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In this PhD project, the investigation of the stability of a laminar diffusion flame and the interaction of the flame with acoustic waves inside an acoustically excited cylindrical tube is presented. Interesting phenomena have been observed by studying both the infrasound and sound effect on the flame structure and dynamics.When a cylindrical tube burner is acoustically excited at one end, a standing wave will be produced along the tube burner. By applying a programming controlled signal from a signal generator, the loudspeaker generates acoustic waves with different frequencies and intensities to excite the flame, which can make the flame relatively stable or unstable, even blow out. Different methods in both frequency domain and time domain have been applied to analyze the flame stability affected by acoustic waves. Both infrasound and sound are tested in this research. Infrasound is the acoustic wave with a frequency too low to be heard by human ear covering sounds beneath the lowest limits of human hearing (20Hz) down to 0.001Hz. It is found that infrasound is able to take over buoyancy-driven flame flickering and make the flame flicker at the same frequency as the forcing infrasound. For some infrasound, half excited frequency has been detected clearly in the power spectrum of CH* chemiluminescence signals acquired by a photomultiplier. On the other hand, some higher frequency acoustic wave can have observable effect on flame flickering but the buoyancy-driven flickering is still the dominant oscillating mode; some other higher frequency acoustic wave can make the flame very stable, such as the acoustic wave at 140Hz. Image processing technique has shown that the influence of acoustic waves on the laminar diffusion flame varies spatially. It is also observed that a diffusion flame may oscillate at different frequency spatially. Taking the flame without acoustic excitation as an example, the inner most area of the flame oscillates at the typical flickering frequency, but the most outer areas of the flame oscillate at the second-harmonic of the typical flickering frequency. Finally, some control strategies are developed for the laboratory tube burner based on the gained physical insights in this research.

Heavier crude oil, tighter environmental regulations and increased heavy-end upgrading in the petroleum industry are leading to the increased demand for hydrogen in oil refineries. Hence, hydrotreating and hydrocracking processes now play increasingly important roles in modern refineries. Refinery hydrogen networks are becoming more and more complicated as well. Therefore, optimisation of overall hydrogen networks is required to improve the hydrogen utilisation in oil refineries. In previous work for hydrogen management many methodologies have been developed for H2 network optimisation, all with fixed H2/Oil ratio and H2 partial pressure for H2 consumers, which may be too restrictive for H2 network optimisation. In this work, a variable H2/Oil and H2 partial pressure strategy is proposed to enhance the H2 network optimisation, which is verified and integrated into the optimisation methodology. An industrial case study is carried out to demonstrate the necessity and effectiveness of the approach. Another important issue is that existing binary component H2 network optimisation has a very simplistic assumption that all H2 rich streams consist of H2 and CH4 only, which leads to serious doubts about the solution's validity. To overcome the drawbacks in previous work, an improved modelling and optimisation approach has been developed. Light-hydrocarbon production and integrated flash calculation are incorporated into a hydrogen consumer model. An optimisation framework is developed to solve the resulting NLP problem. Both the CONOPT solver in GAMS and a simulated annealing (SA) algorithm are tested to identify a suitable optimisation engine. In a case study, the CONOPT solver out-performs the SA solver. The pros and cons of both methods are discussed, and in general the choice largely depends on the type of problems to solve.

In the past decade, biofuel development in the UK has been supported by regulations that were justified by government on the basis of their potential benefits for the environment, rural economies and fuel security. As concerns were raised about the negative impacts that biofuel development may have upon food prices and land use, particularly outside Europe, a controversy emerged. A number of technical and infrastructural responses to these concerns have led to the promise of as yet unrealised second, third and even fourth generation developments of the technology. Regulatory responses to concerns can already be identified and further responses, such as mandatory certification schemes, appear likely in the coming years. This relationship between the development of the technology and the controversy is subject to theoretical and empirical examination in the thesis. A critical realist account of the technology-society has been forwarded recently but remains embryonic, unapplied to specific problems, and untested empirically. Here, this conceptualisation is developed to consider the dialectic, mutual conditioning relationship between technical artefacts and the controversies that surround them. This development includes an articulation of how semiotic processes can operate under realist conditions, emphasising the triad of objects, their names and the meanings that are associated with them. These semiotic processes are understood as the unfolding of technical reality. The resulting theoretical framework is developed into an analytical lens for the study of specific controversies about specific technical artefacts. Material representing various positions from the biofuel controversy is analysed and discussed with reference to the theoretical framework, considering how the technology conditions the development of the controversy and vice versa. Biofuel technology is a collection of highly variable combinations of different feedstocks that are processed in different ways. These combinations have divergent relationships with various other environmental and economic realities and, as such, support the maintenance of a similarly variable collection of discourses about them. By supporting the relative endurance of discursive conflicts, the technology provides appropriate conditions for the emergence of a controversy. Some actors' discourse is engaged in the negotiation of the organisation of biofuels' internal variety by defining more specific subcategories and broadening the associated vocabulary. This activity may lead to the resolution of some conflicts within the controversy, as it emerges that some conflicts result from the insufficiency of the vocabulary to represent the internal variety of the technology. Furthermore, the controversy also provides the conditions under which the technology develops as engineers, regulators and others rise to new challenges. For example, certification schemes may follow the redistribution of language in selectively incentivising some feedstock-process combinations whilst restricting the development of others. Other conflicts in the controversy have emerged around biofuels produced by the same feedstock-process combination. These differ from conflicts resulting from a single name referring to many different objects, as a single object is understood and represented in different ways. Whilst other social and technical negotiations may still respond to such conflicts, they are unlikely to be resolved through expanding vocabularies.

The emission of sulphur oxides during the combustion of coal is one of the causes of an environmental problem known as acid rain. Biodesulphurisation technology applied as a method to remove sulphur before coal combustion was investigated in this work. The desulphurisation abilities of three specific bacterial strains including Rhodococcus erythropolis IGTS8, R. erythropolis X309 and Shewanella putrefaciens strain NCIMB 8768 have been evaluated. R. erythropolis IGTS8 and X309 were found to be able to remove both inorganic and organic sulphur from model compounds and coal samples. Their abilities to remove sulphur from benzothiophene were observed for the first time. A novel desulphurising bacterium, S. putrefaciens was also found to be able to remove inorganic and organic sulphur from coal samples. The bacterium, however, lost its ability to remove organic sulphur from model compounds during the investigation. R. erythropolis IGTS8 presented the greatest desulphurisation efficiency among the three bacterial strains. Nevertheless, the desulphurisation activity of R. erythropolis IGTS8 was too low for an economical coal biodesulphurisation process as it removed only 32.0% of total sulphur in bituminous coal, and 21.1% of total sulphur in anthracite coal. Alternatively, coal biodesulphurisation can be carried out in inexpensive conditions by using the bacteria inherent in the coal itself. The type of coal has an important effect on desulphurisation efficiency since the sulphur reduction in bituminous coal, which is in a lower rank than anthracite, was greater than the sulphur reduction in anthracite coal. This work also developed and evaluated the analytical methods used in the field. A HPLC method was developed to detect the desulphurisation metabolites of model compounds. The techniques for measuring sulphur in coal were improved.

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