Bring on the chemists

Process engineers are having to learn much more about basic molecular science to aid product design. The benefits, as Sean Ottewell reports, apply across the board, from consumer products to chemicals plants

Bulk chemical manufacturing may have lost much of its lustre, at least in Western Europe, but demand for process engineers is growing in less traditional sectors. Rather than manufacturing fertilisers or formaldehyde, today’s process engineers are more likely to be involved in work on chocolate bars or lipsticks.

The success of such products depends on how they taste, feel, or look. This demands a molecular-level understanding of the products and the processes by which they are made. This point is starting to get across to the more traditional companies, as well as the university departments educating tomorrow’s process engineers.

Nick Emery, director of masters courses at Birmingham University’s school of chemical engineering, says it is a question of giving students a better understanding of basic colloid science. At the same time, as part of their design projects, undergraduates are being encouraged to think more about how product end-use is linked to fundamental physical and chemical properties.

The chemical expertise of process engineers is becoming an integral part of product design, and is becoming crucial to their commercial success. `For example, the feel of a cream on the skin is very important to a company like Unilever,’ says Emery.

Designing the right molecule at the start can have a bearing on the end product. It can also save valuable time to market.

An example of this trend is modern pharmaceutical tablets. One new strategy involves coating active ingredients with specially-developed polymers. These dissolve at the point in the digestive system which ensures fastest absorption into the bloodstream.

Such an understanding at a molecular level to produce bespoke products is having spin-off benefits in the design of process plants themseves. With a better grasp of the chemistry of how the process works, several stages of the conventional plant design process can be omitted.

BP Chemicals’ new vinyl acetate monomer (VAM) plant in Hull is a good example of this.

VAM is a widely used chemical found in paints, packaging and glues. When the 250,000 tonnes/year plant is commissioned at the end of 2000, it will use what BP claims is the most significant development in VAM manufacturing in over 30 years.

Known as Leap, it is at the centre of the company’s worldwide VAM restructuring plan.

In the past, when developing a product, the chemical industry has undertaken laboratory-scale experiments, built a semi-commercial plant, then built a full-scale facility. BP Chemicals, aware that the semi-commercial stage would add more years to the project length and £10-15m to the cost, looked for ways to bypass it.

The Leap team used modelling and investigation techniques to understand the process in detail. `We now have a more fundamental understanding of what is happening at the reactor and catalyst level,’ says Aidan Hurley, process technology manager for vinyl acetate at Hull. `If this is mathematically understood, scale-up will be that much easier. The first time it will all be put together is when the commercial unit comes on stream.’

In one of the techniques used to understand what is happening at the molecular level, the normal raw materials – acetic acid, ethylene and oxygen – are replaced with molecules containing isotopes so the progress of atoms through the reaction can be followed.

This provides detailed information about a reaction. It is possible to follow an individual atom of carbon from an ethylene molecule through the reaction and see where it ends up in a VAM molecule.

It also gives information about how long different reactants take to come through the process and for how long they are in contact with the catalyst. The benefits have reduced the VAM plant’s capital costs by 30%.

Such a process of tracking atoms through a reaction can reduce the development time of complex chemical plants.