1. Results from CESAR1 testing at the CO₂ Technology Centre Mongstad. Verification of Residual Fluid Catalytic Cracker (RFCC) baseline results (2022)

Scott A. Hume^b*, Blair McMaster^a,c, Audun Drageset^a, Muhammad I. Shah^a and Eirik R.

Kleppe^a,d, Matthew Campbell^a

^aTechnology Centre Mongstad, 5954 Mongstad, Norway

^bElectric Power Research Institute, Inc., 1300 West WT Harris Blvd, Charlotte, NC 28262, USA

^cTotalEnergies EP Norge AS, Finnestadveien 44, Dusavik, 4029 Stavanger, Norway

^d Equinor ASA, PO Box 8500, 4035 Stavanger, Norway

Abstract

Gå til overskriften

Technology Centre Mongstad (TCM DA) was established in 2012 to test, verify, and demonstrate different post-combustion capture (PCC) of carbon dioxide technologies. The company is a joint venture between Gassnova (on behalf of the Norwegian state), Equinor, Shell, and TotalEnergies with a common vision for testing and research and development of carbon capture for the deployment of large-scale carbon capture. The facility is located next to the Equinor refinery in Mongstad, Norway and is provided flue gas from a nearby combined cycle gas turbine-based heat-and-power (CHP) plant as well as residue fluid catalytic cracker (RFCC) flue gas from the refinery.

The CESAR1 solvent, developed in the EU CESAR project, was utilized for the first time at TCM for the ALIGN CCUS (Accelerating Low Carbon Industrial Growth Through Carbon Capture Utilization and Storage) project test campaign in 2019. CESAR1 solvent is a blend of 27% wt 2-amino-2-methylpropan-1-ol (AMP) and 13% wt piperazine (PZ). This solvent is considered a better solvent than monoethanolamine (MEA) in terms of thermal energy performance and stability (lower degradation) and has been proposed by the IEAGHG as their new benchmark solvent. TCM DA carried out baseline testing of CESAR1 solvent in June 2020 using flue gas from the CHP source, controlled at 5% CO₂ to simulate state of the art gas turbine flue gas, and continued with additional testing that lasted into late 2020 using flue gas from the RFCC source that has higher CO₂ concentration. The main objectives of these campaigns were to produce knowledge and information that can be used to reduce the cost as well as technical, environmental, and financial risks of commercial-scale deployment of PCC using the CESAR1 solvent. This includes the establishment of an RFCC baseline performance with CESAR1 solvent.

The Electric Power Research Institute, Inc. assessed the performance of the CESAR1 process using an independent verification protocol (IVP) previously developed for TCM DA during CHP baseline testing MEA solvent. The IVP was also previously updated for use with the RFCC flue gas as this gas contains 13–14% CO₂ content whereas the CHP flue gas has ~3.5% CO₂ content by volume. The IVP provides a structured testing procedure for assessing the thermal and environmental performance of PCC processes under normal operating conditions. During the RFCC testing, TCM DA manually collected extractive samples from the depleted gas outlet and the product CO₂ outlet throughout the testing period. As part of the IVP, EPRI also assessed plant critical instrumentation at TCM DA for accuracy and precision error based on a comparative analysis during testing operations and against calibration checks.

The CESAR1 baseline process was evaluated during twelve individual test periods over three days in November 2020. During the tests, extractive samples were taken to measure process contaminants such as aldehydes, ketones, amines (AMP/PZ), and ammonia. The extractive sampling and associated analysis techniques applied were consistent with the IVP recommendations. Sulfur oxides and nitrogen oxides were continuously monitored using Fourier transform infrared (FTIR) analyzers on the depleted flue gas and the product CO₂ streams. Multiple measurements of the CO₂ concentration (FTIR, non-destructive infra-red, and gas chromatography) are available at TCM allowing comparative confirmation of test period stability. The capture rate was calculated via four methods. CO2 recovery (mass balance) was evaluated, and the thermal performance (energy consumption) was assessed based on measured data taken during the tests.

