NOVELTY - An acoustic agglomerator for removing constituent from a fluid stream comprises an acoustic generator to generate an acoustic field in the fluid passageway of the duct to promote sorption of at least some of the constituent for collection by the collection device.    USE - Removing a constituent from a fluid stream, preferably for enhancing mass transfer from a dilute vapor towards the surface of a sorbent, wherein the constituent is vapor, oxidized mercury, elemental mercury, oxide of sulfur, oxide of nitrogen or fly ash and the fluid stream is a gas exhaust stream from a coal-fired power plant, lignite-fired power plant, natural gas-fired power plant, municipal waste-fired power plant, diesel power generator or agricultural-fired power plant (claimed).    ADVANTAGE - Application of the acoustic field provides for movement and/or mixing of the constituents, including mercury, relative to the activated carbon sorbent to expose the sorbent to portions of the fluid stream having the highest concentrations of mercury, not merely the surrounding or immediately adjacent constituents. The process does not contaminate the removed fly ash constituent with hazardous or undesirable constituents, e.g. mercury. It also provides for increased sorption by the limestone slurry, allowing for less slurry to be required or improved removal of the constituents to be achieved.    DETAILED DESCRIPTION - An acoustic agglomerator for removing constituent from a fluid stream comprises:    (a) a duct (12) having a fluid passageway (14) to receive a fluid stream (16) having constituent (18);    (b) a collection device coupled to the duct and in communication with the fluid passageway to filter the fluid stream;    (c) a sorbent injector to inject a sorbent in the fluid passageway of the duct, wherein the injection of the sorbent into the fluid passageway is upstream of the collection device; and    (d) an acoustic generator (20) to generate an acoustic field (22) in the fluid passageway of the duct to promote sorption of at least some of the constituent for collection by the collection device.    INDEPENDENT CLAIMS are also included for:    (1) a method of determining a frequency of sound to increase the acoustical stimulation of vapor diffusion by:    (i) selecting a sound pressure level of an acoustic field;    (ii) calculating a time harmonic acoustic displacement of a fluid stream;    (iii) calculating a time harmonic displacement of an agent particle in response to the acoustic field and an associated viscous drag effect;    (iv) calculating a relative displacement amplitude of the agent particle by subtracting the displacement of the agent particle from the displacement of the fluid stream; and    (v) calculating the relative displacement over several frequencies to produce a curve such that the curve includes a global maximum, wherein the global maximum is the frequency to increase the acoustical stimulation of vapor diffusion; and    (2) a method for extending the useful life of a filtration device by:    (i) providing a duct defining a fluid passageway;    (ii) providing a filtration device operable to filter a fluid stream;    (iii) injecting a sorbent in the fluid stream;    (iv) applying an acoustic field in the fluid stream to promote sorption of at least some of the constituent;    (v) collecting the constituent and at least some of the sorbent with the filtration device; and    (vi) removing the constituent and sorbent from the filtration device to clean the filtration device.    DESCRIPTION OF DRAWING(S) - The figure shows an acoustic agglomerator.    Duct (12)    Fluid passageway (14)    Fluid stream (16)    Constituent (18)    Acoustic generator (20)    Acoustic field (22)