WO1992018261A1

WO1992018261A1 - Combustible gas production/collection method and tip

Info

Publication number: WO1992018261A1
Application number: PCT/GB1992/000694
Authority: WO
Inventors: Robert Henry Bowman
Original assignee: Robert Henry Bowman
Priority date: 1991-04-19
Filing date: 1992-04-15
Publication date: 1992-10-29
Also published as: AU1548492A; GB9108450D0

Abstract

A combustible gas production/collection method comprises constructing a tip (1) from non-toxic waste (W) at least some of which is compressed into baled cuboids (3) on a surface site on a naturally and/or synthetic base (2) impervious to gases and liquids, as a stable mound of desired height; providing a liquid and gas impermeable coating or covering to the flank(s) of the tip; discharging/distributing a liquid or gaseous flowable material (such as water, sewage, slurry, shale, clay, concrete, air, or other gases) within the tip (1); collecting any liquid leachate seeping from the tip (1) and to conveying same away; collecting combustible gas(es) generated within the tip (1); conveying the collected gas(es) either to storage means (25) for subsequent use or to combustion means (21) for immmediate use to drive an electrical generator (22); and monitoring conditions within the tip (1) to determine any required rate of infeed of flowable materials and hence to have a degree of control over the rate of gas production. The invention also includes a waste disposal tip operating in accordance with the above defined method.

Description

COMBUSTIBLE GAS PRODUCTION/COLLECTION METHOD AND TIP

This invention relates to a combustible gas production/collection method and to a tip, thereby serving additionally for the disposal of waste, such as household rubbish, sewage, and other non-toxic waste.

Conventionally, household rubbish is disposed of at land fill sites by the dumping and filling of worked out quarries, ravines etc, with the rubbish compacted as filling progresses. Whilst this system enables a local authority to dispose of rubbish, the technique produces two largely uncontrollable problems, the first being production of combustible gases, particularly methane, within the rubbish and its emission from random and unknown locations at the surface of the tip, usually through a top soil covering, the second being the build up of water (through rain, streams, springs, etc) at the base of the tip and the eventual leakage of a resulting liquid leachate from the base of the tip and its possible hazardous entry into the water table, if not its pollution of nearby streams or rivers. Attempts have been made to collect the methane etc emitted by a tip, with a view to benefiting from this free source of energy by burning the collected methane for heating and/or electricity generation, but not with any notable success due to the two basic problems referred to above. Futhermore, most suitable sites near large centres of urban population have long since been filled, with the result that many local authorities must now cart rubbish tens of miles to a landfill site, with attendant costs.

According to a first aspect of the present invention, there is provided a combustible gas production/collection method comprising:-

(i) constructing a tip from non-toxic waste at least some of which is baled on a surface site on a naturally and/or synthetic base impervious to gases and liquids, to a mound of desired height; e.g. to a tip generally pyramid or inverted cone shape,

(ii) providing a liquid and gas impermeable coating or covering to the flank(s) of the tip;

(iii) discharging/distributing a liquid or gaseous flowable material (such as water, sewage, slurry, shale, clay, concrete, air, or other gases) within the tip;

(iv) collecting any liquid leachate seeping from the tip and to conveying same away;

(v) collecting combustible gas(es) generated within the tip;

(vi) conveying the collected gas(es) either to storage means for subsequent use or to combustion means for immediate use to drive an electrical generator; and

(vii) monitoring conditions within the tip to determine any required rate of infeed of flowable materials and hence to have a degree of control over the rate of gas production.

According to a second aspect of the invention there is provided a combustible gas production/collection waste disposal tip wherein :

(i) the tip is constructed from non-toxic waste, as a mound of desired height, preferably to the shape of a pyramid or an inverted cone, on a natural and/or synthetic base impermeable to water and gas;

(ii) providing a discharge/distribution piping within the tip for a liquid or gaseous flowable material (such as water, sewage, slurry, shale, clay, concrete, air, or other gases) which piping has at least one discharge orifice and at least one inlet for the introduction into the piping of the flowable material;

(iii) providing fluid collection piping at the base of or beneath, the tip and extending at least around the perimeter of the tip for the collection of any liquid leachate seeping from the tip and to convey same away;

(iv) providing a liquid and gas impermeable coating or covering on to the flank(s) of the tip;

(v) providing combustible gas(s) collection means; (vi) providing means to convey the collected gas(s) to storage means or to a combustion means to drive an electrical generator; and

(vii) providing means to monitor conditions within the tip.

