The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture

This study investigates the possibility of capturing CO₂ from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO₂ capture are presented. CO₂ is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO₂ capture penalty of approximately 8 percentage points (including 90% CO₂ capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO₂ capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.     

Preferred modes of travel among older adults: What factors affect the choice to walk instead of drive?

Introduction

There are many factors that influence older adults' travel choices. This paper explores the associations between mode of travel choice for a short trip and older adults' personal characteristics.

Methods

This study included 406 drivers over the age of 64 who were enrolled in a large integrated health plan in the United States between 1991 and 2001. Bivariate analyses and generalized linear modeling were used to examine associations between choosing to walk or drive and respondents' self-reported general health, physical and functional abilities, and confidence in walking and driving.

Results

Having more confidence in their ability to walk versus drive increased an older adult's likelihood of walking to make a short trip by about 20% (PR = 1.22; 95% CI: 1.06-1.40), and walking for exercise increased the likelihood by about 50% (PR = 1.53; 95% CI = 1.22-1.91). Reporting fair or poor health decreased the likelihood of walking, as did cutting down on the amount of driving due to a physical problem.

Discussion

Factors affecting a person's decision to walk for exercise may not be the same as those that influence their decision to walk as a mode of travel. It is important to understand the barriers to walking for exercise and walking for travel to develop strategies to help older adults meet both their exercise and mobility needs. Impact on Industry: Increasing walking over driving among older adults may require programs that increase confidence in walking and encourage walking for exercise.     

Implications of turnover and trust for safety attitudes and behaviour in work teams

Turnover potentially leads to a new individual being selected into a work team. This study investigated the safety-specific trust which team members place in their organisation’s selection and induction processes, and related this to the perceived risk from new employees. The research was conducted with teams working in forest harvesting, an occupation which has high-turnover, high risk and a high accident rate. Results indicate that trust in induction processes was negatively correlated with perceived risk from a new employee. Team members also engaged in a number of safety ensuring behaviours when a new individual joined the team, and these were related to the level of perceived risk, and how much they cared about their team members’ safety. It is argued that trust in the safety-specific characteristics of an organisation’s selection and induction process may have negative consequences for safety.     

A method for ranking components importance in presence of epistemic uncertainties

Importance Measures (IMs) are used to rank the contributions of components or basic events to the system performance, e.g. its reliability or risk. Most times, IMs are calculated without due account of the uncertainties in the model of the behavior of the system. The objective of this work is to investigate how uncertainties can influence IMs and to develop a method for giving them due account in the corresponding ranking of the components or basic events. The uncertainties considered in this work affect the model parameters values and are assumed to be described by probability density functions. The method for ranking the contributors to the system performance measure is applied to the auxiliary feedwater system of a nuclear pressurized water reactor.     

Organizational justice,voluntary learning behavior,and job performance: A test of the mediating effects of identification and leader‐member exchange

This paper presents and tests an integrative model of voluntary learning behavior. Drawing on social exchange theory, we argue that individuals are more likely to pursue learning activities when they identify with their employing organization and have a high quality leader–member exchange (LMX) relationship with their supervisor. We further argue that organizational identification is enhanced by both distributive and procedural fairness, whereas LMX quality is enhanced by interpersonal and informational fairness. Moreover, we contend that effective learning behavior improves job performance. The model was tested with a sample of 398 employees from a large automobile dealership. Results supported most predictions. Copyright © 2009 John Wiley & Sons, Ltd.     

What is most important for safety climate: The company belonging or the local working environment? – A study from the Norwegian offshore industry

Obtaining knowledge about factors affecting health, safety and environment (HSE) is of major interest to the petroleum industry, but there is currently a severe shortage of relevant studies. The aim of this study was to examine the relative influence of offshore installation (local working environment) and company belonging on employees’ opinions concerning occupational health and safety. We analyzed data from a safety climate survey answered by 4479 Norwegian offshore petroleum employees in 2005 on the dimensions “Safety prioritisation”, “Safety management and involvement”, “Safety versus production”, “Individual motivation”, “System comprehension” and “Competence” using one way analysis of variance (ANOVA), effect size and mixed model. The companies differed significantly for “Safety prioritisation”, “Safety versus production”, “Individual motivation”, “System comprehension” and “Competence”. The local offshore installation explained more of the safety climate than the company they were employed in or worked for did.     

Injury and loss concentration by sinkings in fishing fleets

Sinkings of fishing vessels, when accompanied by human loss, are accidents which lead to a great social upheaval, especially in the local area where they occur. In order to avoid or reduce these accidents, national governments must include in their legislation for this sector the appropriate safety measures. These resources and their distribution must be assigned in accordance with the needs of the accidentality, this requiring a detailed knowledge of the concentration of accidentality of a country’s fishing sector. In this context, the aim of the present work is twofold: first, to formulate a methodology for the fishing sector of a country, allowing the inequalities in the concentration of sinking accidents to be analysed; and second, to apply this methodology to the Spanish fishing fleet. Thus, two indices are constructed per region and type of fishing, for two variables: fishermen and vessels. Results are obtained both for the concentration of accidents and the associated Lorenz curves. An increase in the inequality in the spatial and functional distribution of these accidents is verified.     

The major accident risk (MAR) process - developing the profile of major accident risk for a large multi national oil company

The paper describes a programme to develop the profile of major accident risk across a large multi national oil company. It describes the concepts, tools and processes for constructing the risk profile and some of the key learnings from the exercise.