US1917736A - Purification of so2 recovered from refining hydrocarbons with so2 - Google Patents

Description

July 11, 1933.. SAEGEBARTH 1,917,736

PURIFICATION OF 50 RECOVERED FROM REFINING HYDROCARBONS WITH S02 Filed'April 28, 1932 2 Sheets-Sheet l amen M101,

July 11, 1933. SAEGEIBARTH 1,917,736

PURIFICATION OF $0 RECOVERED FROM REFINING HYDROCARBONS WITH S03 Filed April 28, 1932 2 Sheets-Sheet 2 I 60 I I 41 1 I A) 56 g 3; 55 56 6T A 62 g 14 4% M I 63 j 17 13 I 1 a? Iii/ q. 4.

Snventor 12 17 qttornegs Patented July 11, 1933 UNITED STATES PATENT OFFICE ERICH SAEGEBARTH, F LONG ISLAND CITY, NEW YORK, ASSIGNOR TO EDELEANU GESELLSCHAFT, M. 13. IL, A CORPORATION OF GERMANY IPURIFICATION OF SO: RECOVERED FROM REFINING HYDROGARBONS WITH SO:

Application filed April 28, 1932, Serial No. 608,109, and in Germany May 1, 1931.

This invention aims to provide an improved method whereby the liquid S0 employed for treating liquid hydrocarbons (as in the well known Edeleanu refining process) may be recovered in a sutliciently pure and'waterfree state for further use.

In practice, the liquid-SO utilized in the treatment of petroleum fractions in a refinery plant is recovered and reused, so that a continuous, cyclical operation is effected. As water forms with liquid-SO objectionable acid products, it is of great importance that the SO: be freed of any water which has been picked up during a cycle of operation, as otherwise a water and acid concentration would soon build up which would seriously interfere with the desired treatment and would tend to cause corrosion of the apparatus.

The Edeleanu system consists, in brief, in dissolving the unsaturated and aromatic constituents of hydrocarbon fractions by means of liquid-S0 A raiiinate is secured which comprises substantially all of the saturated constituents, together with a relatively small quantity of liquid-SO (about 12 to 15 percent), and an extract which comprises the unsaturated and aromatic constituents dissolved in a relatively large amount of liquid-S0 The ratlinate and extract, respectively, are then freed of SO by multi-stage distillation. The first stage in each case is usually operated at a pressure to lbs. per sq. inch) sutlicient to permit of the direct condensation of the evolved SO vapors at cooling water temperatures, and at a temperature insutiicient to evolve appreciable hydro-carbon vapors. The last stage may be under vacuum.

Frequently this first stage treatment is carried on in a plurality of steps for reducing the heat consumed a-nd'for convenience in handling the volume of evolved SO gas, for'example. as described in Cattaneo Patent No. 1,758,595, wherein there are two high pressure evaporators preceding the evaporator operating at condenser pressure, these high pressure evaporators operating atea.

pressure in excess of 90 lbs. per sq. in., andthe evolved SO as being condensed at pressures somewhat in excess of condenserpressure and discharging into the liquid S0 supply at condenser pressure.

It has been found that the major quantity of the water entering the evaporators is vaporized in the extract condenser-pressure stage, and that by removing the water vapor from the S0 vapor given off at this stage a sufllciently complete removal of water is effected during a cycle to permit of a successful operation of the process in a continuous refining system. The present invention embodies this discovery and embraces various modes of removing water from the S0 vapors given off from the extract condenserpressurc evaporator.

The previous practice has been to remove water by sending the S0 vapors, derived from the low pressure and vacuum evapora tors for rafiinate and extract, through a drying apparatus operated at aboutatmospheric pressure, and also to steadily redistill a part of the liquid-SO coming from the S0 con-. denser.

The present invention, therefore, provides a much simpler and more inexpensive way of eliminating the water dilficulty from the Edeleanu system of refining than has been available heretofore. Other objects and results of the invention will be apparent from the following detailed description.

