WO2020053552A1

WO2020053552A1 - Municipal solid waste wet separation process

Info

Publication number: WO2020053552A1
Application number: PCT/GB2019/052460
Authority: WO
Inventors: Ian PARNABY
Original assignee: Derek Parnaby Cyclones International Limited
Priority date: 2018-09-10
Filing date: 2019-09-04
Publication date: 2020-03-19
Also published as: GB201814666D0

Abstract

An apparatus (2) for separating and processing the components of Municipal Solid Waste (MSW) is described. Shredded MSW is fed into a first separator means (8) comprising a cylindrical container portion (10) in which auger means (12) is disposed. The auger means generally acts as an Archimedes screw and comprises a plurality of blades (14) disposed around the inner circumference of the barrel (10). The waste fed into first separator means (8) is mixed with water and the barrel (10) rotated. Solid waste of higher density tends to be spun under a centrifugal force towards the wall of barrel (10) and is moved upwardly by the blades (14) to a first outlet (14), Solid waste of lower densities mixed with water tends to flow downwardly towards second outlet (16).

Description

Municipal Solid Waste Wet Separation Process

The present invention relates to a method of separating the components of solid waste and relates particularly, but not exclusively to a method and apparatus for separating the components of municipal solid waste (MSW) to extract useful by-products and reduce the amount of municipal solid waste sent to landfill.

Municipal solid waste (MSW) usually known as rubbish in the United Kingdom and trash or garbage in th United States is everyday waste that is generally not sent for recycling. For example, in the United Kingdom homes generally a e a recycle bin in which glass, plastics, metal cans , card and paper can be placed to be sent to a recycling facility. Such homes will also have a general waste bin in which bagged waste that usually cannot be recycled such as food, some types of plastic, fabrics, batteries and other items are placed. The bags are then taken away to be processed.

The bags may be shredded and the shredded waste is then passed through a trommel (a rotating perforated cylindrical sieve or screen. The material that passes through the trommel is generally placed in landfill .

Some countries are introducing legislation to either

significantly reduce or completely eliminate landfills. It is therefore highly desirable to reduce the volume of

municipal solid waste that is sent to landfill.

WO20G6/128166 describes an aggregate washing a d

classification system including a perforated sand classifier having an internal auger which is rotated relative to the stationary barrel. The classifier is submerged. in a pool of water and has different grades of perforations chosen to sift particular sizes of gravel and rock as the auger lifts material along the classifier. This apparatus is perforated and therefore cannot retain and direct a flow of fluid. It therefore must be submerged in a pool of fluid in order to operate and is unsuitable for separating the wride variety of materials found in mixed household waste. GB2513129, W02G08/129101, KR20090132343, US3807558, GB679166 and JP2001096186 all describe apparatus for processing aggregate type material that operate augers submerged in a pool of water to lift heavy material out of the pool. The apparatuses are unsuitable for separating the wide variety of types of material found in mixed household waste and are unable to retain and direct a flow of fluid since the augers comprise central shafts and rotate relative to stationary barrels . A preferred embodiment of the present invention seek to overcome one or more of the above disadvantages of the prior art .

According to an aspect of the present invention, . the e is provided a method of separating the components cif solid waste, the method comprising introducing a mixtiire of solidwaste and water into first separator means, whe·rein the first separator means comprises: a container portion for retaining and. directing a flow of fluid ; auger means disposed in the container portion, the auger means configured to rotate and urge at least some of the solid waste of higher densities towards a first outlet; and wherein the container portion is configured such that at least some of the solid waste of lower densities flows in a stream of water to a second outlet,

This provides the advantage of a method to efficiently remove aggregates (rock, ceramic, glass etc.) from municipal solid waste (MS ) trommel fines to reduce the weight of the waste being processed. This also provides the advantage of separating rigid plastics such as bottle tops and toys from MSW, This is advantageous because such rigid plastic contains chlorine, meaning that it cannot be burned as refuse derived fuel (RDF) .

