SIMULATION OF SULFUR DIOXIDE REMOVAL FROM A GAS STREAM IN A FLUIDIZED-BED REACTOR

The combustion performance of a bio-solid waste from a wastewater treatment plant was studied in terms of efficiency and gaseous emissions, by carrying out experiments in a bubbling fluid bed unit and was compared with that of an agricultural waste. The effects of excess air and fuel feeding rate were investigated and a factorial design and modelling was developed in order to provide optimal values of process variables for minimizing emissions. The results showed that sewage sludge fuel burned at a much lower temperature than the woody fuel. CO emissions were low, SO2 emissions from the agricultural waste negligible, while those of sewage sludge exceeded legislation limits when excess air was below 50%. An increase in excess air from 30 to 50%, or of fuel feeding rate from 0.48 to 0.6kg/h, resulted in higher NOx emissions from the woody fuel, exceeding emission guidelines. Concerning SO2 and NOx emissions from sewage sludge fuel, the effect of feeding rate was the same, however that of excess air was opposite, reducing their levels in flue gases. Combustion efficiency for both fuels was high, between 98.5 and 99.6%. Factorial design analysis and modeling indicated that for the woody fuel the optimum emission performance was accomplished when the feeding rate was 0.48 kg/h and the excess air 30%. For the sewage sludge fuel the optimum combustion and emission performance was achieved when the feeding rate was 0.72 kg/h and the excess air 50%.

Parameter study and optimization on filtration and resistance characteristics of granular bed filter

This paper reports a study on the simultaneous removal characteristics of SO3 in a wet flue gas desulfurization (WFGD) system. The impacts of the operating parameters, including liquid-to-gas (L/G) ratio, inlet SO3 concentration, flue gas temperature, superficial velocity, and slurry temperature, on the SO3 removal efficiency and SO3 aerosol characteristic were studied. Results showed that the overall SO3 removal efficiency varied from 20% to 55% under the experimental conditions. For the SO3 aerosol, particles measuring 0.5 μm had a higher removal efficiency, whereas particles measuring 0.1–0.5 μm were relatively difficult to remove in the WFGD system. Increases in L/G ratio and SO3 concentration exerted positive effects on the SO3 aerosol capture, whereas superficial velocity, flue gas temperature, and slurry temperature had negative effects. After installing a sieve plate, the SO3 removal efficiency increased from 49.88% and 53.46% to 51.77% and 58.05%, respectively, under two typical cond...

Modelling and simulation of coal gasification process in fluidised bed

A Twin Fluid-Bed Reactor for Removal of CO 2 from Combustion Processes

Experimental and theoretical study of fluidized bed for SO 2 recovery as sulfur from effluent gases from sulfur production unit

Catalytic pre-mixed fibre burners

Parallel LES-DEM simulation of dense flows in fluidized beds

The paper presents a study of the flow in a fluidized bed. The analysis is based on measurements made on an experimental stand and computer simulations. Free software packages have been used for simulations. Simulation is done used the most common model for this kind of problem. The first type of model is the Eulerian-Eulerian type and have as their first approximation, the assimilation of the solid phase with a continuous environment. The second category of models is Eulerian-Lagrangean type, they treat the fluid phase as continuous and the solid phase as individual particles or groups of particles “parcels” with similar characteristics. The results of the simulations were compared with the measurements performed on an experimental stand. The experimental stand is composed of a glass column with a diameter of 75mm and a height of 500mm and allows the study of flow in a fluidized bed containing spherical glass beads of 250–500μm in diameter. The results of the simulation were in good agreement whit measured data and in accordance whit the result presented in other specialized studies.

The emission from FBC is very dependent on a number of operating conditions (temperature, staged air, fuel feed rate, excess air, etc.) and fuel properties. This paper describes the experimental results taken in a staged air fluidized bed combustion laboratory scale, using palm fiber and palm shell as fuels and silica sand as the inert bed material. In this experiment, a variation of excess air and secondary air were measured. Measurement of gas emissions of CO and CO2 concentrations, combustion efficiency and temperature, were taken along the combustor height as well as in flue gas. The experimental results show that the axial temperature profiles decrease successively along the FBC height. The CO emission obtained was lower for the staged- air condition than for the un-staged-air condition. The combustion efficiencies show satisfactory values.

Simulation of the layer inversion phenomenon in binary liquid--fluidized beds by DEM–CFD with a drag law for polydisperse systems

Emissions from a conical FBC fired with a biomass fuel

Influence of air bubble size on float–sink of spheres in a gas–solid fluidized bed

An innovative semidry process has been developed to simultaneously remove NO and SO₂ from flue gas. According to the conditions of the flue gas circulating fluidized bed (CFB) system, ferrate(VI) absorbent was prepared and added to humidified water, and the effects of the various influencing factors, such as ferrate(VI) concentration, humidified water pH, inlet flue gas temperature, residence time, molar ratio of Ca/(S+N), and concentrations of SO₂ and NO on removal efficiencies of SO₂ and NO were studied experimentally. Removal efficiencies of 96.1% for SO₂ and 67.2% for NO were obtained, respectively, under the optimal experimental conditions, in which the concentration of ferrate(VI) was 0.03 M, the humidified water pH was 9.32, the inlet flue gas temperature was 130 °C, the residence time was 2.2 s, and the molar ratio of Ca/(S+N) was 1.2. In addition, the reaction mechanism of simultaneous desulfurization and denitrification using ferrate(VI) was proposed.

The effect of particle size and bed height on the expansion of mixed phase (gas—liquid) fluidized beds