Small-scale operations

However, chromatographic processes stiH have a considerable appHcabiHty (106) (see Analytical methods). For instance, in small-scale operations, the greater simplicity of the chromatograph may more than compensate economically for the larger adsorbent inventory and desorbent usage. 

Process probably not competitive for small-scale operations (>10 20 t/d product gas). 

The first commercial shipment of diatomite ia the United States was made ia 1893 and consisted of material from a small quarry operation ia the vast deposit near Lompoc, California. It went to San Francisco to be used for pipe iasulation. Small-scale operation of parts of the Lompoc deposit continued until it was acquired by the Kieselguhr Co. of America, which later became the CeHte Co. (4). Siace that first work, the iadustry has grown immensely, and diatomite products are used ia almost every country. 

Through-ckculation compartments employ perforated or screen bottom trays and suitable flow baffles so gas is forced through the material. If material is not inherently pervious to gas flow, it may be mechanically shaped iato noodles, pellets, or briquettes. These dryers are used ia small-scale operations to dry explosives, foods, and pigments. Dryer efficiency is 50—70%. Based on tray area, water vaporization rates are 1—10 kg/(h-m ). 

Selection of Equipment Packed columns usually are chosen for very corrosive materials, for liquids that foam badly, for either small-or large-diameter towers involving veiy low allowable pressure drops, and for small-scale operations requiring diameters of less than 0.6 m (2 ft). The type of packing is selected on the basis of resistance to corrosion, mechanical strength, capacity for handling the required flows, mass-transfer efficiency, and cost. Economic factors are discussed later in this sec tion. 

It should therefore not be surprising that for relatively small-scale operations involving solids handling within the fine and intermediate chemicals industry, batch operation is preferred. Similarly, continuous processes that involve precipitation or crystallization, a common unit operation in fine chemicals, are rare. Small-scale examples are known, for instance, a continuous crystallization process was used by Bristol-Myres Squibb in order to improve dissolution rates and bioavailability of the product [12]. The above does indicate that not all process or parts thereof are suited for conversion from B2C, given the current technology. 

It is a well-known fact (or urban myth. ) that small-scale operations favor batch processes while large-scale manufacture requires continuous processing. Consider the typically assumed general trends (Figure 14.5) where the capital costs of batch... 

A filter pump discharging into an aspirator, fitted with an outlet at the top for air and an outlet at the bottom for water, will give enough air for small-scale operations of glass-working. W. A. Shenstone (1889) described this device. 

A procedure for preparation of sodium hyponitrite involving reduction of nitrogen oxide by the ketyl, followed by extraction into water [1], had been operated routinely on the small scale. A 41-fold scaled up run exploded and ignited after 200 ml of water had been added as part of the work-up. This was attributed to the presence of an unusually large proportion of coagulated unreacted sodium in the ketyl. Small-scale operation with precautions is urged [2],... 

The operation of industrial scale synthetic organic chemistry in an environmentally acceptable manner requires that all these effluent categories be dealt with properly. In small scale operations in a research or academic setting, provision should be made for dealing with the more environmentally offensive categories. 

Dianor [Diamond Alkali, Oronozio de Nora] A process for cracking naphtha to ethylene, adapted for small-scale operation so that polyvinyl chloride could be made by developing nations. Developed in the 1970s by Chem Systems and the two named companies, but not commercialized. 

Fixed bed gasifiers are generally used for small-scale operation with gas engines, having an electrical output of about 80-500 kWe. They divide into updraft and downdraft gasifiers. 

The key to safe handling of chemicals is a good, properly installed hood, and the referenced book devotes many pages to hoods and ventilation. It recommends that in a laboratory where people spend much of their time working with chemicals there should be a hood for each two people, and each should have at least 2.5 linear feet (0.75 meter) of working space at it. Hoods are more than just devices to keep undesirable vapors from the laboratory atmosphere. When closed they provide a protective barrier between chemists and chemical operations, and they are a good containment device for spills. Portable shields can be a useful supplement to hoods, or can be an alternative for hazards of limited severity, e.g., for small-scale operations with oxidizing or explosive chemicals. 

