Deioniser design

Quantity of water to be treated per service cycle. The amount of process water deionised per service run cycle is (250 gpm)(60 min/h)(12 h/cycle) = 180,000 gal (681 m ). 

Cation load. Since the influent cation load is expressed as ppm equivalents as CaCOs, it is necessary to convert to units consistent with resin manufacturer s capacity data expressed as kdograins (as CaC03) per of resin. Total cation load in this case is 75+ 50+ 25 = 150 ppm. Convert to kgr (150 ppm)(180,000 gal/cycle)/(1000 gr/kgr) (17.1 ppm/g/gal) = 1580 kgr as CaC03 per cycle. 

Quantity of cation-exchange resin. The cation load per cycle is 1580 kg from above, and the resin capacity is given as 15.61 /ft in Section 6.7.1. Therefore, the amount of resin needed is 1580 kgr/(15.6 1 /ft ) = 101 ft (2.86 m ). 

Resin bed pressure drop and backwash flow rate. A minimum head-space (freeboard) is required for bed expansion at the design backwash flow rate. Typically, the bed expansion is 50—60%. The flow rate required for this expansion is specified as 6.4gpm/ft. Thus the backwash flow rate is 6.4 gpm/ft x 28.9 ft = 185 gpm (42 m /h). The pressure drop (AP) per foot of bed depth is specified as 0.75 psi. Thus AP for the cation-resin bed is (0.75 psi/ft) X (3.5 ft) =2.6 psi (17.9 kPa). This excludes the pressure drop due to valves, fittings, or Hquid distributon or collectors. Overall, the AP should be 10 psi (68.9 kPa). 

Rinse water flow rates. The column must be rinsed with DI/RO water after regeneration to remove traces of acid. Bed rinse is done at two flow rates to remove aU traces of acid. The rinse water requirements are specified as 25—50 gal/ft resin. For the resin volume of 101 ft, the rinse water requirement is about 2500—5000 gal (9.5—19 m ). For the slow rinse step, the flow rate is (one bed volume — 101 ft X 7.48 gal/ft, or 750 gal) at 50 gpm (11.4 m /h) for 15 min. For the fast rinse step, the flow rate is based on the remainder volume, i.e. at 150 gpm (34.1 m /h) for 50 min. 

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Although stationary phases were initially made from resins designed to deionise water, the stationary phases presently used are as complex as those found in HPLC. These materials follow the same requirements of microporosity, granular-metric distribution, mechanical resistance and stability under extreme pH conditions. 

The design issues of thermal management sub-system depend on the total produced heat and of consequence on the sizing of the stack. The mass flow rate of coolant (usually deionised water) can be derived by the definition of thermal capacity described by the following equation ... 

For a better comparison of the catalysts, the manganese oxides were also treated with 50 cm of deionised water, then evaporated, dried and calcined in the same way as the modified samples. The catalysts are designated hereafter as MnT-X, where T refers to the calcination temperature of the precursors (823 or 1373 K) and X refers to the additive used, that is S for sulfuric acid, Cit for citric acid, Na for sodium nitrate and Cs for cesium nitrate. No suffix was used in the case of the pure unmodified manganese oxides (Mn823 and Mnl373). 

The MB deionisers are designed to produce demineralised water with resistivity >16.0 Mf2-cm (conductivity <0.063 pS/cm). All operating modes — service, standby, and regeneration — are controlled by the PLC, which opens and closes the pneumatic valves and the corresponding solenoid valves. The process operating conditions are given in Section 4.2. Valve operations are detailed in Table 4.4. 

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