Experimental Study On Adsorption Mechanism Of SF₆ Insulation Equipment Adsorbent And Its Hazards Reduction Treatment Method

SF₆ gas will decompose under partial discharge,overheating,etc.,and chemically react with micro-water and micro-oxygen in the equipment to generate toxic and harmful substances.Therefore,adsorbent is often placed in SF₆insulation equipment to control the content of micro-water and SF₆ decomposition products,to ensure the insulation of the equipment and safe operate.The adsorbent will adsorb toxic and harmful substances during operation,if it is directly discarded without treatment after decommissioning,the adsorbate in the adsorbent will cause serious harm to the environment.In this paper,the adsorption mechanism of the adsorbent is analyzed and discussed,and the experimental study on the harm reduction treatment of the adsorbent is carried out.Based on the first-principles density functional theory（DFT）,this paper uses the Dmol³module to calculate and study the adsorption mechanism of SO₂F₂ and SOF₂on the surface ofα-Al₂O₃（0 0 0 1）.Further,chemical precipitation-coagulation method was used to reduce the harm of the decommissioned SF₆ adsorbent,which involving theoretical knowledge in electrical,chemical,material and other aspects.Its main work and conclusions are as follows:（1）Using the Fourier transform infrared spectrometer,research on adsorbate detection in adsorbent is carried out,it is found that the SF₆ adsorbent mainly adsorbs SF₆ decomposition products such as SOF₂,SO₂,SOF₄,SO₂F₂ and HF,etc.（2）Based on the DFT,research on the adsorption mechanism of SO₂F₂ and SOF₂ on the surface ofα-Al₂O₃（0 0 0 1）is carried out.Results show that the adsorption effect of SOF₂molecules on the surface ofα-Al₂O₃（0 0 0 1）is stronger,and the architecture changes significantly before and after adsorption.Also,the adsorption process is an exothermic phenomenon,with a large charge transfer,the adsorption process is mainly chemical adsorption.And the adsorption parameters of SO₂F₂ gas molecules are small,the adsorption process is mainly physical adsorption.（3）On the basis of shaking leaching method,the fluorides in decommissioned SF₆adsorbents are leached in ionic form.And lime is used as the precipitant to defluorination.Under the conditions of the calcium-fluorine molar ratio of 3,the p H of the reaction solution of9,and the reaction standing time of 1.5 h,the residual fluorine in the effluent reaches 67.64mg/L.（4）Based on the treatment of lime precipitation,PAC is selected as coagulant and PAM as coagulant aid for deep defluorination.During the coagulation process,under the circumstances that process parameter of p H is around 6 to 7,the process parameter of the dosage of PAC is150 mg/L and the process parameter of the dosage of PAM is 2 mg/L,the defluorination effect is the best,the residual fluorine in the effluent is reduced to 7.29 m/L which is in line with the national classⅠemission standard,the harm reduction of the decommissioned sulfur hexafluoride insulating equipment adsorbent is realized preliminarily.