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Advantages of the ammonium sulfite pulping process

The ammonium subnitrate pulping process is designed to avoid the hydrolysis of cellulose and hemicellulose in acidic solutions, prevent the delignification reaction occurring in alkaline solutions, and utilize alkaline hydrolysis to enhance the pulp yield.

Solid ammonium sulfite is a colorless monocrystal that is hygroscopic, with the molecular formula (NH₄)₂SO₃·H₂O and a molecular weight of 134.16. At 25°C, its specific gravity is 1.41. In 100 mL of water, ammonium sulfite dissolves 32.4 g at 0°C and 60.4 g at 100°C.

Ammonium sulfite pulping from straw

Rice straw is a low-cost material (with a purchase price of less than 100 yuan per ton) and belongs to the annual monocotyledonous grass family Poaceae.

China's papermaking industry

among these, wheat straw and rice straw—due to their abundant availability and low cost—are currently the primary raw materials for China's paper industry

Fiber raw materials form the material foundation of the papermaking industry.

This paper investigates sodium disulfite bleaching under the following process conditions: Na₂S₂O₄ at 1.0% concentration (5%), pH 5.5, temperature 60°C, and DTPA at 0.1%. The experimental results showed a whiteness value of 68.7% ISO and a potassium permanganate value of 2.6.

This paper investigates the completely chlorine-free bleaching of rice straw ammonium sulfamate pulp, with a focus on the OAP bleaching process workflow.