Name: tracing flow patterns in packed bed reactors
Uploaded: 2023-04-30T07:01:40.000Z
Duration: 10 min 39 s
Channel: JoVE

1. Starting up the apparatus
The apparatus is primarily operated through the distributed control system interface. A Perm P&#38;ID schematic appears and opening/closing automated valves is point and click.
<ol>
	<li>To establish water flow to either bed #4 or #5, open the inlet and exit valves to the bed being tested and the water supply solenoid.</li>
	<li>Use the flow controller to start water flowing through the bed, raising it gradually. Good starting points are 400 mL/min for bed #4 and 500 mL/min for bed #5. Monitor the differential pressure across the beds. Vary the flow to cover the entire possible range of the DP transmitter.</li>
	<li>Power up the spectrometer equipment and establish communication with the control console. Spectrometer procedures are detailed in the operating manual (SpectraSuite). The calibration of the spectrometer for the fluorescent dye standards will be provided.</li>
	<li>Perform one tracer test each on beds #4 and 5 using 50 ppm dye in DI water as the tracer, at a single average flow rate for each bed.</li>
	<li>Insert the spectrometer probe into the probe sample point (Fig. 1). At the PERM interface, change injection valve status from &#34;Running&#34; to &#34;Charging.&#34;</li>
	<li>Inject the tracer using the syringe provided into the sample valve. Change the status to &#34;Running&#34;.</li>
	<li>Clean out the injection chamber of the sample valve by changing its status back to &#34;Charging&#34;, detaching and loading the syringe with water, then injecting at least 100 mL of water into the valve. When the injected sample has completely exited the bed (spectrometer absorbance returns to base line), change the valve state back to &#34;Running&#34; and let the water flow through the valve for 10 - 15 min at a high flow rate before using it again.</li>
</ol>
2. Conducting Two-Phase Flow Pressure Drop Experiments
Be sure that the water valves to the beds are closed, the inlet and exit valves to bed #5 are open, the drain valve is open, and that the manual valve for the air to the beds is closed.
<ol>
	<li>Slowly open the air regulator to establish an air flow (&#60; 5 psig at first). Open the manual valve for the air to the beds.</li>
	<li>Set water flow controller at desired setpoint (700 mL/min) and open manual valve. Route water/air flow to gas-liquid separator (see valving in Fig. 1).</li>
	<li>Confirm that water is exiting to drain. Close the valve to the drain for a period of time to build up a liquid head in the gas-liquid separator. This will result in better separation of the air and water.</li>
	<li>Adjust air flow (typically &#60; 2 SCFM) as desired using the pressure regulator and the dry test meter on the gas exit line. Close the drain valve for short periods of time to get a correct gas flow reading on the wet test meter.</li>
	<li>Conduct two-phase flow pressure drop (use DP transmitter) experiments using bed #5, at multiple air rates. Try to cover the range of the DP transmitter. Disconnect the dry test meter if you see water exiting from the gas exit line.</li>
</ol>

In this experiment the real flow behavior of horizontal packed beds, both in single and two-phase flow, was contrasted to the simpler theoretical models for pressure drop and dispersion (flow spreading in the axial direction, deviating from plug flow). The utility of tracer tests in probing for maldistribution (&#34;channeling&#34;) in such beds has been demonstrated, and it has even been shown that certain metrics calculated from the tracer tests can give some idea of the cause of the channeling. These calculations usin...