The CO₂ capture rate achieved during the testing was about 91%, providing specific reboiler duties (SRD) of 3.2–3.3 GJ/t-CO₂ and the CO₂ gas mass balance closures were close to 100%. These data and assessments, along with the results from TCM DA sampling during these tests, will be presented in this paper and provide a baseline case for CESAR1 solvent in higher concentration flue gas capture cases.

1.  Introduction

Gå til overskriften

The CO₂ Technology Centre Mongstad (TCM) is located next to the Equinor refinery in Mongstad, Norway. TCM DA is a joint venture owned by Gassnova representing the Norwegian state, Equinor, Shell, and TotalEnergies. TCM is home to one of the largest post-combustion CO₂ capture (PCC) test centres in the world and recently marked the completion of 10 years of technology testing. This facility entered the operational phase in August 2012 and is dubbed the “amine plant.” A unique aspect of the facility is that either a flue gas slipstream from a natural gas-fired combined- cycle gas turbine (CCGT) based combined heat-and-power (CHP) plant or an equivalent volumetric flow from a residual fluid catalytic cracker (RFCC) unit can be used for CO₂ capture. The CHP flue gas contains about 3.5% CO₂ and the RFCC flue gas contains about 13–14% CO₂, the latter of which is comparable to CO₂ levels seen in a coal- fired flue gas.

The amine plant, designed and constructed by Aker Solutions and Kværner, is a highly flexible and well- instrumented facility that can accommodate a variety of technologies with capabilities of treating flue gas streams of up to 60,000 Sm³/hr. The plant is offered to developers of solvent-based CO₂ capture technologies to test the performance of their solvent technology and to verify technologies aimed to reduce the atmospheric emissions and environmental impact of solvent emissions and degradation products from these processes.

The objective of TCM DA is to test, verify, and demonstrate CO2 capture technologies suitable for deployment at full scale. A significant number of vendors have already successfully tested using the TCM DA facilities to assess their CO2 capture technologies. Multiple tests using the CESAR1 solvent have been carried out at TCM to define the baseline performance of the solvent for defined operating conditions using RFCC flue gas at 13.5% CO2 content in accordance with an independent verification protocol (IVP), which provides a structured testing procedure, developed by the Electric Power Research Institute, Inc. (EPRI) [1].

2.  Amine Plant

Gå til overskriften

The TCM 234 tonnes-CO₂/day amine plant was designed to be flexible to allow testing of different process configurations. The amine plant is configured to remove CO₂ from a natural gas-fired combustion turbine-based CHP plant flue gas or a RFCC off-gas. The typical characteristics of the RFCC gas stream is shown in Table 1.

Table 1. Nominal characteristics of flue gas supplied to TCM

* controlled via Brownian demister filter

The RFCC type flue gas was used for the tests performed in this work. A process flow diagram showing high-level equipment contained within the amine plant along with key existing instrumentation is shown in Figure 1.

Major system components include:

• An induced draft (ID) blower to overcome pressure drops and blow the flue gas through the plant with an output capacity of up to 270 mbar and 60,000 Sm³/hr.
• A direct-contact cooler (DCC) system to initially lower the temperature of and saturate the incoming flue gas

by a counter-current water flow to improve the efficiency of the absorption process and provide pre-scrubbing of the flue gas. The DCC system has two individually operated packed columns for operations with the CHP flue gas and the RFCC flue gas, respectively. When operating with RFCC flue gas, including the tests reported in this paper, caustic (NaOH) is injected under pH control with a target pH of 8 to reduce levels of acidic SO₂ aerosols.

• A Brownian demister module designed to remove particulate and aerosol particles from the flue gas when

using the RFCC. The module has a bypass line to facilitate controlled aerosol levels entering the downstream absorber unit.

• An absorber to remove CO₂ from the flue gas using multiple packed sections. The absorber also has water- wash systems located in the upper region of the tower to scrub and clean the flue gas, particularly of any solvent

carry over. When operating with RFCC flue gas, the upper water wash is operated with maximum cooling duty, the lower water wash with minimum cooling duty and additionally, the upper 6 m of absorber packing is utilized as a 3^rd “once through” water wash section. The CO₂ depleted flue gas passes through a mesh mist eliminator before exiting the absorber column to the atmosphere through a stack located at the top of the column.

