Overview and some issues related to co‐firing biomass and coal

Low heating values, variable chemical compositions, peculiar physical properties, high investment cost and insecurity of biomass feedstocks supply limit the applications of biomass for energy and other processes. Co‐firing biomass and coal has potential for the development of biomass‐to‐energy capacity with significant economic, environmental, and social benefits. However, co‐firing is not straightforward, and some questions need to be addressed due to the differences in chemical compositions and physical properties of biomass and coal. This paper highlights key issues related to co‐firing, including reactor types, feeding, hydrodynamics, ash sintering, fouling, and corrosion, based on previous studies, as well as calculations and analysis. Direct co‐firing is the most common option for biomass and coal co‐firing currently, mostly due to relatively low investment needed to turn existing coal power plants into co‐firing plants. For direct co‐firing, the physical characteristics and chemical compositions of the fuel entering the combustors or gasifiers are critical to an optimum operation. Any biomass mixed with coal needs to have acceptable physical properties. More research is needed on co‐firing biomass and coal, including work on: preparation, handling, storage, and feeding of biomass feedstocks (e.g. drying, torrefaction, pelletization); co‐firing mechanisms; hydrodynamic analysis of co‐firing combustors and gasifiers; boiler/gasifier capacity, slagging, fouling, corrosion, efficiency, reliability, fuel flexibility; lower emissions and gas cleaning; catalyst poisoning; investment and operating costs.     

Frictional testing of wood—Initial studies with a new device

In the chip refining process used for mechanical pulp production, wood fibers are treated in a narrow gap between rotating plates. The process is energy consuming and much of the electrical energy supplied to the refiner is transferred to the fiber material through friction forces. Even though the importance of friction has been discussed frequently, little has been proven due to the complexity of the process and the process conditions. This paper presents a new apparatus for studying the frictional properties of wood, in lab-scale, under conditions which are aimed at simulating those prevalent in a chip refiner. Tests can be performed in saturated steam at high temperature/pressure with sliding velocities as high as 150 m/s. Studies at room temperature showed that the friction coefficient between spruce wood and smooth steel increased with the moisture content of the specimens. Impregnation by wood extractives lowered the friction coefficient for dry wood sliding at high speed. When tests were performed in a saturated steam environment, the frictional properties were affected and varied by the temperature of the surroundings. This is interesting in view of the fact that the friction coefficient is usually considered constant in analytical and numerical models of the process.     

On the Outskirts of Physics: Eva von Bahr as an Outsider Within in Early 20th Century Swedish Experimental Physics

Abstract.   Eva von Bahr (1874–1962) got her doctorate in experimental physics at the Physics Institute at Uppsala University in 1908. Subsequently she became the first woman assistant professor in physics in Sweden. In the face of many obstacles, she worked as a physicist for six years in Uppsala and Berlin. In 1914 she took a position as a school teacher. This article explores von Bahr's trajectory through academic experimental physics. It is argued that network connections with male scientists enabled her work. Her associations were a mix between institutional relationships and informal connections, resulting in what is labeled a 'hybrid of connections'. Furthermore it is argued that von Bahr became an 'outsider within' in academic experimental physics. Her connections created openings, but these coexisted with hindrances. It is argued that von Bahr oscillated between being an insider and an outsider which created a fractured identity. Her position and identity was a mix between membership and non-membership. Through examining von Bahr's career this article aims to bring together historical research on women in science and theoretical work in science studies. Furthermore, the article argues the analytical value of feminist perspectives on scientific collaborations as a way to a deeper understanding of the network structures of science.     

A simple model for simulation of particle deaggregation of few‐particle aggregates

A proper mechanistic understanding of the deaggregation process of small colloidal particle aggregates is of generic importance within many fields of science and engineering. The methodology for modeling colloidal deaggregation is currently limited to analytical solutions in the two‐particle case and time consuming numerical algorithms, such as Brownian Dynamics (BD) simulations, for many‐particle aggregates. To address this issue, a simplified alternative model that describes deaggregation of few‐particle aggregates is presented. The model includes end‐particle deaggregation and a particle reconfiguration mechanism, which are the two most important mechanisms for deaggregation. Comparison of the calculated first passage time distribution for various two‐, three‐, four‐, and five‐particle aggregates with the corresponding result using BD simulations confirms the validity of the model. It is concluded that the dominating mechanism behind deaggregation can be quantified using a deaggregation number, which reflects the time scale for reconfiguration relative to the time scale for end‐particle deaggregation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1863–1869, 2014     

Influence of Plate Size on the Evaporation Rate of a Heated Droplet

The purpose of this study is to numerically investigate how the width of a plate influences natural convection around a droplet. Droplets evaporating on hot surfaces have many applications including drying of dishes and paint. Evaporation rate and deposition of particles withheld in the fluid are of great importance in both cases. As a first step to investigate how the drying rate and deposition mechanisms can be controlled, this work aims to investigate how the external flow around a water droplet influences the evaporation rate. Natural convection caused by the hot plate on which the droplet rests is considered and the effect of different widths is examined. Results show that an extension of the plate past the droplet will increase the maximum velocity in the domain due to natural convection while the flow close to the surface is decreased due to the no-slip condition and temperature gradient. A decrease of the evaporation rate is therefore observed when the plate is extended past the droplet as compared to the case when the plate and droplet have the same diameter. Simulations furthermore show that the results from the heat and mass transfer analogy only compare well to the results of Fick's law when the droplet and plate have the same width.     

