Hydrogen storage of energy for small power supply systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 91-92).Power supply systems for cell phone base stations using hydrogen energy storage, fuel cells or hydrogen-burning generators, and a backup generator could offer an improvement over current power supply systems. Two categories of hydrogen-based power systems were analyzed: Wind-hydrogen systems and peak-shaving hydrogen systems. Modeling of base station requirements and alternative power supply system performance was carried out using MATLAB. Final results for potential alternative systems were compared to those for the current power systems. In the case of the wind- hydrogen systems, results were also compared to those of a wind-battery system. Overall feasibility was judged primarily on the net present cost of the power supply systems. Other considerations included conformity to present regulations. Sensitivity analysis of the wind-hydrogen model was carried out to identify the controlling variables. Numerous parameters were varied over realistic ranges. Important parameters were found to include wind resource, electrolyzer size, distance from electricity grid, price of diesel fuel, and electrolyzer and fuel cell cost. The model verified cell phone industry figures regarding the geographical conditions favorable to diesel genset use. Final results for wind-hydrogen systems suggest that for today's electrolyzer and fuel cell costs, wind-battery-diesel systems are the most suitable power system more than 8km from the existing electricity grid, with an annual average wind speed of 7m/s or more, and where diesel costs more than $2.20/gallon.(cont.) Thinking to the future, with 20$2/gallon. Within 8km the grid, in all cases, grid connection is most suitable. Outside this range, with diesel prices below $2/gallon, a genset only system is most suitable in most cases. Analysis of the peak-shaving hydrogen system suggests that it is not suitable for deployment under any realistic circumstances. Replenishment of hydrogen stores has a substantial power requirement.by Rory F.D. Monaghan.S.M

Dynamic reduced order modeling of entrained flow gasifiers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references.Gasification-based energy systems coupled with carbon dioxide capture and storage technologies have the potential to reduce greenhouse gas emissions from continued use of abundant and secure fossil fuels. Dynamic reduced order models (ROMs) that predict the operation of entrained flow gasifiers (EFGs) within IGCC (integrated gasification combined cycle) or polygeneration plants are essential for understanding the fundamental processes of importance. Such knowledge can be used to improve gasifier reliability, availability and maintainability, leading to greater commercialization of gasification technology. A dynamic ROM, implemented in Aspen Custom Modeler, has been developed for a range of EFGs. The ROM incorporates multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. The ROM employs a reactor network model (RNM) that approximates complex fluid mixing and recirculation using a series of idealized chemical reactors. The ROM was successfully validated for steady-state simulation of four experimental gasifiers. The throughputs of these gasifiers range from 0.1 to 1000 metric tonnes per day (3 kWth - 240 MWth). Sensitivity analysis was performed to identify the parameters most important to ROM accuracy. The most important parameters are found to be those that determine RNM geometry, particle physical and kinetic properties, and slagging. The ROM was used to simulate the steady-state and dynamic performance of a full-scale EFG system. In steady-state mode, the ROM was used to establish base case and fluxant requirements. The base case performance agreed with design specifications. Steady-state simulation was also used to determine important states for dynamic simulation. Six cases were examined in dynamic mode, including gasifier cold start. Dynamic results showed agreement with industrial experience for gasifier start-up times.by Rory F. D. Monaghan.Ph.D

Cost estimation of a biorefining network for forest residues in Ireland

The forestry sector in the Republic of Ireland (ROI) is mainly focused on harvesting timber from the stems of spruce trees. The remaining 30-35% of unharvested wood volume, typically known as forest residues or brash, is left on the forest floor. Only a small geographically specific portion of forest residues are bundled and sold at low cost as fuel for industrial combined heat and power (CHP). The volume of unused forest residues in ROI is estimated to be 700 thousand m3 a-1, and its distribution is shown in Figure 1[1]. This significant quantity can be mobilized as biomass feedstock to biorefineries for high value bio-products. The composition, quantity and type of feedstock available in Ireland indicate that pyrolysis and hydrothermal liquefaction (HTL) are the most effective biorefining pathways. Bio-oils produced from pyrolysis have high energy value and HTL uses forest residues with high moisture content as feedstock saving the cost of drying. Both of these technologies have the capability to be energy neutral and therefore have potential at the small, distributed scale found in Ireland [2]. The highly dispersed nature of forest residues coupled with low energy density presents challenges in sustaining substantial availability of feedstock to the biorefinery. Selection of an optimum location for building a biorefinery can help design an efficient supply chain to reduce transportation cost and environmental impact. Multi-criteria decision analysis (MCDA) coupled with geographic information system (GIS) analysis is a popular and effective method to analyse location suitability. Localised criteria can either be factors, which influence location suitability, or constraints, which limit development in that vicinity. These criteria are weighted using the analytical hierarchy process (AHP) and combined in GIS to give a final site suitability map. Selection of the most cost-effective location out of all suitable sites requires a cost estimation model that will compare the operational cost for both technologies and transportation cost of the resources and final product. Please click Additional Files below to see the full abstract

