Incineration of Dilute Non-Condensable Gasses in the Recovery Boiler at Pacifica Papers, Powell River, British Columbia, 2002 Fall Technical Conference

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The incineration of dilute non-condensable gasses (DNCG) and concentrated non-condensable gasses (CNCG) is increasingly used in the pulp and paper industry to address safety and environmental issues. These gasses may be incinerated in the lime kiln, power boiler, dedicated incinerator, or in the recovery boiler. Historically, mills have been hesitant to use the recovery boiler as an incineration site. The recovery boiler offers some advantages for NCG incineration, however, and the Black Liquor Recovery Boiler Advisory Committee (BLRBAC) has issued recommendations for the incineration of waste streams in recovery boilers. Many mills around the world have recognized the advantages and installed NCG incineration systems on their recovery boilers.

DNCG and CNCG collection and treatment systems have different design requirements based on their differing explosive limits, flame propagation speeds, fuel values, etc. They also have different incineration and burner requirements. For example, CNCG systems typically require a dedicated burner whereas DNCG systems do not. The collection and treatment of the waste stream prior to incineration is very important to the safe and effective operation of an incineration system. Equally important is the proper design of the combustion system. This paper will focus on the injection and combustion of a DNCG stream in a recovery boiler.

In the spring of 2001, Pacifica Papers (now NorskeCanada) installed a DNCG collection, treatment, and incineration system at their Powell River mill site. Anthony-Ross Company designed the boiler modifications, distribution piping, and injection nozzles, and managed the turnkey installation of the combustion system. A CFD boiler combustion model was commissioned to examine various alternatives for the injection of the DNCG stream. The incineration system was designed using the results of the CFD model to improve the overall combustion in the furnace. Following the boiler modifications and start-up, the DNCG system was put into operation. The mill reported improved combustion in the furnace and complete incineration of the DNCG. The system was deemed a complete success by the mill. Unfortunately, the pulp mill ceased operation six months after start up of this project.

A summary of the requirements and design of the collection and treatment system will be given, and the requirements of the incineration system will be highlighted. Illustrations and photographs will be provided of the DNCG incineration system, as well as details and specifications of the injection nozzles and air system improvements. Results of the CFD model will be examined to explore the advantages and disadvantages of various combustion system arrangements. It will be shown that a properly designed DNCG incineration system can effectively dispose of the waste stream and simultaneously improve the overall combustion of a recovery boiler.