Abstract: Disclosed herein are methods for removing and recovering metalloids from gasification systems. Also disclosed are methods for on-line removal of deposited entrained materials from a heat exchanger unit. A method is provided for on-line removal and recovery of deposits from fossil fuel gasification systems to improve plant performance and recover a valuable metalloid. Plant performance will be improved by decreasing impedance to gas flow and decreasing downtime required to clean the gas cooling system by providing an effective method to remove deposits while the gasification system is operating. In the preferred embodiment of the method, the deposits rich in condensed metals and metalloids are captured on heat transfer surfaces within the range of temperatures of about 400° C. to about 600° C., the temperature of the heat transfer surface is cycled causing the deposit to spall from the steel surface, and the deposits are removed from the gasifier without impacting gasifier operation.