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.

In this study, two regenerative thermal oxidizers (RTO) were used to test the thermal destruction, thermal recovery efficiency and the gas pressure drop over the beds characteristics when burning, respectively, airborne chlorine- and nitrogen-containing volatile organic compounds (VOCs). First, an electrically-heated RTO containing two 0.5 m ¡Ñ 0.5 m ¡Ñ 2.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0116 m and a height of up to 1.48 m with a void fraction of 0.41 in the packed section was used to study the destruction characteristics of chlorine-containing VOCs (trichloroethane, TCE and dichloromethane, DCM). With a valve switch time (ts) of 1.5 min, preset maximum destruction temperatures (TS) of 500-800 oC and superficial gas velocity (Ug) of 0.17-0.33 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the thermal recovery efficiency (TRE) and the pressure drop for the air stream without VOC in the influent air stream have been performed. With a ts of 1.5 min, Ts of 500-800 oC and Ug of 0.17-0.24 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the degree thermal destruction of VOCs with influent air streams containing one of the two VOCs: trichloroethylene (TCE) and dichloromethane (DCM) have been done. Second, an electrically-heated RTO containing two 0.152 m ¡Ñ 0.14 m ¡Ñ 1.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0111 m and a height of up to 1.0 m with a void fraction of 0.42 in the packed section was used to study the destruction and NOx formation characteristics of DMF (N, N-dimethylformamide). With a ts of 1.5 min, Ts of 750-850 ¢Jand Ug of 0.39-0.78 m/s (evaluated at an influent air temperature of around 30 ¢J), TRE and the pressure drop for the air stream without VOC in the influent air stream have been tested. With a ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 ¢J), and Ts of 750-950 ¢J and, thermal destruction efficiencies and nitrogen oxides (NOx) formation characteristics in burning air streams containing either DMF or DMF mixed with methyl ethyl ketone (MEK) were performed. Results demonstrate that: (1) a RTO is suitable for destruction of low concentrations (<1,000 ppm as methane) of airborne highly chlorinated VOCs such as TCE and DCM and the destructed products contain no chlorine and only trace of COCl2 (< 1% of the influent VOC); (2) for TS = 800 oC and Ug = 0.17-0.24 m/s, complete oxidation products of TCE and DCM are HCl, CO2, and H2O, and the main intermediates are CO and COCl2; (3) with ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 oC) and TS of 750-950 ¢J, no NOx was present in the effluent gas from the RTO when it was loaded with DMF-free air; (4) when only DMF was present in the influent air, the average destruction efficiencies exceeded 96%, and increased with the influent DMF concentration from 300 to 750 mg/Nm3. The ¡§NOx-N formation/DMF-N destruction¡¨ mass ratios were in the range 0.76-1.05, and decreased as the influent DMF concentration increased within the experimental range; (5) when both DMF and MEK were present in the influent gas, the NOx formation ratio was almost the same and the DMF destruction efficiency increased with the influent MEK/DMF ratio from 150/300 to 4500/300 (mg/mg) and in the preset temperature range. The NOx formation ratios were in the range 0.75-0.96; (6) the TRE decreased as Ug increased but was invariant with Ts; and (7) the Ergun equation was found to suffice in the estimation of the pressure drop when the gas flowed over the packing beds.

Performance studies on the treatment of VOCs in air streams by a pilot-scale regenerative catalytic oxidizer (RCO) and a full-scale regenerative thermal oxidizer (RTO) were conducted. The pilot-scale RCO was constructed with two 20-cm x 200-cm (inside diameter x packing height) regenerative beds packed with gravel (average particle size = 1.25 cm) used as the thermal regenerative solid material. Experimental results indicate that destruction efficiencies of 97 and 90%, respectively, were obtained for methyl ethyl ketone and toluene at a superficial gas velocity of 0.372 m/s (evaluated at 25¢J) and a maximum bed temperature of 400¢J. It was estimated that an electrical thermal energy of approximately 84 kWh was required for treating 1,000 m3 of the waste air stream by the RCO. The full-scale RTO was constructed with two regenerative beds of 100-cm square x 200-cm height packed with the gravel used in the RCO. A paint solvent containing methyl ethyl ketone, ethyl benzene, xylenes, and ethyl acetate was used for the target VOCs. Experimental results indicate that, at a superficial gas velocity of 0.372 m/s (evaluated at 25¢J), VOC destruction efficiencies of 84, 92, 95 and 98% were obtained for the beds at temperature ranges of 200-300, 300-500, 400-700, and 500-700¢J. These conditions corresponded to empty gas retention times of 1.07, 0.85, 0.41, and 0.39s, respectively, for the cited temperature ranges. Finally, it was estimated that electrical watts of approximately 0.10, 0.45, 1.78, 2.43 kWh were required for treating 1,000 m3 of the waste air stream, respectively, at bed temperature ranges of 200-300, 300-500, 400-700, and 500-700¢J.

