Fireside corrosion in oxy-fuel environments and the influence of fuel and ash characteristics on corrosion and deposition

The development of advanced techniques (such as carbon capture and storage) for future power plants and the implementation of retrofit technologies to existing ones (like biomass co-firing) in order to reduce pollutant emission, has raised several concerns for the power industry. One such problem, which also forms the basis of this thesis, is the effect of these measures on corrosion and deposition of the boiler heat transfer surfaces. This research work can be divided into two parts. The first part involved studying the corrosion behaviour of a typical waterwall and a superheater material under simulated oxy-fuel environments with and without the influence of an ash deposit. A custom-built, laboratory scale, corrosion rig with the ability to simulate a range of flue gas compositions and temperatures, in addition to generating a heat flux through the specimen, was set up for this purpose. The second part of this work deals with evaluating the properties of a UK power station coal and four biomass samples with the help of laboratory techniques and thermodynamic modelling in order to predict their fusion and deposit forming tendencies in combustion systems. A series of experiments were performed on the corrosion rig to assess the influence of individual variables on the rate of corrosion. The results indicated that the increased concentration of SO2 in oxy fuel combustion due to recycling of the flue gas, can lead to an increase in corrosion rates especially in the presence of reactive alkali containing deposits. Under the conditions studied, the presence of a biomass ash deposit aggravated the corrosive propensity of the environment while coal ash lessened it. With regard to predicting the fusion behaviour of different ashes, the standard ash fusion tests proved inadequate for explaining the relationship between high alkali constituents in biomass ash and the expected higher slagging and fouling tendencies. Simultaneous thermal analysis was more useful in assessing the physical & chemical changes taking place in the ash. Prediction of the fuel behaviour using FactSage thermodynamic analysis showed that ash melting commences at much lower temperatures than those predicted from laboratory techniques. This would help to explain the increased risk of deposition and corrosion linked with burning high alkali containing fuels

Understanding “green” multicellularity: do seaweeds hold the key?

International audienceLiving organisms are unicellular, composed of a single cell, or multicellular, where a group of up to ~1012 cells functions co-operatively (Kaiser, 2001). All multicellular organisms evolved from single-celled ancestors; every individual organism arises from a unicell and reproduces by forming unicells. Multicellularity enables competitive advantages, and may have shaped our oxygen-rich atmosphere (Grosberg and Strathmann, 1998; Kaiser, 2001; Schirrmeister et al., 2013). Multicellularity has evolved multiple times: animals, plants, algae, amoebae, fungi, and bacteria are or can all be multicellular (King, 2004; Grosberg and Strathmann, 2007; Rokas, 2008; Claessen et al., 2014). Multicellularity can be clonal (arising from division of a single cell) or aggregative (aggregation of genetically diverse cells), with clonal multicellularity considered evolutionarily more stable (Grosberg and Strathmann, 1998). The molecular mechanisms by which organisms become multicellular are not well understood. In this article, we outline eukaryotic multicellular evolution, and discuss how to increase our future understanding

How Motivational Factors Affect the Online Shopping Behavior: An Insight of Developing Economy Consumers

In recent years, usage of the internet in a developing economy like Pakistan rose exponentially which also enable users to use social media and eventually buy and order anything online. The trend of marketing changed all over the country as renowned brands and businesses started to shift their respective platforms. Some faced difficulties in that while others reached new heights of accomplishments. The online market is quite different from the conventional physical market and retailer’s sales generally depend upon the buyer’s mood, attitude, and behaviors which comprises trust, purchase intent, and motivational factors. Retailers must be aware of the ongoing trends and know-how and when to post what. For the purpose of the study, the data was collected from 265 respondents and Partial Least Structural Equation Modelling (PLS-SEM) was used for the analysis. The results showed that motivational factors i.e. Social, Empowerment, and Remuneration have a significant relationship with Trust and Online Purchasing Intent. From the results, several implications can be derived for marketers, policymakers, and online retailer

