US2574116A - Series distillation process - Google Patents

Description

Nov. 6, 1951 J. LOUMIET ET LAVIGNE 2,574,116

SERIES Di STILLATIQN PROCESS Filed May 10, 1945 6 Sheets-Sheet l grime/WW5 JEAN LGUM/ T E' 7' LAI IG Nov. 6, 1951 2,574,l l 6 J. LOUMIET ET LAVIGNE SERIES DISTILLATION PROCESS Filed May 10, 1945 6 SheetsSheet 2.

JEAN LOUMIET' ET LA V/6-NE 1951 J. LOUMIET ET LAVIGNE 2,574,116

SERIES DISTILLATION PROCESS Filed May 10, 1945 e Sheets-Sheet 5 T JEAN Loam/ET 7 LAV/GNE Nov. 6, 1951 J. LOUMIET ET LAVIGNE SERIES DISTILLATION PROCESS 6 Sheets-Sheet 4 Filed May 10, 1945 gwue/wfm JEAN LOUM/ET ET LAV/G/VE Nov. 6, 1951 J. LOUMlET ET LAVIGNE 2,574,116 7 SERIES DISTILLATION PROCESS Filed May 10, 1945 6 Sheets-Sheet 5 JEAN ZOOM/ET ET LAV/GNE Nov. 6, 195] J. LOUMIET ET LAVIGNE SERIES DISTILLATION PROCESS 6 Sheets-Sheet 6 Filed y 10, 1945 JEAN LOUM/ET ET LAM/6N5 BMW Patented Nov. 6, 1951 UITED STATES PATENT ()FFICE SERIES DISTILLATION PROCESS Jean Loumiet ct Lavigne, Italic, Cuba Application May- 10, 1945, Serial No. 592,950 In Cuba May 25, 1944 2 Claims. 1

the recovery of the latent heat of evaporation as well as the sensible heat contained in the products of distillation, by causing water to ab-. sorb said heat to generate steam, and by applying the resulting steam for heating in the .dif ferent distillation steps.

A further object of the invention is to efiect all the heat transmissions with liquids into which is injected steam or inert gas, in the evaporating, heating or cooling of the products, and to heat the liquid-steam or gas mixture While flowing through externally heated tubes.

Another object of the invention is to provide in connection with each distilling phase, for the rectification of the vapor produced in that phase by means of the petroleum residue from the preceding distilling phase.

Another object of the invention is to provide a process of fractional distillation of Petroleum utilizing heat recuperators wherein each successive distillation is effected under constant pressure and temperature conditions, and under a fluid injection which is also constant, the several constants being determined in accordance with the product desired.

According to the invention, the system includes generally a plurality of evaporating or distilling units connected in series and adapted to be operated at different pressures and temperatures but differing structurally only in diametric size, and from which vapors of different kinds are extracted in succession from the residue petroleum which is conducted from unit to unit until finally depleted of its desired products. In these units, a vapor current is injected at the bottom of each one of their tubes. The tubes of the.calandria are contained in several sectors thereof of different cross-section and through which sectors heate ing vapors are conducted in succession from the large to the small sector to heat the tubes and the liquid and openings being so provided in the sector walls that the heating vapors alternatively from sector to sector pass in at the top and then at the bottom. The distilled vapors are collected in a dome or tank at the top of the evaporating unit and before passing to their outlet are made to. pass over a bafif'le or partition so that entrained oil particles will be adhered thereto and the baffle being positioned to cause they adhered oil particles on both top and the bot-.- tom sides thereof to be. returned to the tank bottom and leave with the liquid residue.

The vapors from the last. four evaporatingunits are directed through recuperators to re-. cover the heat therefrom. This heat is returned to preceding evaporating units to. heat the ver-.

tica1 tubes thereof through which the liquid is the final liquid residue.

being passed. Other heat is used to warm the initial petroleum supplied to the first unit. Also recovery of heat is made in these recuperators of Adequate apparatus is provided throughout the system to rectify, sepae rate and condense the resulting vapor products. The first units are heated from the exhaust steam of the pump engines.

Balance regulating means is provided for controlling the infiowof petroleum to the system. A continuously replenished quantity of liquid residue is weighed and mechanism is efiected should its density depart from the desired set densityto instantly alter the petroleum inflow.

