Gas Removal Efficiency Research Articles

Removal of livestock odor gas ammonia, hydrogen sulfide, methanethiol by electron beam in a continuous flow system

Odor is becoming one of the serious environmental issues as the industry develops. Electron beam technology has recently attracted attention as an AOP (Advanced Oxidation Process) for air purification, water treatment, and soil remediation. This work studied the removal of major livestock odor such as ammonia (NH3), hydrogen sulfide (H2S), and methanethiol (CH3SH) using a continuous gas flow electron beam treatment process. The effects of initial odor gas concentration, type of background gas, absorbed dose of the electron beam, voltage of the electron accelerator, and odor gas flow rate on the removal of odor gas were all studied in this continuous gas flow treatment system. As the absorbed dose of electron beam was increased, the removal efficiencies of odor gases NH3, H2S, and CH3SH all increased gradually. As the initial concentration of odor gas was decreased and as the flow rate of odor gas was increased, the removal efficiencies also increased. Regarding background gas, the odor gas removal efficiency was found to be in descending order of O2 > air > N2. The lower the voltage (MeV) of the electron beam, the higher the odor gas removal efficiency. This was attributed to the fact that, to set the same absorbed dose (kGy), as the voltage decreases, the current value (mA) increases. For the byproducts, as the absorbed dose of electron beam was increased, the concentration of byproducts increased. Regarding the gas-phase continuous electron beam treatment reactions, the optimal operating conditions must be derived by considering various operational variables, including the initial concentration, electron beam dose, background gas type, gas flow rate, and electron beam voltage. The results of this study show that, among several possibly relevant variables in removing odor gases in the continuous flow electron beam irradiation process, the current value can be considered one of the most important variables, along with the initial concentration and background gas.

Evaluating the efficacy of biogeochemical cover system in mitigating landfill gas emissions: A large-scale laboratory simulation.

Municipal solid waste (MSW) landfills are a significant source of methane (CH4) emissions in the United States, contributing to global warming. Current landfill gas (LFG) management methods, like the landfill cover system and LFG collection system, do not entirely prevent LFG release. Biocovers have the potential to reduce CH4 emissions through microbial oxidation. However, LFG also contains carbon dioxide (CO2) and trace hydrogen sulfide (H2S) depending on waste composition, temperature, moisture content, and age of waste. An innovative biogeochemical cover (BGCC) was developed to tackle these concerns. This cover comprises a biochar-based biocover layer overlaid with a basic oxygen furnace (BOF) steel slag layer. The biochar-based biocover layer oxidizes CH4 emissions, while the BOF slag layer reduces CO2 and H2S through carbonation and sulfidation reaction mechanisms. The BGCC system's field performance remains unexamined. Therefore, a large-scale tank setup simulating near-field conditions was developed to evaluate the BGCC system's ability to mitigate CH4, CO2, and H2S from LFG simultaneously. Synthetic LFG was passed through the BGCC in five distinct phases, each designed to simulate the varying gas compositions and flux rates typical of MSW landfill. Gas profiles along the depth were monitored during each phase, and gas removal efficiency was measured. After testing, biocover and BOF slag samples were extracted to analyze physico-chemical properties. Batch tests were also conducted on samples extracted from the biocover and BOF slag layers to determine potential CH4 oxidation rates and residual CO2 sequestration capacity. The results showed that the BGCC system's CH4 removal efficiency decreased with higher CH4 flux rates, achieving its highest removal (74.7-79.7%) at moderate influx rates (23.9-25.5g CH4/m2-day) and reducing to its lowest removal (27.4%) at the highest influx rate (57.5g CH4/m2-day). Complete H2S removal occurred during Phase 3 in the biocover layer of BGCC system. CH4 oxidation rates were highest near the upper (277.9µg CH4/g-day) and lowest in the deeper region of the biocover layer. In the tank experiment, CO2 breakthrough occurred after 156days due to drying of the BOF slag layer, with an average residual carbonation capacity of 46 gCO2/kg slag after moisture adjustment. Overall, the BGCC system effectively mitigated LFG emissions, including CH4, CO2, and H2S, at moderate flux rates, showing promise as a comprehensive solution for LFG management.