In the accompanying drawings, wherein I have shown two embodiments of my invention for purposes of illustration, and in which like numerals designate like parts,

Fig. 1 is a diagrammatical representation of apparatus for performing the invention, wherein a sulfuric acid drying tower is employed;

Fig. 2 shows diagrammatically the use of rectification means in place of the sulfuric acid drying tower of Fig. 1;

Fig. 3 is a diagrammatical representation of apparatus for performing the invention, wherein a'condenser and a redistilling tank are employed; and

Fig. 4 shows diagrammatically a modification of the form shown in Fig. 3.

.111 the first embodiment of the invention selected for illustration and shown in Fig. 1 of the drawings, the flow sheet commences with pipe lines 1 and 6 which bring the extract and raitinate, respectively, from the mixer (not shown) where the untreated hydrocarbon fractions have been treated with liquid-S0 The extract is passed through condenser-pressure evaporator, or still, 2, atmospheric pressure evaporator 3, and vacuum evaporator 4, the finished extract, freed of S0 being withdrawn through line 5. Lines 21, 16 and 12 serve to convey away the S0 vapors evolved in the respective evaporators.

In like manner, the rafiinate, entering by line 6, is passed through similar condenserpressure evaporator 7, atmospheric-pressure evaporator 8, and vacuum evaporator 9, the finished rafiinate, freed of S02, being withdrawn through -line 10. The evolved S0 vapors are withdrawn from the respective evaporators by lines 26, 15 and 11.

Pump 13 serves to maintain a vacuum in evaporators 4'and 9 and forces the evolved S0 vapors into line 14 at atmospheric pressure. Pump 19 serves to maintain evaporators 3 and 8 at atmospheric pressure and forces the evolved S0 vapors drawn through lines 16. 15, 17 and 18, together with the SO;- vapors from line 14, into line 20 at condenserpressure.

What has been-described is a conventional Edeleanu system and apparatus and is well known refinery practice. Reference may be made if desired to the patent to Gattaneo et al, 1,840,765, which described a complete Edeleanu treating system.

The presentinvention is predicated upon the discovery that most of this water is present in the extract and will vaporize off with the S0 under the conditions prevailing in condenser-pressure evaporator 2. It has been found that by substantially removing the water from the S0 vapors evolved from this extract condenser-pressure evaporator, the water concentration in the Edeleanu treatment cycle may be kept sufficiently low so as not to interfere with its proper operation. Some water will be contained in the S0 vapors from the other evaporators (including the rafiinate condenser-pressure stage) and will condense in the S0 condenser and pass into the mixer. However, such water will be largely drawn 01f with the extract and removed according to the present invention. Hence the present invention will prevent the cumulation of water in the treatment cycle even as to water carried by the raflinate.

In the first embodiment of the invention, shown in Fig. 1, sulfuric acid drying tower 22 is employed to remove the water vapors from the S0 vapors passing off through line 21 from extract condenser-pressure evapora- 'tor 2. Tank 23 contains sulfuric acid for drying. Pump 32 draws the sulfuric acid 55 from tank 23 through line 29 into tank 24 and forces it through line 31 (regulated by valve 30) into the top part of tower 22, where it issues downwardly through nozzle 33 in the form of a spray. The vapors from line 21 enter the bottom part of the tower and pass upwardly, countercurrently to the descending sulfuric acid. Intimate contacting is effected by the filling material 34.

The sulfuric acid, together with the ab sorbed water, leaves the bottom of tower 22 by line 35 (regulated by valve 36) and passes into storage tank 23. Exhausted acid may be removed from, and fresh acid introduced into, tank 23 through line 37 (controlled by valve 38).

It will be seen that drying tower 22 operates at condenser pressure, that is, at a pressure of 45 to 75 pounds per squareinch, and at a temperature not greatly lower than that of evaporator, 2. It might be feared that under these conditions there'would be a condensation of SO vapors passing through the tower and that undesired chemical reactions would occur. It has been discovered, however, that the method can be made to operate without producing these harmful results.

The SO vapors, substantially freed of water, leave dryingtower 22 by line 25, at condenser pressure, and are joined by the E50 vapors coming by line 26 from ratlinate condenser-pressure evaporator 7. The united vapors pass through line 27 and enter line 28 together with the SO; vapors from line 20.