The invention thus provides for the controlled production of combustible gas(es) within a tip and collection of these gases, and thereby provides a free source of energy, whilst simultaneously providing for the ready disposal or dumping of not only non-toxic waste such as domestic rubbish but also sewage at any suitable site proximate to the centres of population, in contrast to an inconveniently located quarry or ravine, with combustible gas(es) produced under controlled conditions by decomposition of sewage etc with controlled quantities of sewage etc being pumped into the tip, as and when required to replace spent sewage and/or to fill voids resulting from gas production. Further operational controls are possible by the ability to pump air and water into the tip to control oxygen input and temperature. Furthermore the gas(es) generated within the tip are also collected in a controlled manner, while any seepage is collected and is conveyed away either for disposal elsewhere or for recirculated into the tip. Thus, the impervious coating prevents rain water penetration into the tip and hence prevents build-up of an unknown quantity of liquid leachate at the base of the tip, and seepage of the same. It follows that any liquid leachate seepage from the proposal of the invention results from injection of excess sewage and/or sewage with an excess water content. Seepage could also result if water injection were deemed appropriate to reduce the temperature within the tip.

The baling of the non-toxic waste most advantageously provides for control and a consistency of the compaction and the density of the tip, and such bales may be used to construct either an inner core of the tip or an outer perimeter of the tip, preferable all the waste is baled.

Preferably, some if not all of the bales are encased in plastic sheeting - as a shrink-wrapped effect. As this wrapping will prevent methane etc., escape the constructed tip requires drilling, so as to puncture the sheeting and for installation of the discharge/distribution piping, to provide a prescribed exit route for gasses, from a bale. If only some of the bales are shrink wrapped, these are used to construct the base levels of the tip and an outer perimeter wall, with non-wrapped bales used to contruct an inner filling.

As the bales are permeable to a greater or lesser extent, they are conveniently impregnated with treated sewage. If the permeability is questionable or the impregnation process inefficient, then a blind a aperture or pocket may be punched into a bale, or the bales may be baled with such pocket (s), to be filled with sewage.

The tip may also be provided with a fluid reservoir, and furthermore pumping means may be provided connected between the fluid reservoir and the discharge/distribution piping.

It is clearly advantageous for the mound to be self- stable, hence the preferred construction to established, self- stable profiles e.g. a pyramid or cone, which completely avoids the need for retaining walls or other structures to preclude slippage or movement.

Degredation of waste and/or sewage in the course of gas production inevitably produces voids within the tip, and the total volume of these voids can be estimated or calculated from gas emission volumes. The voids induce a propensity for shrinkage, with possible stressing and resultant splitting particularly of the liquid and gas impermeable flank coatings or coverings of the tip, and consequently the voids are preferably filled from time to time, not only by the discharging of replenishment sewage into the tip, which would be infrequently required, but the injection of stability enhancing materials such as concrete or coal tip shale, fly ash etc that may in themselves present a disposal problem and hence that are readily and cheaply available.

Furthermore, methane concentrations within the tip inhibit further methane production, and accordingly, in accordance with another preferred feature, vibrations are induced within the tip e.g. by the insertion (or implantation during tip construction) of vibrators - such as the pokers currently in use in the construction industry - to encourage methane escape to the piping network, into which the methane may be allowed to rise by convection resulting from the heat within the tip, or if required the methane may be positively drawn off by pumping.

It is also preferred for the height of the tip to be built up from several layers or courses, extending generally horizontally, of bales, in which case, a liquid and gas impermeable membrane e.g. one layer or multiple layers, of plastic sheeting, is interposed between each course.

In addition to the exclusive use of baled waste, the tip could also include, or have a core, constructed from, another article presenting a substantial disposal problem viz: the used vehicle tyre. If the tip is constructed with such a core, the latter again being constructed generally to the shape of a pyramid or inverted cone, the flank(s) of the core is/are covered with baled rubbish contained in synthetic plastic bags - possibly several layers of such bags - so that upon the inevitable compaction of the tip, the bags provide an additional seal and barrier to the uncontrolled escape of combustible gas(es) generated within the tip. Further the bales could be constructed from a combination of non-toxic waste and vehicle tyres, possibly sprayed with sewage etc. during the baling process.

In detail, the natural or impervious base may be clay e.g. of 5m thickness. This may be augmented, if considered necessary, by several layers of synthetic plastics sheeting, while the impervious coating or covering of the flank(s) may also be clay e.g. of <2m thickness, again augmented if considered necessary by synthetic plastics sheeting. The impervious coating may be applied directly to unbagged, baled rubbish or to bagged baled rubbish, as reliance for gas sealing can be placed solely on the plastic bags.

