The invention discloses a 
waste heat recycling 
system of a complete set of 
waste oil treatment equipment, and relates to a heating device for 
waste oil regeneration. The 
system is characterized in that a bottom line oil 
heat exchanger, a side line oil 
heat exchanger, a 
flue gas rear-section 
heat exchanger and a 
flue gas front-section heat exchanger form four-stage heating of 
waste oil; a heating medium of the bottom line oil heat exchanger is bottom line oil of a fractionating 
tower, a heating medium of the side line oil heat exchanger is side line oil of the fractionating 
tower, a heating medium of the 
flue gas rear-section heat exchanger is 
flue gas of the rear section of a 
waste gas burner, and a heating medium of the 
flue gas front-section heat exchanger is 
flue gas of the front section of the 
waste gas burner; the bottom line oil heat exchanger and the side line oil heat exchanger are horizontal cylindrical tank bodies with the same structure, and the flue gas rear-section heat exchanger and the flue gas front-section heat exchanger are vertical hanging type tank bodies with the same structure; and four stages of waste oil heaters are connected in series through pipelines and 
pipe fittings. The 
system is scientific and reasonable in structure, safe and reliable, saves energy, reduces the cost of waste oil regeneration, greatly improves high-temperature emission of flue gas, facilitates emission and has popularization value.