US2037677A - Apparatus for fractionally distilling oils - Google Patents

Description

April 14, 1936. G. c. coNNoLLY ET AL 2,037,677

APPARATUS FORFRACTIONALLY DISTILLING oILs Filed May 15, 193C Patented Apr. 14, 1936 UNITED STATES APPARATUS FOR FRACTIONALLY DISTILLING OILS Gerald C. Connolly and Albert F. Wurzbacher,

Baltimore, Md., assignors, by mesne assignments, to The Davison Chemical Corporation, Baltimore, Md., a corporation of Maryland Application May 15, 1930, Serial No. 452,737

2 Claims.` (Cl. 202-163) The present invention relates to stills and to a method of operating the same, whereby an increased yield of valuable products is obtained.

'I'he present application is a continuation in 5 part of the copending application Ser. No. 444,061, led April 21, 1930.

More specifically the present case relates to a method of operating stills for the recovery of motor fuel from light oil, said fuel being either of the type known as motor benzol, or a blend of such motor benzol with other fuels, for example gasoline, alcohol, or other suitable material which can be blended with the motor benzol, whereby the distillation may be carried much further than was heretofore customary while avoiding dangerous operating conditions due to the possibility of obstructing the condensers and the pipes or lines by solid matter, such for example as naphthalene or the like which is vaporized in the still and s0- lidies in the condensers. This is accomplished by providing a circulation of a solvent or even a mechanically acting remover for said deposited solids, consisting of a liquid which may be the product of the distillation itself or the same substance regardless of its origin, or some other liquid compatible with the said product, or a mixture of both,'as the conditions existing and the nature of the case may require. The deposit is thus removed by being dissolved, by being mechanically loosened and carried along, or by a combination of both said ways.

The recirculated oil may be delivered to anyv point of the tower or column, or of the condenser, or the pipes connecting the same together, or even to the still itself. ,l

A further object of the invention is to increase the yield still further by eliminating the step, heretofore customary, of draining the condenser of all oil after each time the still was shut down. 4o This step was heretofore considered necessary in order to avoid any naphthalene or other solids present from clogging or otherwise obstructing the ports or the like. 'Ihe result of such draining was that the condenser then operated for a time, when again put into serviceLwithout the oil seal,

so that the most volatile portions of the still products were lost because no liquid solvent was present to retain them. The recirculating feature makes the draining unnecessary and therefore a liquid seal is always present, and retains these valuable volatile constituents which heretofore were lost. l l

However, we have found that in certain cases it may be advantageous to drain the condensersA for a different reason: When the still first begins to give oil gases. the rst portions are mainly air, mixed with a very little of the condensable vapors, and if this air .were allowed to pass through .the condensers while the liquid seal is present, it would of course be forced to bubble through the 5 said seal, thereby again evaporating some of the more volatile constituents previously retained in the said seal. This would result in losing some of the most valuable products, as well as in discharging a combustible mixture of ain saturated with l0 the vapors thereof, which would increase the danger of re or explosion. In such cases we may drain off the seal, and allow the air to pass freely through the condensers until the still commences to give off vapors, whereupon the liquid seal is im- 15 mediately restored by operating the circulating means or pump so as to supply a fresh seal of condensate or other solvent, which moreover is maintained in constant circulation so that fresh portions are continually presented to exert their 20 solvent eects on the vapors coming from the still. Another feature of the present case is that it may sometimes be preferred to provide in the condensers a liquid seal which consists of the heavy, relatively slightly volatile products of dis- 25 tillation instead of the lighter benzol or the like. This is advantageous in. that these heavy oils have a greater solvent power for the extremely volatile wild products first produced, and are, moreover, more stable themselves so that little or none of the heavy solvent is lost by evaporation when the hot air and the vapors or gases are passed thereinto at the beginning of a run. 'I'his may be accomplished easily by merely circulating or recirculating the heavy ends rather than the lighter distillates, by providing separate tanks and pump connections for the various fractions desired.

The process may be carried out with crude oil and cracked hydrocarbon distillates. When crude oil or cracked distillates are used the condenser is usually of the banked type, and there is of course no naphthalene or similar product to guard y against, so that the main object of the recirculation in this case is to keep the condenser seal in proper condition to recover even the most volatile fractions.

