US 2445741 A
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July 20, 1948. A. o. FRANZ ET AL APPARATUS FOR THE MANUFACTURE OF EXPLOSIVES Filed March '51, 1943 [HI lllllllllll ll llllillllllllill I INVENTOR AP VEL 0. FEANZ 3 OE/NCAEPt/NGEE BY am a. w
ATTORNEY Patented July 20, 1948 APPARATUS FOR THE MANUFACTURE OF EXPLOSEVES Arvel 0. Franz and Orin C. Keplinger, Alton, Ill.,
assignors to Olin Indu of Delaware stries, Inc., a corporation Application March 31, 1943, Serial No. 481,369
6 Claims. 1
This invention relates to the manufacture of explosives and more particularly to a continuous nitration apparatus for use in the manufacture of explosives, The nitration process set forth herein is described and claimed in our co-pending application, Serial No. 481,368, filed March 31, 1943, issued as U. S. Patent 2,415,423.
Heretofore explosives have been manufactured in both intermittent typeand continuous type nitration apparatus. Such intermittent apparatus has the serious disadvantage of being relatively large and expensive with a relatively large amount of explosive in process. Prior continuous apparatus are attended by the disadvantage that overnitration and oxidation of the materials to be nitrated at times occurs, with a resultant decrease in efiiciency of production and a lowering of quality of the product. Such overnitration or oxidation is usually the result of failure to maintain each portion of the material to be nitrated in contact with its proper portion of nitrating acid until the reaction is completed, or failure to maintain the reaction mixture at the proper temperature. With certain of the prior nitration apparatus the disadvantage is also obtained that the reaction mixture is recirculated in the reaction vessel so that the nitrated product is continually brought into contact with fresh nitrating acid.
It is therefore an object of this invention to provide a continuous apparatus for the manufacture of such explosives free of the disadvantages attending such prior apparatus.
Another object of the invention is to provide an improved continuous nitration apparatus for manufacturing polynitrated explosives.
A further object of this invention is to provide an improved apparatus for continuous nitration in which oxidation and overnitration are prevented.
A still further object of the invention is to provide a continuous apparatus for effecting aneflicient nitration in the manufacture of polynitrated explosives in which the temperature is readily controlled at the desired level.
Other objects and advantages will become apparent from the following description and drawing in which,
Figure 1 shows a plan view of a nitrating apparatus illustrating one embodiment of this invention, and
Figure 2 is a vertical section, taken at XX", of
the nitrating apparatus of Figure 1, and I Figure 3 is a sectional view taken along lin 3-3 of Figure 2, and
Figure 4 is a sectional view taken along line 44 of Figure 2.
These objects and advantages are obtained in accordance with the present invention by the provision of a novel apparatus in which the nitrating acid and the material to be nitrated are uninterruptedly brought together, uniformly mixed, and the resulting mixture is progressively passed along an extended path through successive zones of forced circulation so controlled as to impede the direct flow of fresh material from the point of entrance to the point of exit and concurrently minimize the possibility of back-flow of treated material from near the point of exit to the point of entrance. During thepassage through said path the mixture is maintained at reaction temperature and subjected to a plurality of zones of opposing forced circulation, the spent acid and nitrated materials being continuously discharged at the end of said path.
In the manufacture of such polynitrated explosives as tetryl, the nitration reaction is not instantaneous but requires a period of time for completion. In the manufacture of such polynitrated explosives as nitroglycerine, no extended period of time is required for the nitration reaction, but a great quantity of heat is developed during the reaction which must be dissipated in order to prevent the mixture from overheating. The apparatus of the present invention is suitable for carrying out both types of reactions.
It has now been found that the heat can be adequately dissipated and the period necessary for reaction is readily obtained when the nitrating mixture is passed through a vertical U-shaped vessel provided with agitators which form the mixture into a plurality of zones of opposing circulation in accordance with this invention.
Referring to the drawing, which represents a preferred embodiment of the apparatus forearrying out the nitration reaction, the tubular vessel is in the form of an upright U-tube I. The U-tube is provided with external cooling or heating jackets 2, 3, 4, 5, 6, 1, and 8 having inlets and outlets 25. Charging inlets 9 and ID are provided for introducing the nitrating acid and material to be nitrated into the entrance leg ll of U-tube I. An outlet 12 is provided on the exit leg 13 of U- tube for discharging the spent acid and product. The inlets 9 and ID for introducing the reagents into the nitrator are preferably maintained at some distance above the surface of the reaction mixture in the nitrator. By thus maintaining the inlets out of contact with" the reaction mixture all possibility for either the reaction mixture or any of its constituents to return through either inlet 9 or III is avoided. This is a distinct advantage over certain of the prior apparatus in which it was possible for the reaction mixture to back up into the feed line for the nitrating acid or the feed line for the material to be nitrated and thus'create a hazardous condition.
