The possibilities to implement bio-CCS and CCS at Högdalenverket : A case study about four different carbon capture technologies and their compatibility at Högdalenverket with regards to technical, economical, environmental and energy related aspects

Increased carbon dioxide in the atmosphere has raised the attention to Carbon Capture and Storage (CCS). Stockholm Exergi is a company conducting research on CCS and bio-CCS, a form of CCS where biogenic CO2 is captured. This master thesis analyzed the possibilities to implement CCS and bio-CCS at Högdalenverket, one of Stockholm Exergi’s combined heat and power plant with waste incineration. The aim was to investigate advantages and disadvantages with different carbon capture technologies (CC technologies) considering technical, economical, and energy related aspects. Industrial and household waste are incinerated in four boilers at Högdalenverket. Two cases were analyzed, one case with all boilers connected to the CC technology and one case with the boiler with the highest degree of CO2 emission connected. The CC technologies taken into consideration were amine technology, Hot Potassium Carbonates (HPC), Compact Carbon Capture (3C), and Svante. Amine technology and HPC use chemical absorption in static columns. The Amine technology is the most investigated and used one. It uses temperature swing absorption with amines as absorbent. HPC uses pressure swing absorption with potassium carbonate as absorbent. The remaining two are new process intensified technologies. 3C uses rotating packed beds and absorbs CO2 chemically using, most commonly, amines. Svante also uses a rotating technique by chemically adsorbing CO2 with nanomaterial as the solid adsorbent. All CC technologies need steam to regenerate CO2. The steam was assumed to be extracted from the existing steam network at Högdalenverket with a pressure and temperature of 36 bar and 400 degrees. The method used in the study was mainly literature review with peer reviewed articles regarding CCS as base. It was of importance to analyze how the flue gases could affect the CC technologies since the waste has an inhomogeneous composition. The flue gas composition was compiled using external and internal measurements from 2019 and 2020. Furthermore, energy and power calculations were performed to investigate how the heat and electricity delivery would be affected if the different CC technologies were implemented. Moreover, economic calculations regarding the cost for heat and electricity were carried out. Two interviews were also conducted, one with a CCS consultant company and one with internal staff at Högdalenverket. According to the literature review, O2, SO2, and NO2 appeared to be the pollutants causing highest risk of solvent degradation in the flue gases. The high O2 content at Högdalenverket could cause oxidative degradation, especially in amine technology. The SO2 and NO2 content in the flue gases was mainly low and would therefore not significantly affect the technologies. Peeks with high content did however occur and amines, especially within the amine technology, could form toxic and cancerogenic nitrosamines with NO2 which should not be released to the atmosphere. The flue gas composition proved not to be the limiting factor for implementation of CC technology on all incinerators. However, it is costly and complex to handle the variations in flue gas flow which can occur when all boilers are used. The technologies showed high need of heat and electricity which would result in significant reductions in delivery from Högdalenverket. The need of heat and electricity would in turn lead to high operating costs. The Amine technology showed the greatest influence on the heat delivery due to the significant steam requirement to regenerate CO2. HPC showed extreme influence on the delivery of electricity due to the flue gas compression needed in pressure swing processes. Both technologies consist of high columns with significant degree of land use which would be difficult to implement within the limited area at Högdalenverket. As a result of these aspects, HPC and Amine technology are not considered to be suitable technologies to implement at Högdalenverket. However, the master thesis presented measures for energy saving that should be considered before excluding the technologies. One energy saving measure is to find the optimal heat recovery, for example by pinch-analysis. Moreover, composition, concentration, and flowrate of the absorbent can be analyzed. In addition, higher columns are associated with lower need of energy. Finally, modifications of the capture process can be investigated, and one example is to split the flow of the absorbent into two streams into the columns. 3C and Svante are compact technologies that require less land and have potential to fit at more locations at Högdalenverket. The compact design also leads to 50 percent less investments costs compared to the other two technologies. Moreover, these technologies are presented as more resistant against degradation of sorbents, and both requires less energy to regenerate CO2. These technologies are therefore more suitable for implementation at Högdalenverket. A drawback is that they are not yet commercially developed, they are only located at 6-7 at the TRL-scale. TRL stands for Technology Readiness Level and implies how developed the technology is. The scale ranges from one to nine where nine means that the technology is commercially developed. Today, there are no economic incentives for the biogenic part of the CO2 emissions. However, there are investigations ongoing to create a market and economic incentives for the bio-genic part, one of the suggestions is reversed auctions. It is important to investigate methods to reduce the technologies need of heat and electricity, e.g., by finding other ways to extract steam instead of using steam with high exergy. Reducing the need of energy is important in the view of cost reduction, but also to avoid potential transfer of emissions to fossil CO2 generating production. The losses of heat and electricity generation that occur when implementing a CC technology need to be replaced. This replacement could end up being production from fossil fuels if no other options are available. Another aspect that needs to be considered is the suitability of using amines to a greater extent since it could cause serious environmental and health issues