Another object of the invention is to make naphthalene. In this case the vapors discharged from the column or tower of the still are by- Y passed around the condenser and the water separator, and the resulting product is then distilled, leaving the naphthalene behind. The body of liquid which accumulates in the tank during the first part of the run acts to condense the vapors,

so that the usual condenser may be put out of service by a bypass during this procedure.

Another way to practice the process is to shift the discharge of vapors, coming from the tower, to alsmall tank as soon as naphthalene vapors begin to appear, in which event the naphthalene will condense in said tank. 'I'hen the benzol from the main tank may be pumped into the small tank and thence back to the main tank, carrying the naphthalene with it. This allows the naphthalene to be blended with the motor benzol in any proportion desired. Or if the naphthalene is to be collected as such, it may be allowed to accumulate in the small tank. In both last named ways of carrying out the process, it will be understood that the regular condenser is left in operation until naphthalene begins to appear, and the condenser is then bypassed only for the remainder of the run.

Thus it will be seen that the invention provides for increased recovery at both ends of the operation, namely, rst it recovers more of the most volatile products, and second, it makes it possible to carry the distillation further at the high boiling end, whereby an increased yield of the least volatile products is also secured, and further that it becomes possible also to recover the naphthalene as such, and also to make a blended motor fuel as the result of the gasoline, alcohol or the like added to the distillate during the recirculating process. il

For a clearer understanding of the invention and the apparatus employed in practicing it, reference should be had to the present specification and the accompanying drawing, illustrating apparatus employed in the same.

In said drawing:

Figure` 1 illustrates diagrarnmatically appara-V tus for carrying out the present invention; and.

Figure 2 is a diagrammatic sectional elevation on a larger scale of the condenser and some of the associated parts.

Referring to Fig.v 1 in detail, there is shown a still I heated in any desired manner, as by hot Water or steam* in the coils 2, and having the usual tower or column 3. A pipe 4, the vapor line, ,connects the top of the tower to the condenser 5, and thence a pipe 1 leads to the water separator 8, a liquid seal 6 being interposed in said pipe 1. From the top of the separator a pipe 9, the run-down line, leads to the run-down tank I0. A pipe I Ileads from a point, preferably at or near the bottom thereof, to the pump I2, which is connected to the tower, condenser or pipe 4 by line I3, the circulating line. Pipe 34 may provide connection between the column 3 and the line I3 and is preferably provided with two shut-off valves 30 and 3|, one arranged at each end of pipe 34, as illustrated. 'I'his pipe, as will be seen, connects I3 to the column at a point near its upper end. It is possible, however, to provide other connections such as 35 likewise provided with a valve 32 at one end and a valve 33 at the other at any desired level of the column 3. A separate source for a recirculating liquid may be provided, as shown at 39, connected by means of a pipe 38 to the tower, condenser or pipe 4,

suitably located valves being provided to control the flow. A tank 31 to contain and collect heavy oil or the like which is to be recirculated may also be provided and connected to the pipe 9 through pipe 36, which has the shut-off valve 26 therein, and a similar valve 21 may be provided in pipe 9 as illustrated.

Referring now to Fig. 2, the condenser 5 of heretofore there -Was Fig. 1 is shown in detail. The vapors from the still column 3 enter the first' compartment I4 of the condenser 5 through the vapor line 4, where the vapors flow somewhat as shown by the arrows, up on one wall and down the next, then out through port I5 to the second compartment, upwardly therein to port I'I, and through said port to the last compartment and downwardly to the discharge pipe 1. 'I'he condensed products maintain the liquid I9 at the level 20, the elevation of the upper end of pipe 1. 'I'he water enters the condenser through the Water inlet pipe 24 passing into the water space 23, thence upwardly through the cooling pipes 25 to the upper water compartment where the water level is maintained at 22, as shownby the water outlet pipe 2| through which the excess water overflows.

In operation, the material to be distilled is introduced into the still I and heated. The vapors produced pass upwardly through column 3, and out through vapor line 4 to thecondenser 5. Any highly volatile products first evolved in the distillation will bubble through the liquid I9 in the seal, and such portions thereof as are soluble in the said liquid or condensable at the temperature thereof will of course be retained thereby. This results in a considerable recovery of the more volatile constituents, which would be lost if the liquid I9 were absent, as it is in the heretofore customary process Where the seal is completely drained after each run.

