Pulse detonation cleaning apparatus

Abstract

The burning of fuel (e.g., coal) in industrial equipment generates an exhaust flow containing airborne particulate. The flow is passed through a rotary heat exchanger to preheat inlet air. The heat exchanger element is subject to fouling and is cleaned by a pulsed combustion device. The device is operated by introducing a fuel and oxidizer charge to at least one conduit and initiating combustion of the charge. The combustion generates a shock wave to which the element is exposed, dislodging and/or otherwise removing the deposits.

1 . An apparatus comprising:
 a combustor;   an inlet air flowpath extending to the combustor;   an exhaust flowpath extending from the combustor;   a rotary heat exchanger along the inlet air flowpath and exhaust flowpath; and   a pulsed-combustion device positioned to direct a shock wave toward a core of the heat exchanger and comprising:
 a source of fuel and oxidizer; 
 at least one combustion conduit coupled to the source to receive charges of said fuel and oxidizer; and 
 at least one ignitor coupled to the combustion conduit to ignite the charges. 
   
   
   
       2 . The apparatus of  claim 1  wherein:
 the combustor is a coal-burning furnace.   
   
   
       3 . The apparatus of  claim 1  wherein:
 the pulsed combustion device comprises first and second said conduits, the first conduit having an outlet upstream of the core along the exhaust flowpath and the second conduit having an outlet downstream of the core along the exhaust flowpath.   
   
   
       4 . The apparatus of  claim 3  wherein:
 the first and second conduits each have a plurality of outlets at different radial positions relative to an axis of rotation of the core.   
   
   
       5 . The apparatus of  claim 4  wherein:
 the first and second conduits have a decreasing cross-sectional area within the exhaust flowpath; and   the plurality of outlets are along respective portions of different cross-sectional area.   
   
   
       6 . The apparatus of  claim 1  wherein:
 said combustion conduits have outlets aimed transverse to a downstream direction of the flowpath.   
   
   
       7 . The apparatus of  claim 1  wherein:
 at least four of said combustion conduits are positioned at essentially a common streamwise location along the exhaust flowpath.   
   
   
       8 . The apparatus of  claim 1  further comprising:
 a smokestack forming an outlet of the exhaust flowpath to atmosphere.   
   
   
       9 . The apparatus of  claim 1  wherein the source comprises:
 a first source of said fuel, said fuel consisting in majority part, by mass, of fuel selected from the group consisting of hydrogen, hydrocarbon fuels, and their mixtures; and   a second source of said oxidizer, said oxidizer consisting essentially of oxygen.   
   
   
       10 . The apparatus of  claim 1  wherein:
 said combustion conduits have lengths of 0.5-4 m and cross-sectional areas of 20-730 cm 2 .   
   
   
       11 . The apparatus of  claim 1  further comprising:
 a controller configured to fire the device a plurality of times to provide circumferential coverage of the core.   
   
   
       12 . The apparatus of  claim 11  wherein:
 the controller configured to synchronize firing of the device relative to rotation of the core.   
   
   
       13 . An apparatus comprising:
 a combustor;   an exhaust flowpath extending from the combustor;   an inlet air flowpath extending to the combustor;   a rotary heat exchanger along the inlet air flowpath and exhaust flowpath; and   pulsed-combustion means for cleaning a core of the rotary heat exchanger.   
   
   
       14 . The apparatus of  claim 13  wherein the combustor is a fossil fuel-burning furnace; 
   
   
       15 . The apparatus of  claim 13  being a boiler system 
   
   
       16 . A method for operating a plant comprising:
 burning a plant fuel and generating a flow containing particles;   passing the flow through a heat exchanger to heat an inlet air flow; and   cleaning a core of the heat exchanger by a pulsed detonation process including:
 introducing a fuel and oxidizer charge to at least one conduit; 
 initiating combustion of the charge; and 
 exposing the core to shock waves generated by combustion. 
   
   
   
       17 . The method of  claim 16  wherein:
 the passing of the flow comprises an axial flow through the core while the core rotates about a core axis.   
   
   
       18 . The method of  claim 16  wherein:
 the plant fuel is selected from the group consisting of coal, fuel oil, hydrocarbon gas biomass, trash, and combinations thereof.   
   
   
       19 . The method of  claim 16  wherein:
 the cleaning comprises exposing said core to said shock waves from a plurality of said conduits.   
   
   
       20 . The method of  claim 16  wherein:
 the cleaning comprises exposing the core to shock waves from opposed outlets of one or more pairs of said conduits.   
   
   
       21 . The method of  claim 16  wherein:
 the charge comprises hydrogen as a by weight majority of the fuel.   
   
   
       22 . The method of  claim 16  wherein:
 the at least one conduit is operated with an air purge before each charge introduction.   
   
   
       23 . The method of  claim 16  wherein:
 the cleaning is initiated responsive to a sensed condition of the core.   
   
   
       24 . The method of  claim 16  wherein:
 the conduit is fired a plurality of times in synchronization with rotation of the core so as to provide a full circumferential cleaning of the core.