Mixed Flow Reactor Experiments and Modeling of Sulfuric Acid Neutralization in Lube Oil for Large Two-Stroke Diesel Engines

Abstract

Lubrication oil for marine diesel engines contains additives in the form of CaCO 3 -based reverse micelles, which can neutralize condensing H 2 SO 4 , and thereby limit uncontrolled corrosive wear of the piston rings and cylinder liner. In the present work, the neutralization mechanism was studied experimentally and through modeling.Using a mixed flow reactor (MFR), the rate of the acid-base reaction was measured as a function of relevant process parameters. In addition, the competition between CaCO 3 reverse micelles and NaOH droplets for a reaction with H 2 SO 4 droplets in a lube oil emulsion was explored in a batch reactor. For the residence times investigated, the results show that CaCO 3 conversion is significantly reduced when reaching a critically low Ca/S ratio. Furthermore, a mathematical model for the neutralization of H 2 SO 4 droplets by CaCO 3 reverse micelles in lube oil under well-mixed conditions was developed. Both the experimental data and simulations support previous results suggesting that the limiting step in the neutralization mechanism is adsorption of reverse micelles onto the much larger H 2 SO 4 droplets. Using the video-microscopy experiments of Fu et al.1 ), 221-225], it was possible to estimate kinetic parameters for the adsorption-controlled reaction. The model was used to predict conversion of H 2 SO 4 in a lube oil film at the cylinder liner surface for conditions relevant for a full-scale application. Calculations indicated that H 2 SO 4 may reach the liner surface regardless of how well-wetted the surface is.

An experimental investigation of the corrosive influence of SO2 relative to H2SO4 of marine engine cylinder liners

“…Cylinder lubrication oils used in large two‐stroke marine engines contain alkaline additives (primarily CaCO 3 ) that neutralise acids . The content of alkaline constituents is defined by the base number (BN).…”

“…19,20 Cylinder lubrication oils used in large two-stroke marine engines contain alkaline additives (primarily CaCO 3 ) that neutralise acids. [21][22][23][24] The content of alkaline constituents is defined by the base number (BN). A 10-20 BN oil is normally used for fuels with a low sulphur content, whereas 70-100 BN oils are used for high sulphur contents.…”

An experimental study of the effect of condensing water vapour on the cold corrosion wear of marine engine cylinder liners

“…Formulated oils contain alkaline additives (mostly metal salts, e.g., CaCO 3 ) that neutralise acidic compounds. 26,27 The content of alkaline constituents is quantified by the Base Number (BN). The 15-40 BN oils are typically used when a ship operates on ultra-to low sulfur fuels, and 70-140 BN is used for high sulfur fuels, such as HFO.…”

Experimental investigation and mathematical modeling of the reaction between SO2(g) and CaCO3(s)-containing micelles in lube oil for large two-stroke marine diesel engines

“…It is therefore important to have general guidelines on how lube oil should be dosed onto the cylinder liners to limit corrosion at a minimal cost. To achieve this, an understanding of the formation of the relevant acids in the gas phase [10,[12][13][14], the transport to the lube oil film [15][16][17], the neutralization mechanism by the base additives [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], and the corrosion of the liner material [1,4,[36][37][38][39][40][41][42][43][44] is pivotal. Information about how base additives (CaCO3 micelles) are consumed is important because this facilitates determination of the lube oil flow rate to the cylinder liners and choice of base additive concentration.…”

“…The reaction conditions of the wet and dry desulfurization processes are different to those prevailing in a lube oil film, primarily due to the presence of the lube oil phase itself. However, the conditions in an engine, with SO2 and O2 in the combustion chamber, water condensing on the liner, absorption of SO2 in the oil, and presence of reactive CaCO3 reverse micelles [12,15,16,19,56], appear favorable for reaction in the lube oil film.…”