An investigation of a process for selective biogas desulfurization and autotrophic denitrification in a membrane supported reactor

A lab-scale dense polydimethylsiloxane (PDMS) membrane bioscrubber (MBS) was used for selective removal of highly toxic H2S from biogas under autotrophic conditions for the first time. The performance of MBS was evaluated under the effects of sulfide loadings, pH, and hydraulic retention time (HRT). The results showed that gradual increase in sulfide loading rate from 131 to 316 g/m3.d boost S/N ratios 1.9–4.0, on average sulfide oxidation efficiencies higher than 95% were achieved. The S/N ratios were determinant on the formation of oxidation products, but not on the H2S gas removal efficiency. The transition of HRT significantly affected the denitrification rather than the sulfide oxidation, when HRT reduced from 24 to 12 h the nitrate removal efficiency suddenly dropped from 98% to 70%. Increasing the pH values from 7.0 to 9.0 also decreased the sulfide oxidation efficiency from 97±0.5–92±1.1%. Denitrification efficiency > 96% was observed between pH value of 7.0 and 8.0, whereas at pH 9.0 dropped rapidly to 82%. In the whole experiment time there was no membrane-induced problem that adversely affected the system performance. Over-all the developed anoxic dense MBS successfully employed for selective removal of 10,000 ppm H2S and nitrate concurrently with low chemical consumption, possibility for recovery of elemental sulfur, enhanced CH4 calorific value and eliminating the risks of explosion and dilution of biogas. The current work showed the PDMS MBS system is a promising alternative way in biological nitrogen removal and biogas desulfurization under anoxic conditions. Its application in real scale would have high economic importance.

Improved deoxygenation beads for trickle bed-based microbial fuel cells to increase isopropanol and styrene-containing exhaust gas removal efficiency and power production

This study is the first to use a trickle-bed microbial fuel cell (TB-MFC) to treat both hydrophilic (isopropyl alcohol) and hydrophobic (styrene) pollutants. During the operation of the TB-MFC, the microorganisms continue to convert pollutants into electrons, improving the removal of hydrophilic and hydrophobic pollutants, and generating electricity. To enhance the growth of electricity-generating bacteria, a novel deoxygenated packing material (DPM) that removes oxygen from the exhaust gas was applied to the TB-MFC. The TB-MFC reached maximum pollutant removal and power generation at a total carbon concentration of 2.20 g/m3, an empty bed residence time of 60 s and a concentration ratio of 1: 1 of isopropanol and styrene. The mean elimination capacity of isopropanol and styrene were 81.5 ± 0.20 g/m3/h and 54.2 ± 0.26 g/m3/h, respectively, and the maximum voltage outputs and power density were 450 mV and 426 mW/m3. A microbial community analysis revealed that the electricity-generating bacteria were mostly Clostridium, Aeromonas, Acinetobacter and Kosakonia. Most of the isopropanol-degrading bacteria (Xanthobacter, Beijerinckia) and styrene-degrading bacteria (Chryseobacterium, Cloacibacterium) were in the TB-MFC. The findings indicate that TB-MFC is capable of generating electricity and treating both hydrophilic and hydrophobic pollutants simultaneously. The improved DPM can be used in the TB-MFC to reduce the concentration of oxygen in industrial emissions and accelerate the growth of electricity-generating bacteria, with the goal of achieving high pollutant removal and electricity generation.

Simulation of acid gas removal unit using DIPA+TEA amine solvent

Due to the inexpensive cost of amine solvent, more than 95 % of natural gas (NG) processing plants use an acid gas removal unit that utilizes an aqueous amine solvent to remove sour gas components such as carbon dioxide (CO2) and hydrogen sulfide (H2S). Different technologies are available to capture CO2 from NG. However, chemical absorption is the most reliable and used technology all over the world. However, it is challenging to determine the amine blend’s optimal composition for the effective removal of CO2 and H2S and solvent regeneration. This is mainly due to the difference in reservoir gas compositions, affecting gas removal efficiency and solvent regeneration energies. The present investigation addresses the performance of using a novel solvent blend of diisopropanolamine (DIPA) and Triethanolamine (TEA) to determine the absorption capacity of CO2 & H2S using Aspen HYSYS software. A study on the effects of solubility on CO2 absorption was performed at varying pressure (10-80 bar) and temperature (25°C to 50°C). The percentage of CO2 removal increased from 80% to 98% as the temperature increased from 25°C to 50°C. The results revealed that the concentration of CO2 and H2S in sweet gas decrease with the increase in pressure while the concentration of CO2 and H2S increases with the increase in temperature.

