National Carbon Capture Center Research Articles

Research on the Development and Policy Evolution of CCUS Industry at Home and Abroad

CCUS is internationally recognized as one of the three major pathways to achieve carbon neutrality goals. It is an important choice for realizing zero emissions from large-scale fossil energy utilization and a feasible technological solution to offset carbon emissions in industries such as power, steel, and cement where emissions reductions are challenging. Systematic analysis of the development and policy evolution of the CCUS industry at home and abroad can provide theoretical basis and practical guidance for China's energy transition and development under the background of carbon emission peaking and achieving carbon neutrality. Guided by the strategic goals of national energy security, carbon emission peaking, and achieving carbon neutrality, this study aims to analyze the global development process and stage characteristics of the CCUS industry, investigate the supporting policies in the CCUS field and their evolution patterns, summarize the current status and trends of the CCUS industry at home and abroad, and provide reference for the implementation of national energy green and low-carbon transformation and the construction of a new energy system. In terms of industry, European and American countries emphasize national-level technological guidance and macro-control. The United States has introduced the progressive 45Q tax credit policy, and the European Union has included CCUS in its carbon trading system. The US National Carbon Capture Center provides a testing environment and facilities for CCUS technology research and development, and has established a carbon dioxide industry cluster and transportation hub. In terms of policies, tax credits and carbon trading policies in Europe and America have attracted various types of capital investment, establishing a relatively complete legal framework system. These regions have been leading in CCUS technology research and deployment, holding dominant positions and decision-making power in mainstream international CCUS organizations such as the CSLF, IEA, GCCSI, and OGCI. This study benchmarks the forward-looking and strategic development status of the CCUS industry at home and abroad, elucidates the challenges facing CCUS industry development, and proposes future trends and policy support needs for the CCUS industry. The research reveals that Europe and America emphasize national-level technological guidance and macro-control, focusing on the construction of regional industrial networks and having established a relatively complete legal and regulatory framework system. Compared to other countries, China needs to establish national-level guidance on CCUS development, regional carbon dioxide capture and transportation networks, and enact specific laws, regulations, and technical standards for CCUS.

Pilot plant results with the piperazine advanced stripper at NGCC conditions

CO2 capture is necessary to decarbonize natural gas combined cycles (NGCC) that will be used to provide power when renewable power is unavailable. The PZAS™ (Piperazine (PZ) with the Advanced Stripper) second generation capture technology has been successfully tested with coal-fired flue gas. This paper reports reliable testing of PZAS at NGCC conditions for 2000 h in a 0.66 m ID absorber at the National Carbon Capture Center (NCCC). Coal-fired flue gas diluted with air entered the absorber at 77 °C. 5 m PZ was regenerated by the Advanced Stripper with 2.45 gJ steam/tonne CO2 at 6.2 bara. With 40 feet of packing and pump-around intercooling the absorber provided 90–95% CO2 removal with a rich loading of 0.40–0.41 mol CO2/mol N. The apparent rate of PZ oxidation was 0.3 kg/tonne CO2. The water wash reduced PZ emission to less than 1 ppm. In the last 400 h of testing, carbon treating clarified the solvent color, reduced ammonia production by as much as 40%, and improved both absorber and stripper performance. Testing with coupons showed that 304 SS had an acceptable corrosion rate even at the severe conditions of the stripper at 150 °C.

