Narva Power Plant

Fortum's innovative solution lowers emissions at old power plant

When Fortum got the call to upgrade an unusual Soviet-era power plant to modern standards some thought it was impossible.

The Estonian city of Narva has a rich past. Nestled at the tip of a wide peninsula formed by the Narva River, the city has been variously part of Denmark, the Teutonic Order, Sweden, Russia and independent Estonia. 

In the summer of 2012 engineers were concerned about another piece of Narva’s legacy: the 40-year old power plant. Strict EU emissions regulations would soon come into effect and Eesti Energia needed to bring the plant into the 21st Century. They had already completed a project to lower sulphur dioxide emissions, but now they also needed to drastically reduce nitrogen oxides (NOx).

“Some wondered if it would work at all,” says Kari Lahti, Head of Performance at Fortum Power Solutions. “There was not much data or experience for these types of projects.”

The problem was the Narva plant was old, of an unusual design, and used oil shale as a power source. Oil shale power plants are uncommon, being primarily used in Jordan, America and Estonia. Applying technical solutions to decrease NOx emissions in this environment was a big unknown. 

“There was no experience in applying such technologies to large combustion plants burning oil shale,” says Rain Veinjärv, Development Manager at the Narva Power Plants. “Fortum had extensive experience in implementing flue gas treatment installations in different power plants, but they also did not have any experience in applying such technologies when it came to oil shale. We had to develop a tailor-made solution.”

Tough targets

The Finnish company Fortum has 30 years’ experience in NOx reduction, having provided over 700 burners to more than 10 countries. They were confident they could meet Eesti Energia’s target of reducing NOx emissions to below 200 milligrams per cubic metre.

“We faced similar challenges before,” continues Lahti. “For instance, the burner in Espoo, Finland uses bio-oil made from wood chips. This fuel is very reactive, contains a lot of water and is acidic. That was quite a challenge, but Narva was unique.”

Oil shale contains high calcium, silicon, iron, alkali metals and sulphur. A major issue was ash. The ash was abrasive, corrosive and it also fouled the boiler heating surfaces. These deposits can’t be easily removed by typical soot-blowing cleaning systems and require boiler outages for special cleaning.

The plan was to complete one boiler first, and if that was successful to upgrade the remainder. Fortum’s solution was a two-stage combustion process with an over fire air system, and the plan was to implement it quickly. Narva provides about 90 per cent of the energy for Estonia and downtime would be costly. They intended to complete a boiler in only five weeks.

A big surprise

Local partner Eesti Energomontaaž was brought in for the installations and immediately had their hands full. The plant had been completed in 1973 and was showing its age. The process equipment had poor insulation and working conditions were dusty and hot for the workers in their protective equipment. Despite the difficulties they finished the first boiler and were in for a surprise.

“As the load increased NOx emissions kept coming down,” Lahti explains. “In a normal coal burner it is the opposite: emissions increase as the load increases. But this wasn’t happening here. There were air leakages in the burners at lower temperatures, and when the temperatures increased emissions dropped.”

Delighted with this great news Eesti Energia exercised the option for Fortum to complete the other seven boilers. By February 2016 the massive undertaking was complete. The results exceeded all expectations.

Looking forward

“The de-NOx project was a real challenge to Fortum and Narva Power Plants, with many complicated technical issues to solve while keeping a very tight time schedule,” says Veinjärv. “Fortum has shown a professional approach and their project team provided high quality work and project management services, which fully satisfied us.”

Now the people of Estonia and all over the Baltic can breathe easier, as the old units are well within the most stringent air quality standards. Fortum is more than happy to put the Narva project on their resume.

“There are more combustion-related projects to look forward to,” concludes Lahti. “We have projects ongoing and our expertise is needed. The experience we gained at Narva will support us in the future.”

 Text: David J. Cord

 

FACT BOX
Narva Power Plant
  • 8 X 200 MW units
  • 7 units oil shale combustion – single wall firing, 1 unit CFB boilers
  • Includes retort gas co-firing

The Project

  • Two stage combustion; OFA system
  • SNCR installation for minimum load on first test boiler
  • Urea unloading and storage station
  • Automation for air distribution
  • No need for burner modification
  • Warranty value: NOx lower than 200 mg / cubic metre

8/15/2016