预焙阳极铝电解槽碳渣零排放试验研究

Experimental Study on Zero Discharge of Carbon Dross from Pre-baked Anode Aluminum Electrolytic Cell

碳渣是铝电解槽生产过程中产生的固体危险废物。本文在马弗炉中进行了碳渣的燃烧试验。试验结果表明,不添加覆盖料时,在温度500℃以下,碳渣很难燃烧;温度500℃时,碳渣开始燃烧;在600℃环境下,碳渣需要5 h才能燃烧充分;在高于700℃环境下,只要2 h,碳渣就能充分燃烧,且碳渣中电解质熔融,冷却后会结焦。添加覆盖料进行碳渣燃烧试验时,在温度500℃以下,覆盖料与碳渣无变化;在550℃条件下燃烧8 h,碳渣呈灰白色,燃烧完全;在温度600℃以上,碳渣燃烧加速,5 h后碳渣完全燃烧;在温度700℃以上,燃烧超过3 h,碳渣易与覆盖料熔化粘结,导致氧浓度变小,碳燃烧困难。电解槽的预焙阳极具有满足碳渣燃烧所需的温度和氧气条件,将碳渣放在更换阳极上,利用电解槽自身的热量燃烧,最后碳渣中的碳基本燃烧完全。经过高锂盐和低锂盐电解质体系电解槽的实践应用,证实碳渣燃烧可实现对外的零排放。

Carbon dross is a hazardous solid waste produced in aluminum electrolytic cell production.A combustion test of carbon dross in Muffle furnace has been conducted.The test results show that when no covering material is added,carbon dross is barely combustible at the temperature of below 500℃;at 500℃,carbon dross starts to be combusted;at 600℃,it takes 5 h for full combustion of carbon dross;at the temperature of above 700℃,only 2 h is needed for full combustion of carbon dross,and the electrolyte in carbon dross is molten and becomes coked after cooling.In case of adding covering material,both carbon dross and covering material have no change at the temperature of below 500℃;at 550℃with the combustion lasting 8 h,carbon dross takes on grey white and is completely combusted;at the temperature of above 600℃,carbon dross speeds up combustion and is fully combusted after 5 h;at the temperature of above 700℃with the combustion lasting for more than 3 h,carbon dross and covering material are molten and bond with each other,resulting in lower oxygen concentration and hindering carbon combustion.The pre-baked anode of electrolytic cell can provide the temperature and oxygen conditions required for carbon dross combustion.Carbon dross on the replaced anode can be combusted completely by using the heat energy released by the anode.The practical application in high and low lithium salt electrolyte system aluminum electrolysis series has proved that zero discharge of carbon dross can be realized by carbon dross combustion.