Pulp undergoes immersion, and the solution preparation process can be further divided into two stages: swelling and dissolution. The swelling stage can adopt the steeping-pressing-crumbling process used in traditional viscose production, where pre-swelling is achieved through the activation of the steeping liquor. The pre-swollen pulp is then pressed and crushed, mixed with a high-concentration NMMO aqueous solution to form a slurry, and subsequently fed into a thin-film evaporator or a horizontal fully mixed dissolution reactor to complete the dissolution process. For convenience of discussion, this process is referred to as the wet swelling process.
