REFINING INDIA 2025

refining india 2025

Valorising plastic pyrolysis oil by co-processing in FCC units for enhanced circularity

Sanju Kumari, Hemant Mishra, Somanath Kukade, and Pramod Kumar Hindustan Petroleum Corporation Limited

Fluid catalytic cracking (FCC) is a vital refining process used to convert heavy hydrocarbon fractions into more valuable, lighter products, such as cracked naph- tha, distillate, and olefins. It relies on a cat- alyst, typically composed of zeolites, to break down large hydrocarbon molecules into smaller, more valuable hydrocarbons. The process occurs in a fluidised bed reac- tor where hot catalyst particles mix with the feedstock, undergoing cracking reac- tions that produce a range of hydrocarbon products. One of the most common feedstocks for FCC is vacuum gas oil (VGO), a heavy distillate obtained from crude oil vac- uum distillation. VGO contains long-chain hydrocarbons that are cracked into smaller, more valuable hydrocarbon products, such as cracked naphtha, liquefied petroleum gas (LPG) distillate, and olefins, through catalytic cracking. The catalyst, after being deactivated by coke deposition, is regener- ated in a separate vessel where the coke is burnt off, restoring the catalyst’s activity for reuse in the process. As refiners explore alternative feed- stocks to reduce their reliance on fossil fuels and address environmental concerns, feedstocks such as plastic pyrolysis oil (PPO) are being considered for process- ing in the FCC unit. PPO is obtained via the thermal pyrolysis of plastic waste, such as LDPE, HDPE, PP, and PTFE, producing a mixture of hydrocarbons that can resemble petroleum-based feedstocks. Integrating PPO into FCC operation offers environ- mental benefits, including diverting plastic waste from landfills, reducing crude oil con- sumption, lowering emissions, and improv- ing sustainability. Figure 1 illustrates the strategy for maximising the value of PPO within a refinery, demonstrating its integra- tion through co-processing in an FCC unit for enhanced circularity. Operational challenges Processing PPO in an FCC unit presents significant challenges. Unlike VGO, which is relatively stable and well-characterised, PPO contains a variety of contaminants, including chloride, nitrogen, sulphur, ole- fins, diolefins, oxygenates, and metals, which can negatively impact catalyst per- formance and operational stability. One major concern is the presence of oxygenates and olefinic components in PPO, which may lead to excessive coke formation during processing in the FCC unit. A high coke yield can reduce catalyst efficiency and necessitate frequent regen- eration cycles, increasing operational costs. Additionally, contaminants such as chlorine, nitrogen, and sulphur can cause corrosion in the main fractionator and gas concentration section of the FCC unit, leading to maintenance issues and possi- ble equipment degradation. A high chloride and nitrogen content of PPO causes ammonium chloride corro-

LDPE & HDPE

Pyrolysis plant

FCC unit

FCC riser

Propylene & fuels

PPO from tanker

VGO

Figure 1 Approach to valorise plastic pyrolysis oil in refinery by co-processing in FCC unit for enhanced circularity

