PROCESS FOR TREATING FINES STREAM DERIVED FROM WASTE PROCESSING FACILITIES

A process for treating a fines stream in a material recover facility (MRF), comprising: providing an MRF fines stream comprising breakable material and ductile material: subjecting the MRF fines streams to a one-pass kinetic pulverization stage to produce a pulverized material comprising a size-reduced fraction derived from the breakable material and an oversized fraction derived from the ductile material; withdrawing the pulverized material from the kinetic pulverizer; and subjecting the pulverized material to separation to produce a size-reduced stream and an oversized stream. Also provided is a system comprising a kinetic pulverizer, a pulverizer conveyor and a screen operatively coupled to the pulverizer conveyor to receive a pulverized stream and produce a sized-reduced stream and an oversized stream. The system can also include a magnetic separator and a dust collection system respectively located upstream and downstream of the kinetic pulverizer.

TECHNICAL FIELD

The technical field generally relates to waste processing facilities-such as materials recovery facilities (MRFs), as well as and composting and waste sorting facilities—and the processing of fines streams from such facilities.

BACKGROUND

Waste processing in MRFs and other facilities typically results in a fines stream after removal of larger items and the fines stream is usually destined for landfill without further treatment or recovery. It has not been efficient to further treat such fines streams using conventional techniques.

SUMMARY

According to one aspect, there is provided a process for treating a fines stream in a material recover facility (MRF), comprising: providing a MRF fines stream comprising: breakable material comprising glass, ceramics, drywall, shingles, rocks and/or aggregates; and ductile material comprising plastics; subjecting the MRF fines streams to a one-pass kinetic pulverization stage wherein the fines stream is fed into a kinetic pulverizer and subjected to self-collisions created by vortices within the kinetic pulverizer to produce a pulverized material comprising a size-reduced fraction derived from the breakable material and an oversized fraction derived from the ductile material; withdrawing the pulverized material from the kinetic pulverizer; and subjecting the pulverized material to separation to produce a size-reduced stream and an oversized stream.

In at least one embodiment, the fines stream is derived from municipal solid waste (MSW), or source separated recyclables.

In at least one embodiment, the fines stream is a compost overs stream.

In at least one embodiment, the fines stream comprises material below 2 inches in size.

In at least one embodiment, the kinetic pulverizer is operated at a rotation speed between 500 RPM to 1,200 RPM.

In at least one embodiment, the kinetic pulverizer is operated at a rotation speed between 700 RPM and 1,000 RPM.

In at least one embodiment, the kinetic pulverizer is operated such that the size-reduced fraction is substantially sand or silt sized particles.

In at least one embodiment, the fines stream has a moisture content between 10% and 50% upon entry into the kinetic pulverizer.

In at least one embodiment, the fines stream has a moisture content between 15% and 40% upon entry into the kinetic pulverizer.

In at least one embodiment, the fines stream is not subjected to a drying stage upstream of the kinetic pulverization stage.

In at least one embodiment, the size-reduced fraction is a homogeneous mixture in the pulverized output stream.

In at least one embodiment, the kinetic pulverization stage effects water removal on the fines stream such that the water removal is between 5% and 8% in the kinetic pulverization stage.

In at least one embodiment, the kinetic pulverization stage and the separation enable the size-reduced stream to have a moisture content that is 5% to 30% lower than that of the fines stream.

In at least one embodiment, the kinetic pulverization stage effects pathogen reduction on the fines stream via air stripping.

In at least one embodiment, the process further comprises incorporating a friable additive into the fines stream such that the friable additive is size reduced and is homogenized with the breakable material to form part of the size-reduced fraction.

In at least one embodiment, the friable additive comprises a porosity agent, a soil additive, a building material additive, a compost additive, peat moss, or a glass product additive.

In at least one embodiment, the friable additive is introduced into the fines stream upstream of the kinetic pulverization stage.

In at least one embodiment, the friable additive is introduced directly into the kinetic pulverizer as a separate stream from the fines stream.

In at least one embodiment, the separation stage comprises screening.

In at least one embodiment, the screening is performed using a trommel screen.

In at least one embodiment, the screening is performed using a vibrating screen.

In at least one embodiment, the separation stage comprises a single screen.

In at least one embodiment, the process further comprises: monitoring at least one feed parameter of the fines stream and/or output parameter of the pulverized material, the oversized stream and/or the size-reduced stream; and adjusting the one-pass kinetic pulverization stage based on the feed parameter and/or the output parameter.

In at least one embodiment, the at least one feed parameter comprises feed rate of the fines stream and/or composition of the fines stream.

In at least one embodiment, the at least one output parameter comprises size properties of the sized-reduced fraction in the pulverized stream, composition of the pulverized stream, flow rate of the oversized stream, flow rate of the sized-reduced stream, composition of the oversized stream, and/or composition of the sized-reduced stream.

In at least one embodiment, the adjusting of the one-pass kinetic pulverization stage comprises adjusting the rotation speed.

In at least one embodiment, the adjusting of the one-pass kinetic pulverization stage comprises adjusting the infeed rate of the fines stream.

