The invention provides a process for minimizing the emission of particulate matter and precursors thereof from a flue gas stream of an engine comprising particulate matter and precursors thereof and at least one gaseous component. The process includes the steps of obtaining a flue gas stream of an engine comprising particulate matter and precursors thereof; increasing the moisture content of the stream by contacting it with a first aqueous medium in an amount and at a temperature at which at least 50% of the water content of the first aqueous medium is evaporated; whereby a moisture laden gas stream, optionally containing suspension droplets, is formed; cooling the moisture laden gas stream whereby suspension droplets are formed; and applying a centrifugal force to the moisture laden gas stream and to the suspension droplets to effect the swirling thereof, whereby a treated gaseous stream and an aqueous stream are formed.