Vessels and tubes, internal protection

The secondary reformer in an ammonia plant is a carbon steel vessel with a dual layer refractory lining. Internal temperatures reach -2,000°F (1,090°C) from burning as a result of air added through a burner at the top of the vessel to the feed gas (hydrogen, carbon monoxide, carbon dioxide, and steam). The burner is a refractory-lined device that is subject to failure if not carefully designed. Quench steam generators have refractory-lined inlet channels and tube sheets. Tubes are often made of carbon steel because the heat transfer from the steam on the outside of the tube is markedly better than that from the synthesis gas inside the tube. As a result, the metal temperature closely approaches the temperature of the steam. The inlet ends of the tubes are protected from the inlet gas by ferrules, usually made of type 310 (UNS S31000) SS with insulation between the ferrule and the tube. The tube material should be selected... 

The VKR-MT nuclear steam supply system uses a direct cycle vessel-type boiling water reactor, which includes (see Fig. X-10 and X-11) (a) The reactor vessel (b) The reactor vessel cover (c) An internal metallic shaft (d) The core (e) Two stages of the centrifugal separators (f) The block of protective tubes (g) Radiation and thermal shielding of the reactor vessel (h) The supporting structure (i) Jet pumps (j) Control rod drives (k) The reloading system for micro fuel elements. 

SPME was developed by Pawlisz)m and coworkers in 1987 [161-163]. The reader may find further information on the historical evolution, principles, and commercially available devices of SPME in an excellent review by the pioneer of the technique [164]. SPME is based on a partitioning equilibrium of the solutes between the sorbent phase and the aqueous and/or gas matrix. A small amount of sorbent phase is dispersed on a solid support, which will be exposed to the sample for a predetermined time. Different implementations were developed such as suspended particles, coated-stirrer, vessel walls, disks, stirrers, or membranes, although the fiber and in-tube are explored theoretically and experimentally in depth. The former consists of a thin, fused-silica fiber-coated with sorbent on its surface and mounted in a modified GC syringe, which protects the fiber and allows handling. The latter in-tube implementation consists of an internally coated tube or capillary. The analytes are extracted by sorption when either coated fiber or tube are immersed in the water sample (direct SPME) or in the headspace above the sample (HS-SPME). 

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