Patent Grant
9968942
The present disclosure relates generally to a method and apparatus for separating contaminants such as stones, glass and synthetic materials such as fibers and plastics from compost and other recyclable materials.
With increasing awareness of potential damage to the environment resulting from recyclables directed to waste landfill dumps or incineration, more industries and municipalities are implementing waste diversion and recycling programs to significantly reduce the volume of waste that must be processed in a conventional manner. However, as the rate of waste diversion and recycling has increased, processing facilities have found that certain recyclables, in particular compostable materials, have increasingly become contaminated with synthetic materials such as fibers and plastics due to improper separation. Furthermore, undesirable stone and glass are often mixed with biodegradable materials when collected for recycling.
Municipal and industrial compost facilities in North America and in other jurisdictions are struggling with a growing contamination problem as they attempt to recycle biodegradable materials in an efficient and cost effective manner. A particular challenge is that there are stones, glass, and numerous types of synthetic materials such as fibers and plastics found in compost which are diverse in shape, size and density. Fibers may vary in shape, size and density, ranging from natural and synthetic textiles such as cotton, wool, burlap, polyester fiber and nylon from apparel, furniture, carpeting, rags, wipes, scrub pads, rope, string, etc. Plastics may vary considerably in shape, size and density, ranging from larger pieces of solid plastics, to thin strips of plastics torn from plastic bags and packaging. Furthermore, biodegradable material often has high moisture content, making effective separation of stone, fibers and plastics from the organic materials technically challenging. These technical challenges result in increased wear on processing machinery, increased labor and operating costs, and a reduction in the market value of the finished compost product. At worst, the processed compost may be so contaminated by that it is unusable altogether and must ultimately be discarded as waste, thereby defeating the purpose of diverting and recycling in the first place.
In U.S. Pat. No. 8,910,797, an earlier patent issued to the present inventor, a novel method and apparatus was disclosed for separating plastics from compost and other recyclable materials. While the method and apparatus described in the issued patent was effective for removal of a substantial amount of plastics contaminants, it was found that other types of contaminants such as stones, glass and other synthetic materials remained in the compost after processing.
Therefore, what is needed is a further improved method and apparatus for separating stones, glass, fibers and plastics contaminants from biodegradable materials that overcomes at least some of the limitations in the prior art.
The present disclosure relates generally to a method and apparatus for separating contaminants such as stones, glass, fibers and plastic contaminants from compost and other recyclable materials. The method and apparatus can effectively remove stones, glass, fibers and plastics contaminants of all shapes and sizes and varying density from recyclable biodegradable materials (e.g. compost, food waste, yard waste, and woodchips) under a wide range of moisture content conditions.
In an aspect, there is provided an apparatus for separating stones, glass, and synthetic materials such as fibers and plastics from compost and other recyclable materials, comprising: an inclined trough having a feed entry at a top end for receiving the feed material, the inclined trough including a plurality of riffles angled to at least partially hinder and unsettle a flow of the feed material flowing down the inclined trough; one or more vibratory motors configured to induce a vibration in the inclined trough; one or more blowers configured to generate an air flow via overhead air vent nozzles positioned over the inclined trough and directing the air flow over the feed material and to one side of the inclined trough, thereby to remove synthetic materials; and a material resilience separator adapted to launch the feed material across a plurality of bins, such that the stones and glass, biodegradable materials, and synthetic fibers in the feed material are separated into different bins based on their respective resilience (hardness) and coefficient of drag.
In an embodiment, the material resilience separator comprises of an inclined plate situated below the lowest end of the inclined trough. The angle of the plate is such that hard material such as stone and glass will bounce somewhat and separate from the softer organic material which will fall directly off the plate without bouncing. As the material types fall under the force of gravity, a clear split occurs between the material types. An adjustable knife is adapted and situated between the separated fractions to improve the efficiency of the split across the plurality of bins.
In another embodiment, the angle of the inclined plate is adapted to be controlled to increase separation of the stones and glass, biodegradable materials, and fibers between the plurality of bins.
In another embodiment, the overhead air vent nozzles are adjustable to vary the amount of air flow across the inclined trough.
