Sep 24, 2008

Pressure Exchanger Cuts Desalination Costs on Malta

KSB isobaric energy recover system implemented in Malta seawater desalination plant

In early July 2008, an isobaric energy recovery system developed by KSB started operation in the Pembroke seawater desalination plant on Malta. Consisting of two SalTec DT250 operating in parallel, the system uses hydraulic power transmission to reduce energy costs compared to conventional solutions such as turbines.

The key element is a pressure exchanger, which transfers the energy of the concentrated brine directly to the raw seawater without the need for mechanical conversion. An electronic control system records all operating modes of the higher-level reverse osmosis (RO) system and adjusts pump and pressure exchanger control as required. It ensures that the water column in the pressure exchanger vessels is accelerated and decelerated so gently that switching the rotating valve of the pressure exchanger does not cause pulsations.

KSB also supplied the high-pressure pump employed to generate the pressure required for the reverse osmosis process and the booster pump used to compensate for the pressure losses in the pressure exchanger circuit. All components are designed to ensure that the production costs for a cubic meter of desalinated water are lower than those of other systems. KSB is the first manufacturer to supply this type of all-in package for the RO process.

The Pembroke plant produces more than 40,000 cubic meters of desalinated water per day and is therefore an important drinking water supplier, both for 400,000 inhabitants and for more than one million tourists who visit Malta every year. By using state-of-the-art pumps and pressure exchanger technology, the plant operator uses around 35% less energy.