Gas quenching

Stoichiometric Air. If the stoichiometric amount of air is added to the combustion zone, the temperature ia that zoae is coatroUed by removing heat from the system. No eaergy leaves the system as chemical eaergy. The heat is removed by an external means such as generating steam or gas quenching. 

Other Considerations Leakage of cold air into a settling chamber can cause local gas quenching and condensation. Condensation can cause corrosion, dust buildup, and plugging of the hopper or dust removal system. The use of thermal insulation can reduce heat loss and prevent condensation by maintaining the internal device temperature of the above the dew point (EPA, 1982). No pretreatment is necessary for settling chambers. 

In direct contact heal exchange, there is no wall to separate hot and cold streams, and high rales of heal transfer are achieved. Applications include reactor off-gas quenching, vacuum condensers, desuperheating, and humidification. Water-cooling lowers are a particular example of a direct contact heal e.xchanger. In direct contact cooler-condensers, the condensed liquid is frequently used as the coolant. 

Plate and frame e.xchangers (plate heat exchangers)-used for heating and cooling in reactor off-gas quenching, vacuum condensers, desuperheating, and humidification. 

Transfer of heat by direct contact is accomplished in spray towers, in towers with a multiplicity of segmented baffles or plates (called shower decks), and in a variety of packed towers. In some processes heat and mass transfer occur simultaneously between phases for example, in water cooling towers, in gas quenching with water, and in spray or rotary dryers. Quenching of pyrolysis gases in transfer lines or towers and contacting on some trays in fractionators may involve primarily heat transfer. One or the other, heat or mass transfer, may be the dominant process in particular cases. 

Quenching Gas Quenching Constant a (torr 1) Quenching Gas Quenching Constant a (torr1)... 

The flame velocity in porous media is determined by the effective longitudinal thermal conductivity, which strongly depends on the velocity of the gas. Quenching of the flame as the cold wall is approached and the resulting incompleteness of combustion of the fuel material have been the subject of investigation in many recent studies, both theoretical and experimental. In particular, the question of flame propagation in a mixture of methanol and air has been considered theoretically,10 and the incomplete combustion of hydrocarbon mixtures was studied experimentally.11... 

In the process (Figure 9-37), the residue feed is slurried with a small amount of finely powdered additive and mixed with hydrogen and recycle gas prior to preheating. The feed mixture is routed to the liquid phase reactors. The reactors are operated in an up-flow mode and arranged in series. In a once through operation conversion rates of >95% are achieved. Typically the reaction takes place at temperatures between 440 and 480°C and pressures between 150 and 250 bar. Substantial conversion of asphaltenes, desulfurization and denitrogenation takes place at high levels of residue conversion. Temperature is controlled by a recycle gas quench system. 

Although the list of applicable species is limited, most are of extreme interest in combustion research. The fluorescence signals will be independent of gas quenching effects if the absorption resonances can be saturated. Two level models, when properly interpreted, are applicable to data reduction, but rotational relaxation/coupling effects need to be quantitatively evaluated. More fundamental research investigations are required to address these questions for this potential to be realized. 

The Sauter mean diameter has been found to be the most useful of the above definitions for characterizing the spray produced by a nozzle. It is a good indicator of a spray s performance in complex interactions with a droplet s surface and volume. Applications include spray drying, evaporative cooling, dry scrubbing, gas quenching, and gas absorption (Stavis, 1991). 

Optimum Cycle Life for a Liquid Quench or Two Gas Quenches... 

Feed powder Feed rate Argon plasma (kW) Quench gas Quench rate (liter/min) Con- version (%) Product Particle size (A) Surface area (m /gm)... 

O. Kebler, F. Hoffmann, and P. Mayr, Distortion of CVD Coated and Gas Quenched Tool Steels, Second International Conference on Quenching and the Control of Distortion, (Proceedings of Conference), Cleveland, Ohio, 1996, pp.171-178. 

The catalyst volume is divided into several beds in which the reaction proceeds adiabatically. Between the individual catalyst beds heat is removed by injection of colder synthesis gas (quench converters) or by indirect cooling with synthesis gas or via boiler feed water heating or raising steam (indirectly cooled multibed converters). 

Table 3 gives difFerent results of the values of CO / H2 and H2 + CO (on molar basis) reported by the literature. They are obtained in very difTerent experinieatal conditions, and their coiKqraiison with those presented in this paper is difficult. They reveal that the ratio CO / H2 may vary between 1,5 and 37 even if the total fraction CO + H2 is relatively constant (roughly between 60 and 80 %). However we can observe that the results of the present work are similar to those obtained by Antal [24] and also in cyclone reactors. In each case, the vapour phase formed near the hot walls and / or near the reacting particles is rapidly mixed with a colder carrier gas (quench). 

Prenflo 1 Dry Up Membrane syngas cooler Gas quench and Oxygen... 

The final choice that we will consider is that of syngas cooling. Here one can select between water quench, gas quench, and radiant cooling together with or without a convective cooler. GE, for instance, offer a choice between a full water quench and (for coal gasification) a radiant cooler. 

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