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Recent content by MatthewL

  1. M

    Dew point for RNG

    shvet, The only dew point of concern is the water dew point, there are no higher hydrocarbons than methane in anything beyond trace (> 0.1%) amounts.
  2. M

    Dew point for RNG

    George, Our process is fairly simple. The landfill gas (which is saturated, and has a dry basis composition of 54% CH4, 40% CO2, 5% N2, and PPM levels of H2S, VOCs and siloxanes) is brought into the plant through a demister vessel using a blower with a discharge pressure of around 5 PSIG. The...
  3. M

    FEA analysis with thermal loads

    What if your lifting tool was heated to closer to 350 C? I would think most of the stress would be from the sudden contact of a much cooler surface, like a quench on heat treated steel. Could you insulate the grab arms to reduce the heat transfer? Does the work piece have good thermal...
  4. M

    Is there a comprehensive chemical odor threshold database?

    If your factory/storage site/transship location is near a residential or business area, odor thresholds and dispersion modeling is very important unless you want the neighbors shutting you down due to odor complaints. I know this from hard experience with plants that used chemicals with a ppb...
  5. M

    Dew point for RNG

    We will, but for the initial startup I don't have a good feel for what dewpoint we should be seeing. We have another plant that uses a slightly different separation tech, and it runs consistently around 0.8 lb/MMSCF. So at least I have a reference point to judge the effectiveness of the new system.
  6. M

    Dew point for RNG

    LittleInch, We do three separate dehydration steps, one using fin/fan aftercoolers, then a glycol chilled HX at ~5 PSIG, 40 F, and finally a high pressure dehydration done at ~200 PSIG, again at ~40 F. Each of these is immediately after a blower/compressor, and serves both a dehydration and...
  7. M

    Dew point for RNG

    And thanks for the link to Prode calculator, apetri!
  8. M

    Dew point for RNG

    With our process, the only major constituents left are methane, carbon dioxide and nitrogen. There are three separate active media beds at the front of the plant to remove H2S, VOCs, and siloxanes, leaving us with a "raw" gas stream of ~55% CH4, 39% CO2, 5% N2 and 1% O2. It then goes to the...
  9. M

    Dew point for RNG

    The psychrometric was at standard pressure. The Shaw website was for 4000 PSI, but it also corrected to standard pressure. The 1 lb/MMSCF is from the transporter and has been proven empirically to not result in issues during offload. I don't have access to HYSIS or another simulation program to...
  10. M

    Dew point for RNG

    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...
  11. M

    Designing a coil for heat exchanging

    KFC, try controlling the pressure on the vapor to make the boiling point 80C. As long as your oven is below 80C, the vapor will condense, releasing heat into the oven. Once the temp reaches 80C, no further condensation will occur, therefore, no further heating. The mass flow of vapor doesn't...
  12. M

    Tubesheet bolting - not using Nuts!!

    Ditto both replies, and would like to add this: using a threaded tubesheet makes reassembly after pulling the channel more difficult and increases the risk of damaged threads on the tubesheet. Frequently, when the channel is slightly misaligned with the tubesheet, the resolution is to use a...
  13. M

    Suitable temp. for insulation calculation

    If the insulation is for heating purposes, use the minimum ambient temp, especially if freezing is a concern. If it is for cooling, use the maximum ambient. Matt Quality, quantity, cost. Pick two.
  14. M

    Heat Pump Refrigerator Analysis

    Ok, let's try again: Your ideal COP (by definition is Qin/W from the enthalpy plot, where Qin is heat absorbed by the fluid and W is the work done to compress the resultant gas, check your thermo textbook) is (from your P/H diagram): (Point1 - Point4)/(Point2 - Point1) Reading the chart (I...
  15. M

    Heat Pump Refrigerator Analysis

    Hah, one minute late! Nice work Nate! Matt Quality, quantity, cost. Pick two.

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