Energy use of piperazine with the advanced stripper from pilot plant testing

Piperazine with the Advanced Stripper (PZAS™) was tested at the National Carbon Capture Center (NCCC) at coal and NGCC conditions. Energy performance was measured with accounting for heat loss. The net heat duty was found to be identical at 2.45 GJ/tonne for both 4 and 12% CO2 at 90% CO2 removal. The average measured heat loss was 0.38 GJ/tonne and represented 30% of the gross heat rate. For PZAS, the warm rich piping before the control valve is the largest in surface area. Heat loss at this location increased heat duty by 80% of the heat loss value. Therefore, the total heat duty was decreased by 80% of the heat loss. The Independence™ model was validated using 112 steady-state pilot plant runs and predicted average net heat duty with an error of 9% and lean loading with an error of 10%.The model was used to simulate process impacts of heat loss for the PZAS and simple stripper configurations. For both strippers, heat loss was found to impact heat duty at locations other than just the steam heater. While heat loss in the steam heater was the most important for PZAS, heat loss in the column was the most important for the simple stripper due to a large top-side pinch and CO2 reabsorption at the same location. CO2 reabsorption in PZAS occurred only at high heat loss values (∼0.14 GJ/hr), compared to low heat loss values (∼ 0.03 GJ/hr) in the PZ-simple stripper. Excessive packing in the PZ-simple stripper caused a large top-side pinch at 0.23 mol/mol lean loading, making the column very sensitive to heat loss. Heat loss in the PZ-simple stripper increased heat duty by 120–150% at typical heat loss values and lean loading of 0.23 mol/mol. Heat loss in the MEA-simple stripper only increased heat duty by 1–13% in a typical lean loading range of 0.1–0.2 mol/mol. A large bottom side pinch at low lean loading for 7 m MEA made the effect of heat loss less pronounced.

Effects of carbon treating on piperazine oxidation in pilot plant testing of PZAS™

From February to June 2019, a pilot plant campaign was run for 2100 h at the National Carbon Capture Center (NCCC) using moderately degraded 5 m PZ with simulated flue gas equivalent to a 0.64 MW natural gas combined cycle. Piperazine with the Advanced Stripper™ (PZAS™) and a baghouse were used, and N2 sparging was applied at the bottom of the absorber. A carbon bed was activated and showed beneficial effects in removing degradation products and reducing the oxidation rate.The cumulative NH3 production was 180 mmol/k, indicating a PZ oxidation rate of 0.07 mmol/kg/h (0.3 kg PZ/tonne of CO2). The total formate before turning on the carbon bed was 41 mmol/kg, and the total Fe was 0.1 mmol/kg. Carbon treating reduced NH3 production from 0.1 mmol/kg/h to 0.056 mmol/kg/h after 400 h of operation, reduced the UV-Vis absorbance of the samples at 320 nm, and caused a decrease of dissolved Cr. Bench-scale experiments were performed using the NCCC solvent and the same type of carbon. In bench-scale experiments, the UV-Vis absorbance and the concentration of Fe, Mn, and Cr all decreased. A linear equilibrium relationship was observed between the UV-Vis absorbance and the carbon loading.

15th 18th March 2021 Abu Dhabi, UAE Effects of carbon treating on piperazine oxidation in pilot plant testing of PZASTM

Aqueous piperazine (PZ) has shown promise as a solvent to reduce CO2 emissions due to its high CO2 absorption rate, capacity, and thermal stability. From February to June 2019, a pilot plant campaign was run for 2100 hours at the National Carbon Capture Center (NCCC) using slightly degraded 5 m PZ with simulated flue gas equivalent to a 0.64 MW natural gas combined cycle. Piperazine with the Advanced Stripper™ (PZAS™) and a baghouse were used throughout the campaign, and N2 sparging was applied at the bottom of the absorber. A carbon bed was activated and showed beneficial effects in removing degradation products and reducing the oxidation rate The cumulative NH3 production was 180 mmol/kg over the 2100 hours, indicating a PZ oxidation rate of 0.07 mmol/kg/hr, equivalent to 0.3 kg PZ/tonne of CO2. The final total formate before turning on the carbon bed was 41 mmol/kg, and the total Fe was 0.1 mmol/kg, both lower than other pilot plant results. Both total formate and ethylenediamine (EDA) were found to accumulate faster at lower temperature Carbon treating reduced NH3 production from 0.1 mmol/kg/hr to 0.056 mmol/kg/hr after 400 hrs of operation, reduced the UV-vis absorbance of the samples at 320 nm from 58.3 A to 17.4 A, and caused a decrease of Cr concentration. Bench-scale experiments were performed using the NCCC solvent and the same type of carbon (8*30 mesh, lignite- based granular activated carbon) In bench-scale experiments, the UV-Vis absorbance and the concentration of Fe, Mn, and Cr all decreased. A linear relationship was observed between the equilibrium UV-Vis absorbance and the carbon loading

