Total Inlet Flow Rate Research Articles

Insights into the gas-solid hydrodynamics and thermochemical characteristics in a pilot-scale chemical looping combustion unit using MP-PIC

Chemical looping combustion (CLC) emerges as an efficient pathway for CO2 capture and storage, yet complex in-furnace phenomena are still far from being understood. Accordingly, the multiphase reactive flow during the CLC process in a pilot-scale dual circulation fluidized bed (DCFB) is numerically investigated by the multi-phase particle-in-cell method considering thermochemical sub-models. After model validations, the thermochemical behaviors and the impact of operating parameters on CLC performance are explored, followed by unveiling the underlying mechanisms of heat and mass transfer characteristics. The pressure gradient is explicitly correlated with the solid holdup in two reactors. Gas-solid flow in the fuel reactor (FR) is more heterogeneous than that in the air reactor (AR) due to complex reactions and large amounts of gas/particle exchanges with other parts of the DCFB, and the whole CLC unit shows good circulating and heat transfer performance. Higher temperatures improve fuel conversion and increase CO2 yield. Elevating the air/fuel ratio (ψ) significantly enhances CLC performance at ψ ≤ 1.0 but it insignificantly affects the CLC performance at ψ > 1.0. A higher total inlet flow rate leads to suppressed fuel conversion and a subsequent decline in CO2 yield. The particle heat transfer coefficient (HTC) in the AR is approximately 450 W/(m2·K), significantly higher than that in the FR of about 300 W/(m2·K).

Experimental study of the effect of viscous media on the hydrodynamic characteristics of a rotating packed bed

A simple and robust quantitative approach was proposed to determine liquid entrainment and flooding in rotating packed beds (RPBs), which complements visual observations and pressure drop measurements. The RPB was modified by installing a hydrocyclone at the gas outlet to quantify the amount of liquid ejected. The original technique previously introduced in the literature for air-water systems, was explored using a viscous mixture to determine the flooding onset. This approach eliminates bias in the criteria used to define the onset of liquid entrainment and flooding in RPBs. The method also minimizes inaccuracies introduced by unexplained pressure drops during flooding in RPBs. In the method, flooding occurred when entrainment exceeds 8% of the total liquid inlet flow rate. The study used a water-glycerine mixture with viscosities of 13 and 30 mPa.s and found that the entrainment of viscous liquids in RPBs begins with a small volume of liquid droplets, progressing to moderate volumes of liquid-film entrainment. The quantitative approach used in this study enhances the reliability of fundamental data essential for the design and scale-up of RPBs. This study is an indispensable guide for using RPBs in high-viscosity mass transfer and separation processes.

Hemodynamic simulation in the aortic arch with the lattice Boltzmann method

Aortic diseases have high mortality rates, wherein wall shear stress (WSS) and oscillatory shear index play important roles. Previous studies focused on describing the WSS distribution; however, no report has investigated how hemodynamic parameters determine the distribution of WSS. This study investigates the parameters affecting the WSS distribution and determines the variations of these parameters. A realistic healthy aortic geometry is reconstructed from computed tomography medical images, and a flow simulation is performed using the lattice Boltzmann method. The inlet velocity waveform from the Doppler ultrasound measurement is imposed as the inlet boundary condition, whereas the three-element Windkessel model is used as the outlet boundary condition. The measured outlet flow rate waveforms are used to validate the simulation. A good agreement is found between the outlet flow rate waveform obtained from the measurement and that from the simulation: the descending artery, innominate artery, left common carotid, and left subclavian artery receive 63.42%, 24.01%, 4.14%, and 8.46%, respectively, of the total inlet flow rate over the cardiac cycle in the measurements and 62.17%, 24.61%, 4.7%, and 8.44%, respectively, in the simulation. The simulation shows that the temporal and spatial distributions of the WSS are separately determined by the flow rate and impacting angle. The flow rate ratio between the inlet and outlet decreases with an increase in Re. This relation can be fitted well by the exponential function. Moreover, the impacting angle between the blood flow and the vessel centerline is determined by the vessel geometry only.

