Reaction fermentative volume

When production volume is sufficient, it is economical to build one plant for one product. Batch production in a single unit may be limited by maximum reactor size. Holdups of greater than 20,000 gal are handled in separate parallel reactors. To use common upstream and downstream facilities, the reactors may not be operated simultaneously but on overlapping schedules. When long reaction times cannot be avoided, the reaction sections operate batch wise however, feeding reactants and recovering products may be continuous for economic reasons. This practice is typical of many processes, such as the saponification of natural fats in intermediate quantities. In the production of ethanol by fermentation, two reactions (saccharification and fermentation) are operated on a batch basis, while hydrolysis (conversion of starch to dextrin) and product recovery by distillation are continuous. 

The chemical reactions and their conversions are shown in Tables 15.10 and 15.11. A typical value for the residence time is 7 days, giving a total fermentation volume of about 60000 m3. This can be arranged in 3 trains, with 5 reactors of 4000 m3 in each train. 

Arthur Humphrey Integration is key here. I say that because I m stunned to hear Jim Douglas talk about these new separatory reactors. We heard about the first extractive fermentation in 1970, assuming that you will consider a fermentation a reaction. Even the first volume of Richardson and Coulson has an example of choosing the optimum ratio of extractant to reactant. I don t think that s new. 

Another variation which attempts to place the test upon a semiquantitative basis involves carrying out the reaction in a Smith fermentation tube. This enables one to obtain a rough idea of the volume of gas formed, but it can be misleading unless a time limit is imposed and the skins are removed. 

There is an interior optimum. For this particular numerical example, it occurs when 40% of the reactor volume is in the initial CSTR and 60% is in the downstream PFR. The model reaction is chemically unrealistic but illustrates behavior that can arise with real reactions. An excellent process for the bulk polymerization of styrene consists of a CSTR followed by a tubular post-reactor. The model reaction also demonstrates a phenomenon known as washout which is important in continuous cell culture. If kt is too small, a steady-state reaction cannot be sustained even with initial spiking of component B. A continuous fermentation process will have a maximum flow rate beyond which the initial inoculum of cells will be washed out of the system. At lower flow rates, the cells reproduce fast enough to achieve and hold a steady state. 

Previous chapters in this volume have been concerned with chemical reaction engineering and refer to reactions typical of those commonplace in the chemical process industries. There is another class of reactions, often not thought of as being widely employed in industrial processes, but which are finding increasing application, particularly in the production of fine chemicals. These are biochemical reactions, which are characterised by their use of enzymes or whole cells (mainly micro-organisms) to carry out specific conversions. The exploitation of such reactions by man is by no means a recent development—the fermentation of fruit juices to make alcohol and its subsequent oxidation to vinegar are both examples of biochemical reactions which have been used since antiquity. 

Several special terms are used to describe traditional reaction engineering concepts. Examples include yield coefficients for the generally fermentation environment-dependent stoichiometric coefficients, metabolic network for reaction network, substrate for feed, metabolite for secreted bioreaction products, biomass for cells, broth for the fermenter medium, aeration rate for the rate of air addition, vvm for volumetric airflow rate per broth volume, OUR for 02 uptake rate per broth volume, and CER for C02 evolution rate per broth volume. For continuous fermentation, dilution rate stands for feed or effluent rate (equal at steady state), washout for a condition where the feed rate exceeds the cell growth rate, resulting in washout of cells from the reactor. Section 7 discusses a simple model of a CSTR reactor (called a chemostat) using empirical kinetics. 

Another problem with conventional fermenters concerns foaming. In traditional systems, the introduction of large quantities of gas into the vigorously agitated fermentation liquor often produces great quantities of foam in the reaction vessel. Biological reactors are particularly susceptible to foaming because of the surfactant properties of most biomolecules. This foam severely limits the usable volume of the vessel and can render the fermentation process inoperable and microbially contaminated when the gas flow exit lines become filled with foam. All of these problems have a substantially adverse influence upon the yield and cost-eflectiveness of conventional fermentation processes. 

Nowadays large volumes of ethanol are made by the reverse reaction, namely acid catalysed hydration of ethylene. However, concern with carbon emissions from other processes and the fact that ethanol is made in very large volumes by fermentation processes, is leading to a new interest in the concept for the production of renewable ethylene and hence renewable plastic. The equilibrium of the reaction is shown in Figure 10.8. 

PROP Light yellow-amber liquid. Pleasant to fruity odor. D 0.923-0.935 15.56° 47-53% of ethanol, by volume, flash p 80.0°F (CC). Made by distillation of fermented malted grains, e.g., corn, rye, or barley. After distillation, whiskey is aged in wooden containers for up to several years. The aging extracts such components as acids and esters from the wood and promotes oxidation of components of raw whiskey and some reactions between organic components to form new flavors. 

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