Degumming
During the last decade, there has been an increasing interest in the production of Hydrotreated Vegetable Oil (HVO). HVO is a high quality biofuel also known as ‘Green Diesel’. It can be used as a ‘green’ transport fuel for road and marine transport. Also, by an adapted hydrotreatment process, HVO can be used to produce SAF (Sustainable Aviation Fuel), which is nowadays a further important growth factor in this quite new industry
The starting raw materials used for the production of HVO are mostly based on fatty acids containing materials (HEFA process). The most available and common feedstocks are vegetable oils (soya, rapeseed, canola oil), but also a lot of low quality oils and fats are used in the raw material blend: Used Cooking Oil (UCO), animal fats, PFAD, POME, fatty acid oils, etc. Moreover, new vegetable crops (‘Cover crops’) are developed to make additional feedstock available – Carinata, Camelina, Pongamia, etc.
Before the raw materials can be hydrotreated in the HVO unit, the oils and fats (or blends thereof) need to be ‘cleaned’ to protect the catalysts used in the hydrotreater units. Strict specifications concerning residual phosphorus (P) and metals need to be met to ensure smooth operation of the HVO units.
Desmet has developed a robust pre-treatment process that is now industrially applied in several high-capacity HVO plants in Europe, Asia and the USA. The first step in the pre-treatment process is the ‘degumming step’.
How does it work?
First, a well-defined blend of feedstocks is prepared, and this blend will be sent, after pre-cleaning, to the degumming section.
The degumming section in an HVO pre-treatment plant will consist of one or multiple degumming lines, depending on the capacity of the unit. Typical capacities range between 800 tpd and 4000 tpd.
The oil blend will then be treated with a strong citric acid solution, and after a well-defined retention time and the addition of some caustic soda solution, the oil will go to the self-cleaning degumming centrifuge, where most of the phosphatides and metals will be removed. To obtain further cleaning, the oil is then washed with some washing water in the second centrifugal separator. From here, the oil will go to the second cleaning step, the ‘bleaching step,’ where the contaminants will be further removed.
This ‘acid degumming process’ is very similar to the processes used in edible oil refining. However, due to the lower quality of the feedstocks that are often used, Desmet has adapted the design of the degumming lines to cope with these challenging raw materials – especially high impurities and corrosion issues are carefully addressed.
For feedstocks that are mostly based on pure vegetable oils like soya, canola, and rapeseed, Desmet recommends using ‘enzymatic degumming,’ because this can increase the yield of the process considerably and reduce the amount of gums to be removed.
Key advantages