Separation and Recovery of Insulation Gas Mixtures by Using a Membrane

SF6气体具有极高的全球变暖潜势(GWP)，世界范围内的减排努力不仅涉及电力行业，还涉及到镁工业、电子工业等其他行业。减少或减少电力设备中SF_6含量的实用方法之一是利用加压气体混合物，其中低含量的电负性气体与普通气体如N_2、CO_2或空气混合。然而，在低浓度SF6混合气体的情况下，常规液化方法很难应用，因为液化过程中SF6的回收损失或释放到大气中的速率很高。一种聚合物膜。实验研究了回收气体中SF_6的浓度、回收损失和气体处理速度。首先，我们研究了从含SF_6的5-20体积混合气体中回收气体。%，并阐明了回收气的纯度和回收损失取决于原料气的混合比、膜温度和进料压力等各种参数。当混合比为10vol.%，如回收气中SF_6的纯度大于90%。其次，我们研究了两个分离器串联的回收方法，以尽可能保持回收气的纯度，并将回收损失降至最低。用该方法可将纯度提高到98Vol。%甚至更高，当气体处理速度约为13NI(正常排气)min^&lt；-1时，采收率损失降低到1%。最后，我们开发了一种系统，它可以自动控制释放的气体浓度，并将回收损失控制在所需的较晚时间。

The worldwide effort of reducing SF_6 gas, which is of extremely high global warming potential (GWP), concerns not only the electric power industry but also other sectors such as the magnesium industry, the electronics industry and so on. One of the practical solutions of reducing or minimizing the amount of SF_6 in electric power apparatus is to utilize a pressurized gas mixture, in which a low content of an electronegative gas is mixed with an ordinary gas such as N_2, CO_2 or air. However, in the case of a gas mixture including a low concentration of SF_6, the conventional liquefaction method is difficult to apply, since the recovery loss or the release rate of SF_6 into the atmosphere during the liquefaction process is very high.We have developed a method to recover SF_6 from gas mixtures composed of SF_6 and N_2 by using. a polymer membrane. The concentration of SF_6 in a recovered gas, the recovery loss and the gas handling speed are investigated experimentally.First, we have investigated gas recovery from gas mixtures containing SF_6 of 5 - 20 vol. % using a single membrane separator, and clarified that the purity of recovered gas and the recovery loss depend on various parameters such as mixing ratio of an original gas, the temperature of the membrane and the feeding pressure. When the mixing ratio is 10 vol. %, for example, the purity of SF_6 in the recovered gas is higher than 90 vol. %, but the recovery loss is inadmissibly high as 20 - 50 %.Second, we have investigated a recovery method using two separators connected in cascade to keep the purity of recovered gas as high as possible and minimize the recovery loss. With this method, the purity increases up to 98 vol. % or even higher, and the recovery loss decreases as low as 1 % at a gas handling speed of about 13 NI (normal litter) min^<-1>. Finally, we have developed a system which allows automatic control of the released gas concentration and keeps the recovery loss at a required late.