Economic utilisation of biogas arising from sewage sludge is hampered by the need to remove siloxanes, which damage gas engines upon combustion. This thesis applies on-line Fourier transform infrared spectroscopy to measure siloxanes in biogas upstream and downstream of the activated carbon vessels designed to adsorb siloxanes. On-line analysis provides accurate measurement of siloxane concentrations with a detection limit below the siloxane limits set by engine manufacturers, high data intensity and timely identification of breakthrough. Cost savings of up to £0.007 kWh- 1 may be realised compared to existing grab sampling. Using on-line analysis, the performance of full-scale and bench-scale carbon vessels were measured. Full-scale carbon contactors are typically operated at Reynold’s numbers close to the boundary between the laminar and transitional regimes (Re = 40 - 55). This thesis demonstrates, at full- and bench-scale, that increasing the Reynold’s number to site the adsorption process in the transitional regime increases media capacity, by 36% in dry gas and by 400% at 80% humidity. It is postulated that the change in gas velocity profile which occurs as Reynold’s number increases reduces the resistance to siloxane transport caused by gas and water films around the carbon particles, and therefore increases the rate of the overall adsorption process. In the laminar regime (Re = 31) increasing humidity from zero to 80% led to the classical stepwise reduction in adsorption capacity observed by other researchers, caused by the increasing thickness of the water film, but in the transitional regime (Re = 73) increasing humidity had no effect as no significant water film develops. It is therefore recommended that siloxane adsorption vessels should be designed to operate at Reynold’s numbers above 55. By choosing a high aspect ratio (tall and thin) both Reynold’s number and contact time can be optimised.

In this study, wet scrubbing and activated-carbon adsorption technologies were tested to investigate their abilities to remove total hydrocarbons (THCs) and other odorous compounds in the effluent gas from food-cooking operations such as frying, toasting, grilling, and steaming. A full-scale scrubber (gas-liquid contacting cross section 0.58 m¡Ñ0.50 m, height 0.80 m) was used in the present study for testing its performance on removing odorous compounds from a gas stream of 102 m3/min drawn from a Japanese-type grilling restaurant located in the Kaohsiung city. The scrubbing liquid had a flow rate of 67.2 L/min which is equivalent to a liquid/gas ratio of (L/G) 0.0065 m3 liquid/(m3 gas). Tap water, aqueous sodium hypochlorite solution, and aqueous hydrogen peroxide solution were used as scrubbing liquids. For the activated carbon tests, a 2-cm i.d. glass column packed with 20 g activated carbon which gives a packing height of 10.5 cm was used to obtain the adsorption isotherms by introducing a 15 L/min gas stream drawn from an oven toasting sausage. The gas flow resulted in a superficial gas velocity of 1.06 m/s over the cross section of the column. In addition, a pilot-scale adsorption unit (cross section 0.50 m sq., packed with 30 kg granular activated carbon) was installed for the adsorption test. A gas flow drawn from a vent of a restaurant kitchen cooking Chinese-type food was introduced into the pilot adsorber. A flow rate of 12.6 m3/min was used and the superficial gas velocity was 0.84 m/s. Results indicate that THC and odor (sensory test) removals of 15-35 and 35-65% were obtained, respectively, form the scrubbing test. There was no significant difference in the performance by using one of water or the two aqueous chemical solutions as the scrubbing liquor. Most of the characteristic food-grilling and flavoring smells were removed by the scrubber and some bitter smells like burnt carbon were found in the scrubbed gas. High moisture contents (around 95% in relative humidity) of the vent gas from the sausage-toasting oven resulted in a significant reduction in the activated carbon adsorption capacity for THCs from the tested gas. From results of the pilot-scale adsorption test, THC removals of 60-80% form the vent gas (around 50-60% in relative humidity) of the Chinese-type kitchen were found during the initial adsorption time of 0-50 hr. A long time (200 hr) operation resulted in a decrease in the THC removal efficiency. However, the adsorber exhibited as an odor equalization unit by reducing peaks of the odor emissions from the kitchen. Characteristic odors from various food cooking operations were reduced by the adsorber. It was estimated that a total of around NT$ 57 is required for the full-scale scrubber for treating the gas flow of 102 m3/min for an operation time of 7 hr per day, and the cost is equivalent to NT$ 1.33/(1,000 m3 gas). The cost for the activated carbon adsorption unit of 13 m3/min was estimated to be NT$ 134 for 8 hr per streaming day. The unit cost is NT$ 22.1/(1,000 m3 gas).

