The less the sulphur, the more the problems

Adopting lower sulphur levels in marine fuel oils is the objective of the International Maritime Organisation (IMO) as it endeavours to reduce atmospheric pollution from shipping. However, will this create more problems than it solves?

Sulphur levels are one of the principal gaseous and particle emissions from ships and depend on the sulphur content of the fuels burnt during combustion and not on technological improvements. As a result, the IMO has set a maximum limit for sulphur content of 4.5 % for marine fuels. In addition there are so-called Sulphur Emission Control Areas (SOxECAs) where the maximum sulphur limit is set at 1.5%. Such areas include the Baltic Sea, the English Channel and the North Sea.

At the same time the European Commission (EC), under an amendment to its 1999/32/EC Directive, has set regulations regarding the English Channel and the Baltic and North Seas that are identical to those of IMO. It also requires all ferries operating between EU countries to use 1.5% fuel and for this to be reduced to a 0.2 % sulphur level in all EU ports. As a result, multiple grades of fuel will have to be kept on ships and ashore.

Availability

The rulings may well reduce atmospheric pollution by ships but also raise a number of questions. Will enough low sulphur fuel be available? What are the implications for lub oils? Is there a safety hazard created when vessels change over from one fuel to another?

Speaking at last year?s Rotterdam bunker conference, Steve Walker of ExxonMobil Marine Fuels, indicated that preliminary research by IMO and the EU Commission suggests that the cost-effectiveness of these proposals would be favourable as it appears likely that the majority of the lower sulphur fuel required could be provided without major investment in desulphurisation technology.

As it is unlikely that a 0.2 % sulphur heavy fuel can be economically produced to meet the EU port requirement, the grades available are likely to be:

l High sulphur bunker fuel oil > 1.5% Sulphur.

l Low sulphur inland fuel oil < 1.0% Sulphur.

l Low sulphur gas oil < 0.2% Sulphur.

Nevertheless, according to the Marintek research group study, estimates of world and European marine fuel consumption is uncertain, making determination of low sulphur fuel requirements equally uncertain. The study concludes that the estimated growth of marine fuel consumption in Europe will result in a demand for 50-57 million tonnes by 2020.

With respect to the future demand for low sulphur bunker fuel, the study however concludes that the figures probably will exceed earlier estimates and that a figure in excess of 20 million tonnes seems realistic in 2007.

Production capacity

According to Marintek, the capability of the oil refining industry to produce more low sulphur fuel for shipping is limited because of factors such as the availability of low sulphur crudes and the configuration of the refineries to cope with the different product volumes associated with high and low sulphur crudes. Also, it is unlikely that the oil industry will consider the marine bunker market as particularly attractive for substantial investments to convert high sulphur components into low sulphur fuel.

One aspect of fuel management highlighted by Steve Walker is that vessels trading internationally will have to cope with three grades of fuel. How will a ship owner segregate and carry these? Walker?s point is that many modern ships have been built on the uni-fuel principle of one grade of fuel, i.e. heavy fuel oil.

These vessels carry a minimal gas or diesel oil fuel supply to allow them to change over fuel prior to dry docking when the fuel heating system will be shut down. When visiting Europe, where will they put and process the low sulphur fuel oil and how will they carry enough gas oil to get them through a port turnaround?

In Walker?s view the ideal would be three complete fuels storage and treatment systems but in reality this may prove impossible to achieve on existing vessels. Ships have only a limited amount of space dedicated to fuel storage with little spare space available for conversion. Modification of existing tanks will be a compromise as the storage capacity for regular sulphur fuel will be reduced.

Lub oil issues

According to Lubmarine, Total?s worldwide maritime lubricants network, despite likely implementation of European regional caps on the sulphur content of marine fuels, ship operators need to remain vigilant when dealing with high sulphur fuels. It points out that despite the new requirements, “there are areas of the world where fuel sulphur content is climbing. Owners and engineers need to pay attention to the possible effects.”

Typical heavy fuels today have a sulphur content of around 3% and owners use BN 70 lub oils, which provide the right alkalinity to match this level. The problem is that as owners adjust to the idea of having to change lub oils to lower BN numbers, with lower alkalinity to cope with the reduced sulphur limits in Europe, they will still have to cope with burning very high sulphur fuels in other areas.

The inevitable conclusion is that at least two grades of lub oil will have to be carried and stored aboard the ship.

The switchover problem

It is believed by Steve Walker that the change over of grade from high to low sulphur fuel oil of the same viscosity is not a problem. The two fuels would require roughly the same heating capacity to achieve injection viscosity. However, changing over from fuel oil to gas oil does raise several potential problems such as thermal shock of the fuel system components. Large slow speed diesel engine fuel pump systems are large pieces of metal designed to contain the extreme pressures of fuel injection.

Introducing low temperature gas oil can cause pump seizure and thermal shock failure of the pump body itself. Introducing gas oil at 40°C into a fuel system that is operating between 135 – 140°C can also cause the system to gas up with the gas oil actually boiling in the system. There is also the more straightforward problem of inability to start an engine after switching the fuel supply.

The result of a machinery breakdown, whatever the cause, could be a loss of engine power or electrical generating power, and thereby vessel manoeuvrability, at the most critical time in any voyage ? when it is entering coastal and highly trafficked waters followed by a port approach. And if this led to a catastrophic grounding or collision, the saving in atmospheric pollution could be far outweighed by the coast and sea pollution that would occur.

Perhaps alternative approaches to reducing air pollution, such as exhaust gas scrubbers, should be actively pursued. And it should be remembered that sulphur is not the only problem since hydrocarbon exhaust can include carbon monoxide and dioxide, nitrous oxides (NOx) and carbon particles which are carcinogenic and which, if less than 10 microns in size, can be inhaled into human lungs.

NYK developing device for removing soot and smoke

NYK, the Japanese shipping giant, has developed, jointly with compatriot company Daiwakogyo, a device using ceramic filters for removing soot and smoke from exhaust gasses of marine diesel engines to protect the marine environment. A patent has been applied for.

This system has been subjected to shipboard performance tests by NYK since February involving passing exhaust gas of an 800kW generator diesel engine through the device on board a NYK-operated pure car and truck carrier. The filter can drastically reduce particulate matter (PM), contained in exhaust gasses, through the dust-collecting ability of ceramic filters and another, unspecified, kind of material. The method of collecting soot is carried out by means of an automatic back-wash system.

In addition to preventing marine air pollution, it is hoped that this device will prevent soot settling on new cars at the loading terminals which is an issue car manufacturers have been unhappy about. The trials onboard the PCTC have confirmed the effectiveness of the new device which produced a 57% reduction in the PM. NYK intends to improve it further for large-scale use suitable for main diesel engines burning marine heavy fuel oil.