Initial CO2 Concentration Research Articles

Performance of different microalgae-based technologies in biogas slurry nutrient removal and biogas upgrading in response to various initial CO2 concentration and mixed light-emitting diode light wavelength treatments

Microalgae-based technologies were studied for nutrient removal in biogas slurry and biogas upgrading in the photobioreactors constitute, which were cost-effective, environment-friendly alternatives to conventional physical-chemical methods. The effects of CO2 concentration on nutrient removal and biogas upgrade using Chlorella vulgaris monocultivation, Ganoderma lucidum-Chlorella vulgaris cocultivation and activated sludge-Chlorella vulgaris cocultivation were investigated. Besides, the influences of three ratios of red to blue light wavelength on nutrient removal and biogas upgrading were also investigated. The results showed that optimum biogas slurry nutrient reduction could be achieved by Ganoderma lucidum-Chlorella vulgaris cocultivation using the pelletization method. The optimal ratio of red to blue light wavelength for nutrient removal and biogas upgrading was 5:5, resulting to maximal mean removal efficiencies of 86.08± 6.27%, 85.69± 6.34%, 86.17± 6.13%, and 79.11 ± 5.97% for chemical oxygen demand, total nitrogen, total phosphorus and CO2, respectively. The results will provide a reference for simultaneously purifying wastewater and upgrading biogas using microalgae-based technology.

Performance of a Carbon Dioxide Removal Process Using a Water Scrubber with the Aid of a Water-Film-Forming Apparatus

With tap water as a physical solvent to absorb CO2 from different concentrations of mixed gases (containing CO2 and N2), an apparatus outfitted with a water-film generator was used to enhance the CO2 dissolution rate as well as the contact between the liquid and gas phases. The operational pressure in the absorption tank, induced gas pressure, initial CO2 content, liquid-to-gas ratio, and temperature had a significant effect on the CO2 removal efficiency and its absorption rate in water. On varying the experimental conditions, the CO2 removal ability and absorption rate varied from 22.9 to 90.0% and 4.5 × 10−4–44.4 × 10−4 mol s−1 L−1, respectively. For instance, the removal and absorption rates reached approximately 90.0% and 12.0 × 10−4 mol s−1 L−1, respectively, when the experiment was operated at 10 °C and 0.30 MPa of gas pressure with 35% CO2 inlet gas content and 1.40 liquid-to-gas ratio. Additionally, a statistical tool, the Taguchi method, was applied to evaluate the effects of four parameters thoroughly and systematically. According to the Taguchi analysis results of nine total runs for four independent variables with three levels for each, the two most significant variables for the removal rate were temperature and liquid-to-gas ratio, whereas those for the absorption rate were inlet gas CO2 concentration and gas compressed pressure. These results may provide evidence to aid in the adoption of this method for large-scale CO2 capture from exhaust gases.

The Effect of Temperature and Initial Methane Concentration on Carbon Dioxide Methanation on Ni Based Catalysts

Abstract A series of Ni based catalysts prepared by incipient wetness method were characterized by chemisorption and studied for CO 2 methanation. Ru had apparently a positive effect on the active metal surface area, and thus the catalytic activity. The CO 2 conversion was greatly affected by temperature where the conversion ranged from 12%-85% at temperatures of 300 to 400 o C on the 12% Ni/Al 2 O 3 catalyst. At 350 o C, higher Ni loading resulted in increased activity. The incorporation of 0.5% Ru lead to a drastic increase in catalytic activity, which can be explained by increased reducibility and a synergetic effect between Ni and Ru, and was further enhanced by increased Ni loading. Addition of CH 4 at twice the initial concentration of CO 2 to the feed gas mixture was found to decrease the conversion from 52% to 48% at 350 o C on the 20% Ni/Al 2 O 3 catalyst, whereas only a slight reduction in selectivity was observed. The results preliminary demonstrate that high methane purity can be achieved from a biogas feed stream over Ni based catalysts.

Crystal growth and stoichiometry-dependent properties of the ferromagnetic Weyl semimetal ZrCo2−xSn

We report the growth of high quality bulk crystals, through crystallization from molten Sn flux, of the predicted ferromagnetic Weyl metal ZrCo2−xSn with the L21 Heusler phase structure. The concentration of Co vacancies in the single crystals is found to be dependent on the initial concentration of Co in the flux. The saturation magnetization increases approximately linearly with decreasing Co deficiency and the ferromagnetic transition temperature changes significantly. p-type carrier conduction and an anomalous Hall effect are observed. The calculated electronic density of states of ZrCo2−xSn shows a significant change in minority and majority spin state occupancies and a shift in the Fermi level with Co deficiency.

