Origin and patterns of distribution of trace elements in street dust. Unleaded petrol and urban lead

The elemental composition, patterns of distribution and possible sources of street dust are not common to all urban environments, but vary according to the peculiarities of each city. The common features and dissimilarities in the origin and nature of street dust were investigated through a series of studies in two widely different cities, Madrid (Spain) and Oslo (Norway), between 1990 and 1994. The most comprehensive sampling campaign was carried out in the Norwegian capital during the summer of 1994. An area of 14 km2, covering most of downtown Oslo and some residential districts to the north of the city, was divided into 1 km2 mapping units, and 16 sampling increments of approximately 150 g were collected from streets and roads in each of them. The fraction below 100 μm was acid-digested and analysed by ICP-MS. Statistical analyses of the results suggest that chemical elements in street dust can be classified into three groups: “urban” elements (Ba, Cd, Co, Cu, Mg, Pb, Sb, Ti, Zn), “natural” elements (Al, Ga, La, Mn, Na, Sr, Th, Y) and elements of a mixed origin or which have undergone geochemical changes from their original sources (Ca, Cs, Fe, Mo, Ni, Rb, Sr, U). Soil resuspension and/or mobilisation appears to be the most important source of “natural” elements, while “urban” elements originate primarily from traffic and from the weathering and corrosion of building materials. The data for Pb seem to prove that the gradual shift from leaded to unleaded petrol as fuel for automobiles has resulted in an almost proportional reduction in the concentration of Pb in dust particles under 100 μm. This fact and the spatial distribution of Pb in the city strongly suggest that lead sources other than traffic (i.e. lead accumulated in urban soil over the years) may contribute as much lead, if not more, to urban street dust.

The intermediate pyrolysis and catalytic steam reforming of brewers spent grain

Brewers spent grain (BSG) is a widely available feedstock representing approximately 85% of the total by-products generated in the brewing industry. This is currently either disposed of to landfill or used as cattle feed due to its high protein content. BSG has received little or no attention as a potential energy resource, but increasing disposal costs and environmental constraints are now prompting the consideration of this. One possibility for the utilisation of BSG for energy is via intermediate pyrolysis to produce gases, vapours and chars. Intermediate pyrolysis is characterised by indirect heating in the absence of oxygen for short solids residence times of a few minutes, at temperatures of 350-450 °C. In the present work BSG has been characterised by chemical, proximate, ultimate and thermo-gravimetric analysis. Intermediate pyrolysis of BSG at 450 °C was carried out using a twin coaxial screw reactor known as Pyroformer to give yields of char 29%, 51% of bio-oil and 19% of permanent gases. The bio-oil liquid was found to separate in to an aqueous phase and organic phase. The organic phase contained viscous compounds that could age over time leading to solid tars that can present problems in CHP application. The quality of the pyrolysis vapour products before quenching can be upgraded to achieve much improved suitability as a fuel by downstream catalytic reforming. A Bench Scale batch pyrolysis reactor has then been used to pyrolyse small samples of BSG under a range of conditions of heating rate and temperature simulating the Pyroformer. A small catalytic reformer has been added downstream of the reactor in which the pyrolysis vapours can be further cracked and reformed. A commercial reforming nickel catalyst was used at 500, 750 and 850 °C at a space velocity about 10,000 L/h with and without the addition of steam. Results are presented for the properties of BSG, and the products of the pyrolysis process both with and without catalytic post-processing. Results indicate that catalytic reforming produced a significant increase in permanent gases mainly (H2 and CO) with H2 content exceeding 50 vol% at higher reforming temperatures. Bio-oil yield decreased significantly as reforming temperature increased with char remaining the same as pyrolysis condition remained unchanged. The process shows an increase in heating value for the product gas ranging between 10.8-25.2 MJ/m as reforming temperature increased. © 2012 Elsevier B.V. All rights reserved.

Solid biofuel production by mechanical pre-treatment of brewers' spent grain

The brewing industry produces large amounts of by-products and wastes like brewers' spent grain (BSG). In Germany, each year approximately 2.1 million tonnes of BSG are generated. During the last years conventional routes of BSG utilization face a remarkable change, such as the decline in the demand as animal feed. Due to its high content of organic matter energetic utilization may create an additional economic value for breweries. Furthermore, in the recent past breweries tend to shift their energy supply towards more sustainable concepts. Although, a decent number of research projects were carried out already, still no mature strategy is available. However, one possible solution can be the mechanical pretreatment of BSG. This step allows optimized energy utilization by the fractionation of BSG. Due to the transfer of digestible components, such as protein, to the liquid phase, the solid phase will largely consist of combustible components. That represents an opportunity to produce a solid biofuel with lower fuelnitrogen content compared to only thermal dried BSG. Therefore, two main purposes for the mechanical pre-treatment were determined, (1) to reduce the moisture content to at least 60 % (w/w) and (2) to diminish the protein content of the solid phase by 30 %. Moreover, the combustion trials should demonstrate whether stable processes and flue gas emissions within the legal limits in Germany are feasible. The results of the mechanical pre-treatment trials showed that a decrease of the moisture and protein content has been achieved. With regard to the combustion trials inconsistent outcomes were found. On the one hand a stable combustion was realized. On the other hand the legal emission levels of NOx (500 mgm -3) and dust (50 mgm-3) could not be kept during all trials. The further research steps will focus on the optimization of the air/fuel ratio by reducing the primary and secondary air conditions. Copyright © 2014,AIDIC Servizi S.r.l.

