The number parallelism (three...four) is a method to list poetic examples. This list shows powers that are never satisfied and often dangerous. See also Proverbs 30:18–19, 21–23, 29–31.
The grave, representing death, never seems to have enough—people keep dying (Proverbs 27:20).
barren womb: Women unable to have children often long for them, like Sarah before Isaac, Rebekah before Esau and Jacob, and Hannah before Samuel.
The thirsty desert and a fire consume everything in their path.