Furthermore, this also provides the advantage of separating and removing at a different outlet a source of fibrous and organic-rich material. This type of material is desirable to create either RDF or anaerobic digestion fuel.

The method enables a dual flow of waste material to be advantageously set up to create three different processible waste outputs. Firstly, heavy aggregate material (sinks) are produced at the first outlet and secondly and thirdly lighter floating and sinking fibrous/organic materials are produced at the second outlet. In a preferred embodiment, the container portion is a

cylindrical barrel configured to rotate about an axis offset from the horizontal to create a downward flow of water towards the second outlet, and wherein the auger means is affixed to the internal surface of the cylindrical barrel and is arranged to lift solid waste of higher densities towards the first outlet.

Use of an auger affixed to the internal surface of the cylindrical barrel provides the advantage that the auger is rotated as the barrel rotates without the need for a central shaft, This facilitates creation of a downward flow of fluid in the barrel.

In a preferred embodiment, the method further comprises the step of temporarily retaining a mixture of water and at least some of the solid waste of lower densities in a pool adjacent said second outlet.

This provides the advantage of enabling greater attrition of desirable floating material at the second outlet.

The method may further comprise the step of passing said mixture of water and at least some of the solid waste of lower densities through a trommel screen to produce low density solid waste smaller than a first particle size.

The method may fur her comprise passing low density solid waste greater than a first particle size produced at said second outlet through a first vibrating dewatering screen.

The method may further comprise the step of passing at least some of the solid waste of higher densities at said first outlet through a second vibrating de atering screen to produce higher density solid waste smaller than a first particle size. This provides the advantage of removing large pieces of inert aggregate material that can be processed to provide aggregate (particles of rock, ceramic, glass etc.) for use as a

construction material for example. This also provides the advantage of enabling further processing of organic material disposed on the higher density waste.

The method may further comprise the step of mixing said low density solid waste smaller than a first particle sire and higher density solid waste smaller than a second particle size with water and feeding the resultant mixture into a first f1oatation tank : wherein higher density solid waste sinks is removed at a first floatation tank outlet; and wherein lower density solid waste floats to the top of said first floatation tank and is passed into a second f1oatat. i.on tank..

This provides the advantage of a single tank system that can be used to process two different grades of waste.

The method may further comprise the step of feeding output water and s?olid waste mixtures from said first and second floatation tanks into respective first and second cyclonic separators to remove inert material and high density plastic ,

This provides the advantage of a final separation step to process and separate inert material and high density plastics from fine organic material, insert silts, fine soils and fine fibres . The method may further comprise the step of feeding output water containing suspended solids from said first and second cyclonic separators into a water tank apparatus to enable any high density solids and heavy metals to separate under gravit .

The suspended solids p edominantly comprises fine organic mater:ia .1 , inert silts, fine soils and fine fibres which can be used to make either RDF or fuel for anaerobic digestion. This step therefore provides the adva

age of separating out pollutants .

The method may further comprise the step of mixing output water containing suspended solids with dilute flocculent and pressurised air to create foam in a thickener apparatus to enable organic material floating on the surface of said thickener apparatus to be raked off.

This provides the advantage of prodi ng a biomass product and fuel for anaerobic digestion.

According to another aspect of the present invention, there is provided an apparatus for separating the components of solid waste, the apparatus comprising first separator means comprising: a container portion adapted to receive a mixture of solid waste and water and retain and direct a flow of the mixture; auger means disposed in the container portion, the auger means configured to rotate and urge at least some of the solid waste of higher densities towards a first outlet; and fluid retaining means arranged adjacent a second outlet to create a pool of water and at least some of the solid waste of lower densities, such that said pool of water and at least some of the solid waste of lower densities is temporarily retained before flowing to a second outlet.

This provides the advantage of an apparatus to efficiently remove aggregates (rock, ceramic, glass etc,} from municipal solid waste (MSW) trommel fines to reduce the weight of the waste being processed. This also provides the advantage of separating rigid plastics such as bottle tops and toys from MSW, This is advantageous because such rigid plastic

contains chlorine, meaning that it cannot be burned as refuse derived fuel (RDF) .