This study investigated the characteristics of volatile organic compounds (VOCs) in the atmosphere at the surrounding area of an oil storage and pumping station from March to June, 2001. The influence of operation condition of storage and pumping station as well as meteorological factors on the distribution of VOCs was also investigated. In this study, a sampling network including six sites around the boundary of the oil storage and pumping station and one site at a nearby village was established for the sampling of VOCs near ground level. Air samples were collected by a carbontrap 300 multi-bed stainless steel sampling tube and were desorbed by a thermal desorption unit (TDU). The desorbed VOCs samples were then analyzed by a gas chromatography with flame ionization detector (GC/FID). In addition, hydrocarbons (both methane and non-methane hydrocarbons) and meteorological condition including wind speed and wind direction were detected automatically in order to correlate with the concentration of VOCs. Results from field measurement indicated that up to twelve VOCs were detected in the atmosphere, which quite consisted with the composition of stored oil including petroleum crude oil, aviation turbine fuel, 95 unleaded gasoline, and naphtha. Major VOCs observed at the surrounding area of the oil storage and pumping station were benzene and toluene, however, in most cases high boil-point organic compounds were also detected. It suggested that the nearby village could not be solely affected by VOCs emitted from oil storage tanks but also from other local sources such as steel plating plants. Furthermore, meteorological condition played an important role on the dispersion of fugitive VOCs at the surrounding area. For instance, the concentration of VOCs at the downwind sites were generally higher than that at the upwind sites while northern and northwestern winds blew in late Spring. Besides, toluene to benzene concentration ratios (T/B) ranged from 1.5 to 2.1 during the southwestern wind period in Summer, which were higher than those (T/B&#x00A3;1.5) during the northern and northwestern wind periods in late Spring. It suggested that the nearby village as a sensitive location could be much more easily affected by local traffics than the oil storage and pumping station during the summer time since T/B ratios were approximately 2.0 in the tail gas exhausted from automobiles. From the viewpoint of health risk assessment, the location with highest potential risk at the surrounding area of the oil storage and pumping station was the floating oil tank zone which required better operation strategies of the oil storage and pumping station for the protection of ambient air quality.

This study investigated the feasibility of glassfiber filter coated with titanium dioxide (TiO2) on removing indoor VOCs using photocatalytic technology, which could further expand the electronic filter¡¦s function . First of all, we coated the titanium dioxide (TiO2) photocatalysts on the glassfiber filter with chemical vapor desposition (CVD) method, then dried it at 120¢J, and calcined it to prepare a nano-sized TiO2 coated filter . Secondly, we collected VOC samples in a printery and analyzed their chemical components. The main components of VOCs (benzene¡Btoluene and acetone) were then conducted in a self-designed laboratory-scaled batch photocatalytic reactor. The decomposition of acetone for different operating parameters, including initial VOC concentration, CVD coating time, and calcination temperature, was further conducted. Besides, a nano-sized photocatalyst indoor air purifier was self-designed for this particular study. The air purifier consists of a set of near-UV light source, a nano-sized photocatalyst glassfiber filter, a stainless shelter, and a circulating fan. The air purifier was tested to ascertain its capability on the removal of indoor VOCs in a well-tight environmental chamber. The testing results indicated the nano-sized photocatalyst glassfiber filter can be used to remove indoor VOCs . In the final stage, a nano-sized TiO2 photocatalyst electronic air cleaner was self-designed for this particular further study in a printery. The air cleaner consists of a set of UV light source, a nano-sized photocatalyst glassfiber filter, a set of electronic filter, carborn filter and a pain coated steel plate shelter. The air cleaner was tested to ascertain its capability on the removal of indoor VOCs in a return air channel of air condition system. The testing results indicated that the nano-sized photocatalyst glassfiber filter can be used to remove indoor VOCs

