Failures brine pump

Chlorine—hydrogen ha2ards associated with mercury cells result from mercury pump failures heavy-metal impurities, particularly those with very low hydrogen overvoltage, ie. Mo, Cr, W, Ni excessively low pH of feed brine low NaCl concentrations in feed brine and poor decomposer operation, which leads to high sodium amalgam concentrations in the cell. 

Brine from the top of the clarifier overflows by gravity to the clarifier pump tank. A turbidity meter in this line can monitor the solids content and provide an alarm in case of an upset in the clarifier operation. Again, operation and control are similar to those discussed in connection with brine saturation. The top of the tank should be at least as high as the top of the clarifier overflow system. This provides more brine storage capacity as well as time to correct a pump failure or other simple operating problems. The normal level in the pump tank is about 50%. Level control options are as in Fig. 11.3 ... 

Most commonly, diaphragm cells are supplied with well brine on a once-through basis. The treated well brine flows to the treated brine storage tanks, which usually have 12-h capacity. From there the brine is fed to the cell room. The flow to each individual electrolyzer is controlled by a rotameter. If the flow of brine to the cells is suddenly disrupted by failure of the brine feed pump, the rectifiers automatically shut down since an inadequate supply of brine to the cells is potentially unsafe. The specifications for brine for diaphragm cells are given in Table 13. 

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