Instantaneous Capture and Mineralization of Flue Gas Carbon Dioxide: Pilot Scale Study

Multiple CO2 capture and storage (CCS) processes are required to address anthropogenic CO2 problems. However, a method which can directly capture and mineralize CO2 at a point source, under actual field conditions, has advantages and could help offset the cost associated with the conventional CCS technologies. The mineral carbonation (MC), a process of converting CO2 into stable minerals (mineralization), has been studied extensively to store CO2. However, most of the MC studies have been largely investigated at laboratory scale. Objectives of this research were to develop a pilot scale AMC (accelerated mineral carbonation) process and test the effects of flue gas moisture content on carbonation of fly ash particles. A pilot scale AMC process consisting of a moisture reducing drum (MRD), a heater/humidifier, and a fluidized-bed reactor (FBR) was developed and tested by reacting flue gas with fly ash particles at one of the largest coal-fired power plants (2120 MW) in the USA. The experiments were conducted over a period of 2 hr at ~ 300 SCFM flow-rates, at a controlled pressure (115.1 kPa), and under different flue gas moisture contents (2-16%). The flue gas CO2 and SO2 concentrations were monitored before and during the experiments by an industrial grade gas analyzer. Fly ash samples were collected from the reactor sample port from 0-120 minutes and analyzed for total inorganic carbon (C), sulfur (S), and mercury (Hg). From C, S, and Hg concentrations, %calcium carbonate (CaCO3), %sulfate (SO42-), and %mercury carbonate (HgCO3) were calculated, respectively. Results suggested significant mineralization of flue gas CO2, SO2, and Hg within 10-15 minutes of reaction. Among different moisture conditions, ~16% showed highest conversion of flue gas CO2 and SO2 to %CaCO3 and %SO42- in fly ash samples. For example, an increase of almost 4% in CaCO3 content of fly ash was observed. Overall, the AMC process is cost-effective with minimum carbon footprint and can be retrofitted to coal fired power plants (existing and/or new) as a post-combustion unit to minimize flue gas CO2, SO2, and Hg emissions into the atmosphere. Used in conjunction with capture and geologic sequestration, the AMC process has the potential to reduce overall cost associated with CO2 separation/compression/transportation/pore space/brine water treatment. It could also help protect sensitive amines and carbon filters used in flue gas CO2 capture and separation process and extend their life

Partial carbon capture – an opportunity to decarbonize primary steelmaking

Climate change requires that all energy-related sectors drastically reduce their greenhouse gas emissions (GHG). To have a high likelihood of limiting global warming to 1.5\ub0C, large-scale mitigation of GHG has to start being implemented and cause emissions to fall well before Year 2030. The process industry, including the iron and steel industry, is inherently carbon-intensive and carbon capture and storage (CCS) is one of the few options available to achieve the required reductions in carbon dioxide (CO2) emissions. Despite its high technological maturity, CCS is not being implemented at the expected rates due inter alia to the low value creation of CCS for process industries, which is often attributed to uncertainties related to carbon pricing and the considerable investments required in CO2 capture. This thesis deals with the concept of partial carbon capture, which is governed by market or site conditions and aims to capture a smaller fraction of the CO2 emissions from an industrial site, thereby lowering the absolute and specific costs (€ per tonne CO2) for CO2 capture, as compared to a conventional full-capture process. Depending on the scale and market conditions these savings hold true especially for a process industry that has large gas flows with concentrations of CO2 ≥20 vol.% and access to low-value heat. Integrated steel mills typically fulfill these conditions.The value of partial capture for the steel industry is assessed in a techno-economic study on the separation of CO2 from the most carbon-intensive steel mill off-gases. The design for partial carbon capture using a 30 wt.% aqueous monoethanolamine (MEA) solvent is optimized for lower cost. Powering the capture process exclusively with excess heat entails a cost of 28–35\ua0(\ub14)\ua0€/tonne CO2-captured and a reduction in CO2 emissions of 19%–\ua043% onsite, depending on design and CO2 source. In contrast, full capture requires external energy to reduce the CO2 site emissions by 76%, entailing costs in the range of 39–54 (\ub15) €/tonne CO2-captured. Furthermore, the use of excess heat has impacts on the cost structure of partial carbon capture, i.e., increasing the ratio of capital expenditures to operational expenditures, as well as on the relationship between carbon and energy intensity for primary steel as an industrial product.The present work concludes that near-term implementation of partial carbon capture in the 2020s will be economically sustainable if average carbon prices are in the range of 40–60 €/tonne CO2 over the entire economic life-time of the partial capture unit (ca. 25 years). Once implemented, partial capture could evolve to full capture over time through either co-mitigation (e.g., with biomass utilization or electrification) or efficiency improvements. Alternatively, partial capture could act as a bridging-technology for new, carbon-free production. In summary, partial carbon capture is found to be readily available and potentially economically viable to initiate large-scale mitigation before Year 2030. Partial capture may represent a starting point for the transition to the carbon-constrained economies of the future in line with the 1.5\ub0C target

