Odour reduction at Richards Bay Mill
At Richards Bay mill, the complaints regarding malodorous gases in the past led to the mill identifying odour reduction as one of the main areas requiring attention and began work on the odour reduction project in 2009.
Project objectives and targets were set and a task team made up of representatives from the different business units (BUs) was established. The task team meets twice a month to discuss progress in identifying new equipment needs, and incidents within their BUs which relate to operational control issues to reduce emissions during normal operation of the plants.
In addition to identifying equipment needs, the management team set about working with operators and mill employees on their role in environmental impacts. This was done by allocating 8% of the employees’ performance bonus every three months for achieving our environmental targets on odour. Says Candice Webb, environmental manager at the Richards Bay mill, “The management team wanted all employees to be aware that their day-to-day actions can have an impact on the mill’s environmental performance.”
This was communicated to employees through a series of newsletters, toolbox talks, notice board articles and the annual Making a Difference Day Campaign. It also became compulsory that every maintenance, repair and cleaning task required the completion of an Environmental Risk Assessment in addition to a Safety Risk Assessment, which helped entrench environmental awareness throughout the workforce.
“Over the past four years the mill’s employees have gained a higher awareness of sustainability issues related to the operation of the mill,” adds Candice. Since 2008 the mill has noted an 80% reduction in the number of odour complaints logged through the local monitoring organisation, the Richards Bay Clean Air Association (RBCAA). In order to continue to improve on this positive performance, Environmental Compliance was introduced as one of the six Key Strategic Focus Elements for the Richards Bay mill in early 2013. This means that management’s KPIs are linked to each of the key elements, which ensures the KPIs are cascaded through the BUs and consolidated in the performance bonus targets. Our Mondi Diamond operational framework helps us to align our efforts across all six elements and the associated awards recognise our teams that contribute to the mill achieving its strategic objectives.
Odour abatement project phases
The €5 million invested in phases 1 and 2 of the odour abatement project addressed the point source emissions.
Commissioned in 2010, phase 1 included the installation of carbon filters for the concentrated non-condensable gas vents. The filters remove the odorous compounds from the gases being emitted to the atmosphere. The secondary condensate system was also upgraded to prevent further distribution of odorous compounds and reduce the carry-over of these compounds to other areas, in particular the lime kiln. Five monitoring stations were set up to measure the total concentration of reduced sulphur compounds in the ambient air.
In 2010, it became evident that the chip bin was a source of TRS emissions and this became the focus, with new equipment being installed and commissioned in 2012. This consisted of a chip bin reboiler generating clean steam, which is free of the odorous TRS gases contained in normal flash steam.
Since commissioning, the filters have significantly reduced the odour from the mills venting points, with recent calculations confirming in excess of 99% efficiency.
In early 2012, sampling from the dissolving tank outlets indicated that an estimated 55kg per day of TRS was being emitted from the dissolving tanks due to blocked scrubbers. It was agreed the dissolving tanks and their associated scrubber upgrades would form phase 3 of the project. This was successfully commissioned during the October 2013 annual shut-down, with an accompanying reduction in background odour being detected at monitoring stations.
During 2013, the odour task team completed the process of scoping phase 4, which is the upgrade of the high-volume low concentration (HVLC) gas system. Continuous pressure monitoring and odour sampling of the HVLC system has shown that the existing system is insufficient to carry the HVLC gases to the recovery boilers. The timing and scope of this project is currently under review.
Diffuse emissions were and are being addressed in phases 3 and 4.
Objectives and targets for the future
“The Richards Bay mill has set a further target of reducing odour complaints in 2014 by 20% based on the number of complaints received in 2013,” concludes Candice.