Study on Preparation of Magnesium Hydroxide by Continuous Forced Circulation Process

Abstract

A continuous process for preparation of magnesium hydroxide with a forced circulation tubular reactor is proposed. The residence time distribution of the liquid in the reactor at different flow rates is measured, and the parameters of the tanks‐in‐series model are obtained. Using soluble magnesium salt and ammonia as raw materials, magnesium hydroxide is prepared. The effect of the flow rates on the product quality is investigated. The results show that the smaller the flow rate, the longer the residence time of the liquid in the reactor and the better the dispersion and crystal morphology of the products. When the total volume of the reactor is 300 mL and the flow rates are 5–50 mL min⁻¹, the values of the average residence time of the liquid are 3094–351 s and the parameters of tanks‐in‐series model are 1.05–1.52. The reactors are closer to the continuous stirred tank reactor. The average particle sizes of the magnesium hydroxide products are 2.32–2.47 µm, and the values of I₀₀₁/I₁₀₁ are 1.17–0.89. The crystal morphology is flaky. Being compared with that from magnesium sulfate, the magnesium hydroxide products from magnesium nitrate have smaller particle size and better dispersibility.