Laser Optics Improve Gasoline Yield

Laurel M. Sheppard

Fluid catalytic cracking of oil feedstocks produces a large portion of the US gasoline supply. This process relies on dispersion-steam-assisted nozzles to atomize the feedstocks. Thus, optimizing nozzle properties, including the degree of atomization and spray patterns, can improve gasoline yield by 1 to 5 percent.

Laser beams crisscross atomized oil feedstocks. Photonic analytical methods are helping researchers at Argonne National Laboratory optimize nozzles used to refine feedstocks and thereby increase gasoline yields by 1 to 5 percent.

Under a cooperative research and development agreement with several major petroleum companies, Argonne National Laboratory has established a unique facility that uses state-of-the-art computer-controlled laser optics instrumentation for characterizing such properties. Argonne initiated the project to test whether a method called phase Doppler particle analysis could help measure the spray distributions from commercial feed nozzles. The technique fires a split laser beam into the spray and measures the velocity and particle size of the droplets. The primary concern was the technique's ability to penetrate deeply into the sprays. The research proved that the analytical technique could be applied to commercial feed nozzles, which meant they can be used to assess a variety of fluid catalytic cracking nozzles, including hollow cone, solid cone, flat spray and multiorifice sprays. This method also characterizes the spray patterns more completely and accurately than in situ techniques.

However, because the optical technique could not accurately count in dense sprays, Argonne incorporated a mechanical system to obtain measurements of high-volume flux and particle-size distribution.

The facility's phase Doppler particle analysis system uses a three-component fiber optic instrument and a computer-controlled, three-dimensional traverse system to measure not only the size and speed of the atomized droplets, but also their distribution in air. It consists of a 5-W argon-ion laser, fiber optics, a transceiver and two transmitters. The laser beam is split into three wavelengths. Shifts in the beam's optical frequency indicate velocity of droplets, while optical scattering -- in combination with interferometry -- provides their size.

Argonne also makes its facility available to outside organizations through research agreements. Researchers can test nozzles with capacities of up to 300 gallons per minute, obtaining data such as local droplet size distribution, axial and radial components of droplet velocities, turbulent fluctuations, joint size and velocity distributions, and axial and radial profiles. Atomization parameters -- such as spray jet penetration, uniformity of oil droplets contacting catalyst particles and oil vaporization, and gas/catalyst temperature fields -- can also be analyzed for their effects on yield.