Study on the effect and mechanism of Ca(H2PO4)2 and CaCO3 powders on inhibiting the explosion of titanium powder

Study on Explosion Characteristics and Mechanism of Electrostatic Spray Powder

In order to fully understand the explosion risk of electrostatic spraying powder, corresponding preventive measures are put forward. The explosion characteristics, ignition sensitivity, and flame propagation of three typical electrostatic spraying powders were tested using a 20 L spherical explosion test device, a G-G furnace test device, and a Hartmann tube test device, and the explosion process and mechanism of electrostatic spraying powders were discussed. The results show that the maximum explosion pressure and the maximum explosion pressure rise rate increase first and then decrease with the increase in mass concentration. The maximum explosion pressure and the maximum explosion pressure rise rate of acrylic powder coating are the largest, which are 0.75 and 85.4 MPa/s, respectively. The shortest burning time is 97.5 ms, and the highest explosion danger level is 23.46 MPa·m/s. The flame propagation of electrostatic spraying powder develops slowly; the flame front spreads linearly and the average flame velocity increases first and then decreases. The explosive development process of powder coating particles is concentrated in the three-phase system of solid particles, molten particles, and pyrolytic gasification combustible gas, which goes through the kinetic process of particle heating melting, cross-linking curing, pyrolytic gasification, combustion, and extinction.

Inhibition Effect of KHCO3 and KH2PO4 on Ethylene Explosion

The explosion risk of ethylene (C2H4) seriously hinders safe development of its production and processing. To reduce the harm caused by C2H4 explosion, an experimental study was conducted to assess the explosion inhibition characteristics of KHCO3 and KH2PO4 powders. The experiments were conducted based on the explosion overpressure and flame propagation of the 6.5% C2H4-air mixture in a 5 L semi-closed explosion duct. Both the physical and chemical inhibition characteristics of the inhibitors were mechanistically assessed. The results showed that the 6.5% C2H4 explosion pressure (P ex) decreases by increasing the concentration of KHCO3 or KH2PO4 powder. The inhibition effect of KHCO3 powder on the C2H4 system explosion pressure was better than that of the KH2PO4 powder under similar concentration conditions. Both powders significantly affected the flame propagation of the C2H4 explosion. Compared with KH2PO4 powder, KHCO3 powder had a better inhibition effect on the flame propagation speed, but its ability to reduce the flame luminance was less than KH2PO4 powder. Finally, the inhibition mechanism(s) of KHCO3 and KH2PO4 powders were revealed based on the powders' thermal characteristics and gas-phase reaction.

Change Law of Lower Limit of Gas Explosion at Ultra-High Temperatures

During coal seam mining, a large amount of low-concentration mine gas will be produced, and it is the main utilization way to pass it into a thermal storage oxidation device to obtain heat energy. The thermal storage oxidation process is carried out in an ultra-high temperature environment. The excessive gas concentration not only reduces the production efficiency but also presents an explosion hazard. To solve the abovementioned problems, the lower explosion limit of a low-concentration gas at ultra-high temperatures (900-1200 °C) was studied through a self-developed high-temperature explosion experimental device. Fluent software was used to simulate the reaction of a low-concentration gas in a high-temperature environment, and the experimental results were verified according to the maximum explosion pressure. Through analysis and discussion, the following are found: (1) the relationship between the instantaneous explosion pressure of the low-concentration gas and the gas concentration as well as the relationship between the maximum explosion pressure near the lower explosion limit and the gas concentration are in accordance with the Boltzmann function. (2) When the temperature rises from 900 to 1200 °C, the lower limit of gas explosion obtained from experiments is reduced from 2.33 to 1.36%. (3) The lower limit of gas explosion decreases with increasing temperature at ultra-high temperatures and the downward trend slows down, this is similar to the change rule of the lower limit of gas explosion at temperatures below 200 °C. These findings have certain practical significance for improving the utilization efficiency of the low-concentration gas in heat storage oxidation.