Inhibition of diammonium phosphate on the wheat dust explosion

Study of Explosion Characteristics and Mechanism of Sucrose Dust

In order to investigate the explosion mechanism of sucrose in the air atmosphere, the explosion intensity under different ignition delay times (IDT), powder input pressures (PIP), and concentrations were studied using a 20L-sphere. The sucrose particles were analyzed in a synchronized thermal analyzer (STA) and scanning electron microscope (SEM). The results are as follows: 1. The DSC curve has two endothermic peaks and one exothermic peak, respectively at T = 180.5 ℃, 510.2 ℃ and 582.6 ℃. 2. The explosion intensity varies with the experiment conditions. The maximum explosion pressure (Pmax) appears when IDT = 90 ms, PIP = 1.5 MPa and concentration = 625 g/m3. 3. The explosive mechanism is a homogeneous combustion mechanism based on particle surface pyrolysis and volatilization. Because of the decomposition, H2, CO, furfural, and other flammable gas-phase products are released, then surface burn appears, which leads to the crystal rupture on account of thermal imbalance, resulting in multiple flame points and a chain explosion. As the temperature of the 20L-sphere rises, more explosive products are released, which causes a rapidly expanding explosion and eventually forms the explosion. This paper can be used as a reference for the prevention of explosion accidents in sucrose production processing.

Inhibition of Four Inert Powders on the Minimum Ignition Energy of Sucrose Dust

In order to evaluate the effect of inert powder on the ignition sensitivity of sucrose dust, this study investigated the effects of NaHCO3, NaCl, NH4H2PO4 and Al(OH)3 on the minimum ignition energy (MIE) of sucrose dust. The results showed that all four different inert powders inhibited the MIE of sucrose dust, and all of them showed a trend that the smaller the particle size of the inert powders, the better the inhibition effect. The inhibition effect was ranked as NaHCO3 > NH4H2PO4 > NaCl > Al(OH)3. NaHCO3 and NH4H2PO4 had both physical and chemical inhibition effects, which were better compared to NaCl and Al(OH)3, which had only physical inhibition effects. Analysis of the flame images showed that the inert powder slowed down the combustion of the sucrose dust flame and reduced the flame height. No flame appeared in the region of higher inert powder concentration.

Investigation on the Inhibition of Aluminum Dust Explosion by Sodium Bicarbonate and Its Solid Product Sodium Carbonate

To characterize the inhibiting effects of sodium bicarbonate (NaHCO₃) on aluminum dust, the inhibiting capacities of NaHCO₃ and its solid product sodium carbonate (Na₂CO₃) on the explosions of 10 and 20 μm aluminum dusts were studied using a standard 20 L spherical chamber. Explosion parameters were analyzed based on the induction period and explosion stage to evaluate the inhibiting effects. The results show that the induction period of 10 μm aluminum dust explosion is 18.2 ms, which is shorter than that of 20 μm aluminum dust. Two aluminum dust explosions can be completely inhibited during the induction period when inert ratios of NaHCO₃ are 350 and 150%, respectively, but that is not observed after adding the corresponding amount of Na₂CO₃. When the inert ratio ranges from 0 to 150%, the physical effect of NaHCO₃ on 10 μm aluminum is poor and the chemical effect is the essential process. But as the inert ratio increased from 200% to 350%, the physical effect of NaHCO₃ is higher than the chemical effect, suggesting that the physical effect is the key factor. With the increase of NaHCO₃, the physical effect increases gradually. However, the chemical effect changes little. The physical effects of NaHCO₃ including heat absorption and isolation play an essential role in the inhibiting process, which has a significant impact on the pyrolysis process and explosion parameters. The results of the present work provide guidance for the prevention and control of aluminum dust explosions.

Investigation on thermokinetic suppression of ammonium polyphosphate on sucrose dust deflagration: Based on flame propagation, thermal decomposition and residue analysis

In this investigation, ammonium polyphosphate (APP) is applied to suppress the deflagration of sucrose dust. Through the systematic research on flame propagation images and temperature, decomposition behavior of powder samples and the compositions of deflagration residue, the suppression performance and mechanism of APP on sucrose deflagration are profoundly summarized. Timing diagrams show that APP contributes to reduce deflagration flame brightness, increases ignition delay time and flame fault area. The minimum inerting concentration of APP for sucrose deflagration is determined to be 8 %. From the collected deflagration flame temperature curves, it is confirmed that APP can delay peak temperature arrival time, weaken temperature fluctuation, and decrease peak values of flame temperature and temperature rising rate. Through the analysis on thermal decomposition of samples and deflagration residue, it is reflected that APP has superior composite suppression effect. It can not only absorb reaction heat, but also decrease deflagration exotherm to improve thermal stability of sucrose particles. Thus, the easily oxidized components in sucrose are protected, and deflagration intensity is effectively weakened. This work provides a new solution for prevention and suppression deflagration of dust waste in sugar industry.