According to another aspect, there is also provided a process for treating a fines stream derived from waste material, comprising: providing a fines stream comprising: breakable material comprising glass, ceramics, drywall, shingles, rocks and/or aggregates; and ductile material comprising plastics; wherein the fines stream is substantially composed of material having a maximum size of 2 or 4 inches; subjecting the fines streams to a one-pass kinetic pulverization stage wherein the fines stream is fed into a kinetic pulverizer and subjected to self-collisions created by vortices within the kinetic pulverizer to produce a pulverized material comprising a size-reduced fraction derived from the breakable material and an oversized fraction derived from the ductile material; withdrawing the pulverized material from the kinetic pulverizer; and subjecting the pulverized material to separation to produce a size-reduced stream and an oversized stream.

In at least one embodiment, the fines stream is derived from source separated single stream material recovery facility (MRF).

In at least one embodiment, the fines stream comprises between 40% and 60% glass, and the size-reduced stream is composed of over 95%, 96%, 97%, 98% or 99% glass.

In at least one embodiment, the fines stream is derived from a mixed waste material recovery facility (MRF).

In at least one embodiment, the fines stream comprises between 50% and 70% organics, and the size-reduced stream is composed substantially of organics with at most 0.5-2% visible contaminants with a size above 4 mm.

In at least one embodiment, the fines stream is derived from a composting facility and comprises compost overs.

In at least one embodiment, the size-reduced stream is composed substantially of organics with at most 0.5-2% visible contaminants with a size above 4 mm.

In at least one embodiment, the process further comprises adding a friable additive to the fines stream for size reduction and homogenization with the size-reduced fraction.

In at least one embodiment, the friable additive is introduced into the fines stream upstream of the pulverization stage.

In at least one embodiment, the friable additive is introduced directly into the kinetic pulverizer.

In at least one embodiment, the process further comprises one or more features as recited above.

According to yet another aspect, there is also provided a system comprising: a kinetic pulverizer configured to receive and process a fines stream to produce a pulverized material; a pulverizer conveyor configured to transport the pulverized material downstream; a screen operatively coupled to the pulverizer conveyor and configured to receive the pulverized stream and produce a sized-reduced stream and an oversized stream.

In at least one embodiment, the system further comprises: a material recovery facility (MRF) that generates the fines stream; a fines conveyor configured to transport the fines stream to the kinetic pulverizer.

In at least one embodiment, the system further comprises one or more features as recited above or as described herein.

In at least one embodiment, the process and/or system also includes magnetic separation of the fines stream prior to the kinetic pulverization.

In at least one embodiment, the process and/or system also includes dust collection associated at least with the pulverized material that exits the kinetic pulverization stage.

DETAILED DESCRIPTION

The treatment of fines streams derived from waste processing can include a one-pass pulverization stage through a kinetic pulverizer where breakable material is sized-reduced and ductile material is liberated and remains as an oversized fraction. The pulverized material is then subjected to a separation stage, which may include screening, to separate the oversized material from the broken-down sized material. The separated oversized material, which is largely plastics and other non-organic material, can then be disposed of, converted to fuel, or further separated to recover sub-fractions depending on its composition. The sized material can be repurposed in various applications, e.g., as a compost additive or feedstock, land applications such as topsoil, soil amendment, fill, building material additive, and so on, depending on its size and composition properties. For some implementations, the sized material can be subjected to additional treatments, such as composting or anaerobic digestion.

Referring toFIG.1, a fines stream10that is derived from the processing of municipal solid waste (MSW)12and/or generated in a materials recovery facility (MRF)14is subjected to kinetic pulverization16to produce a pulverized output stream18. The fines stream10includes ductile material and breakable material. The breakable material is typically hard, brittle or friable such that the kinetic pulverization facilitates notable size reduction, converting the breakable material into a sized reduced fraction. The breakable material is size-reduced, for example to sand or silt sized particles, and is homogenized with the pulverized output stream18. Examples of breakable materials include glass, ceramics, drywall, shingles, rocks and aggregates, as well as organics such as food and yard waste in addition to woods that are not necessarily hard but are friable and sized-reduced. The ductile material, on the other hand, is softer and not significantly sized reduced by the kinetic pulverization16. Examples of the ductile material include plastic film, fibers, hard plastics and soft plastics. Thus, the pulverized output stream18includes a sized-reduced fraction composed of a broken-down fraction, and a larger ductile fraction.

The pulverized output stream18can then be subjected to separation20to recover a sized-reduced stream22largely composed of the broken-down fraction, and an oversized material stream24largely composed of the larger ductile fraction. The separation step20can be performed in one or more stages, and can use a variety of separation equipment. For example, various types of screens can be used, such as a vibrating screen and/or a trommel screen. Other types of separation equipment can also be used. The separation equipment could be new and dedicated for the fines treatment process described herein, or could be part of an existing separation stage in the facility. In some implementations, the pulverized output stream18is subjected to separation to produce more than two streams that may have various properties that aid separation and enable downstream repurposing or disposal. The separation stage can, for example, include multiple separators (e.g., screens) arranged in parallel or in series.

Regarding the feedstock that is supplied to the kinetic pulverization stage16, it can be a fines stream that is generated in an MRF and would conventionally be disposed of without further processing or recovery. The MRF receives, separates and prepares recyclable materials for marketing to end-user manufacturers, and can be a source separated single stream MRF or a mixed waste or “dirty” MRF. The composition of the fines stream can vary and will depend on the composition of the waste material received by the MRF as well as the processing equipment and operation of the MRF. The feedstock can also be a fines stream within a composting facility or another types of waste treatment facility, for example.

