Increase Of Inlet Concentration Research Articles

Numerical analysis of oxidation performance of basalt fiber bundle thermal flow-reversal reactor

• Using low-dimensional devices and mixed runners to enhance heat transfer. • Reducing the self-sustained concentration to 0.1%. • Gas processing capacity per unit volume increased by 1.03–2.5 times. • The benefit of carbon emission reduction is increased by at least 1.95. • The efficiency of waste heat utilization is increased by 2.5 times. This paper uses Ansys Fluent software to conduct a two-dimensional numerical study on the oxidation performance of basalt fiber bundle thermal flow-reversal reactor (TFRR). The influence of inlet methane concentration, inlet flow rate and circulation period on the oxidation performance of TFRR is analyzed. The results show that the maximum temperature in the reactor increases significantly with the increase of inlet concentration and flow rate. At the same time, the lower limit of the concentration that can be handled by the reactor was studied, and it was found that the basalt fiber bundle TFRR can completely treat the gas with the concentration of 0.1%, under the operating parameters of t c = 80 s, v in = 0.65 m/s or t c = 60 s, v in = 1.0 m/s. In addition, the device was compared with the honeycomb ceramic TFRR in terms of economic efficiency. It was found that the clean development mechanism(CDM) emission reduction benefit of the former was 1.95 times than that of the latter, and the economic benefit of waste heat utilization was 2.5 times than that of the latter.

Efficient purification of toluene gas by anoxic denitrification.

As a part of volatile organic compounds (VOCs), toluene does harm to human health. This paper reported the purification of toluene waste gas by liquid-phase absorption and anoxic denitrification. In this work, two same biofilm reactors were set to treat toluene waste gas, one of which was added into nitrate as an electron acceptor. Then, the purification properties of toluene waste gas treated by anoxic denitrification and biological methods were compared. The results indicate that with the increase of toluene mass concentration, the toluene removal rate of the denitrifying reactor decreased slightly. When the inlet concentration increased from 50mgm-3 to 3440mgm-3, the removal efficiency of the denitrifying reactor remained over 94.1% while the removal efficiency of the traditional bioreactor decreased to 82.9%. The highest removal capacity of the denitrifying reactor was 127.2gm-3h-1, which was 11.8% higher than that of the traditional bioreactor. Toluene was degraded by denitrification inside the biofilm microenvironment hypoxia; the denitrification rate increased along with the increase of inlet concentration within certain limits and reached a maximum of 2.4mg NO3--NL-1h-1. Nitrate can act as an electron acceptor, and denitrification can promote aerobic degradation and intensify the concentration gradient inside the biofilm to strengthen the toluene transfer process.

Experimental Research of Activated Carbon on Adsorption of Oil Vapor

The adsorption properties of pillared activated carbon (PAC) on the oil vapor were studied through physical characterization and the dynamic adsorption measurement. The PAC was a typical microporous material with the well-developed interstitial structure and appropriate to be used as adsorbent for recovering of oil vapor. The influence factors of the ambient moisture, the inlet concentration, and supplying velocity on the adsorption amount of oil vapor were investigated using simulation device. During the first adsorption stage, the adsorption amount of oil vapor and the adsorption layer temperature increased remarkably with time, while the adsorbed vapor was relatively difficult to remove as using the vacuum pumping. A competitive adsorption between water and the hydrocarbon molecules reduced the adsorption performance of the PAC. When the supplying velocity increased, the adsorption amount of oil vapor on the PAC decreased for the shortening of contact time.With the increase of inlet concentration, the adsorption amount of oil vapor increased, while the adsorption time decreased.

Experimentation and CFD modeling of continuous degradation of formaldehyde by immobilized Ralstonia eutropha in a semi-pilot-scale plug flow bioreactor.

This study focuses on continuous formaldehyde (FA) biodegradation by Ralstonia eutropha immobilized on polyurethane foam in a semi-pilot-scale plug flow packed-bed bioreactor. The stepwise increasing of the influent FA concentration from 43.9 to 1325.1mgL-1 was studied in the bioreactor during 70days of operation. A complete removal of FA was achieved for inlet concentration up to 425.5mgL-1 and the initial specific biodegradation rate reached to its maximum value about 44.3mggcell-1h-1 at 425.5mgL-1. However, further increase of inlet concentration resulted in decrease of the biodegradation performance of the immobilized cells due to the inhibitory effect of FA on the enzymatic system involved in the biodegradation process. Based on kinetic modeling results, the Luong equation with the following constants could best describe the behavior of the bio-system: maximum specific FA biodegradation rate (qmax) of 124mggcell-1h-1, half-saturation constant (KS) of 337.2mgL-1, maximum degradable FA concentration (Smax) of 1582mgL-1, and shape factor (n) of 1.49. Also, three-dimensional simulation of the bioreactor was performed using an integrated computational fluid dynamics (CFD) approach that takes into account both the biokinetic constants of the immobilized system as well as the fluid properties under steady-state condition. Eulerian computations successfully anticipated the concentration gradients through the reactor for different inlet FA concentrations, and uniform vertical velocity pathlines and non-dispersed plug flow inside the reactor were verified by the presented velocity distribution and flow streamlines.

