Improved Distillation Plants for Petroleum Products

Crude oil samples and petroleum products are usually fractionated by following the ASTM-standards D2892 (TBP) and D5236 (Potstill).

The thermodynamic definition of ASTM D2892 (packed column, separation efficiency ~15 theoretical plates, thus overlapping range ~15...20°C) results in an FBP (final boiling point) of ~400°CAET at 2 mmHg (Torr).

The corresponding data of ASTM D5236 (open tube column, no reflux ratio, separation efficiency ~2 theoretical plates, thus overlapping range ~18...30°C) result in an FBP range 540...565°CAET at 0.1 mmHg (Torr).

As bitumen ranges from 560...600°CAET, thus far beyond the D5236 capabilities, many end-users require a modified D5236 unit to additionally cover the bitumen range, and provide “bitumen data” in a safe and reliable mode.

This demand can be easily realised by a modified Potstill unit, which is based on extended thermodynamic D5236 conditions enabling a significantly lower operating pressure (vacuum) of 0.001 mmHg with reasonably high distillation rate (better than original D5236 units). The extended D5236 conditions actually guarantee an FBP range of 620...650°CAET. However, the overlapping range of an extended D5236 unit (i-Fischer^® Dist D-5236 HV) is identical to the original D5236 unit (i-Fischer^® Dist D-5236 CC). Here it is essential to realise, that any constant long-term operating pressure (high vacuum) of 0.001 Torr cannot be achieved by a simple oil diffusion pump, and this fact is taken into account in ILUDEST’s/i-Fischer’s design.

Increasingly and for several years, the ASTM related fundamental conditions no longer sufficiently satisfy modern research requirements when developing new “high-end” petroleum products. Consequently, distillation units related to improved thermodynamic conditions are required. The overlapping range depends on the separation efficiency of columns. While the ASTM-norms deliver a quite “moderate” overlapping range, a problem can be that the data yields of D5236 are quite poor considering modern research requirements such as high separation efficiency with reduced overlapping range in the case of heavy products (400°CAET “+”).

With these considerations in mind ILUDEST/i-Fischer developed a distillation unit similar to D2892, characterised by: high separation efficiency (25…30 theoretical plates) - also under vacuum 0.1 Torr (!); low overlapping range 5...10°C; operating temperature range up to 560°CAET; operating pressure range ATM….0.1 Torr (mmHg); covering the temperature ranges as per ASTM D2892 and D5236, combined in one single plant equipped with a packed column; distillation rate better than comparable D2892 unit, and flask size 30 ltr.

This unit was installed and commissioned at a client’s site in Germany in 2012, and continues to perform to the high standard expected. 

Even these sophisticated technical requirements were surpassed by a request received from a customer in South Africa, a major player in the Petro Chemical Field, looking for an even more extended operating range up to 600°CAET(!). Again, ILUDEST/i-Fischer developed a distillation unit similar to D2892, characterised by: high separation efficiency (30 theoretical plates) - also under vacuum 0.001 Torr (!); low overlapping range 5...10°C; operating temperature range up to 600°CAET; operating pressure range ATM….0.001 Torr (mmHg); covering the temperature ranges as per ASTM D2892, D5236 and extended D5236 HV, combined in one single plant equipped with a packed column; distillation rate significantly better than comparable D2892 and D5236 units despite much lower operating pressure (100...1,000 times lower vacuum), and flask size 30 ltr.

In 2014 this unit was installed and commissioned in South Africa. 

These innovative projects “Make the Impossible Happen” and were served by ILUDEST’s/i-Fischer’s original high-end brand FISCHER^® AUTODEST^®, known and respected worldwide.

At ILUDEST’s/i-Fischer’s it is essential to install with their products a set of comprehensive features as per the international refinery safety standards as well as the European Machine Directives. In this respect ILUDEST’s/i-Fischer are always ready to consider any additional requirements as specified by their potential users.