Mechanized separation and recovery system for solid waste
Methods and systems for separating a mixed waste into a wet organic fraction, a dry organic fraction, and an inorganic fraction are achieved by (i) comminuting the mixed solid waste, (ii) fractionating the comminuted stream by size to produce two or more particle-sized waste streams, and (iii) processing one or more of the particle-sized waste streams using density separation to produce an intermediate wastes stream, and (iv) recovering a homogenous product (e.g., a recyclable material or an organic fuel) from the intermediate waste stream.
1. A method for separating solid waste comprising:
providing a mixed solid waste stream that includes wet organic waste, dry organic waste, and inorganic waste;
shredding the mixed solid waste in a shredder to produce a comminuted waste having a first size distribution, wherein the shredder has cutting blades or knives configured to cut paper, plastic, rubber, wood, and/or textiles to a size and shape suitable for separation in an air density separator;
fractionating the comminuted solid waste by size to produce an under fraction enriched in wet organic material and an over fraction enriched in dry organic material including at least two materials selected from the group consisting of paper, plastic, rubber, wood, and textiles; and
fractionating the over fraction in a first density separator to produce a heavy fraction and a light fraction and separating the heavy fraction in a second density separator to produce a wet organic fraction and an inorganic fraction; and
recovering one or more dry organic products from the light fraction or a downstream portion thereof, the dry organic products including a mixture of at least two materials selected from the group consisting of paper, plastic, rubber, wood, and textiles.
2. The method of claim 1 , wherein the light fraction or a downstream portion thereof includes aluminum and the aluminum is separated from the stream in an eddy current separator.
3. The method of claim 2 , further comprising recovering a metal product from the under fraction or a downstream portion thereof.
4. The method of claim 1 , wherein the shredded waste is comminuted to a size of about 16 inches and below, and the over fraction has a second size distribution with a ratio of small particles to large particles of less than 1:8.
5. The method of claim 1 , wherein the shredded waste is comminuted to a size of about 12 inches and below, and the over fraction has a second size distribution with a ratio of small particles to large particles of less than 1:6.
6. The method of claim 1 , wherein the over fraction has a bottom cut size of greater than 4 inches.
7. The method of claim 1 , wherein the under fraction is fractionated using a first density separation unit to produce a heavy fraction and a light fraction.
8. The method of claim 7 , further comprising:
processing the under fraction using a second size separation unit situated downstream from the first size separation unit and upstream of the first density separation unit,
wherein the second size separation unit is configured to produce a second over fraction having a second size distribution with a ratio of small particles to large particles of less than about 5 inches and a second under fraction having an upper particle size of less than about ⅕ of the large particle size of the over fraction and wherein the second under fraction comprises a wet organic product.
9. The method of claim 7 , further comprising processing the light fraction from the first density separation unit using a second density separation unit to produce a dry organic product and a wet organic product.
10. The method of claim 9 , wherein fractionating the over fraction using density separation is performed using a third density separation unit to produce the heavy fraction and the light fraction and wherein the heavy fraction from the third density separation unit is further separated by density using a fourth density separation unit to produce an inorganic fraction and a wet organic fraction.
11. The method of claim 10 , further comprising:
using at least one of a magnetic separation unit or an eddy current separation unit to recover ferrous metal fraction or a non-ferrous metal fraction from the under fraction or a downstream portion thereof.
12. The method of claim 10 , further comprising processing the wet organic product from the second size separation unit to remove at least a portion of a residual inorganic debris.
13. The method of claim 10 , wherein the first and/or second density separation units includes an air drum separator and/or a gravity/air separation unit.
14. The method of claim 1 , wherein the density separation of the over fraction is performed using an air drum separator.
15. The method of claim 1 , wherein the wet organic fraction is processed to produce a wet organic product, the method further comprising processing the wet organic product using a microbial digestion system or drying the wet organic product to produce an organic fuel.
16. The method of claim 1 , further comprising processing the dry organic product to produce a dry organic fuel.
17. A method as in claim 1 , wherein the light fraction from the density separator has a density of less than 10 lbs/ft 3 .
18. A system for separating solid waste, comprising:
a shredder configured to receive a mixed solid waste and comminute the mixed waste to produce a comminuted waste having a first size distribution, wherein the shredder has cutting blades or knives configured to cut paper, plastic, rubber, wood, and/or textiles to a size and shape suitable for separation in an air density separator;
at least a first size separation unit configured to receive comminuted waste from the comminuting device and fractionate the comminuted waste based on size to produce an under fraction and an over fraction, wherein the over fraction includes paper, plastic, rubber, wood, and/or textiles;
a first density separation unit configured to receive the over fraction and separate the over fraction based on density to produce light fraction and a heavy fraction;
a second density separation unit configured to receive the heavy fraction and produce a wet organic fraction and an inorganic fraction; and
one or more conveyors configured to recover a dry organic fuel from the light fraction or a downstream portion thereof, the dry organic fuel having at least two materials selected from the group consisting of paper, plastic, rubber, wood, and textiles.
19. The system recited in claim 18 , wherein the shredder is configured to shred the solid waste to a size of about 16 inches and below.
20. The system recited in claim 18 , wherein the over fraction from the first size separation unit has a second size distribution with a ratio of small particles to large particles of less than about 8 inches, and wherein the under fraction from the first size separation unit has as upper particle size of less than about ⅙ of the large particle size of the over fraction.