Environment & Safety Gas Processing/LNG Maintenance & Reliability Petrochemicals Process Control Process Optimization Project Management Refining

November 2023

Process Optimization

Sample high-viscosity fluids safely in refinery settings

In a modern refinery setting, production processes are expected to be streamlined to maximize value from beginning to end.

Swagelok: Dixon, M.

In a modern refinery setting, production processes are expected to be streamlined to maximize value from beginning to end. Reducing waste is paramount, and refineries should always examine their processes to ensure every product and byproduct are optimized (FIG. 1).

FIG. 1. Enabling quality and efficiency at refineries requires frequent examination of processes to ensure every product and byproduct are optimized.

One of the byproducts most frequently seen in refineries is bitumen—a dense, large-molecule liquid resulting from the traditional vacuum distillation of crude oil. Bitumen is a key ingredient to make asphalt, which is frequently used in the construction industry. Asphalt’s many uses include roads, runways, parking lots, roofing and other applications. For many refineries, combining bitumen and aggregate to produce asphalt can add value to their bottom lines.

Bitumen is not uncommon, as it is produced in refineries everywhere; instead, its value relies on its relatively low cost as a feedstock, and refineries usually sell their excess bitumen to local asphalt plants. As a specialty product, asphalt production carries higher profit margins than other bitumen uses.

Producing this value from the bitumen byproduct means operators must regularly sample it to ensure quality and consistency throughout the process. What makes bitumen challenging to sample is that it is a high-viscosity fluid, making grab sampling a more complex operation than with other fluids. Therefore, several things must be considered when sampling bitumen or other high-viscosity fluids and liquids.

Keeping the sampling system clog free

Unless proper temperatures are maintained, high-viscosity liquids may solidify. It is crucial to keep them heated to at least 20°C (68°F) above their pour temperature to keep them in liquid form (FIG. 2). It is vital to design a sampling system with the proper heating elements to keep the fluid flowing and prevent clogs from forming when sampling at those temperatures. If a clog forms, it may lead to a lengthy, messy and potentially dangerous cleaning process.

FIG. 2. Large molecule, high-viscosity fluids like bitumen must be maintained to the proper temperatures throughout the sampling process to preserve the sample’s integrity.

Keeping the entire sampling system at or above minimum temperatures is critical, including from the lines to the sampling point. Ensuring the system design is as simple as possible allows operators to maintain consistent temperatures throughout. To that end, systems should be well insulated to prevent cold spots, and designers should avoid unnecessary components. In addition, a stinger nozzle—which uses a steam jacket to keep the system media hot right up to where the sample is collected—is often incorporated.

Bitumen sampling systems are particularly susceptible to clogs and are difficult to get flowing properly again once the system is clogged. This requires completely melting the system media already in the tubes, which is challenging. Cold spots often develop in the system, preventing a full melting from taking place. Mechanical interventions may become necessary, but they can be costly in downtime and replacement parts. That is why preventing clogs from forming is crucial to keep a system operating at peak performance.

Safe sample capture

Since the high-viscosity liquids in the tubes are often significantly heated to keep them flowing, sampling them can pose potential risks to the workers. Taking the necessary precautions to ensure operators can sample these fluids safely is essential. Bitumen typically flows at temperatures above 204°C (400°F), meaning contact with the fluid can cause severe burns.

Several options are available to protect the workers sampling the liquids and prevent these hazards from affecting work at a facility. For example, facilities can put in a “no bottle, no flow” mechanism, which prevents the system from allowing any liquid flow unless a container is in place. Not only can this mechanism keep fluids from being dispensed accidentally, but it also prevents messes from being created that can cost time and money to clean up. In addition, operators should ensure the proper containers—typically made of metal—are used so the high temperatures do not damage the container.

It also may make sense to enclose the sampling point to keep accidental splashing from injuring operators. The enclosure may also be steam-heated to prevent clogs by keeping the media at the proper temperature.

Lastly, using the right components in a bitumen sampling system is important to ensure the increased temperatures do not cause inadvertent damage. The tube fittings, valves and other system parts should be specified with the required temperature ratings to accommodate the system media. A reputable supplier should be able to advise on what components will work best for a system.

Have sampling specialists available

Sampling plays a vital role in helping to deliver the high-quality products that customers expect. After all, sampling validates fluids composition, enables insight into following applicable regulations and keeps the overall facility profitability at optimal levels.

It is vital to work with a reputable supplier who can offer astute advice and provide best practices for constructing and using sampling systems (FIG. 3). Suppliers should be able to provide field engineers who can consult on sampling systems at all locations. In addition, work with suppliers with the experience to handle niche fluids like bitumen and other high-viscosity fluids. They can help design simple systems that perform at maximal potential without the possible problems a more complex system might entail. They should also be able to offer solutions to particularly challenging sampling problems with onsite engineering advice. HP

FIG. 3. Suppliers should send field engineers to inspect each system to ensure it is designed with safety in mind.

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