This study deals with poly(ether block amide) (PEBA) (type 2533) membranes for gas separation. A new method was developed to prepare flat thin film PEBA membranes by spontaneous spreading of a solution of the block copolymer on water surface. The membrane formation is featured with simultaneous solvent evaporation and solvent exchange with the support liquid, i.e. water. The formation of a uniform and defect-free membrane was affected by the solvent system, polymer concentration in the casting solution and temperature. Propylene separation from nitrogen, which is relevant to the recovery of propylene from the de-gassing off-gas during polypropylene manufacturing, was carried out using flat PEBA composite membranes formed by laminating the aforementioned PEBA on a microporous substrate. The propylene permeance was affected by the presence of nitrogen, and vice versa, due to interactions between the permeating components. Semi-empirical correlations were developed to relate the permeance of a component in the mixture to the pressures and compositions of the gas on both sides of the membrane, and the separation performance at different operating conditions was analyzed in terms of product purity, recovery and productivity on the basis of a cross flow model. To further understand gas permeation behavior and transport mechanism in the membranes, sorption, diffusion, and permeation of three olefins (i.e., C2H4, C3H6, and C4H8) in dense PEBA membranes were investigated. The relative contribution of solubility and diffusivity to the preferential permeability of olefins over nitrogen was elucidated. It was revealed that the favorable olefin/nitrogen permselectivity was primarily attributed to the solubility selectivity, whereas the diffusivity selectivity may affect the permselectivity negatively or positively, depending on the operating temperature and pressure. At a given temperature, the pressure dependence of solubility and permeability could be described empirically by an exponential function. The limiting solubility at infinite dilution was correlated with the reduced temperature of the permeant. The separation of volatile organic compounds (VOCs), which are more condensable than olefin gases, from nitrogen stream by the thin film PEBA composite membranes for potential use in gasoline or other organic vapour emission control was also studied. The membranes exhibited good separation performance for both binary VOC/N2 and multi-component VOCs/N2 gas mixtures. The permeance of N2 in the VOC/N2 mixtures was shown to be higher than pure N2 permeance due to membrane swelling induced by the VOCs dissolved in the membrane. The effects of feed VOC concentration, temperature, stage cut, and permeate pressure on the separation performance were investigated. Additionally, hollow fiber PEBA/polysulfone composite membranes were prepared by the dip coating technique. The effects of parameters involved in the procedure of polysulfone hollow fiber spinning and PEBA layer deposition on the permselectivity of the resulting composite membranes were investigated. Lab scale PEBA hollow fiber membrane modules were assembled and tested for CO2/N2 separation with various flow configurations using a simulated flue gas (15.3% carbon dioxide, balance N2) as the feed. The shell side feed with counter-current flow was shown to perform better than other configurations over a wide range of stage cuts in terms of product purity, recovery and productivity.

Organic solvent production plants emit waste gases containing volatile organic compounds (VOCs) which are usually harmful to the environments and public healths. Plant managers are obligated to control the VOC emission to meet regulations at reasonable costs. A solvent plant located in southern Taiwan emits VOC-containing gas streams from some distillation columns and storage vessels with a total ventilation gas flow rate of 2.6-3.6 m3/min which contains VOCs with concentrations of less than 1,000 mg C/m3. Due to a concern of plant¡¦s safety, the plant managers constructed a full-scale biofilter for eliminating a part of the VOCs and the associated odors in the waste gas. This study aimed to investigate the effects of operation parameters such as EBRT (empty bed retention time) of the gas through the biofiltration media and organic loading to the media on the VOC