Burning issues in Romania

From internationally-isolated hyper-centralisation under a crackpot communist dictatorship barely ten years ago to a modern liberalised market economy and EU membership. This is the difficult transformation that Romania, population 23 million, currently finds itself embarked upon.

The power generation sector, in particular, is in the throes of major and painful restructuring, the eventual goal being an industry sufficiently liberalised to meet the requirements of the EU electricity directive – a target that is proving difficult enough for some of the longer established market economies to achieve. In Romania, as in other formerly centrally planned economies, manning levels have traditionally been very high (in 1996 the old state power company RENEL had an installed capacity of 22500 MWe and a workforce of no less than 100 000) while changing the entrenched culture is never easy.

With around 50 per cent of thermal power plants more than 20 years old, modernisation and improved competitiveness are priorities. Significant overcapacity in power generation – largely the result of economic problems depressing demand for most of the past decade – means that only the fittest power plants will survive. A number of non-competitive stations have been taken out of operation and those in poor condition will be permanently decommissioned.

Although the process of power plant privatisation has yet to begin, market forces are already making their presence strongly felt in the power plants of Romania.

It was indeed basic economics that was the driver for two recent major upgrade projects at CONEL cogeneration plants in the north-east of Romania.

The plants in question, Suceava (pictured above, during the renovation project) and Iasi II, which provide district heating, process steam and electricity to their local communities and factories, were built in the early 1980s. At that time energy independence rather than cost competitiveness was seen as the key issue, so Romania’s indigenous lignite was the obvious choice of fuel for the two 420t/h, 540°C/137 bar power generation boilers at each site.

But a feasibility study carried out in the mid 1990s showed that switching to world traded hard coal, for example from neighbouring Ukraine, or from Russia, Poland or even South Africa, with its higher heat value (typically 25 MJ/kg) and low moisture, could cut production costs by 30-40 per cent compared with lignite, which has low heat value (6-7.5 MJ/kg) and high moisture.

Transport of the indigenous lignite was by rail, over a distance of 600 km. The envisaged savings from switching to hard coal stem from the anticipated reduction in fuel transport costs and the lower fuel throughput needed with hard coal relative to lignite to achieve the same power output, around 45 t/h of hard coal, compared with 150 t/h of lignite. The lower throughput, in turn, leads to reduced auxiliary power consumption, less man-power and smaller capacity fuel handling and storage facilities, which are currently a very dominant feature of the power plant sites.

There is also scope for reduced slag and ash arisings, with the possibility of closing the existing facilities for handling them.

Typically, the high reactivity of lignite means that only coarse grinding is needed for good combustion. But the high moisture content means that flue gas must be used for drying the lignite before it enters the coal mills. In the original design, therefore, each coal mill was served by a flue gas drying-tower, which is eliminated in the new configuration.

In contrast, the low moisture level of hard coal means that the primary air alone is sufficient for drying. On the other hand the lower reactivity of hard coal compared with lignite means that fine grinding is needed, so new coal mills are necessary.

Another part of the upgrade project was installation of flue gas recirculation. This was needed to keep the heat transfer profile of the boiler as near as possible to the original, despite the reduced amounts of combustion air and flue gas associated with hard coal compared with lignite (again due to the difference in moisture content and heating values).

A further key element of the fuel conversion projects is fitting of RI-Jet low NOx burners, developed by IVO (now Fortum) and originally based on Hitachi technology. Among the main features of these burners are: rapid ignition and devolatilisation of the fuel; high temperature flame, with the high temperature achieved in the early stages of the flame; and fuel-rich inner zone in the flame, with separation of main combustion air from the inner zone, high concentration of hydrocarbons in the inner zone and destruction of NOx by reactions with hydrocarbons. These characteristics produce a stable flame with high combustion efficiency and low NOx .

While the basic physical size and shape of the boilers have remained unchanged, the positions of the burners within the furnaces have been altered as part of the project.

Implementing the projects

The contract for the fuel conversion project was signed with Fortum Engineering in September 1997, with loans from Nordic institutions underwritten by the Romanian government, and early spring 2000 saw commercial handover of the first of the converted boilers at each site, with handover of the second unit at each site scheduled for autumn 2000. The key challenges in the project were the limited space for access and the dismantling of the existing, Romanian-made, equipment.

The conversion project includes modification of the burners and of the evaporators, installation of new coal mills (supplied by BMH Claudius Peters), installation of flue gas recirculation system and installation of related instrumentation and control (Neles hardware/Fortum Engineering software).

Overall, boiler efficiency will increase by 1 per cent. The cost of the fuel conversion projects is around US $15 million per plant and the payback time is estimated at three years.

Using lignite in the old boilers the NOx emissions levels attained were around 538 mg/Nm3. Using hard coal in these boilers would have caused the NOx level to rise by a factor of 2.45, to around 1340 mg/Nm3. However, with the new burners the estimated NOx level with hard coal is reduced to 660 mg/Nm3, well within the current Romanian limit of 800 mg/Nm3. Judging by early experience with the refurbished units, actual performance should be better than these figures, perhaps 350-500 mg/Nm3.

Romanian market opportunities

The Suceava and Iasi II projects will be the first to be completed of several that Fortum Engineering is currently involved with in Romania. The contract for an IBRD/EBRD/EIB financed rehabilitation of Bucharest South units 3 and 4 (2 x100 MWe cogen) was awarded in 1998 to an Alstom-led consortium which includes Itochu and Fortum, the Fortum scope being I&C&E and balance of plant modernisation. In April 1999 a consortium, again consisting of Alstom, Fortum and Itochu, signed a contract for upgrading the Braila plant (210 MWe cogen), with Fortum responsible for I&C&E as well as auxiliary system modernisation. Finally, in December 1999, a Fortum led consortium (again with Alstom and Itochu) won a World Bank financed US $ 65 million contract to rehabilitate a 200 MWe coal-fired unit at Mintia (Deva). Fortum Engineering is responsible for boiler retrofit, new combustion systems, I&C&E and auxiliary system modernisation. The project is due for completion by late 2001.