Primary-1 back-reactors

Higher levels of conversions (> 99%) can be achieved by a two-stage MTBE synthesis process (Figure 3.26). The first reactor is a typical MTBE synthesis, using isobutene and methanol as feeds over a packed-bed ion-exchange reactor. The product is separated in a debutanizer tower and the overhead of this reactor is charged to another synthesis reactor to achieve higher conversion of isobutene. A secondary debutanizer is used to separate the additional MTBE produced in the secondary packed bed reactor. Methanol removed from the overhead stream is recycled back to the primary synthesis reactor [52]. 

Efficiency of Intermediate Formation. The variation of the efficiency of a primary intermediate with conversion of the feed hydrocarbon can be calculated (22). Ratios of the propagation rate constants ( 2 / i) reactor type (batch or plug-flow vs back-mixed) are important parameters. 

Eig. 2. Efficiency to a primary intermediate as % of maximum (zero conversion) efficiency x axis is feed conversion. Parameters are oxidation rate-constant ratios ( 2 / i) for primary intermediate vs feed and reactor type A, plug-flow or batch B, back-mixed. 

The continuous-stirred tank reactor is one of the two primary types of ideal flow reactors. It is also referred to as a mixed-flow reactor, back-mix reactor, or constant-flow stirred-tank reactor. 

The concepts discussed so far indicate that the major challenge in asymmetric operation is correct adjustment of the loci of heat release and heat consumption. A reactor concept aiming at an optimum distribution of the process heat has been proposed [25, 26] for coupling methane steam reforming and methane combustion. The primary task in this context is to define a favorable initial state and to assess the distribution of heat extraction from the fixed bed during the endothermic semicycle. An optimal initial state features cold ends and an extended temperature plateau in the catalytic part of the fixed bed. The downstream heat transfer zone is inert, in order to avoid any back-reaction (Fig. 1.13). 

Methane, acetic acid, acetaldehyde, and ethanol constitute approximately 90 carbon atom percent of the primary products from the hydrogenation of CO over Rh/SiO and Rhr-Mn/SiOi catalysts at 250 -300°C and 30-200 atm pressure in a back-mixed reactor with H /CO = 1. The rate of reaction and the ratio, CHj /C chemicals, vary with (Pjy / The addition of 1% Mn raises the synthesis rate of a 2.5% Rh/SiOfi catalyst about tenfold. The kinetics and the product distribution are consistent with a mechanism in which CO is adsorbed both associatively and dissodatively. The surface carbon produced by the dissociative CO chemisorption is hydrogenated through a Rh-CHs intermediate, and CO insertion in that intermediate results in formation of surface acetyl groups. 

In order to make measurements of caesium-137 activity, special device containing graphite pellet was installed in the loop connected in parallel to the primary sodium purification system. Just after the event of January 21, 1987, some decrease of the system indications was observed. Further, indications of the system came back to the previous level, however, some feature in caesium behaviour was noticed. While in the period preceding described events the decrease of the system indications in case of the reactor shutdown and sodium temperature reduction down to 250°C was 30-40%, later this decrease became as large as 10-12 times. After full power of the reactor had been reached, sodium temperature being as high as 530-540T, indications of caesium activity measurement system returned to the rated level. 

The primary sodium pumps were initially fitted with strainers in place of non-return valves during first criticality to trap any construction debris/impurities in sodium. Pumps were removed from primary system, decontaminated, refitted with NRVs and put back in the circuit. One CRDM, which was removed from reactor due to, failure of metallic bellows was decontaminated and its non-active parts were retrieved for reuse. Similarly guide tube under sodium scanner, CCMD and periscope were decontaminated after their use in reactor. 

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