• Stripper columns to recover the captured CO₂ and return CO₂-lean solvent to the absorber. The amine plant consists of two independent stripper columns with a common overhead condenser system. The two stripper

columns are operated independently considering the CO₂ content in the flue gas due to column design, hydraulics, and gas velocity effects. Both strippers circulate solvent to the reboilers by thermosiphon. The RFCC stripper also has a circulating pump to assist at low-load operation and during startup. The RFCC reboiler is a shell-and-tube arrangement.

• Balance of plant units include a lean-solvent trim cooler, pumps used to move the CO₂-lean and CO₂-rich solvent streams between the absorber and stripper, a cross heat exchanger to recover heat from the lean stream, a

reflux drum, stripper condenser, and pumps to dry the product CO₂ that exits the stripper.

More details of these components are available in Hume et al [2].

The TCM facility can test virtually any PCC solvent-based process as the amine plant has been designed to accommodate a variety of technologies. The facility also has excellent instrumentation and an on-site lab for detailed analysis.

An IVP was developed to be used as part of the overall performance assessment of amine-based processes and has been updated over time to apply to either CHP or RFCC operation on the TCM amine facility. The IVP is designed to provide a structured testing procedure for assessing thermal and environmental performance of PCC processes under normal operating conditions.

3.  CESAR1 RFCC Campaign Overview

Gå til overskriften

The CESAR1 solvent, developed in the EU CESAR project [3], was utilized for the first time at TCM for the ALIGN CCUS (Accelerating Low Carbon Industrial Growth Through Carbon Capture Utilization and Storage) project test campaign in 2019 [4,5]. CESAR1 is a blend of 27% wt 2-amino-2-methylpropan-1-ol (AMP) and 13% wt piperazine (PZ). This solvent is considered a better solvent than monoethanolamine (MEA) in terms of thermal energy performance and stability [6,7] and has been proposed by the IEAGHG as their new benchmark solvent [6]. TCM DA carried out baseline testing of CESAR1 solvent in June 2020 using flue gas from the CHP source, controlled at 5% CO₂ to simulate state of the art gas turbine flue gas [2]. During the baseline testing of CESAR1 solvent with RFCC flue gas reported in this paper the average measured solvent concentration was 28.8 / 10.4% wt AMP/PZ.

RFCC flue gas capture performance assessment periods were conducted in November 2020. During the testing, personnel from TCM DA manually collected extractive samples from the depleted gas outlet and the product CO₂ line downstream of the RFCC stripper. In previous tests, this was sometimes performed by an independent testing

contractor. However, TCM DA’s competency related to performing this testing was deemed adequate by EPRI during prior MEA baseline campaigns, especially since TCM DA is not commercially involved in the outcome and hence can be considered to be unbiased.

While EPRI was unable to travel to the site to observe TCM’s in-house sampling campaign for the CESAR1 solvent firsthand as a result of travel restrictions due to the SARS-CoV-2 pandemic, several meetings were conducted remotely during the planning phase of the test campaign and EPRI received the data for the tests from TCM DA for analysis. Data logs for all sampling periods containing pertinent flows, temperatures, pressures, and concentrations measured by permanent plant instruments were supplied by TCM DA for the entire test period. The sampling time periods, and sampling period designators are shown in Table 2 along with additional sampling undertaken on each day.

Table 2. CESAR1 RFCC Sampling Periods

4.  Instrument assessment

Gå til overskriften

To determine the process plant performance, a key component is the quality of the instrumentation installed for measuring the respective compositions and flow rates. Instrumentation quality is determined using two parameters:

Accuracy/bias: This represents the difference between the instrument reading (or average of a set of readings under unchanging process conditions) being assessed and the true value of the parameter being measured. Appropriate determination of the “true value” must be achieved by simultaneous measurement of the parameter using a reference method or instrument with calibration that can be traced to primary standards.

Precision: A determination of the variability of the instrument reading when stream conditions are known to be steady state. Precision is therefore a measure of the random error associated with the measurement.

