Standortplanung für die Herstellung CO2‐basierter Chemikalien am Beispiel der Olefinproduktion

The use of CO₂ as raw material is increasingly gaining in importance as an option for climate protection and as an alternative raw material feedstock. Both direct electrochemical syntheses and thermochemical processes are associated with a high demand for electrical energy. A contribution to climate protection is only possible in the case of low‐carbon power generation, as can be realized, e.g., by wind power or solar energy. This article presents a methodology for identifying suitable sites for the CO₂‐based production of olefins in Germany.     

CO2‐Abtrennung für fossil befeuerte Kraftwerke

An overview of technologies for fossil fuel power plants with drastically reduced CO₂ emissions is given. Post combustion capture, Pre combustion capture, and Oxyfuel technology are introduced and compared. Current research results indicate that Post combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with Oxyfuel technology is complex and costly, and retrofitting of Pre combustion capture is not possible. On the other hand, Post combustion capture is suited for retrofitting. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, Post combustion capture using reactive absorption is discussed here in some detail.     

CO2 Capture for Fossil Fuel‐Fired Power Plants

An overview of technologies for fossil fuel‐fired power plants with drastically reduced CO₂ emissions is given. Post‐combustion capture, pre‐combustion capture, and oxyfuel technology are introduced and compared. Current research results indicate that post‐combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with oxyfuel technology is complex and costly, and retrofitting of pre‐combustion capture is not possible. On the other hand, post‐combustion capture can be retrofitted to existing power plants with only minimal effort. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, post‐combustion capture using reactive absorption is discussed here in some detail.     

A superstructure‐based mixed‐integer programming approach to optimal design of pipeline network for large‐scale CO2 transport

Pipeline transport is the major means for large‐scale and long‐distance CO₂ transport in a CO₂ capture and sequestration (CCS) project. But optimal design of the pipeline network remains a challenging problem, especially when considering allocation of intermediate sites, like pump stations, and selection of pipeline routes. A superstructure‐based mixed‐integer programming approach for optimal design of the pipeline network, targeting on minimizing the overall cost in a CCS project is presented. A decomposition algorithm to solve the computational difficulty caused by the large size and nonlinear nature of a real‐life design problem is also presented. To illustrate the capability of our models. A real‐life case study in North China, with 45 emissions sources and four storage sinks, is provided. The result shows that our model and decomposition algorithm is a practical and cost‐effective method for pipeline networks design. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2442–2461, 2014     

Modularisierung von Gaswäschern für die CO2‐Entfernung aus Biogas

Modularization has been identified as one of the research fields of the ?50 % idea”?. A development methodology for modules must consider both the economies of scale for investment costs and costs of operation and maintenance. In this paper, the impact of an absorber module, which is offered as discretized diameter scaling, on the total process is investigated at the example of the CO₂ separation from biogas. The simulation shows the effect of this approach to the stripper diameter and the energy demand of the process. The calculations form the basis for applying cost models.     

Modeling of CO2‐Hydrate Formation at the Gas‐Water Interface in Sand Sediment

Sub‐seabed geological storage of CO₂ in the form of gas hydrate is attractive because clathrate hydrate stably exists at low temperature and high pressure, even if a fault occurs by diastrophism like a big earthquake. For the effective design of the storage system it is necessary to model the formation of CO₂‐hydrate. Here, it is assumed that the formation of gas hydrate on the interface between gas and water consists of two stages: gas diffusion through the CO₂‐hydrate film and consequent CO₂‐hydrate formation on the interface, between film and water. Also proposed is the presence of a fresh reaction interface, which is part of the interface between the gas and aqueous phases and not covered with CO₂‐hydrate. Parameters necessary to model the hydrate formation in sand sediment are derived by comparing the results of the present numerical simulations and the measurements in the literature.     

Development of a Scalable Method for Manufacturing High‐Temperature CO2 Capture Sorbents

An engineered process for scalable manufacture of a calcium aluminum carbonate CO₂ sorbent with production amounts of about 1000 g per hour has been developed. The process includes mixing and heating, solid‐liquid separation, drying and extrusion, crushing and conveying, and calcined molding steps. The sorbent preparation involves the coprecipitation of Ca²⁺, Al³⁺, and CO₃^2– under alkaline conditions. By adjusting the Ca:Al molar ratio, a series of Ca‐rich materials could be synthesized for use as CO₂ sorbents at 750 °C. A calcium acetate‐derived sorbent exhibited better cyclic stability than sorbents originating from CaCl₂ and Ca(NO₃)₂. The initial sorption capacity increased with CaO concentration. High stability of more than 90 % was maintained by the Ca:Al sorbents after 40 looping tests.     

