Abstract: Apparatus for endothermic dissolutions in water, including: a mixing tank 40, wherein solute is slurried with water; pump 59 and spray pipe 63, for spraying slurry into spray box 70; and fan 75 for drawing ambient air upwardly, in direct heat exchange relationship with descending slurry droplets. Dissolution is promoted, as the droplets extract heat from the countercurrent flow of air.

Abstract: An energy efficient, economical method for dissolving urea, and other endothermic materials, e.g. potassium chloride, ammonium nitrate, etc., in water, without the use of fossil fuel-derived heat, which comprises: forming a slurry of such material and water, said slurry including said material as both a dissolved and solid phase; forming droplets of said slurry; and contacting said droplets of said slurry, in direct heat exchange relationship, with a moisture-containing air stream, having a temperature greater than the temperature of said droplets of said slurry, at conditions whereby both heat and moisture are removed from said moisture-containing air to thereby dissolve at least a portion of said solid phase. This process is especially useful for forming aqueous forming urea solutions, useful in agricultural applications and having from 19 to 23 percent, by weight, nitrogen. An apparatus, useful in said method, is also disclosed and claimed.