Three-phase separator for separating gas and solids from a three-phase mixture containing liquid, gas and solids, comprising: - an inlet region for the three-phase mixture, - an outlet for a fraction rich in solids, - an outlet for liquid, - a first separator for separating gas from the three-phase mixture, forming a two-phase mixture which contains liquid and solids, the first separator forming the inlet region for the three-phase mixture or being connected to the inlet region for the three-phase mixture, the first separator having four plate blocks (22, 22', 22'', 22"') each having at least three mutually parallel plates, between which a flow channel is formed in each case, and the first separator being configured such that the mixture entering through the inlet region is led from top to bottom in the flow channels, relative to the vertical, and - a second separator for separating solids from the two-phase mixture formed in the first separator, the second separator having a plate block having at least three mutually parallel plates, between which a flow channel is formed in each case, and the second separator being configured and arranged in relation to the first separator such that the two-phase mixture emerging from the first separator enters the flow channels of the second separator from below, relative to the vertical, and is led upward in said channels, wherein the three-phase separator is configured in such a way that the three-phase mixture can enter the first separator of the three-phase separator only via the inlet region, and, wherein each of the two side surfaces of each plate block (22, 22', 22'', 22''') of the first separator adjoins a side surface of another plate block (22, 22', 22 ", 22"'), so that the individual plate blocks (22, 22', 22'', 22"'), as seen from the cross section of the three-phase separator, are arranged in the form of a lozenge, and the second separator has one plate block which, as seen from the cross section of the three-phase separator, is arranged in the middle of the lozenge formed by the four plate blocks (22, 22', 22'', 22"') of the first separator or in each case one of the two side surfaces of two plate blocks (22, 22', 22'', 22"') of the first separator adjoins each other at an angle of inclination of 10° to 80° relative to the longitudinal direction of the plate block (22, 22', 22'', 22"'), and the two plate block packs formed from the two plate blocks (22, 22', 22'', 22"') that adjoin each other in this way are connected to each other via a wall connecting the side surfaces of the plate block packs in each case, so that the four plate blocks (22, 22', 22'', 22"') and the two walls, as seen from the cross section of the three-phase separator, are arranged in the form of a hexagon, and the second separator has one plate block which, as seen from the cross section of the three-phase separator, is arranged in the middle of the hexagon formed by the four plate blocks (22, 22', 22'', 22"') and the two walls of the first separator. - an inlet region for the three-phase mixture, - an outlet for a fraction rich in solids, - an outlet for liquid, - a first separator for separating gas from the three-phase mixture, forming a two-phase mixture which contains liquid and solids, the first separator forming the inlet region for the three-phase mixture or being connected to the inlet region for the three-phase mixture, the first separator having four plate blocks (22, 22', 22'', 22"') each having at least three mutually parallel plates, between which a flow channel is formed in each case, and the first separator being configured such that the mixture entering through the inlet region is led from top to bottom in the flow channels, relative to the vertical, and - a second separator for separating solids from the two-phase mixture formed in the first separator, the second separator having a plate block having at least three mutually parallel plates, between which a flow channel is formed in each case, and the second separator being configured and arranged in relation to the first separator such that the two-phase mixture emerging from the first separator enters the flow channels of the second separator from below, relative to the vertical, and is led upward in said channels,