Hi all,
It's been a while since I've checked in, but I have a question about water dew point in a RNG (renewable natural gas) stream. I did read the related posts, but none of them seemed to deal with the kinds of pressures and low water content I have. We are capturing landfill gas and separating the methane out for sale as RNG, but due to the location of the landfill, we have to truck the RNG to an injection point. The company we are contracting with for the trucking has a requirement of 1 lb water/MMSCF max due to condensation and freezing issues due to J-T effects during offload, plus moisture spikes that the pipeline operator doesn't much care for (and understandably so). I'm trying to wrap my head around the dew point that the 1 lb/MMSCF represents, and no matter how I have approached it, I get wildly varying results. The gas composition is approximately:
CH4 - 95%+
950 BTU/SCF
CO2, N2 - Total less than 5% (CO2 should be ~2%, N2 ~3%)
O2 - Less than 0.2%
No appreciable C2+
Total sulphur < 10 PPM
Water - Less than 1 lb/MMSCF
Some of the dew point numbers I got for a 1 lb/MMSCF water content were -116 F using a psychrometric calculator and -67 F using a calculator on the Shaw website. We will load the trailers to ~4000PSIG.
The reason I'm looking for a dew point is we have several on line dew point analyzers at process equipment prior to final compression and loading. The final quality check is performed by GC, so there is the potential to load off spec material during the time between injections and results (up to 15 minutes). If I can catch the issue earlier in the process, I can divert to flare until results meet my specs and avoid some gas processing costs.
Regards,
Matt
It's been a while since I've checked in, but I have a question about water dew point in a RNG (renewable natural gas) stream. I did read the related posts, but none of them seemed to deal with the kinds of pressures and low water content I have. We are capturing landfill gas and separating the methane out for sale as RNG, but due to the location of the landfill, we have to truck the RNG to an injection point. The company we are contracting with for the trucking has a requirement of 1 lb water/MMSCF max due to condensation and freezing issues due to J-T effects during offload, plus moisture spikes that the pipeline operator doesn't much care for (and understandably so). I'm trying to wrap my head around the dew point that the 1 lb/MMSCF represents, and no matter how I have approached it, I get wildly varying results. The gas composition is approximately:
CH4 - 95%+
950 BTU/SCF
CO2, N2 - Total less than 5% (CO2 should be ~2%, N2 ~3%)
O2 - Less than 0.2%
No appreciable C2+
Total sulphur < 10 PPM
Water - Less than 1 lb/MMSCF
Some of the dew point numbers I got for a 1 lb/MMSCF water content were -116 F using a psychrometric calculator and -67 F using a calculator on the Shaw website. We will load the trailers to ~4000PSIG.
The reason I'm looking for a dew point is we have several on line dew point analyzers at process equipment prior to final compression and loading. The final quality check is performed by GC, so there is the potential to load off spec material during the time between injections and results (up to 15 minutes). If I can catch the issue earlier in the process, I can divert to flare until results meet my specs and avoid some gas processing costs.
Regards,
Matt
