Combustion of Volatiles

When released from the coal in the pyrolysis process, volatiles (mainly CO, CH4, H2, hydrocarbon liquids, and tars) combust in the gas phase with the oxidant surrounding the coal particles. These reactions are very exothermic, raising the temperature of the product gases significantly. However, in a gasification environment, 

Volatile combustion is a gas-phase homogeneous reaction, so there is no mass transport limitation between phases. There is, however, a mass transfer resistance due to gas-phase mixing of combustible gases and oxidizers. In general, volatile combustion is much faster than the pyrolysis process, which in turn is much faster than the char gasification process. 

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SL/RN Process. In the SL/RN process (Fig. 4), sized iron ore, coal, and dolomite are fed to the rotary kiln wherein the coal is gasified and the iron ore is reduced. The endothermic heat of reduction and the sensible energy that is required to heat the reactants is provided by combustion of volatiles and carbon monoxide leaving the bed with air introduced into the free space above the bed. The temperature profile in the kiln is controlled by radial air ports in the preheat zone and axial air ports in the reduction zone. Part of the coal is injected through the centerline of the kiln at the discharge end. The hot reduced iron and char is discharged into an indirect rotary dmm cooler. The cooled product is screened and magnetically separated to remove char and ash. 

Scire S, Minico S, Crisafulli C, Satriano C, Pistone (2003) Catalytic combustion of volatile organic compounds on gold/cerium oxide catalysts. Appl Catal B Environ 40(1-8) 43 19... 

The conceptual model of the conversion of a single particle is usually assumed to be divided into two phases, namely the flame phase and the glowing phase, see Figure 42. Due to the evolution and combustion of volatiles during the flame phase, oxygen is prevented from reaching the particle surface [57], Consequently, char combustion cannot start until the pyrolysis has finished. 

The combustion of coal and carbon particles has been extensively studied by Hottel and associates (5G, 10G, llfi). Individual particles of coal experience three periods in their combustion—ignition, distillation and combustion of volatile matter, and combustion of the fixed carbon. A discussion of the laws of particle distributions is included (6Cf). 

As is known, Belyaev [1] used convincing arguments to prove that in the combustion of volatile secondary explosive materials the explosive material is first heated to the boiling temperature, then evaporates, and the vapors of the explosive material enter into chemical reaction after further heating. 

When a fat or oil is heated, thermal instability may cause decomposition, and depending on the temperature reached, subsequent combustion of volatile gaseous decomposition products (Mehlenbacher, 1960). The thermal stability of fats and oils is thus essentially a chemical characteristic. However, stability is characterized by measuring certain critical temperatures, the smoke, flash and fire points, at which certain heat-induced changes become apparent. It is appropriate, therefore, to include here methods for measuring these critical points. 

Pina MP, Menendez M, and Santamaria J. The Knudsen-diffusion catalytic membrane reactor an efficient contactor for the combustion of volatile organic compounds. Appl. Catal. B Environ. 1996 11(1) L19-L27. 

To maximise the cold gas efficiency of the CASST process, heat supply by combustion of volatiles and heat demand by gasification of charcoal should be balanced. A preliminary system assessment study showed that charcoal yields of 0.38 kg/kg dry fe are required to balance heat demand and supply (3). 

When cleanup of the flue gas produced by the combustion of volatiles is required, the total hardware costs for a CASST/CC system are sli tly higher than for an ABG/CC. The necessity for flue gas cleanup depends on a numbtf of foctors ... 

An extensive parametric modeling study on conversion of fuel nitrogen during combustion of volatiles from biomass was performed. The variations of different parameters such as temperature, fuel-N content, air-to-fuel ratio, fuel load, and HCN/fuel-N ratio have shown contrary effects in the emission of NO and N2O as summarized in Table 3. 

Fig S Prototype Turbo Stove data on peanut shell pellets, showing water boiled, water temperature, and fuel remaining at high, medium and low gasification and combustion of volatiles and charcoal cooking after 31 minutes... 

