Diluting sampler and a method for collecting and diluting a gaseous sample

1. A diluting sampler for collecting a gaseous sample disposed at a temperature substantially higher than the normal temperature from a sample space, the sampler comprising:

a sampling tube having a first end for introducing a flow of sample into the sampling tube as well as a second end; and

a diluter for receiving the flow of sample from the second end of the sampling tube and for diluting the sample, the diluter comprising a tubular:

gas permeable first jacket forming a sample channel, into which the second end of the sampling tube opens; and

gas tight second jacket enclosing the first jacket and forming between the first jacket and the second jacket a dilution gas space for the dilution gas to be introduced through the first jacket into the sample channel, the second jacket being connected by its end situated on the side of the sampling tube to the sampling tube at a first connecting point;

wherein the outer diameter of the second end of the sampling tube is smaller than the inner diameter of the first jacket;

wherein the second end of the sampling tube projects into the first jacket to a second distance from the first connecting point for directing the dilution gas to form a substantially laminar protection flow disposed longitudinally to the sample channel and enclosing the flow of sample;

wherein the diluter comprises a gas tight third jacket enclosing the second jacket and forming between the second jacket and the third jacket a cooling agent space for cooling the dilution gas with a cooling agent to be introduced into the cooling agent space, the third jacket being connected by its end situated on the side of the sampling tube to the second jacket at a second connecting point; and

wherein the second connecting point is disposed at a first distance from the first connecting point in the longitudinal direction of the sample channel, the first distance preferably having at least the size of the second distance for arranging a heat transfer connection between the sample space and the dilution gas space.

2. The diluting sampler as defined in claim 1 , wherein, in the vicinity of the second end, the sampling tube has got a throttling for accelerating the flow velocity of the sample.

3. The sampler as defined in claim 1 , wherein the outer diameter of the second end of the sampling tube is about 10 mm; the inner diameter of the first jacket is about 15 to 20 mm; and the first distance is about 20 mm and the second distance is about 10 to 15 mm.

4. The diluting sampler as defined in claim 1 , wherein the sampling tube is made from austenitic stainless steel resisting high temperatures.

5. The diluting sampler as defined in claim 4 , wherein the austenitic stainless steel contains 0.08% carbon, 21% chrome and 11% nickel, as well as silicon, nitrogen and cerium.

6. A diluting sampler for collecting a gaseous sample disposed at a temperature substantially higher than the normal temperature from a sample space, the sampler comprising:

a sampling tube having a first end for introducing a flow of sample into the sampling tube as well as a second end; and

a diluter for receiving the flow of sample from the second end of the sampling tube and for diluting the sample, the diluter comprising a tubular:

gas permeable first jacket forming a sample channel, into which the second end of the sampling tube opens; and

gas tight second jacket enclosing the first jacket and forming between the first jacket and the second jacket a dilution gas space for the dilution gas to be introduced through the first jacket into the sample channel, the second jacket being connected by its end situated on the side of the sampling tube to the sampling tube at a first connecting point;

wherein the outer diameter of the second end of the sampling tube is smaller than the inner diameter of the first jacket;

wherein the second end of the sampling tube projects into the first jacket to a second distance from the first connecting point for directing the dilution gas to form a substantially laminar protection flow disposed longitudinally to the sample channel and enclosing the flow of sample; and

wherein the sampling tube comprises a heat insulator adapted in the vicinity of the second end to extend to a distance from the first connecting point on its both sides to decrease the cooling of the inner surface of the sampling tube.

7. A method for collecting and diluting a gaseous sample disposed at a temperature substantially higher than the normal temperature from a sample space, the method comprising:

collecting a flow of sample into a sampling tube;

directing the flow of sample from the sampling tube into a sample channel formed by a gas permeable first jacket;

introducing dilution gas into a dilution gas space formed by a second jacket enclosing the first jacket and connected by its end to the sampling tube, and further from it through the first jacket into the sample channel;

conducting heat from the sample space into the dilution gas space for warming up the dilution gas which comes into contact with the sampling tube; and

forming from the warmed up dilution gas a substantially laminar protection flow which encloses the flow of sample being released from the sampling tube into the sample channel and is disposed longitudinally to the sample channel.

8. The method as defined in claim 7 , wherein the flow of sample is accelerated in the sampling tube in the vicinity of the end thereof situated on the side of the sample channel.

9. The method as defined in claim 7 , wherein the conduction of heat from the sampling tube into the second jacket connected to it is reduced.