Silicon carbide and alumina open-cell foams activated by Ni/CeO2-ZrO2 catalyst for CO2 methanation in a heat-exchanger reactor

This work investigates and compares the performances over the CO2 methanation reaction of two structured catalysts based on high thermal conductivity silicon carbide (SiC) and low thermal conductivity alumina (Al2O3) 40 PPI Open Cell Foams. The active phase (25 wt%Ni/20 wt%CeO2-55 wt%ZrO2) was coated by the In Situ-Solution Combustion Deposition (IS-SCD) method with sequential steps to reach the desired catalyst loading (0.5 g/cm3) for both supports. TEM, SEM, XRD, TPR and adhesion tests were used to characterize the prepared structured catalysts. A bench-scale reactor (total inlet flow rate = 0,585–2,215 Nm3 h−1) with an integrated cooling system was used to carry out the catalytic tests, varying the Gas Hourly Space Velocity (12,420–47,027 h−1) at a constant reactant ratio (CO2:H2:N2 = 1:4:0.5). Air was used as a cooling medium both in counter- and co-current flow configuration. Temperature profiles along the reactor in axial and radial directions were registered, compared and discussed. The results show that the improved thermal management enhances the CO2 methanation reaction for both catalysts. For the investigated conditions, the SiC sample enabled a favourable temperature distribution due to its higher thermal conductivity, leading, also at the high space velocity (GHSV = 47,027 h−1) higher performances (χCO2 = 71.1%; SCH4 = 94.2%; FCH4,OUT = 260 NL h−1) compared to the Al2O3-based catalyst (χCO2 = 56.7%; SCH4 = 89.1%; FCH4,OUT = 202 NL h−1). Moreover, an operating pressure of 2.80 bar slightly improved the SiC catalysts performance: a CO2 conversion of 77.1% and a CH4 selectivity of 95,6% were obtained while the overall CH4 productivity increased up to 285 NL h−1 (12.1 NL h-1gcat.-1).

Sewage sludge ashes as a primary catalyst for the abatement of tar in biomass gasification: Bubbling versus spouted‐fluidized bed configuration

AbstractSewage sludge (SS) ashes, rich in iron and calcium, have been tested as a primary catalyst during air gasification of commercial wood pellets in a pre‐pilot scale fluidized bed (FB) reactor. The shifting from a conventional fluidized bed to a spouted‐fluidized bed configuration has been assessed on the catalyst performance. Specifically, at constant total air inlet flow rate, two different values of the air flow rate in a central spouting nozzle have been adopted, which correspond to 20% and 37.5% of the total inlet gas flow rate. Under the conventional fluidized bed configuration (i.e., bubbling regime), SS ashes exhibit good performance in term of tar reduction (about 20% decrease compared to a bed of inert silica sand), without significantly affecting the syngas composition. Concerning the transition to the spouted‐fluid bed configuration, the gas‐solid contact efficiency is enhanced at lower air flow rates through the central nozzle, with respect to the FB regime, leading to better gasification performance in terms of tar reduction (around 40% less) and syngas quality. A slightly worse gasification performance is obtained at high values of air flow rate in the central nozzle, due to a progressive increase of gas bed bypassing. Furthermore, moving from the conventional FB configuration to the spouted‐fluid bed one dramatically boosts the elutriation rate of carbon fines as well as the attrition of catalyst particles.

Working diagrams to identify the operating range of a bubbling fluidized bed reactor for the CO2 methanation

AbstractFluidized bed reactors for the catalytic CO2 methanation is a promising concept within the power‐to‐gas (methane) process. Due to the intermittency of renewable electricity generation and thus hydrogen production, the subsequent methanation reactor should also be able to operate at lower feed flow rates, while maintaining fluidized bed conditions. Bubbling fluidized bed reactors offer the required flexibility as shown with the new type of working diagrams. These working diagrams visualize a decision window for (a) determining the reactor diameter and (b) operating the fluidized bed reactor with a turndown ratio of 0.5‐1.1. Reducing the turndown ratio (ie, inlet flow rate) could lead to defluidization, thus increasing temperature or reducing the pressure are alternatives to maintain fluidization conditions. The former method is not desired, as a temperature increase would significantly reduce the CH4 yield due to thermodynamic constraints and therefore reduce the overall efficiency. An industrial CO2 methanation reactor, for example, that is designed for 10 bara (1 bara = 100 kPa) and 340°C with a total inlet flow rate of 5000 m3N · h−1 (H2/CO2 = 4) can be operated at a turndown ratio of 0.5 (2500 m3N · h−1) at the same temperature and the same u0/umf ratio by reducing the pressure to 5 bara with only a slight decrease in the CO2 equilibrium conversion from 96.7% to 94.6%.

