Pyrolysis Oil Truck Unloading Systems

Receiving pyrolysis oil safely comes down to three layers of checks: paperwork and an acceptance sample before the truck is discharged, monitoring of stratification and pump suction while it is being discharged, and quantity reconciliation plus line cleaning afterwards. Because pyrolysis oil changes with feedstock, process and storage time, these checks go further than routine fuel receipt, and the acceptance criteria should be agreed in writing between buyer and supplier before the first delivery.

Suction-side design, air elimination and verifying the received quantity are covered in general terms on the truck unloading systems page. This page deals with what is specific to pyrolysis oil.

Before discharge: documents and the acceptance sample

Industry guidelines for bulk liquid road transport list the documents that may change hands at delivery, such as weighing ticket, delivery note, certificate of analysis and cleaning document, and they advise avoiding sampling from vehicles or, where it is required, leaving it to qualified site staff. With pyrolysis oil that principle carries extra weight. The supplier's certificate describes the batch as produced; only an acceptance sample shows whether the oil in the truck belongs to that batch and has not changed in transit.

Published specifications for biomass-derived pyrolysis liquid test heat of combustion, water, pyrolysis solids, kinematic viscosity, density, sulfur, ash, pH, flash point and pour point. That list is a reasonable backbone for an acceptance program for biomass oil. Tire and plastic oils fall outside those specifications, so for them the contract should define which parameters matter, based on what affects the buyer's own process.

Checkpoints when receiving pyrolysis oil

Stratification in the truck: why the first and last portions differ

During the trip and any waiting time, pyrolysis oil in the tank can stratify. VTT's report on fast pyrolysis bio-oils describes solids agglomerating into a bottom sludge, a lighter top phase separating out depending on feedstock, and an aqueous phase forming as water is produced by aging. In a bottom-discharged truck this can mean sediment-rich oil at the start and differently composed oil at the end. A single spot sample may not represent the load, so the sampling method, and where needed samples from several levels, should be written into the acceptance procedure.

Discharge method and pump selection

Bulk liquids are discharged by pump, by pressurizing with gas, or from the top through a dip pipe. A key safety advantage of pump discharge is that stopping the pump immediately stops the flow in an emergency. If pressure discharge is chosen, compressed air must not be blown into a tank that may hold a flammable atmosphere; inert gas is used instead, and the truck must be depressurized before it leaves. Viscosity and solids content are the main criteria for pump type; positive displacement pumps are often considered for viscous, particle-laden products, but tolerance of internal clearances to solids needs checking with the manufacturer.

Suction is the critical part of any unloading system. When net positive suction head available (NPSHA), the margin of suction pressure above the liquid's vapor pressure, falls too low, the pump cavitates. With a viscous product, friction losses on the suction side are high, which is why a short, generously sized suction line, a low-loss basket strainer and a differential pressure reading across it matter. Cold weather raises viscosity and can upset that balance; whether heating is needed follows from the product analysis.

Heating: only as much as needed, and no hot return to the tank

Heating may look like the easy answer for cold, viscous oil, but biomass pyrolysis oil ages faster at higher temperature. VTT advises against circulating heated oil back to the tank without cooling and notes that prolonged recirculation with thermal cycling seriously degrades quality. Any hot circulation loop between truck and storage tank should be designed with that in mind. How to heat and within which limits is covered on the heated transfer systems page for pyrolysis oil.

Wrong-tank discharge and mixing

Biomass pyrolysis oil does not mix with petroleum oils, so discharging it into a fuel oil tank by mistake produces a two-phase blend that is hard to use. Industry guidelines name unmarked, unlocked intake points and drivers without a document showing the tank number as causes of wrong-tank discharge. A product-specific connection type, a labeled and locked intake point, and a discharge permissive tied to the document check all reduce that risk.

After discharge: cleaning the line

Oil left standing in the line thickens over time and makes the next discharge harder. Fresh biomass pyrolysis oil dissolves largely in alcohols such as methanol or ethanol, while lignin-derived deposits can be removed with dilute alkaline solutions. In both cases compatibility with pump seals and flange gaskets must be checked, and the collection and disposal route for cleaning liquids belongs in the design.

How TLY Enerji can help

Depending on project scope, TLY Enerji can provide engineering support for selecting and supplying the unloading pump, strainers and measurement and control equipment from process data, integrating document-linked discharge permissives into a PLC-based control system, and for site installation, testing and commissioning. Acceptance criteria and sampling procedure remain the buyer's quality responsibility; that boundary and the equipment scope are defined together at project start.

Information for an unloading facility review

·         Origin of the oil to be received and sample supplier certificates

·         Contractual acceptance criteria and sampling obligations

·         Truck type, discharge outlet location and whether trucks carry their own pump

·         Expected product temperature in winter and summer

·         Receiving tank location, distance and elevation difference to the pump

·         Quantity basis: meter, weighbridge or tank gauging

·         Existing provisions for collecting and disposing of cleaning liquids

Related pages

·         Pyrolysis oil truck loading systems: Straining, uniformity and truck cleaning decisions on the shipping side.

·         Tank-to-tank transfer skids for pyrolysis oil: Moving received oil between tanks on site.

·         Truck unloading systems: General engineering of suction, air elimination and quantity verification.

·         Pyrolysis oil metering skids: Choosing meter technology for the received quantity.

Receiving pyrolysis oil: questions and answers

Is an acceptance sample needed when the supplier sends a certificate of analysis?

Yes. The certificate describes the batch at the time of production, while pyrolysis oil can stratify or age during transport and waiting. Only a sample confirms that the oil in the truck is the batch on the paperwork. An acceptance sample, with at least a few quick field tests, lets obvious deviations be caught before the oil enters the site tank.

Why does the pump struggle or the meter drift toward the end of discharge?

Sediment and separated phases collected at the bottom of the truck usually arrive at the beginning or end of discharge. Sludge-laden oil can quickly plug the strainer, lowering suction pressure and pushing the pump toward cavitation, and air entering as the truck empties affects metering. Watching strainer differential and suction pressure keeps this phase under control.

Can pyrolysis oil be discharged with compressed air?

Industry guidelines do not accept blowing compressed air into a tank that may contain a flammable atmosphere. If pressure discharge is needed, inert gas is used and the truck is depressurized on site, and the tank's pressure rating must be confirmed. Pump discharge is usually preferred because stopping the pump stops the flow immediately.

Is it good practice to keep the unloading line in constant hot circulation?

Not for biomass pyrolysis oil. Heat accelerates aging, and returning heated oil to the tank without cooling, combined with long thermal cycling, degrades quality and raises viscosity. If heat is needed, apply it indirectly, only where required and for short periods, within limits set from the product analysis.