Advances in pump and drive technology have made new-generation reverse osmosis modular systems for industrial applications economically sustainable, as demonstrated by a Danfoss application in Italy


pump and drive solution from Danfoss has allowed Acciona to create an

innovative sea water reverse osmosis (SWRO) modular desalination plant for the Sarlux refinery in Sardinia, Italy, reducing energy consumption compared to traditional solutions. The process of seawater desalination is

energy intensive. Therefore, operating costs related to electricity consumption are significant. However, the use of high- pressure pumps; the introduction of isobaric systems for energy recovery, and the use of the new Low Energy osmotic membranes; and electronic control by means of VLT drives, have made it possible to change the rules of the game. On average, a volume of about

1,000m3 /h of water is required for the

operation of the refinery and of the electricity generating plant in Sarroch. Previously, this water was supplied by Sarlux from the local aqueduct and several existing desalination plants, which were high in energy consumption. The solution Acciona offered Sarlux

comprises a six-year full-line supply contract for an ultrapure water supply service. Pietro Tota, design and construction manager at Acciona Agua said: “We took care of everything, from the planning of the project proposal to its financing, from the executive project to the construction of the plant, and now of

its management and of the scheduled and unscheduled maintenance.” The solution includes four modular

reverse osmosis desalination lines, which are capable of supplying a total of 12,000m3

of pure water a day with a

guaranteed 97% availability over the entire year. The structure of each modular line in the plant is similar, and consists of four main sections: 1. Pre-processing with ultrafiltration membranes 2. Reverse osmosis first stage with working pressures of about 60 bar 3. Reverse osmosis second stage for the refinement of the water 4. Final stage of refinement, using ion exchange membranes The entire modular system is housed in

17 containers, including the one dedicated to the medium-voltage electric substation. This has reduced construction time to just six months. After the usual certifications and controls by the competent authorities, the site became fully operational in 2018. In a reverse osmosis desalination plant,

the most energy-intensive process is in the first osmosis stage. Danfoss high- pressure axial piston pumps, combined with Danfoss iSave isobaric energy recovery devices, proved suitable for creating a modular plant in the right size containers for the Sarroch refinery. Tota explained: “The volumetric technology of Danfoss high-pressure


An on-site trial at a ciabatta bakery has demonstrated that it is possible to successfully pump viscous, sticky dough products, even when they are mixed with baked bread. SEEPEX UK’s customised enclosed, automated waste removal solution has optimised the bakery’s waste handling process, reducing labour and improving hygiene levels in the production area. The owners of the bakery identified the manual removal of its

waste bread and dough as an inefficient task. Joao Rodrigues, applications engineer, said: “Dough is a highly viscous product – it is dense, wet and sticky; fresh bread is light and compressible; and waste bread is hard and non-flowable.” The solution proposed by SEEPEX comprises a BTM open hopper pump with an auger that mixes the

different products and prevents them from bridging in the hopper. It also contains integral static and rotating knives which produce a pumpable consistency. This then passes into the pumping elements of the stator and rotor, and is transferred through enclosed pipework into the removal lorries. Unlike the existing system, the only open part of the new solution is the hopper, into which waste

product is loaded. Every other part is enclosed, meaning there is no need for anyone to enter and exit the factory. The reduction of spillage also keeps the factory floor clean and tidy. The fully automated solution only requires one person to load product into the hopper, freeing resources

for production. Furthermore, the pump only starts running when there is product to handle and stops the moment the hopper is empty, making it an energy-efficient solution. SEEPEX

The first months of system operation have already proved the effectiveness of the technologies in reducing energy consumption. While the main stage of a typical reverse osmosis desalination plant based on centrifugal high- pressure pumps and energy recovery devices typically requires around 2.7 kW/m3

of water

produced, the volumetric high pressure pumps and iSave isobaric energy recovery devices enable the production of ultrapure water with energy consumption as low as 2.4 kW/m3

. This

reduction represents 11% savings in energy consumption

pumps enables us to create systems that are not only energy-efficient but also extremely compact and can be placed in a container. Thanks to their small size and simplified internal design, they can therefore be installed even when space is limited and, just as importantly, they require very little periodic maintenance. iSave devices, which recover the hydraulic energy of the reverse osmosis process discharge flow, drastically reducing energy consumption, are also extremely compact and can be integrated with Danfoss high- pressure pumps”. AC drives are also used to regulate the

flow rate and help minimise energy consumption. The adoption of the compact Danfoss VLT AQUA Drive family allowed Acciona to optimise the overall efficiency of the plant and the space occupied inside the containers. Thanks to the combined design of the

control and flow regulation system carried out jointly by Acciona and Danfoss, the system has improved the energy efficiency in all operating conditions, depending on the flow rate, environmental conditions and level of salinity of sea water. The construction of the desalination

plant in a modular format delivers clear advantages in terms of operating flexibility and reliability. In fact, when preventive or corrective maintenance activities have to be performed, it is not necessary to completely stop the water supply, which avoids potentially critical consequences for water consumers. “The high-pressure pumps are

extremely easy to maintain, and this is one of the most valuable features of Danfoss technology,” confirmed Tota. “Unlike traditional centrifugal pumps, which typically need to be shipped to an authorised workshop for maintenance tasks, we are able to perform maintenance of these Danfoss volumetric high-pressure pumps directly in Sarroch within a couple of hours, with obvious benefits in plant availability.”


8 JULY/AUGUST 2019 | PROCESS & CONTROL 

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