Parametric Process Design and Economic Analysis of Post-Combustion CO2 Capture and Compression for Coal- and Natural Gas-Fired Power Plants

Utilizing Gelatin Waste for Efficient Bimodal Porous Silica Adsorbents for Carbon Dioxide Capture

This study explores the modification of pore structures in porous silica materials synthesized using sodium silicate and waste gelatin, under varying silica-to-gelatin ratios. At ratios of 1.0-1.5, bimodal porous silica with mesopores and macropores emerged due to spaces between silica nanoparticles and clusters, following gelatin elimination. The study further evaluated the obtained bimodal porous silica as polyethyleneimine (PEI) supports for CO2 capture, alongside PEI-loaded unimodal porous silica and hollow silica sphere for comparison. Notably, the PEI-loaded bimodal silica showcased superior CO2 uptake, achieving 145.6 mg g-1 at 90 °C. Transmission electron microscopy (TEM) revealed PEI's uniform distribution within the pores of bimodal silica, unlike the excessive surface layering seen in unimodal silica. Conversely, PEI completely filled the hollow porous silica's interior, extending gas molecule diffusion distance. All sorbents displayed nearly constant CO2 adsorption across 20 cycles, demonstrating outstanding stability. Notably, the bimodal porous silica displayed a negligible capacity loss, underscoring its robust performance.

Feasibility Study of the CO2 Regenerator Parameters for Oxy-Fuel Combustion Power Cycle

The atmosphere carbon dioxide content grows subsequently due to anthropogenic factors. It may be considerably mitigated by the development of thermal power plants with near zero emissions. A promising way is the transition to the semi-closed oxy-fuel combustion power cycles with carbon dioxide and water vapor mixture as a working fluid. However, their wide implementation requires reduction of the metal consumption for the highly efficient regeneration system. This paper discloses the results of feasibility study for the regeneration system of the prospective oxy-fuel combustion power plant. The effect of operating parameters on the cycle energy efficiency, overall dimensions, and the cost of the regenerator was determined. Underheating increase in the regenerator by 1 °C leads to the net efficiency factor drop of the oxy-fuel combustion power cycle by 0.13% at average and increases fuel costs by 0.28%. Increase of pressure drop in the hot channel by 1% leads to efficiency drop by 0.14%. The optimum set of design and operating parameters of the feed heating system has been determined, which ensures the best technical and economic indicators of electrical power generation: the minimum cumulative costs are achieved when underheating in the regenerator is 20 °C and pressure drop in the hot channel is 4%, under the use of S-shaped fins channels.

Kinetic and Thermodynamic Analysis of High-Pressure CO2 Capture Using Ethylenediamine: Experimental Study and Modeling

One of the alternatives to reduce CO2 emissions from industrial sources (mainly the oil and gas industry) is CO2 capture. Absorption with chemical solvents (alkanolamines in aqueous solutions) is the most widely used conventional technology for CO2 capture. Despite the competitive advantages of chemical solvents, the technological challenge in improving the absorption process is to apply alternative solvents, reducing energy demand and increasing the CO2 captured per unit of solvent mass. This work presents an experimental study related to the kinetic and thermodynamic analysis of high-pressure CO2 capture using ethylenediamine (EDA) as a chemical solvent. EDA has two amine groups that can increase the CO2 capture capacity per unit of solvent. A non-stirred experimental setup was installed and commissioned for CO2 capture testing. Tests of the solubility of CO2 in water were carried out to validate the experimental setup. CO2 capture testing was accomplished using EDA in aqueous solutions (0, 5, 10, and 20 wt.% in amine). Finally, a kinetic model involving two steps was proposed, including a rapid absorption step and a slow diffusion step. EDA accelerated the CO2 capture performance. Sudden temperature increases were observed during the initial minutes. The CO2 capture was triggered after the absorption of a minimal amount of CO2 (~10 mmol) into the liquid solutions, and could correspond to the “lean amine acid gas loading” in a typical sweetening process using alkanolamines. At equilibrium, there was a linear relationship between the CO2 loading and the EDA concentration. The CO2 capture behavior obtained adapts accurately (AAD < 1%) to the kinetic mechanism.

