Looking for lighthouses
Quo vadis process intensification?

The Chemical Process Industry (CPI) has only just begun the discussion of process intensification. Is the subject a magic formula for efficient processes and products which are economical with resources and exhibit new, intelligent characteristics, or is it just a case of old wine in new bottles?

It’s good that we have talked about it.” There is gentle irony in the voice of the participant as he sums up the result of the presentations and discussions at the end of the ‘Process Intensification’ information day. Admittedly, the wheel was not reinvented during the event, staged at the end of May at the Dechema headquarters (Dechema is a not-for-profit society for chemical engineering and biotechnology based in Frankfurt am Main/Germany), and anyone as intensively engaged with the subject as the participant being quoted did not come away having had some new and ground-breaking discoveries revealed. But the information day, organized by the new specialist division at Dechema, provided those interested in finding out about the current status of the process intensification approach with an overview of what the major players in the European Chemical Process Industry understand by the term – and whilst their understanding is similar in principle, as so often the devil and the differences are in the details.

Old goals – new methods
Dr. Andrzej Gorak, Professor of Process Engineering at Dortmund University, explained that the aim was to achieve familiar objectives using new methods, and he alluded to the “Mission Statement” for the specialist division, which states: “Process intensification aims to achieve a dramatic, economic and ecological increase in the efficiency of chemical and biotechnological processes and in generating new products or product characteristics.” For Dr. Helmut Mothes, at Bayer Technology Services (BTS for short), Senior Vice President Process Technology and head of the specialist division at Dechema, a key approach is therefore microreaction technology (MRT for short), whereby the nano- and micro-scale effects of microstructures are exploited. Mothes believes that this microtechnology makes it possible to manufacture new products, since the smaller equipment can work with a high degree of selectivity. Mothes points to the procedure which BTS developed last year to synthesize carbon nano-tubes. For this, the microreactor creates a much narrower distribution in the size of the fibers than is achievable in the batch reactor, therefore making a significant contribution to the economic competitiveness of the procedure. A further objective is being pursued at BTS, in the form of the modular toolbox manufactured by the company of Ehrfeld. The know-how of the Ehrfeld micro-specialists had been brought into the BTS fold a few years earlier. Their particular expertise lies in the process development of APIs, or active pharmaceutical ingredients. The background to this is that the ingredient manufacturers are currently occupied in working on questions such as “Can a process which has been trialed in the laboratory later be mastered equally well on an industrial scale?” or “How does one square the circle of flexibility and cost optimization?” Given that the interval between the decision to invest and the actual construction of the plant is becoming ever shorter, often companies do not yet know the products which will actually be synthesized in the plant. The consequence of this is that in order to be equipped for every eventuality, multipurpose plants often house 40 per cent more equipment that is actually necessary. Mothes believes that microreaction technology can make it possible to realize more flexible solutions and thus make it easier to take investment decisions. Currently under discussion at BTS is “production on demand” using MRT – a concept which would hold particular attraction for the fine chemistry sector, since the production volumes in this sector can fluctuate markedly in line with market requirements.
Making it smaller and better
But process intensification is not just about making plant smaller. This is shown by the approach being taken by Degussa, the specialty chemistry company, under a new project venture. An interdisciplinary team is developing process strategies for three product areas: Functional Materials – for applications in the automotive and packaging industry; Intensive Dispersing, as a cross-platform technology for the manufacture of dispersing systems such as for dye pastes; and intensifying the oxygen feed in fermentation processes.
A joint project with the engineering company of Uhde is the development of a microstructure reactor for industrial-scale manufacture of vinyl acetate. Degussa is responsible for developing the catalyst and the coating technology for the metal sheets in the microreaktor. The process engineers also want to drive forward the development of new process engineering methods which facilitate the combining of several process stages. “Process intensification combines process integration and process amplification”, says Dr. Martin Strohrmann, Senior Vice President Process Engineering at BASF.
A model example of process amplification is the BASIL process, which is the first large-scale engineering process using an ionized fluid. A change in the processes prevents any solid matter from forming, making it possible to achieve a continuous process in the jet nozzle reactor and increasing production output from eight to 690 000 kilograms. As part of its work on process integration (where the focus is on reducing the number of stages through developing integrated process stages), BASF is committed to an EU research project known as ‘INSERT’, which stands for Integrating Separation and Reaction Technologies. These include processes such as reactive distillation or the use of heat exchange reactors and catalytic wall reactors. Reactive distillation, for example, is a typical hybrid process under which the chemical reaction and distillation are carried out in a single unit. This saves on investment costs and operating costs. Another example of integrated equipment is the dividing wall column, which can replace at least two conventional distillation columns, thereby saving on operating and investment costs. BASF has already been using dividing wall columns in its operations since 1985. “Despite this, in the chemicals sector hybrid processes such as reactive extraction and reactive adsorption continue to be characterized as niche solutions,” laments Prof. Gorak.
No light without shade
One reason for this is self-evident: amortized plants and proved processes are not replaced unless there is a compelling need to do so. A second reason is offered by BASF’s own expert, Martin Strohrmann: “Process intensification always entails a loss of degrees of freedom as well”. The fact is that when integrating two unit operations, such as extraction and distillation, the two stages need to be accommodated within the same process window. But in microreaction technology too, despite numerous reports of success, not everything which glitters is gold. Mothes notes that “MRT can only be used meaningfully in terms of the economics of the business if it not only involves individual components, but where whole processes are revised. Just changing a single mixer is not a sensible step forward”. And given the high reaction speed, he notes that controlling the individual microstructures continues to be difficult, so that dwell times and distribution of product flows can be managed precisely. It remains to be seen whether Siemens can overcome such problems in the process engineering with its new modular microprocess system “Siprocess”. The system, exhibited for the first time at this year’s ACHEMA, comprises full configuration of ten components necessary for chemical synthesis, all of which are controlled via the Simatic PCS 7. The baptism of fire for the system which will come with its application in practice still lies ahead. To date, innovative approaches such as MRT and process intensification have suffered from the fact that even within the teams themselves, a great deal of work needs to be done to convince team members. “MRT and process intensification also call for a change in the culture,” says Mothes. Symptomatic of this is the sobering recognition at BTS that “you can sell microreaction technology in China better than here”. Mothes offers a downbeat summary: “Here too, we need two or three projects which stand out like lighthouses”.