Pilot Study On The Preparation Of Activated Magnesium Oxide With Multilayer Fluidized Bed

As an important inorganic chemical product, activated magnesium oxide has been widely used in the preparation of chloroprene rubber, adhesive, tire, conveyor belt,medicine, steel, phosphor and other various industries. Different activities and other properties of activated magnesium oxide are required in the different process industries. At present, the preparation methods of activated magnesium oxide is mainly obtained by calcination of magnesite, bischofite, brucite, magnesium carbonate and magnesium hydroxide, and the calcinators are including rotary calciner and spiral flow calcinator in commercial process. Because the diameter of rotary calcinator is often pretty large, the temperature in the furnace is difficult to maintain the same between internal and furnace wal, which results in different activity of product powder. Due to short contact time in spiral flow calcinator, the activities of product are also not controllable. Multilayer fluidized bed calciner as magnesium hydroxide calcination equipment was proposed in this thesis in order to realize the controllability and homogeneity of activity.Firstly, experiments on static calcination of magnesium hydroxide from Nafine Group Co. Ltd. were made in a muffle furnace. The influence factors including calcination temperature, calcination time and heating rate on the activity of activated magnesium oxide were examined. The results show that the highest activity of magnesium oxide was reached in the conditions: calcining temperature of 450 ℃, calcining time of 1h, 20 min heating rates. The iodine absorption can reach a maximum of 127 mgI2/g MgO, the purity reached to 92%, BET is 57m2/g.Cold model multilayer fluidized bed was design and manufactured to explore its suitable structure including distribution plates and connecting pipe between adjacent layers. The experimental results show that distributor with hood type is suitable for this powder. The arrangement gas-jet hole is square, hole spacing is 22 mm, hood height is22 mm, the distribution plate for louver single rotary guide baffle, and the connecting pipe is a straight pipe type overflow pipe. Multilayer fluidized bed calcinator with above structure gave good fluidization effects.Based on the cold model experimental results, hot model multilayer fluidized bed calcinator was design and manufactureed. The calcinating experiments were made on this hot model device. The results show that the temperature inside the bed layer is uniform,and magnesium hydroxide powder is in a good fluidized state. By adjusting the feedingquantity and the calcination temperature of each layer, higher activity of activated magnesium oxide can be reached, and iodine value and specific surface area values are higher, compared to the static calcination experiments. The iodine absorption can reach142 mgI2/gMgO, the purity can reach 92%, and the BET value is up to 147m2/g.