WO2007142508A1

WO2007142508A1 - Solid waste collection system

Info

Publication number: WO2007142508A1
Application number: PCT/MY2007/000037
Authority: WO
Inventors: Sri Skanda Rajah S. Ratnam
Original assignee: Nexaldes Sdn. Bhd.
Priority date: 2006-06-06
Filing date: 2007-06-05
Publication date: 2007-12-13
Also published as: MY141070A

Abstract

The present invention relates to a method and system of pneumatic conveying of solid waste from a plurality of holding areas within buildings or outdoors through reticulated collecting conduit systems (22) to at least two Remote Separation and Collection Stations (RSCS) (14) which are distanced apart by at least two hundred metres. The system operates by using an air suction apparatus (10) to generate sub-atmospheric pressures in a reticulated vacuum conduit system (12) to at least two control valves (24) connected to the at least two RSCS. This in turn generates a flow of air from at least one air valve (18) connected to at least one holding area (16) for the pneumatic conveying of the solid waste to at least one RSCS (14) when at least one control valve (24) is open.

Description

SOLID WASTE COLLECTION SYSTEM

FIELD OF INVENTION

The present invention relates to a system and method of conveying solid waste from solid waste holding areas to solid waste collection stations by using an air suction apparatus to generate sub-atmospheric pressure in a conduit system to generate air movement to convey the solid waste to the solid waste collection stations.

BACKGROUND OF THE INVENTION

Existing Pneumatic Solid Waste Collection Systems (PSWCS) convey, by air movement, solid waste from several intermediate holding areas (IHA) which are fed by indoor gravity chutes or outdoor throw stations to a central collection point called the Refuse Collection Station (RCS) by a network of surface and underground pipes and air valves. In longer pipe installations a transfer station may be added along the pipe to collect and re-transfer the solid waste to the RCS.

The RCS itself is a self-contained facility combining the major components of refuse separator(s), compactor(s), container(s), vacuum equipment, filtration system(s), deodorising system(s), valves, pipes, control system and electrical power supply panel.

In large developments there would be several self-contained RCS each covering a section of the development. The limitation of the system is the maximum conveying distance of the solid waste between the furthest IHA and the RCS which is about 3 kilometres, after which the system becomes extremely inefficient in terms of energy consumption.

Whilst the concept of PSWCS is readily accepted by most building owners and managers alike, the greatest obstacles remain high investment cost, lack of space within the development and the maintenance of the specialised equipment in such a facility that has to be undertaken by skilled technicians.

A critical factor in pneumatic solid waste collection systems is to maintain a minimum air speed, which ranges from 18-25 m/s (corrected to standard atmospheric pressure of 1013 mbar) within the pipes which can support the efficient movement of the solid waste in the pipe between the IHA and RCS. Due to this high minimum conveying air speed the frictional and pressure losses for a given length of pipe are great leading to high energy costs whilst also limiting the practical conveying distances. The combination of higher capital costs for vacuum equipment and energy costs for operations, generally limit the distances and reduce the scale of coverage of Pneumatic Solid Waste Collection

Systems using conventional methods.

Conventionally designed PSWCS use pipes that generally vary in diameter from 400mm to 500mm although in exceptional cases where very long solid waste transfer distances are required the pipes can reach up to 600mm diameter. The problem with using the 600mm diameter pipe for the conveying of the solid waste is that the sub-atmospheric pressures to generate the huge quantities of air movement is needed to be generated by the vacuum equipment to maintain the minimum air speed in the pipe required for conveying the waste. This translates to the use of very costly and high powered vacuum equipment to generate the sub-atmospheric pressures to create the air movement which in turn leads to high operating costs for the system.

Another shortcoming of conventional design which indirectly leads to a disproportionate higher initial investment cost is the idling of the system between conveying cycles. Typically the operating time of the vacuum equipment in smaller developments may be no more than 90 minutes in a day.

