System and method for controlling scale build-up in a wfgd

Abstract

The present invention relates generally to the cleaning of a flue gas and, in one embodiment, to a device, system and method that mitigates and/or prevents slurry deposition at the flue inlet to a wet flue gas desulfurization (WFGD) unit in order to keep the inlet dry and minimize deposition (e.g., deposition scale) at the flue inlet to the WFGD tower. In one embodiment, a wet flue gas desulfurization (WFGD) unit, system and/or method according to the present invention comprises, among other features, a scale prevention system comprising a plenum air device and/or forced-air box located proximate the inlet transition zone. In another embodiment, a wet flue gas desulfurization (WFGD) unit, system and/or method according to the present invention comprises, among other features, a scale prevention system comprising at least one chill plate located proximate the inlet transition zone.

What is claimed is: 
     
         1 . A scale prevention system for a wet flue gas desulfurization unit, the system comprising:
 a flue structure, wherein the flue structure is connected to a flue inlet of a wet flue gas desulfurization unit;   at least two air nozzles, each air nozzle having a respective air supply line, wherein the at least two air nozzles are positioned on the interior of the flue structure so as to provide air coverage across the horizontal width of a flue inlet to the wet flue gas desulfurization unit; and   at least one inlet awning designed to deflect a slurry from the wet flue gas desulfurization unit, the at least one inlet awning being position above the flue inlet to the wet flue gas desulfurization unit.   
     
     
         2 . The system of  claim 1 , wherein the flue structure has a rectangular or square cross-sectional shape and the at least two air nozzles are positioned on opposite interior walls of the flue. 
     
     
         3 . The system of  claim 2 , wherein the at least two air nozzles are positioned on opposite vertical interior walls of the flue. 
     
     
         4 . The system of  claim 1 , wherein the at least two air nozzles receive temperature controlled air that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         5 . A scale prevention system for a wet flue gas desulfurization unit, the system comprising:
 a flue structure, wherein the flue structure is connected to a flue inlet of a wet flue gas desulfurization unit and the flue structure has a cross-sectional shape selected from a rectangle or a square;   at least two air nozzles, each air nozzle having a respective air supply line, wherein at least one air nozzle is positioned on each opposite vertical interior wall of the flue structure so as to provide air coverage across the horizontal width of a flue inlet to the wet flue gas desulfurization unit; and   at least two lateral air nozzles, each lateral air nozzle having a respective air supply line, wherein each lateral air nozzle is positioned internally of each of the at least two air nozzles and are positioned at the top edge of the flue inlet to the wet flue gas desulfurization unit so as to provide air coverage across the horizontal width of the flue inlet to the wet flue gas desulfurization unit.   
     
     
         6 . The system of  claim 5 , wherein the at least two lateral air nozzles are separated by a baffle plate. 
     
     
         7 . The system of  claim 5 , wherein the system further comprises at least one inlet awning designed to deflect a slurry from the wet flue gas desulfurization unit, the at least one inlet awning being position above the flue inlet to the wet flue gas desulfurization unit. 
     
     
         8 . The system of  claim 5  wherein the at least two air nozzles receive temperature controlled air that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         9 . A scale prevention system for a wet flue gas desulfurization unit, the system comprising:
 a flue structure, wherein the flue structure is connected to a flue inlet of a wet flue gas desulfurization unit; and   at least two chill plates, each chill plate having a respective supply line, wherein the at least two chill plates are positioned on the interior of the flue structure so as to provide temperature control across the horizontal width of a flue inlet to the wet flue gas desulfurization unit.   
     
     
         10 . The system of  claim 9 , wherein each chill plate receives temperature controlled gas. 
     
     
         11 . The system of  claim 9 , wherein each chill plate receives temperature controlled liquid. 
     
     
         12 . The system of  claim 9 , wherein the at least two chill plates receive a temperature controlled gas that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         13 . The system of  claim 9 , wherein the at least two chill plates receive a temperature controlled liquid that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         14 . The system of  claim 9 , wherein the system further comprises at least one inlet awning designed to deflect a slurry from the wet flue gas desulfurization unit, the at least one inlet awning being position above the flue inlet to the wet flue gas desulfurization unit. 
     
     
         15 . The system of  claim 9 , wherein the flue structure has a rectangular or square cross-sectional shape and at least one chill plate is positioned on each of the opposite vertical interior walls of the flue structure. 
     
