US2321294A - Method of control of temperatures in regeneration of catalysts - Google Patents

Description

June 8, 1943. Q HEMMlNGER ETAL 2,321,294

METHOD OF CONTROL OF TEMPERATURES IN REGENERATION OF CATALYSTS Filed Sept. 27, 1958 OUTLET 6A 5 Auve COOLER Oll- INLAT OAS LIN 14/7? INLET Patented June 8, 1943 METHOD OF CONTROL OF TEMPERATURES IN REGENERATION OF CATALYSTS Charles E. Hemminger, Westfleld, and Charles W. Tyson, Summit, N. 1., asslgnors to Standard Oil Development Company, a corporation oi Delaware Application September 27, 1938, Serial No. 231,870

3 Claims.

The present invention relates to improvements in the regeneration of solid catalysts. More particularly the present invention relates to the regeneration of a contact catalyst comprising an adsorbent material by combustion of the tarry or carbonaceous deposits thereon to form removable gaseous combustion products. A particularly important application of this invention has reference to the revivification or regeneration of the type of synthetic catalyst employed in the catalytic cracking of relatively heavy hydrocarbon oil of petroleum origin or derived from the destructive distillation of coal, to form lighter fractions boiling within the gasoline range.

When the vapors of a relatively heavy hydrocarbon oil are passed through a mass of catalyst at suitable cracking temperatures, a coky or tarry deposit is gradually formed upon the catalyst. When the amount of the tarry deposit is from 2-5%, based on the weight of the catalyst, it is necessary to discontinue the cracking operation and regenerate or revivify the catalyst. Numerous proposals have been made by others for revivifying the catalyst, including treatment with solvents and combustion of the contaminating carbon material. The combustion method has been widely used heretofore. To prevent injury of its structure, the catalyst should not be heated above a certain maximum temperature, usually in the neighborhood of 1000" F. and certainly not far above 1100 F., during regen'eration. The present combustion methods of regenerating catalysts often lead to baking and fusion of the catalyst, due to poor control of combustion temperatures, and furthermore are very time consuming.

It is a principal object of the present invention to regenerate the catalyst employed in the catalytic cracking of heavy hydrocarbons by the combustion method under carefully controlled conditions, so that the catalyst is very rapidly regenerated while baking and overheating of the catalyst is avoided. Stated very generally, at first, the improvement comprises initiating combustion at one end of a catalytic body in the presence of an oxygen-containing gas at a temperature equal to or somewhat above that necessary to support combustion, and then after the combustion zone or flame front has progressed a short distance through the catalyst bed, lowering the temperature of the incoming oxygen-containing gas to a. point below that necessary to support combustion. The oxygen-containing gas which is at a temperature below that necessary to support combustion as it enters the catalyst bed, will chtain the added heat necessary to support combustion by contact with the hot catalyst, which has been regenerated.

Reference is now made to the accompanying drawing and the following description from which a clear understanding of the invention will be readily obtained.

The figure is a diagrammatic arrangement of a reactor, shown in elevation and broken away in part, with merely sufficient accessory apparatus to illustrate the present invention. It will be assumed in the ensuing description that the reactor shown forms part of the conventional system of preheaters and fractionating equipment, commonly employed in catalytic cracking operations, it being unnecessary to illustrate such apparatus in describing the present invention.

In the illustration now about to be given, it will be assumed that a cracking operation had just been terminated, due to the fact that the catalyst has become contaminated with tarry orcarbonaceous deposits and the succeeding descriptions will proceed from that point. Referring to the drawing, reactor or cracking chamber R contains 4 beds of catalyst C, viz., beds I, II, III and IV. The first step in the regeneration is to purge the catalyst with an inert gas such as superheated steam, which is at a temperature of about 820 F. to 900 F., higher or lower temperatures being permissible. This steam may be admitted through valved line 1) and withdrawn through valved line 0, i. e., the steam or other inert gas flowing through the reactor in a direction opposite that of the oil flow during cracking. Of course, it is obvious that to cause the steam to flow out through valved line 0, the valves in all other lines entering reactor R except those in lines o and 1) must be closed. Also, good results are obtained by closing the valves in lines o and p and admitting superheated steam through line I into line 2, and thence into reactor B. through lines 3, 4 and 5, finally withdrawing the steam through lines 5 and 6. This withdrawn steam may be mixed with air and the mixture used in the regeneration proper.

