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Fouling of heat-transfer surfaces by fireside deposits can be of significant concern in industrial boilers burning poor-quality fuel. It is commonly controlled by sootblowers that blast deposits with high-pressure supersonic steam or air jets. However, sootblowing is expensive, which motivates efforts to fundamentally understand how sootblower jets behave and how they interact with heat-exchanger geometries and deposits, to guide efforts to improve and optimize sootblower use. Here, we report on the development of a computational fluid dynamics (CFD) model to predict the flow behavior of sootblower jets, work that began with the customization of a research code but has more recently led to an implementation using the commercial CFD software ANSYS Fluent, which makes the model more accessible to the wider engineering community. CFD model results are compared to experimental data that we obtained for jet flow within model tube bank geometries, which are representative of superheaters and generating banks in...

Zn and Cl have been found in deposits in municipal solid waste (MSW) boilers and industrial boilers. This leads to the general belief that ZnCl2 may play a role in corrosion of heat-transfer tubes, owing to its low melting temperature and high corrosivity. In this study, the thermal stability of the compounds ZnCl2, ZnSO4, and ZnO as well as mixtures of ZnCl2 and NaCl/KCl was investigated by means of thermogravimetric analysis/differential scanning calorimetry (TGA/DSC). The reactions of the Zn compounds with SO2/SO3 and HCl were also investigated. The results obtained show that ZnCl2 melts at 320 °C. Above 400 °C, ZnCl2 vaporizes and is partly oxidized to ZnO. ZnSO4 is stable up to 680 °C, at which it decomposes and, subsequently, forms ZnO above 900 °C. ZnO is stable at a much higher temperatures but can be chlorinated to ZnCl2 in the presence of HCl at temperatures around 300 °C. In the presence of a large amount of NaCl/KCl, which is typically the case in actual boilers, ZnCl2 reacts with NaCl/KCl to ...

This paper is the second in a series of two on the slagging and fouling behavior of rice husk when fired alone or in combination with other fuels in a fluidized-bed boiler. The first paper involved the fuel properties of rice husk, as investigated by a variety of laboratory methods. In this second paper, we report the results of fireside fouling measurements when burning rice husk alone and together with eucalyptus bark in various ratios. This study is based on short-term (3−10 h) deposit samples taken with air-cooled deposit probes in the superheater region of a large-scale (157 MWth) bubbling fluidized-bed (BFB) boiler burning rice husk and eucalyptus bark. Using an entrained-flow type of pilot furnace, we further made more, systematic measurements of the influence of the fuel mixture ratio on the fouling tendency of the fly ash formed. Burning of rice husk alone did not result in any detectable fouling, neither in the pilot furnace nor on the deposit probes in the superheater area of the fluidized-bed ...

A method for predicting the conditions that lead to plugging of the boiler bank by submicrometer condensation aerosols of alkali-metal salts in kraft recovery boilers has been developed and evaluated against field observations. The method is based on recent data on the phase behavior and sintering characteristics of compacts of dusts from kraft recovery boilers, both of which are dependent on the inorganic composition of the particles. The method also takes into account the thermal load on the boiler and the specific design characteristic of the gas temperature entering the boiler bank versus thermal load on the boiler. The prediction method presented in this paper has been tested against data from 20 different recovery boilers. It correctly predicted whether the boiler did or did not encounter problematic fume deposits for 80% of those boilers.