A New Mathematical Model for the Prediction of Internal Recirculation in Impinging Streams Reactors

A mathematical model for the prediction of internal recirculation of complex impinging stream reactors has been presented. The model constitutes a repetition of a series of ideal plug flow reactors and CSTR reactors with recirculation. The simplicity of the repeating motif allows for the derivation of an algebraic relation of the whole system using the Laplace transform. An impinging streams reactor system with one axial and two tangential inlet fluid streams was constructed and considered as a case study. The model predicts satisfactorily the complex and flow rate dependent experimental residence time distribution functions obtained employing a pulse tracer method for different total flow rates of the incoming feed. The variation of the controlling parameters with changing the total inlet flow rate is discussed. The presented model can predict complex internal recirculation streams within the impinging streams reactor system.

Plasma catalytic steam methane reforming for distributed hydrogen production

Abstract Steam methane reforming (SMR) via thermal catalytic approach is one of the dominant sources of industrial hydrogen, however it proceeds with slow response and low specific productivity. Here we demonstrate a plasma catalytic SMR for distributed hydrogen production, for which warm plasma by gliding arc discharge initiates the reaction, followed by Ni-based catalyst in a heat-insulated reactor without extra heating. In terms of the plasma alone process, specific energy input (SEI), steam/CH4 ratio (S/C) and total inlet flow rate (Ft) contribute to the methane conversion. In parallel, SEI and S/C account for the decrease in C2Hx selectivity hence the increase in selectivity of CO and CO2, while with Ft all the selectivity is approximately constant. The reaction pathway represented by the selectivity can be influenced by SEI and S/C rather Ft. To utilize the heat and active species with the reaction in plasma zone, Ni/CeO2/Al2O3 catalyst bed is coupled. For the coupled process, the conversion approaches the thermodynamic equilibrium values, with the favorable dismissed C2Hx selectivity thus the complete selectivity to CO and CO2. The coupled process was maintained steady for six hours, and the methane conversion of 90% at total hydrogen (t-H2) production rate of 2.7 SLM is achieved under optimum conditions of SEI, S/C, Ft and gas hourly space velocity (GHSV) of 110 kJ/mol, 3, 3 SLM and 18,000 ml·g−1 h−1. Compared to 59% and 2.3 kW h/Nm3 of the plasma alone process, such a coupled process achieves the energy efficiency (of methane to t-H2) of 75% and the low energy cost of 1.5 kW h/Nm3. Consequently, our approach of plasma catalytic SMR features the merits of rapid response, compact system and high specific productivity, which can be anticipated for the emerging needs of distributed hydrogen generation.

Experimental and modelling study of an electrochemical hydrogen compressor

The energy world is changing rapidly pushed also by the need for new green energy sources to reduce greenhouse gas emissions. The fast development of renewable energies has created many problems associated with grid management and stability, which could be solved with storage systems. The hydrogen economy could be an answer to the need of storage systems and clean fuel for transportation. The Electrochemical Hydrogen Compressor (EHC) is an electrochemical device, which could find a place in this scenario giving a solution for the hydrogen purification and compression for storage. This work analyzes, through experimental and modeling studies, the performance of the EHC in terms of polarization curve, Hydrogen Recovery Factor (HRF) and outlet hydrogen purity. The influence of many input parameters, such as the total inlet flow rate, the hydrogen inlet concentration, the contaminant in the feed, and the cathode pressure have been investigated. Furthermore, the EHC performance have been modelled in a 1D + 1D model implemented in Matlab® solving the Butler-Volmer system of equations numerically. The experimental campaign has shown that high purities can be obtained for the hydrogen separation from N2 and CH4 and purities over 98% feeding He. An increase in the cathode pressure has shown a slight improvement in the obtained purity. A comparison between PSA unit and EHC for a mixture 75% H2 – 25% CH4 at different outlet hydrogen pressure and purity was performed to analyze the energy consumption required. Results show PSA unit is convenient at large scale and high H2 concentration, while for low concentration is extremely energy intense. The EHC proved to be worthwhile at small scale and higher outlet hydrogen pressure.

A dynamic mesh-based approach to analyse hydrodynamic interactions between a fluidic hammer and drill bit

The main goal of this study was to reveal the hydrodynamic interactions between a fluidic hammer and drill bit. For this purpose, a computational fluid dynamics analysis based on a dynamic mesh technique was used instead of the conventional steady analysis. The results show that the effect of the drill bit on the performance of the fluidic hammer is negligible. However, the fluidic hammer has a significant effect on the bit hydraulics. The flow fluctuation caused by the fluidic hammer can significantly influence the bottom-hole flow fields and upwards flow velocity in annular space. It is also found that the flow fluctuation ratio is nearly constant during the variation of total inlet flow rate, while it can be largely affected by the mass of the steel mass block, piston diameter, and piston rod diameter. To improve the borehole cleaning, the lowest average velocity in the annular space during flow fluctuation should be higher than the critical velocity or the corresponding velocity associated with the desired cutting concentration. The conclusions can also serve as a reference for the study of other hydraulic hammers or vibrators.