Furthermore, this provides the advantage of separating and removing at a different outlet a source of fibrous and organic-rich material. This type of material is desirable to create either RDF or anaerobic digestion fuel.

Moreover, provides the advantage of enabling greater- attrition of desirable floating material at the second outlet , The apparatus enables a dual flow of waste material to be advantageously set up to create three different processible 'waste outputs. Firstly, heavy aggregate material (sinks) are produced at the first outlet and secondly and thirdly lighter floating and sinking fibrous/organic materials are produced at the second outlet.

In a preferred embodiment, the container portion is a

cylindrical barrel configured to rotate about an axis offset fro the horizontal to create a downward flow of water towards the second outlet, and wherein the auger means is arranged to lift solid waste of higher densities towards the first outlet ,

Said fluid retaining means comprises an annular disc.

Said auger means defines a screw and the apparatus may further comprise a plurality of blades disposed between the threads of the screw adjacent said second outlet.

Said fluid retaining means may comprise an annular cone.

The apparatus may further comprise at least one lifter to direct fluid flow.

In a preferred embodiment, the apparatus further comprises a trommel screen disposed adjacent said second outlet to produce low density solid waste smaller than a first particle size ,

According to a further aspect of the present invention, there is provided a tank apparatus for separating a mixture of water and waste particles of different sizes and densities, the tank apparatus comprising: a first floatation tank comprising a first deflector plate to direct denser particulate material towards the base of said first floatation tank; a first pump to remove a mixture of water and said denser material from the base of said first floatation tank; a second floatation tank arranged to receive an overflow of water and lighter particulate material from said first floatation tank, wherein said second floatation tank further comprises a second deflector plate to direct the overflow to create a turbulent flow; and a second pump to remove a mixture of water and said lighter particulate material fro the base of said second floatation tank.

This provides the advantage of a tank system that can be used to process severe different arades of waste.

According to a further aspect of the present invention, there is provided a cyclonic separator for separating a mixture of water and waste particles of different sizes and densities, the cyclonic separator coraprising: a cylindrical portion defining a longitudinal axis and comprising an inlet to receive a mixture of water and waste particles of different sizes and densities; a conical portion comprising a spigot aperture outlet for separated denser particles; a vortex portion disposed alone: the longitudinal axis and comprising an aperture inlet and a vortex outlet for

separating lighter particles; wherein said cyclonic separator is arranged to be inclined and declined. This provides the advantage of enabling further processing of MSW to separate inert material and high density plastics from fine organic material, insert silts, fine soils and fine ibres .

Said vortex portion may be moveable along said longitudinal

3Xi. S .

The size of said aperture inlet may be adjustable.

The size of said spigot aperture outlet may be adjustable.

A preferred embodiment of the present Invention will now be described by way of example only and not in any limitative sense, with reference to the accompanying drawings in which;

Figure 1 is schematic of a method embodying the present invention for separating the components of solid waste;

Figure 2 is a schematic of the floatation tank method of the system of Figure I;

Figure 3 is a schematic of the thickener of the method of Figure 1;

Figure 4 is a schematic of the first separator means of the method of Figure 1; and

Figure 5 is a schematic of a cyclonic separator of the method of Figure

Municipal solid waste iMSW) is generally supplied to

processing facilities in the form of plastic bags containing a wide variety of waste products such as food, paper, cardboard, glass, metal cans, metal foil, plastic films, plastic containers, batteries, small electrical goods, inert waste such as rock and ceramics, clothing, fabrics, aerosol spray cans and other everyday household items. It should be understood that the term "solid waste" used herein refers to what is known as municipal solid waste, i.e. trash or garbage in the United States, rubbish in the United Kingdom or mixed municipal waste in the EU,

Referring to Figures 1 and 4, an apparatus 2 is designed to separate the components of such waste. The bagged solid waste is shredded and then dry trommelled to a size of 60mm to 80mm or less, This materia1 is known as "MSW trommel fines" and is placed on conveyor 4 over 'which a magnet 6 is placed to remove ferrous metals

The waste (MSW trommel fines) is then fed into a first separator means 8 comprising a cylindrical container portion known as barrel 10 in which auger means 12 is disposed- The axis of rotation of the barrel is offset from the horizontal and may also be adjustable. The auger means generally acts as an Archimedes screw and comprises a screw portion 14 disposed around the inner circumference of the barrel 10. The waste (MSW trommel fines) fed into first separator means 8 is mixed with water at nlet 9 to form a combined slurry. The barrel 10 is rotated to rotate screw portion 14 which is attached to the inner circumference of the barrel 10.