CFD Modeling of a Carbonation Reactor with a K‐Based Dry Sorbent for CO2 Capture

A 2D CFD simulation of the carbonation reactor is carried out to evaluate the performance of potassium‐based dry sorbent during the CO₂ capture process. A multiscale drag coefficient model is incorporated into the two‐fluid model to take the effects of clusters into account. The influence of several parameters on CO₂ removal is investigated. The results indicate that increasing the reactor height and reducing the gas velocity can lengthen the residence time of particles and enhance the CO₂ removal. The operating pressure has a significant influence on the performance of solid sorbents. A higher pressure will decrease the CO₂ removal efficiency.     

Synthese von aliphatischen Aldehyden aus Alkanen und Kohlendioxid: Valeraldehyd aus Butan und CO2 – Machbarkeit und Grenzen

During the last decades, the engineering of chemical processes has focused more and more on energy efficiency and reduction of climate‐changing emissions. Regarding the synthesis of aldehydes, the photocatalytic dehydrogenation of alkanes to olefins, using visible (sun) light, and the subsequent hydroformylation of such olefins with CO₂ seem to be capable to achieve both targets. This work deals mainly with catalyst concepts for both reaction steps. Here, kinetic studies of the photocatalytic alkane dehydrogenation are presented, and the feasibility of hydroformylation using CO₂ is described in a continuous gas phase reaction. The problems that have to be solved befoe the technical application are discussed and an economic and ecological evaluation for both processes is carried out.     

Application of polyethylenimine‐impregnated solid adsorbents for direct capture of low‐concentration CO2

A systematic study of CO₂ capture on the amine‐impregnated solid adsorbents is carried out at CO₂ concentrations in the range of 400–5000 ppm, relating to the direct CO₂ capture from atmospheric air. The commercially available polymethacrylate‐based HP2MGL and polyethylenimine are screened to be the suitable support and amine, respectively, for preparation of the adsorbent. The adsorbents exhibit an excellent saturation adsorption capacity of 1.96 mmol/g for 400 ppm CO₂ and 2.13 mmol/g for 5000 ppm CO₂. Moisture plays a promoting effect on CO₂ adsorption but depends on the relative humidity. The presence of O₂ would lead to the decrease of adsorption capacity but do not affect the cyclic performance. The diffusion additive is efficient to improve the adsorption capacity and cyclic performance. Moreover, the adsorbents can be easily regenerated under a mild temperature. This study may have a positive impact on the design of high‐performance adsorbents for CO₂ capture from ambient air. © 2014 American Institute of Chemical Engineers AIChE J, 61: 972–980, 2015     

A new model for correlation and prediction of equilibrium CO2 solubility in N‐methyl‐4‐piperidinol solvent

In this work, the equilibrium CO₂ solubility in the aqueous tertiary amine, N‐methyl‐4‐piperidinol (MPDL) was measured over a range of temperatures, CO₂ partial pressures and amine concentrations. The dissociation constant of the MPDL solution was determined as well. A new thermodynamic model was developed to predict the equilibrium CO₂ solubility in the MPDL‐H₂O‐CO₂ system. This model, equipped with the correction factor (C_f), can give reasonable prediction with an average absolute deviation of 2.0%, and performs better than other models (i.e., KE model, Li‐Shen model, and Hu‐Chakma). The second‐order reaction rate constant (k₂) of MPDL and the heat of CO₂ absorption (–ΔH_abs) into aqueous MPDL solutions were evaluated as well. Based on the comparison with some conventional amines, MPDL revealed a high‐equilibrium CO₂ loading, reasonably fast absorption rate when compared with other tertiary amines, and a low energy requirement for regeneration. It may, therefore, be considered to be an alternative solvent for CO₂ capture. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3395–3403, 2017     

Heat Transfer Characteristics of CO2 Desorption from N‐Methyldiethanolamine Solution in a Microchannel Reactor

The heat transfer performance and energy consumption of CO₂ desorption from rich N‐methyldiethanolamine (MDEA) solution were determined experimentally in a straight microchannel reactor. Nucleate boiling was found to be the dominant heat transfer mechanism in this experiment. The heat transfer coefficients were strongly dependent on the heat flux. The solution flow rate was the most influential factor on the heat flux, followed by desorption temperature, MDEA concentration, and CO₂ loading. In addition, an empirical correlation was proposed to predict the experimental heat transfer coefficients.     

Untersuchung der CO2‐Absorptionskinetik in wässrigen Lösungen von N,N‐Diethylethanolanmin und N‐Ethylethanolamin

N‐Ethylethanolamine (EEA) and N,N‐diethylethanolamine (DEEA) represent promising alkanolamines for CO₂ removal from gaseous streams, as they can be prepared from renewable resources. In this work, the reaction rate constant for the reaction between CO₂ and EEA and the liquid‐side mass transfer coefficient were determined from the absorption rate measurements in a blend comprising DEEA, EEA and H₂O. A stirred‐cell reactor was applied for the absorption studies, whereas a zwitterion mechanism for EEA and a base‐catalyzed hydration mechanism for DEEA were used to describe the reaction kinetics.     