Fixed-bed column and batch reactors performance in removal of diazinon pesticide from aqueous solutions by using walnut shell-modified activated carbon

Abstract This paper evaluates adsorption of diazinon pesticide from aqueous solution onto walnut shell-modified activated carbon using fixed-bed column and batch system. Contact time, initial concentration, and pH were considered as variable parameters to obtain maximum adsorption capacity using batch technique. The pseudo-first-order, the pseudo-second-order, and Webber and Morris models were chosen to analyze adsorption kinetic data. The results indicated that adsorption process followed closely the pseudo-second-order kinetic model. The equilibrium adsorption data fitted the Freundlich isotherm well, with K f = 53 . 82 , n = 1.98, and R 2 = 0 . 9966 . For continuous fixed-bed column studies, the effect of inlet concentration (15–40 mg.lit−1), flow rate (9.5–16.5 lit.h−1), and bed height (10–30 cm) was investigated. Results showed that increase in inlet concentration and also bed height lead to increase of bed capacity. In addition, changes in flow rate from 9.5 to 14.5 lit.h−1 caused a decrease in bed capacity. However, a minor increase in bed capacity was observed via an increase in flow rate from 14.5 to 16.5 lit.h−1. The highest bed capacities were 34.98 and 34.31 mg.g−1 for the same initial concentration of 40 mg.lit−1, flow rates of 12 and 9.5 lit.h−1, and bed heights of 30 and 20 cm, respectively. Dynamic behavior of column was investigated by Bohart–Adams and Yoon–Nelson models. According to obtained results, Yoon–Nelson model can describe well the adsorption process. The findings of the current study show that the walnut shell-modified activated carbon can be successfully applied to remove diazinon pesticide from aqueous solution.

Role of centrifugal force on solid-liquid two-phase flow through rotating channel

The work reveals an interesting and contra-intuitive observation in numerically simulating the solid-liquid flow field through a straight rotating channel. A previous study (Gupta and Pagalthivarthi, 2007) showed that at moderate rotation rates, increase in rotational speed results in an asymmetric velocity profile, because the Coriolis acceleration tends to increase the level of turbulence on the pressure-side and decrease on the suction-side. The present work contra-intuitively shows that higher rotation rates enhance centrifugal acceleration that pushes the velocity maxima towards the pressure-side of the channel. Centrifugal acceleration is also seen to play a prominent role with increase in inlet concentration.

Size-Exclusion Colloidal Transport in Porous Media--Stochastic Modeling and Experimental Study

Suspension, colloidal, and emulsion flow in rocks with particle size-exclusion may have a strong effect on the reservoir and on the well behavior during fines migration and production, drilling-fluid invasion into oil- or gas-bearing formations, or injection of seawater or produced water. The stochastic microscale equations for size-exclusion colloidal transport in porous media (PM) are derived. The proposed model includes the following new features: It accounts for the accessible flux in the expression for capture rate, it accounts for the increase of inlet concentration caused by the injected particles entering only the accessible area, and it accounts for the dilution of effluent accessible flux in the overall flux of the produced suspension.

Biofiltration of ethyl acetate by Pseudomonas putida immobilized on walnut shell

A biofilter packed with walnut shells was used to eliminate ethyl acetate from an air stream. The shells treated with NaOH were used as medium for immobilization of Pseudomonas putida PTCC 1694. At an empty bed residence time (EBRT) of 60s, a removal efficiency of 99% was achieved at inlet concentrations lower than 430ppm of ethyl acetate. The removal efficiency decreased below 80% with an increase in inlet concentration of ethyl acetate. When the EBRT was increased to 75 s, the removal efficiency remained above 80% even though the inlet loading rate was increased to 421g/m3h. Michaelis–Menten type and zero-order diffusion limited models were employed and the predicted data perfectly matched the experimental data. Thus P. putida immobilized on walnut shell has potential for the removal of ethyl acetate from air streams.

