Eo reactor, process and thermocouple placement (Shell)

CATEGORY: REACTORS 
Eo reactor, process and thermocouple placement (Shell)

Type	Patent
Inventor	Paul Michael Mcallister
URL	Free Full Text Source:  http://www.google.com/patents/US20140135513
Assignee	Shell Oil Company
Patent Number	US20140135513 A1
Issue Date	May 15, 2014
Abstract	Techniques are provided for determining the proper way to load thermocouple reactor tubes in multi-tubular ethylene oxide reactors containing a large number of reactor tubes containing silver catalysts. In these techniques, it is necessary to adjust the pressure drop so that oxygen conversion by thermocouple reactor tubes will closely match that of non-thermocouple reactor tubes. BACKGROUND OF THE INVENTION Ethylene oxide is an important industrial chemical used as a feedstock for making such chemicals as ethylene glycol, ethylene glycol ethers, ethanol amines and detergents. One method for manufacturing ethylene oxide is by epoxidation of ethylene—i.e., the catalyzed partial oxidation of ethylene with oxygen yielding ethylene oxide. The ethylene oxide so manufactured may be reacted with water, an alcohol or an amine to produce ethylene glycol, ethylene glycol ether or an ethanol amine. In ethylene epoxidation, a feedstream containing ethylene and oxygen is passed over a bed of catalyst contained within a reaction zone that is maintained at certain reaction conditions. The relatively large heat of reaction makes adiabatic operation at reasonable operation rates impossible. While some of the generated heat may leave the reaction zone as sensible heat, most of the heat needs to be removed through the use of a coolant. The temperature of the catalyst needs to be controlled carefully as the relative rates of epoxidation and combustion to carbon dioxide and water are highly temperature dependent. The temperature dependency together with the relatively large heat of reaction can easily lead to run-away reactions. A commercial ethylene epoxidation reactor is generally in the form of a shell-and-tube heat exchanger, in which a plurality of substantially parallel elongated, relatively narrow tubes are filled with catalyst particles to form a packed bed, and in which the shell contains a coolant. Irrespective of the type of epoxidation catalyst used, in commercial operation the internal tube diameter is frequently in the range of from 20 to 60 mm, and the number of tubes per reactor may range in the thousands, for example up to 12,000. Reference is made to U.S. Pat. No. 4,921,681 and U.S. Pat. App. No. 2009/0234144. With the catalyst bed present in narrow tubes, axial temperature gradients over the catalyst bed and hot spots are practically eliminated. In this way, careful control of the temperature of the catalyst can be achieved and conditions leading to run-away reactions are substantially avoided. The temperature in the reactor tubes is often measured by the use of thermocouples placed in a few of the many thousand reactor tubes. It is extremely important to know the actual temperatures within the reactor tubes so that all the components and rates may be controlled to achieve the desired selectivity and productivity. Therefore, it is vitally important that the temperature within the reactor tubes be measured accurately and that such measurement reflects the temperature in all of the reactor tubes, not just the reactor tubes containing thermocouples.