A Feasibility Study on Reducing Flowability of Vacuum Tower Bottoms Using Aggregate

Vacuum Tower Bottom (VTB) is a final bottom product of distillation at a crude unit and accumulates at the bottom of vacuum towers. When the tower is cleaned, VTB is removed and often buried in landfills. However, relatively high temperature and overburden pressure in the landfill may result in VTB becoming soft and flowing out. The outflow of VTB in landfills creates challenges to the management of landfills. To reduce the flowability of VTB in landfills, aggregate may be mixed with VTB before its placement. In this study, California Bearing Ratio (CBR) tests were carried out to investigate the feasibility of using aggregate to reduce the flowability of VTB. VTB was mixed with two types of aggregate at different weight ratios. The mixtures were compacted and tested for CBRs at two temperatures (21 and 60 °C). The test results showed that an increase of the amount of aggregate increased the CBR value. The well-graded aggregate improved the CBR value of the mixture more than the poorly graded aggregate. An increase of the temperature from 21°C (70°F) to 60 °C (140°F) reduced the CBR value of the mixture.