Another problem with conventionally designed systems conveying large masses of solid waste over very long distances is the problem of abrasion in the pipes. Due to this abrasion, steel pipes have often been selected as the most suitable material. The downside of this material though has been corrosion as solid waste is often wet and generates a highly acidic liquid called leachate which attacks metals. The corrosive attack on both the internal and external surfaces of the pipe can be reduced with cathodic protection which is costly and requires regular inspection and maintenance. Generally the longer the pipe in a system the larger the area covered, the higher the solid waste load, the greater the abrasion, the shorter the performance life of the pipe.

The problem with traditional PSWCS is that smaller developments limited to one or two buildings tend to avoid investing in the system due to the high initial capital cost and large space requirement for the RCS.

The scope of the present invention is to address these concerns and to allow for a greater penetration of these useful systems into large developments and districts that may be under planning, in construction or even existing but in the process of being upgraded.

OBJECTS OF THE PRESENT INVENTION

It is the primary object of the present invention to increase the efficiency and reduce the initial investment in the Pneumatic Solid Waste Collection Systems (PSWCS) facility for individual building owners and/or developers, minimise the space requirement for housing the facility either within the building and/or within a complex of buildings and remove the duties of maintaining complex vacuum equipment and changing filters/deodorisers for such a facility from the owners of the buildings.

SUMMARY OF THE INVENTION The present invention relates to a method and system of conveying solid waste from a plurality of holding areas into a plurality of collection stations. The method comprising steps of periodically generating air movement by creating sub-atmospheric pressure conditions from an air suction apparatus to at least two control valves connected to at least two collection stations through a reticulated vacuum conduit system and generating a flow of air from at least one air valve connected to at least one holding area by opening at least one control valve for the pneumatic conveying of solid waste to at least one collection station by at least one reticulated collecting conduit system. The air suction apparatus is spaced apart from at least two collection stations and it is connected by a reticulated vacuum conduit system and wherein the two collection stations are distanced apart by at least two hundred meters.

The conveying system comprises of at least two reticulated collecting conduit systems connecting at least two holding areas to at least two collection stations which exclude air suction apparatus and where the two collection stations are distanced apart by at least two hundred metres, an air suction apparatus spaced apart from the collection stations and which comprises of vacuum equipment and control systems and a reticulated vacuum conduit system connecting the air suction apparatus to at least two collection stations. Air speed within the reticulated vacuum conduit system operates at between 6-17 ms^"1 corrected to equivalent standard atmospheric pressure of 1013 mbar. Air speed within the reticulated collecting conduit systems operates at between 18-25 ms^"1 corrected to equivalent standard atmospheric pressure of 1013 mbar. The diameter of the reticulated collecting conduit systems is between 400mm to 500mm. The diameter of the reticulated vacuum conduit system is between 550mm to 1000mm. As a variation, the reticulated vacuum conduit system can be used for pneumatic transfer of light density materials from any point anywhere along the vacuum conduits to a collecting station before the air suction apparatus. The reticulated vacuum conduit system can be also used in vacuum services for buildings.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given herein below and accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:

Figure 1 shows a diagrammatic view of all the intermediate holding areas (IHA) linked to a particular Remote Separation & Collection Station (RSCS) typically known as a Precinct. Figure 2 shows a diagrammatic view of all the Precincts supported by a District Vacuum Plant (DVP) known and referred as air suction apparatus.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE

INVENTION

The present invention relates to a method and system of pneumatic conveying of solid waste from a plurality of holding areas (16) within buildings or outdoors through at least two respective reticulated collecting conduit systems (22) to at least two Remote Separation and Collection Stations (RSCS) (14) which are distanced apart by at least two hundred meters. An embodiment of the invention relates to a District Vacuum Plant (DVP) (10) which is connected by a reticulated vacuum conduit system (12) to at least two Remote Separation & Collection Stations (RSCS) (14). The DVP (10) is known and referred to as air suction apparatus. Each RSCS (14) in turn supports a plurality of Intermediate Holding Areas (IHA) (16) that may be located within buildings (such as schools, offices, houses, low and high rise buildings) or outdoors (as is typical of the current systems). The intermediate holding areas (IHA) (16) are connected to the RSCS (14) through reticulated collecting conduit systems (22). The reticulated collecting conduit systems pneumatically convey solid waste from the intermediate holding areas (IHA) (16) to RSCS (14). The furthest Intermediate Holding Area (16) is at least 3.5km from the air suction apparatus (10). The reticulated collecting conduit systems (22) are a plurality of networks of collecting conduits. The reticulated vacuum conduit system (12) is a single network of vacuum conduits. For the convenience of describing the system the area of coverage of all the IHA

(16) linked to a particular RSCS (14) is referred to as a Precinct as shown in Figure 1. The area of coverage of all the Precincts supported by an air suction apparatus (10) is referred to as the District as shown in Figure 2. One air suction apparatus (10) is capable of supporting at least two RSCS (14).

