Field of the Invention

[0001 ] The present invention relates to a method and apparatus for the

introduction of fluids. More particularly the method and apparatus of the present invention are intended for use in the introduction of fluids into a material in which a microbiological process is operating.

[0002] The method and apparatus of the present invention are considered to find particular application in the pulsed introduction of fluids into an organic material, such as organic waste, animal manure, and/or biomass that is undergoing an aerobic composting process and/or an anaerobic decomposition process.

Background Art

[0003] It is known that solid organic waste material may be treated under either anaerobic or aerobic conditions to produce a bioactive, stable end product that, for example, may be used as compost for gardens. This process is achieved through the action of, respectively, anaerobic or aerobic microorganisms that are able to metabolise the waste material to produce the bioactive, stable end product.

[0004] It is also known that the aerobic decomposition of solid organic waste material takes place in the presence of oxygen. The temperature of the waste material rises as some of the energy produced during aerobic decomposition is released as heat, often reaching temperatures of 75°C under ambient conditions. The solid end product is often rich in nitrates which are a readily bio-available source of nitrogen for plants, making the end product particularly suitable as a fertiliser. [0005] It is further known that the anaerobic digestion of solid organic waste material takes place in the absence of oxygen. Anaerobic microbial metabolism is understood to be optimised when the solid organic waste is heated to temperatures at which mesophilic or thermophilic bacteria are operative. The process of anaerobic microbial metabolism results in the production of biogas, in turn predominantly methane and carbon dioxide. The solid product of the process is often rich in ammonium salts. Such ammonium salts are not readily bio- available and are, consequently, generally treated under conditions in which aerobic decomposition will occur. In this manner the material is used to produce a product that is bio-available.

[0006] Typically, systems for the biodegradation of organic waste material are directed to either aerobic or anaerobic processes. However, there are a small number of systems that have sought to combine both anaerobic and aerobic biodegradation processes. The processes of German Patent 4440750 and International Patent Application PCT/DE1994/000440 (WO 1994/024071 ) each describe the combination of an anaerobic fermentation unit and an aerobic composting unit. Importantly, these systems describe discrete and separate vessels for the aerobic and anaerobic biodegradation processes.

[0007] International Patent Application PCT/AUOO/00865 (WO 01/05729) describes an improved process and apparatus in which many of the inefficiencies of the previous processes and apparatus are overcome. The improved process and apparatus are characterised at a fundamental level by the sequential treatment of organic waste material in a single vessel, through an initial aerobic step to raise the temperature of the organic waste material, an anaerobic digestion step and a subsequent aerobic treatment step. During the anaerobic digestion step a process water or inoculum containing micro organisms is introduced to the vessel to create conditions suitable for efficient anaerobic digestion of the contents and the production of biogas. The introduced inoculum also aids in heat and mass transfer as well as providing buffer capacity to protect against acidification. Subsequently, air is introduced to the residues in the vessel to create conditions for aerobic degradation. It is further described that the water introduced during anaerobic digestion may be sourced from an interconnected vessel that has undergone anaerobic digestion.

[0008] In known prior art processes one of the significant challenges has proven to be the even distribution of fluids, including liquids, being introduced to the mass of material being composted. The earlier prior art processes described hereinabove have often used mechanical agitation. Mechanical agitation brings with it various disadvantages, including loss of heat and moisture from the material. Further, mechanical agitation may result in the liberation of large volumes of volatile nitrogen early in the composting process. This will inevitably result in a reduction in the nitrogen content of the solid material produced by way of the process and may result in the release of odours from that material.

