Water. desalination + reuse

TECHNOLOGY Figure 4. Payback Period versus Energy Costs A multiplier of zero correlates to zero CF installation and capex costs, and a multiplier of one corresponds to the capex costs given in the original costs and assumptions. It should be noted that, over the range of flows considered in this study, on average, 25% of the lifecycle energy savings are offset by expense of replacing the AP system's spare-parts. The primary reasons for replacement include wearing of the sliding/bearing surfaces, which decrease the overall efficiency and reliability of AP pumps. Water quality can play a major role in the life expectancy of water-lubricated machinery, because small particulates in the RO feed water (lubricating fluid) can accelerate the wear on the bearings. This is particularly true in the case of the plastic-stainless bearings used by some manufacturers. On the other hand, one AP pump manufacturer uses ceramic-ceramic bearings and claims extended service intervals over the plastic-stainless steel bearings. Therefore, a sensitivity analysis was performed varying the replacement cost/ interval for a typical AP system. Similar to the capital cost analysis, a Figure 6. Payback Period versus Installed CAPEX Costs Figure 5. Payback Period versus RO Feed Pressure multiplier of 0.5-3 was used to adjust the Total 20-Year AP Spares/Consumables Costs shown in the original costs and assumptions. Applying a multiplier of 0.5 reduces Total 20-Year Spares/Consumables Costs by a factor of 2 or equivalently extends the assumed replacement intervals by 2x, while a multiplier of three increases the these costs by a factor of three or equivalently shortens the assumed replacement intervals by one third. A multiplier of one corresponds to the same spares and consumables costs and replacement interval (/pump/year) found in the original costs and assumptions. CONCLusiONs In addition to the obvious energy efficiency advantage that positive displacement pumps maintain over CF units, the technology also improves the operation and control of the system thereby yielding additional gains in the net system efficiency. There are also potentially significant cost efficiency gains related to manufacturing and building modular systems around a standardized unit. Some of the advantages and disadvantages associated with the Modular High Pressure Pump System using AP Pump Technology include the following: AdvANTAGEs • Significant energy savings due to the 90% efficiency of positive displacement pumps compared to CF pump designs. • Applying one standardized high efficiency pump as a building block in multi-unit modules allows smaller trains to be as efficient as the largest systems. • A standardized modular design reduces inventory requirements for spare parts. Relatively small and inexpensive service kits and spare parts can support modular arrays whereas large CF pumps require massive spare motor(s) and/or rotor kits, mechanical seals, etc. • Lead times for large CF pumps are significant and substantially lengthen project deliveries whereas AP pumps can be kept on the shelf and used as building blocks for any size system to significantly reduce project delivery times. • Smaller standardized pumps can be maintained in-house with minimum Figure 7. Payback Period Versus AP Annual Spares Costs November-December 2013 | Desalination & Water Reuse | 31 |

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