The air suction apparatus (10) includes vacuum equipments, utilities and control systems and is housed in a building to generate required sub-atmospheric pressure in the vacuum conduit system to at least two control valves (24) connected to at least two RSCS (14) through a reticulated vacuum conduit system. When at least one control valve (24) is opened the sub-atmospheric pressure conditions generate a flow of air from the at least one RSCS (14) to the control valve (24) which in turn generates a flow of air from at least one air valve (18) connected to at least one IHA (16) for the pneumatic conveying of solid waste from the IHA (16) to the at least one RSCS (14) through at least one reticulated collecting conduit systems (22). The reticulated vacuum conduit system (12) conveys only filtered air from the RSCS (14) to the air suction apparatus (10). For the avoidance of doubt the air suction apparatus (10) is designed to generate enough sub-atmospheric pressure in the vacuum conduits to allow one or more RSCS (14) to operate simultaneously. The air suction apparatus is designed to run continuously for long periods to supply the sub-atmospheric pressure needs for many RSCS (14) unlike small conventional systems that are on standby and not running for most part of the day.

The air suction apparatus (10) preferably also houses secondary filtration and deodorising systems that treat exhaust air from the air suction apparatus (10) before it is discharged to atmosphere. The filtration and deodorising systems include filter media, activated carbon, ultraviolet treatment, chemical sprays and such like based on the requirements and regulations of the State.

A Master Controller in the air suction apparatus (10) is linked by a standard communication system (e.g. wired, wireless, fibre optics, communication cable, etc) to a Remote Terminal Unit (RTU) spaced apart from the control valves (24) connected to each RSCS (14) that allows the air suction apparatus (10) to control the flow of air from the

RSCS (14) thereby controlling air speed in the reticulated collecting conduit systems (22).

There is a controller in each RSCS that communicates with the RTU located at each IHA

(16) to control the systematic discharge and collection of waste from the IHA (16) to the RSCS (14) through the respective reticulated collecting conduit systems (22).

It is expected that as the number of RSCS (14) increases within a District that more than one RSCS (14) will be provided its conveying air requirements at any one time. The air suction apparatus (10) will use present and historical data to predict RSCS (14) activation of conveying cycles and allow for optimised use of the sub-atmospheric pressures generated by the vacuum equipments in the air suction apparatus. There will be an increase in vacuum equipments in the air suction apparatus (10) as the demand for more conveying air increases over time due to increased numbers of RSCS (14) and/or the increased frequency of transport cycles due to the increased waste generation in the area covered by the RSCS. The vacuum equipments in the air suction apparatus is easily expanded to cater for the conveying air needs as more RSCS are connected within the District and is therefore particularly suitable where building projects are undertaken in multiple phases over an extended period of time. The vacuum equipments such as turbofans, roots blowers, multi-stage centrifugal fans and such like generate sub- atmospheric pressures with airflow more energy efficiently giving lower operating costs to the operator of the air suction apparatus (10).

Each RSCS will have its own waste separation and collection equipment. The RSCS (14) are self-contained for primary separation of solid waste from the conveying air stream. The separated solid waste is collected and/or compacted in containers. It is expected that the RSCS (14) will have one or more of each of the above components to cater for the solid waste collection needs of the Precinct. As the containers are filled with the solid waste they are removed from the RSCS periodically on trucks to be emptied at landfills, incinerators or recycle centres. There is an interfacing control and protection filter chamber (20) which is spaced apart from the RSCS (14) to ensure that the air moving from the RSCS (14) to the air suction apparatus (10) is almost free of all solid waste except very fine particles that may escape this filtration system. The chamber comprises a safety filter, differential pressure monitoring system, a velocity monitor, control valves (24) comprises of a variable control valve and a shut-off valve. The valves are controlled by motors and/or cylinders that may be electrically or pneumatically controlled. The above components are monitored by a Remote Terminal Unit (RTU) that is controlled from the air suction apparatus (10).