Solid waste of higher density tends to be spun under

centrifugal force towards the wall of barrel 10 and is moved upwardly by the screw 14 to a first outlet 14. It can be seen that the barrel 10 is inclined towards a second outlet 16, Solid waste off lower densities mixed with water tends to flow downwardly towards second outlet 16, At this end, an annular disc 15 is pro ided to create an internal pool of liquid 17, Several blades 19 are also arranged between the threads of screw 14 to assist in the attrition of floating material. As a alterna11ve , an annu 1.ar cone 21 cou Id a so be use. Lifters 23 are also provided to direct fluid flow. The pool of liquid 17 provides high levels of attrition to break up lower density material. This liberates fine organics and contaminants, as well as breaking down larger fibrous

material to create a cleaner and dryer >12mm low density material output. The >12mm material tends to float and therefore passes out of second outlet 16. High pressure spray bars 18 are also provided for cleaning.

A trommel screen 22 rotates with the barrel 10 and comprises a plurality of perforations to enable low density solid waste smaller than a first particle size to be removed. In the embodiment shown, the preferred first particle size is less than 12mm, The <12m particle size material exists trommel screen 22 in the form of a slurry. Trommel screen 22 therefor effectively forms a third outlet to the barrel 10.

Low density solid waste greater than a first particle size tends tends to be floating fibrous and organic waste that comes out of second outlet 16, Thi material can be further processed to create fuel products, The lower density solid waste greater than 12mm is therefore passed through a first vibrating dewratering screen 24, Some of this waste is also further dewatered under a screw press 48.

At the first outlet 14, the denser material removed by the auger means 12 tends to be aggregate material such as rock, glass and ceramics. This material is passed through a second vibrating dewatering screen 26 to separate out solid waste of higher densities smaller than a second particle size. In the embodiment shown, the preferred second particle size is less than 5mm. Higher density solid waste larger than this is then sprayed with clarified water and passed under magnet 30 to remove ferrous materials. The material is then distributed onto an eddy current separator 28 to remove course non- ferrous material. This process produces separated output products of ferrous materials 32 and course and fine

aggregate material 3 . This aggregate material can be sold for uses such as construction and pipe bedding.

Referring to Figures 1 and 2, the denser aggregate material of less than 5mm and a slurry of water and lighter material of less than 12ram are then comingled to increase water content in a first flotation tank 36. The slurry of water and lighter material of less than 12mm enters the top of first floatation tank 36. The <5mm aggregate is fed into inlet 35 of first floatation tank 36 where it hits a deflector plate 37 to direct this denser material towards the bottom of the tank to be removed by first pump 38. The flow of 'water sets up a constant overflow to inlet 39 of second floatation tank 40. The lighter material is generally trapped in this overflow. A second deflector plate 41 directs the overflow into second floatation tank 40 to set up a turbulent flow.

The turbulent flow has been found to effectively drive any floating material less dense than water to the base of the tank to be removed by second pump 43.

The output mixtures from pumps 38 and 43 are then fed into respecti e first and second cyclonic separators 42 and 44. Referring o Figure 5, cyclonic separator 42 comprises a cylindrical portion 60 defining a longitudinal axis ana comprising an inlet 62 to receive a mixture of water and denser material from pump 38. A conical portion 64 comprises a spigot aperture outlet 66 for separated denser particles. A vortex portion 68 is disposed along the longitudinal axis and comprises an aperture inlet 70 and a vortex outlet 72 for separating lighter particles.

