Experimental validation of properties on new fluidized-bed catalyst cooler

Key words:  external catalyst cooler  heat pipe  heat transfer  fluidized bed  reactor  catalytic cracking  methanol to olefins

Abstract:

In view of the complex system, low long-period reliability and low heat transfer efficiency of traditional external catalyst cooler which is commonly used in industrial fluidized bed reactors, a new fluidized-bed catalyst cooler based on the heat pipe with a higher reliability was proposed. In order to investigate the heat transfer and fluidization characteristics of the new catalyst cooler, a small-scaled hot pilot plant was designed and established. The starting-up, fluidization hydrodynamics and effects of different factors on the dense-bed heat transfer coefficient of the heat pipe were systematically studied. The results show that the heat pipe has a very high heat transfer efficiency, which manifests that the heat transfer characteristics measured by the new catalyst cooler are generally in agreement with the convective heat transfer characteristics of dense fluidized bed reported by previous literature. The measured heat transfer coefficients also have the similar range of value. The maximum heat transfer coefficient of heat tube measured in the fluidized bed of FCC particles is up to 620 W/(m²·K), which is higher than the reported data of all industrial FCC external catalyst coolers. This fact can fully validate the feasibility of heat pipe as a new heat transfer element in external catalyst coolers. Among the factors affecting the heat transfer coefficient, the apparent gas velocity is the most important, followed by the bed height and the bed temperature.