Continuous small-scale production

More recent examples include Ampac Fine Chemicals (AFC) in California, who implemented a multipurpose continuous small-scale plant for the production of several hundred tons of API per year [31], and Sigma-Aldrich s Fine Chemicals, which has been adding continuous-process technology within its Buch facility [32]. 

Finally, incremental process improvements in the form of continuous, small-scale innovations add significantly to the productivity of mature nonassembled products. There, innovation is almost exclusively the province of the incumbent producers who are motivated chiefly by cost competition. When combined with the leaps forward made by the few radical innovations, productivity gains tend to follow the pattern shown in Fig. 7-3. In glass manufacture and similar industries, the productivity gains that accrue from these incremental changes and those from radical changes in process architecture appear about evenly divided (Utterback, 1994). The hydrogen experience would probably be close to that shown in Fig. 7-3. 

Thus, it is more flexible to run both reactions continuously [64]. A microreactor is used for the more demanding, highly exothermic reaction, whereas a static mixer is sufficient for the second reaction. After laboratory process development, a pilot phase in the so-called continuous small-scale production (c-SSP) comprising microreactor technology followed (see Figure 11.16). The c-SSP plant is a multipurpose and modular approach and can operate from cryogenic to high temperature. 

Biopolymer Extraction. Research interests involving new techniques for separation of biochemicals from fermentation broth and cell culture media have increased as biotechnology has grown. Most separation methods are limited to small-scale appHcations but recendy solvent extraction has been studied as a potential technique for continuous and large-scale production and the use of two-phase aqueous systems has received increasing attention (259). A range of enzymes have favorable partition properties in a system based on a PGE—dextran—salt solution (97) ... 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

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. 

Membrane Chemistry Three chemical families dominate the RO-NF membrane industry. Many other products are made on a small scale, and the field continues to attract significant R D resources. But three types command most of the market. 

The first reactor plugged up irreversibly in the first minutes of operation. A second reactor was made and production started. The polyethylene was dark and stinking but the Navy needed the material. As the war ended, the product was improved when competition started, quality accelerated significantly. Fourteen year after production started, the first pilot-plant was built, since the continuous process was difficult to study in small scale. A few more years later, three polyethylene pilot-plants were running day... 

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. 

The fine chemicals business is characterized by a small volume of products manufactured. Therefore, batch production predominates and small-scale reactors are used. The need to implement fine chemistry processes into existing multiproduct plants often forces the choice of batch reactors. However, safety considerations may lead to the choice of continuous processing in spite of the small scale of operation. The inventory of hazardous materials must be kept low and this is achieved only in smaller continuous reactors. Thermal mnaways are less probable in continuous equipment as proven by statistics of accidents in the chemical industries. For short reaction times, continuous or semicontinuous operation is preferred. 

Batch-type production processes, particularly those with small batch sizes, have less energy efficiency as compared to continuous processes. A typical example of a batch operation on a relatively small scale is the production of titanium in 1-ton batches of the metal. The energy efficiency of the process is much less than that of continuous methods such as iron being produced in a blast furnace, or even of large-scale batch methods such as basic oxygen steel-making. The heat losses per unit of production are much less in continuous and large-batch processes, and this also enables the waste heat from process streams to be used. 

Batch dryers are normally used for small-scale production and where the drying cycle is likely to be long. Continuous dryers require less labour, less floor space and produce a more uniform quality product. 

Both continuous and batch process operations can be used. Batch processes are generally preferred for small-scale and specialty chemicals production. 

Batch reactors are often used for liquid phase reactions, particularly when the required production is small. They are seldom employed on a commercial scale for gas-phase reactions because the quantity of product that can be produced in reasonably sized reactors is small. Batch reactors are well suited for producing small quantities of material or for producing several different products from one piece of equipment. Consequently they find extensive use in the pharmaceutical and dyestuff industries and in the production of certain specialty chemicals where such flexibility is desired. When rapid fouling is encountered or contamination of fermentation cultures is to be avoided, batch operation is preferable to continuous processing because it facilitates the necessary cleaning and sanitation procedures. 

Reliable mechanistic conclusions require high intrazeolite yields that account for the majority of the substrate mass balance. This can be a challenge because of the small-scale reactions often conducted for mechanistic studies. In addition, rapid removal of the products from the zeolite, and/or low conversions to decrease residence time, is occasionally necessary because of the sensitivity of the reaction products to the zeolite environment.44,45 Intrazeolite products are generally recovered by extractive techniques from either the intact zeolite, or from a mixture formed after mild digestion of the zeolite. Polar solvents such as tetrahydrofuran or acetonitrile coupled with a continuous extraction technique is in particular an effective means to remove polar products with an affinity for the interior of the zeolite.44 Zeolite digestion with mineral acids, in order to liberate the products, must be conducted with care in order to prevent acid catalyzed product decomposition or reaction.46,47... 

While batch reactors remain the workhorse in fine chemical production, the need to switch to continuous processes will increase the use of meso- and micro-structured reactors both at the laboratory scale (for discovery, process data determination, demonstration, small-scale production) and at the production level. 

Unfortunately, the appeal of solid phase extractions on small scale fades as the scale increases due to the cost and inconvenience of using large amounts of fluorous silica gel. Here, modified techniques to reduce the tedium of repeated extractions are attractive. For example, Crich has recently introduced the minimally fluorous selenide C6Fi3CH2CH2C6H4SeH[171. This selenol is added in catalytic quantities to tin hydride reductions of reactive aryl and vinyl radicals. The high reducing capacity of the aryl selenide suppresses undesired reactions of product radicals without suppressing the reactions of the aryl and vinyl radicals themselves. After the reaction is complete, the selenol can be recovered by a modified continuous extraction procedure. 

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. 

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