removal efficiency. The biofilter is constructed of RC (reinforced concrete) with outer dimensions of 8.45 mL ¡Ñ 3.30 mW ¡Ñ 3.00 mH. The filter was also instrumented with inverters for control of speed of induced fans, and with thermometers, hygrometers, and wind speed meters. Fern chips with a total packing volume of 36 m3 was used as the biofiltration media. After inoculation with suitable microorganisms, the waste gas was introduced to the filter for VOC elimination. Nutrients (urea, milk, and a phosphate salt) and water were supplemented to the media on a daily basis. The investigation period is July, 2008 to May, 2010. In the period, THC (total hydrocarbon) concentrations for the influent and effluent gases to and from the reactor were daily measured. In addition, on a weekly basis, compositions of the VOCs in gas samples were detected by a gas chromatography equipped with a flame ionization dector (FID). On the same time basis, pH, COD (chemical oxygen demand), SS (suspended solids) in a sample of the trickled liquid from the media was analyzed. Media pH and moisture content were also analyzed for understanding the environmental conditions around the microorganisms for the VOC degradation. Results indicated that the media was in conditions of pH = 4.5-7.0, moisture = 11-61 % in the experimental phase. Trickled liquid had low COD and SS contents which can be easily treated by the existing wastewater unit in the plant, or be recycled to the media. Avarage THC, NMHC (nonmethane hydrocarbon), and VOCs were 71, 73, and 79%, respectively, with gas EBRTs of 4.2-6.3 min. With media pH of 4-5 and moisture contents 51-57%, over 90% of the influent VOCs coulb be eliminated. However, nearly dried media (moisture around 10%) had VOC removal efficiencies of lower than 30%. Nutrition tests indicate that the VOC removal efficiency was nearly proportional to milk supplementation rate. Removal of ethnaol and acetic could easily be removed with an efficiency of over 97% while 2-pentane was only 74%. Odor intensities of the treated gas could be controlled to <1,000 (dilutions to threshold) according to 3 test data.

This study aimed to develop a biofilter packed only with fern chips for the removal of air-borne low concentration VOCs (volatile organic compounds) emitted from various industries such as semiconductor manufacturing and electronic ones. The fern chip biofilters could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. The study contains two topics. The first is a performance test on the elimination of mixed VOCs used in semiconductor manufacturing industries in an air stream. The second is the one on the elimination of a single VOC (methyl ethyl ketone) in a waste gas drawn from a CCL (copper clad laminate) plant. Two pilot-scale biofilters consisted of two columns (0.40 mW¡Ñ0.40 mL¡Ñ0.70 mH acrylic column) arranged in series were used for the performance tests. Each of the two columns was packed with fern chips to a packing volume of around 56 L (0.40 mW¡Ñ0.40 mL¡Ñ0.35 mH). A sprinkler was set over the packed fern chips for providing them with water and nutrition solutions. Liquid leached from both layers of chips were collected in the bottom container of the column. In the first topic, tests were performed for biofiltration removal of VOCs in simulated semiconductor manufacturing emitted gases which consisted of IPA (isopropyl alcohol), acetone, HMDS (hexamethylene disilazane), PGME (propylene glycol monomethyl ether), and PGMEA (propylene glycol monomethyl ether acetate). From the results, it could be proposed that for achieving over 94% of the VOC removal, appropriate operation conditions are media moisture content = 52-68%, media pH = 7-8, influent VOC concentration = 150-450 mg/Am3, empty bed residence time (EBRT) = 0.75 min, and volumetric organic loading L to the whole media = 11.4-34.1 g/m3.h. In the second topic, performances of biofiltration for the removal of methyl ethyl ketone (MEK) in a gas stream from a copper clad laminate (CCL) manufacturing process were tested. Experimental results indicate that with L of <115 g /m3.h., EBRT = 0.5-1.28 min , media pH = 5.3-6.8, influent MEK concentration = 215-1,670 mg/Am3, MEK removal efficiencies of over 91% were obtained. Instant milk powder was essential to the good and stable performance of the biofilter for MEK removal.