Response surface method for modeling the removal of carbon dioxide from a simulated gas using water absorption enhanced with a liquid-film-forming device

This paper presents the results from using a physical absorption process to absorb gaseous CO2 mixed with N2 using water by producing tiny bubbles via a liquid-film-forming device (LFFD) that improves the solubility of CO2 in water. The influence of various parameters—pressure, initial CO2 concentration, gas-to-liquid ratios, and temperature—on the CO2 removal efficiency and its absorption rate in water were investigated and estimated thoroughly by statistical polynomial models obtained by the utilization of the response surface method (RSM) with a central composite design (CCD). Based on the analysis, a high efficiency of CO2 capture can be reached in conditions such as low pressure, high CO2 concentration at the inlet, low gas/liquid ratio, and low temperature. For instance, the highest removal efficiency in the RSM–CCD experimental matrix of nearly 80% occurred for run number 20, which was conducted at 0.30MPa, CO2 concentration of 35%, gas/liquid ratio of 0.71, and temperature of 15°C. Furthermore, the coefficients of determination, R2, were 0.996 for the removal rate and 0.982 for the absorption rate, implying that the predicted values computed by the constructed models correlate strongly and fit well with the experimental values. The results obtained provide essential information for implementing this method properly and effectively and contribute a promising approach to the problem of CO2 capture in air pollution treatment.

Rapid adsorption of cobalt (II) by 3-aminopropyltriethoxysilane modified halloysite nanotubes

The adsorption of cobalt (II) by 3-aminopropyltriethoxysilane (APTS) modified halloysite nanotubes (HNTs) was studied. The modified halloysite was characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD) and thermogravimetry (TG). In addition, a batch method was used to study the adsorption behavior and the mechanism of removal Co (II) by modified HNTs; the effective factors influencing the adsorption process including adsorbent concentration, contact time, initial pH, temperature and the initial concentration of Co (II) have been investigated. The results showed that the APTS was successfully grafted on the HNTs surface. The modified HNTs exhibited rapid adsorption speed, which reached the adsorption equilibrium within 30 min. The adsorption capacity of the adsorbent increased significantly with the increase of pH. The adsorption data of Co (II) on the modified HNTs are well consistent with the Langmuir model and the pseudo-second-order kinetic model.

Removal of carbon dioxide from flue gases in packed column using ionic liquids

ABSTRACTThe study of CO2 absorption in ionic liquids (ILs): [Emim] [Ac], [Bmim] [Ac] in a packed column is presented. The influence of mass transfer resistances, initial CO2 concentration, absorption temperature and 2, 5, 10% wt. water addition on CO2 removal efficiency was investigated. The resistance in series model and estimated values of enhancement factor were used to predict with good accuracy mass fluxes of absorbed carbon dioxide for both ILs. The CO2 absorption efficiency in packed column depends on temperature and initial CO2 concentration. The addition of small amounts of water to [Emim][Ac] is of minor effect on CO2 absorption.

Three-dimensional cobalt microspheres composed of nanosheets assembled via facile hydrothermal method

We report a template-free approach to prepare three-dimensional cobalt microspheres composed of nanosheets by a facile hydrothermal method. The synthesized 3D cobalt microspheres with diameter of approximately 1–2µm have a nanosheet of ca. 18nm. The samples were characterized by X-ray diffraction, SEM, TEM, and VSM techniques. It was found that the initial concentration of Co(NO3)2·4H2O and surfactant played an important role in the formation of 3D cobalt microspheres. The Ms value of 3D cobalt microspheres which obtained under the cationic surfactant is about 122.55emu/g. Due to the specific structure and magnetic properties, these 3D cobalt microspheres are expected to have potential applications as candidates for catalysis, sensor and energy storage.

