淘洗六水氯化铝过程中晶体沉降速度与纯化规律分析

针对粉煤灰酸法制氧化铝工艺中六水氯化铝结晶纯度难以控制、需进一步纯化的问题建立液固淘洗过程模拟实验，考察了液相密度、黏度、颗粒粒度及体积分数对颗粒沉降速度的影响，并用液体对颗粒的抵抗阻力对其修正，建立了关于沉降速度的计算模型，相对误差小于10%，能够较好地预测该体系下颗粒的沉降速度。按照淘洗过程模拟实验条件及对应的颗粒沉降速度设计静态实验，考察了钠、钙、镁和钾4种杂质离子随淘洗时间的变化规律，得到较优淘洗时间为60s。实验结果表明，杂质离子脱除率依次为Na⁺>Ca²⁺>Mg²⁺>K⁺，且最高脱除率均可达80%以上，杂质离子脱除率随着液固比的增大而提高，与沉降速度计算模型趋势一致，研究结果可为淘洗工艺的设计计算和优化提供参考。

Analysis of crystal settling velocity and purification law in the elutriation process of aluminum chloride hexahydrate

Aiming at the problem that the crystal purity of aluminum chloride hexahydrate was difficult to control in the process of preparing alumina from the fly ash by acid method and further purification was needed, a simulation experiment of liquid-solid elutriation process was established. The effects of liquid phase density, viscosity, particle size, and particle volume fraction on the settling velocity of the particles were investigated and corrected by the resistance of the liquid to the particles, and a calculation model for settling velocity was established, which had relative error of less than 10% and could better describe the settling velocity under the system. Designing the static test according to the simulated experimental conditions of the elutriation process and the corresponding particle settling velocity, the change rule of four impurity ions of sodium, calcium, magnesium and potassium with elutriation time was investigated, and the better elutriation time was 60s. Experimental results show the removal rate of impurity ion is Na⁺>Ca²⁺>Mg²⁺>K⁺, and the highest removal rate of each ion can reach more than 80%; the impurities elutriation removal rate of the crystals increase with the increase of the liquid-solid ratio, which is consistent with the settling velocity calculation model; and the research result provides a reference for the design calculation and optimization of the elutriation process.