Study on regeneration process and effect of activated carbon for water treatment in multiple hearth furnace

China has the highest consumption of coal-based activated carbon in the world,especially in the field of water treatment.If saturated or ineffective activated carbon for water treatment has been abandoned without recycled,not only is a waste of resources,but also will cause secondary pollution and other problems.Thermal regeneration is the most effective regeneration method for saturated activated carbon.Multiple hearth furnace has the advantages of accurate temperature control,adjustable atmosphere in the furnace,and high degree of automation,it is ideal thermal regeneration equipment for saturated activated carbon.However,the regeneration process and regeneration effect of saturated activated carbon for water treatment by multiple hearth furnace are not clear.The thermal regeneration process conditions were initially explored by the laboratory rotary furnace,and then the industrial multiple hearth furnace was used for the thermal regeneration production.The key process parameters were adjusted and correlated with the regeneration yield,iodine value and hardness of the activated carbon after regeneration to optimize the regeneration process.The results show that the iodine value of activated carbon after regeneration is increased from 546 mg/g to 995 mg/g in the temperature range of 470～917 ℃, and the adsorption performance is recovered by 97.5%, which is better than the regeneration effect of laboratory rotary furnace; the regeneration end-point temperature of bottom furnace is the key parameter of regeneration process, and the iodine value of activated carbon after regeneration decreases with the decrease of regeneration end-point temperature,the strength increases accordingly. At 810 ℃, the iodine value of activated carbon reach 917 mg/g, the strength reach 95.1%, and the reprocessing rate is about 73%. Under the weak oxidizing atmosphere of multiple hearth furnace, a small amount of O2 promotes the oxidation and decomposition of organic matter in the pores of activated carbon, and improves the adsorption performance of regenerated activated carbon. Under high temperature,O2 will inevitably ablate the activated carbon, resulting in low reproduction rate and low strength of the regenerated activated carbon.