The cyclonic separator 42 can be inclined and declined about pivot point 74. This enables the cyclonic separator 42 to be biased towards either denser or lighter material. The vortex portion 68 is moveable along said longitudinal axis, the size of said aperture inlet 70 is adjustable and the size of the spigot aperture outlet 66 is also adjustable. All of these features enable the flow path to be adjusted to remove entrapment and entanglement points for fibrous material .

Cyclonic separator 44 is constructed in the same manner as separator 42. The cyclonic separators do not require the addition of a mediu (such as iron filings) to assist

separation .

Cyclone 42 is arranged to separate heavier inert material which is then fed to aggregate dewatering screen 26 and comingled on eddy current separator 28 to produce course aggregate .

The output of cyclone 44 (fibrous and low density plastic material) is fed to rotosieve 46 and dewatered using screw press 48. This provides an output of coarse residuals and fibre/fine low density plastics of low chlorine content which can be used as refuse derived fuel (RDF) .

The lighter material is processed in cyclone 44 to reduce inert material content and is then passed to rotosieve 46. The lighter inaterial predominantly consists of fine organics, inert silts, fine soils and fine fibres whic h can be further processed as a fuel for anaerobic digestion or a biomass fuel product .

Referring to Figures 1 and 3, the lighter material comprising fine organics, inert silts, fine soils and fine fibres is formed from a mixture of water and <lmm particlates in slurry. This material is merged in ta k 50 with a flocculent to agglomerate the particulates. White water (water through which high pressure air is pumped to create foam) is added. The mixture is then pumped into thickener 52. The organic material naturally floats on the surface of the thickener and is raked off and gravity fed to a buffer tank 54. Heavier silts settle to the bottom of the thickener and are extracted by pump 56 to provide a concent ate of heavy metals and inert materials . The thickener 52 therefore assists in removing heavy metals such as lead and zinc from the organic

concentrate .

The organic concentrate that has been raked off the surface of thickener 52 is fed from the buffer tank 54 to a multi role filter press 58. This creates an organic filter cake output product that can be used in anaerobic digestion processes or as a biomass fuel product.

Even though the method and apparatus disclosed has been described with reference to use of Municipal solid waste (MSW) as a source of raw material, other materials that can also be processed using the disclosed method and apparatus include :

·.« Material Recycling Facility (MRF) Glass; « Road Sweepings and Gulley Waste;

» Waste Electrical and Electronic Equipment (WEES) ;

• Contaminated Soils;

® Commercial and Industrial (C&I) Waste;

• Construction and Demolition (C&D) Waste;

Mixed Plastics including separation of Brominated Flame Retardant (3FR) Plastics;

• Automotive Shredder Residue (ASR) and its sub fraction Shredder Light Fraction (SLF) ; and

® Incinerator Bottom Ash { I3A) .

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

Claims

1. A me :hod of separating the components of solid waste, the method comprising introducing a mixture of solid waste and water into first separator means , wherein the first separator mea n s comprises: a container portion for retaining and directing a flow of liquid; auger means disposed in the container portion, the anger means configured to rotate and urge at least some of the solid waste of higher densities towards a first outlet; and wherein the container portion is co figured such that at least some of the solid waste of lower densities flows in a stream of water to a second outlet.

2, A method according to claim 1, wherein the container >ortion is a cylindrical barrel configured to rotate about an axis offset from the horizontal to create a downward flow of water towards the second outlet, and wherein the auger means is affixed to the internal surface of the cylindrical barrel ana is arranged to lift solid waste of higher densities towards the first outlet.

3 , A method according to c1a im 1 or 2, further comprising the step of temporarily retaining a mixture of water and at least some of the solid waste of lower densities in a pool adjacent said second outlet.

