Abstract
Scientific and reasonable treatment of dredged silt can not only protect the ecological environment but also play an essential role in the utilization of silt resources. Due to high water content, low permeability and high organic matter content of the silt, a large amount of bacteria and harmful gases are often produced during the process of silt sedimentation. Thermal drying has been taken as a technically attractive method for harmless treatment of contaminated dredged silt. In this study, ultrasound technology is introduced to shorten the time needed for silt drying. A preliminary laboratory study is carried out to assess the effectiveness of ultrasound on thermal drying. A series of thermal drying tests, with and without ultrasound, were conducted on kaolin soil specimens that were prepared by settling and self-weight consolidation. The test results show that the length of drying time can be shortened by increasing temperature and ultrasound power. The drying time plays a dominant role in the determination of the total energy consumption. This is because reduction of drying time leads to significant decrease in energy consumption for thermal drying, and the energy consumption for additional ultrasound is relatively marginal. For thermal drying at temperatures 60 and 100°C, when combined with 100 W ultrasound, the length of drying time was shortened by 44.19% and 45.16%, and the energy consumption was saved by 30.07% and 38.16%, respectively; when combined with 60 W ultrasound, the length of drying time was shortened by 4.65% and 6.45%, but the energy consumption was increased by 9.79% and 0.48%, respectively. The combination of thermal drying and 100 W ultrasound is found to be optimal in terms of drying rate and energy consumption for silt drying.
Highlights
There are many navigable rivers around the world
It can be seen from the p values that both the temperature and ultrasound power have significant effects (p < 0.05) on the energy consumption
In this study, drying experiments of different modes were conducted to solve the problems existing in the process of harmless treatment and recycling of silt
Summary
There are many navigable rivers around the world. A large amount of silt deposits on the riverbeds due to sedimentation every year. Dredging is a common method used to maintain the navigable capacity of rivers In this method, silt is sucked out from riverbeds and pumped into an open area for natural settling and artificial treatment, during which the organic compounds contained in the dredged silt generate and release unpleasant odors and cause pollution [1]. The dredged silt is taken as waste until it can be transported without being leaked/spilled out of containers, and utilized as a valuable material without pollution [2] It is difficult for pore liquid of silt to migrate outward [3,4,5], and the natural settling process without the aid of artificial treatment may last for years. The thermal drying technology, which is widely used in chemical industry, is considered a time and cost–effective method for harmless dehydration treatment of dredged silt. The results are discussed, followed by the summary and conclusions
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