Evaluation of bed-to-tube heat transfer in a fluidized bed heat exchanger in a 75 MWth CFB boiler for municipal solid waste fuels

Bed-to-tube heat transfer has been investigated for a tertiary superheater in a 75 MWth Circulating Fluidized Bed (CFB) boiler in Norrk\uf6ping, Sweden. The boiler is used for incineration of solid waste fuels. Two fluidized bed heat exchangers are located in loop seals, connecting the cyclones and the furnace. The heat exchangers are placed in series, with respect to the steam side, and in parallel, with respect to the particle side. The total heat transfer surface area is roughly 44 m2, distributed over 72 tubes. The total effect transferred most often is in the range 2–6 MW. The incoming steam temperature in the first superheater is 380–400 \ub0C, while the exiting steam temperature from the second is around 450\ub0, at 65 bar pressure. The bed temperature in the Fluidized Bed Heat Exchanger (FBHE) is 850–875 \ub0C. The analysis is based on operational data from two time periods (2002–2005 and 2014–2021). The two periods use different heat exchanger designs, following a retrofit in 2005. The aim of the study is to establish the bed-to-tube heat transfer coefficient in an industrial FBHE unit and investigate how it varies over different time periods, for two different bed materials and for two different designs. Also, the experimentally determined heat transfer coefficients are compared with an established heat-transfer correlation, for prediction of heat transfer from bubbling fluidized bed to tubes. Operation with two bed materials were evaluated, namely silica sand and crushed and beneficiated ilmenite. Both materials are classified as Geldart B particles. Air is used as fluidization gas in the FBHE. The analysis show, with a few exceptions, comparably low heat-transfer coefficients from bed to tube of 100–150 W/(m2K). The results were similar for silica sand and ilmenite, but the highest measured heat transfer coefficient was for a period with ilmenite. The heat transfer was lower than expected based on literature data from FBHE units and fluidized bed boilers in general, and much lower than bed-to-tube heat transfer coefficients from lab-scale experiments and empirically derived predictive expressions. The difference could be related to one or more of several factors, such as the effect of very small tube spacing, unknown thermal conductivity of one of the layers in the tube bundle, the effect of lateral particle flow and the effect of fouling due to ash layers forming on the tube surfaces. It is suggested that it should be possible to significantly increase the bed-to-tube heat transfer by increasing the tube pitch, which is expected to improve bed mixing without increasing the risk of corrosion

The nitty gritty of life cycle management: Exploring the organization of LCM

Climate change and environmental degradation threaten to cause serious effects on the planet and on society. Scientists thus advocate an urgent shift towards a more sustainable development. Herein, industry is said to play a vital role, as it could positively influence sustainable production and consumption. In this, life cycle management (LCM) is suggested as a possible approach towards corporate management of environmental impacts, as it implies holistic environmental management along the whole product life cycle, from raw material extraction through to product end-of-life.Studies of the management and organization of LCM in industry practice are scarce, resulting in a need to study this practice in the setting of multinational corporations (MNCs). The aim of this dissertation is thus to explore the ‘nitty gritty’ details of organizing LCM; focusing on the 1) initiatives and activities of LCM, their scope of inclusion, how these develop over time, 2) the role of actors in performing and forming these practices, and 3) the activities of these practitioners.Studies both in the field (i.e. industry practice) and of literature have been conducted, resulting in five papers (Papers I-V). One group of papers target LCM as it is practiced in one MNC (Paper I-III), by focusing on contemporary practice (Paper I), the LCM development over time (Paper II), and in the context of a product chain collaboration (Paper III). Another group of papers (Papers IV-V) takes a broader perspective on LCM throughout industry and society, focusing explicitly on the practitioners of LCM and their activities (Paper IV), and the different types of LCM that exist (Paper V).The results show the assiduous efforts of life cycle (LC) practitioners in integrating, adapting and promoting LCM in their organizations, and their importance in bridging discussions in a practice of creative problem-solving, through a process best understood as translation. Adaptation depended much on possible activities, rather than on rational choice for implementation. In this, LCM was made relevant by being connected to existing corporate logics and practices, in turn facilitating the uptake of LCM. The results concretize the many practices of LCM and provide a collected and enriched LCM vocabulary, thereby generating a better understanding of developing industry LCM practice

Oxygen Carrier Aided Combustion in Fluidized Bed Boilers in Sweden - Review and Future Outlook with Respect to Affordable Bed Materials