The following examples of feedstock fines streams can be processed using the process described herein and used to produce size-reduced streams. The feedstock includes sized material, pre-conditioned from a sorting and/or processing system, compost facility, or MRF where the input is mixed waste (e.g., MSW), source separated recyclables (e.g., single-stream), construction and demolition debris, yard waste, food waste, or other commingled waste streams. It is understood that the MRF fines feedstock described herein may include pieces of construction and/or demolition debris that are in the mixed waste feedstock. However, it should be understood that in the present description the term “MRF fines” does not include a stream that is considered construction and demolition (C&D) fines recovered from a construction and demolition debris recovery operation.

Regarding mixed waste MRF fines, the average composition (% by weight) can be the following: organic matter (e.g., yard waste, food waste, dirt) up to approximately 50-70%; cellulosic matter (e.g., paper, diapers, tissues or the like) approximately 10-15%; broken glass approximately 8% to 12% or around 10%; metals from approximately 0.5% to 2%; plastics (rigid and film) approximately 10%-15%; and fabrics approximately 0-2%. Variations of these compositions can also occur where there is little to none of one or more of the component categories mentioned above. The sized-reduced streams generated from mixed waste MRF fines can include an organic concentrate product with 0.5-2% visible contaminants (e.g., metal, glass, plastic) with a size above 4 mm. The organic matter capture rate from the feedstock can be about 60-85% depending on factors such as screen configuration and material quality requirements. The oversized stream would be a mix of contaminants (e.g., plastic, metal, glass) and a small amount of oversized organic matter.

Regarding source separated single stream MRF fines/residue, the average composition (% by weight) can be the following: broken glass approximately 70-80%; organic matter (e.g., yard waste, food waste, dirt) approximately 0-5%; cellulose matter (e.g., paper, diapers, tissues or the like) approximately 5-10%; metals up to approximately 5%; plastics (rigid and film) approximately 5-10%; and fabric approximately 0-2%. Variations of these compositions can also occur where there is little to none of one or more of the component categories mentioned above. The sized-reduced streams generated from source separated single stream MRF fines can include pulverized glass below 50 mesh with less than 1% non-glass product. The glass capture rate from the feedstock can be greater than 97% depending on factors such as screen configuration and material quality requirements. The oversized stream would be a mixed non-glass material.

Regarding biomass compost overs, the average composition (% by weight) can be the following: biomass products approximately 65%-75%; glass and aggregate approximately 15-20%; and plastic up to approximately 5%. The sized-reduced streams generated from biomass compost overs can include an organic concentrate with 0.5-2% visible contaminants (e.g., metal, glass, plastic) having a size above 4 mm. The organic matter capture rate from the feedstock can be at approximately 70-80% depending on factors such as screen configuration and material quality requirements. The oversized stream would be a mix of contaminants (e.g., plastic, metal, glass) and oversized organic matter.

Regarding construction and demolition (C&D) fines, the average composition (% by weight) can be the following: aggregate (e.g., rock, brick, concrete, ceramics, glass, dirt) of approximately 50-70%; cellulose matter (e.g., cardboard, fiber board, paper) approximately 5%; wood approximately 5-15%; gypsum: approximately 20-40%; metals approximately 0.5-1%; and plastics approximately 5%. The sized-reduced streams generated from C&D fines can include inert, soil-like concentrate with up to 0.5% visible contaminants (e.g., metal, glass, plastic) with a size over 4 mm. The refuse stream can be a mix of visible contaminants (e.g., plastic, metal, glass) and oversized organic matter (e.g., wood).

In addition, the fines stream10can be fed directly to the kinetic pulverization stage16without pre-treatment, such as drying pre-treatment, as the kinetic pulverizer is capable of effectively handling wet feed material. For example, the fines stream can have a moisture content of up to 50% or between 10% and 40%, and can be fed directly into the kinetic pulverizer without pre-drying. For wetter fines streams having a moisture content over 50%, a pre-drying step can be performed to dry the material below 50%.

Various infeed feedstocks can be envisioned for the process. One example feedstock is commingled or complex material streams-typically derived from municipal, commercial or industrial solid wastes—that have been pre-processed or screened to remove recyclable content and/or items exceeding 2 inches (although 3 inch minus, 4 inch minus or higher is also possible) that have limited use or negative value, usually destined for disposal. Example types include screenings from mixed waste processing facilities, single stream recycling facilities, construction and demolition debris processing plants, and composting facilities, which contain a combination of hard/brittle and soft/ductile components-commonly referred to as “fines”, “rejects”, or “residual” material. Another example feedstock is glass including pane and/or laminated glass where the pulverization stage allows liberation of glass and film lamination layer in one pass and then separation through sizing and separation equipment in one step. Another example feedstock includes compost overs where the pulverization stage allows recovery of clean organic content through conventional sizing equipment in one step. Compost overs is a compost material (either finished or unfinished) that includes some plastic film and glass, and thus it can benefit from the size reduction, homogenization of size-reduced particles, liberation of oversized material, and separation facilitated by the present process to remove the oversized plastics and obtain a valuable sized-reduced material.

Regarding the kinetic pulverization stage, a single kinetic pulverizer can be implemented and operated as a one-pass stage. For example, the feedstock can be fed into an upper part of the kinetic pulverizer, which includes a drum with baffles and an internal rotating stem with multiple arms that create vortexes within the drum chamber. The feed material passes into the vortices and experience self-collision for size reduction of the breakable material. The material passes to a bottom region of the kinetic pulverizer and is expelled via a lower outlet as the pulverized output stream18. The rotation speed can be operated between 500 RPM to 1,200 RPM or between 600 RPM and 1,100 RPM or between 700 RPM and 1,000 RPM, and can be adjusted in response to other process parameters or maintained relatively constant. In some implementations, the rotation speed is adjusted to control the size and quality of the output material.