Research and Development of the Oxy-Fuel Combustion Power Cycles with CO2 Recirculation

The transition to oxy-fuel combustion power cycles is a prospective way to decrease carbon dioxide emissions into the atmosphere from the energy sector. To identify which technology has the highest efficiency and the lowest emission level, a thermodynamic analysis of the semiclosed oxy-fuel combustion combined cycle (SCOC-CC), the E-MATIANT cycle, and the Allam cycle was carried out. The modeling methodology has been described in detail, including the approaches to defining the working fluid properties, the mathematical models of the air separation unit, and the cooled gas turbine cycles’ calculation algorithms. The gas turbine inlet parameters were optimized using the developed modeling methodology for the three oxy-fuel combustion power cycles with CO2 recirculation in the inlet temperature at a range of 1000 to 1700 °C. The effect of the coolant flow precooling was evaluated. It was found that a decrease in the coolant temperature could lead to an increase of the net efficiency up to 3.2% for the SCOC-CC cycle and up to 0.8% for the E-MATIANT cycle. The final comparison showed that the Allam cycle’s net efficiency is 5.6% higher compared to the SCOC-CC cycle, and 11.5% higher compared with the E-MATIANT cycle.

Advanced Ultra-Supercritical Coal-Fired Power Plant with Post-Combustion Carbon Capture: Analysis of Electricity Penalty and CO2 Emission Reduction

This article presents the performance analysis of a 700 MW future planned advanced ultra-supercritical (A-USC) coal-fired power plant fitted with post-combustion carbon capture and storage (CCS) technology. The reference A-USC unit without CCS achieves a net efficiency of 47.6% with CO2 emissions of 700 kgCO2/MWh. Relatively to subcritical units, the net efficiency of the A-USC is 8%-pts higher while CO2 emissions are 16.5% lower. For a CO2 removal rate of 90%, the net efficiency of the CCS integrated A-USC unit is 36.8%. The resulting net efficiency loss is 10.8%-pts and the electricity output penalty is 362.3 kWhel/tCO2 for present state CCS technology. The study continues with the assessment of interface quantities between the capture unit and the steam cycle affecting the performance of the A-USC. Improved CO2 absorbents could alleviate the net efficiency loss by 2–3%-pts, and enhanced CO2 compression strategies and advanced heat integration could further reduce the efficiency loss by 0.5–1.2%-pts and 0.4–0.6%-pts, respectively. The total efficiency gain from CCS technology upgrades is estimated at 3.6%-pts, thus bringing down the net efficiency loss to 7.2%-pts and the electricity output penalty to 241.7 kWhel/tCO2.

K2CO3-Impregnated Al/Si Aerogel Prepared by Ambient Pressure Drying for CO2 Capture: Synthesis, Characterization and Adsorption Characteristics

A new potassium-based adsorbent for CO₂ capture with Al aerogel used as support is proposed in this work. The adsorbents with different surface modifiers (tetraethyl orthosilicate (TEOS) and trimethyl chlorosilane (TMCS)) and different K₂CO₃ loadings (10%, 20%, 30% and 40%) were prepared by sol-gel and iso-volume impregnation processes with ambient pressure drying. The CO₂ adsorption performance of the adsorbents were tested by a fixed-bed reactor, and their adsorption mechanisms were studied by scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray fluorescence spectrometry (XRF). Furthermore, the adsorption kinetics and the cycling performance were investigated. The results show that using TEOS to modify the wet gel can introduce SiO₂ to increase the strength of the skeleton. On the basis of TEOS modification, TMCS can further modify –OH, thus effectively avoiding the destruction of aerogel structure during ambient drying and K₂CO₃ impregnation. In this work, the specific surface area and specific pore volume of Al aerogel modified by TEOS + TMCS are up to 635.32 cm²/g and 2.43 cm³/g, respectively. The aerogels without modification (Al-B), TEOS modification (Al/Si) and TEOS + TMCS modification (Al/Si-TMCS) showed the best CO₂ adsorption performance at 20%, 30% and 30% K₂CO₃ loading, respectively. In particular, the CO₂ adsorption capacity and K₂CO₃ utilization rate of Al/Si-TMCS-30K are as high as 2.36 mmol/g and 93.2% at 70 degrees Celsius (°C). Avrami’s fractional order kinetic model can well fit the CO₂ adsorption process of potassium-based adsorbents. Al-B-20K has a higher apparent activation energy and a lower adsorption rate during the adsorption process. After 15 adsorption-regeneration cycles, Al/Si-TMCS-30K maintain a stable CO₂ adsorption capacity and framework structure, while the microstructure of Al/Si-30K is destroyed, resulting in a decrease in its adsorption capacity by nearly 30%. This work provides key data for the application of Al aerogel in the field of potassium-based adsorbent for CO₂ capture.