High level technical review
Factor
Mechanical filtration
Electrostatic separator Higher initial investment
Capital cost
Moderate
Operating cost
High (filters, labour, waste)
Low (no consumables, less maintenance)
Yield improvement
Limited Variable
Increased (due to lower losses)
Product quality
Consistently high
Downtime
Frequent for changeouts Significant (spent filters)
Minimal Minimal
Waste generation
Additional equipment
Significant (extra vessels, pumps,
Minimal, standalone system
and on-site construction)
Backflush medium cost
Significant (high-value product)
Low (backflushed with FCC feed)
Table 3
Mechanical filters capture suspended solids via porous media. This medium can be made of sintered metal or a mesh configuration. Examples of these filters include pressure leaf filters and cartridge filters (see Figure 1 ). In comparison, a mechanical filtration system can have more than 300 individual cartridges in a single vessel, and most systems will have redundancy for reliability. Up to four vessels could be used for a single process. The advantages and limitations surrounding mechanical filtration are summarised below:
Figure 1 Mechanical filtration cartridge
a desalter, the electrostatic separator relies on the dielectric properties of contaminants in oil, allowing them to be captured by a glass bead medium (see Figure 2 ). Higher conductive oils or feedstocks with high moisture content can disrupt these fields. Fortunately, electrostatic systems are automated to adjust conductivity and backflush rates in real time to prevent off-spec product or penalties to operational efficiency.4 The advantages and limitations surrounding electrostatic filtration are summarised below. Advantages • Unaffected by asphaltene or wax fouling that typically blinds mechanical filters. • Removes particles below 1 micron, including uncharged catalyst fines. • Produces higher-clarity oil with lower solids content. • No filter media to replace, reducing labour and waste. • Removes up to 99+% of catalyst fines, including sub-micron particles. • Continuous operation with automated solids removal.
Advantages • Familiar technology. • Broad operational experience. • Moderate capital cost.
Limitations • Blockage by asphaltene and waxes in resid operation. • Filters require frequent changeout and cleaning. • Lower solids removal efficiency, especially for sub-micron particles. • Significant ongoing maintenance and disposal costs. • Lower yield of clarified oil (higher oil losses with filter cake). • High differential pressure as solids load increases, creating a variable backflush volume over time. • Frequent media replacement or cleaning. • Variable efficiency for sub-micron particles. Electrostatic separation technology uses high- voltage fields to coalesce and remove charged and uncharged particles from slurry oil. Like
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