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I am looking for a solution to measure the actual total mass of carbon dioxide (CO2) emitted from a diesel engine used for power generation. Infrared CO2 sensors generally measure the gas concentration, describing the amount of gas by volume of the air, which is not useful in my application. Flow sensors are already installed in the diesel supply and return lines to determine the amount of diesel consumed, and hence the amount of CO2 created, but I need to correlate these measurements with actual measurements of CO2 mass produced at the output of the exaust system.

Any idea on how to approach this problem would be greatly appreciated.

Thanks.

EDIT:

The question can be reformulated as to measure the CO2 emission rate from the engine exhaust system. A typical solution in practice is to find a dedicated sensor or a monitoring system that does that.

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  • $\begingroup$ This is for a research application? I.e. you want to test this in a lab? Or a product for a production environment? If the former, you might want to try Chemistry.SE? $\endgroup$
    – LShaver
    Apr 26 at 20:47
  • $\begingroup$ Both applications apply. $\endgroup$
    – AEW
    Apr 26 at 20:56
  • $\begingroup$ So you're looking to develop a product? I ask because if you want to test something in a lab vs deploy at scale in the field, the answers may be very different. $\endgroup$
    – LShaver
    Apr 26 at 21:00
  • $\begingroup$ This is primarily considered a research problem that will later be developed in a commercial setting. A solution will first be tested in a lab environment, and then ultimately deployed in a power generation station. $\endgroup$
    – AEW
    Apr 26 at 21:08
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    $\begingroup$ mass of CO2 = X times mass of fuel. X varies a little bit due to small variations in mass% carbon in the fuel. icbe.com/carbondatabase/fuels/Diesel_Info.html $\endgroup$
    – Phil Sweet
    Apr 27 at 0:37

3 Answers 3

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Pull off a sample of the exhaust gas of known volume and bubble it through a calcium hydroxide solution, to convert all the CO2 to CaCO3. filter, dry, and weigh the CaCO3. knowing how much CO2 was in the inlet mixture you can find the difference, which came from the combustion process. Balancing the chemical equation then lets you calculate the mass flow rate of CO2 in the exhaust stream if you also know the volumetric flow rate of gas exiting the engine.

Remember to account for the temperature of the exhaust.

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  • $\begingroup$ I was wondering if there is a way to do that in real-time, in an industrial context, e.g., using specialized sensors and a monitoring system. Again, I am looking to measure the total amount of CO2 emitted from the engine, and not just from a sample. $\endgroup$
    – AEW
    Apr 26 at 23:18
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I think that Phil Sweet has the right idea in a comment above - measure the fuel flow and apply an emission factor.

But if you really need to measure it, my thought would be to run the gas stream through a chiller to condense the moisture out, and then measure the volumetric flow and temperature of the dry gas, and use gas analyzers to measure oxygen and carbon dioxide. Then calculate the answer by assuming the rest of the gas is nitrogen.

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  • $\begingroup$ As I mentioned in the question, the consumed fuel is already being measured, and the CO2 being estimated knowing the amount of carbon per gallon of diesel. However, I am looking for a redundant accurate method to measure the gas mass emitted from the exhaust stack. $\endgroup$
    – AEW
    Apr 27 at 17:27
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Your problem isn't a trivial one; it actually falls into R&D. I disagree that the gas concentration is not a useful measurement--you could convert it into ppm/ and then into mass, even though that mass will be per volume (I'd assume $mg/m^3$). It might be possible to relate that number to the mass, however.

In one of your comments you mention that you'd like to do it in real-time and in an industrial context--you probably will have to develop that yourself. You could start with a proof-of-concept and hook up some CO2 sensors to an Arduino or multiple Arudinos and try to get the rate of change of the concentration. If you can enclose the exhaust outlet in a closed and known volume and have the sensors be put there, that could make the development of an algorithm much easier (because you would have to develop an algorithm of how to relate whatever the sensors measure to what you want to get--and that is the mass of CO2 emitted from the diesel engine).

What you might want to look into is the research that has been done with various techniques to measure and quantify methane emissions, both in the lab and in the field. This link provides some techniques which researches and people in the industry use to do so.

Edit: if you could do what @niel nielson has mentioned, then you'd have a baseline of what to expect. That would make the development of the above mentioned algorithm much easier, since you'd have a good estimate of which values to expect.

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