Safe incineration of explosive air mixtures

Abstract

An explosive gas incinerator system comprises a fume source inlet for receiving a process exhaust with a volatile material that is explosive when its concentration exceeds a lower explosive limit (LEL). A source flowmeter measures the volume of process exhaust being input. A temperature sensor measures the temperature of the process exhaust. A motorized damper is used for diluting the process exhaust with an ambient air input to produce a damper outflow with an explosive concentration less than the LEL. A damper flowmeter measures the total mixture volume of the process exhaust and ambient air input in the damper outflow. Another temperature sensor measures the temperature of the damper outflow. A gas monitor measures the concentration of volatile material in the damper outflow. An oxidizer burns the damper outflow in a flame to produce a cleaner exhaust, and a fan forces gas flows through the oxidizer. A system controller is connected to receive measurement data from the flowmeters, gas monitor, and temperature sensors, and is connected to control the motorized damper to maintain the damper outflow into the oxidizer below the corresponding LEL of the volatile material. Operator errors and attempts at sabotage can be detected and controlled.

1 . An explosive gas incinerator system, comprising: 
 a fume source inlet for receiving a process exhaust with a volatile material that is explosive when its concentration exceeds a lower explosive limit (LEL);    a source flowmeter for measuring the volume of said process exhaust being input;    a temperature sensor for measuring the temperature of said process exhaust;    a motorized damper for diluting said process exhaust with an ambient air input to produce a damper outflow with an explosive concentration less than said LEL;    a damper flowmeter for measuring the total mixture volume of said process exhaust and ambient air input in said damper outflow;    a temperature sensor for measuring the temperature of said damper outflow;    a first gas monitor for measuring a concentration of said volatile material in said damper outflow;    an oxidizer for burning said damper outflow in a flame to produce a cleaner exhaust; and    a fan for forcing gas flows through the oxidizer; and    a controller connected to receive measurement data from the flowmeters, gas monitor, and temperature sensors, and connected to control the motorized damper to maintain said damper outflow into the oxidizer below the corresponding LEL of the volatile material.    
   
   
       2 . The system of  claim 1 , wherein the controller uses said temperature, gas monitor, and flow measurement data to dilute said damper outflow to the oxidizer to be just under the LEL concentration.  
   
   
       3 . The system of  claim 1 , further comprising: 
 a second gas monitor for measuring said concentration of said volatile material in said damper outflow.    
   
   
       4 . The system of  claim 2 , wherein the controller compares data measurements from both the first and second gas monitors to improve the accuracy of measurement of volatile material concentration.  
   
   
       5 . The system of  claim 2 , wherein the controller uses data measurements from both the first and second gas monitors to provide a redundant measurement of the volatile material concentration.  
   
   
       6 . The system of  claim 1 , further comprising: 
 an alarm connected to the first gas monitor that will terminate system operation if the concentration of volatile material in said damper outflow exceeds a predetermined limit.    
   
   
       7 . The system of  claim 1 , further comprising: 
 an operator-error and sabotage detection function included in the controller.    
   
   
       8 . The system of  claim 7 , wherein: 
 the operator-error and sabotage detection function includes start-up charts that are self-generated during controlled start-ups and that are subsequently compared to in-field operating conditions operating conditions where the excursions of particular variables from their norms are interpreted as operator errors or attempts at sabotage and used to signal an alarm or shut down the process.    
   
   
       9 . A method for operator-error and sabotage detection in an exhaust incineration system, comprising: 
 building start-up charts of key operating variables in an incineration system during controlled conditions; and    subsequently comparing in-field operating condition variables such that excursions of particular variables from their norms are interpreted as operator errors or attempts at sabotage and used to signal an alarm or shut down the system.