Calcined gypsum slurry mixing apparatus having variably positionable lump ring and method for manufacturing gypsum product using same

A method of manufacturing a gypsum product using a mixing apparatus for producing aqueous calcined gypsum slurry, the method comprising:

• inserting calcined gypsum and water into a mixing chamber defined by a housing of a mixing apparatus through at least one inlet defined within a top lid of the housing, the top lid including a lid ring, and said at least one inlet disposed radially within the lid ring, the mixer housing including a bottom and a peripheral sidewall, the top lid and the bottom in spaced relationship to each other along a normal axis, the peripheral sidewall extending along the normal axis between the bottom and the top lid, the mixer housing defining the mixing chamber therewithin, the lid ring having an end face, the lid ring extending from the lid along the normal axis toward the bottom;
• rotating a rotor of a rotor assembly disposed within the mixing chamber about a normal axis to form an aqueous dispersion of the calcined gypsum, an upper surface of the rotor being separated from the lid ring along the normal axis by a lid ring gap, the rotor assembly including the rotor and a drive shaft, the drive shaft extending along and rotatable about the normal axis, the rotor being connected to the drive shaft such that the rotor extends radially from the drive shaft and is rotatively coupled therewith, the rotor having an upper surface, the upper surface of the rotor being in spaced relationship to the end face of the lid ring such that the lid ring and the upper surface of the rotor are separated by a lid ring gap along the normal axis, the rotor having a rotor outer periphery, the lid ring being positioned radially within the rotor outer periphery;
• discharging the aqueous dispersion of the calcined gypsum from the mixing chamber through a discharge outlet defined by the housing into a discharge conduit, the discharge outlet disposed radially outward of the lid ring;
• moving, using an actuator system, the rotor along the normal axis relative to the lid ring such that the lid ring gap changes, the actuator system arranged with the rotor assembly to selectively move the rotor over a range of travel along the normal axis between a lowered position and a raised position, wherein the lid ring gap has a first value when the rotor is in the lowered position and a second value when the rotor is in the raised position, the first value being greater than the second value.