'Ihe condensed products pass into the water separator 8 which is provided with the usual drain outlet for the water and thence through the run-down line 9 to the receiving tank I0.

In order to recover as much as possible of the useful matter contained in the material being distilled, the distillation should be carried as far as possible, that is, until relatively high boiling products pass over into the condenser. However, great danger of causing a stoppage of the run-down line by solid products of. high boiling point if it was attempted to push the distillation to the limit, when such substances, especially naphthalene, were vaporized and subsequently condensed to the solid form in the 'condenseror in the said run-down line. Such stoppages might result in explosions and also of course would interrupt the operation of the apparatus until they were removed in some way. The result of these conditions was that formerly the attendants of the still would stop the distillation long before the end of the process was actually reached, for fear of the disastrous results mentioned, thus losing a great deal of useful distillate.

The present invention in its simplest form removes -these dangers and inconveniences by providing the recirculation system comprising pipe II, pump I2 driven by any suitable source of power, and pipe I3 connecting to the tower, condenser or connecting pipe 4. When the pump I2 is operated it withdraws condensate from the receiving tank I0, and forces it through line I3 into the vapor line 4, whence it passes through the condenser 5, the water separator 8 and the run-down line 9 back to the tank I0. The condens'ate thus recirculated serves several purposes. Primarily, it dissolves solids such as naphthalene, wax or the like which may have been deposited in the condenser 5 or the lines leading therefrom to the tank I0, or prevents such deposits from forming. Second, it helps to condense vapors coming from the vapor line 4, because it is rela.-

amount to from 1 to 4% CII Cil

tively cool, and thus retains some of the more volatile products either by condensing or dissolving them. Third, it acts mechanically due f In some cases the nature of the material being" distilled is such as to render it advisable to drain the condenser. This is the case for example when cracked gasoline or other comparatively light hydrocarbons are distilled. The first products evolved by the still are mainly composed of air, and if this air bubbled through the liquid seal in the condensers, it would tend to evaporate the more volatile hydrocarbons and waste them. To avoid this loss, the seal is drained off and the air is allowed to escape freely without coming into contact with the liquid condensate. When the vapors begin to appear in sufficient quantity, the seal may be at once restored by starting the pump I2 as stated. The pump may then be continued in operation as long as it is deemed advantageous to do so, so as to keep the condensate in constant circulation and thus continually expose fresh unsaturated portions thereof to the vapors solve or otherwise retain same, thus increasing the effectiveness of the recovery.

With this recirculation system in the apparatus the operator of the still need not fear that obstructions would occur, and hence the distillation may be carried .toits logical end instead of stopping prematurely because explosion or other dangers are feared. As a result, a material increase of yield is obtained, because distillation may proceed in the ordinary Way until a frosting of naphthalene appears at the condenser, whereupon thefpump is started and the process continued as long as necessary, or until the oil produced goes olf color. In addition to the increased yield at the high boiling end, there is the further increase attributable to the recovery of additional amounts of the low boiling constituents due to the elimination of the necessity for draining off the condenser seal, which may of the Whole.

In operating the apparatus in this way it Will be seen that no use has been made of the various bypass pipes 34, 35 illustrated, or of the tanks 31 and 39 and the pipes and valves connected thereto. In said operation the only material recirculated has been some of the distillate itself,

and certain objections may at times exist to such procedure. For example, the benzol contained in the run-down tank I0 is relatively volatile and is not as eflicient as a condenser seal as would be a less volatile product, such as those obtained late in the run. This is true for two reasons, rst, the volatile product would be lost to a certain extent by evaporation ,when the hot air or hot vapors and gases coming from the still bubble therethrough, and, second, it has been found that the high boilingproducts are better solvents for the highly volatile ones. To take advantage of this fact, means have been provided for substituting a heavy oil which is to be recirculated for the relatively lighter distillation products by making use of a separate source of recirculating liqin order to dis' uid, for instance, the tank 39 which may be filled with any desired liquid of suitablev characteristics which may then ilow through the pipe 38 and valve 28, which is open for this purpose, into the condenser 5,'where it may serve as a seal, or may be supplied to the tower 3, according to the operation of the valves. The valve 29 in the pipe I3 must, of course, be closed while the seal is thus being established. It is also possible to provide a separate tank 31 to collect heavy oil which is to be used for such recirculation purpose, this tank being connected to the line 9 bymeans of pipe 36 and valve 26. Toward the end of the run, when the heavier products are being evolved, valve 21 may be closed and valve 26 opened to collect the heavy products in tank 31, and when desired, these may be supplied to pump, I2 through pipe 50, and thence through pipe I3 to the tower, condenser or pipe 4. This is in a way alternative to the use of the tank 39, although it is possible to use both said tanks simultaneously to contain the same or different liquids. Since this heavy recirculation oil is a portion of the distillate, it may be blended direct without any subsequent treatment.