A plurality of agitators, for instance l4, l5, I6,
20, 2 I, and 22, maintain the mixture uniform andmaintain any undissolved material uniformly distributed throughout the mixture. The agitators may be so adjusted that no appreciable head of I liquid occurs in either arm II or l3 and are so shaped and arranged th'at they form the mixture into at least two zones of opposing circulation so that practically no part of the mixture in arm I3 returns to arm H.
An outlet I8 is provided at the bottom'of vessel I so that the nitrator can be completely drained in case of emergency, or for cleanin purposes and the like. In operation the reagents are fed in proper proportion through inlets -9 and ill in the arm H to form an initial reaction zone with thorough mixing by the agitator I4, and during the initial reaction, the mixture is cooled to the desired temperature by heat exchange with the cooling medium circulated. through the jacket 2. Thermometer wells such as are illustratedat 26 may be employed to determine the temperature of the mixture in the vessel. The mixture then passes through thesucceeding zones of localized agitation, the temperaturebeing controlled by meansof jackets, for instance 3, 4, 5, 6, 1, and 8, and the product and spent acid are discharged by overflowing from theoutlet l2 at a rate corresponding to the feed. of raw materials. Vents suchas 23 and 24 may be employed toremove fumesor for instance to maintain the mixture at atmospheric pressure.
Propeller type, paddle type,- or any other suitable type of agitators may be employed, provided they are so adjusted thatat least some of the successive. agitatorsact differently on the fluid thereadjacent, respectively. For instance, when the agitator shafts l1 and i9. are rotated in a clockwise direction (as seen in Figure 1) the mixture in both the charging and discharging arms I I and I3, respectively, tends toswirl likewise in a clockwise direction (as viewed from above), but at the bottom of the U, where the two columns of mixture join, the-direction of circulation of the one opposes. that of the other so that zones of opposing circulation. are set up. Any suitable mechanism may be employed for driving the shafts l1 and I9 in the same direction as viewed from above (1. e., opposite directions if viewed along the axis-of the U-tube from one end). For example, each of shafts IT and! maybe provided with pinions 3! and 39, respectively, meshing with a single drive gear38.
By feeding the raw materials into one arm of the U-shaped. vessel and controlling the agitation to form suchopposing zones of forced circulation, the rawmaterials are prevented from short circuiting from the inlets 9 and lllto the'outlet I2" before the-reaction has been completed and likewise, the completely reacted material is we ventedfrom returningto the inlet arm. so that during .thetravel of the constituents from the inlets.9.and. l through the vesselto the discharge outlet. I2, each portion of thematerial to.be.nitrated. is kept uniformly mixed with, its proper proportion of, nitrating acid.
By. way of illustration following, is atypical embodiment of the invention describing the use of the apparatus for the manufacture of tetryl.
One part of dinitromethylaniline is dissolved in 2.43 parts by weight of sulfuric acid (66 B.). The nitrating acid employed contains 68% nitric acid, 16% sulfuric acid, and 16% water. The diameter of the tube forming the U-shaped vessel [employed is about 16 inches and the apparatus is about 4 /2 feet high. The mixture travels about 1 1 feet in going from the inlets 9 and I9 to the outlet l2.
In firststarting the nitration the above described nitrating acid is run into the nitrator throughinlet Illv at the rate of 18.8 gallons per houruntil'thenitrator is about A; full. The feed of the acid-is then stopped and the above described solution of dinitromethylaniline is run into the-nitrator at the rate of 50 gallons per hour for an equal length of time. When this is accomplished the nitrator is sufiiciently filled for the continuous nitration operation to be started. The. dinitromethylaniline solution is then fed'in through inlet 9 at a rate of about 50 gallons per hour andthenitrating acid'is simultaneously fed in. through .inlet Ill at the rate of about"l'8;8 gallons per. hour, thus providing about 0.765 part by weightof'nitric acid per eachpart by weight of'dinitromethylaniline, or only about 20% over the theoretical. acid; requirement. At this :rateof feed, i. e., a nitration cycle of minutes', a yield of about 300 pounds of tetryl per hourwasobtained.
