lab or bulk scale, were sourced from Sigma-Aldrich, Merck chemicals, Alfa Aesar, or other bulk chemical industries. Foulant scales, crude oils, and short residues were acquired from HPCL refineries in Visakh and Mumbai. Novel in-house antifoulant formulations were prepared by synthesising active chemical compounds and subsequently blending them with hydrocarbon diluents.
The evaluation of these antifoulant formulations was conducted using the Refinery Process Fouling Simulator (RPFS), as illustrated in Figure 1 . This dynamic simulation device is widely utilised for comparing and assessing the relative fouling tendencies of hydrocarbon feedstocks. In scenarios where foulant removal through hydrodynamic forces is absent, the unit is designed to accelerate depositional fouling on a metal surface under high temperatures and pressures for extended periods. RPFS experiments involve charging the reservoir with a feed, such as crude oil, under sufficiently high nitrogen pressure (500 psi) to avoid vaporisation. The crude oil, typically at an initial temperature (Ti) between 50 and 80°C, is pumped at a steady flow rate through the fouling rod setup. The surface of the rod is electrically heated and maintained at 360°C to 425°C. Heat is transferred from the rod to the flowing crude oil. Over time, due to fouling on the rod surface, the outlet temperature decreases as the heat transfer efficiency from the rod to the oil diminishes. Thermocouples are utilised to continuously monitor the temperatures of the rod surface and the fluid at both the inlet and outlet of the heated section. The crude oil flow is once- through, and after the experiment, the feed
Figure 1 Refinery Process Fouling Simulator (RPFS)
increases the length of the molecular chains to a point where solubility is surpassed, resulting in deposition. The literature indicates that reported antifoulant formulations primarily consist of dispersants, polyamines, and derivatives of succinic anhydride. 6,7,8 To effectively mitigate fouling, it is vital to thoroughly comprehend the differences between these two categories. Furthermore, examining the crudes being processed and the fouling scales within them is key to creating effective antifoulant formulations. HPGRDC developed a cost-effective antifouling formulation by characterising and analysing the fouling deposits gathered from different preheat exchangers in the refinery and by understanding the various mechanisms of fouling that led to their formation. Materials and experimental procedure All chemicals necessary for the preparation of in-house antifoulant formulations, whether at
RPFS test parameters
RPFS testing parameter Tube/rod set temperature
Operating condition
360-525 o C 300-500 psi
System pressure
CHNS analysis of fouling scales
Sample quantity (feed)
800 ml
Flow rate
1-5 ml/min 0.01-0.1 wt%
Foulant scale sample
N, %
C, %
H, % 5.88 5.17
S, %
Antifoulant dosage
Tube side Shell side
1.97 20.28 5.03 34.07
5.12
Run time
6-12 hr
5.2
Table 1
Table 2
Refining India
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