Absorber Height Research Articles

Techno‐Economic Analysis of Glycerol Steam Reforming with Amine‐Based Carbon Capture for Blue Hydrogen Production: A Rate‐Based Kinetic Model Approach

ABSTRACTThis study outlines a comprehensive process design utilising glycerol‐steam reforming for an H2‐enriched gas stream, coupled with carbon dioxide removal via a chemical absorption system, followed by a techno‐economic analysis. The Aspen Plus economic analyser assesses the developed model, incorporating simulation results and literature data. Initially, the CO2 capture unit was planned with a standalone absorber and stripper, later integrated for solvent makeup calculation. Findings reveal that as catalyst loading increased from 5 to 50 kg, glycerol conversion and product molar fraction improved. For a targeted H2 production of 10 t/day, optimal reactor dimensions are 3.2 m diameter and 30 m length, corresponding to a reactant flow of 105 t/day and a 2.52 MW heat duty at stoichiometry conditions. To capture 95% CO2 from the reformed product stream, absorber and stripper packing heights of 12 and 7 m, respectively, with column diameters of 1.25 and 2.71 m are necessary. The production cost of H2 is determined to be $3.8 per kg, as revealed by the techno‐economic analysis. Calculated values for net present value, discounted payback period, and internal rate of return stand at $30 million, 5 years, and 25.0%, respectively. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Investigation of the performance of a parabolic trough collector outfitted with annular absorber tubes

The current work recommends a novel absorber tube for parabolic trough solar collectors. Annular absorber tubes with and without spiral tape have been investigated as an alternative to conventional absorber tubes. This work employs numerical analysis through the usage of CFD code. The pitch ratio (P/D), width ratio (W/D), and height ratio (H/D) of the spiral tape are each different. Within the annular absorber tube, these ratios have an impact on the performance of heat transfers, pressure drop, and entropy generation. The results reveal that an annular absorber tube without spiral tape has a higher Nu ratio than a conventional absorber tube. In an annular absorber tube with P/D = 1.4, the Nusselt number increases. In an annular absorber tube, the spiral tape thickness ratio has no effect. The average Nu ratio is 24.5% greater at a height ratio of 0.3 than it would be in an annular absorber tube without spiral tape. The annular absorber tube's spiral tape's pitch ratio, thickness ratio, and height ratio all generate less total entropy than a conventional absorber tube does. The wall temperature of the absorber tube with the lowest spiral tape pitch ratio decreases, which results in a reduction in the thermal stress on the absorber wall. On the other hand, spiral tape and an annular absorber tube have a higher friction ratio. It exceeds the friction ratio of the annular absorber tube without spiral tape by 41.7 times.

PERFORMANCE ANALYSIS OF AN EFFICIENT NEW-DESIGN SOLAR AIR HEATER BY CFD METHOD

The main contribution of this study is to present a modified V-corrugated grooved absorber plate in the construction of plane solar air heaters for higher performance. The combined effects of extended heat transfer area due to the V-shaped absorber, the suction process by the grooves that maintains the convective flow closed to the heated absorber and the jet impingement enable high efficiency of the proposed solar collector. For simulation purposes, the conduction equation is employed for temperature computations inside the solid elements, while the turbulent airflow equations are solved based on the CFD method using the κε− turbulence model. The present finite element-based analysis is performed using the COMSOL Multi-physic software. To demonstrate the rate of irreversibilities in a solar collector, the entropy generation due to heat transfer and viscous friction and, accordingly, the second law efficiency are computed at different steady operating conditions. The numerical procedure is validated by comparing the obtained numerical findings with the experimental results reported in the literature. From the obtained results, it is found that the proposed absorber plate has a triple-edged sword positive effect on the solar air heater performance, such that the thermal efficiencies up to 80% are computed. Moreover, about 10% improvement in the thermal efficiency of the proposed solar collector compared with its competitor (solar air heater with a simple V-corrugated absorber) reveals the positive impact of the designed absorber plate. Also, the increase in the height of V-shaped absorber from 𝐻𝐻0=2 𝑐𝑐𝑐𝑐 𝑡𝑡𝑡𝑡 𝐻𝐻0=4 𝑐𝑐𝑐𝑐 leads to about 11% improvement in the heater thermal efficiency. The numerical findings can be considered as a good reference to find an alternative for efficient solar collectors.

