The invention relates to a system for crystallizing a material that is dissolved in a solvent and that is to be crystallized, comprising a crystallization device through which a solution that is to be concentrated and that comprises the solvent containing the material to be crystallized and dissolved in said solvent, and a liquid, comprising a lower temperature than the solution to be concentrated, flows, wherein the crystallization device comprises at least one flow channel guiding the solution to be concentrated and at least one flow channel guiding the liquid, wherein the inner space of each respective flow channel guiding the liquid is delimited at least in part by a membrane wall that is permeable for the vaporous solvent, however not for the liquid solvent and a respective flow channel guiding the liquid is adjacent to at least one respective flow channel guiding the solution to be concentrated, whereby a vapor pressure difference sets in via the membrane wall, such that the solvent passes from the solution to be concentrated across the membrane wall.