Adaptation of Regulatory Systems in Schoolchildren, Residing in Industrial Area

The article presents the results of the study of heart rate variability (HRT) in apparently healthy volunteers of both sexes without bad habits, aged 16-18, residing in industrial region (Temirtau) and the ones, studying under innovative technologies. HRT was registered with the help of computer-controlled devices “Varikard” (Russia). The changes of HRT spectral indexes towards integral impact of vegetative regulation mechanisms and parasympathetic activity decrease and regulatory systems overexertion, demanding correction methods implementatio

Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels

Electric discharge machining (EDM) is one of the most efficient manufacturing technologies used in highly accurate processing of all electrically conductive materials irrespective of their mechanical properties. It is a non-contact thermal energy process applied to a wide range of applications, such as in the aerospace, automotive, tools, molds and dies, and surgical implements, especially for the hard-to-cut materials with simple or complex shapes and geometries. Applications to molds, tools, and dies are among the large-scale initial applications of this process. Machining these items is especially difficult as they are made of hard-to-machine materials, they have very complex shapes of high accuracy, and their surface characteristics are sensitive to machining conditions. The review of this kind with an emphasis on tool and die materials is extremely useful to relevant professions, practitioners, and researchers. This review provides an overview of the studies related to EDM with regard to selection of the process, material, and operating parameters, the effect on responses, various process variants, and new techniques adopted to enhance process performance. This paper reviews research studies on the EDM of different grades of tool steel materials. This article (i) pans out the reported literature in a modular manner with a focus on experimental and theoretical studies aimed at improving process performance, including material removal rate, surface quality, and tool wear rate, among others, (ii) examines evaluation models and techniques used to determine process conditions, and (iii) discusses the developments in EDM and outlines the trends for future research. The conclusion section of the article carves out precise highlights and gaps from each section, thus making the article easy to navigate and extremely useful to the related research communit

On Test Vector Reordering for Combinational Circuits

The cost of testing is a major factor in the cost of digital system design. In order to reduce the test application time, it is required to order the test vectors in such away that reduces the time a defective chip spends on a tester until the defect is detected. In this paper, we propose an efficient test vector reordering technique that significantly reduces both the time and memory complexities of reordering procedures based on fault simulation without dropping. Experimental results demonstrate both the efficiency and effectiveness of our proposed technique

A Class-based Clustering Static Compaction Technique for Combinational Circuits

Static compaction based on test vector merging is a very simple and efficient technique. However, for a highly incompatible test set, merging achieves little reduction. In this paper, we propose a new static compaction technique in which a test vector is decomposed into its atomic components before it is processed. In this way, a test vector that is originally incompatible with all other test vectors in a given test set can be eliminated if its components can be merged with other test vectors

Test Vector Decomposition Based Static Compaction Algorithms for Combinational Circuits

Testing system-on-chips involves applying huge amounts of test data, which is stored in the tester memory and then transferred to the chip under test during test application. Therefore, practical techniques, such as test compression and compaction, are required to reduce the amount of test data in order to reduce both the total testing time and memory requirements for the tester. In this paper, a new approach to static compaction for combinational circuits, referred to as test vector decomposition (TVD), is proposed. In addition, two new TVD based static compaction algorithms are presented. Experimental results for benchmark circuits demonstrate the effectiveness of the two new static compaction algorithms

A Retiming-Based Test Pattern Generator Design for Built-In Self Test of Data Path Architectures

Recently, a new Built-In Self Test (BIST) methodology based on balanced bistable sequential kernels has been proposed that reduces the area overhead and performance degradation associated with the conventional BILBO-oriented BIST methodology. This new methodology guarantees high fault coverage but requires special test sequences and test pattern generator (TPG) designs. In this paper, we demonstrate the use of the retiming technique in designing TPGs for balanced bistable sequential kernels. Experimental results on ISCAS benchmark circuits demonstrate the effectiveness of the designed TPGs in achieving higher fault coverage than the conventional maximal-length LFSR TPGs