Process for regenerating catalyst in a fluid catalytic cracking unit (UOP)

PATENT
Process for regenerating catalyst in a fluid catalytic cracking unit (UOP)
Publication number US20130225396 A1
Publication type Application
Application number US 13/858,724
Publication date Aug 29, 2013
Filing date Apr 8, 2013
Also published as EP2563879A2, 5 More »
Inventors
Daniel N. Myers, Paolo Palmas, David N. Myers
Original Assignee
Uop Llc
US 20130225396 A1
Abstract
One exemplary embodiment can be a process for regenerating catalyst in a fluid catalytic cracking unit. Generally, the process includes providing a feed to a riser of a reaction vessel, and providing a stream to a distributor positioned within a void proximate to an inlet receiving unregenerated catalyst in a regenerator. The feed can include at least one of a gas oil, a vacuum gas oil, an atmospheric gas oil, a coker gas oil, a hydrotreated gas oil, a hydrocracker unconverted oil, and an atmospheric residue
FIELD OF THE INVENTION
This invention generally relates to a process for regenerating catalyst in a fluid catalytic cracking unit.
DESCRIPTION OF THE RELATED ART
Fluid catalytic cracking can create a variety of products from heavier hydrocarbons. Often, a feed of heavier hydrocarbons, such as a vacuum gas oil, is provided to a fluid catalytic cracking reactor. Various products may be produced, including a gasoline product and/or another product, such as at least one of propylene and ethylene.
Sometimes, fluid catalytic cracking (may be abbreviated as “FCC”) units operate with feeds having low sulfur and relatively shorter carbon chain lengths, such as hydrotreated vacuum gas oil feed stocks, which can be referred to as “clean” feeds. Typically, it may be desirable to reduce coke yield from about 6%, by weight, to about 4%, by weight. As such, the liquid products' yield, e.g., light cycle oil, liquid petroleum gas, gasoline, and/or clarified oil, can increase from about 91.5-about 93.5%, by weight. Processing such clean feeds may create operating challenges due to low regenerator temperatures, which may be a result of the lack of coke on the spent catalyst. Thus, the regenerator can have insufficient heat and run at lower than desired temperatures, such as a range of about 650-about 670° C. However, at these low temperatures, it can be difficult to burn carbon monoxide to carbon dioxide due to complications, such as afterburning. In addition, catalyst regeneration difficulties may arise that can impact product quality.
One possible solution is burning methane to replace the heat provided by coke, which may provide up to about 15% of the heat duty required by the regenerator. Recently, there has been an emphasis on reducing carbon dioxide emissions due to legal and regulatory requirements. As such, burning methane can reduce carbon dioxide emissions by about 13.1%, by weight. In addition, reducing coke yield from about 5%, by weight, to about 4%, by weight, can reduce carbon dioxide emissions from the regenerator by about 7.9%, by weight.
However, burning methane in the heater of the regenerator may also create other undesirable side effects. These adverse side effects can include creating high gas velocities at the outlet of the direct fired heater resulting in catalyst attrition. Moreover, thermal damage from localized high temperatures can occur deactivating the catalyst. Generally, the temperature ceiling to prevent catalyst damage is no more than about 790° C. Additionally, an air grid at an outlet of the direct fired air heater can limit outlet temperatures to, e.g., about 750-about 780° C. due to potential metallurgical failures. Thus, firing the heater to add heat to the regenerator can cause unwanted catalyst degradation and possible equipment damage.
Thus, it would be desirable to provide an FCC process receiving clean feeds without having adverse effects as discussed above.
SUMMARY OF THE INVENTION
One exemplary embodiment can be a process for regenerating catalyst in a fluid catalytic cracking unit. Generally, the process includes providing a feed to a riser of a reaction vessel, and providing a stream to a distributor positioned within a void proximate to an inlet receiving unregenerated catalyst in a regenerator. The feed can include at least one of a gas oil, a vacuum gas oil, an atmospheric gas oil, a coker gas oil, a hydrotreated gas oil, a hydrocracker unconverted oil, and an atmospheric residue.
Another exemplary embodiment may be a process for regenerating catalyst in a fluid catalytic cracking unit. The process can include providing a feed to a riser of a reaction vessel and introducing an uncombusted stream, which may include a first stream having oxygen and a second stream having at least one of a hydrocarbon and hydrogen, proximate to an inlet receiving unregenerated catalyst for a regenerator. Generally, the feed includes at least one of a gas oil, a vacuum gas oil, an atmospheric gas oil, a coker gas oil, a hydrotreated gas oil, a hydrocracker unconverted oil, and an atmospheric residue. Usually, the first and second streams are mixed together in a heater before introduction, and the heater does not ignite at least one of the hydrocarbon and hydrogen.
A further exemplary embodiment can be a process for regenerating catalyst in a fluid catalytic cracking unit. The process can include providing a feed to a riser of a reaction vessel, mixing a first stream having air and a second stream having at least one of a hydrocarbon and hydrogen in a direct fired heater to form an uncombusted stream exiting the direct fired heater, and introducing the uncombusted stream proximate to an inlet receiving unregenerated catalyst for a regenerator. Generally, the feed includes at least one of a gas oil, a vacuum gas oil, an atmospheric gas oil, a coker gas oil, a hydrotreated gas oil, a hydrocracker unconverted oil, and an atmospheric residue.
The embodiments provided herein can add the requisite heat to the combustor to facilitate effective operation of the fluid catalytic cracking apparatus. Particularly, at least one of hydrogen and a hydrocarbon, such as one or more C1-C5 hydrocarbons, can be added to the regenerator in an uncombusted state to provide the requisite heat without adverse side effects, such as catalyst attrition, due to excessive velocities created by igniting a fuel gas outside the combustor and routing the oxidation products to the regenerator. In any event, whether hydrocarbon or hydrogen is utilized, preferably in one exemplary embodiment the total volume of hydrogen and hydrocarbon does not exceed about 3%, by volume, based on the volume of the uncombusted stream. In another exemplary embodiment, the at least one of hydrocarbon and hydrogen may be directly supplied to the combustor at or above the auto-ignition point of the at least one hydrocarbon and hydrogen. Thus, the embodiments provided herein can provide the requisite heat to the regenerator while still avoiding unnecessary catalyst attrition.
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