Submerged Oxyfuel Combustion for Brine Concentration Without Pyrohydrolytic Acid Release

Abstract High-intensity thermal concentration of chloride brines is limited by a chemical failure rather than an energetic one. Magnesium chloride reacts with water during heating to give, in stages, magnesium hydroxychloride and then magnesium oxide, releasing gaseous hydrogen chloride. The hydrolysis begins in the range of roughly 220 to 300 °C and is substantially complete by 500 to 600 °C — temperatures that any high-intensity thermal brine process reaches. The acid attacks refractory linings, heat exchange surfaces and downstream equipment, and the co-produced oxide leaves as an airborne particulate that fouls whatever it lands on. This is not an exotic edge case. It is the reason thermal chloride brine concentration is built either at low intensity — large surfaces, moderate temperature, slow — or with acid-resistant materials throughout and an accepted maintenance burden. This disclosure describes an evaporation chamber in which the combustion takes place beneath the liquid surface rather than above it. Burner lances are submerged 10 to 20 centimetres into the brine. The flame burns inside a stable gas pocket at the nozzle, and the surrounding liquid clamps the phase boundary to the local boiling point. The dissolved salts therefore never enter the gas phase: they remain in solution, reach saturation as pure water is boiled off, crystallise, and settle by gravity through a conical floor for continuous withdrawal as concentrate or solid. The combustion uses hydrogen with pure oxygen in a non-premixed configuration, ignited outside the lance, so that the exhaust is water vapour that joins the process stream without dilution and the lance body never reaches flame temperature. The individual elements are established practice. What is disclosed here is their combination for the specific purpose of suppressing pyrohydrolytic acid release during high-intensity brine concentration, together with the geometric conditions under which the combination works. Relationship to the HCTGS concept series This mechanism was developed as part of the thermal cascade architecture published in the HCTGS series, where it occupies the base of the tower and serves three functions simultaneously: salt separation as described here, momentum transfer into the rising column, and initiation of rotation at the liquid surface. Those additional functions are specific to that architecture and are not part of this disclosure. What is disclosed here is the evaporation and separation mechanism alone, because it is applicable wherever chloride brine has to be concentrated thermally, and because burying it inside a document about something else would make it unfindable to the people who have the problem. This document is published as open prior art. Its purpose is to place the described configuration on the public record with a date, so that no party can obtain exclusive rights over it. The configuration is offered for reading, citation and non-commercial use under CC BY-NC-ND 4.0. Commercial implementation requires a separate licensing agreement.