Residence Time Distribution

AIM: To study the residence time distribution in a series of continuous stirred tank reactor and to compare the exit age distribution with the theoretical and also to find the number of tanks in series.
Materials required
Chemicals: Glacial acetic acid, sodium hydroxide and phenolphthalein indicator.
Glassware: Beakers (50ml) --- 20 Nos. Measuring jar, thermometer.
Instruments: Stop clock, Hypodermic syringe, titration set up.

In this mode, the fluid flows through a set of stirred tanks arranged in series. A pulse signal is used for the study of Residence time distribution in this flow system. The stimulus is a tracer input to the fluid entering the vessel,. Whereas the response is a time record of the tracer leaving the vessel. Any material that can be detected and which does not disturb the flow pattern in the vessel can be used as a tracer. Here, glacial acetic acid is used as a tracer.
Initially, water is allowed to flow through the system at a chosen flow rate (200-300 ml/min). The actual flow rate is measured using measuring jar and stop clock. This flow rate is kept constant throughout the experiment. The stirrer is switched as and an optimum rate of stirring is set up without aeration. A few minutes are passed for the attainment of steady flow condition.
The normality of Na0H to be used is found out with the help of standard oxalic acid solution. 3ml of glacial acetic acid injected in to the first reactor of the system. At regular intervals of time, the samples of the outgoing liquid are collected and analyzed for their concentration.

1. Mean residence time,

2. Spread of distribution,

3. If N is the number of stirred tanks in series, then N is related to as N =

4. Exit age distribution,

5. Normalized distribution function

Theoretical calculation of

All values are tabulated.

GRAPH: Theoretical and experimental are plotted against .

RESULT: The RTD in a series of CSTR’s is studied and is compared with theoretical behavior.

CALCULATIONS: 1. Standardization of Na0H
Normality of Oxalic acid taken
Volume of oxalic acid taken: ml
Volume of Na0H rundown: ml
Normality of Na0H: N

2. Volume of sample collected: ml

Flow rate F: ml/min.



Mean residence time,

Spread of distribution,

No. of stirred tanks in series, N =

Exit age distribution,

Normalized distribution function

Theoretical calculation of

Sl.No. Time t (min) Volume of Na0H ml Tracer conc.x 103 gmol/lt
C t2C E(t) E( )