Biomass driving down heating costs
In 2012, Lithuanian district energy provider AB Kauno Energija embarked on an ambitious renovation, conversion and expansion investment programme. Celebrating over 50 years of service to Kaunas, the second largest city in Lithuania, the company has managed to reduce consumer prices to amongst the lowest in the country. Changes in national legislation have encouraged increased heat competition and energy efficiency, reduction of distribution losses and a switch to biomass fuel.
Originally founded in 1963, present-day AB Kauno Energija was formed in 2000 and it is majority-owned by Kaunas City Municipality. The company produces, supplies and distributes heat to consumers in Kaunas and Jurbarkas cities and different settlements in the Kaunas region via a number of separate heating networks. Over five decades the company and networks have grown from just over 8 km to over 450 km.
Legislative changes facilitate investment
As expected the single largest heat network, over 405 km, is the Kaunas integrated city network. However a unique situation for the municipal utility in Lithuania, indeed perhaps an unusual situation anywhere, is that Kauno Energija does not have a monopoly on heat production for this network. In fact, until 2012, the company was obligated to purchase at least 80 percent of the heat consumed in the city’s integrated heat network from UAB Kauno
In fact, until 2012, the company was obligated to purchase at least 80 percent of the heat consumed in the city’s integrated heat network from UAB Kauno termofikacijos elektrinė (KCHP), a 170 MW electric capacity gas-fired combined heat and power (CHP) plant in the city. In 2012, Kauno Energija produced slightly more than six percent of the heat supplied to the integrated city network. In addition, over 92 percent of its own heat production used imported fossil gas as fuel.
In 2012, Kauno Energija proposed a draft set of rules, reputedly the first of its kind in Europe, which described in great detail the current and planned requirements for the connection of independent heat producers to a district heat supply network as well as the principles, methods and processes for the sale and purchase of heat.
The heat purchase obligation with KCHP was subsequently abolished in 2012, though heat is still bought from the company on the open market. Together with changes in national legislation allowing independent heat producers to compete on heat production, favourable conditions for investing in the construction and modernisation of heat production plants emerged.
By the end of 2012 three new independent heat suppliers, each having built new biomass-fired heat plants entered the Kaunas heat production market. Kauno Energija too embarked on an ambitious LTL 192.4 million (≈ EUR 56 million) investment programme, partly funded with European Union (EU) structural funds, for the period 2012-2015. The objective of its programme is to ensure fail-safe heat supply, increase the share of renewables in the company’s heat production to at least 23 percent by 2020, expand the district heat market and its own relative share.
Biomass heat capacity added
By the end of 2014, Kauno Energija had spent some LTL 143 million (≈ EUR 42 million) in numerous network refurbishment and boiler replacement projects, including 72 MW of new biomass heat capacity for the integrated city network.
Two new hot-water boilers, 8 MW and 10 MW, with a 4 MW condensing economiser for its Šilkas heat plant, two new 8 MW hot-water boilers and a 4 MW condensing economiser for its Inkaras heat plant, and finally two 12 MW hot water boilers with a 6 MW condensing economiser for its Petrašiūnai power station reconstruction.
Together these plants provide the company with the capacity to supply up to 25 percent of the heat demand for this network in an average heating season.
Reduced operating costs
The results thus far have been significant, radically changing the Kaunas heat market while lowering prices to heat consumers who paid an average of 23.10ct/kWh excluding VAT in 2014. This is a 14.5 percent decrease compared to 2013, placing Kaunas on the second lowest rate in Lithuania in 2014.
Last year the company produced over 21 percent of the total heat supplied to all networks, up 80 GWh on 2012, purchasing just over 1 TWh heat from eight independent producers including KCHP, still the dominant supplier. Kauno Energija more than doubled its heat share to the integrated city network, from just over 6 percent in 2012 to 16 percent in 2014.
Furthermore although fossil gas is still the main fuel, its share dropped to 71 percent having been replaced by cheaper solid biomass and a fraction of biogas and peat.
Other benefits include a reduction in fuel and electricity consumption per MWh heat produced, a reduction in heat losses in the distribution networks and an over 11 percent reduction in the amount of water needed to supplement the network. More GWh of their own heat was supplied but at a lower rate. The decrease in the comparable expenses has led independent producers of heat, from which the company buys and distributes the heat to the consumers, to reduce the cost of sold heat.
All of these add up to almost 27 percent reduction in operating costs compared to 2013, increasing the profitability of the company despite a 22 percent drop in revenue from heat sales.
