WASTE HEAT RECOVERY SYSTEM

摘要

A system for recovering the waste heat normally exhausted into the atmosphere by chemical or other processing plants. The system comprises a substantially self-contained apparatus for coupling to an exhaust stack and an inlet air plenum for furnaces so as to extract the waste heat from the exhaust gas for delivery to the inlet air. The system may include temperature and pressure controls which enhance the safety and efficiency of the system's operation, and further may include flow control in a multiple burner installation so that the desired fuel air ratios and heat distribution may be achieved. While the primary control is generally determined by a lower temperature limit for the exhaust gas below which condensation may occur, over-temperature and other controls are also provided. By building the present invention as a substantially selfcontained and self-supporting assembly, on site installation time and the required alteration and reinforcing of pre-existing on site equipment may be minimized, thereby affecting substantially economic savings by minimizing the resulting down time of the processing plant for installation. Embodiments for a single burner nest heater, multiple nest cabins and grade level stack systems, as well as a specific embodiment of heat exchanger for use in the systems of the present invention, are disclosed. The waste heat recovery apparatus comprises an exhaust gas duct having an inlet and an outlet for coupling to said furnace stack for carrying exhaust gas therethrough; a first heat exchanger means disposed within said exhaust gas duct for absorbing heat from the exhaust gas flowing through; at least one inlet air duct for coupling to said corresponding inlet air plenum of said furnace; and at least one second heat exchanger means disposed within said corresponding inlet air duct for heating the inlet air passing therethrough. The inlet of said second heat exchanger is in communication with the outlet of said first heat exchanger and the outlet of said second heat exchanger is in communication with the inlet of said first heat exchanger through conduit means so as to define a flow circuit for a heat transfer fluid. There is a reservoir in communication with said flow circuit for maintaining a heat transfer fluid reserve; and pumping means for circulating a heat transfer fluid through said flow circuit.