Testing microwave dewatering as a solution for reducing clay disposal pond areas

ABSTRACT Phosphate processing plants produce an excessive amount of phosphatic clay. This clay represents a serious environmental problem due to their disposal in huge ponds. Finding a feasible method to reduce the clay disposal area is needed. Although the flocculation process, in the presence of fibrous material, seems to be a good dewatering process for phosphatic clay wastes, the maximum solid percentage of flocculated clay does not exceed 18% (starting from 3 to 4%). Recently, the microwave proved a better performance in several research areas as compared to the conventional drying. In this study, clay dewatering by microwave was investigated. Several factors affecting the dewatering process were studied such as heating time, microwave power efficiency, and fiber percentage. Using the microwave, the solid content significantly increases in a reasonably short time. The time and power are the most significant among the studied factors. In addition, sand–clay mix was tested to improve the solid percentage to be used as a filling material. The results showed that the presence of sand enhances the clay drying due to the transparency of sand to the microwave irradiation as well as increasing the clay bed porosity, which facilitates migration of liquid water and/or water vapor toward the surface of dried material.

[1]  T. Kudra,et al.  Uniformity Issue in Microwave Drying , 2011 .

[2]  N. Rowson,et al.  Microwave treatment of minerals-a review , 1998 .

[3]  Guangwei Yu,et al.  Influence of microwave irradiation on sludge dewaterability , 2009 .

[4]  P. Rattanadecho,et al.  Microwave and Hot Air Drying of Wood Using a Rectangular Waveguide , 2011 .

[5]  S. Kocakusak,et al.  Drying of wet boric acid by microwave heating , 1998 .

[6]  Kaida Khalid,et al.  Microwave Drying of Palm Oil Mill Effluent , 1998 .

[7]  K. Khalid,et al.  Drying of silica sludge using microwave heating , 2004 .

[8]  Hao Jiang,et al.  Recent Developments in Microwave-Assisted Drying of Vegetables, Fruits, and Aquatic Products—Drying Kinetics and Quality Considerations , 2010 .

[9]  Chenghai Liu,et al.  Optimization of Parameters for Microwave-Assisted Foam Mat Drying of Blackcurrant Pulp , 2011 .

[10]  W. Mcminn,et al.  Thin-Layer Modeling of Microwave, Microwave-Convective, and Microwave-Vacuum Drying of Pharmaceutical Powders , 2005 .

[11]  H. El-Shall,et al.  Process for dewatering and utilization of mining wastes , 2004 .

[12]  Zhiyong Cai,et al.  Microwave Drying of Wood Strands , 2005 .

[13]  N. J. Miles,et al.  Microwave heating applications in environmental engineering—a review , 2002 .

[14]  D. H. Gray.  Geotechnical Practice for Disposal of Solid Waste Materials , 1977 .

[15]  K. E. Haque,et al.  Microwave energy for mineral treatment processes—a brief review , 1999 .

[16]  S. Kowalski,et al.  Analysis of Effectiveness and Stress Development during Convective and Microwave Drying , 2007 .