PTQ Q4 2023 Issue

Operating parameters of Unicracking unit at start-of-run and end-of-run

UOM kg/hr wt%

Start-of-run

End-of-run

Feed flow rate

297,210

Cracked feed ratio Make-up H₂ flow rate

Nm3/hr

73,449

75,499

Temperature at 1st reactor inlet Temperature at 2nd reactor outlet Average catalyst bed temperature High-pressure separator pressure H₂ partial pressure at reactor outlet

°C °C °C

378 410 398

422 449 438

Bar g Bar g

161.9

140

Recycle gas flow rate

Nm³/m³ of fresh feed

2,046

2,047

Recycle gas hydrogen purity

mol%

89.2

Recycle oil ratio

wt%

LHSV

hr-1

0.94

Table 1

allows them to find room for energy saving, productivity increase, and fuel consumption reduction. 4,5 Saeid Shokri et al. studied the application of particle swarm optimisation (PSO) algorithm using Visual Basic 6.0 in modelling an exist - ing industrial hydrocracking unit in 2017. The produced model gives good predictions regarding product yield distribution with an error of less than 1% for operating parameters within building model limits. In 2009, a fluid catalytic cracking (FCC) unit was modelled using the fourth-order Runge-Kutta algorithm (Visual Basic) to opti - mise the FCC naphtha yield of this industrial unit process - ing mainly VGO in a riser reactor by Kenneth Dagde. This study depends mainly on the five-lump kinetic scheme to describe the cracking reactions.6 An extensive literature review has been conducted to study the technologies and equipment used industrially in the hydroprocessing of WCO and WLO individually and the co-hydroprocessing mixture of them blended with petro - leum feedstock. Axens recently started marketing its new proprietary technology (Revivoil) developed jointly by Axens and Itelyum (formerly Viscolube Italiana SpA), which goes a long way to put WLO re-refining on the fast track to success. UOP also has its proprietary Ecofining technology developed by UOP and ENI for hydroprocessing plant-derived oil. Feedstocks include plant-derived oils such as soybean, rapeseed, and palm. Not only process technology develop - ers are interested in waste oils co-processing, but refiners as well. For example, Petrobras’ proprietary H-Bio hydro - genation technology processes a mixture of waste vege - table oil and mineral oil to produce renewable diesel using hydrotreating units in existing oil refineries. CEPSA refinery in Tenerife successfully co-processes waste frying oils in a gasoil hydrodesulphurisation unit (HDS-I). Research cen - tres also give great importance to this topic. The research centre of CanmetENERGY supports and funds these types of research activities. It was noticed that most refiners choose to inject WCO (on a large scale) or WLO (on a small scale) with VGO for co-hydroprocessing units rather than installing a separate unit to hydroprocess pure WCO or WLO, taking into consideration the high degree of similar - ity between technologies and catalysts used in these units. The novelty of this work is to study the co-hydroprocessing

of VGO, WCO, and WLO blend over commercial, industrial hydrocracking catalyst.7 Against this backdrop, this study simulates a conceptual design of an industrial hydrocracking unit utilising the same catalyst used in our previous experimental work.1 This con - ceptual design has been performed using HYSYS V.11 with its unique built-in hydrocracker model (HCR). The HCR model simulates light and heavy petroleum fractions hydro - processing based on the built-in reaction network and kinetic lumps. This simulation case can be used to evaluate – technically and economically – the co-hydroprocessing of the normal unit feedstock of VGO vs blends of unconven - tional feedstocks of WCO and WLO with VGO. Simulation case The industrial hydrocracking unit licensed by UOP, commer - cially referred to as Unicracking, is simulated using HYSYS V.11. The selection of this unit is based on its utilisation of the experimentally used catalyst (TK-711 and DHC-8) with a similar reactor bed configuration. The unit reaction section consists of two reactors. The first reactor contains three beds, one for hydrotreating and the others for hydro - cracking. The second reactor contains two beds for hydroc - racking. The five beds are roughly equal in weight. This unit was designed to process 33,500 barrels per stream day (BPSD) of combined feed consisting mainly of vacuum gasoil (VGO) from the vacuum distillation unit and heavy coker gasoil (HCGO) from the delayed coker unit. The target of this unit is to produce light fuel products from heavy petroleum distillates, in addition to removing the majority of impurities such as sulphur, nitrogen and oxygen. Process design Hydrocracking is carried out at elevated temperatures and pressures in a hydrogen atmosphere. Hydrogen partial pressure at the reaction section outlet is 140 bar g, and reactors working inlet temperatures range from 378°C to 422°C. Table 1 shows the recommended operating param - eters for the simulated unit. The process consists of two main sections: the reaction section and the fractionation section. Fresh feed is directed to the unit feed surge drum, then pumped by the feed

PTQ Q4 2023