Ammonia production, specific rate

The above are equilibrium reactions, and their successful exploitation requires that they be carried out under conditions in which the equilibrium favors the product. Specifically, this requires that the adsorbed species in Reactions (D)-(I) not be held so tightly on the catalyst surfaces as to inhibit the reaction. On the other hand, strong interaction between adsorbate and catalyst is important to break the bonds in the reactant species. Optimization involves finding a compromise between scission and residence time on the surface. Although we are especially interested in metal surfaces, those constituents known as promoters in catalyst mixtures are also important. It is known, for example, that the potassium in the catalyst used for the ammonia synthesis shifts Equilibrium (F) to the right and also increases the rate of Reaction (D) by lowering its activation energy from 12.5 kJ mole to about zero. 

For most cell lines it is found to increase with the specific growth rate. Thus the specific rates of lactate production can be expressed as a function of p by Equation 4.3.4, which contains two parameters the non-growth-associated specific lactate production rate, mLac (mmol lactate 10 cells h ), and the lactate to biomass stoichiometric yield, (mmol lactate 10 cells). A similar expression is often applicable to the specific rate of ammonia production (Equation 4.3.6) and antibody secretion (Equation 4.3.7). 

Linear relationships are also apphcable to the specific rates of lactate, ammonia and antibody production ... 

Specific ammonia production rate (mmol 10 cells h )... 

The interior pellet pH is a function of the urease loading and the urea concentration profile in the pellet. The for urease hydrolysis of urea is 2.9 mM, [29] so with 0.01 M (10 mM) urea, we are initially consuming urea at approximately 78% of Fmax at the surface of the pellet. Increasing the bulk concentration of urea will result in increased ammonia production and an increase in the interior pellet pH. Depending upon whether the interior pH is above or below the pH for optimum XI activity, an increase in interior pH will decrease or increase the rate of xylose isomerization. To achieve optimal isomerization in the co-immobilized pellet system, the urea concentration in the bulk solution can be optimized for a specific urease loading and should be maintained at a constant concentration throughout the isomerization to allow maximal, constant XI activity. 

The steam specification stipulates the need for superheated steam at 380°C and 4000 kPa. This medium-pressure product is of sufficient quality for the plant steam-turbine and ammonia superheater, with the remaining portion to be sold to another plant. A heat balance over the entire steam-production circuit concludes that this steam product may be produced at the rate of 5775 kg/h. This result determines the required heat duty for the steam superheater as 585 kW. 

Figure 4.3.2 Evolution with time of the specific growth and death rates (a), the specific consumption rates of glucose (b) and glutamine (c) and the specific production rates of lactate (b), ammonia (c) and monoclonal antibodies (d) in VO 208 batch culture (data from Figure 4.3.1).

Figure 4.3.3 Relationships between specific glucose (a) and glutamine (c) consumption rates, lactate (b), ammonia (d) and monoclonal antibody (e) production rates and specific growth rate during lag and growth phases of VO 208 batch culture.

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