Concentration Limits of Hydrogenous Mixtures

In a heated 5-cm diameter and 1.8 m-length vertical tube, the flame propagation limits (lower ignition) have been measured at 295, 373 and 473 K temperatures and 0.1 MPa pressure [8]. In accordance with the obtained data, the amount of N2 necessary for complete suppression of the combustion at 295 K is equal to 87% and increases up to 92% at 473 K. The range of the obtained temperature limit data has been extended to 523 K, and the pressure limit data range to 2 MPa [12]. For the test [12] a heated vessel of about 50-L volume has been used. 

The measured data shows that the initial pressure increase in a H2 + O2 + N2 mixture decreases the combustibility region to some extent. The maximum N2 amount (N2 concentration at the limit triangle tip ) required for suppression of combustion resulting from all compositions is 93% N2 at 523 K, 0.1 MPa pressure 

The limit curves of the ternary mixtures containing H2 are characterized by the higher limit of the diluent (N2) content and the lower limit of H2 concentration in the curves tip area than they are in stoichiometric compositions in the same area. This characteristic relates to the high diffusivity of H2, the effect of which is small in comparison with the stoichiometry the Le number is noticeably less than unity. 

The pressure effect in the stoichiometric mixtures H2 + O2 + N2 at three values of the initial temperature is shown in Fig. 4.2. The greatest pressure effect on the H2 

The limit curve for H2 + O2 + CO2 mixture is presented in Fig. 4.3 at an initial pressure of 0.1 MPa and 293 and 523 K temperatures. The lower branch of the curve is shifted towards the reduction of the H2 concentration limit. 

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Concentration Limits of Hydrogenous Mixtures with Helium... 

Bone s data shows that the concentration limits of mixtures of hydrogen with air do not, within the limits of experimental error, depend... 

Fig. 3.21 The combustion limits of hydrogen + air + saturated steam + micro-droplets mixture versus the steam volume concentration 1 - the upward flame propagation [31] 2 - the downward flame propagafion [31] fhepoints -measuremenf dafa [28-30]...

During large -scale experiments performed at normal conditions [1], 4% H2 low concentration limit (LCL) hydrogen-air mixtures have been tested at the lower ignition limit (small portions of H2 burn due to diffusion and most of the H2 does... 

Concentration Limits of Combustion of Hydrogenous Mixtures with Water Steam 77... 

Because internal combustion engines can work using hydrogen + hydrocarbon mixtures (including natural gas), some measurements of concentration limits of flame propagation in multi-component combustible gas mixtures have been performed. Information on the methodology used to obtain the data can be found in [17, 22-24]. Some useful information from the aforementioned publications is given below. 

Cu-CuO% nanoparticles (with a content of about 10 wt.%) on titania are effective for the production of hydrogen under sacrificial conditions [176-178], A fairly low concentration of Cu (2.5 wt.%) was sufficient to allow promising H2 production from ethanol-water and glycerol-water mixtures in the case of CuO% nanoparticles encapsulated into porous titania [179]. A key limitation of this system is photocorrosion under oxidizing conditions (oxygen and carboxylic adds as by-products of partial oxidation of the sacrificial agent). However, in the presence of UV irradiation, Cu photodeposition can occur, preventing loss of Cu [179]. 

Homogeneous mixtures of concentrated peroxide with alcohols or other peroxide-miscible organic liquids are capable of detonation by shock or heat [1]. Furfuryl alcohol ignites in contact with 85% peroxide within 1 s [2], Detonability limits of mixtures with 2-propanol have been measured. Approximately stoichiometric combinations of 50% hydrogen peroxide and the alcohol could be made to detonate, as could a wider range of mixtures with higher test peroxide [3],... 

The peroxyacids were until relatively recently the most powerful oxidants of all organic peroxides, and it is often unnecessary to isolate them from the mixture of carboxylic acid and hydrogen peroxide used to generate them. The pine lower aliphatic members are explosive (performic, particularly) at high, but not low concentrations, being sensitive to heat but not usually to shock. Dipicolinic acid or phosphates have been used to stabilise these solutions. The detonable limits of peroxyacid solutions can be plotted by extrapolation from known data. Aromatic peroxyacids are generally more stable, particularly if ring substituents are present [1],... 

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