The heavy fuel oil scare

Malta’s power stations have been running on heavy fuel oil for over 70 years but most people got to know of its existence only recently, when it was described by the opponents of the Delimara power station extension as a scary fuel which, if used at the new plant, will cause grievous damage to health and the environment.

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Opposition journalists combed the internet to find references on its hazardous nature, one going so far as quoting the Material Safety Data Sheet, a document that contains information for the safe handling, use, storage and disposal of potentially hazardous chemicals. The journalist highlighted the fact that the MSDS described the fuel as toxic. But he omitted to say that it is also unsafe to drink diesel or inhale natural gas!

Only a minority of power stations in Europe use fuel oil (the exception is Italy). The predominant fuel is coal, though the use of natural gas has increased in recent years. The reason for this is that these are the cheapest fuels.

Malta has experimented with the use of coal for some years but its location at Marsa and the storage method used were clearly unsuitable and the amount of dust generated forced the boilers to be converted to the use of HFO within a short time.

Malta had also an opportunity to change over to natural gas but the project happened at a time of political instability and was left to lapse.

Unfortunately, turning back the clock has proved to be very difficult.

But what is actually HFO?

Known by various other names (residual oil, Bunker C, or No. 6 diesel), it is derived from crude oil, which is processed at the refineries to separate the various “fractions”. After extracting petrol, diesel, jet fuel and the other components used in transport or industry, the residue is HFO. This is, by its nature, the cheapest refinery product and special methods need to be employed to burn it and to control its emissions.

Since power stations are large and use huge amounts of fuel, it is economical for them to install sophisticated combustion and exhaust gas cleaning equipment rather than use expensive refined fuels that burn more readily.

HFO is a black treacly liquid that doesn’t burn easily. In fact, it has to be heated to a high temperature before it is injected into the burners on power station boilers or diesel engines.

Transportation through pipes is also difficult and, unless the pipelines are heated, there is the danger of the oil solidifying and blocking the pipework.

For these reasons, HFO is not used in small industrial boilers and ships. It is only in power stations and in very large ships or industries that HFO is used.

HFO comes in various grades. These depend on the crude oil used as a source and of the refinery processes that remove the other fractions. Up to the 1970s, the refineries used straight fractional distillation to extract the lighter fractions but, since then, various other processes have been employed to maximise the amount of transport fuels by converting more of the crude using thermal and catalytic processes. This has led to a deterioration in the quality of the residual oil.

This does not mean, however, that all refinery residues are acceptable for use in power stations. In fact, power stations only purchase fuel oils that meet certain minimum specifications. These include physical quantities such as viscosity, specific gravity and calorific value, and also maximum quantities of impurities such as sulphur, lead, nickel, vanadium, etc. Exceeding these limits would result in pollution or damage to the combustion plant.

Sulphur is the major constituent of these impurities and fuel oil is marketed in various grades depending on the amount of sulphur in it.

Burning fuel containing sulphur will cause the emission of sulphur dioxide in the air, causing respiratory troubles and acid rain. This has been recognised by the European Union and other countries and, as far back as 1987, there have been restrictions on the use of high sulphur fuels together with the mandatory use of sulphur removal plant in power stations, cement kilns, waste incinerators, ships, and other users of large amounts of fuel.

Prior to Malta’s entry in the EU, the power stations used fuels with 3.5 per cent sulphur content. This high amount caused distress and protests in the Marsa area, with episodes of schools in the vicinity closing down because of the unbearable smell. The protests stopped when Malta joined the EU and converted to one per cent sulphur oil in accordance with European legislation. With the further tightening of EU limits, the maximum limit of sulphur in imported fuel oil was lowered to 0.5 per cent.

European environmental limits are progressively revised and the limits for new plant are more rigid than that for existing plant. For this reason, the new plant at Delimara, besides using low sulphur fuel, has to be equipped with gas cleaning equipment that removes sulphur dioxide from the power station exhaust gases. Other equipment removes NOx (nitrogen oxides) and dust particles.

So the new plant will be decidedly cleaner than the rest of the Delimara power station and out of all comparison with the Marsa plant as we know it.

So why all this fuss?

Using diesel oil will remove the need for sulphur dioxide cleaning plant and dust filters and, in fact, it is known that, in the event of malfunctions in the gas removal plant, the new plant will temporarily change over to the use of diesel fuel. Diesel is a refined fuel and is comparatively expensive, so using it instead of HFO would probably increase our electricity bills by some 30 per cent.

Using diesel would only bring marginal improvement at a high price. I have my doubts whether natural gas will ever be economical as the huge investment is only worthwhile if used in large quantities.

The cable connection to Italy also needs to operate at a high load factor to be economical, so it’s either a cable connection or a gas pipeline, not both, especially with Enemalta’s bad financial situation. Thus, I think it will be HFO for a long time.

In the past, the government persisted in the use of high sulphur fuel in order to keep its promise of low electricity rates (a wrong policy, in my opinion). We now have a taste of what high electricity rates are. The public cannot afford the luxury of using fancy fuels when, thanks to EU emission regulations, sufficient safeguards now exist to ensure the safety of using HFO.

An engineer, the author is a former manager generation with Enemalta.