Gas-oxygen mixtures

FIGURE 4.23 Methane laminar flame velocities in various inert gas-oxygen mixtures (after Clingman et al. [27]). 

The IEC testing apparatus according to Fig. 1.2 has been improved for the application in precompressed gas-air/vapour-air mixtures and for gas-oxygen mixtures [17,18]. The main changes are as follows (Fig. 1.4) ... 

There are a number of burners, lamps and crossfires available. Most of them are designed to burn coal gas-air, coal gas-air-oxygen or coal gas-oxygen mixtures. Such burners are not suitable for use with hydrogen, namral gas or liquid petroleum gases. 

It is known that for the same specific heat loads (kJ/m ) on a melt surface the amount of combustion products for a gas-air mixture is 5 times higher than for a gas-oxygen mixture, and aerosol entrainment are 10 - 12.5 times higher for a gas-air mixture than for a gas-oxygen mixture. 

Montecatini Process. This partial combustion process operates at higher pressure, 405—608 kPa (4—6 atm), than the BASF and SBA processes. The burner dimensions are proportionately smaller. Because of the higher pressure, the danger of premature ignition of the methane—oxygen mixture is higher so that 2 vol % of steam is added to the gas mixture to alter the flammabiUty limits. 

Background Indirect coal liquefaction differs fundamentally from direct coal hquefaction in that the coal is first converted to a synthesis gas (a mixture of H9 and CO) which is then converted over a catalyst to the final product. Figure 27-9 presents a simplified process flow diagram for a typical indirect coal hquefaction process. The synthesis gas is produced in a gasifier (see a description of coal gasifiers earlier in this section), where the coal is partially combusted at high temperature and moderate pressure with a mixture of oxygen and steam. In addition to H9 and CO, the raw synthesis gas contains other constituents (such as CO9, H9S, NH3, N9, and CHJ, as well as particulates. 

Another application is in tire oxidation of vapour mixtures in a chemical vapour transport reaction, the attempt being to coat materials with a tlrin layer of solid electrolyte. For example, a gas phase mixture consisting of the iodides of zirconium and yttrium is oxidized to form a thin layer of ytnia-stabilized zirconia on the surface of an electrode such as one of the lanthanum-snontium doped transition metal perovskites Lai j.Srj.M03 7, which can transmit oxygen as ions and electrons from an isolated volume of oxygen gas. 

Purging a system of flammable gas/vapor mixtures generally involves adding an inert gas such as nitrogen to the system. Sometimes the volumes of nitrogen are large, but it is still less expensive than most other nonflammable gas (even CO and C02 have to be used cautiously) and certainly air cannot be used because it introduces oxygen... 

Another consequence of the effect of pressure on gas solubility is the painful, sometimes fatal, affliction known as the bends. This occurs when a person goes rapidly from deep water (high pressure) to the surface (lower pressure), where gases are less soluble. The rapid decompression causes air, dissolved in blood and other body fluids, to bubble out of solution. These bubbles impair blood circulation and affect nerve impulses. To minimize these effects, deep-sea divers and aquanauts breathe a helium-oxygen mixture rather than compressed air (nitrogen-oxygen). Helium is only about one-third as soluble as nitrogen, and hence much less gas comes out of solution on decompression. 

Consider the combination of nitric oxide and oxygen. Nitric oxide (a colorless gas) when mixed with oxygen gas (also colorless) becomes reddish-brown. The color is identical to that of another gas, nitrogen dioxide. All the properties of the nitric oxide-oxygen mixture are consistent with the conclusion that the gas nitrogen dioxide has... 

An anesthetic gas, cyclopropane has a rapid onset of action and may be used for induction and maintenance of anesthesia Skeletal muscle relaxation is produced with full anesthetic doses. Cyclopropane is supplied in orange cylinders. Disadvantages of cyclopropane are difficulty in detecting the planes of anesthesia, occasional laryngospasm, cardiac arrhythmias, and postanesthesia nausea, vomiting, and headache Cyclopropane and oxygen mixtures are explosive, which limits the use of this gas anesthetic. 

Several examples were reported for conducting routes in the explosive regime [18]. Among them and most prominent was the detonating-gas reaction, using pure hydrogen and oxygen mixtures. 

Figure 5.11 Variation in the catalytic activity of an Mg(0001) surface when exposed to a propene-rich propene- oxygen mixture at room temperature. The surface chemistry is followed by XPS (a), the gas phase by mass spectrometry (b) and surface structural changes by STM (c, d). Initially the surface is catalytically active producing a mixture of C4 and C6 products, but as the surface concentrations of carbonate and carbonaceous CxHy species increase, the activity decreases. STM images indicate that activity is high during the nucleation of the surface phase when oxygen transients dominate. (Reproduced from Ref. 39).

Addition of bromine to the gas-phase mixture initiated an explosion, but see Oxygen Halocarbons (reference 3). 

Action of chlorine trifluoride causes incandescence [1]. Manganese dioxide catalytically decomposes powerful oxidising agents, often violently. Dropped into cone, hydrogen peroxide, the powdered oxide may cause explosion [2], Either the massive or the powdered oxide explosively decomposes 92% peroxomonosulfuric acid [3], and mixtures with chlorates ( oxygen mixture , heated to generate the gas) may react with explosive violence [4], Cuban pyrolusite can be used in place of potassium dichromate to promote thermal decomposition of potassium chlorate in match-head formulations [5],... 

Caballero, M. A. Aznar, M. P. Gil, J. Martin, J. A. Frances, E. Corella, J., Commercial steam reforming catalysts to improve biomass gasification with steam-oxygen mixtures. 1. Hot gas upgrading by the catalytic reactor. Industrial and Engineering Chemistry Research 1997,36(12), 5227-5239. 

When an ignition source is brought into contact with a flammable gas or mixture of gases, a combustion chemical reaction will occur at the point of introduction provided an oxidizer is present, normally oxygen. The combustion components are commonly referred to as a simple fire triangle ... 

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