Models post-combustion

Zhang, L., and Oeters, F., A Model of Post-Combustion in Iron-Bath Reactors, Part 1 Theoretical Basis, Steel Res., 62 95 (1991a)... 

In the post-combustion modeling, the partial transformation of combustion energy into mechanical energy is treated reproducing the complicated structure of a shock wave and determining the pressure distribution on buildings. Pressure loads depend on the mutual orientation of the incoming wave and the loaded surface. 

The Lost Foam models are made of polystyrene (EPS) or PMMA, with small amoimts of pentane, glue and a mineral coating. Since both EPS and pentane are pure hydrocarbons, organic carbons are formed upon pyrolysis of the model. In order to minimise emissions of the organic decomposition products of EPS, post combustion of the off-gases is performed. 

Another direction is towards the mixture of AMP and PZ, a solvent typically used for post-combustion CO2 capture. A model based on 52 calibration samples is currently being made and will be used and validated during several weeks of operation at an industrial pilot plant. 

Combinations of in-line measurement techniques with multivariate modelling show promising properties for nse as real-time monitoring applications of the liqnid composition in acid gas absorption processes. Both spectroscopic and non-spectroscopic analytical techniques can be nsed. Althongh the first developments were mostly aimed at predicting CO2 and amine concentrations in post-combustion CO2 capture processes, recent developments are also directing into applications involving acid gas removal from natural gas and the use of solvents that inclnde mixtures of two active components. 

This chapter has provided a range of mathematical models that can be used to characterize the effects of minor components on membrane performance. However, the quantity of good experimental data that can be used to fit these models remains quite limited. Good characterization of membrane performance in both pre-combustion and post-combustion flue gases will require accurate experimentally based determination of parameters such as Flory-Huggins interaction parameters, Langmuir constants and plasticization potentials. 

Kawabata M, Kurata O, Iki N, Tsutsumi A, Furutani H. System modelling of exergy recuperated IGCC system with pre- and post-combustion CO2 capture. Appl Therm Eng 2013 54 310-8. 

A comparison of the calculated relationships between the partial pressures of the highest oxides (B2O3, CO2) and suboxides (B2O2, CO) in the presence and absence of elemental boron and carbon (Figures 7, 9) with the distribution of boron and carbon oxides along the combustion wave (Figures 6, 8) indicates that a zone of minor postcombustion probably exists for the Mo-B system, but post-combustion is entirely absent in Ta-C system. It is also obvious from this comparison that, by the time t2, i.e., by the end of the reaction zone, the interactions in the systems are completed and boron in Mo-B system as well as carbon in Ta-C system are completely reacted. Thus, the model of wide zones (14,15) which assumes the interaction of the overwhelming bulk of the reactants far behind the front in a reactive diffusion mode, is not realized in the combustion of the systems under study. 

Based on the basic modeling methodology which has been detailed in the previous section, difierent issues of the post-combustion CO2 capture can be tackled. Basically, the main questions that have to be addressed can be summarized as follows. 

The input requirements for post-flashover types of models can be quite broad. Besides the compartment and vent dimensions, detailed fuel combustion characteristics are often needed. The fuel characteristics include the fraction of carbon, hydrogen, nitrogen, and oxygen that make up the fuel, the burning efficiency, and the quantity of fuel available for burning. Mechanical ventilation flow rates and the material properties of the compartment boundaries may be necessary. Some models can account for the heat transfer through the boundaries in detail, and may even allow the user to supply time-dependent material properties. An example of a post-flashover fire model is COMPF (Babrauskas, 1979). 

Soot formation and oxidation In fires, soot is usually the dominant emitter and absorber of radiation. The modeling of soot formation and oxidation processes is therefore important for the accurate prediction of radiant emissions. Detailed models that solve for soot number density and mass fraction have been developed over the years, and implemented also in fire CFD models such as SOFIE [64], and more recently in [65] and [66], In post-flame conditions, the problem is mostly following of the soot produced in the flame zone. Currently, FDS can only follow this passive soot, but engineering models for soot formation and oxidation that rely on the laminar smoke point height have been postulated [67-69], Unfortunately, the soot formation and oxidation processes are sensitive to the temperature and the same problems appear as in detailed combustion modeling. 

One major topic of the work is an extension of the CFD code with a post-processor for the fuel nitrogen to NOx conversion, A reduced kinetic scheme has been obtained which describes quite well the combustion emission behaviour with respect to NOx formation. Figure 9 shows a comparison between experimentally observed NH conversion to NO and modeling with this modified post processor. The agreement is reasonably good for experiments at 0.5 and 0.7 Mpa. Significant deviation between model and experiment is seen for an experiment at 0.4 MPa. This is attributed to a measurement error at that pressure, A recommendation is to perform more experiments at this or lower pressure. 

The performance of the gas turbine combustor in the Delft PDU with respect to main combustion product formation and fuel NO, was quite well predicted by FLUENT CFD modelling with a modified post-processor, although validation at pressures lower than 0.5 MPa is recommended. 

Post, L. "Modeling of Flow and Combustion in a Glass Melting Furnace." PhD diss.. Delft University of Technology, Holland, 1988. 

Thermal combustion reactions are very fast. The sub-stoichiometric combustion of methane is a complex process with many radical reactions [466]. The reaction pattern depends on the residence time/temperature distribution. Hence, it is important to couple the kinetic models with CFD simulations by post processing [466] or by direct coupling in more advanced calculations. 

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