In some cases, the process, kinetic pulverization stage16and/or kinetic pulverizer50can be operated in continuous mode or in semi-batch mode. It is also possible to pulverize the material in a single pass or using multiple passes through the kinetic pulverizer50. When multiple passes are used, the pulverized material from a first pass can be screened and only a fraction fed through a subsequent pass. More generally, certain materials or fractions can be subjected to multiple pulverization stages, which may be done in the same kinetic pulverizer50via recycling. Each pass through the kinetic pulverizer50may be done at the same or different operating conditions (e.g., rotation speed, feed rate) where variations in operating conditions are determined based on the composition of the feed for each pass, for example.

The kinetic pulverization stage can not only enable targeted size reduction of the breakable material, but can also facilitate drying and pathogen reduction for a higher quality output stream. For example, the overall process including kinetic pulverization and separation can produce a sized material that has a moisture content 30% (or 15% to 25%) lower than the infeed waste material. In some implementations, the pulverizing stage reduces the moisture by 5-8% and then the separation stage enables the sized fraction to have a further lowered moisture content. In addition, the pulverization stage can facilitate air stripping of the feedstock material which can, in turn, result in pathogen reduction.

The kinetic pulverization stage16can facilitate the use of kinetic energy, vortices and matter-on-matter collisions to achieve size reduction of the breakable material, homogenization of the broken-down material, liberation and separation of ductile material, blending of additives that may be incorporated, drying, pathogen reduction. For streams having certain features-mixed materials, moisture, pathogens, etc.—the one-pass kinetic pulverization can facilitate efficient treatment and recovery of materials.

Regarding the pulverized output stream18, in some implementations the pulverization stage16generates material that ranges from dust-sized particles to larger particles, with the majority (e.g., over 50% or between 50% and 70% or even over 90%) passing a ⅜ inch sieve. Oversized material includes the lower density, flexible fraction of feedstock, while pulverizing of the breakable material-which is brittle, hard, friable-homogenizes this size-reduced fraction to facilitate liberation and separation from the larger ductile fraction through various separation technologies that can include screening. The oversized fraction can be substantially composed of plastic materials and can also include other materials, such as fibers, film, metal, and so on.

Regarding the separation stage20, the oversized fraction can be separated from the sized fraction using a size-based separation technique, such as screening. The screening can be performed using various types of mechanical screens, such as a vibrating screen, a tumbler screen, a trommel screen, among others. The mechanical screen can be configured or operated based on the composition and size distribution of the pulverized output stream18to favour separation of the sized and oversized fractions from each other. The screen can be provided to favour or maximize high purity or high yield of the oversized stream (e.g., plastics), or to favour other parameters related to the separated streams22,24. The separated streams22,24can then be subjected to further processing and recovery, if desired.

In some implementations, the separation stage20and the pulverization stage16are coordinated such that the operation of one can influence the other. For example, the screen and the pulverizer can be monitored and controlled via a controller26to achieve a desired parameter, such as certain properties of the separated streams22,24. For example, if a change in the input feedstock results in the pulverizer generating a larger sized-fraction in the pulverized stream18, the screen can be controlled accordingly to favour a certain desired separation. In addition, the pulverizer can be controlled, e.g., to increase the rotation speed by controlling the motor28, to bring the sized fraction back to within a target range to facilitate a desired separation. Monitoring instrumentation, such as an inlet detector DI30and an outlet detector Do32, can be provided to monitor properties of the streams (e.g., size distribution, composition, mass and/or volume flow rates). Depending on the sized product to be produced, the screen and the kinetic pulverizer can be operated and designed in certain ways to generate a product having a maximum size, for example. When glass is the dominant component of the sized material, the screen can be 50 mesh and the kinetic pulverizer operates to size reduce the glass below 50 mesh. When organics are a dominant component of the sized material, the screen can be ⅜ inch or ½ inch. For compost applications, the screen could be ½ inch or ¼ inch, for example. However, it is noted that the screen design can be market driven to provide various size distributions of the size-reduce material.

In some implementations, the various streams are transported between stages using conveyor systems to facilitate continuous operation, although other transport methods can be used. The process can be continuous, batch feed, or operated according to other schemes depending on the facility and other factors.

Regarding the kinetic pulverizer, it is noted that the unit can have various structural and operational features. It some implementations, the kinetic pulverizer can have one or more features as described in PCT/CA2019/050967, which is incorporated herein by reference.

Referring now toFIG.2toFIG.10, there is shown a pulverizer50, in accordance with one embodiment. The pulverizer50is adapted to receive an input material as described herein and to pulverize or comminute the input material.

It will be understood that the terms “pulverize”, “pulverization”, “comminute” and “comminution” are used herein to refer to a reduction in size of the particles in the input material.

