Arbejdsrapport fra Miljøstyrelsen, 13/2006 – Privat anvendelse af petroleumskoks

Privat anvendelse af petroleumskoks

Summary and conclusions

Origin and utilization

Petcoke is a residue from refineries, where a substantial part of the polluting substances in the crude oil is concentrated. Most remarkable is the high concentration of sulphur, nickel and vanadium, where the concentrations mainly are depending on the concentrations in the crude oil, and to some extend in which refinery-processes it has been treated.

The world petcoke production is more than 60 million tons/year, and most of it is produced at refineries near the coast of North and South America

Cement factories and Power Plants are worldwide the biggest consumers of Petcoke. Some minor consumers are brickyards and for heating purpose in Europe. In addition, special types of petcoke with very low sulphur and heavy metal content are used for production of some sorts of chemicals and graphite anodes for the aluminium smelting industry.

The growing consumption of higher sulphur crude oil, because the supply of low sulphur crude oils is falling, means that the sulphur content in petcoke on average is rising. Most of the worldwide production of petcoke has sulphur content between 2% and 8%. Only a minor part is below 2%, and it is difficult to find petcoke with less than 1%.

Private consumption of petcoke in Denmark

A part of the total Danish consumption of petcoke in residential homes is coming from domestic sales, but the main part is from cross-frontier sales, which is not burdened with Danish duties.

The total sale in Denmark has been made up to app. 8,000 t/year, while the cross-frontier sales cannot be made up very accurately, because no formal registration is going on. A substantial part of the cross-frontier sales is exported from the Danish sellers, and that part can be made up to app. 20,000 t/year. Additionally is a considerable amount, which is imported directly by the German traders. This amount is estimated to be in the range of 5 to 15,000 t/year.

In total the Danish consumption in private homes can be made up to be in the range of 33 to 43,000 t/year. The industrial sector has informed the Danish EPA, that they have estimated the consumption to be around 40,000 t/year.

Property and emissions

Petcoke is not suitable for all sorts of stoves or boilers, as it will burn at a very high temperature. Independent of the size, the firing place must be adapted to the high combustion temperature. Primary combustions air must be injected below the grate, which should be made from cast iron, and firebricks should cover the furnace and it should not be too large. Several stove producers can deliver cast iron grades for firing coke as accessories, and some have it as standard equipment.

The sulphur in petcoke can give smell nuisances, especially when lightning the fire. Additionally, it can give severe corrosion of steel chimneys, and in some cases even in the upper part of the stove.

The emission of SO₂ by using petcoke is very high, because of the high sulphur content. By 1% sulphur in the petcoke, the emission of SO₂ will be 1,300 mg/m³ and by 1.3% it will be 1,700 mg/m³ at standard conditions and 10% O₂ in the flue gas.

Even if most of the households in a stylistic residential quarter solely are using petcoke for heating the houses, a calculation with the OML dispersion model shows that the C-value (the Danish immission limit value) for SO₂ will not be exceeded.

The ash from burning petcoke contains 6-7% nickel, and must be classified as hazardous waste. The municipal regulation for waste generally instructs that ashes should be wrapped and discharged as domestic refuse. The extent of deposition or spreading the ashes in gardens is unknown, but the amount is estimated to be low.

Consequences by fixing the limit for sulphur content to1%

It can be very difficult to provide enough petcoke with less than 1% sulphur, to cover the whole Danish market, including the cross-frontier sale. Increasing prices will undoubtedly be the result of the small supply of petcoke with less than 1% sulphur on the world market. The Danish market can consequently get so uninteresting for the Danish importers and sellers that all trading of petcoke, also from Germany, will stop.

As the present Danish demand for petcoke can be expected to continue, it is assumed, that the cross-frontier sale of the present petcoke with 1.3% sulphur (or higher) might continue to some extent. Without the Danish importers and traders delivering to the German cross-frontier sellers, the sales of petcoke with higher content of sulphur could increase, because it is impossible for the customers to control the sulphur content. Even if the Danish consumption of petcoke is decreased, the total amount of sulphur could be unchanged.

Consequences by a total ban of petcoke

A real ban of petcoke in small stoves and furnaces smaller than 5 MW could be easier to handle. The basis for the German cross-frontier sale of petcoke in bags would totally disappear, because it would be illegal to use in small stoves and furnaces in both Germany and Denmark. It is assumed that the German traders consequently would stop selling petcoke, because no legal market would exist.

Most Danes are expected to observe a ban of petcoke, even if it was still possible to buy it in Germany.

Consumer guidance

Nickel and compounds of nickel are carcinogenic, but it is mostly known as a strong allergenic compound, mainly against women. 10- 15% of all Danish women are allergic to nickel.

The petcoke ash contains 6-7% nickel, and handling can cause severe exposure of nickel. In generally, consumers are not aware of this, as well as they are not aware of the potential corrosion problems that the use of petcoke can cause.

It is recommended to investigate the options for efficient information to the consumers, mainly about the high nickel content in the petcoke ash as well as the connected potential allergic and cancerogenic risk, and secondly about the corrosion problems that the use of petcoke can cause.

A proper labelling directly on the petcoke bags is obvious, and it could be combined with demands for distribution of the same labelling if petcoke is bought in bulk. Such a demand for labelling, which naturally should be carried out by the sellers, is supposed to give enough focus on the problems with petcoke, that even people buying not labelled petcoke in Germany would be aware of the Danish demands for labelling. A consequence of such a labelling could be a declined consumption of petcoke, because some consumers will drop petcoke due to the mentioned risks.

Petcoke substitute fuels

The existing users of petcoke must change to other fuels, if the use of petcoke gets less attractive because of supply problems and rising prises or if it is banned.

Other solid fuels also bought in Germany, e.g. coal, brown coal, coke or anthracite, could replace some of the consumption. These fuels are more expensive and have a lower heating value compared to petcoke, so the overall saving is less by collecting these fuels in Germany. It is expected that a considerable amount of the consumption will be replaced by domestic biofuels, e.g. firewood, wood pellets, corn etc, which also gives a substantial saving compared to oil or natural gas.

Conclusions

A confirmation of the 1% limit for sulphur in petcoke will most likely entail delivery problems and rising prises, and the risk that traders are selling petcoke with too high sulphur content will consequently be increased.

A real ban on the use of petcoke in small stove and furnaces up to 5 MW is expected to end the cross-frontier sales, as such a ban already exists in Germany.

If the limit for sulphur is fixed to 1,3%, the consumption of petcoke is expected to continue at the present level, with a slightly declining tendency.

It is recommended to investigate the options for efficient information to the consumers, mainly about the high nickel content in the petcoke ash, and the connected potential allergic and carcinogenic risk, and secondly about the corrosion problems the use of petcoke can cause. A proper labelling directly on the petcoke bags is obvious, and it could be combined with demands for distribution of the same labelling if petcoke is bought in bulk.