A wall for a fluidized bed boiler, the wall comprising - a first heat exchanger pipe comprising a first primary portion and a first secondary portion, - a second heat exchanger pipe arranged in parallel with the first heat exchanger pipe, the second heat exchanger pipe comprising a second primary portion and a second secondary portion, - a first connector (211, 241) fixed to the first primary portion and to the second primary portion, and - a first gap between the first secondary portion and the second secondary portion, wherein - at least a part of the first secondary portion and at least a part of the second secondary portion extend straight, in parallel, and within an imaginable plane and - at least a part of the first gap penetrates through the plane such that particulate material is able to propagate through the first gap from a first side of the plane to the opposite second side of the plane, the wall comprising - a refractory arranged on at least one side of a part of the first secondary portion and a part of the second secondary portion such that - a part of the first secondary portion extends from the refractory to a first direction, - a part of the second secondary portion extends from the refractory to the first direction, and - the first gap extends from the refractory to the first direction; wherein - an outer diameter of the first secondary portion is less than or equal to an outer diameter of the first primary portion, - an outer diameter of the second secondary portion is less than or equal to an outer diameter of the secondary primary portion, and - the first direction forms an angle of at most 30 degrees with an upward vertical direction (Sz). - a first heat exchanger pipe comprising a first primary portion and a first secondary portion, - a second heat exchanger pipe arranged in parallel with the first heat exchanger pipe, the second heat exchanger pipe comprising a second primary portion and a second secondary portion, - a first connector (211, 241) fixed to the first primary portion and to the second primary portion, and - a first gap between the first secondary portion and the second secondary portion, wherein - at least a part of the first secondary portion and at least a part of the second secondary portion extend straight, in parallel, and within an imaginable plane and - at least a part of the first gap penetrates through the plane such that particulate material is able to propagate through the first gap from a first side of the plane to the opposite second side of the plane, the wall comprising - a refractory arranged on at least one side of a part of the first secondary portion and a part of the second secondary portion such that - a part of the first secondary portion extends from the refractory to a first direction, - a part of the second secondary portion extends from the refractory to the first direction, and - the first gap extends from the refractory to the first direction; wherein - an outer diameter of the first secondary portion is less than or equal to an outer diameter of the first primary portion, - an outer diameter of the second secondary portion is less than or equal to an outer diameter of the secondary primary portion, and - the first direction forms an angle of at most 30 degrees with an upward vertical direction (Sz).