Rate-based Approaches for the Carbon Capture with Aqueous Ammonia Without Salt Precipitation

The aim of this paper is the evaluation of the influence of the kinetic of the NH3-CO2-H2O reactions in the absorber with respect to the electric power losses due to the steam bleeding from the turbine for the regeneration of the solvent. The results exposed conclude that there are few works about the kinetic of the aqueous reaction of the system NH3-CO2-H2O and data from the literature are not in agreement among them probably due to a dependence of the kinetic constants on the ammonia concentration in the liquid. The kinetic parameters have a strong influence on the specific electric power losses

Kinetic study of a Layout for the Carbon Capture with Aqueous Ammonia without Salt Precipitation

This paper focuses on carbon capture in an Ultra Super Critical power plant. The technology selected for CO2 capture is based on cooled ammonia scrubbing in post-combustion mode, as recently investigated by the authors in another work. Here, a rate-based approach is adopted. In detail, a specific primary energy consumption for CO2 avoided (SPECCA) of 2.77 MJ/kgCO2 is calculated in case of 85% of CO2 capture, with an ultimate power plant efficiency of 37.27%. Published by Elsevier Ltd

Experimental data of the aqueous NH3and CO2absorption at temperatures from 15 °C to 35 °C, NH3concentrations from 5% to 15% and CO2 loadings from 0.2 to 0.6 measured with the Wetted Wall Column

The absorption between aqueous NH3and CO2is studied using the Wetted Wall Column in order to show the effect of the solvent condition on the rate of reaction. A total of 27 different cases are investigated in the region defined by temperatures from 15 °C to 35 °C, NH3concentrations from 5% to 15% and CO2loadings from 0.2 to 0.6. The paper reports the data measured during the experiments, the experimental apparatus description and the experimental procedure. The data here presented are both the raw data measured with their uncertainty and the final value of the overall mass transfer coefficient. The overall mass transfer coefficient is the result of the raw data treatment explained in the research paper related to this data. The data here reported are analyzed in the paper by Lillia et al. (2018) [1]

A Layout for the Carbon Capture with Aqueous Ammonia without Salt Precipitation

Post-combustion carbon capture technologies seem to be necessary to realize the CO2 mitigation policies internationally shared for the next future, despite none of them appears to be ready for full-scale applications. This work considers the aqueous ammonia-based process for a coal-fired Ultra Super Critical power plant. Two layouts are simulated with Aspen Plus employing the recently recalibrated Extended UNIQUAC thermodynamic model. The first one operates at chilling conditions, which yield to salt precipitation, and is taken as reference because already analyzed in previous studies. The second layout operates at cooled conditions, which does not yield any salt precipitation. The Chilled layout reveals low specific heat duty and SPECCA equal to 2.2 and 2.86 MJ/kgCO2, respectively. In contrast, the Cooled layout presents a higher specific heat duty of almost 3 MJ/kgCO2 but, importantly, a lower SPECCA of 2.58 MJ/kgCO2. The latter layout is a better choice also from the perspective of the plant operation since it does not present the salt precipitation

Innovative Process Cycle with Zeolite (MS13X) for Post Combustion Adsorption

This paper reports the integration of Electric swing adsorption (ESA) Process in a Natural Gas Combined Cycle. This process was investigated in the MATESA FP7 project financed by European Commission. The ESA process is modelled through ASPEN Adsorption using both heat and electricity for regenerating the sorbent. The overall heat duty of the sorbent is 4 MJ/kgCO2 where half of this is recovered in the regeneration cycle. The resulting CO2 avoided is around 90% with a net electric efficiency of about 40%. The low efficiency is consequence of the higher energetic value of electricity with respect to the thermal power typically adopted in MEA regeneration. Being the first attempt of simulating this process using multiple heat sources and the recent development of sorbents, significant improvements can be expected by ESA reducing the gap with conventional post-combustion CO2 capture technologies

Results from Process Modeling of the Mixed-salt Technology for CO2 Capture from Post-combustion-related Applications