This study armed to develop a biotrickling biofilter packed only with fern chips for the removal of air-borne low concentration VOCs (volatile organic compounds) emitted from a solvent refinery located in Kaohsiung county of southern Taiwan. The fern chips could avoid the shortcomings of traditional media, such as compaction, drying, and breakdown, which lead to the performance failure of the biofilters. A pilot-scale biofilter (0.80 mL ¡Ñ 0.75 mW ¡Ñ 1.50 mH) packed with 0.24 m3 fern chips was used for the performance study. The study was conducted in the plant by drawing vented gas streams from two distillation columns and two solvent storage vessels. The gas streams contain aromatics and oxygenated hydrocarbons such as benzene, alcohols, and esters. Results indicated that suitable nutrition rates are 10, 100, and 10 g/m3.d, respectively, of milk powder, Urea-N, and K2HPO4-P, accompanied with a water spraying rate of 125 L/m3.d. Around 85% of VOCs in the influent gas with concentrations of 600-3,200 ppm (as CH4) could be removed under an average loading of 60 g VOC (as methane)/m3.h. A test indicated that odor intensity (expressed as dilution to threshold (D/T) ratio) of the influent gas could be reduced from around 7,330 to 73.

Volatile organic compounds (VOCs) can detrimentally affect human health directly and indirectly. However, the main environmental concern of VOCs involves the formation of smog. In the presence of nitrogen oxides, VOCs are the precursors to the formation of ground level ozone. Isopropyl alcohol (IPA) and toluene are extensively used in industry as solvents. They are all highly toxic to animals and humans. Accordingly, IPA and toluene are strongly associated with problems of VOCs. Catalytic incinerations and a regenerative catalytic oxidizer (RCO) were adopted to decompose VOCs herein. Various catalysts were prepared and developed in this study. The screening test of catalytic activity and the influences of the operational parameters on VOCs removal efficiencies were widely discussed through catalytic incinerations of VOCs. The more effective and cheaper catalysts through above discussions of catalytic incineration were selected. And they were utilized in an RCO to investigate their performance in VOCs oxidation and RCO operations. Experimental results demonstrate that 10 wt%CuCo/(G) catalyst performed well in an RCO because it has the excellent performance in incineration efficiency and economic efficiency. The achievements of this study are summarized as follows: (1) Treatment of isopropyl alcohol (IPA) using ceramic honeycomb(CH) catalyst The eighteen ceramic honeycomb catalysts we prepared by various methods (co-precipitation, wet impregnation and incipient impregnation), various metal weight loadings (5 ~ 20 wt %), and various metals (Cu and CuCe) were used in the experiment. The results indicate that 20 wt%CuCe/(CH) catalyst prepared by wet impregnation had the best performance in CO2 yield because TC50 and TC95 were 245¢J and 370¢J, respectively, under the following operating conditions; a space velocity of 12000 hr-1, an inlet IPA concentration of 1600 ppm, an oxygen concentration of 21%, and a relative humidity of 25%. Given the operational parameters of IPA oxidation experiments, the CO2 yields increased with higher temperature and oxygen concentration, but decreased with inlet IPA concentration, space velocity and the relative humidity increased. Moreover, the stability test results show that the 20 wt%CuCe/(CH) catalyst had excellent stability. (2) Treatment of toluene using molecular sieve(MS) catalyst Molecular sieve catalysts with various metals (Cu, Co, Mn, CuMn, CuCo, MnCo) and various loadings (5~10 wt %) were produced by wet impregnation to treat toluene. The results indicate that 10 wt%CuCo/(MS) had the best performance in toluene conversion because T50 and T95 were 295¢J and 425¢J, respectively, at an influent concentration of toluene of 900 ppm, an oxygen concentration of 21%, a space velocity of 12000 hr-1, and a relative humidity of 26%. The conversions of toluene increased with the reaction temperature and the influent concentration of oxygen, but decreased as the initial concentration of toluene and the space velocity increased. Moreover, we did not find any decay between the fresh and used catalysts using SEM and EDS. (3) Treatment of isopropyl alcohol (IPA) using Cu/(CH) and CuCo/(CH) catalysts We used the 20 wt% CuCo/(CH) and 20 wt% Cu/(CH) catalysts in a pilot RCO to test IPA oxidation performance under various conditions. The best catalyst was selected, and the economic efficiency of RCO and the phenomenon of RCO operations were more widely discussed. The results demonstrate that 20 wt% CuCo/(CH) catalyst performed well in an RCO because it was effective in treating IPA, with a CO2 yield of up to 95%. It also had the largest tolerance of variations in inlet IPA concentration and gas velocity. The 20 wt% CuCo/(CH) catalyst in an RCO also performed well in terms of TRE, pressure drop and selectivity to CO2. The thermal recovery efficiency (TRE) decreased as gas velocity increased. The temperature difference (Td) and pressure drop increased with gas velocity and heating zone temperature. The TRE range was from 87.8 to 91.2 % and the Td ranged from 22.1~35.1¢Junder various conditions. Finally, the stability test results indicate that the 20 wt% CuCo/(CH) catalyst was very stable at various CO2 yields and temperatures. (4) Treatment of toluene using CuCo/(CH) catalysts with various carriers In this work, three catalysts (10 wt%CuCo/(G)¡B10 wt%CuCo/(MS) and 20 wt% Cu/(CH)) were prepared by wet impregnation, and used in an RCO to test their performance in incineration efficiency and economic efficiency under various operational conditions. Then the best catalyst was selected and the phenomenons of RCO operations were further investigated. Experimental results demonstrate that 10 wt%CuCo/(G) catalyst performed well in an RCO because it is effective in treating toluene with a toluene conversion of up to 95% at the heating zone temperature (Tset) = 400¢J under various conditions. The 10 wt% CuCo/(G) catalyst had the greatest tolerance against the effects of inlet toluene concentration and gas velocity, and exhibited the best performance in terms of TRE , Td and pressure drop. The TRE range was from 90.2 to 92.9 % and Td ranged from 18.2 to 30.9¢J under various conditions at Tset = 300~400¢J. Moreover, when 10 wt% CuCo/(G) catalyst was used in an RCO, the results demonstrate that (1) high selectivity to CO2 ; (2) decrease in TRE and increase in Td as increasing the shifting time; (3) an insignificant effect of shifting time on pressure drop and (4) excellent stability of 10 wt% CuCo/(G) catalyst in a long period test.