In the illustrated embodiment, the pulverizer50includes a base52and a housing60mounted over the base52. Specifically, the housing60includes a bottom end62connected to the base52and a top end64opposite the bottom end62. The housing60is hollow and includes a housing sidewall66extending between the top and bottom ends64,62to define an interior chamber68in which the pulverization occurs. Specifically, the housing60includes an inlet70located at the top end64to receive the input material and an outlet72located at the bottom end62through which the pulverized material may be discharged once having been pulverized in the interior chamber66. In the illustrated embodiment, the outlet72allows pulverized material to be discharged in a tangential direction to the housing sidewall66. It will be understood that the outlet72may be configured differently. For example, the outlet72may be located in a bottom face of the housing60such that the pulverized material may be discharged in an axial direction downwardly from the housing60. It will also be understood that alternatively, the outlet72may be positioned substantially towards the bottom end62but may not be positioned exactly at the bottom end62of the housing60. Similarly, the inlet70may not be positioned exactly at the upper end64of the housing60and may instead be located generally towards the upper end64.

In the illustrated embodiment, the housing60is generally cylindrical and defines a central housing axis H extending between the top and bottom ends64,62of the housing60. The housing60is adapted to be disposed such that the central housing axis H extends substantially vertically when the pulverizer50is in operation. In this configuration, the input material fed into the inlet70will ultimately tend to fall down towards the outlet72by gravity.

In the illustrated embodiment, the airflow generator100includes a pulverizing rotor assembly102disposed within the interior chamber68and a rotary actuator104operatively coupled to the pulverizing rotor assembly102for rotating the pulverizing rotor assembly102in order to generate the airflow. Specifically, the pulverizing rotor assembly102includes a rotatable shaft106located in the interior chamber68and extending between the top and bottom ends64,62of the housing60, along the central housing axis H, and a plurality of pulverizing rotors108a,108b,108csecured to the rotatable shaft106so as to rotate about the central housing axis H when the rotatable shaft106is rotated.

Each pulverizing rotor108a,108b,108cincludes a rotor hub120and a plurality of rotor arms122extending outwardly from the rotor hub120and towards the housing sidewall66. The rotatable shaft106extends through the rotor hub120such that the rotor arms122are disposed in a rotation plane R which extends orthogonally through the central housing axis H. In this configuration, when the rotatable shaft106is rotated, the rotor arms122therefore remain in the rotation plane R and move along the rotation plane R. Alternatively, instead of all being disposed in a rotation plane, the rotor arms122could instead be angled upwardly or downwardly relative to the rotatable shaft106. In yet another embodiment, the rotor arms122could instead be pivotably connected to the rotatable shaft106such that the rotor arms122could selectively be angled upwardly and downwardly as desired, either manually or automatically using one or more arm actuators.

In the illustrated embodiment, the plurality of airflow deflectors200includes six deflectors200which are substantially similar to each other and which are substantially evenly spaced from each other in an azimuthal direction (i.e. along a circumference of the housing sidewall66) around the central housing axis H. Alternatively, all the deflectors200may not be similar to each other, may not be spaced from each other evenly and/or the pulverizer50may include more or less than six deflectors202. For example, the pulverizer50may include between two and eight deflectors200.

In the illustrated embodiment, each deflector200is elongated and extends substantially parallel to the housing axis H. Specifically, since the housing60is positioned such that the central housing axis H extends substantially vertically, the deflectors200also extend substantially vertically.

As best shown inFIGS.6to8, each deflector200includes a top end202located towards the top end64of the housing60and a bottom end204located towards the bottom end62of the housing60. In the illustrated embodiment, each deflector200is positioned so as to intersect the rotation plane R of the upper pulverizing rotor108aand of the intermediate pulverizing rotor108c. More specifically, the top end202of the deflectors200is located above the upper pulverizing rotor108awhile the bottom end204of the deflectors200is located below the intermediate pulverizing rotor108c, and the deflector200extends continuously between its top and bottom ends202,204.

It will be understood that rotation of the rotor arms122will cause the air within the interior chamber68to move outwardly towards the housing sidewall66. In the above configuration, since the deflectors200are horizontally aligned with the upper and intermediate pulverizing rotors108a,108c, the air will be moved outwardly by the upper and intermediate pulverizing rotors108a,108cagainst the deflectors200to be deflected by the deflectors200to form the vortices V, best shown inFIGS.9and10.

In the illustrated embodiment, each deflector200is generally wedge-shaped. Specifically, each deflector200has a generally triangular cross-section and includes a flow facing deflecting surface206which faces towards the airflow when the rotatable shaft106is rotated and an opposite deflecting surface208which faces away from the airflow. The flow facing deflecting surface206and the opposite deflecting surface208extend away from the housing sidewall26and converge towards each other to meet at an apex210which points towards the housing central axis H. The flow facing deflecting surface206is angled relative to an inner face34of the housing sidewall26at a first deflection angle θ1and the opposite deflecting surface208is angled relative to the inner face74of the housing sidewall76at a second deflection angle θ2.

In the illustrated embodiment, each deflector200is symmetrical about a symmetry axis S which extends along a radius of the housing60. In this embodiment, the first deflection angle θ1is therefore substantially equal to the second deflection angle θ2. In one embodiment, the first and second deflection angles θ1, θ2may be equal to about 1 degree to 89 degrees, and more specifically to about 30 degrees to 60 degrees. Alternatively, the deflector200may not be symmetrical and the first and second deflection angles θ1, θ2may be different from each other.

In the illustrated embodiment, the apex210of each deflector200is spaced radially inwardly from the inner face74of the housing sidewall by a radial distance of about 7¾ inches or about 20 cm. Still in the illustrated embodiment, the apex210is further spaced radially outwardly from a tip130of the rotor arms122by a radial distance of between about ½ inch or about 1 cm and about 2 inches or about 5 cm. In one embodiment, the radial distance or “clearance space” between the tip130of the rotor arms122and the apex210may be selected such that the vortices V may be formed as desired when the rotatable shaft106is rotated.