Hot-melted asphalt (HMA) plants use sized gravels, asphalt and/or recycled asphalt as raw materials. In the plant, the materials are heated to certain preset temperatures and blended at fixed ratios at around 170oC to prepare the required HMA for road paving. In the asphalt-melting, hot-blending and dumping operations, fumes and particulates emit from the process equipments. The emitted gases contain various volatile organic compounds (VOCs) and poly aromatic hydrocarbons (PAHs) which are harmful to the health of the plant workers and nearby residents. Complaints from the residents also come with the fume and odorous emissions. In this study, an oxidation-reduction-in-series scrubbing process was tested to remove odorous compounds in waste gases emitted from HMA plants. Waste gas samples for test were collected from the vent hole of an oven which contains a heated sample of asphalt or recycled asphalt concrete. Sodium hypochlorite solution was used to scrub and oxidize the compounds and hydrogen peroxide to reduce the chlorine emitted from the oxidative scrubber. A gas chromatography with a mass spectrophotometric detector (GC-MSD) was used for the identification of the odorous species and their concentrations in the waste gases. Sensory tests were also used to determine the odor removal efficiency. GC-MSD examination results indicates that alkanes, arenes, alkenes, halides, esters, and carbonyl compounds were detected in the test gas. Scrubbing test results indicate that with oxidative solution of 50-60 mg/L residual chlorine at pH 7.0-7.5 and reductive solution of 35 mg/L hydrogen peroxide at pH >12, over 90% of the VOCs in the tested gas could be removed. Odor intensities could be reduced from 3,090 (expressed as dilutions to threshold) to 73. Pungent asphalt odor in the test gas was turned into slight sulfur smell after the scrubbing. For removing the odors from 500 Nm3/min of the flue gas vented from a HMA plant, an analysis indicates the required total cost for chemicals (sodium hypochlorite solution, hydrogen peroxide and sodium hydroxide) added to the scrubbers was around 2,800 NT$/day (US$ 95/day) for a daily operation time of 10 hours. The cost is far lower than that by the traditional thermal incineration one (25,000 NT$/day or US$ 850/day) or by the regenerative thermal oxidation (RTO) one (14,300 NT$/day or US$ 485/day). This study has successfully developed an economical and effective chemical scrubbing technology for the removal of odorous compounds in gases emitted from HMA plants.

Recently, restaurant employees exposing to cooking oil fume with potential lung cancer was highly concerned, indicating cooking oil fume emitted from restaurants might cause tremendous hazard to human health. This study combined photocatalytic oxidation and ozone oxidation technology to decompose VOCs from the exhaust of cooking oil fume from restaurants. Firstly, this study selected three different types of restaurants to implement air pollutant measurements in the indoor dinning room and stack emission. Indoor TVOCs continuous monitoring data showed that the highest TVOCs concentration was generally observed in the dining peak time. In this study, photocatalyst coated fiberglass filter was prepared by impregnation procedure and its characteristics was analyzed by SEM and XRD. Experimental results showed that the particle size of photocatalyst ranged from 25 to 50 nm and had high percentage of Anatase, suggesting that it had high photocatalytic reactivity. This study designed a continuous-flow reaction system combined nano-sized TiO2 photocatalysis with ozone oxidation technology to decompose VOCs from cooking oil fume. After passing through a fiberglass filter to remove oil droplets, the cooking oil fume then coated with nano-sized titanium oxide (UV/TiO2) fiberglass filter purification system, and then injected ozone into the system to decompose residual VOCs. This study further investigated the influences of operating parameters, including TVOCs initial concentration, O3 injection concentration, and reaction temperature on the decomposition efficiency of TVOCs by using the UV/TiO2/O3 technology. When the photocatalytic reaction temperature was 35~50¢J, the TVOC decomposition efficiency slightly increased with reaction temperature, however, when the reaction temperature went up to 55¢J, the TVOC decomposition efficiency increased only slightly, but did not increased linearly. Combination of photocatalysis and ozone oxidation system performance test results showed that ozone could decompose approximately 34% VOCs, and followed by the photocatalytical reaction of residual pollutants, achieving an overall decomposition efficiency of about 75%; while photocatalytic reaction can remove 64% of TVOCs and followed by O3 for the decomposition of residual pollutants, achieving an overall decomposition efficiency up to 94%. It showed that the combined UV/TiO2+O3 system could effectively remove VOCs in the cooking oil fume from the exhaust of restaurants. By using GC/MS to qualitatively analyze the speciation of TVOCs from cooking oil fume before and after UV/TiO2/O3, the results showed that the composition of VOCs had a decreasing trend. The peak area and dilution factor were applied to estimate the decomposition efficiency of different VOCs species. The decomposition efficiencies of pentane, 2-acrolein, acrolein, heptane, pentanal, hexanal, 2-hexenal, heptanal, heptenal and ethylhexenal were 56.21%, 72.88%, 51.33%, 32.23%, 59.04%, 69.22%, 73.53%, 41.37%, 92.57%, and 96.02%. Finally, a Langmuir-Hinshelwood kinetic model was applied to simulate the photocatalytic decomposition efficiency with the initial concentration of cooking oil fume. Model simulation results showed that the reaction rate increased with the initial TVOCs concentration. However, when TVOCs concentration increased gradually, the reaction rate became constant since the activated sites on the photocatalyst¡¦s surface was limited and cannot allow more VOC molecules diffuse to the activated sites for further photocatalytic reaction.

