PTQ Q2 2023 Issue

Anti-fouling additives to improve heavy oil processing A continuous pilot testing evaluation shows how magnesium sulphonated-based nano-additive is highly effective in mitigating and reducing upgrader/refinery fouling

Darius Remesat University of Calgary Youssef Elgahawy Suncor Energy

Edward Maharajh Energy Technical Resources Justin Martin Western Research Institute

A dditives have been developed to disperse fouling- generating molecules, such as asphaltenes and inorganics, and mitigate fouling that poses opera- tional concerns and production upsets to upgraders and refineries across the world. A comparative analysis of different dispersive additives in a continuous pilot testing environment is provided to determine the effectiveness of these additives in mitigating or reducing the fouling in two specific areas of concern: intermediate piping, vessels, and exchangers in bitumen upgraders; and the kerosene pumparound zone. Results from larger-scale continuous pilot testing vs limited batch lab testing give operators con- fidence when deciding if or how to incorporate an additive programme into their facility to improve reliability and/or debottleneck operations. Notably, a nano-additive magne - sium sulphonate base appears to be effective on numer- ous types of fouling mechanisms experienced at heavy oil upgraders/refiners. Fouling in upgraders and refineries challenges operability and profitability through long-term accumulation that can reduce throughput or, in severe cases, lead to operational upsets that trigger unplanned outages. Chemistry has been developed that can play a role in improving and/or main - taining performance, with the inclusion of nanoparticles in formulations stretching the applicability of additives. However, offerings from additive suppliers are based on proprietary experiential data supported by lab-scale

testing of the problematic fluid and/or foulant, which does not address the specific operating scenario of concern to the operator. To improve confidence in the claimed benefits of the additive, continuous flow testing at operating con - ditions was carried out at the Western Research Institute (WRI) in Laramie, Wyoming. Though not at a commercial scale, the test facility oper - ates at elevated temperatures and pressures, with flow capabilities in both the laminar and turbulent regimes for extended periods to provide insight into additive perfor- mance closer to actual operations. Various additives were tested in different environments to inform both additive vendors and operators and support decision-making when choosing fouling mitigation strategies for towers, heat exchangers, reactors, and piping in upgraders/refineries. Coke/foulant formation Foulants can be generated from various mechanisms, and combinations of accumulated foulant can be found in many locations within an upgrader/refinery. Some typical fouling mechanisms and locations are shown in Table 1 . Additives are formulated to address a specific foul - ing mechanism and thus different foulants typically require different formulations (concentration and type of addi - tive). The challenge is identifying the appropriate fouling mechanism and creating an additive that addresses the foulant.

Fouling mechanisms and typical locations for foulant accumulation

Fouling mechanism

Location examples

Hydrocarbon physical – asphaltenes separated, precipitated as a solid out of solution and agglomerate onto surfaces

Lines between vacuum and coking units

Feed to ebullated bed reactors

(ex. Intimate diluent contact)

Atmospheric, vacuum and coker preheater circuits

Heavier hydrocarbon thermal – asphaltenes cracked to coke and precipitate as solid adhered to metal surfaces

Coker unit exchangers

Bottom of coker fractionators Ebullated bed reactors

Lighter hydrocarbon thermal – distillate range polymeric coke formation

Coker fractionator fractionation zones

Inorganic physical – concentration, accumulation of minerals, rust, scale

Low points in lines, vessels with low velocities

Combination of above - typically, operations will have two or three types of foulant material mixed together (ex. hydrocarbon and inorganic physical)

All of the above

Table 1

PTQ Q2 2023