Desalination

Over recent years, membrane science and technology have resulted in substantial innovation in engineering of processes, offering new opportunities in the design, realization and optimization of innovative products, for sustainable growth in the industrial system in full respect of the environment.

The main advantages offered by membrane technology in respect to traditional technologies are:

  • Efficiency and simplicity in operations
  • High selectivity and permeability for transporting specific components
  • Low energy requirements
  • Good stability and compatibility among diverse membrane operations
  • Environmental compatibility
  • High flexibility and easy scale-up
  • Advanced level of automation and remote control
  • Absence of moving parts

All of these properties make membrane technology fall into perfect alignment with a Process Intensification strategy. Aqurex also adopts this new philosophy in the development of industrial processes that indicates and defines criteria for remodeling a more sustainable and environmentally compatible processing industry, with low energy consumption and low consumption of raw materials, reduced production costs for the final product, low waste products, as well as significant reduction in the dimension/productive capacity ratio of the system, resulting in safer, more flexible processes. 40% – 50% of the energy consumed today by industry is used in separation processes. Membrane operations represent an important opportunity to reduce this consumption substantially. In desalination processes, for example, in a context characterized by growing global energy demand and scarcity of water. The only way to try to address the negative impacts of climate change caused by the increase in greenhouse gases in the atmosphere is to significantly reduce these emissions. The technical “options” are many, but it is clear that recovery of CO2 requires additional costs. New materials and new technologies, the focus of the efforts of researchers around the globe, are today being studied with the objective of creating a membrane that can capture the CO2 produced by power generation systems, one of the major sources of greenhouse gas. The CO2 captured by these systems could then be stored in underground geological sites and used to improve extraction of natural gas and oil. The most common desalination method is reverse osmosis (RO): Physical type RO (reverse osmosis) procedures permit separating the water from the saline solution through the use of mechanical energy as opposed to thermal energy.

In the RO system pretreatment is very important because the surfaces of the membrane must be kept clean and microbiologically pure; therefore, the remaining suspended solids must be removed and the water must be pretreated to ensure that the precipitation salts or traces of microbiological growths do not attach to the membrane, the heart of the reverse osmosis system. In general, pretreatment consists of careful filtration and addition of products designed to prevent the infiltration of precipitates or insurgence of micro-organisms. High pressure pumps supply the necessary power to permit the water to pass through the membrane and remove mineral salts: this pressure ranges from 15 to 25 Bar for seawater.

Thermal desalination methods available for desalination of seawater are basically two types: Multi Stage Flash and Multiple Effect Distillation. These two processes are widely proven and based on the same principles of physics and thermodynamics, but differ in some aspects and fundamental characteristics: MSF is especially suited to large systems, while the MED process is better suited to small/medium systems (most of the recently installed units currently functioning have capacities ranging from 5.0 and 8.0 MIGD).

According to the specific demands and available resources, either one technology or the other may be preferable: the MED system has a capacity from 13-17 MIGD (approximately 60 million to approximately 75 million liters a day) and can be applied where the available pressure is quite low (2.0 Bar). Where thermal efficiency is high, the MED with capacity ranging from 5.0 to 8.0 MIGD (approximately 20 million to approximately 30 million liters a day) must be powered with MP steam and coupled to a Thermal Vapor Compressor (TVC). MSF can be applied in cases where the low pressure steam is available at 2.5 Bar, and can reach high thermal efficiency values independently of the LP steam pressure. Both cases ensure a substantial reduction in production and maintenance costs.

After the customer’s approval, Aqurex takes charge of transport and installation according to agreed schedules to the customer’s premises, thanks to a fleet of vehicles suitable for safely transporting the various components for the system without any additional costs. Once the system is up and running, the customer will receive appropriate training, along with local workers, in order to ensure autonomous ordinary and extraordinary maintenance on the system, substantially reducing costs over the long term.

After having installed the system at the customer’s premises, Aqurex remains a point of reference over time for ordinary and extraordinary maintenance. For any problems or technical inquiries, telephone assistance is always available to respond and propose solutions for the case in question, or to schedule an intervention by specialized personnel to resolve the issue, and if requested, to provide further training to the local personnel.