Numerical study on the distribution of flue gas residence time in the desulfurization and denitrification system by the optimization of the model

Abstract During the operation of the CSCR activated carbon desulfurization and denitrification flue gas purification system, due to the unreasonable design of flue gas pipe diameter and the uneven distribution of activated carbon porosity, the uniformity of flue gas distribution is prone to problems, which affects flue gas removal efficiency and increases operating costs. In this article, the Fluent software was used to establish a three-dimensional numerical model of the flue gas purification system, and the flow characteristics of the flue gas were studied by continuously optimizing the structure of the system model. The effects of different pipe diameters, the accumulation method of activated carbon in the desulfurization and denitration module and the distribution of porosity on the flue gas are analyzed, and the effects on the average residence time and variance of flue gas were further analyzed. The results show that the average residence time, the variance, the dead volume fraction, and well-mixed volume decreased, while the dispersed plug volume fraction increased for a module after optimization. The average residence time and the dispersed plug volume fraction decreased. While the variance, the dead volume fraction, and well-mixed volume fraction increased for the system after optimization.

Testing of Sorbents for Removal of Acid Gases from Biomass Gasification

A number of various commercial technologies are available to remove contaminants from gasification gases, particularly those from biomass. However, new cheaper technologies are needed to meet the stringent requirements in gas cleaning, especially for biomass gas production. In this paper, we discuss the suitability of various sorbents prepared by us based on oxides or carbonates of various metals (Al2O3, CaO, CuO, Fe2O3, MgO, MnO, Na2O and ZnO) for the removal of acid gases from flue gas during biomass gasification process at elevated temperatures. The acid gas removal efficiencies were experimentally verified for all prepared sorbents under specific conditions such as raw gas composition and temperature. The experimental results showed that the sorbents based on aluminum, copper and zinc oxides have high sorption capacity for selective sorption of hydrogen chloride and hydrogen fluoride. In the case of sulfane, sorbents based on copper and zinc oxides have a high sorption capacity. All these sorbents can then be used to remove acid gases from biogas produced by biomass combustion at elevated temperatures.

Study of dynamics and mechanism of HCl, SO2, or NO removal by MnO2/Mg–Al layered double hydroxide

The gas exhaust generated by waste incinerators contains toxic acid gases such as HCl, SO2, and NOx, which require appropriate treatment following their release. Although several methods exist for this purpose, they have various drawbacks. Thus, toward the search for a new removal method, the ability of Mg–Al layered double hydroxide (Mg–Al LDH) to eliminate HCl, SO2, and NO gases from simulated exhaust gas was examined. In addition, the impact of the amount of LDH employed was investigated in terms of the toxic gas removal efficiencies and process temperature. Furthermore, the mechanism of removing HCl, SO2, and NO by MnO2/Mg–Al LDH was considered. More specifically, HCl removal proceeded mainly by the reaction of HCl with the CO32− and OH− species present between the Mg-Al LDH layers, while that of SO2 took place through the adsorption of SO2 onto the LDH and MnO2 surfaces. Moreover, NO was removed through the oxidation of NO to NO2 by MnO2, followed by the reaction of NO2 with the CO32− and OH− species present between the Mg–Al LDH layers. These results are expected to help pave the way for the use of Mg–Al LDH to remove toxic acid gases from the gas exhausts of waste incinerators, thereby addressing the various issues related to the use of current technologies.