Petroleum coke-derived activated carbons were prepared and used for the adsorptive removal of a single-ring naphthenic acid (NA) from synthetic oil sands tailings pond water (TPW). The overall adsorption process was found to be intra-particle diffusion-controlled. The Weber-Morris intra-particle diffusion rate constants decreased from 7.43 to 1.23 mg/g min0.5 after activated carbon was post-oxidized with oxygen, suggesting a hindering effect of oxygen surface groups. The Freundlich model fit of the equilibrium adsorption isotherms and the small negative ΔHo pointed to a physisorption-dominated process and the importance of specific surface area. It was estimated that about 2.7 g/L of basic CO2-activated carbon is needed to reduce NA concentration from 120 mg/L to 2.5 mg/L (~98% removal) in synthetic TPW. However, equilibrium adsorption capacity was found to vary significantly after oxygen or nitrogen groups were introduced onto the surface. Therefore, there is a potential for enhanced adsorption by chemical functionalization of carbon.

Petroleum coke-derived activated carbons were prepared and used for the adsorptive removal of a single-ring naphthenic acid (NA) from synthetic oil sands tailings pond water (TPW). The overall adsorption process was found to be intra-particle diffusion-controlled. The Weber-Morris intra-particle diffusion rate constants decreased from 7.43 to 1.23 mg/g min0.5 after activated carbon was post-oxidized with oxygen, suggesting a hindering effect of oxygen surface groups. The Freundlich model fit of the equilibrium adsorption isotherms and the small negative ΔHo pointed to a physisorption-dominated process and the importance of specific surface area. It was estimated that about 2.7 g/L of basic CO2-activated carbon is needed to reduce NA concentration from 120 mg/L to 2.5 mg/L (~98% removal) in synthetic TPW. However, equilibrium adsorption capacity was found to vary significantly after oxygen or nitrogen groups were introduced onto the surface. Therefore, there is a potential for enhanced adsorption by chemical functionalization of carbon.

In this work, adsorption of cadmium and lead from waste solutions by activated carbon was investigated. The activated carbons were produced from ion exchange resins and agricultural wastes in previous thesis studies under different conditions. BET surface areas of the activated carbons were given in previous studies. They were further characterized in this study. Slurry pH was measured by change in pH of water in which activated carbon was added. Methylene blue numbers were determined by adsorption of methylene blue onto activated carbons. Isoelectric points were determined by measuring zeta potential of activated carbons at different equilibrium pH. Results of the first part of sorption experiments showed a strong dependency of adsorption on pH since adsorption mechanism was exchange of heavy metal ions with H+ ions on the surface. Activated carbon produced from hazelnut shell had the highest removal efficiency with 95% Pb removal and 50% Cd removal at pH 6. However, activated carbon produced from apricot stone removed only 25% and 80% of Cd and Pb, respectively at the same pH. Initial concentration had positive effect on percent removal as shown by the second part of sorption experiments. This can be explained with saturation of available active sites as initial concentration increased. Activated carbon produced from hazelnut shell could remove 42% of Cd and 85% of Pb, but the one produced from synthetic resin couldn&amp / #8217 / t remove Cd and Pb more than 20% and 35%, respectively at initial concentration of 100 mg/l. Langmuir and Freundlich isotherms were plotted and both isotherms were in good agreement with experimental data.

abstract: The world is grappling with two serious issues related to energy and climate change. The use of solar energy is receiving much attention due to its potential as one of the solutions. Air conditioning is particularly attractive as a solar energy application because of the near coincidence of peak cooling loads with the available solar power. Recently, researchers have started serious discussions of using adsorptive processes for refrigeration and heat pumps. There is some success for the >100 ton adsorption systems but none exists in the <10 ton size range required for residential air conditioning. There are myriad reasons for the lack of small-scale systems such as low Coefficient of Performance (COP), high capital cost, scalability, and limited performance data. A numerical model to simulate an adsorption system was developed and its performance was compared with similar thermal-powered systems. Results showed that both the adsorption and absorption systems provide equal cooling capacity for a driving temperature range of 70-120 ºC, but the adsorption system is the only system to deliver cooling at temperatures below 65 ºC. Additionally, the absorption and desiccant systems provide better COP at low temperatures, but the COP's of the three systems converge at higher regeneration temperatures. To further investigate the viability of solar-powered heat pump systems, an hourly building load simulation was developed for a single-family house in the Phoenix metropolitan area. Thermal as well as economic performance comparison was conducted for adsorption, absorption, and solar photovoltaic (PV) powered vapor compression systems for a range of solar collector area and storage capacity. The results showed that for a small collector area, solar PV is more cost-effective whereas adsorption is better than absorption for larger collector area. The optimum solar collector area and the storage size were determined for each type of solar system. As part of this dissertation work, a small-scale proof-of-concept prototype of the adsorption system was assembled using some novel heat transfer enhancement strategies. Activated carbon and butane was chosen as the adsorbent-refrigerant pair. It was found that a COP of 0.12 and a cooling capacity of 89.6 W can be achieved. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011

