Chemical centrifuges are impacting Zhejiang’s chemical industry.

Chemical alkali production is currently one of the largest chemical industries in China. In the production of alkali salts, separating alkali salt crystals from the electrolyte solution through evaporation, concentration, and cooling is a crucial step in the alkali-making process, directly affecting product quality and energy consumption during production. Before the 1990s, the equipment commonly used for recovering alkali salts in the evaporation systems of chemical alkali production was the scraper-discharge centrifuge. However, with advancements in science and technology, the shortcomings of scraper-discharge centrifuges—such as low output, poor production efficiency, short service life, and high labor intensity for workers—have become increasingly apparent, gradually making them unable to meet the demands of both production and the market.

In the mid-to-late 1990s, many chemical alkali-producing enterprises began to experiment with domestically manufactured two-stage piston-discharge centrifuges and gradually promoted their widespread adoption. In the application of two-stage piston-discharge centrifuges in chemical alkali production, since the feeding, separation, washing, dehydration, and discharge processes of the salt sludge are all carried out under full-speed operation of the centrifuge, it is particularly important to strictly control and monitor parameters such as the viscosity of the centrifuged material, the size of crystal particles, and the solid-liquid ratio. If the viscosity is too high, solid-liquid separation becomes more difficult; if the crystal particle size is too small, the separation efficiency will be poor; if the feed rate is too low, the filter layer formed by the material will be too thin, easily leading to uneven thickness of the material layer inside the drum, disrupting dynamic balance and causing machine vibration. When the solid-liquid ratio falls below 50%, the machine's efficiency declines, inevitably requiring an increase in the feed rate to meet production demands. However, an excessively high feed rate can also result in unstable filter layer thickness, again triggering machine vibration. Maintaining a relatively higher solid-liquid ratio and keeping the feed rate relatively stable are conducive to the normal operation of the centrifuge.

NC is primarily used in two major sectors: military and civilian. In the military sector, NC is mainly employed in the production of ordnance and explosives, where it is subject to strict military product management. In the civilian sector, NC is widely used in the manufacture of synthetic fibers, coatings, cosmetics, celluloid, and inks for motion-picture film. The chemical production process for NC is illustrated in Figure 2.Figure 2: Chemical Production Process for NitrocelluloseThe P-series two-stage pusher centrifuge has now been successfully applied in three key NC processing steps: centrifugal acid removal, centrifugal dehydration, and centrifugal alcohol removal, yielding remarkably impressive results. Previously, when WH-type pusher centrifuges were used for NC acid removal and dehydration, the separation factor was extremely low, resulting in an NC product with an acid content as high as 40%. This necessitated large volumes of water for washing away the residual acid. Moreover, the dehydration step required heating to reduce the residual moisture content to between 30% and 35%. However, after adopting the P-series two-stage pusher centrifuge, the acid content of NC has been reduced to just 20%, and the residual moisture content can be lowered to between 28% and 32% even at room temperature. This significantly reduces the safety risks associated with heating and also leads to substantial energy savings.