# Enhancement of CO2 Removal Efficacy of Fluidized Bed Using Particle Mixing
## 2 Experimental  
### Experimental Setup  
Figure 1 shows the schematic diagram of the experimental setup. The test section comprised a 1-m-long vertical Perspex column of 70-mm internal diameter. A perforated plate distributor, located at its bottom, ensured a uniform distribution of inlet gases. The distributor was a 10-mm-thick Plexiglas plate with 1.5-mm holes and 4% open area. To eliminate entry effects, a 250-mm-long calming section was provided below the distributor, as shown in the figure. The outlet gases from the column were released outside the lab to prevent nitrogen and CO\({}_{2}\) build-up. Openings along the column height provided ports for the measurement of the pressure drop and the carbon dioxide concentration. Before the start of the experiment, the setup was tested for any leaks by ensuring inlet and outlet flows were equal. Figure 1: Schematic of the experimental setup for the CO\({}_{2}\) adsorption from the mixture of N\({}_{2}\)–CO\({}_{2}\) gases. Single black broken lines represent voltage signal connections of different equipment with data acquisition system (DAQ); double black broken lines represent communication of DAQ with computer. As shown in Figure 1, the inlet gas flow assembly comprised two separate inlet lines from compressed cylinders of nitrogen and carbon dioxide. To ensure accurate measurement of the flow rates of gases, two different electronic flow controllers of different ranges were used. For nitrogen, the range was 0-2 SLPM (FMA-2605A-V2P), while 0-200 CCPM (FMA-2618A-V2P) was used for the carbon dioxide. Excellent linearity between the voltage output and the flow rate was noticed. The analog voltage inputs and outputs of the mass flow controllers were connected to the data acquisition system (DAQ) for controlling and monitoring the flow of gases to the column. Both gases were mixed in fixed proportion before entering the test section of the fluidized bed. For the measurement of the carbon dioxide concentration, we used an oxygen/carbon dioxide analyzer (Model 902P, Quantek Instruments, Grafton, MA, USA) in view of its high accuracy and measurement stability. The analog output options for the carbon dioxide and the oxygen were configured and connected to the data acquisition system. The minimum CO\({}_{2}\) detection limit was 0.01%, while the upper concentration range was 20%. National Institute of Standards and Technology (NIST) traceable calibration certificate, supplied by the manufacturer, was used for converting the voltage output to percentage volumetric concentration. The voltage signals from the analyzer were captured by DAQ running LabView software and then transferred to a computer for further processing. We employed a fast response pressure transducer for monitoring the local transients of the fluidized bed. It was a sensitive, differential, bidirectional pressure transducer (PX163-005 BD5V, Omega, Stamford, CT, USA) with a response time of 1 millisecond. As shown in Figure 1, the lower pressure port was located at a distance of 50 mm from the distributor, while the upper port was placed 250 mm above the distributor, thus providing crucial information about the local bed dynamics. The pressure tap, flush with the column wall, was covered with a fine nylon mesh. The pressure transducers were carefully calibrated from volts to Pa using a pressure calibrator (Fluke Model 718). The calibration showed excellent linearity of voltage-Pa profiles. Five hundred grams of the activated carbon was loaded in the bed before starting the experiment. The static height of the bed was 225 \(\pm\) 3 mm. First, a number of fluidization and defluidization experiments were carried out using only nitrogen gas to study the fluidization hydrodynamics of the bed. There were initially some losses (<1% of the total solid mass) of the activated carbon due to elutriation, which were replenished to keep bed height constant throughout the experiment. These results, which are related to bed hydrodynamics, are reported elsewhere [47].