Sosial kapital blant marginaliserte

Begrepet sosial kapital i moderne samfunnsvitenskap er knyttet til en sentral idé i sosialt arbeid – at sosiale relasjoner og nettverk representerer ressurser som kan hjelpe folk videre i livet. I forskningen er denne forestillingen så sterk at kontakt med familie, venner og naboer ofte brukes som indikator på ressurser. I denne artikkelen skilles det mellom nettverk og ressurser og belyses hvilke ressurser som finnes i det sosiale nettverket til brukerne av Frelsesarmeen og Kirkens Bymisjons tjenester. Undersøkelsen viser at brukerne har mye kontakt med venner, men lite med familien. Deres nettverk gir tilgang til ressurser som kan hindre ytterligere marginalisering, mens de har færre sosiale relasjoner som gir tilgang til ressurser som kan bidra til at de bedrer sin situasjon

Materials challenges in hydrogen-fuelled gas turbines

With the increased pressure to decarbonise the power generation sector several gas turbine manufacturers are working towards increasing the hydrogen-firing capabilities of their engines towards 100%. In this review, we discuss the potential materials challenges of gas turbines fuelled with hydrogen, provide an updated overview of the most promising alloys and coatings for this application, and highlight topics requiring further research and development. Particular focus is given to the high-temperature oxidation of gas turbine materials exposed to hydrogen and steam at elevated temperatures and to the corrosion challenges of parts fabricated by additive manufacturing. Other degradation mechanisms such as hot corrosion, the dual atmosphere effect and hydrogen diffusion in the base alloys are also discussed.acceptedVersio

Perovskite oxygen carrier with chemical memory under reversible chemical looping conditions with and without SO2 during reduction

Oxygen carrier materials (OCM) are usually exposed to sulfur-contained gases in the fuel reactor for chemical looping combustion. This work provides both experimental and model work to understand the SO2 effect on the heterogeneous redox kinetics of a CaMn0.375Ti0.5Fe0.125O3-δ-based perovskite oxygen carrier. The cycle reactivity and redox kinetics under reducing conditions were conducted with and without SO2 in a micro-fluidized bed thermogravimetric analysis technology (MFB-TGA). The redox kinetic behaviors were simulated by a bubbling fluidized bed reactor model coupled with a two-stage kinetic model. The SO2 can react with the perovskite to increase the oxygen transfer capacity from 4 wt% to 5 wt%. When the temperature is higher than 1173 K, SO2 has almost no effect on the H2 reduction reactivity, while the oxidation reactivity decreases by 50%, but the oxidation is still fast enough to achieve 4 wt% capacity within 8 s. When the temperature is lower than 1173 K, there is a significant sulfur-poisoning effect during oxidation and reduction. The analyses of XRD, SEM-EDS, and in-situ DRIFTS indicated that most of the absorbed sulfur mainly existed in the sulfate/sulfide shell on the particle surface. The chemical kinetics and physical structure of CaMn0.375Ti0.5Fe0.125O3-δ perovskite can be completely recovered in the absence of SO2, and this perovskite oxygen carrier is chemically memorable and reversible in its solid structure. The fundamental understanding of the sulfur effect on the redox kinetics and solid structure of the perovskite oxygen carrier provides a new insight to the material development and corresponding reaction mechanisms.acceptedVersio

Industry-scale production of a perovskite oxide as oxygen carrier material in chemical looping

How to upscale the production of oxygen carrier particles from laboratory level to industrial level is still challenging in the field of chemical looping. The upscaled oxygen carrier must maintain its physical and chemical properties. In the present contribution, a spray drying granulation protocol was developed to produce a perovskite oxygen carrier (CaMn0.5Ti0.375Fe0.125O3-δ) at an industrial scale. The micro-fluidized bed thermogravimetric (MFB-TGA) experiments were performed to measure the oxygen uncoupling and redox reaction kinetics under the fluidization state with enhanced heat and mass transfer, and the obtained experimental data at different temperatures were fitted by a fluidized-bed reactor coupled with a semi-empirical kinetic model. The physical and chemical properties of granulates were compared with those of the same perovskite composition prepared at the laboratory level. The results show the volume fraction of particle size at 75–500 μm is greater than 90% for the upscaled granulats, and the particles show no degradation in reactivity and no agglomeration for more than 20 redox cycles at high temperatures. The heterogeneous reaction rates are high, especially for the oxidation, e.g. it only spent ∼ 5 s to achieve full oxidation. Low attrition index of 3.74 wt% was found after the five-hour attrition test. The industrial-scale particles possess similar chemical and physical properties as the laboratory-scale particles with regards to the reaction kinetics, attrition index, crystalline phase, etc. The required bed inventories and fan energy consumption were finally estimated and found to be lower than other oxygen carriers reported in the literature.acceptedVersio

