Synthetic gypsum and gypsum boards produced therefrom

A process of producing synthetic gypsum, the process comprising:

• step 1 which comprises mixing Calcium Carbonate (CaCO3) and one of Calcium Hydroxide (Ca(OH)2) and Calcium Oxide (CaO) in a ratio of 2:1˜8, with water to form a suspension with 20%˜40% solid content;
• step 2 which comprises adding a 20%˜60% sulfuric acid solution at normal pressure in a volume equivalent to 1˜1.5 times a molar amount of Calcium, and stirring and mixing the sulfuric acid solution with the suspension, wherein, during step 2, a temperature of a mixture of the sulfuric acid solution and the suspension continues to rise and gas is produced, until gas production stops, to obtain an intermediate product;
• and
• step 3 in which:
• the intermediate product is centrifuged to be dehydrated,
• the dehydrated intermediate product is mixed and stirred with water and a dilute sulfuric acid solution to obtain a product of pH of 3˜5,
• the product of the pH of 3˜5 is allowed to settle and precipitate,
• the settled and precipitated product is centrifuged to be dehydrated, and then washed with water, and
• the washed product is dried to produce synthetic gypsum.

A process of producing a gypsum board, comprising:

• step 1 which comprises mixing a predetermined ratio of Calcium Carbonate (CaCO3) and one of Calcium Hydroxide (Ca(OH)2) and Calcium Oxide (CaO), and adding water to form a suspension with a predetermined concentration of solid;
• step 2 which comprises adding a sulfuric acid solution of a predetermined concentration under normal pressure and in a volume equivalent to a predetermined multiple of a molar amount of Calcium, and stirring the sulfuric acid solution with the suspension, wherein, during step 2, a temperature of a mixture of the sulfuric acid solution and the suspension continues to rise and gas is generated, until the gas production stops, to obtain an intermediate product;
• step 3 in which:
• the intermediate product is centrifuged to be dehydrated,
• the dehydrated intermediate product is mixed with water and a dilute sulfuric acid solution to obtain a product of pH of 3˜5,
• the product of the pH of 3˜5 is allowed to settle,
• the settled product is centrifuged to be dehydrated, and then washed with water, and
• the washed product is dried to produce synthetic gypsum;
• step 4 which comprises:
• drying, grinding, and calcining the synthetic gypsum to produce 10˜50% alpha-hemihydrate calcium sulfate plaster powder, and then
• pulverizing and storing the alpha-hemihydrate calcium sulfate plaster powder;
• step 5 which comprises forming a gypsum slurry by mixing the alpha-hemihydrate calcium sulfate plaster powder, water, and auxiliary materials;
• and
• step 6 in which:
• the gypsum slurry is injected into a paper-lined mold, with a top or face paper and a bottom or back paper, to form continuous wet boards, and
• the wet boards are hardened, transferred, cut, dried, and trimmed to produce gypsum boards.

A process of producing a gypsum board, comprising:

• step 1 which comprises mixing Calcium Carbonate (CaCO3) with one of calcium hydroxide (Ca(OH)2) and calcium oxide (CaO) in a ratio of 2:1˜8, and adding water to form a suspension with a solid concentration of 20%˜40%;
• step 2 which comprises adding a 20%˜60% sulfuric acid solution at normal pressure in a volume equivalent to 1˜1.5 times a molar amount of calcium, and stirring and mixing the sulfuric acid solution with the suspension, wherein, during step 2, a temperature of a mixture of the sulfuric acid solution and the suspension rises and gas is generated, until gas production stops, to obtain an intermediate product;
• step 3 in which:
• the intermediate product is centrifuged to be dehydrated,
• the dehydrated intermediate product is mixed and stirred with water and a dilute sulfuric acid solution to obtain a product of pH of 3˜5,
• the product of the pH of 3˜5 is allowed to settle and precipitate,
• the settled and precipitated product is centrifuged to be dehydrated, and then washed with water, and
• the washed product is dried to produce synthetic gypsum;
• step 4 in which the synthetic gypsum is dried, ground, and calcined to produce a plaster powder containing 10˜50% alpha-hemihydrate calcium sulfate, which is then pulverized and stored;
• step 5 which comprises mixing the plaster powder, water, and auxiliary materials to form a gypsum slurry;
• and
• step 6 in which:
• the gypsum slurry is injected into a paper-lined mold, with a top or face paper and a bottom or back paper, to form continuous wet boards, and
• the wet boards are hardened, transferred, cut, dried, and trimmed to produce gypsum boards.