08/11/2011 | Author / Editor: Robert P. Absil / Marion Henig
Pilot plant testing is considered as an independent protection layer – to reduce technical risk – when implementing new process technologies in refineries and chemical plants.
Several types of risk exist when implementing a new technology in the refining and chemical industries. These include safety risks, financial risks and technical risks. The technical risk is that the technology to be implemented at the plant will not deliver the expected performance as measured, among others, by petroleum coke properties, deasphalted oil metal content or temperature required to make Ultra-Low Sulphur Diesel (ULSD) sulphur specification. Obviously, technical risk is closely tied to safety and financial risks.
When considering risk in the refining industry, one variable is the feedstock. Conventional crude oil is a complex mixture of hydrocarbon species – that boil over a wide range of temperature. The hydrocarbon species include paraffins, cycloparaffins, aromatics, resins and asphaltenes. Crude oil also includes compounds containing heteroatoms, i.e., sulphur, nitrogen, oxygen and metals. The compounds present in the various distillation fractions, such as diesel, vary with crude origin. The complexity of a crude oil or its fractions can be illustrated by considering just the number of isoparaffins that can exist at a given carbon number – refer table 1. Similar structural variations also exist for cycloparaffins, aromatics, resins and asphaltenes at a given carbon number.
Due to the complexity of the crude oil, it is difficult to predict the behaviour of the fractions in noncatalytic processes, such as deasphalting and delayed coking. While the only variable is the feedstock composition, questions still arise how feedstock will interact with paraffinic solvents in deasphalting or how it will thermally crack in delayed coking and visbreaking operations at process conditions. This increases the risk when implementing new processing technologies in refineries. The risk especially increases when feedstocks, quite different from conventional resources, are tested.
These feedstocks may originate from unconventional resources, such as oil shale, oil sands or biomass. The wide variability in quality across the oil sands reservoir is an issue that needs to be taken into account with bitumen concentration varying considerably vertically and across the reserve.
This article is protected by copyright. You want to use it for your own purpose? Infos can be found under www.mycontentfactory.de (ID: 28639300) | Fotos: Picture: depositephotos, Elvira Rakhmanov