Gas analysis system providing simultaneous analysis and multi-point sample acquisition
A gas handling system capable of simultaneous sample analysis and multi-point sample acquisition is provided. An exemplary system has N gas inlets and N+1 sample storage loops (having a high aspect ratio), where N≧2. The high aspect ratio of the sample storage loop prevents significant sample diffusion along the length of the loop. Therefore each loop preserves a time axis for its contents. The sample loops can be disposed to simultaneously admit samples from different points in space. A gas switching manifold can be employed to connect the sample storage loops sequentially and one at a time to the gas analysis instrument for analysis. A common time axis for all samples can be reconstructed from the switching and flow conditions. Thus a simultaneous multi-point measurement using a single analysis instrument is provided.
1. Apparatus for gas sample acquisition and analysis, the apparatus comprising:
N gas sample inlets disposed at spaced apart locations, wherein N is an integer greater than or equal to two;
N+1 gas sample storage chambers;
a gas analysis instrument; and
a gas flow control manifold capable of connecting the gas sample storage chambers to the gas sample inlets and to the gas analysis instrument;
wherein the gas flow control manifold is capable at least of connecting any of the gas sample storage chambers to the gas analysis instrument while at least one other of the gas sample storage chambers is connected to one of the gas sample inlets.
2. The apparatus of claim 1 , wherein the apparatus is configured such that gas is admitted from the gas sample inlets to the gas sample storage chambers at an acquisition flow rate, wherein gas is admitted from a selected one of the gas sample storage chambers to the gas analysis instrument at an analysis flow rate, and wherein the acquisition flow rate and the analysis flow rate differ by 40% or more of the acquisition flow rate.
3. The apparatus of claim 2 , wherein the analysis flow rate is faster than the acquisition flow rate.
4. The apparatus of claim 2 , wherein the analysis flow rate is slower than the acquisition flow rate.
5. The apparatus of claim 1 , wherein the gas sample storage chambers are configured as tubes having a length to diameter ratio of 100 or more.
6. A method for gas analysis, the method comprising:
providing N gas sample inlets disposed at spaced apart locations, wherein N is an integer greater than or equal to two;
providing N+1 gas sample storage chambers;
providing a gas analysis instrument; and
providing a gas flow control manifold capable of connecting the gas storage chambers to the gas sample inlets and the gas analysis instrument;
wherein the gas flow control manifold is capable at least of connecting any of the gas sample storage chambers to the gas analysis instrument while at least one other of the gas sample storage chambers is connected to one of the gas sample inlets.
7. The method of claim 6 , further comprising reconstructing a common time axis for two or more gas samples from switching and flow conditions of the gas flow control manifold, and known connection molar volumes.
8. The method of claim 6 , wherein the gas flow control manifold is configured and operated such that between successive times a selected gas sample storage chamber is connected to the gas analysis instrument, the selected gas sample storage chamber is connected to a single one of the gas sample inlets.
9. The method of claim 8 , wherein the gas flow control manifold includes a first rotary valve having 2N ports and a second rotary valve having 2N+2 ports, wherein the gas sample inlets are connected to alternating ports of the first rotary valve, wherein the gas sample storage chambers are connected to alternating ports of the second rotary valve, wherein N ports of the first rotary valve not connected to gas sample inlets are connected to N ports of the second rotary valve not connected to the gas sample storage chambers, and wherein the gas analysis instrument is connected to a port of the second rotary valve not connected to the first rotary valve or to a gas sample storage chamber.
10. The method of claim 9 , further comprising:
first switching the first rotary valve; and
second switching the second rotary valve, wherein a time of the second switching is later than a time of the first switching by a switching delay time;
wherein the switching delay time is selected to account for gas flow time between the first and second rotary valves.
11. The method of claim 10 , wherein connections between the first and second rotary valves have substantially equal lengths and diameters.