Chemical process to produce hydrogen chloride and chloride-free compound potassium sulfate fertilizers or other metal sulfates

Abstract

A method is disclosed for production of a sulfate-containing salt and anhydrous gaseous HCl from a metal chloride (MClx) and oleum. MClx and oleum are mixed together with a water-containing liquid, forming gaseous HCl and a solution of a sulfate-containing salt or double salt. The salt is precipitated from the solution, and in a preferred embodiment, the supernatant liquid from the precipitation is recycled to the reaction mixture as the water-containing liquid in subsequent reaction cycles. In a preferred embodiment, HCl discharged from the reaction mixture is scrubbed to remove dust, water vapor and traces of H2SO4, yielding anhydrous HCl of >90% purity. The exothermicity of the reaction between the water-containing liquid and the oleum is sufficient that, unlike methods known in the prior art, the process proceeds quickly and efficiently without any necessity for additional heating of the reaction mixture. This method provides high-purity, low-chlorine sulfates, including the novel potassium sulfate double salts K3(NH4)(SO4)2, 3K2SO4*MgSO4 and 3K2SO4*CanMg2-nSO4.

Description

technical field

[0001] This invention relates to processes for the production of hydrogen chloride and metal sulfates from metal chlorides and, in particular, to an improved process for the production of metal sulfates and hydrogen chloride from the reaction of metal salts with oleum. Background technique

[0002] The most common industrial method for the production of hydrogen chloride and sodium sulfate or potassium sulfate uses the reaction of sodium chloride or potassium chloride with sulfuric acid at high temperature (generally 500-840°C) and is called the Mannheim process (schematically shown in Figure 1 sexual display). Because the reaction takes place at high temperatures, the Mannheim process is energy inefficient, using about half a barrel of oil per ton of sulfate. Furthermore, sulfates produced by the Mannheim process typically contain a few percent chloride impurity while HCl is evolved as a low concentration (-10%) mixture with combustion gases. In other proc...

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