For most ship owners and operators high fuel costs are a huge headache and a serious threat to their  profitability. If you had a magic wand that could cut fuel costs for your ship or fleet by 2%, you would probably start waving it! Now, the magic wand is available, only in another form. The magic wand is a new product from Alfa Laval called PureDry, a highly innovative high-speed separator with the capability to recover re-usable fuel from waste fuel oil. With a totally unconventional design, the separator recovers energy by recycling the heavy fuel oil fraction in the waste fuel oil tank, leaving only super-dry solids that can be landed as dry waste. The separator also incorporates what the company describes as “a solids removal twist”! Alfa Laval sees “waste fuel recovery” as a new, game-changing application that will bring the shipping industry huge savings on the fuel bills.
With high oil prices, bunker fuel oil accounting for around 60% of a vessel’s operating costs, and increasingly stringent emission controls, a fuel strategy and ways to cut fuel bills are at the top of the agenda for most ship owners and operators today. In addition to looking at technical measures to cut fuel bills, such as exhaust gas cleaning and other technologies, shipowners are being compelled to reduce speed, remove destinations from their itineraries, and so on.
However, it is now permissible to re-use waste fuel and, according to Alfa Laval, for the first time there is a technically and economically efficient method of recovering waste fuel from fuel oil residues. With waste fuel recovery, WFR, a direct saving of up to 2% on fuel bills can be achieved with an investment that pays for itself and gives a healthy profit in the first year. Sounds too good to be true?
How does WFR work?
Waste fuel oil comes from settling and day tank drainages, leakages, filters and purifiers and is today collected in the waste oil tank and subsequently landed or incinerated.
Alfa Laval’s WFR concept involves installing two waste oil tanks, one each for lube oil (LO) and fuel oil (FO), respectively (some vessels already have this arrangement). Although to the observer the waste fuel oil tank appears to contain just black oil, it is actually oil polluted water containing 20 – 30 % energy in the form of recoverable fuel oil. The remainder is oil polluted water 70 - 80% and, accumulating at the bottom, suspended solids approx 1%.
Re-usable FO returned to the bunker tank
Described by Alfa Laval as the first truly successful technology for waste oil treatment, the PureDry separator recovers the fuel oil from the oily water in the waste FO tank and it is returned to the fuel oil bunker tank for re-use after normal treatment. For the ship owner, the result is a reduction of up to 2% in the total volume of fuel oil consumed and a corresponding reduction in the ship’s fuel bill.
The process reduces the volume of waste oil by 99%, producing typically 5-15 kg per day of non-pumpable “super-dry” solids that can be landed as dry waste and disposed of in the same way as oily rags and used filter cartridges. There are no oil losses and no additional wastes are generated. The separated water, now with an oil content of less than 1,000 ppm, is pumped to the bilge water system.
Profit within the first year
Pauli Kujala, Senior Business Manager, Oily Waste Treatment Systems, Alfa Laval Marine & Diesel Equipment: “A large container vessel or cruise ship sailing 52 weeks per year typically burns 1,000 tonnes of fuel per week. Now, with PureDry recovering fuel that would otherwise be treated as waste, it will be possible to cut the ship’s fuel bill by up to 2%, which amounts to at least USD 500,000 per annum at today’s bunker prices!”
Alfa Laval calculates that once an existing vessel has been retrofitted with the PureDry system and separate FO and LO tanks, during the first year alone the ship owner’s fuel savings will pay for both the equipment and the tank installation. For a newbuilding, the profit will be even higher since it mainly involves the capital cost of the PureDry system.
In addition to cutting the ship’s fuel bill, there will be savings on waste oil incineration and landing for disposal and in the case of newbuildings, the volume of the waste oil tank can be halved, saving valuable space.
A second PureDry can be installed for waste LO to reduce the volume of waste and save on incineration and landing costs. Or if there is extra capacity in the PureDry for waste FO, this could be used to treat waste LO.
Problems with full waste oil tanks eliminated
PureDry also solves the problem of the waste oil tank filling up. The waste oil is treated instead of being stored for subsequent incineration or landing.
If the oily water separator (OWS) does not function properly, the bilge water goes into recirculation and fills up the bilge water tank. When this is full it is usually pumped to the waste oil tank. When the waste oil tank has no more capacity the ship has a problem. Incineration of the waste oil means burning up to 80% water and to do this it is necessary to add costly diesel fuel. It is in situations like these that environmental infringements may occur. Alfa Laval’s new waste oil treatment concept solves the problem.
Landing waste oil can be costly
There are also issues today surrounding landing of waste oils. In many ports, it is difficult. For instance, California is not prepared to handle waste oil. If landed, it has to be transported by road tanker to a neighbouring state for disposal. This, of course, means the ship owner has to pay dearly for it.
In some places it is possible to sell waste oil, probably for around USD 110 per tonne, although the price depends on the water content. But in those cases, ship owners are getting paid for oil they once purchased at full price. In fact, they are selling it at a huge discount to someone else, when they could re-use it themselves.
Flows metered and recorded
The PureDry system has accurate flow metering in the EPC 60 control unit. The feed is monitored, recovered oil is metered, the water is metered and a load cell registers when the dry solids container is full. All this is digitally recorded for presentation to the authorities during, for instance, Port State Controls. Fuel has been recycled, but no oily waste is missing from the ORB records because the recovered oil has been metered and logged.
Have any sludge treatment systems recovered waste fuel oil in the past? To some extent, but they have been costly to operate compared to the amount of fuel they have recovered. They have also created more waste. Ship owners and operators have found them cumbersome and difficult to operate and many are currently installed but not working to satisfaction.
