In May this year Dürr’s Environmental and Energy Systems business unit successfully secured an order via its US location in Plymouth to engineer, fabricate and supply a high-pressure catalytic oxidation system. The Ecopure HPX system was installed at the Italian manufacturing facility of the PET specialist Equipolymers in Ottana. The Ecopure HPX system removes pollutants such as methyl bromide, volatile organic compounds (VOC) and carbon monoxide (CO) from the process exhaust air.

Equipolymers is an international joint venture for the manufacturing and marketing of polyethylene terephthalate (PET) and for the production of purified terephthalic acid – PTA for short – that is manufactured in Ottana. Equipolymers was formed in 2004 by The Dow Chemical Company (Dow) and Petrochemical Industries Company (PIC), a wholly owned subsidiary of Kuwait Petroleum Corporation.

PTA is the major raw material for the production of polyethylene terephthalate. PET is a high-quality plastic for use in the packaging industry and in particular for the production of beverage, food and other liquid containers.

The Ecopure HPX system installed by Dürr in Ottana consists of a multi-stage exhaust air heating system via heat exchangers and a catalyst stage where the pollutants contained in the exhaust air are removed at high process pressure. In the first stage the exhaust air is preheated with a high-pressure steam heat exchanger, followed by an effluent heat exchanger for recovering the heat generated in the catalyst bed. Only during start-up, an indirect fired heater is used to heat up the Ecopure HPX to the required operating temperature. In addition, the purge / start-up system, low-pressure circulation system, controls and safety functions were provided by Dürr.

As the equipment is specially designed to meet customers’ requirements, the job was extremely complex to handle. For the high-pressure vessels and piping Dürr used certified 316/316L stainless-steel material with Pressure Equipment Directive (PED) markings. A control system is also used that meets the Safety Integrity Level (SIL) requirements. A global cooperative effort between Dürr offices in the US, Germany and the UK were needed to facilitate obtaining these high-level equipment certifications.

Along with treating the process exhaust air stream from the PET and PTA manufacturing facility, the Dürr Ecopure HPX system benefits the customer by operating in a wide flow range while maintaining high pollutant destruction and removal efficiency. The system also has a low-pressure independent start-up capability.

The system was designed for low energy consumption under normal operating conditions. As a result, no natural gas is needed during normal operation and the high-pressure steam consumption was kept to a minimum.

To sum up, one may say that the HPX system reduces primary energy input, as the heat generated during oxidation of the pollutants can be recovered by means of recuperators. Moreover, the process exhaust air enters the oxidation system under high pressure. The purified exhaust air can be fed to an expander installed further downstream for energy recovery.

The complete system was installed and commissioned on time, and has been online without operational setbacks or delays. Another Ecopure HPX system with three times the capacity is currently being built by Dürr in China.