PPO

PPO storage vessel

Lift steam

Flow meter

100% FCC feed 0.5% PPO + 99.5% FCC catfeed 5% PPO + 95% FCC catfeed

PPO pump

Figure 3 Process flow scheme of PPO skid

and 5% of PPO, was used as feedstock. The properties of catfeed and PPO are given in Table 1 , while the characteristics of the Mumbai refinery resid FCC equilib- rium catalyst (E-cat) used in the experi- ments are provided in Table 2. The catalytic cracking experiments were carried out at 540°C with a catalyst-to-oil ratio of 7. The lab results observed that co- processing PPO increases LPG, dry gas, and coke, while reducing cracked naphtha, LCO, and resid yield. The product yields obtained during the experiments with 0.5% and 5% PPO processing are given in Figure 2 . Operational Scheme for PPO processing in the FCC unit Since PPO is not a typical feedstock for the FCC unit in a refinery, a dedicated PPO skid was installed near the FCC unit to facilitate the injection of PPO into the riser. The skid includes a storage tank, an inlet hose for receiving PPO from a tanker, an outlet hose, a pump, and a flow meter. PPO, along with lift steam, was injected into the riser, with no heating provisions provided for the storage tank and feeding line. The process flow scheme of the PPO skid is illustrated in Figure 3 . Demonstration of pPO co-processing in FCC unit A trial for co-processing PPO was carried out at the Mumbai refinery resid FCC unit, which has a feed capacity of 1.27 MMPTA. During the trial, 0.5% of PPO was pro- cessed with FCC catfeed. No gum forma- tion or atomisation issues were observed when injecting the PPO. Based on the chloride and nitrogen content of PPO, the ammonium chloride sublimation tempera- ture was estimated to be around 104°C. Consequently, the main fractionator top temperature was kept higher than the sub- limation temperature to avoid ammonium chloride corrosion in the top trays of the main fractionator. Due to the low sulphur and nitrogen con- tent of PPO used for trial, no ammonium sulphide corrosion was anticipated. The main fractionator top temperature and respective ammonium sublimation temper-

Dry gas

LPG

CRN

LCO

Resid

Coke

Conversion

Figure 2 Product yields obtained in lab catalytic cracking for 0.5% and 5% PPO processing

S. No Parameters

Unit

PPO

FCC catfeed

Parameters

Unit

Value

Density

g/cc

0.79

0.938

MAT

wt%

Conradson carbon residue wt%

Nickel

ppmw

3,746

0.1 58 2.8

1.7

Vanadium

ppmw

2,283

3 4 5 6 7

Bromine number

2 0

m 2 /g

121

Total surface area

Diene

Sulphur Chloride

ppm ppm ppm

23,352

Apparent bulk density

g/cc

0.83

50 70

1.1

P2O5

wt%

0.57

Total nitrogen

752

RE2O3

wt%

3.45

Table 2 FCC E-cat properties

Table 1 FCC catfeed and PPO properties

gate corrosion issues in the main fraction- ator and gas concentration section, and injection in the FCC riser. Various quali- ties of PPO are evaluated to identify those with minimal chlorine, sulphur, nitrogen, oxygenates, and diene content, ensuring reduced negative effects on FCC prod- uct yields. This selection process helps mitigate operational challenges, such as corrosion and gum formation. Catalytic cracking experiments using the opti- mised PPO were conducted at HPGRDC to assess its performance and feasibility in FCC applications. Catalytic Cracking experiments Catalytic cracking experiments for co- processing PPO with FCC feed were car- ried out in a fixed-fluid-bed micro-reactor unit. The product gas was analysed in a Micro-GC, while liquid product was ana- lysed with low- temperature simulated distillation equipment. The liquid prod- uct cuts considered were cracked naph- tha (C₅ at 221°C), LCO (221°C–343°C), and resid (343°C and higher). Conversion was obtained by the sum of the yields of dry gas, LPG, cracked naphtha (CRN), and coke. For the experiments, Mumbai refinery resid FCC unit catfeed, along with 0.5%

sion in the top trays of the main fractiona- tor, whereas a high sulphur content causes ammonium sulphide corrosion in the main fractionator overhead condenser. Ammonium chloride salt deposition can be avoided by operating the main frac- tionator column top temperature above the ammonium chloride sublimation tem- perature, whereas ammonium sulphide corrosion can be reduced in the overhead section by using wash water and corro- sion inhibitors. The composition of PPO also tends to vary depending on the source and type of plastic waste used in pyrolysis, making process optimisation challenging. Ultimately, while FCC is a highly efficient process for converting VGO into valuable products, adapting it for alternative feed- stocks like PPO requires overcoming tech- nical and operational challenges. Advances in catalyst technology, feedstock treat- ment, and process optimisation will play a crucial role in enabling the successful integration of plastic waste-derived feed- stocks into existing refining infrastructure. Co-processing of PPO in the FCC unit Co-processing of PPO included selecting oil suitable for HPCL FCC units, studying the impact of PPO on FCC product yields, tuning FCC process parameters to miti-