Thermochemical conversion of Brewers Spent Grain combined with catalytic reforming of pyrolysis vapours

The brewing process is an energy intensive process that uses large quantities of heat and electricity. To produce this energy requires a high, mainly fossil fuel consumption and the cost of this is increasing each year due to rising fuel costs. One of the main by-products from the brewing process is Brewers Spent Grain (BSG), an organic residue with very high moisture content. It is widely available each year and is often given away as cattle feed or disposed of to landfill as waste. Currently these methods of disposal are also costly to the brewing process. The focus of this work was to investigate the energy potential of BSG via pyrolysis, gasification and catalytic steam reforming, in order to produce a tar-free useable fuel gas that can be combusted in a CHP plant to develop heat and electricity. The heat and electricity can either be used on site or exported. The first stage of this work was the drying and pre-treatment of BSG followed by characterisation to determine its basic composition and structure so it can be evaluated for its usefulness as a fuel. A thorough analysis of the characterisation results helps to better understand the thermal behaviour of BSG feedstock so it can be evaluated as a fuel when subjected to thermal conversion processes either by pyrolysis or gasification. The second stage was thermochemical conversion of the feedstock. Gasification of BSG was explored in a fixed bed downdraft gasifier unit. The study investigated whether BSG can be successfully converted by fixed bed downdraft gasification operation and whether it can produce a product gas that can potentially run an engine for heat and power. In addition the pyrolysis of BSG was explored using a novel “Pyroformer” intermediate pyrolysis reactor to investigate the behaviour of BSG under these processing conditions. The physicochemical properties and compositions of the pyrolysis fractions obtained (bio-oil, char and permanent gases) were investigated for their applicability in a combined heat power (CHP) application.

Effect of Cu and Sn promotion on the catalytic deoxygenation of model and algal lipids to fuel-like hydrocarbons over supported Ni catalysts

The ability of Cu and Sn to promote the performance of a 20% Ni/Al2O3 catalyst in the deoxygenation of lipids to fuel-like hydrocarbons was investigated using model triglyceride and fatty acid feeds, as well as algal lipids. In the semi-batch deoxygenation of tristearin at 260 °C a pronounced promotional effect was observed, a 20% Ni-5% Cu/Al2O3 catalyst affording both higher conversion (97%) and selectivity to C10-C17 alkanes (99%) in comparison with unpromoted 20% Ni/Al2O3 (27% conversion and 87% selectivity to C10-C17). In the same reaction at 350 °C, a 20% Ni-1% Sn/Al2O3 catalyst afforded the best results, giving yields of C10-C17 and C17 of 97% and 55%, respectively, which contrasts with the corresponding values of 87 and 21% obtained over 20% Ni/Al2O3. Equally encouraging results were obtained in the semi-batch deoxygenation of stearic acid at 300 °C, in which the 20% Ni-5% Cu/Al2O3 catalyst afforded the highest yields of C10-C17 and C17. Experiments were also conducted at 260 °C in a fixed bed reactor using triolein − a model unsaturated triglyceride − as the feed. While both 20% Ni/Al2O3 and 20% Ni-5% Cu/Al2O3 achieved quantitative yields of diesel-like hydrocarbons at all reaction times sampled, the Cu-promoted catalyst exhibited higher selectivity to longer chain hydrocarbons, a phenomenon which was also observed in experiments involving algal lipids as the feed. Characterization of fresh and spent catalysts indicates that Cu enhances the reducibility of Ni and suppresses both cracking reactions and coke-induced deactivation.

