微波辐照再生活性炭试验研究

Experimental Study on Regeneration of Activated Carbon by Microwave Irradiation

针对载金用活性炭热再生能耗高、耗时长、炭损高和活化程度低等问题,基于炭材料良好的吸波性,开展微波辐照再生活性炭的试验研究。单因素试验表明活化效果与再生温度呈正相关,再生温度以650~750℃为宜;贫炭水份以30%左右为佳,过高或过低均会降低活化效果,可能与介电能力相关;多次辐照作业只有在高温时(≥700℃)有明显作用。相比热再生技术,达到同等活化程度时,新技术节能30%~50%,且炭损更少。在700℃、30%水份条件下微波再生炭碘值接近新炭。在之后的酸洗作业中,微波再生炭更易被清理,元素和物相分析表明炭中的CaO等无机污染物被大量去除。BET测试和SEM表征显示微波再生炭的比表面积和总孔容比热再生炭更高、孔道更粗,支持了上述结论。

Activated Carbon(AC)is widely used as adsorbent in the process of gold extraction.In the cycle of gold leaching-adsorption-desorption,the AC needs to be activated regularly for reuse,which mainly depends on thermal regeneration,that is,the whole rotary kiln is heated and then AC are heated from outside to inside by heat conduction,where the pollutants are volatilized or decomposed,cleaning the carbon surface and dredging the pores.The thermal regeneration method still has the shortcomings of high energy consumption,large carbon loss and long operation time.The evaporation of pore water takes prolonged time and absorb extensive heat,restricting the improvement of efficiency and effect,which is difficult to be solved.Considering that AC is a good wave-absorbing material,it can be heated directly from the inside to the outside by microwave irradiation,which can greatly improve the energy efficiency.The technique of AC regeneration with 2.45 GHz microwave was studied by experiments where iodine value,specific energy and carbon loss were investigated.The results show that high temperature improves activation efficiency significantly and 650~750℃ is recommended;The moisture of AC was optimum at 30%,which might be related to dielectric variation;Execution times could only play a role at high temperature(≥700℃).Compared with thermal regeneration,the technique saved 30%~50% energy to achieve equal activation with a lower carbon loss.At 700℃ temperature,30% moisture,the regenerated carbon and fresh carbon have approximate iodine value.In the regenerated carbon processed by the technique is feasible to pickling operation that inorganic pollutants(e.g.calcium oxide)are cleaned up effectively.Moreover,BET and SEM detections also supporte the above results at a micro level,i.e.the specific surface area and total pore volume of the carbon is higher than the ones processed by thermal regeneration.