| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 95 === This study summarized the techniques of recycling and reusing leather waste. The boiling treatment to recycle the leather waste used by a factory was chosen as a case study. In the study, the chemical compositions of the discharged volatile organic pollutants and the efficiency of reducing the pollutants by using the chemical scrubbing method were measured. Furthermore the cost of treatment was also estimated for this case study. In the recycling process, the boiler was the major source to emit the pollutants since the chemicals like degreasing agent and tannic acid used on the leather were treated under high-temperature and high-pressure process. Totally 58 VOCS compositions of the emitted gas from the boiler were analyzed. The results showed that the discharged VOCS before the scrubbing process contained acetone, 2-butanone, acrylonitrile, methylene chloride, benzene, toluene, n-pentane, heptane and octane. The proportion of acetone and 2-butanone was the highest (55.7%) among these nine species.
The solution used in the scrubber contained 12% of sodium hypochlorite oxidant. High scrubbing efficiencies approximately 98% were obtained for removing acetone, benzene, acrylonitrile, 2-butanone, n-pentane, heptane, octane and methylene chloride from the exhaust gas. However, the efficiency of eliminating toluene was only 22%. The major remained species from the exhaust after the scrubber were 68% of toluene and 28% of acetone. The reason for the lower efficiency in reducing toluene could be the concentration of toluene (only about 3ppm) too low so that the control efficiency was low as well. Overall the process used in this case study was economical since the price of sodium hypochlorite was cheaper than the other oxidants. The preliminarily estimated charge was about NT$ 27,213 dollars for reducing 1-ton of VOCS by the scrubber.
In analyzing comprehensively the control efficiency, equipment operation and maintenance as well as cost benefit, the boiling process with the oxidative scrubbing to recycle the leather waste could be rated as a “reasonably available control technology (RACT)”. But adopting sodium hypochlorite as the oxidant would produce the waste water containing chlorine which not only increased the expenses of wastewater treatment, but also caused environmental impact to some extent. Therefore it still needed further evaluation whether the process adopting oxidative scrubbing could be rated as the best available control technology (BACT).
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