This research focuses on the performance study of a full-scale biofilter for treating a stream of vent gas with airborne VOCs generated from a chemical plant wastewater treatment facility. The biofilter consists of two parallel 20-ft standard containers in each a space of 5.98 m in length, 2.35 m in width and 0.50 m in height were filled with biofiltering media prepared by blending swine-manure compost and fern chips in a certain proportion. The vent gas contains methane, methanol, ethanol, acetone, dichloromethane, methyl ethyl ketone, ethyl acetate and toluene as major components and has an average flow rate of 1,320 m3/h (22 m3/min) and a temperature of 16-40oC. The purposes of this research were to confirm the VOC removal efficiency and to evaluate the elimination capacity for each VOC by monitoring operating parameters, including gas flow rate, system temperature, influent and effluent VOC concentrations of the biofilter. Experimental results show the system has a volumetric influent gas flow rate 1,153-1,470 m3/h which resulted in an average gas empty bed retention time (EBRT) of 0.64 min through the bed, a moisture of 25-70% and a pH of 2.4-6.9 for the media. Removal efficiencies of methane, methanol, ethanol, acetone, dichloromethane, MEK, ethyl acetate, toluene, NMHC and THC were 23.1, 79.3, 95.2, 82.9, 53.5, 63.7, 83.9, 41.2, 76.2 and 50.5%, respectively. Results also indicate that the VOC removal efficiency for each compound was not directly related to such important operating parameters of the biofilter as influent gas flow rate, media temperature, media pH, and the VOC concentration of the influent gas. However, the volumetric elimination rate (K) was approximately linearly varied with the corresponding loading (L) for the biodegradable VOCs in the influent gas. An average removal efficiency (K/L) of 24.5% was obtained with loadings of L < 70 g/m3h for methane. K/L of 91 and 54% were obtained for methanol with L = 0-7 and 15-22 g/m3h, respectively. Average K/L of 95% was obtained for both ethanol and acetone with L < 40 g/m3h. Removal efficiencies of 48 and 76% were obtained for methanol with L = 0-10 and 18-35 g/m3h, respectively. For MEK, an average removal of 89% was obtained with L = 0.5-4 g/m3h. Removal efficiencies of 84, 37, 48, 76 and 51% were obtained with L < 20, 0-0.2, 0.3-0.8 <60 and <120 g/m3h for ethyl acetate, toluene, NMHC and THC, respectively. This full-scale biofilter is effective in removing ethanol, ethyl acetate, acetone, methanol, and MEK. There is no significant removal efficiency for dichloromethane, toluene and methane. The performance can hopefully be improved by controlling the media in suitable conditions of moisture 50-60% and pH 7-8.

Abstract Biological processes have been proven to be economical and effective for control of VOCs with concentration of <1,000 mg C/m3. This study armed to develop a biofilter packed only with fern chips for the removal of airborne isopropyl alcohol (IPA). A three-stage down-flow biofilter (2.2 m in height and 0.4 m¡Ñ0.4 m in cross-sectional area) was constructed for the performance test. The first stage serviced as a humidifier for the incoming gas and the following two stages, both packed with fern chips with a packing space of 0.30 m ¡Ñ 0.40 m ¡Ñ0.40 m, as trickling bed biofilters for the VOC removal. Air with a nearly constant IPA concentration of 100 mg/Am3 (@ an average temperature of 34 oC) and a flow rate in the range of 100-400 L/min was fed to the reactor in Phase I test. The flow rate gave an empty bed retention time (EBRT) in the range of 12-48 s for the gas flowing through the two bed media. Solutions of urea-N, phosphate-P, and milk powder were supplied daily to the fern chips for the microbial nutrition in Phase I experiment which lasted for 26 days. Following the Phase, Phase II test operated with a constant EBRT of 12 s and without any nutrient supplementation for 30 days. Experimental results show that with an influent gas temperature of 29-40oC (average 34 oC) and relative humidity of 43-93% (average 73%), with a proper moistening of the bed media, the effluent gas could achieved a temperature of 26-35oC (average 29 oC) and a relative humidity of 98%. The proceeding medium experienced a greater moisture variation (12-68%, average 38%) than that (65-82%, average 72%) of the following one. The former and the latter media had pH in the range of 6.11-7.78 (average 6.77) and 6.13-7.36 (average 6.59), respectively. With no additional nutrient supplementation for 30 days, approximately 98% of the influent IPA of 100 mg/m3 could be removed at the EBRT of as short as 12 s which corresponded to a loading of 60 g IPA/m3.h.

