Carbon mass balance

That the carbon mass balance was not perfect in the initial period of Stage 1 may be interpreted as due to the formation of polymeric compounds on the catalyst surface. The formation of C02 and CO in Stage II is considered as a result of decomposition of these products. The consistency for the total carbon balance through Stages I and II suggests that the products on the catalyst surface were completely oxidized to C02 and CO. 

In each run, one channel was loaded with graphite or quartz and used as bypass reference, and one channel was loaded with reference catalyst (commercial or proprietary) for comparison. The temperature was varied from 100 to 250 °C, with a 5 min isotherm every 20 °C. Reaction products were monitored by fast gas chromatography (micro-GC) and on-line mass spectrometry (MS). The carbon mass-balance was calculated by monitoring the effluents from the bypass reactor and kept between 98 and 102%. 

Dillon, P. J., and L. A. Molot. 1997a. Dissolved organic and inorganic carbon mass balances in central Ontario lakes. Biogeochemistry 36 29-42. 

This provides an explanation for the unaccounted glucose loss during the acid hydrolysis process. It also gives an explanation for the generally low yield for dilute acid hydrolysis processes and previously unclosed carbon mass balance. 

The reactor was fed with 1.6 Nl/min of 1000, 2000 and 4000 ppm of methane in air. The mixtures were obtained by mixing N-50 synthetic air and 2.5 % (vol.) CH4 in N-50 synthetic air (Air Products). 40 ppm of SO2 (from a cylinder of 370 ppmV SO2 in N-50 synthetic air. Air Products) were added when the effect of sulphur on the catalysts activity was studied. Flow rates were controlled by calibrated mass flow controllers (Brooks 5850 TR). Exhaust gas was analysed by gas chromatography (Hewlett Packard HP 5890 Series II). Methane in the inlet and outlet streams was analysed using a 30 m fused silica capillary column with apolar stationary phase SE-30, and a FID detector. CO and CO2 were analysed using a HayeSep N 80/100 and a molecular sieve 45/60 columns connected in series, and a TCD detector. Neither CO, nor partial oxidation were detected in any experiment, the carbon mass balance fitting in all the cases within 2%. Methane conversions were calculated both from outlet methane and CO2 concentrations, being both values very close in all the cases. Methane (2000 ppmV) and SO2 (40 ppmV) concentrations have been selected because they are representative of industrial emissions, such as coke oven emissions. 

The soil carbon mass balance is hypothesized to be, for grassland soils, a function of... 

A common approach to estimating the contribution of microorganisms to Fe(III) and Mn(IV) reduction based on carbon mass balance. Total anaerobic microbial respiration is estimated by measuring the carbon mineralization rate (i.e., Y.CO2 + CH4 production). The carbon that was respired by SO -reducing bacteria and methanogens is subtracted from the total, and the difference is assumed to be the contribution of Fe(III)- and Mn(IV)-reducing bacteria (Canfield et al., 1993b Thamdmp, 2000). Typically, the contribution of aerobic metabolism to carbon... 

Carbon mass balance Product composition (dry basis) H2 CO CO2... 

The carbon mass balances for each of the six compartments follow the development in Chapter 2. For example, for the carbon in the atmosphere, we have... 

Under UV light, all forms of titania oxidize propane to carbon dioxide. The conversion was followed by periodical illumination with dark periods of 5 min during which propane was found to be the only weakly adsorbed in the dark. Analysis of the carbon mass balance (Figure 4.2) obtained by online MS indicates the formation and accumulation of intermediate reaction products at the catalyst surface whose concentration increases with reaction time in the order anatase > rutile >= mixed anatase/rutile > P25. Taking into account the specific surface areas, the turn over number (TON) increases in the order anatase (9) rutile (15) P25 (112). The activity of titania P25 is higher by a factor of 10 compared to rutile, anatase, or their physical mixture. 

These branching ratios were only inferred from end product analysis [3] and thus could be questioned since the carbon mass balance was usually very poor during the oxidation of aromatics (no more than 60 % of the initial reactant recovered in the collected end products). We have measured the branching ratios by a direct spectroscopic method based on a monitoring of the benzyl radical relative concentrations by LIF. 

Cumene (0.25 kPa) diluted in Argon was fed with a constant flow of 20 ml/min (STP) into the reactor, while the flow rate of the jet stream was varied. Samples were taken with a syringe and analysed in a GC. Carbon mass balances were better than 95%. The extrudates were crushed to three different sizes (diameter = 0.15, 0.085, 0.065 cm). The reactions were carried out for 3 hrs. The extrudates were calcined at 480°C in air for 12h between experiments. Kinetic studies with the powder form (0.5 pm) were measured in a plug flow reactor at a constant contact time (WHSV=0.7 g cat/(g hr))... 

The carbon mass balance (2.1) takes into account the mixing of solids and the combustion reaction and is of reaction diffusion type with Neumann boundary conditions, i,e. the value of the normal derivative dCc/dn of the carbon concentration on the boundary is prescribed. The first two terms in the enthalpy balance (2.3) express the enthalpy flux due to the mixing of solids in the bed, the others the flue gas enthalpy flux, the heat sink due to the heat exchanger tubes and the heat source caused by the combustion. The balance is of convection diffusion type with third type Dirichlet-Neumann boundary conditions, i.e. the temperature values on the boundary depend on the corresponding gradients. Finally, the oxygen balance (2.2) considers the oxygen flux in upward direction and the combustion reaction. This ODE is explicitly solvable in dependence of the carbon concentration Cc and the temperature T ... 

Is there an explanation for this strong deviation In the model (2.1)-(2.3) the fuel feed is considered within the boundary condition of the carbon mass balance (2.1). Technically this corresponds to the feed of dry coal into the reactor through the sidewall. On the contrary in the existing PFBC plants coal is fed into the reactor as a coal water mixture (CWM) with a water... 

The second effort one was to create a benthic ecosystem model and to combine it with the seafloor plume diffusion and resedimentation model. The ecosystem model was created based on a carbon mass balance in the bottom layer. Then a series of preliminary test calculations under the resedimentaion and the direct desfiuction conditions were conducted introducing the JET and DIETS data, respectively. 

In a similar way a carbon mass balance can be made for the cell where the CC and the carbon dust (CD) formation can be determined independently of the CE [2-5]. The theoretical carbon consumption (CQj,) per second can be calculated by Faraday s law ... 

Figure 5. (a) Photocatalyzed mineralization of perchloroethylene (PCE) vs. time. PCE (O), product CO2 (X). Solid curves kinetic model for PCE disappearance carbon mass balance for CO2 appearance. [PCEq] = 207 juM. (b) Photocatalyzed benzene mineralization vs. time. Benzene ( ), product CO2 (X). Solid curves kinetic model for benzene disappearance assuming no one, one, and two important intermediates. Taken from [38]. 

It is easier to achieve a carbon mass balance by temporally separating the peroxidation process from the biodegradation process. As discussed in Chapter 3, several workers have successfully applied this technique to degradable rubbers and polyolefins. CO2 formation begins abiotically during thermal (and photo-) oxidation and continues during the bioassimilation of the polymer. In the case of rubbers it has been found possible to correlate mass-loss with the mass of the protein produced by the polymer in soil. 

Liquid Fuel Crossover Many DAFCs suffer large performance losses from crossover. In the case of liquid DAFCs, the crossover current can be determined from chemical species measurement of the cathode effluent gas. Since the product of oxidation of methanol or other fuel crossover is mostly carbon dioxide and carbon monoxide, measurement of these gases along with any residual crossover fuel vapor and minor species can be used to perform a carbon mass balance and deduce the crossover fuel current. 

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