US2398186A - Catalyst regeneration - Google Patents

Description

yventional compressors..

.eliminates the need for such items of equipment and, provides a simplified and more elcient v method and arrangement of apparatus for eilecntivelycarrying out the regeneration of spent catalyst. 'It will be evident to those skilled in the Patented Apr. 9, 1946 CATALYST REGENEBATION John W. Loy, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application April 17, 1943, Serial No. 483,425 2 (llaims.lk (Cl. 25g-242) This invention relates to catalytic conversion o! hydrocarbons and more particularly to catalytic conversion of hydrocarbons with provision for regenerating or reactivating the catalyst after it has become so laden on-stream with combustible carbonaceous material such as carbon that the rate of conversion is no longer economical. Still more particularly it relates to an improved process and apparatus for reactivating such a catalyst in situ.

The present invention is an improvement over the catalyst regeneration disclosed in application Serial N0. 414.850, illed October 13, 1941.

In catalytic cracking operations where high carbon deposits are encountered, large volumes of air are required to burn off the carbon and regenerate the catalyst. With chamber-type operation and stationary catalyst beds. it is essential that the regenerative gases be handled at pressures above atmospheric in order to decrease the diameter of conveying conduits and decrease differential pressure drop acrossthe system.

The air compression required is relatively costly both as to initial investment and operating cost. Also. a diluent such as steam or ue gas must b'e used with the air to limit the temperature to a reasonable maximum in burning off the carbon.

As it is generally advantageous to recover the heat of regeneration by means of waste heat boilers, the present invention contemplates. among other things. the use `ozt' steam from such boilers to inject combustion air into the catalyst chambers. Steam is generated in waste heat boilers, which waste heat boilers serve as a quenching lmeans for the conversion step and recover the `heat from the spent regenerative gases.

The steam may acquire a pressure of 200 pounds per square' inch, for example, andunder this pressure; itis forced through a-'st'eam Jet into the catalyst chamber. 'I'he steamin going through the steam 'Jet has an aspirating action and draws airlo'r other free oxygen containing gas in with -thelsteam,ywhich air supports combustion in the respective'catalyst beds.

` One of the main advantages of the present invention resides in the fact that it eliminates certain expensive items of equipment, including con- The present invention artythatthe practice of my invention greatly reduces the investment cost, minimizes replacement expenses, and requires relatively lowmaintenance and operation expense, both in equipment and in necessary personnel to handle the same.

In operation, superheated steam, at 200 pounds per square inch and 900 F., for example, with inducted air or other i'ree oxygen containing gas, is injected into the top of the catalyst chamber,

the mixture of steam and air being at high enough temperature, such as 800 F., and high enough air content. such as 10% b'y volume, to initiate combustion of the carbon deposit. The steam expands through the jet at high velocity, the kinetic energy resulting therefrom is sumcient to inject a mixture of steam and air into the chamber, whose static pressure is less than the initial steam pressure. The spent reactivated gases and steam are removed from the bottom of the catalyst chamber. Where the catalyst cham- I'ber employed is divided into a plurality of compartments, auxiliary jets using steam and air at lower temperatures than those indicated above are used to promote combustion of deposited carbon in subsequent compartments, since admixture of the secondary regenerative gas with the hot gas from initial combustion produces a mixture at high enough temperatures to ignite the remaining carbon. In effect, higher free oxygen content is permissible in cool secondary regenerative gas, and the total amount of gas handled is decreased.

It is a primary object of the present invention to employ the pressure of a diluent gas, such as steam, to maintain the required pressure in a catalytic process and further to pass the steam under pressure through a `iettingdevice and by the aspirator action of the :letting device, draw and then inject the necessary i'ree oxygen containing gas into the process, to support combustion during the regenerative step.

It is a further object of this invention to Drovide a system of the character indicated which'is less expensive in initial, maintenance, and operating costs than similar systems for regenerating spent catalysts that have been employed heretofore.

It is a still further object of the invention to conserve on the amount of critical metals employed in carrying out a catalyst regeneration process.

Other objects and advantages will appear from the description as it continues and from the annexed drawing which is a diagrammatic view or the process.

Referring to the drawing, a catalyst chamber I is provided at its topfwitn an :niet 2. a suitable hydrocarbon feed stock is supplied to inlet 2 durbottom of the catalyst chamber for removing converted hydrocarbons by way of a line l or alternatively for removing spent reactivating gases by way of a line 1.

For the purpose of illustration only, I have shown catalyst chamber I as being divided into a plurality of compartments or sones I, I, Il and Il of progressively increasing volume reading downwardly. It is to be understood that my invention may be effectively practiced whether the catalyst chamber is divided into a plurality of compartments, as illustrated, or whether it consists of a 'single compartment. Furthermore, while four compartments or sones are denoted in the drawing, it will be apparent that any desired suitable number of sones may be employed. with equal success. The sections are separated byl material that is supported on and above leach member I2.