In another embodiment, the overhead air vent nozzles are adjustable to change the angle of air flow across the inclined trough.
In another embodiment, flexible skirts are positioned perpendicularly to the inclined trough and on either side of a set of overhead air vent nozzles to create a compartmentalized air flow corridor across the inclined trough.
In another embodiment, the apparatus further comprises a bar screen located at the feed entry to separate the incoming feed material.
In another embodiment, the apparatus includes at least one cross conveyor to change the direction of the processed feed material at least once.
Other features and advantages of the present invention will become apparent from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples are given by way of illustration and not limitation. Many modifications and changes within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.
In the drawings, embodiments of the invention are illustrated by way of example. It is to be expressly understood that the description and drawings are only for the purpose of illustration and as an aid to understanding, and are not intended as a definition of the limits of the invention.
As noted above, the present disclosure relates generally to a method and apparatus for separating contaminants such as stones, glass, fibers and plastics from compost and other recyclable materials. The method and apparatus can effectively remove these different types of contaminants of all shapes and sizes from recyclable biodegradable materials under a wide range of moisture content conditions.
In an aspect, there is provided an apparatus for separating contaminants such as stones, glass, and synthetics such as fibers and plastics from compost and other recyclable materials, comprising: an inclined trough having a feed entry at a top end for receiving the feed material, the inclined trough including a plurality of riffles angled to at least partially hinder and unsettle a flow of the feed material flowing down the inclined trough; one or more vibratory motors configured to induce a vibration in the inclined trough; one or more blowers configured to generate an air flow via overhead air vent nozzles positioned over the inclined trough and directing the air flow over the feed material and to one side of the inclined trough, thereby to remove plastics; and a material resilience separator adapted to launch the feed material across a plurality of bins, such that the stones and glass, biodegradable materials, and fibers in the feed material are separated into different bins based on their respective resilience (hardness) and coefficient of drag.
In an embodiment, the material resilience separator comprises of an inclined plate situated below the lowest end of the inclined trough. The angle of the plate is such that hard material such as stone and glass will bounce somewhat and separate from the softer organic material which will fall directly off the plate without bouncing. As the different material types fall under the force of gravity, a clear split occurs between the material types. A discharge hopper system has been devised with adjustable blades located between and dividing the bins to improve the efficiency of the split across the plurality of bins.
In another embodiment, the angle of the inclined plate is adapted to be controlled to increase separation of the stones and glass, biodegradable materials, and fibers between the plurality of bins, given a variation in feed material moisture content.
In another embodiment, the bins have adjustable blades which can control the width of at least one of the bins, thereby providing further control over separation of the different types of materials.
In another embodiment, a blower is adapted to be controlled to increase separation of the stones and glass, biodegradable and fibers between the plurality of bins.
In another embodiment, the overhead air vent nozzles are adjustable to vary the speed and volume of air flow across the inclined trough.
In another embodiment, the overhead air vent nozzles are adjustable to change the angle of air flow across the inclined trough.
In another embodiment, flexible skirts are positioned perpendicularly to the inclined trough and on either side of a set of overhead air vent nozzles to create a compartmentalized air flow corridor across the inclined trough.
In another embodiment, the plurality of riffles include at least some riffles that are positioned diagonally to the flow of feed material flowing down the inclined trough and to the air flow, such that heavier materials are directed away from the edge of the inclined trough over which the plastics are blown.
In another embodiment, the apparatus further comprises a bar screen located at the feed entry to separate (pre-size) the incoming feed material.
In another embodiment, the apparatus includes at least one cross conveyor to change the direction of the processed feed material at least once.
By way of example, and not by way of limitation,
A first stage is a material intake stage with a feed entry 104 for receiving feed material from a feed conveyor 108. In an embodiment, the first stage may include a scalping separator or bar screen 103 which removes oversized objects such as plastic bottles, plastic pails, and other larger objects before they enter the inclined trough (102). In this illustrative example, the screen 103 comprises a plurality of parallel screen bars 105 spaced apart to allow feed material under a particular width to fall through the screen 103 and into the second stage. As will be detailed further below, the scalping screen 103 vibrates under an induced vibration to help direct oversized materials down the parallel screen bars 105. In addition, one or more blowers 107A, 107B may be used to blow light plastics and either directly deposit them onto a cross conveyor 111, or in the case of heavier films, assist their passage down the scalping screen 103 to the cross conveyor 111. The cross conveyor 111 carries the oversized materials to a plastics discharge chute (not shown) and then into a roll off bin (not shown).
