Live steam gets in external of tube of single-effect heating chamber for heating materials in tube, with the function of vacuum and pump, the heated feed liquid circle from the bottom-up, then crushing evaporation chamber, separating vapour and liquid, through return conduit, feed liquid is heated by sending to tube with pump, crushing evaporation chamber again for forming circulation, and the secondary steam enters outside of dual-effect heating chamber, for heating materials which exists in tube, and so, the dual-effect circle pump crushes the heated materials evaporation chamber through tube to form circulation, the stream produced by dual-effect is taken away by vacuum pump, after concentration and sampling, if qualified, to discharge from discharging port.