2023_CHEE423_Lab3_Manual

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McGill University *

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Chemistry

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Dec 6, 2023

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McGill University CHEE 423 Department of Chemical Engineering 1 Lab 3 - Residence Time Distribution Due date: Two weeks after the laboratory experiment at 23:59 PM (TA amirhossein.farzi@mail.mcgill.ca ) Problem Statement In reality, industrially used reactors rarely behave ideally. However, it is of great interest to obtain data on their behavior and to calculate their deviation from the exemplar. The objective of this laboratory exercise is to study the performance of one of two reactors, those being a stirred tank reactor (representing a CSTR) or a tubular reactor (representing a PFR). Experiment In order to quantitatively describe the behavior of a reactor, the residence time distributions for a chosen set up will be determined. This will be done by injecting a tracer in a pulse input fashion. The tracer used will be a sodium chloride (NaCl) solution whose concentration will be recorded at the exit of the reactor via a conductance cell. Protocol - CSTR 1) Fill the reactor with tap water up to the given mark. The reactor volume is 625 ± 10 mL. 2) Start the pump and adjust the flowrate by setting the rotameter to a desired value (settings of interest will be given during the laboratory). 3) Start and adjust the rate of the stirrer to a desired value (settings of interest will be given during the laboratory). 4) Pour some of the tracer solution (2 mol/L ± 0.02 mol/L) into a beaker and extract 20 mL of it in a syringe. Do not pour the remaining tracer solution back into the stock due to risk of contamination. 5) Start the chart recorder and zero the pen of the recorder using tap water as a reference. Set the speed of the recorder to 2 cm/min and set the full-scale voltage to 1V (this is used to convert voltage readings to conductance). The equations required to covert the conductance readings in units of mmho to concentration of NaCl can be found at the end of this handout. 6) Inject the tracer into the reactor at the designated site of interest. This location will be given to you during the laboratory. Keep in mind to press the syringe as quickly as possible to simulate a pulse input. At the same time as this is done, a second group member should mark the recorder paper to indicate the start of the experiment. 7) Record the concentration at the outlet of the reactor until the conductance returns to that of tap water (~ 0.25-0.29 mmho). 8) Record the temperature of the water used. (It may be assumed that this remains constant throughout the experiment) 9) Restart from step 1 under a different set of conditions to be given out during the laboratory.

McGill University CHEE 423 Department of Chemical Engineering 2 Protocol - PFR 1) Start the pump at a higher flowrate to fill the reactor with water and expel air bubbles. The reactor liquid volume is 715 ± 20 mL. The reactor has a length of 157 cm and an inner diameter of 3.8 cm. The dead volume below the reactor inlet is 16 mL. 2) Wait until the conductance readings reach that of tap water (~ 0.25-0.29 mmho). 3) Adjust the flowrate by setting the rotameter to a desired value (settings of interest will be give during the laboratory). 4) Pour some of the tracer solution (2 mol/L ± 0.02 mol/L) into a beaker and extract 10 mL of it in a syringe. Do not pour the remaining tracer solution back into the stock due to risk of contamination. 5) Start the chart recorder and zero the pen of the recorder using tap water as a reference. Set the speed of the recorder to 10 cm/min and set the full-scale voltage to 1V (this is used to convert voltage readings to conductance). The equations required to covert the conductance readings in units of mmho to concentration of NaCl can be found at the end of this handout. 6) Inject the tracer into the reactor through the septum. Keep in mind to press the syringe as quickly as possible to simulate a pulse input. At the same time as this is done, a second group member should mark the recorder paper to indicate the start of the experiment. 7) Record the concentration at the outlet of the reactor until the conductance returns to that of tap water (~ 0.25-0.29 mmho). 8) Record the temperature of the water used. (It may be assumed that this remains constant throughout the experiment) 9) Increase the water flowrate to purge out any tracer that could remain in the system. 10) Restart from step 1 under a different set of conditions to be given out during the laboratory.

McGill University CHEE 423 Department of Chemical Engineering 3 Useful Data and Equations Volts to mmho: 1 mmho = 0.1 V (1) Conductance (G) measured in mmho at a certain temperature in (°C): ࠵? !!°# = $ ! %&’(.(!∙(!!’,). [mmho] (2) NaCl concentration (mol/L): ࠵? /012 = 0.01004 ∙ ࠵? !!°# − 0.00164 (3) CSTR - Volume of tracer solution injected: 20 ± 1 mL - NaCl concentration: 2 ± 0.02 mol/L - Reactor volume: 625 ± 10 mL (without tracer addition) - Rotameter calibration: Flowrate [mL/min] = 5.4 × (Rotameter Reading) + 7 - Volume of outlet pipe in between the reactor and conductivity cell: 10-20 mL - Speed of paper on strip chart recorder: 2 cm/min - Full scale voltage on strip chart recorder: 1 Volt PFR - Volume of tracer solution injected: 10 ± 0.5 mL - NaCl concentration: 2 ± 0.02 mol/L - Reactor liquid volume (volume of the glass beads subtracted): 715 mL ± 20 mL (not including the volume of the pipe leading to the conductivity cell) - Reactor dimensions: Length: 157 cm. Inner diameter: 3.8 cm - Rotameter calibration: Flowrate [mL/min] = 10.036 × (Rotameter Reading) – 61.386 - Diameter of glass beads: 6 mm - Speed of paper on strip chart recorder: 10 cm/min - Full scale voltage on strip chart recorder: 1 Volt

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McGill University CHEE 423 Department of Chemical Engineering 4 Stirred Tank Reactor (CSTR) One of the following conditions will be investigated by the laboratory groups: • Stir speeds: 0 and 6 • Flowrates: Rotameter reading at 30 and 60 Tubular Reactor (PFR/PBR) One of the following conditions will be investigated by the laboratory groups: • Flowrates: Rotameter reading of 30 and 60 or 60 and 90

McGill University CHEE 423 Department of Chemical Engineering 5 Report Use the "2022_Guidelines for Assignment and report writing in CHEE" as a guide to prepare your team lab report. Report Requirements: Data information Name, ID number, course, professor name, lab assistant name, date, RTD Lab Report. Abstract • A summary of the lab exercise containing key results Introduction • Background information • Lab objectives clearly stated Analysis Protocol • All the appropriate steps and calculations Results • Plot concentration (conductivity) C vs. t. • Calculate and plot Eexp(t) and Etheo(t) vs. t for both configuration • Calculate the average residence time • Calculate variance σ2 and dispersion number D/uL (for PFR only) • Calculate variance σ2, TIS model residence time and n-value (for CSTR only) • Make tracer molar balance Discussion • Compare ideal vs. experimental conditions • What are the deviations from ideality • State possible sources of error • Discuss the effectiveness of the employed reactor model

McGill University CHEE 423 Department of Chemical Engineering 6 Conclusion • Were the findings succinctly restated? Sample Calculations (Appendix) • Equations, models, and integration techniques are presented.

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