Photocatalytic oxidation of trimethylamine and isovaleraldehyde in an annular reactor: Influence of the mass transfer and the relative humidity

Abstract This study presents an experimental investigation of the photodegradation of two volatiles organic compounds (VOCs): Trimethylamine (TMA) and isovaleraldehyde (ISOV). Experiments were performed by using an annular plug-flow reactor. The influence of the inlet concentration, flowrate and relative humidity (RH) on the conversion rate has been studied for the two VOCs. The increase of inlet concentration leads to a lower conversion rate due to the availability of the active sites. The flowrate increase also induces a lower degradation rate due to the shorter residence time. A kinetic model based on the Langmuir–Hinshelwood (L–H) approach and taking into account the mass transfer step was developed. This allows us to determine the adsorption and kinetic degradation constants with no influence of mass transfer. This latter could be estimated by a semi-empirical correlation. In small amounts, the presence of water vapor has a promoting effect on the degradation due to the formation of OH radicals. When the RH increases, the competition between water molecules and VOCs toward the active sites becomes predominant and the degradation rate decreases. A bimolecular L–H model, including mass transfer step, was developed. A good agreement with the experimental results was observed. Moreover by derivating the equation model, the optimum RH values could be estimated for the two pollutants. These RH values are equal to 40% for isovaleraldehyde and 25% for trimethylamine.

Performance and Kinetic Evaluation of Ethyl Acetate Biodegradation in a Biofilter Using Pseudomonas Putida

Biodegradation of ethyl acetate in batch and continuous cultures was investigated. Pseudomonas putida was selected as a biological agent to biodegrade ethyl acetate. In batch experiment, biodegradation of ethyl acetate was performed in the range of 25-35 C. Walnut shells treated with alkaline solution as natural packing materials provided an appropriate environment for the growth and immobilization of microorganisms. The active biofilm was fully established on the surface of natural packing material. In the early stage, experiments were performed at Empty Bed Resistance Time (EBRT) of 60 s. Maximum removal efficiency of 99% was achieved at inlet concentrations lower than 430 ppm of ethyl acetate. The removal efficiency dropped to 80% with an increase of inlet concentration of ethyl acetate. In order to enhance the removal efficiency, the EBRT was increased from 60 to 75 s. At EBRT of 75 s, the removal efficiency was maintained above 80% even though the inlet concentration increased to 5150 ppm. Michaelis-Menten and Logistic models were perfectly fitted to experimental data. In addition, the kinetic parameters of presented models were defined.

Experiment and simulation of diffusion of micron-particle in porous ceramic vessel

The general behavior of micron-particles in the inner domain of porous ceramic vessel was simulated by computational fluid dynamics software in terms of sampling experimental data. The results show that there is an optimum porosity of 0.32 to get a higher efficiency and lower pressure drop during filtration. According to the results of simulation and experiment, it is evident that lower inlet velocity can maintain lower pressure drop and obtain higher collection efficiency and inlet concentration also has a crucial influence on the collection efficiency. The collection efficiency of equipment increases significantly with the increase of inlet concentration when the inlet concentration is less than 6.3 g/m 3, but it gradually tends to be stable in the range of 97.3%-99.7% when the inlet concentration is over this concentration.

Destruction of naphthalene via ozone-catalytic oxidation process over Pt/Al2O3 catalyst

This study investigated the application of ozone in conjunction with Pt/Al(2)O(3) catalysts, called ozone-catalytic oxidation (OZCO) process, to destruct gaseous naphthalene (Nap). The experiments were carried out at various constant reaction temperatures (T), space velocities (SV) and inlet concentrations of ozone (C(O3,in)). The results indicate that the required T for the effective decomposition of Nap decreases with the increase in inlet concentration of ozone (C(O3,in)) at the same conversion level of Nap (X(Nap)). Further, the values of X(Nap) and mineralization extent of Nap (M(Nap)) increase linearly with the increase of C(O3,in.) Regarding the T at X(Nap)=50% (T(50)), there is about 20K reduction at SV=100,000 h(-1) for the case of OZCO process with C(O3,in) of 1750 ppmv (T(50)=460 K) compared to the process without ozone (T(50)=480 K). Further, the power law can be applied to describe the data by using the second order expression with respect to ozone and Nap concentration. The observed activation energy and frequency factor are 68.3 kJ mol(-1) and 5.36 x 10(12)L(2)mol(-1)g(-1)-cat.s(-1), respectively. The information obtained is useful for the rational design and operation of the treatment of Nap via the OZCO process.

