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Helsinki, Finland

Kymalainen M.,University of Helsinki | Makela M.R.,University of Helsinki | Hilden K.,University of Helsinki | Kukkonen J.,Helsingin Energia
European Journal of Wood and Wood Products

Storage is a challenging stage in the supply chain of any solid biofuel, as they readily absorb moisture. Increased moisture content (MC) bears many negative consequences, such as biological degradation, reduced heating value and worker health problems. A five-month storage trial served to determine how certain properties of torrefied wood, charcoal and thermally treated pellets change when exposed to natural weathering in a covered and uncovered storage area. Biological degradation and changes in MC and composition were recorded. The pellets also underwent a durability test. Different fungi were isolated from the stored samples and the genus of selected isolates was identified with internal transcribed spacer polymerase chain reaction. Significant changes were detected in the carbon content of the wood material following the trial. The samples in the uncovered storage area had absorbed substantial amounts of water and, after incubation, 99 % of these samples showed visible fungal growth, compared to only 20 % of the covered samples. The pellets showed varying responses to storage in terms of durability and moisture absorption, with the steam explosion pellets possessing more favourable properties than torrefied and untreated pellets. © 2015, Springer-Verlag Berlin Heidelberg. Source

Sipila J.,Helsingin Energia | Auerkari P.,VTT Technical Research Center of Finland | Heikkila A.-M.,VTT Technical Research Center of Finland | Krause U.,Otto Von Guericke University of Magdeburg
Journal of Risk Research

The risk and prevention of autoignition in underground coal storage facilities are reviewed in the light of the recent incidents of smouldering fires. Also, the opportunities are considered on the efficiency of the alternatives to prevent and extinguish closed-space fires. The complexities in avoiding and extinguishing underground fires are highlighted in the case example, describing the observations and outcome of a smouldering coal fire in the storage. The principles of self-heating and most critical factors in spontaneous combustion such as the condition and quality of coal are fairly well known, but usually only provide partial help in fire prevention. The documented cases and the case example suggest that nitrogen injection can be useful for extinguishing controllable fires. Three-phase foams and oxygen-displacing exhaust gases appear preferable against uncontrolled fires, particularly if access to the fire area is limited or impossible. Otherwise, efficient fire extinction during power plant operation can be challenging, as any air ingress tends to feed the fire and results in losses of the extinguishing agent and the heating value of coal. Methods and indicators for detecting and predicting the ignition are discussed, and improvements are suggested to enhance the storage and plant availability. © 2013 Taylor and Francis Group, LLC. Source

Sipila J.,Helsingin Energia | Auerkari P.,VTT Technical Research Center of Finland | Holmstrom S.,Joint Research Center Petten | Vela I.,BAM Federal Institute of Materials Research and Testing
Risk Analysis

Early warning or leading indicators are discussed for unexpected incidences in case of large-scale underground coal storage at a power plant. The experience is compared with above-ground stockpiles for which established procedures are available but where access for prevention and mitigation are much easier. It is suggested that while the explicit organization, procedures, and the general safety systems aim to provide the targeted levels of performance for the storage, representing new technology without much precedence elsewhere in the world, the extensive experience and tacit knowledge from above-ground open and closed storage systems can help to prepare for and to prevent unwanted incidents in the underground storage. This kind of experience has been also found useful for developing the leading or early warning indicators for underground storage. Examples are given on observed autoignition and freezing of coal in the storage silos, and on occupational hazards. Selection of the leading indicators needs to consider the specific features of the unique underground facility. © 2014 Society for Risk Analysis. Source

Santasalo-Aarnio A.,Aalto University | Lokkiluoto A.,Helsingin Energia | Virtanen J.,Aalto University | Gasik M.M.,Aalto University
Journal of Power Sources

One of the largest obstacles for SO2 depolarized electrolyser (SDE) commercialization is the material stability in rough operating conditions. In this work stainless steel bipolar plates have been coated with thin Au layer having bifunctional role: providing electrocatalytic surface for both electrode reactions and simultaneously improves the stainless steel support corrosion tolerance at the potential window of SDE. The stability and performance of the coated bipolar plates were tested in a bench-scale electrolyser set-up and the results indicate that these plates can be utilized as economic catalyst for SDE, moreover, they show corrosion resistance in SDE operation. © 2015 Elsevier B.V. Source

Korpinen L.,Tampere University of Technology | Kuisti H.,Fingrid Oyj | Paakkonen R.,Finnish Institute of Occupational Health | Vanhala P.,Helsingin Energia | Elovaara J.,Fingrid Oyj
Annals of Occupational Hygiene

The aim of the study was to measure occupational exposure to electric and magnetic fields during various work tasks at switching and transforming stations of 110 kV (in some situations 20 kV), and analyze if the action values of European Union Directive 2004/40/EC or reference values of International Commission on Non-ionizing Radiation Protection (ICNIRP) were exceeded. The electric (n = 765) and magnetic (n = 203) fields were measured during various work tasks. The average values of all measurements were 3.6 kV m -1 and 28.6 μT. The maximum value of electric fields was 15.5 kV m -1 at task 'maintenance of operating device of circuit breaker from service platform'. In one special work task close to shunt reactor cables (20 kV), the highest magnetic field was 710 μT. In general, the measured magnetic fields were below the reference values of ICNIRP. © 2011 The Author. Source

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