Towards the improvement of thermal efficiency in lignite‐fired power generation: Concerning the utilization of Polish lignite deposits in state‐of‐the‐art IGCC technology

Integrated coal Gasification Combined Cycle (IGCC) is the most advanced technology for coal‐fired power generation. The two‐stage entrained flow gasification process allows for the use of a wide range of coal, as long as the gasification temperature is above the ash melting point of a used fuel. In this gasification technology, lignite, which often has a low ash melting point, can be preferably utilized. However, ash fluidity is also another importance, because the behaviour of molten slag can diminish a stable ash discharge from a gasifier. As the eligibility of coal ash properties is a considerable factor, water physically and chemically kept in lignite (30 – 60% in mass) attributes to deteriorating gasification efficiency, because it causes significant heat loss and increasing oxygen consumption. Developing a thermal evaporative lignite drying method will be a necessary attempt to apply lignite to the coal gasification process. For those preceded objectives, coal and ash properties and drying characteristics of several grades of Polish lignite, extracted from Belchatow and Turow deposits, have been experimentally investigated in a preliminary study evaluating the applicability and consideration for its utilization in state‐of‐the‐art clean coal technology, IGCC. This paper particularly discusses the eligibility of Polish lignite from the perspective of the fusibility and fluidity of ash melts and the fundamental drying kinetics of lignite in superheated steam in the light of water removal. The viscosity of ash melts is measured at high temperature up to 1700 °C. In the drying tests, the significant influence of structural issues, because of the provenance and origin of lignite on the drying characteristics, was found by applying the method of sensitivity analysis of physical propensity. This paper concludes that the investigated Polish lignite has characteristics favourable for utilization in IGCC technology, once the precautions related to its high moisture have been carefully addressed. Copyright © 2016 John Wiley & Sons, Ltd.     

Life cycle assessment of fuels for district heating: A comparison of waste incineration,biomass- and natural gas combustion

The aim of this consequential life cycle assessment (LCA) is to compare district heating based on waste incineration with combustion of biomass or natural gas. The study comprises two options for energy recovery (combined heat and power (CHP) or heat only), two alternatives for external, marginal electricity generation (fossil lean or intense), and two alternatives for the alternative waste management (landfill disposal or material recovery). A secondary objective was to test a combination of dynamic energy system modelling and LCA by combining the concept of complex marginal electricity production in a static, environmental systems analysis. Furthermore, we wanted to increase the methodological knowledge about how waste can be environmentally compared to other fuels in district-heat production. The results indicate that combustion of biofuel in a CHP is environmentally favourable and robust with respect to the avoided type of electricity and waste management. Waste incineration is often (but not always) the preferable choice when incineration substitutes landfill disposal of waste. It is however, never the best choice (and often the worst) when incineration substitutes recycling. A natural gas fired CHP is an alternative of interest if marginal electricity has a high fossil content. However, if the marginal electricity is mainly based on non-fossil sources, natural gas is in general worse than biofuels.     

On the hydration of grain boundaries and bulk of proton conducting BaZr0.7Pr0.2Y0.1O3-δ

We report here for the first time bulk and grain boundary conductivities from impedance spectra of a ceramic proton conductor (BaZr_0.7Pr_0.2Y_0.1O_3-δ) taken during hydration and H/D isotope exchange transients (at 400 °C). The results suggest that water moves quickly along grain boundary cores, and then interact from there with the space charge layers and, in turn, grain interiors. Hydration and H/D isotope exchange have simple monotonic effects on the bulk conductivity in line with what is expected from it being dominated by protons. The transients for grain boundary conductivity exhibit however hysteresis: During hydration, the core charge and grain boundary resistance appear to go through transient minima related to non-equilibrium distributions of defects between the core and grain interior – notably because protons diffuse faster than oxygen vacancies between the grain boundary and grain interior. At equilibrium, hydration increases the core charge and the depletion of positive charge carriers in the space charge layers. During H/D isotope exchange relatively fast hysteretic transients indicate that the space charge layers experience changes in charge carrier (D⁺ vs. H⁺) mobility as well as in D₂O vs. H₂O hydration thermodynamics.     