The air suction apparatus (10) building can be located at a piped (12) distance ranging from a few metres to more than 6 kilometres from the RSCS (14) buildings within the District. This invention extends coverage area of the Pneumatic Solid Waste Collection Systems (PSWCS) by more than 400%. The reticulated collecting conduit systems (22) operate at air speed between 18-25 ms^"1 (corrected to standard atmospheric pressure of 1013 mbar) with diameter ranging from 400mm to 500mm between the IHA (16) and the RSCS (14). The embodiment of the invention also allows for a reduction in the air speed to 6-17 ms^'1 (corrected to standard atmospheric pressure of 1013 mbar) in the reticulated vacuum conduit system (12) with diameter ranging from 550mm to 1000mm between the RSCS (14) and the air suction apparatus (10) which is free of the solid waste. By using larger diameters for reticulated vacuum conduits it allows for the air to be conveyed over longer distances whilst consuming equal or less energy when compared to shorter vacuum conduits with higher air speeds. The diameter of the reticulated vacuum conduit system is generally larger than diameter of the reticulated collecting conduit systems. A benefit of the invention as a result of allowing longer distances between the air suction apparatus (10) and the RSCS (14) is the coverage of the system within a District which covers more buildings, a larger population and therefore more solid waste to move from IHA (16) to RSCS (14). As a consequence it increases the operating time of the air suction apparatus whilst reducing the energy consumed per ton of solid waste collected compared with present systems.

The invention method with at least two RSCS (14) connected to the air suction apparatus (10) means shorter collecting conduits per system translating into lesser solid waste loads and therefore lesser abrasion in the conduits. This gives rise to the usage of cheaper and longer lasting plastic pipes and non- metallic materials that are not only abrasion resistant but which also resist corrosion.

In addition, the present invention reduces space requirements within the RSCS with the absence of air suction apparatus, filtration and deodorising systems and associated equipment and plant room requirements like acoustic treatment which is now located in the air suction apparatus (10). In any case the solid waste will be handled more efficiently and healthily. The reduced space requirement also allows for the RSCS to be located away from truck inaccessible building areas and yet have the ability to serve the solid waste collection needs of a large community. The accessibility of the RSCS to the trucks that haul the solid waste-filled containers is an important criterion for locating the RSCS.

In addition, the present invention allows for the pneumatic conveying of waste from IHA to under or above ground container(s) by the reticulated collecting conduit systems (22) and where such containers may be emptied by mobile vehicles for disposal purposes.

The invention also supports a recycling system where the solid waste of a particular type in particular IHA (16) are transported to a particular container(s), the movement of the waste to the respective container being controlled by a system of diverter valves known to those familiar in the art.

The reticulated vacuum conduit system (12) is not limited to solid waste conveying system but can be obviously used in the following areas with minor variations: i) vacuum services in buildings for cleaning purposes. ii) pneumatic conveying of light density materials in loose or sealed bag at lower air transport speeds.

For the vacuum services, the reticulated vacuum conduit system (12) is coupled to a reticulated vacuum cleaning conduit system in a building that terminates in strategically located vacuum inlet valves on walls, floors or ceilings to which a flexible hose may be coupled for cleaning purposes. Waste materials like dust, dirt, paper, paper clips and other such material can be vacuumed to a filter separator in the basement of the building which is emptied periodically.

The reticulated vacuum conduit system (12) can be used for pneumatic conveying of light density materials from any point anywhere along the vacuum conduits to a collection station before the air suction apparatus (10).

