From pilot to product

'Our business is the production of high value, essential polymers into a commodity market,' says John Moss, business director of Harlow-based Synthomer, part of the polymers division of Yule Catto.

Of the three main processes used for PVC, suspension polymerisation accounts for around 80 per cent of the world market. Suspension agents, such as Synthomer's Alcotex range of polyvinyl alcohols (PVA), have a critical influence on the morphology of the finished product, and hence the quality of the PVC resin.

'There is good long-term growth in basic plastics, but it's happening in the Pacific Rim countries where we weren't well-known, and had no real way of demonstrating the benefits of our products,' Moss says, explaining the reasoning behind the decision to ask Strata Technology to design, build and commission a PVC pilot plant.

Part of the problem in addressing these new markets was paradoxically the company's success in other markets. 'Don't forget that most of our business is customer confidential,' says Moss. 'We are instrumental in helping customers to develop specific formulations and in providing answers to production problems.' As he points out, that knowledge can't be shared, which prevented Synthomer from using its past experience to convince potential customers.

Describing the importance of the PVC pilot plant to his company's future growth plans, Moss says: 'the development with Strata is a large investment for a company with our turnover. But because profitability has been poor in the PVC market for some time, our customers are cutting back on their own R&D.

The new plant puts us in a position to undertake customer recipe development and to carry out troubleshooting for them. It will allow us to 'think in our customers' shoes' and it's a major element in our strategy of continuous development in customer service.'

The over-riding objective was to design a plant with zero emissions and one which could mimic conditions in any commercial reactor. PVC manufacturers had to be confident that the pilot plant results could be replicated in a full-scale process.With all the complexity of a full-scale design, including the risk elements, the engineering challenges posed by the pilot plant were considerable - not least because of the highly toxic and flammable nature of vinyl chloride monomer (VCM) and the exothermic nature of the reaction.

In-house experience

Set up four years ago by a team of former BP employees, Strata Technology could offer Synthomer its own combination of mechanical, electrical, control and design engineers, coupled with chemical engineering and process experience - a combination of skills that Synthomer describes as 'practical in-house experience, which was essential to the project.'

Synthomer wanted a PC-based control system, with efficient VCM containment in the reactor and essential safety and failsafe alarm systems to avoid reactor temperature and pressure excursions. There was also to be dedicated VCM mass metering with a venting and extraction capability for the entire plant area, in addition to VOC destruction to >99.99 per cent for gases released to the environment.

Strata's design incorporates a dual, interchangeable 10-litre reactor system with geometries matching the two principal current technologies - a short squat reactor, and a tall thin one. Designed using 3D modelling, the reactors have a design pressure to 18barg and a maximum operating temperature of 80 degrees C.

Double automated valves were an absolute necessity for process containment and were a specific Synthomer requirement for safety reasons. Any VOCs produced during the VCM stripping process are destroyed by oxidation in a separate, external Thermox unit. The pilot plant's dedicated PC-based automation and control system interfaces with VOC detection systems for added safety.

Housed within a ventilated unit, the pilot plant needs only one operator and, says Synthomer's technical manager Peter Shaw, 'gives us a real position in the polymer industry. It's been a very good project, delivered in cost and on time.'