Primary reactor

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 per pass ethylene conversion in the primary reactors is maintained at 20—30% in order to ensure catalyst selectivities of 70—80%. Vapor-phase oxidation inhibitors such as ethylene dichloride or vinyl chloride or other halogenated compounds are added to the inlet of the reactors in ppm concentrations to retard carbon dioxide formation (107,120,121). The process stream exiting the reactor may contain 1—3 mol % ethylene oxide. This hot effluent gas is then cooled ia a shell-and-tube heat exchanger to around 35—40°C by usiag the cold recycle reactor feed stream gas from the primary absorber. The cooled cmde product gas is then compressed ia a centrifugal blower before entering the primary absorber. 

Amino acids, sugars, and minerals pass through the small intestine into the circulatory system, where they are mixed with blood. The primary reactor organs in processing blood are muscle and the kidneys. The fluid flows in nearly total recycle through arteries and veins, which are basically the pipes in the system, and capillaries, where most of the transfer to and from the reactors and separators occurs. 

Boundary condition 1 occurs because the pulse is instantaneously mixed only into the primary reactor in the model. Boundary condition 2 indicates that, as the dead zone disappears, the reactor becomes a standard complete mix reactor. Applying boundary condition 1 gives... 

Naphtha transfer line Recycle gas transfer line Reheat outlet Primary reactor Secondary reactor Pressure, lb./sq. inch gage Feed rate, bbl./day Space velocity, vol./hour/vol. 

There are five primary reactor designs based in theory batch, semibatch, continuous-stirred tank, plug flow, and fluidized bed. The operating expressions for these reactors are derived from material and energy balances, and each represents a specific mode of operation. Selected reactor configurations are presented in Fig. 1. 

The batch reactor, one of the five primary reactor configurations, is the oldest reactor scheme. 

Fluidized reactors are the fifth type of primary reactor configuration. There is some debate as to whether or not the fluidized bed deserves distinction into this classification since operation of the bed can be approximated with combined models of the CSTR and the PFR. However, most models developed for fluidized beds have parameters that do not appear in any of the other primary reactor expressions. 

Additional reactors exist that are either completely or partially based on the five primary reactor types discussed in Section II. They receive special attention due to specific applications and/or unique mass transfer characteristics. 

The primary reactor design consideration was the arrangement of reactor components to insure rapid gas-solid contact. The measuring devices had to be capable of operating at high temperatures, and they had to have millisecond time constants. The internal reactor volume must be minimized. Catalyst volume was chosen to cause a detectable pressure change in the system during the experiment. 

The methanol, which need not be the highest grade chemical methanol, is produced and stored prior to feeding to the methanol to olefins (MTO) plant. The conversion of methanol into olefins is highly exothermic and in order to help control heat evolution some processes use a primary reactor to convert some of the methanol into dimethyl ether (DME) by the reaction ... 

After mixing, the gases are passed to the primary reactor (usually of steel or lead-lined construction) containing the activated charcoal catalyst. In normal circumstances,... 

This section provides brief descriptions of industrial processes in which noncatalytic gas-solid reactions play a major role. Although by no means complete, the discussion includes both traditional processes, such as the blast furnace for the production of iron from ore and the regeneration of fluidized-bed catalytic cracking catalyst, and newer processes such as the dry capture of SO2 from flue gas and the production of silicon for semiconductor applications. Each of the three primary reactor types is represented in the processes described. 

This can be carried out in several (4) agitated reactors in series or in a column with several injection levels. In the former case, hydroxylamine sulfate reacts with an approximately equal-weight mixture of cyclohexanone and oxime in the primary reactor. The sulfuric acid is then neutralized by ammonia. The liquid oxime rises above the solution of ammonium sulfate and hydroxylamine sulfate. In the secondary reactor, this solution reacts with the fresh cyclohexanone feed. This is followed by a second neutralization by ammonia, in order to obtain the initial effluent (50 50) of cyclohexanone and oxime fed to the primary reactor. 

UF4 is converted to UF by reaction with fluorine at 425 to 53S C in an air-cooled, monel fluid-bed reactor charged with CaF2 diluent to improve heat transfer. Because of nonvolatile fluorides present in the crude UF4 feed, a small amount of CaF2 is continuously removed from the bed and processed for uranium recovery by reaction with fluorine in an ash cleanup reactor. Product gases from the primary reactor are passed through a cold trap to condense most of the UFg. Unreacted fluorine in off-gas from the cold trap is removed by reaction with UF4 in a fluorine cleanup reactor. Effluent passes through a filter, additional cold traps, and a KOH scrubber. 

The elemental sulfur that is formed in the primary reactor system is condensed in a horizontal shell-and-tube steaming condenser (17). This represents over 40% of the total recovered sulfur. The process gas stream then enters the first stage (18) of a two-stage Claus reactor system where the following exothermic reaction occurs ... 

Following completion of the bench scale test program, an engineering contractor conducted a study and prepared the preliminary design for a pilot plant having a nominal production capacity of 20 short tons of sulfur/day when treating pure sulfur dioxide. This study found that fixed-bed catalysis was more practical. The preliminary pilot plant design, therefore, provided for a fixed-bed primary reactor of the shell-and-tube type in which the catalyst would be in the tubes. 

Based on this engineering study we concluded that further laboratory studies should be made more fully to define the primary reactor catalyst loadings required to approach equilibrium conversion of sulfur dioxide to sulfur vapor over the range of pilot plant operating conditions. The reactor used in this additional study duplicated as nearly as possible the geometry of the proposed pilot plant reactor. The laboratory reactor was fabricated of type 304 stainless steel pipe. An electrically heated molten lead bath maintained the desired operating temperature. 

The gas stream leaves the primary reactor at approximately the inlet temperature and is essentially at equilibrium, which amounts to conversions of sulfur dioxide to sulfur vapor of approximately 69% when treating a 12% sulfur dioxide gas and about 80% when reducing pure sulfur dioxide. 

The second major problem involved the catalyst used for the primary reactor. Specifically, decrepitation of catalyst pellets in the first few inches of the bed increased the pressure drop through the primary reactor. No loss of catalyst activity has been detected. An extensive laboratory investigation isolated the cause of physical failure and evaluated possible alternative solutions. 

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