Flue gas waste heat and condensation recovery system of gas-fired hot water boiler

The invention provides a flue gas waste heat and condensation recovery system of a gas-fired hot water boiler, and relates to the technical field of boiler equipment. The system comprises a screw heat pump unit, a heat exchanger, a variable-frequency fan, a baffle plate demister and a water supplementing tank. The screw heat pump unit is connected with a heating pipeline and also connected with a heat exchange pipeline of the heat exchanger. The heat exchanger is arranged in a flue gas channel, the variable-frequency fan is arranged in an outlet of the flue gas channel, and a bypass flue is further arranged in a flue gas inlet of the flue gas channel. The baffle plate demister is arranged in the flue gas channel, a condensate pipe is further arranged at the bottom of the flue gas channel, and the condensate pipe is connected with the water supplementing tank. A chemical dosing device is arranged on the water supplementing tank, and a water supplementing pump is connected with the water supplementing tank and