72 entry visa for china

Anna, may I know where you will go to after your stopover in Hangzhou? If you will fly back to the country you departed, you cannot apply for the 72 hour free transit.
But if you will fly to a third country or region rather the last one you departed, you can apply for the free transit. When you board the plane, you should inform the carrier and then the carrier will declare your request to the immigration office at the airport. After getting off, you can follow the direction signs to the 72 hour transit lane to handle the relevant procedures to apply for the 72 hour permit.