A process for causing gaseous trace element particles to pass from a flowing hot gas into a fine particulate material by means of water. A mixture of the hot gas and water drops is caused to flow substantially upwards at such a velocity that the water drops remain in the gas flow and for a period long enough for most of the mass of the water drops to evaporate in order to cool the gas and to increase its relative humidity. After the gases have reached their wet temperature, they are brought into a turbulent state in order to cause the dust particles and the water drops which have decreased through evaporation to impinge against each other in order to produce in the aqueous film which covers the dust particles an exothermal ion reaction between the gaseous water-soluble trace element particles and the fine particles. Thereafter, the mixture is caused to flow further in order to evaporate the remaining water by means of the heat of reaction so that a dry end product is obtained.