Investigation of continuous carbothermal reduction of magnesia by magnesium vapor condensation onto a moving bed of solid particles
Investigation of continuous carbothermal reduction of magnesia by magnesium vapor condensation onto a moving bed of solid particles
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DOI：
10.1016/j.powtec.2019.01.067
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发表时间：
2020-04-01
影响因子：
5.2
通讯作者：
Weimer, Alan W.
中科院分区：
文献类型：
--
作者：
Chubukov, Boris A.;Rowe, Scott C.;Weimer, Alan W.
如果实现高的镁金属产率，则通过碳热还原（CTR）生产镁金属相对于硅热或电解生产可以减少工艺排放和能量需求。研究了一种新的工艺，其中产物镁气体在高温（>= 300 ℃）和真空下冷凝到固体颗粒的移动床上，以最小化逆转并促进晶体生长。使用人工产生CTR产物气体的半系统，镁连续冷凝到钢、氧化物或碳化物颗粒上，对于P-Mg = 0.5 kPa，产率>85%。钢颗粒表现出最大的床保留和易于分离，因此该介质用于按比例放大到全系统，其中MgO CTR在1400 ℃-1550 ℃的固定床气化器中产生Mg-（g）和CO。初始还原导致高Mg产率（>80%），但产率随着反应进行而降低。Mg ~（2+）和返原产物在冷凝器中的积累促进了返原的进一步发展。通过使用高表面积颗粒来促进传热和传质，从而缩短固体和气体在冷凝器中的停留时间，可能会提高工艺产率。反应器管和颗粒床的有限体积模型描述了还原反应器中的动力学、传热和传质现象。该模型预测床的中心比炉冷>50 ° C，并且产物气体压力接近平衡。宽的直接加热的反应器可以克服这些传热和传质限制。(C)2019 Elsevier B. V.版权所有。
Magnesium metal production by carbothermic reduction (CTR) can reduce process emissions and energy requirements relative to silicothermic or electrolytic production, if high magnesium metal yields are achieved. A novel process was investigated where product magnesium gas condensed onto a moving bed of solid particles at high temperatures (>= 300 degrees C) and in vacuum to minimize reversion and promote crystal growth. Using a half-system in which CTR product gases were artificially generated, magnesium continuously condensed onto steel, oxide, or carbide particles at yields >85% for P-Mg = 0.5 kPa. Steel particles exhibited the greatest bed retention and ease of separation, so this medium was used for scale-up to a full-system in which MgO CTR in a fixed bed gasifier at 1400 degrees C-1550 degrees C produced Mg-(g) and CO. The initial reduction resulted in high Mg yield (>80%), but yield decreased as the reaction proceeded. The accumulation of Mg-(s) and reversion product in the condenser promoted further reversion. The process yield could likely be improved by using high surface area particles to promote heat and mass transfer, allowing for shorter solid and gas residence times in the condenser. A finite volume model on the reactor tube and pellet bed described the kinetics, heat transfer, and mass transfer phenomena in the reduction reactor. The model predicted that the center of the bed was >50 degrees C cooler than the furnace, and the product gas pressures were near equilibrium. A wide and directly heated reactor could overcome these heat and mass transfer limitations. (C) 2019 Elsevier B.V. All rights reserved.