No description available.

No description available.

Case hardened Uddeholm Orvar® Superior (Orvar) has the potential to replace currently used materials in shafts inside transmissions, which would lower the overall weight and thus result in lower fuel consumption while maintaining the necessary mechanical properties. However, previous studies have failed to reliably carburize the steel during the case hardening process. The case contains tempered martensite, which has high wear resistance, hardness, and good fatigue properties, and will be affected by the absence of the additional carbon. The presence of passive oxide layers such as chromia and silica is believed to inhibit the carburization, this by their impact of the adsorption and diffusion. One suggested solution is a preoxidation step before the carburization, to promote the formation of iron oxides which are preferential for carburization due to higher diffusion. To evaluate the impact of preoxidation different times, temperatures, and cooling methods were used and analyzed by LOM, XRD, SEM, and hardness measurements. The results indicate that reliable carburization can be obtained by preoxidation performed at 600 °C for 24 hours followed by immediate case hardening. / Sätthärdat Uddeholm Orvar® Superior (Orvar) har potential att ersätta nuvarande material i drivaxlari växellådor, detta skulle minska vikten och därmed sänka bränslekonsumtionen medan de nödvändiga mekaniska egenskaperna behålls. Tidigare studier har emellertid misslyckats med att tillförlitligt uppkola stålytan under sätthärdningen. Ytan består utav tempererad martensit som har hög slitstyrka, hårdhet, och bra utmattningsegenskaper, och påverkas utav avsaknaden av tillfört kol. Närvaron av passiva oxidskikt som kiseldioxid och kromoxid tros hindra uppkolningen, detta på grund utav deras påverkan på adsorption och diffusion. En föreslagen lösning är ett föroxideringssteg innan sätthärdningen, för att gynna bildandet utav järnoxider vilka är fördelaktiga för uppkolningen på grund utav högre diffusion. För att utvärdera påverkan av föroxideringen användes olika tider, temperaturer, och kylningsmetoder som blev analyserade utav LOM, XRD, SEM, och hårdhetsmätningar. Resultaten indikerar att tillförlitlig uppkolning kan uppnås med föroxideringutförd vid 600 °C i 24 timmar följt utav omedelbar sätthärdning.