This study armed to develop a biofilter packed only with fern chips for the removal of air-borne propylene glycol monomethyl ether acetate (PGMEA). The fern chip biofilters could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. In the present study, a three stage down-flow biofilter (2.18 m in height and 0.4 m¡Ñ0.4 m in cross-sectional area) was constructed for the performance test. The first stage serviced as a humidifier for the incoming gas and the following two stages, both packed with fern chips of 0.30 m ¡Ñ 0.40 m ¡Ñ0.40 m, as trickling bed biofilters for the VOC removal. The experiment was divided into four phases. Operation conditions of an empty bed retention time (EBRT) of 1.60min and influent PGMEA concentrations of 9.33-329 (average 78.4) mg/m3 were used in the Phase I experiment which lasted for 99 days. An average PGMEA removal of only 68% was obtained in this phase. For improving the PGMEA removal in the following phases, a fixed dosage of milk powder of 1.0 g/(m3 media. day) added as aqueous milk suspension was added to the media for nutrition of the biofilms on the fern chip surfaces. After an additional operation time of 20 days (the 127th day from the startup time), a stable PGMEA removal of 91% was achieved. Following Phase II, PGMEA removals of 93 and 94% were obtained with EBRTs of 0.40 and 0.27 min, respectively, in Phases III and IV experiments. The results indicate that EBRT was not a key influencing factor to the PGMEA removal as long as the media had a high ability for the VOC degradation. Experimental data obtained from Phases II-IV reveal that with volumetric loadings (L) of less than 250 g PGMEA/(m3.h) to the up-streaming half of the whole media, 90% of the influent PGMEA could be removed in this half media. An additional 80% of the influent PGMEA to the following half media could be removed with L < 100 g PGMEA/(m3.h) to the half media. The PGMEA elimination capacities were proportional to the volumetric loadings of less than 250 g PGMEA/(m3.h). From the results, it could be proposed that for achieving over 93% of the PGMEA removal, appropriate operation conditions are media moisture content = 52-65%, media pH = 7.2-7.4, influent PGMEA concentration = 100-400 mg/Am3, EBRT = 0.27-0.40 min, and L to the whole media = 45-180 g PGMEA/(m3.h).

This study investigates characteristics of odorous materials and their odor intensities emitted from various commercial and industrial sources in the Kaohsiung City. An overview of odor complaints from the city people is presented and discussed. Results indicate that, due to the increasing people concerns about the odor emission problems, more frequent checks done by the City EPA officers, governmental assistances to the pollution makers on the pollution control technologies, and the enforcement of more stringent environmental protection regulations, odor-complaint cases in this city are decreasing in recent years. However, people are giving more attention to odors from food-cooking emissions and the associated complaint cases are increasing. Emissions from restaurants and plants become the two major odor sources in this city. For the plant emissions, odorous chemicals emitted from the Kaohsiung Refinery, located in northern Zouying District, were detected to be benzene, toluene, xylenes, and styrene. The Chianjhen storage and pumping station, located by the Kaohsiung Harbor, emits some 40 different chemicals. The majors among them are methanol, ammonia, ethylene, n-pentane, chlorodifluoromethane, methyl tert-butyl ether (MTBE), propylene, cyclohexane, styrene, acetone, 1,2-dichloroethane, propylene oxide and vinyl chloride. Prompt leaks from the storage tanks and during the loading and unloading operations account for the emissions. Plants located in the Chianjhen Export Processing Zone emit chemicals, mainly methyl methacrylate, toluene, propylene glycol monomethyl ether acetate (PGMEA), ammonia, ethyl acetate and ethanol, which cause only a few complaint cases. The emitted chemicals are among the ones used by the plants as feed stokes or solvents. Restaurant located in Chianjhen and Hsiogang Districts emit large amount of food-cooking odorants, however, the percentage of odorous complaining for the emissions is relatively high in the Zouying District as compared to the other administrative districts investigated in this study. Major components of the food-cooking emissions include hydrogen sulfide, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), ammonia, and methylamine. Relative percentages among these chemicals depend on the cooking materials and styles. Results also indicate that industries or businesses, such as petrochemical, surface coating, paint manufacturing, fuel station, storage vessels, semiconductor manufacturing, adhesive tape manufacturing and cloth dry-cleaning, are major odor and chemical emission sources which need to be continuously implemented for getting more emission reductions in the near future.

