BLEACHING EARTHS With the EU’s revised Renewable Energy Directive (RED II) adopted for the 20212030 period, biofuel producers – hoping to meet stringent new requirements – are facing two main feedstock challenges: availability and quality (see Figure 1, below). New feedstock variants, in limited supply and with a diverse range of impurities, greatly impact filterability during pre-treatment, and consequently, production yields and profits. Overcoming these problems requires novel adsorbents and innovative technical strategies that can facilitate high throughput purification.
Pre-treatment of feedstocks
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New biofuel feedstocks, new adsorbents
Increasing biofuel regulations are forcing producers to turn to alternative feedstocks, which pose major purification challenges. Now, next-generation adsorbents aim to help producers overcome these challenges, maximising throughput and yields Carlos Rodriguez, Vinicius Ribeiro Celinski Availability 2020-2030
Main quality challenges
Secondgeneration feedstocks
UCO/RUCO
Moderate to good
Alkaline metals, metals, oil stability, polymers
Animal fat (category I & II)
Moderate
N-content, metal content, acidity
Advanced feedstocks
POME
Moderate
Acidity, alkaline metals, metals, P-compounds
Extracted oil from Low bleaching earth
Purest feedstock (already treated), some heavy metals from previous purification
Algae
Metals, polymers
Low
UCO = used cooking oil, RUCO = repurposed cooking oil, POME = palm oil mill effluent Figure 1: Availability and quality challenges of new biofuel feedstock variants www.ofimagazine.com
Clariant bleaching.indd 2
Fresh focus on filtration
Source: Clariant
Feedstock
In a feedstock market that is stretched to its limits, quality and availability are in direct relationship. Insufficient choice and supply of feedstock have forced producers to use lower qualities than their facility designs allow, adding considerable stress to their units. The ability to “tame” difficult-to-treat feedstocks would give producers a strong competitive advantage. In the case of fatty acid methyl esters (FAME) or hydrotreated vegetable oils (HVO), the feedstocks’ regulatory compliant specifications mean that the process remains stable. However, problems are found further upstream, in the pre-treatment unit. With such alternative feedstocks, there should be a fresh focus on two important steps: adsorption and filtration (see Figure 2, following page). An adsorbent is required to reduce many undesirable substances that cannot be removed in the degumming steps. Compared to vegetable oils, alternative feedstocks can contain higher levels of different types of contaminants, such as phosphorous compounds, that can greatly affect efficiency as well as the adsorption step (see Figure 3, following page). Aside from the batch reactor, the filter is one of the most important sections of a pre-treatment unit. Conventionally, horizontal leaf filters (Niagara type) were used with screens that had larger pores than modern designs in order to allow maximum flowthrough during filtration. Since a filter cake is formed with the adsorbent, its quality and development are critical. A stable and, especially, homogenous filtration ensures that contaminant removal is spread across the entire filter cake and leads to more efficient use of the adsorbent. Assuming a parallel channel through u OFI – JUNE 2021
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