Local biomass technology
One of the key suppliers to the various biomass boiler projects is a local company, Kaunas-based combustion technology specialist Enerstena Group. Founded in 2002 the company has grown into a major developer and manufacturer of biomass combustion and ancillary solutions. Deliveries include turnkey plants to some of the independent heat producers in Kaunas but also to industrial heat and steam applications in countries like Latvia and France.
One of the larger installations for Kauno Energija was the Petrašiūnai power plant conversion that started in 2013. Built on the banks of the Nemunas River and commissioned in 1930, it is one of the oldest power plants still operating in Lithuania.
It is, reportedly, the first cogeneration unit in the country – in 1947 steam from the plant was used for space heating in neighbouring industrial buildings. Run on fossil gas the 60.5 MW electric capacity Petrašiūnai plant has in more recent years been the main reserve heat generation source for the Kaunas integrated heat supply network. It is also the point where fresh water from the river is drawn to top up the network.
At Petrašiūnai, Enerstena first installed a flue gas condenser for the remaining 100 MW gas boiler. This was followed by the installation of two 12 MW woodchip fired hot water boilers with a 6 MW condensing economiser.
A practical legacy from the Soviet era, industrial buildings were built with future expansion in mind so there is plenty of space to maneuver, commented Nerijus Rinkevičius, Vice Director, Enerstena Research & Development Center, during a visit to the plant pointing out where the two boiler units were literally dropped into place through a hole in the wall.
Enerstena also provided the boiler infeed, woodchip fuel receiving bunkers and renovated a railway spur.
– As far as I know, this is the only biomass heat plant in the country that can receive and unload woodchips by rail, said Rinkevičius.
Designed by the R&D arm of Enerstena in cooperation with the Kaunas University of Technology, the combustion furnace has an oblique moving grate with a water-cooled frame and it is designed to handle biomass with a moisture content of up to 55 percent. To ensure complete combustion the process is continuously monitored and adjusted using CO and O₂ levels in the flue-gas as guidelines. Access doors and hatches with covers are mounted on all sites where the operation, maintenance or repair of the furnace may be necessary.
– The design of the furnace allows for a substantial improvement of the combustion process and provides a competitive advantage to our company and its clients, said Nerijus Rinkevičius, adding it received Gold Medal as Lithuanian Product of the year in 2012.
Installed vertically the two boilers are of a flue-tube type with three courses. They are equipped with an automated pneumatic soot cleaning system as well as maintenance hatches and inspection openings allowing for more efficient operation, a unique feature according to Enerstena. The stainless steel economiser is a shell and tube heat exchanger of condensing type.
– When using stainless steel economisers, heat production can be substantially increased with the combustion of the same amount of fuel in the boiler. Due to deep cooling of the flue gas and the condensation of water vapour, the economiser recovers up to 20–30 percent of additional heat, said Rinkevičius.
The higher the moisture content of the fuel, the higher performance of the economiser. This is due to a large portion of the combustion heat used to evaporate moisture from the fuel being recovered.
Before excess condensate from the condenser can be discharged to the municipal wastewater treatment system it needs to be pre-treated to remove particles and adjust the pH. Firstly the pH is adjusted, by adding an acid or alkaline solution, to pH 6.5-6.8. After neutralisation, a coagulant agent is added to coagulate small particles into larger ones. The coagulated particles are then flocculated using a flocculent agent, preparing the condensate for filtration to remove the particles.
This is achieved by using a laminar flow filter “Lamella” designed by Enerstena. To maintain the uninterrupted operation of the condensing system, and to increase the heat transfer efficiency, the treated and filtered condensate is recirculated back into the system with only the excess discharged. This eliminates the need to use additional cold water in the condensate treatment system.
This article was first published in Bioenergy International no. 5-2015. Note that as a magazine subscriber you get access to the e-magazine and articles like this before the print edition reaches your desk!
About Kauno Energija and Enerstena
Founded in 1963 and owned by the city of Kaunas, AB Kauno Energija has a total installed capacity (2014) of 496.08 MW thermal and 8.75 MW electric. Serving over 111 000 household consumers and 3 500 businesses and organisations in Kaunas city and region, it supplies heat, hot-water and electricity. The company maintains and operates over 405 km of district heat networks.
Founded in 2002 Enerstena Group is one of the largest energy companies in the Baltic countries. The group consists of four companies, that between them cover the design and manufacture of biomass boilers, ﬂue gas condensers, furnaces and other technological equipment for biomass boiler plants, consultancy and trade of industrial equipment for energy and industrial objects, process automation and provides heat services to the town of Alytus.