Reactor size

If k-2 increases faster than kx, operate at low temperature (but beware of capital cost, since low temperature, although increasing selectivity, also increases reactor size). Here there is an economic tradeoff between decreasing byproduct formation and increasing capital cost. 

Reaction and Transport Interactions. The importance of the various design and operating variables largely depends on relative rates of reaction and transport of reactants to the reaction sites. If transport rates to and from reaction sites are substantially greater than the specific reaction rate at meso-scale reactant concentrations, the overall reaction rate is uncoupled from the transport rates and increasing reactor size has no effect on the apparent reaction rate, the macro-scale reaction rate. When these rates are comparable, they are coupled, that is they affect each other. In these situations, increasing reactor size alters mass- and heat-transport rates and changes the apparent reaction rate. Conversions are underestimated in small reactors and selectivity is affected. Selectivity does not exhibit such consistent impacts and any effects of size on selectivity must be deterrnined experimentally. 

Approach to Equilibrium As equilibrium is approached the rate of reaction falls off, and the reactor size requireci to achieve a specified conversion goes up. At some point, the cost of increased reactor size will outweigh the cost of discarded or recycled unconverted material. No simple rule for an economic appraisal is really possible, but sometimes a basis of 95 percent of equilibrium conver-... 

Example 10 Reactor Size with Recycle For first-order reaction with Cq/C<) = 10 and i = 5, C ICo = 2.5. The relative reactor sizes with recycle and without are... 

When the catalyst is expensive, the inaccessible internal surface is a liabihty, and in every case it makes for a larger reactor size. A more or less uniform pore diameter is desirable, but this is practically reahz-able only with molecular sieves. Those pellets that are extrudates of compacted masses of smaller particles have bimodal pore size distributions, between the particles and inside them. Micropores have diameters of 10 to 100 A, macropores of 1,000 to 10,000 A. The macropores provide rapid mass transfer into the interstices that lead to the micropores where the reaction takes place. 

On what scale has this product has been made before (for example, reactor size, throughput)... 

S/ze of a three phase reactor Size of a single-phase reactor... 

Imposing a limit on reactor size, to ensure adequate heat transfer area per unit volume. 

Adesina [14] considered the four main types of reactions for variable density conditions. It was shown that if the sums of the orders of the reactants and products are the same, then the OTP path is independent of the density parameter, implying that the ideal reactor size would be the same as no change in density. The optimal rate behavior with respect to T and the optimal temperature progression (T p ) have important roles in the design and operation of reactors performing reversible, exothermic reactions. Examples include the oxidation of SO2 to SO3 and the synthesis of NH3 and methanol CH3OH. 

Ca plug flow)- the case where the effluent composition is fixed instead of the reactor size. Equations 8-152 and 8-154 can be manipulated to show that for small Dg /uL,... 

Tubular reactors often offer the greatest potential for inventory reduction. They are usually simple, have no moving parts, and a minimum number of joints and connections that can leak. Mass transfer is often the rate-limiting step in gas-liquid reactions. Novel reactor designs that increase mass transfer can reduce reactor size and may also improve process yields. 

Heat transfer problems become more severe as reaction rates are increased and water-to-monomer ratios are reduced. In addition, as reactor sizes are increased for improved process economics, the amount of wall heat transfer surface area per unit volume will drop and result in a lower reactor space-time yield. 

Suppose the reactor sized in Problem 13.14 is converted to manufacture a styrene-acrylonitrile copolymer containing 36% acrylonitrile by weight. Assume 50% conversion as before. What is the required feed composition to the reactor and what is the composition of the unreacted monomer mixture ... 

The fact that the kinetics at the same power per volume are also independent of the reactor size, i. e. of the number of circuits made by the particles, points to... 

A pilot-scale rsactor that can produce 50 kg of GBL per one batch was designed. The reactor size was calculated on the basis of maleic anhydride conversion of 100% and GBL yield of 50%. By assuming the saturate liquid densily of reactant and product at the reaction conditions of 250 C and 70 atm undo- the condition of no solvent, the daisity and specific... 

With increasing reactor size, the withdrawal of the heat evolved during the reaction becomes more difficult. This gives rise to a nonuniform temperature distribution within the reactor and thus a differentiation of conditions for the efectrochemical reaction in different reactor parts. In a number of cases the thermaf conditions can be improved through coofed efectrodes. 

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