The discharge/distribution piping may consist of a network of apertured piping of "Christmas tree" configuration, and/or a plurality of individual apertured pipes introduced radially, or generally so, into the tip.

Preferably, the discharge/distribution piping is provided with valve means, whereby discharge of sewage, air etc. may be zonally controlled. Thus, a greater quantity of sewage, air etc. may be discharged at a "cold" zone indicating little or no chemical reaction and hence methane generation - then a "hot zone", and monitoring of conditions, particularly temperatures at different zones within the tip may simply be achieved by inserting a suitable probe. Alternatively or in addition, permanently located sensors may be inlaid into the tip during its construction or be provided at the inner end of radially introduced discharge/distribution piping.

Some or all of the piping may be telescopic to accommodate settling of the tip, and preferably the piping is of a heat resistant and chemically inert plastics.

With the tip built as a mound to pyramid or inverted cone shape, it follows that the impervious coating or mantle applied to the flank(s) of the tip will, together with the elevated temperature within the tip, channel the combustible gas(es) upwardly towards the apex of the tip, and hence it is at the apex that the gas collection means is located. For a cubic tip several gas collection points would be required at different zones.

The collected gas is conveniently conveyed by piping from the collection means to either a storage tank or an internal combustion engine.

Furthermore, in accordance with another feature of the invention, a further pipe network may permeate the tip with water inlet and outlet ends, whereby "cold" water may be pumped into this network and "hot" water extracted, thereby not only obtaining hot water at but the cost of pumping but also controlling to some extent the internal temperature of the tip by the rate of pumping. Again valving of the hot water network provides a greater degree of control. Water supply may be from a man-made lake in the vicinity of the tip, possibly filled at least in part, with industry waste water e.g., from breweries, steelworks etc.

Conveniently, the combustion means comprises at least one the internal combustion engine, and to smooth fluctuations of supply of methane, the combustion means may be connected to a natural gas mains supply, for augmented fuel requirements.

It will be understood, that a tip as described above whilst highly efficient for the controlled disposal of both domestic rubbish and sewage may be objectionable on aesthetic grounds. Hence, in accordance with a further feature, the tip e.g., containing 1 million cubic metres of waste, is landscaped firstly by a covering, on the impervious cover, of inert material such as builders/demolition rubble, and secondly by top soil, so that the upper surface may be grassed and/or planted with shrubs and trees.

The combustible gas producing/collection method and tip in accordance with the two aspects of the invention are shown by way of example only in the accompanying diagrammatic drawings, in which

Figure 1 is a perspective view, partially cut away, of a completed tip;

Figure 2 is a perspective view similar to Figure 1, at the start of tip construction;

Figure 3 is a diagrammatic plan view of the tip of Figure 1;

Figure 4 is a side elevation of Figure 3;

Figures 5 and 6 correspond to Figure 4, but show further details, and

Figure 7 indicates a baled cuboid.

In the drawings, a combustible gas production/collection and waste disposal tip 1 is constructed from non-toxic waste, such as domestic rubbish, built as a mound e.g. generally to the shape of a pyramid, on a surface site on a natural base 2 e.g. a layer of clay of adequate thickness impermeable to water and gas or a synthetic base 2 e.g. multiple layers of synthetic plastics sheeting similarly impermeable to water and gas. So as to have control over firstly the density of the tip and secondly gas escape routes, the waste W (Figure 7) is firstly baled, with a prescribed compression e.g. to shape of a cube brick or block, from which the mound can be readily constructed with overlap joints of brickwork. Baling to a cuboid 3 is best illustrated in Figure 6, the cuboid 3 then being wrapped in plastics sheeting 4 with appropriate heat-sealed or otherwise secured sheeting joints to ensure that the cuboid 3 is gas tight and watertight. Thus, with baling effected at a refuse collection point or site, bales or cuboids 3 are there constructed which are odour free, coherent, and' are readily handleable and transportable to the site of the intended tip 1.