[0009] Known methods for the introduction of air to organic materials in aerobic composting processes include forced aeration, in which large volumes of air are blown or sucked into a vessel at low pressure. This requires the organic material to be sufficiently and consistently porous for the introduced air to reach the entire volume of organic material. However, more often than not the introduced air will follow the path(s) of least resistance through the material, with areas of the material blinded to the air flow, being the areas of higher bulk density and low porosity. Further drawbacks of such a method include uneven temperature distribution as the areas of good air flow or porosity will tend to cool more rapidly than others when air flow is excessive, as occurs from time to time. At lower air flow rates the temperature of these areas will be hotter than more consolidated areas in the material. Still further, large volumes of circulating air remove moisture from the composting material. Additionally, there are significant odour control requirements as a result of large volumes of introduced air. The blockage of one or more of the air introduction points to the vessel will result in little or no air flow to that portion of the material being treated adjacent that point. [0010] Passive aeration is also used in some prior art aerobic processes. Such processes require the stacking of the organic material to be treated in a manner whereby the temperature difference between the organic material and the ambient temperature results in the establishment of a convection current. This current draws in fresh cool air to the stacked material. Again, this process is limited by the blinding of areas of the heap that are not sufficiently porous to facilitate air flow therethrough. Consequently, materials of a high bulk ^' density are not suitable for such passive aeration.

[001 1 ] International Patent Application PCT/AU01 /01372 (WO 02/34694) describes a method and apparatus for aeration of an organic waste material mass. This method requires the introduction of air to a vessel that contains the organic waste material at a pressure of above atmospheric pressure, initially creating a pressure differential within the vessel which is allowed to subsequently equilibrate over a period of time. In this time air is proposed to flow from areas of high pressure to areas of low pressure, thereby ensuring even distribution of air throughout the organic material. However, areas of particularly high bulk density are still resistant to the equilibration intended in this prior art process.

[0012] Liquids being introduced to an organic waste material, such as proposed in International Patent Application PCT/AUOO/00865 (WO 01/05729) described above, are similarly subject to preferential flow paths which results in portions of the waste material being blinded to the liquids, which in turn results in inhibited degradation and reduced biogas production, This inhibition may be the result of increased acidity in blinded portions of the waste material which can inhibit the activity of microorganisms that would otherwise be contributing to the decomposition of the waste material.

[0013] In International Patent Application PCT/US93/07946 there is described a method for the in situ remediation of subsurface soil or groundwater contaminated by chlorinated hydrocarbons. In the method described an oxygenated fluid is continuously injected through a well and drawn through a contaminated plume. A nutrient fluid selected to stimulate the growth of indigenous subsurface microorganisms, for example methane, is injected and drawn through the plume periodically, with a treatment cycle of a few days to longer than a week. A treatment cycle is described as consisting of the injection of methane/air for a time followed by injection of only air. The intent behind the cycle is described as creating 'feast' conditions for methanotrophs present, alternating with 'starve' conditions. This is said to force the methanotrophs to consume the contaminants present in the plume. The long cycle time employed in this prior art method is not suitable to the avoidance of preferential flow paths, which may be expected to be a particular concern and limitation with the treatment of high bulk density materials.

[0014] In US Patent 7604744 there is described a method for maintaining a biomass disposed on a substrate in a bioreactor tank, in the context of the treatment of a liquid waste stream. The method described utilises a ^' plurality of bioreactors each having a bioreactor tank, each tank having a fluid inlet and a fluid outlet. The tanks have an amount of one or more inert substrate materials such as lava stone or ceramic beads provided therein, at least some of which are selected for their ability to provide a medium for microorganism attachment and growth. A waste influent is received through an inlet whilst an effluent fluid is dispensed through a fluid outlet. At least one of the bioreactors is arranged so as to be able to be isolated from the remaining reactors so as to provide a 'dry cycle' which encourages endogenous growth within that reactor. A dry cycle is described as typically being in the order of 6 to 7 hrs duration. The aim of the 'dry cycle' is to ensure as much as possible that microorganism growth remains in the 'log stage'.

[0015] An increase in turbulence in the waste material flow through the substrate layers in the bioreactors is described as providing a benefit in improved aeration and oxygen distribution. This is described as being achieved through the arrangement of differing sizes of media comprising the substrate layers causing variation in flow between the media. Reference is also made to air frothing and water pulsing being possible within the bioreactors. Both air frothing and water pulsing are described as being conducted at 'periodic intervals' and are both effected 'at or near' the bottom of the bioreactor tank. No detail is provided around the specific nature of the air frothing and water pulsing, nor its duration or volume, for example, other than to suggest it is a 'function of the waste material and the characteristics of the tank'.

