Abstract: A method for finely feeding granular solids into a liquid, in which method granular solids and a liquid are fed into a mixing space and mixed together, and a mixture of small solid particles and liquid is discharged from the mixing space. The granular solid matter in the mixing space is subjected to a liquid flow in such a manner the granular solids are brought to roll controllably in a controlled rolling space locating in the mixing space, whereby the grains of the granular solids abrase one another while rolling and tiny particles detaching in abrasion are carried away from the mixing space along with the liquid and large grain particles continue rolling in the controlled rolling space.

Abstract: A method for collecting a surface layer of a liquid into confined area, method including forming confined area by means of wall structure and moving some of surface layer of liquid into confined area by means of a flow of air directed into confined area through an opening made into wall structure of confined area so that amount of substance in surface layer of the liquid increases in confined area in comparison with surroundings. The bottom edge of opening made into wall structure of confined area is arranged to be below surface level of liquid outside confined area whereas its top edge is substantially above surface level of liquid outside confined area. The surface level of liquid inside confined area is arranged to be kept substantially on same level with surface level of liquid outside by providing a continuous liquid flow connection through lower portion of confined area into surroundings.

Abstract: A method for collecting a surface layer of a liquid into confined area, method including forming confined area by means of wall structure and moving some of surface layer of liquid into confined area by means of a flow of air directed into confined area through an opening made into wall structure of confined area so that amount of substance in surface layer of the liquid increases in confined area in comparison with surroundings. The bottom edge of opening made into wall structure of confined area is arranged to be below surface level of liquid outside confined area whereas its top edge is substantially above surface level of liquid outside confined area. The surface level of liquid inside confined area is arranged to be kept substantially on same level with surface level of liquid outside by providing a continuous liquid flow connection through lower portion of confined area into surroundings.