A modified rectifier for first rectifying the produced vapor is provided wherein liquid residue from a preceding evaporating unit can be used as the rectifying medium. 'The rectifier includes a series of spiral coils about the evaporator casing and closed at their outer peripheries by a rectifier casingwhereby to provide a spiral path for the vapors being cleaned and adjacent turns beingin places alternately close together and farther apart so as to alter the velocity ofthe vapors traversing the path and to effect the separation of solid liquid particles by centrifugal action. The rectifying liquid is cascaded through apertures in certain loops of the coils to provide a curtain of the liquid in the vapor path through which the vapors will be forced and cleaned.

A modified arrangement of the evaporators is shown wherein space and piping is conserved. The last or high temperature evaporator is placed in the center and the other evaporators are nested about it. The domes of the several'units are shaped and fitted to provide in appearance. a single dome.

For otherobjects and a better understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawing, in which Figs. 1 and 2 are respectively diagrammatic lay-out views of a petroleum distillation plant embodying features of the present invention;

3 Fig. 3 is a cross-sectional view, in elevation, of one of the evaporators;

Fig. 3a is a horizontal cross-sectional view taken at the station 3a--3a of Fig. 3;

Fig. 4 is a perspective view of a group of evaporators arranged for successive operation and with portions broken away to illustrate interior wherein the rectification is effected by passing the products resulting from the distilling process of the evaporator through petroleum remaining from that process. 1

Referring now particularly to Figs. 1 and 2,. petroleum is forced into the system by a pump 0, at the outlet of which is a by-pass valve By. Regulating mechanism is provided for operating the by -pass valve By in response to the density of the liquid residue. For this purpose, a float Fl is located in a container Zr, which is always kept full of the residue leaving the system through tube R2. The control is set for a desired density of residue, and if this density is altered the valve By will be operated in response thereto to decrease or increase the inflow of petroleum to the system and thereby re-establish the desired density of the residues. Another form of control mechanism will be discussed hereinafter.

The petroleum is pumped through a pipe T to a tank A surrounding heat recuperators B1 and B2. On passing through tank A, the petro leum absorbs the heat radiated outwardly by the recuperator B2 through an intermediate cylindrical wall. The petroleum leaves tank A through tube T and enters through tube T1 into the first evaporator or distilling apparatus D1 where are also injected at the bases of each one of the distilling tubes hydrocarbons forced from gasometers Gs, by a blower Go through tube Gt and regulated at its point of injection into the evaporator by a valve G1.

Within the evaporator D1 the petroleum is heated by exhaust steam from the steam engine which operates vacuum pump M and is conducted to evaporator D1 by a tube Sis. A part of the petroleum will be evaporated, The vapors are collected in a tank Y1 at the top of the evaporator and conducted through pipe V1 to a rectifier U1 to be purified. The vapors will surround the bailie X1 and liquid still within these vapors which adheres to the baffie surface will be collected by the baffle and returned thereby to the lower part of tank Y1.

The rectifier is the same as that disclosed in my U. S. Patent #2330255. A small amount of condensation is produced by cooling in the corrugated tube U1 and this condensate trickles downwardly so that the distilled vapors upon passing upwardly and through the tube will come the evaporator through tube 131 extending QQWI the side of the evaporator D1 to the lower part of the evaporator to join with the initial supply pipes T and T1. A valve r1 controls the supply of the vapor to the tube V1.

In the cooler E2 a large part of the vapors coming from the evaporator D1 are condensed, the mixed condensed liquid and uncondensed vapors are conveyed to separator F1 through pipe L1. The separated liquid passes to another cooler E1, where it loses part of its heat, and then is passed through a pipe P1, Fig. l, to a storage reservoir, not shown. The gas from separator F1 is passed to the gasometer Gs by a tube G.

The liquids from the tank Y1 and the rectifier U1 of eva orator D1 are drained therefrom by tubes t2, T2, Fig. 2, and conducted to a second evaporator D2. The tube T2 is in the form of a syphon so that in case of absence of liquid in tank Y1 vapor is prevented from entering the evaporator D2. 7

The liquid which enters evaporator D2 is similarly injected at its entrance to evaporator Dz with the hydrocarbons pumped from gasometer Gs by blower Go. A valve G2 regulates the supply of hydrocarbons to the evaporator D2. Fvaporator D2 is heated, the same as D1, by exhaust steam from the steam engine which runs the vacuum pump M and conducted to the evapo: rator Dz through the same tube or pipe Ste.