[0016] The method and apparatus of the present invention have as one object thereof to overcome substantially, or at least provide a useful alternative to, the abovementioned prior art and any problems associated therewith.

[0017] The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0018] Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0019] Throughout the specification and claims, unless the context requires otherwise, the word "pulse" or variations thereof such as "pulsed" or "pulses", will be understood to imply a flow in which the velocity, volume, or pressure of that flow varies periodically and may specifically include an upward or downward variation in fluid flow or pressure, steam/biogas injection or by way of an applied mechanical force. Further, the terms "pulsed injection" or "pulsed manner" refers specifically to the introduction of fluid as a series of pulses.

[0020] Throughout the specification and claims, unless the context requires otherwise, the word "fluid" or variations thereof, will be understood to imply either a gas or a liquid of any type or composition, or any combination of gas or liquid. Further, it is to be understood to include gases, liquids, or combinations thereof, that may contain solids or liquids, suspended therein or otherwise conveyed thereby.

[0021 ] Throughout the specification and claims, unless the context requires otherwise, the term "body of organic material" or variations thereof, will be understood to imply an organic mass composed of man-made or natural organic material. Such may include food, kitchen, animal, garden, vegetable or other putrescible material suitable for anaerobic and aerobic action, the by-products of which are at least a gas, more specifically a biogas, and a composted, carbon reduced end product, water and inoculum. The biogas may comprise at least hydrocarbons such as methane and ethane, carbon dioxide, hydrogen, nitrogen, oxygen, and sulphurous gases such as hydrogen sulphide in any ratio.

Disclosure of the Invention

[0022] In accordance with the present invention there is provided a method for the introduction of a fluid to a body of material that is undergoing a microbiological process, characterised in that the fluid is introduced as a series of pulses of fluid.

[0023] Preferably, the series of pulses in the introduction of the fluid occurs about every 1 second to 10 minutes.

[0024] Still preferably, each pulse within the series of pulses lasts between about 0.001 to 1 second.

[0025] Still further preferably, the fluid is introduced to the body of material at more than one point.

[0026] The fluid introduction points are preferably arranged in spaced apart relation. [0027] The fluid is preferably introduced to the body of material over a period of four or more days. Preferably, the fluid is introduced to the body of material over a period of between about four to twelve days. /

[0028] In one form of the present invention the spaced apart fluid introduction points are spaced apart in substantially equidistant relation.

[0029] In another form of the present invention the body of material is a mass of organic material that is undergoing biological degradation or composting.

[0030] Preferably, the introduced fluid penetrates the body of material and neutralises or buffers at least a portion of any acid that may have accumulated therein.

[0031 ] In a further form of the present invention the fluid being introduced contains a microbial inoculum.

[0032] In accordance with the present invention there is further provided a method for increasing biogas production from a body of organic material that is undergoing microbiological degradation, the method characterised by the step of introducing a process liquor to that body of organic material as a series of pulses such that preferential flow paths through the body of organic material are substantially avoided and biogas production from the microbiological degradation of the organic material is increased relative to that produced when preferential flow paths predominate.

[0033] Preferably, the series of pulses in the introduction of the process liquor occurs about every 1 second to 10 minutes.

[0034] Still preferably, each pulse within the series of pulses lasts between about 0.001 to 1 second. [0035] Still further preferably, the process liquor is introduced to the body of material at more than one point.

[0036] The process liquor introduction points are preferably arranged in spaced apart relation.

[0037] In one form of the present invention the spaced apart process liquor introduction points are spaced apart in substantially equidistant relation.

[0038] The liquor is preferably introduced to the body of material over a period of seven or more days. Preferably, the liquor is introduced to the body of material of a period of between about seven to twelve days.

[0039] Still preferably, the introduced liquor penetrates the body of material and neutralises or buffers at least a portion of any acid that may have accumulated therein.

