Process intensification reduction

If the segmented flow pattern is used for a reaction catalyzed at the walls of the capillary channels, then the mass transfer is actually improved by reducing the amount of energy that is dissipated in the system. This allows the simultaneous achievement of two goals of process intensification reduction of energy requirement and reduction of equipment size. 

Stankiewicz and Moulijn extend the definition of process intensification from size reduction of apparatus to dramatic improvements in key features of chemical processing [25]. Substantial decreases in the following process-engineering properties are listed ... 

In practice, the process regime will often be less transparent than suggested by Table 1.4. As an example, a process may neither be diffusion nor reaction-rate limited, rather some intermediate regime may prevail. In addition, solid heat transfer, entrance flow or axial dispersion effects, which were neglected in the present study, may be superposed. In the analysis presented here only the leading-order effects were taken into account. As a result, the dependence of the characteristic quantities listed in Table 1.5 on the channel diameter will be more complex. For a detailed study of such more complex scenarios, computational fluid dynamics, to be discussed in Section 2.3, offers powerful tools and methods. However, the present analysis serves the purpose to differentiate the potential inherent in decreasing the characteristic dimensions of process equipment and to identify some cornerstones to be considered when attempting process intensification via size reduction. 

Figure 1.28 Illustration of a future plant using process-intensification equipment, aiming at giving the corresponding shape or perception. Compared with today s plants, a reduction in size is predicted [25].

In summary, the Avada process is an excellent example of process intensification to achieve higher energy efficiency and reduction of waste streams due to the use of a solid acid catalyst. The successful application of supported HP As for the production of ethyl acetate paves the way for future applications of supported HP As in new green processes for the production of other chemicals, fuels and lubricants. Our results also show that application of characterization techniques enables a better understanding of the effects of process parameters on reactivity and the eventual rational design of more active catalysts. 

Figure 4 shows the impact of process intensification for this hypothetical case. With a temperature increase of only 41°C, the number of reactors for such comparatively big units is reduced from 20, hardly feasible in view of costs and process control, to four, feasible for the same reasons. Thus, the costs decrease by almost a factor of five (not exactly, since fixed costs have a small share). Another 21°C temperature increase halves the number of reactors again, and at 249°C, which is 149°C higher than the base temperature, an equivalent of 0.2 micro-structured reactors is needed. This means that practically one micro-structured reactor is taken and either reduced in plate number or in the overall dimensions. The costs of all microstructured reactors scales largely with their number only at very low numbers do fixed costs for microfabrication lead to a leveling off of the cost reduction. 

Both in the paper by Ramshaw and in the report from the UMIST conference, first definitions (or rather descriptions) of process intensification can be found. Ramshaw (11) describes PI as devising an exceedingly compact plant which reduces both the main plant item and the installation s costs, while according to Heggs (12) PI is concerned with order-of-magnitude reductions in process plant and equipment. In one of his subsequent papers, Ramshaw writes about typical equipment volume reduction by two or three orders of magnitude (13). 

Often this low reactive content can lead to designing for total containment i.e., no relief system is required by which further emission reductions are achieved. Moreover, the diffusive emissions (smell) can be reduced by reducing the number of flanges and valves. Because the size of the plant will also be reduced, it is likely that the social status of a chemical plant can be raised by the introduction of process intensification. 

Dematerialization. By scale, the reduction of material and energy intensity by process intensification should reduce environmental impact. 

Acidification. The acidification and thermal pollution impacts of a chemical plant in general do not come from the plant itself but are related to the conversion of fossil fuel to energy (steam, electricity) hence the same emission reduction factor as for carbon dioxide is assumed for the process intensification potential. 

But via, for instance, high-heat exchange reactors (HEX reactors) that allow a much shorter reaction time and at the optimal temperature, process intensification can also reduce the formation of by-products considerably. A by-product reduction by a factor of 4 is achieved via a HEX reactor (46). This means a considerable reduction in feedstock cost and waste handling. 

We have designed and implemented a reactive divided wall distillation column for the production of ethyl acetate from acetic acid and ethanol. Important aspects derived from steady state simulation were considered for instance, a side tank was implemented in order to split the liquid to both sides of the wall and a moving wall inside the column that allows to fix the split of the vapor stream. The dynamic simulations indicate that it is possible to control the composition of the top and bottoms products or two temperatures by manipulating the reflux rate and the heat duty supplied to the reboiler, respectively. The implementation of the reactive divided wall distillation columns takes into account important aspects like process intensification, minimum energy consumption and reduction in Carbon Dioxide emission to the atmosphere. 

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 is achieved by the superimposition of two or more processing fields (such as various types of flow, centrifugal, sonic, and electric fields), by operating at ultrahigh processing conditions (such as deformation rate and pressure), a combination of the two, or by providing selectivity or extended interfacial area or a capacity for transfer processes. In heat and mass transfer operations, drastic reduction in diffusion/conduction path results in equally impressive transfer rates. As the processing volume (such as reactor... 

Catalytic distillation is a rapidly developing field with applications in many processes for the chemical, petrochemical, and petroleum industry. It is emerging as a tool for green process and technology innovations because it utilizes process intensification to achieve energy efficiency and the reduction of greenhouse gases. 

Miniaturization in biocatalysis and fermentation is another necessary step. This will allow continuous processes with the benefits that could derive in terms of process intensification and reduction of waste. Miniature (less than 10 mL) stirred reactors and microtiter plates (MTP) have been introduced mainly with the idea of allowing high-throughput screening to speed up bioprocess development, even though they are available now also for production uses [172-174]. Notably, problems emerge with these miniature bioreactors (MBRs), such as evaporation and surface tension, which determine the performances, but which are masked in larger bioreactors. 

---