CO2 Inlet Concentration

An experimental fluidized bed reactor has a 2.5 cm in diameter and 230 cm in height, and the distributor has 32 holes and each hole was 2 mm in diameter. 200 mesh net was put on the distributor to prevent particles from falhng down. The cyclone was made by standard proportion to collect fine particles. Air flow rate was controlled by a flow meter, CO2 (99.9%) flow rate was controlled by mass flow controller and then 10% CO2 inlet concentration was maintained by mixing in a mixing chamber. CO2 outlet concentration was also measured by CO2 analyzer (CD 95, Geotechnical instruments, England). 

The CO2 content in experiment 2 was increased to 30 vol% CO2. The increased CO2 inlet concentration resulted in a higher saturation temperature (-91.5 °C versus -94.5 °C), and, therefore, the packing storage capacity slightly increased. However, due to the higher... 

CO2 will move slower in this case, and a breakthrough is observed after approximately 350 seconds. The development of the H2O front is not influenced by the decrease in the CO2 inlet concentration, as shown in Figure 2.15d. 

The reduction in equipment size and required flows is cancelled out by this decrease. An inlet concentration of 5 vol% results in avoidance costs of 95.7/ton, which are substantially higher than that for the base case ( 52.8/ton). The increase in costs is especially high when going to even lower concentrations, which is related to the CO2 emissions caused by the extra power required. The ratio of the additional required power to the amount of CO2 captured becomes high at low concentrations. Figure 2.27 also shows that a CO2 inlet concentration of 15% results in lower avoidance costs. At even higher CO2 concentrations, recovery of the beds becomes more diflflcult, as the heat stored in the first zone of the bed during the capture step becomes insufficient. Additional heat has to be supplied to the process to recover CO2 in those cases. 

Duo et al. (1992) studied the kinetics of reaction of NO, NH3 and (excess) 02 in connection with a process to reduce NO, emissions. They used an isothermal PFR, and reported measured ratios Cno/c no.o and cNH3/cNH3,ofor each of several residence times, t. For T = 1142 K, and inlet concentrations Cno, 0 - 5.15X 10-3, Cnh3,o= 8.45-10-3, and Co2>0 = 0.405 mol m-3, thee obtained results as follows (as read from graphs) ... 

From Table 8.3-3 it is evident that the recycled CO2 (stream C02IN1) is not pure. To assure a THF flow rate of 5.76 kg/h in the precipitator, the THF make-up has to be less than this amount. As a consequence, the polymer solution injected in the precipitator is more concentrated than was tested in the pilot plant [4], In this particular case, the different inlet concentration should not make any difference in the precipitate morphology. However, in general, changing the polymer concentration can lead to the formation of either microparticles of small size or to polymer fibres [5]. 

Fig. 2. Bifurcation diagrams describing the behavior of the CO/O2 system as CO pressure is varied, (a) CO2 effluent concentration (which is proportional to the reaction rate) as a function of CO inlet concentration at four different temperatures in an atmospheric reactor over a pulverized Pt/silica/alumina catalyst. Oscillation existence regions are indicated by vertical hatching (from Ref. 98). (b) Work function maxima and minima plotted as a function of CO pressure at 540 K on Pt(l 10). The periodicity of the oscillations (as indicated above the curve) is seen to increase as CO pressure is decreased. (From Ref. 231.)...

Fig. 26. Effect of CO2 inlet gas concentration on IhS breakthiough time. Gas composition 0.5 % H2S, 0-50% COj, balance N2, T=823K, P=1 atm [107]. Reprinted wth permission from M.P. Cal, B.W. Strickler and A. A. Lizzio. Carbon, 38 POOO) 1757...

Fig. 12.14 The effect of H2S inlet concentration on the permeate stream gas concentration flux of membrane GTC-6. Feed consisting of 51% H2, 21% H2O, 26% CO2, and 2% CO at psia and 350°C...

The experimentally measured reactor inlet concentrations were used to produce model predictions for the concentration responses at the reactor outlet. The reactor inlet concentrations of N2, CO2, N2O and NO2 were always kept zero. 

Continuous fermentations have also been used to improve PDO productivity. In a continuous Klebsiella pneumoniae fermentation, when glycerol was added in excess at an inlet substrate feed of approximately 74 g/1, PDO and various by-product acids were the major products. Under glycerol limitation (an inlet concentration of approximately 15 g/1), ethanol and hydrogen were the major products. The effect could be monitored by the evolution rates of hydrogen and C02- In glycerol excess, CO2... 