In commencing the regeneration of the catalyst, which is at a temperature of say 820 F. to 900 F., and considering conditions in bed I which is illustrative of conditions as to amount of carbonaceous deposit, temperature of catalyst and the like, in each bed, air and an inert gas such as steam are admitted through valved feed lines la and l respectively, into line 2 where they mix and the mixture is then pumped into reactor R through valved lines 3, 4 and 5 respectively. The inert gas which is admitted through line I, may be superheated steam at a temperature of about 820 1". and may be, as previously stated, the gas used in the prior purging of the reactor R of hydrocarbon vapors from the cracking operation. Suillcient air is led into the system through valved line Ia to give this original mixture of air and inert gas entering reactor R, an oxygen concentration of about 1%. The temperature of this initial gas may be from about 820 F. to 900 F. and its pressure about 40 lbs./sq. in. Under the conditions just now described, combustion of the tarry material dcposited upon catalyst C will take place at once in a horizontal zone indicated by a, and the products of this combustion will pass through the catalytic mass through zones b; c, d and exit through valved lines 5 and 6 to line 1 to be recirculated in whole or in part. The products of combustion in valved line I flow through motor operated valve I and through cooler 9 into feed line 2. In the meantime, the active combustion zone which was initiated at a in beds I, II, III

and IV, will have advanced toward zone b. At this time additional air admitted through valved line la mixes with the cooledgases in line 2 and this gaseous mixture used after combustion has been initiated and containing about 5% oxygen is then pumped into the reactor and passes through the regenerated zone a to zone b, which at this moment, it is assumed, is the active combustion zone. During the passage of these cooler gases whose inlet temperature is about 650 F., and which are under a gauge pressure of 40 lbs/sq. in., through regenerated zone a, they are heated by contact with the hot regenerated catalyst, absorbing sufilcient additional heat to bring them up to combustion temperatures when they reach active combustion zone b and by the same token, the catalyst in zone a is cooled. The process continues under the conditions just now de-,

scribed as to oxygen concentration, temperature and pressure, as the combustion zone advances through the zones b, c and d until the entire catalyst has been regenerated, except near the completion of the regeneration, as hereinafter explained.

In order to provide for a very accurate control of the regeneration of the said catalyst, various expedients are resorted to to accomplish the foregoing result. For example, assuming that it was not desired tocool the gases in line I, the hot gas may be shunted around the cooler 9, through shunt line ll, into gas feed line 2, to speed up the combustion in its very early stages or for any other reason,

Furthermore, a portion or all of the gas may be withdrawn from the gas circulating system through line lb in which is disposed regulator l5 adapted to adjust the gas pressure in the system to the desired value.

In order to cause the process to operate, at least in part automatically, butterfly valves l0 and I! are operated by motor l3, the operation of .the motor being responsive to the temperatures prevailing in the several zones of the catalyst beds. through ordinary base metal thermocouples l1, l8, l9 and 20, disposed in an elec trical circuit including potentiometer I6 and motor is. When the temperature of the catalyst in some zone, as indicated by the corresponding thermo-couple exceeds some fixed value, say 900 R, an electrical impulse from potentiometer I8 is transmitted through a relay to said motor l3 causing the latter to close valve l2 and open valve II by means of any known mechanism (not shown), the gases passing through cooler 8.

when the temperature 01' the catalyst exceeds say 1000' F., indicating that the regeneration is nearly completed, motor is responsive to said temperature condition through potentiometer l0, closes valve II and opens valve II. It is obvious, of course, that valves I 0 and I! may be hand operated and that the thermo-couples l1, I8, I! and 20 may be employed merely to indicate temperature conditions.

