EIS Safety First - Case Study
EIS was invited by a UK company to provide a fully automated VOC / odour abatement system treating the exhausts from multiple processes and needing multiple safety systems. The abatement plant would be part of the construction of a new factory based in Scotland, so the timing and installation of the system would be critical to the plant coming on stream at the planned date.
The production process consisted of multiple high temperature batch furnaces operating continuously and producing exhaust streams with VOC levels exceeding 50% LEL. The requirement for a safe and robust abatement system that would meet the stringent demands of the operating regime was the design challenge accepted by EIS.
The design of the system was based on a clear understanding of the client’s production process and the specific requirement for a safe operating system under all production conditions, bearing in mind that once started each batch will continue to produce VOC and cannot be stopped.
EIS design engineers based the heart of the solution on a 95% thermally efficient three canister Regenerative Thermal Oxidiser complete with a high solvent bypass to accommodate the high solvent loadings.
The process exhaust is collected from each of the multiple outlets that are on line at any one time and is fed into a dedicated self- balancing ductwork system that directs the fume into the inlet of the RTO.
A separate parallel ducting system is installed as a safety feature to be used in case of an upset process condition and ensuring that in this event the exhaust is vented to atmosphere via a separate inlet connection into the main exhaust stack.
In addition to the main exhaust flows from the furnaces, there are small exhaust flows from other areas of the production process that are either directed to the main exhaust stack through a separate ductwork system, or when the streams have a high concentration of VOCs, are ducted to an inlet port adjacent to the burner mounted on the RTO’s combustion chamber. To ensure the process and the RTO are integrally safe, flame arresters are fitted into the ductwork in close proximity to identified ignition sources.
Additional safety features included duty and standby bypass fans, whilst the integrity of the PLC, which controls the integration between the process and the RTO, is maintained with an uninterrupted power supply and the duty and standby-fans are backed up by a diesel generator.
To ensure that the ceramic media in each of the three heat exchanger canisters is not effected by particulate carry over from the process the PLC program has provision for an automatic bake out procedure. The system was installed on time and to the required safety standards.