Boiler Flue Gas and Oven Exhaust Economizer Systems

Abstract

A representative mechanical draft system includes an in-line draft inducer that comprises a motor and a backward-inclined impeller. The mechanical draft system also includes an economizer coupled to the in-line draft inducer, where the economizer comprises a housing and a horizontally mounted heat recovery unit.

At least the following is claimed: 
     
         1 . A mechanical draft system, comprising:
 an in-line draft inducer comprising a motor and a backward-inclined impeller; and   an economizer coupled to the in-line draft inducer, the economizer comprising a housing and a horizontally mounted heat recovery unit.   
     
     
         2 . The system of  claim 1 , wherein the motor is a variable speed motor and is mounted externally to a housing of the in-line draft inducer. 
     
     
         3 . The system of  claim 1 , wherein the economizer comprises at least one bypass damper controlled by an actuator, wherein the actuator is configured to control a position of the least one bypass damper to control a flow of gases through the economizer. 
     
     
         4 . The system of  claim 3 , wherein the at least one bypass damper comprises a fin having a semi-circular cross section. 
     
     
         5 . The system of  claim 3 , wherein the at least one bypass damper comprises one of a butterfly damper and a multi-blade damper. 
     
     
         6 . The system of  claim 3 , wherein the actuator is configured to configure the at least one bypass damper in one of a neutral position and a blocking position, wherein the neutral position allows free flow of gases through the economizer, and wherein the blocking position inhibits the flow of gases. 
     
     
         7 . The system of  claim 1 , wherein the heat recovery unit comprises a water-based radiator. 
     
     
         8 . The system of  claim 1 , wherein the heat recovery unit is mounted on a guide rail assembly within the economizer. 
     
     
         9 . The system of  claim 1 , wherein the guide rail assembly is horizontally disposed along a centerline of the economizer. 
     
     
         10 . The system of  claim 1 , wherein the economizer further comprises a tapered inlet for channeling exhaust flow. 
     
     
         11 . The system of  claim 1 , wherein the tapered inlet is coupled to a boiler unit and is configured to receive hot exhaust from the boiler. 
     
     
         12 . The system of  claim 1 , wherein the heat recovery unit comprises rectangular plate fins and a plurality of die-extruded tube collars. 
     
     
         13 . A mechanical draft system, comprising:
 an in-line draft inducer comprising a motor and a backward-inclined impeller; and   an economizer detachably coupled to the in-line draft inducer, the economizer comprising a cylindrical housing for horizontally mounting a heat recovery unit that partitions the housing into an upper chamber and a lower chamber.   
     
     
         14 . The system of  claim 13 , wherein the economizer further comprises a dual-damper configuration controlled by separate actuators, wherein each actuator is configured to control a position of the corresponding damper to control exhaust flow through the economizer. 
     
     
         15 . The system of  claim 14 , wherein the actuator controls a position of each damper to allow flue gases entering the economizer to flow in one of two exhaust flow configurations,
 wherein the first exhaust flow configuration comprises exhaust flow through only one of the upper chamber and the lower chamber to bypass the heat recovery unit, and   wherein the second exhaust flow configuration comprises turbulent exhaust flow through one of the lower chamber and upper chamber, through the heat recovery unit, and into the other chamber.   
     
     
         16 . The system of  claim 14 , wherein the actuator is configured to place each damper in one of a neutral position, a first blocking position, and a second blocking position;
 wherein the neutral position allows free exhaust flow, and wherein each of the first and second blocking positions inhibits exhaust flow.   
     
     
         17 . The system of  claim 13 , wherein the economizer further comprises:
 a single damper disposed on one end of the economizer; and   a fixed end plate disposed on another end of the economizer;   wherein the damper is controlled by an actuator, wherein the actuator is configured to control a position of the damper to control exhaust flow through the economizer.   
     
     
         18 . The system of  claim 13 , wherein the economizer comprises a circular inlet and a circular outlet, wherein the circular inlet and circular outlet each include mounting flange fittings. 
     
     
         19 . A method implemented in a draft controller in a mechanical draft system comprising an in-line draft inducer and an economizer, the economizer comprising a heat recovery unit and a damper assembly, the method comprising:
 in response to a heat recovery request, increasing a fan speed of the in-line draft inducer based on a predetermined draft set point value;   upon reaching the draft set point value, opening a valve of the economizer to allow fluid to flow through the heat recovery unit;   placing the damper assembly in a closed position to channel exhaust flow through the heat recovery unit; and   in response to the damper assembly being placed in a closed position, increasing the fan speed of the in-line draft inducer to maintain the predetermined draft set point value.   
     
     
         20 . The method of  claim 19 , further comprising:
 in response to a temperature of the fluid flowing through the heat recovery unit reaching a first predetermined temperature, placing the damper assembly in a partially open position; and   in response to a temperature of the fluid flowing through the heat recovery unit reaching a second predetermined temperature, placing the damper assembly in a fully open position.