Closed carbonate system

Controlled cutting and opening of closed carbon systems Direct applications of CNTs (requires 20-100 nm in length) Inner filling and impregnation of CNTs with metal nanoparticles and complexes... 

Several reaction pathways are built into the FREZCHEM model including (1) temperature change, (2) evaporation, (3) pressure change, (4) equilibrium or fractional crystallization and, for gas hydrates, (5) open or closed carbon systems, and (6) pure or mixed gas hydrates. Under the temperature change option, the user can specify the upper and lower temperature range and a decremental temperature interval (AT) at which equilibrium at a fixed pressure is calculated (e.g., 298.15 to 253.15K with AT = 5 would result in... 

The number of components under Mass balance is nine, which means eight independent components for this system. Had we specified a closed carbon system for both CO2 and CH4, then the total number of independent components would have been ten instead of eight because the masses associated with CO2 and CH4 would then be fixed. 

Figure 7.8. Model la. Saturation values of Me for closed carbonate system with Cj = constant (= 3 x 10" M). The diagram gives the maximum soluble [Me ] as a function of pH for a given Cj. Dashed portions of the curves indicate conditions under which MeC03(s) is not thermodynamically stable. The inset gives the essential features for the constmction of the diagram.

A closed carbonate system is defined as one in which the carbon dioxide (carbonic acid) initially present in the water is not replenished as it is consumed in carbonate mineral dissolution. This may simply reflect that soil moisture/infiltration is charged with CO2 chiefly in the A horizon of the soil, whereas carbonate mineral dissolution by H2CO3 takes place at greater depths in the soil C horizon or below the water table in the absence of further sources of carbon dioxide. (There may be, however, sources of additional CO2 at depth, including pollution. See Chap. 5.)... 

Sec. 6.6 Open and Closed Carbonate Systems This can be integrated with the result... 

TABLE 4-8 Comparison of Composition and pH of Open and Closed Carbonate Systems... 

Let us now turn our attention to the calculation of solution composition following the addition of strong acid or strong base to the closed carbonate system. The results and methods that we derive from this exercise will... 

An interesting and novel use of a soHd desiccant, the reduction of cold condensate corrosion in automotive exhaust systems, illustrates a hybrid closed—open system. Internal corrosion occurs in mufflers when the water vapor in the exhaust condenses after the engine is turned off and the muffler cools. Carbon dioxide dissolves in the condensate to form an acidic soup. In an essentially closed static drying step, an acid- and heat-resistant desiccant located in the muffler adsorbs water vapor from the exhaust gas as it cools to prevent formation of corrosive acidic condensate. When the engine is restarted, the system becomes open, and the desiccant is regenerated by the hot exhaust gas to be ready for the next cooldown step (19). 

As you might have already gathered, the majority of industrial fermentations are batch processes. In closed batch systems, the growth medium is inoculated with cells and growth and product formation is allowed to proceed until the required amount of conversion has taken place. After harvesting the culture the vessel is cleaned, sterilised and filled with fresh medium prior to inoculation. For some processes, addition of all the feedstock prior to inoculation, as is done in closed batch fermentations, is undesirable and it is preferable to incrementally add the carbon source as the fermentation proceeds. Such a process is known as fed-batch culture and the approach is often used to extend the lifetime of batch cultures and thus product yields fed-batch cultures are considered further in Section 2.7.4. 

Continuous Stirred Tanks with Biomass Recycle. When the desired product is excreted, closing the system with respect to biomass offers a substantial reduction in the cost of nutrients. The idea is to force the cells into a sustained stationary or maintenance period where there is relatively little substrate used to grow biomass and where production of the desired product is maximized. One approach is to withhold some key nutrient so that cell growth is restricted, but to supply a carbon source and other components needed for the desired product. It is sometimes possible to maintain this state for weeks or months and to achieve high-volumetric productivities. There will be spontaneous cell loss (i.e., kd > 0), and true steady-state operation requires continuous purging and makeup. The purge can be achieved by incomplete separation and recycle... 

In this chapter I explained how isotope ratios may be calculated from equations that are closely related, but not identical, to the equations for the bulk species. Extra terms arise in the isotope equations because isotopic composition is most conveniently expressed in terms of ratios of concentrations. I illustrated the use of these equations in a calculation of the carbon isotopic composition of atmosphere, surface ocean, and deep ocean and in the response of isotope ratios to the combustion of fossil fuels. As an alternative application, I simulated the response of the carbon system in an evaporating lagoon to seasonal changes in biological productivity, temperature, and evaporation rate. With a simulation like the one presented here it is quite easy to explore the effects of various perturbations. Although not done here, it would be easy also to examine the sensitivity of the results to such parameters as water depth and salinity. 

In a closely related system, Huffmann et al. have reported that when a toluene solution of (tj 5-C5H5 )2Ti(CO)2 is treated with a mixture of hydrogen and carbon monoxide at 150°C, methane, but no methanol, is produced (41). 

Another source of divergence is the use of different models for the aqueous carbonate systems. Precipitation and dissolution experiments can be carried out in closed or open systems and various ways of pH-adjustments (see 8.2). 

Although equilibrium was not established, it was more closely approached in the KCl-KBr-H20 system than in carbonate systems. For example, in a similar analysis of the strontianite-aragonite solid solution system (4 ), it was found that the experimental distribution coefficient for Sr substitution from seawater into aragonite is 12 times larger than the expected equilibrium value. Most of the distribution coefficients for the KCl-KBr-H20 system are within a factor of two of the equilibrium value, but clearly not at equilibrium. Considerable caution should be exercised before reaching the conclusion that equilibrium is established at relatively low temperatures in other solid solution-aqueous solution systems. 

The integrated function of the vasculature and heart, as a closed circulatory system, supplies nutrients and oxygen to critical organs and removes metabolic wastes and carbon dioxide. This integrated system results from the careful control of cardiac output, arterial blood pressure (systolic and diastolic pressures integrated to derive mean arterial pressure), and systemic vascular resistance, thereby maintaining blood perfusion through... 

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