As was indicated above, a diluent. such as super-heated steam, with inducted air is supplied to the top of the chamber at desired pressure and temperature. The diluent. preferably steam, is conducted through line 4 to a letting device or inlector Il. A line I1 transmits a free oxygen containing gas, such as air, to letting device It. As the steam is letted through device II, it draws or inspirates air from line I 1, the steam and air being thoroughly mixed within device Il and then aspirated into upper sone l of the catalyst chamber. It will be apparent that the mixture of steam and air may be forced into the chamber by virtue of the kinetic energy developed while these materials are being passed through letting device Il.

Mixing zones I3, I4. and Il are provided between the catalyst beds.. 'Ihe hot gases issuing from top sone a are admixed with fresh reactivated gas and steam that are introduced through letting devices or inlectors Il, Il. and 2l as the gas and steam pass downwardly through catalyst zones l, Il, and II, respectively. The resulting mixture of iluid materials in the various sones at desired temperature, volume, and oxygen content passes through each lower bed successively and burns the carbon deposited on the spent catalyst to thereby reactivate the catalyst. It will be evident that the temperature developed in the various sones should be such as not to exceed the safe limits of the materials of the chamber, and further, so as not to inlure the catalyst itself in the course of reactivation. The recommended range of temperatures for safely and emciently operating the system is generally between "100 and 1500 l".

The enluent products, when the process is on assenso steam, that may be generated in the practice of this invention, to other uses. Line Il may be employed to supply additional steam from a suitable source when such additional steam is required in the process. Valved line 2| conducts the steam to valved lines 21, 2l, and Il which in turn connect into the letting devices Il, Ii, and Il, respectively. .Connecting into each of these letting devices are the valved air lines Il, SI, and l2. The steam passing through the letting devices draws in air through the lines l., II. and Si and mixes the air with the steam before the mixture passes into the sones Il, Il, and I l. The action of letting devices Il, Il. and Il is the same as that of letting device Il. described above.

It is thought that the operation is obvious without any further detailed description thereof. The operation of the catalyst chamber, both on wnversion and reactivation is fully discussed in 8erial No. 414,850, filed October 18, 194i, and since the catalyst chamber is the same. reference is made to this application for a full understanding of its operation.

The letting devices II, Il, II. and 2l are a standard article of commerce, available from any number of sources making equipment to handle steamJ generation anddistribution, and applicant makes no claim of novelty for the specific letting devices employed. The free oxygen containing gas supplied by lines I1, il, Il. and for I2 may be either at atmospheric or superatmospheric pressure, as desired. The pressure of this gas before it is admitted into the corresponding letting devices should be auch that pressure' of the combined diluent, such as steam and air. will be sufilcient to carry out the purposes this invention.

It is recommended and within the purview of this invention to recycle spent regenerative gas from line 'I to lines I1, Il, II, and for I2 when it is found that the conditions for operating the catalyst chamber in regenerating spent catalyst warrants the use of more diluent than that normally supplied to the catalyst chamber downstream of the individual letting devices.

yIirom the foregoing, it is believed that the method and apparatus of the present invention will be readily comprehended by persons skilled the conversion cycle, or spent regenerative gases,

.generating gases admixed with a steam diluent is contacted with said catalytic material under combustion conditions in a regeneration sone to removed said carbonaceous material, wherein the catalytic material in said regeneration sone is arranged in a series of beds having free spaces therebetween, and wherein oxygen-containing regenerating gas is introduced intoeachof said beds under combustion conditions to effect regeneration thereof, wlich comprises nowing hot combustion gases from said regeneration sone in heat exchange with a stream of water, generating superheated steam at elevated pressure thereby. flowing said superheated steam through a plu.- rality of injector means each communicating with spaanse a source ot free oxygen-containing regenerating gas, admixing said oxygen-containing regenerating gas with said steam by the inspirating action of said steam in passing through said injector means, and directly injecting said mixture into each of said free spaces whereby intimate mixing thereof with combustion products iiowing from the preceding -bed and distribution into the succeeding bed occurs, and maintaining combustion conditions in each oi' said beds in order to eiect combustion of the carbonaceous material therein.

2. A catalyst regeneration system which comprises a catalyst chamber. a series of spaced catalyst beds in said chamber, a plurality oi injector means each positioned immediately adjacent to a corresponding space between said beds, one of said injector means being positioned ahead of the iirst bed in said series to directly introduce oxygen-containing regeneration gas under combustion conditions into the spaces between said beds and ahead o! the rst or said series of beds. means for removing hot combustion gases from said chamber, a waste heat boiler, means for owing said hot combustion gases through said waste heat boiler in heat exchange with a stream of water introduced therein to generate steam under pressure, means for flowing said steam through said injector means, a source o! free oxygen-containing gas communicating with said injector whereby said gas is admixed with said steam by the inspirating action thereof to form the oxygen-containing regeneration gas and is injected into said spaces in a manner to eiIect intimate mixing of said steam and oxygen-containing gas with the products of combustion from the preceding bed in said spaces and ahead of said first bed by the kinetic energy of said steam.

JOHN W. I DY.

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