITTEE located so that as the weigher drops the bag i t falls onto the slat DR. RALPH W. LANGLEY, Chairman, 84 McKinley Ave., conveyor where the bag sewer gets it. The bag travels till it Haven, Conn. is discharged at the end, down a chute, where the chute man di- New PROF. H. W. FOOTE, Sterling Chemistry Laboratory, rects i t onto a truck-three 200-lb. bags or five 135-lb. or six 100- New Haven, Conn. lb. bags being dropped onto a hand truck. The truck man has DR. E. MUNROEBAILEY,621 Elm St., New Haven, Conn.
HANDLING ACIDPHOSPHATE