     
         16 . The system of  claim 9 , wherein the flue structure has a cross-sectional shape selected from a rectangle or a square and at least one chill plate is positioned on each of the opposite bottom interior corners of the flue structure. 
     
     
         17 . A scale prevention system for a wet flue gas desulfurization unit, the system comprising:
 a flue structure, wherein the flue structure is connected to a flue inlet of a wet flue gas desulfurization unit;   at least two air nozzles, each air nozzle having a respective air supply line; and   at least two chill plates, each chill plate having a respective supply line,   wherein the combination of the at least two air nozzles and the at least two chill plates are positioned on the interior of the flue structure so as to provide temperature control across the horizontal width of a flue inlet to the wet flue gas desulfurization unit.   
     
     
         18 . The system of  claim 17 , wherein the system further comprises at least one inlet awning designed to deflect a slurry from the wet flue gas desulfurization unit, the at least one inlet awning being position above the flue inlet to the wet flue gas desulfurization unit. 
     
     
         19 . The system of  claim 17 , wherein the flue structure has a rectangular or square cross-sectional shape and the at least two air nozzles are positioned on opposite vertical interior walls of the flue. 
     
     
         20 . The system of  claim 17 , wherein the flue structure has a rectangular or square cross-sectional shape and at least one chill plate is positioned on each of the opposite vertical interior walls of the flue structure. 
     
     
         21 . The system of  claim 17 , wherein the flue structure has a cross-sectional shape selected from a rectangle or a square and at least one chill plate is positioned on each of the opposite bottom interior corners of the flue structure. 
     
     
         22 . The system of  claim 17 , wherein the at least two air nozzles receive temperature controlled air that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         23 . The system of  claim 17 , wherein the at least two chill plates receive a temperature controlled gas that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         24 . The system of  claim 17 , wherein the at least two chill plates receive a temperature controlled liquid that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         25 . A scale prevention system for a wet flue gas desulfurization unit, the system comprising:
 a flue structure, wherein the flue structure is connected to a flue inlet of a wet flue gas desulfurization unit;   at least two air nozzles, each air nozzle having a respective air supply line, wherein at least one air nozzle is positioned on each opposite vertical interior wall of the flue;   at least two lateral air nozzles, each lateral air nozzle having a respective air supply line, wherein each lateral air nozzle is positioned internally of each of the at least two air nozzles and are positioned at the top edge of the flue inlet to the wet flue gas desulfurization unit; and   at least two chill plates, each chill plate having a respective supply line, wherein the at least two chill plates are positioned on the interior of the flue,   wherein the combination of the at least two air nozzles, the at least two lateral air nozzles and the at least two chill plates are positioned on the internal surfaces of the flue structure so as to provide temperature control across the horizontal width of a flue inlet to the wet flue gas desulfurization unit.   
     
     
         26 . The system of  claim 25 , wherein the at least two lateral air nozzles are separated by a baffle plate. 
     
     
         27 . The system of  claim 25 , wherein the system further comprises at least one inlet awning designed to deflect a slurry from the wet flue gas desulfurization unit, the at least one inlet awning being position above the flue inlet to the wet flue gas desulfurization unit. 
     
     
         28 . The system of  claim 25 , wherein the flue structure has a rectangular or square cross-sectional shape and the at least two air nozzles are positioned on opposite vertical interior walls of the flue. 
     
     
         29 . The system of  claim 25 , wherein the at least two lateral air nozzles are separated by a baffle plate. 
     
     
         30 . The system of  claim 25 , wherein the flue structure has a rectangular or square cross-sectional shape and at least one chill plate is positioned on each of the opposite vertical interior walls of the flue structure. 
     
     
         31 . The system of  claim 25 , wherein the flue structure has a cross-sectional shape selected from a rectangle or a square and at least one chill plate is positioned on each of the opposite bottom interior corners of the flue structure. 
     
     
         32 . The system of  claim 25 , wherein the at least two air nozzles receive temperature controlled air that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         33 . The system of  claim 25 , wherein the at least two chill plates receive a temperature controlled gas that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature. 
     
     
         34 . The system of  claim 25 , wherein the at least two chill plates receive a temperature controlled liquid that is within a range of about −25° F. to about +25° F. of the wet flue gas desulfurization unit slurry temperature.