A second distillation of the petroleum now takes place. The distillation is effected in all the evaporators from D2 to D1, in the same manner that it is eiiected in D1. These other evaporators are of similar construction, except that they are reduced in size as the volume of the petroleum is reduced due to evaporation, and thereby to maintain approximately the same ve locity of flow in the evaporator tubes. The vapor in D2 passes over baffle X2 and to the rectifier U2, separator Z2, valve r2, tubing V1, condenser E2, separator F2. From the separator F2 the liquid passes through cooler E1 and tubing P2 to a reservoir. The non-condensed gases or vapor from separator Fz pass through tubing G to the gasometer Gs.

Petroleum which was not distilled in D2 passes through syphon tube T3 to the evaporator D: where it receives a new injection of gas coming from the gasometer Gs and regulated by valve G3. This evaporator D3 is heated by a vapor. produced in recuperator B2 by the products from the following phases of distillation, and conducted to evaporator D3 by the tubing Stz.

The vapor produced in D3 containing the injected gas leaves through the rectifier Us and passes through separator Z3, tube V3 and condenser pipe La, separator F3 and cooler E1. From cooler E1, the cooler liquid passes through pipe P3 to the reservoir. Gas separated in F3 passes through tubing G to the gasometer Gs.

Starting with D. the fluid injected in the petroleum entering in the tubes of the successive evaporators is constituted by exhaust steam from the steam engine of the vacuum pump M by way of the tubing Sta. The evaporator D4 is heated by vapor produced in the recuperator B1 and conducted thereto through the tubing St1.

The vapor from the tank Y4 passes through rectifier U1, separator Z4 but instead of passing from the separator through the cooler E2 as in the case of the preceding evaporators just described, is conducted through pipe V4 to the re-- cuperator B2 where it will be condensed. At the outlet of the reeuperator B1 mixed vapor and l q d a e conveyed y p p a to cool r E4. e 1.

and separator F4. The separated liquid passes down through tube P4 through cooler E3 and then to the reservoir. The separated vapor passes up through tube H and governor valve I to be treated together with vapors from separators F5, F6, F7, in a manner to be shortly described.

The evaporators D5, D6, and D7 are heated by high pressure live steam delivered to the same through tubing St. While only one live steam tubing is shown it shall be understood that several steam generators may be utilized so that different high steam pressures can be used'for the dif-- ferent evaporators D5, D6, and D7, with the higher pressure being in D7.

The vapors produced by these evaporators D5, D5, and D7 are conveyed by separate tubing V5, V6 and V7 to the recuperator B1 where they are condensed and cooled and then passed through tubes L5, L6, L7 to coils in recuperator B2 for further cooling. From the recuperator B2 the vapors and condensed liquids pass through extensions of tubes L5, L6 and L1 to cooler E4 and the separators F6 and F7. In the recuperators, heat is recovered from the vapors and the condensed liquids. The liquids separated in the respective separators leave through tubes P5, P6 and P: which pass through cooler E3 and deliver the liquids to the reservoirs. The separated vapors are drawn along with vapors from F4 by the vapor injector I operated by exhaust steam from line Sis and are discharged thereby into a barometric condenser C. The vacuum created by this operation is transmitted to separators F4, F5, F6 and F7 and is controlled by valves in the individual pipes connecting the pipe H with the sepa rators.

Between the injector I and condenser C is a small rectifier J into which a small quantity of water is injected to cool the vapors and insure liquefaction of all or the petroleum vapors. Only the water vapor which was injected in the petroleum will remain in the vapor state. In most cases, the passing of air or water over the outside of the rectifier will be suiiicient to condense all of the petroleum vapors but in rare cases the injection of water, is desirable. At the outlet of the rectifier J is a centrifugal separator K which removes the liquid products from the rectifier J. This liquid is conducted through a tube 11. to the evaporator Do by way of the syphon tubing T6.

The recuperator B1 is heated by the vapors produced in the evaporators D5, D6, and D1 and conducted to the same through tube V5, V6 and V7 and also by means of the residue from the last evaporator, D1 which passes from tank Y1, through tube R to recuperator B1. Recuperator B2 is heated by the same fluids which heat the recuperator B1 and also by the vapors produced in the evaporator D4 and conducted by tubing V4 to recuperator B2.