Also, in the past, if any fuel was recovered at all and re-used, there would be an inconsistency in the ship’s Oil Record Book. If the ship claimed to have recycled the missing oil as fuel, authorities tended to remain unconvinced and suspect environmental infringements.
Changed MARPOL regulations
Today, according to MARPOL rule MEPC.1/Circ.642, it is permitted to recover and re-use the HFO fraction of the waste oil as fuel for the diesel engines. “Regeneration of oil residue should be an approved means of disposal of oil residue according to the supplement to the IOPP Certificate.”
This change in the regulations, which took place in 2008, was one of the drivers for Alfa Laval’s development of PureDry and the WFR concept. Another driver was Marpol Annex VI (air emissions). This prohibits incineration of oily wastes in ECA areas, therefore fewer owners will be installing incinerators and even larger waste oil tanks will be required.
Centrifugal separators increasingly sophisticated
Alfa Laval introduced its first marine centrifugal separator for cleaning mineral oil in the 1920s. It comprised a disc stack within a solid wall bowl. Cleaning involved opening the machine and removing the separated solids manually.
Since the advent of self-cleaning designs in the 1950s, marine mineral oil separators have become steadily more mechanically advanced. Today’s high speed separators feature automatic solids discharge via an aperture located at the outermost periphery of the bowl. Inside the bowl, a water operated hydraulic mechanism opens and closes at regular intervals at high speed to discharge solids. Thus, many high precision moving parts are involved which require regular service and maintenance.
The PureDry ‘devolution’
The new PureDry generation represents a paradigm shift in high speed disc stack separator solids discharge design. With PureDry, there is no aperture in the bowl and no sensitive hydraulic system installed to actuate solids discharge.
And here’s the “twist” that Alfa Laval refers to. A patented, spiral-shaped device called the XCavator transports the super-dry solids to the base of the machine where they exit down into a container below the machine.
There are just two main moving/rotating parts – the separator insert including the XCavator, and the outer bowl shell. They move in the same direction but at different speeds, thus transporting the dry solids out of the machine.
“It’s a kind of devolution,” says Pauli Kujala. “We have utilized the simplicity of the old solid wall separator designs, except that now we don’t need to open the machine and remove solids manually.”
Why PureDry?
The essence of the PureDry concept and the thinking behind the choice of name is that no water is added. The new design completely eliminates the need for displacement water prior to discharge, as well as water needed for conventional hydraulically controlled discharge mechanisms. Also, as mentioned earlier, the solids are discharged in super-dry form.
Alfa Laval believes that PureDry has the potential to change the seafarer’s view of centrifugal separators as being sophisticated pieces of equipment needing regular maintanence. PureDry requires no conventional maintenance and the design makes operation almost as simple as a centrifugal pump, with no manual engagement needed.
‘Maintenance and Service by Exchange’
PureDry’s innovative approach does not end with the design of the machine. Alfa Laval has developed an innovative, module-based maintenance concept called Maintenance and Service by Exchange (MSE).
PureDry is supplied with an Exchange Kit, which includes a new separator insert (rotor and disc stack), a new XCavator, and a Consumables kit. After one year, the crew replaces the separator insert as simply as replacing the insert in a filter, and the XCavator. The used parts are returned to the nearest Alfa Laval Service Center, and the ship orders a new Exchange (and Consumables) Kit.
“The customer is not purchasing new parts – we supply the Kit at an exchange price,” emphasizes Pauli Kujala, “and the PureDry separator remains under continuous warranty. This is virtually all that needs to be done to keep the equipment in good operating order. The aim is to give customers the opportunity to budget and maintain a fixed operating cost.”
For full operational security, PureDry is equipped with an advanced integrated condition-based monitoring (CBM) system that records temperature and vibration via the EPC 60 control unit. The system can give the crew an early alert or even shut down the machine if the running conditions should suddenly deviate from specifications. Action can then be taken based on recommendations from the CBM system – it may be a recommendation to run the Cleaning-in-Place (CIP) process or exchange a component using the Exchange Kit.
Integrated waste oil and bilge water system
Together, PureDry and Alfa Laval’s PureBilge bilge water separator form an integrated waste oil and bilge water handling system. It recovers waste FO that is returned to the fuel oil bunker tank, treats waste LO to reduce the volume, cleans the bilge water to 0-5 ppm for discharge overboard, and generates small volumes of super-dry solids for landing as dry waste.
PureBilge is the first system of its type to pass the new, more stringent DNV 5 ppm type approval process for oily water separators. It provides a cleaning performance in real life conditions of 0-5 ppm oil content in the water without chemicals, adsorption filter or membranes. PureBilge is delivered with the integrated tamperproof BlueBox bilge data recording system.
Impressive environmental benefits
Will ship owners and operators grasp the full implications of PureDry and the new waste fuel recovery application in terms of cutting their fuel bills and reducing the impact of their operations on the environment?
If the world’s merchant fleet cut its fuel bill by 2%, there would be a reduction in HFO consumption of approximately 10.4 million tonnes per year and the amount of CO2 released annually would be reduced by 32 million tonnes.
‘Pure thinking’ for the marine industry
PureDry and PureBilge are part of a range of sustainable solutions designed by Alfa Laval to help the marine industry reduce operating costs and comply with IMO’s increasingly stringent environmental regulations relating to many aspects of ship operation.
Other products in the range are PureBallast for ballast water treatment, PureVent for crankcase gas cleaning, and the PureSOx exhaust gas cleaning system.
Source: Alfa Laval