PURPOSE: To simplify the system structure of a product water recycling device by constituting a direct contact type heat exchanger and a demister of the filling layer of a metallic meshy body to simultaneously serve as a reaction type phosphoric acid collection part and at the same time providing a cleanout operation facilitation means.

CONSTITUTION: A direct contact type heat exchanger and a demister comprise a filling layer of a metallic meshy substance and simultaneously act as a reaction type phosphoric acid scavenger part, and at the same time a clean operation facilitation means 21 for periodically cleansing for removal of scavenged water soluble and nonacqueous phosphoric acid compounds is provided. That is, since a product water recycling device 11 simultaneously acts as a phosphoric acid scavenger, so that the operation of cleaning the scavenged phosphoric acid compounds becomes necessary, a means 21 for hermetically coupling the side plate 18 in one of the surfaces of the square tower-like container 12 of the device 11 with the flange 20 of the main body side through a packing 19 is provided. As a result, since the side plate 18 can be removed during the operation of the device and the operation of cleaning the accumulated phosphoric acid compounds and so forth can be easily performed from the outside of the container, the system construction of the device may be simplified and the initial cost thereof and so forth can be reduced.