Heat transfer and antiscaling performance of a Na2SO4 circulating fluidized bed evaporator

Abstract

An circulating fluidized bed evaporator of Na2SO4 solution is designed and built to investigate heat transfer and antiscaling performance by varying the amount of added particles (0.5%–2.0%), heat flux (6.47–13.65 kW·m−2) and circulation flow velocity (0.38 m·s−1–2.07 m·s−1). SiC particles are used as inert solid particles. The experiments are operated under normal pressure, and the operating temperatures of fluid is about 101–103 °C within the experimental range. The research results show the addition of SiC particles can not only effectively enhance the heat transfer performance in Na2SO4 solution, but also remove and prevent scaling. The effect of heat transfer performance is strongly dependent on the particle size. The maximum enhancing factor of 1 mm SiC particles is 17.1% at ε = 2%, u = 0.38 m·s−1 and a heat flux of 8.97 kW·m−2. With an appropriate amount of added particles, 1 mm SiC particles can effectively prevent scaling in the evaporation of Na2SO4 solution. The research findings may be beneficial to the application of fluidized bed heat transfer and antiscaling technology to industry.