Two-phase flow in converging and diverging microchannels with CO 2 bubbles produced by chemical reactions

The present study investigates experimentally the evolution of two-phase flow pattern and pressure drop in the converging and diverging, silicon-based microchannels with mean hydraulic diameter of 128 μm and CO 2 bubbles produced by chemical reactions of sulfuric acid (H 2SO 4) and sodium bicarbonate (NaHCO 3). Three different concentrations of 0.2, 0.5 and 0.8 mol/L of each reactant at the inlet before mixing and 10 different flow rates from 1.60 × 10 −9 m 3/s to 16.0 × 10 −9 m 3/s are studied. Flow visualization is made possible by using a high-speed digital camera. It is found that the present design of the microchannel, with the inlet chamber, results in much more intensive chemical reactions in the diverging microchannel than that in the converging one. The void fractions at the entrance and exit regions and pressure drop through the channel are also measured. The results reveals that the presence of small void fraction, <0.1, at the inlet may promote CO 2 generation in the microchannel, irrespective of the channel is converging or diverging, indicating the agitation effects of bubbly flow in the microchannel. The increase of inlet concentration of reactants does not increase the pressure drop in the converging microchannel significantly, while the inlet concentration presents significant but mild effects on the pressure drop in the diverging microchannel. The two-phase frictional multiplier may be positively correlated with the mean void fraction in the channel linearly, and the data agree well with predictions from the correlations in the literature.

Effects of gas flow‐rate and inlet concentration on nitric oxide removal in an autotrophic biofilter

AbstractThe effects of inlet gas concentration and gas flow‐rate on the NO elimination process were studied in a laboratory‐scale biofilter and the removal process is discussed. Various pollutant inlet concentrations and gas flow‐rates were tested in the biofilter. The results showed that the removal efficiency increased with increase in the empty bed residence time (EBRT) and finally reached a steady state. The mass transfer process became the limiting step of NO removal when the EBRT was less than 2 min. A removal efficiency of ∼73% was obtained in the biofilter at an inlet concentration of 107.1 mg m−3. The removal efficiency decreased with increase in inlet concentration, whereas the removal capacity increased. The removal process consisted of chemical oxidation and bio‐nitrification in the biofilter. The bioprocess mainly contributed to the removal. Copyright © 2006 Society of Chemical Industry

고정층 활성탄 흡착반응기에서 기상 톨루엔의 흡착특성

Adsorption characteristics of toluene vapor, which is one of important source of volatile organic compounds (VOCs), by activated carbon were investigated using a fixed bed adsorption column. The operating parameters such as breakthrough curve, adsorption capacity, mass transfer zone (MTZ), and length of unused bed (LUB) were studied. The experimental results showed that the breakthrough time decreased with increasing inlet toluene concentration and gas flow rate. MTZ and LUB increased with the increase of inlet concentration, gas flow rate, and particle size of activated carbon. The adsorption capacity increased with the increase of inlet toluene concentration, while it decreased with increasing particle size. However, it was kept at constant value regardless of the increase of gas flow rate. Adsorption isotherm of toluene vapor could be represented by the Freundlich adsorption equation fairly well. From the adsorption experiments using some VOC gases such as toluene, xylene, butyl acetate. butanol and acetone, it was also found that the adsorption capacity was higher in the case of gas with higher boiling point and lower vapor pressure.

Removal of Toluene in Gas Streams by a Fibrous-Bed Trickling Filter

A novel fibrous-bed trickling filter was developed to remove toluene present in contaminated air. Pure culture of Pseudomonas putida F1 was attached on fibrous-bed and utilized toluene as the carbon source. Experimental results indicated the removal efficiency decreased with the increase of inlet concentration. In general, the removal efficiency of toluene was greater than 90% when the inlet loading capacity was below 70 g m−3h−1. The elimination capacity increased with increasing inlet loading capacity, but the increased rate decreased gradually. When the inlet loading capacity increased to 300 g m−3h−1, the elimination capacity could approach to 130 g m−3h−1. The first order kinetics model was useful to describe the removal of toluene in this filter and an excellent linear relationship was found between the apparent first order parameter and inlet concentration (ranging from 1.2 g m−3 to 3.5 g m−3). Also, the performance of fibrous-bed trickling filter was relatively stable during the four-month period of continuous operation. Slight clogging phenomena of filters were observed only under high loading capacity.