Oxygen carriers are metal oxide particles that could potentially enhance both fuel conversion and heat distribution in fluidized bed combustion, resulting in e.g., lowered emissions of unconverted species and better possibilities to utilize low‐grade fuels. A related technology based on fluidized beds with oxygen carriers can separate CO2 without large energy penalties. These technologies are called oxygen carrier aided combustion (OCAC) and chemical‐looping combustion (CLC), respectively. In the past few years, a large number of oxygen carriers have been suggested and evaluated for these purposes, many of which require complex production processes making them costly. Affordable metal oxide particles are, however, produced in large quantities as products and byproducts in the metallurgical industries. Some of these materials have properties making them potentially suitable to use as oxygen carriers. Uniquely for Sweden, the use of oxygen carriers in combustion have been subject to commercialization. This paper reviews results from utilizing low‐cost materials emerging from metallurgical industries for conversion of biomass and waste in semi‐commercial and commercial fluidized bed boilers in Sweden. The paper further goes on to discuss practical aspect of utilizing oxygen carriers, such as production and transport within the unique conditions in Sweden, where biomass and waste combustion as well as metallurgical industries are of large scale. This study concludes that utilizing metal oxides in this way could be technically feasible and beneficial to both the boiler owners and the metallurgical industries

LCM development: Focusing on the LC promoters and their organizational problem-solving

Purpose:\ua0Life cycle management (LCM) implies a specific sustainability perspective which extends environmental managementalong the product life cycle, with the aim of decreasing negative environmental impact throughout the product chain. Researchhas identified that the adoption of LCMin the industry depends upon its situational adaptation to the organizational context. Evenso, little is known about the specifics of this adaptation. With this paper, our aim is to add knowledge on LCM adoption andadaptation.Methods: A systematic analysis of empirical material on life cycle (LC) activity in six multinational corporations (MNCs) isconducted, by applying a secondary analysis of qualitative data (Heaton 2008). In order to study instances of LCM adoption andadaptation, we focus on the acts and situations of LC promoters. The identified instances are analyzed through the lens of situatedproblem-solving (Kuhn and Jackson 2008).Results and discussion: Sixty-seven instances of LC promotion were identified and analyzed, resulting in the identification ofeight categories of problem-situations typically encountered by LC promoters. The identified problem-situations representdifferent situations when the organizational appropriateness of the LC approach is at stake and to which responses tailored tothe organization are put forward by a LC promoter. The results bring to the fore the ubiquity of organizational and creativeproblem-solving, highlighting the role of LC promoters as change agents for LCMadoption, and depict the development of LCMas an emergent practice, rather than an implementation process.Conclusions: This paper provides a first systematic analysis of LC promoters enacting a variety of responses to organizationallychallenging LC situations, thus detailing the adaptation necessary for embedding LCM in the industry. Findings show that thedevelopment of LCM to a great extent is about the promotion of a LC approach, and that LC promoters need organizationalknowing, in addition to LC knowing, to make the LC approach relevant to management and business

Oxygen Carrier Aided Combustion (OCAC) of Wood Chips in a 12 MWth Circulating Fluidized Bed Boiler Using Steel Converter Slag as Bed Material

The novel combustion concept Oxygen Carrier Aided Combustion (OCAC) is realized by addition of an active oxygen-carrying bed material to conventional fluidized bed boilers. The active bed material is meant to become reduced in fuel-rich parts of the boiler and oxidized in oxygen-rich parts, thus potentially providing advantages such as new mechanisms for oxygen transport in space and time. In this study, oxygen-carrier particles prepared from so called Linz-Donawitz (LD)-slag are examined as active bed material in a 12 MWth Circulating Fluidized Bed (CFB) boiler. LD-slag is the second largest by-product in steel making and is generated in the basic LD oxygen converter process. The experimental campaign lasted for two full weeks. The fuel was wood chips. LD-slag worked well from an operational point of view and no problems related to handling, agglomeration or sintering were experienced, albeit the production of fly ash increased. The boiler temperature profile suggested that fuel conversion in the main boiler body was facilitated, but the effect did not readily translate into reduced emissions from the stack. Spraying an aqueous solution of ammonium sulphate directly into the cyclone outlet with the aim of rejecting alkali metals as alkali suphates was found to solve the problems related to carbon monoxide emissions, suggesting that the problems could be due to the poor ability of LD-slag to absorb certain ash components. Use of a mixed bed consisting of 10-50 wt% LD-slag, with the remaining part being silica sand for ash absorption, also worked well. It is concluded that LD-slag could be a very cheap and readily available oxygen-carrying bed material for use in fluidized bed applications