These measurement errors can be combined to assess the aggregate uncertainty in each measurement. In the absence of a calibration against primary standards for the entire measurement range needed, the uncertainty published by the instrument supplier represents only the precision error.

When the process parameter being measured does not change, precision is a measure of repeatability. In real plant situations, when attempting to operate at steady-state conditions, often process parameters (flow, pressure, and temperature) do vary over the measurement period. Thus, measurements over long periods of time (greater than process time constants) will also include an error term related to process uncertainty.

5.  Gas Phase Composition

Gå til overskriften

5.1 CO₂ Measurement of Flue Gas Supply and Depleted Flue Gas

Gå til overskriften

Figure 2 (a) displays the RFCC flue gas supply CO₂ concentration data over the test campaign periods. The FTIR data have been corrected to be on a dry basis using the FTIR moisture assessment. The FTIR is biased 1% high and the GC is biased over 1% low in comparison to the HNDIR. Note that the CO₂ concentration of RFCC flue gas is beyond the measurement range for the LNDIR and hence cannot be used for these evaluations. As per previous campaigns, the HNDIR data were used in preference to the FTIR and GC data as the NDIR instruments exhibit a higher precision due to a lower measurement spread for the same sampled conditions.

Figure 2 (b) shows the depleted flue gas CO₂ measurements with the FTIR instrument included though it showed an excessive precision error. The GC and NDIR instruments agree well regarding changes in gas composition throughout each test day, typically to within 0.01% vol (dry). Although the GC was in good agreement with the NDIR(Hi), it showed a slightly lower precision, therefore as with prior tests, the NDIR(Hi) measurements were used for performance analysis for these tests.

5.2 Oxygen Measurement of Flue Gas Supply and Depleted Flue Gas

Gå til overskriften

Figure 3 shows both the supply and the depleted flue gas oxygen measurements with the GC for the RFCC test period. As the capture rate was constant throughout the period, the concentrating effect, i.e., from 6% vol to 7% vol, for all other components can be clearly seen from the oxygen measurements.

Variations in the inlet oxygen are represented with a similar response on the outlet stream. However, the apparent low precision error exhibited by this commensurate response cannot be determined as each measurement point is from the same core instrument (i.e., variation could indeed be from the instrument and not the process).

6.  Gas Phase Flow Rates

Gå til overskriften

6.1 Flue Gas Supply Flows

Gå til overskriften

The RFCC flue gas supply flow is measured by two independent multi-point pitot tube instruments. FIC-0024-ACC and FT-2039, with FIC-0024-ACC attaining a lower precision uncertainty as shown in Table 3. The flow data for the test periods is shown in Figure 4.

Table 3. Key flue gas supply flow instrumentation

All calculations for CESAR1 RFCC flue gas tests are based on the measured RFCC flue gas flow using FIC-0024.

6.2 Depleted Flue Gas Flows

Gå til overskriften

The depleted flue gas flow was measured by a single multi-pitot tube flow meter whose characteristics are listed in Table 4. Actual measurements depict poor accuracy showing consistent and variable negative bias, as shown in Figure 5, which is likely from plugging in the pitot tube elements caused by the condensation due to the super-saturated moisture condition of the depleted flue gas at this location. This instrument was therefore not utilized to determine the resultant absorber outlet flow. Instead, the conservation of inert components from the inlet stream (oxygen, nitrogen, and argon) was used to determine the appropriate flowrate achieved.

Table 4. Key depleted gas flow instrumentation

All performance calculations are based on the conserved oxygen and nitrogen method from the flue gas supply measurement as the depleted flue gas flow indication (FT-2431) was shown to not be accurate due to inconsistent measurements with a substantial negative bias due to the saturated flue gas at the absorber outlet.

6.3 Product CO₂

Gå til overskriften

The product CO₂ flow is normally measured by the vortex flow meter (FT-0010) and the precision uncertainty for this instrument are listed in Table 5.