The recycle of wood is thus evidently needed. Since the suspension leaving the riser is quenched in the external steam generating bed, further devolatilisation will be low. Since combustion of volatiles is a fast reaction, volatiles will be completely burned in the outlet duct after the cyclone. 

Nickel oxide is utilized as a catalyst support material in methane decomposition [81], oxidation of ammonia [82], and the combustion of volatile organic compounds [83]. To determine how nickel centers bind oxygen, CID experiments were conducted on NiO Ni O Ni O ", and Ni O The general trends in the CID fragments for... 

Morales MR, Barbero BP, Cadus LE (2007) Combustion of volatile organic compounds on manganese iron or nickel mixed oxide catalysts. Appl Catal B Environ 74 1... 

Coal gasification is actually comprised of several processes (a) evaporation of moisture (b) coal pyrolysis, releasing volatile matter (tar, CO, CIt, H2, C02, etc.) (c) reaction of volatiles in the gas phase (d) heterogeneous reaction of char with gas-phase species (such as H20 and C02) and (e) mineral matter release and transformation. Coal moisture is rank dependent low-rank coals such as lignites and subbituminous coals may have up to 35% moisture by weight, whereas bituminous coals generally contain less than 5% moisture by weight. The heat to evaporate this moisture must come from the combustion of volatiles and reduces the efficiency of... 

This contribution describes some physical properties of reverse w/o microemulsions, physical-chemical properties of platinum catalysts prepared by classical impregnation from water solutions of HaPtCle and from reverse w/o microemulsions comprising chloroplatinic acid and their activity in combustion of volatile organic compounds (VOC). In our study we concentrated on TweenSO (polyoxlethylen(20)sorbitan monoleate), as the surfactant does not comprise any potentially harmful ions (like sodium in AOT or bromide in CTAB) that could affect the activity of platinum in catalytic combustion. 

In order to optimise the catalytic processes involving NOx abatement and total combustion of volatile organic compounds (VOC), it is prerequisite to elucidate the mechanism of these processes. In the lecture three processes will be discussed. 

The major problem to be addressed in the present paper is how the phenomenon of the surface transformations under the non-steady-state conditions can generally be applied for the NO abatement and for the combustion of volatile organic compounds (VOC). Two phenomena must be considered here ... 

Sf, = the source/sink terms due to the combustion of volatiles, radiation, and heat transfer between combusting char particles and gas phase. 

With the large captive particles, the particles only pyrolyzed, with simultaneous combustion of volatiles and formation of a char particle. When pyrolysis stopped, char combustion started. This sequence of events is well known for large particles—particularly lumps on a grate— and it was also the accepted mechanism for small particle combustion of pulverized coal (about 1-100 /xm). With very small particles, the rates... 

If the contributions from ash-forming reactions to the total reaction enthalpy are relatively low, only the combustion of volatile fuel components can be considered for the enthalpy balance calculations. This is the case when the ash components are contained in... 

Fire is a phenomenon in which combustible materials, especially organic materials containing carbon, react chemically with the oxygen in the air to produce heat. Flame arises from the combustion of volatile liquids and gases evolved and spreads the fire. 

Bio-briquette combustion decreases the generation of dust and soot to one-fifth to one-tenth that of direct coal combustion. Direct coal combustion increases the generation of dust and soot because the volatile matter released at low temperatures (200°C-400°C [390°F-750°F]) does not completely combust To the contrary, bio-briquettes simultaneously combust the low ignition point biomass, which permeates the coal particles, assuring the combustion of volatile matter at low combustion tanperatures. As a result, the amount of generated dust and soot is significantly reduced. 

The circulation loop reactor (CLR) is a novel dynamic reactor concept, which has been developed at our institute during the last years for the catalytic combustion of volatile organic compounds in waste air. It is described in [1] in detail. The reactor design presented in Fig.2.1 consists of three parts a heating zone at the reactor inlet, which is only used for the start-up procedure, a... 

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