Fluidized Bed Combustion for Clean Energy

This paper gives a brief overview of the status and prospects for fluidized bed combustion (FBC) for clean energy, with focus on power and heat generation. The paper summarizes recent development trends for the FB technology and makes an outlook into the future with respect to challenges and opportunities for the technology. The paper also identifies areas related to fluidization, which are critical for the technology and, thus, will require research. The main advantage with the FBC technology is the fuel flexibility. A compilation of 715 FB boilers (bubbling and circulating) worldwide illustrates the two main applications for the FBC technology: 1. Small and medium scale heat only or combined heat and power boilers (typically of the order of or less than 100 MW thermal), burning biomass or waste derived fuels, including co-firing with coal and 2. larger (up to 1,000 MWth) power boilers using coal (black coal or lignite) as fuel. Emerging development includes circulating fluidized beds with supercritical steam data (power boilers) with the first project coming on-line in the near future and research on oxy-fuel fired circulating fluidized beds for CO2 capture (O2/CO2 recycle schemes as well as chemical looping combustion). Research needs on the topic of fluidization are mainly related to mixing of fuel, solids and gas, including penetration and mixing of secondary air. The larger the cross section of the furnace, the more critical is the fuel mixing, i.e. this is critical for large power boilers. For small and medium scale FBC boilers burning waste and waste derived fuels, there is also a need to understand fuel and gas mixing in order to be able to lower the excess air ratio and, thus, to increase the efficiency

CO2 emissions abatement in the Nordic carbon-intensive industry – an end-game in sight?

Analysing different future trajectories of technological developments we assess the prospects for Nordic carbon-intensive industries to significantly reduce direct CO2 emissions in the period 2010–2050. This analysis covers petroleum refining, integrated iron and steel production, and cement manufacturing in the four largest Nordic countries of Denmark, Finland, Norway, and Sweden. Our results show that the implementation of currently available abatement measures will not be enough to meet the ambitious emissions reduction targets envisaged for the Year 2050. We show how an extensive deployment of CCS could result in emissions reductions that are in line with such targets. However, large-scale introduction of CCS would come at a significant price in terms of energy use and the associated flows of captured CO2 would place high requirements on timely planning of infrastructure for the transportation and storage of CO2. Further the assessment highlights the importance of, especially in the absence of successful deployment of CO2 capture, encouraging increased use of biomass in the cement and integrated iron and steel industries, and of promoting the utilisation of alternative raw materials in cement manufacturing to complement efforts to improve energy efficiency

Managing the costs of CO2 abatement in the cement industry

This article investigates how the costs associated with deep reductions in CO2 emissions from the cement industry will influence the costs across the entire value chain from cement production to the eventual end-use, in this case a residential building. The work is motivated by the substantial difference between the pricing of CO2 emissions and the costs of mitigation at the production sites of energy-intensive industries, such as cement manufacture. By examining how CO2 trading and investments in low-carbon kiln systems affect costs and prices further up the supply chain of cement our analysis provides new perspectives on the costs of industry abatement of CO2 and on the question of who could or should pay the price of such abatement. The analysis reveals that the cost impacts decrease substantially at each transformation stage, from limestone to final end-uses. The increase in total production costs for the residential building used as the case study in this work is limited to 1%, even in the cases where the cement price is assumed to be almost doubled. Policy relevance With the price of emission allowances under the EU Emissions Trading System (EU ETS) currently far below the levels required to unlock investments in low-CO2 production processes in carbon-intensive industry (i.e. petroleum refining, iron and steel production and cement manufacturing), this article seeks to pave the way for a discussion on complementary policy options. The results from this study, using the supply of cement and concrete to a residential building as a case study, suggest that because cement and concrete typically account for a limited proportion of the total cost of most construction and civil engineering projects, a policy scheme designed to allocate more of the costs of CO2 abatement to the end-users (of cement) would neither (significantly) alter the cost structure nor (dramatically) increase overall project costs

Material Requirements, Circularity Potential and Embodied Emissions Associated with Wind Energy

Wind energy, which is often posited as a key decarbonisation option, represents one of the fastest-growing energy sources globally in recent years. Research on the material requirements for transitioning to a low-carbon electricity system at national levels, as well as research exploring the potential of the electricity system to serve as a source of secondary materials remains underexplored. We address these gaps in the knowledge by analysing the stocks and flows in a wind power system towards 2050 using Sweden as a case study, including the demands for bulk (concrete and steel) and critical materials (neodymium and dysprosium), through a dynamic material flow analysis based on policy-relevant scenarios. We demonstrate that some of the investigated scenarios generate substantial increases in the stocks and flows of bulk and critical materials. We show that, after 2045, the year by which Sweden has committed to reducing greenhouse gas emissions to net-zero, the inflows show a decreasing trend while the outflows show an increasing trend, suggesting the beginning of the closing of the material loops, provided untapped circularity potentials transform into actual capacities. For wind power to comply with emissions targets, the steel and concrete production processes will need to be decarbonised at a rate in line with the climate targets. We show that the adoption of mitigation measures to decarbonise the concrete and steel industries aligned with Sweden\u27s climate change mitigation agenda, has the potential to reduce embodied carbon emissions for wind power infrastructure in 2045 from corresponding to around 4 % of current total national emissions in the absence of measures to practically negligible levels. National policies need to focus on promoting the implementation of circularity strategies and decarbonising the entire value chain of the involved materials

Modeling Fuel Mixing in a Fluidized Bed Combustor

This paper presents a 3-dimensional model for fuel mixing in fluidized bed combustors. The model accounts for the mixing patterns experimentally shown to govern the mixing in the different zones of the riser and the return leg and can be applied both under bubbling and circulating regimes. Thus, the semi-empirical basis of the model was previously validated in different large-scale fluidized bed combustors and is combined with a model for fuel particle conversion to obtain the fuel concentration. Results obtained with the model are compared with experimental data from the Chalmers 12 MWth CFB combustor, yielding reasonably agreement

The BECCS Implementation Gap–A Swedish Case Study

The IPCC has assessed a variety of pathways that could still lead to achievement of the ambitious climate targets set in the Paris Agreement. However, the longer time that climate action is delayed, the more the achievement of this goal will depend on Carbon Dioxide Removal (CDR) technologies and practices. In the models behind these pathways, the main CDR technology is Bioenergy combined with Carbon Capture and Storage (BECCS). We review the role that BECCS could play in reaching net-zero targets based on the existing 1.5\ub0C scenarios. Such scenarios presented in the literature typically have BECCS at a GtCO2 per year scale. We also assess the potentials and obstacles for BECCS implementation at the national level, applying Sweden as a case study. Given that BECCS deployment has scarcely started and, thus, is far from capturing 1 GtCO2 per year, with lead times on the scale of multiple years, we conclude that there will be a large implementation gap unless BECCS development is immediately intensified, emissions are reduced at a much faster pace or removals realized through other CDR measures. In the national case study, we show that Sweden has favorable conditions for BECCS in that it has large point sources of biogenic emissions, and that BECCS has been identified as one potential “supplementary measure” for reaching the Swedish target of net-zero emissions in 2045. Yet, work on planning for BECCS implementation has started only recently and would need to be accelerated to close the implementation gap between the present advancement and the targets for BECCS proposed in a recent public inquiry on the roles of supplementary measures. An assessment of two ramp-up scenarios for BECCS demonstrates that it should in principle be possible to reach the currently envisaged deployment scales, but this will require prompt introduction of political and economic incentives. The main barriers are thus not due to technological immaturity, but are rather of a socio-economic, political and institutional nature