is collected in a separate reservoir, which is isolated from the feed reservoir by a sealed piston. Various test parameters for these experiments are presented in Table 1. Evaluation of the antifoulant formulations against short residue was performed using the same RPFS setup. These experiments were conducted by filling the feed reservoir with a short residue under adequate nitrogen pressure (300 psi) to prevent vaporisation. The feed reservoir and crude pumping lines were heated with a heat jacket at 100°C, while the tube/rod set temperature was maintained at 525°C.
XRF analysis of fouling scales
Foulant scale sample Mg, ppm
Al, % 0.37 0.45
Si, %
S, %
Cl,%
Ca, % Fe, %
Tube side Shell side
87 74
0.98 10.07 0.96
0.36
57.4 41.0
0.35
8.46 19.1
0.3
Table 3
RPFS results of various crudes, crude blends, DHDS feed, and short residue
S. No.
Feed
w/o Antifoulant Benchmark antifoulants HP ThermoPro
1 2 3 4 5 6 7
Crude – A Crude – B Crude – C Blend – A Blend – B DHDS feed
35.6 66.8 31.8 20.6 37.6
10.1 18.3
5.2
14.6
5.6 8.6
1.5 4.6 7.3 1.0 8.2
14.6
9.0
2.1
Short residue
34.2
22.3
Table 4
antioxidants that can capture radicals and halt polymerisation reactions. Metals like nickel expedite the dehydrogenation of asphaltenes that accumulate on preheat exchangers, resulting in coke formation. Thus, metal deactivators should to be included in antifoulant formulations. Based on this understanding, a range of in-house antifoulant formulations has been developed, containing one or more of the aforementioned four categories in varying amounts of individual components, to effectively mitigate fouling in preheat exchangers. To evaluate the effectiveness of in-house- developed antifoulant formulations compared to control experiments (w/o antifoulant) and benchmark antifoulants, various crudes, crude blends, diesel hydrodesulphurisation (DHDS) feed, and short residue were tested using RPFS. The testing parameters were maintained as shown in Table 1. resulting in coke formation. Thus, metal deactivators should to be included in antifoulant formulations ” “ Metals like nickel expedite the dehydrogenation of asphaltenes that accumulate on preheat exchangers,
Results and discussions To gain a deeper understanding of the fouling process, fouling scales obtained from both the tube and shell sides of preheat exchangers were examined using a CHNS analyser and X-ray fluorescence (XRF). The analysis revealed that the fouling scales consist of up to 70% inorganic species, with the remainder being organic species. This finding aligns with the literature reported by the Macchietto group. 9 Iron sulphide compounds are the predominant components in the foulant scales. The results are presented in Tables 2 and 3 . Surfactants are well recognised for their ability to cleanse inorganic species. They prevent asphaltene molecules from growing larger and separating from the refinery stream. Corrosion products such as FeS, Fe 2 S 3 , and Fe 2 O 3 typically accelerate the fouling process. Therefore, corrosion inhibitors should be a fundamental component of antifoulant formulations. Organic fouling may result from polymerisation reactions triggered by fouling precursors such as dienes and alkenes. As polymerisation occurs, the length of the molecular chain increases to a level where solubility is surpassed, leading to deposition. Consequently, antifoulant formulations should incorporate
Refining India
25
Powered by FlippingBook