Carbon and energy balances

The adsorption of hydrocarbons by activated carbon is characterized by the development of adsorption isotherms, adsorption mass and energy balances, and dynamic adsorption zone flow through a fixed bed. 

Succinic add source of carbon and energy improves metabolic balance between carbon flux from glucose and oxidation throgh TCA cyde. 

Let us construct mass and energy balances on the particle, which we assume to be a sphere of pure carbon of radius R. The reaction is... 

Proteln-conq>lexlng polyphenols are broadly effective against herbivores, especially those not specifically adapted to eat plants containing polyphenols (47). They may constitute 10% or more of the leaf dry weight (12, 37, 44), and this requires allocation of significant amounts of carbon and energy to their construction. The use of limited reserves for such quantitative defenses must be balanced against the requirements of rapid canopy development and new shoot extension. 

The fermentation of 1,3PD from glycerol (see Fig. 8.8c) was discovered in the late 19th century [60]. It has since been found that a considerable number of bacteria can use glycerol as a source of carbon and energy under anaerobic conditions and the reaction pathways have been elucidated [61]. Out of every three molecules of glycerol, one is oxidized, phosphorylated into DHAP and subsequently metabolized via the glycolysis pathway and the TCA cycle the other two are converted into 1,3PD, to maintain redox balance (see Fig. 8.9), via dehydration and NADH-driven reduction. 

Recently we found [35] that Methanosarcina barkeri can grow on pyruvate as sole carbon and energy source after an adaptation period of several weeks in the presence of pyruvate. During growth only CO2 and CH4 were found as end products. H2 was not formed. The fermentation balance during growth on pyruvate can best be described by the following partial reactions ... 

In cases where heat recovery was practiced, the overall thermal efficiency was assumed to be 507o. The major heat loss was the hot flue gases, but other losses included sensible heat plus the unburned fixed carbon in the ash, and radiation losses from the incinerator unit. Figure 1 shows a summary of the mass and energy balances for a metric ton refuse input to the incinerator. Some auxiliary fuel consumption was assumed (based on discussions with system designers and the actual operating experience of users) for startup, temperature control, and pilot burners in the secondary combustion chambers. 

The final mass and energy balance are shown in the stream table (Table 7.2). By checking the mass balances around each unit, you can see that they balance except for a small discrepancy between streams 9 and 10. The hydrogen flow rate is off by 0.05 lb mol/h, compared with a total flow of 1490 lb mol/h. The overall conversion (100 mol nitrogen to 197.5 mol ammonia) is reasonable. The rest of the raw materials are lost. Most of the carbon dioxide goes out in the ammonia so perhaps the purge stream was not necessary. 

Material and energy balances are as well the basis of ecological assessments. These should not only focus on possible achievements concerning reductions of greenhouse gases or primary resource consumptions but also on other environmental impacts too. Life-cycle assessment (LCA, see ISO 14040 and 14044) is the tool to do this. LCA quantifies and evaluates a number of environmental impacts caused by products, production systems or services. Contrary to other concepts, Uke for example, the carbon footprints or CO2 abatement costs LCA provides the possibility to cover ecological issues more comprehensively and differentiated. 

Exopolysaccharide production ntay be improved by tiie provision of various organic con xments, otiier Aan the main carbon and energy source. These can improve growth of the production organism (growth factors) and/or directly enhance the synthesis of exopolysaccharide. Additions that improve polymer yield include tricarboxylic add (TCA) cyde intermediates, which are thou t to improve metabolic balance between carbon flow frcnn carbohydrate substrate through the catabolic pathwaj arul oxidation through the TCA cyde. 

Problem 9.5 In the process below, all streams are mixtures of methane/carbon monoxide with molar compositions indicated on the flow chart in Figure q-2. Calculate the material and energy balances and perform an entropy analysis of the mixing point, the heat exchanger, and of the entire process. The heat capacities of methane and carbon monoxide are Cpa = 40.8 J/mol K, and Cpb = 29.4 J/mol K, respectively. 

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