Heat Exchanger Performance in Pilot Plant Testing of Piperazine with the Advanced Stripper™

The performance of four key heat exchangers at the National Carbon Capture Center (NCCC) during 4000 hours of operation is analyzed in this paper. A 0.5 MW integrated absorption-stripping pilot plant using Piperazine with the Advanced StripperTM (PZASTM) was used, with 5 m piperazine (PZ) as the capture solvent. Data from the coal and Natural Gas Combined Cycle (NGCC) campaigns were used, with flue gas compositions of 12% and 4% CO2. For the steam heater, data from multiple campaigns at the Separations Research Program (SRP) at the University of Texas J. J. Pickle Research Campus were used. All the exchangers were simulated in Aspen Plus®, and the IndependenceTM model was used to estimate properties not measured on-site. The performance metric used was the number of transfer units (NTU) for the cold, hot, and CO2 exchangers, and the overall heat transfer coefficient for the steam heater. The cold and hot exchangers exhibited similar performance throughout both campaigns, averaging a lean side NTU of 13.4 and 4, respectively. The pressure drop on both sides of both exchangers was correlated with the operating variables, with an added term to represent the flashing of the rich stream in the hot exchanger. Model deviations were under ± 25% for both units. The steam heater at NCCC underperformed in relation to design expectations. When compared to the performance of the steam heater at SRP, the low fluid velocities measured at NCCC suggest pool boiling operation, which is characterized by low thermal performance. The CO2 exchanger performed better than expected, with average NTU of 3.7 and 5.4 on the CO2 and rich sides. The cold, hot, and CO2 exchangers were analyzed for performance loss during the NCCC campaigns. The cold and CO2 exchangers did not show any statistically significant loss of performance during the campaigns, but the performance of the hot exchanger degraded slightly over time, suggesting the presence of fouling or leaking due to corrosion of the SS316L plates by the flashing rich stream.

U.S. Department of Energy National Carbon Capture Center, Supporting Technology Scale-up and International Collaboration

