Because many industrial processes already employ steam, there is a wide-spread preference to use steam in place of compressed air as the atomizing fluid in two-fluid atomizers [i.e.- air blast nozzle, air atomizer]. Also, some processes, for safety and product quality reasons, cannot accommodate the introduction of large quantities of air.

spray research, inc. has the-house capability to evaluate dual-fluid atomizer performance using steam as the atomizing fluid. This testing is absolutely necessary in order to define the operational envelope of the particular atomizer under consideration and to identify the most cost-effective operating parameters. The steam testing can also provide the data from which a cold flow model can be developed to more accurately predict steam performance from compressed air tests.

We have performed extensive steam|water studies of FCCU feed injectors and flue gas quench atomizers.

Unfortunately, most of the performance data available for two-fluid atomizers is based on tests using compressed-air as the atomizing fluid. A common mistake is to assume that providing a similar mass flow ratio of steam|water as that used in the air|water tests will result in similar spray performance.

Air-atomizers intimately mix the two fluids. When used with steam and cool water, air-atomizers function as very efficient steam condensers, resulting in a much-reduced liquid flow capacity. Reductions in flow capacity to 5% or 10% of the air|water values are typical. Although the flow capacity can be increased by pre-heating the liquid stream, significant improvements are not achieved until the pre-heat approaches the saturated steam temperature.

Other spray performance differences encountered when steam is used in place of compressed air include a modest degradation in dropsize performance, reduced mean droplet velocities and  narrower effective spray angle and coverage.