Alternatively, the deflectors200could be differently shaped and/or sized. For example, the flow facing deflecting surface206and the opposite deflecting surface208may not be planar, but may instead be curved. In another embodiment, the deflectors200may not comprise an opposite deflecting surface208. In yet another embodiment, instead of being wedge-shaped, the deflectors200may instead have a rectangular cross-section, or may have any other shape and size which a skilled person would consider suitable.

FIG.10is a schematic representation of the vortices V generated within the interior chamber68when the pulverizer50is in operation.

During operation of the pulverizer10, the rotatable shaft106is rotated about the housing axis H such that the rotor arms122form the circular airflow revolving about the housing axis H. In the example illustrated inFIG.10, the rotatable shaft106is rotated in a clockwise direction when viewed from above to form a counterclockwise airflow in the interior chamber68.

The rotatable shaft106may be rotated at relatively high speed to provide the desired pulverizing effect in the pulverizer. In one embodiment, the rotatable shaft106is rotated at a rotation speed of between about 700 rpm and about 1100 rpm, and more specifically at a rotation speed of between about 1000 rpm and about 1100 rpm. Alternatively, the rotatable shaft106may be rotated at a different rotation speed which would allow the formation of the vortices as described below.

The airflow travels generally along the inner face34of the housing sidewall66, but is interrupted by the flow facing deflecting surface206of the deflectors200which cooperates with the rotor arms122, and more specifically with the tip of the rotor arms122to form the vortices V. As shown inFIG.10, the vortex V may further be guided back inwardly towards the central housing axis H by an adjacent deflector200′.

Still referring toFIG.10, each vortex V further overlaps at least one adjacent vortex V1, V2 to cause input material particles in suspension in the vortex V to collide with input material particles in suspension in the adjacent vortex or vortices V1, V2. More specifically, each vortex V created generally includes an outwardly moving portion500defined generally by airflow circulating from the shaft106towards the housing sidewall66and an inwardly moving portion502defined generally by airflow circulating from the housing sidewall26towards the shaft106. As shown inFIG.10, the outwardly moving portion500of each vortex V overlaps the inwardly moving portion502of a first adjacent vortex V1, and the inwardly moving portion502of each vortex overlaps the outwardly moving portion500of a second adjacent vortex V2.

In this configuration, the input material particles in the vortex therefore collide with input material particles moving at twice the movement speed of the particles in the vortex V. For example, in one embodiment, the vortices V, V1, V2 are rotating at about a third of the speed of sound. When input material particles from the first and second adjacent vortices V1, V2 collide with the input material particles in suspension in the vortex V, which move at the same speed but in the opposite direction, the particles will collide with each other at about two thirds of the speed of sound.

In one embodiment, in addition to the collision of the input material particles via the airflow and vortices V, the input material may further be pulverized by the rotor arms122impacting the input material particles in the interior chamber68as the rotatable shaft106is rotated. In this embodiment, the combined effect of the input material particles impacting each other in the overlapping vortices V, V1, V2 and of the rotor arms122impacting the input material particles may increase the efficiency of the pulverizer. Moreover, since the overlapping vortices V cause the particles to impact each other rather than surfaces inside the housing20, the wear of the components inside the housing20may be reduced.

It will be understood that the vortices V illustrated inFIGS.9and10have been simplified for ease of understanding and that in practice, the vortices V may not be exactly circular as illustrated or be exactly located as indicated inFIG.10.

In the illustrated embodiment, the pulverizer50further includes a plurality of shelves300a,300bwhich extend inwardly from the housing sidewall26. Specifically, the plurality of shelves300a,300bincludes an upper shelf300aand a lower shelf300bspaced downwardly from the upper shelf300a. Each shelf300a,300bextends circumferentially around the housing axis H and along the housing sidewall26. It will be understood that the shelves therefore extend substantially orthogonally to the deflectors200. Specifically, the deflectors200extend generally parallel to the housing axis H and can therefor be said to extend in an axial direction relative to the housing60, while the shelves can be said to extend in an azimuthal direction relative to the housing60. In the illustrated embodiment, the deflectors200extend generally vertically while each shelf300a,300bis disposed in a generally horizontal plane and therefore extend generally horizontally.

Still in the illustrated embodiment, each shelf300a,300bextends substantially continuously around the housing sidewall66. Alternatively, the shelves300a,300bmay not extend continuously around the housing sidewall66and could instead include a plurality of shelf segments spaced from each other to define gaps between adjacent shelf segments.

In the illustrated embodiment, the upper shelf300ais substantially horizontally aligned with the upper pulverizing rotor108aand the lower shelf300bis substantially horizontally aligned with the intermediate pulverizing rotor108c. Alternatively, each shelf300a,300bcould be located slightly below the corresponding pulverizing rotor108a,108c.

In the illustrated embodiment, each shelf300a,300bincludes a top shelf face302which extends downwardly and away from the housing sidewall66. Specifically, since the shelf300a,300bextends along the housing sidewall66and around the housing axis H, the top shelf face302is substantially conical. Still in the illustrated embodiment, the top shelf face302is angled relative to the housing sidewall66at an angle of between about 1 degree, where the top shelf face302would be almost flat against the housing sidewall66, and about 89 degrees, where the top shelf face302would be almost orthogonal to the housing axis H. In one embodiment, the top shelf face302could be angled relative to the housing sidewall66at an angle of between 30 degrees to 60 degrees.

