1D Modeling Approach for Heat Transfer in Packed Beds with Embedded Heat Sources

To improve heat transfer in packed bed temperature swing adsorption processes for direct air capture, reactors with embedded cylindrical heating pipes have been developed. Optimization of these inherently dynamic systems currently requires a transient two-dimensional (2D) model, which is computationally very expensive. In the present work, a method is therefore developed to translate a 2D fixed bed geometry into an equivalent one-dimensional (1D) model by placing line heat sources along the direction modeled in 1D. To determine these sources’ strength, a Nusselt correlation is required. It is found that for staggered cylinder configurations, the single cylinder correlation works well. For in-line configurations, an analytical correction factor is successfully developed to account for the effect of the thermal wake of the upstream cylinders on the heat transfer around a cylinder. The 2D to 1D translation approach is then tested with three different cylinder-packing geometries at varying Péclet numbers and for steady-state and dynamic simulations. For the steady-state simulations, the 1D model has a maximum deviation of 10% in the bed mean temperature and for the outlet temperature from the 2D results (scaled to the maximum temperature difference), thus showing good agreement. For the dynamic simulations, the deviation is below 20% for most conditions, showing reasonably good agreement. The merit of the translation approach becomes apparent when looking at the computational time: the 1D model calculations are a factor of 500 faster than the 2D calculations

Maximizing Lipid Yield in Neochloris oleoabundans

(Graph Presented) The extraction yield of lipids from nonbroken Neochloris oleoabundans was maximized by using multiple extraction stages and using stressed algae. Experimental parameters that affect the extraction were investigated. The study showed that with wet algae (at least) 18 h extraction time was required for maximum yield at room temperature and a solvent/feed ratio of 1:1 (w/w). For fresh water (FW), nonstressed, nonbroken Neochloris oleoabundans, 13.1 wt % of lipid extraction yield (based on dry algae mass) was achieved, which could be improved to 61.3 wt % for FW stressed algae after four extractions, illustrating that a combination of stressing the algae and applying the solvent N-ethylbutylamine in multiple stages of extraction results in almost 5 times higher yield and is very promising for further development of energy-efficient lipid extraction technology targeting nonbroken wet microalgae

Stability of a Benzyl Amine Based CO2 Capture Adsorbent in View of Regeneration Strategies

In this work, the chemical and thermal stability of a primary amine-functionalized ion-exchange resin (Lewatit VP OC 1065) is studied in view of the potential options of regenerating this sorbent in a CO2 removal application. The adsorbent was treated continuously in the presence of air, different O2/CO2/N2 mixtures, concentrated CO2, and steam, and then the remaining CO2 adsorption capacity was measured. Elemental analysis, BET/BJH analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis were applied to characterize adsorbent properties. This material was found to be thermally and hydrothermally stable at high temperatures. However, significant oxidative degradation occurred already at moderate temperatures (above 70 °C). Temperatures above 120°C lead to degradation in concentrated dry CO2. Adding moisture to the concentrated CO2 stream improves the CO2-induced stability. Adsorbent regeneration with nitrogen stripping is studied with various parameters, focusing on minimizing the moles of purge gas required per mole of CO2 desorbed

Evaluating Regeneration Options of Solid Amine Sorbent for CO2 Removal

Biogas is one of the most popular alternative energy resources to replace fossil fuels. The product of anaerobic fermentation in a digester contains several impurities such as H2S and especially CO2 that needs to be removed in order to upgrade the gas quality. Supported amine sorbents (SAS) might provide an attractive option to remove these impurities. However, little is known about the regeneration of the sorbent. This study evaluates experimentally and by modeling the options for regeneration of the SAS. Theoretically, pressure swing adsorption without purge flow is the most energy efficient method (1.7 MJ/kg CO2). It was found that when using a purge flow the desorption rate is strongly influenced by the equilibrium between the gas and adsorbed phase. With elevated temperature (>80 °C) both the working capacity and the productivity increase significantly. Finally, an energy evaluation for a typical biogas case study is carried out, showing the trade-offs between power consumption, heat demand, and sorbent inventory. Interestingly, at the expense of a somewhat higher power consumption, the use of inexpensive air as purge gas at 60 °C could be an attractive option, but case-specific costs are needed to identify the economic optimum

A Multistage Fluidized Bed for the Deep Removal of Sour Gases: Proof of Concept and Tray Efficiencies

Currently there are significant amounts of natural gas that cannot be produced and treated to meet pipeline specifications, because that would not be economically viable. This work investigates a bench scale multistage fluidized bed (MSFB) with shallow beds for sour gas removal from natural gas using a commercially available supported amine sorbent. A MSFB is regarded as a promising adsorber type for deep sour gas removal to parts per million concentrations. A series of experiments was conducted using carbon dioxide as sour gas and nitrogen to mimic natural gas. Removal below 3 mol ppm was successfully demonstrated. This indicates that gas bypassing is minor (that is, good gas–solid contacting) and that apparent adsorption kinetics are fast for the amine sorbent applied. Tray efficiencies for a chemisorption/adsorption system were reported for one of the first times. Current experiments performed at atmospheric pressure strongly indicate that deep removal is possible at higher pressures in a multistage fluidized bed