Sponsored by the U.S. Department of Energy (DOE) and operated and managed by Southern Company, the National Carbon Capture Center (NCCC) is a cornerstone of U.S. innovation in advancing the development of technologies to reduce greenhouse gas emissions. Bridging the gap between laboratory research and large-scale demonstrations, the center works to accelerate the development of carbon capture technologies from natural gas- and coal-based power plants. The facility evaluates next-generation carbon dioxide (CO₂) reduction processes from third-party developers, focusing on the early-stage development of the most promising, cost-effective technologies for future commercial deployment. Since its creation in 2009, the NCCC has performed more than 115,000 hours of technology testing. Through pilot testing of more than 60 technologies, the center has directly participated in the reduction of the projected cost of carbon capture from fossil power generation by approximately one-third. As the demand for post-combustion CO₂ capture options grows, work in this area continues to reduce the cost of carbon capture and bring new technologies closer to the marketplace. Evaluation of developing second-generation and transformational carbon capture technologies using actual flue gas under industrial conditions provides critical information on material and process suitability for scale-up to commercial applications. The center has broadened its research scope to expand testing of carbon capture technologies for natural gas power generation in addition to its existing coal-fueled testing capability. Integration of the new natural gas flue gas equipment with the existing infrastructure will allow each carbon capture project to receive either natural gas or coal flue gas independently of other projects. In addition, current and future testing at the NCCC will support research and development (R&D) of CO2 utilization technologies that will efficiently, economically, and cleanly transform CO₂ into value-added products. As its focus broadens to negative carbon concepts, the center is also extending its research to help advance direct air capture (DAC) technologies. Because reduction of CO₂ emissions is an international issue, the NCCC provides worldwide technology development leadership – it co-founded the International Test Center Network, a global coalition focused on research, development, and deployment of carbon capture, use, and storage (CCUS). Formed in 2012 in collaboration with DOE’s Office of Fossil Energy, the ITCN facilitates knowledge-sharing among carbon capture test facilities around the world to accelerate the commercial deployment of carbon capture technologies. The ITCN now has 14 test facilities that are members. The NCCC has also been active in establishing test collaborations with international groups. The facility has successfully tested technologies from seven different countries. In addition to the important work of developing cost-effective technologies, many other aspects of successful commercial deployment must be mastered. Establishing relationships to secure funding, gaining management support, meeting test goals, and satisfying legal requirements of both the international organization and the NCCC are significant achievements and forms a strong basis for future partnerships for larger-scale development. Oil and gas companies have joined the NCCC and have a strong international presence which will support international collaboration worldwide. Unanticipated benefits to the NCCC’s international collaboration have emerged in addition to establishing relationships that could form the basis for partnerships for scale-up of technology. These benefits include (1) adding value to CCUS technologies by meeting requirements of international markets, (2) increasing the value of input into studies, roadmaps and policy development by including international perspective, (3) attenuation of inconsistent support of CCUS R&D among individual countries, and (4) encouragement of passionate participants in CCUS R&D to stay in the field by expanding interest from new, international funders. The NCCC hopes to build on the international relationships that have been established to contribute to the important step of moving from early-stage R&D projects to a commercial product. In conclusion, the NCCC has demonstrated its ability to bring on board and manage a multitude of projects to develop the most promising technologies for clean, efficient fossil-fuel energy production with ultra-low CO₂ emissions. Operations at the center have resulted in significant scale-ups, process enhancements, and technological breakthroughs. The NCCC is also providing international leadership to promote the level of readiness for carbon capture technologies. This paper will detail the center’s capabilities, role in supporting international collaboration, and future plans.

Pilot Plant Results With the Piperazine Advanced Stripper at NGCC Conditions

CO2 capture is necessary to decarbonize natural gas combined cycles (NGCC) that will be used to provide power when renewable power is unavailable. The PZAS™ (Piperazine (PZ) with the Advanced Stripper) second generation capture technology has been successfully tested with coal-fired flue gas. This paper reports reliable testing of PZAS at NGCC conditions for 2000 hours in a 0.66 m ID absorber at the National Carbon Capture Center (NCCC). Coal-fired flue gas diluted with air entered the absorber at 77 oC. 5 m PZ was regenerated by the Advanced Stripper with 2.45 gJ steam/tonne CO2 at 6.2 bara. With 40 feet of packing and pump-around intercooling the absorber provided 90–95% CO¬2¬ removal with a rich loading of 0.40–0.41 mol CO2/mol N. The apparent rate of PZ oxidation was 0.3 kg/tonne CO2. The water wash reduced PZ emission to less than 1 ppm. In the last 400 hours of testing, carbon treating clarified the solvent color, reduced ammonia production by as much as 40%, and improved both absorber and stripper performance. Testing with coupons showed that 304 SS had an acceptable corrosion rate even at the severe conditions of the stripper at 150 oC.

Large Pilot Testing of Linde-BASF Advanced Post-Combustion Carbon Dioxide Capture Technology at a Coal-Fired Power Plant

This first-of-its-kind, large-scale pilot is vital to the carbon capture knowledge base and experience. It will also serve as a reference for future commercial projects and provide critical design and operations information needed to scale-up the technology for commercial implementation, while minimizing costs and risks. The pilot is a 10 MWe slipstream taken from Dallman #4 at City Water, Light, and Power (CWLP) in Springfield, Illinois. The post-combustion capture technology being demonstrated is the Linde/BASF advanced capture system, which has been previously demonstrated at the National Carbon Capture Center at a 1.5 MWe level. The successful construction and operation of this plant will provide a means to demonstrate an economically attractive and transformational capture technology that can be used to retrofit existing plants and be deployed at new plants. The regional economic benefit and the ability to repurpose some exiting workforce at CWLP will also demonstrate how carbon capture can aid regional economies when it is deployed. If the technology performs as planned, the capture plant will remain in place and be utilized for future testing of capture and utilization technologies.

