Patent Application
20210154636
The present disclosure relates to chemical processing, and more particularly relates to a method for catalyst testing in fluidized bed reactors using catalyst capsules.
Ebullated-bed reactors are one of the types of reactors currently used in hydrocracking of heavy oils and other chemical processing. The ebullated-bed reactor is a fluidized-bed three phase system in which back-mixing of both the reactor liquid composition and the catalyst particles occurs. The catalysts used in the ebullated-bed reactor are kept in a fluidized state through the upward lift of liquid reactants and gas (feed oil plus recycled products) which enter the reactor and are distributed across the bed through a distributor and grid plate. Fresh catalyst can be added and spent catalyst withdrawn to control the level of catalyst activity in the reactor.
Ebullated-bed reactors have several advantages over fixed-bed reactors: the ebullating bed does not get plugged by solids present in some heavy feeds; the liquid recycle provides a high magnitude of mixing within the reactor, thus ensuring that temperature gradients are minimized; and catalysts can be added and withdrawn continuously, allowing long operating runs without shutting down the reactor. The catalyst pellets should be small enough to facilitate suspension by the liquid phase in the reactor. The rate of catalyst addition and withdrawal is set in order to maintain constant conversion. It is noted that slurry-bed reactors have similar advantages to the aforementioned advantages of ebullated-bed reactors.
Catalyst testing containers for fixed reactor beds are not designed optimally for ebullated-bed reactors. For example, catalyst baskets described in commonly-assigned U.S. Pat. No. 9,802,173 (by the present inventor) are designed to be loaded with large amounts of catalysts, on the order of 100 cubic centimeters to 10 liters, and for use at a fixed location in a fixed-bed reactor. Such catalyst baskets cannot be applied in reactors in which catalysts are mobile and are replaced daily.
What is therefore needed is a method of providing catalyst materials in fluidized bed reactors for testing procedures in which a plurality of different catalysts can be tested simultaneously.
The present disclosure provides a method for testing catalysts in a fluidized bed reactor. The method comprises enclosing catalyst material inside capsules having pores or holes smaller than the catalyst material, inserting the capsules filled with catalyst material to into a port of the fluidized bed reactor, and recovering at least a portion of the capsules from the fluidized bed reactor after use through an additional port of the fluidized bed reactor, wherein the capsules move with a flow of uplifted fluid and gas in the fluidized bed reactor. The method can be implemented in ebullated-bed reactors and slurry-bed reactors.
In some embodiments, the capsule includes a housing made of two separable sections, connectable via a hinge. The capsule can also be connectable by a threaded surface or a snap-fit feature. The housing can be made from a wire mesh material and include a rim having a hinge. The housing of the capsule can alternatively be formed from a metal sheet including an arrangement of holes. In certain embodiments, the housing of the capsule is formed from a grid of wires.
The capsules can be formed in a variety of shapes. For example, in some embodiments, the capsule is spherical in shape. In other embodiments, the capsule is cylindrical or rectangular in shape.
The pores or holes are a salient feature of the capsules as they determine the rate at which the catalyst material within the capsules interacts with the fluid feedstock within the reactor; smaller holes or pores yield a lower reaction rate. However, pores cannot be so large as to allow unreacted catalyst material to escape from the capsules. The diameter of the pores or holes is 50 percent or less than the smallest dimension of the catalyst material.
In most fluidized bed reactors, the catalyst capsules are added to a port positioned at a top section of the reactor and the catalyst capsules are recovered at a port positioned at a bottom section of the reactor.
Some embodiments of the method further comprise fixing the catalyst material inside the capsules using a fixing material. In some implementations, the fixing material comprises paraffin.
These and other aspects, features, and advantages can be appreciated from the following description of certain embodiments and the accompanying drawing figures and claims.