<p>In this thesis the sink-effect in indoor materials wasstudied using mathematical modelling and experimental studies.The sink-effect is a concept which is commonly used tocharacterise the ability of different indoor materials to sorbcontaminants present in the indoor air. The sorption process ismore or less reversible, i.e. molecules sorbed in materials athigh contaminant concentrations may again be desorbed at lowerconcentrations. Knowledge of the sorption capacity of materialsand the rate at which sorption and desorption takes place is offundamental importance for mathematical simulation of indoorair quality. The aim of this work is to contribute withknowledge about how the sink-effect can be described inmathematical terms and how the interaction parametersdescribing the sorption capacity and sorption/desorptionkinetics can be determined. The work has been of amethodological nature. The procedure has been to set upphysically sound mathematical models of varying complexity andto develop small-scale chamber experiments. Two differentdynamic chamber methods have been used. One is based on amodified standard FLEC-chamber while the other uses a chamberwith two compartments, one on each side of the material. The"twin-compartment" method was designed due to the observationthat the contaminant readily permeated straight through theselected materials, which resulted in uncontrolled radiallosses in the FLEC-chamber. In order to be useful forcomparison between experiments and calculations and parameterfitting, the boundary conditions in the chambers must beprecisely known and controlled. This matter has shown to be themost crucial and difficult problem in the research. A varietyof mathematical models for the sink-effect have been proposed.In some models advanced fluid simulations were used in order totest the influence ofill-defined flow boundary conditions. Theaim of the modelling is to find a formulation with a minimum ofinteraction parameters, which is generally useful, i.e. both insmall-scale laboratory environments and in full-scale like anoffice room. Estimated model parameters are shown to be able toyield a reasonably good fit to experimental data for thesorption process but a less satisfactory fit for the desorptionprocess.</p><p><b>Keywords:</b>sink-effect, sorption, adsorption, diffusion,indoor air quality, volatile organic compounds, VOC,contaminants, building materials</p>

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

Source: Masters Abstracts International, Volume: 47-06, page: 3475. Adviser: Thomas H. Stock. Includes bibliographical references.