Carbon feed rate

The dynamic and steady-state characteristics of a shallow fluidized bed combustor have been simulated by using a dynamic model in which the lateral solids and gas dispersion are taken into account. The model is based on the two phase theory of fluidization and takes into consideration the effects of the coal particle size distribution, resistance due to diffusion, and reaction. The results of the simulation indicate that concentration gradients exist in the bed on the other hand, the temperature in the bed is quite uniform at any instant in all the cases studied. The results of the simulation also indicate that there exist a critical bubble size and carbon feed rate above which "concentration runaway" occurs, and the bed can never reach the steady state. 

The effect of carbon feed rate, as expressed in terms of the carbon feed rate function, on the steady-state carbon concen-... 

It can be seen that the shapes of the concentration profiles remain almost unchanged. This appears to indicate that the carbon feed rate has a negligible effect on the concentration gradient it only influences the average amount of carbon in the bed. This result was also observed in a previous study (11). 

In Figure 7 the effects of carbon feed rate and bubble size on the steady-state average carbon concentration are shown. The existence of critical bubble size for a fixed carbon feed rate can clearly be observed in this figure. It can also be observed that a critical carbon feed rate exists above which concentration runaway occurs, and a stable or steady-state condition can not be reached for a given bubble size. The value of the critical feed rate increases with a decrease in the bubble size. Under the critical condition, the maximum attainable rate of oxygen transfer from the bubble phase to the emulsion phase is reached, and it becomes the rate determining step for combustion as explained previously. To increase the carbon feed rate to a fluidized bed combustor, either the oxygen concentration in the air (gas) stream or the rate of mass transfer between the bubble and emulsion phase needs to be increased. ... 

Figure 6. Effect of carbon feed rate on the (---------) steady-state carbon concentration and (---------------) bed temperature profiles in the type A combustor...

Figure 7. Effect of carbon feed rate and bubble size on the steady-state average carbon concentration in the type A combustor...

A non-isothermal dynamic model has been developed for a shallow fulidized bed combustor, which can be used to predict, at least qualitatively, the transient and steady-state characteristics of such systems. Parametric studies have been conducted to examine the effects of excess air flow rate, bubble size and carbon feed rate. It has been shown that an appreciable carbon concentration gradient does exist in the bed. This explains why it is necessary to use multiple feed points in large fluidized bed combustors. A surprising result obtained is that the temperature iii the bed is essentially uniform under all conditions studied even though the carbon concentration is not uniform laterally. 

It has been illustrated that the bubble size has strong influences on both the transient and steady-state carbon concentrations. The effects of the carbon feed rate, expressed as the carbon feed rate function on the steady-state carbon concentration and bed temperature profiles are negligible under the conditions... 

Multiple hearth furnace for regeneration of adsorbent carbon furnace only including drive and motor, exit screw conveyor and inlet feeder. FOB cost = 6 325 000 at carbon feed rate = 1 kg/s with n = 0.60 for the range 0.02-10 kg/s. TM = 2.1-2.2. L/M = 0.3. 

The pilot plant duct provided a 2 second residence time. For most tests, the duct mercury removal was between 9 and 19%, and was independent of carbon type, carbon feed rate, temperature, and mercury species. AC-C showed a somewhat larger in-duct HgCh removal (36%). These results indicated that removal in the duct is limited by bulk gas mass transfer. 

The devolatilized coal particles are transported to a direct-fired multihearth furnace where they are activated by holding the temperature of the furnace at about 1000°C. Product quaUty is maintained by controlling coal feed rate and bed temperature. As before, dust particles in the furnace off-gas are combusted in an afterburner before discharge of the gas to the atmosphere. Finally, the granular product is screened to provide the desired particle size. A typical yield of activated carbon is about 30—35% by weight based on the raw coal. 

SNR s fluidized-bed cogeneiation system is an early example of the commercial development of AFBC technology. Foster Wheeler designed, fabricated, and erected the coal-fired AFBC/boHer, which generates 6.6 MWe and 37 MW thermal (also denoted as MWt) of heat energy. The thermal energy is transferred via medium-pressure hot water to satisfy the heat demand of the tank farm. The unit bums 6.4 t/h of coal and uses a calcium to sulfur mole ratio of 3 to set the limestone feed rate. The spent bed material may be reiajected iato the bed as needed to maintain or build bed iaventory. The fly ash, collected ia two multicyclone mechanical collectors, may also be transferred pneumatically back to the combustor to iacrease the carbon bumup efficiency from 93%, without fly ash reiajection, to 98%. 

Temperature, pH, and feed rate are often measured and controlled. Dissolved oxygen (DO) can be controlled using aeration, agitation, pressure, and/or feed rate. Oxygen consumption and carbon dioxide formation can be measured in the outgoing air to provide insight into the metaboHc status of the microorganism. No rehable on-line measurement exists for biomass, substrate, or products. Most optimization is based on empirical methods simulation of quantitative models may provide more efficient optimization of fermentation. 

Loss of throughput. The combustion of hydrogen to water produces 3.7 times more heat than the combustion of carbon to carbon dioxide. The increase in the regenerator temperature caused by excess hydrocarbons could exceed the temperature limit of the regenerator internals and force the unit into a reduced feed rate mode of operation. 

As was noted for experiments HGR-12, HGR-13, and HGR-14, the rate of catalyst deactivation increased as the fresh gas feed rate increased. It is possible that higher rates of carbon deposition and metal sintering occur at the higher feed rates with resultant higher deactivation rates. 

NOTE When calculating amine feed rates, in theory some allowance should be made for the production of carbon dioxide at high pressures. However, because of the recycling action provided by most amines and other variables, in practice this allowance calculation becomes a meaningless exercise. 

When the filming amine condenses, the hydrophilic polar radical of the molecule (the head) adsorbs onto the metal surface and the hydrophobic, long chain (the tail) is directed at a 90° angle of inclination away from the metal surface. Provided the feed rate is adequate, the critical concentration is eventually reached and a continuous monomolecular surface film is formed. At this stage, the physical size of the interstices between the polar groups is smaller than the molecules of water, carbon dioxide, or oxygen, and these molecules are thus physically prevented from reaching the metal surface. 

Time courses of dehydrogenation activities with carbon-supported platinum catalyst under superheated liquid-film conditions in laboratory-scale continuous operation. Catalyst platinum nanoparticles supported on granular activated carbon (Pt/C, 5 wt-metal%), 1.1 g. Feed rate of tetralin 0.5 mL/min (superheated liquid-film conditions). Reaction conditions boiling and refluxing by heating at 240°C and cooling at 25°C. (Reproduced from Hodoshima, Sv Shono, A., Satoh, Kv and Saito, Yv Chem. Eng. Trans8,183-188, 2005. With permission.)... 

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