4, A method according to claim 3, furthei comprising the step of passing said mixture of water and at least some of the solid waste of lower densities through a trommel screen to produce low density solid waste smaller than a first particle size, 5, A method according to any one of the preceding claims, further comprising the step of passing lo density solid waste greater than a first particle size produced at said second outlet through a first vibrating dewatering screen,

6. A method according to any one of the preceding claims, further comprising the step of passing at least some of the solid waste of higher densities at said first outlet through a second vibrating dewatering screen to produce higher density solid waste smaller than a first particle size,

7. A method according to claim 6, further comprising the step of mixing said low density solid waste smaller than a first particle size and higher density solid waste smaller than a second particle size with water and feeding the resultant mixture into a first floatation tank : wherein higher density solid waste sinks is removed at a first floatation tank outlet; and wherein lower density solid waste floats to the top of s d first floatation tank and is passed into a second floatation tank.

8, A method according to claim 7, further comprising the step of feeding output water and solid waste mixtures from said first and second floatation tanks into respective first and second cyclonic separators to remove inert material and high density p1astic S. A method according to claim 8, further comprising the step of feeding output water containing suspended solids from said first and second cyclonic separato s into a water tank. apparatus to enable any high density solids and heavy metals to separate under gravity.

10. A method according to claim 9, further comprising the step of mixing said output water containing suspended solids with dilute flocculent and pressurised air to create foam in a thickener apparatus to enable organic material floating on the surface of said thickener apparatus to be raked off.

11. An apparatus for separating the components of solid waste, the apparatus comprising first separator means comprusing ; a container portion adapted to receive a mixture of solid waste and water and retain and direct a flow of the mi.xvra e ; auger means disposed in the container portion, the auger means configured to rotate and urge at least some of the solid waste of higher densities towards a first outlet; and fluid retaining means arranged adjacent a second outlet to create a pool of water and at least some of the solid waste of lower densities, such that said pool of water and at least some of the solid 'waste of lower densities is temporarily retained before flowing to a second outlet,

12. An apparatus according to claim 11, wherein the container portion is a cylindrical barrel configured to rotate about an axis offset from the horizontal to create a downward flow of water towards the second outlet, and wherein the auger means is arranged to lift solid waste of higher densities towards the first outlet,

13. An apparatus according to claim 11 or 12, wherein said fluid retaining means comprises an annular disc.

14. An apparatus according to any one of claims 11 to 13, wherein said auger means defines a screw and the apparatus further comprises a plurality of blades disposed between the threads of the screw adjacent said second outlet.

15. Art apparatus according to claim 11 or 12, wherein said fluid retaining means comprises an annular cone.

16, An apparatus according to any one of claims 11 to lo, further comprising at least one lifter to direct fluid flow.

17, An apparatus according to any one of claims 11 to 16, further comprising a trommel screen disposed adjacent said second outlet to produce low density solid waste smaller than a first particle size.

16. A tank apparatus for separating a mixture of water and waste particles

different sizes and densit;Les, the tank apparatus comprising : a first floatation tank comprising a first defie :ctor plate to direct denser particulate material towards the base of said first floatation tank; a first pump to remove a mixture of water anci said denser material from the base of said first floatation tank; a second floatation tank arranged to receive an overflow of water and lighter particulate material from said first floatation tank, wherein said second floatation tank further comprises a second deflector plate to direct the overflow to create a turbulent flow; and a second pump to remove a mixture of water and said lighter particulate material from the base of said second floatation tank.

19. A cyclonic separator for separating a mixture of water and waste particles of differ ent sizes and densities, the cyclonic separator comprising: a cylindrical portion defining a longitudinal axis and comprising an inlet to receive a mixture of water and waste particles of different sizes and densities; a conical portion comprising a spigot aperture outlet for separated denser particles; a vortex portion disposed along the longitudinal axis and comprising an aperture inlet and a vortex outlet for separating lighter particles; wherein said cyclonic separator is arranged to be inclined and declined .

20. A cyclonic separator according to claim 19, wherein

d vortex portion is moveable a 1ong sa1d 1ongit ud ina 1 a xis .

21. A cyclonic separator according to claim 19 or 20, wherein the size of said aperture inlet is adjustable.

22, A cyclonic separator according to any one of claims 19 to 21, wherein the size of said spigot aperture outlet is adj ustable .