Biofuel developments in Mozambique. Update and analysis of policy,potential and reality

Climate change, rising oil prices and concerns about future energy supplies have contributed to a growing interest in using biomass for energy purposes. Several studies have highlighted the biophysical potential of biofuel production on the African continent, and analysts see Mozambique as one of the most promising African countries. Favorable growing conditions and the availability of land, water and labor are mentioned as major drivers behind this potential. Moreover, the potential of biofuel production to generate socio-economic benefits is reflected in the government’s policy objectives for the development of the sector, such as reducing fuel import dependency and creating rural employment. This article provides an overview of biofuel developments in Mozambique and explores to what extent reality matches the suggested potential in the country.     

Improved photon management in a photoelectrochemical cell with Nd-modified TiO2 thin film photoanode

Photon management involving particularly an up-conversion process is proposed as a relatively novel strategy for improving the efficiency of hydrogen generation in photoelectrochemical cells (PEC) with wide-band gap photoanodes. Optically active photoanode has been constructed by electrodeposition of titanium dioxide nanopowders containing Nd³⁺ ions, synthesized via a sol-gel method, onto ITO/TiO₂(thin film) substrates. Thin films of TiO₂ have been deposited by means of RF magnetron sputtering in an ultra-high-vacuum system. X-ray diffraction, scanning electron microscopy, UV-VIS-NIR spectrophotometry, and photoluminescence have been applied to assess the properties of photoanodes. In experiments involving photon-assisted water splitting, an external up-converter containing Yb³⁺/Er³⁺ rare-earth ions has been used. Photocurrent as a function of voltage (V_B) under illumination with white light is relatively high (280 μA at V_B = 0 V) for pure TiO₂ thin films and it is not affected by the electrodeposition of TiO₂:Nd³⁺ powders. NIR-driven up-conversion with laser excitation at λ = 980 nm has been found responsible for a 13-fold increase in photocurrent at V_B = 0 V in the modified PEC configuration.     

Energy saving in existing buildings by an intelligent use of interoperable ICTs

In this paper, we report a methodology, developed in the context of Smart Energy Efficient Middleware for Public Spaces European Project, aimed at exploiting ICT monitoring and control services to reduce energy usage and CO₂ footprint in existing buildings. The approach does not require significant construction work as it is based on commercial-off-the-shelf devices and, where present, it exploits and integrates existing building management systems with new sensors and actuator networks. To make this possible, the proposed approach leverages upon the following main contributions: (a) to develop an integrated building automation and control system, (b) to implement a middleware for the energy-efficient buildings domain, (c) to provide a multi-dimensional building information modelling-based visualisation, and (d) to raise people’s awareness about energy efficiency. The research approach adopted in the project started with the selection, as case studies, of representative test and reference rooms in modern and historical buildings chosen for having different requirements and constraints in term of sensing and control technologies. Then, according to the features of the selected rooms, the strategies to reduce the energy consumptions were defined, taking into account the potential savings related to lighting, heating, ventilation, and air conditioning (HVAC) systems and other device loads (PC, printers, etc.). The strategies include both the control of building services and devices and the monitoring of environmental conditions and energy consumption. In the paper, the energy savings estimated through simulation, for both HVAC and lighting, are presented to highlight the potential of the designed system. After the implementation of the system in the demonstrator, results will be compared with the monitored data.     

Assessment of layered La2-x(Sr,Ba)xCuO4-δ oxides as potential cathode materials for SOFCs

