Removal of polyhalogenated biphenyls from organic liquids

A continuous process for the removal of PCB's from a transformer oil contained in an operating transformer which comprises:

• (a) removing from said operating transformer a first portion of transformer oil contaminated with PCB's;
• (b) passing said first portion through a first column containing a carbon adsorbent to selectively adsorb PCB's from said first portion;
• (c) returning a first partially purified portion to said transformer;
• (d) removing from said operating transformer a further portion of transformer oil contaminated with PCB's;
• (e) passing said further portion through said first column to selectively adsorb PCB's from said further portion;
• (f) returning a further partially purified portion to said transformer;
• (g) repeating steps(d), (e) and (f) a sufficient number of times, N, until the adsorptive capacity of said first column is diminished to the point where no further appreciable adsorption of PCB's can be effected by passing further portions of PCB-contaminated transformer oil through said first column;
• (h) removing adsorbent of diminished adsorptive capacity from said first column and replacing with fresh carbon adsorbent;
• (i) removing from said transformer an (N+1)th portion of transformer oil contaminated with PCB's;
• (j) passing said (N+1)th portion through a second column containing fresh carbon adsorbent to selectively adsorb PCB's from said (N+1)th portion;
• (k) returning the partially purified (N+1)th portion to said transformer;
• (l) removing from said operating transformer a further portion of transformer oil contaminated with PCB's;
• (m) passing said further portion through said second column to selectively adsorb PCB's from said further portion;
• (n) returning a further partially purified portion to said transformer;
• (o) repeating steps (l), (m) and (n) a sufficient number of times, M, until the adsorptive capacity of said second column is diminished to the point where no further appreciable adsorption of PCB's can be effected by passing further portions of PCB-contaminated transformer oil through said second column;
• (p) removing adsorbent of diminished adsorptive capacity from said second column and replacing with fresh carbon adsorbent;
• (q) alternately repeating steps (d), (e), (f), (g) and (h) and steps (l), (m), (n), (o) and (p) until the transformer oil in said transformer contains less than about 500 ppm of PCB's, and
• (r) disposing of the carbon adsorbent of diminished adsorptive capacity removed from said first or second column and the PCB's adsorbed thereon by combustion in a molten salt, the carbon adsorbent of diminished adsorptive capacity being removed from said first column during passage of portions of transformer oil through said second column and the carbon adsorbent of diminished adsorptive capacity being removed from said second column during passage of portions of transformer oil through said first column.