Modeling and Simulation of CO2 Capture Unit using Mixed Solvent of Aqueous Methyldiethanolamine and Piperazine for 6.4 MWe Power Plant

Carbon dioxide emissions are the largest greenhouse gases contributor, which is attributed to global warming. Therefore, the capture of CO2 is necessary, especially from large point sources. Post-combustion capture using chemical solvents is the most matured capture technology. In this paper, mixed solvents of methyldiethanolamine (MDEA) and piperazine (PZ) were studied to potentially address some issues related to the use of conventional monoethanolamine (MEA). Steady-state modeling and simulation of the post-combustion carbon capture using the mixed solvents for a typical 6.4 MWe power plant were done. The model developed was validated against experimented data with relative error between 1 – 4.73% for the absorber on CO2 capture efficiency and between 2.93 – 10.2% relative errors on CO2 regeneration efficiency. The model was scaled up to capture CO2 from the flue gas of a typical 6.4 MWe power plant. The scaled-up results showed packing height and diameter of absorber to be 5.5 m and 1.5 m; while that of the stripper was 5.08 m and 1.45 m respectively. Effect of flue gas temperature on the capture efficiency was studied, it was observed that as the temperature increased from 20 ºC, the capture efficiency increased, but at 70 ºC, the efficiency showed no significant increase which could be associated with the existence of a temperature bulge. Capture efficiency increases with an increase in PZ concentration due to increase in the rate of reaction with concentration. The absorption and regeneration results suggest that an aqueous MDEA/PZ blend could be a prospective absorbent for CO2 capture.

The prototype, mathematical model, sensitivity analysis and preliminary control strategy for Adaptive Tuned Particle Impact Damper

The paper presents a novel approach for prototyping and modelling of the Adaptive Tuned Particle Impact Damper (ATPID). After introducing the operation and potential disadvantages of the classical Particles Impact Dampers (PIDs) the authors propose the concept of single-grain controllable damper, which can adapt to actual dynamic excitation by a real-time change of the container height. The investigations focus on the methodology of simplified mathematical modelling of the ATPID damper based on grain physical properties, nonlinear soft contact theory, and control function of the absorber height being a novel component used to optimize dynamic response of the system. The proposed ATPID model is positively verified against the experimental results obtained from the developed test stand including a vibrating beam equipped with the proposed innovative attenuator. The conducted analyses clearly reveal the operating principles of the ATPID damper, the types of grain movement, the influence of shock absorber parameters on the vibrating system response and the energy balance of the system. The solution of the formulated optimization problem aimed at minimization of vibration amplitudes allows to find the optimal damper height for various physical parameters of the grain and the external excitation and to achieve a high efficiency of the proposed damper reaching 90%. In addition, a real-time control strategy providing adaptation of the ATPID damper to changing amplitude of kinematic excitation and effective mitigation of steady-state vibrations is proposed and verified experimentally.

Experimental study on the performance of pyramid solar still with novel convex and dish absorbers and wick materials