CHARACTERIZATION AND THERMAL-HYDRAULIC MODELING OF ENGINEERED BARRIERS FOR A CANADIAN DEEP GEOLOGICAL REPOSITORY FOR USED NUCLEAR FUEL

Within Canada there are more than 2.5 million bundles of spent nuclear fuel with another approximately 2 million bundles to be generated in the future. Canada, and every country around the world that has taken a decision on management of spent nuclear fuel, has decided on long-term containment and isolation of the fuel within a deep geological repository. At depth, a deep geological repository consists of a network of placement rooms where the bundles will be located within a multi-layered system that incorporates engineered and natural barriers. The barriers will be placed in a complex thermal-hydraulic-mechanical-chemical-biological (THMCB) environment. A large database of material properties for all components in the repository are required to construct representative models. Within the repository, the sealing materials will experience elevated temperatures due to the thermal gradient produced by radioactive decay heat from the waste inside the container. Furthermore, high porewater pressure due to the depth of repository along with possibility of elevated salinity of groundwater would cause the bentonite-based materials to be under transient hydraulic conditions. Therefore it is crucial to characterize the sealing materials over a wide range of thermal-hydraulic conditions. A comprehensive experimental program has been conducted to measure properties (mainly focused on thermal properties) of all sealing materials involved in Mark II concept at plausible thermal-hydraulic conditions. The thermal response of Canada’s concept for a deep geological repository has been modelled using experimentally measured thermal properties. Plausible scenarios are defined and the effects of these scenarios are examined on the container surface temperature as well as the surrounding geosphere to assess whether they meet design criteria for the cases studied. The thermal response shows that if all the materials even being at dried condition, repository still performs acceptably as long as sealing materials remain in contact.

Evaluation of strontium-site-deficient Sr2Fe1.4Co0.1Mo0.5O6-δ-based perovskite oxides as intermediate temperature solid oxide fuel cell cathodes

In this paper strontium-site-deficient Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ-based perovskite oxides (S_xFCM) were prepared and evaluated as the cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). All samples exhibited a cubic phase structure and the lattice shrinked with increasing the Sr-deficiency as shown in XRD patterns. XPS results determined that the transition elements (Co/Fe/Mo) in S_xFCM oxides were in a mixed valence state, demonstrating the small polaron hopping conductivity mechanism existed. Among the samples, S_1.950FCM presented the lowest coefficient of thermal expansion of 15.62 × 10^-6 K^-1, the highest conductivity value of 28 S cm^-1 at 500 °C, and the lowest interfacial polarization resistance of 0.093 Ω cm² at 800 °C, respectively. Furthermore, an anode-supported single cell with a S_1.950FCM cathode was prepared, demonstrating a maximum power density of 1.16 W cm^-2 at 800 °C by using wet H₂ (3% H₂O) as the fuel and ambient air as the oxidant. These results indicate that the introduction of Sr-deficiency can dramatically improve the electrochemical performance of Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ, showing great promise as a novel cathode candidate material for IT-SOFCs.

Recovery of palladium from a spent automobile catalyst leaching solution by a thiodiglycolamide derivative

In the sequence of previous research on the development of novel liquid-liquid amidetype compounds to efficiently and selectively extract platinum-group metals (PGMs) from concentrated hydrochloric acid media, a specific thiodiglycolamide derivative – N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) – has been applied for the recovery of palladium(II) from a spent automobile catalyst leaching solution, containing palladium(II) and rhodium(III) as PGMs. The results obtained are rather promising, since the DMDCHTDGA behavior towards the two PGMs is similar to that observed for hydrochloric acid aqueous media studied before, simulating the real leaching phases. Within eleven metal elements co-existing in solution, the majority in high fold-excesses, only aluminum(III) and cerium(III) interfere in the palladium(II) liquid-liquid extraction process, requiring further optimization.

Integrated micro fuel cells with on-board hydride reactors and autonomous control schemes

Miniaturization of power generators to the MEMS scale, based on the hydrogen-air fuel cell, is the object of this research. The micro fuel cell approach has been adopted for advantages of both high power and energy densities. On-board hydrogen production/storage and an efficient control scheme that facilitates integration with a fuel cell membrane electrode assembly (MEA) are key elements for micro energy conversion. Millimeter-scale reactors (ca. 10 µL) have been developed, for hydrogen production through hydrolysis of CaH2 and LiAlH4, to yield volumetric energy densities of the order of 200 Whr/L. Passive microfluidic control schemes have been implemented in order to facilitate delivery, self-regulation, and at the same time eliminate bulky auxiliaries that run on parasitic power. One technique uses surface tension to pump water in a microchannel for hydrolysis and is self-regulated, based on load, by back pressure from accumulated hydrogen acting on a gas-liquid microvalve. This control scheme improves uniformity of power delivery during long periods of lower power demand, with fast switching to mass transport regime on the order of seconds, thus providing peak power density of up to 391.85 W/L. Another method takes advantage of water recovery by backward transport through the MEA, of water vapor that is generated at the cathode half-cell reaction. This regulation-free scheme increases available reactor volume to yield energy density of 313 Whr/L, and provides peak power density of 104 W/L. Prototype devices have been tested for a range of duty periods from 2-24 hours, with multiple switching of power demand in order to establish operation across multiple regimes. Issues identified as critical to the realization of the integrated power MEMS include effects of water transport and byproduct hydrate swelling on hydrogen production in the micro reactor, and ambient relative humidity on fuel cell performance.