Heat exchanger using non-pure water for steam generation

A high temperature thermochemical process for hydrogen production, the thermochemical process comprising:

• in a shell of a tube of a tube-and-shell heat exchanger, spraying non-pure water against an outer surface of a tube of the tube-and-shell heat exchanger to form a water film, the water containing impurities;
• transferring heat from a molten material inside the tube of the tube-and-shell heat exchanger to the water film formed by the non-pure water sprayed against the outer surface of the tube, the molten material obtained in the high temperature thermochemical process, causing the non-pure water to evaporate inside the shell side of the tube-and-shell heat exchanger to generate steam from the non-pure water, with impurities in the non-pure water being reduced to a precipitate, a slurry or a concentrated aqueous solution, which can be disposed of, or subjected to further processing;
• collecting the steam at a first location of the shell side of the tube-and-shell heat exchanger;
• removing the steam from the shell side of the tube-and-shell heat exchanger;
• producing hydrogen using the steam;
• collecting the impurities introduced in the shell side of the tube-and-shell heat exchanger by the non-pure water containing impurities received inside the shell of the tube-and-shell heat exchanger, the impurities deposited in the shell side of the tube-and-shell heat exchanger, wherein the impurities are collected at a second location of the shell side of tube-and-shell heat exchanger spaced apart from the first location along tube-and-shell heat exchanger;
• and
• removing the impurities from the shell side of the tube-and-shell heat exchanger;
• wherein spraying the non-pure water against the outer surface of the tube is at a third location of the shell side of the tube-and-shell heat exchanger between the first location and the second location.