The tip 1 is constructed as follows. Firstly. as shown in Figure 2, a rectangular excavation 5 is made to a depth of e.g. 1-2 m, within which is laid a network of apertured pipework 6 to collect any leachate seeping from the base of the tip 1 and convey collected leachate to storage tank 7. Clearly, this piping would be ineffective if crushed by the weight of the tip, and whilst plastics piping, in contrast to steel piping, is corrosion proof, its crush resistance is negligible. Hence concrete slabs 8 are preferably provided to define channels in which the piping 6 is laid. A sewage storage tank 9 is connected to the piping 6, with an associated pump 10. Suitable valves and controls are not indicated, but the intention is to pump sewage from the tank 9 into the interior of the tip 1, and to re-circulate any collected leachate from storage tanks 7 into the interior of the tip 1.

A base membrane e.g. consisting of several layers of plastics sheeting 10, is then laid over the piping 6, upon which a bottom layer 11 of baled cuboids 3, typically numbering 20 by 20 square so as to include 400 cuboids, the cuboids 3 being butted together at joints 12. A first intermediate membrane 13 is then laid over the bottom layer 11 for the next layer of baled cuboids numbering say, 19 by 19 square, with the cuboids of this layer overlapping the joints 12 of the bottom layer 11. This process is repeated until eventually, a rectangular perimeter wall 14 at least two cuboids thick is constructed from wrapped cuboids 3 to leave a rectangular core 15 which is filled with unwrapped cuboids 16 of baled, domestic rubbish impregnated before, during or after tip construction with sewage. During tip construction a network 17 of perforated plastics piping is constructed serving for both gas collection at an apex 18 and sewage introduction from the tank 9 and leachate introduction from the tanks 7. The flanks of the pyramid are sealed by multiple layers of wrapped cuboids 3 to provide a liquid and gas impermeable coating. In addition, layers of plastics sheeting or a clay mantle can be applied for enhanced sealing. Thereafter, builders rubbish and finally topsoil 19 can be applied to give the tip 1 the appearance of a natural mound or hillock.

Methane collected at the apex 18 is conveyed by a pipe 20 to an internal combustion engine 21 adapted to drive a generator 22, with electrical output e.g. to a grid. A series of probes 23 dispersed throughout the tip and installed during tip construction serve to monitor temperatures at respective zones of the tip, with output via thermally protected leads 24. Gas supply may be to a storage tank 25 for subsequent transport away from the site, or to serve as a reservoir for the engine 22 should diminished methane volumes be generated. Also, to aid release and movement of methane, a series of vibrators 26 are strategically located throughout the tip, in a predetermined pattern. The vibrators 25 may be in-built during tip construction or, as with the probes 23, they may be fitted after tip construction by drilling suitable vibrator or probe receiving bore(s). Such retro-fitting may in any event be necessary if it is subsequently found that vibration and/or temperature data is required for a particular zone of the tip where no vibrator or probe was initially installed, or possibly where an initially installed vibrator or probe has failed in service and cannot be readily extracted.

Finally, one or several sinuous water heating ceils 2^" (Figure 3) may be in-built into the tip 1 with a "cold" water inlet end 28 and a "hot" water outlet end 29. The end 28 may incorporate a pump if water circulating pressure is not available from another source, such as an elevated tank or even a tarn, lake or reservoir usable for leisure activities.

Claims

1. A combustible gas production/collection method comprising:-

(i) constructing a tip from non-toxic waste at least some of which is compressed into bales on a surface site on a naturally and/or synthetic base impervious to gases and liquids, as a stable mound of desired height, preferably to the shape of a pyramid or an inverted cone;

(iii) discharging/distributing a liquid or gaseous flowable material (such as water, sewage, slurry, shale, clay, concrete, air, or other gases ) within the tip;

(v) collecting combustible gas(es) generated within the tip;

2. A method as claimed in claim 1, wherein the tip is constructed at least in part from bales compresses to cubic. or similar shape, with an outer wrapping of synthetic plastics sheeting.

3. A method as claimed in claim 2, wherein the wrapped bales are used to construct an outer, sealing perimeter wall and a base.

4. A method as claimed in claim 3, where an inner cove, within the outer perimeter, is constructed from unwrapped bales.

5. A method as claimed in claim 3, where an inner cove, within the outer perimeter, is constructed from used vehicle tyres.

6. A method as claimed in claim 3, wherein an innercove, within the outer perimeter, is constructed from both unwrapped bales and used vehicle tyres.

7. A method as claimed in claims 2 to 6, wherein the tip is constructed from a plurality of layers. or courses of bales, with at least one layer of interposed plastics membrane extending through the tip, between two adjacent layers.

8. A method as claimed in claims 2 to 7 wherein the constructed tip is drilled out along a plurality of axes were piping is required to be installed, to penetrate the bale wrappings and interposed membrane.