In‐situ‐Reaktionsverfolgung mittels ATR‐IR‐Spektroskopie bei der CO2‐Hydrierung zu Ameisensäure

In the hydrogenation of carbon dioxide to formic acid, the analysis is a challenge due to the unfavorable position of equilibrium and the complex reaction medium. Low yields, despite the use of a Ru/γ‐Al₂O₃ catalyst, the formation of formic acid‐amine adducts, and subsequent reactions with the solvent complicate the analytics. The coupling of the reactor to the ATR‐IR spectroscopy allows precise in situ monitoring of the reaction. Another advantage is the easy accessibility of the initial kinetics. That way, a deviation from the Arrhenius behavior was found.     

Inline‐Bestimmung der CO2‐Beladung von wässrigem Diglykolamin in Abhängigkeit von Viskosität und Temperatur

The solvents CO₂ loading is an important factor when evaluating the efficiency of an absorption/desorption process. There is almost no possibility to measure the CO₂ loading inline. Therefore experiments were made to determine a correlation between the CO₂ loading and the solvents viscosity as well as the solvents temperature. The correlation was verified using control tests and values from the literature. An overall maximum relative error under 10 % could be observed. Simultaneously investigations were made to understand if the solvents electrical conductivity and pH value are suitable for a similar correlation.     

SO42−/ZrO2 supported on γ‐Al2O3 as a catalyst for CO2 desorption from CO2‐loaded monoethanolamine solutions

In this work, the composite catalysts, SO₄²/ZrO₂/γ‐Al₂O₃ (SZA), with different ZrO₂ and γ‐Al₂O₃ mass ratios were prepared and used for the first time for the carbon dioxide (CO₂)‐loaded monoethanolamine (MEA) solvent regeneration process to reduce the heat duty. The regeneration characteristics with five catalysts (three SZA catalysts and two parent catalysts) of a 5 M MEA solution with an initial CO₂ loading of 0.5 mol CO₂/mol amine at 98°C were investigated in terms of CO₂ desorption performance and compared with those of a blank test. All the catalysts were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption experiment, ammonia temperature programmed desorption, and pyridine‐adsorption infrared spectroscopy. The results indicate that the SZA catalysts exhibited superior catalytic activity to the parent catalysts. A possible catalytic mechanism for the CO₂ desorption process over SZA catalyst was proposed. The results reveal that SZA1/1, which possesses the highest joint value of Brφnsted acid sites (BASs) and mesopore surface area (MSA), presented the highest catalytic performance, decreasing the heat duty by 36.9% as compared to the catalyst‐free run. The SZA1/1 catalyst shows the best catalytic performance as compared with the reported catalyst for this purpose. Moreover, the SZA catalyst has advantages of low cost, good cyclic stability, easy regeneration and has no effect on the CO₂ absorption performance of MEA. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3988–4001, 2018     

Stabilized Performance of Al‐Decorated and Al/Mg Co‐Decorated Spray‐Dried CaO‐Based CO2 Sorbents

The sharp loss‐in‐capacity in CO₂ capture as a result of sintering is a major drawback for CaO‐based sorbents used in the calcium looping process. The decoration of inert supports effectively stabilizes the cyclic CO₂ capture performance of CaO‐based sorbents via sintering mitigation. A range of Al‐decorated and Al/Mg co‐decorated CaO‐based sorbents were synthesized via an easily scaled‐up spray‐drying route. The decoration of Al‐based and Al/Mg‐based supports efficiently enhanced the cyclic CO₂ capture capability of CaO‐based sorbents under severe testing conditions. The CO₂ capture capacity losses of Al‐decorated and Al/Mg co‐decorated CaO‐based sorbents were alleviated, representing more stable CO₂ capture performance. The stabilized CO₂ capture performance is mainly attributed to the formation of Ca₁₂Al₁₄O₃₃, MgAl₂O₄, and MgO that act as the skeleton structures to mitigate the sintering of CaCO₃ during carbonation/calcination cycles.     

Degradations‐ und Energieverhalten reaktiver Amin‐Lösungen bei der CO2‐Absorption/Desorption

Reactive absorption using aqueous amine solutions is the technically most feasible retrofit option for the separation of CO₂ from flue gases. Frequently discussed issues are the realization of a cost‐effective increase in efficiency in the sophisticated overall absorption process and the minimization of the energy demand for solvent regeneration under operating conditions. However, the influence of degradation phenomena on capacity and energy efficiency during the absorption‐regeneration cycles using blended monoethanolamine solutions has been less considered so far. The decrease in capacity depends in particular on time, temperature, O₂‐ and SO₂ concentration in the flue gas and has to be considered in plant design. Addition of degradation inhibitors decreases the energy requirements.