Year 1997
Tom Mäenpää

Prevention of Odorous Gas Emissions from a Kraft Pulp Mill

This thesis focuses on odorous gases released from a kraft pulp mill. The odor is predominantly caused by the sulphur compounds referred to as total reduces (TRS). The TRS gases involved are hydrogen sulphide, methyl mercaptan, dimethyl disulphide, and dimethyl disulphide. The purpose was to conduct an odorous gas emission inventory and to determine process measurements (such as temperatures, pressures, and flow rates) which could be used to detect emissions. The purpose was also to find methods to eliminate or at least minimise the most important occasional emissions.

The inventory was conducted using five measuring methods. Occasional emissions were detected using movable temperature sensors and process measurements connected to the plant automation and information system. The concentration of the individual TRS components was measured using a gas accomplished using an analyser based on UV- fluorescence Chlorine dioxide was also determined in one experiment. This measurement was based on iodometric titration.

Five occasional emission sources were examined including chip bin, turpentine condensers, weak odorous gas washer/cooler, bleaching plant Iscrubeer, and heat recovery system. Based on the results received reduction of emission from several sources seem to be possible using process control methods.

Finally, an estimation of the emission from the most important emission sources was conducted. Sources releasing odorous gases continuously as well as occasionally were included in this estimation. Results from a ranking of different types of sources showed that four sources including heat recovery system, recovery boiler 1 & 2, accounted for about 90 % of total TRS emissions.

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