Numerous systems and methods are known in the art where fluid is injected into a gas phase using one or more spray nozzles to ensure relatively fine distribution of the fluid in the gas stream (see e.g., U.S. Pat. No. 4,568,022 or U.S. Pat. No. 6,141,986). While most of these systems will operate satisfactorily for their intended purpose, problems are often encountered where the gas phase includes components that can deposit on, corrode, or plug the downstream flow path.
For example, most currently known hydrotreating and hydrocracking units produce an effluent gas or gas/liquid mixture having a temperature of above 250° F. at pressures ranging from 400 to 2800 psig. The effluent typically contains varying concentrations of hydrogen sulfide, hydrogen chloride, and ammonia. To help prevent these compounds from forming corrosive solid deposits in downstream conduits and/or devices, wash water is often injected upstream of the reactor effluent air cooler (REAC) or water cooler. The wash water injection rate is typically adjusted such that a predetermined fraction of the injected water remains unvaporized (assuming the effluent and water will mix sufficiently to reach equilibrium) or such that a predetermined ammonium bisulfide concentration is achieved in a downstream positioned high-pressure separator. In many instances, it is very important that the unvaporized liquid be well distributed in the downstream flow path. In most known configurations, wash water injection is typically performed using spray nozzles or injection quills that produce about millimeter-sized droplets. Unfortunately, such relatively large droplet size is typically associated with reduced heat and mass transfer and a high rate of gravity settling, leading to droplet coalescence and maldistribution of the injected water. Such problems are often associated with plugging of some exchanger tubes and concurrent under-deposit corrosion while the remaining operating tubes will be subjected to high effluent flow and erosion-corrosion.
To circumvent at least some of the problems associated with low heat and/or mass transfer and with ammonium salt deposits, the wash water injection point can be located at a maximal distance upstream of the REAC. However, such a configuration does not necessarily improve the downstream distribution of the unvaporized water. In an attempt to mitigate maldistribution, specific criteria can be used in the design of the piping manifold upstream of the REAC. While such design features tend to improve heat and mass transfer and distribution to at least some degree, achieving these objectives is still hampered by the undesirably large water droplets which tend to coalesce and form a stratified-wavy or semi-annular free water phase downstream of the injection point.
It is well known that droplet size can be reduced using non-assisted pressure jet or pressure-swirl type atomization nozzles (e.g., U.S. Pat. No. 5,644,608). However, it should be noted that such nozzles at the required water flow rates require in most cases prohibitively high differential pressure (e.g., 100 to 700 psi) to produce sufficiently small droplets (e.g., micron-sized droplets). Moreover, even if one would use such nozzles, the very small orifices of such nozzles are often easily plugged in an industrial setting, with the potential for high fluid velocity-induced erosion. Still further, steam pressure levels in refineries do not typically exceed 600 psig. Therefore, suitably high pressure steam is typically not available for use as an assist gas in the relatively high pressure environments that exist in many hydroprocessing units.
Therefore, it should be appreciated that currently known configurations and methods for water injection in the hydrotreater/hydrocracker effluent have several disadvantages that result in reduced heat and mass transfer, non-homogenous distribution of the water droplets, and/or disruption in operation. Thus, there is still a need for improved configurations and methods for injection of fluids into a gas phase, and especially injection of fluids into a gas phase or gas/liquid mixture upstream of a heat exchanger, to achieve high mass and heat transfer as well as more homogenous distribution of the injected fluid.
USPTO Backgrounds
USPTO Backgrounds