Table 5. Key product CO₂ gas flow instrumentation

TCM installed an additional Coriolis flow meter instrument (FT-2215), which previously offered agreement with and exhibited a higher precision than FT-0010 during prior MEA baseline testing. However, this instrument has not undergone an accuracy study and so the precision uncertainty cannot be defined for these tests. The data from both flow meters are shown in Figure 6 for reference. The product CO₂ flow was relatively steady throughout the test periods.

6.4 Steam/Condensate

Gå til overskriften

High-pressure (HP) steam is delivered from the refinery to the TCM amine plant at a pressure of approximately 30 bar, superheated to 240–310°C. The HP steam is throttled to a pressure near the stripper reboiler steam pressure (approximately 4 barg) and then desuperheated with condensate. The stripper reboiler condensate collects in a receiver from which it is returned to the refinery. A small amount of medium-pressure (MP) steam is reduced to a lower pressure for use in steam heat tracing. The low-pressure (LP) steam condensate is returned to the same receiver as the stripper reboiler condensate. The reboiler steam flow rate for the CESAR1 RFCC tests is shown in Figure 7.

7.  Results & Discussion

Gå til overskriften

7.1 CO₂ Capture Efficiency/Recovery

Gå til overskriften

CO₂ capture efficiency can be quantified in several ways depending on how measurements have been taken and the expected accuracy of each individual measurement. EPRI commonly uses the four individual methods that are indicated in Table 6.

These methods can rely on combinations of the available information to determine a capture efficiency, using the measured gas flowrates in combination with the CO2 analyser measurements. Method 4 simplifies the measurement uncertainty by utilizing only CO2 concentration data and making the well-founded assumption that all incoming inert gases (such as nitrogen and oxygen) will be unchanged through the absorption process. Hence, Method 4 can be used to compare against the other methods that utilize the flow measurements. In addition, the “CO2 Recovery” calculation is indicated in Table 6. The CO2 Recovery is a measure of the CO2 mass balance, being the fraction of CO2 mass flow in the flue gas supply that is accounted for by measured CO2 mass flows in the depleted flue gas and product CO2. It is therefore a measure of the degree to which the CO2 mass balance is closed.

Table 7 shows the four calculation methods of CO₂ capture and recovery for the test periods. Note that CO₂ product flow can be based on either the measured CO₂ product flow (P) or by using the difference between the NDIR-measured CO₂ supply and depleted flows (S – D). CO₂ capture rates calculated by Methods 2, 3, and 4 were in good agreement within each test period, with Method 1 giving a consistently slightly higher value for CESAR1 CHP testing. It should be noted that Methods 3 and 4 are equivalent due to using the conserved oxygen and nitrogen method for outlet gas flow determination. The CO₂ recovery (mass balance) was slightly above 100% for the RFCC tests.

Table 7. CO₂ capture results

he uncertainty in measurement of flow and composition propagates into the uncertainty in the CO₂ capture. The uncertainty calculations and representative results from each of the calculation methods are shown in Table 8. The following assumptions were used:

• Flow metering uncertainties are those theoretically estimated and calculated by internal work at TCM DA for the indicated flow meters
• Concentration uncertainties for the flue gas flows are those described in previously in Section 6
• Concentration uncertainty for the product CO₂ is arbitrarily assigned to be 1% vol, which allows for actual CO₂ content as low as 99% vol
• CO₂ capture of 90% is representative of that measured during all test periods
• The uncertainty in CO₂ capture (ECO2) is almost all due to uncertainty in CO₂ content of the flue gas supply for the assigned total (low) flow uncertainties. The CO₂ capture uncertainty is relatively insensitive to both the product CO₂ content uncertainty and the depleted flue gas CO₂ content uncertainty.

7.2 Thermal Use

Gå til overskriften

The thermal results are detailed in Table 9. The reboiler heat duty or the heat released in the reboiler is calculated as the difference between steam enthalpy at reboiler inlet and the saturated water enthalpy at the reboiler condensate temperature. The specific thermal use is then calculated by dividing the reboiler heat duty by the product CO₂ flow. The two corresponding values for specific thermal energy consumption are shown in results and were consistent during all test periods.

