A method of processing waste iron chloride solution including ferrous chloride, ferric chloride or mixtures thereof and optionally free hydrochloric acid, includes concentrating waste iron chloride solution into concentrated liquid having iron chloride concentration of at least 30%-40% by weight; optionally oxidizing ferrous chloride in the concentrated liquid from the concentration step to ferric chloride providing liquid containing ferric chloride; hydrolyzing the liquid containing ferric chloride from the oxidation step at 155-350° C., maintaining the ferric chloride concentration at least at 65% by weight, generating steam containing hydrogen chloride and liquid containing ferric oxide; separating ferric oxide from the liquid containing ferric oxide in the hydrolysis step; condensing steam containing hydrogen chloride in the hydrolysis step, recovering hydrochloric acid at a concentration of at least 10%-15% by weight; and using condensation energy of the hydrogen chloride containing steam in the recovery step to heat the concentration step performed under reduced pressure.