Heated graphite scrubber to reduce interferences in ozone monitors
The present invention provides a means of greatly reducing interferences from mercury vapor, UV-absorbing compounds and water vapor in the measurement of ozone by UV absorbance. A heated graphite scrubber destroys greater than 99% of ozone passing through it while reducing biases from typical atmospheric UV-absorbing interferents by large factors compared to conventional ozone scrubbers. Substitution of a heated graphite scrubber in place of traditional ozone scrubbers such as hopcalite, metal oxides and heated silver scrubbers, results in a more accurate measurement of ozone by reducing the responses to UV-absorbing interferences and water vapor. The heated graphite scrubber also may be used in combination with other ozone sensors, such as electrochemical and HMOS sensors, to provide a reference measurement with ozone selectively removed and thus greatly reduce contributions from interfering species in those measurement devices as well.
1. An ozone scrubber for reducing interferences from water vapor, mercury and UV-absorbing compounds in the measurement of ozone in a sample gas, the ozone scrubber comprising:
at least one graphite tube forming a chamber, the at least one graphite tube being at least a majority graphite by composition;
the chamber adapted to allow the sample gas to flow through and contact the graphite of the at least one graphite tube before exiting;
the at least one graphite tube surrounded by a heating block;
the heating block in thermal communication with a heater;
the heater adapted to maintain the at least one graphite tube at a temperature when the ozone scrubber is functioning;
wherein the temperature is maintained in the range of 70-110° C.;
wherein more than 50% of ozone in the sample gas is scrubbed by the at least one graphite tube when the ozone scrubber is functioning;
wherein at least 50% of water vapor, mercury, p-xylene or phenol in the sample gas passes through the chamber when the ozone scrubber is functioning.
2. The ozone scrubber of claim 1 , wherein the at least one graphite tube of the chamber comprises a plurality of graphite tubes plumbed in series or in parallel.
3. The ozone scrubber of claim 1 , wherein the temperature is maintained high enough that approximately 99% or more of the ozone in the sample gas is destroyed by the ozone scrubber when the scrubber is functioning.
4. The ozone scrubber of claim 1 , wherein the sample gas is flowed through the chamber at a flow rate between 0.5 and 3.0 L/min.
5. The ozone scrubber of claim 1 , wherein the ozone scrubber is mounted in a single beam or dual beam ozone monitor which measures UV absorbance of the sample gas.
6. The ozone scrubber of claim 5 , wherein the ozone monitor further comprises a sulfonated polytetrafluoroethylene polymer tube arranged downstream from the ozone scrubber.
7. An ozone scrubber for reducing interferences from water vapor, mercury and UV-absorbing compounds in the measurement of ozone in a sample gas, the ozone scrubber comprising:
a chamber adapted to allow the sample gas to flow through the chamber and come into contact with material packed inside the chamber before exiting the chamber;
the material packed inside the chamber being at least a majority graphite by composition;
a heater adapted to maintain the material packed inside the chamber at a temperature when the ozone scrubber is functioning;
wherein the temperature is maintained in the range of 70−110° C.;
wherein more than 50% of ozone in the sample gas is scrubbed by the material packed inside the chamber when the ozone scrubber is functioning;
wherein at least 50% of water vapor, mercury, p-xylene or phenol in the sample gas passes through the chamber when the ozone scrubber is functioning.
8. The ozone scrubber of claim 7 , wherein the chamber is packed with graphite particles.
9. The ozone scrubber of claim 7 , wherein the temperature is maintained high enough that approximately 99% or more of the ozone in the sample gas is destroyed by the ozone scrubber when the scrubber is functioning.
10. The ozone scrubber of claim 7 , wherein the sample gas is flowed through the chamber at a flow rate between 0.5 and 3.0 L/min.
11. The ozone scrubber of claim 7 , wherein the ozone scrubber is mounted in a single beam or dual beam ozone monitor which measures UV absorbance of the sample gas.
12. The ozone scrubber of claim 11 , wherein the ozone monitor further comprises a sulfonated polytetrafluoroethylene polymer tube arranged downstream from the ozone scrubber.
13. An ozone scrubber for reducing interferences by water vapor, mercury and UV-absorbing compounds in the measurement of ozone in a sample gas, the ozone scrubber comprising:
a chamber adapted to allow the sample gas to flow through the chamber and come into contact with one or more interior surfaces of the chamber before exiting the chamber;
at least a majority of the one or more interior surfaces of the chamber being at least a majority graphite by composition;
the chamber housed within a heating block;
the heating block in thermal communication with a heater;
the heater adapted to maintain the one or more interior surfaces of the chamber at a temperature when the ozone scrubber is functioning;
wherein the temperature is maintained in the range of 70−110° C.;
wherein more than 50% of ozone in the sample gas is scrubbed by the one or more interior surfaces of the chamber when the ozone scrubber is functioning;
wherein at least 50% of water vapor, mercury, p-xylene or phenol in the sample gas passes through the chamber when the ozone scrubber is functioning.
14. The ozone scrubber of claim 13 , wherein the one or more interior surfaces of the chamber are formed by at least one graphite tube.
15. The ozone scrubber of claim 14 , wherein the at least one graphite tube of the chamber comprises a plurality of graphite tubes plumbed in series or in parallel.
16. The ozone scrubber of claim 13 , wherein the one or more interior surfaces of the chamber are coated in graphite.
17. The ozone scrubber of claim 13 , wherein the temperature is maintained high enough that approximately 99% or more of the ozone in the sample gas is destroyed by the ozone scrubber when the scrubber is functioning.
18. The ozone scrubber of claim 13 , wherein the sample gas is flowed through the chamber at a flow rate between 0.5 and 3.0 L/min.
19. The ozone scrubber of claim 13 , wherein the ozone scrubber is mounted in a single beam or dual beam ozone monitor which measures UV absorbance of the sample gas.
20. The ozone scrubber of claim 19 , wherein the ozone monitor further comprises a sulfonated polytetrafluoroethylene polymer tube arranged downstream from the ozone scrubber.