Capital intensification

The lines in Eig. 3.5, adapted from Ref. [22], show the relationship between scale down ratio and required capital intensification factor for scale up exponents of 0.5,... 

Fig. 3.5 Required capital intensification for various scaledown ratios and various cost exponents (0.5, 0.6, 0.7). (Adapted from Ref [22].)...

Minimization goes much further than storage, however. For many processes the largest inventory of hazardous materials is in the reactor. If, through radical reactor design, inventories and equipment size can be reduced whilst throughput is maintained, then this presents opportunities for improved safety and possibly reduced capital costs. This is the concept behind Process Intensification which is discussed more fully below. 

The concept of process intensification does not need to apply to the whole of an API production process. There is merit in looking at hybrid reaction schemes, which retain the benefits of, or capital investment in, batch equipment but use continuous processes for the generation of hazardous intermediates [17] or for certain unit processes. Of these, hydrogenation [18], filtration [19], phase separation [20], crystallisation [21] and drying [22] are good examples. 

This route is emblematic of the new intensification approach currently used in the chemical industry, which is aimed at finally developing a safer, less-capital and energy intensive and more flexible production of bulk chemicals. 

For the same 98% conversion, the volume of each of the two tanks is only 32.5 m3 with a 2.74 m diameter. Thus the total volume has been reduced by a factor of 4 from 262 m3 in the case of one CSTR to only 65 m3 when two CSTRs are run in series. This is a tremendous decrease in capital investment and represents a great intensification. 

Innovation is the key issue in today s chemical process industries. The main directions are sustainability and process intensification. Sustainability means in the first place the efficient use of raw materials and energy close to the theoretical yields. By process intensification the size of process plants is considerably reduced. The integration of several tasks in the same unit, as in reactive separations, can considerably simplify the flowsheet and decrease both capital and operation costs. 

However, the integration of PIM also creates synergy in the development of intensified processes, novel product forms, and size dependent phenomena, which in turn provides novel intensified processes. Process intensification-miniaturization is seen as an important element of sustainable development because it can deliver 1) at least a 10-fold decrease in process equipment volume 2) elimination of parasitic steps and unwanted by-products, thus eliminating some downstream processing operations 3) inherent safety because of reduced reactor volume 4) novel product forms 5) energy, capital, and operating cost reduction, and an environment friendly process 6) plant mobility, responsiveness, and security and 7) a platform for other technologies. 

Process intensification reduces the number of process equipment and hence reduces the capital cost. 2. 

Figure 3.3 PI provides radically innovative principles in process and equipment design that can benefit process and chain efficiency, capital and operating expenses, quality, wastes, process safety and more, and align perfectly with the Triple-P philosophy of sustainable industrial chemistry. Source adapted from EU Roadmap for Process Intensification (www.creative-energy.org).

Process intensification is one of the chemical engineering solutions to clean technology. The main benefits are often lower energy uses, lower capital costs and increased throughput from a smaller plant derived from different engineering conceptual designs. The next generation of plants will be smaller, cheaper, and more environmentally friendly to run. 

In its broadest sense, process intensification can be defined as a series of methodologies aimed at reducing the capital cost associated with chemical processing, by removing existing limitations . 

Two case studies are presented below to illustrate the impact of process intensification. They show how distributed production of hydrogen-age fuels can compete with a larger scale centralized production followed by transportation, provided one can invoke logistical circumstances as well as very intense capital utilization. 

This chapter has introduced the concept of process intensification (PI) as a collection of methodologies aimed at reducing the capital cost of chemical processing. Examples have been given of successful and less successful strategies. The area of microreaction technology has also been situated for some cases, an attempt has been made to quantify the degree of PI achievable. 

There is growing interest in Process Intensification, where studies to obtain a basic understanding of unit operations - often via miniaturization approaches - is important to reducing capital and operating costs. This approach has resulted in the application of micro-instrumentation to the areas of process development and process optimization. 

Capital-investment reduction. As mentioned, process intensification lead to significant reduction in the equipment size and capital costs. However, reducing the number of units by better flowsheet design can have a larger impact. 

Present research is being directed towards the development of catalysts that can maintain sufficient activity at high partial pressures of hydrogen and carbon dioxide and can operate at temperatures above the present limit of 500 °C. Process-intensification steps such as these should, if successful, improve efficiency and reduce both capital and operating costs. 

The adoption of membrane processes is driven by economics. Membrane processes commonly are more capital intensive due to membrane costs. However, these costs are offset by either 1) reduced energy consumption, 2) the ability to separate labile components, or 3) process intensification (increased throughput per unit volume). The energy savings provided by membrane processes will attract increasing attention as global competition for energy increases and costs rise. 

The expected significant process simplification and intensification would capitalize on a new industrial paradigm offered by equipments combining reaction and separation in one step. New reactors and overall plant design strategy have to be defined. 

Transport phenomena are crudal in the scale-up of conventional, large-scale chemical reactors because many processes are heat and/or mass transfer controlled. Since transport coeflEcients are typically inversely proportional to the characteristic dimension of the system, miniaturization of chemical systems leads to a substantial increase in transport rates. This increase in turn enhances the overall rate of processes that are transport limited, leading to considerable process intensification, i.e. the same throughput can be achieved with a much smaller device and thus with much lower capital. Alternatively, much higher throughput can be achieved using a system of the same size as a conventional one, but made up of many small components (scaling out). 

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