The reaction takes place at S00°-800°F, depending on the coal type and SO2 inlet concentration. Ash and unreacted coal are removed from the bottom of the reactor, and can be burned in the boiler or disposed of with the boiler ash. The reactor off-gas contains elemental sulfur, H2S, CO2. COS, CS2, and H2. A downstream condenser removes the elemental sulfur. The uncondensed gas, typically containing 6% H2S and 4% SO2, is sent to an incinerator, and the incinerator off-gas is returned to the FGD system. Ninety to ninety-five percent conversion of the SO2 to elemental sulfur and 99.95% sulfur purity have berai achieved (Behrens et al., 1984). 

Show the calculations leading to the statement in Ex. 2.4 that reducing the inlet concentration of CO2 from 12 mol % to 0.039 mol % increases the required reversible work by a factor of 2.9. 

The catalysts were tested for their CO oxidation activity in an automated microreactor apparatus. The catalysts were tested at space velocities of 7,000 -60,000 hr . A small quantity of catalyst (typically 0.1 - 0.5 g.) was supported on a frit in a quartz microreactor. The composition of the gases to the inlet of the reactor was controlled by mass flow controllers and was CO = 50 ppm, CO2 = 0, or 7,000 ppm, HjO = 40% relative humidity (at 25°C), balance air. These conditions are typical of conditions found in spacecraft cabin atmospheres. The temperature of the catalyst bed was measured with a thermocouple placed half way into the catalyst bed, and controlled using a temperature controller. The inlet and outlet CO/CO2 concentrations were measured by non-dispersive infrared (NDIR) monitors. 

The MCFC has also been tested as a true concentrator, with electric power supplied instead of H2 [32], With inlet C02 at 0.25% (in air), the outlet could be brought as low as 75 ppm, albeit with the rather low current efficiency of 40% (based on 1 mol CO2/2 F). The parasitic current is due to transport of oxyanions (Of " or 02) which are discharged as molecular oxygen at the anode. For lower C02 utilization, say below 80%, the polarization is quite acceptable, as seen in Fig. 23. Application to manned spacecraft, however, is handicapped by the high temperatures needed (> 500 °C). 

An application for multiplexed diode-laser sensors with a potentially large impact is for measurements of important parameters at several locations in a gas turbine combustion system. In this example, illustrated schematically in Fig. 24.1, the multiplexed diode lasers are applied for simultaneous absorption measurements in the inlet, combustion, afterburner, and exhaust regions. For example, measurements of O2 mass flux at the inlet may be determined at the inlet from Doppler-shifted O2 absorption lineshapes near 760 nm. Measurements of gas temperature and H2O concentrations in the combustion and afterburner regions may be determined from H2O lineshape measurements near 1.4 pm. Finally, measurements of velocity, temperature, and species concentrations (e.g., CO, CO2, unburned hydrocarbons) may be recorded in the exhaust for the determination of momentum flux (component of thrust) and combustor emissions. 

The differences in reactions at different reactor positions was studied by Springmann et al. who reported product compositions for ATR of model compounds as a function of reactor length in a metal monolith coated with a proprietary noble metal containing Rh. As expected, the oxidation reactions take place at the reactor inlet, followed by the SR, shift, and methanation reactions. Figure 32 shows the product concentration profiles for a 1-hexene feed, which are typical results for all the fuels tested. These results show that steam, formed from the oxidation reactions, reaches a maximum shortly after the reactor inlet, after which it is consumed in the shift and reforming reactions. H2, CO and CO2 concentrations increase with reactor length and temperature. In this reactor, shift equilibrium is not reached, and the increase in CO with distance from the inlet is the net result of the shift and SR reactions. Methane is... 

Fig. 14.12 Stack concentrations of UHC as function of NO in the exhaust of a lean-burn natural gas fired engine [234], The following conditions can be assumed for the exhaust system inlet composition CH4 = 4410 ppm, C2H6 = 490 ppm, O2 = 8.5%, H2O =13%, CO2 = 6.5%, NO = 10-1813 ppm, NO2 = 3-544 ppm, balance nitrogen temperature = 680°C, reactor residence time = 210 ms, pressure = 1.7 bar.

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