Simulation of a bubbling fluidized bed reactor for phosphogypsum decomposition with carbon monoxide

Abstract

Phosphogypsum (PG), a by-product of the phosphoric acid industry and rich in calcium sulphate (CaSO₄), has an unfavourable environmental impact, making its management one of the crucial issues of phosphoric acid production. As a result, PG production is integrated with or without treatment in many industries, such as agriculture, building materials, and sulphuric acid. In the latter application, carbon monoxide (CO) is used to decompose PG to extract the sulphur according to a two-parallel reaction producing calcium sulphide (CaS) and calcium monoxide (CaO) in the solid phase. To depict the effect of the solid temperature (T), CO partial pressure (P_CO), inlet gas velocity (U₀), residence time ($\tau$), particle size (PS), and solid exchange coefficient ($K_p$) on the overall fluidized bed reactor performance, a simulation study was performed according to the dynamic two-phase model. The results show that CO partial pressure, solid residence time, particle size, and inlet gas velocity have the most significant effect on the PG conversion. On the other hand, the temperature and partial pressure of CO have the most critical effect on product selectivity. The concentration profiles of both reactants CaSO₄ and CO reveal that the reaction in the emulsion phase is faster than in the bubble phase due to the good mixing in this phase.