Abstract: No gap desulfurization( NGD) has great prospects for the pulverized coal industrial boilers due to low investment and operating costs,saving space,saving water and refraining from the colored plume.However,the investigations reported mainly pay attention to the reaction process of desulfurization and its influence factors.It's still unclear about the flow field and the energy consumption inside the NGD reactor.Based on the entropy generation theory,a model for quantitatively predicting the energy consumption inside a NGD reactor was established.The energy consumption results from the heat loss of flue gas and the flow of viscous fluid.The energy consumption of flow is mainly attributed to the turbulent dissipation and fluid friction near the wall.In addition,the potential energy should not be neglected at the pressure drop of inlet and outlet as the NGD reactor is usually higher than 20 m.Thus,the pressure drop of NGD reactor can be attributed to the potential energy,turbulent dissipation and fluid friction near the wall.The numerical investigation was carried out for a NGD reactor from a 30 t/h pulverized coal industrial boiler by using CFD method.And the energy consumption and distribution inside the NGD reactor was analyzed by using the energy consumption model based on the CFD data.The results show that the CFD method and the energy consumption model can precisely predict the inlet and outlet pressure drop of NGD reactor with the deviations of 0.4% and 9.6% compared with the measured data,respectively.Therefore,CFD method and energy consumption analysis model can accurately predict the energy consumption caused by viscous fluid flow in the desulfurization reactor.The flow of viscous fluid is the main factor of energy consumption because the ratios of energy consumption due to the flow of viscous fluid and heat loss are 96.2% and 3.8%.It can be seen that viscous fluid flow plays a leading role in the energy consumption of NGD,and the pressure drops due to the change of potential energy,the turbulent dissipation and the fluid friction near the wall are 237.6,347.4 and 57.5 Pa respectively,indicating that the turbulent dissipation is the main factor for the energy consumption.The NGD reactor is divided into the middle part of speed-up zone and the underpart of flue gas inlet zone.Because the energy dissipation in the viscous fluid flow comes from the friction dissipation caused by the velocity difference of different flow layers,the energy consumption depends on the velocity gradient of fluid flow.The high velocity and the high non-uniform flow field inside the middle part of speed-up zone results in the highest entropy generation due to turbulent dissipation per volume. Therefore,although its volume accounts for only 3.6%,the ratios of entropy generation inside the middle part of speed-up zone is 53.8% with a small part of volume.The ratios of entropy generation and volume inside the upper part of main reaction zone are 40.1% and 88.3% with a low velocity and relatively homogenous flow field.The entropy generation increases with position with a low average velocity and a high non-uniform flow field inside the underpart of flue gas inlet zone.The ratio of entropy generation is 6.1% and the ratio of volume is 13.1%.It can be seen that the energy is mainly consumed in the upper part and the middle part.And,it will be most useful to decrease the energy consumption by modifying the middle part.