US2224014A - Method for control of catalytic processes - Google Patents

Description

. 3, 1940. e. s. DUNHAM ETAL METHOD FOR CONTROL OF CATALYTIC PROCESSES Filed Oct. 18, 1938 2 Sheets-Sheet l 9, L@ M MM |NVENTOR3 ATTORNEY Dec. 3,. 1940. 5, DUNHAM AL 2,224,014

METHOD FOR CONTROL OF CATALYTIC PROCESSES Filed Oct. 18, 1938 2 Sheets-Sheet 2 INVENTOR Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE METHOD FOR CONTROL OF CATALYTIC PROCESSES George S. Dunh..m, Ar

back, Oakmont, Pa.,

dmore, and Ernest Utterassignors to Socony- Application October 18, 1938, Serial No. 235,564

6 Claims.

Known methods for the conversion of hydrocarbons, as for example the vapor phase cracking of hydrocarbons, involve passing the hydrocarbons, at reaction temperatures, through a contact mass capable of catalytically promoting the desired conversion. During the desired conversion there is deposited upon the contact mass a combustible carbonaceous material. The contact mass is regenerated in situ by burning off this combustible material. The conversion reaction is usually slightly endothermic. The regeneration is highly exothermic. The contact mass is usually susceptible to deterioration for various reasons at high temperatures. To prevent the attainment of such temperatures during the exo thermic operation of regeneration it is usual to remove heat from the contact mass by means of a fluid heat transfer medium circulated through tubes imbedded therein. An operating set up for commercial operation consists of several cases or chambers each containing contact mass. At least one of these will be operation on conversion, at least one will be undergoing regeneration, and there will usually be at least one additional case which either will be standing idle awaiting conversion or regeneration, or will be undergoing purging to remove conversion reactants prior to regeneration or to remove regeneration reactants prior to going on conversion.

This invention has for its object the provision of a process whereby the several cases comprising a commercially operating catalytic conversion set up may be so handled with respect to their various heat requirements that each case may be conveniently maintained at a temperature level appropriate to its place in the operating cycle. An important object is the provision of heat control medium at proper levels to facilitate catalytic operations. A further object is the balancing of heat requirements among the several cases of such a system in such manner as to avoid, insofar as is possible, the wasting of heat to a point outside the system. A further object is the accomplishment of these purposes through the use of a minimum circulation of fiuid heat transfer medium. Other objects are in part obvious or will be referred to hereinafter.

In order to explain the invention, reference is made to the drawings attached to this specification, the two figures of which show, in diagrammatic form, how the invention may be applied.

In Figure 1 there are shown three catalyst cases or chambers, 3, 4, 5, each containing contact mass 6 supported by grids The chambers 3, 4, 5 are respectively furnished with hydrocarbon reactant inlets 8, 9, Ill and reactant outlets l2, l3; with regeneration inlets |4, |5, l8 and regeneration outlets l1, l8, l9; and with purging inlets 20, 2|, 22 and purging outlets 23, 24, 25. All such connections are valved. For purposes of illustration it will be noted that chamber 3 is on reaction, chamber 4 is purging or idle, and chamber 5 is on regeneration.

The chambers 3, 4, 5 are respectively equipped with coils 26, 21, 28 embedded in the contact mass therein and pumps 29, 3|], 3| serve to circulate heat transfer medium through the coils. Pipe 32 conducts heat transfer medium from chamber 5 to pump 29, pipe 33 from chamber 3 to pump 30, pipe 34 from chamber 4 to pump 3|. Bypass 35 leads, through check valve 36, waste heat boiler 31 and exchanger 38 to pumps 39, 40, 4|. Pipe 42 leads from pump 4| through check valve 43 to the suction side of pump 29. Pipe 44 leads from pump through check valve 45 to the suction side of pump 30. Pipe 46 leads from pump 39 through check valve 41 to the suction side of pump 3|. Thermocouples may be provided at 48, 49, to observe the temperature within the contact mass in 3, 4, 5 respectively. Thermocouples 5|, 52, 53 may be provided to ob- .serve the temperature in the heat transfer medium leaving chambers 3, 4, 5 respectively. As indicated, either or both of the thermocouples of the pair 485| may be operatively connected, through the use of instruments known to the art, to control operation of pump 4|. Similarly the pair 49-52 may control pump 40. Similarly the pair 50-53 may control pump 39.

