Separation Vessels for Use in Polymerization Processes and Methods for Cleaning Same

Abstract

Both a system and method for cleaning a tow pressure separation vessel of a high pressure polyethylene polymerization plant are provided. The system includes a polytetrafluoroethylene lining that covers the interior surfaces of the vessel, and a cover mounting assembly including an annular clamp for detachably mounting a cover over the vessel. The mounting assembly includes a clamp actuator for quickly securing and releasing the cover with respect to a top rim of the vessel. The vessel is drained of liquid polyethylene and allowed to cool to ambient temperature, thus creating a frozen “skin” of polyethylene around the interior surfaces of the vessel. The clamp actuator releases the cover. The polyethylene skin is peeled off the interior sides the vessel and gathered up at the top to form a neck, thus peeling the polyethylene skin away from the polytetrafluoroethylene lining along with any degraded polymers or other impurities that have accumulated on the interior surfaces of the vessel.

1 .- 62 . (canceled) 
     
     
         63 . A separation vessel system for use in a polymerization process comprising:
 a carbon steel vessel comprising interior surfaces;   a detachable cover; and   a lining that covers at least a portion of the interior surfaces of the vessel, wherein such lining comprises a first layer comprising nickel and having from about 0.050 and 0.150 mm thickness, a second layer comprising polytetrafluoroethylene and having a dry film thickness from about 0.02 and 0.20 mm and a third layer comprising a polyethylene polymer or a polypropylene polymer;   
       wherein the third layer is disposed on the second layer and the second layer is disposed on the first layer. 
     
     
         64 . The system defined in  claim 63 , wherein the vessel is a component of a high pressure polymerization plant. 
     
     
         65 . The system defined in  claim 63 , wherein the detachable cover has a mounting assembly adapted to maintain the cover in a pressure-tight relationship with the vessel. 
     
     
         66 . The system defined in  claim 65 , wherein the mounting assembly comprises a clamp. 
     
     
         67 . The system defined in  claim 65 , wherein the mounting assembly comprises a clamp and a clamp actuator that secures and releases the clamp into and out of a clamping position that pulls together said cover and a top rim of said vessel. 
     
     
         68 . The system defined in  claim 67 , wherein the mounting assembly further includes a gasket interposed between the cover and the top rim of the vessel. 
     
     
         69 . The system defined in  claim 67 , wherein the mounting assembly further includes opposing flanges disposed along an outer periphery of both the cover and the top rim of the vessel, wherein the clamp captures and pulls together said opposing flanges when in said clamping position. 
     
     
         70 . The system defined in  claim 63 , further comprising a hoist that pulls away the second layer present on the first layer. 
     
     
         71 . The system defined in  claim 67 , wherein the mounting assembly comprises a mounting mechanism including an annular clamp for detachably mounting said cover over the top rim of the vessel. 
     
     
         72 . The system defined in  claim 70 , further comprising at least one scraping tool for separating the second layer and the first layer. 
     
     
         73 . The system defined in  claim 71 , wherein the annular clamp comprises an actuator having at least one hydraulic cylinder for securing and releasing the clamp into and out of a clamping position that pulls together said cover and the top rim of the vessel.