This second oracle stresses not the boiling of meat in the pot but the cleansing of the pot by superheating, a second stage in God's judgment process.
24:9-10 The Lord pronounced woe on the bloody city of Jerusalem and promised to make the pile of bones of the slain inhabitants great. Therefore Ezekiel was to kindle a strong fire, to boil the meat well, to mix in the spices normally used when meat was cooked this way, and to let the bones burn. All this symbolized the fierceness of the attack on Jerusalem and the many people that would die there.
24:11 Then Ezekiel was to keep the empty caldron on the coals with the fire burning hotly under it so it would glow and all the impurities in it would burn up. This represented the continuing purification of Jerusalem after all the Jews had left it. It would remain empty, and that condition would free it from all sinful pollution for many years to come.
24:12 Jerusalem had wearied Yahweh as He toiled to scour its sin away in the past. The city would remain under judgment because its rust-like sin needed purging away (cf. 36:22-32).
24:13 Adultery in its many forms was part of Jerusalem's filthiness. It clung to the city even though the Lord had sent many prophets to clean it up and had already deported many of the people (in 605 and 597 B.C.). Now it was time for a thorough purging of the pot by the fire of God's wrath since cleansing with water had not been effective.