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Monitoring the content of dissolved ozone in purified water is often mandatory to ensure the appropriate levels of disinfection and sanitization. However, quantification bears challenges as colorimetric assays require laborious off-line analysis, while commercially available instruments for electrochemical process analysis are expensive and often lack the possibility for miniaturization and discretionary installation. In this study, potentiometric ionic polymer metal composite (IPMC) sensors for the determination of dissolved ozone in ultrapure water (UPW) systems are presented. Commercially available polymer electrolyte membranes are treated via an impregnation-reduction method to obtain nanostructured platinum layers. By applying 25 different synthesis conditions, layer thicknesses of 2.2 to 12.6 µm are obtained. Supporting radiographic analyses indicate that the platinum concentration of the impregnation solution has the highest influence on the obtained metal loading. The sensor response behavior is explained by a Langmuir pseudo-isotherm model and allows the quantification of dissolved ozone to trace levels of less than 10 µg L−1. Additional statistical evaluations show that the expected Pt loading and radiographic blackening levels can be predicted with high accuracy and significance (R2adj. > 0.90, p < 10−10) solely from given synthesis conditions.

The interaction between charge, heat and mass transfer occurring in SOFCs is investigated applying a finite-volume-based SOFC model. The strong interactions are the consequence of the high degree of integration of different processes (chemical/electrochemical reactions, diffusion, heat and mass transfer) within SOFCs. The understanding of these interactions is a key for the future development and application of SOFCs. The investigation was conducted by means of a sensitivity analysis for two different fuel gases, where one gas features a considerable amount of methane inducing steam reforming reactions as additional disturbance factor in the energy and mass balance system of SOFCs. In order to isolate the impact of the varied model parameters and the according changes in the interactions of charge, mass and heat transfer from side effects, the sensitivity analysis was conducted at constant fuel utilization. It was found that the impact of different fuel gases on the operational conditions of SOFCs dominates geometrical and material-induced phenomena. The power output was most affected by the fuel, followed by the values for the activation polarization activation energy that reflects the employed electrode catalysts activity.

In future, new biomass technologies can gain significant importance in the Swiss energy sector. Therefore, this paper assesses the economic conditions under which new biomass technologies become competitive. The focus of this assessment is on the production of synthetic natural gas (bio-SNG) from wood in a methanation plant. The assessment is conducted with the cost-optimization model SWISS-MARKAL (MARKet ALlocation). SWISS-MARKAL projects future technology investments and provides an integrated analysis of primary, secondary, final and end-use energy in Switzerland. In addition to a reference scenario, the effects of increasing oil and gas prices, the effects of allocating subsidies to the methanation plant and the effects of competition between the methanation plant and a biomass-based Fischer–Tropsch (FT) synthesis are evaluated. Moreover, a sensitivity analysis is performed by varying investment costs of the methanation plant. The results are in favour of bio-SNG in the transportation sector where the synergetic use of bio-SNG and natural gas reduces the dependence on oil imports and the level of CO 2 emissions.

The regenerative effect of fluidization on catalysts in methanation reactors was shown by in situ measurements of the axial gas phase concentration profiles. The profiles prove strong carbon exchange processes between the catalyst and the gas phase. These exchange processes structure the bed into three zones: carbon deposition, predominantly by CO dissociation, at the inlet; predominant gasification of solid carbon species from the catalyst in the following zone, and predominant carbon deposition by methane dissociation in the upper part of the bed. By analyzing the carbon-balance, locally up to 20% excess carbon was found in the gas phase, mainly in form of methane. The excess methane decomposes again, forming less reactive carbon with a slow rate. Due to an intensive catalyst mixing, the build-up of unreactive carbon can be prevented by regeneration in the middle zone of the reactor. As these processes are influenced by the particle movement, conclusions about regions of up- and down-flow of the catalyst particles can be drawn.

The gasification reaction of fir charcoal with CO2 was studied by isothermal thermogravimetric analysis under kinetic control. The derived reaction rate (r = dX/dt) as a function of the converted carbon mass (X) was compared with random pore model predictions and found to be much higher at elevated conversion levels than predicted by theory. Similar enhanced reaction rate behaviour was evidenced after removing the natural alkali catalyst from the charcoal by acid washing, suggesting that with untreated charcoal the late reaction rate contribution stems from both, catalytic and additional structure effects. Literature attributes the unpredicted late reaction rate behaviour to the disintegration of the porous char particle into small fragments, which, in line with percolation theory predictions, seems to occur only after a critical conversion level has been reached. However, our gasification data reveal a gradual rise in the charcoal reactivity thereafter, suggesting a breaking up (embrittlement) of the solid phase accompanied by the exposure of fresh surface area from fracturing. The original random pore model derivation given by Bhatia and Perlmutter is extended to account also for these peculiarities and the resulting kinetic relation described our reaction rate data well over the entire conversion range. (C) 2002 Elsevier Science Ltd. All rights reserved.