Scenario for near-term implementation of partial capture from blast furnace gases in Swedish steel industry

Iron-and-steel making is a carbon-intensive industry and responsible for about 8% of global CO2 emissions. Meeting CO2 reduction targets is challenging, since carbon is inherent in the dominating production route in blast furnaces. Long-term plans to phase out carbon and change production technique are under way, such as iron ore reduction with hydrogen[1][2] won from renewable energies or electro winning[3], however unlikely to be implemented at scale before 2040 [4]. Until a transition to such technologies is completed, carbon leakage will remain to be a threat to steel industry inside EU ETS system. CCS remains an option for steel industry to comply with reduction targets and meet rising allowance (EUA) prices, currently above 20 €/t. Most studies on CCS propose a capture rate of ≥ 90 %[5–7], however, CCS could be considered as a part of a series of measures (e.g. fuel change, energy efficiency measures) that together achieve a significant reduction in CO2 emissions until a carbon-neutral production is in place. This line of thought motivates the concept of partial capture, where only the most cost effective part of the CO2 emissions are separated for storage [8]. In steel industry, high CO2 concentrations at large flows and the availability of excess heat make partial capture attractive. Previous work on the steel mill in Lule\ue5, Sweden, emits around 3.1 Mt CO2 per year, has found that 40-45 % of site emissions can be captured fueled by excess heat alone[9]. Therein, five heat recovery technologies were assessed, ranging from back pressure operation of CHP turbine to dry slag granulation. Promising CO2 sources on site include flue gases from hot stoves and the combined-heat and power plant, and the process gas originating from the blast furnace – blast furnace gas (BFG). BFG is a pressurized, low value fuel used for heating on site. CO2 separation from BFG requires less reboiler heat for MEA regeneration, and the enhanced heating value of the CO2 lean BFG increases energy efficiency of the steel mill [9].This work discusses the near-term (the 2020s) implementation of partial capture at a Swedish steel mill and the economic viability of such implementation dependent on the energy price, carbon price, and required reductions in CO2 emissions. Based on previous work [9][10,11] on partial capture in steel industry a cost estimation of a capture system for the BFG is conducted including CAPEX and OPEX of the MEA capture unit, gas piping, and recovering heat from the steel mill. The costs are summarized as equivalent annualized capture cost (EAC) and set into relation to transport and storage costs as well as carbon emission costs to form the net abatement cost (NAC) according to Eq. (1)\u1d441\u1d434\u1d436=\u1d438\u1d434\u1d436+ \u1d461\u1d45f\u1d44e\u1d45b\u1d460\u1d45d\u1d45c\u1d45f\u1d461&\u1d460\u1d461\u1d45c\u1d45f\u1d44e\u1d454\u1d452 \u1d450\u1d45c\u1d460\u1d461 −\u1d450\u1d44e\u1d45f\u1d44f\u1d45c\u1d45b \u1d45d\u1d45f\u1d456\u1d450\u1d452[€/\u1d461\u1d436\u1d4422](1)Figure 1 shows how EAC for BFG varies with the capture rate and the cost of steam for different heat recovery technologies represented by the steps in the curve ( see explanation in [9]). Note that partial capture from BFG is more economical than the full capture benchmark. The most cost-efficient case of 28 €/t CO2 captured is achieved for BFG capture fueled by steam from back-pressure operation (at the expense of electricity production), flue gas heat recovery and flare gas combustion. The transport and storage cost applied in Eq (1) represent ship transport from the Bothnian Bay to a storage site in the Baltic Sea , according to Kj\ue4rstad et el.[12]. Transport and storage cost range within 17 – 27 €/t CO2 depending on scale.These installation and operation cost for capture, transport and storage are set into relation with various scenarios on future carbon and energy (electricity) prices in Europe and Sweden. For example, Figure 2 illustrates a scenario in line with IEA’s sustainable development scenario to restrict global warming to 2\ub0C. The carbon prices are adapted from WEO 2018 [13] and increase from 20 € to 120 € per tonne CO2 by 2040 and the electricity prices of 42-52 €/MWh (increasing with time) are based on latest results from the NEPP project [14]. In this scenario, partial capture from BFG could become economic viable in 2029, construction in 2020 with operation from 2022/23 onwards is likely to pay off within a lifetime of 20 years only. This work demonstrates the viability of partial capture as cost-efficient mitigation measure for the steel industry and illustrates conditions for an early implementation in the 2020s.This work is part of the CO2stCap project (Cutting Cost of CO2 Capture in Process Industry) andfunded by Gassnova (CLIMIT programme), the Swedish Energy Agency, and industry partners

Partial capture from refineries through utilization of existing site energy systems