If the tank 39 be filled with a liquid of different nature from the distillate, for instance, gasoline or alcohol, these contents may be introduced at the proper time into the circulating system by opening the valve 28, in which case the gasoline or alcohol will serve the function of clearing the condenser and its connected pipes from naphthalene or other deposits, and at the same time, the gasoline or alcohol or the like will blend with the benzol to produce a blended motor fuel.

It will be seen thatbypasses 34 and 35 have been provided, each of these being closed off from the two portions connected thereby by valves 30, 3|, 32, and 33, respectively. The purpose of these bypasses is to permit the liquid which is to be circulated or recirculated tobe introduced into the column 3 directly, either at the top through bypass 34 or at any desired intermediate level through bypass 35 located at the corresponding elevation. In this way, the incrustation removing liquid may be introduced directly into the co1- umn 3 instead of intothe condenser, thus becoming heated and serving more eciently to remove the naphthalene or other deposits. In this method of operation, of course, it will be understood that usually only one of the bypasses will be in operation, the other being closed oi at both ends by means of the valves, and pipe I3 will likewise be shut off from direct connection with pipe 4 by means of valve 29, so that the liquid will be forced to vpass through the still column 3,

instead of passing directly into the condenser.

When it is desired to recover naphthalene, the products of distillation will be treated as previously described, until naphthalene begins to distill over. When this point is reached, the valves 46 and 41 are shut off and valve 48 is opened,`

whereupon the products coming through pipe 4 will pass into the tank 40 through pipe 4I, and. will condense there as solid naphthalene. Inf 1t be desired to collect the naphthalene as such, no further procedure is necessary, except to remove the naphthalene from the tank when the same is full. However, if it be desired to introduce the naphthalene into the contents of tank IU, in

/order to serve as an ingredient of the motor benzol or the like contained therein, the valve 45 will be opened and the pump 5I started, whereupon benzol will be pumped from tank I0 through pipes I I and 43 into the naphthalene tank 40 and thence through pipe 44 back to the tank I0, this operation being continued until` all the naphthalene in tank 40 has been dissolved. Instead of using the small tank 40, the heavy ends may be discharged into tank l0 through bypass pipe 4I and pipe 9. The body of liquid already in tank I0 will act to condensethe heavy ends.

It is'to be understood that suitable valves are provided Where necessary.

The method is applicable to any type of still, Whether batch, semi-continuous or continuous.

Having thus described the invention and illustrated apparatus which may be used to carry out the same, it is to be clearly understood that the present specification and drawing are purely illustrative and that many modifications may be made in the apparatus and method as well as in the raw materials distilled and the products thereof Without departing from the invention, which is dened only by the following claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A benzol recovely plant comprising a still, means for heating the same, a condenser, a vapor conducting means leading from said still to said condenser, a condensate seal trap, a Water separator, a conduit leading from said condenser to said separator through ysaid trap, a receiving reservoir, a conduit leading from said separator to said reservoir, a conduit connecting said reservoir to said vapor conducting means, and a pump in said last named conduit.

2. An apparatus for distilling comprising a still and a column cooperating therewith; a condenser; a run-down tank; a pump, and a naphthalene tank; a pipe connecting the column to the condenser; pipes connecting the condenser, the run-down tank, the pump and the naphthal lene tank in a closed circuit in the order named;

an` additional valved pipe connecting the rundown tank With the naphthalene tank, a. by-pass pipe around the condenser, and control valves in said pipes.

GERALD C. CONNOLLY. ALBERT F. WURZBACHER.

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