Separation-regenerator vessel

The use of a fluidized-bed reactor has a number of advantages in the MTO process. The moving bed of catalyst allows the continuous movement of a portion of used catalyst to a separate regeneration vessel for removal of coke deposits by burning with air. Thus, a constant catalyst activity and product composition can be maintained in the MTO reactor. Figure 12.10 demonstrates the stability of a 90 day operation in the fluidized-bed MTO demonstration unit at the Norsk Hydro Research Center in Porsgrunn, Norway. A fluidized-bed reactor also allows for... 

The treatment or service cycle occurs across a mixed bed contained in the operator vessel. Upon termination of the service cycle all the resin is hydraulically transferred to a separation-regenerator vessel for separation by backwashing. Instead of adopting insitu regeneration in this vessel the anion resin is further physically transferred to another column for separate regeneration, whilst the cation resin is separately regenerated in the separation vessel. Finally, the cation resin is transferred to the anion vessel, air mixed, rinsed, and returned to the operator. 

In an early embodiment of this reaction, known as the oxidant process (Fig. 9), hydrocarbon is fed to a reactor filled with metal oxide at high temperature to produce the desired selective oxidation products. The resulting reduced metal oxide is then lifted to a separate regeneration vessel where air is also fed, which reoxidizes the catalyst before it is... 

Scheme 2 illustrates the principle of S Zorb process . Based on the principle, it appears that the sorbent is based on reduced metal that reacts with sulfur to become metal sulfide. The spent sorbent is continuously withdrawn from the reactor and transferred to the regenerator section. In a separate regeneration vessel, the sulfur is burned off of the sorbent and SO2 is sent to the sulfur plant. The cleansed sorbent is further reduced by hydrogen and the regenerated sorbent is then recycled back to the reactor for removing more sulfur. The rate of sorbent circulation is controlled to help maintain the desired sulfur concentration in the product. Because the sorbent is continuously regenerated, Phillips estimates that the unit will be able to... 

Service Cycle - As far as the mode of operation is concerned, the service cycle of a mixedbed unit is very similar to a conventional two-bed system, in that water flows into the top of the vessel, down through the bed, and the purified effluent comes out the bottom. It is in the regeneration and the preparation of it that the mixed-bed differs from the two-bed equipment. The resins must be separated, regenerated separately, and remixed for the next service cycle. 

The fluidized reactor system is similar to that of a refineiy FCC unit and consists of riser reactor, regenerator vessel, air compression, catalyst handling, flue-gas handling and feed and effluent heat recovery. Using this reactor system with continuous catalyst regeneration allows higher operating temperatures than with fixed-bed reactors so that paraffins, as well as olefins, are converted. The conversion of paraffins allows substantial quantities of paraffins in the feedstream and recycle of unconverted feed without need to separate olefins and paraffins. 

The process options reflect the broad range of compositions and gas volumes that must be processed. Both batch processes and continuous processes are used. Batch processes are used when the daily production of sulfur is small and of the order of 10 kg. When the daily sulfur production is higher, of the order of 45 kg, continuous processes are usually more economical. Using batch processes, regeneration of the absorbant or adsorbant is carried out in the primary reactor. Using continuous processes, absorption of the acid gases occurs in one vessel and acid gas recovery and solvent regeneration occur in a separate reactor. 

The Socony Vacuum design consisted of separate vessels for reaction and regeneration. Units constructed in the late 1940s employed a pneumatic lift design which allowed for high catalyst circulation rates. A typical design is shown in Figure 20, which allowed for a primary air stream to convey the catalyst. A... 

LOCAT units can be used for tail-gas clean-up from chemical or physical solvent processes. They can also be used directly as a gas sweetening unit by separating the absorber/oxidizer into two vessels. The regenerated solution is pumped to a high-pres.sure absorber to contact the gas. A light slurry of rich solution comes off the bottom of the absorber and flows to an atmospheric oxidizer tank where it is regenerated. A dense slurry is pumped off the base of the oxidizer to the melter and sulfur separator. 

Sylvestrene tetrabromide, CjoHjf.Br, is prepared when pure sylvestrene, regenerated from its ihydrochloride and dissolved in acetic acid, is heated with bromine until a permanent yellow colour is produced. Water is added to the reaction product, but not sufficient to precipitate the bromide, and the vessel allowed to stand in a cold place. The bromide separates and can be purihed by recrystallisation from alcohol. It forms mono-symmetric crystals melting at 135° to 136°, and having a specihc rotation -t- 73 7°. 

Cation units usually contain a sulphonic acid resin whilst anion resins fall into the two main categories of strongly basic, with quaternary ammonium groupings and weakly basic, with tertiary amine groups. The final unit is the mixed bed in which, by a mixture of cation and anion resins in the same vessel, the effect is achieved of a multiplicity of separate cation and anion units. Resin separation is necessary for regeneration purposes. Considerable improvements in water quality are obtainable by these means. 

In fluidized beds, the temperature is uniform within a few degrees even in the largest vessels, but variation of comnposition is appreciable in large vessels, and is not well correlated for design purposes. One currently successful moving bed process is the UOP "Stacked Reactor" platforming where the catalyst is transported and regenerated in a separate zone. When the activity of the catalyst declines fairly rapidly, its variation with time and position must be taken into account by the mathematical formulation. 

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