The Scale of Production

Factors that affect the safety of a production system include (1) the scale of production (2) the quantity of hazardous chemicals involved (3) the hazardousness of the chemicals involved (4) batch versus continuous processing (5) the presence of pressure or temperature extremes (6) storage of intermediates versus closed loop processing and (7) multi-stream versus single-stream plants. These factors are discussed briefly below. 

Chemical production is typically characterized by economies of scale. Based on a generalized formula for the chemical industry, a doubling of plant capacity increases 

Handbook of Green Chemistry Volume 9 Designing Safer Chemicals, First Edition. Edited by Robert Boethling and Adelina Voutchkova. 

---

The scale of production has increased rapidly in recent years and in 1980 exceeded 33 million tonnes in the USA alone though much of this is used in integrated plants, on site. 

The scale of production also influences efficiency. Small-scale batch processing for metals such as titanium, tungsten, and zirconium leads to higher energy use and costs. 

The necessity for interaction between biotechnologists and chemical engineers increases with the scale of production. In chemical manufacture three categories of product can be defined according to the scale of production (Table 2.2). 

Raffin, R. P., Jornada, D. S., Re, M. L, Pohimann, A. R. Guterres, S. S. (2006). Sodium pantoprazole-loaded enteric microparticles prepared by spray drying Effect of the scale of production and process validation. International Journal of Pharmaceutics, Vol. 324,1, (October 2006), pp. (10-18), ISSN 0378-5173... 

Although there is no universal consensus as to the scale of production and use of chemical substances, it is estimated that the average annual world production of such substances is in excess of 450 million tonnes. Other estimates indicate that there are currently identified over five million distinct chemical compounds, with this number increasing at the rate of over a third of a million per year. Whilst many of these compounds are clearly not in everyday commercial or industrial use, it is estimated that at least 100,000 chemical substances can be considered to be in everyday use on a substantial scale, and that this number is being added to at the rate of at least several hundred per year, in the case of substances which are produced in quantities in excess of one tonne per year. 

Because of this, when designing a process for a commodity chemical, it is usually important to keep operating costs as low as possible. The capital cost of the process will tend to be high relative to a process for fine or specialty chemicals because of the scale of production. 

Polymers play an integral role in modem society. Over 150 million tonnes are made annually. The scale of production varies enormously from a 200,000 tonnes per annum continuous operational plant for commodity polymers to a batch process producing a few kilograms of a specialised polymer (advanced material). 

Depending on the scale of production, an important parameter determining the economic viability of poly(3HB) production (besides overall yield and poly(3HB) content) is productivity. Productivities of poly(3HB) production at-... 

One of the most important electrolytic processes is the extraction of aluminum from an ore called bauxite. This ore is mainly composed of hydrated aluminum oxide, AI2O3 XH2O. (The x in the formula indicates that the number of water molecules per formula unit is variable.) In industry, the scale of production of metals is huge. The electrolytic production of aluminum is over two million tonnes per year in Canada alone. As you know from Faraday s law, the amount of a metal produced by electrolysis is directly proportional to the quantity of electricity used. Therefore, the industrial extraction of aluminum and other metals by electrolysis requires vast quantities of electricity. The availability and cost of electricity greatly influence the location of industrial plants. 

Many microorganisms represent attractive potential production systems for therapeutic proteins. They can usually be cultured in large quantities, inexpensively and in a short time, by standard methods of fermentation. Production facilities can be constructed in any world region, and the scale of production can be varied as required. 

The price of a prodnct is obvionsly a major determinant of the demand for it by customers. The demand for the product then establishes the scale of production, i.e. the supply of the product. The relationship between the price of a product, the amount of product that a manufacturing company can profitably sell, and the amounts of product that will be bought by customers can be sununarised by means of supply and demand curves (Figure 13.9). A supply curve gives the relationship... 

Some typical commercial biotechnology products are citric acid, semi-synthetic penicillins and cephalosporins, and vitamin B12. World production volumes and bulk prices show a considerable range of values. Prices tend to be inversely proportional to the amount of product sold, that is, the scale of production, and to the concentration at which it can be produced in the bioreactor. The importance of the concentration at which each product is produced in determining the cost of purification and isolation, and thus the... 

The reaction rates in this system are presumably first-order in catalyst concentration, as implied by the scaling of product formation rates proportionately to rhodium concentration (90, 92, 93). Responses to several other reaction variables may be found in both the open and patent literature. Fahey has reported studies of catalyst activity at several pressures in tet-raglyme solvent with 2-hydroxypyridine promoter at 230°C (43). He finds that the rate to total products is proportional to the pressure taken to the 3.3 power. A large pressure dependence is also evident in the results shown in Table VII. Analysis of these results indicates that the rate of ethylene glycol formation is greater than third-order in pressure (exponents of 3.2-3.5), and that for methanol formation somewhat less (exponents of 2.3-2.8). The pressure dependence of the total product formation rate is close to third-order. A possible complicating factor in the above comparisons is the increased loss of soluble rhodium species in the lower-pressure experiments, as seen in Table VII. Experiments similar to those of Fahey have also been... 

The amount of hazardous chemicals on-site can be reduced by methods other than altering the scale of production. For example, the amount of hazardous material stored on-site can often be significantly reduced, and if not, the hazardous materials can be stored in many small containers in separate facilities rather than in a single container. Therefore, if a container fails, the size and catastrophic potential of the release are much reduced. In addition, the amount of material needed in the production process can be reduced by using specially designed equipment (such as Higee columns, which replace conventional distillation columns). 

The scale of production of a fine chemical can range from a few t/a up to tens of kt/a. Two of the final intermediates in the synthesis of the world s top selling drug, the anticholesterol Lipitor , or atorvastin, are only produced on a scale of 500 t/a each. The consequence of the smaller scale and more specialist nature of these industries, is that the processes are far more likely to be batch or discontinuous. Thus process units will be flexible to produce more than one product and the product s lifetime in the market may be comparatively short, either for economic or performance reasons. However, product added value is high. 

Industrial production of perfluorinated ionomers, Nafion membranes, and all perfluorinated membranes is costly due to several factors first, the monomers used are expensive to manufacture, since the synthesis requires a large number of steps and the monomers are dangerous to handle. The precautions for safe handling are considerable and costly. Secondly, the PSEPVE monomer is not used for other applications, which limits the volume of production. The most significant cost driver is the scale of production. Today, the volume of the Nafion market for chlor-aUcali electrolysis (150,000 m year ) and fuel cells (150,000 m year ) is about 300,000 m year resulting in a production capacity of 65,000 kg year. When compared to large-scale production of polymers like Nylon (1.2 x 10 m year ), the perfluorinated ionomer membrane is a specialty polymer produced in small volumes. 

---