By increasing the rate of feed of the reagent thenitration cycle can be reduced to as short a time as 20 minutes oreven shorter. with satisfactory results; Such increased feed of reagents provides a proportionately increased production rate. This'flexibility-of production rate is of de cided advantage over prior" apparatus; I
The agitator l4 provides. for immediate and uniform mixing ofthe acid. and dinitromethylaniline; Agitatorshafts l1 and [9 are rotated in a' clockwisedirection (aszseen in Figure 1), the several. agitatorblades, in the form shown, being of the'type tendingjto' force at least th suspended particles of adjacent non-homogeneous mixturein a horizontalldirection. Agitators M, I6, and have their'blades so adjusted as to direct at least the suspended particles in the mixture away from the. side walls of the container,. as illustrated bythe arrows'39, and agitators. I5, 20, ancl2l have-their*blades'adjusted' so as to direct at least the suspended particles in. the mixture toward the side walls, as illustrated by arrows 29. Thus within the swirling mixture of each leg of'the U-tubethere are zones of locally opposing circulation wherein'at least the suspended particles travel outwardly or inwardly in relationto the central axlsof the tube depending upon the angle of the blades of each stirrer spider to the radius. Consequently at least the suspended particles follow a generally spiral course, of travel down one legof the U-tube and up the otherleg'to the discharge outlet, the spiral varying in diameter and pitch depending upon the angle at which the blades are set' on' the stirrer with-theresultthat'a crossmixing effect of components is obtained while the mixture. as:a' whole continues to swirl in one direction inone leg; of the U-tube and in. the" opposite direction (as viewed along 'the'axis'of the U-tube from oneend only). inthe other leg, of the vU-tube. The mixture is kept at. a reactiontemperature. of; about 55? C. by flowing, water. or other. coolantas-required through the temperature controlling jackets 2, 3, 4, 5, 6, I, and 8. The mixture in the '5 initial reaction zone has a purplish colorwhich disappears usually before reaching the bottom of the U-shaped vessel l and changes to'a yellow color which persists up to the outlet l2.
By virtue of the vigorous agitation maintained throughout the vessel any tendency of the precipitated product to settle out is prevented. Tetryl is obtained in a yield correspondingto about 95% to 99% of theoretical, having a-pale yellow color and after moderate washing, a melting point in the range of about 127 C. to 129 C. and an acidity calculated as sulfuric acid, equal to about 0.1% to 0.3%, or even less.
Practically all over nitration and oxidation of the dinitromethylaniline is prevented by adding the proper proportion of nitrating acid, preferably not less than or not more than in excess of the theoretical requirement, to each part of the dinitromethylaniline and maintaining a uniform mixture of materials in each zone of circulation while uniformly controlling the temperature of the mixture below 80 C. and preferably between and C. throughout the nitraton' Accordingly, the nitration temperature is maintained from the time of mixing of the raw materials until the reaction is completed, the necessity of starting the reaction at relatively low temperatures as in customary processes and equipment is avoided and a shorter nitration cycle is thus provided, The precipitation of tetryl during nitration tends to thicken the mixture and thus materially aids in the baffling effect, resulting from the zones of opposing circulation, which prevents undesirable intermixing of the various strata of the mixture in the nitrator.
Following is another embodiment of the inveniton describing the use of the apparatus in the manufacture of nitroglycerine.
The nitrating acid employed is composed of about 50% nitric acid and 50% sulfuric acid. The nitrator has about the same dimensions as those described in the above embodiment for the nitrator used in the manufacture of tetryl. In first starting the operation, the nitrator is filled with a spent acid containing about 20% nitric acid, 64% sulfuric acid, and 16% water. Anhydrous glycerine is then fed in through inlet 9 at a rate of about 18.1 gallons per hour and the nitrating acid is simultaneously fed in through inlet If! at the rate of about 72.5 gallons per hour, thus providing about 5 parts by Weight of nitrating acid per each part by weight by glycerine, with only about 28% excess over the theoretical nitric acid requirement. At this rate of feed, a yield of about 441 pounds of nitroglycerine per hour was obtained.
The mixture in the nitrator is kept at a reaction temperature of about 16 C- to 20 C. by flowing any suitable refrigerant through the jackets 2, 3, 4, 5, 6, 1, and 8. Any fumes that develop during the reaction are readily disposed of through vents 23 and 24. The large amount of heat involved in such reactions is readily dissipated in accordance with this invention by means of the large cooling surface provided per unit volume of reaction mixture and the turbulence of agitation,
Although the manufacture of tetryl and nitroglycerine are described in the above specific embodiments, the apparatus of this invention can be used in the manufacture of other polynitrated explosive compounds presenting similar manufacturing problems, for instance trinitrotoluene, s-cyclotrimethylenetrinitramine, tetranitroaniline, picric acid, trinitroresorcinol, pentaerythiii an U
6 ritolt'etranit'rate, the polynitrocresols, hexanitro mannite, andthe like. 1 1
In accordance with this invention the solution to be 'nitrated and the nitrating acid after being thoroughly mixed in the initial reactionzone in the nitrator tend to travel toward the discharge outlet with practically no intermixing with subsequently added raw materials, or with more completely reacted materials, while at the same time a thorough localized circulation of the mixture is provided until the reaction is complete and the productis discharged from the nitrator. By thus providing a'columnar mass of a circulating reaction mixture, a large temperature exchange surface is provided perunit volume of the mixture, and the temperature of the mixture can consequently be very accurately controlled thus greatly increasing the production efficiency over that obtained with prior continuous apparatus.