CO2 capture performance of bi-functional activated bleaching earth modified with basic-alcoholic solution and functionalization with monoethanolamine: isotherms, kinetics and thermodynamics

CO2 capture performance of bifunctional activated bleaching earth (ABE) was investigated at atmospheric pressure. The sorbents were characterized by means of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Caron-Hydrogen-Nitrogen analysis (CHN), Fourier transform infrared (FT-IR) and thermal gravimetric analysis (TGA). The CO2 capacity was enhanced via basic-modification and monoethanolamine (MEA) loading of the ABE sorbent to obtain a bifunctional surface property. Here, basic-modified calcined ABE with a 30wt.% MEA loading (SAB-30) showed the highest CO2 capture capacity, but this was decreased with excess MEA loading (>30wt.%). At a 10% (V/V) initial CO2 concentration feed, the maximum capacity of SAB-30 increased from 2.71mmol/g at 30°C (without adding moisture to the feed) to 3.3mmol/g at 50°C when adding 10% (V/V) moisture to the feed. Increasing the moisture concentration further reduced the maximum CO2 capacity due to the blocking effect of the excess moisture on the sorbent surface. However, SAB-30 could completely capture CO2 even in a 100% (V/V) initial CO2 concentration feed. A maximum CO2 capacity of 5.7mmol/g for SAB-30 was achieved at 30°C. Varying the ratio of sorbent weight to total flow rate of the gas stream had no discernible effect on the equilibrium CO2 capture capacity. Avrami's equation and Toth's isotherm model provided a good fitting for the data and suggested the presence of more than one reaction pathway in the CO2 capture process and the heterogeneous adsorption surface of SAB-30. Thermodynamics studies revealed that CO2 capture on the bifunctional SAB-30 is feasible, spontaneous and exothermic in nature.

Thermodynamic analysis of sorption-enhanced water-gas shift reaction using syngases

Sorption-enhanced water–gas shift (SEWGS) reaction performance using syngas as the feedstock is investigated in this study based on thermodynamic equilibrium analysis. It was found that the capability of CO2 sorbent in CO2 removal was independent of the dry syngas composition. Regardless of the dry gas composition, CO2 sorbent loses its adsorption capability as the reaction temperature increases higher than a temperature limit. This CO2 adsorption temperature limit was found to depend on the steam to carbon (SC) ratio and reaction pressure. With the decrease in SC and increase in pressure the CO2 adsorption temperature limit can be raised to a higher value. However, the initial CO2 content in the syngas composition affects the carbon and CH4 formations in SEWGS. For syngas with low CO2 concentration, carbon formation can be completely eliminated and CH4 formation can be reduced by CO2 removal. For syngas with high CO2 concentration, no carbon and CH4 suppression can be found. It was also found that the temperature at which no carbon and CH4 formations was increased to a higher value as the initial CO2 concentration was increased. Copyright © 2016 John Wiley & Sons, Ltd.

Removal of CO2 in a multistage fluidized bed reactor by diethanol amine impregnated activated carbon

ABSTRACTTo mitigate the emission of carbon dioxide (CO2), we have developed and designed a four-stage fluidized bed reactor. There is a counter current exchange between solid adsorbent and gas flow. In this present investigation diethanol amine (DEA) impregnated activated carbon made from green coconut shell was used as adsorbent. This type of adsorbent not only adsorbs CO2 due to the presence of pore but also chemically reacts with CO2 and form secondary zwitterions. Sampling and analysis of CO2 was performed using Orsat apparatus. The effect of initial CO2 concentration, gas velocity, solid rate, weir height etc. on removal efficiency of CO2 have been investigated and presented. The percentage removal of CO2 has been found close to 80% under low gas flow rate (0.188 m/s), high solid flow rate (4.12 kg/h) and weir height of 50 mm. From this result it has been found out that multistage fluidized bed reactor may be a suitable equipment for removal of CO2 from flue gas.

Fractional crystallization of Si-undersaturated alkaline magmas leading to unmixing of carbonatites on Brava Island (Cape Verde) and a general model of carbonatite genesis in alkaline magma suites

