Gas-Cooled

The gaseous ammonia is passed through electrostatic precipitators for particulate removal and mixed with the cooled gas stream. The combined stream flows to the ammonia absorber where the ammonia is recovered by reaction with a dilute solution of sulfuric acid to form ammonium sulfate. Ammonium sulfate precipitates as small crystals after the solution becomes saturated and is withdrawn as a slurry. The slurry is further processed in centrifuge faciHties for recovery. Crystal size can be increased by employing one of two processes (99), either low differential controUed crystallization or mechanical size enlargement by continuous compacting and granulation. 

Special designs of direct rotaiy dryers, such as the Renneburg DehydrO-Mat (Edward Renneburg Sons Co.), are constructed especially to provide lower retention during the falling-rate diy-ing period for the escape of internal moisture from the solids. The DehydrO-Mat is a cocurrent diyer employing a smaU-diameter shell at the feed end, where rapid evaporation of surface moisture in the stream of initially hot gas is accomplished with low holdup. At the solids- and gas-exit end, the shell diameter is increased to reduce gas velocities and provide increased holdup for the solids while they are exposed to the partially cooled gas stream. 

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. 

Seawater services on onshore platforms, for drinking, washing and firefighting services on off-shore platforms Seawater lift pumps for cooling gas compressors on oil platforms... 

Fig. 5. The gas flow path of an AGR. Note the flow is reentrant, i.e., a fraction of the coot gas from the circulator flows up around the outside of the core entering the core from the top, then flows downward through the core, between the moderator and fuel element assembly, to the bottom where it mixes with the cool gas from the circulator and flows up the fuel channel inside the graphite fuel sleeves to the steam generators. Reprinted from [33], 1977 Wilmington Business Publishing, Dartford, U.K., with permission.

Hot gases can be handled easily and economically. The hot gas is cooled at the collector inlet so that the collector can be sized to handle the smaller cooled gas volume. 

We assume low velocity (constant pressure) mixing of the extra cooling gas mass flow (ifi) at absolute temperature T2 with the gas stream (of unit mass flow), which has been heated to the maximum temperature = Tg. From the steady flow energy equation, if both streams have the same specific heat (Cp), it follows that... 

Fig. 4.6 shows diagrammatically both (t )iu and (t )ici plotted against maximum temperature (in Fig. 4.6a). The efficiency of the cooled gas turbine (t )ici (point A) is less...

For two step cooling, now with irreversible compression and expansion, Fig. 4.7 shows that the turbine entry temperature is reduced from Ti. to by mixing with the cooling air i/ H taken from the compressor exit, at state 2, pressure p2, temperature T2 (Fig. 4.7a). After expansion to temperature Tg, the turbine gas flow (1 + lp ) is mixed with compressor air at state 7 (mass flow i/h.) at temperature Tg. This gas is then expanded to temperature T g. 

Fig. 5.2 shows that for the single-step cooled CBT plant at a given combustion temperature, the overall efficiency of the cooled gas turbine efficiency increases with pressure ratio initially but, compared with an uncooled cycle, reaches a maximum at a lower optimum pressure ratio. Fig. 5.3 shows that for a given pressure ratio the efficiency generally increases with the combustion temperature even though the required cooling fraction increases. 

Once the bed has been dried in this manner, it is necessary to flow c(X)l gas through the tower to return it to normal operating temperatures (about 100°F to 120°F) before placing it back in service to dehydrate gas. The cooling gas could either be wet gas or gas that has already been dehydrated. If wet gas is used, it must be dehydrated after being used as cooling gas. A hot tower will not sufficiently dehydrate the gas. 

A mixture of 3,000 scfin, dry basis, (14.7 psia and 60°F), 60% methane and 40% nitrogen is to be compressed from 16 psig to 3500 psig. Suction temperature is 90°E Intercoolers will use 85°F water cooling gas to 90°F, and the installation is essentially at sea level. The gas is saturated with water vapor. Five lb pressure drop is to be allowed for the interstage coolers. 

Hydrocarbons heavier than methane that are present in natural gases are valuable raw materials and important fuels. They can be recovered by lean oil extraction. The first step in this scheme is to cool the treated gas by exchange with liquid propane. The cooled gas is then washed with a cold hydrocarbon liquid, which dissolves most of the condensable hydrocarbons. The uncondensed gas is dry natural gas and is composed mainly of methane with small amounts of ethane and heavier hydrocarbons. The condensed hydrocarbons or natural gas liquids (NGL) are stripped from the rich solvent, which is recycled. Table 1-2 compares the analysis of natural gas before and after treatment. Dry natural gas may then be used either as a fuel or as a chemical feedstock. 

The function of the evaporator will be to cool gas, liquid or other product load. In most cases air or a liquid is first cooled, and this is then used to cool the load. For example, in a coldroom air is cooled and this air cools the stored produce and carries away heat leaking through the structure in a water chiller system, the water is circulated to cool the load, etc. 

Kozlov D. N., Pykhov R. L., Smirnov V. V., Vereschagin K. A., Burshtein A. I., Storozhev A. V. Rotational relaxation of nitrogen in argon collisional broadening of Q-branch components in coherent Raman spectra of cooled gas, J. Raman Spectr. 22, 403-7 (1991). 

TeGrotenhuis et al. studied a counter-current heat-exchanger reactor for the WGS reaction with integrated cooling gas channels for removal of the reaction heat. The computational domain of their 2-D model on the basis of the finite-element method... 

Figure 2.55 The effect of cooling gas flow rate and inlet temperature on CO conversion in the WGS reactor, as described in [165]. The cooling gas flow rate was varied for a fixed reaction gas flow rate and three different inlet temperatures were considered.

Heating Electrical resistance heating within the pgauze Product gas channel width cooling gas channel width 60 pm 90 pm... 

The coke oven is treated in the by-product plant to recover some important chemicals from it, after which the coke oven gas is used as gaseous fuel in the furnaces of steel plant. Coke oven gas is emitted at about 700 °C and is cooled to 80 °C with ammoniacal liquor (NH4OH) by spraying its goose neck. Here, the tar from the coke oven gas is condensed and separated in the separator. A further cooling of the gas to about 30 °C is accomplished in the primary cooler by water, and a further quantity of tar is condensed. The last traces of tar vapour present in the gas are removed in the next operation, which involves bringing the cooled gas to the electrostatic tar precipitator. This sends the tar-stripped gas to the... 

Chen et al. [70] suggested that temperature gradients may have been responsible for the more than 90 % selectivity of the formation of acetylene from methane in a microwave heated activated carbon bed. The authors believed that the highly nonisothermal nature of the packed bed might allow reaction intermediates formed on the surface to desorb into a relatively cool gas stream where they are transformed via a different reaction pathway than in a conventional isothermal reactor. The results indicated that temperature gradients were approximately 20 K. The nonisothermal nature of this packed bed resulted in an apparent rate enhancement and altered the activation energy and pre-exponential factor [94]. Formation of hot spots was modeled by calculation and, in the case of solid materials, studied by several authors [105-108],... 

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