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USE OF MINERAL OIL TO SUPPRESS SHEETING IN CHROME BASED GAS PHASE POLYETHYLENE REACTORS

IP.com Disclosure Number: IPCOM000033627D
Publication Date: 2004-Dec-20
Document File: 2 page(s) / 130K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention relates to the use on deaerated mineral oil for start up and successful operation of gas phase polyethylene reactors using chromium based catalysts. The mineral oil acts to prevent static charge build up and reduces resin accumulation and agglomeration which can cause shutdown. The mechanism is a coating of resin and reactor wall surfaces with a high boiling agent which acts to prevent direct contact between resin and metal surface, thus reducing static charging.

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USE OF MINERAL OIL TO SUPPRESS SHEETING IN CHROME BASED GAS PHASE POLYETHYLENE REACTORS

This invention relates to the use on deaerated mineral oil for start up and successful operation of gas phase polyethylene reactors using chromium based catalysts. The mineral oil acts to prevent static charge build up and reduces resin accumulation and agglomeration which can cause shutdown. The mechanism is a coating of resin and reactor wall surfaces with a high boiling agent which acts to prevent direct contact between resin and metal surface, thus reducing static charging.

Deaeration of the mineral oil eliminates poisons to the catalyst system especially water and oxygen. Addition to the reactor during start up reduces static voltage which has been shown to cause particle adhesion to the walls and result in sheeting. This can be seen in the thermocouples near the wall. With high static and adhesion, these become insulated and lose heat transfer. As a result, they heat up and melt causing sheets. The use of mineral oil reduces this effect. Mineral oil acts to coat the reactor walls and resin particles which reduces static generation. The oil can be fed separately from the catalyst or the catalyst can be prepared in an oil slurry and delivered to the reactor.

During production of a high density Chrome catalyzed gas phase polymerization, mineral oil was added at 0.5 wt% (on a resin basis). As a result, the static charge (as measured by a voltmeter in situ) was less than plus or minus 10...