PTQ Q2 2023 Issue

Unrevealed additional WASA additive performance at European refinery Study of the response of winter and summer grade diesel fuels to static dissipator additive and the effect of other additives on the electrical conductivity of the fuel Rosen Dinkov, Ivo Andreev, Dicho Stratiev, Ilian Kolev and Miroslav Atanasov LUKOIL Neftohim Burgas AD Katarzyna Grabowska Brenntag Oil & Gas Research and Application Center Cobbin Mackenzie Infineum Business and Technology Centre

S evere hydrotreating has not only a positive ecological effect on emissions from burning engine fuels; it also decreases the ability of diesel boiling range hydro- carbons to dissipate static charge. Therefore, to turn the electrical conductivity of hydrotreated gasoils back to safe limits (150 pS/m), LUKOIL Neftohim Burgas AD (LNB) uses the most effective way – adding conductivity-improving additives or so-called static dissipator additive (SDA). The response of summer and winter grade diesel fuels to SDA is different from the antagonistic effect of middle distil- late flow improver (MDFI) and wax anti-settling additives (WASA). WASA is proven to dissipate static charge in a concentration above 100 ppm. Winter grade low-sulphur diesel fuels with 125 ppm WASA and without dosing SDA are safe (at electrical conductivity above 150 pS/m) to be stored and transported. Severe hydrotreating Since the introduction of a 10 mg/kg sulphur cap on 1 January 2009 for diesel fuels by Directive 2003/17/EC, 1 European refineries have begun to severely hydrotreat their gasoil fractions into lower sulphur content. These severe conditions lead to the deterioration of some other prop- erties 2 of diesel fuel, including lubricity, 3 cetane number, and electrical conductivity. 4 Together with sulphur, many organic compounds containing nitrogen and oxygen atoms and poly-aromatic compounds are also removed. During hydrotreating, cyclic organic compounds respon- sible for the electrical conductivity of diesel fuel are removed. Thus, electrical conductivity drastically dimin- ishes and can cause the generation and accumulation of electrostatic charges (static electricity), which can result in static discharges. 4 Static discharge poses a serious threat when moving petroleum products through the distribution system. Hydrocarbons are poor conductors of electricity, and static electricity may accumulate and take significant time to leak off to the ground. There have been cases where such accumulations dis- charged as high energy sparks have caused fires or explo - sions under certain air/fuel vapour conditions. This is particularly true for modern ULSD because of their high purity, high pumping rates, and the use of filtration capable of producing a high rate of charge separation and static

build-up in the fuel. 5 Conductivity of ULSD is very low at 0-2 pS/m against higher sulphur diesel fuels, which exhibits electrical conductivity between 150 to 250 pS/m (depend- ing on the sulphur content) 6 and thus static charge at ULSD cannot dissipate quickly. Ways to cope with a lower rate of static charge dissipa- tion are described in Guide for Generation and Dissipation of Static Electricity in Petroleum Fuel Systems (ASTM D4865). 4 It recommends measures to prevent explosions, such as earthing (bonding and grounding), pumping rate limits, and ‘time for charge dissipation’ (relaxation time), before the fuel is exposed to air. Another way to improve the electrical conductivity of fuel is via the implementation of additives. 4,7 Static discharge poses a serious threat when moving petroleum products through the distribution system SDAs (also known as conductivity-improving additives, antistatic additives, or electrical-conductivity additives) are needed to replace lost natural polar components. Besides relaxation time, SDA is the only way to increase conduc - tivity effectively. 5 These additives do not hinder electrical charge generation but increase only the rate of charge dis- sipation by increasing the conductivity of the fuel and thus relaxing static charges. 4 Materials and methods In this project, several gasoils originated from an LNB commercial unit – straight-run (straight-run light gasoil [SRLGO] 180-240°C; straight-run middle gasoil [SRMGO] 200-300°C; straight-run heavy gasoil [SRHGO] 240- 360°C; light vacuum gasoil [LVGO]) – and from a secondary origin (FCCPT diesel; FCC light cycle oil [LCO] and H-Oil diesel) are analysed and their properties are summarised in Table 1 . These gasoils are hydrotreated in LNB commer- cial hydrodesulphurisation (HDS) units, and two types of hydrotreated gasoils are produced: light and heavy.

PTQ Q2 2023