Expanded anodes

Eig. 3. Expandable anode for diaphragm chlorine cells (a) clamped and (b) expanded. 

An expandable anode involves compression of the anode stmcture using cHps during cell assembly so as not to damage the diaphragm already deposited on the cathode (Eig. 3a). When the cathode is in position on the anode base, 3-mm diameter spacers are placed over the cathode and the cHps removed from the anode. The spring-actuated anode surfaces then move outward to bear on the spacers, creating a controlled 3-mm gap between anode and cathode (Eig. 3b). This design has also been appHed to cells for the production of sodium chlorate (22). 

Table 13.1 Structural specifications of MDC-55 using ESA versus a standard expandable anode.

Each electrolytic application demands a unique approach to anode structure design and fabrication. Factors such as current distribution, gas release, ability to maintain structural tolerances, electrical resistance, and the practicality of recoaiing must be taken into account. The most commercially accepted design for diaphragm chlorine cells is that of the expandable anode (Fig. I). 

Fig. I. Expandable anode fnr diaphragm chlorine cells mi clani ied and (by expanded...

DSA expanded anode, steel cathode + polymer modified diaphragm -2.48 -0.27 -0.46 -0.27 -3.48... 

FIGURE 4.5.22. Expandable anode for diaphragm cells (a) clamped G>) expanded [106,108]. (Reprinted with permission of John Wiley Sons, Inc.)... 

FIGURE 5.23. ELTECH s MDC cell (a) Brine feed rotameter (b) Head sight glass (c) Cell head (d) Cathode assembly (e) Tbbe sheet (f) Grid plate (g) Cathode tube (h) Grid protector (i) DSA expandable anode. (With permission flom ELTECH Systems Coiporaticxi.)... 

OxyTech MIX -55 cell with Modified Diaphragm and expandable anodes. Conditions anolyte temperature 93 C. anolyte NaCI concentration 250 g/L, catholyte NaOIl concentration 130 g/L. 

In the recent past, the conventional anodes shown in Figure 70 [168] have been further developed to optimize the energy consumption of the cells by replacing the simple flat expanded metal with complex structures [170], At present very few plants are still operating without expandable anodes. 

---