A review of the tidal current energy resource in Norway

As interest in renewable energy sources is steadily on the rise, tidal current energy is receiving more and more attention from politicans, industrialists, and academics. In this article, the conditions for and potential of tidal currents as an energy resource in Norway are reviewed. There having been a relatively small amount of academic work published in this particular field, closely related topics such as the energy situation in Norway in general, the oceanography of the Norwegian coastline, and numerical models of tidal currents in Norwegian waters are also examined. Two published tidal energy resource assessments are reviewed and compared to a desktop study made specifically for this review based on available data in pilot books. The argument is made that tidal current energy ought to be an important option for Norway in terms of renewable energy.     

An environmental impact assessment of exported wood pellets from Canada to Europe

There have been increased interests on exporting wood pellets from Canada to Europe to meet the increased demand on biofuels in European countries. The wood pellet industry in Canada, especially in the west coastal region, has grown at an annual rate of more than 20% averaged over last 5 years due to the steady supply of wood residues. This paper attempted to analyze the fuel consumption and air emissions associated with the wood pellet production in British Columbia and export to Sweden based on a streamlined life cycle analysis, starting from tree harvesting for wood residue production to the shipping of wood pellets from Vancouver to Stockholm in Sweden. The results showed that about 7.2 GJ of energy is consumed for each tonne of wood pellets produced and shipped to Europe, representing about 39% of the total energy content of the wood pellets. Among those energies consumed over the life cycle, about 2.6 GJ is associated with long-distance ocean transportation. The ocean transportation is also the major contributor to environmental and health impacts, followed by the pellet production processes. The fossil fuel content, which quantifies the amount of fossil fuel consumed over the life cycle, for exported wood pellets ranged from 19% to 35%, depending on whether natural gas or wood residue is used in the drying operation during the wood pellet production stage. To reduce the fossil fuel content and the environmental impacts, wood residues should be used in the drying operation and, if possible, local market should be explored to reduce the energy consumption associated with wood pellet transportation over long distances.     

Lipoprotein composition and serum cholesterol ester fatty acids in nonwesternized melanesians

In this study, the relationships between dietary fat [as measured by serum cholesterol ester fatty acids (CE-FA)], age, smoking, body mass index, and serum lipids were analyzed in 151 subsistence horticulturalists, aged 20–86 yr, from Kitava, Trobriand Islands, Papua New Guinea. Their diet consists of tubers, fruit, coconut, fish, and vegetables with a negligible influence of western food and alcohol. Total fat intake is low [21% of energy (en%)], while saturated fat intake from coconuts is high (17 en%, mainly lauric and myristic acid). In multivariate analysis, 11–43% of the variation of the serum lipoprotein composition was explained by CE-FA, age, and smoking habits. The proportion of CE20∶5n-3 explained much of the variation of triglycerides (TG, negative relation) and high density lipoprotein-cholesterol (HDL-C, positive) in both sexes and serum apolipoprotein A1 (ApoA1, positive) in the males. CE16∶0 was positively related to TG and negatively related to HDL-C and ApoA1 in both sexes, and in males it related negatively to total cholesterol (TC) and low density lipoprotein-cholesterol (LDI-C). In males, negative relationships were present between CE18∶2n-6 and TC and between CE14∶0 and serum lipoprotein(a). Smoking was independently associated with lower ApoA1 in both sexes and with lower HDL-C and higher TG, TC, LDL-C, and apolipoprotein B in males. In conclusion, marine n-3 fatty acids and linoleic acid showed the same potentially beneficial relationships with lipoproteins and apolipoproteins as in western populations. The relations of palmitic acid to serum lipids may be explained in terms of endogenous fat synthesis at a low-fat intake, rather than reflecting its relative intake.     

Persistent complex subliminal activation effects: First experimental observations.

A strong recent focus on unconscious processes has increased interest in subliminal stimulation and other experimental activation technologies. Five experiments using male and female university students (N = 365) were carried out to compare 5-ms exposures of "mommy and I" stimuli with 5-ms control stimulation. Measures of self-mother similarity and other variables taken 7-14 days after exposure were more strongly correlated among experimental participants. Such complex, persistent effects may follow when powerfully activating stimuli administered under wholly unconscious conditions provokes schematic processing of social information and behavioral confirmation. These scientifically exciting and ethically problematic findings imply a need for further reduction of the role accorded to conscious volition and control in psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)