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Anguil Environmental Systems has revealed that Corus is using a Spooner Anguil regenerative thermal oxidiser (RTO) to improve efficiency and reduce its carbon footprint.

Corus Colors – Shotton Works, located at Deeside, north Wales, produces organic-paint-coated, prefinished steel principally for cladding, composite walling and roofing applications.

There are two manufacturing processes at Shotton Works for coating steel strip with paint.

It uses a series of driven roller coaters and industrial curing ovens, controlled within a continuous process line, that are capable of applying protective and decorative high-quality finishes to the galvanised flat steel strip substrate.

The No1 Colorcoat Line process is capable of coating strip widths up to 1,400mm with a thickness up to 1.6mm, giving a weekly throughput capability of up to 4,000 tonnes, subject to product type and dimensions.

This manufacturing process requires large amounts of natural gas to ensure proper application and fast curing time in the ovens, which in turn generates a substantial amount of CO2 and nitrous oxides.

In addition to these emissions, the solvent-based coatings release hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) during the drying process that need to be treated by an air pollution control device such as an oxidiser.

New oxidiser systems are capable of destroying more than 99 per cent of the HAPs and VOCs through the process of high-temperature destruction with little fuel consumption.

However, older technologies can be a source of CO2 and nitrous oxides as well as the requirement for high maintenance and large operating expenditures.

Corus has been monitoring and controlling oven emissions at the Shotton Works since the 1970s.

Its first oxidiser/incinerator was installed on the paint-coating processes for abating exhaust gases and solvents.

The company utilised waste heat from these older oxidisers/incinerators to pre-heat the ovens and to supply its manufacturing facility with additional process steam.

However, as environmental regulations tightened, energy prices increased and new technologies emerged, the company re-evaluated its entire system.

The objective was to reduce gas consumption by at least 45 per cent, increase processing speeds on certain products and reduce the works’ carbon footprint.

Corus turned to Spooner Industries, which completed several upgrades that brought the system up to current standards and increased its flexibility.

Each zone was retrofitted with a special low nitrous oxides burner to reduce emissions.

Variable frequency drives or inverters on every oven fan were incorporated into the control system to make each section more efficient and reduce electrical consumption.

The ductwork was changed to bring hot air into the system quickly, reducing maintenance issues.

New thermocouples (temperature measurement), pressure transmitters, pressure switches and flow measurement systems were installed in the ovens to bring the equipment up to today’s technology standards, allowing for remote monitoring and fine-tuning.

A computer-controlled system was integrated with the Scada program.

The proper programmable logic controller (PLC) allows the central Corus system to communicate with the ovens so they can be set up for different production runs, eliminating errors and decreasing setup time.

The oven alterations brought this production line from the least efficient in the Corus group to the most, meeting one of the two objectives for the company.

While some of these improvements reduced the company’s environmental footprint and gas consumption, the increased throughput would further complicate its environmental responsibilities.

Two existing, inefficient oxidisers for the prime and finish ovens were being used to control VOC and HAP emissions at the north Wales facility.

To achieve proper destruction the systems required large amounts of natural gas, which affected operating expenses and contributed to CO2 and nitrous oxides emissions.

Furthermore, breakdowns and maintenance problems were costing the company money to repair and also revenue in lost production.

Because the oven and oxidiser are so vital to each other, Corus wanted a solution provider with experience and knowledge on both.

In addition, it was looking for a system with low operating costs and heat recovery capabilities that could achieve 99.5 per cent destruction removal efficiency (DRE), which was well above its permit requirements.

Spooner, having partnered with Anguil Environmental Systems in the US to fabricate and install its oxidiser designs on applications throughout Europe, was confident that it could be done.

After consulting with the engineers at both Spooner Industries and Anguil Environmental Systems, Corus made the decision to replace its multiple air pollution control systems with one RTO from Spooner Anguil.

The oxidiser is a three-chamber design that processes 83,000NM3/hr (55,000SCFM) of air, achieving more than 99 per cent DRE without visible emissions and more than 85 per cent heat recovery for energy-efficient operation.

The RTO self-sustains at low solvent-loading conditions, meaning that once the oxidiser is at operating temperature and receiving process airflow it requires no additional fuel for emission destruction, releasing very little CO2 and nitrous oxides.

A secondary heat exchanger sends waste heat directly back to the ovens, reducing the amount of natural gas required for product curing.

Stainless-steel components throughout the system prevent corrosion and allow for high-temperature process streams.

A hot-gas bypass on the RTO is used during high-loading situations to avoid over-heating the oxidiser.

An intelligent bake-out feature cleans the RTO of condensable organics without internal fires or safety concerns.

The control panel has a large operator screen with a built-in maintenance manual and troubleshooting guide.

The reduction in carbon emissions and energy consumption from this facility is dramatic, according to Anguil Environmental Systems.

Its gas usage has dropped by more than 60 per cent, an average reduction of 522m/hr (or 5742 kW) per hour – saving more than GBP1m a year.

At 181g of CO2 produced per kWh used, Corus is preventing one tonne of carbon from reaching the atmosphere each hour – nearly 8,000 tonnes per year.

Anguil Environmental Systems

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