Activated Bio-Carbons Prepared from the Residue of Supercritical Extraction of Raw Plants and Their Application for Removal of Nitrogen Dioxide and Hydrogen Sulfide from the Gas Phase.

The waste materials left after supercritical extraction of hop cones and marigold flowers were tested as precursors of activated bio-carbons. Adsorbents were produced by means of the physical (also called thermal) activation method using CO2 as the gasifying agent. All the activated bio-carbons were tested for the removal of NO2 and H2S from the gas phase under dry and wet conditions. The effects of the type of precursor and the activation procedure on the porous structure development, the acid-base properties of the surface, as well as the sorption capacities of the materials produced were also checked. The final products were bio-carbons of medium developed surface area with a basic surface nature, characterized by their high effectiveness in removal of gas pollutants of acidic character, especially nitrogen dioxide (sorption capacities in the range from 12.5 to 102.6 mg/g). It was proved that the toxic gas removal efficiency depends considerably on the sorption conditions and the activation procedure. All materials showed greater effectiveness in gas removal when the process of adsorption was carried out in the presence of steam.

Physicochemical properties and photocatalytic de-NOx performance of TiO2 nanostructures via microwave hydrothermal strategy

TiO2 nanostructures have been prepared via microwave hydrothermal process using different NaOH concentrations. The physicochemical properties of the products were systematically investigated by using UV–vis Diffuse Reflectance Spectra, X-ray Photoelectron Spectra, Photoluminescence Spectra, Raman, N2 adsorption-desorption, and Transmission Electron Microscope analysis. The results indicated a close correlation between the NaOH concentration and different types of nanostructured titania products obtained from the microwave-assisted hydrothermal process. At low NaOH concentrations (4 M and 6 M), the precursor TiO2 nanoparticles partially converted into a mixture of one dimensional (1D) nanostructures (e.g., nanorods or nanowires) and 2D nanostructures such as nanosheets. As the NaOH concentration is increased to 8 M and 10 M, the obtained TiO2 products contain nanosheet and nanotube-like structures, respectively, with a significantly larger specific surface area. The photocatalytic performance of the synthesized TiO2 products, prepared under different NaOH concentrations, were evaluated through the toxic NOx gas removal efficiencies. The nanostructured TiO2 samples prepared at a higher NaOH concentration have shown improved de-NOx efficiencies than the TiO2–P25 precursor.

Study on the Removal of Odorous Gases from Composting Process using Local Bio-Media of Vietnam

Odor pollution is an increasing problem in Vietnam as a tropical country during the urbanization and industrialization. The odor from sewage systems, farms of poultry, pig, and beef, food processing companies, composting factory, and landfills is a severe problem in many nearby residential areas. In this study, two lab-scale biofiltration systems where pristine local bio-media and cultured bio-media with specially formulated microorganisms were employed in biofilters and bio-trickling filter for controls of odor (i.e., hydrogen sulfide and ammonia) from composting process were fabricated and operated. The odorous gas flow was created by composting solid waste collected from an agricultural market (i.e., mainly vegetable), containing low concentrations of 1.32 ± 0.32 mgNH3 m-3 and 5.20 ± 0.28 mgH2S m-3 under stable condition. For the biofilter model, commercial compost and cow manure were used as substrates and packed into the models. For the bio-trickling filter model, K3 bio-media with biofilm developed by contacting activated sludge was used as packing material. The results showed that adding specially formulated microorganisms could reduce adaption time and lead to slightly better odor control performance. Among the substrates, cow manure provided the highest odorous gas removal efficiency of ≥ 90% during the stable phase with the elimination capacity of 0.0492 gNH3 m-3 h-1 and 0.225 gH2S m-3 h-1. The study results show a high potential of cow manure biofilter for control of H2S and NH3 gases in the practical application under Vietnam’s condition.

