| Wet desulphurization is the main process for controlling sulfur dioxide emissions in coal-fired power plants.The process has high energy consumption and the removal rate of pollutants is also affected by the parameters of the inlet flue gas.The desulphurization and dust removal performance of the integrated desulphurization and dust removal tower can be improved by adjusting the parameters of the inlet flue gas.Meanwhile,the system has a great potential of waste heat recovery,which can combine the parameters adjustment of the inlet flue gas with waste heat recovery,so as to realize the operation of the system with high efficiency and low energy consumption.In this paper,the influence characteristics of inlet flue gas velocity,temperature,SO2 mass concentration and liquid-gas ratio on desulfurization and dust removal performance were studied by CFD.At the same time,coupling process systems of flue gas conditioning and heat recovery are put forward.And combined with the economic analysis method,the energy consumption and coal saving are calculated to provide a reference for the system optimization.The study of desulfurization performance shows that the inlet flue gas velocity is a direct factor affecting the flow field uniformity of desulfurization tower.The velocity uniformity index has a negative correlation with the inlet flue gas velocity and a positive correlation with the liquid-gas ratio.When the liquid-gas ratio is greater than12.08 L/m~3,regulating the inlet flue gas velocity cannot effectively change the desulfurization efficiency.The increasing of inlet flue gas temperature is not conducive to the absorption reaction of SO2 in the tower.The higher the SO2 concentration at the inlet,the lower the desulfurization efficiency is.Which is due to the limitation of droplet absorption capacity.With the increasing of liquid-gas ratios,the desulphurization efficiency increases rapidly at first and then slows down as the amount of slurry increases greatly.The optimal operating parameters were determined as inlet velocity is 8 m/s,inlet temperature is 85℃,inlet concentration is 1000～3500 mg/Nm~3,liquid-gas ratio is 13～15 L/m~3.The results of the study on the performance of the desulfurization tower show that the contribution of inertia capture is the largest,but the contribution of thermophoresis and interception is lower.The removal efficiency of submicron particles is poor in the desulfurization tower,while the removal efficiency of particles larger than 3μm is close to 100%.Dust removal efficiency is mainly affected by flue gas velocity,temperature and liquid-gas ratio.The particle removal efficiency greater than 1μm is less affected.The removal efficiency of particles less than 1μm increased with the increase of the three parameters,but the removal efficiency is low.When the flue gas velocity at the entrance of desulfurization tower increased,the total dust removal efficiency is kept at81%.When the inlet flue gas temperature increased,the total dust removal efficiency also increases,but the change range is less than 2%.When the liquid-gas ratio increased,the total dust removal efficiency increased rapidly and then slowed down.Total dust removal efficiency up to 86%.Four coupling processes of inlet flue gas conditioning and waste heat recovery are also studied.Thermal economy calculation shows that when condensate is used as heat transfer medium,the total waste heat recovery capacity is higher,and the system investment and energy consumption are lower.In scheme D,when the waste heat is imported into the heat return system,according to the theory of energy cascade utilization and the principle of minimum temperature difference at the inlet point,the waste heat is recovered to the sixth and seventh level of the unit respectively,which significantly reduces the effective energy loss of the system and maximizes the economic efficiency of the system.The percentage of exergy loss was 1.05%,and the energy consumption increased by 1163 k W,which reduced the coal consumption of 660MW generator set by 2.373 g/k W·h. |
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