The experimentally observed rise in the single pass methanol production with CO2 and H-2 (T = 200 degreesC, P = 4.3 bar) by in situ product removal over a perm-selective Nafion (R) membrane is verified by model simulations. For this purpose, software was developed which addresses the two rivalling processes (synthesis and permeation) for given catalyst activity and permeation performance of the membrane. The program predicts the production rate of all the reactor gas components leaving the reactor by explicit integration of the gas component and (reactor and mantle) space specific differential rate equations along the symmetry axes of the tubular membrane reactor. The activity of the CO2-tolerant catalyst used was characterized independently by kinetic model analysis; the experimentally determined permeation performance of the membrane for the various reactant gas components by Arrhenius type temperature dependencies. The model confirmed the membrane reactor results satisfactorily well. It was estimated that with 10 mum thin membrane surfaces implemented in commercial methanol synthesis plants and operated under technically relevant conditions (T = 200 degreesC, P = 40 bar, GHSV = 5000 h(-1)), the single pass reactor yield improves by 40% and that the additional costs for the membrane material are two production months only. (C) 2001 Elsevier Science B.V. All rights reserved.

It is our vision to separate volatile toxic contaminants from waste by thermal treatment. In this context the evaporation behavior of heavy metal traces (Cd, Cu, Pb, and Zn) from model compounds and mixtures, and from fly ash (FA) of municipal solid waste incineration (BCR No. 176) was investigated. In this study we tested a new method which allows on-line detection of heavy metals in hot gases using conventional Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) equipment. A quantitative relation between the amount of evaporated heavy metal traces and the ICP-OES signal was established. In addition, gaseous HCl was successfully used for the total removal of heavy metal traces from non-volatile compounds. The evaporation behavior predicted by speciation calculations were in agreement with the experimental results. The experiments have shown that the method could become a complementary tool for common analytical digestion and measuring methods for the determination of heavy metal traces in solid samples. As our method combines extraction and analytical steps it therefore can shorten conventional procedures. It allows simultaneous, and compared to a conventional digestion and ICP-OES analysis, more sensitive measurements of several elements. The application could become especially powerful for the analysis of contaminated soil and waste residuals.

In view of the laboratory tests performed at PSI with a Nafion tubular membrane reactor module for the catalysed methanol synthesis with CO2 and H-2 at 200 degrees C, the mechanical stability of a commercially available Nafion hollow fiber was tested at elevated temperatures (T=160-200 degrees C) and pressures (P

The enrichment with heavy metals of bottom ash from municipal solid waste incinerators limits its sustainable use as a construction material. Part of the heavy metals evaporate during the incineration process. In order to determine the factors influencing the volatility coefficients of the heavy metals, the complex processes in the furnace of an MSW incinerator were simulated in a tubular furnace in batch operation with small quantities of synthetic waste. It was shown that the results obtained from this experimental modeling can be transferred to real systems.

The efficiency of separation of Zn compounds from incinerator fly ash by evaporation at temperatures up to 1000°C depends on a number of factors and competing reactions. Model experiments with ZnCl2 and a number of oxide matrices of defined composition (silica, alumina, a silica-alumina-calcia glass, and heat treated fly ash) in moist air were carried out in order to identify the chemical reactions involved and to investigate the relative importance of temperature, ZnCl2 concentration, surface area and composition of the matrix oxide. Thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) were used as experimental techniques. The hydrolysis and subsequent immobilisation of ZnO in the matrix oxide dominates the process at low temperatures and low ZnCl2 concentrations. At high ZnCl2 concentrations evaporation becomes more dominant. The Zn evaporation is governed by the vapour pressure of ZnCl2 and limited by mass transfer to the purging gas stream. The development of new technologies for improved separation of Zn (and other heavy metals) from fly ash should focus on improving the mass transfer from particle grain to gas phase and avoid long residence times at temperatures below 600°C.