The carbonatites of Brava Island, Cape Verde hot spot, allow to investigate whether they represent small mantle melt fractions or form through extreme fractionation and/or liquid immiscibility from CO2-bearing silicate magmas. The intrusive carbonatites on Brava Island are part of a strongly silica-undersaturated pyroxenite, ijolite, nephelinite, nepheline syenite, combeite–foiditite, carbonatite series. The major and trace element composition of this suite is reproduced by a model fractionating olivine, clinopyroxene, perovskite, biotite, apatite, titanite, sodalite and FeTi oxides, all present as phenocrysts in the rocks corresponding to their fractionation interval. Fractionation of ~90 wt% crystals reproduces the observed geochemical trend from the least evolved ultramafic dikes (bulk X Mg = 0.64) to syenitic compositions. The modelled fractional crystallization leads to alkali enrichment, driving the melt into the carbonatite–silicate miscibility gap. An initial CO2 content of 4000 ppm is sufficient to saturate in CO2 at the point where the rock record suggests continuing unmixing carbonatites from nephelinites to nepheline syenites after 61 wt% fractionation. Such immiscibility is also manifested in carbonatite and silicate domains on a hand-specimen scale. Furthermore, almost identical primary clinopyroxene, biotite and carbonate compositions from carbonatites and nephelinites to nepheline syenites substantiate their conjugate character and our unmixing model. The modelled carbonatite compositions correspond to the natural ones except for their much higher alkali contents. The alkali-poor character of the carbonatites on Brava and elsewhere is likely a consequence of the release of alkali-rich CO2 + H2O fluids during final crystallization, which cause fenitization in adjacent rocks. We propose a general model for carbonatite generation during alkaline magmatism, where the fractionation of heavily Si-undersaturated, alkaline parent melts results in alkali and CO2 enrichment in the evolving melt, ultimately leading to immiscibility between carbonatites and evolved Si-undersaturated alkaline melts. Early saturation in feldspathoids or feldspars would limit alkali enrichment preventing the formation of carbonatites. The complete and continuous fractionation line from almost primitive melts to syenitic compositions on Brava underlines the possibly important role of intrusives for hot spot volcanism.

Carbon dioxide absorption in a packed column using imidazolium based ionic liquids and MEA solution

The study of CO2 absorption in ionic liquids: [Emim][Ac], [Bmim][Ac] and 15wt.% MEA solution in a packed bed column is presented. Absorption column of inner diameter 0.05m and 0.35m length was filled with Raschig rings ϕ5mm×5mm×1mm. Investigations were performed at atmospheric pressure what is important in the case of post combustion flue gases. The influence of mass transfer resistances in gas and liquid phase as well as initial CO2 concentration and absorption temperature on CO2 removal efficiency was investigated. In calculations the resistance in series model of the absorption process was applied. The estimated values of enhancement factor of the reaction between CO2 and investigated liquids were used to predict mass fluxes of absorbed carbon dioxide for both ILs and MEA solution. The comparison of experimental and calculation results show that in the same experimental conditions the investigated ILs and MEA solution have comparable CO2 absorption capacities. The liquid side mass transfer coefficients in the case of ILs are several times lower than for MEA solution. The research for new ILs characterized by chemisorption mechanism, low viscosity and price is needed to take advantages of applying ionic liquids in the process of CO2 separation in a packed column.

Influence of Sediment Acidification on Water Quality in Carbonate Environments: A Laboratory Experiment

A sediment leaching experiment was conducted in a controlled laboratory setting. The sediments were collected from a carbonate-rich waste mine tailings site in MO. Dissolved inorganic carbon (DIC), major ions, and stable carbon isotope ratios of DIC (d13CDIC) leachate were analyzed. The purpose was to investigate the carbon dioxide produced from acid neutralization by carbonate-rich sediments that may occur at an acid mine drainage contaminated site (e.g. Neosho County SE Kansas) during the loss of CO2(g) during groundwater discharge. Results show that there is rapid decrease in DIC and an increase in pH during the first 48 hours of leaching the tailings with 0.1N sulfuric acid. The decrease in DIC is due to the loss of excess carbon dioxide CO2(aq) dissolved in water as neutralization is occurring. This loss of CO2(g) leads to a kinetic enrichment of the stable carbon isotopes d13CDIC. The magnitude of the d13CDIC enrichment is shown to depend on the (1) initial concentration of the excess CO2(aq) (at time = t0+1) in the leachate, (2) the amount of DIC and (3) the rate at which the CO2(g) is lost from the reactor. These results are important in our understanding of the long-term effect from the exploitation of natural resources that can generate carbon dioxide in the environment.

Analysis of a New Liquefaction Combined with Desublimation System for CO2 Separation Based on N2/CO2 Phase Equilibrium

Cryogenic CO2 capture is considered as a promising CO2 capture method due to its energy saving and environmental friendliness. The phase equilibrium analysis of CO2-mixtures at low temperature is crucial for the design and operation of a cryogenic system because it plays an important role in analysis of recovery and purity of the captured CO2. After removal of water and toxic gas, the main components in typical boiler gases are N2/CO2. Therefore, this paper evaluates the reliabilities of different cubic equations of state (EOS) and mixing rules for N2/CO2. The results show that Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) fit the experimental data well, PR combined with the van der Waals (vdW) mixing rule is more accurate than the other models. With temperature decrease, the accuracy of the model improves and the deviation of the N2 vapor fraction is 0.43% at 220 K. Based on the selected calculation model, the thermodynamic properties of N2/CO2 at low temperature are analyzed. According to the results, a new liquefaction combined with a desublimation system is proposed. The total recovery and purity of CO2 production of the new system are satisfactory enough for engineering applications. Additionally, the total energy required by the new system to capture the CO2 is about 3.108 MJ·kg−1 CO2, which appears to be at least 9% lower than desublimation separation when the initial concentration of CO2 is 40%.