Experimental investigation on hydrodynamics and mass transfer of a novel fission gas removal equipment for molten salt reactor

The separation of fission gases like 135-Xe and 85-Ke from the liquid nuclear fuel is a focused topic in the molten salt reactor (MSR) community. In this paper, a compact fission gas removal equipment with a serpentine tube as the gas-liquid contactor is introduced. The novel design is free of any moving or rotating components, bringing great convenience in the real-time fuel treatment. As crucial factors influencing the gas removal performance, the two-phase hydrodynamics and interfacial mass transfer characteristics in the vertical serpentine tube are investigated under a water-nitrogen-oxygen system. Both highspeed photographing and conductivity probe are employed to capture the evolution of bubbly flow inside the tubular contactor. The oxygen concentration differences between the inlet and outlet of the device are measured under various operating conditions, and the overall volumetric mass transfer coefficient kla is derived to evaluate the gas removal efficiency. Experiment results imply a periodic transition of volume fraction profile between the off-center distribution in the downward flow and the near-wall distribution in the upward flow due to the centripetal effect in the U-bends. Bimodal distributions of bubble equivalent diameter are observed because of the intensive bubble coalescence inside the elbow. The overall kla is found to be linearly proportional to the liquid Reynolds number and gas volume fraction. The dimensionless mass transfer correlation proposed in this work predicts well the overall volumetric mass transfer coefficient.

Removal Characteristics of Toxic Gas on Activated Carbon Fiber Based Paper Filter

Objectives:A paper filter was prepared by pitch based activated carbon fibers to investigate the removal efficiency of toxic gas. Also, changes in pore characteristics and mechanical properties according to the ratio of the adsorbent and the binder were observed to optimize the decrease in specific surface area and micropore, which are the unique characteristics of activated carbon fibers. In addition, it is intended to establish optimized paper filter derived activated carbon fiber manufacturing conditions through evaluation of toxic gas removal characteristics.Methods:The pore characteristics of the activated carbon fiber and prepared paper were analyzed by measuring the BET specific surface area, and SEM analysis was performed on the fine surface shape. Tensile strength and air permeability were performed according to ISO 1924-2 and ASTM D737: 04, respectively. The adsorption performance of the prepared filter was evaluated as a gas removal efficiency using a gas detection tube (GV-110S).Results and Discussion:As the content of the binder increased in the paper manufacturing process, it was confirmed that the specific surface area of ​​the prepared filter decreased by up to 39.5% compared to the activated carbon fiber. It is considered that the micropores were closed because the surface of the activated carbon fiber was coated with the excessive addition of the binder. The removal efficiency showed a removal rate of 90% of ammonia, and methyl mercaptan and hydrogen sulfide showed a removal rate of about 60%. This result might be due to the difference in the physical adsorption rate according to the vapor pressure of each material.Conclusions:An activated carbon fiber-based paper filter for removing of toxic gas was prepared. It was confirmed that the mixing ratio of the adsorbent and the binder was an important process parameter for determining moldability and adsorption performance. Finally, optimum condition was selected as weight ratio condition of 8:2.

Synthesis of Polyketone Anion Ion Exchange Fibers by Paal-Knorr Reaction and Its Physico-Chemical Properties

In this study, polyketone anion exchange fibers were synthesized by the amination of polyketone via a Paal-Knorr reaction and a quaternization reaction. The amination reaction proceeded at different reaction times and amine N,N-dimethylethylene diamine (DME) concentrations. The ion exchange capacity (IEC) and water uptake (W.U.) increased with increasing amination reaction time and DME concentration, and the maximum IEC and W.U. were 1.03 meq/g and 19.2%, respectively. The tensile strength decreased significantly with increasing amination time and amine concentration. TGA showed that the thermal decomposition temperature of the fibers was 220 °C. The HCl gas adsorption properties of the aminated polyketone ion exchange fibers were evaluated, and the HCl gas removal efficiency remained at 100% in 40 min at 300 ppm.