Nonlinear dynamic analysis of parallel three uniformly heated channels with water at supercritical pressures

This study develops a nonlinear dynamic model of parallel supercritical uniformly heated channels based on three-region methodology coupled with polynomial profile approximations between flow density and flow enthalpy. The validation results against the experimental data indicate that the present model has the capability to investigate the stability issues of parallel uniformly heated channels with supercritical water. Nonlinear characteristics, stability maps and parametric effects of three uniformly heated channels with supercritical water are investigated. The results illustrate that channel-to-channel interactions among three channels will drive the system more unstable due to a more asymmetric power distribution. In addition, the hottest channel with the highest steady state flow rate would oscillate with the largest amplitude and out-of-phase with the other less heated channels under constant total inlet flow rate condition. This study also reveals that the nonlinear oscillations between inlet flow velocity and outlet flow velocity in each channel tend to present out-of-phase. It could demonstrate that increasing the pressure drop of heavy fluid region (region 1) would stabilize the system, while increasing the pressure drop of light fluid region (region 3) would destabilize the system. The parametric studies on system stability of three uniformly heated channels suggest that increasing inlet flow resistance or enlarging the channel diameter would stabilize the system, while increasing outlet flow resistance or lengthening the channel length would destabilize the system.

Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 2: TRACE/PARCS model and physical explanation

Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K boiling water reactor (BWR) models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in BWR out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The previous paper (“Part 1”) presented a series of results to examine this rotating behavior with a reduced-order model. The goal of the present study is to provide additional analyses of the predicted rotating mode behavior using higher-fidelity numerical modeling, as well as a physical explanation for why this mode is favored over side-to-side or other oscillatory behaviors from a TH perspective. Results are presented using TRACE and TRACE/PARCS for a small number of parallel channels, which confirmed that the conclusions developed from the reduced-order model remain applicable when applying a full two-fluid, six-equation, finite-volume modeling approach. From these results, a physical explanation has been put forth to explain why the rotating symmetry line behavior is preferred from a TH standpoint, demonstrating that predominantly out-of-phase unstable systems are most unstable when the variation in the total inlet flow rate is minimized (which minimizes the effective single-phase to two-phase pressure drop ratio) and that the rotating mode is the most successful in minimizing this total flow rate variation as compared with the side-to-side case or any other oscillation pattern. The conclusion is that the rotating mode will be favored for any out-of-phase unstable system of parallel channels with no neutronic feedback or relatively weak neutronic feedback. Previous analyses have indicated that systems with sufficiently strong neutronic coupling may favor the side-to-side oscillation mode over the rotating mode; this topic is left as a subject of future investigation.

Simultaneous Removal of SO2 and NO by Using Piperazine-urea-triethylene Diamine Ternary System

Performance of simultaneous removal of SO2 and NO from the simulated thermal power plants gas using piperazine-urea-triethylene diamine ternary system absorbent was investigated in this paper. Furthermore, the influences of the concentration of triethylene diamine, pH value, the absorption temperature and the total inlet flow rate of the simulated gas on simultaneous absorption behavior were discussed by means of the removal efficiency of SO2 and NO. A better simultaneous desulfurization and denitration behavior could be obtained under the absorption condition of triethylene diamine concentration of 0.3 mol/L, pH value of 6, inlet simulated gas flow rate of 500 ml/min, and the absorption temperature of 40 °C. Under the above absorption condition, the simultaneous NO removal efficiency of 70.28% and SO2 removal efficiency of 99.30% could be obtained.

