Method and apparatus for converting oxidized mercury into elemental mercury

Abstract

An oxidized mercury converter utilizes a combination of heat, reduced pressure, and dilution when converting oxidized mercury in a gas sample into elemental mercury. The converter applies heat to a gas sample to thermally convert oxidized mercury within a gas sample into elemental mercury and an oxidizing component, and thereafter reduces the pressure of the gas sample to minimize combination of the elemental mercury with other oxidizing compounds present in the gas sample and/or with byproducts of the thermal conversion (e.g., the oxidizing components). The converter thus allows an accurate analysis of the total amount of mercury, both oxidized and elemental forms, present within a gas sample without the need to use consumable reagents in the mercury conversion process.

1 . An oxidized mercury converter comprising: 
 a housing having an inlet for receipt of a fluid sample and an outlet for discharge of a fluid sample, said housing defining a first chamber and a second chamber, the first chamber configured to receive a fluid sample and contain the fluid sample substantially at a first pressure and the second chamber configured to receive the fluid sample from the first chamber and contain the fluid sample at a second pressure less than the first pressure;    a heater in thermal communication with the first chamber, the heater configured to heat the fluid sample received by the first chamber to convert oxidized mercury present within the fluid sample into an elemental mercury component and an oxidizing component; and    a pressure reduction apparatus operable to reduce the pressure of the fluid sample from the first pressure within the first chamber to the second pressure within the second chamber.    
   
   
       2 . The oxidized mercury converter of  claim 1  wherein the pressure reduction apparatus includes a flow restrictor between said first and second chambers.  
   
   
       3 . The oxidized mercury converter of  claim 1  wherein the pressure reduction apparatus is operable to reduce the pressure of the fluid sample to between approximately 0.1 and 0.3 atmospheres.  
   
   
       4 . The oxidized mercury converter of  claim 1  wherein the heater is in thermal communication with the second chamber and is operable to heat the fluid sample within the second chamber.  
   
   
       5 . The oxidized mercury converter of  claim 1  comprising a chemical scrubber positioned within or downstream of the second chamber so that a fluid sample passing through the converter flows through or in proximity to the chemical scrubber.  
   
   
       6 . The oxidized mercury converter of  claim 1  wherein the second chamber is operable under a partial vacuum to draw the fluid sample into and through the first chamber, through the flow restrictor, and into the second chamber.  
   
   
       7 . The oxidized mercury converter of  claim 1  wherein the housing has a second inlet for receipt of substantially mercury-free dilution fluid.  
   
   
       8 . The oxidized mercury converter of  claim 7  wherein the second inlet permits flow of substantially mercury-free dilution fluid into the second chamber.  
   
   
       9 . The oxidized mercury converter of  claim 1  wherein the heater is configured to heat a fluid sample to a temperature of between approximately 650 degrees Celsius and 800 degrees Celsius.  
   
   
       10 . A method for processing oxidized mercury in a fluid sample comprising: 
 heating a fluid sample having oxidized mercury to convert the oxidized mercury present within the fluid sample into an elemental mercury component and an oxidizing component; and    as the heated fluid sample passes through the flow restrictor limiting recombination of the elemental mercury component and the oxidizing component.    
   
   
       11 . The method of  claim 10  wherein reducing a pressure of the heated fluid sample comprises reducing the pressure of the gas sample to between approximately 0.1 and 0.3 atmospheres.  
   
   
       12 . The method of  claim 10  comprising adding a substantially mercury-free fluid to the fluid sample to dilute the fluid sample.  
   
   
       13 . The method of  claim 12  comprising adding substantially mercury-free fluid to the fluid sample after heating the sample to separate the oxidized mercury present within the sample.  
   
   
       14 . The method of  claim 12  comprising diluting the fluid sample at a dilution ratio from between approximately 10:1 to 250:1.  
   
   
       15 . The method of  claim 10  wherein: 
 the heating comprises heating the fluid sample within a first chamber; and    reducing the pressure comprises flowing the heated fluid sample through a flow restrictor between the first chamber and a second chamber.    
   
   
       16 . The method of  claim 15  further comprising heating the fluid sample within the second chamber.  
   
   
       17 . The method of  claim 16  comprising passing the separated fluid sample through, or in proximity to, a chemical scrubber.  
   
   
       18 . An oxidized mercury converter comprising: 
 a housing having an inlet for admitting a fluid sample into a space defined by the housing and an outlet for delivering the fluid sample to a fluid destination;    a heater operable to heat the fluid sample admitted into the space defined by the housing so as to convert oxidized mercury present within the fluid sample into an elemental mercury component and an oxidizing component; and    a pressure reduction apparatus operable to decrease the pressure of the fluid sample.    
   
   
       19 . The oxidized mercury converter of  claim 18  wherein the pressure reduction apparatus comprises a flow restrictor oriented in proximity to the inlet of the housing.  
   
   
       20 . The oxidized mercury converter of  claim 18  wherein the pressure reduction apparatus comprises a flow restrictor oriented in proximity to the outlet of the housing.  
   
   
       21 . The oxidized mercury converter of  claim 18  wherein the pressure reduction apparatus is operable to reduce the pressure of the fluid sample to between approximately 0.1 and 0.3 atmospheres.