System and method for seal flush (Chevron)

System and method for seal flush (Chevron)

Type	Patent
Inventor	Thanh Nguyen
Inventor	John D. Hottovy
URL	Free Full Text Source:  http://www.google.com/patents/US20140116513
Assignee	Chevron Phillips Chemical Company Lp
Patent Number	US20140116513 A1
Issue Date	May 1, 2014
Abstract	Techniques are provided for seal flush systems. A system may include a reactor circulation pump configured to circulate a slurry through a polymerization reactor. The slurry may include an olefin monomer, a catalyst, and a diluent. The system may also include a catalyst-inhibiting additive system configured to supply a catalyst-inhibiting additive to a seal of the reactor circulation pump and a seal flush system configured to generate a seal flush mixture and supply the seal flush mixture to the seal of the reactor circulation pump. BACKGROUND The present disclosure relates generally to seal flush systems, and more particularly, to seal flush systems for polymerization reactor systems. This section is intended to introduce the reader to aspects of art that may be related to aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art. Polyolefins, such as polyethylene and polypropylene, may be prepared by particle form polymerization, also referred to as slurry polymerization. In this technique, feed materials, such as monomer, catalyst, slurry, and additives, are fed to a loop reactor to establish a slurry. In the loop reactor, the slurry is circulated while polymerization occurs, forming product slurry. The product slurry, which contains solid polyolefin particles in a liquid medium, is then taken off or withdrawn from the reactor. In a loop polymerization operation, the fluid slurry is circulated around the loop reactor using one or more pumps, such as axial flow pumps having propellers disposed within the reactor. The pumps provide the motive force for circulation of the fluid slurry. In addition, the pumps may include a seal to help prevent leakage of the fluid slurry to the environment. A seal flush fluid may be provided to the seal to help lubricate and remove heat from the seal and/or clean surfaces of the seal, such as the seal faces. It is now recognized that undesirable issues may arise when the flow of the seal flush to the pump is interrupted, discontinued, or lost. For example, the lack of lubrication may cause the seal to overheat, thereby causing leakage of the fluid slurry from the pump. In addition, it is now recognized that when the seal flush is lost, the fluid slurry may backflow into the seal, thereby causing undesired polymerization within the pump. The resulting polyolefin material may grow in size within the pump until the polyolefin contacts one or more stationary and/or moving surfaces of the pump. Such contact of the polyolefin with the internal surfaces of the pump may cause drag, wear, and other forces that contribute to seal degradation.