When Chinese firms deposit the dollars earned in foreign trade in Chinese banks, these banks then turn the dollars over to the Chinese central bank, the People's Bank of China. The dollars that were deposited in Chinese banks and made their way into the forex reserves of the People's Bank of China are available to Chinese firms who want to import goods or purchase foreign assets. The firms simply go to their banks and exchange renminbi for dollars. The commercial banks can always replenish their supply of dollars and other foreign currencies by going to the People's Bank of China and making a similar exchange. This is part of the reason China does not face the same sort of debt crisis as South Korea, Thailand, and Indonesia.
Chinese entities can also purchase foreign real estate.
China has not, therefore, had to kow-tow to the foreigners. Far from it. China has been so successful in foreign trade that there was some expectation that the Chinese government would make a further liberalization of its monetary system by allowing the renminbi to be fully convertible. As it turns out, it is up to the government of a country to decide whether or not it will allow its domestic currency to be freely bought and sold on forex markets. A country can, in fact, make it illegal for the domestic currency to be taken out of the country or severely restrict the quantity that can be taken out.