Parametric study of lab-scale and pilot-scale biomass torrefaction for the production of woodstove briquettes

Conversion of torrefied olive residues to high-density briquettes is a potential solution to solid waste problems as well as to the lack of locally available fuel wood in Ireland. In this study, olive stones were torrefied at various temperatures and holding times in a fixed-bed reactor. Effects of process parameters such as heat treatment temperature from 200 to 300℃, residence time from 30 to 60 min, and particle size from 0.18 to 3 mm on the yield and composition of products were investigated and the results were compared with the mass balances from industrial-scale torrefaction plant at the Arigna Fuels (Carrick-on-Shannon, Ireland). The olive stones of larger particle size produced more liquid and gaseous products than smaller particles in a fixed bed reactor, whereas particle size had significantly less influence on the product yields than residence time and heat treatment temperature. The analysis of liquid products of the industrial-scale plant showed a greater content of heavy molecular products compared to the lab-scale pyrolysis using high-performance liquid chromatography and size exclusion chromatography techniques. New value-added products were developed from the tar compounds produced at the industrial-scale torrefaction plant. In addition, the lab-scale experiments showed that the ash content of torrefied biomass significantly increased with the increased feedstock particle size. The torrefied olive stones briquettes using different binders were tested in a conventional woodstove. Torrefaction of olive stones has been found to reduce the emissions by approximately 60% compared to the non-treated feedstock. This demonstrates that torrefaction has good potential as a cost-effective and sustainable process for the production of woodstove briquettes from low-quality feedstocks

Characterization of woodstove briquettes from torrefied biomass and coal

peer-reviewedUsing waste biomass materials offers the potential to reduce the greenhouse gas emissions from fossil fuels. Torrefaction is very useful for improving the fuel properties of biomass in order to better match those of coal. The aim of this work is to compare the properties of torrefied low quality biomass briquettes against coal equivalents. The composition of the briquettes was characterized by 13C CP/MAS, proximate analysis, and X-ray diffraction and the results were compared with equilibrium calculations. In addition to these techniques, we report for the first time on the use of XμCT for characterizing such materials. The XμCT analysis showed that the briquette structure contains carbon, binder and inorganic matter, with quartz retained from the original feedstock in torrefied biomass and coal briquettes. The CO2 reactivity of pulverized briquettes was investigated by thermogravimetric analysis. Results showed that the inorganic matter influences the reactivity less than the organic composition and porosity. Importantly from a technological standpoint, the increase in binder concentration and replacement of starch with resin binder did not influence the reactivity and calorific value of a pulverized briquette