A Novel Solar Expanding-Vortex Particle Reactor: Influence of Vortex Structure on Particle Residence Times and Trajectories

A novel configuration of Solar Vortex Reactor (SVR), termed the Solar Expanding-Vortex Particle Reactor, is proposed for heating particles for applications such as steam-gasification. This configuration differs from the previous configurations by features including utilising a conical entry at the opposite end of the cavity to the aperture and a radial exit. The new configuration offers potential to achieve a residence time distribution of feedstock particles that increases with the particle size, in a way that is augmented by a vertical orientation of the device. In addition, it also offers potential to mitigate particle deposition onto the reactor window. The effect of changing the reactor geometric features, particle size and total inlet flow rate on the vortex structure, particle trajectories and particle residence time within the reactor flow field is analysed with a three-dimensional computational fluid dynamics (CFD) model employing Lagrangian particle dispersion for the discrete phase. This is used to develop hypotheses of potential mechanisms with which to 1) mitigate particle deposition onto the reactor window, and 2) to preferentially recirculate the larger particles within the chamber. The validity of the CFD model was assessed by comparison with the available published experimental data from related configurations and found to yield good agreement. The model is then used to identify configurations that are predicted to achieve the above two target outcomes. It also finds that the cone angle is a critical geometrical parameter in influencing both of these effects through its influence on the vortex structure and particle trajectories.

The Adsorption and Desorption Breakthrough Behavior of Hydrogen Chloride Gas Mixture on Zeolite 13X Pellet in a Fixed Bed Reactor

The adsorption and desorption breakthrough test of hydrogen chloride (HCl) was performed by loading zeolite 13X pellet (molecular sieve 13X, Aldrich Co., U.S.A.), a commercial adsorbent, onto a fixed bed reactor (height 15 cm, inside diameter 0.5 cm). The breakthrough test was carried out by changing various experimental conditions such as inlet flow rate (0.5, 1, 1.5, 2 L/min), HCl concentration (200, 350, 500, 650 ppm), reaction temperature (30, 50, 70, 90°C), and reaction pressure (1, 5, 10, 15, 20 bar) with considering the retention time and space velocity. After evaluating the adsorption and the desorption characteristics of HCl on the MS-13X, the consecutive cyclic test (5 times of adsorption step, 4 times of desorption step) was carried out with optimum condition. At the adsorption step, pressure was 20 bar, temperature was 30°C, HCl concentration was 200 ppm, total inlet flow rate was 0.5 L/min (HCl+N2). At the desorption step, pressure was 1 bar (atmospheric pressure), temperature was 280°C, total inlet flow rate was 0.5 L/min (N2 only), desorption time (regeneration time) was 7 h. The optical, physical, and chemical characteristics of MS-13X were analyzed using BET, XRD, SEM, EDX, and TGA before and after breakthrough tests.

CFD study on effect of channel confluence angle on fluid flow pattern in asymmetrical shaped microchannels

Five asymmetrical shaped microchannels were used to investigate the effect of channel confluence angle, flow rate and flow rate ratio on the mixing performance in a passive mixing test. The flow characteristics for all geometries were studied experimentally and numerically using CFD technique. The results reveal that the mixing performance depends on the channel geometry, total flow rate and inlet flow rate ratios. The classical T-shape microchannel had the worst performance in the lower flow rate and in higher Re numbers its performance was placed between the other ones. Furthermore, the mixing effectiveness for all microchannels was defined and measured at various feed flow rates. The results indicate that the mixing effectiveness increases with increasing flow rate ratio and decrease of confluence angle. The reasons for the observed experimental results were analyzed by the predicted CFD flow patterns.

Exposure to Chlorpyrifos in Gaseous and Particulate Form in Greenhouses: A Pilot Study

Phase distribution of airborne chemicals is important because intake and uptake mechanisms of each phase are different. The phase distribution and concentrations are needed to determine strategies of exposure assessment, hazard control, and worker protection. However, procedures for establishing phase distribution and concentration have not been standardized. The objective of this study was to compare measurements of an airborne semivolatile pesticide (chlorpyrifos) by phase using two different procedures. Six pesticide applications in two facilities were studied and at each site, samples were collected for three time slots: T1, the first 1 or 2 hr after the commencement of application; T2, a 6-hr period immediately following T1; and T3, a 6-hr period after the required re-entry interval (24 hr for chlorpyrifos).Two phase-separating devices were co-located at the center of each greenhouse: semivolatile aerosol dichotomous sampler (SADS) using flow rates of 1.8 l.min−1 and 0.2 l.min−1, corresponding to a total inlet flow rate of 2.0 l.min−1 with a vapor phase flow fraction of 0.1; and an electrostatic precipitator (ESP), along with a standard OVS XAD-2 tube. Chlorpyrifos in vapor and particulate form in a SADS sampling train and that in vapor form in an ESP sampling train were collected in OVS tubes. Chlorpyrifos in particulate form in the ESP setting would have been collected on aluminum substrate. However, no chlorpyrifos in particulate form was recovered from the ESP. Overall (vapor plus particle) concentrations measured by OVS ranged 11.7 – 186.6 μg/m3 at T1 and decreased on average 77.1% and 98.9% at T2 and T3, respectively. Overall concentrations measured by SADS were 66.6%, 72.7%, and 102% of those measured by OVS on average at T1, T2, and T3, respectively. Particle fractions from the overall concentrations measured by SADS were 60.0%, 49.2%, and 13.8%, respectively, for T1, T2, and T3. SADS gives better guidance on the distribution of chlorpyrifos than does the ESP, although the accuracy of the concentration distribution cannot be verified in the absence of a standardized procedure for determining phase division.