9. A method' as claimed in any preceding claim substantially as hereinbefore described with reference to the accompanying drawing.

10. A combustible gas production/collection waste disposal tip wherein :

(i) the tip is constructed from non-toxic waste, built as a mound e.g. generally to the shape of a pyramid or an inverted cone, on a natural and/or synthetic base impermeable to water and gas; (ii) providing a discharge/distribution piping within the tip for a liquid or gaseous flowable material (such as water, sewage, slurry, shale, clay, concrete, air, or other gases) which piping has at least one discharge orifice and at least one inlet for the introduction into the piping of the flowable material;

(vii) providing means to monitor conditions within the tip.

11. A tip as claimed in claim 10, wherein some if net all of the bales are encased in plastic sheeting - as a shrink-wrapped effect.

12. A tip as claimed in claim 11, wherein shrink-wrapped bales are used to construct the base levels of the tip and an outer perimeter wall, with non-wrapped bales used to construct an inner filling.

13. A tip as claimed in any one of claims 10 to 12, wherein at least some of the bales are impregnated with treated sewage.

14. A tip as claimed in any one of claims 10 to 13, wherein at least some of the bales are provided with a blind aperture or socket to be filled with sewage.

15. A tip as claimed in any one of claims 10 to 14 provided with a fluid reservoir.

16. A tip as claimed in claim 15, comprising pumping means connected between the fluid reservoir and the discharge/distribution piping.

17. A tip as claimed in any one of claims 10 to 16, vibrators are inserted or implanted into the tip.

18. A tip as claimed in any one of claims 10 to 17, wherein the height of the tip is built up from several layers or courses, extending generally horizontally, of bales, with a liquid and gas impermeable membrane eg one layer or multiple layers, of plastic sheeting, interposed between each course.

19. A tip as claimed in any one of claims 10 to I8 including, preferrably as a core, used vehicle tyres.

20. A tip as claimed in claim 19, wherein the flank(s) of the core is/are covered with baled rubbish contained in synthetic plastic bags - possibly several layers of such bags - so that upon the inevitable compaction of the tip, the bags provide an additional seal and barrier to the uncontrolled escape of combustible gas(es) generated within the tip.

21. A tip as claimed in any one of claims 10 to 20, wherein the bales are constructed from a combination of non-toxic waste and vehicle tyres, possibly sprayed with sewage etc. during the baling process.

22. A tip as claimed in any one of claims 10 to 21, wherein the natural or impervious base is clay augmented, if considered necessary, be several layers of synthetic plastics sheeting.

23. A tip as claimed in any one of claims 10 to 21 , wherein the impervious coating or covering of the flank's, is also clay, again augmented if considered necessary by synthetic plastics sheeting.

24. A tip as claimed in any one of claims 10 to 22, wherein the discharge/distribution piping consists of a piping network of Christmas tree configuration, and/or a plurality of individual pipes introduced radially, or generally so, into the tip.

25. A tip as claimed in claim 24, wherein the discharge/distribution piping is provided with valve means, whereby discharge of sewage, air etc. may be zonally controlled.

26. A tip as claimed in any one of claims 10 to 25, wherein permanently located sensors to monitor conditions within the tip such as temperature are inlaid into the tip during its construction or be provided at the inner end of radially introduced discharge/distribution piping.

27. A tip as claimed in any one of claims 10 to 26, wherein some or ail of the piping is telescopic to accommodate settling of the tip.

28. A tip as claimed in any one of claims 10 to 27 , wherein the piping is of a heat resistant and chemically inert plastics.

29. A tip as claimed in any one of claims 10 to 23, built as a mound to pyramid or inverted cone shape, with the gas collection means located at the apex.

30. A tip as claimed in any one of claims 10 to 29, wherein a further pipe network permeates the tip with water inlet and outlet ends, whereby "cold" water may be pumped into this network and "hot" water extracted.

31. A tip as claimed in claim 30, wherein the further piping is provided with control valving.

32. A tip as claimed in any one of claims 10 to 31, wherein the combustion means comprises at least one the internal combustion engine.

33. A tip as claimed in claim 32, wherein to smooth fluctuations of supply of methane, the combustion means is connected to a natural gas mains supply, for augmented fuel requirements.

34. A tip as claimed in any one of claims 10 to 33, landscaped firstly by a covering, on the impervious cover, of inert material such as builders/demolition rubble, and secondly by topsoil, so that the upper surface may be grassed and/or planted with shrubs and trees.

35. A tip substantially as hereinbefore described with reference to the accompanying drawing.