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

Highlights: • Fluidized bed technology is introduced into evaporation process of Na₂SO₄ solution. • The addition of SiC particles can enhance heat transfer in Na₂SO₄ solution. • 1 mm SiC particles can enhance heat transfer more effectively. • Enhancing factor decreases with the increase in heat flux. • Amount of added particles of 1.5% may be the optimum for antiscaling in tested range. -- 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.