Heat Loss and Energy Use in Pilot Plant Testing of Piperazine With the Advanced Stripper

Piperazine with the Advanced Stripper (PZAS™) was tested at the National Carbon Capture Center (NCCC) at coal and NGCC conditions and its energy performance and heat loss were measured. The net heat duty was found to be 2.45 GJ/tonne at 4% and 12% CO2 at 90% removal. The average measured heat loss was 0.38 GJ/tonne and represented 30% of the gross heat rate. Carbon treating increased the NTU of the cold and hot exchangers by 1.8% and 1.5%, respectively, by removing viscous solvent degradation products. The Independence™ model was validated using 112 steady-state pilot plant runs and predicted average net heat duty with an error of 9% and lean loading within 10% of the measurements. The model captured the effect of carbon treating on heat exchanger performance and predicted a reduction in heat duty of 1.2% but failed to predict the step decrease of 8% seen in measured heat duty data. In PZAS™, the warm rich pipe before the control valve is deemed the most important for heat loss due to its high surface area and its ability to increase flashing across the valve and decrease the total rich bypass temperature. Heat duty is corrected for 80% of the heat loss value, corresponding to the sensitivity of heat duty to heat loss at the same location. In the simple stripper, a large topside pinch makes heat duty most sensitive to heat loss in the column. Water condensation by heat loss increases the L/G and causes reabsorption at low heat loss values (~0.02 GJ/hr). Overdesigning strippers must therefore be avoided to mitigate this effect. Reabsorption in PZAS™ is not as sensitive to heat loss and occurs only at high values (~0.14 GJ/hr) due to the even temperature pinch in the column. 7 m MEA with the simple stripper has a lower measured heat duty than 5 m PZ due to the insignificant effect of heat loss in the column on with 7 m MEA. Unlike 5 m PZ, 7 m MEA has a bottom-side pinch that mitigates the effect of heat loss by water condensation.

National Carbon Capture Center: advancing fossil energy technology solutions

National Carbon Capture Center: advancing fossil energy technology solutions

Development of a framework for sequential Bayesian design of experiments: Application to a pilot-scale solvent-based CO2 capture process

In this paper, a methodology is developed for sequential design of experiments (SDoE) for process systems and applied to a solvent-based CO2 capture system. In this approach, the prior knowledge of the system is used to prioritize process data collection at specific operating conditions. These data are then incorporated into a Bayesian inference methodology for updating a stochastic model by refining estimations of its underlying parameters, and the updated model is then used to generate the next set of test runs. Thus, the new knowledge obtained from the data is used to guide subsequent iterations of the experimental runs, ensuring that the overall data collection is maximally informative given that most experimental campaigns, especially at pilot or higher-scale plants, are costly, time-consuming, and resource-limited. The test run objective for this work was to minimize the maximum model prediction uncertainty for key output variables, but the methodology is generic and can be readily applied to other test run objectives. This methodology is applied to an aqueous monoethanolamine (MEA) pilot plant campaign at the National Carbon Capture Center (NCCC) in Wilsonville, Alabama, USA. The SDoE framework was utilized for two iterations, while collecting 18 sets of data representing different process conditions, and this resulted in an overall average reduction in uncertainty of approximately 50% in the prediction of CO2 capture percentage. Moreover, 11 additional data sets were obtained with variation of absorber packing height for further model validation. This work shows the capability of the SDoE framework to maximize learning given limited resources, allowing for the reduction of model uncertainty, which is of great importance for many applications including reduction of technical risk associated with scale-up and economic analysis.

