Mixed flow reactor continuous tracer

Adding a tracer spike to an ideal mixed flow reactor produces a step increase in the tracer concentration just as in the batch reactor case, but in this case the tracer s concentration declines over time as the reactor s effluent carries it away. If the amount of solution in the reactor remains constant and no more tracer is added by the feed solution or by generation in the reactor, the continuity equation simplifies to make the rate of accumulation equal to the rate of loss by the effluent flow. 

Continuous tracer addition to a mixed flow reactor... 

Non-ideal reactors are described by RTD functions between these two extremes and can be approximated by a network of ideal plug flow and continuously stirred reactors. In order to determine the RTD of a non-ideal reactor experimentally, a tracer is introduced into the feed stream. The tracer signal at the output then gives information about the RTD of the reactor. It is thus possible to develop a mathematical model of the system that gives information about flow patterns and mixing. 

You have designed the following tracer experiment to determine whether your continuous flow reactor for pilot-scale study is perfectly mixed, like an ideal CSTR. At time t = 0, you inject 100 g of an inert tracer into the 100 L reactor after establishing a feed flow rate of 25 L per min. Your technician measures the tracer concentration in the outlet stream for a few minutes and provides you with the following data ... 

The exit concentration data shown in Table P4.8 were obtained from a tracer experiment studying the mixing characteristics of a continuous flow reactor. Calculate the RTT> function, cumulative distribution function, mean residence time, and the variance of the RTD function of this reactor. 

How can tracer methods help us in solving these two problems We know that reactor performance, as measured by conversion of the limiting reactant or by product selectivity, is a function of kinetics, flow pattern and mixing pattern in the reactor. The flow and mixing phenomena in various reactor geometries are complex, and we are currently unable to characterize them completely (at an economical cost). The only reactors that we know how to design, predict their performance and scale up with confidence, are those that behave as the two ideal reactor types, i.e. the plug flow (PFR) and the continuous flow stirred tank reactor (CSTR). 

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