Real‐time and offline evaluation of myoelectric pattern recognition for the decoding of hand movements

Pattern recognition algorithms have been widely used to map surface electromyographic signals to target movements as a source for prosthetic control. However, most investigations have been conducted offline by performing the analysis on pre‐recorded datasets. While real‐time data analysis (i.e., classification when new data becomes available, with limits on latency under 200–300 milliseconds) plays an important role in the control of prosthetics, less knowledge has been gained with respect to real‐time performance. Recent literature has underscored the differences between offline classification accuracy, the most common performance metric, and the usability of upper limb prostheses. Therefore, a comparative offline and real‐time performance analysis between common algorithms had yet to be performed. In this study, we investigated the offline and real‐time performance of nine different classification algorithms, decoding ten individual hand and wrist movements. Surface myoelectric signals were recorded from fifteen able‐bodied subjects while performing the ten movements. The offline decoding demonstrated that linear discriminant analysis (LDA) and maximum likelihood estimation (MLE) significantly (p < 0.05) outperformed other clas-sifiers, with an average classification accuracy of above 97%. On the other hand, the real‐time investigation revealed that, in addition to the LDA and MLE, multilayer perceptron also outperformed the other algorithms and achieved a classification accuracy and completion rate of above 68% and 69%, respectively

On-to-off-path gaze shift cancellations lead to gaze concentration in cognitively loaded car drivers: A simulator study exploring gaze patterns in relation to a cognitive task and the traffic environment

Appropriate visual behaviour is necessary for safe driving. Many previous studies have found that when performing non-visual cognitive tasks, drivers typically display an increased amount of on-path glances, along with a deteriorated visual scanning pattern towards potential hazards at locations outside their future travel path (off-path locations). This is often referred to as a gaze concentration effect. However, what has not been explored is more precisely how and when gaze concentration arises in relation to the cognitive task, and to what extent the timing of glances towards traffic-situation relevant off-path locations is affected. To investigate these specific topics, a driving simulator study was carried out. Car drivers’ visual behaviour during execution of a cognitive task (n-back) was studied during two traffic scenarios; one when driving through an intersection and one when passing a hidden exit. Aside from the expected gaze concentration effect, several novel findings that may explain this effect were observed. It was found that gaze shifts from an on-path to an off-path location were inhibited during increased cognitive load. However, gaze shifts in the other direction, that is, from an off-path to an on-path location, remained unaffected. This resulted in on-path glances increasing in duration, while off-path glances decreased in number. Furthermore, the inhibited off-path glances were typically not compensated for later. That is, off-path glances were cancelled, not delayed. This was the case both in relation to the cognitive task (near-term) and the traffic environment (far-term). There was thus a general reduction in the number of glances towards situationally relevant off-path locations, but the timing of the remaining glances was unaffected. These findings provide a deeper understanding of the mechanism behind gaze concentration and can contribute to both understanding and prediction of safety relevant effects of cognitive load in car drivers

Systemic galectin-3 in smokers with chronic obstructive pulmonary disease and chronic bronchitis: The impact of exacerbations

Purpose: The carbohydrate-binding protein Galectin-3 is increased in several inflammatory diseases and has recently been forwarded as a systemic biomarker in chronic obstructive pulmonary disease (COPD). In this longitudinal study, we characterized the level of systemic Galectin-3 using blood from smokers with a history of COPD and chronic bronchitis (COPD-CB), during stable clinical conditions and exacerbations. Patients and Methods: The study population comprised 56 long-term smokers with COPD-CB, 10 long-term smokers without lung disease (LTS) and 10 clinically healthy never-smokers (HNS). Blood samples were analyzed for levels of Galectin-3, leukocyte populations and C-reactive protein (CRP). In addition, sputum samples from the COPD-CB group were analyzed for bacterial growth. Results: When comparing stable clinical conditions and exacerbations in the COPD-CB group, we found that the level of Galectin-3, just like that of CRP, leukocytes and neutrophils, respectively, was increased during exacerbations. However, this exacerbation-associated increase of Galectin-3 was modest. During stable clinical conditions of COPD-CB, the level of Galectin-3 was not elevated in comparison with HNS or LTS. Nor did this level of Galectin-3 distinguish patients that remained in a clinically stable condition throughout the study to those that developed an exacerbation. In addition, neither during stable clinical conditions nor during exacerbations, did the presence of bacterial growth in sputum alter Galectin-3 levels. In contrast to Galectin-3, the level of CRP, leukocytes and neutrophils, respectively, were increased during clinical stable conditions in the COPD-CB group compared with the other groups and were further enhanced during exacerbations. Conclusion: Systemic Galectin-3 is increased in a reproducible but modest manner during exacerbations in smokers with COPD-CB. During stable clinical conditions, the level of systemic Galectin-3 does not distinguish patients that remain clinically stable from those that develop exacerbations. This makes it less likely that systemic Galectin-3 may become a clinically useful biomarker in the current setting

