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LOW BED LEVEL TRANSITION DURING STAGED REACTOR OPERATIONS

IP.com Disclosure Number: IPCOM000021573D
Publication Date: 2004-Jan-23
Document File: 1 page(s) / 26K

Publishing Venue

The IP.com Prior Art Database

Abstract

The general concern about running an olefin polymerization reactor with a low bed level is the sheeting of the expanded section. These reactors can be used to produce polyethylene, polypropylene, EPDM rubbers and similar thermoplastic products. Sheets are formed due to poor or no scrubbing of resin off the conical section of the reactor by the fluid bed. However, in staged reactor operation the first reactor may not be prone to this phenomenon for three reasons. First, the catalyst activity is retarded due to operating the reactor at relatively low ethylene partial pressure (30-40 psig). This low activity is beneficial since the polymer particles do not generate a tremendous amount of heat in a short period of time. Second, the sticking temperature of the resin is approximately 30 degree C greater than the operating temperature of the reactor. This large delta combined with the low activity may prevent the resin "hung-up" in the expanded section from melting and forming a sheet. Third, even if the resin did become sticky and agglomerate, it is questionable whether this fractional flow index resin would flow and form a sheet. More likely it would sinter and become crust, only to break apart when the bed level was raised to the neck or raised further to scrub the expanded section.

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LOW BED LEVEL TRANSITION DURING STAGED REACTOR OPERATIONS

The general concern about running an olefin polymerization reactor with a low bed level is the sheeting of the expanded section. These reactors can be used to produce polyethylene, polypropylene, EPDM rubbers and similar thermoplastic products. Sheets are formed due to poor or no scrubbing of resin off the conical section of the reactor by the fluid bed. However, in staged reactor operation the first reactor may not be prone to this phenomenon for three reasons. First, the catalyst activity is retarded due to operating the reactor at relatively low ethylene partial pressure (30-40 psig). This low activity is beneficial since the polymer particles do not generate a tremendous amount of heat in a short period of time. Second, the sticking temperature of the resin is approximately 30 degree C greater than the operating temperature of the reactor. This large delta combined with the low activity may prevent the resin “hung-up” in the expanded section from melting and forming a sheet. Third, even if the resin did become sticky and agglomerate, it is questionable whether this fractional flow index resin would flow and form a sheet. More likely it would sinter and become crust, only to break apart when the bed level was raised to the neck or raised further to scrub the expanded section.

If the first reactor is able to be run at low bed levels for extended periods of time (6 hours or more), then the first reactor could be...