Temperature evolution during magma ascent in basaltic effusive eruptions: A numerical application to Stromboli volcano

The dynamics of magma ascent are controlled by the complex, interdependent processes of crystallisation, rheological evolution, gas exsolution, outgassing, non-ideal gas expansion and temperature evolution. Temperature changes within the conduit, in particular, play a key role on ascent dynamics, since temperature strongly controls the crystallisation process, which in turn has an impact on viscosity and thus on magma ascent rate. The cooling produced by gas expansion is opposed by the heat produced by crystallisation, and therefore the temperature profile within the conduit is quite complex. This complexity means that unravelling the dynamics controlling magma ascent requires a numerical model. Unfortunately, comprehensive, integrated models with full thermodynamic treatment of multiple phases and rheological evolution are challenging to produce, due to the numerical challenges involved. Until now, models have tended to focus on aspects of the problem, without a holistic approach in which petrological, thermodynamic, rheological and degassing processes, and their interactions, were all explicitly addressed and quantified.Here, we present a new, multiphase steady-state model for magma ascent in which the main physical and chemical processes, such as crystallisation, degassing, outgassing, rheological evolution and temperature variations, are quantitatively calculated. Basaltic magma's crystallisation and flow are sensitive to initial temperature and volatile content, and therefore we investigate temperature variations during magma ascent in a basaltic system with a range of volatile contents. As a test case, we use one of the most well-studied recent basaltic effusive eruptions: the 2007 eruption of Stromboli, Italy.Assuming equilibrium crystallisation and exsolution, we compare the solutions obtained both with and without an isothermal constraint, finding that temperature variations within the conduit have a significant influence on the ascent dynamics and therefore cannot be ignored when modelling basaltic volcanism. Furthermore, we find good agreement between model results and volcanological observations when the non-isothermal condition is assumed. We investigate, through a sensitivity analysis, the role of magma chamber temperature on mass flow rate and crystal content. We find that a temperature variation of 30 K at the base of the conduit has a bigger effect on mass discharge rate than an increase of 1 wt% in water content. Finally, we find that whilst variations in initial CO2 concentration can affect the temperature, pressure and viscosity profiles along the conduit, they do not alter the macroscopic behaviour of the system.

Quantification of the CO2 budget and H2O–CO2 systematics in subduction-zone magmas through the experimental hydration of melt inclusions in olivine at high H2O pressure

Reliable evaluation of CO2 contents in parental arc magmas, which can be preserved in melt inclusions in phenocrysts, is required to verify the proposed efficiency of CO2 recycling at convergent margins. Quantification of bulk CO2 concentration in melt inclusions requires their complete homogenization. Using samples from lavas from the Bulochka vent of Klyuchevskoy Volcano (Kamchatka), we applied a novel experimental approach to homogenize and re-equilibrate naturally dehydrated (<1 wt.% H2O) melt inclusions from high-Fo (85–91 mol.%) olivine. The experiments were performed at temperatures of 1150–1400 °C, pressures of up to 500 MPa, under dry to H2O-saturated conditions and with oxygen fugacity ranging from CCO to QFM+3.3. No homogenization was achieved at dry conditions. Complete dissolution of fluid bubbles (homogenization) in the melt inclusions was achieved at H2O pressures of 500 MPa and temperature of 1150 °C, when water content in the melt inclusions reached 4–5 wt.% H2O. The CO2 content in the homogenized inclusions is 3800±140 ppm and CO2/Nb = 3000 ± 420, which are the highest values reported so far for the typical middle-K primitive arc melts and fall within the range of values inferred from the magmatic flux and volcanic gas data for primary arc magma compositions. About 83% of the CO2 in Klyuchevskoy magmas is likely to be derived from the subducting slab and can be attributed to flux melting with a fluid having a CO2/H2O ratio of ∼0.06. The H2O and CO2 contents in the melt inclusions after hydrous experiments were found to correlate positively with each other and negatively with the volume of fluid bubble, reflecting increasing internal pressure in melt inclusions with increasing melt hydration. Therefore, similar trends observed in some natural sets of melt inclusions can be attributed to a partial dehydration of melts after entrapment, operating simultaneously with or following post-entrapment crystallization. Our study implies that the process of post-entrapment dehydration can be completely reversed under high pressure experimental conditions. If temperature, redox conditions and pressure of melt inclusion entrapment can be independently estimated, then our novel experimental approach (homogenization at high H2O pressure) can be used to reconstruct the initial CO2 content and also the entire composition of melt inclusions in olivine, including their initial H2O content, from any type of volcanic rock. With this approach volatiles in ancient lavas can also be determined, expanding our knowledge of volatile recycling further back in Earth history.

