Liquid-filled capacitors are designed to produce rapid, very high voltage electrical pulses and are typically used in particle accelerators. Frequently, deionized (DI) water is the preferred dielectric, as it is environmentally safe and inexpensive to replenish, when compared with alternative fluid media, such as oils, which degrade.
A DI water system was required to service the water capacitors in a new facility at the Russian Federal Nuclear Centre – All-Russian Scientific Research Institute of Experimental Physics (part of the State Atomic Corporation ROSATOM). These high-voltage capacitors produce the burst of energy needed to create high power X-ray radiation used in radiology experiments at the Institute.
However, as the charge/discharge cycle affects the conductivity (and insulation capability) of the DI water between the capacitor plates, it must be flushed out and replaced periodically. This procedure maintains the performance level of the capacitors. Conventional water systems in this application used a mixed-bed deionization plant for the final purification stage. Unfortunately, the process required chemical regeneration of the resin beads in the ion exchange vessels and disposal of spent reagents.
Working to strict environmental safety standards, ROSATOM looked to avoid specifying equipment with such an adverse environmental impact. Consequently, the water treatment system design and build specialists, Hydrotech, proposed an alternative to mixed-bed deionization.
Hydrotech had previously constructed a number of successful turnkey water systems for ROSATOM and were familiar with the environmental restrictions in place. The task was to develop a water treatment system operating for eight hours per day, using deep-well abstraction as the water source.
With a typical feed water quality of 300-400 µS/cm, the system needed to produce a DI water conductivity ≥15 MΩ-cm (≤0.067 µS/cm). A flow rate of 30-150 m3/h with under step-less regulation was also specified, to enable the capacitors to be refilled efficiently after several discharges.
Hydrotech already had the answer to chemical-free deionization, as an established installer of IONPURE® Continuous Electrodeionization (CEDI) modules. These modules are fully established technology of choice in modern power generation plants and microelectronics manufacturing, where mixed-bed DI used to predominate. The company designed, constructed, and commissioned a fully automated water treatment system comprising:
- Media filtration
- Two-pass reverse osmosis (RO)
- Membrane deaeration
- 1 micron filtration
- IONPURE CEDI
The deionization stage consists of two CEDI assemblies, both with five IONPURE VNX55EP-2 modules supplying DI water storage tanks. Each unit of five modules has a nominal output of 75 m3/hr, allowing a total flow capacity of up to 150 m3/hr if required. The system delivers a measured output quality of 17.2 MΩ-cm (≤0.058 µS/cm), exceeding the insulation properties needed by the water capacitor equipment.