Stevan Nemoda

Two-dimensional mathematical model of liquid fuel combustion in bubbling fluidized bed applied for a fluidized furnace numerical simulation

Lately, experimental methods and numerical simulations are equally employed for the purpose of developing incineration bubbling fluidized bed (BFB) facilities. The paper presents the results of the 2-D CFD model of liquid fuel combustion in BFB, applied for numerical simulation of a fluidized bed furnace. The numerical procedure is based on the two-fluid Euler-Euler approach, where the velocity field of the gas and particles are modeled in analogy to the kinetic gas theory. The proposed numerical model comprises energy equations for all three phases (gas, inert fluidized particles, and liquid fuel), as well as the transport equations of chemical components that are participating in the reactions of combustion and devolatilization. The model equations are solved applying a commercial CFD package, whereby the user submodels were developed for heterogenic fluidized bed combustion of liquid fuels and for interphase drag forces for all three phases. The results of temperature field calculation were compared with the experiments, carried out in-house, on a BFB pilot facility. The numerical experiments, based on the proposed mathematical model, have been used for the purposes of analyzing the impacts of various fuel flow rates, and fluidization numbers, on the combustion efficiency and on the temperature fields in the combustion zone.

Fluidized combustion chamber CFD simulation based on Euler-Euler granular flow model

U radu je predložen dvodimenzijski model numeričke simulacije sagorevanja tečnih goriva u fluidizovanom sloju, koji se zasniva na dvo fluidnom Euler – Euler pristupom modeliranja fluidizovanog sloja uz određivanje polja brzina gasa i čestica u dvofaznim, granularnim tokovima zasnovane na analogiji sa kinetičkom teorijom gasova (KTGF). Sveobuhvatan model kompleksnih procesa u fluidizacionoj komori sagorevanja podrazumeva, pored određivanja polja brzina gasne i čestične faze, inkorporiranje energetskih jednačina gasne i čestične faze, kao i transportnih jednačina hemijskih komponenti sa izvornim članovima usled konverzije komponenata. Brojni numerički eksperimenti pokazuju da je izbor koeficijenata u izrazima za sile trenja prilikom interakcije faza ima izuzetan značaj i mora se sprovesti za svaki, značajno različit režim fluidizacije, posebno. Urađene su serije numeričkih eksperimenata sa simulacijom procesa sagorevanja u FS sa i bez značajnog sadržaja vode u gorivu. Proračuni su nestacionarni, a modelirani vremenski period odgovara vremenu za koje gas prođe kroz celu visinu reaktora. Numerički eksperimenti, na osnovu predloženog matematičkog modela, su takođe korišćeni za potrebe analize uticaja različitih snaga pri kojima radi reaktor, kao i različitih stepena fluidizacije, na efikasnost sagorevanja kao i na profile temperatura u zoni sagorevanja. Ključne reči: CFD modeliranje; sagorevanje; fluidizovani sloj, granularni tok, tečna goriva, A comprehensive 2D numerical model of the bubbled fluidized bed with combustion of liquid fuels is proposed in the paper. The proposed numerical model is based on the Eulerian–Eulerian granular flow modeling with the kinetic theory of granular flow. The model includes the following basic governing equations: the continuity equations of the solid and gas phase, the momentum conservation equations of the gas and solid phase, the energy equations of gas, and the solid phase and conservation equations for chemical components. The choice of the semi empirical constants of the inter-phase interaction drag force model is significant and these constants must be adjusted for each particular regime of fluidization. Presented numerical experiments primarily were applied to verification of the assumptions about the impact of water content in a liquid fuel on FB combustion intensity. The numerical experiments, based on the proposed mathematical model, also have been used for the purposes of analyzing the impacts of various reactor powers as well as fluidization numbers, on the combustion efficiency and on combustion zone temperature fields.

Results of combustion of different waste fuel in fluidized bad

The sustainable development of the national energy sector implies the rational use of energy resources, use of RES, and waste management with satisfying environmental regulations. A way to simultaneously fulfill the above objectives is the utilization of low-calorific and waste materials, applying the technology of fluidized bed combustion (FBC). This paper presents experimental results of combustion of number of solid and liquid wastes, conducted on two installations: industrial demonstration (capacity up to 100 kW) and experimental FB boiler (capacity up to 500 kW). The furnace temperature distribution, the composition of flue gas at the exit of furnace, and the other combustion parameters of the fuels are given. On the basis of these results, an evaluation of the waste fuels FB combustion and possibility of utilization of their energy potential is given.