Air-assist flare

Abstract

An air-assist flare includes a flare body, a fan, a gas feed pipe, a pilot burner, a pressure sensor and a controller. The fan operates at a plurality of fan speed settings to drive a flow of air through the flare body. The gas feed pipe is coupled to a source of flammable gas and includes an output port within the flare body. The pilot burner is configured to ignite a mixture of the flammable gas discharged through the output port and the flow of air. The pressure sensor is configured to generate a pressure output signal that is indicative of a pressure within the gas feed pipe. The controller is configured to adjust the fan speed setting based on the pressure output signal. When the controller detects an error in the pressure output signal, the controller sets the fan speed setting to a predetermined fan speed setting.

What is claimed is: 
     
         1 . An air-assist flare comprising:
 a flare body;   a fan configured to operate at a plurality of fan speed settings to drive a flow of air through the flare body at a plurality of flow rates, the fan speed settings including a minimum fan speed setting corresponding to a minimum flow rate, and a maximum fan speed setting corresponding to a maximum flow rate;   a gas feed pipe coupled to a source of flammable gas and having an output port within the flare body;   a pilot burner configured to ignite a mixture of the flammable gas discharged through the output port and the flow of air;   a pressure sensor configured to generate a pressure output signal that is indicative of a pressure within the gas feed pipe; and   a controller configured to adjust the fan speed setting based on the pressure output signal,   wherein when the controller detects an error in the pressure output signal, the controller sets the fan speed setting to a predetermined fan speed setting.   
     
     
         2 . The air-assist flare according to  claim 1 , wherein the predetermined fan speed setting is the minimum fan speed setting. 
     
     
         3 . The air-assist flare according to  claim 1 , wherein the error in the pressure output signal includes a no-signal condition. 
     
     
         4 . The air-assist flare according to  claim 1 , wherein the error in the pressure output signal includes a pressure output signal that is outside a predefined range. 
     
     
         5 . The air-assist flare according to  claim 1 , wherein the pressure sensor comprises:
 a tap to the pressure within the gas feed pipe; and   a pressure transducer coupled to the tap and configured to produce the pressure output signal.   
     
     
         6 . The air-assist flare according to  claim 5 , wherein:
 the air-assist flare includes a main pipe connecting the source of flammable gas to the gas feed pipe;   the pressure sensor comprises a pitot tube having an impact pressure opening that is coupled to a first end of the tap;   the pressure transducer is coupled to a second end of the tap; and   the pressure output signal is indicative of a pressure at the impact pressure opening.   
     
     
         7 . The air-assist flare according to  claim 6 , wherein:
 the main pipe is oriented transversely to the gas feed pipe;   the main pipe is connected to the gas feed pipe through a coupling; and   the pitot tube is located upstream of the coupling relative to a flow of the flammable gas.   
     
     
         8 . The air-assist flare according to  claim 6 , wherein the flow of flammable gas within the main pipe is substantially laminar at the location of the pitot tube. 
     
     
         9 . An air-assist flare comprising:
 a flare body;   a fan configured to drive a flow of air through the flare body;   a gas feed pipe including an output port within the flare body;   a main pipe connecting a source of flammable to the gas feed pipe;   a pressure sensor comprising:
 a pitot tube within the main pipe; 
 a tap having a first end coupled to an impact pressure opening of the pitot tube; and 
 a pressure transducer coupled to a second end of the tap and configured to produce a pressure output signal that is indicative of a pressure at the impact pressure opening; and 
   a controller configured to adjust a fan speed setting based on the pressure output signal.   
     
     
         10 . The air-assist flare according to  claim 9 , wherein:
 the main pipe is oriented transversely to the gas feed pipe;   the main pipe is connected to the gas feed pipe through a coupling; and   the pitot tube is located upstream of the coupling relative to a flow of the flammable gas.   
     
     
         11 . The air-assist flare according to  claim 10 , wherein the flow of flammable gas within the main pipe is substantially laminar at the location of the pitot tube. 
     
     
         12 . The air-assist flare according to  claim 9 , wherein:
 the fan is configured to operate at a plurality of fan speed settings to drive the flow of air through the flare body at a plurality of flow rates, the fan speed settings including a minimum fan speed setting corresponding to a minimum flow rate, and a maximum fan speed setting corresponding to a maximum flow rate; and   when the controller detects an error in the pressure output signal, the controller sets the fan speed setting to a predetermined fan speed setting.   
     
     
         13 . The air-assist flare according to  claim 12 , wherein the predetermined fan speed setting is the minimum fan speed setting. 
     
     
         14 . The air-assist flare according to  claim 13 , wherein the error in the pressure output signal includes a no-signal condition. 
     
     
         15 . The air-assist flare according to  claim 13 , wherein the error in the pressure output signal includes a pressure output signal that is outside a predefined range. 
     
     
         16 . A method of operating an air-assist flare, which includes
 a flare body;   a fan configured to operate at a plurality of fan speed settings to drive a flow of air through the flare body at a plurality of flow rates;   a gas feed pipe coupled to a source of flammable gas and including an output port within the flare body;   a pressure sensor configured to generate a pressure output signal that is indicative of a pressure within the gas feed pipe; and   a controller configured to adjust a fan speed setting based on the pressure output signal,   
       the method comprising:
 delivering a flow of flammable gas from the source of flammable gas to the output port through the gas feed pipe; 
 generating the pressure output signal using the pressure sensor; and 
 adjusting the fan speed setting based on the pressure output signal using the controller. 
 
     
     
         17 . The method according to  claim 16 , wherein:
 the air-assist flare comprises a main pipe connecting the source of flammable gas to the gas feed pipe; and   the pressure sensor comprises:
 a pitot tube within the main pipe; 
 a tap having a first end coupled to an impact pressure opening of the pitot tube; and 
 a pressure transducer coupled to a second end of the tap and configured to produce the pressure output signal that is indicative of a pressure at the impact pressure opening and in the gas feed pipe. 
   
     
     
         18 . The method according to  claim 17 , wherein:
 the main pipe is oriented transversely to the gas feed pipe;   the main pipe is connected to the gas feed pipe through a coupling; and   the pitot tube is located upstream of the coupling relative to a flow of the flammable gas; and   the flow of flammable gas within the main pipe is substantially laminar at the location of the pitot tube.   
     
     
         19 . The method according to  claim 16 , wherein:
 the fan is configured to operate at a plurality of fan speed settings to drive the flow of air through the flare body at a plurality of flow rates, the fan speed settings including a minimum fan speed setting corresponding to a minimum flow rate, and a maximum fan speed setting corresponding to a maximum flow rate; and   the method includes:
 detecting an error in the pressure output signal using the controller; and 
 setting the fan speed setting to a predetermined fan speed setting using the controller. 
   
     
     
         20 . The method according to  claim 19 , wherein the predetermined fan speed setting is the minimum fan speed setting.