Laboratory-scale operations

A third factor affecting the quantity to be processed is the scale of the processing operation. A laboratory-scale operation will typically require less sample than a pilot-scale operation and much less than a commercial scale operation. Throughout the process, each unit operation must be supplied sufficient material to operate the process adequately while providing representative samples from the process. 

Disruption of microbial cells is rendered difficult due to the presence of the microbial cell wall. Despite this, a number of very efficient systems exist that are capable of disrupting large quantities of microbial biomass (Table 6.1). Disruption techniques, such as sonication or treatment with the enzyme lysozyme, are usually confined to laboratory-scale operations, due either to equipment limitations or on economic grounds. 

In contrast to laboratory scale operations, four-bond formation processes are of considerable importance as industrial routes to pyridine derivatives and have been investigated in Considerable detail. Vapour phase condensation of aldehydes and ketones with ammonia and amines in the presence of a variety of silica/alumina catalysts containing different promoters (e.g. cobalt(II) chloride) can give excellent yields of substituted pyridines (e.g. equation 151), and the nature of the products formed can be largely controlled by change in the stoichiometry of the reactants and variation of experimental conditions (equation 152). 

This reactor also allows for easy laboratory scale operation for determining rate data, since the flow rate is low. Experimental-scale trickle beds can be on the order of 0.5 in. in diameter. Trickle bed reactors are used for the hydrodesulfurization of liquid petroleum fractions. 

For laboratory-scale operation the following order in relative importance of the various gradients can be indicated ... 

The cleavage of 4-phenyltriazole by butyllithium in hexane and THF at 0 °C to afford iV-phenylcyanamide (79TL3129) may have advantages in laboratory scale operations but appears too expensive for large scale purposes. 

In a batch operation, substrates are placed in a reactor, and plasma polymerization coating is carried out as a unit operation. Repeating the same operation treats a large number of substrates. The batch processing is the primary mode for nearly all laboratory-scale operations. The batch processing can be done in a closed system or in a flow system. Because the number of molecules in a reactor under low pressure is small, it is often necessary to use a flow system to obtain a sufficient amount of coating. 

In some cases, a process that is dominated by nucleation can result in an acceptable process outcome. The process may appear satisfactory in a laboratory-scale operation. However, there are several potential problems with this type of process for laboratory and pilot plant operation or when scaling up for manufacturing, including ... 

The Katz patent states that about 15% of the coffee beans in the extractor are discharged and admitted during a semicontinuous pulse. To provide an estimate of the scale of the process we here calculate the amount of coffee beans moved during a pulse. The vessel is 70 ft tall X 7 ft diameter this equates to an internal volume of about 2500 ft. Coffee beans have a density of about 40 Ib/ft, so the extraction vessel holds about 100,000 lb of coffee beans. A 15% replenishment is a rate of 15,0001b per pulse, and the pulse happens about every 30 to 60 min—this is not laboratory scale operation. There are still many other hops extraction, coffee decaffeination, and spice extraction plants throughout the United States and Europe several of them operate at 30 to 60 million Ib/yr throughput, further exemplifying that SCF extraction is not just a laboratory curiosity. 

Batch or semicontinuous processing is appropriate for many laboratory scale operations. However, continuous processes are typically used by industry to allow higher throughput with smaller equipment size. To gain scale-up information, the importance of relatively inexpensive but fully operable pilot plants (or miniplants) cannot be overestimated. Many types of continuous reactors (fixed bed, fluidized bed, continuous stirred tank CSTR) can be adapted for high pressure service. 

When used in laboratory-scale operations CSTRs are frequently referred to as chemostats. Chemostats are often employed in scientific studies intended to elucidate the metabolic processes associated with particular microorganisms because they are better equipped to monitor transient situations involving a transition from one set of operating conditions to another, for example, when there is a shift in the composition of the stream being fed to a unit operating at steady state. By comparison with large-scale CSTBRs, small-scale chemostats are characterized by shorter response times and are more readily instrumented to facilitate acquisition of data that are useful in optimization of the performance of these reactors. 

The bromate method, however, has been found to be admirably suited for laboratory-scale operations but not for large quantities because of the expense. It presents three very definite advantages over the other methods first, no extraneous materials are introduced into the precipitate second, the solution is rendered practically free from cerium in a minimum of operations and, third, the basic cerium-(IV) nitrate so obtained is practically free from other rare earths. Little or no reworking of the precipitate is necessary in order to obtain a cerium compound of high purity, and only very small amounts of the other rare earths are carried out of the solution. 

In summary, among the currently available resources, MSDSs remain the best single source of information for the purpose of evaluating the hazards and assessing the risks of chemical substances. However, laboratory workers should recognize the limitations of MSDSs as applied to laboratory-scale operations ... 

Similarly, regulatory agencies equivalent to the U.S. Environmental Protection Agency or U.S. Occupational Safety and Health Administration, where they exist, may not have jurisdiction over laboratory-scale operations, or they are ineffective. As a result, there is no external audit of safety practices of chemical laboratories. 

For laboratory scale operations, the system adopted in the UK is commonly known as the Brenner method which classifies a GMO on the basis of three factors ... 

Stock solution preparation Predetermined amounts of drug and polymer are dissolved in the solvent. In a small laboratory-scale operation, both drug and polymer... 

An alternative commercial system is the Gyropilot (Pharmacia) which is a fluidized system using polyethjdene carriers (Cytoline) and supports 12 x 10 cells/ml carrier (42). It is available as the Cytopilot-Mini (400 ml bed) for laboratory scale operation as well as sizes up to 25 litres. The unit has a magnetic stirrer that drives the medium up through a distribution plate into the upper... 

This may require a change in the laboratory-scale operating conditions so that the product is economically achievable in a commercial process. The intentional lessening of product goals in the laboratory or pilot plant to enable economic scaleup is called diplomatic scaleup because it may require diplomacy to convince the bench chemist and management. 

---