A Scale-Up Project for Operating a 115 MWth Biomass-Fired CFB boiler with Oxygen Carriers as Bed Material

Oxygen Carrier Aided Combustion (OCAC) is a concept that uses an oxygen-active bed material to increase the overall efficiency in fluidized bed (FB) combustors. The introduction of oxygen carriers (OCs) in existing FB plants is an attractive opportunity to investigate OCs under industrially-relevant conditions at a low economic risk. In this way, important experience and knowledge of the physiochemical properties of OCs can be gained during long-term operation, which in turn can be used for the scale-up of oxygen-looping techniques, e.g. chemical-looping combustion. The overall aim of this experimental study was to investigate, develop and collect data to increase the knowledge of how OCs can be deployed in commercial FB boilers, while at the same time granting the plant operator benefits from an increased revenue. This paper summarizes the first results from an experimental campaign performed during three weeks of OCAC operation in a 115 MWth commercial CFB boiler, which is fired with a mix of recycled waste-wood and wood chips. During the campaign, the silica-sand bed material was gradually replaced by the mineral ilmenite. It was shown that ilmenite operation, in comparison to operation with silica-sand, facilitated a reduction in the air surplus by as much as 30 %, while increasing the boiler load from 115 MWth to 123 MWth. During ilmenite operation no problems related to the external or internal bed-material logistics nor in the overall boiler operation. However, during ilmenite operation slightly higher emissions of NOx and consumption of ammonia were detected in comparison to operation with silica-sand

Association of MC1R Variants and host phenotypes with melanoma risk in CDKN2A mutation carriers: a GenoMEL study

<p><b>Background</b> Carrying the cyclin-dependent kinase inhibitor 2A (CDKN2A) germline mutations is associated with a high risk for melanoma. Penetrance of CDKN2A mutations is modified by pigmentation characteristics, nevus phenotypes, and some variants of the melanocortin-1 receptor gene (MC1R), which is known to have a role in the pigmentation process. However, investigation of the associations of both MC1R variants and host phenotypes with melanoma risk has been limited.</p> <p><b>Methods</b> We included 815 CDKN2A mutation carriers (473 affected, and 342 unaffected, with melanoma) from 186 families from 15 centers in Europe, North America, and Australia who participated in the Melanoma Genetics Consortium. In this family-based study, we assessed the associations of the four most frequent MC1R variants (V60L, V92M, R151C, and R160W) and the number of variants (1, ≥2 variants), alone or jointly with the host phenotypes (hair color, propensity to sunburn, and number of nevi), with melanoma risk in CDKN2A mutation carriers. These associations were estimated and tested using generalized estimating equations. All statistical tests were two-sided.</p> <p><b>Results</b> Carrying any one of the four most frequent MC1R variants (V60L, V92M, R151C, R160W) in CDKN2A mutation carriers was associated with a statistically significantly increased risk for melanoma across all continents (1.24 × 10−6 ≤ P ≤ .0007). A consistent pattern of increase in melanoma risk was also associated with increase in number of MC1R variants. The risk of melanoma associated with at least two MC1R variants was 2.6-fold higher than the risk associated with only one variant (odds ratio = 5.83 [95% confidence interval = 3.60 to 9.46] vs 2.25 [95% confidence interval = 1.44 to 3.52]; Ptrend = 1.86 × 10−8). The joint analysis of MC1R variants and host phenotypes showed statistically significant associations of melanoma risk, together with MC1R variants (.0001 ≤ P ≤ .04), hair color (.006 ≤ P ≤ .06), and number of nevi (6.9 × 10−6 ≤ P ≤ .02).</p> <p><b>Conclusion</b> Results show that MC1R variants, hair color, and number of nevi were jointly associated with melanoma risk in CDKN2A mutation carriers. This joint association may have important consequences for risk assessments in familial settings.</p&gt