Still referring to
While the inclined trough 102 may operate anywhere between about 30 degrees from horizontal and 10 degrees from horizontal, in a preferred embodiment, the incline of trough 102 is approximately 20 degrees from horizontal. This incline has been found through experimentation to provide a good flow of biodegradable material through trough 102, while simultaneously allowing the biodegradable material to attain a hindered settling condition behind each of the riffles 410, 412, 414, 416 on the trough 102.
The inclined trough 102 is preferably mounted to a plurality of flexibly resilient supports 110. The supports 110 may be positioned to keep trough 102 spaced apart but movable relative to an underlying supporting frame 120. The supporting frame 120 may itself be mounted on a base 140 to sufficiently raise the materials discharge end 106 of the second stage to a suitable height and to position a third stage 130 under the material discharge end 106 in order to further separate the processed material, as described below.
In an embodiment, one or more vibratory motors 128 are adapted to induce a vibration to the entire first and second stage of the apparatus, including the inclined trough 102, feed entry 104, and bar screen 103. Preferably, the vibratory motion induced by the vibrating motors 128 is a reciprocating vibratory motion that is symmetrical and linear. This vibratory motion allows the biodegradable material to remain substantially in constant contact with the surface of the trough 102, thus increasing the effects of hindered settling along the length of trough 102 as the biodegradable material travels down the slope of the trough 102.
In a preferred embodiment, the vibratory motion has a frequency in the range from about 600 cycles per minute to about 1200 cycles per minute, at an amplitude range of about 1/16th inch to about ¾ inch. However, vibratory motions outside of this range are also possible.
Still referring to
As best shown in
In an illustrative embodiment that is not meant to be limiting, the grid of overhead air vent nozzles 310 may be 4″ internal diameter pipes which are arranged at a spacing of 7″ on centre along each row across the trough, and 10″ on centre between each row. Each overhead air vent nozzle 310 may be positioned at an exit angle of approximately 60 degrees from horizontal as formed by the top surface of the inclined trough 102.
In an embodiment, this grid of overhead air vent nozzles 310 is adapted to direct air flow perpendicularly across the downward flow of feed material in a generally perpendicular direction. By directing air at a right angle to the material flow down the trough incline, plastics and other contaminants are caught by the air flow and transported across the trough to the plastics discharge chute.
In another embodiment, the plurality of overhead air vent nozzles 310 may be adjustable to vary the amount of air flow across the inclined trough 102, and to vary the angle of air flow across the inclined trough 102. Varying the angle of the overhead air vent nozzles 310 also allows the apparatus to further agitate the plastics to separate them from the feed material flowing down the inclined trough 102.
In another embodiment, the plurality of overhead air vent nozzles 310 may be angled up or down diagonally.
Still referring to
Through experimentation, it has been found that an air flow speed in the range of about 300 feet per minute to 600 feet per minute provides good results. However, air flow speeds outside of this range are also possible, given the type of feed material and the type of plastics.
In a preferred embodiment, the lower ends of the baffles 320 are flexible and are adjusted to lightly brush the surface of the feed material as it flows down the inclined trough 102. The effect of this brushing action is twofold.
First, a virtual air channel is formed that in effect creates duct-like conditions formed by the plurality of overhead air vent nozzles 310 above, the trough surface below, and the baffles on either side, which concentrate and direct air and plastic flow directly to the plastic discharge. These compartmentalized air flow corridors contain the air flow across the inclined trough 102 and further agitates and separates the loose plastics to be blown to one side of the inclined trough 102. This greatly improves the transportation ability of the air flow, even with hard plastic fragments, and reduces the volume and force of air required.
A second effect of the baffles 320, is that they tend to trap plastic behind them, whilst the rest of the feed material flows beneath. In effect, they are skimming the plastic off the surface of the feed material, as the feed material passes over the riffles. This skimming effect ensures very effective and thorough separation of even the smallest, barely visible plastic fragments.
