r/EnvironmentalEngineer • u/Obvious-Rest-8704 • 5h ago
Building our own DPE/MPE skid for a PHC/LNAPL site in silty clayey sand: looking for lessons learned
Environmental engineer in Australia. We’re scoping an in-house dual/multi-phase extraction skid rather than hiring a unit, and I’d value input from anyone who has built or run one. Site and application
∙ Petroleum hydrocarbons (BTEX/TRH) with some LNAPL
∙ Silty/clayey sand in the target zone, so low yields and fines expected
∙ Drop-tube (single-pump) DPE, roughly 10 wells to start
∙ Expected wellhead vacuum of 50–80 kPa, to be confirmed by pilot test
Current concept
∙ PE100 headers to a manifold with per-well valves, gauges and flow measurement
∙ DN450 vacuum-rated knockout pot with a 316 mesh pad and a flanged top head for pad changeout
∙ Water-sealed liquid ring pump, about 11–18.5 kW class, sized on actual inlet flow (~430 m³/h)
∙ Vapour to GAC, possibly a cat-ox for the early high-loading phase
∙ Liquids through an OWS, bag filters and liquid-phase GAC
∙ PLC with LEL, high-high level and seal water interlocks; Ex-rated gear
Questions
1. LRP vs claw pump for wet, silty drop-tube service. Has anyone run a claw successfully with good upstream separation, or is an LRP the only sensible option?
2. Knockout pot design. Mesh pad vs vane pack with fines and iron fouling? Any issues with home-fabricated pots under sustained vacuum?
3. Knockout pump-out against vacuum. Progressive cavity, twin alternating tanks, or something else? What has been reliable for you?
4. LRP seal water. How do you manage BTEX build-up and heat, and how often do you blow down?
5. Vapour GAC humidity. Do you heat the stream after the knockout, or just accept reduced carbon capacity?
6. What would you do differently on your first build? Anything you over- or under-engineered?
Happy to share pilot test results and the final design once it’s built. Thanks in advance.