Abstract
Fired equipment suffers from local overloading and fouling of heat transfer surfaces, products are not of the required quality, and operating costs are increased due to the high pressure drop of process fluids. Such operational issues are affected by the non-uniform distribution of fluid flow and heat flux variability. Detailed numerical analyses are often applied to troubleshoot these problems. However, is this common practice effective? Is it not better to prevent problems from occurring by using quality equipment design? It is, according to the general consensus. Still, the experience of designing fired apparatuses reveals that the established standards do not reflect the real maldistribution sufficiently. In addition, as found from the given overview of modelling approaches, the radiant chamber and the convection section are usually analysed separately without significant continuity. A comprehensive framework is hence introduced. The proposed procedure clearly defines the interconnection of traditional thermal-hydraulic calculations and low-cost modelling systems for radiant and convection sections. A suitable combination of simplified methods allows for the reliable design of complex equipment and fast identification of problematic areas. The utilisation of selected low-cost models, i.e., the second phase of the systematic framework, is presented regarding the example of a steam boiler.
Highlights
Hot utilities are the most energy-consuming and the costlier apparatuses in any industrial plant
Since experiments can be carried out on the fired equipment in only a very limited scale, simplified modelling methods and numerical analyses based on computational fluid dynamics (CFD) have an irreplaceable role in the designing process
For the reliable design of both parts of fired equipment, it is necessary to identify the distribution of heat flux and process fluids
Summary
Hot utilities are the most energy-consuming and the costlier apparatuses in any industrial plant. For the reliable design of both parts of fired equipment (radiant and convection sections), it is necessary to identify the distribution of heat flux and process fluids. An assumption of average radiant heat flux and the neglecting of the burner’s actual thermal profile contributes to a decrease in efficiency and increased wear of the whole equipment or of some of its parts Underestimation of this issue often causes serious operational problems of fired heaters: increased fouling of the tubular system (e.g., deposition of coke), overheating of the tube material with subsequent deformation and a dramatically increased pressure drop. The problematic flow behaviour in the tubes causes uneven loading of the heat transfer surfaces, especially when it is negatively influenced by flue gas maldistribution A detailed but time-consuming CFD simulation can effectively analyse these bottlenecks
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