Inmaculada Arauzo

Combustion and heat transfer monitoring in large utility boilers

As a result of the quick and vast development of instrumentation and software capabilities, the optimization and control of complex energy systems can presently take advantage of highly sophisticated engineering techniques, such as CFD calculations and correlation algorithms based on artificial intelligence concepts. However, the most advanced numerical prediction still relies on strong simplifications of the exact transport equations. Likewise, the output of a neural network, or any other refined data-processing device, is actually based in a long record of observed past responses. Therefore, the implementation of modern diagnosis tools generally requires a great amount of experimental data, in order to achieve an adequate validation of the method. Consequently, a sort of paradox results, since the validation data cannot be less accurate or complete than the predictions sought. To remedy this situation, there are several alternatives. In opposition to laboratory work or well-instrumented pilot plants, the information obtained in the full scale installation offers the advantages of realism and low cost. This paper presents the case-study of a large, pulverized-coal fired utility boiler, discussing both the evaluation of customary measurements and the adoption of supplementary instruments. The generic outcome is that it is possible to significantly improve the knowledge on combustion and heat transfer performance within a reasonable cost. Based on the experience and results, a general methodology is outlined to cope with this kind of analysis.

Reflections on lumped models of unsteady heat conduction in simple bodies

Abstract This paper re-examines the venerable lumped model of unsteady heat conduction by means of a detailed study of the exact temperature distributions in bodies of elementary geometry (i.e., large slab, long cylinder and sphere). The space-mean temperature is used as a vehicle for demonstrating that the lumped calculation directly follows as a particular case from the infinite series solution of the general distributed model. In this manner, several methods to find a limit Biot number can be established as simpler alternatives to the traditional procedure. Additionally, the discussion offers a different perspective of this classical subject of heat conduction theory, gaining more insight on the limiting behavior of unsteady temperature distributions.

Exergy as an Indicator for Resources Scarcity: The Exergy Loss of Australian Mineral Capital — A Case Study

Over the span of the 20th century, the global demand for metals and minerals has increased dramatically. This is associated with a general trend of declining ore grades from most commodities, meaning higher quantities of ore needed to be processed and thus more energy. Hence, quantifying the loss of mineral capital in terms of mass is not enough since it does not take into account the quality of the minerals in the mine. Exergy is a better indicator than mass because it measures at the same time the three features that describe any natural resource: quantity, composition and a particular concentration. For the sake of better understanding the exergy results, they are expressed in tons of Metal equivalent, tMe, which are analogously defined to tons of oil equivalent, toe. The aim of this paper is 1) to show the methodology for obtaining the exergy loss of mineral resources throughout a certain period of time and 2) to apply it to the Australian case. From the available data of production and ore grade trends of Australian mining history, the tons of Metal equivalent lost, the cumulative exergy consumption, the exergy decrease of the economic demonstrated reserves and the estimated years until depletion of the main base-precious metals are provided, namely: for gold, copper nickel, silver lead and zinc.Copyright