This study armed to develop a biofilter packed only with fern chips for the removal of air-borne low concentration VOCs (volatile organic compounds) emitted from semiconductor manufacturing industries. The fern chip biofilters could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. Performance of biofiltration for removal of simulated semiconductor manufacturing emitted gases consisting of IPA (isopropyl alcohol), acetone, HMDS (hexamethylene disilazane), PGME (propylene glycol monomethyl ether), and PGMEA (propylene glycol monomethyl ether acetate) was studied in a pilot-scale biofilter consisted of two columns (40-cmW x 40-cmL x 70-cmH acrylic column) arranged in series. Each column was packed with fern chips to a packing volume of around 56 L (0.40 m¡Ñ0.40 m¡Ñ0.35 mH). A sprinkler was set over the packed fern chips for providing them with water and nutrition solutions. Liquid leached from both layers of chips were collected in the bottom container of the column. The experiment lasted for 182 days which was divided into four phases with varying influent gas flow rates and VOC concentrations. Gas samples collected around 3 times per week from the influent as well a the first and second stage effluents were analyzed for VOC concentrations. On a weekly basis, fern chips sampled from each column were also analyzed for getting pH, moisture, and the absorbed VOC content of the chips. Phase shifted if it obtained a quasi-steady state which was judged by the nearly unchanging VOC removal efficiencies. Operation conditions of an empty bed retention time (EBRT) of 1.50 min and influent VOC concentrations of 159-284 mg/m3 were used in the Phase I experiment which lasted for 15 days. Nutrition of 1.34 g milk powder/m3.d was used in this phase and the conditions gave an average volumetric VOC loading (L) of 15.1 g/m3.h. Effluent VOC concentrations were 3-18 mg/m3 and an average VOC removal of 96% was obtained in this phase. An EBRT of 0.75 min, L of 11.44 g/m3.h, and nutrition of 1.34 g milk powder/m3.d were used in the Phase II experiment. VOCs in the gas could be removed from 90-126 to 1-19.6 mg/m3 and an average efficiency of 94% was obtained. Following Phase II, an average VOC removal of only 48% was obtained with an EBRT of 0.75 min, nutrition of 2.0 g milk powder/m3.d, and L of 22.8 g/m3.h in Phases III experiment during the 56-97th days from the startup time. Additional nitrogen (urea) and phosphorus (potassium dihydrogen phosphate) was added to the media from the 105th day and the VOC removal increased to 80% at the 107th day. An average VOC removal of around 93% was obtained in phase III experiment. The results showed that enough nutrition is essential to the successful performance for the biofiltration process. Phase IV experiment lasted for 59 days with an EBRT of 0.75 min, L of 34.1 g/m3.h, and nutrition of 2.0-6.0 g/m3.d. During the initial period of this phase, media pH dropped from 7.8 to 5.8 due to an excess nitrogen (ammonium chloride) addition as high as 12.35 g N/m3.d which resulted in nitrification reaction in the media. By stopping nitrogen, increasing milk powder dosing, and addition of NaHCO3 at the 140th day, pH restored to 7.5 in the following days. VOC removal increased to an average of 92% in the rest operation days. From the results, it could be proposed that for achieving over 90% of the VOC removal, appropriate operation conditions are media moisture content = 52-65%, media pH = 7-8, influent VOC concentration = 150-450 mg/Am3, EBRT = 0.75 min, and L to the whole media = 11-34 g/m3.h.