On offshore oil and gas platforms and vessels, a supply of freshwater is essential, not only for drinking but also to keep critical machinery and equipment operational. Rig managers, water quality managers and design engineers face several challenges when it comes to finding the right desalination solution for generating potable and ultra-pure water. Since watermakers come in all sizes, getting help on sizing and selection is key.
Before selecting a system, consider the following factors:
Desalination is a process that purifies seawater by removing salt and other minerals, making it suitable for human consumption (potable) and various industrial uses such as ultra-pure applications.
Ultra-pure water is water that has been treated to the highest levels of purity for all contaminant types, including organic and inorganic compounds, dissolved and particulate matter, volatile and non-volatile, reactive and inert, hydrophilic and hydrophobic, and dissolved gases. A typical ultra-pure water system has three stages:
Many technical applications on offshore rigs such as turbine wash, water-based hydraulic fluids, boiler feed, turbine cooling and power augmentation require ultra-pure water.
Reverse osmosis (RO) is a popular technology used for desalination. Seawater is passed through semi-permeable membranes to remove salt and minerals. The water is then treated by electrodeionization. In this stage, the water produced is sent to gas-liquid separation membranes that allow gas, but not liquid, to pass through before the water is sent to an electrodeionization water treatment module. This module utilizes electricity and ion exchange resin to deionize the water to further reduce dissolved ions (impurities) and produce ultra-pure water.
Environmentally friendly, an RO system replaces single-use ion exchange media and devices that use salt for regeneration of the media. Unlike ion exchange technology, there is no need to purchase and ship materials back and forth and there is less waste to dispose of.
Most ion exchange systems are comprised of pressure vessels filled with ion exchange resin operated on a cyclic basis. Water flows through the resin until the resin is considered exhausted when water leaving the exchanger contains more than the desired maximum concentration of the ions being removed. Resin is then regenerated by sequentially backwashing the resin bed to remove accumulated solids, flushing removed ions from the resin with a concentrated solution of replacement ions, and rinsing the flushing solution from the resin. Production of backwash, flushing, and rinsing during regeneration of ion exchange media limits the usefulness of ion exchange for a number of applications as it creates a waste stream that must be disposed of.
Using membrane-based desalination technology carries many advantages including:
The chart below shows contaminant removal achieved with various membrane filtration systems.
Before contacting a desalination system supplier, it’s advisable to have the scope of the requirement in perspective. Prepare a list of key specifications and priorities. Detail the conditions, resources and primary objectives for application of the system for the supplier. It’s also important to prepare questions and concerns that the experts in the technology can address. Tapping the knowledge base of a qualified, experienced supplier can be invaluable to the ultimate success of the project. Be prepared to answer these questions about your application:
When selecting a desalination system, choosing the right supplier is critical for reliable, cost-efficient operation. Downtime is not an option on a remote vessel. Important factors to consider include:
Well-known for its engineering excellence, product quality and premier customer service, Parker Hannifin has been providing desalination and water purification systems to the oil and gas, marine, defense, disaster relief, and power generation markets for over 35 years.
Parker specializes in vertical system integration, meaning that all system parts and components are manufactured by Parker. The advantages of partnering with a one system solution provider include improved efficiency, immediate parts availability, design expertise, and lower overall system cost. With locations in 50 countries, 13,000 distribution outlets, and 24/7 worldwide support, global parts availability and service is guaranteed.
The Parker Ultra-Pure Water Generation System, designed for offshore, upstream oil and gas installations, uses RO technology to produce an endless supply of ultra-pure, high-grade water for a variety of critical applications. Features include:
Selecting the right desalination system for an offshore installation can be challenging. It’s important to not only look at the capabilities of the system but to also consider the supplier and its reputation, level of experience, design expertise, global presence, and support services. That’s the formula for success.
This article was contributed by Paul Kamel, Product Manager II, Water Purification, Parker Bioscience and Water Filtration.