HVO biofuel pretreatment FAQ

1.  What process is followed to remove polyethylene contaminants? 
First, we check to ensure that the polyethylene (PE) is in solution, then we cool the feed so that the PE solidifies and can be removed by filtration. 

2.  How does the pretreatment process impact the lifespan of the hydrotreating catalyst? 
In general, catalyst lifetime is determined by how pressure drop builds up and by catalyst deactivation; one of the two will determine catalyst lifetime. Impurities can affect both. It is known that phosphorus leads to an increase in pressure drop. The HVO licensors provide an acceptable max. limits of impurities to secure reasonable lengths between catalyst replacement. 

3.  How is Alfa Laval technology advancing in this PTU? 
We continuously advance and fine-tune the technology/application to optimize flexibility to handle a wide range of waste oils.  The use of enzymes can be mentioned as one such advance. 

4 .Do innovative non-crop feeds like pongamia oil also require pretreatment, and if so, can Alfa Laval process them? 
Non-edible oils (NEO), such as pongamia oil, require pretreatment and can be processed in an Alfa Laval PTU.  

5.  What would be the typical (%) removal of Phosphorous and Metals in the PTU? 
We quote absolute figures rather than % removal. P is typically reduced to max. 3 ppm and metals to 5 ppm or 10 ppm, depending on what is included in the list of metals. 

6.  In the degumming step, which is preferred: citric acid or phosphoric acid? 
Citric acid. 

7.  What is the difficulty in removing organic chlorides? Any impact if we don’t remove organic chloride? 
Organic chlorides are present in many different types of compounds in the oil/fat. The chloride is bound to the rest of the molecule and cannot be washed out, unlike inorganic chlorides.  In case of some polarity of the organic chloride molecule, there can be some removal in the adsorption section. There is no impact on the PTU if the organic chlorides are not removed. 

8.  How does the PTU differ from traditional alkali refining and bleaching? 
The main difference is that we do not want to reduce the FFA content of the feedstock. So instead of alkali refining the oil, we degum the oil. This removes contaminants but does not remove any FFA. The adsorption process is similar to bleaching. 

9.  How can you handle 3000 tpd in one line? Can the components like vessels, pumps, heat exchangers, and centrifuges handle such a large capacity? 
3000 tpd is a large capacity for an edible oil plant, but a small to medium capacity for a petrochemical refinery. There are limitations to equipment size, so we need to use multiple components in parallel for high-capacity units. 
 

10. Alfa Laval enzymatic degumming uses only Novonesis enzyme, or is it open to other enzyme suppliers? 
A customer can choose to use other types of enzymes; the Alfa Laval performance guarantee is tied to the Novonesis enzyme or an enzyme with equal or better performance. 
 

11. Can wet degumming/water degumming take care of chloride? Hence, eliminating the chloride mitigation step. 
Water degumming is not suitable for use in a pretreatment as it does not remove sufficient P and metals. 
 

12. Can you talk more about “almost” zero effluent in PTUs? 
If a wastewater evaporation unit is included in the PTU, then we generate clean water from the wastewater. This clean water can be recycled and used again in the PTU. For some items of equipment, we still like to use a small amount of fresh water, which is why we currently do not say zero liquid effluent discharge. This is also an area of ongoing development. 

13. Can you go into more detail on the waste streams from HVO? E.g., what quality is the wastewater? What are the characteristics of spent earth, and how best to handle this material? 
Wastewater usually contains up to 3% fatty matter. The spent earth is a clay containing up to 25% oil. We normally recommend that the spent earth is either burnt, for example, in a cement powder factory or sent to a biogas unit. 

14. What % of yield losses can be expected from the HVO process? 
Yield depends on the amount of impurities in the feedstock. A typical range is from 94% to 98%. 

15. What are the typical materials used for pipes, valves, and valve types in the PTU unit? 
Typical construction materials are 316 or 304 stainless steel. 

16. What is the source of polyethylene in animal fat and used cooking oil (UCO)? 
Typical sources of polyethylene from animal fats may include items such as ear tags that pass into the rendering process to separate oil from the waste. Another source is the polyethylene packaging material from packaged meat that has passed its last use-by date. Because UCO is an undefined product, there may be residues in UCO from other waste oils. 

17. Which of the contaminants are more harmful to the HVO process? 
Of key importance are phosphatides and metals. In general, a hydrotreating catalyst can deactivate via two mechanisms: (1) pressure drop, or (2) loss of catalyst activity. Phosphatides tend to cause a pressure drop as they build upon the catalyst particle in the trickle bed reactor. This reduces the void space and creates premature loss of catalyst life.  

18. Except for FFA removal, what are the main differences in plant configuration between pretreatment for biodiesel and pretreatment for HVO? 
The main difference in plant configuration is the chloride and polyethylene removal sections (if needed) and the bleaching (adsorption) section used in HVO pretreatment plants. The HVO process generally occurs at temperatures above 350°C in a fixed or trickle bed reactor, which means it is much more sensitive to impurities compared to the liquid phase reaction in the fatty acid methyl esters (FAME) process. Pretreatment, therefore, needs to be fine-tuned to a higher degree to remove impurities. 

19. How do you treat spent adsorbent (general treatment) to meet regulations? 
In most locations, landfill is not an option. Some plants can deliver the spent adsorbent, which holds about 23% oil and has value as fuel, to cement producers to burn as a support fuel. Furthermore, some companies reclaim the adsorbed oil through solvent extraction as their core business. 

20. What is the difference between wet degumming and dry degumming? 
Wet degumming assumes that gums are separated from the oil by means of a centrifuge. Dry degumming is used for oils with a low amount of P in crude oil  (like palm oil, 30-50 ppm); removal can therefore be combined with bleaching without having a negative impact on the clay filtration process. 

21. What are the minimum and maximum design capacities of a PTU (speaking of production rate)? 
The minimum is largely set by the main PTU unit; the high CAPEX demand requires a certain minimum size to be economical, probably about 3000-5000 bpd. There is, in theory, no upper limit because there is a certain capacity for parallel lines. More likely, the upper limit will be set by the feedstock supply chain as well as other logistics and infrastructure. 

22. We've seen that enzyme additions to the pretreatment process of vegetable oils and biodiesel feedstocks have demonstrated lower losses (higher yields) and lower gum volumes. 
Correct, we have a long list of references for enzymatic deep degumming in pretreatment for fatty acid methyl ester biodiesel, particularly applicable for soybean oil feedstocks. The PLA-type enzymes produce lysophospholipids that are more water-soluble and will reduce emulsion. This results in deeper P removal as well as lower oil losses. 

23. Does Alfa Laval have experience in designing HVO pretreatment units with used cooking oil as their feedstock? 
Yes, we do. We have some pretreatment units in service and/or are currently designing units that use UCO as feedstock. 

24. If 100% CPO is used as feedstock, can the special degumming section be eliminated and instead move directly to the adsorption section? The acid gums collected in the spent adsorbent? 
Indeed, due to the low phosphorus (P) content in CPO, only the adsorption unit is required.  Although used cooking oil (UCO) also has a low P content, it is not advisable to have aonly n adsorption section since other impurities may interfere with the adsorption process. 

25. If the cooking oil has P content below 50 ppm, can the special degumming process be eliminated? 
The gums will be absorbed by bleaching clay and separated by the filter. Therefore, the clay will be used for gum absorption. Removal of methyl ester is the primary task of clay since wet degumming is not too effective here. Therefore, we potentially can use less clay by applying wet degumming, and this clearly has benefits for P > 50 ppm.