A liquid ejection apparatus for cleaning of a tank, the liquid ejection apparatus being configured to be attached to a liquid line that extends into the tank, and to receive a liquid from the liquid line, the liquid ejection apparatus comprising: a base member having a first end for receiving the liquid from the liquid line, and a second end, wherein an outer circumference (Cbm) of a section of the base member increases in a direction towards the second end, a rotary head that is rotatably connected to the second end of the base member, a rotary nozzle hub that is rotatably connected to the rotary head and comprises a primary liquid ejection nozzle for ejecting the liquid, the rotary head being rotatable about a first geometrical axis and the rotary nozzle hub being rotatable about a second geometrical axis that is arranged at an angle (β) relative to the first geometrical axis, such that the liquid ejected by the primary liquid ejection nozzle is ejected in a pattern towards an interior surface of the tank, wherein the primary liquid ejection nozzle has an outer, concave surface that faces the rotary head, characterised in that the liquid ejection apparatus comprises a gap located between the base member and the rotary head, for allowing an amount of the liquid to flow out from the gap, wherein the outer, concave surface of the primary liquid ejection nozzle is positioned such that a flow of the liquid from the gap impinges on the outer, concave surface of the primary liquid ejection nozzle during at least a part of a revolution of the rotary nozzle hub, whereby the flow of the liquid on the outer concave surface of the primary liquid ejection nozzle follows the outer concave surface thereby cleaning the primary liquid ejection nozzle. a base member having a first end for receiving the liquid from the liquid line, and a second end, wherein an outer circumference (Cbm) of a section of the base member increases in a direction towards the second end, a rotary head that is rotatably connected to the second end of the base member, a rotary nozzle hub that is rotatably connected to the rotary head and comprises a primary liquid ejection nozzle for ejecting the liquid, the rotary head being rotatable about a first geometrical axis and the rotary nozzle hub being rotatable about a second geometrical axis that is arranged at an angle (β) relative to the first geometrical axis, such that the liquid ejected by the primary liquid ejection nozzle is ejected in a pattern towards an interior surface of the tank, wherein the primary liquid ejection nozzle has an outer, concave surface that faces the rotary head, characterised in that the liquid ejection apparatus comprises a gap located between the base member and the rotary head, for allowing an amount of the liquid to flow out from the gap, wherein the outer, concave surface of the primary liquid ejection nozzle is positioned such that a flow of the liquid from the gap impinges on the outer, concave surface of the primary liquid ejection nozzle during at least a part of a revolution of the rotary nozzle hub, whereby the flow of the liquid on the outer concave surface of the primary liquid ejection nozzle follows the outer concave surface thereby cleaning the primary liquid ejection nozzle.