Indirect potable reuse has been practiced with the potential to enhance sustainability of water resources if planned accordingly. Depending on the pretreatment implemented for potable reuse, emerging contaminants; such as pharmaceuticals, personal care products, industrial solvents, bacterial/viral pathogens, and disinfection byproducts, might be present in source water and difficult to remove via various water treatment technologies. Low molecular weight organic compounds are especially challenging to remove and may require treatment optimization. The overarching purpose of this study was to demonstrate the feasibility of a carbon-based advanced treatment train; including ozonation, biological activated carbon (BAC) filtration and granular activated carbon (GAC) adsorption to achieve water quality suitable for potable reuse and assess the impact of a range of operating conditions for emerging contaminant removal at pilot-scale. The results from this study showed that carbon-based treatment train is equally effective as more commonly used, and more costly, membrane-based treatment trains in terms of pathogen and disinfection byproduct removal. A multiple-barrier approach was implemented, with each treatment stage capable of removing total organic carbon (TOC). GAC was responsible for removal of most of the TOC and emerging contaminants and this removal depended on the number of bed volumes of water processed by GAC. Empty bed contact time was another factor that dictated the extent of TOC removal in the BAC and GAC units as the carbon media was exhausted. Among the emerging contaminants detected, sucralose, iohexol and acesulfame-k were present in the highest concentrations in the influent and were detected consistently in the GAC effluent, thus making them good indicators of treatment performance. Apart from organics removal, BAC played an important role in removal of nutrients, such as ammonia via nitrification. N-Nitrosodimethlyamine (NDMA) was formed in the treatment process by ozone, but was shown to be effectively removed by BAC. EBCT, temperature, ozone dose and presence of pre-oxidants, such as monochloramine, played an important role in determining the amount of NDMA removed. These factors can be further optimized to improve NDMA removal. Sodium bisulfite was used for dechlorinating monochloramine residual post ozone. Nitrification in the BAC was shown to be inhibited by excess of sodium bisulfite dose. Thus monochloramine residual needs to be dechlorinated with sodium bisulfite to help with NDMA degradation but at the same time the sodium bisulfite dose needs to be monitored to allow complete nitrification in the BAC. 1,4-dioxane, another contaminant of emerging concern, was monitored in the treatment process. Biodegradation of 1,4-dioxane was enhanced via addition of tetrahydrofuran as a growth substrate. Biodegradation of 1,4-dioxane can help reduce energy and capital costs associated with advanced oxidation processes that are currently used for 1,4-dioxane removal. Further, relying on biodegradation for the removal of 1,4-dioxane can help avoid the formation of disinfection byproducts associated with advanced oxidation processes such as ozone with peroxide or ultraviolet disinfection with peroxide. The results from this project can be useful for designing potable reuse treatment trains and provide a baseline for removal of organic carbon and emerging contaminants. The conventionally used reverse osmosis and ultrafiltration approach is useful for organics removal in areas where the rationale behind potable reuse is water scarcity. Operational difficulties encountered during this study can prove to be important as this treatment process is scaled up to treat a total of 120 MGD of water for managed aquifer recharge. Overall the lessons learnt from this study can give a better understanding of a carbon-based treatment and further the advancement of reuse projects that have drivers other than water scarcity. / Doctor of Philosophy / The increased growth in urban areas has been accompanied by an increase in potable water demand, leading to depletion of surface and groundwater. Further, the discharge of nutrients such as nitrogen and phosphorus into some of these water bodies can lead to algal blooms. Water reuse involves treating used water and discharging into either a surface or groundwater body. Water reuse has been sought after as a solution to prevent these nutrients being discharged into surface water and to provide a sustainable solution for depletion of water sources. Direct or indirect potable reuse can include a combination of advanced treatment methods such as membrane filtration using ultrafiltration and reverse osmosis, biological filtration, granular or powdered activated carbon adsorption and disinfection methods such as ozonation and ultraviolet disinfection. This study focused on Hampton Roads Sanitation District's managed aquifer recharge project 'sustainable water initiative for tomorrow' (SWIFT), two different advanced water treatment strategies, namely carbon-based and membrane-based were implemented on a pilot-scale (20,000 L/day). The driver for indirect potable reuse in this study was not related to water shortage but aimed at reducing the nutrients discharged into the Chesapeake Bay. Other reasons for implementing reuse included recharging the depleting groundwater levels, land subsidence, and preventing flooding and seawater intrusion near the coastal areas. Membrane-based treatments, such as reverse osmosis, have been well established and studied for potable reuse. The less frequently used carbon-based treatment, that includes used of activated carbon for adsorption and biodegradation of organics (not involving any membrane barrier), was shown to be cost-effective and provided equal protection as that of the membrane-based system in terms of removal of pathogens. Further, since there is no membrane involved in the carbon-based treatment the energy requirements are less than that of the membrane-based treatment and concentrated brine solution is not produced, which makes it favorable for potable reuse where water scarcity is not an issue. This carbon-based treatment which included ozonation and activated carbon filtration and adsorption was further monitored and optimized for removal of organic contaminants and disinfection byproducts. Emerging contaminants such as pharmaceuticals, industrial solvents and personal care products can be harmful to human health and water ecology even at low concentrations. These contaminants are often present in wastewater effluent and can enter drinking water sources if untreated. These emerging contaminants were shown to be effectively removed by ozonation and granular activated carbon adsorption. The formation of disinfection byproducts such as N-nitrosodimethylamine in the treatment process and its removal in the biological activated carbon filtration was also monitored. The impact of temperature, presence of pre-oxidants and design factors such as ozone dose and empty bed contact time affected the removal of all these contaminants. This study provided an understanding of implementing carbon-based treatment for managed aquifer recharge for optimizing removal of bulk organic carbon and emerging contaminants. The results from this study can be utilized for designing advanced water treatment systems and can prove to be a guideline for monitoring and removing emerging contaminants.