Melt inclusion evidence for CO2-rich melts beneath the western branch of the East African Rift: implications for long-term storage of volatiles in the deep lithospheric mantle

We present new major element, trace element, and volatile (H2O, CO2, S, F, and Cl) concentrations of olivine-hosted melt inclusions from five high-K, low-silica basanites from the western branch of the East African Rift System and use these data to investigate the generation of H2O- and CO2-rich melts at up to ~150 km depth. Measured H2O and CO2 concentrations reach ~2.5 and ~1 wt%, respectively, representing some of the highest CO2 concentrations measured in a melt inclusion to date. These measurements represent direct evidence of the high CO2 and H2O concentrations required to generate high-K alkaline lavas, and the CO2 that has been previously inferred to be necessary for the low mantle potential temperatures in the area. Ratios of CO2/Nb, CO2/Ba, and CO2/Cl are used to estimate an initial melt CO2 concentration of 5–12 wt%. The measured CO2 concentrations are consistent with CO2 solubilities determined by molecular dynamics calculations and high-pressure experiments for melt generation at 3–6 GPa; the depth of melting suggested by previous studies in the area. These melt inclusions measurements represent direct evidence for the presence of H2O- and CO2-rich melts in the deep upper mantle that have been proposed based on experimental and seismic evidence. Primitive-mantle normalized trace element patterns more closely resemble those found in subduction settings rather than ocean island basalt, and ratios of slab fluid tracers such as Li/Dy and B/Be indicate that the measured volatile abundances may be related to Neoproterozoic subduction during the assembly of Gondwana, implying the storage of volatiles in the mantle by subduction-related metasomatism.

An investigation of the chemical kinetics of biogas combustion

Chemical kinetic aspects of the combustion of biogas (containing CH4,CO2 and possibly H2) have been investigated. Five reaction mechanisms were considered and tested with respect to the ignition delay times of H2–CO2–O2 and CH4–CO2–O2 mixtures measured in shock tubes. While the GRI (Gas Research Institute) mechanism 3.0 could not reproduce the first set of measurements, it brought up the best match for the second one directly relevant to biogas. Consequently it was employed for predicting the amounts of CO and NO produced under the same conditions. It was found that for stoichiometric and lean mixtures an increase in the initial CO2 concentration lowers the production of NO and raises that of CO at higher temperatures. For rich mixtures, the production of NO is far smaller and does not follow this simple pattern. Kinetically, the reaction H+CO2→OH+CO plays a greater role in the presence of CO2 and must hence be accurately known. For some conditions, the environmentally problematic N2O is produced. The effects of hydrogen addition on biogas have also been predicted using GRI 3.0. The addition of 2% of H2 always raises the concentration of produced CO when compared to the mixture without hydrogen. The formation of NO is increased for higher H2 amounts at p=1bar but decreased at p=10bar. Overall, the present study supports the viability of the GRI-mechanism for the simulation of biogas combustion.

Computational investigation of solid sorbent carbon dioxide capture in a fluidized bed reactor

This paper presents a computational investigation of the hydrodynamics and the reaction behavior in a fluidized-bed CO2 capture reactor. Integrating CO2 adsorption kinetics with the two fluid model, a multiphase flow and reaction model is established. Computational fluid dynamics analyses are performed, and the influences of various operating conditions are evaluated. The results indicate that velocity, volume fraction and species concentration of the gas and particle phase are significantly nonuniform inside the fluidized-bed reactor. Adsorption reaction mainly takes place in the bottom bubbling fluidized bed. CO2 capture efficiency decreases with increasing the initial CO2 content in the flue gas. A low gas velocity of 0.13–0.16m/s leads to a higher CO2 capture efficiency. High reaction temperatures and large sorbent circulation rates are beneficial to CO2 removal in the current reactor.