Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Fluidized bed
Reexamination Certificate
2000-06-01
2001-09-18
Yildirim, Bekir L. (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Fluidized bed
C422S144000, C422S147000, C208S140000, C502S035000
Reexamination Certificate
active
06290916
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the art of catalytic conversion of hydrocarbons to useful hydrocarbon products. More specifically, it relates to the regenerating of spent hydrocarbon conversion catalyst so that the catalyst can be reused in a hydrocarbon by conversion reaction.
BACKGROUND OF THE INVENTION
Catalytic processes for the conversion of hydrocarbons are well known and extensively used. Invariably the catalysts used in these processes become deactivated for one or more reasons. Where the accumulation of coke deposits causes the deactivation, regenerating of the catalyst to remove coke deposits restores the activity of the catalyst. Coke is normally removed from catalyst by contact of the coke-containing catalyst at high temperature with an oxygen-containing gas to combust and remove the coke in a regeneration process. These processes can be carried out in-situ or the catalyst may be removed from a vessel in which the hydrocarbon conversion takes place and transported to a separate regeneration zone for coke removal. Arrangements for continuously or semicontinuously removing catalyst particles from a reaction zone and for coke removal in a regeneration zone are well known.
In order to combust coke in a typical regeneration zone, a recycle gas is continuously circulated to a combustion section and a flue gas containing by-products of coke combustion, oxygen and water is continually withdrawn. Coke combustion is controlled by recycling a low oxygen concentration gas into contact with the coke-containing catalyst particles. Thus, the flue gas/recycle gas is continuously circulated through the catalyst particles. A small stream of make-up gas is added to the recycle gas to replace oxygen consumed in the combustion of coke and a small amount of flue gas is vented off to allow for the addition of the make-up gas. The steady addition of make-up gas and the venting of flue gas establishes a steady state condition that produces a nearly constant concentration of water and oxygen in the recycle gas and the flue gas.
In a continuous or semi-continuous regeneration process, coke-laden particles are at least periodically added and withdrawn from a bed of catalyst in which the coke is combusted. Regions of intense burning that extend through portions of the catalyst bed develop as the coke is combusted. One problem associated with localized regions of intense coke combustion is catalyst deactivation. The combination of temperature, water vapor, and exposure time determines the useful life of the catalyst. Exposure of high surface area catalyst to high temperatures for prolonged periods of time will create a more amorphous material having a decreased surface area which in turn lowers the activity of the catalyst until it reaches a level where it is considered deactivated. Deactivation of this type is permanent, thereby rendering the catalyst unusable. When moisture is present—water is a by-product of the coke combustion—the deactivating effects of high temperature exposure are compounded.
SUMMARY OF THE INVENTION
The removal of moisture from high temperature catalytic processes where water is present as a by-product can produce geometric increases in the life of the catalyst that is employed in the process. In order to take advantage of this extended catalyst life, a moisture removal method that can be readily integrated into existing catalytic processes without large capital expenditures or greatly increased complexity for the system is provided. Thus, this invention is in one of its broad aspects a method of controlling the water content in a catalytic process by making inexpensive alterations to the arrangement and operation of the catalytic process. In addition, this invention is an apparatus for controlling the water content in the water-generation section of a catalyst regeneration vessel. This invention is broadly applicable to any catalytic process that employs a water-containing recycle gas stream that contacts catalyst that can sorb water and from which water can be desorbed. It is believed, however, that this invention is most applicable to those sections of typical catalyst regeneration zones that operate at high temperature and employ a water-containing recycle gas stream. Such regeneration sections include, but are not limited to, coke combustion sections, metal redispersion sections, and rehalogenating sections.
It has been discovered that the catalyst particles themselves, rather than a separate sorbent, can selectively sorb the water from the flue gas/recycle gas stream of the combustion section of a regeneration zone, thereby dramatically decreasing the water content of the flue gas/recycle gas. Unlike conventional methods of drying a flue gas/recycle gas stream by adsorbing water onto a separate adsorbent, this invention uses the catalyst particles entering the regeneration zone to capture and reject water from the regeneration zone. In order to take advantage of this property of these -catalysts to sorb water from the flue gas/recycle gas, a water sorption step and a water desorption step that can be readily integrated into existing regeneration processes without employing a separate sorbent is provided. This invention selectively sorbs water from the flue gas/recycle gas on catalyst particles and subsequently selectively desorbs water from catalyst particles. Both steps can occur prior to, or subsequent to, the actual regeneration of the catalyst particles in the regeneration zone. This invention is particularly applicable to regeneration zones that combust coke from coked, alumina particles, especially spent naphtha reforming catalysts and spent paraffin dehydrogenation catalysts.
In this invention, a sorption and desorption arrangement in combination with the regeneration zone of a catalytic hydrocarbon conversion process removes water that would otherwise remain in the process. The operating conditions of the sorption zone can be selected independently of those of the regeneration zone in order to maximize the selective sorption of water from the flue gas/recycle gas, while minimizing the sorption of components besides water that are present in the flue gas/recycle gas. In addition, the operating conditions of the desorption zone can be selected independently of the operating conditions of the sorption zone to maximize the selective desorption of water and to minimize the desorption of components besides water that may happen to have been sorbed on the catalyst particles in the sorption zone. Venting of the desorption zone outlet gas with its high water content decreases the amount of water in the flue gas/recycle gas. In this way, the overall equilibrium concentration of water in the flue gas/recycle gas is kept at a low level.
It has also been recognized that, even though unregenerated and regenerated catalyst particles are like traditional sorbents in that they are capable of sorbing up to, say, only about from 2 to 3 percent of their weight in water from a flue gas/recycle gas that contains hydrogen chloride and/or chlorine, a process that uses the catalyst particles entering or leaving the regeneration -zone to sorb water from the flue gas/recycle gas stream can nevertheless be useful because of the large quantity of catalyst available for sorption. Accordingly, in one of its embodiments, this invention is a process in which spent catalyst that is about to be regenerated is not passed to the regeneration zone but instead is first passed to a sorption zone. In the sorption zone, the spent catalyst particles sorb water from the flue gas/recycle gas. In part because the regeneration flue gas/recycle gas has a high content of hydrogen chloride and chlorine, the spent catalyst sorbs up to, say, only about from 2 to 3 percent of its weight in water. The spent catalyst, having sorbed what water it can, is withdrawn from the sorption zone and is then passed to the desorption zone. Whatever water the spent catalyst sorbed in the sorption zone is desorbed in the desorption zone and vented from the process, thereby decreasing the water in the regen
Robinson Delmar W.
Schlueter William D.
Sechrist Paul A.
Moore Michael A.
Spears, Jr. John F.
Tolomei John G.
UOP LLC
Yildirim Bekir L.
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