Utility OEMs must guarantee broad domains of fuel quality to accommodate switches from one coal to another, or to blends of a coal on coal or pet coke on coal or biomass on coal. Do your CFD simulations accurately depict the impacts on flame temperatures, in-furnace operational issues, and emissions for fuel switching? If you rely on default thermophysical properties and rate parameters from a CFD firm, then the answer is certainly “No.” Three dozen utility OEMs and service companies, including many of the largest OEMs worldwide, have already found a much more accurate solution: They use NEA’s PC Coal Lab®. In seconds on ordinary PCs, PC Coal Lab® issues a one-page report that contains sample-specific values for the thermophysical properties and for the product distributions, rate parameters, and stoichiometric coefficients for devolatilization, volatiles conversion including soot, and char conversion for any coal, pet coke, or biomass sample. All you provide are the proximate and ultimate analyses of the fuel samples and nominal operating conditions (gas and wall temperatures, reactive gas concentrations, pressure, particle size) for your pyrolyzer, furnace, or gasifier. You continue to use the same CFD chemistry submodels. PC Coal Lab® simply gives you the parameter values that generate the reaction rates and yields from your rate expressions that match the predictions from NEA’s comprehensive and fully validated fuel conversion mechanisms.
For every solid fuel sample, PC Coal Lab® specifies the bulk particle density, specific heat, emittance for radiant transfer, and a swelling factor that describes particle size as a function of the extent of devolatilization. In fact, all these properties are functions of the initial fuel composition, temperature, and the extent of devolatilization, and the swelling factor is also a strong function of pressure. For the associated gaseous volatiles, the package specifies mean molecular weight, an elemental composition, mean heat capacity, and the heat of formation. For the associated char and soot, it gives the elemental compositions and yields of soot and char, plus the swollen initial size and density of char.
The most important fuel property in a CFD simulation is the total volatiles yield because it governs near-burner heat release rates and the amount of char remaining to be slowly burned out across upper furnace elevations, or to be converted even more slowly via gasification chemistry. Correlations based on Q-Factors, Fuel Ratios, or other primary fuel indices cannot accurately forecast the distinctive, sample-specific yields of volatiles from different fuels. Even the other network depolymerization models hardly do better than an arithmetic average of reported yields for different coal ranks. FLASHCHAIN® is the only current means to accurately predict total volatiles yields from any solid fuel at any operating conditions. And the only required sample-specific information are the proximate and ultimate analyses. Time and time again, in blind evaluations across the globe, FLASHCHAIN® consistently predicts total yields within the measurement uncertainties in nine of ten cases. Is it any wonder that most of NEA’s licensees to PC Coal Lab® first tried a competing scheme because they are either free or available at minimal cost ? CFD practitioners who absolutely need an accurate volatiles yield need FLASHCHAIN®. Learn More.
Devolatilization kinetics are assigned by matching the predictions from the simple rate expressions used in CFD to the predicted devolatiilization history based on FLASHCHAIN®. In other words, the FLASHCHAIN® module within PC Coal Lab® is used as a virtual fuels laboratory to synthesize “rate data” that is interpreted by conventional means to specify the rate parameters in simple rate laws. For devolatilization, PC Coal Lab® supports a single, first-order reaction (SFOR), the two-step, competing reaction model (C2SM), and a distributed activation energy model (DAEM). Any of these rate laws can be fully specified for total volatiles yield as well as for the yield of any particular devolatilization product, including volatile-nitrogen species. Learn More.
For CFD, volatiles are described in aggregate with a yield, elemental composition, mean molecular weight, heat capacity, and heat of formation. PC Coal Lab™ provides this information for whole primary volatiles as well as for the noncondensable fuels that actually burn in flames and entrained flow gasifiers, which contain CH4, C2H2, CO, H2, HCN, and H2S. Soot yields and properties are resolved separately so you can lump soot with volatiles or treat it as a separate species; either way, the conversion parameters you need are in the report.
Stoichiometric coefficients and the heats of reaction are reported for complete combustion, partial oxidation, and reforming to accurately describe volatiles conversion in all the major coal utilization technologies. One set of values describes whole volatiles including soot. Two other sets explicitly resolve contributions for noncondensable volatiles and soot.
In commercial CFD furnace simulations, the volatiles conversion parameters from PC Coal Lab® have already significantly improved the accuracy of predicted furnace NOX emissions and the associated impact of even small adjustments to burner settings and burner tilt angles. And in commercial CFD gasifier simulations, these volatiles conversion parameters have enabled more accurate predictions for the overall carbon conversion efficiency, especially under conditions where unconverted soot constitutes an appreciable portion of unconverted carbon in synthesis gas.
Neither char nor soot is pure carbon. PC Coal Lab™ gives the elemental compositions, combustion stoichiometries, and heats of combustion for both char and soot. It also gives the gasification stoichiometries and heats of reaction for gasification by H2O, by CO2, and by H2.
Simple, nth-order kinetics for char oxidation can accurately describe the bulk of char conversion, simply because burning rates are almost always limited by bulk O2 diffusion. But much more accurate rate expressions are needed to forecast the final few percent on the conversion scale which, in turn, determine unburned carbon emissions and flyash LOI. That’s why the char oxidation kinetics from PC Coal Lab™ are based on an extended version of the Carbon Burnout Kinetics (CBK/E) package. We also provide examples of user-defined functions to help you quickly install NEA’s kinetics into your CFD platform. Learn More.
The vast majority of CFD gasifier simulations use kinetics for char and soot conversion that are woefully inadequate. The main problem is that H2 strongly inhibits steam gasification and CO strongly inhibits CO2 gasification. Rate expressions that omit these crucial inhibition terms cannot possibly describe gasifier carbon conversion efficiencies across broad operating domains or for a diverse assortment of solid fuels. That’s why the gasification kinetics from PC Coal Lab® for char and soot are based on NEA’s proprietary version of the Carbon Burnout Kinetics (CBK/G) package for gasification. Learn More.
NEA developed ChemNet™ CFD Post-Processing as a means to couple our fully validated reaction mechanisms for the solid fuel phase with comprehensive elementary reaction mechanisms for chemistry in the gas phase and on soot. This method is especially suitable whenever the levels of emissions and other minor species must be predicted for a diverse assortment of solid fuels across a broad domain of operating conditions; in other words, in the most demanding simulation applications. It has already been demonstrated in pulverized fuel flames at lab-, pilot-, and full-scale; in pilot- and full-scale CFBCs; in pilot- and full-scale gasifiers; and along utility flue gas cleaning systems. Learn More.