Darren Dale discusses the issue of marine growth fouling in critical technology and the benefits of innovative electrochlorination systems
Seawater is widely used across the oil and gas industry as a heat transfer medium and although it is a low-cost and effective coolant, its inhabitants make marine growth prevention (MGP) technology critical for keeping facilities in production, on and offshore. If seawater is left untreated, biofouling from bacteria and sea life can cause corrosion of vital systems and blockages in equipment. Cooling water intake screens remove larger animals and debris, but shellfish such as mussels, oysters and barnacles can easily breed in the warmth of the cooling system. Ultimately, this will lead to a loss of efficiency, downtime and can shorten the life of affected equipment.
MGP technology is therefore essential to prevent the build-up of contamination and biofouling for any seawater process. But in a sector that is reliant on meeting production output targets, it is also vital any solution reduces downtime and maintenance requirements for engineers. Furthermore, with the life of many oil and gas platforms being extended to meet current global energy demands, it’s now more important than ever to protect the life of ageing assets to keep them operating longer.
Finding The Right Solution
Traditionally, a range of chemicals have been used to prevent marine growth in seawater processes, including oxidising and non-oxidising biocides, heavy metals and electrolytically produced copper ions. Copper is an effective biocide but increasingly the limits on copper concentration in marine discharges are precluding its use. Non-oxidising biocides such as glutaraldehyde and phenol are also widely banned for reasons of toxicity. Oxidising biocides such as chlorine (or sodium hypochlorite), ozone and chlorine dioxide have for many years been found to be highly effective but carrying and storing large quantities of chemicals comes with safety risks. Today, many plants are turning to electrochlorination – the in-situ electrolytic generation of sodium hypochlorite from seawater – as the process of choice.
Electrochlorination eliminates the storage and handling of hazardous chemicals on board, is safe, environmentally friendly and, importantly, protects and prolongs the life of oil and gas assets. It is well proven having been in use for more than four decades but recent advances in cell technology have increased its power, reduced its footprint and boosted wider operational benefits.
The technology works by taking a small amount of water from a seawater line that remains constantly under pressure. The water passes – at high velocity – through the electrolytic cells where part of the salt is converted to sodium hypochlorite. This dilute, safe solution of sodium hypochlorite is directly injected into the water circulation, preventing the growth of common marine species. This immediately frees operators and engineers from the cost and risk of purchasing, handling and storing potentially dangerous chemicals, while effectively protecting wetted components from biofouling.
As well as the safety benefits of electrochlorination, the lifetime cost of ownership is significantly lower than ongoing chemical purchasing. Removing the need for chemical inventory also increases a plant’s operational resilience as there’s no reliance on chemical suppliers.
Eliminating The Maintenance Burden
One of the greatest advantages of electrochlorination technology for the oil and gas industry is its low maintenance requirements. Some traditional MGP technologies are time-intensive for engineers to manage; reducing this burden on maintenance engineers frees up time and personnel costs. It also makes the technology ideally suited for use on unmanned offshore platforms.
Electrochlorination technology, such as Evoqua’s Chloropac system, has a self-cleaning ability, which means that the system does not require acid wash or other external electrode cleaning methods. This task is a significant time commitment for engineers, when you consider an average system may need acid washing every three weeks. Plus, during this maintenance time plant production may need to be reduced or stopped all together. Electrochlorination technology allows system users to operate at design output capacity at all times, as the systems can be maintained in-situ versus other technologies which have to be removed from site and returned to the manufacturer.
The Future Is Here
When it comes to protecting production within the oil and gas sector and long-term viability, the right technology solutions are critical. Whether operators are building a new plant, retrofitting technology or extending the life of an ageing platform, production can be protected with the right technology solution. Although MGP technology will protect and preserve the life of critical oil and gas assets that use seawater for cooling, today’s operators can demand more. With an electrochlorination system that is designed to meet the unique demands of on and offshore oil and gas plants, engineers can benefit from increased uptime, considerably reduced maintenance requirements, a safer process and improved whole life costs.
Darren Dale is with Evoqua Water Technologies