To illustrate operation according to Figure l, we may assume chamber 3 to be on reaction, and that it is desirable to maintain therein a temperature of 850 F. Assume chamber 4 to be purging, or idle, and it is desired that this chamber shall not cool below 825 F. Assume chamber 5 to be regenerating, when it is desired that the contact mass temperature shall not rise above about 1000 F., but that the heat transfer medium shall not rise above about 855 F. From these conditions it is obvious that pipe 32 will contain heat transfer medium, hereinafter brief ly spoken of as medium, at a temperature of 855 F., and that pump 4| by pulling some of that medium through pipe 35 and the attendant cooling devices will have available medium at a temperature substantially below 855 F. Subject to control, either manual, or automatic as shown, pump 4| will supply sufiicient colder medium to pump 29 to hold the temperature within 3 to the desired 850 F. range, the medium in coil 26 1 .'.cycle, chambers 3, 4, 5 will change their place in the cycle, 4 going on conversion, 5 idle, 3 regenerating, the controls will be changed or reset if automatic, and the operation proceed as before. In such operation the heaviest volume of medium will flow through the circulating system connected with the chamber undergoing regeneration, as, for example the system comprising 28, 35, 31, 38, 39, 48, 3| in the example shown where 5 was regenerating.

Figure 2 shows a modification of the system of operation set forth in Figure 1. In Figure 2 we have chambers 3, l, 5, as before, containing contact mass 6 on grids 1, fitted with valved inlets and outlets 8 to 25 inclusive, as before, and with coils 26, 21, 28, as well as pumps 29, 30, 3|, to supply heat transfer medium to coils 26, 21, 23, respectively. Also we have pipe 32 carrying a flowing stream of maximum temperature heat transfer medium and bypass pipe 35, equipped with check valve 36, passing through waste heat boiler 31 and heat exchanger 38 to furnish a supply of cooled medium. All of these items are identical in position and function with the similarly numbered items in Figure 1. But where the flow path in Figure 1 i is a modified series flow, that of Figure 2 is a parallel flow. To this end pipe 54 leads medium from coil 26 back to pipe 32, and pipe 55 leads medium from coil 21 back to pipe 32. Pump 56 draws colder medium from pipe .35 and delivers it through pipe 5'! and check valve 58 to the suction side of pump 29. Pump 59 draws colder medium from pipe 35 and delivers it through pipe 60 and check valve 6| to the suction side of pump 30. Pump 62 draws colder medium from pipe 35 and delivers it= through pipe 63 and check valve 64 to the suction side of pump 3|. Thermocouples 65, 66, 61 are provided to observe temperature of the contact mass within the respective cases, and thermocouples 68, 69, 10 are provided to observe the temperature of the medium leaving the respective coils. As before, either or both of the thermocouples of each pair may be operatively connected, through the use of instruments known to the art, to control operation of the corresponding pumps. The pairing will be 65-68 with pump 56, 6669 with 59, and 61-10 with pump 60.

Without going into detailed temperatures, which for an exemplary operation would be the same as those previously given, it will be noted that each of the pumps 56, 59, 62, subject to the demands of their respective cases, either as interpreted by an operator and followed by manual adjustment, or as interpreted and adjusted for by an automatic instrument, will supply a suflicient amount of cold medium to maintain the desired temperature within the respective chambers.

It will also be understood that in each type of operation, pumps 29, 36, and 3| are subject to such control, either manually or by instrumentation as will enable them to properly operate in tandem with their respective cold medium pump.

An important feature of the present invention is the abiltyto so control the temperature of heat exchange medium as to greatly faciltate the desired catalytic operations. For example, assuming a given contact mass, say Case 5, in

. Figure 1, is on regeneration. In the early portion of the cycle, the rate of regeneration is high and the rate of delivery of exothermic heat is high. For a given desirable exit temperature of heat exchange medium in pipe 32, a relatively great amount of cold medium is supplied through pipe 46. In short, the heat transfer medium in coil 28 is heated through a longer temperature range, and, the mean temperature difference between burning contact mass and the heat transfer medium is great, thus promoting efiicient heat removal. Now, as the carbon is gradually burned off, the intensity of burning becomes less. Also, it becomes necessary to maintain temperatures at combustion levels to insure complete regeneration. Too great a temperature difference cannot be used. Consequently, while still maintaining the same desired heat transfer medium exit temperature, the mean temperature difference may be decreased to values sufficiently small so that efiicent complete regeneration may be accomplished.

It will be noted that both of these systems have in common the feature of maintainng two flowing streams of medium substantially diiferent in temperature. Further, each system draws proportlonately from both streams to provide medium at appropriate temperature for each contact mass, dependent upon its operating phase. Further, in each the volume of the flowing stream of cold mixture is available and directly proportionate to the demand therefor.

It will be noted further with respect to the stream of cold medium that the cooling devices hereon comprise a waste heat boiler 31 and a heat exchanger 38. Of course, the heat exchanger may be used alone and if so preferably should be equipped with means for varying the flow of cooling water, etc., in proportion to the amount of heat transfer medium flowing therethrough. The use of a waste heat boiler is preferred, since by pressure control on steam therein generated, wide variation in cooling of medium can be accomplished with relatively little change in temperature level of cooling. This will tend to hold uniform the temperature of medium in pipe 35, and so stabilize the general operation. In such a system the actual temperature of cooled medium is not of moment so long as it is sufficiently low to avoid the circulation of excessive quantities of medium. With hot medium at above 800 F., even a high steam pressure waste heat boiler offers an attractive temperature differential. Consequently another advantage of the present system is its ability to dispose of waste heat at a high temperature level.

