A method for conversion of magnesium chloride into magnesium oxide and HCl includes the steps of providing a magnesium chloride compound to a thermohydrolysis reactor, the reactor being at a temperature of at least 300° C., withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing an HCl containing gas stream from the thermohydrolysis reactor. The magnesium chloride compound provided to the thermohydrolysis reactor may be a solid magnesium chloride compound which comprises at least 60 wt. % of MgCl.sub.2.4H.sub.2O.

A method for conversion of magnesium chloride into magnesium oxide and HCl includes the steps of providing a magnesium chloride compound to a thermohydrolysis reactor, the reactor being at a temperature of at least 300° C., withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing an HCl containing gas stream from the thermohydrolysis reactor. The magnesium chloride compound provided to the thermohydrolysis reactor may be a solid magnesium chloride compound which comprises at least 60 wt. % of MgCl.sub.2.4H.sub.2O.

A method for conversion of magnesium chloride into magnesium oxide and HCl includes the steps of providing a magnesium chloride compound to a thermohydrolysis reactor, the reactor being at a temperature of at least 300° C., withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing an HCl containing gas stream from the thermohydrolysis reactor. The magnesium chloride compound provided to the thermohydrolysis reactor may be a solid magnesium chloride compound which comprises at least 60 wt. % of MgCl.sub.2.4H.sub.2O.

An object of the present invention is to provide magnesium oxide for an annealing separator which is useful for obtaining grain-oriented electromagnetic steel sheets with excellent magnetic properties and insulating properties. To resolve the above object, an aspect of the present invention resides in magnesium oxide for an annealing separator having a Blaine specific surface area of 2.5×10.sup.3 to 7.0×10.sup.3 m.sup.2.Math.kg.sup.−1 and CAA of 50 to 170 seconds.

An object of the present invention is to provide magnesium oxide for an annealing separator which is useful for obtaining grain-oriented electromagnetic steel sheets with excellent magnetic properties and insulating properties. To resolve the above object, an aspect of the present invention resides in magnesium oxide for an annealing separator having a Blaine specific surface area of 2.5×10.sup.3 to 7.0×10.sup.3 m.sup.2.Math.kg.sup.−1 and CAA of 50 to 170 seconds.

Magnesium chloride solutions including providing aqueous magnesium chloride solution with magnesium chloride concentration of 10-30 wt. % to concentration step where water is evaporated, resulting in concentrated magnesium chloride solution with magnesium chloride concentration of 30-50 wt. %, wherein concentration step is carried out in one or more stages, wherein at least one of the stages is conducted at elevated pressure, withdrawing concentrated magnesium chloride solution from concentration step, and providing it to thermohydrolysis reactor of at least 300 C., withdrawing MgO from thermohydrolysis reactor in solid form, and withdrawing a HCl containing gas stream of at least 300 C. from thermohydrolysis reactor, providing the HCl-containing gas stream of at least 300 C. to cooling step, where HCl-containing gas stream is contacted with cooling liquid, withdrawing HCl-containing gas stream below 150 C. from cooling step, circulating cooling liquid through heat exchanger where energy is transferred to heating liquid which circulates from heat exchanger to concentration step.

Magnesium chloride solutions including providing aqueous magnesium chloride solution with magnesium chloride concentration of 10-30 wt. % to concentration step where water is evaporated, resulting in concentrated magnesium chloride solution with magnesium chloride concentration of 30-50 wt. %, wherein concentration step is carried out in one or more stages, wherein at least one of the stages is conducted at elevated pressure, withdrawing concentrated magnesium chloride solution from concentration step, and providing it to thermohydrolysis reactor of at least 300 C., withdrawing MgO from thermohydrolysis reactor in solid form, and withdrawing a HCl containing gas stream of at least 300 C. from thermohydrolysis reactor, providing the HCl-containing gas stream of at least 300 C. to cooling step, where HCl-containing gas stream is contacted with cooling liquid, withdrawing HCl-containing gas stream below 150 C. from cooling step, circulating cooling liquid through heat exchanger where energy is transferred to heating liquid which circulates from heat exchanger to concentration step.

A method for conversion of magnesium chloride into magnesium oxide and HCl includes the steps of providing a magnesium chloride compound to a thermohydrolysis reactor, the reactor being at a temperature of at least 300 C., withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing an HCl containing gas stream from the thermohydrolysis reactor. The magnesium chloride compound provided to the thermohydrolysis reactor may be a solid magnesium chloride compound which comprises at least 60 wt. % of MgCl.sub.2.4H.sub.2O.

A method for conversion of magnesium chloride into magnesium oxide and HCl includes the steps of providing a magnesium chloride compound to a thermohydrolysis reactor, the reactor being at a temperature of at least 300 C., withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing an HCl containing gas stream from the thermohydrolysis reactor. The magnesium chloride compound provided to the thermohydrolysis reactor may be a solid magnesium chloride compound which comprises at least 60 wt. % of MgCl.sub.2.4H.sub.2O.

The invention pertains to a method for providing a succinic acid solution, comprising the steps of providing a first magnesium succinate containing medium with a magnesium succinate concentration of 18-23 wt. % to a first acidification reactor where it is contacted with hydrogen chloride to form a solution of succinic acid, magnesium chloride and hydrogen chloride, providing a second magnesium succinate containing medium with a magnesium succinate concentration of 25-50 wt. %, and contacting it in a second acidification reactor with the solution of succinic acid, magnesium chloride and hydrogen chloride withdrawn from the first acidification reactor, to form an aqueous mixture comprising magnesium chloride and succinic acid with a succinic acid concentration of at least 18 wt. %. The method according to the invention makes it possible to obtain a solution comprising succinic acid and magnesium 20 chloride with an increased succinic acid concentration.