The explosion characteristics of aluminum powder in air, hydrogen and nitrogen were studied in a 20-L spherical explosion vessel. Particle agglomeration affected the actual particle size distribution in dust clouds. In air, the smaller the actual particle size, the larger was the explosion overpressure. Adding hydrogen increased system explosion risk; the smaller the theoretical particles, the more pronounced was the effect of hydrogen. However, when hydrogen was added at a concentration of ? 15%, the explosive properties of the mixture weakened. In a constant volume container, the two-phase explosion of flammable gas and flammable dust caused a secondary explosion. Secondary explosion occurrence was affected by fuel composition. Experimental curve analysis explained the cause of the secondary explosion and the two-phase explosion process mechanism. Nitrogen had obvious detonation suppression effects on dust explosions. The higher the nitrogen concentration, the longer was the combustion time. Nitrogen has great influence on fine particles. These experimental conclusions may aid in preventing aluminum powder explosions during industrial production and reducing the harmful consequences of dust explosions. (C) 2020 Elsevier B.V. All rights reserved.