Sample preparation and experimental set-up

208-C granular activated carbon from the Chemviron Company with 13×30 US

sieve mesh size (1.5 mm × 0.6 mm, Appendix E), previously used in the permeability test, was used to make five packed beds with different densities for thermal measuring purposes. The packed densities of the five test-samples were 546.7 kg.m-3,

661.9 kg.m-3, 707.7 kg.m-3, 749.8 kg.m-3 and 768.1kg.m-3.

Figure 4.8 shows the cylindrical sample holder, made from a stainless-steel seamless tube with 25.4 mm OD, 204 mm total length and 0.71 mm wall thickness. Two 5 mm

stainless steel caps were welded to the top and bottom. The filled height after welding the caps was 200 mm. To pass the inside thermocouple into the centre sample holder, another seamless stainless steel tube (the thermocouple tube) with

3.175 mm OD and 2.1 mm ID was welded to the top cap. The thermocouple tube was

located at the middle of sample holder with 105 mm distance from the top cap surface. To avoid blocking the thermocouple tube during the process of packing with carbon particles, the steel wire passes through the tube. Later the steel wire was replaced by the thermocouple after finishing the packing process. To fabricate each reactor, the following stages were considered:

1. The themocouple tube was welded to the top cap.

2. The top cap was welded to the main sample holder body.

3. The carbon was packed at the desired density, via a special process, into the sample reactor. Figure 4.13 shows the carbon was packed to a height of 200 mm. The bottom cap was secured into place to prevent any damage to the carbon pack.

4. The sample reactor was sent for a second welding run and the bottom cap was fixed at the desired position.

5. The protecting wire was replaced with the thermocouple and the specific connection for the leak test was assembled.

6. Each individual sample was tested for sign of any leak up to 25 bar (twice working pressure) with compressed air.

The first sample reactor was filled with granular active carbon in particle form by vibration process only. The sample holder was filled with carbon up to the desired

adsorbent length while being kept on the vibration desk, which is shown in Figures 4.8 and 4.13.

In order to make the other packed density, the same procedure as in the permeability test was followed. A special plunger (Figure 4.14, left) and structural support (Figure 4.14, right) were designed and fabricated. A preliminary test was conducted in order to understand the granular carbon particle behaviour during the packing process. The following points were established:

 The height occupation of 10 gm, 5 gm and 2 gm of granular carbon in the sample reactor with vibration process.

 The minimum height that could be achieved by the packing process and applying the force to the particles for 10 gm, 5 m and 2 gm of granular carbon.

 The maximum packing force that can be applied to the sample holder and support without damaging the sample holder tube or the integrity of the holder.

 The amount of “spring back” after the packing process. After removing the packing force the packed carbon column was shown to have increased the most. Therefore, to accommodate an accurate packing density, the “spring back” effect of the packed carbon column was assisted.

This information was used to understand the packing force, the packing time for each density, and the length of the plunger, extension tube and support pipe.

Figure 4.13. The 2 mm gap between packed carbon surface and sample holder edge (left). Down cap in desired place before second-time welding process; the 3 mm edge was designed to ensure the

The structure of the sample holders was monitored by measuring the height and outside diameter, in order to spot any inconsistencies during the packing and sample fabrication. The outside diameter was measured at three specific points before and after the packing process. The average of those points was used as the outside diameter of the sample in general modelling. The heights were measured three times during the fabrication:

 After welding the top cap and the thermocouple tube.

 After the packing process.

 After welding the bottom cap.

Table 4.3 shows the summary of each sample holder in terms of outside diameter (OD), mass of packed carbon and number of packing courses. The packing course shows the number of fillings and plunging force applied to reach the desired density. The outside diameter of the sample holders during the packing process was expanded within a maximum amount of 2%.

Density (kg.m-3) Carbon weight (gm) Average OD Before (mm) Average OD After (mm) Packing Course 546.7 49.23 25.45 25.45 0 625.9 56.53 25.52 25.52 2 661.9 59.63 25.46 25.47 3 707.7 64.1 25.51 25.52 3 749.8 68.25 25.51 25.58 4 768.1 72.55 25.48 26.03 5

Table 4.3. Thermal conductivity sample information for transient test.

Figure 4.14 shows that the structural support was made from galvanised pipe with a

25.4 mm inside diameter, with 5.6 mm wall thickness. In order to prevent the sample holder from sticking to the structural support inside wall and for an easy disconnecting process, the galvanised pipe was split the two sections. During the packing process, two sections of the support pipe were attached to each other and held in place using four special clips from the outside.

Figure 4.14. Left (A): Plunger: section 1 is a pipe with 4 mm wall thickness and 12.7 mm OD. Section 2 OD is 24± 0.15 mm and has passage for a thermocouple tube with a 3.3 mm OD. Right (B): Structural support: 1 is a split support pipe, 2 represents the sample holder wall and 3 shows the

fastener clips.

The loose carbon height at some stages of the packing process was higher than the sample holder’s total length. Therefore, the extension tube (Figure 4.15) was located in line at the top of the sample holder to guide the plunger into the main section of the sample holder and prevent any carbon being lost during the packing process. Figure 4.15 shows the wooden block provided to protect the thermocouple tube from bending and absorbing any sudden force during the packing process, and to prevent deformation of the sample holder. Finally, the granular particles were packed by press machine, as shown in Figure 4.15. The machine has the capability of controlling the displacement speed per second and force, which is transferred to the packed bed from the moveable load head.

Figure 4.15. A: 1 is the sample holder, 2 is the plunger – B: 1 is the sample holder, 2 is the plunger, 3 is the extension tube, 4 is the wooden support – C: 2 is the plunger, 3 is the extension tube, 4 is the wooden support, 5 is the fastener clip, 6 is the split support pipe – D: 2 is the plunger, 3 is the extension tube, 4 is the wooden support, 5 is the fastener clip, 6 is the split support pipe, 7 is the press

machine’s moveable head and 8 is the press machine’s fixed head.