While the enhanced air flow significantly increases the ability to direct plastics to one side, the enhanced air flow as described above can also cause lighter or drier organic material to migrate across the trough towards the plastics discharge chute, as the feed material flows down the trough incline. This can cause excessive amounts of organic material to be discharged along with the plastics. To overcome this challenge, the riffle layout has been changed in such a way as to counter the force and action of the air flow.
As shown in
In an embodiment, the diagonal riffles 414, 416 may be angled at approximately between 30 degrees and 60 degrees from the parallel riffles 410 and the vertical riffles 412, and positioned to one side of the inclined trough 102 starting approximately half way across the width of the table (in this illustrative example shown in
The riffles are of a sufficient height and sufficient angle such that while they provide an obstacle to unhindered flow of biodegradable material down inclined trough 102, they do not stop the flow entirely. The dimensions of the riffles 410, 412, 414, 416 including height, profile, and angles may be selected based on the type of biodegradable materials being processed.
In an embodiment, the height of the riffles 410, 412, 414, 416, as measured perpendicular to the trough 102, relates to the particle size and shape of the feed material being processed. The height of the riffles 410, 412, 414, 416 are also related to the design depth or thickness of the bed of feed material as it flows down the trough 102. If the feed material consists mostly of large particles, the feed material may flow over a low riffle without attaining a satisfactory state of hindered settling, thereby reducing separating efficiency.
Adjusting the height of the riffles 410, 412, 414, 416 according to the median particle size is therefore important. In a preferred embodiment, the bed depth, which is the thickness of the material perpendicular to the trough surface as it flows down the incline, is no more than about 1 to 1.5 times the median particle diameter, with the riffle height being about 2 times the median particle diameter.
In a preferred embodiment, the cross section of the riffles 410, 412, 414, 416 is such that each face that constitutes the riffle is inclined at between about 40° to 50° (e.g. 45°) from the surface of the inclined trough 102. Experimentation has shown that other inclinations and riffle face shapes may not perform as well under wide ranging conditions.
In an embodiment, the number of riffles per unit length of the trough, in combination with the trough frequency and amplitude, determine the feed rate for a given separation efficiency. Experimentation has shown that there is a trade-off between the feed rate and the separation efficiency, when contamination is held constant. Separation efficiency drops as feed rate increases. To maintain satisfactory feed rate at 90% to almost 100% separation, it is preferable to space the riffles no less than about 6 inches peak to peak, and no greater than about 12 inches peak to peak. Finer feed material demands the closer riffle spacing, coarser material requires wider spacing.
As flowing biodegradable material meets the perpendicular or diagonal riffles 410, 414, 416, the biodegradable material begins to boil or churn rapidly behind the perpendicular or diagonal riffles 410, 414, 416 before spilling over the peak of the perpendicular or diagonal riffles 410, 414, 416. In other words, perpendicular or diagonal riffles 410, 414, 416 induce hindered settling of the biodegradable material on the surface of trough 102, and together with the vibrating motion of trough 102 induces a constant churn.
As the biodegradable material churns, the plastics contaminants rise to the surface of the churning biodegradable material. It is believed that this separation is due to a combination of phenomena, which include the differences in specific gravity, particle shape, and particle size between the plastic contaminants and the biodegradable materials.
In experimentation, the second stage of apparatus 100 has been found to effectively remove plastics of all shapes, sizes, compositions and densities from biodegradable materials and woodchips. The plastics separation has been found to be effective under a wide range of compost moisture content levels, ranging from about 20% to 60% of water present, relative to the oven dry weight of the sample. It has also been found that the apparatus of the present disclosure will effectively remove plastics of all kinds, shapes and sizes from tiny fragments of film, to plastic bottle tops, to large sheets of film, to shoe soles, and so on. Thus a key advantage is to be able to process a wide range of plastics types in one processing line.
Experimental testing has shown consistently high separation rates under wide ranging conditions of extremely high contamination (up to 20% plastics by volume). Results of separation average 99% film plastic and 96% hard plastics and fibers.
