Evaluation of Pressure Filtration of Coal Refuse Slurry: Effects of pH, Filtration, and Air-Blow Times

Coal refuse slurry impoundments have potential environmental concerns associated with water contamination and impoundment stability. Pressure filtration can be used as an alternative method of handling such coal waste streams as it offers an opportunity to stack the dewatered refuse solids for subsequent disposal, reducing or eliminating the need for the impoundment. A response surface methodology approach was used to evaluate the effects of pH, filtration time, and air-blow time on pressure filtration, whose response was measured in terms of final cake moisture. Cake moistures as low as 19.2% were obtained in this study. Experimental results showed a decrease in cake moisture by 13% with an increase in filtration time from 40 minutes to 50 minutes. One third reduction in cake moisture was achieved for a test with 10 minutes of air-blow after 30 minutes of filtration time compared to a test with 40 minutes of filtration time. The effect of pH was significant on both the residual moisture content and the amount of solids deposited in the cake, with acidic pH increasing the filtration performance. A linear fit was developed to relate the amount of solids deposited in the cake as a function of pH and filtration time. A regression model for the response surface with respect to the predictor variables had an R(2)value of about 0.99 with almost all the main effects, their square terms, and the interaction effects statistically significant.

Automated summary

Pressure filtration can be used to handle coal refuse slurry, reducing the need for impoundments and improving filtration performance. Experimental results showed that filtration time and pH have significant effects on cake moisture and the amount of solids deposited in the cake.