Table 9. Stripper reboiler thermal use calculation

Previous testing at TCM [8] using conventional 5M MEA solvent (30% wt) with RFCC flue gas at approximately 190 tonnes per day load yielded a regeneration energy range of 3.43–3.55 GJ/t-CO₂ using the product CO₂ flow (P) and 3.51–3.65 GJ/t-CO₂ using the gas-side difference method (S – D), all carried out at a nominal 91% capture rate. The CESAR1 RFCC tests achieved circa 187 tonnes per day load and delivered a regeneration energy range of 3.21-

3.26 GJ/t-CO₂ using product flow (P) and a very consistent 3.21-3.28 GJ/t-CO₂ using gas-side difference method (S – D). The capture rate was a commensurate 90% for these tests, allowing direct comparison with the MEA tests. The CESAR1 regeneration energy at the same nominal load and capture rate had between 8-10% lower regeneration energy than 5M MEA. The liquid-gas ratio (L/G) for the CESAR1 testing, 2.7 kg/Sm³, was lower than the 5M MEA testing,

3.8 kg/Sm³ due to the higher cyclic capacity of the CESAR1 solvent.

A notable difference between the conditions of the RFCC flue gas testing with 5M MEA and CESAR1 was the flue gas inlet temperature to the absorber. A temperature of 31^oC was used for the 5M MEA testing, however due to precipitation in the lower absorber packing, the flue gas temperature was raised to 40^oC with CESAR1 to allow stable operation [5]. This increased flue gas temperature for CESAR1 is likely to incur a regeneration energy penalty relative

to testing at the same temperature as 5M MEA. Benquet et al, reported results from early TCM testing with CESAR1 solvent and CHP flue gas including regeneration energy penalty for higher flue gas temperatures due to precipitation issues [5].

7.3 Process Contaminats

Gå til overskriften

Formaldehyde, acetaldehyde, and acetone concentrations were determined by extractive sampling during the CESAR1 RFCC test periods, as shown in Table 10.

Table 10. Depleted flue gas aldehyde/ketone concentrations and mass rates

The formaldehyde levels are substantially higher than the previous MEA RFCC baseline testing measured concentration of 0.06 mg/Sm³. The acetaldehyde levels are considerably lower with CESAR1 than the MEA RFCC test samples of 1.7 mg/Sm³. Acetone levels measured during the MEA tests were sufficiently low at or below the detection limit of 1 mg/Sm³, while with CESAR1 they were between 1–3 mg/Sm³. CO₂ product results are shown in Table 11.

Table 11. Product CO₂ aldehyde/ketone concentrations and mass rates

For the CO₂ product, the formaldehyde levels detected were 2x higher the manual sampled measurements during the MEA RFCC baseline campaign (0.06 mg/Sm³) and the acetaldehyde levels are considerably lower than the previous level of 6.2 mg/Sm³. Unlike the MEA tests, acetone was easily detected in the CO₂ product, whereas in the previous MEA baseline all measurements taken were below the detection limit of 0.9 mg/Sm³.

The data suggests that formaldehyde and acetone are generated from the CESAR1 solvent at higher relative rates to acetaldehyde than is the case for MEA.

TCM DA measured concentrations of solvent components (AMP and PZ) along with ammonia during the CESAR1 testing, results of these manually extracted samples are shown in Table 12.

Table 12. Depleted flue gas stream ammonia and solvent component concentrations and mass rates

The solvent components of CESAR1 appear to show substantially lower vapor pressure than is associated with MEA solvent. PZ concentrations were lower than AMP, and the combined AMP/PZ concentrations are ~10 times lower than the MEA equivalent case of 2.9 ppmvd [8]. Ammonia levels are far lower than the MEA tests results, suggesting that ammonia does not represent a significant degradation product of CESAR1.

Extractive solvent and ammonia samples were taken from the CO₂ product, and the results are shown in Table 13. In this instance, the AMP measurements were higher than the MEA samples, that were below the detection limit. PZ was detected in 2 of 3 samples, but was present at very low concentrations. Ammonia desorption into the product gas is almost 2 orders of magnitude lower than the depleted flue gas levels, it is comparable with the ammonia concentration detected from the MEA RFCC tests.