While the above described process has been found to remove a substantial amount of the plastic contaminants, with up to 100% of film plastics in ideal conditions, it has been found that other types of contaminants including stones, glass, and fibers may remain mixed in with the biodegradable materials as they cannot be removed by air flow alone. In order to remove these remaining contaminants to achieve a higher grade of biodegradable material by removing these contaminants, the apparatus includes a third stage comprising a material resilience separator.
An illustrative embodiment of a material resilience separator third stage is shown in
In the embodiment shown in
In an embodiment, adjustable bin blades or knives 760A, 760B may be adjusted to change the position of the cutting edges of the bins 720, 730, 740. This allows for adjustment due to changes in material moisture content and feed material properties.
Thus, in an aspect, there is provided an apparatus for separating contaminants from biodegradable materials in a feed material, comprising: an inclined trough having a feed entry at a top end for receiving the feed material, the inclined trough including a plurality of riffles angled to at least partially hinder and unsettle a flow of the feed material flowing down the inclined trough; one or more vibratory motors configured to induce a vibration in the inclined trough; one or more blowers configured to generate an air flow through overhead air vent nozzles positioned over the inclined trough and directing the air flow to one side of the inclined trough; and a material resilience separator for separating the contaminants from the biodegradable materials in the remaining material.
In an embodiment, the material resilience separator comprises an inclined plate adapted to cause contaminants to separate based on differences in material resilience and hardness, whereby contaminants bouncing off the inclined plate assume a trajectory of fall different from the biodegradable materials based on coefficients of elasticity, such that the contaminants are substantially separated from the biodegradable materials.
In another embodiment, the angle of the inclined plate is adapted to be controlled to produce increased separation of the contaminants from the biodegradable materials between a plurality of bins.
In another embodiment, the apparatus further comprises a blower adapted to provide a controlled air flow to increase separation of the contaminants and the biodegradable materials between the plurality of bins.
In another embodiment, the apparatus further comprises adjustable blades located between and dividing the plurality of bins to increase separation of the contaminants from the biodegradable materials.
In another embodiment, the contaminants comprise stones, glass, and synthetic materials including fibers and plastics.
In another embodiment, the apparatus further comprises overhead air vent nozzles are adjustable to change the angle of air flow across the inclined trough.
In another embodiment, the apparatus further comprises flexible skirts positioned perpendicularly to the inclined trough and on either side of a set of overhead air vent nozzles to create a compartmentalized air flow channel across the inclined trough.
In another embodiment, the apparatus further comprises a bar screen located at the feed entry to separate larger contaminants from the incoming feed material.
In another embodiment, the apparatus further comprises at least one cross conveyor to divert the direction of the processed feed material during processing.
In another aspect, there is provided a method of separating contaminants from biodegradable materials in feed material, comprising: supplying the feed material to an inclined trough including a plurality of riffles angled to at least partially hinder and unsettle a flow of the feed material flowing down the inclined trough; inducing a vibration in the inclined trough utilizing one or more vibratory motors; generating an air flow across and to one side of the inclined trough utilizing a plurality of overhead air vent nozzles positioned over the inclined trough; and separating the contaminants from the biodegradable materials in the remaining feed material utilizing a material resilience separator.
In an embodiment, the material resilience separator comprises an inclined plate adapted to cause contaminants to separate based on differences in material resilience and hardness, whereby contaminants bouncing off the inclined plate assume a trajectory of fall different from the biodegradable materials based on coefficients of elasticity, such that the contaminants are substantially separated from the biodegradable materials.
In another embodiment, the method further comprises varying the angle of the inclined plate to increase separation of the contaminants from the biodegradable materials between a plurality of bins.
In another embodiment, the method further comprises providing a controlled air flow to increase separation of the contaminants and the biodegradable materials between the plurality of bins.
In another embodiment, the method further comprises adjusting an angle of blades located between and dividing the plurality of bins to increase separation of the contaminants from the biodegradable materials.
While various embodiments and illustrative examples have been described above, it will be appreciated that these embodiments and illustrative examples are not limiting, and the scope of the invention is defined by the following claims.
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| 20180001323 A1 | Jan 2018 | US |