Each catalyst bed may be provided with four thermo-couples as shown in bed I, but since substantially the same conditions prevail in each bed, it is preferable to employ thermo-couples in communication with the potentiometer only in one bed.

It will be understood that zones 11, b, c and d are not physically separate but are merely regions of a continuous bed of catalyst where diflerent temperatures may prevail. There is no sharp line or temperature difference at zone boundaries during regeneration, the temperature difference from zone to zone being gradual. In a bed of great depth the number of zones represented here by a, b, c and (I obviously would be greatly multiplied. Without placing any limitation on the depth of these zones, it maybe said that in the illustration shown each zone may have a depth of about 15 inches. Depending on numerous factors such as size of catalyst, amount of impurities and the like, this figure may vary considerably.

In the description of the manner of operating the process of regeneration lust given, the illustration included initiating the combustion with an original oxygen-containing gas at a temperature at or above that necessary to support combustion. The same results may be accomplished, however, by using a lower temperature and increasing the concentration of oxygen to a point or say 5%. Furthermore, the pressure on the system, as indicated by pressure gauge G may be from 5 lbs/sq. in. to 105 lbs/sq. in. The combination of high pressure (say 100 1bs./sq. in.) and relatively high oxygen concentration (say 5%), serves to enable the regeneration to be initiated at a lower gas temperature (about 750 F.) than where the pressure is considerably lower or the concentration or the oxygen in the oxygencontaining gas is much lower. In like manner the inlet temperature of the gas employed after the regeneration has been initiated may be decreased below 650? F. by increasing the pressure and/or oxygen concentration. In any event, however, it is advisableto' conduct the final stages of the regeneration using an oxygen-containing gas having a temperature of about between 820' -F. to 1000 F. for the purpose of imparting a uniform temperature to the catalyst through its entire mass, so that after purging with superheated steam at a temperature of say 820 F., it is well conditioned for the resumption of crackmg.

It will be understood, of course, that the present process is applicable to the regeneration of a catalyst in one single unitary bed, as well as the reactor containing a plurality oi chambers and beds of catalysts.

What we claim is:

1. The process of regenerating a spent catalyst mass containing carbonaceous deposits which mass under superatmospheric pressure and at an inlet temperature within the range of from about 820 F. to 900 F. to cause immediate combustion of said deposits upon contact of said gas with deposits, thereafter reducing the inlet temperature of the said gas to about 650 F. until near the completion of the combustion of all the carbonaceous deposits contained in the catalyst mass and then raising the inlet temperature of the regeneration gas to about its original inlet temperature during the final phase of the regeneration. v

2. The process of regenerating a solid catalyst contaminated with combustible material which comprises forcing a heated oxygen-containing gas into said catalyst at an inlet temperature at least sumciently elevated to cause immediate combustion of the said contaminants upon contact with the said gas and thereafter supplying under superatmospheric pressure a further quantity of oxygen-containing gas to the said catalyst, through a regenerated portion thereof to support further combustion of said contaminants in unregenerated portions, the inlet temperature of the last-named gas being substantially elevated above atmospheric temperature, but below that necessary to cause immediate combustion of the contaminants at th pressure employed, whereby the regenerated portion of the catalyst is cooled x and the last-named portion of gas is heated to ignition temperatures, and then raising the inlet temperature of the regeneration gas to about its original inlet temperature during the final phase of the regeneration.

3. The process set forth in claim 2 in which the catalyst at the beginning of the regeneration is at, a temperature of about 820 F. to 900 F., the initial temperature of the regeneration gas is from about 820 F. to 900 F., the intermediate gas inlet temperature is about 650 F., and in which process the gases are under a pressure of about 40 lbs. per square inch gauge.

CHARLES E. HEMMINGER. CHARLES W. TYSON.

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