PURPOSE: To provide the titled economical cooler having a structure to receive a joint stream of at least two sulfuric acid streams selected from the circulating sulfuric acid passing through a pump tank and an absorption column, the circu lating sulfuric acid passing through a pump tank and a drying column, and the produced sulfuric acid delivered from a pump tank.

CONSTITUTION: The cooler 1 is a multi-tube heat-exchanger composed mainly of the body 12 containing a bundle of heat-transfer tubes 11 having a required heat-transfer area, and plural buffles 15 dividing the body into plural cooling zones. The cooler is of an anodic protection type. A cathode 16 is attached to an end of the body and extended along the center axis of the body 12. A cathode terminal of a power unit is connected to the cathode, and the anode terminal of the unit is connected to the body 12. The inner surface of the body contacting with sulfuric acid is positively charged by this arrangement. The cooler 1 has a structure to receive a joint stream of at least two sulfuric acid streams selected from the circulating sulfuric acid passing through the pump tank 2 and the absorption column 3 or the drying column 4, and the produced sulfuric acid delivered from the pump tank 2.