Numerical optimization of process parameters in HLLW spray calcination

Abstract

To address the issues of incomplete reactions and potential solids accumulation in high‑level liquid waste (HLLW) spray calcination, this study developed a 3D computational domain utilizing a species transport model to simulate the combustion of a nitric acid, sucrose, and nitrate solution. The impacts of wall heating temperature (200–1200 °C), porous media porosity (0–1), inlet velocity (0.001–0.2 m/s), and reactant concentrations on the sodium oxide (Na 2 O) product mass fraction were systematically investigated. Simulation results demonstrate: (1) wall temperature positively correlates with Na 2 O formation, with the mass fraction rising from 0.089 to 0.360 as temperature increases from 200 °C to 1200 °C; (2) higher porosity facilitates product formation, though growth stagnates within the 0.2–0.8 range; (3) inlet velocity dictates reaction kinetics, peaking at an optimal 0.01 m/s (Na 2 O mass fraction 0.287), whereas velocities >0.05 m/s cause incomplete reactions; and (4) doubling sucrose concentration boosts Na 2 O yield by 115% and 180% more than equivalent increases in nitric acid and nitrates, respectively. Enhancing solid product recovery requires elevating wall temperature, regulating inlet velocity at approximately 0.01 m/s, and optimizing the sucrose reductant ratio.