Experimental investigations on synergistic inhibition of aluminum hydroxide and aerosil on ignition sensitivity of Niacin dust

As an important pharmaceutical intermediate product, niacin is widely used in the production process where dust explosions could occur if processed in powdered form. Aluminum hydroxide and aerosil are commonly used in the manufacturing process as pharmaceutical excipients. The effects of dust concentration and dispersed pressure on the lowest ignition temperature of niacin dust cloud were experimentally investigated. Results show that niacin dust has an optimal ignition concentration and the lowest ignition temperature basically remains unchanged and then increases with the dispersed pressure. Inerting experiments of niacin dust were conducted at different dust concentrations, dispersed pressures and the addition of inert dust. With inert dust of aluminum hydroxide, aerosil or mixed aluminum hydroxide-aerosil, the lowest ignition temperature increases with inert dust concentration, and the inhibition effectiveness increases in the order of aluminum hydroxide, aerosil and mixed aluminum hydroxide-aerosil. The synergistic inhibition effect of aluminum hydroxide and aerosil is efficient, and its inhibition mechanism is mainly manifested by thermal stability, diluting the oxygen, and as a third body which has passive influence on the combustion chemical kinetic reaction. This work provides reference for prevention and mitigation of accidental explosions during processing, storage and transportation in the industry of pharmaceuticals.