Method and apparatus for recovering heat from flue gases and for cleaning the same

Heat exchange apparatus for recovering heat and separating substances from a flue gas having a casing (20) provided with connections (21, 22) for a first incoming and outgoing medium (43) and comprising inlet and outlet modules (41, 42), side modules (37, 38) and bottom and top modules (39, 36) and heat exchange elements in the form of plastic tubes (30) for a second medium located within said casing, each of said tubes having helical form and two ends (31, 32) intended to be connected to means (33, 34) for incoming and outgoing, medium, the helical, plastic tubes (30) and the connections (21, 22) for the first medium being so arranged that this medium streams essentially perpendicularly to the longitudinal axis of the tubes (30), characterized in that

• the helical plastic tubes (30) being so located in relation to each other that the distance between the centres of two adjacent tubes is less than the sum of the radii of the circles circumscribing the two tubes, enclosing a common space (81);
• two adjacent helical tubes (71, 72) being locked in relation to each other by one end (73 U) of another helical tube (73) being inserted into the common space (81) of the two adjacent tubes (71, 72);
• the two ends (31, 32) of each plastic tube (30) going through a plate of the top module (36) of the casing (20) via holes (35) in the plate, each tube end (31, 32) being sealingly applied into the respective hole (35) of the plate;
• each side module comprising a metallic plate (50) and insulation (52) covered by a plastic layer (53), the plastic layer being in contact with the first medium (43).