Biofuel Truck Loading Systems

Biodiesel and HVO share the biofuel label, but at the loading rack they call for quite different precautions. Biodiesel made as fatty acid methyl ester (FAME) clouds and gels at higher temperatures than most petroleum diesel, is prone to oxidation during storage and handling, and is incompatible with certain metals and elastomers. Hydrotreated vegetable oil (HVO), by contrast, is produced by hydroprocessing, which yields compounds identical to some of those in conventional diesel, so at the rack it behaves much more like fossil diesel. Designing a biofuel loading point therefore starts with three questions: which product, at what blend level, in what climate.

The generic pump, filter, meter, control valve and loading arm sequence is described on the Truck Loading Systems page. This page focuses on cold flow, oxidation, materials and product segregation at bays that load neat biodiesel (B100), biodiesel blends and HVO.

FAME versus HVO at the rack

In practice, an HVO bay can often be designed along the lines of a diesel bay, whereas a bay handling B100 or high biodiesel blends needs its own review of heating, insulation, materials and storage time. HVO's diesel-like behavior should still be confirmed against the product specification and any FAME content.

Cold-weather flow: heating and insulation

The cloud point of B100, the temperature at which crystals first appear as the fuel cools, starts around −3 °C and may reach 16 °C depending on feedstock, with higher values reported in rare cases. The pour point is usually only a few degrees lower, so once crystals form, gelling can follow quickly. As B100 begins to gel, viscosity climbs fast, filters plug and pumps are put under stress.

Handling guidance recommends storing B100 at least 2.5–5 °C above its cloud point and protecting aboveground tanks, lines, pumps and dispensing equipment with heating and insulation suited to the local climate. For a truck loading system, that translates into four questions:

·         Dead sections: Loading arms, meters, filters and short pipe runs sit without flow between loads and cool fastest, so heat tracing and insulation are evaluated there first.

·         Upper heating limit: Heat is one of the factors that accelerate oxidation, so the heating system is controlled to keep the product safely above cloud point without overheating it.

·         Heating in hazardous areas: Where electric heat tracing is used, trace heater standards for explosive atmospheres and the area classification drive equipment selection.

·         Transport by truck: For cold-weather B100 shipments, truck insulation or heating is assessed together with transit time and ambient temperature so the product does not arrive below its cloud point.

Heated loading lines resemble the approach used for heated metering skids in heavy oil service, but the goal with biodiesel is to stay out of the crystallization zone rather than to reduce viscosity.

Oxidation, storage time and wetted materials

Biodiesel is thermally very stable but susceptible to oxidation in storage and handling, which can produce peroxides, acids, gums and sediment, raise viscosity and plug filters. Exposure to air, heat and light accelerates the process, and so do certain metals: copper, brass, bronze, lead, tin and zinc are reported to speed degradation and increase sediment. Wetted parts in the loading chain should avoid these metals and galvanized surfaces.

With prolonged exposure, B100 can soften or degrade some hoses, gaskets, seals and plastics; some nitrile rubber compounds, polypropylene and polyvinyl materials are singled out as vulnerable. Ask suppliers for B100 compatibility data on pump seals, meter and valve seals, swivels and hoses. B100 is also a good solvent that can loosen deposits left in tanks and lines by diesel, so filter plugging often rises during the first period after conversion; monitoring filter differential pressure helps manage it.

Oxidation stability declines with storage time. For product held longer, periodic monitoring of oxidation stability and acid number, nitrogen blanketing and antioxidant additives are recommended practices. The loading system provides sample points and records for this monitoring; additive dosing is covered on the additive injection page.

Segregation, truck preparation and blending

A biofuel terminal may handle fossil diesel, B100, several blend levels and HVO on the same site. Dedicated product lines or changeover procedures for shared lines, whether meters and arms are shared, blend labeling and quality protection should be settled early in design. On the truck side, pre-loading checks cover water and previous cargo in compartments, B100 compatibility of hoses and seals, and whether the previous load is acceptable.

At terminals, biodiesel is usually added to diesel by ratio or in-line blending during loading, and a thoroughly mixed blend does not separate over time as long as it stays above its cloud point. Ratio control and verification are covered on the Biofuel Blending Systems page.

TLY Enerji's role

Depending on project scope, TLY Enerji provides engineering support in selecting measurement and control technology for the biofuel loading point, supplying product-suitable meters, valves, pumps and temperature and pressure instruments, integrating the system with PLC- or SCADA-based monitoring, and carrying out site installation and commissioning. Whether heating and insulation work falls within the scope of supply is defined for each project.

Inputs to define for biodiesel and HVO loading

·         Products to be loaded: B100, blend levels, HVO, and whether fossil diesel shares the bay

·         Product specifications and the cloud point range stated by the supplier

·         Minimum site ambient temperature and exposed lengths of loading equipment

·         Available heating media: steam, hot water, thermal oil or electric heat tracing

·         Typical storage time, nitrogen blanketing and antioxidant use

·         Product changeover frequency and shared lines or loading arms

·         Insulation or heating capability of the truck fleet and typical transit times

Related pages

·         Biofuel metering skids: Managing viscosity and temperature effects when metering FAME and HVO.

·         Biofuel blending systems: Adding biodiesel to diesel at the correct ratio during loading.

·         Truck loading system components: The product-independent loading chain and flow profile.

·         Biofuel additive injection: Dosing cold flow improvers, antioxidants and other additives.

Biodiesel and HVO loading FAQ

Does HVO need a separate loading system?

HVO is produced by hydroprocessing, which yields compounds identical to some found in fossil diesel, and it can be made to meet different cloud point requirements. In many cases the equipment and design approach of a diesel bay can therefore be considered for HVO. The product specification, any FAME content and supplier views on wetted materials should still be checked, and whether dedicated lines are needed depends on the terminal's segregation policy.

Is heating always required on a B100 loading line?

No. It depends on the product's cloud point and the site's minimum ambient temperature. Because B100 cloud point ranges from about −3 °C to 16 °C depending on feedstock, aboveground equipment may need protection even in moderate climates. If the product can be kept a few degrees above its cloud point, insulation may be enough; otherwise heat tracing is evaluated for arms, meters and filters that sit without flow.

Which materials should be avoided in biodiesel service?

Copper, brass, bronze, lead, tin and zinc can accelerate biodiesel degradation and increase sediment, and galvanized surfaces are not recommended. Some nitrile rubber compounds, polypropylene and polyvinyl materials can degrade with prolonged exposure. Stainless and carbon steel are widely used; for seals and hoses, request B100 compatibility data from each supplier.

Why do filters plug more often after switching to biodiesel?

B100 is a good solvent and can dissolve varnish and sediment left in tanks and lines by diesel or other fuels. Filter plugging may therefore rise in the period after conversion, returning to normal as the system cleans up. Oxidation stability and acid number tests help distinguish this cleaning effect from sediment caused by fuel aging.