Process intensification product replacement

The productivity can be greatly improved by the implementation of continuous operations and the use of process-intensification techniques, such as reactive distillation. The replacement of a homogeneous catalyst by a heterogeneous one is highly desirable. These aspects will be discussed in greater detail in the next section. 

Basically, process intensification aims at replacing large, expensive, energy-intensive equipments or processes with ones that are smaller, cheaper and more efficient. At the same time, they have to minimize environmental impact, increase safety, improve remote control and automation and ensure a better product quality. 

The small reactor volumes and the flexible arrangement of microstructured devices can be applied to design multipurpose plants, and traditional batch and semibatch reactors can be replaced. A considerable process intensification and enhanced product selectivity and yield have been shown [20]. Furthermore, continuous reactor operation may help in providing consistent product quality. 

The last chapter gives a more comprehensive approach and discusses the role of membrane gas separation and membrane engineering in the re-designing of industrial applications in terms of new, recently introduced metrics. It provides an analysis of some processes for hydrogen production/separation that can be easily extended in other separation processes. This is a useful tool for the evaluation of pros and cons during the design phase of a new plant, where the membrane operations would replace traditional ones to pursue the strategy of process intensification. 

In these process alternatives that are completely dedicated to the unit operation crystallization, one can find remarkably often, though, some other unit operations used to intensify the crystallization in separating components and to make the entire process more feasible (process intensification). Best examples are the discoloration with activated carbon or the use of a washing thickener for replacing the mother liquor (Figure 16.4). In the case of washing thickener, one uses the countercurrent washing principle to treat the suspension of the crystals from second crop with the purest solution available in this system, which is the feed solution. Even a solution prepared by redissolution of product could be taken. 

Substitution If intensification is not possible, then an alternative is to consider using a safer material in place of a hazardous one. Thus it may be possible to replace flammaole solvents, refrigerants, and heat-transfer media by nonflammable or less flammable (high-boiling) ones, hazardous products by safer ones, and processes which use hazardous raw materials or intermediates by processes which do not. As an example of the latter, the product manufactured at Bhopal (carbatyl) was made from three raw materials. Methyl isocyanate is formed as an intermediate. It is possible to react the same raw materials in a different order so that a different and less hazardous intermediate is formed. 

Intensification of the technological flow motion, during various production processes, leads to increasing the process rates. This is especially true for the chemical interaction occurring in ideal mixing reactors. If it is impossible to replace them with small-sized devices and maintain the intensive mixing of the reaction mixture, an external circuit system may be used to pump the reaction mass (Figure 5.14). Multiplicity of the reaction mixture is defined by specific chemical reaction conditions and the required parameters of the end products. 

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