Mixed-salt technology, a solvent-based technology for removing CO2 from flue gas streams offers a significant advantage over conventional amine-based CO2 removal technologies (e.g., Fluor Econamine FG PlusSM technology). SRI International (SRI) is currently investigating the application of mixed-salt technology for pulverized coal combustion (PCC) power plant retrofit applications for removing >90% CO2 at a cost not to exceed $40/tonne of CO2 captured. The research was performed at a large bench-scale level with funding from the United States Department of Energy (DOE), National Energy Technology Laboratory (NETL). Very recently, a successful demonstration of mixed-salt technology at 0.25 tonne/day system was conducted in the USA, and the data obtained from the tests was used to develop a rate-based model to determine the mass and energy balance for a carbon dioxide recovery (CDR) removing 90% CO2 from a 550-MW supercritical power plant. In this paper, we present the process modeling data including the preliminary techno-economic evaluation (TEA) of mixed-salt technology. CO2 capture and CO2 pipeline purity specifications were met in all the process configurations investigated in this study. SRI's mixed-salt process can strip CO2 at high pressure as the stripper for rich-solvent regeneration is operated at higher pressure than the Fluor Econamine FG PlusSM process. Thus, the electrical power required for compressing CO2 to delivery pressures (> 130 atm) is greatly reduced in the mixed-salt process compared to other solvent-based technologies operating with lower-pressure regenerations. Ammonia-based technologies require absorber solvent cooling and treated gas washing to reduce ammonia emissions, and the raw water consumption of the process combines the water being used in the two water-wash sections. The Fluor Econamine FG PlusSM technology requires a large water recycle in the CDR unit for cooling purposes (1,173,350-1,286,900 lpm or 310,000-340,000 gpm), which greatly exceeds the PC plant cooling water requirement (643,450-757,000 lpm or 170,000-200,000 gpm). SRI's mixed-salt process requires a relatively smaller recycle for cooling purposes, and the overall cooling water recycled was 71% less in the mixed-salt process compared to the baseline case. As such, the auxiliary power required for mixed-salt process CDR unit was 60% less than the baseline case. The heat duty for the mixed-salt process was calculated to be 2.0 MJ/Kg of CO2 recovered (in the stripper reboiler). This accounts for a 44% decrease in the heat duty requirement in the mixed-salt process compared to the baseline case. Published by Elsevier Ltd

Experimental study of the aqueous CO₂-NH₃ rate of reaction for temperatures from 15 °C to 35 °C, NH₃ concentrations from 5% to 15% and CO₂ loadings from 0.2 to 0.6

The absorption reaction between aqueous NH3and CO2was studied using the Wetted Wall Column. A total of 27 different cases are investigated in the region defined by temperatures from 15 °C to 35 °C, NH3concentrations from 5% to 15%, which are the typical solvent conditions in absorption columns, and lastly CO2loadings from 0.2 to 0.6. The resulting overall mass transfer coefficient of absorption measured follows the trends described by the modelling of the reactor and the equations used to describe the rate of the absorption reactions. Moreover, the overall mass transfer coefficient of absorption is in agreement with data available in the literature, valid in smaller portions of the investigated region. From the data analysis, the kinetics of the absorption reactions in the liquid phase is characterized. The equation proposed to fit the data is a power law equation which reproduces the experimental results measured at different CO2loadings. This represents a novelty because in literature the kinetic model of the reaction is usually fitted only to data for unloaded solutions (CO2loading equal to zero). Hence, in this case there is an experimental evidence that the kinetic model holds true in every loading conditions. The kinetic model intercept the values found in literature in every range of concentration. Consequently, the model is valid in every conditions and the rate of the reaction between NH3and CO2in liquid phase is described with an Arrhenius constant with a pre-exponential factor of 1.41·108[mol/(m3s)] and an activation energy of 60,680 [J/mol], a linear dependence on the CO2concentration and a dependence on the NH3with an exponent γ = 1.89. The proposed equation is found to be appropriate for implementation into process simulation software

Analysis of the K2CO3-NH3 Solvent Properties for Carbon Capture Applications

Absorption-based systems that typically employ amines such as monoethanolamine (MEA) are in commercial use for scrubbing CO2 from industrial flue and process gases. However, many challenges must be overcome when applying amine-based technology for the treatment of pulverized coal-fired power plants such as toxicity, degradation, high energy consumption associated with regeneration of the solvent, low regeneration pressure and cost of the chemicals. Other solvents such as aqueous solutions of ammonia (NH3) (Chilled Ammonia Process) and aqueous solution of potassium carbonate (K2CO3) are mature non-amine alternatives to the state-of-the-art MEA technology. Technology based on NH3 is capable of capturing CO2 at high loadings compared with MEA-based technology. In addition, NH3-based technology can strip CO2 at high pressure, thereby reducing CO2 compression costs and it has a kinetic of absorption comparable to the amine technologies at temperatures around 25°C. However, this process requires gas washing to reduce the NH3 emissions in the scrubbed flue gas [1-2]. The K2CO3-based process has lower regeneration energy requirements and no emission issues. However, it has a low kinetic of absorption, a very low loading capacity, and low-pressure of CO2 regeneration. Both the solvents (NH3 and K2CO3) have no problems of degradation and toxicity and they have low costs compared to the amines [3]. The aim of this work is the study of the thermodynamic properties and the kinetic of absorption of the mixture between the NH3 and K2CO3 in the same solvent in order to investigate a solution with low heat duty of regeneration reducing the ammonia slip and maintaining a higher regeneration pressure [4]. The novelty is the analysis of the thermodynamic and the kinetic of absorption of the Mixed-salt Technology solvent for the carbon capture application applied on the pulverized coal-fired exhausts with 13% of CO2 concentration. The thermodynamic analysis of the properties is conducted with the Extended UNIQUAC thermodynamic model proposed by Thomsen and Rasmussen [5] in its new version calibrated with both the experimental data of the ternary systems NH3-CO2-H2O and K2CO3-CO2-H2O, while the kinetic of absorption is studied experimentially with the Wetted Wall Column