Selective removal of SO2 from coal-fired flue gas by alkaline solvents using a membrane contactor

The presence of SO2 in coal-fired flue gas has adverse effects on the amine solutions used for CO2 capture. In addition, SO2 emissions in the atmosphere are also a primary source of pollution. In this study, the SO2 removal efficiency of three aqueous alkaline absorbents NaOH, Na2SO3, and CaO was studied using a membrane contactor. The morphology of the used membrane was examined using SEM and contact angle characterization techniques. Gas removal efficiency was studied within a feed gas flow rate of 0.5–5 m3/h, absorbent flow rate of 5–100 mL/min, and absorbent concentration of 0–0.01 mol/L. The gathered results showed that aqueous CaO has superior gas removal performance. It achieved a SO2 removal efficiency of 99.99 % at a concentration of 0.0025 mol/L, while the aqueous NaOH and Na2SO3 absorbents achieved 99.99 % removal efficiency at concentrations of 0.001 mol/L. Through comprehensive experimental work, the optimum operating parameters needed to achieve maximum SO2 removal efficiency were also determined. Furthermore, the durability of the membrane was tested in a four week continuous gas removal test and SEM images were recorded weekly to observe module morphology. The obtained results indicated that the membrane was quite durable and did not deteriorate noticeably.

Experimental and modeling of CO2 removal from gas mixtures using membrane contactors packed with glass beads

The efficiency of gas removal using hollow fiber membrane (HFM) contactors and liquid solvents is determined by several factors. The liquid film resistance has been identified as one of the important factors affecting the overall mass transfer coefficient. The present work describes the use of spherical glass beads as additional packing in the shell (solvent) side to act as solid baffles which should impart stirring effect in the flowing solvent and increase its velocity. These two effects should decrease the liquid film resistance and consequently enhance the gas removal efficiency. Two types of custom-made hollow fiber membrane contactors (HFMC) were constructed from thick-walled acrylic tube (20 mm ID, OD 30 mm) and equipped with the commercially available poly(tetrafluoroethylene-co-perfluorinated alkyl vinyl ether) (PFA) hollow fibers. In one type of the contactors, glass beads were introduced in the shell side. The two types of contactors (with and without beads) were tested and compared in terms of CO2 removal efficiency from gas mixtures (5% CO2 − 95% CH4) using aqueous sodium hydroxide and several amine solutions. Different parameters were studied to evaluate the performance of the membrane contactors at feed gas pressures up to 25 bars. The obtained results indicated an increase of up to 21% enhancement in CO2 removal efficiency when the shell compartment was packed with the glass beads. The results obtained from the overall mass transfer coefficient model showed good agreement with those of the experimental data.

Experimental optimization of a spray tower for ammonia removal

Spray tower scrubbers ordinarily have low air resistance and gas removal efficiency. Although packed-bed wet scrubbers are efficient in gaseous contaminants treatment, a significant limitation of packed-bed wet scrubbers is that they have high pressure drop and primary costs. Appropriate features of the nozzle play an important role in system cost, efficiency, low operational costs, and optimization of spray towers. Operating pressure, nozzles size, and number of nozzles could increase mass transfer and removal efficiency and decrease investment and save operational costs. The objective of the present study was to develop a spray tower through optimization of the design and operating parameters for removal ammonia emissions from the air streams. Spray tower design parameters included nozzle type, number of stages of spray nozzle, and operating parameters such as operating pressure and inlet NH3 concentration. Among the studied parameters, only increasing ammonia concentration was in inverse proportion to the spray tower efficiency. The spray tower was optimized as equipped with an 8010SS spray nozzle with three stages working together, spraying 0.01% H2SO4 scrubbing liquid counter-current to the air stream with operating pressure of 12 bars and inlet NH3 concentration of 24.1 ppm. The highest removal efficiency was 97.92% at an 8010SS spray nozzle with three stages working together, H2SO4 solution, pressure 12 bars and inlet ammonia concentration of 24.1 ppm. The results of this study demonstrated that caustic spray tower could be a very effective technology for removal of NH3 from air stream.

