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Equipment and Unit Operations
16 Февруари 2015

SUMMARY OF BEST PRACTICE

This Best Practice describes a number of possible energy efficiency improvements in process unit operations, such as distillation, evaporation, extraction, crystallisation and drying (see the Best Practices on solid drying and liquid/solid separation). For practicality, this needs to be provided in a generic way, as there is so much variation across chemical processes. Whether or not they can be applied in your specific situation needs to be evaluated with the input of technical experts in this field.

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INTRODUCTION

The choice of equipment and the type of unit operations has been traditionally governed by a number of factors: reactions kinetics, conversion and selectivity, product properties and desired quality, performance know-how, process control and plant management.

In the present days, energy consumption has become a prime factor. Not only regarding the required energy input for the chemical conversion and product isolation, but also for the possibilities for heat recovery and secondary heat use.

Energy efficiency needs to be considered as one of the major design parameters in constructing process installations. For existing installations, information about improving energy efficiency is given in the various Best Practices in this section.

For new installations or in case of retrofitting existing installations new possibilities have emerged:

  • Process intensification: a design approach in which several process elements are combined in a single piece of equipment (e.g. reactive distillation, divided wall columns, membrane reactors)
  • Micro reactors: down scaling the size allows for better selectivity, higher conversion and better temperature control. (e.g. micro flow reactors, spinning disc reactors)
  • Bio-based chemistry: the use of bio-based raw materials or intermediates or bio conversion processes (enzymatic conversions) enables lower energy demands for the value chain process
  • Catalysis: new catalyst developments enable higher conversion, better selectivity and better process conditions
  • The use of new solvents (e.g. supercritical carbon dioxide, deep eutectical fluids)

Although certainly not a common practice yet, there are already quite a number of successful applications of these new technologies.

LINKS TO KEY RESOURCES

ISPT - The Dutch Institute for Sustainable Process technology

It is a co-operation between industry, universities, and knowledge institutes, which aims at speeding up innovation processes and make them more efficient than they are at present.

Apart from developing knowledge, the institute aims at the development, demonstration and application of breakthrough technology with a special focus on process technology. Breakthrough results are valued on their impact on the global process technology envelop – from raw materials to end products. The final result should be a considerable improvement of the competitive position of the (Dutch) Process Industry.

Technology Roadmap - Energy and GHG Reductions in the Chemical Industry via Catalytic Processes

This roadmap focuses on the role of catalytic processes in reducing energy use and GHG emissions in the chemical sector. Around 90% of chemical processes use catalysts for efficient production. Catalysis is an important source of technology-based efficiency improvement potential; indeed, this work shows an energy savings potential approaching 13exajoules (EJ) by 2050 – equivalent to the current annual primary energy use of Germany.

Heterogeneous catalysis

It is of paramount importance in chemical industry, but it often involves incorporating difficult and mass transfer limited unit operations. The SpinPro Reactor has proven itself to drastically increase solid-liquid mass transfer rates, while simultaneously tackling the problems involved in downstream solids handling.

The SpinPro consists of three rotor-stator stages in series. Each compartment consists of a rotating disc, the rotor, which rapidly spins at velocities up to 3,000 RPM. The stationary encasing, the stator, is in close proximity to the disc. Typical rotor-stator distances are of the order of a millimeter. The high degree of turbulence invoked by the disc and the large amount of shear in the narrow cavity result in strongly improved mass transfer behaviour.

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