CO2 Absorption from Gas Turbine Flue Gas by Aqueous Piperazine with Intercooling

Amine scrubbing is the most mature technology for postcombustion carbon capture. Much bench- and pilot-scale work has been focused on CO2 capture from coal-fired flue gas. Because natural gas is inexpensive and readily available in the United States and other countries, the natural gas combined-cycle (NGCC) has been replacing coal for electricity generation. Carbon capture for NGCC is therefore an important technology for the modern power plants. The Piperazine (PZ) Advanced Stripper (PZAS) technology has been established as a benchmark system for second-generation amine scrubbing for CO2 capture from coal-fired flue gas. It has a fast absorption rate, good energy performance, and strong resistance to thermal degradation and oxidation. PZAS was operated with simulated NGCC flue gas (4.3 mol % (dry) CO2) at the National Carbon Capture Center (NCCC) in Wilsonville, Alabama in 2019. This paper presents the absorber performance and model validation for the campaign. The absorber was tested with in-and-out and with pump-around intercooling. The variable operating conditions included lean loading (0.19–0.25 m CO2/mol alkalinity), gas temperature (40, 78 °C), and intercooling temperature (35, 40 °C). Using 5 m PZ CO2 removal from 82% to 96% was achieved with intercooling and only 12 m of packing. A rigorous, rate-based absorber model accurately predicted the CO2 removal and temperature profile. The model shows that the delta loading of the solvent at NGCC conditions for 90% removal is greater than at coal conditions, but high CO2 removal (99%) is more difficult to achieve with NGCC gas than with coal-fired flue gas. The pump-around intercooling was effective, and the intercooling temperature had a large impact on the absorber performance. With pump-around, the delta loading penalty for hot gas feed into absorber without a direct contact cooler was less than 5%.

Demonstration of 99% CO2 Removal from Coal Flue Gas by Amine Scrubbing

Abstract A post-combustion CO2 capture campaign was conducted at the National Carbon Capture Center (NCCC) with 5 m PZ (piperazine) using the advanced flash stripper configuration. 68 steady-state runs were identified and 90% or to 99.1% CO2 removal was achieved with a 12 m of packing in the absorber. A 20% increase in solvent rate enhanced CO2 removal from 90% to 99% and the rich loading decreased from 0.40 to 0.38 mol CO2/mol alkalinity. With high removal, the temperature profile from modeling indicated there was a mass transfer pinch in the absorber, which means 12 m packing is more than needed even for 99% removal. The rich loading did not decrease significantly at high CO2 removal, therefore the energy cost for regeneration remained practically unchanged. The material balance around the absorber based on CO2 loaded calculated from density and viscosity closed within 2.3%. The rate-based Aspen Plus® model under-predicted the number of transfer units in the absorber by an average of 16%. This was caused by the difference between CO2 concentration measured by titration and calculated from density and viscosity. With the advanced flash stripper (AFS), the process heat duty was between 1.9 and 2.5 GJ/t CO2 and did not increase more than 5% at higher CO2 removal. Due to the fast reaction kinetics of PZ, the 12 m absorber was overdesigned for 99% CO2 removal and the rich loading was unchanged at high removal. Further, the superior design of the AFS recovered the latent heat of water vapor and minimized the energy consumption for solvent regeneration. Therefore, it is feasible to capture 99% of the CO2 from coal-fired flue gas with PZ scrubbing at a reasonable energy cost.

