Biodiesel Plant
Process Overview
Biodiesel Plant — Process Overview
A biodiesel plant converts vegetable oil, used cooking oil or animal fat into fatty acid methyl ester (FAME). Feedstock is degummed and bleached; high free-fatty-acid oils are first esterified with methanol over an acid catalyst. The oil is then transesterified with methanol and sodium methoxide catalyst, and the reaction mixture separates into crude biodiesel and glycerin. Biodiesel is washed and dried, glycerin is treated, and excess methanol is recovered by distillation and recycled.
For compressed biogas and cellulosic ethanol see Compressed Biogas & 2G Ethanol; for molasses and grain ethanol see Molasses-Based Distillery.
Key Sealing Challenges
- Methanol: flammable and toxic; tandem seals with a Plan 52 buffer are used, and standard FKM is avoided because methanol attacks it.
- FAME: biodiesel swells NBR and EPDM, so FKM is used on finished biodiesel.
- Alkaline catalyst: sodium methoxide attacks reaction-bonded SiC; sintered SiC is specified.
- Acid esterification: sulphuric acid catalyst calls for Alloy 20 metal parts.
Which elastomer is used in biodiesel plant pumps?
It depends on the stream. Methanol attacks standard FKM, so EPDM or FFKM is used on methanol and methoxide. Biodiesel (FAME) swells EPDM and NBR, so FKM is used on finished biodiesel. Where both are present, as in the transesterification reactor, FFKM covers both, in a tandem seal with a Plan 52 buffer.
Root-Cause Failure Analysis — Field Example
Symptom: Transesterification pump seal O-rings swell and the seal leaks within weeks.
├── Incorrect Response: "Change to a harder face material."
├── Diagnostic Evidence Required:
│ ├── Which elastomer is fitted, and is it attacked by methanol (FKM) or FAME (EPDM)?
│ ├── Is the catalyst attacking reaction-bonded SiC faces?
│ └── Check buffer fluid condition on the tandem seal.
└── Engineered Solution:
├── FFKM elastomers for mixed methanol and FAME service.
├── Sintered SiC vs sintered SiC faces.
└── Tandem seal with Plan 52 buffer for the flammable methanol.
Frequently Asked Questions
Why is a tandem seal used on methanol pumps?
Methanol is flammable and toxic. A tandem seal with an API Plan 52 buffer contains any inner-seal leakage and lets it be vented safely.
Can the same seal be used on biodiesel and glycerin?
The seal design can be the same, but elastomers differ: FKM for biodiesel, EPDM for glycerin with methanol. FFKM suits both.
Related: Compressed Biogas & 2G Ethanol · Edible Oil Refinery · Molasses-Based Distillery · Refinery.
Request a Seal Selection
Send your pump make and model, fluid, temperature, pressure, shaft size and speed to info@gipfelengg.com or use our enquiry form. Gipfel Engineering (ISO 9001:2015, NSIC-registered MSME, Mumbai) designs and manufactures mechanical seals, seal support systems and process pumps.
Equipment solutions: Reactors & GLR · Overhung Pumps · Positive Displacement Pumps.
Pump Duty & Mechanical Seal Selection Matrix
Typical values for selection guidance only. Final selection is made against the customer duty sheet.
| Pump duty | Fluid | Typical temp. | Typical pressure (bar) | Seal arrangement | Faces / elastomer | API piping plan |
|---|---|---|---|---|---|---|
| Feedstock Oil Pump | Vegetable oil, used cooking oil or animal fat | 40–80 °C | 3–6 bar | Balanced multi-spring cartridge | SiC vs carbon / FKM | API Plan 11; add Plan 62 steam quench for fats that solidify |
| Bleaching Slurry Pump (pre-treatment) | Oil with bleaching earth, under vacuum | 90–110 °C | Suction under vacuum | Double cartridge, back-to-back (pressurised) | SiC vs SiC / FKM | API Plan 53A (barrier ≥ 1.4 bar above seal chamber) |
| Esterification Circulation Pump | High-FFA oil with methanol and sulphuric acid catalyst | 60–70 °C | 2–5 bar | Balanced multi-spring cartridge with Alloy 20 metal parts | Sintered SiC vs sintered SiC / FFKM (methanol rules out standard FKM) | API Plan 11 |
| Methoxide / Methanol Feed Pump | Methanol with sodium methoxide (alkaline, flammable) | Ambient–40 °C | 3–6 bar | Tandem double cartridge (Arrangement 2) | Sintered SiC vs sintered SiC / EPDM or FFKM | API Plan 11 + Plan 52 |
| Transesterification Reactor Circulation Pump | Oil, methanol and catalyst | 55–65 °C | 2–5 bar | Tandem double cartridge (Arrangement 2) | Sintered SiC vs sintered SiC / FFKM | API Plan 11 + Plan 52 |
| Biodiesel (FAME) Transfer Pump | Fatty acid methyl ester | 40–90 °C | 2–5 bar | Balanced multi-spring cartridge | SiC vs carbon / FKM (FAME swells NBR and EPDM) | API Plan 11 |
| Crude Glycerin Pump | Glycerin with methanol, soaps and salts; viscous | 50–80 °C | 2–4 bar | Balanced multi-spring cartridge | Sintered SiC vs sintered SiC / EPDM | API Plan 11 + Plan 62 hot-water quench |
| Methanol Recovery Column Pump | Recovered methanol | 60–70 °C | 2–5 bar | Tandem double cartridge (Arrangement 2) | SiC vs carbon / EPDM or FFKM (not standard FKM) | API Plan 11 + Plan 52 |
Reviewed by Gipfel Engineering’s technical team.
Technical Information Disclaimer
The information on this page, including process descriptions, flow diagrams, operating ranges, seal arrangements, materials and piping plans, is general technical guidance for information only. Values shown are typical industry ranges, not guaranteed ratings or specifications of any Gipfel Engineering product. Each application differs. Seal selection, material compatibility, installation and operation must be verified by qualified personnel against the specific equipment data sheet, process conditions, applicable codes and the pump manufacturer’s instructions. A binding recommendation is given only in a written quotation or technical offer from Gipfel Engineering.
References to standards (such as API 682, ISO 21049, ISO 3069, FDA 21 CFR 177.2600 and NACE MR0175 / ISO 15156) describe common industry practice. They do not mean that any product is certified, qualified or approved to that standard unless this is confirmed in writing for a specific order. Third-party company and product names, including “equivalent to” references, are used for identification only and remain the trademarks of their owners. No affiliation, endorsement or OEM approval is implied.
Compliance with safety, hazardous-area, environmental and statutory requirements at the user’s site remains the responsibility of the plant owner or operator. To the extent permitted by law, Gipfel Engineering accepts no liability for loss or damage arising from reliance on this general information without a confirmed written recommendation. Content may change without notice.