In a steam assist fuel oil atomizer, the steam pressure is higher than the oil pressure at __________.

Correct Answer: Option D — minimum boiler load

At minimum boiler load, low fuel oil pressure and flow rate provide insufficient natural atomization energy, requiring higher atomizing steam pressure to maintain proper droplet dispersion. Conversely, at high loads, increased oil pressure supplies the primary kinetic energy, necessitating lower relative steam pressures to prevent over-atomization.