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 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 (P) and - at least a part of the first gap penetrates through the plane (P) such that particulate material is able to propagate through the first gap from a first side (S1) of the plane (P) to the opposite second side (S2) of the plane (P), 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 (Dir1), - a part of the second secondary portion extends from the refractory to the first direction (Dir1), and - the first gap extends from the refractory to the first direction (Dir1); wherein - an outer diameter (d12) of the first secondary portion is less than or equal to an outer diameter (d11) of the first primary portion , - an outer diameter (d22) of the second secondary portion is less than or equal to an outer diameter (d21) of the secondary primary portion , and - the first direction (Dir1) 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 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 (P) and - at least a part of the first gap penetrates through the plane (P) such that particulate material is able to propagate through the first gap from a first side (S1) of the plane (P) to the opposite second side (S2) of the plane (P), 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 (Dir1), - a part of the second secondary portion extends from the refractory to the first direction (Dir1), and - the first gap extends from the refractory to the first direction (Dir1); wherein - an outer diameter (d12) of the first secondary portion is less than or equal to an outer diameter (d11) of the first primary portion , - an outer diameter (d22) of the second secondary portion is less than or equal to an outer diameter (d21) of the secondary primary portion , and - the first direction (Dir1) forms an angle of at most 30 degrees with an upward vertical direction (Sz). <EOS>