By injecting exhaust steam into the small tube R at m by means of tube Sta, the nature of the residue liquid in tube R is modified. A gas or vapor in a small or medium diameter tube containing liquid, occupies the central part and forces the liquid against the walls to provide an annular part. The liquid is spread out thin and is thus more readily heated by the gas or vapor and that increases its heat transmitting efiect. At the same time the velocity of the liquid is increased and that too increases the heat transmitting effect of the liquid. The form of the steam and liquid within tube R is maintained even though the tube becomes horizontal, as in the recuperator B1. In this way, heat is added to therecuperators, and their efliciency is accordingly increased.

The condenser C receives cold water from pump N through pipe W. Heated cooling water leaves the condenser C through a large pipe N and is delivered to a reservoir N" located adjacent the pump N. The non-condensable gases are removed from the condenser through tube q and vacuum pump M. The pump N not only supplies cool water to the condenser but also supplies cooling water to the various coolers E1, E2, and E3 and E4. The water circulates from the pump N through tubing W1, cooler E1, tubing W2; cooler E2, tubing W3, cooler E3, tubing W4, cooler E4, and tubing W5 back to reservoir N.

It will be apparent that instead of two recuperators, three or four may be used, each operated by the fluids which heat the preceding recuperators and with condensate from the first evaporators, as well as from the latter evaporators, as in the case just described.

The blower Gv forces the gases from gasometer'Gs through the evaporators D1, D2, and D3 and various other equipment associated therewith and back to the gasometer Gs. Gases join with the vapors produced in these evaporators and are returned from separators F1, F2, F3 to gasometer Gs by pipe G. The pipe Gr is connected to the pipe Gt and upon turning the valve 91 excess gas may be drawn from the gasometer system.

Referring now to Fig. 3, a single evaporator is shown. Petroleum enters the evaporator through tube '1 at the bottom and rises in a chamber 9' above the same to the open bottom ends of vertically extending tubes a. Treating vapor enters through the pipe SG and the nozzle arrangement 1 lying within chamber 9 which has a nozzle cover e with a plurality of spouts (1 respectively aligned with the open bottom ends of the tubes at. Through these spouts treatin vapors are injected into the evaporator and the liquid is treated at the bottom ends of the tube (1. Pipe 10 connects with the nozzle arrangement 1 to permit cleaning when necessary.

At the upper part of the calandria is tank Y in which the produced vapors are separated from the liquid. This liquid leaves the lower part of the tank Y through the pipe T while the vapors leave tank Y through the pipe V located in the upper part thereof above a baiile wall X. Such liquid as is collected in the bafile X is returned to the lower part of the tankY through a drain 3:. A skirt portion y prevents the direct entrance of the distilled vapors and liquid particles into pipe V which are drawn to the top of the bafiie X. A cover it is disposed over an opening in the top of the tank through which the baiile and tank can be cleaned.

The calandria D is divided into a central sector and several peripheral sectors through which the heating vapor circulates alternatively upwardly and downwardly. The cross-sectional area of the chamber through which the heat vapor is first passed is the largest of all the sectors and the remaining sectors decrease in size as the heat vapor moves toward the smallest sector. Condensate is drawn from the bottom of the sectors by drain means not shown.

A closure plate is for supporting the lower ends of the tubes 11 is carried on the housing g and secured thereto by a flange on evaporator casing D. A similar plate is is disposed on the upper 1 end of the casing D and secured by tank Y. Vertically extending partitions b divide the interior of the casing into sectors and in these partitions are openings 01, c2 and 03 for permiting the flow oi the heated steam between sectors. Steam entering through St, Figs. 3, 3a, rises in the first sector and leaves it through opening c1. The steam then enters the central sector, moves downwardly, and leaves through opening 02 to enter a second peripheral sector. In the latter sector, it moves upwardly and enters the next peripheral sector through opening 03. The steam moves through the remaining sectors in this manner and through other openings, not shown.

Referring now to Fig. 4, there is shown a novel arrangement of the evaporators wherein all of the various evaporators are consolidated or nested into a more or less single unit. The evaporator D7 operating at the highest temperature is located in the center and the other six evaporators surround the evaporator D1. The tanks at the top of the apparatus are constructed so as to appear as one single dome. The cup shaped chambers g are left round. The spaces between them may be filled with asbestos or other insulating material to limit the loss of heat. Similar lettering and numerals are given to this arrangement as given to the line arrangement shown in Fig. 2.

