Systems and methods to treat flue gas desulfurization waste to produce ammonium sulfate and calcium carbonate products

A system, comprising:

• a calcium sulfate feedstock comprising calcium sulfate and at least one metal component;
• a mixer to mix an ammonia compound, carbon dioxide, and water resulting in a first reagent;
• a first reactor to react the calcium sulfate feedstock with the first reagent to form a first reacted slurry comprising an ammonium sulfate liquor and a metal bearing calcium carbonate, wherein the metal bearing calcium carbonate comprises calcium carbonate and the at least one metal component;
• a first filter to separate the metal bearing calcium carbonate from the ammonium sulfate liquor;
• at least one of an evaporator, a crystallizer, a centrifuge, and a dryer to process the ammonium sulfate liquor to produce ammonium sulfate crystals;
• a second reactor to dissolve the metal bearing calcium carbonate in a second reagent resulting in a second reacted slurry comprising a first solid and a first metal bearing processed liquor, wherein the first metal bearing processed liquor comprises the metal bearing calcium carbonate;
• a second filter to separate the first solid from the first metal bearing processed liquor;
• a third reactor to selectively precipitate the at least one metal component from the first metal bearing processed liquor resulting in a second metal bearing processed liquor, wherein the second metal bearing processed liquor comprises the calcium carbonate and the at least one metal component, wherein the selective precipitation is achieved by adding a first quantity of a base to the third reactor to elevate a pH of the first metal bearing processed liquor to a first predetermined pH level, wherein the first predetermined pH level causes the at least one metal component to precipitate;
• a third filter to separate the at least one metal component from the second metal bearing processed liquor;
• a fourth reactor to selectively precipitate a second metal component from the second metal bearing processed liquor, wherein the selective precipitation is achieved by adding a second quantity of the base to the fourth reactor to elevate a pH of the second metal bearing processed liquor to a second predetermined pH level, wherein the second predetermined pH level causes the second metal component to precipitate;
• and
• a fourth filter to separate the second metal component from the second metal bearing processed liquor.