A chemical plant for performing a chemical reaction between particles of a material such as lithium metal, and a reagent such as butyl chloride in solution in hexane, in which one reaction product is a solid material, includes a reaction vessel (12). Several ultrasonic transducers (16) are attached to a wall of the vessel (12) so as to irradiate ultrasonic waves into the vessel, the vessel being large enough that each transducer irradiates into fluid at least 0.1 m thick, each transducer irradiating no more than 3 W/cm2, and the transducers being sufficiently close to each other and the number of transducers being sufficiently high that the power dissipation within the vessel is at least 10 W/liter but no more than 200 W/liter. The high intensity of ultrasound ensures that lithium chloride is cleaned off the surface of lithium metal particles throughout the vessel (12).