Optimum reactor size

The purpose of the reaetor design is to aequire the optimum reaetor size. However, the ideal optimum reaetor size (V/F o)opp obtained by integrating the optimum temperature profile. That is. 

Inerease X, from X to X -i- h, where h is the step size for X in the numerieal integration proeess. Again, evaluate T 

Repeat the eheek in step 1 followed by step 2 until (lb) is satisfied. At this point, the OTP is now being followed. Inerease X to X -i- h estimate T p. Use this value to ealeulate kj and kj, and henee (-i A)opf Repeat step 4 until X = X.  

Eor an exothermie, liquid-phase, reversible reaetion A R oeeuning in a CESTR, with a feedrate of 600 mol/min a feeH eoneentra-tion (C o) of 6 mol/L (Cro f ) fraetional eonversion (X ) 

The minimum volume and residenee time required for tlie reaetor. 

The minimum volume and residence time required for the reactor. 

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ILLUSTRATION 8.9 DETERMINATION OF OPTIMUM REACTOR SIZES FOR A CASCADE OF TWO CSTR s... 

The amount of C required is 95 mole/h. In extracting C from the reacted mixture A and B are destroyed hence recycling of unused reactants is not possible. Calculate the optimum reactor size and type as well as feed eomposition for this process. 

From the above discussion, it is clear that a given rate of production can be achieved by different combinations of reactor size and power consumption. The selection of the optimum reactor size is based on the annualized cost of the reactor. The annualized cost consists of the cost of capital (depreciation and interest on fixed cost) and the operating cost. The fixed cost consists mainly of equipment cost (that is, the material cost plus fabrication cost), and the operating cost consists mainly of electricity (power) cost. For the purpose of this illustration, five different materials of construction were selected having costs 0.3,1.0, 3.0,10.0, and 30.0 /kg. This range of costs covers practically all of the materials commonly used in industry, such as mild steel, stainless steel, glass-lined vessels, Hastelloy, titanium-lined vessels, and so forth. Two levels of (depreciation + interest) were examined 20% and 50% per annum. Three costs of electricity were used 0.035, 0.10, and... 

ILLUSTRATION 8.9 Determination of Optimum Reactor Sizes for a Cascade of Two Dissimiiar CSTRs... 

With many batch processes, the production rate will decrease during the production period for example, batch reactors and plate and frame filter presses, and there will be an optimum batch size, or optimum cycle time, that will give the minimum cost per unit of production. 

Using this modified operating line, the procedure for finding the reactor size and optimum operations follows directly from the discussion on adiabatic operations. 

What reactor size, feed rate, and conversion should be used for optimum operations What is the unit cost of B for these conditions if unreacted A is discarded ... 

Dynamic models solve the differential material and energy balances for the reactor both before and during relief. A relief system size is assumed, and the model calculates the pressure versus time and temperature versus time histories. Examination of these can then determine whether the maximum accumulated pressure for the reactor would be exceeded with the assumed relief size. Multiple runs are required to find the optimum relief size which yields a maximum pressure which just equals the maximum accumulated pressure (see 5.2.1). 

Although cost considerations and economic balances are the basis of most optimum designs, there are times when factors other than cost can determine the most favorable conditions. For example, in the operation of a catalytic reactor, an optimum operation temperature may exist for each reactor size because of equilibrium and reaction-rate limitations. This particular temperature could be based on the maximum percentage conversion or on the maximum amount of final product per unit of time. Ultimately, however, cost variables... 

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