Solar still is a famous technique of the desalination methods, but it suffers from the low productivity. In this paper, novel structured convex absorbers were proposed in a pyramid solar still. The performance of the pyramid solar still (PSS) was experimentally investigated when using a convex cylinder absorber shape (CCPSS) and dish shape of absorber (CDPSS) instead of the flat absorber. The proposed absorber shapes increased the surface areas of exposure and evaporation and reduced the water depth to minimum inside the distiller. Also, the experimentations were conducted when using different heights of convex dish shape (5, 10, 15, and 20 cm) to obtain the optimum convex height of the dish absorber. Besides, the system was experimentally investigated when using two different wick materials of cotton cloth and jute wicks that were put over the convex surface. Furthermore, the performance of CDPSS was tested when painting the absorber by black paint mixed with different nanocomposites of titanium oxide (TiO2) copper oxide (CuO) and silver (Ag). Systems performance based on economic, enviroeconomic, CO2 reduction, and energy point of view was studied. Experimental results revealed that the CDPSS provided better performance than either CCPSS or PSS. Also, the optimum height of dish absorber that obtained the best performance of CDPSS was 15 cm, where at this height (15 cm), the increase in productivity of CDPSS was 54% with jute cloth over that of the PSS. The highest productivity of CDPSS was obtained when using Ag followed by CuO and then TiO2, where the average daily productivity of CDPSS with jute and Ag was 6750 mL/m2.day compared to 3800 mL/m2.day for that of PSS (improvement = 78% and efficiency = 45.7%). Besides, the rate of CO2 mitigation for the CDPSS with Ag, CuO, TiO2 and without nanoparticles was about 13.5, 12.7, 12.5, 10.17 tons/y respectively. Also, the enviroeconomic parameter (Z^') was 147.6, 181.2, 184.1, and 195.1 per year for the (CDPSS), (CDPSS + TiO2), (CDPSS + CuO), and (CDPSS + Ag), respectively for 365 operating days and lifetime 20 years. Finally, the costs of the distilled water of PSS and CDPSS with jute cloth and silver nanoparticles were 0.018 and 0.015 $/L, respectively.

Hydrogen production via solid waste gasification with subsequent amine-based carbon dioxide removal using Aspen Plus

This simulation study presents the municipal solid waste gasification, along with a detailed design of CO2 capturing unit using monoethanolamine (solvent). The gasifier's operational parameters, such as pressure, temperature, and equivalence ratio, are chosen to optimize the gasified H2-enriched product stream. At optimal operational parameters, such as temperature (800 °C), pressure (1 bar), and equivalence ratio (0.2), a maximum H2 content of 27.9% could be attained. Following that, 39.5% H2 is found at the high-temperature shift reactor's exit, followed by 42.1% at the low-temperature shift reactor's output. It is observed that the absorber (16.5 m) and stripper (6 m) packing heights are required to capture 95% CO2 from the product effluent obtained after shift reactors, along with column diameters of 2.70 and 3.61 m, respectively. Hence, the proposed model can give vital information for large-scale gasifier and CO2 capture unit design, operation, and optimization with respect to different flue gases.

Energy assessments of onboard CO2 capture from ship engines by MEA-based post combustion capture system with flue gas heat integration

An early phase feasibility study was carried out for offshore CO2 capture from ship engines of a CO2 transport ship. A flexible in-house process simulator was applied in the assessments. Parametric studies of the overall onboard process were enabled by a fast data-driven capture plant model derived from supervised machine learning by PLS regression of a large dataset of rigorous simulations. The results show, based on the given models and assumptions, that the thermal energy coming from the ship engine exhaust gas is not sufficient alone to cover the thermal energy demand of an absorption-based CO2 capture unit operating above 50% capture rate using 30 wt% MEA (mono-ethanolamine) as solvent. The thermal energy demand can be met using a fuel afterburner as heat source. The added fuel consumption is estimated to increase the fuel consumption by 6–9% when operating with liquefied natural gas (LNG) as fuel source, while an increase of 8–12% is expected with diesel as fuel source. The effect of absorber height on energy consumption at a given CO2 capture rate is limited, especially for lower capture rates, and may be an important degree of freedom for optimizing the CAPEX/OPEX trade-offs. Use of state-of-the art solvents with lower specific energy consumptions will shift the results towards higher capture rates before a fuel afterburner is required to meet the thermal energy demands.