In this paper, selected layered cuprates with La_2-x(Sr,Ba)_xCuO_4-δ formula are evaluated as candidate cathode materials for Solid Oxide Fuel Cells. Two synthesis routes, a typical solid state reaction and a sol-gel method yield well-crystallized La_1.5Sr_0.5CuO_4-δ, La_1.6Ba_0.4CuO_4-δ and La_1.5Sr_0.3Ba_0.2CuO_4-δ materials having tetragonal I4/mmm space group, but differing in morphology of the powder. Fine powders obtained using sol-gel route seem to be more suitable for preparation of the porous cathode layers having good adhesion on the solid electrolyte, but powders obtained after the solid state route can be also successfully utilized. Investigations of structural and transport properties, the oxygen nonstoichiometry and its change with temperature, thermal expansion, as well as chemical and thermal stability are systematically performed, to evaluate and compare basic physicochemical properties of the oxides. At room temperature the average valence state of copper is found to be in 2.2–2.35 range, indicating oxygen deficiency in all of the compounds, which further increases with temperature. The conducted high-temperature X-ray diffraction tests reveal moderate, but anisotropic thermal expansion of La_2-x(Sr,Ba)_xCuO_4-δ, with higher expansion at temperatures above 400 °C occurring along a-axis, due to the oxygen release. However, the corresponding chemical expansion effect is small and the materials possess moderate thermal expansion in the whole studied temperature range. All compounds show relatively high electrical conductivity at the elevated temperatures, related to the Cu²⁺/Cu³⁺ charge transfer, with the highest values recorded for La_1.5Sr_0.5CuO_4-δ. Comprehensive studies of chemical stability of the selected La_1.5Sr_0.5CuO_4-δ material with La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ solid electrolyte revealed complex behavior, with stability being dependent apart from temperature, also on morphology of the powders. A model describing such behavior is presented. While it is possible to minimize reactivity and characterize electrochemical properties of the La_1.5Sr_0.5CuO_4-δ-based cathode layer, usage of the buffer layer is indispensable to maintain full stability. It is shown that mutual chemical compatibility of La_1.5Sr_0.5CuO_4-δ and commonly used La_0.4Ce_0.6O_2-δ buffer layer material is excellent, with no reactivity even at 1000 °C for prolonged time. Laboratory-scale fuel cell with the La_1.5Sr_0.5CuO_4-δ cathode sintered at the optimized temperature is able to deliver 0.16 W cm^?2 at 800 °C while fueled with wet hydrogen.     

Effect of processing on the amino acid content of New Zealand spinach (Tetragonia tetragonioides Pall. Kuntze)

The aim of this work was to evaluate the effect of processing on the amino acid content and protein quality of New Zealand spinach (Tetragonia tetragonioides Pall. Kuntze). In this research, fresh and cooked New Zealand spinach as well as two frozen products prepared for consumption, one obtained using the traditional method (blanching–freezing–storage–cooking) and the other a convenience food product obtained using a modified process (cooking–freezing–storage–defrosting and heating in a microwave oven), were analysed. Glutamic acid was the dominant amino acid in fresh New Zealand spinach, and the limiting amino acids were cystine and methionine. Technological and culinary processing caused a significant increase in amino acid content in 100 g of edible portion, with the exception of methionine and cystine in frozen products prepared for eating. Changes in amino acid content expressed in g/16 g of N (which corresponded to 100 g tissue protein) were not significant, with the exception of the lower glutamic acid content in the frozen product obtained using traditional processing method.     

Characterisation of Aronia powders obtained by different drying processes

Nowadays, food industry is facing challenges connected with the preservation of the highest possible quality of fruit products obtained after processing. Attention has been drawn to Aronia fruits due to numerous health promoting properties of their products. However, processing of Aronia, like other berries, leads to difficulties that stem from the preparation process, as well as changes in the composition of bioactive compounds. Consequently, in this study, Aronia commercial juice was subjected to different drying techniques: spray drying, freeze drying and vacuum drying with the temperature range of 40–80 °C. All powders obtained had a high content of total polyphenols. Powders gained by spray drying had the highest values which corresponded to a high content of total flavonoids, total monomeric anthocyanins, cyaniding-3-glucoside and total proanthocyanidins. Analysis of the results exhibited a correlation between selected bioactive compounds and their antioxidant capacity. In conclusion, drying techniques have an impact on selected quality parameters, and different drying techniques cause changes in the content of bioactives analysed. Spray drying can be recommended for preservation of bioactives in Aronia products. Powder quality depends mainly on the process applied and parameters chosen. Therefore, Aronia powders production should be adapted to the requirements and design of the final product.