Study On Numerical Simulation Of Brimstone Furnace And Structural Optimization

The brimstone furnace is one of the main installations in producing the sulphur dioxide in sugar production project. And the combustion is an important part of brimstone furnace. In studying the combusting process of the combustion chamber in the brimstone Furnace, theories of dynamics, heat transfer, and chemical reaction have to be applied. In the past, the design of the combustion chamber always depended on experience. However, with the rapid development of the numerical simulation in combustion, it provide strong tool for structure optimization and design.Based on the structure of combustion chamber and the character of combustion, the mathematical and physical models were established. The mathematical models mainly consist of continuity equation, momentum equation, energy equation and component equation. Thephysical models include standard k -εturbulence model, finite-rate or eddy-dissipationmodel, non-premixed combustion model and evaporation discrete phase model. The boundary conditions and solving method of model were set up.The combustion process in traditional self-fluxing brimstone furnace was simulated by computational fluid dynamics method. Under the different excess air ratio, obtained the optimum excess air ratio with 1.6 and the velocity field, the temperature field and the mass fraction field in the combustion chamber. The velocity field, the temperature field and the mass fraction field in combustion process were analyzed, and it is discovered that there are not well for mixing in the traditional self-fluxing brimstone furnace and have a quantity of SO₂, S₂, and SO₃ at the exit of furnace. Under the optimum excess air ratio, the molar fraction of SO₂, S₂, and SO₃ respectively achieve 13.0%, 0.011% and 0.088%. In order to prove numerical simulation method feasibility and the accuracy, the simulation results were compared with actual results. The numerical simulation results showed reasonably good agreement with the actual data under the same boundary conditions. The results showed that it was reasonable for choosing the model and the simulation method.In order to overcome the flaw in traditional self-fluxing brimstone furnace, the combustion process by using the way of cyclone borning was studied on numerical simulation. The 6 t/d vertical cyclone brimstone furnace was designed according to vertical cyclone boiler's combustion characteristic.The combustion process in the vertical cyclone brimstone furnace was simulated by numerical simulation under the different excess air ratio. It was obtained the optimum excess air ratio with 1.6 and the velocity field, the temperature field and the mass fraction field in the secondary combustion chamber.Then the secondary combustion chamber was optimized by numerical simulation. The optimal structure parameters were obtained and as follows: increasing excessively annular combustion (excessive angle 45°),the mixing fule gas's import diameter 0.125 m,the secondary air's import diameter 0.065 m,the pretage combustion and the postpositioned diameter ratio 1/0.80 and the secondary air's import high 0.80 m. Under the optimal structure parameters, the molar fraction of SO₂, S₂, SO₃ respectively achieve 18.8%, 0% and 0.0188%.By the result in vertical cyclone brimstone furnace constrasted with the result in traditional self-fluxing brimstone furnace, the conductions were obtained that the combustion efficiency in vertical cyclone brimstone furnace was higher than that in the traditional self-fluxing brimstone furnace. In the vertical cyclone brimstone furnace the quantity of S₂ was zero and the quantity of SO3 were very few. It can be concluded that the vertical cyclone brimstone furnace is better the traditional self-fluxing brimstone furnace.