All of the SO vapors evaporated from the extract and raiiinate, in a substantially Waterfree state, are led by line 28 into the SO: condenser 40. Cooling water enters the condenser water space line 39 and leaves by line 42. The term condenser-pressure has been used herein to denote that pressure at which the SO: vapors would condense at the cooling-water temperature employed. The

S0 vapors therefore condense in condenser 40 without being further compressed. The liquefied S0 leaves the condenser by line 41 and is returned to the Edeleanu treatment cycle for continued use.

Another embodiment of the invention 1s 1llustrated in Fig. 2 of the drawings, wherein rectification tower 43 replaces drying tower 22 of Fig.1. As before, the extract from the mixer is conveyed by line 1 to evaporator 2 and the S0 vapors evolved, which contain most of the water picked up during the treatment cycle, are led by line 21 to the water removal means, which in this embodiment comprises the rectification tower 43. The lower part of the tower is provided with a heater 48,

tacting of vapors, and are positioned in the upper and lower portions of the tower, respectively. r

The SO vapors are led by line 21 into the tower and the rectification to which they are subjected causes the water vapor content to pass downwardly and the S0 vapor content upwardly, so that line 25 withdraws substanti ally water-free SO gas from the top of the tower, while line 49 withdraws the removed water from the bottom of the tower. The SO gas in line 25 is disposed of as already described in connection with the first embodiment of the invention illustrated in Fig. 1. x I

A third embodiment is illustrated in Fig. 3, wherein an SO condenser (50) and a redistilling tank (57) are used for effectin the removal of water from the S0 vapors from the extract-condenser-pressure evaporator (2), being used in place of the drying tower (22) of Fig. 1 and the rectification tower (43) of Fig. 2.

The opeeration of this system is as follows: The S0 vapors from the raffinate condenserpressure evaporator 7 are led by lines 26, 27 and 28 to condenser 40 which is water cooled as before and operates at a pressure suflicientto condense the SO at the temperature of the cooling water. This condenser also serves to condense the S0 vapors in line 20 as in the previous embodiments. The condensed SO leaves by line 41 and passes to liquid-SO storage vessel 62 from which it is withdrawn through line 64, controlled by valve 63, for reuse in the treatment mixture. Thus condenser 40 takes care directly of all the S0 vapors from the low pressure stages and those from the raflinate condenser-pressure evaporator.

The S0 vapors from the extract condenserpressure evaporator 2 pass through line 21 to condenser 50., Cooling water enters the condenser water space by line 51 and leaves by line 52. The resulting condensate, which contains a comparatively high percentage of water, leaves condenser 50 by line 53 which divides into two parts: line 56, controlled by valve 54; and line 61, controlled by valve 55 Line 61 leads to line 41 which carries the condensate from condenser 40 and line 56 leads to redistilling tank 57. By this arrangement the condensate from condenser 50.may be wholly or in part redistilled, or may be led directly to liquid-SO storage vessel 62 when the redistilling tank is not in operation.

Redistilling tank 57 is operated at atmospheric pressure, valve 54 serving to'reduce the pressure in line 56 which takes the condensate from line 53 at condenser-pressure. The redistilling tank may be heated by a water bath 58. The distilled water-free S0 vapors are drawn off through line 60 which connects with line 18- and pump 19. The water and light oil parts which remain in the redistilling tank after each distilling period may be drawn off by pipe 59. Pump 19 serves to suck the S0 vapors off from redistilling tank 58 and compresses them up to condenser-pressure along with the SO vapors from lines 14 and 17. The united S0 vapors, at condenser-pressure, are led by line 20 to line 28, where they are joined by the SO: vapors from rafiinate condenser-pressure evaporator 7, and are condensed as before described.

The redistillation is done periodically so that the water content of the treatment system will not rise above a predetermined harmful amount. The described arrangement permits all of the condensate from condenser 50 to be returned directly to the treatment cycle (through storage vessel 62) when the redistillation unit is not in operation, and when it is in operation as much or as little of the condensate may be redistilled as desired. In this way great flexibility is obtained in removing water from the S0 from the treatment cycle.

