CENG0011 Particulate Systems and Separation Processes II 2023/2024

Project

Analysing andReflecting on your Experimentation

Referring to the activity carried out during the experimentation module, and the theory discussed as a part of the PSSP syllabus, reflect critically on the experimentation activities conducted in the lab by answering the following questions.

Cooling Crystallisation

1.  Background Briefly explain, in your own words, the operating principles of cooling crystalliza- tion using thermodynamics.   [3]

2.  Literature Survey and Physical-Chemical basis. Define the solubility curve and produce a plot of the solubility curve for K2SO4  in water.  In this process compare the theoretical predictions obtained by applying the thermodynamic definition of solubility, with experimental data that you might find in the scientificliterature.

Hint 1:  to use the the thermodynamic definition of solubility you will need to find physical-chemical properties of K2SO4  (activity coefficient in water, melting temperature, enthalpy of melting, etc...).  The online notes can help you in identifying the parameters needed to solve this problem.

Hint 2: To research experimental measurements of K2SO4  solubility in water you can use any resource on the web, from scientific search engines (scopus.com, accessible from the UCL network) to Wikipedia, make sure that in any case you can retrieve a bibliographic reference for the data used.  [7]

3.  Methods

• By reading through the experimental brief identify and report the steps in the experimen- tal procedure that change the state of your solution by modifying its composition (the sample is diluted or concentrated) and/or by changing its temperature.  [5]

• On the solubility curve diagram produced at point 2, represent all the steps identified in the experimental brief.  [2]

• Briefly explain the motivation behind every step identified and reported in the previous steps.  [3]

4.  Results Report the results obtained from the crystallization experiment, including:

• The total mass of crystals precipitated.   [5]

• The initial and final K2SO4 concentration in solution.  [5]

• The initial and final supersaturation.  [5]

• The average volumetric growth rate of the crystals obtained in cm3 /s.   [5]

Hint: for every point show all the calculations performed and explain the equations used. Organise your results in a readable format.

5.  Predict / Extrapolate / Discuss Answer the following questions with reference to the analysis conducted at the previous points:

• Would the total amount of crystals produced in the experiment be larger or smaller than measured if crystallization was carried out at T=20oC?  [5]

• Would you expect an experiment without seeds to proceed faster or slower than the ex- periment conducted in your lab session, and why?   [5]

Hint: you can use the solubility curve, and your understanding of material balances to support your reasoning.

Reverse Osmosis

1.  Methods Produce a simplified sketch of the process that you have operated in the lab, and define all the relevant variables of the process.  Describe in your own words the role of every stream, and unit involved in the process.  [5]

2.  Data Collection and Analysis Report the results obtained from the reverse osmosis experiment, including:

• One table per dataset collected (similar to Table 2 in the Lab Brief) where you report, as a function of time the Flowrate, Conductivity, Temperature, and Concentration for all the variations of the experimental conditions tested in the lab (i.e. different pressures).  [5]

• A single plot jointly reporting the permeate flow rate as a function of time for all the operating conditions investigated.  [5]

• A single plot jointly reporting the permeate flow rate as a function of NaCl concentration for all the operating conditions investigated.  [5]

• A plot reporting the permeate flow rate as a function of temperature in all the operating conditions investigated.  [5]

3.  Extract information

• Using your understanding of reverse osmosis principles obtain an estimate of the osmotic pressure dependence on concentration from experimental data.

Hint: in doing so you can consider constant the product of permeance and area of the membrane PmA, when the temperature is approximately constant. You can also consider the Osmotic pressure to be linearly dependent from the concentration of solute.  Using a linear regression algorithm is suggested.   [10]

• Compare and critically discuss your results in relation with the theoretical definition of osmotic pressure learned in class.   [5]

Readability / Clarity / Conciseness of the report   [10]