The heat transfer medium used herein, should be a liquid having low vapor pressure,- low viscosity, and high specific heat at the temperatures, (600-1200 F.) encountered. Fused metals, fused alloys, and fused inorganic salts are suitable. A preferred medium is a fused mixture of alkali salts of oxy-acids of nitrogen.

We claim: 1

1. A method for the control of catalytic operations involving an endothermic reaction and an exothermic regeneration in a system including at least one contact mass on reaction, and one contact mass undergoing regeneration, comprising circulating fluid heat exchange medium in heat transfer relationship with each contact mass, maintaining two flowing streams of heat exchange medium, substantially diflerent in temperature, admixing medium from both streams at a point prior to each individual contact mass to form a mixture of desired temperature toflow through said contact mass, returning medium from contact mass temperature control duty to the hot flowing medium stream, and withdrawing medium from the hot stream and cooling it to form the cold stream.

2. A method for the control of catalytic operations involving a reaction and an exothermic regeneration in a system including at least one contact mass on reaction, and at least one contact mass undergoing regeneration, comprising circulating fluid heat exchange medium in heat transfer relationship with each contact mass. maintaining two flowing streams of heat exchange medium, substantially diiferent in temperature, admixing medium from both streams at a point prior to each individual contact mass to form a mixture of desired temperature to flow through said contact mass, returning medium from contact mass temperature control duty to the hot flowing medium stream. withdrawing medium from said hotter stream at a variable rate to form said colder stream and extracting a variable amount of heat from the medium so withdrawn to give a cold medium stream of substantially constant temperature.

3. A method for temperature control of catalytic operations involving a reaction and an exothermic regeneration in a system including at least one contact mass on reaction. and at least one contact mass undergoing regeneration, comprising circulating fluid heat exchange medium in heat transfer relationship with each of said contact masses, maintaining a flowing stream of high temperature heat transfer medium withdrawing a variable amount of medium from said high temperature stream and passing it in contact with a cooling medium of substantially constant temperature to establish a second flowing stream of medium of a temperature substantially below said first named stream flowing the hotter stream serially through all contact masses and admixing with it, prior to passage through each contact mass, sufllcient medium from the colder stream to form a mixture of desired amount and temperature for the particular contact mass.

4. A method for temperature control of catalytic operations involving a reaction and an exothermic regeneration in a system including at least one contact mass on reaction, and at least one contact mass undergoing regeneration, comprising circulating a separate mixture of fluid heat exchange medium in heat transfer relationship with each of said contact masses, maintaining a flowing stream of high temperature heat transfer medium, withdrawing a variable amount of medium from said high temperature stream and passing it in contact with a cooling medium of substantially constant temperature to establish a second flowing stream of medium of a tem-- perature substantially below said flrst named stream separately admixing medium from both streams to form a mixture of desired amount and temperature for the particular contact mass and after passage through said mass returning said mixture to the hotter stream.

5. A method for the control of catalytic operations involving an endothermic reaction and an exothermic regeneration in a system including at least one contact mass on reaction, and at least one contact mass undergoing regeneration, comprising circulating fluid heat exchange medium in heat transfer relationship with each contact mass, maintaining two flowing streams of heat exchange medium, substantially different in temperature, admixing medium from both streams to form for each contact mass an individual mixture oi medium of desired temperature to flow through said contact mass, withdrawing medium from the hot stream and cooling it to form the cold stream, maintaining a predetermined substantially constant fluid heat exchange medium outlet temperature on each of the masses undergoing regeneration while varying the inlet temperature of the medium flowing to each of such regenerating masses to secure an inlet temperature progressively approaching the outlet temperature as the regeneration approaches completion.

6. A method for the control of catalytic operations comprising conducting an exothermic combustion regeneration of a contaminated contact mass in contact with a flowing stream of fluid heat exchange mediiun, maintaining the exit temperature of said stream substantially constant across the period of regeneration, and varying the temperature of the inlet of said stream during the period of regeneration to secure an inlet temperature progressively approaching the outlet temperature as the regeneration approaches completion.

GEORGE S. DUNHAM. ERNEST U'I'I'ERBACK.

Patent no; 2',22h,o1 h. December 5, 191m.

' GEORGE s. mnmm, 'ET AL.

It is hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 2, sec- 0nd. column, line 1+5, for "hereon" read --thereon--; page 3, first column,

line 1, claim 1, after the'word "and" -insert"- --at 1eest--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

5151166 a dsealed this 251m day-of .mrch, '1 1m Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.

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