arriving by plane, leaving by train within 24 hours

Hello,
I am arriving by plane to Guangzhou Baiyun Airport and want to take a direct train from Guangzhou to Hong Kong the same day so I won't spend in China more than 24 hours altogether. Is it possible to use the Chinese 24 hour free schedule for this trip?
btw. With my passport I don't need visa to enter Hong Kong.
Thank you.