Disposal of spent filter cake generated by oil processing plans has known risks. In particular, the spent filter cake is spontaneous combustible. That’s why it requires special conditions for disposal (in windrows).
There is no developed technology for spent filter cake recycling.
Most common strategies of spent cake disposal include:
|Spent Filter Cake disposal method
||What makes it non-working
|Direct disposal – landfill. Hauled off for burial. Oil saturated spent filter cake does possess the potential for spontaneous combustion so care must be taken to keep the spent cake in covered, fireproof dumpsters at the plant site; note that the addition of water will help to reduce the possibility of ignition.||Aside from the safety issue, many localities are restricting the types of industrial wastes they will accept and almost all are charging higher prices for dumping them.|
|Direct disposal – farmland. Direct disposal of spent cake on farmland is another option that has been examined and found to work well. Studies have shown that 60-90% of the oil is decompressed during the course of a normal six-month-growing season by soil bacteria and that this approach works best in warm climates on sandy soils where some fertilizer has been added. Plants grown on soils treated with plant spent cake were quite normal and may even have benefited from improvements in soil water retention caused by the spent cake.||This method does not cost efficient for farmers. Spent filter cake doesn’t increase fertility, so farmers are not interested in its disposal.|
|Use as an animal feed supplement. Spent cake can also be used as an animal feed supplement.||Again, farmers are not interested in this disposal method. Also, it creates additional risks for animals health because a source of the filter cake is not always known.|
|Use as low-grade fuel for power/heat generation. The heating value for soybean oil is 39,500 kJ/kg (16,987 BTU/lb). Assuming 30-40% oil retention, it can be estimated that spent filter cake should possess heating values of about 11,900-15,800 kJ/kg (5100-6800 BTU/lb). In comparison, the heating value for lignite falls in the range 14,650-19,300 kJ/kg (6300-8300 BTU/lb). For boilers equipped to handle high-ash fuels such as coal and lignite, the incorporation of relatively high percentages of spent filter cake in the boiler feed should pose no problem.||Physycal characteristics of spent filter cake don’t allow burn out oils easily. This method requires custom-designed equipment.|
Also, know some theoretical approaches to the spent filter cake regeneration problem:
- Base extraction.
- High-temperature water extraction.
- Hexane extraction.
- High-pressure CO2 extraction.
- High-temperature aqueous regeneration.
- High-temperature wet oxidative waste regeneration.
But these technologies not developed at the manufacturing level yet.