Table 13. Product CO₂ ammonia and solvent component concentrations and mass rates

* ‘<’ indicates sample measured below detection limit

Test C7-6 has abnormally low solvent and ammonia levels, not consistent with online measurements. Sulfur dioxide and nitrogen oxide components were measured using FTIR, as shown in Table 14. Prior SO₂ measurements for the MEA campaign were under <1 ppmv and this test period was similar. The NO gas appears to largely pass through the absorption process without significant interaction with the solvent. However, the majority of NO₂ entering the absorber will react with the solvent as reported by Campbell et al [9].

Table 14. Depleted flue gas SO₂ and NO concentrations and mass rates

1. Comparison to earlier TCM RFCC CESAR1 Testing

7.4 Comparison to earlier TCM RFCC CESAR1 Testing

Gå til overskriften

The EPRI verification period in November 2020 was the last section of a longer TCM test campaign with CESAR1 solvent and RFCC flue gas. From parametric testing earlier in this campaign, not verified by EPRI, TCM identified a test condition, B4REP2, with an optimum SRD of 3.06 GJ/t-CO₂ for 90% capture rate testing with 18m absorber packing height. This case was selected to be repeated during the EPRI verification period. From TCM internal analysis, both overall and CO₂ mass balance closure during the B4REP2 test were within 2%.

During the EPRI verification period, higher SRD values than the original B4REP2 test were observed. The major contributing factor to this difference is likely to be foaming in the stripper, which can incur significant SRD penalties as shown in CESAR1 CHP baseline testing. During the EPRI verification period, repeated addition of antifoam had very limited remedial effect. This led to the solvent circulation rate being increased from 85,000 to 95,000 kg/h which reduced but did not eliminate the foaming behaviour. This increase in solvent circulation rate moved the testing during the EPRI verification period away from the optimum L/G ratio identified earlier in the TCM test campaign and incurred an SRD penalty, as described in Table 15 where an additional test condition at 95,000 kg/h from earlier in the campaign, B1, is also included for comparison.

Table 15 – Comparison of CESAR1 RFCC EPRI Baseline Verification Period with earlier TCM CESAR1 RFCC Testing

Another contributing factor to the higher-than-expected SRD value is variation in concentration and quality of the CESAR1 solvent due to preferential losses of the piperazine component particularly due to reaction with NO₂ as reported by Benquet et al [5], as shown in Table 15. During the EPRI verification period, the average measured solvent concentration was 28.8 / 10.4% wt AMP/PZ compared to the target concentration of 27 / 13% wt AMP/PZ.

7.3 Comparison to pilot and demonstration sites reported in literature

Gå til overskriften

SRD results from previous pilot or demonstration scale testing with CESAR1 solvent with similar capture rate and flue gas CO₂ concentration to this TCM EPRI verified baseline are shown in Table 16 with a range of packing materials, solvent concentrations and plant configurations used across the various sites. From the reported results, foaming issues do not appear to have been as prevalent at other sites when compared to TCM.

Table 16 – SRD Results from CESAR1 Pilots at 90% Capture Rate and 13-15% CO₂

The SRD results reported in this paper are within but towards the upper range of the results reported by other CESAR1 test sites. From this comparison, recommendations for future CESAR1 testing at TCM should include the effect of absorber intercooling, mitigation measures for foaming behavior and variation of the piperazine content in the solvent within the precipitation limits.

8.  Conclusions

Gå til overskriften

The CESAR1 baseline with RFCC flue gas comparison to the earlier 30% wt MEA baseline performed at TCM DA using the same flue gas source [8] is shown in Table 17.

Table 17. Comparison of TCM DA RFCC baseline conditions and results with CESAR1 and MEA solvents

The CESAR1 baseline case was conducted at conditions as close to the MEA baseline as possible using the same flue gas source along with an identical packing height, flue gas flowrate, targeted capture rate and the stripper regeneration temperature. The CESAR1 solvent did exhibit precipitation in the absorber packing when the flue gas temperature was too low, hence the higher inlet temperature. The liquid to gas ratio is lower than MEA and was determined based on the solvent characteristics and performance during the tests. The SRD achieved using CESAR1 solvent was 9% lower than what was possible using 30% wt MEA solvent in the same configuration.

