Plant multipurpose

Allow the use of standardized multipurpose equipment for the production of a variety of products from the same plant. 

The development section serves as an intermediary between laboratory and industrial scale and operates the pilot plant. A dkect transfer from the laboratory to industrial-scale processes is stiH practiced at some small fine chemicals manufacturers, but is not recommended because of the inherent safety, environmental, and economic risks. Both equipment and plant layout of the pilot plant mirror those of an industrial multipurpose plant, except for the size (typically 100 to 2500 L) of reaction vessels and the degree of process automation. 

In order to make a multipurpose plant even more versatile than module IV, equipment for unit operations such as soHd materials handling, high temperature/high pressure reaction, fractional distillation (qv), Hquid—Hquid extraction (see Extraction, liquid-liquid), soHd—Hquid separation, thin-film evaporation (qv), dryiag (qv), size reduction (qv) of soHds, and adsorption (qv) and absorption (qv), maybe iastalled. 

Batchwise operated multipurpose plants are per defmitionem the vehicle for the production of fine chemicals. There are, however, a few examples of fine chemicals produced ia dedicated, coatiauous plants. These can be advantageous if the raw materials or products are gaseous or Hquid rather than soHd, if the reaction is strongly exothermic or endothermic or otherwise hazardous, and if the requirement for the product warrants a continued capacity utilization. Some fine chemicals produced by continuous processes are methyl 4-chloroacetoacetate [32807-28-6] C H CIO [32807-28-6], and malononittile [109-77-3] C2H2N2, made by Lonza dimethyl acetonedicarboxylate [1830-54-2] made by Ube and L-2-chloropropionic acid [107-94-8] C2H C102, produced by Zeneca. 

Fig. 2. Schematic of a multipurpose fine chemicals plant. Computer-assisted process control is utilized.

The production building is only one part of a full-fledged fine chemicals plant. Apart from the multipurpose plant building there is usually an office and R D building, the warehouse, the maintenance shop, tank farms, the iaciaerator, and wastewater treatment faciUties. 

Figure 3 shows the capacity utilization resulting from the production program ia a multipurpose plant. The aimual percentage of occupation is shown on the x-axis reflecting the overall busiaess condition, and the level of equipment utilization is shown on thejy-axis, reflecting the degree of sophistication of the fine chemicals to be produced. Several conclusions can be drawn ...

Fig. 3. Multipurpose plant capacity utilization where D represents products A, B, C, D, and E U the changeovers and X the time the plant was idle.

Quality Control. Because fine chemicals are sold according to specifications, adherence to constant and strict specifications, at risk because of the batchwise production and the use of the same equipment for different products ia multipurpose plants, is a necessity for fine chemical companies. For the majority of the fine chemicals, the degree of attention devoted to quahty control (qv) is not at the discretion of the iadividual company. This is particularly the case for fine chemicals used as active iagredients ia dmgs and foodstuffs (see Fine chemicals, standards). Standards for dmgs are pubHshed ia the United States Pharmacopeia (USP) ia the United States (6) and the European Pharmacopeia ia Europe (7). 

Another quaHty control problem of multipurpose plants is the clean out for a product change. A test for residual cleaning solvents in the ppm level is a necessity. The best vaHdation of the cleaning process is to develop an analytical method that is able to find the previous product in the new product at a level of not more than 1 ppm. Tests should be mn on at least the first three batches. 

Cost Calculation. The main elements determining production cost are identical for fine chemicals and commodities (see Economic evaluation), a breakdown of production cost is given in Table 2. In multipurpose plants, where different fine chemicals occupying the equipment to different extents are produced during the year, a fair allocation of costs is a more difficult task. The allocation of the product-related costs, such as raw material and utiHties, is relatively easy. It is much more difficult to allocate for capital cost, labor, and maintenance. A simplistic approach is to define a daily rent by dividing the total yearly fixed cost of the plant by the number of production days. But that approach penalizes the simple products using only part of the equipment. 

Most aroma chemicals are relatively high boiling (80—160°C at 0.4 kPa = 3 mm Hg) Hquids and therefore are subject to purification by vacuum distillation. Because small amounts of decomposition may lead to unacceptable odor contamination, thermal stabiUty of products and by-products is an issue. Important advances have been made in distillation techniques and equipment to allow routine production of 5000 kg or larger batches of various products. In order to make optimal use of equipment and to standardize conditions for distillations and reactions, computer control has been instituted. This is particulady well suited to the multipurpose batch operations encountered in most aroma chemical plants. In some instances, on-line analytical capabihty is being developed to work in conjunction with computer controls. 

Bromothiophene is produced in Europe by Solvay and SCL, at up to 50 metric tons per year, with a 98%-pure specification and prices commensurate with production levels. 3-Bromothiophene is stiU a specialty product as of the mid-1990s, produced in multipurpose plant by SCL in hundreds of kilos per year, but at this level of market demand and also on account of the complexity of the synthesis, it commands a relatively high price. 

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]. 

Batch plants will have fewer MPls due to multipurpose utihzation of equipment... 

Hendry, G.A.F., Chlorophylls and chlorophyll derivatives, in Natural Food Colorants, 2nd Ed., Hendry, G.A.F. and J.D. Houghton, Eds., Blackie, Glasgow, 1996, 131. Singh, V., ed., Seabuckthom, A Multipurpose Wonder Plant, Vol. I, Indus International, India, 2005. 

Plants for the manufacture of fine chemicals are discussed in Chapter 7 with emphasis put on multiproduct plants. Types of production plants and typical equipment for multiproduct plants with cost considerations are presented in more detail. Problems of designing and scheduling multiproduct and multipurpose plants with particular emphasis given on process data needed to realise this task are discussed. 

Finally, in multipurpose plants compounds, which can be deposited in various places (e.g. corners, zones near sealings) in equipment, can contaminate products of the subsequent batch. Therefore, all equipment must be thoroughly cleaned before the next production campaign starts. Contaminants can be formed in the process, sometimes at ppm level, and be recycled with streams of solvents and/or reactants. Hence, the influence of recycling on process performance indices must be included in the program of laboratory studies, at least in their final stage. 

There are three basic types of plants for the manufacture of fine chemicals dedicated plants, multiproduct and multipurpose plants, and mixed plants. 

There are numerous constraints and factors that affect procedures for design of multiproduct and multipurpose plants ... 

Example 7.4-6. Optimal design of a multipurpose plant (after Faquir and Karimi (1988)... 

The death of old products, the birth of new ones, changing demands, and the need to compose the optimal hierarchical production plan with an optimal use of the equipment and the shortest possible total production time make the timing of production more important than plant design. The use of rigorous optimization techniques can be most profitable at production planning and scheduling of existing batch plants, especially multipurpose plants. 

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