Characteristics of HFC-134a absorption rate with [Bmim][Tf2N] in falling film type absorber

To develop an absorption heat pump with a hydrofluorocarbon refrigerant, this study evaluated its absorption rate with a falling liquid film type absorber. The HFC-134a refrigerant and [Bmim][Tf2N] ionic liquid were selected as the absorbent pair. The experimental apparatus was designed using the volumetric method, and the effects of the absorbent mass flow, temperature, and pressure conditions on the absorption rate were evaluated. Additionally, we calculated the absorption rate coefficient using the HFC-134a absorption transport model. The experimental results revealed that the absorption rate affected the desired amount of absorption equilibrium under the given temperature and pressure conditions. The absorption rate increased, while the amount of absorption at the set temperature and pressure decreased. Additionally, the outlet amount of absorption in the absorber increased as the absorbent mass flow down onto the heat exchanger tube increased. However, the amount of absorption was saturated as the absorbent mass flow increased. We monitored the absorbent flow behavior in the heat exchanger tube. The gas–liquid surface area was not changed by the absorbent mass flow, and the thickness of the absorbent liquid film increased. The absorption rate coefficient was determined using the HFC-134a absorption transport model, and the absorber height was calculated for up-scaling. The calculation results revealed that, to achieve 80% of absorption equilibrium, the absorber height must be 4.3 times greater than the experimental value. Thus, the heat exchanger with high wettability must be designed with a high absorption rate.

ВИБРОСЕЙСМО ЗАЩИТА ЗДАНИЙ И СООРУЖЕНИЙ ОТ ДИНАМИЧЕСКОГО ВОЗДЕЙСТВИЯ ПРИРОДНОГО И ТЕХНОГЕННОГО ХАРАКТЕРА

In this article, the authors analyze results of their long-term researches on protection of buildings and structures against dynamic loads caused by the nature and/or human activities. They also give the grounds for necessity to provide vibration insulation of buildings, and show how to choose and calculate proper parameters for rubber vibroseismic insulators. Specifics of finite element method applied for static calculating the vibroseismic insulators is also described. In order to take into account weak compressibility of rubber, a moment finite element scheme was used, which assumes a triple approximation of the displacement vector components consisting of strain tensor and volume change function. Stress-strain state of the shock absorbers was determined for different standard sizes and diameters. The authors also describe two variants of calculation depending on the method of fixing the insulator’s ends. In the first case, the ends are vulcanized to the metal plates. In the second variant, the ends are free and can move in a horizontal plane. Influence of ratio of the shock absorber height and radius to the strain state of a structure was also analyzed. In order to determine factual levels of the soil and pile vibration (in two horizontal and one vertical directions), vibrodynamic studies were carried out. The obtained vibration signals were registered by the one-component vibration transducers 731A (vibration sensors) produced by the Wilcoxon Research company (the USA). Then, the vibration records were processed by the specialized program “Seismic Monitoring”. Based on the results of these studies, numerical calculations were performed in order to determine whether the predicted levels of the residential building vibrations are in compliance with the existing sanitary standards when exposed to real technogeneous loads. Vibrodynamic tests on vibration acceleration levels of the vibration-insulated reinforced concrete slabs and floors in residential building confirmed high effectiveness of the used vibroseismic insulation system with the rubber elements: the registered vibration acceleration levels in the residential building on all floors did not exceed acceptable levels set by the sanitary standards, and ensured comfortable living conditions under different dynamic impacts. The results of this work make it possible to design buildings with anti-seismic protection by using the designed rubber elements in accordance with the local conditions of the city of Almaty.

Onboard CO <sub>2</sub> Capture From Ship Engines

An early phase feasibility study has been carried out for offshore CO2 capture from ship engines of a CO2 transport ship. Capture of CO2 from ship engines is a challenging task, especially considered the limited space and energy available onboard, and the logistics involved in bringing the captured CO2 to permanent storage. In this relation, CO2 transport ships could be a special case that is viable, since the capture plant would be located next to dedicated tanks already heading for a storage site. The aim of the current work was to explore the possibility of capturing CO2 from the exhaust gas emitted by the engines of CO2 transporting ships as part of CO2LOS II (CO2 Logistics by Ship Phase II) project. A flexible in-house process simulator was applied in the assessments. Parametric studies were enabled by a fast data-driven capture plant model derived from a large dataset of rigorous simulations. The results show, based on the given models and assumptions, that the thermal energy coming from the ship engine exhaust gas is not sufficient alone to cover the thermal energy demand of an absorption-based CO2 capture unit operating above 50 % capture rate using 30wt% MEA (monoethanolamine) as solvent. The thermal energy demand can be met using a fuel afterburner as heat source. The added fuel consumption is estimated to increase the fuel consumption by 6-9 % when operating with liquefied natural gas (LNG) as fuel source, while an increase of 8-12 % is expected with diesel as fuel source. The effect of absorber height on energy consumption at a given CO2 capture rate is limited, especially for lower capture rates, and may be an important degree of freedom for optimizing the CAPEX/OPEX trade-offs. Use of state-of-the art solvents with lower specific energy consumptions will shift the results towards higher capture rates before a fuel afterburner is required to meet the thermal energy demands.

