Key Points
Some points in the Determination of Mass Transfer Co-efficient are:
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At high pressure, the mass transfer of CO2 into an H2O-rich phase in a capillary can be examined.
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A method for calculating the volumetric mass transfer coefficient is described.
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To determine CO2 concentrations in mass transfer, a thermodynamic model and Raman spectroscopy are used.
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It is possible to investigate the effect of flow rates on the volumetric mass transfer coefficient.
- The mass transfer coefficient varies along the micro-capillary tube's length.
Theory
There are various models that can be used to calculate or volumetric mass transfer theorem kLa. All models used to calculate kLa assume perfect mixing of the two phases in the reactor and low barrier to oxygen transfer across the interface in the gas phase. This experiment used the dynamic gassing out approach, which yields the oxygen mass transfer model shown below:
dCL/dt = kLa(C* – CL)
where CL is the dissolved oxygen concentration in the solution and C* is the saturated dissolved oxygen concentration.
Experimental Methods
Apparatus Required
The following apparatus is required in the Determination of Mass Transfer Co-efficient:
Fermenter
In this experiment, a 5L bioreactor (New Brunswick Scientific, BioFlo 3000 Model) was used. This reactor has temperature, agitation, and dissolved oxygen automatic feedback controllers built in. A marine propeller stirrer and a radially conveying flat-blade disc stirrer make up the agitation system. The disc stirrer is 6.5 inches from the head plate (3.5 inches above the sparger) and has a 3.0-inch diameter. Each blade has a width of 0.0625 inches, a height of 0.625 inches, and a length of 0.75 inches. The diameter of the marine propeller is 2.25 inches, and it measures 9.625 inches from the head plate to the sparger. There are three blades, each 0.125 inches wide.
Dissolved Oxygen (DO) Probe
In this experiment, a Type T DO Probe (12mm Diameter, Teflon Membrane) was used. For 98% concentration, the time constant specified in the requirements is the 90s. During calibration, it was discovered that the probe had a time constant of 99s for 100%.
Procedure
The Determination of Mass Transfer Co-efficient is the given steps:
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The time constant in the DO probe was measured by rapidly shifting the probe from a nitrogen-sparged liquid to an oxygen-sparged liquid and measuring the probe's response time to record saturation.
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The response time of the probe was measured when it was placed back into the nitrogen-sparged liquid to check for hysteresis. There was some hysteresis seen, but it was ignored because all measurements were taken from a nitrogen-sparged solution to an oxygen-sparged solution.
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The change in dissolved oxygen was measured using the dynamic gassing out method. At the same flow rate and agitation rate, the solution was sparged with nitrogen, then with oxygen. The dissolved oxygen concentration was measured until the solution became saturated.
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The agitation rate remained constant at 500 rpm while the aeration rate was adjusted at 0.5, 1.0, 3.0, 4.0, and 6.0 L/min in order to observe the relative impacts of the aeration rate on kLa. The aeration rate remained constant at 3.0 L/min while the agitation rate was tested at 50, 100, 500, 700, and 1000 rpm to see the impacts of the agitation rate.
- To test the effects of fermentation media on kLa, distilled water was replaced in the bioreactor with McCoy's 5A Medium (Sigma, M-6523), and only agitation was changed. To compare the results, the same values were utilized as with distilled water. Due to medium contamination, a different batch of McCoy's 5A Medium was used for 500 and 700 rpm.
Also see, Mercurial
Frequently Asked Questions
What's the distinction between vapor and gas?
A vapor is created when any liquid is heated, and it can be condensed under atmospheric conditions by either lowering the temperature or increasing the pressure. However, gas has already surpassed the critical temperature and cannot be condensed using the procedures described above.
When to use gear pumps?
Gear pumps are used to handle highly viscous liquids since they have a higher discharge pressure (up to 200 bars) than centrifugal pumps. They are used to pump paints, resins, adhesives, pitch, diesel, and crude oil, among other things. Positive displacement pumps are what they are called.
When to use the absorption factor method to calculate the plates?
The number of theoretical plates would be limitless if the operational data line and equilibrium line in the Mccabe Thiele method ran parallel. As a result, finding the number of plates would be impossible because the two will never touch at any moment.
What is priming in centrifugal pumps?
Priming is a technique for removing air trapped in the suction line of a centrifugal pump. If the air in the suction line is not eliminated, the pump will be unable to suck the liquid from the reservoir since air is a lighter medium and liquid is a heavier medium.
Conclusion
This article explains the concepts of the Determination of the Determination of Mass Transfer Co-efficient, some key points, and its experimental methods, along with some frequently asked questions related to the topic. I hope this article Determination of Mass Transfer Co-efficient was beneficial and you learned something new.
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