Acknowledgements

Gå til overskriften

The authors gratefully acknowledge the staff of TCM DA, Gassnova, Equinor, Shell and Total for their contribution and work at the TCM DA facility. The authors also gratefully acknowledge Gassnova, Equinor, Shell, and TotalEnergies as the owners of TCM DA for their financial support and contributions.

References

Gå til overskriften

• Thimsen D, Maxson A, Smith V, Cents T, Falk-Pedersen O, Gorset O, Hamborg ES, Energy Procedia 2014; 63:5938- 5958.
• Hume SA, Shah MI, Lombardo G, Kleppe ER. Results From CESAR1 Testing with Combined Heat and Power (CHP) Flue Gas at the CO2 Technology Centre Mongstad, TCCS-11 Trondheim Conference on CO2 Capture, Transport & Storage, Trondheim, Norway, June 21-23 2021. Pg 355 – 361
• Kvamsdal HM, Haugen G, Svendsen HF, Tobiesen A, Mangalapally H, Hartono A, Mejdell T. Modelling and simulation of the Esbjerg pilot plant using the CESAR 1 solvent. Energy Procedia 2011; 4:1644-1651.
• Accelerating      Low     carbon      Industrial      Growth     through     CCUS:     ALIGN-CCUS,     project      homepage https://www.alignccus.eu/ accessed: 15.11.2021
• Benquet C, Knarvik A, Gjernes E, Hvidsten OA, Kleppe ER, Akhter S. First Process Results and Operational Experience with CESAR1 Solvent at TCM with High Capture Rates (ALIGN-CCUS Project), 15^th International Conference on Greenhouse Gas Control Technologies, GHGT-15, 15^th -18^th March 2021 Abu Dhabi, UAE http://dx.doi.org/10.2139/ssrn.3814712
• Further Assessment of Emerging CO2 Capture Technologies for the Power Sector and their Potential to Reduce Costs IEAGHG, 2019-09
• Wiechers G, Moser P, Benquet C, Gibbons J, Monteiro J, Hartono A, Solli KA, Knuutila H. Guidelines for effective solvent management, Deliverable Nr. D1.2.6, ALIGN-CCUS.
• Hume SA, Shah MI, Lombardo G, de Cazenove T, Feste JK, Maxson A, Benquet C. Results from MEA testing at the CO2 Technology Centre Mongstad. Verification of Residual Fluid Catalytic Cracker (RFCC) baseline results, 15^th International Conference on Greenhouse Gas Control Technologies, GHGT-15, 15^th -18^th March 2021 Abu Dhabi, UAE
• Campbell M, Akhter S, Knarvik A, Zeeshan M, Wakaa A. CESAR1 Solvent Degradation and Thermal Reclaiming Results from TCM Testing, 16th International Conference on Greenhouse Gas Control Technologies, GHGT-16, 23^rd– 27^th October 2022, Lyon, France.
• Moser P, Wiechers G, Schmidt S, Garcia M, Monteiro J, Goetheer E, Charalambous C, Saleh A, van der Spek M, Garcia
• S. ALIGN-CCUS: Results of the 18-Month Test with Aqueous AMP/PZ Solvent at the Pilot Plant at Niederaussem – Solvent Management, Emissions and Dynamic Behaviour (February 8, 2021). Proceedings of the 15th Greenhouse Gas Control Technologies Conference 15-18 March 2021, http://dx.doi.org/10.2139/ssrn.3812132

• Mangalapally HP, Hans H. Pilot plant experiments for post combustion carbon dioxide capture by reactive absorption with novel solvents. Energy Procedia 2011; 4:1-8.
• Rabensteiner, Markus, et al. “Pilot plant study of aqueous solution of piperazine activated 2-amino-2-methyl-1-propanol for post combustion carbon dioxide capture.” International Journal of Greenhouse Gas Control 51 (2016): 106-117.
• Schumacher N, et al. “CESAR 1 solvent test campaign at the pilot facility at Esbjerg power station”, CESAR Project Deliverable (2010).