ANC CONTROL

EXPERIMENT 1. GLASS COLUMN AS FLUIDIZED LIME FEEDER

INTRODUCTION

The first experimental task was to check the feasibility of a fluidized lime bed suspended in a tall column. This was the simplest model that could be used as a lime feeder. The aim was to find the optimum upflow velocity that would mix the lime uniformly and keep it suspended without causing a great amount of undissolved lime to go out with the effluent. Upflow velocity can be calculated by dividing the flow rate by the cross sectional area of the column. Since the area is constant, upflow velocity is directly proportional to the flow rate. The equation of up flow velocity is shown below.

Vup flow: Velocity of the inlet flow.
As top: Superficial area at the top of the tube.
Qlime feeder: Flow rate employed on the experiment.
The aim of this experiment was to ascertain a range of upflow velocities to maintain a fluidized bed of lime. This was an initial experiment and hence most of the quantities were taken through approximation.

PROCEDURE

The schematic diagram for the experimental set up can be seen in Figure 1.


Figure 1: Schematic Diagram of Experimental Set up

The apparatus consisted of a vertical column. Water flowed through the column from the bottom. The flow rate was controlled by an automatic peristaltic pump. Lime was added from the top of the column before operation. Once the experiment was running, the effluent, super saturated with lime, came out from the top.
 

Figure 2: Experimental Apparatus

Figure 2 above shows the actual apparatus used for the first trial. The vertical glass column ( having 2.4cm inner diameter and 61cm length) is connected to the water source and is its flow rate is regulated by means of a peristaltic pump.

RESULTS

The optimum flow rate which kept the lime bed suspended without excessive lime coming out (as observed visually) was about 85ml/min. This flow rate corresponds to an up flow velocity of 22.7 cm/min (3.78 mm/s).

The results were summarized in Table 1.

The details of the exact quantities of lime and flow rates as well as the results obtained can be found on ANC-Initial Experiment Spreadsheet.