化学反应工程课外题-CRE.docVIP

Conversion and Reactor Sizing Additional Homework Problems For the irreversible gas-phase reaction: the following correlation was determined from laboratory data (the initial concentration of A is 0.2 g mol/L): ? The volumetric flow rate is 5 m3/s. Over what range of conversions are the plug-flow reactor and CSTR volumes identical? What conversion will be achieved in a CSTR that has a volume of 90 L? What plug-flow reactor volume is necessary to achieve 70% conversion? What CSTR reactor volume is required if effluent from the plug-flow reactor in part (c) is fed to a CSTR to raise the conversion to 90%? If the reaction is carried out in a constant-pressure batch reactor in which pure A is fed to the reactor, what length of time is necessary to achieve 40 % conversion? Plot the rate of reaction and conversion as a function of PFR volume. Critique the answers to this problem. Conversion and Reactor Sizing Additional Homework Problems Solution Over what range of conversions are the plug-flow reactor and CSTR volumes identical? So that it is easier to visualize the solution, we first plot the inverse of the reaction rate versus conversion. This type of plot is often called a Levenspiel Plot.: ? Recalling the mole balance equations for a CSTR and a PFR: Until the conversion (X) reaches 0.5, the reaction rate is independent of conversion and the reactor volumes will be identical. i.e. ? What conversion will be achieved in a CSTR that has a volume of 90 L? For now, we will assume that conversion (X) will be less that 0.5. We start with the CSTR mole balance: ? Our calculated conversion is extremely small. ? What plug-flow reactor volume is necessary to achieve 70% conversion? This problem will be divided into two parts, as seen below: The PFR volume required in reaching X=0.5 (reaction rate is independent of conversion). ? The PFR volume required to go from X=0.5 to X=0.7 (reaction rate depends on conversion). ? Finally, we add V2 to V1 and get