Fig. 4 illustrates a modification of the method just described and shown in Fig. 3. In this arrangement, the redistillin-g tank 57 is operated at condenser pressure and the evolved water-free-SO vapors at condenser pressure are led by line 60 directly to line 20 which is at condenser pressure. The rest of the system is as before. 4

Under some circumstances, where an unusually large amount of water is picked up during a treatment cycle, it may be necessary to also. remove water from the S0 vapors passing off from the raflinate condenser-pressure evaporator 7. This may be done by employing one of the water removal means already described. Ordinarily, this expedient need not be resorted to, and the methods illustrated applied to the extract condenserpressure evaporator will be sufiicient.

Also, in case the condenser pressure or first stage treatment is carried on in a plurality of steps, some of which may operate at a somewhat higher pressure than that of the main condenser, the removal of water may be effected from some or all of these steps, as may be convenient, all being comprised within what is herein termed'the condenser pressure stage.

The present invention may also be employed in connection with treatment cycles which utilize liquid-SO -mixed-solvents, such as liquid-SO and benzol, liquid-S0 and low-boiling Edeleanu extract, or liquid- SO and acetone, etc., in place of liquid-SO, alone as the extracting agent.

The invention obviously is not restricted to the particular embodiments thereof herein illustrated and described.

Having disclosed two illustrative embodiments of the invention, what is claimed and desired to be secured by Letters Patent is as follows 1. An improvement in the process for continuous treatment of moisture Containing liquid hydrocarbons with liquid-S0 wherein a closed treatment cycle is maintained by separately subjecting the moisture contain ing rafiinate and extract solutions from the mixer to multi-stage evaporation for recovcry of the S0 for reuse in the mixer, which consists in conducting the first stage extract-evaporation at condenser pressure, drying only S0 evolved from the extract condenser pressure stage of evaporation without returning the removed water to the extract, and adding said dried SC) to the undried SO evolved from the other stages, thereby preventing the accumulation of a harmful water concentration in the treatment cycle.

2. An improvement in the process for continuous treatment of moisture containing liquid hydrocarbons with a mixed-solvent containing liquid-S0 wherein a closed treatment cycle is maintained by separately subjecting the moisture containing rafiinate and extract solutions from the mixer to multistage evaporation for recovery of the solvent for reuse in the mixer, which consists in con-' ducting the first stage extract-evaporation at condenser-pressure, drying only solventevolved from the extract condenser-pressure stage of evaporation without returnin the removed water to the extract, and at ding said dried solvent to the undried solvent evolved from the other evaporation stages, thereby preventing the accumulation of a harmful water concentration in the treatment cycle.

3. The method specified in claim 1 in which S0 evolved from the extract condenserpressure stage of evaporation is dried by contacting with a suitable desiccant.

4. The method specified in claim 1 in which the S0 vapor evolved from the extract con-- 5. The method specified in claim 1 in which the S0 vapor evolved from the extract condenser-pressure stage of evaporation is rectified before condensation and thereby substantially dried.

6. The method specified in claim 1 in which the S0 vapor evolved from the extract condenser-pressure stage of evaporation is directly condensed and then redistilled for removal of water.

7. The method specified in claim 1 in which the SO vapor evolved from the extract condenser-pressure stage of evaporation is directly condensed and a sufiicient proportion redistilled for removal of water to prevent the accumulation of a harmful water concentration in the treatment cycle.

8. The method specified in claim 2 in which solvent evolved from the extract condenserpressure stage of evaporation is dried by contacting with asuitable desiccant.

9. The method specified in claim 2 in which the solvent vapors evolved from the extract condenser-pressure stage of evaporation are passed counter-cm'rently to a spray of sulfuric acid before condensation and thereby substantially dried.

10. The method specified in claim 2 in which the solvent vapors evolved from the extract condenser-pressln'e stage-of evaporation are rectified before condensation and thereby substantially dried. I

11. The method specified in claim 2 in which the solvent vapors evolved from the extract condenser-pressure stage of evaporation are directly condensed and then redistilled for removal of water.

12. The method specified in claim 2 in which the solvent vapors evolved from the extract condenser-pressure stage of evaporation are directly, condensed and a sufiicient proportion redistilled for removal of water to prevent the accumulation of a harmful water concentration in the treatment cycle.

In testimony whereof, I have signed my name to this specification.

ERICH SAEGEBAR'IH.

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