SSP of recycled PET (RPET) can be performed as either a continuous or a batch process. A continuous SSP offers a constant and overall higher productivity, as well as a more consistent product treatment, lower operating costs [117] and better process integration with a downstream manufacturing process. A batch SSP offers a larger degree of flexibility for small-scale operations with a large variation of raw material and final product specifications. 

In practice, the HETP concept is used to convert empirically the number of theoretical stages to packing height. As most data in the literature have been derived from small-scale operations, these do not provide a good guide to the values which will be obtained on full-scale plant. The values given in Table 11.5 may, however, be used as a guide. 

In small-scale operations, ClFsO can conveniently be purified by complexing it with KF at room temperature. Impurities, such as FCIO2, that do not form an adduct under these conditions can be pumped off. 

Simple manual dispensing systems designed for low-volume concrete plants depend solely on the care of the concrete plant operator in batching the proper amount of admixture into a calibration tube and discharging it into the batch. These types of dispensing equipment are used in small-scale operations where admixtures are only occasionally used. For small and occasional additions, hand-dispensing equipment may be used to measure reasonably accurate quantities. A hand-operated plunger can be used to... 

Note that because fixed costs are proportionally more important for small-scale operations the influence of research and development work on reducing the imit process costs on smaller scale processes will often be significantly difierent than when applied to larger scale operations. Also equipment will not necessarily be used imder conditions which maximise its performance, but rather under conditions that minimise cost, thus for instance a fermenter will not be operated at maximum agitation rates as the power required will be too expensive. Other savings can be made by finding uses for wastes, such as the spent biomass from fermentations, and also for any out-of-specification product that is made. 

Accdg to Clark (Ref 14a), only a small scale operation was producing hydrazine prior to WWII In WWII the Germans discovered that N2H4 was an excellent rocket fuel when used with hydrogen peroxide, oxygen or fuming nitric acid. They used hydrazine as the proplnt of their first rocket plane... 

The Mesopotamian campaign against the Turks developed from a small-scale operation into one that absorbed considerable resources. An Indian Army division was dispatched to the head of the Persian Gulf in October 1914 to protect the oilfields at Abadan (of particular interest to the Admiralty following the decision to build oil-burning warships) and to prevent the expansion of Turkish influence towards India. The... 

In relatively small-scale operations, where frequent shutdowns may be desirable, as at night or during week ends, the mixer-settler plant offers the advantage that concentration gradients are maintained within the plant indefinitely even though operations have stopped. On start up, steady-state conditions are established immediately, product specifications are met with the first effluents, and recycling of the first products withdrawn is unnecessary. The agitated vessel is also eminently suitable for purely batch processes, which are likely to be on a small scale. 

All these organometallic compounds, except for [V], were isolated in pure crystalline state. The stereospedfic polymerization of acetaldehyde was catalyzed by [I] to [IV], and that of propylene oxide by [V] to [VIII]. The crystalline organometallic compound is superior to the liquid one for our purpose, because the former can be purified more easily and extensively than the latter in a small scale operation. 

Can be used for small-scale operations requiring a low capital investment. 

A practical consideration in working with ethanethiol is the pervasive stench of this and other volatile thiols, especially as such thiols are used in minute concentration as odor markers for natural gas. It is not easy to perform the standard preparative procedures, during which transfer and filtration operations are performed, in a closed system, and vapors carried through a venting system are detectable at considerable distances, hr small-scale operations, it may be possible to employ a sodium hypochlorite trap to convert the thiols into nonvolatile, oxidized products. 

Another disadvantage of chemical synthesis is that when it is used to produce certain biologically important compounds, such as amino acids, a racemic mixture of D and L isomers results. Since organisms, by and large, metabolize the L-form selectively, as in the case of amino acids, the use of such racemates in biological investigations is somewhat unphysical and may lead to undesirable confusion. Methods for the resolution of racemic mixtures are available. Most of these are tedious and not suited for small-scale operation. 

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