;In recent year, the collected amounts of the general household solid wastes decreased significantly, thus the large municipal solid waste incinerators (MSWI) in Taiwan have headroom capacity to handle the general industrial solid waste. Consequently, due to the great changes in nature and composition of the solid wastes into MSWI, the emission concentration of acid gas pollutants with high fluctuating conditions was occurred frequently. In order to realize the stability of the facility for controlling the acid gas pollutants, a full scale of MSWI in northern Taiwan, using semi-dry scrubbers to remove acid pollutants in the flue gas, was employed in this study. The effects of the operating variables, include type of chemicals, reaction temperature and stoichiometric ratio of chemical, on the removal efficiency of acid gas pollutants were investigated. Scenario simulation experiments were also carried out to understand the strategies for maintaining stability of the flue gas control system.
The results shown that when the flue gas at the temperature of 150 ℃ and using hydrate lime and sodium hydroxide as chemical agent at the stoichiometric ratio of excess dosing was 2.4 and 1.6, respectively, the HCl acid gas removal efficiency were both of over 96% and the SOx removal efficiency was above 86% and 78%, respectively. However, the increase of temperature of the flue gas, the HCI and SOx acid gas removal efficiency was gradually decreased. It also found that when the temperature of the flue gas increased to 210 ℃, only bicarbonate sodium at the stoichiometric chemical dosing ratio of 1.6, the HCl and SOx acid gas removal efficiency could be maintained above 96% and 85%, respectively.
In addition, the strategies for maintaining stability of the acid gas control system, the result of this study indicated that adding an extra cooling water spray system to control the temperature of flue gas approximately between 140 ~ 150 ℃ if at the necessary. So that the best acid gas removal efficiency could be obtained at the lowest stoichiometric dosing ratio of hydrate lime. Establish a new dry hydrated lime spray system for supplying the extra hydrate lime to enhance the removal efficiency of acid gases, when the exhaust gas emission concentration of acid gases suddenly changes. Besides, use crane to blend all kinds of solid wastes in the refuse bunker in order to make the nature of the feed into the waste incinerator maintaining at a uniform steady state at all operation time.