Absorption of Carbon Dioxide with Hot Potassium Carbonate Solution: Modeling and Statistical Analysis of Known Experimental Data

The process of absorbing carbon dioxide with an aqueous solution of hot potassium carbonate is widely used in industry for gas purification. The results of numerical modelling of the process are compared with a limited set of experimental data in well-known works. In this paper, a mathematical model of the process in a packed absorber is developed; fitting parameters are taken on the basis of processing known experimental data. The model is based on the equations of heat and mass transfer. Main characteristics: concentrations of substances and temperatures in the liquid and gas phases, depend on one coordinate z directed along the height of the absorber. The heat and mass transfer coefficients were calculated using the Onda formulas. The CO2 equilibrium at the liquid-gas interface was determined by Sechenov relation. The adequacy of the model was checked by comparing the calculations of carbon dioxide concentration along the absorber with the known experimental data not included in the sample from which the model parameters were determined. The numerical dependences of the CO2 content in the scrubbed gas on the physical characteristics of the process are obtained.

Operational optimization of absorption column in capturing CO2 from flue gas in coal-fired power plant

The solvent scrubbing method is one of the promising technologies to capture CO2 from flue gas. In this technology, CO2 is absorbed from flue gas using a liquid solvent in an absorption column and subsequently, solvent and CO2 are separated in a stripper column. The recovered solvent from the stripper unit is recycled to an absorption unit along with the makeup of the fresh solvent. Aqueous monoethanolamine (MEA) is widely used as the solvent in this method. The cost of solvent for continuous makeup in the absorber is one of the major operating costs. The goal of this study is to minimize the flow rate of the MEA stream to capture the specified amount of CO2 from flue gas to reduce the operating cost. Various scenarios are simulated in commercial process plant simulator by varying the CO2 loading in lean MEA stream and absorber height. Flue gas compositions are obtained from the Rocky Mountain Hunter Power Plant (coal-fired), Utah, USA. We have shown that more than 80% CO2 is captured using absorber heights of 25–40 m and CO2 loading in MEA of 0.2 and less using the minimum flow rate of MEA. An insignificant amount of MEA (<0.2%) is lost from the absorption and stripper units. Other than the purchasing cost of the solvent, operating costs related to pumping, cooling, handling, etc. can be significantly reduced using the method developed in this study.

Techno-Economic Assessment for CO2 Capture From Air Using a Conventional Liquid-Based Absorption Process

Carbon dioxide (CO2) capture of directly from ambient air in a conventional monoethanolamine (MEA) absorption process was simulated and optimised using a rate-based model in Aspen Plus. The process aimed to capture a specific amount (148.25 Nm3/h) of CO2 from the air, which was determined by a potential application aiming to produce synthetic methane from the output of a 2.7 MW electrolyser. We conducted a sensitivity analysis around different parameters such as air humidity, capture rate, CO2 loading and reboiler temperature, and evaluated the energy consumption and overall cost in this system. To meet the design requirement for standard packed columns, the rich absorption liquid was circulated to the top of the absorber. A capture rate of 50% was selected in this process as a baseline. At higher capture rates, the required energy per tonne of captured CO2 increases and at lower capture rates, the size of equipment, in particular, absorber and blowers increases due to the need for processing a significantly larger volume of air at the given CO2 production volume. At the base case scenario, a reboiler duty of 10.7 GJ/tCO2 and an electrical energy requirement of 1.4 MWh/tCO2 were obtained. The absorber diameter and height obtained were 10.4 and 4.4 m, respectively. The desorber is found to be relatively small at 0.54 m in diameter and 3.0 m in height. A wash water section installed at top of the absorber decreased the MEA loss to 0.28 kg/tonne CO2. However, this increased capital cost by around 60% resulting in CO2 capture costs of $1691 per tonne CO2 for the MEA base scenario. Based on the techno-economic analysis, assuming a non-volatile absorbent rather than MEA thereby avoiding a wash water section, and using an absorption column built from cheaper materials, the estimated cost per tonne of CO2 produced was reduced to $676/tCO2. The overall cost range was between $273 and $1227 per tonne of CO2 depending on different economic parameters In order to reduce the cost further, the use of innovative cheap gas-liquid contactors that operate at lower liquid to gas ratios is crucial.

