Using recovered heat for the district heating network

Project Description

The city of Sundsvall has a well-established district heating network. Hot water is distributed by Sundsvall Energi AB to private and commercial consumers by a 300 km pipe network. In 2006, heat from flue gas originating from steam production was recovered and delivered to the district heating network. In 2013 SCA and Sundsvall Energi AB built on their relationship with an initiative aiming at increasing delivery of hot water from SCA based on renewable energy, thereby reducing consumption of heating oil and emissions of carbon dioxide.

Project Purpose

Prior to this investment, district heating was heavily dependent on fossil fuels. It had also become obvious that Sundsvall Energi AB needed to increase its capacity to ensure it met customer needs. The goal of the BioCoop project was thus to reduce consumption of heating oil and to offer district heating based on renewable sources, as well as avoiding a very costly investment to convert the Sundsvall Energy AB boiler from oil to biofuel. The capacity increase was achieved by:

a. Installing two new condensers and redesigning two of the existing boilers at Ortviken paper mill: Wood powder burners were installed, improved flue gas cleaning was achieved by complementing and upgrading the electrostatic precipitators and a plant for processing wood pellets into wood powder was built. The design capacity was 60 MW.

b. Utilising recovered secondary heat from SCA Östrand pulp mill with a new 10 km district heating pipe connected to Sundsvall Energi AB.

The two projects provide a potential reduction of CO2 emissions by 73,000 tonnes per year, of which 13,000 tonnes originate from replacing oil with wood pellets for internal steam production at the Ortviken paper mill.

Project Evaluation

Since the launch in 2014, in addition to the 100 GWh of recovered heat based on flue gas, 120 GWh per year based on renewable energy has been delivered by SCA Ortviken paper mill and SCA Östrand kraft pulp mill to the district heating network. Sundsvall Energi AB has reduced its emissions of fossil CO2 by approximately 35,000 tonnes per year. CO2 emissions by the Ortviken paper mill have been reduced by 15,000 tonnes per year, or 65%, compared to the years 2004 to 2013.

Per Asplund

Manager of Projects and Engineering at Ortviken and Östrand mills

“The capital cost for converting the municipal oil boiler far exceeded the cost of new equipment and conversion at the mills, so the project offered a much more attractive solution for all parties. We have biomass within our own business loop – giving us better control over supply, quality and costs. Most of the wood pellets fuelling the Ortviken boilers are produced at SCA’s pellet plant about 40 km away. To get a flying start on the project, we began the site preparation in advance of the decision. We had the advantage of previous experience from 2011, when a new lime kiln fired by wood powder was installed at the Östrand paper mill. We basically copied the Östrand design so we could get started on pre-fabrication, meaning it took less than one year from the decision to the launch of operations.”

Main Features:

CO2 Emissions saved (tCO2)

50,000 tonnes/year

Investment SEK

500 million (Sundsvall Energi AB, kr 100 million; SCA Östrand pulp mill, kr 60 million and SCA Ortviken paper mill, kr 340 million)

Partnerships

Sundsvall Energi AB, SCA Östrand pulp mill and SCA Ortviken paper mill