Status of Technology Development at the National Carbon Capture Center

Status of Technology Development at the National Carbon Capture Center

Impacts of aerosol nuclei on amine emissions

Amine emissions are an environmental and economic concern for CO2 capture by amine scrubbing. Aerosol nuclei, including hydrolyzed SO3 and fly ash, can lead to amine aerosol emissions. Aerosol grows by collecting water and amine while passing through the absorber column; current mitigation techniques are ineffective at capturing the aerosol prior to atmospheric release. This work measures the varying impacts of aerosol nuclei on amine emissions at multiple pilot plants. Aerosol emissions were quantified by the use of Fourier Transform Infrared Spectrometry (FTIR). MEA emissions were measured in the Slipstream Solvent Test Unit (SSTU) at the National Carbon Capture Center (NCCC). The effect of baghouse pretreatment of the inlet flue gas on the aerosol emissions was observed by FTIR and Phase Doppler Interferometry (PDI); these tests were performed before and after the installation of a pulsed-jet baghouse designed for flue gas mercury control. The baghouse resulted in a ten-fold reduction of amine aerosol emissions, due to the collection of SO3 aerosol nuclei, probably on injected Ca(OH)2. This emissions reduction was due to a decrease in the inlet SO3 content from a max of 9 ppm to 0.5 ppm. FTIR sampling was used to quantify this emissions reduction. PDI analysis confirmed the absence of aerosol at diameters greater than 0.1 μm. Aerosol generation was performed through the injection of sulfur trioxide into the process inlet at the University of Texas Separations Research Program (UT-SRP) Pilot Plant. SO3 was generated by the oxidation of sulfur dioxide in air over a heated vanadium pentoxide catalyst bed. The 8% SO2/Air mix was fed at flow rates up to 6 liters per minute, and resulted in up to 110 ppm of SO3 at the absorber inlet. The generator converted an average of 94 % SO2 into SO3, with production rates up to 1.7 grams per minute of SO3. The injected aerosol was allowed to grow within the absorber and water wash. SO3 was found to increase PZ emissions by up to 7.6 mol PZ per mol SO3. Increasing inlet SO3 correlated with increasing PZ emissions.

Pilot plant demonstration of piperazine with the advanced flash stripper

Amine scrubbing is an important alternative for CO2 capture from coal- and gas-fired power plants. 5 m piperazine (PZ) with the Advanced Flash Stripper (AFS) has all the attributes of a benchmark system for the second-generation amine scrubbing process for CO2 capture. This process has been demonstrated with more than 2000 h of operation on 0.6 MWe of coal-fired flue gas at the National Carbon Capture Center. In the first 600 h, the AFS configuration was used, and the stripper sump level was kept high at 80%. From 600 to 850 h, the system switched to simple stripper configuration and from 850 to 1100 h, switched back to AFS. After 1100 h, the mitigation methods for oxidation were tested with the AFS, including nitrogen sparging, applying the SO2 prescrubber to remove NO2, and lowering the stripper sump level to 15%. The energy required per tonne CO2 removed was less than 2.1 GJ steam and less than 232 kW h total equivalent work. The stripper operated at 150 °C, producing CO2 up to 6 bara. The 5 m PZ solvent was used reliably with little solids precipitation. CO2 removal from 90 to 99% was achieved with less than 12 m of packing. PZ oxidation was less than 0.1 kg PZ/tonne CO2 with the AFS and the absence of NO2. As estimated from NH3 production, the mitigation methods reduced the PZ oxidation rate by 13%. The trends in dissolved iron correlated with the PZ oxidation rate rather than the extent of oxidation. PZ emissions were managed to less than 1 ppm with water wash and an elevated lean solvent temperature. With aqueous PZ, carbon steel was frequently protected by deposition of FeCO3, making it an attractive alternative to stainless steel.

Demonstration of 99% CO2 removal from coal flue gas by amine scrubbing

A post-combustion CO2 capture campaign was conducted at the National Carbon Capture Center (NCCC) with 5 m PZ (piperazine) using the advanced flash stripper configuration. 68 steady-state runs were identified and 90% or to 99.1% CO2 removal was achieved with a 12 m of packing in the absorber. A 20% increase in solvent rate enhanced CO2 removal from 90% to 99% and the rich loading decreased from 0.40 to 0.38 mol CO2/mol alkalinity. With high removal, the temperature profile from modeling indicated there was a mass transfer pinch in the absorber, which means 12 m packing is more than needed even for 99% removal. The rich loading did not decrease significantly at high CO2 removal, therefore the energy cost for regeneration remained practically unchanged.The material balance around the absorber based on CO2 loaded calculated from density and viscosity closed within 2.3%. The rate-based Aspen Plus® model under-predicted the number of transfer units in the absorber by an average of 16%. This was caused by the difference between CO2 concentration measured by titration and calculated from density and viscosity.With the advanced flash stripper (AFS), the process heat duty was between 1.9 and 2.5 GJ/t CO2 and did not increase more than 5% at higher CO2 removal. Due to the fast reaction kinetics of PZ, the 12 m absorber was overdesigned for 99% CO2 removal and the rich loading was unchanged at high removal. Further, the superior design of the AFS recovered the latent heat of water vapor and minimized the energy consumption for solvent regeneration. Therefore, it is feasible to capture 99% of the CO2 from coal-fired flue gas with PZ scrubbing at a reasonable energy cost.