Thermal treatment is a promising way for the decontamination and inertization of residues from waste incineration. The evaporation of heavy metal compounds thereby is of great significance. It is the goal of this work to identify, by analyzing evaporation rates, the predominant thermochemical reactions of the heavy metals with other constituents of fly ash, with respect to volatilization. To this end, experiments were performed with fly ash from a municipal solid waste (MSW) incineration plant as well as with synthetic powder mixtures in the temperature range of 670−1000 °C. The rates of Cd, Cu, Pb, and Zn evaporation can be described accurately by a simple first-order rate law and a rate coefficient which itself follows an exponential temperature dependence analogous to the Arrhenius equation. The degrees (completeness) as well as the rates of evaporation of the heavy metals are markedly influenced by chlorides contained in the fly ash, largely as NaCl. Experiments with model substrates indicate that the...

Methanol synthesis from CO 2 and H 2 is a promising chemical energy storage reaction for hydrogen. The methanol yield of the synthesis is limited by the thermodynamic equilibrium at the temperatures required by state-of-the-art catalysts. Substantial conversion improvements would be achieved by selective product separation from the catalyst bed of a synthesis reactor. A perfluorinated cation exchange material (Nafion ® , DuPont) is evaluated for use as a vapour permeation membrane at temperatures up to 200°C. The permselectivities for methanol and water with respect to hydrogen depend on the counter ion in the polymer, and drop as a function of temperature. With respect to long term stability and performance, lithium is best suited as a counter ion, with permselectivities of 32 for water, and 5.6 for methanol, respectively. Permeability and permselectivity are found to increase with increasing partial pressures of both methanol and water vapours. The capability of the Li-Nafion membrane to separate products from a commercially available catalyst bed operating on CO 2 and H 2 at 200°C is demonstrated using a simple tubular membrane reactor module.

Publisher Summary The development of suitable low-cost, regenerable absorbents with long lifetime is one of the major challenges of the high temperature CO2 capture. The purpose of the experiment described in this chapter is to carry out a screening of natural minerals that are able to take up CO2 in a reversible manner. The selected minerals were characterized in terms of absorption capacity, cycle stability, and mechanical stability. Furthermore, the influence of different parameters such as presence of steam, particle size, and sorbent loading degree on the cycle stability was investigated. The tested minerals were selected among different classes of carbonates and silicates. Thermogravimetric analysis was performed employing a Netzsch apparatus STA 409 CD. Experiments were conducted in isothermal and quasi-isothermal manner. The quasi-isothermal experiments were carried out in controlled gas flow atmosphere. The chemical/cycling stability is dependent on the chemical composition of the minerals; an increased concentration of inert components influences positively the cycling stability of the sorbent materials. Natural complex silicates containing calcium carbonate showed poor CO2 sorbent qualities, however, they produced good cycling and mechanical stability results. The presence of steam in the gas atmosphere increases the absorption reaction rate, but reduces the sorbent lifetime. Crushing and milling can influence the absorption behavior of the sorbents due to the change of their chemical composition.

In this work, the impact of moisture on the volatility of heavy metals present in municipal solid wastes (MSW) in a laboratory scale simulated incinerator was studied, using synthetic waste consisting of 5.4 g of wood powder, 2.6 g lava, 1.9 polythene, 0.19 g polyvinyl chloride, and a given quantity of water and heavy metals represented by lead, zinc and copper in forms of metallic, chlorides and oxides. It is found that the presence of high moisture in MSW will greatly reduce the volatilization of heavy metals in MSW in the incineration process. The volatilization behavior of chlorides, oxides and the metallic species with respect to the effect of moistures is quite different. For copper, the presence of moisture in MSW depresses the volatilization of oxides, and increases that of chloride and the metallic species, while in contrast, the volatilization of both lead and zinc is always depressed by the presence of moisture in MSW, regardless of the chemical forms used. The chemical mechanisms, which govern the volatilization behaviors of different chemical forms in the incineration process, are proposed. Hydrolysis, dewatering of hydrolyzed species, sublimation, chemical transformation of less volatiles to more volatiles or reverse, may participate in and affect the volatilization of heavy metals in MSW. (C) 2004 Elsevier Ltd. All rights reserved.