While certain specific details are set forth herein it should be understood that considerable modification can be made without departing from the spirit and scope of the invention and that the invention is not to be limited thereby except as set forth in the appended claims.
What we claim is:
1. Continuous nitrating apparatus comprising a vessel having elongated substantially vertical portions connected at the bottom, agitator shafts in each of said substantially vertical portions, agitators carried by said shafts at a plurality of elevations in each of said substantially vertical portions, said agitators at one elevation having blades slanted substantially opposite tothe blades of an agitator at a different elevation in each of said substantially vertical portions, means for controlling the temperature of the contents of said vessel, inlets for the reagents at one end of said vessel and an outlet for the reaction products at the other end of said vessel.
2. Continuous nitration apparatus comprising a vessel formed of two upwardly extending arms connected together at the bottom to form a continuous substantially unrestricted passage therethrough, agitators at a plurality of elevations in each of said arms with at least one of said agitators in at least one of said arms having its impelling surface pitched substantially opposite to the impelling surface of an agitator in said arm at a different elevation, inlets for the raw materials at one end of said vessel, and an outlet for discharging the reaction products from the other end of said vessel.
3. Continuous nitration apparatus comprising a vessel formed of two upwardly extending arms connected together at the bottom to form a continuous substantially unrestricted passage therethrough, agitating means having agitators at a plurality of elevations in each of said arms with at least one of said agitators in one arm having its impelling surface slanted to direct at least the suspended particles of mixture contained in the vessel in a direction opposite that of at least one agitator in the other arm, means for controlling the temperature of the contents of said vessel, inlets for the reagents at one end of said vessel, and an outlet for the reaction products at the other end of said vessel.
4. Continuous nitration apparatus comprising a vessel formed of two upwardly extending arms connected together at the bottom to form a continous substantiall unrestricted passage therethrough, an agitator shaft in each of said arms, agitators carried by said shafts at a plurality of elevations, means for rotating said agitator shafts 2 inaopposite ,di-rectionssarsuviewed alongythesaxisof said vessel from one end onlygmeansior.controh ling: the temperature: oiitha-contents: of; said ivessel;v inlets; for: thezreagentsat; oneeend: of said vessel, and: anx-outlet: for: the reaction" products atitherothergend'oiisaidlvessel.
Apparatus ="0fr'the character describedicomprisinga tubular vessel, apluraiityofi agitator shafts 'arranged in=axial succession in-said-vessel, meansfor driving said-gagitator shafts in; oppo site directionsrelative :to. the axis of the. vessel (as; viewed: from one: end thereof), to-impart op-.- positeyswirling motions :to; fluid adj acentathewespeetive' agitators so, that the, columnoffluid adjacent one :of the agitators swirls in :one direc tiontabout the axis of thelvessel and the column of; fluid: adjacent; a succeeding agitator swirls in the opposite,direction,-. the first agitator-shaft of the succession :ha-vingiat least one blade; pitched oppositely; t0v at least one: blade; of the-succeeding. agitator shaft.
6. Apparatushof the-characterdescribed:c'omprising a:tubular1 vessel, apluralityof agitator shafts arranged in axial 2 succession .-in said.- vessel and adapted to-impartopposite-swirling motions to fiuid thereadjacent, respectivelygmeans forpdrivingsaid agitator shafts so thatv the 001-, umn otfluidnadjacent one of the agitators-swirls inone directionabout. the axis of the vessel and the column of fluid: adjacent a succeeding agi-. tator. swirlsinthe-opposite direction, the first agitator shaft. of: the succession having a blade pitchedoppositely to at least one blade of-the succeeding agitator shaft, and, other blades on each saideagitator'shafts at different axial positionsrand at adifferent pitch from the. first mentioned; blade. thereon, respectively.
ARVEL O. FRANZ.
ORI-N C, KEPLINGER,
REFERENCES CITED The following references areof record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1 1,363,368 Sonstagen Dec. 28-, 1940 1,961,420 Hildebrandt- June 5; 1934 2,074,988: OBrien Mar, 23, 1937 2,103,592 Millikan Dec; 28, 1937 2,194,666 Meissner Mar. 26;. 1940