From Standby to Active District Heating Producer – A 40-Year-Old Electric Boiler Revived After Decades

Lappeenrannan Energia Group is committed to developing environmentally friendly and cost-effective energy and water services in the South Karelia region. Lappeenrannan Lämpövoima Oy, a subsidiary responsible for energy and water production, has actively implemented carbon-neutral heat production solutions over the past twenty years, increasingly moving away from combustion. The goal is to become a carbon-neutral energy and water company by 2026.

The Boiler Installed in Lappeenranta

The Mertaniemi 1 gas turbine power plant, located by Lake Saimaa in Lappeenranta, was completed in 1975. In 1982, a 40 MW electrode boiler manufactured by Sulzer (now VAPEC) was installed at the power plant. The electrode boiler was operated at night, while during the day, the gas turbine combined power plant was in use. This routine continued for about ten years until the use of the electrode boiler gradually decreased, eventually becoming occasional. By the 1990s, the boiler was no longer in use. It was decided to preserve the boiler using chemicals, leaving it almost entirely unused.

Occasional test runs and electrical system tests were conducted on the boiler, and its automation was updated during the refurbishment of the Mertaniemi 1 gas and oil boilers. Regulatory inspections were also carried out as required, but eventually, it was found that the safety systems did not meet current standards. As a result, the idea of dismantling the boiler was raised, and justifying its preservation became increasingly challenging.

The Boiler's New Life

However, the boiler was never dismantled and remained out of use until 2021. In 2021, the boiler was brought back into operation in conjunction with the commissioning of Olkiluoto 3, where it served as a system backup for Olkiluoto. In the spring of 2023, the boiler underwent an extended shutdown during which additional safety automation was installed.

Before the boiler was reactivated, a study was conducted to determine whether it would be more cost-effective to acquire a brand-new boiler or modernize the old one. Inspections confirmed that the old boiler and equipment were still in good condition. Before reactivation, inspections were carried out on the pressure equipment, and the availability of spare parts was checked. The district heating exchangers were replaced, and the safety systems were updated. Modifications were made to the periodic operational monitoring, such as adding and replacing instruments, and the electrical circuit breaker was replaced.

The 40-year-old boiler is now back in operation, supplying heat to the district heating network in the Lappeenranta area. The boiler's peak output is 40 MW. In the electrode boiler, the power is adjusted by control rods, which influence the length of the current path between the electrodes.

VAPEC Electrode Boilers from Finess

VAPEC (SULZER) is a Swiss boiler manufacturer. VAPEC electrode boilers are a reliable and emission-free way to produce heat or steam, making them suitable for the efficient production of steam and hot water in district heating and industrial applications. Their long service life and reliability are due to high quality, technical innovations, and annual inspections. As a result, reliability is extremely high, maintenance intervals are long, and maintenance costs are low. The compact design, excellent control features, and high efficiency of VAPEC electrode boilers make them ideal for various applications in energy production and industry.