generated from crude oil distillation. They con- tain oxygenate species (triglycerides and organic acids) and reactive olefins/diolefins that can be biologically degraded/oxidised. The breakdown products can be precursors to both gum/coke for - mation and stable emulsion formation. These species can also have greater corrosion potential, especially when there is a small amount of free water present. Volatile biological break - down products can result in objectionable odours if they are vented from the tank due to filling or natural tank breathing (daily temperature cycling). To minimise renewable feed degradation, nitrogen blanketing is strongly recommended for renewable feed tankage, with any venting routed to flare or vapour management systems. Additionally, any water level formed at the bot - tom of the tank should be monitored and removed aggressively to avoid the formation of emulsions/ solids and the initiation of biological activity in the tank. Depending on the level of free fatty acids in the feed, upgraded metallurgy or special coatings may be required to mitigate against rapid metal loss. The renewable feeds also often contain high wax levels, which can solidify at low tempera - tures. This can require the use of external heat exchangers (with tank mixers/circulation) or inter - nal heating coils to ensure proper flow during cold winter temperatures.
Typical renewable feeds
Feed
Soybean Rapeseed Corn
Tall oil
Used UCO 31.1
Animal
(Canola)
oil
fatty acid cooking oil
fat
Alternate name
TOFA
Tallow
API
21.6
22.0
21.3
18.8
32.1
Chloride (est), wppm 20
20
20
20
150
20
Moisture (est), wt%
2
2
4
2
2 7
2
FFA, vol%
0.5
0.5
12
100
15
Sulphur (est), wppm 100
100 77.1 12.1 10.8
100 76.9 12.2 10.9
8
100 75.8 12.7 11.4
100 75.7 12.6 11.7
C, w% H, w% O, w%
77.0 12.1 10.9
76.2 12.5 11.3
Total wt%
100.0
100.0
100.0
100.0
100.0
100.0
Glycerides dist, wt% 12:00
0.30 0.81
14:00 16:00 16:01 18:00 18:01 18:02 18:03 20:00 20:01 22:00 22:01 Total
0.50 10.0
3.00
03.49
13.10
4.00
13.84
27.00
0.00 0.85
0.10 2.30
0.61
5.00
4.00
1.98
25.66 53.23
21.00 41.00
23.00 53.00
64.40 22.30
28.40 53.80
32.00 50.00 12.00
4.75 0.10 0.40 0.30
2.00 1.00
8.00 0.50 0.50
8.96
1.30 0.40 0.30 0.30
0.02
0.50
100.00
100.00 100.00 100.00
100.00
100.00
Table 1
• Hydrogen make-up availability • Heat release • Quench capabilities • Reactor size • Wash water system for reactor effluent or system metallurgy. Some units are not suitable for revamp due to the quality of the target renewable feed; instead, specific purpose-built units may be required (or new pretreatment units). Revamp or new unit designs for co-processing need to consider hydrogen requirements and sources, operating conditions/catalyst selection, reactor or preheat system foul - ing risks, catalyst poisons (and any needed trap materials), and corrosion/material selection. 100% renewable hydroprocessing Segregated units with 100% renewables processing as a revamp or new design have similar considerations as co- processing units. However, because of the greater concen - tration of renewable feeds, the fouling and corrosion issues tend to be more significant. 10,11,12,13 100% Renewable pyrolysis processing Renewable feed pyrolysis or FCC unit processing are other options that can be considered but still require downstream hydrotreating to manage product quality (see Figure 5 ). These processes convert solids to gas and liquids. The use of wood waste is an example of the application of this technology. The wood waste is converted to a low pH pitch
Receipt via marine vessels or barges can require special - ised heating systems to manage reasonable flow rates of waxy renewable feeds. For significant processing levels of renewable feeds, truck delivery will require multiple unloading bays/locations and specific setups for quality control testing/segregation. Pre-processing/treating Renewable feeds can see wide variations in properties depending on the source materials (vegetable oils, render - ing plant products, cellulose fibre processing, used cook - ing oils) and the level of pretreatment provided by the feed supplier (acid treatment, olefin saturation, degumming, fractionation). Pretreatment that reduces the renewable feed olefin content, nitrogen, sulphur, chlorides, phosphorus, free fatty acids, and gums can make a substantial difference in the ability of existing refinery infrastructure to co-process the renewable material successfully or with the minimum amount of modification. Where pretreatment is essential for reducing corrosion risk or managing feed contaminant levels, rigorous feed quality inspection and specifications should be established to ensure no unacceptable quality feed is accepted. Refining co-processing The amount of renewable feed that can be co-processed in an existing refinery unit will often be limited by one of the following factors: 20,21,22,23,24,25,26,27
49
PTQ Q3 2022
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