Ventilation Performance Investigation of Roof Top Solar Chimney

The solar chimney is an innovation, which has been as of now demonstrated of being able to create electrical vitality from the sun likewise it has been introduced in different structures for ventilation, and next to no is thought about their genuine presentation and very panics are the application. This research work deals with the development of a physical, mathematical and computational models of roof solar chimney to rationalize the performance of ventilate in residential house. A thermal model enables to easily determine the inclination angle, absorber area, cavity width of the chimney and the air flow rate, using MATLAB. The simulation has been done for selected residential house of 264m³ located at Bahir Dar city, Ethiopia @ 11° latitude and 37° longitude. At comfort air speed (2m/s), a south faced system being tilted at an angle of 45° will have absorber length, the absorber height and cavity width about 3m, 4.24m, and 0.5m respectively. This will enable the residential house to circulate the air 560kg per hour. The maximum air temperature obtained at chimney outlet is 44.5°C. For a month of April an average solar intensity value is 900 W/m². The main factor to induce buoyancy is solar insolation since it directly influences the air temperature, and the efficiency is about 44.4%.

Modelling and simulation study of CO2 capturing process in coal fired power plant using various amine solvents

In the present world, Scientists are very much concern on to reduce the concentration level of carbon dioxide in environment to save the world. In the present work, the CO2 capturing efficiencies of three different amine solvents were analyzed. The selected solvents were mono-ethanol amine (MEA), solvent containing mixture of methyl diethanol amine (MDEA) and piperazine (PZ) called activated -MDEA and aqueous ammonia (NH3) solution. Rigorous simulation method was considered in the current study. The effects of different key parameters for different solvents on the CO2 removal efficiency were analyzed. Packing height, solvent temperature and absorber height were the significant influential parameters for MEA system whereas for activated-MDEA (a-MDEA), those are the ratio of the solvent to feed quantity and the mixed solvent PZ concentration level. For aqueous NH3 solution, absorber and stripper’s temperature, CO2 loading, concentration of NH3, height of the absorber, lean and rich solvent flow rate, boil up ratio, regeneration energy, temperature of the condenser, and duty of the reboiler were considered. The comparative study showed that MEA process recovered the maximum CO2 from flue gas. But it was suffered by the maximum regeneration duty. a-MDEA with PZ recovered 91% CO2. Overall, technically, a-MDEA was the best choice as solvent. Compared to a-MDEA and MEA, aqueous ammonia was identified as more propitious and environment friendly solvent due to its satisfactory performance and easy availability.

Influence of Key Factors on the Characteristics of Flue Gas Desulfurization of Basic Aluminum Sulfate by Bubbles.