single and two-phase flow in a packed bed reactor

Single and Two-phase Flow in a Packed Bed Reactor

Source: <a href="https://www.jove.com/author/Kerry+M._Dooley">Kerry M. Dooley</a> and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
The goal of this experiment is to determine the magnitude of maldistribution in typical packed bed reactors in both single phase and two-phase (gas-liquid) flow and evaluate the effects of this maldistribution on pressure drop. The concepts of residence time distribution and dispersion are introduced through the use of tracers, and these concepts are related to physical maldistribution.
Channeling in a single-phase flow can occur along walls or by preferential flow through a larger portion of the bed cross-section. Channeling in two-phase flow can result from even more complex causes, and simple two-phase flow theories seldom predict pressure drops in packed beds. A design goal is always to minimize the extent of channeling by finding the optimal bed and particle diameters for the design flow rates and by packing a bed in a way to minimize settling. It is always important to quantify how much maldistribution might occur and to over-design the unit to account for its occurrence.
The permeameter apparatus measures pressure drop, ΔP, and the concentration of tracer (dye) exiting horizontal packed beds of armored glass for either water, air, or two-phase flow (Figures 1 and 2). Water enters through a control valve and can be routed through manual valves to any of five beds (48" long, 3" I.D.) with different size glass bead dumped (random) packings. The pressure drop is measured using a pressure transmitter. The water flow is measured by a differential pressure (DP, orifice) transmitter and the air flow by a dry test meter (similar to a home gas meter). The dye sample is injected upstream by an automated sampling valve. The exit concentration of the dye from a bed is measured using a UV-Vis spectrometer. Residence time distributions are calculated from the tests and compared to the predictions of theories on dispersion in packed beds. Two-phase flow will be studied in bed 5, which contains the largest particles.
<img alt="Fluidized bed system diagram, highlighting process flow, control, and sampling points." src="/files/ftp_upload/10431/10431fig1.jpg" data-altupdatedat="1761830439000" data-alt="Figure 1"> 
Figure 1: Process and instrumentation diagram of the apparatus.
<img alt="Chemical process system diagram, showcasing piping and instrumentation for industrial separation." src="/files/ftp_upload/10431/10431fig2.jpg" data-altupdatedat="1761830439000" data-alt="Figure 2"> 
Figure 2. 3-D rendering of the apparatus. Bed #1 is at the top, bed #5 at the bottom. The water control valve is on the left (red bonnet). The DP transmitter is at the top center (blue).

Obtain the RTDs (E-curves, using Equations 1-2) after subtracting an appropriate baseline (if necessary) from the spectrometer signals. An example of baseline correction for Bed #3 (not used here) is in Figure 3. Using Equations 1-3, calculate the average porosity, tracer mass, mean residence time, variance and variance divided by mean squared from the RTDs. Compare calculated tracer mass with injected mass - if they aren't within expected precision, examine ...

Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
The goal of this experiment ...

Packed bed reactors are one of the most common types of reactor used in the chemical industry, due to their high conversion rates. Packed bed reactors are typically tubular reactors filled with solid catalyst particles. The reaction occurs on the surface of the solid particle. Thus, small particles enable a high surface to volume ratio and therefore high conversion. Ideally, fluid flows through the reactor in a plug fashion, thus, these reactors are sometimes called plug flow reactors. However, maldistribution of flow or channeling can occur, where flow no longer keeps the even plug-like distribution. This causes the pressure drop in the reactor to decrease and affects the reaction conversion rate. In this video, we will discuss the basics of a packed bed reactor and demonstrate how to measure the pressure drop and flow distribution of one-phase and two-phase flow in the packed bed.In single-phase packed bed systems, the fluid can be either a gas or liquid. In two-phase reactors, both liquid and gas flow over the solid particles in either co-current or counter-current beds. In both one-phase and two-phase systems, the reactor can be oriented either horizontally or vertically. This

single-and-two-phase-flow-in-a-packed-bed-reactor

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tracing flow patterns in packed bed reactors

Packed bed reactors can show uneven flow patterns in both single-phase and two-phase systems. This experiment examines that maldistribution and how it changes pressure drop across the bed. It also uses tracers to connect residence time distribution and dispersion to the way fluid moves through the packing.

In single-phase flow, channeling can develop along the walls or through a larger part of the bed cross-section. In two-phase flow, channeling can arise from more complex causes. Simple two-phase flow theories often do not predict pressure drops in packed beds very well, so the experiment helps show why real systems need careful testing.

A key design goal is to reduce channeling by choosing the right bed and particle diameters for the design flow rates. The bed also must be packed to limit settling. Engineers must measure how much maldistribution may occur and then over-design the unit to account for it.

The permeameter apparatus measures pressure drop, ΔP, and the dye tracer concentration leaving horizontal packed beds of armored glass. The system can run with water, air, or two-phase flow. Water enters through a control valve and can be sent by manual valves to any of five beds, each 48 inches long and 3 inches in inside diameter, with different random glass bead packings.

Pressure drop is measured with a pressure transmitter. Water flow is measured with a differential pressure orifice transmitter, and air flow is measured with a dry test meter, which works like a home gas meter. The dye sample is injected upstream with an automated sampling valve, and the exit dye concentration is measured with a UV-Vis spectrometer.

Residence time distributions are calculated from the tests and compared with theories for dispersion in packed beds. Two-phase flow is studied in bed 5, which contains the largest particles. The apparatus is shown in process and instrumentation diagrams and in a 3-D rendering, with bed 1 at the top, bed 5 at the bottom, the water control valve on the left, and the DP transmitter at the top center.

Tracing Flow Patterns in Packed Bed Reactors

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Measure pressure drop and tracer movement in packed bed reactors to study channeling, maldistribution, and residence time distribution in single- and two-phase flow.

Tracing Flow Patterns in Packed Bed Reactors

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