Referring now to Fig. 5, the details of the recuperators are more clearly shown. The inner recuperator B1 produces a vapor of higher pressure and temperature than the outer recuperator B Both of the recuperators are cylindrically shaped and are closed at their ends by fiat cover plates. The heated vapors which operate these recuperators pass through horizontal coils. A perforated plate p placed near the upper cover divides the recuperator B1 into two parts, a lower part containing the heating coils, and an upper part receiving the water upon being returned from the calandrias. The perforations in the plate 1) are such as to always maintain a small depth of water in the upper part. The water leaving through the perforations contacts the first horizontal coil and maintains a thin layer of water over the same. In this manner, the water drips from coil to coil and layers of water are formed over all of the coils from the top to the bottom of the recuperator. The vapor produced rises between the coils and leaves the recuperator through the pipe Sh. Recuperator B2 almost completely surrounds the recuperator Bi and is constructed in a similar manner. Vapors from D! are conducted by tube V: to the first of two horizontal coils S107. The diameter of the pipe decreases with each coil throughout the entire length of the coils. The small end of the bottom coil connects by tube L7 with coil S11 in recuperator B From recuperator B2 the vapors pass as above described, in connection with Figs. 1 and 2.

Vapors from D6 are conducted by tube V6 to similar horizontal coils Spa in B1 and then through tube Ls wound into coil Sls in recuperator B: from which they are passed in a manner as above described.

Vapors from D5 are conducted by tube V5 to coils Spa in Bi and leave the same through tube L5 wound into coil SZs in B2 and passing to other parts of the system as above described. Thus, in the manner just described, the vapors from evaporators D5, D6 and D7 are respectively conducted through horizontal coils Sps, Spa and $137 of recuperator B1 and horizontal coils S15, S16, and S11 of recuperator B2. The liquid residue from tank Y; of the last evaporator D7 is passed through pipe R to four horizontal coils SpR in recuperator B1 and then through pipe R1 to three horizontal coils SIR in recuperator B2. The residue leaves recuperator B: through pipe R2. Recuperator B2 is further heated by vapors from evaporator D4 passed thereto by pipe V4 and entering horizontal coils Sp: thereof and leaving through L4, Fig. 1. All vapors are substantially condensed before leaving recuperator B2.

The recuperator B2 is surrounded by tank A through which the petroleum used in the operation is passed at a low velocity so as t reduce as much as possible the loss of heat through the cylindrical surface of the recuperator B2. Such loss is thus utilized by heating the petroleum being distilled.- All of the apparatus is highly insulated wherever possible to avoid loss of heat. Thus, usable heat is recovered from the evaporators D4, D5, D5 and D1 by the recuperators B1, B2.

Referring now to Fig. 6 there is shown a, modifled form of rectifier for rectifying the vapors resulting from each distilling phase, in which the rectifier is made concentric with the evaporator so that the products resulting from the fractional distillation in that evaporator are rectified therein. This rectifier comprises generally a spiral coil having loops s surrounding the upper part of the evaporator calandria Dn+l, a spiral coil having loops p surrounding the lower part of the calandria and an outside casing RC surrounding the coils S, and the evaporator calandria. The coil loops are thus supported be-' tween the evaporator calandria and the outside casing RC.

Vapors produced in the calandria Dn+l leave the dome or tank Yn+l through tube Vn+l and are delivered to the lower end of the casing RC.

In the casing the vapors pass upwardly through the spiral paths provided between loops 1] and S. The loops p of the coils are not of equal distance apart throughout the length of the coils whereby the cross-section of the spiral path diminishes and increases at intervals throughout its length thereof.

The residue liquid from the preceding evaporator is supplied to the third pair of loops p from the bottom by tube Tn+1 which enters the easing RC and delivers the liquid throughout a container to the lower loop of that pair. This liquid flows lengthwise of the spiral constituted by the successive loops p, but that flow is broken and liquid falls through the openings 1' to the immediate lower loop p, forming a cascade across the full width of the loop 11. In this manner, the vapors are forced to pass through those cascades, atomizing the liquid, and entering into intimate contact with the atomizing liquid, to cause rectification of said vapors. These apertures r are located in the constricted area of the path and where the velocity is at a maximum. Upon leaving this point of high velocity, the vapors are passed to the area of greater cross-section and their velocity is decreased. Liquid particles are projected against the wall RC by centrifugal force and will adhere to it and descend down the wall surface onto the outside of the loop and rearwardly along said loop to join the rectifying liquid. The vapors are accordingly freed each turn in the path by this centrifugal action upon the liquid particles.

