Fuel treatment solutions for power plants are additive formulations dosed into heavy fuel oil (HFO) and other residual fuels at low treatment ratios to improve combustion completeness, modify troublesome ash, and protect boilers, burners, and fuel systems. In HFO-fired stations the most important class is the magnesium-based combustion improver: an oil-soluble organo-magnesium compound that promotes carbon burnout in the flame and converts corrosive vanadium ash into a dry, friable deposit that sootblowers can remove. The result the operator sees is cleaner heat-transfer surfaces, less unburned carbon in the ash, and fewer fouling-driven outages — benefits that should always be confirmed on your own unit through a structured trial.
Why heavy fuel oil needs chemical treatment
Heavy fuel oil is the residue left after refineries extract the lighter, cleaner fractions from crude. What remains is dense, viscous, and concentrated in exactly the elements a boiler operator would rather avoid: vanadium, sodium, sulfur, and asphaltenes. When HFO burns, these constituents follow predictable and expensive paths. Vanadium oxidizes to vanadium pentoxide (V₂O₅), which melts at about 690 °C — below the surface temperature of superheater tubes in most utility boilers — so it arrives as a sticky, molten ash that bonds to the hottest surfaces. Sodium compounds lower the melting point of the ash mixture further and accelerate the attack. Sulfur burns to SO₂, and a small fraction oxidizes on to SO₃, which condenses as sulfuric acid on cold-end surfaces such as air heaters and economizers.
- Slagging: molten vanadium-sodium ash bonds to superheater and reheater tubes, insulating them and forcing higher firing rates for the same steam output
- High-temperature corrosion: molten vanadate slag dissolves the protective oxide layer on tube steel, thinning tubes and shortening their service life
- Cold-end acid corrosion: condensed sulfuric acid attacks air heaters, economizers, ductwork, and stacks
- Unburned carbon: incomplete combustion of heavy asphaltenic fractions wastes fuel and can turn flyash into a disposal problem
How magnesium-based combustion improvers work
Organo-magnesium fuel additives are oil-soluble magnesium compounds — typically magnesium carboxylates carried in a high flash point hydrocarbon solvent — that disperse uniformly through the fuel before it reaches the burners. Because the magnesium is fuel-soluble rather than a slurry, every droplet of atomized fuel carries its own share of the metal into the flame, where it converts to finely divided magnesium oxide (MgO). This fine MgO does two jobs. First, it provides a catalytic surface that promotes the oxidation of carbon particles in the flame zone, encouraging more complete burnout of the heavy fractions and reducing unburned carbon in the ash — an effect operators typically observe as a visible change in flyash character and improved combustion efficiency, with the magnitude depending on the unit, the fuel, and the baseline excess air.
The second job is ash modification. Magnesium oxide reacts preferentially with vanadium compounds to form magnesium vanadates such as Mg₃V₂O₈, whose melting point lies above 1,100 °C — comfortably higher than superheater metal temperatures. Instead of arriving molten and sticky, the vanadium now arrives as a dry, powdery ash that does not bond to tube surfaces and is removed by normal sootblowing. This is the mechanism that interrupts vanadium-induced hot corrosion and keeps heat-transfer surfaces clean between outages.
Cold-end and sulfur-related protection
Excess MgO remaining after the vanadium reaction is not wasted: it is alkaline, and it neutralizes a portion of the SO₃ formed during combustion before that SO₃ can condense as sulfuric acid on cold-end surfaces. Plants firing high-sulfur fuel typically see this as reduced acid smut, less aggressive corrosion at air heaters, and room to operate at somewhat lower exhaust temperatures without dewpoint attack. The effect is real but site-specific — flue gas acid dewpoint should be measured before and after treatment rather than assumed.
Choosing an additive grade
Organo-magnesium additives are supplied at different active-metal concentrations, and the right grade is mostly a question of logistics and dosing precision rather than chemistry. CHIMI MAG 30 carries 30% active organo-magnesium, which minimizes the volume that must be stored and pumped for a given magnesium demand — usually the right choice for large units burning fuel with significant vanadium content. CHIMI MAG 20, at 20% active organo-magnesium, delivers the same chemistry at a lower concentration, which suits smaller dosing systems that need a higher, more controllable volumetric feed rate. Both are liquid products handled with standard chemical dosing pumps.
- Fuel analysis first: the vanadium, sodium, and sulfur content of actual fuel deliveries sets the magnesium demand
- Target Mg:V ratio: the dose is set as a ratio of magnesium to vanadium, then confirmed by inspecting deposits and ash
- Dosing equipment: match additive concentration to your pump turndown so the feed rate stays in the pump's accurate range
- Injection point: dose where turbulence guarantees mixing — upstream of transfer pumps or into the suction line, not into a quiescent tank
- Storage and handling: review the technical and safety data sheets for tank materials, flash point, and safe-handling requirements
Dosing and monitoring in practice
A treatment program starts from the fuel analysis: the vanadium and sodium content of each fuel batch sets the magnesium demand, and the dose is adjusted when the fuel changes — a fixed dose against a variable fuel is the most common cause of disappointing results. Once dosing begins, track a short list of indicators over weeks, not days: unburned carbon in flyash, stack appearance, flue gas exit temperature (a rising trend signals fouling), sootblowing frequency, and — at the next opportunity — a visual inspection of superheater deposits, which should trend from glassy slag toward dry powder. Keep the baseline data from before treatment; without it, no one can say what the additive achieved.
Common mistakes
- Dosing at a fixed rate while fuel vanadium varies from batch to batch — the ratio, not the rate, is what matters
- Injecting additive without enough turbulence to mix it, so part of the fuel is overtreated and part untreated
- Judging results after days instead of weeks — existing deposits take time to shed and ash trends take time to stabilize
- Stopping treatment between fuel deliveries and losing the protective ash conditioning already established
- Skipping the pre-treatment baseline, which turns any later cost-benefit review into guesswork
Getting started
The practical first step is a recent fuel analysis. Send your fuel specification and vanadium, sodium, and sulfur figures to the CHIMI ART technical team, and they will recommend a grade, an initial treatment ratio, and a trial protocol with the baseline measurements worth capturing before the first drum is dosed. Technical data sheets and safety data sheets for CHIMI MAG 30 and CHIMI MAG 20 are available on request, and a companion article on this site sets out how to build the return-on-investment case for a fuel additive program.