The shelves300a,300bare configured to deflect the airflow directed towards the shelf upwardly. This allows the input material particles to be temporarily maintained in suspension above the shelf300a,300b. The input material particles can therefore be subject to the effect of the vortices and to pulverization by impact with the rotor arms122for a longer period of time, resulting in additional reduction in the size of the input material particles as they travel downwardly towards the next rotor stage or towards the outlet72.

The upward deflection of the airflow may further contribute to the vortices V within the interior chamber68. More specifically, as shown inFIG.9, the vortices V may rotate in a plane generally parallel to the housing axis, i.e., upwardly-downwardly, in addition to rotating in a plane orthogonal to the housing axis H as illustrated inFIG.10. The combined effect of the shelves300a,300band the deflectors200therefore contribute to forming vortices V which are tridimensional such that air within the vortices V moves along a tridimensional path of travel, which may further promote collisions between the input material particles of adjacent, overlapping vortices V.

This configuration further allows the number of vortices V generated by the deflectors200to be multiplied by the number of shelves300a,300bin the housing60. For example, in the illustrated embodiment, the pulverizer50includes six deflectors200which can form six vortices above each shelf300a,300b, for a total of 12 vortices in the entire interior chamber68.

The pulverizer can be designed and sized to handle the fines stream for one-pass processing. For example, the pulverizer can be sized to handle 5 to 20 tonnes per hour, or 10 to 15 tonnes per hour, of a waste stream that comprises a mixture of components as described above, while operating as a one-pass unit with a rotation speed between 500 RPM and 1,200 RPM to produce one or more of the output sized streams as described herein.

Referring toFIG.11, it is also possible to provide a kinetic pulverizer50for one-pass operation and capable of processing various different feedstocks with no operational changes or with changes only related to rotation speed and/or feed rate. For instance, the kinetic pulverizer50could be implemented in a large plant1000that generates multiple different fines streams A, B, C to pulverize the fines streams at different times and produce respective output streams that can be subjected to separation which may occur in one screen or in respective screens that are designed for the given feedstock and end product to produce. Thus, a single kinetic pulverizer50along with one or more screens could be implemented in a plant that generates multiple residual fines streams A, B, C to facilitate production of various end products.FIG.11shows a plant1000that receives waste1002and generates recovered materials1004, as well as at multiple fines or residual streams A, B, C that are supplied to respective tanks or storage locations1006. Alternatingly, one of the fines streams is supplied to the pulverizer50, and is optionally combined with a friable additive1008as described above. The pulverizer generates a pulverized output stream that is supplied to a corresponding screen A, B or C to produce the corresponding size-reduced material. In this manner, a single pulverizer can be used to upgrade multiple fines streams generated by a waste processing plant1000.

Referring now toFIG.12, in some embodiments the process includes a magnetic separation stage2000upstream of the kinetic pulverization stage16to capture ferrous metal from the fines stream10. The separated metal2002can be supplied as scrap metal for resale or can be disposed of. The metal depleted fines stream2004can be fed to the kinetic pulverization stage16. The magnetic separator can be designed and operated to remove tramp metal with a high weight density to reduce wear and damage on the KP. For example, the magnetic separator can be provided based on nominal size of the feedstock and ferrous objects that would be desirable for removal. For instance, the magnetic separator can be provided to ensure removal of solid ferrous objects that have a high weight in an overall low volume. While some geometries, such as flat sheets, may pose little concern to the operation of the KP, other geometries such as blocks, chunks, and the like can increase wear and damage and thus the magnetic separation stage2000facilitates removal to enhance downstream processing. The magnetic separator can be configured based on size of the feedstock, ferrous object size, and material burden depth. The magnetic separator could be actively controlled or simply turned on to enable the separation. The magnetic separation stage2000facilitates reduced risk of wear and damage to the KP stage16, and also diverts more waste from going to landfill by recovering scrap metal material.

The magnetic separation stage2000can use various types of magnetic separators which can be selected based on the feedstock and throughput. For example, the magnetic separator can be a dry-type magnetic separator or wet type magnetic separator depending on the moisture content of the feedstock. The magnetic separator can have a magnetic field strength that is designed for removal of target ferrous metal objects that could be problematic for the KP stage16. The magnetic separator could also include a permanent magnet and electromagnetic magnetic separator. The magnetic separator can also have various design and structural features, e.g., drum type, roller type, disc type, ring type, belt type, among others. The magnetic separator can also use constant, alternating, pulsating, or rotating magnetic fields depending on the design and configuration of the system and the feedstock. The magnet itself can be composed of various materials.

While magnetic separation is a preferred mechanism to remove metals from the feedstock, there are various other metal removal methods that could be used instead of or in addition to magnetic separation. An additional metal removal stage could be designed to remove non-ferrous metals, for example, particularly metal debris that has a high weight density and are thus relatively heavy and thick. In some implementations, the metal removal method (e.g., magnetic separation) is performed to remove all metal debris having an average diameter of 1 inch or greater. Metal debris that is lump shaped or elongated is removed, while metal debris that has a flat sheet shape is optionally removed.

Referring now toFIGS.13and14, two example configurations are shows for the magnetic separation stage2000.FIG.13shows a belt magnetic separator2006including a self-cleaning magnetic belt2008that is above a conveyor2010. The magnetic belt2008discharges the ferrous metals into a bin2012. The magnetic belt2008can be mounted to a magnet frame2014that spans across the conveyor2010.FIG.14shows an alternative configuration including a stationary magnet2018on rails2020mounted above the conveyor2010and configured to move back and forth.