Many studies indicate that carbon capture and storage operations need to be ramped up in the coming decades to limit global warming to well-below 2\ub0C. Partial CO2 capture from carbon-intensive industrial processes is a promising starting point for initial CO2 transport and storage infrastructure projects, such as the Norwegian full-chain CCS project “Northern Lights”, since specific capture cost (€/t CO2) for single-stack capture can be kept low compared to full capture from all, often less suitable stacks. This work highlights the importance of utilizing existing site energy systems to avoid significant increase in marginal abatement cost when moving from partial to full capture. A systematic and comprehensive techno-economic approach is applied that identifies a mix of heat supply sources with minimum cost based on a detailed analysis of available heat and capacity within the existing site energy system. Time-dependent variations are considered via multi-period, linear optimization. For single-stack capture from the hydrogen production unit (~0.5 Mt CO2 p.a.) of a Swedish refinery in the context of the current energy system, we find avoidance cost for the capture plant (liquefaction, ship transport, and storage excluded)of 42 €/t CO2-avoided that is predominantly driven by steam raised from available process heat in existing coolers (~6 €/t steam). For full capture from all major stacks (~1.4 Mt CO2 p.a.), the avoidance cost becomes twice as high (86 €/t CO2-avoided) due to heat supply from available heat and existing boiler capacity (combustion of natural gas) at costs of ~20€/t steam. The analysis shows that very few investments in new steam capacity are required, and thus, that the utilization of existing site energy systems is important for lowering capture cost significantly, and thus the whole-chain cost for early CCS projects

Techno-economic evaluation of retrofitting CCS in an integrated pulp and board mill - Case studies

Urgently reducing global greenhouse gas emissions (GHG) could be achieved by carbon sinks or negative emissions, i.e. removing CO2 from the atmosphere and offsetting historical CO2 emissions. Negative emissions can be achieved when CO2 is captured from processes based on biomass feedstock (bio-CCS). Biomass withdraws atmospheric CO2 through natural processes such as the photosynthesis. Capturing and permanently storing this CO2 away from the natural carbon cycle enables a withdrawal of CO2 from the atmosphere. Sustainable growth and harvest of biomass resources is critical to achieve carbon negativity and to allow for sound biomass regrowth. As a result, bio-CCS provides a potential mitigation tool to reduce the CO2 concentration in the atmosphere. The pulp and paper industry is one of the potential candidates for large scale demonstration of bio-CCS and industrial CCS application. In Europe, the pulp and paper industry is the largest user and producer of biomass energy, contributing to around 60% of the biomass based electricity and heat production. There are three main sources of CO2 emissions in the pulp and paper production (via Kraft pulping process): (1.) the Kraft recovery boiler, (2.) the lime kiln and (3.) the multi-fuel boiler (bark boiler). Typically, over 90% of CO2 emissions from a pulp mill are of biogenic origin as fossil fuel is used only for firing the lime kiln. The main function of the recovery boiler is to recover the spent cooking chemicals from the black liquor for reuse in wood chips cooking and the combustion of the organic matter in the black liquor to produce heat for steam and electricity generation. The lime kiln is part of the chemical recycle loop and this includes the calcination of the lime mud (mainly calcium carbonate) to produce CaO that is used in the recovery of the cooking chemicals (i.e. processing of the green liquor). As a result, the lime kiln produces a flue gas with high concentration of CO2. The multi-fuel boiler is typically used to burn any wood waste and residue biomass (i.e. bark and bio-sludge) from the pulp production to produce steam used in the process and for power production. This study addresses the operational costs, capital investment costs and technical aspects of retrofitting a modern Kraft market pulp mill with a split flow post-combustion CO2 capture based on amine absorption. The pulp production units and the CO2 capture units are presented with detailed mass and energy balances. Two types of mills were evaluated; i) Stand-alone pulp mill producing 800 000 adt of softwood pulp annually and ii) Integrated pulp and board mill producing 740 000 adt of softwood pulp and 400 000 3-ply folding boxboard annually. Annual CO2 emissions are 2.1 Mt CO2/a. Six different cases were studied for each mill type; CO2 capture from the three individual point sources and three combinations of these. The implementation of a post-combustion CO2 capture process requires additional steam for the amine reboiler and additional power input for pumps and compressors. In some cases the excess power production at the pulp mill may be sufficient to support the integration of a CO2 capture plant. In other cases an additional auxiliary boiler is required. The split flow MEA-based capture process enables a reduction in the heat duty for the CO2 stripper reboiler. The average reboiler duty was calculated to around 2.7 – 2.8 MJ/kg captured CO2. Steam is provided from the steam turbine island. A major focal point of the study was to investigate the optimal extraction of steam and condensate return. Most pulp and paper mills are self-sufficient with electricity and produce excess electricity that is exported to the local/national grid. 90% CO2 capture was assumed for all cases, but in future evaluations partial CO2 capture might prove more viable, depending on the amount of excess steam or electricity available at the mill. This is also affected by the price of electricity, price of emission allowances and any renewable energy subsidies/incentives. Capturing biogenic CO2 could potentially create additional revenues for the mill operator, depending on whether the emission of biogenic CO2 would be accounted for as negative CO2 emissions in emission allowance trading schemes. As a result, accounting for negative CO2 emissions could potentially be a low-hanging fruit and lead to demonstration or large scale industrial business cases for the implementation of CCS in the near future