Particle model for simulating limestone reactions in novel fluidised bed energy applications

The development of carbon capture and storage (CCS) has raised interest towards novel fluidised bed (FB) energy applications. In these applications, limestone can be utilized for S02 and/or CO2 capture. The conditions in the new applications differ from the traditional atmospheric and pressurised circulating fluidised bed (CFB) combustion conditions in which the limestone is successfully used for SO2 capture. In this work, a detailed physical single particle model with a description of the mass and energy transfer inside the particle for limestone was developed. The novelty of this model was to take into account the simultaneous reactions, changing conditions, and the effect of advection. Especially, the capability to study the cyclic behaviour of limestone on both sides of the calcination-carbonation equilibrium curve is important in the novel conditions. The significances of including advection or assuming diffusion control were studied in calcination. Especially, the effect of advection in calcination reaction in the novel combustion atmosphere was shown. The model was tested against experimental data; sulphur capture was studied in a laboratory reactor in different fluidised bed conditions. Different Conversion levels and sulphation patterns were examined in different atmospheres for one limestone type. The Conversion curves were well predicted with the model, and the mechanisms leading to the Conversion patterns were explained with the model simulations. In this work, it was also evaluated whether the transient environment has an effect on the limestone behaviour compared to the averaged conditions and in which conditions the effect is the largest. The difference between the averaged and transient conditions was notable only in the conditions which were close to the calcination-carbonation equilibrium curve. The results of this study suggest that the development of a simplified particle model requires a proper understanding of physical and chemical processes taking place in the particle during the reactions. The results of the study will be required when analysing complex limestone reaction phenomena or when developing the description of limestone behaviour in comprehensive 3D process models. In order to transfer the experimental observations to furnace conditions, the relevant mechanisms that take place need to be understood before the important ones can be selected for 3D process model. This study revealed the sulphur capture behaviour under transient oxy-fuel conditions, which is important when the oxy-fuel CFB process and process model are developed.

Insiders´ views as a predictor of stock performance : can insider trading be used to predict stock performance on the United States stock market?

This thesis studies the possibility of using information on insiders’ transactions to forecast future stock returns after the implementation of Sarbanes Oxley Act in July 2003. Insider transactions between July 2003 and August 2009 are analysed with regression tests to identify the relationships between insiders’ transactions and future stock returns. This analysis is complemented with rudimentary bootstrapping procedures to verify the robustness of the findings. The underlying assumption of the thesis is that insiders constantly receive pieces of information that indicate future performance of the company. They may not be allowed to trade on large and tangible pieces of information but they can trade on accumulation of smaller, intangible pieces of information. Based on the analysis in the thesis insiders’ profits were found not to differ from the returns from broad stock index. However, their individual transactions were found to be linked to future stock returns. The initial model was found to be unstable but some of the predictive power could be sacrificed to achieve greater stability. Even after sacrificing some predictive power the relationship was significant enough to allow external investors to achieve abnormal profits after transaction costs and taxes. The thesis does not go into great detail about timing of transactions. Delay in publishing insiders’ transactions is not taken into account in the calculations and the closed windows are not studied in detail. The potential effects of these phenomena are looked into and they do not cause great changes in the findings. Additionally the remuneration policy of an insider or a company is not taken into account even though it most likely affects the trading patterns of insiders. Even with the limitations the findings offer promising opportunities for investors to improve their investment processes by incorporating additional information from insiders’ transaction into their decisions. The findings also raise questions on how insider trading should be regulated. Insiders achieve greater returns than other investors based on superior information. On the other hand, more efficient information transfer could warrant more lenient regulation. The fact that insiders’ returns are dominated by the large investment stake they maintain all the time in their own companies also speaks for more leniency. As Sarbanes Oxley Act considerably modified the insider trading landscape, this analysis provides information that has not been available before. The thesis also constitutes a thorough analysis of insider trading phenomenon which has previously been somewhat separated into several studies.

Kirjoituksia iäkkäiden ihmisten asumisesta

Kirjallisuusarvostelu

Tilaa mielekkäälle työlle

Kirsi LaPointen väitöskirja Moral struggles, subtle shifts : narrative practices of identity works in career transitions (Aalto-yliopiston kauppakorkeakoulu 2011).

Kohtaamisia terveydenhuollossa : tietämisen moninaiset haasteet

Kirjallisuusarvostelu

Sotapolitiikalle alistetut : Helsingin selviytymistarina

Kirjallisuusarvostelu

Monitoimialus Louhen käyttömahdollisuudet öljyntorjuntatehtävässä

Kasvanut alusliikenne on lisännyt tarvetta tehokkaaseen öljyntorjuntakykyyn Suomenlahden rikkonaisella rannikolla. Avomerellä tarvitaan itsenäiseen öljynkeruuseen kykeneviä aluksia, jotka voivat ryhtyä torjuntaan heti alueelle saavuttuaan torjuntatöiden johdon alaisuudessa. Suomen öljyntorjuntavalmiuden ongelmakohtia ovat öljynkeräys jääolosuhteissa, kovassa merenkäynnissä ja näkyvyyden ollessa huono. Tässä tutkimuksessa selvitetään miten monitoimialus Louhi kykenee vastaamaan öljyntorjuntamenetelmillään ja -tehtävillään Suomen ympäristökeskuksen ja muiden öljyntorjuntaa määrittävien järjestöjen suosituksiin ja vaatimuksiin omassa toimintaympäristössään. Tutkimuksen pääkysymys on: mitkä ovat monitoimialus Louhen käyttömahdollisuudet öljyntorjuntatehtävässä? Alakysymykset: minkälainen on monitoimialus Louhen toimintaympäristö? Minkälainen kalusto ja öljyntorjuntakyky aluksella on? Miten alusta voidaan käyttää öljyntorjuntatehtävässä eri sääolosuhteissa? Tutkimusmenetelmänä on asiakirja-analyysi. Tutkimusaineistona ovat olleet valmiit dokumentit ja asiantuntijahaastattelut. Kirjallisuusaineisto koostuu ympäristövahinkojen torjunnan kansainvälisistä sopimuksista, kansallisesta ja kansainvälisestä lainsäädännöstä, artikkeleista, tutkimuksista ja raporteista. Tärkeimpinä lähteinä ovat olleet Suomen ympäristökeskuksen raportit, manuaalit ja ohjeet sekä asiantuntijoiden antamat haastattelut. Tutkimustuloksista selviää monitoimialus Louhen hyvät valmiudet toimia öljyntorjuntatehtävissä eri rooleissa vaikeissakin olosuhteissa. Haasteeksi muodostuu todellinen öljynkeräyskyky, jota on vaikeaa arvioida, sillä siihen vaikuttavia tekijöitä on paljon. Yksi tärkeimmistä tutkimustuloksista on, ettei alukselle ole asetettu suorituskykyvaatimuksia, jotka määrittäisivät, kuinka paljon aluksen tulisi kyetä keräämään öljyä erilaisissa sääolosuhteissa. Louhella on hyvä liikkeellelähtökyky ollessaan päivystysvuorossa, joskaan se ei täytä Helsingin komission (Helsinki Commission, HELCOM) suosituksia kahden tunnin lähtövalmiudesta.