Towards biofuel combustion with an easily extruded clay as a natural catalyst

The present work aims to investigate an innovative application of natural clay as a catalyst for biofuel combustion. The mineralogical, chemical, thermal and textural characterizations of the natural clay suggest an intrinsic catalytic potential without any prior treatment. The catalytic performance was studied with respect to the combustion of n-butanol as a representative biofuel using different forms of the natural clay: fine powder, pressed pellets and extruded honeycomb monoliths. No major difference was found among these forms regarding texture, morphology and stability. In terms of performance, this clay proved competitive relative to cobalt oxide spinel, which is one of the most reactive non-noble transition metal oxides. The significant amount of naturally occurring transition metals such as iron and some elements considered as promoters in the clay were proposed to account for the catalytic properties. A systematic investigation of the catalytic performance of the clay as a function of the equivalence ratio and of the total flow rate was performed using gas-phase FTIR spectroscopy. Increase of the equivalence ratio at a fixed flow rate yielded a lower catalytic performance toward n-butanol combustion producing a consequent fraction of carbon monoxide and ethylene. At a constant equivalence ratio of 0.6, the performance of the clay was not affected by increasing the total inlet flow rate up to 30sccm. These findings may initiate the development of a new catalyst for biofuel combustion based on relatively low-cost and abundantly available raw materials such as the natural clay investigated here.

Removal of beta-pinene and limonene using compost biofilter

Composting is widely used for the treatment of solid organic wastes; however, emissions from composting are becoming a threat to humans due to the release of toxic volatile organic compounds (VOCs). VOCs from composting operations are characterized by high flow rates and, normally, low pollutant concentration. Typical VOCs include a large amount of terpenes (∼65% of total VOCs). This study was to investigate the efficiency of biofiltration in controlling terpene emissions from composting operations using a laboratory-scale unit. The performance of a biofilter was investigated as a function of inlet flow rate, inlet concentration, and bed length/bed diameter (L/D) ratio of bed. At the lowest total inlet flow rate, removal efficiency of limonene and β-pinene was more than 90%. With the decrease in inlet concentration and increase in L/D ratio, the removal efficiency was effectively increased. Removal efficiency of more than 85% for Limonene and 45% for β-Pinene was attained at a loading rate of 55 g/m3-hr. The maximum elimination capacity was found for 109.7 g/m3-hr for limonene and 10.3 g/m3-hr for β-pinene at a critical loading of 150.1 g/m3-hr. Based on this study, the compost bed could function as a biofilter for controlling terpene odors during the composting process. Implications: The purpose of this research project is to investigate the efficiency of biofiltration in controlling limonene and β-pinene emissions from composting operations using a laboratory scale. In addition, the performance of a biofilter as a function of inlet flow rate, inlet concentration, and L/D ratio of bed was evaluated. Establishing a nexus between the operational parameters and efficiency would be useful in design and operation of compost bed as a biofilter for controlling terpene odors during the composting process.

Enhanced NOx Reduction by Combined Staged Air and Flue Gas Recirculation in Biomass Grate Combustion

Flue gas recirculation (FGR) is a conventional means of reducing NOx emissions that involves lowering the peak flame temperature and reducing the oxygen concentration in the combustion region. Staged air combustion is also an effective means of NOx reduction, especially in biomass combustion. This article reports results on NOx emissions in a set of experiments combining FGR and staged air combustion in a grate-fired laboratory-scale reactor. Two different compositions of the recirculated flue gas were used: CO2 and CO2 + NO. The CO2 concentration varied between 0–8 vol % of the total inlet flow rate and the NO concentration varied between 0 and 64 ppm. Two different FGR locations were also tested: above and below the grate. The results are compared with a reference experiment performed without FGR. The NOx reduction level from staged air combustion at the optimal primary excess air ratio is ∼70%, while employing FGR can reduce the NOx emissions by an additional 5%–10%. The optimal primary excess air rati...