Temperature, reactant concentration, bubble flow field characteristics, and mass-transfer characteristics play an important role in flue gas desulfurization of basic aluminum sulfate (aluminum base). The influence of various factors on desulfurization efficiency (ηabs) was determined from the macroscopic and microscopic levels through experiments and numerical simulations. The temperature of absorption solution had a significant effect on ηabs, and low temperature was advantageous for SO2 absorption performance of aluminum base. The value of ηabs increased with increasing reactant concentration. When the aluminum base concentration was higher than 50%, ηabs remained above 90%. The low aluminum base shortened the beginning time of the rapid decline of ηabs. This outcome was related to the low concentration of active Al2O3. At a low concentration range of 2000–5000 ppm of inlet SO2, the reaction rate determined the ηabs level, and gas-phase mass-transfer resistance was the main factor restricting the increase in ηabs. However, reaction rate and gas-phase mass-transfer resistance determined the ηabs level when the inlet SO2 concentration was as high as 50 000 ppm. The aeration rate affected the bubble size, number, and diffusion state. In addition, a higher aeration rate reduced the gas–liquid contact time and speeded up the consumption of aluminum base. As a result, bubbles along the absorber height showed different desulfurization characteristics, that is, 0–0.1 m was the initial stage of bubble formation and desulfurization (the ηabs was lower than 15%), 0.1–0.34 m was the main stage of bubble diffusion and desulfurization (the ηabs rapidly increased to 86.4%), and 0.34–0.4 m was the stable stage of desulfurization (the ηabs slowly increased to 92.5%).

Theoretical performance analysis of new class of Fresnel concentrated solar thermal collector based on parabolic reflectors

The main advantage of Fresnel systems is their capability to use flexible reflectors which are cheaper in comparison to glass reflectors. In this study, the effects of using parabolic reflectors instead of flat reflectors on Fresnel solar concentrator have been studied for the first time. For this new system by ray trace statistical method, local concentration ratio distribution has been determined. The new system is compared with linear Fresnel reflector (LFR). The effect of geometrical parameters, such as absorber height and reflectors width, on the concentration ratio is studied. The results have shown that using the parabolic reflectors with low curvature has a pronounced effect on the absorber pipe diameter. Comparison of the performance of linear and parabolic systems with identical parameters such as reflectors width, reflectors number and absorber pipe height showed that the absorber tube diameter in a parabolic system is smaller than the absorber tube diameter in a linear system, thus decreased rate of heat loss from the pipe surface. Comparison of the two systems under equal solar energy radiation and absorber pipe diameter showed that in parabolic system wider reflectors can be used, thus reduced number of reflectors and simpler control system.

Micro-computed tomography evaluation of volumetric polymerization shrinkage and degree of conversion of composites cured by various light power outputs

This study evaluated the influence of different light-curing modes on the volumetric polymerization shrinkage and degree of conversion of a composite resin at different locations using micro-computed tomography and Fourier transform infrared spectroscopy (FTIR). Specimens were divided into 4 groups based on the light-curing mode used (Bluephase 20i): 1 -High (1,200 mW/cm2); 2 -Low (650 mW/cm2); 3 -Soft-start (650-1,200 mW/cm2); and 4 -Turbo (2,000 mW/cm2). Degree of conversion was calculated by the measurement of the peak absorbance height of the uncured and cured materials at the specific wavenumbers, and was performed by FTIR 48 h after curing resin samples. Degree of conversion was analyzed using two-way ANOVA. No significant differences were observed independent of the region of the restoration investigated (p>0.05). Different curing modes did not influence volumetric shrinkage neither degree of conversion of class I composite resin restorations.

Experimental Studies on Spray Absorption with the Post Combustion CO2 Capture Pilot-Plant CASPAR

Previous experiments with the spray scrubber pilot-plant CASPAR have demonstrated a CO2 removal rate (RR) of nearly 90% at 47 m overall spray column height with a 30 wt-% monoethanolamine (MEA) solution, a liquid-to-gas (L/G) ratio of 4.9 L m-3 (STP) and a sauter mean diameter D3/2 of 1.6mm and confirmed the applicability of a spray absorption technology for post combustion CO2 capture (PCC). Further investigations with 30 wt-% MEA and different spray nozzles show positive effects on the absorption behaviour due to smaller droplet sizes. With D3/2 of 1.1 mm it was possible to achieve a RR of 83% at 44.5 m overall absorber height, where the RR is 11 percentage points higher than for D3/2 of 1.6 mm at the same height. The influence of the solvent properties dynamic viscosity and surface tension on the droplet size and mass transfer performance is discussed and is also presented.