Flue Gas Water Recovery by Indirect Cooling Technology for Large-Scale Applications: A Review

With social development and economic enhancement,energy is facing significant worldwide demand,and fossil fuels are the prime energy sources for various energy systems over past decades.Furthermore,among fuel-consumed applications,power plants are the primary source of energy consumption.There is a lot of waste heat and steam accompanied by the latent heat produced in the exhaust flue gas.Therefore,the latent heat recovery from the flue gas plays an important role in increasing the efficiency of the system and saving water.To recover the heat and mass in power plants,three primary methods are proposed to condense the vapor based on previous studies:(1)flue gas condensation technology,(2)liquid desiccant-based dehydration(LDD)technology and(3)membrane technology.This paper mainly reviews and summaries the indirect cooling technology in flue gas condensation technology.The numerical simulation and theory of flue gas condensation are introduced.Different heat exchanger types and conducted experiments are also summarized.The performance of the indirect cooling technology is affected not only by its own configuration and design but also by the flue gas inlet temperature,velocity,water vapor mass fraction,etc.The major concerns and outlook of practical applications for further study are attributed to the heat exchanger size and cost,acid corrosion,ash accumulation in flue gas,etc.

Experimental study of the flow and heat transfer of a gas–water mixture through a packed channel

Waste heat recovery from the flue gas of gasfired boilers was studied experimentally by measuring the flow and heat transfer of air and water through six kinds of packing with saturated humid air as the simulated flue gas.The experiments measured the effects of inlet air temperature, inlet air velocity and circulating water flow rate on the flow and heat transfer. The results show that higher inlet air temperatures and lower inlet air velocities lower the flow resistance and increase the heat transfer coefficient. The stainless steel packing had better surface wettability and larger thermal conductivity than the plastic packing, which enhanced the heat transfer between the water and the saturated moist air. When both the flow resistance reduction and the heat transfer enhancement were considered, the experimental results gave an optimal packing-specific surface area. A packed heat exchanger tower was designed for waste heat recovery from the flue gas of gas-fired boilers based on the experimental results which had better flow and heat transfer characteristics with lower pump and fan power consumption, more stable system operation and less thermal fluctuations compared with a non-packed heat transfer system with atomized water.

非金属烟气净化换热器传热及除尘试验研究

针对电厂烟尘排放超标、烟气余热浪费及烟气段金属换热器腐蚀等问题，设计制作一台试验台及由聚四氟乙烯制成的非金属烟气净化换热器，将其放置在电厂脱硫塔后的烟道中测试。通过对非金属烟气净化换热器前后的相关温度和压力点进行试验监测，得出换热器的冷凝传热系数可达170～190w／（m2·K），换热性能良好，除尘效果优异，可推广应用于烟气余热利用、烟气除尘领域。

铝扁锭车间熔炼/保温炉除尘优化改造

文章以某公司扁锭车间熔炼/保温炉组除尘改造为工程实例,结合烟气特性、生产操作过程特点提出了新的烟气净化工艺。经过长期运行,该烟气净化系统运行稳定,污染物排放浓度达标,车间空气环境质量得到极大改善。

Heat Transfer Enhancement and Vortex Flow Structure in the Spirally Fluted Tubes

The turbulence kinetic energy and heat transfer performance of air in spirally fluted tube were numerically studied at a constant wall temperature with Reynolds number(Re)between 5000 and 45000.Furthermore,the flow dynamics and heat transfer performance of spirally fluted tubes with five different geometric parameters as well as the effects of separation vortex and swirling wake flow on heat transfer and flow resistance were analyzed.According to the results,heat transfer is enhanced mainly because the fluid hit the windward side of the flute,thus generating a strong turbulence kinetic energy to further reconstruct the boundary layer.The second reason is that the formation of the recirculation zone between the flutes disturbs the boundary layer caused by the flow separation.With the increase of flute depth ratio(L_(d)/D),the separation vortex will become stronger and larger on the leeward side of flute.The separation vortex will break the boundary layer and improve the heat transfer capacity which is accompanied with the increase of fluid resistance.As the flute pitch length ratio(L_(p)/D)decreases,the spiral flow is strengthened,and meanwhile more wake flow is generated.The spiral flow causes little impact on enhancing heat transfer but inhibits the development of the separation vortex and fluid pulsation;in addition,the fluid resistance is reduced at the same time.The maximum value of the average Nusselt number appears when Re=5000,L_(d)/D=0.25 and L_(p)/D=1.00,which is 2.53 times the value of smooth tube.In view of the whole range of Reynolds number,the thermal performance enhancement factor indicates that L_(d)/D=0.15 and L_(p)/D=1.00 are the optimal geometric design parameters.