A system for measuring bubble voidage and frequency around tubes immersed in a fluidized bed of particles.
Gas-solid fluidized beds are common in chemical processing and energy production industries. These types of reactors frequently have banks of tubes immersed within the bed to provide heating or cooling, and it is important that the fluid dynamics within these bundles is efficient and uniform. This paper presents a simple, low-cost method for quantitatively analyzing the behavior of gas bubbles within banks of tubes in a fluidized bed cold flow model. Two probes, one containing an infrared emitter and one containing an infrared (IR) detector, are placed into adjacent glass tubes such that the emitter and detector face each other. As bubbles pass through the IR beam, the detector signal increases due to less solid material blocking the path between the emitter and detector. By calibrating the signal response to known voidage of the material, one can measure the bubble voidage at various locations within the tube bundle. The rate and size of bubbles passing through the beam can also be determined by high frequency data collection and subsequent analysis. This technique allows one to develop a map of bubble voidage within a fluidized bed, which can be useful for model validation and system optimization.
Using expert opinion to identify and determine the relative impact of threats to sea turtles in Mozambique
Although robust and consistent long-term datasets are lacking, it is commonly accepted that sea turtle populations face significant human threats while using Mozambique's coastal habitats. While multiple threats have been identified, their relative impact - and thus the ability to prioritize limited conservation resources - is poorly known. To obtain a better understanding of these threats, information from experts was elicited through a semi-structured survey using open and closed-ended questions. Experts in research, conservation and management of sea turtles were identified and asked to identify key threats and to complete pairwise comparison matrixes to determine the relative weight (w) of each threat (13 criterion, n = 24 questions). Weights for the perceived impact of threats were calculated from scores given in the pair-wise matrix using the analytic hierarchy process. Responses (n = 18) to open-ended survey questions were thematically coded and discussed according to common themes (e.g. extent of knowledge, limitations, conservation management tools) identified. Bycatch from commercial trawling (w = 13.65), artisanal fishing (w = 12.30) and hunting of nesting turtles (w = 11.33) were the top threats identified, in order of relative impact. While two of the three top threats are widely distributed and likely to be logistically and resource intensive to address, the top-scoring threat, 'bycatch from commercial trawling', is a clearly defined target for conservation intervention. Given a lack of baseline or published data, soliciting expert opinion was an efficient way to identify emergent threats, along with the success and limiting factors influencing sea turtle conservation in a developing nation. The methodology and technique implemented here are transferable. Expert surveys can provide valuable insights in locations with similar socio-economic environments and limited empirical data to help clarify the relative impact of various threats.
Quantitative and qualitative relationship between swirl burner operatingconditions and pulverized coal flame length
Abstract Currently, there are used in power plants two types of burners to combustion the pulverized coal: jet burners and swirl burners. Most of the published works in the field of analysis of burners operating conditions are related to jet burners and are limited to initial region of the flame at the outlet of the burner. For jet burners an offset between the burner outlet and the flame beginning point could be analyzed. In the case of swirl burners with the pre-mixing diffuser chamber an offset between flame ignition point and burner outlet is usually not visible. Because already in the pre-mixing diffuser chamber of swirl burner occurs the ignition of coal-dust together with oxidant-gas cloud and thereby the formation of the flame. Therefore, the analysis of operating conditions for this types of burners requires a different approach. There is a lack of researches, in which will be analyzed changes of the flame length, that are caused by changes of design and operating parameters of swirl burner with the pre-mixing diffuser chamber. Therefore the aim of this study was to implement and verify the methodology for estimating the flame length, which will allow monitoring changes of operating conditions, that are caused by changes of design and operating parameters of swirl burner with the pre-mixing diffuser chamber. To carry out the analysis of the image of the coal flame, the two algorithms have been presented. This two algorithms, being based on the video images of the coal flame allows to specify and detect the end point of the flame and on that basis the length of the flame, as well as the fluctuation changes of flame length can be later determined. Both, the change thermal loads of coal burner, streams of secondary air, as well as the constructional change of the angle of swirler assemblies, resulted in distinct changes in the length of the pulverized coal flame.