Referring still toFIG.12, the system can also include a dust collection stage3000for recovering dust that is part of the pulverized output stream18exiting the KP stage16. The pulverized output stream18enters the dust control stage3000which recovers a dust stream3002and produces a dust reduced pulverized stream3004that is fed to the separation stage20. The dust collection stage3000facilitates dust control and can include various units, such as a setting chamber and a baghouse or cyclone filtration unit.

Referring toFIG.13, the dust collection stage3000can include a dust collector3006that is coupled to the exit of the KP stage16and may include a settling chamber3008that has dust outlets3010positioned on its top. The dust outlets can be in fluid communication via ducting3012to a dust recovery unit3014that includes a baghouse or cyclone filtration unit3016having a dedicated motor3018. The dust recovery unit3014can also include a dust recovery vessel3020that receives the dust from the baghouse or cyclone filtration unit, for example via a hopper.

The settling chamber3008can receive all of the output from the KP stage16and thus receives relatively fine particles which are deposited on an outfeed conveyor3022so that the fines are added to the diverted output. Fine particles settle on the outfeed conveyor3022, while very fine dust particles are accumulated and withdrawn from the settling via the dust outlets3010. The setting chamber3008can extend over a part or the entire length of the outfeed conveyor3022depending on the process design and the target level of dust control. The setting chamber3008can be in communication with the outlet of the KP unit via a flexible tubular member since the KP unit can experience vibration.

The quantity of dust in the pulverized output stream18is highly dependent upon the type and dryness of the feedstock supplied to the KP stage16. For instance, output diversion rates as high as about 30% have been observed for some feedstocks, while for MWS fines the diversion rate is much lower. With feedstocks such as C&D material, diversion rates will be higher.

It is noted that the power and suction of the dust collection stage3000can be adjusted to increase the amount of material capture in the dust collector. For example, the dust recovery unit3014can be controlled to provide a desired suction in the dust collector3006. Therefore, the dust collection stage3000can be designed and operated to be a tool in the separation of the outbound material from the KP stage16. It is also noted that the dust collector3006can also pick up plastic film pieces, which are relatively light, and such plastic film pieces can therefore be separated by both the separate stage20and the dust collection stage3000.

Still referring toFIG.13, the baghouse filtration or cyclone filtration3016traps finer and lighter material, which can be stored in the vessel3020. This fine recovered material3024can be added back into the diverted output stream, disposed of and/or kept as a fines product for sale. The fine recovered material3024can be recycled back into one or more stages of the system. Preferably, the fine recovered material3024would be supplied into the dust reduced stream3004or the size-reduced stream22, or would be kept as a distinct product stream that could be sold or mixed with other materials to provide a commercial product. It is noted that the recovered dust material can be treated, transported and used in various ways, some of which are described herein.

EXPERIMENTATION

Comparative experiments were conducted on an MRF fines material obtained from an MSW processing plant. The MRF fines taken as feedstock was below 2½ inch material and samples were subjected to size reduction in a kinetic pulveriser as described herein as well as in a grinder device (Rotochopper®). The size-reduced material was then subjected to ½ inch screening to obtain a screened fraction and an oversized reject fraction. A vibration screen was used for the comparative tests.

In terms of observations and results, the quality and the yield of the screened fraction when using the KP were notably higher compared to the grinder device. In addition, for the KP less organic material reported with the reject oversized fraction compared to the grinder device.

For example, with the KP the rejects in the screened fraction represented a percentage of 11%; for the grinder, 21%. This means that undesirable materials were excessively size reduced by the grinder such that they tended to pass through the screen with the desirable material such that the quality of the product was inferior compared to the KP. In contrast, the KP facilitated liberation and separation of such undesirable materials resulting in a higher quality screened product. In the tests, the KP facilitated production of a screened fraction with almost half the amount of undesirable materials compared to the grinder tests.

In addition, for the KP the proportion of man-made objects such as glass, ceramic, plastics, etc., in the reject material was 4.5%; for the grinder, 8.1%. This indicates that the KP was able to size reduce hard man-made materials for inclusion in the screened fraction whereas the grinder was unable to achieve such size reduction and so a greater weight percentage of man-made objects reported to the oversized fraction.

Thus, the KP was able to size reduce organics and hard man-made objects such that almost 90% of the input MRF fines was size reduced and included in the screened product fraction. With the KP, very little organics were lost to the oversized fraction thus providing enhanced organics recovery for the final product.

The follow table provides a more detailed overview of the comparative test results with size distribution and contaminant composition data. The test results confirm that the use of the KP for processing feedstocks such as MRF fines facilitates several advantages.

As can be noted from the table, the KP enabled a size distribution with much high proportions of smaller particles compared to the grinder. For example, with the KP, 75% of the screened material had a particle size below 2 mm, whereas only 29.5% of the screened fraction from the grinder was below 2 mm. In addition, the proportion of total plastics decreased due to screening of the KP size reduced material, whereas the proportion of total plastics increased for the grinder size reduced material. The film plastics were significantly reduced from screening for the KP size reduced material as the film plastics were liberated rather than overly sized reduced, whereas the proportion of film plastics stayed the same after screening the grinder size reduced material. In general, the contaminant concentrations were lower when using the KP for the size reduction stage.