Method and device for processing solid waste
Organic waste is polished to remove floatable contaminants prior to being biologically treated. In one application, pressed organic waste is polished before being sent to a wet anaerobic digester, optionally to be co-digested with wastewater treatment plant sludge. The organic waste is polished by flinging globs of the organic waste against a screen while flowing air across the flinging globs. The polishing can be performed in a device having a rotor with discrete paddles inside of a cylindrical screen.
1. A device for separating floatable contaminants from organic waste comprising,
a horizontal cylindrical chamber;
a rotor, the rotor having,
a plurality of discrete blades distributed along the length of the rotor within a cylindrical porous portion of the chamber such that the discrete blades rotate relative to the porous portion of the chamber;
one or more blades within a non-porous portion of the chamber, the one or more blades, with or without the rotor and/or discrete blades, forming a blower for generating airflow from the porous portion to the non-porous portion to carry separated floatable contaminants toward the non-porous portion of the chamber, wherein the non-porous portion of the chamber has a discharge opening, wherein the airflow makes up the totality of airflows in the chamber;
an auger in communication with the discharge opening to carry the separated floatable contaminants away from the discharge opening.
2. The device of claim 1 further comprising a diverging discharge chute in communication with the discharge opening and the auger, the diverging discharge chute expanding away from the discharge opening.
3. The device of claim 2 wherein the chute is configured to provide an air passage for the airflow to flow over the auger, and includes an expansion chamber configured to cause a decrease in the velocity of the air flow over the auger in the expansion chamber.
4. The device of claim 1 wherein the rotor is supported on bearings located outside of the chamber.
5. The device of claim 1 wherein the rotor has a plate at one or both ends of the chamber.
6. The device of claim 5 having a scraping blade between the plate and the end of the chamber.
7. The device of claim 1 wherein each of the blades located within the porous portion of the chamber spans across 20 to 40 degrees of the circumference of the rotor.
8. The device of claim 1 wherein each of the blades located within the porous portion of the chamber extends across an arc of between 70 and 150 degrees of the circumference of the porous portion.
9. The device of claim 1 wherein the discrete blades lie obliquely to the rotation axis of the rotor.