Alkylation Unit And Method Of Modifying

CATEGORY: ALKYLATION
PATENT
Alkylation Unit And Method Of Modifying
United States Patent Application 20120136188
Inventors:
Dunham, Daryl (Ponca City, OK, US)
Shields, Dale Jame (Grayslake, IL, US)
Application Number: 13/368518
Publication Date: 05/31/2012
Assignee: UOP LLC (Des Plaines, IL, US)
Abstract:
One exemplary embodiment can be a method of modifying an alkylation unit to increase capacity. The method may include combining a first alkylation zone with a second alkylation zone. Generally, the first alkylation zone includes a first settler having a height and a width. Typically, the width is greater than the height. In addition, the second alkylation zone may have a second settler having a height and a width. Usually, the height is greater than the width.
FIELD OF THE INVENTION
This invention generally relates to an alkylation unit, particularly to an alkylation unit using an acid catalyst.
DESCRIPTION OF THE RELATED ART
Generally, alkylation is a process that can be used to produce a high quality, high octane gasoline from lower boiling feeds. Usually, commercial refinery plants alkylate a feed including an isoparaffin stream, typically including isobutane, and an olefin stream, typically including one or more C3-C4 olefins, to form branch chain paraffin products boiling in the gasoline range, which can include hydrocarbons boiling up to about 200° C.
Increasing capacity of an alkylation unit may be implemented by adding a second stage reactor and settler. This addition can make efficient use of the existing fractionation equipment and the isoparaffin recycle stream. However, such a modification can double the alkylation catalyst inventory. In a gravity-fed alkylation system, a settler can provide an alkylation catalyst via gravity at a lower operating pressure. However, such a system uses more alkylation catalyst as compared to other systems. Although doubling the acid inventory can obtain a corresponding increase of about 25 to about 50%, by weight, in alkylation capacity, the alkylation catalyst may be an acid that can create health, safety, and environmental concerns.
Therefore, minimizing the amount of acid in inventory can be desired. The inventory of the acid catalyst in the process and the number of locations of parts joined by flanges or moving parts, such as pump seals, can create risk of acid escaping from the process. Reducing the amount of acid inventory and the handling of acid by pumps are desirable to improve safety and minimize containment failures.
SUMMARY OF THE INVENTION
One exemplary embodiment can be a method of modifying an alkylation unit to increase capacity. The method may include combining a first alkylation zone with a second alkylation zone. Generally, the first alkylation zone includes a first settler having a height and a width. Typically, the width is greater than the height. In addition, the second alkylation zone may have a second settler having a height and a width. Usually, the height is greater than the width.
Another exemplary embodiment may be an acid alkylation unit. The acid alkylation unit can include a first alkylation zone and a second alkylation zone. The first alkylation zone can include a first settler having a height and a width. Usually, the width is greater than the height and adapted to receive an acid reaction alkylation effluent. The second alkylation zone may include a second settler having a height and a width. Usually, the height is greater than the width and adapted to receive another acid reaction alkylation effluent.
A further exemplary embodiment may be a method of modifying an acid alkylation unit to increase capacity. The method can include combining a first alkylation zone with a second alkylation zone. Generally, the first alkylation zone has a first settler providing an acid catalyst via a fluid transfer device to a first alkylation reactor. Typically, the second alkylation zone includes a second settler providing an acid catalyst via gravity to a second alkylation reactor.
The embodiments disclosed herein can provide an increase in an alkylation unit capacity by adding another reactor and settler in series to an existing reactor receiving an alkylation catalyst via gravity from a settler. However, the added unit can lower alkylation catalyst inventory by utilizing a settler and reactor arrangement providing separated acid from the settler by using a fluid transfer device. As such, the added equipment can lower acid inventory as compared to providing a reactor fed by an alkylation catalyst via gravity. Providing an alkylation catalyst via a fluid transfer device can operate at an acid:hydrocarbon volume ratio of about 1.1 to about 2.5, as compared to providing an alkylation catalyst via gravity that typically operates at an acid:hydrocarbon volume ratio greater than about 2.5:1. Alternatively, a gravity-driven zone can be added to a fluid transfer zone to minimize the use of pumps, and also may have a lower overall acid inventory as compared to a system solely using gravity to transfer catalyst.
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