Flue gas discharged from waste incinerator contains various harmful substances including dust, acid gases such as hydrogen chloride and sulfur oxides, nitrogen oxides, dioxins, and heavy metals such as mercury. Turbo Chemical Baghouse (this product) is an epoch-making product that realizes removal of acid gas, dioxins, and mercury, which require strict regulatory values that cannot be met by the widely used general-purpose dry type flue gas treatment as well as significant reduction of unreacted slaked lime.
2．Background of the development
In order to treat flue gas generated by waste incineration, a dry treatment method, in which chemicals (slaked lime and activated carbon) are continuously blown into the flue gas and reacted and adsorbed with the flue gas in the flue gas duct and on the filter cloth surface in the bag filter, is widely used.
However, in this method, contact between the harmful components in the flue gas and slaked lime is not sufficient, and the amount of unreacted slaked lime increases. As the result, the ash collected by the bag filter has a strong alkali characteristic and heavy metals can be easily eluted. Therefore, stabilizing agent is also required for the final disposal.
Furthermore, when strict regulation values are required for the emission of harmful gases in metropolitan area etc., the dry treatment cannot handle such requirement. Because of this, instead, wet treatment, which requires complicated equipment and time-consuming maintenance, has been adopted. For the reason mentioned above, there has been a strong demand for a product that employs a dry treatment method that does not require wastewater treatment, can reduce maintenance costs and has high flue gas treatment performance.
3．Details of the product
The outline and internal structure of this product are shown in Fig. 1 and Fig. 2. In the general-purpose dry treatment, chemicals (slaked lime and activated carbon) are continuously blown into the flue gas duct to react and adsorb the harmful components in the flue gas duct and on the filter cloth inside the bag filter. With this method, contact efficiency between slaked lime or activated carbon and harmful components in the flue gas is not sufficient.
On the other hand, with this product, by blowing the chemicals at once in a short time (the chemicals required for 4 hours of treatment is blown into the flue gas in about 10 minutes), uniform thickness reaction / adsorption layer of slaked lime and activated carbon is continuously formed onto the filter cloth surface to treat the flue gas. Therefore, contact efficiency between the chemicals and harmful component is high.
By applying this method, dust in the flue gas can be completely removed on the surface of the reaction / adsorption layer of the chemicals, and acidic harmful substances (hydrogen chloride and sulfur oxides) in the flue gas can be removed with high efficiency because of the high contact efficiency with slaked lime and activated carbon. When slaked lime has not reacted with the flue gas or the differential pressure of the bag filter’s filter cloth has increased due to the treatment amount of the flue gas, the deposits on the filter cloth (toxic substances removed by the filter and the slaked lime that has reacted) are separated and dropped from the filter cloth. After that, slaked lime is blown again in a short time to form a new layer of chemicals on the filter cloth surface, and the flue gas treatment is continued.
As a devise, this product employs a movable chemical spray nozzle to quickly separate and drop deposits on the filter cloth and to form a new chemical layer on the filter cloth efficiently and a control mechanism with a damper that adjusts the amount of the flue gas.
4．Features of this product
This product can be adapted to any type of waste incinerator, and since the chemicals used for flue gas treatment can contribute to high removal efficiency of harmful substances, reduce the concentration of harmful gas to a level that exceeds the conventional wisdom about dry treatment, and significantly reduce the initial cost and running cost.
In addition, the product does not leave unreacted slaked lime very much for the flue gas treatment, reduce the amount of ash collected by the bag filter that requires final disposal as well as the chemical for stabilizing heavy metals, which also contributes to the reduction of the environmental load.
The 1st unit of this product was delivered for Kyoto University Hospital in 1994. Since then, enhancement and improvement of this product has been continuously made, and its performance continues to evolve. To date, 156 units of this product have been delivered for medical waste treatment, industrial waste treatment, disaster waste treatment, and general waste treatment plant.
Turbo Chemical Baghouse is a product made though experiences, research and development of 161 plants of incineration plants delivered by PLANTEC, and a technology that has responded to a wide variety of wastes and changes in wastes over half a century.
PLANTEC would like to disseminate the technology of the product widely, and work on further technological development of the product in order to contribute to the development of a recycling-oriented society.
Corporate Member，1-6-17 Kyomachibori, Nishi-ku, Osaka , JAPAN