Jaran Bunyakan, Janthima Chungsiriporn, and Ratchadaporn Thepchai

pp. 825 - 836

Abstract

Ammonia is a common chemical used in various industries. Emission of air contaminated with ammonia to the atmosphere without any treatment causes several effects on human health and environment. A high efficiency method for ammonia removal from waste air is then necessary. In this research, an absorption coupling with chemical reaction was investigated for ammonia removal from waste air using a packed column. The packed column of 10 cm diameter and 200 cm height was packed with 1.4x1.4 cm Raschig rings.
Three liquids including water, NaOCl and H₂SO₄ solution were used as an absorbent for the investigation. The objectives of this research were to determine a suitable absorbent and the optimum condition for ammonia removal from waste air. The packed column was operated at room temperature and atmospheric pressure. The tested conditions were as follows: the gas to liquid ratio (G:L ratio) was 35-90 m³gas/m³  liquid, the inlet concentration of ammonia was 150-500 ppm and the air flow rate was 18 m³/h. The results showed that the ammonia removal efficiency depends on type of the absorbent and the operating condition. The efficiencies increased with decreasing of G:L ratio and with increasing absorbent concentration. They were 70%, 80-92%, and 95-100% for pure water, sodium hypochlorite solution and sulphuric acid solution, respectively. The efficiency decreased with time when water was used as an absorbent while it was almost constant when NaOCl and H₂SO₄ solution were applied. The ammonia removal efficiency when using H₂SO₄ as the absorbent was not dependent on G:L ratio and inlet ammonia concentration, in the range used in this investigation. Since H₂SO₄ solution gave the highest removal efficiency and can reduce ammonia concentration in waste air to levels which meet the TLV-TWA standard, it is recommended as an absorbent solution for ammonia removal from waste air.