Loops p are inclined downwardly from its outer periphery toward its inside periphery so as to distribute the liquid uniformly over the loop during its passage downward over the same.

This operation proceeds in the same manner throughout the upper loops P of the lower coils. The rectifier liquid for the loop is the liquid separated from the upper coil of loops S. The same is drained from the loops S and dropped on the upper loop P. Slight cooling which is effected through the walls causes condensation in the region of the upper coils. This condensation will leave the rectifier with the rectifying liquid. A channel m on the inner peripheral face of the wall RC and extending in a direction intermediate the direction of vapor flow and a vertical direction conducts the separated liquid to the lower part of the upper separator for deposit upon the lower loops 7). Liquid is picked up by channel m at all turns along the height of CD11 of loops S. The loops S instead of inclining downwardly from the outside toward the inside incline downwardly from the inside toward the outside, and upon nearing the outside they incline abruptly so as to form with the wall RC an outer channel S" following the loops S and extending through the length of the coil. The liquid particles projected against the wall RC by centrifugal force descend along said wall in this channel S" which empties either into wall channel m or directly at its bottom end. The rectified vapor leaves the rectifier through tube Vn+ I and passes to a recuperator. The rectifying liquid leaves the rectifier through the pipe T'n-l-I and is injected into an adjacent evaporator.

The general use of steam as the heat transmitter in each distilling step, makes it possible for each step to be independently controlled and regulated in accordance with the products desired from each step. The pressure applied in each step and the amount of gas or vapor in- ,iected are maintained constant once they are set. With a constant temperature, constant pressure, constant quantity of fiuid injected, and constant velocity of the fluid through the apparatus, the homogeneity of the products is maintained. If the composition of the petroleum varies and the same products are still desired, one or more these conditions can be altered to adapt the process to the new petroleum.

To maintain a constant steam output of the recuperators, live steam may be added to bring the recuperator steam to the desired pressure and temperature. I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the appended claims.

I claim:

1. In a fractional distillation process of distilling a complex liquid comprising passing said liquid successively through a plurality of stills while maintaining said stills at various temperatures, the lower temperatures being in the initial group of stills and the higher temperatures in the terminal group of stills, passing the distillate vapors from the terminal group of stills and the final residue from the last still into heat exchange relationship successively with a first and a second stream of heat exchange liquid to vaporize each of said streams to produce vapors at different temperatures, heating the last still of the initial group by the first vapor stream and heating the next to the last still of the initial group by the second vapor stream.

2. In a fractional distillation process of distilling a complex liquid comprising passing said liquid successively through a plurality of stills while maintaining said stills at various temperatures, the lower temperatures being in the initial group of stills and the high-er temperatures in the terminal group of stills, passing the distillate vapors from the terminal group or stills and the final residue from the last still into heat exchange relationship successively with a first and a second stream of heat exchange liquid to vaporize each of said streams to produce vapors at different temperatures, heating the last still of the initial group by the first vapor stream and heating the next to the last still of the initial group by the second vapor stream, and passing the vapors generated in the last said still of the initial group in heat exchange relationship with said second stream of liquid.

JEAN LOUMIET ET LAVIGNE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 559,857 Lillie May 12, 1896 1,575,643 Salich Mar. 9, 1926 1,615,407 Rogers et a1. Jan. 25, 1927 1,616,209 Weisgerber Feb. 1, 1927 1,640,444 Faragher et al. Aug. 30, 1927 1,668,602 Pew et al May 8, 1928 1,780,286 Watson Nov. 4, 1930 1,877,811 Coleman Sept. 20, 1932 1,882,606 Howard et a1 Oct. 11, 1932 1,965,334 Eglofi July 3, 1934 2,164,593 Rector July 4, 1939 2,230,253 Loumiet et Lavigne Feb. 4, 1941 2,314,822 Quesada Mar. 23, 1943 2,350,507 Hemminger June 6, 1944 FOREIGN PATENTS Number Country Date 320,135 Great Britain Oct. 17, 1929 OTHER REFERENCES Wentworth et al., Transactions of American Institute of Chemical Engineers, vol. 39, pages 565-576 (1943).

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