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Stockholm Exergi to test carbon capture at Värtan bioenergy plant

Stockholm Exergi AB, the energy utility joint venture (JV) between the Swedish capital city and the Finnish energy major Fortum Oyj has revealed that it will install a carbon capture test facility at its biomass-fired KVV8 unit at Värtan combined heat and power (CHP) plant in Stockholm."The goal is that all Stockholmers should be able to take a hot shower and know that they simultaneously remove carbon dioxide from the atmosphere," said Erik Dahlén, R&D manager at Stockholm Exergi.

Stockholm Exergi will install a carbon capture test facility at its biomass-fired KVV8 unit at its Värtan combined heat and power (CHP) plant in Stockholm, Sweden.

Dubbed Bioenergy Carbon Capture and Storage (BECCS), the technology enables the capture of carbon dioxide (CO2) from the biomass fuel in the post-combustion flue gases. The CO2 is compressed into liquid form and stored in underground rock formations.

During 2019, Stockholm Exergi will install a test facility at its biomass-fired combined heat and power (CHP) plant KVV8 in Värtan. It is a step towards creating a so-called carbon sink in Stockholm.

We already know that the technology works and we know about how much it costs. Now we are launching a project where we will investigate all other necessary details in order to be able to make a decision on a pilot plant on an industrial scale or a full-scale plant, said Erik Dahlén.

Hot Potassium Carbonate

Stockholm Exergi will install a test facility during autumn 2019 and then start an eight-month test programme. Space has been prepared on top of the roof of KVV1 at the Värtan complex, where the test rig needs to be placed in order to be able to extract flue gases that are led away from the KVV8 unit.

The detailed test programme prepared for the start will include both practical tests and analyzes as well as simulations in calculation programmes. The test programme has plans to include a complete set of operating cases, optimization of efficiency and a larger spectrum of modeled and simulated possibilities subject to grant support from the Swedish Energy Agency.

Following a technology and supplier screening that was completed in January 2019, Stockholm Exergi has chosen a technology called Hot Potassium Carbonate (HPC), which the company says best meets the requirements for a plant located at Värtan. This includes high energy efficiency, siting requirements, high availability, the possibility to scale up to full scale, environmental impact and low risk.

BECCS feasibility study

Stockholm Exergi is currently conducting an in-depth feasibility study, concerning a BECCS plant located at Värtan’s unit KVV8. With support from the Swedish Energy Agency, the feasibility study aims to show how a BECCS plant should be placed, designed and integrated to function at Värtan.

A BECCS plant, regardless of technology, is energy-intensive thus the reuse of excess heat within the CHP process at Värtan would be a key advantage. This integration will be one of the most important issues to investigate in the feasibility study.

We are convinced that it works, but we need answers to many questions about how we do it in the best way with flue gases from KVV8. For example, we want to know how we optimize the plant, how the intended absorbents, catalysts and additives are affected by many operating hours, explained Erik Dahlén.

Stockholm Exergi’s calculations show that there is the potential to capture 800 000 tonnes per annum of CO2 from KVV8 at Värtan. Looking at the whole of Stockholm including the heat and power production from other companies, the potential is estimated to be around 2 million tonnes annually.

Carbon sinks are needed partly because countries with a greater dependence on fossil fuels are unable to achieve a sufficiently rapid changeover, partly because developing countries need space to increase their welfare. After the technology and supplier screening we carried out, we can conclude that there are suppliers who can deliver this technology and leave guarantees, but what we plan to do at KVV8 is nonetheless unique in the world. We are among the very first in the world to install carbon capture at a biomass-fired combined heat and power plant, explained Fabian Levihn, System Development, Stockholm Exergi.

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