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Average morphological content of unselected municipal solid waste is given in the following table:
Depending on the waste collection mode, we distinguish:
According to experience for the recovery of damp waste a green container of 120 l can be used, and for the dry waste a blue container of 240 l. Of course, what is implemented in a concrete application depends on the features of municipal vehicles and on the waste collection frequency.
Dual-flow waste recovery system enables application of standardly equipped sorting systems.
Dangerous household waste, construction debris and bulk waste is collected at special collecting stations and is transported to the facility specialized for processing such materials.
Functional Description of a Uniformed Facility of Capacity 10 t per hour
At the entrance of the facility, material radioactivity can be controlled in trucks that bring in the municipal waste.
The facility is composed of the following units: input and output electronic scales for measuring the volume of collected waste, receiving premises, preselection and comminuting of bulk waste, chemical treatment unit (pH value stabilization) and stocking raw materials.
Handling material in the receiving unit is performed by a dredge.
Facility can also be equipped with an area and equipment for receipt and sanitation of dangerous household waste (autoclave).
A dredge inputs material into the receptacle, from which, by an alimentator with hydraulic regulation of layer height, it is conducted to the device for shredding bags. In this device packed material is freed and is taken by a short plate transporter to the belt transporter for presorting. Within the presorting area, workers control material flow and composition by extracting from the material flux components that could, by their volume or content, cause grave problems in the normal material flow, or the facility does not accept them for processing. These components are stocked into special containers that are placed beneath the cabin for presorting.
Usually, during presorting about 5% of the total mass is separated, i.e. 0.2 t/h or 5m3/h of extra volume components and approximately 15% or 1.5 t/h, i.e. 10m3/h material that is not accepted by the facility for processing.
Material is then, by a skew belt transporter, taken into the revolving screen divided into two sections. The first section has openings with diameter of 50 mm and the second section has openings of 180 mm diameter. In case of the single-flow municipal waste, screen perforation is 80 mm and 180 mm to achieve maximum extraction of the organic component.
Figure 1. Uniformed Facility of 10t/h Capacity
Through openings of the first screen section passes about 15% of the input material, that is 1.5 t/h or 10m3/h. This minute mixed material is not processed in the facility, but is directed by a system of belt transporters toward the containers for waste material. In case of unselected material in the single-flow municipal solid waste collection, this material contains mainly organic components so that it can be directed for biological treatment in separate facilities, whether for biostabilization, composting or biogas generation.
Through perforations of the second screen section passes 40% (particles of 50-180 mm) of material or about 4 t/h, i.e. 35m3/h.
This material is, by a belt transporter, placed in the axial screen plane directed by a transversally placed belt transporter to the location, where ferromagnetic particles are extracted from the material flux by electromagnetic separator (overband magnet). It is possible to install, instead of the belt transporter placed in the axial screen plane, a vibratory screen in order to completely extract residual minute particles. Minute particles that pass through this screen drop onto the transporter for waste material located below the screen.
Electromagnetic separator extracts about 2-3% or 0.2-0.3 t/h, i.e. 3.5m3/h of ferromagnetic material, which is by the belt transporters taken to the container for the receipt of ferromagnetic component of municipal waste.
Leftover material of 50-180 mm is taken by the planar belt transporter to the eddy current separator where, under the effect of Foucault currents, aluminum particles are separated. Depending on the morphological composition of input material, about 0.2-0.3% matter is extracted, i.e. 0.02-0.03 t/h or 1m3/h.
Aluminum particles are transported by the belt transporter to the container for such particles.
37% or 3.8 t/h, i.e. 29m3/h of the original material volume of 50-180 mm dimension, is taken with belt transporters to the special vibratory separator for separating planar goods and vessels, i.e. rotating parts.
This separator extracts approximately 3 t/h or 17.5m3/h, i.e. about 29% of the initial volume of planar parts which are separated directly onto the transporter for sorting planar parts of 50-180 mm dimension. In the sorting cabin on this transporter four sorters work who, by applying the positive sorting method, separate foils, tetra-packings, cardboard goods, paper and aluminum foils. The remaining mass represents mixed paper which is put into the box for mixed paper. Each sorter has at his disposal two receptacles. Bigger receptacle, for the material being extracted, is used to lower material into the bunker for respective material. The smaller receptacle is used for extracting waste material. It is constructed to direct such material onto one of transporters of the waste material system. In the sorting cabin, these transporters are located below transporters for sorting. Vessels or rotating parts are directed by the belt transporter to another special vibratory separator for separating light and heavy parts, i.e. for separating glass and plastic parts. This separator separates about 5%, i.e. about 0.5 t/h or 1.6m3/h of glass containers, whose flow is controlled by a worker in the cabin for sorting glass. This sorter separates, from the flow of glass containers, plastic containers accidentally placed there, and transfers them onto the transporter for plastic goods. Flux of glass containers is directed by a respective transporter to the container for glass parts.
Vibratory separator separates 1.5% or 5m3/h PET containers, 1.5% or 5m3/h of PVNG containers, and 0.5% or 5m3/h of tetra-packing containers, as well as 0.3% of aluminum containers, that is, a total 10-15m3/h or 3% or 0.3 t/h of the input material volume.