The Behaviors and Relationships of PCDD/Fs and Chlorobenzenes in the Whole Process of one Municipal Solid Waste Incinerator

We examined the characteristics of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and chlorobenzenes (CBzs) in the flue gas and fly ash of a municipal solid-waste incinerator in four locations: the outlet of the furnace, the outlet of the high-temperature superheater, the inlet of the semi-dry scrubber and the stack after air pollution control device (APCD) processing. Both PCDD/Fs and CBzs were mostly formed at low temperatures. The dominant PCDD/Fs generated in the gaseous phase were 23478-PeCDF and TCDF, and 124-TrCBz was the major CBz in both the gaseous and solid phase. More PCDD/Fs were found in the solid phase with the decrease of temperature, while CBzs exhibited the opposite trend. Furthermore, activated carbon with a low surface area and mesoporous volume showed low flue gas removal efficiencies for PCDD/Fs and CBzs in the flue gas. The fraction of PCDD/Fs in the solid phase largely decreased when the flue gas passed through the fabric filter. Additionally, the memory effects of the aged filters increased the fractions of 234678-HxCDF, 1234678-HpCDF and 1234678-HxCDD. Most important, the relationships between PCDD/Fs and CBzs in the flue gas and fly ash were analyzed, respectively. In the gaseous phase, most of the CBzs displayed high correlation coefficients with PCDD/Fs, especially 123-TrCBz (R2 > 0.8). In the solid phase, low correlation coefficients were found between CBzs and PCDD/Fs except for 135-TrCBz and 123-TrCBz (R2 = 0.8). A remarkable correlation was also found between 124-TrCBz in the flue gas and PCDD/Fs in the fly ash. We conclude that TrCBzs may be regarded as the best indicator for PCDD/Fs in both flue gas and fly ash.

A novel electrostatic precipitator-type small air purifier with a carbon fiber ionizer and an activated carbon fiber filter

We developed and investigated the air cleaning performance of a novel electrostatic precipitator (ESP)-type small air purifier with a carbon brush ionizer and an activated carbon fiber (ACF) filter. This version had a high particle charging rate and a low ozone emission rate. Applying a negative voltage of 10kV to the carbon brush ionizer increased the single-pass particle collection efficiency of 0.3-μm particles from 17.8% to 47.1%. The flow rate was maintained at 362L/min, and the efficiency increased to 64.2% as we applied a negative voltage to the collection stage and increased the voltage to 10kV. This was relatively low when compared to a market-leading commercial HEPA filter-type small air purifier (80.7%). However, our novel purifier showed a particle clean air delivery rate (CADR) of 0.31m3/min, approximately a 1.7 times higher than that for the commercial purifier (0.18m3/min) due to its high flow rate and low pressure drop. We measured the gas removal efficiency in a 1-m3 test chamber with acetic acid, acetaldehyde, and ammonia; after 30min of operation, the results were 97.9%, 92.4%, and 87.8% for the novel purifier and 95.2%, 65.4%, and 57.9% for the commercial purifier, respectively. The ozone concentration was measured in a closed test chamber (30.4m3) over 15h of continuous operation, and it showed a maximum value of 2.5 ppb, much lower than the current standard for ESPs (50 ppb).

Separation of nitrous oxide from aqueous solutions applying a micro porous hollow fiber membrane contactor for energy recovery

Abstract Nitrous oxide (N 2 O) is a potent green-house gas, but has also recently been acknowledged as sustainable energy source that can intentionally be produced by bioreactor systems such as the C oupled A erobic-anoxic N itrous D ecomposition O peration (CANDO). In this study, the application potential of a porous hollow fiber membrane contactor has been assessed at expected conditions of an operating CANDO system in shell-side liquid feed operation for N 2 O removal. At varying feed concentrations, liquid and gas flow rates, off-gas concentrations, removal efficiencies, trans-membrane fluxes and mass-flows have been assessed and compared to previous studies on CO 2 . Under the applied operational conditions, the gas flow rate had no significant effect on the results. Removal efficiencies up to 77% of the module feed load demonstrated a high application potential for the CANDO process and indicate a promising removal potential greater 90% in reference to typical initial substrate loads in an operating CANDO system. Additionally, considerably higher off-gas concentrations compared to recently published results applying conventional stripping technology of 3700 ppmv were generated reducing sweeping gas demand by 70%. The mass transfer was dominated by the superficial velocity on the liquid side and its behavior could be well described by Sherwood correlations. However, previously published mass transfer correlations over-estimated the results. Hence, a more appropriate correlation is presented to describe the observations of this study.