When preparing plaster using desulfurized building gypsum, the fineness of the desulfurized gypsum affects the performance of the plaster.

Desulfurized gypsum is an industrial byproduct obtained through desulfurization and purification of flue gas from coal combustion. It is formed by the reaction between finely ground lime or limestone and sulfur dioxide in the flue gas, resulting in finely divided, high-moisture, and high-density calcium sulfate dihydrate. The fineness typically ranges between 40-60 micrometers (with a fineness less than 160 mesh at 0.7%, between 160-180 mesh at 4.23%, between 180-200 mesh at 83.53%, between 200-250 mesh at 9.03%, and greater than 250 mesh at 2.4%). The particle size curve is narrow and slender, which leads to issues when using desulfurized gypsum alone to produce plaster gypsum, such as poor slurry and plasticity, inadequate bonding performance, low water retention, severe segregation, and high product density. During the production of desulfurized plaster gypsum, the particle size distribution can be altered through different calcination equipment and processes, but they all tend towards finer particles. However, the plaster gypsum required for plastering is not the finer, the better, as different types of plaster gypsum require varying levels of fineness. Desulfurized plaster gypsum has a fine fineness, large specific surface area, narrow particle size range, high standard consistency water content, poor thixotropy and plasticity, poor resistance to sagging, and poor workability, with an insufficiently smooth surface finish of the gypsum products. Therefore, the particle characteristics of desulfurized gypsum should be fully considered, and additional process treatments such as grinding, blending, or recrystallization may be necessary. The plaster gypsum products we require should not only meet the technical requirements of national building materials industry standards but also pay attention to relevant performance in construction applications, such as plasticity, sag resistance, crack resistance, prevention of bleeding and segregation, evenness of slurry dispersion during mixing (absence of clumping), and other operational properties. An excellent plaster gypsum product must possess both good technical performance and construction application properties.