Waste incineration is a technology which is more than 100 years old. The technology was first introduced at the end of the 19th century to reduce the volume and mass of MSW in order to save landfill space. In a time when smoking stacks were synonymous with progress, nobody cared about the emissions from incinerators into the air. Only when air pollution became a high priority issue in the early 1980s was it found that MSW incinerators were in fact contributing substantially to the overall emission of air pollutants, notably of HO, dioxins and various heavy metals. Once this drawback to MSW incineration was acknowledged, legislation intervened and forced the environmental technology industry to develop suitable air pollution control (APC) technology, which in turn required that operators of incinerators invest large sums to limit the emission of acid gases, particulates and toxic trace compounds. The era of environmental technology from 1980 to 2000 has in fact brought down the emissions from incineration to levels that have made MSWI a minor contributor to air pollution for all emission categories [48].

Municipal solid waste management , Municipal solid waste management , کتابخانه دیجیتال جندی شاپور اهواز

There has been growing concern about the way cultivating biomass for the production of agro-biofuels competes with food production. To avoid this competition biomass production for biofuels will, in the long term, have to be completely decoupled from food production. This is where microalgae have enormous potential. Here we propose a novel process based on microalgae cultivation using dilute fossil CO2 emissions and the conversion of the algal biomass through a catalytic hydrothermal process. The resulting products are methane as a clean fuel and concentrated CO2 for sequestration. The proposed gasification process mineralizes nutrient-bearing organics completely. Here we show that complete gasification of microalgae (Spirulina platensis) to a methane-rich gas is now possible in supercritical water using ruthenium catalysts. 60–70% of the heating value contained in the algal biomass would be recovered as methane. Such an efficient algae-to-methane process opens up an elegant way to tackle both climate change and dependence on fossil natural gas without competing with food production.

The way municipal solid waste is handled greatly determines its impact on the local as well as the global environment. New technologies have emerged for the treatment of waste, for the recovery of raw materials and energy, and for safe final disposal. The environmental performance of technologies, their social acceptance and their economic viability are key issues to be considered in sustainable waste management. This book provides an overview of current practices in waste management and a synthesis of new developments achieved through interdisciplinary discussions of recent research results.

"Thermal desorption experiments" were carried out during which heavy metal evaporation was studied by on-line monitoring. This could be achieved by the use of a tubular furnace connected to a heavy metal detector, i.e. an ICP-OES (inductively coupled plasma optical emission spectrometer), by a specially designed and patented interface. The spectrograms typically had a time resolution of four different elements per minute using a conventional (sequentially operating) ICP-OES. This study shows how thermo-desorption spectrometry (TDS) can be applied to study the evaporation of high boiling substances, such as heavy metal and alkali metal compounds. The future scope of the method is discussed.

The catalytic influence of major metal species found with waste wood (Na, K, Ca, Mg, Zn, Pb, Cu) was studied during the gasification of nitrate salt impregnated charcoal with CO2 at 800degreesC in the kinetically controlled regime. In contrast with literature, the respective reaction rate data were analysed over the entire carbon conversion (X) range by using extended kinetic relations to quantify catalyst metal-specific reaction rate contributions not accounted for by the original random pore model of Bhatia and Perlmutter. The kinetic analysis provided valuable insights in the underlying mechanisms. With alkali nitrate impregnated charcoal, it is demonstrated that the often found reaction rate maximum around X similar to 0.7 may merely reflect increasing catalytic activity resulting from alkali accumulation in the charcoal, superimposed on structural changes in the charcoal micropore domain. Impregnated earth-alkali nitrates revealed substantial activity as well, but only during the early gasification stage (X < 0.2), hereby, underlining their sintering propensity in combination with the localised deposition of the earth-alkaline nitrate salt in the former wood cells by the impregnation procedure. Added heavy metal nitrates revealed no activity, apart from lowering the charcoal reactivity over the entire conversion range by ca. 15% compared with the untreated charcoal, suggesting inhibition by covering, hence, blocking of otherwise accessible active charcoal surface sites and/or by deactivation of neighbouring indigenous alkali due to immobilisation at the heavy metal oxide surfaces formed during pyrolysis. The extended kinetic relation reproduced all of our reaction rate data well over the entire gasification stage, hereby, supporting the superposition of micropore domain and catalyst specific effects. (C) 2002 Elsevier Science Ltd. All rights reserved.

Nickel iron oxide (NiFe2O4) has been tested as a combined catalyst precursor and oxygen transfer material for improved conversion of methane into syngas. Thermogravimetric measurements with simultaneous gas analysis have demonstrated the superior behavior of nickel iron oxide compared to iron oxide. The enhanced catalytic activity is attributed to the generation of fresh nickel surfaces in the course of the reduction of the metal oxide. This allows for a periodic in situ generation of fresh, catalytically active nickel. (C) 2006 Elsevier Ltd. All rights reserved.