IMECE2009-12985 REDUCED ORDER MODELING OF ENTRAINED FLOW SOLID FUEL GASIFICATION

ABSTRACT Reduced order models that accurately predict the operation of entrained flow gasifiers as components within integrated gasification combined cycle (IGCC) or polygeneration plants are essential for greater commercialization of gasification-based energy systems. A reduced order model, implemented in Aspen Custom Modeler, for entrained flow gasifiers that incorporates mixing and recirculation, rigorously calculated char properties, drying and devolatilization, chemical kinetics, simplified fluid dynamics, heat transfer, slag behavior and syngas cooling is presented. The model structure and submodels are described. Results are presented for the steady-state simulation of a two-metric-tonne-per-day (2 tpd) laboratory-scale Mitsubishi Heavy Industries (MHI) gasifier, fed by two different types of coal. Improvements over the state-of-the-art for reduced order modeling include the ability to incorporate realistic flow conditions and hence predict the gasifier internal and external temperature profiles, the ability to easily interface the model with plant-wide flowsheet models, and the flexibility to apply the same model to a variety of entrained flow gasifier designs. Model validation shows satisfactory agreement with measured values and computational fluid dynamics (CFD) results for syngas temperature profiles, syngas composition, carbon conversion, char flow rate, syngas heating value and cold gas efficiency. Analysis of the results shows the accuracy of the reduced order model to be similar to that of more detailed models that incorporate CFD. Next steps include the activation of pollutant chemistry and slag submodels, application of the reduced order model to other gasifier designs, parameter studies and uncertainty analysis of unknown and/or assumed physical and modeling parameters, and activation of dynamic simulation capability

Combined analytical strategies for chemical and physical characterization of tar from torrefaction of olive stone

The advance in analytical methodology is critical for progress in 1) biorefinery and 2) torrefaction product commercialization. The chemical characterisation of torrefaction liquid and concentrated tar produced by Arigna Fuels’ pyrolysis plant allowed identification of polar, volatile, non-volatile compounds, species containing organically bound sulphur and nitrogen heteroatoms. The results suggest that only combined use of ion chromatography with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, and 1H-13C HS-QC can provide comprehensive information on sugar-like material and lignin-derived compounds. Due to the technical robustness and short analysis time, Fourier Transform Ion Cyclotron Resonance Mass Spectrometer was found to be a promising tool for tar analysis containing heavy molecular compounds. Importantly from a technological standpoint, the presence of aromatic and saturated compounds in both liquid and concentrated tar samples indicated the predominance of lignin-derived compounds over products originating from cellulose and hemicellulose polymers.publishedVersio

Combined analytical strategies for chemical and physical characterization of tar from torrefaction of olive stone

The advance in analytical methodology is critical for progress in 1) biorefinery and 2) torrefaction product commercialization. The chemical characterisation of torrefaction liquid and concentrated tar produced by Arigna Fuels’ pyrolysis plant allowed identification of polar, volatile, non-volatile compounds, species containing organically bound sulphur and nitrogen heteroatoms. The results suggest that only combined use of ion chromatography with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, and 1H-13C HS-QC can provide comprehensive information on sugar-like material and lignin-derived compounds. Due to the technical robustness and short analysis time, Fourier Transform Ion Cyclotron Resonance Mass Spectrometer was found to be a promising tool for tar analysis containing heavy molecular compounds. Importantly from a technological standpoint, the presence of aromatic and saturated compounds in both liquid and concentrated tar samples indicated the predominance of lignin-derived compounds over products originating from cellulose and hemicellulose polymers.publishedVersio

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Fingerprinting coal-derived gases from the UK

The large-scale extraction of unconventional hydrocarbons in the United States has led to fears of methane contamination of shallow groundwaters. Differentiating between the deep gas released during extraction (shale gas, coal bed methane and underground coal gasification) and natural shallow-sourced methane is imperative for the monitoring and managing of environmental risks related to the extraction process. Here, for the first time, we present measurements of the major gas, and stable and noble gas isotope composition of coal bed methane (CBM) from central Scotland and coal mine methane (CMM) from central England, UK. The molecular (C1/(C2+C3) = 21 to 120) and stable isotope compositions (δ13CCH4 = -39.5 to -51.1‰; δDCH4 = -163 to -238‰) indicate a thermogenic origin for the methane. They are distinct from the majority of shallow-sourced gases in UK. Both sample suites exhibit high He concentrations (338 to 2980 ppmv) that are considerably above atmospheric and groundwater levels. Simple modelling shows that these high 4He concentrations cannot be solely derived from in situ production since coal deposition, and hence the majority is derived from the surrounding crust. The Scottish CBM contains a resolvable mantle He, Ne and Ar contribution that may originate from melts in the deep crust, demonstrating the UK coals have acted as a store for deep volatiles for 10s of millions of years. The high 4He in the coal-derived gases has the potential to be used as a novel diagnostic fingerprint to track fugitive release of deep methane from future unconventional gas extraction operations in the UK