Pyrolysis Oil Metering Skids

For a pyrolysis oil whose composition keeps changing, reliable metering usually means measuring on a mass basis, choosing a meter that tolerates viscosity and solids, and making sure the meter sees clean, uniform product at a controlled temperature. When density and water content move from batch to batch, measuring volume and converting it with a fixed density introduces errors that nobody notices until the reconciliation fails. Meter technology is therefore selected together with the product analysis and with the quantity the business actually invoices.

Metering skid layout in general, and how custody transfer results are verified, are covered on the relevant SKD pages. The focus here is on what pyrolysis oil demands from the metering technology.

What makes pyrolysis oil hard to meter

IEA Bioenergy gives the density of biomass fast pyrolysis oil at 15 °C as 1.10–1.30 g/ml, against roughly 0.85 g/ml for fuel oil, with 20–30 wt% water and 15–35 cSt viscosity at 40 °C. Those ranges describe biomass oil only; tire and plastic oils have different density and viscosity and must be characterized from their own analysis. Whatever the source, the metering design has to deal with the same set of issues.

·         Variable density: Differences between batches and sources make volume-to-mass conversion uncertain.

·         Viscosity and aging: In biomass oil viscosity rises with storage time, so the meter's operating range has to cover the drift.

·         Solids: Wear and jamming risk for meters with tight clearances or moving parts.

·         Fouling: Oil that thickens on hot surfaces or during long standstills can leave deposits on wetted surfaces.

·         Acidity: Total acid numbers of 90–100 are common in biomass oils, which drives wetted-part material choice.

How meter technologies fit pyrolysis oil

Meter technology screening for pyrolysis oil (general framework; final choice rests on product analysis and manufacturer data)

The table is a list of questions to ask, not a ranking. Coriolis meters are frequently considered where product is traded by mass and density varies; in VTT's biomass pyrolysis oil combustion trials, the oil passed through a filter and pre-heater before a mass flow meter. PD meters tend to come up where existing infrastructure is volume-based, because of their tolerance to viscosity. Either way, the meter's own accuracy figure is not the uncertainty of the metering system; filtration, temperature stability and installation determine the system result.

Density data as a quality signal

The density reading from a Coriolis meter also says something about the product. Once the normal band for oil from a given source is known, a clear departure can indicate a change in water content, a separated phase passing through, or a different product entering the line. Because biomass oil and petroleum oils differ so much in density, a wrong-product event tends to stand out. Density alone is not an analysis, though: alarm limits should be derived from the product's own history, and excursions confirmed with a lab sample.

Wetted materials: separate from the piping decision

Coriolis manufacturers' corrosion guides stress that general corrosion tests do not reveal pitting or stress corrosion cracking, and that localized corrosion can start fatigue cracks in vibrating tubes. A material that suits the pipework is therefore not automatically right for the meter. For acidic biomass oil, the tube material should come from the manufacturer's product-specific assessment; for tire and plastic oils the same process applies, sharing whatever components stand out in the analysis.

Fouling, cleanability and temperature control

Biomass pyrolysis oil ages with heat and can thicken or coke at overheated spots. On a metering skid that risk is handled in three ways: proper filtration upstream with strainer differential monitoring; isolation valves, a bypass and flushing connections so the meter can be cleaned in place, with the flushing alcohol or alkaline solution checked against seals and liners; and steady meter temperature through indirect, limited heating. If a heating jacket is fitted on the sensor, ambient limits of the electronics also apply, and a remote-mount transmitter may be needed.

Cold spots and insulation on heated skids are discussed on the heated metering skids page for heavy oil and fuel oil. The difference with pyrolysis oil is that the goal is not only keeping it fluid but staying below its thermal stability limit, which is set from the product analysis.

Process metering or custody transfer?

Monitoring consumption on site and selling the oil carry different requirements. International recommendations for dynamic liquid measuring systems under legal metrology control apply to metered systems regardless of measuring principle, but whether a pyrolysis oil sale falls under legal control depends on national law and the contract. Where custody transfer applies, meter verification, sealing and records need to be defined at the start. Batch metering, sampling and traceability are covered on the batch metering systems page for pyrolysis oil.

TLY Enerji's role on a metering skid

Depending on project scope, TLY Enerji can review the product analysis and operating conditions and support metering technology selection, supply of Coriolis or other flow meters, temperature and pressure instruments and valves, flow meter installation and commissioning, and PLC- or SCADA-based data acquisition and reporting. Meter material compatibility is confirmed together with the manufacturer's assessment and the operator's product knowledge.

Data we need for a metering skid

·         Density, viscosity and water content for several batches, ideally also after aging

·         Solids content and particle size information

·         Acidity, or the source-specific components that stand out in the analysis

·         Minimum, normal and maximum flow; operating pressure and temperature

·         Purpose of measurement: in-plant monitoring, consumption or sale

·         Invoicing unit (mass or volume) and the verification method agreed with the buyer

·         Signals to be passed to the control system and reporting needs

Related pages

·         Batch metering systems for pyrolysis oil: Batch-based metering, sampling and traceability.

·         Heated transfer systems for pyrolysis oil: Keeping meter and line temperature within the thermal stability limit.

·         Heated metering skids: Cold spots and insulation on heated skids.

·         Chemical metering skids: General approach to wetted-part selection for corrosive fluids.

Pyrolysis oil metering: questions

Why can volume metering alone fall short for pyrolysis oil?

Pyrolysis oil density changes with source and batch, and biomass oils differ sharply from petroleum oils. Measuring volume and converting with a fixed density creates errors that grow unnoticed as the product changes. If the oil is sold by mass, either measure mass directly or back volume measurement with continuous density data.

Is a Coriolis meter always suitable for pyrolysis oil?

Not always. Direct mass measurement and a density output are strong advantages, but tube material in acidic oil, pressure drop with viscous product and deposits inside the tubes all need separate assessment. The choice depends on the product analysis, the flow range and the manufacturer's material review.

Can the meter's density reading replace lab analysis?

No. Density monitoring can give early warning of a change in water content, a separated phase or a wrong product, but it cannot explain on its own why density moved. Set alarm limits from the product's history and confirm excursions with a lab sample.

How can deposits in the meter be avoided?

The basics are adequate filtration upstream, no overheating of product in the meter and no long stagnant periods. The skid should include valves and flushing connections so the meter can be cleaned without removal, and the flushing liquid must be compatible with seal and liner materials.