Less than a day in arrival and return.

Hello. I am traveling to South Korea but I have a layover in Beijing for less than 24 hours. I want to visit the Great Wall during the time. After staying in Korea for 3 weeks. Then I return from South Korea to USA with a layover again in Beijing for less then 24 hours. Can I take advantage of the 24 hours entry (double) for my going and return trip?
Thank you!