Field trial of spiral-wound facilitated transport membrane module for CO2 capture from flue gas

A field trial with 1.4 m2 spiral-wound (SW) membrane modules fabricated from an amine-containing facilitated transport membrane was conducted with actual flue gas at the National Carbon Capture Center in Wilsonville, AL, U.S.A. Prior to the field test, the membrane modules were systematically evaluated with simulated flue gas to identify the optimal operating conditions, including feed flow rate, feed pressure and operating temperature. With the actual flue gas, the membrane modules showed ca. 1450 GPU CO2 permeance and 185 CO2/N2 selectivity at 67 °C with feed and permeate pressures of 4 and 0.3 atm, respectively. A 500-h stability was demonstrated in spite of the interference of system upsets and flue gas outages. During the field trial, carbon capture rates of better than 40% were achieved by a single SW module with coal-derived flue gas. Except for a few flue gas upsets, the CO2 purities in the captured stream were 94.5% or better on dry basis. The data obtained from this project validates the membrane material and provide basis for the design and fabrication of full-scale SW module with a membrane area larger than 50 m2. It should be noted that no significant amounts of Cr, As and Se were deposited onto the membrane during this 500-h test.

Small Pilot Test Results from a Polaris Membrane 1 MWe CO2 Capture System

To mitigate the harmful effects of global climate change, CO2 in combustion sources must be captured and either sequestered or utilized. Membrane technology is an attractive CO2 capture option because of advantages such as energy-efficient passive operation, small footprint, no hazardous chemical emissions, handling or storage issues, near instantaneous response, no steam use, and reduced water requirements. Working with the U.S. Department of Energy (DOE), Membrane Technology and Research, Inc. (MTR) has developed new membranes and process designs to recover CO2 from combustion gases. The Polaris™ class of membranes offer the highest combination of CO2 permeance and CO2/N2 selectivity of any commercial membrane today. These membranes are combined with a novel two-step process design that uses incoming combustion air to sweep membranes and recycle CO2 to the combustion process. The benefits of this two-step membrane design include an increased CO2 concentration to the membrane capture step and a reduction in the fraction of CO2 removal required by the capture step. Design calculations estimate that this membrane process can capture CO2 at a cost of <$40/tonne under partial capture conditions. Between 2012 and 2015, MTR operated a bench-scale test system at the U.S. National Carbon Capture Center (NCCC) in Wilsonville, AL testing commercial-scale Polaris membrane modules capturing 1 tonne CO2/day. Overall, this system accumulated a run time of over 11,000 hours, and demonstrated stable membrane performance while processing real coal-fired flue gas. The test system also operated as a field laboratory that allowed for evaluation of new membrane module designs and validation of advanced membranes under real world conditions. With this experience, MTR designed and built a scaled-up small pilot unit to treat 20 tonnes CO2/day from a slipstream at NCCC (equivalent to 1 MWe-scale coal-fired power generation). This system was operated for approximately 1,500 hours in 2015 over two different test campaigns. The small pilot membrane system exhibited stable performance and reached up to a 90% capture rate during operation in both winter and summer field test conditions. During the second test campaign, advanced Polaris sweep modules demonstrating higher packing density, lower pressure drop, and higher permeance were validated.