Integration of chemical looping oxygen production and chemical looping combustion in integrated gasification combined cycles

Abstract Energy penalty is the primary economic challenge facing CO2 capture technology. This work aims to address this challenge through a novel power plant configuration, capable of achieving 45.4% electric efficiency from coal with a 95% CO2 capture efficiency. The COMPOSITE concept integrates chemical looping oxygen production (CLOP) and packed bed chemical looping combustion (PBCLC) reactors into an integrated gasification combined cycle (IGCC) power plant. Hot gas clean-up technology is implemented to boost plant efficiency. When commercially available cold gas clean-up technology is used, the plant efficiency reduces by 2%-points, but remains 2.3%-points higher than a comparative PBCLC-IGCC power plant and 8.1%-points higher than an IGCC power plant with pre-combustion CO2 capture. It was also shown that the COMPOSITE power plant performance was not sensitive to changes in the performance of the CLOP reactors, implying that uncertainties related to this novel process component do not reduce the potential of the COMPOSITE concept. The outstanding efficiency obtained for this concept is made possible by a complex and highly integrated plant configuration, whose operability and techno-economic feasibility must be demonstrated

A numerical homogenisation strategy for micromorphic continua

Cellular materials are of special interest according to their peculiar mechanical properties. In this paper, special attention is paid to the simulation of size-dependent microtopological effects. We introduce a numerical homogenisation scheme for a two-scale problem dealing with a micromorphic continuum theory on the macroscale and a classical Cauchy continuum on the microscale. The transitions between both scales are obtained by projection and homogenisation rules derived from an equivalence criterion for the strain energy, also known as the Hill-Mandel condition

Ammonia and methane emissions from small herd cattle buildings in a cold climate

Ammonia (NH3) and methane (CH4) emission measurements that reflect local production conditions are required to track progress in national emission policies and verify emission factors. The findings can also be used to better understand key factors influencing emissions. This is especially important in Norway, which has long cold winters, and small cattle herds in mechanically ventilated buildings. However, until now, NH3 and CH4 emissions from Norwegian cattle buildings have not been reported in literature. Moreover, in other cold climates, NH3 and CH4 emissions are often taken from large dairy herds in naturally ventilated buildings, with less focus on suckler cows. The objectives were to assess indoor climate, report NH3 and CH4 emissions and examine the impact of climatic factors on NH3 and CH4 emissions in three small herd dairy and suckler cow buildings over three seasons. Three of the buildings had mechanical ventilation, while one was naturally ventilated. The suckler building had higher relative humidity (RH > 90 %) and NH3 concentrations (> 25 ppm) due to lower minimum air change rate (ACH = 1.2 h−1). The suckler building also had the highest NH3 emissions (2.04 g Livestock Unit (LU)−1 h−1) followed by the mechanically ventilated dairy building (1.92 g LU−1 h−1) with the highest ACH. These two buildings had the lowest stocking densities and floor areas. In contrast, the suckler building had the lowest CH4 emissions (6.8–10.7 g LU−1 h−1). Methane emissions from the dairy building with the supply-exhaust air mixing system (16.4–19.3 g LU−1 h−1) was higher than the other dairy buildings (11.7–13.8 g LU−1 h−1). Temperature influenced NH3 emissions however, the direction of association between temperature and NH3 emissions differed among buildings. Relationship between RH and NH3 emissions was positive, but the correlation coefficient (R2 = 0.67) was strongest in the building with the highest RH.publishedVersio