Claims

1. A method of conveying solid waste from a plurality of holding areas (16) into a collection station (14) utilising air valves, holding areas (16), reticulated collecting conduit system, solid waste collection station (14) that includes components of solid waste separators, compactors, containers, air suction apparatus, valves, a vacuum conduit, control system and electrical power supply panel comprising steps of pneumatic conveying of the solid waste to the collection station (14) by a collecting conduit system by air transport , characterized in that the method includes:

i) periodically generating sub-atmospheric pressure conditions by an air suction apparatus (10) to at least two control valves (24) connected to at least two collection stations (14) through a reticulated vacuum conduit system (12);

ii) generating a flow of air from at least one air valve (18) for pneumatically conveying the solid waste from the at least one holding area (16) to at least one collection station (14) by opening at least one control valve (24);

wherein the air suction apparatus (10) is spaced apart from at least two collection stations (14) and it is connected by a reticulated vacuum conduit system (12) and wherein the two collection stations are distanced apart by at least two hundred metres; and

wherein the sub-atmospheric pressure conditions is generated by the air suction apparatus (10) to the at least two control valves (24) to at least two collection stations (14); and

wherein the flow of air from the at least one air valve (18) connected to the at least one holding area (16) is generated by the sub-atmospheric pressure conditions in at least one collection station (14) through at least one reticulated collecting conduit system (22); and

wherein the diameter of the reticulated vacuum conduit system (12) is generally larger than the diameter of the reticulated collecting conduit systems (22).

2. A pneumatic conveying system for solid waste disposal comprising air valves, holding areas (16), reticulated collecting conduit system, solid waste collection stations (14) that includes components of solid waste separators, compactors, containers, air suction apparatus, valves, vacuum conduit, control system and electrical power supply panel characterized in that the pneumatic conveying system comprises:

i) at least two reticulated collecting conduit systems (22) connecting at least two holding areas (16) to at least two collection stations (14) wherein the at least two collection stations (14) exclude air suction apparatus and are distanced apart by at least two hundred metres;

ii) an air suction apparatus (10) spaced apart from the collection stations (14) and which comprises of vacuum equipments and control systems;

iii) a reticulated vacuum conduit system (12) connecting the air suction apparatus to the at least two collection stations (14).

3. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein diameter of the reticulated vacuum conduit system (12) is generally larger than diameter of the reticulated collecting conduit systems (22).

4. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the air suction apparatus (10) is stationed remotely from at least two collection stations (14).

5. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the air suction apparatus (10) serves a plurality of collection stations (14) and wherein the collection stations (14) are spaced apart and wherein each collection station (14) serves one or a plurality of holding areas (16).

6. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the reticulated collecting conduit systems (22) operates at air speeds between 18-25 ms^"1 corrected to standard atmospheric pressure of 1013 mbar.

7. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the reticulated vacuum conduit system (12) operates at air speeds between 6- 17 ms^"1 corrected to standard atmospheric pressure of 1013 mbar.

8. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the reticulated vacuum conduit system (12) is adapted for use in vacuum services for buildings.

9. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein diameter of the reticulated collecting conduit systems (22) is between

400mm to 500mm.

10. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein diameter of the reticulated vacuum conduit system (12) is between 550mm to 1000mm.

11. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the reticulated vacuum conduit system (12) is adapted to pneumatic transfer of light density materials from any point anywhere along the reticulated vacuum conduit system (12) to a collection station (14) before the air suction apparatus (10).

12. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the material for the reticulated collecting conduit systems (22) and the reticulated vacuum conduit system (12) are of non-metallic 'material'.

13. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein an interfacing control and protection filter chamber (20) and control valves (24) is placed along the reticulated vacuum conduit system (12) between the air suction apparatus (10) and each collection station (14).

14. A pneumatic conveying system for solid waste disposal as claimed in claim 13 wherein the filtering chamber (20) is used to ensure air moving from the collection stations (14) to the air suction apparatus (10) is free of all solid waste except fine particles.

15. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the furthest holding area (16) is at least 3.5 km distanced apart from the air suction apparatus (10).

16. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein the collection station (14) may be above or under ground and a mobile vehicle is used to convey collected waste into a container attached to the vehicle.

17. A pneumatic conveying system for solid waste disposal as claimed in claim 2 wherein a provision for recyclable material held in designated holding areas (16) is pneumatically conveyed using reticulated collecting conduit systems (22) and by a system of diverter valves conveyed to one or more designated containers.