The present disclosure provides a method of testing catalysts in fluidized bed reactors, such as mobile-bed, ebullated-bed, and slurry-bed reactors, using catalyst capsules. Embodiments of the catalyst capsule comprise casings with small holes that are used to house catalyst particles in fluidized-bed reactors. The capsules are made of high-temperature resistant material such as stainless-steel mesh and can have a variety of form factors. The linear dimensions of the capsules are in a range of 0.5 to 3 cm in the particular embodiments described herein. The mesh or hole sizes can be half the size or smaller than the catalyst grains, which typically range from ¼ inch down to 1/32 of an inch in diameter. In ebullated-bed reactors, the catalyst capsules are entrained within the moving fluid through upward lift of liquid reactants and gas. Fresh catalyst capsules can be added and spent catalyst in the capsules can be withdrawn to control the level of catalyst activity in the reactor. The capsules can be added and collected from the reactor after completion of a preset duration. Used capsules can be recycled for further testing procedures.
The capsules of the present disclosure can take a variety of forms.
The dimensions of the capsule 200 vary depending on the application and size of catalysts. The diameter, length and depth of the capsule 200 ranges from about 0.5 cm to about 10 cm. The catalyst grains range from about 0.03 inches to about 0.25 inches. The holes in the hemispherical mesh 202, 204 to be used with the present method are to be half the size or smaller than the smallest dimension of the catalyst grains to ensure that grains do not escape through the mesh of the capsule. The mesh can be made from stainless steel. In some embodiments, rather than a mesh, the capsules contain wire structures, which can be made from metallic materials. High temperature silicon and ceramic material composites can also be used.
In operation, catalyst capsules can be added to the reactor daily for a certain time period to ensure the required level of activity. After use, the capsules are recovered through a withdrawal port of the reactor. The recovered capsules can then be refilled with catalyst material and recycled back to the reactor.
When catalyst grains are loaded into the capsules, they can be left in their original condition with some space remaining in the capsules. In this case, the catalyst grains have some degree of mobility within the capsules. In other implementations, the catalyst material can be fixed in the capsule, for example using a paraffin fixing material.
Ebullated-bed reactors typically operate at a temperature of 380-500 degrees Celsius, or more narrowly from 400 degrees to 440 degrees Celsius. The total pressure typically ranges between 50 and 200 bar, and more usually between 100 to 200 bar. The liquid hourly space velocity is about 0.1-4, or more preferably from 0.25-1.5 h−1. The catalyst replacement rate (Kg/barrel of feed) can range from 0.1 to 10, and more typically from 0.3 to 2.5 Kg/bbl. The liquid superficial velocity of the reactor inlet generally ranges from 0.4 to 0.8 Meters/Second and the gas superficial velocity at the reactor inlet generally ranges from 4 to 8 Meters/Second.
The embodiments of catalyst capsules disclosed herein provide greater flexibility for catalyst testing in fluidized bed reactor systems. The capsules are small enough to become entrained and move with the gas and liquid flows in the reactor. The capsules can be designed in various shapes suited for particular catalysts and desired activity rates. Importantly, the capsules can be withdrawn from use in the reactor when the catalysts are expended or complete their targeted service time.
It is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the systems and methods, but rather are provided as a representative embodiment and/or arrangement for teaching one skilled in the art one or more ways to implement the methods.
It is to be further understood that like numerals in the drawings represent like elements through the several figures, and that not all components or steps described and illustrated with reference to the figures are required for all embodiments or arrangements.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.
Terms of orientation are used herein merely for purposes of convention and referencing and are not to be construed as limiting. However, it is recognized these terms could be used with reference to a viewer. Accordingly, no limitations are implied or to be inferred.
Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
The subject matter described above is provided by way of illustration only and should not be construed as limiting. Various modifications and changes can be made to the subject matter described herein without following the example embodiments and applications illustrated and described, and without departing from the true spirit and scope of the invention encompassed by the present disclosure, which is defined by the set of recitations in the following claims and by structures and functions or steps which are equivalent to these recitations.