Planar belt transporter takes this volume to the transporter for sorting in the cabin for sorting plastic materials, where four workers extract plastic containers according to material type and place them into respective bunkers. The remaining volume is put down into the bunker with mixed plastics.
Parts that pass through the rotating screen, whose dimension is greater than 180 mm, make about 40% of the input volume, i.e. 4 t/h or 20 m3/h, and are placed onto the transporter for sorting, from which eight workers, in the sorting cabin, separate foils, tetra-packings, cardboard goods, paper and aluminum foils. The remaining volume is lowered into the bunker with mixed paper.
In this way, sorted materials are, by using the plate transporter and the planar belt transporter, taken to the press for baling. Expected volume is about 7 t/h. Either a receptacle or a perforator, depending on the material that is to be baled, is installed at the input of the baling press. These elements are exchanged by a hydraulic cylinder. Baled material is stocked and is ready for delivery.
By alternative design of the basic facility, all the vessels are directed to the sorting transporter, and at its end glass packings are extracted. These packings are not lowered into the bunker, they are rather directed by the belt transporter into the conveyor for glass packings. In this way, one special vibratory separator is omitted, but extracting these packings is more complicated.
Management premises, wardrobe and lavatories are located within the facility. Within the facility, there are also premises for spare parts and working fluids, chemical laboratory, ambulance, electric power supply unit, compressor station, and heating station in case the facility cannot be connected to the external heat supply system.
Adequate light is installed in sorting cabins.
The entire facility area has to be equipped with a system for dedusting and aeration. Sorting cabins are equipped with the air conditioning system. Air which is extracted from the facility has to be purified and freed from unpleasant odors and solid particles.
Facility has to be equipped with a system for purifying technological process water.
If necessary, at the exit of the facility, a system is installed for washing vehicles that bring in municipal waste is installed.
Result of material separation in the basic facility is the following assortment of secondary raw materials:
Basic Facility Upgrade
Upgrade of basic facility consists in adding a module for automatic sorting of plastics and glass, module for selecting minute waste material, and a press for metal bricketing.
Fine waste material is, instead into a containers for waste material, taken into a specialized module for preparing material for biological or thermal treatment. Where, from this waste, using overband magnets, are extracted Fe metals, Al parts are extracted using eddy current separators. Material is crushed so that its granulation does not exceed 40 mm, it is sorted by using a ballistic transporter, and loaded into roll containers storing material intended for biological or thermal treatment. Separated Fe and Al materials are, by strip transporters, taken to bunkers for these secondary raw materials, and the heavy component, separated by the ballistic transporter, which is mainly composed of inert materials, fine glass, ceramics, batteries, gravel, demolition debris, etc. - is loaded into roll containers for refuse material. Plastics can be separated from the light component by using an electrostatic separator. In this way separated minute plastics, sorted according to type, are loaded into bags, and can be used as a secondary raw material or as refuse material.
Remaining material is taken to the facility for biological treatment.
Module for sorting glass according to color consists of a glass crusher, and two NIR sorters for separating glass into colorless, green and amber glass. Separated glass waste is transported, by respective strip transporters into the station for automatic loading into bags, sewing, and transport of bags to the area for shipment.
If the facility is upgraded by a module for sorting PET plastics according to color, plastics are not immediately directed for baling, but rather to the machine for sorting PET plastics according to color into colorless and colored PET. In this way separated PET is, by respective belt transporters, directed to respective bunkers for PET secondary raw materials.
Ferromagnetic materials and aluminum are, before shipment, directed to the module for bricketing.
The result of material separation in this upgraded facility is the following assortment of secondary raw materials:
It is clear from the above that by upgrading the basic sorting facility, we increase assortment quality and the quality of separated secondary raw materials, and the quality of their packing and transport to the consumer, but also that these upgrades increase the price of the facility.
Designed Capacity, Necessary Space , and Number of Employees
Designed facility capacity is 10 t of packing waste per hour.
The facility is located in an object of dimensions 60x40 meters, of 12 m height. Municipal waste density varies due to the variation of particular components, depending on geographic location, season, depositing time, degree of compactness, decomposition state, and other conditions. Average density of free waste is 115 kg/m3, but during collection it is rapidly compacted, so that its density varies from 235 to 300 kg/m3.
Material receipt area has dimensions 20x30m, that is about 600 m2, where the height of the material layer is about 3.6 m.
In case the municipal waste is brought to the facility every third day, it is necessary to provide a total of 1000 m2 for the waste receipt, which means approximately 500 m2 of additional space, or facility extension with an object of dimension 20x25 m2, and height about 6 m.
Area for stocking baled materials is often, due to waiting for expedition, expanded up to 1800 m2, which enables 14 days of stocking. This also means that additional storage warehouse area is needed of about 1200 m2, which can also be outdoors, so that here an extension is planned in the form of an object of 20x25 m2, and of height of about 6 m.
Technological area of the basic facility is 60x20m, i.e. 1200 m2.
Number of employees in one work shift is given in the following table:
Dr Slobodan Stojković
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