There are various types of waste heat recovery methods that use waste heat for efficient heating, each with different temperature ranges and energy-saving effects.
Regenerative System
Normally, two burners with a built-in heat exchangers are used as a set, alternating between combustion and exhaust for short periods of time. While one burner is burning, the other burner flues the hot exhaust gases through the heat exchanger to store heat in the heat exchanger. Conversely, when that burner is burning, combustion air is preheated by passing it through the high-temperature heat exchanger.
Example: Regenerative burner, Self-regenerative burner, etc.
Recuperator System
Exhaust gases from equipment are passed through a heat exchanger to exchange heat with combustion air.
Examples: Centralized recuperator (concentrating furnace exhaust heat in one place) + hot air burner, self heat recovery type (= recu-burner: burner with built-in recuperator)