BACK TO BASICS WITH FOUL GAS INCINERATION

摘要

Australian Paper operates a dedicated Foul Gas Incinerator (FGI) for the destruction of kraft mill foul gases, including Concentrated Non Condensable Gases (CNCG), Stripper of Gases (SOG) and Dilute Non Condensable Gases (DNCG). The operation of this plant is critical to meeting Australian Paper's air emissions license and community expectations through the destruction of odourous gases The Foul Gas Incinerator (FGI) recorded higher than normal total reduced Sulphur (TRS) emissions in 2017 and 2018. Investigations into the root cause of TRS emissions found that focusing on standard operating parameters while minimising process disturbances could significantly reduce TRS. According to TAPPI Tip 416-09, three basic parameters are needed to successful destruct of TRS; Time, Temperature and Oxygen. By reviewing plant operations, targeting correct operating parameters, minimising disturbances and tuning the control system, the three basic parameters of time, temperature and oxygen were stabilised and TRS emissions were reduced. This FGI system is subject to the running conditions of the rest of the plant, any variation in this system can lead to non-optimal process conditions. Plant operating personal found one such variation and identified a new correlation in a seal tank and TRS emissions. This correlation allowed improvement work to be conducted on SOG flow. SOG was stabilised and smoothed to reduce the impact of methanol and TRS at the FGI. By applying TAPPI TIP 416-09 and controlling excess Oxygen levels in the FGI, Oxygen in the FGI is now controlled to provide a buffer to prevent low Oxygen excursions resulting in TRS. TRS emissions have reduced while FGI process parameters have stabilised with a reduction in Natural Gas use. To achieve this improvement, oxygen measurement was reinstated in the flue gas to provide feedback control to forced draft air supply. Balancing of the DNCG from the Batch Kraft Mill allowed stabilisation of the oxygen supply that allows excess Oxygen content to be optimised. The stabilisation and reduction of DNCG allows for increased thermal efficiency and reduced natural gas usage. By focusing on basic operating parameters, talking to operating personal, following TAPPI Tip's and identifying the root causes of disturbances, the overall performance of the Foul Gas Incinerator has improved with a reduction in TRS emissions.