Silicon carbide heat exchangers and graphite heat exchangers are both chosen for corrosive services that rule out metal, but they are not interchangeable. Graphite offers excellent thermal conductivity and lower cost for most acids and solvents, while silicon carbide handles a wider range of aggressive chemicals, including hydrofluoric acid, and tolerates higher pressure and thermal shock.
Chemical Resistance Range
Impervious graphite resists most mineral acids, organic acids, and solvents, but it is attacked or permeated by strong oxidizers and some fluoride compounds over extended exposure. Silicon carbide is essentially inert across this same range and additionally holds up in hydrofluoric acid and highly oxidizing mixed-acid duties where graphite is not recommended.
Mechanical and Thermal Differences
Graphite blocks are more tolerant of thermal cycling and mechanical shock than silicon carbide, which is harder but more brittle. Silicon carbide, however, supports higher operating pressures and generally has a longer service life in continuous, high-severity duty because it does not permeate or swell.
Cost and Availability
Graphite heat exchangers are typically less expensive to fabricate and are readily available in standard block and shell-and-tube configurations. Silicon carbide equipment costs more upfront but often has a lower total cost of ownership in HF or oxidizer service, where a graphite unit would need premature replacement.
Making the Right Choice
The deciding factor is usually the specific chemistry and pressure rating of the duty, not price alone. GreyTec supplies both graphite heat exchangers and Silicon Carbide Super-SiC heat exchangers, and our engineering and consultancy team can help match the material to your process conditions rather than defaulting to the more familiar option.