[0040] In one form of the present invention, the fluid being introduced contains a microbial inoculum.

[0041 ] In accordance with the present invention there is still further provided an apparatus for the introduction of a fluid to a body of material that is undergoing a microbiological process, the apparatus being characterised in that it comprises a digestion vessel in which the body of material may be located, the vessel having at least one fluid introduction point provided therein, the fluid introduction point being in direct or indirect communication with a means for producing a flow in a series of pulses in the fluid to be introduced.

[0042] Preferably, the series of pulses in the introduction of the fluid occurs about every 1 second to 10 minutes. .

[0043] Still preferably, each pulse within the series of pulses lasts between about 0.001 to 1 second. [0044] Preferably, there are provided multiple fluid introduction points in the vessel.

[0045] Still preferably, the multiple fluid introduction points are arranged in spaced relation about the vessel.

[0046] In one form of the present invention the spaced apart fluid introduction points are spaced apart in substantially equidistant relation.

[0047] Fluids that contribute to the anaerobic digestion and aerobic composting phases of organic material may be introduced in a pulsed manner at multiple points to a body of organic material provided in a digestion vessel. The introduction at multiple points improves the fluid distribution throughout the body of organic material. The introduction points are preferably distributed both vertically and horizontally about the vessel. The introduction points may be provided in a repeating pattern or in a random manner.

[0048] The pulsed introduction of the fluids is understood to improve contact between the microorganisms and the body of organic material, and to improve the availability of food and/or buffer and/or metabolites for the microorganisms, which in turn improves the anaerobic degradation or digestion process through the reduction of preferential flow paths (paths of least resistance) in the body of material. This in turn produces greater volumes of biogas and greater degradation of the organic material than might otherwise have been achieved.

[0049] An inert gas, or a biogas, may be introduced to the body of organic material in the pulsed manner proposed to provide agitation during anaerobic digestion. This agitation improves contact between the microorganisms and the organic material and overcomes the need for internal mechanical agitation.

[0050] During the aerobic phases of digestion, air, enriched air, or an oxygen rich gas may be introduced into the body or organic material in a pulsed manner. This is understood to aid in conditioning and pasteurisation of the body of organic material, and to increase oxygen availability to the microorganisms contained within the organic material which in turn increase the degradation rate.

[0051 ] In accordance with the present invention there is still further provided a method for the introduction of a fluid to a body of material that is undergoing a microbiological process, the microbiological process comprising both aerobic and anaerobic stages of digestion conducted in a single reactor vessel, characterised in that the fluid is introduced as a series of pulses of fluid.

[0052] Preferably, the series of pulses occurs in the introduction of the fluid occurs about every 1 second to 10 minutes.

[0053] Still preferably, each pulse within the series of pulses lasts between about 0.001 to 1 second.

[0054] Preferably, the fluid is introduced to the body of material at more than one point.

[0055] Still preferably, the fluid introduction points are arranged in spaced apart relation.

[0056] In one form of the present invention, the spaced apart fluid introduction points are spaced apart in substantially equidistant relation.

[0057] In a further form of the present invention, the body of material is a mass of organic material that is undergoing biological degradation or composting.

[0058] Preferably, the introduced fluid penetrates the body of material and neutralises or buffers at least a portion of any acid that may have accumulated therein.

[0059] In another form of the present invention, the fluid being introduced dontains a microbial inoculum. Brief Description of the Drawings

[0060] The present invention will now be described, by way of example only, with reference to one embodiment thereof and the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of a body of organic material provided within a digestion vessel of a digestion apparatus in accordance with the prior art, showing a fluid introduction point at which a non-pulsed flow of process water is being introduced;

Figure 2 is a diagrammatic representation of a body of organic material provided within a digestion vessel of an apparatus for the introduction of a fluid to a body of material in accordance with the present invention, showing a single fluid introduction point at which a pulsed flow of process water is being introduced to the vessel and body of material; and

Figure 3 is a side elevational view of a digestion vessel that may form a portion of an apparatus for the introduction of a fluid to a body of material that is undergoing a microbiological process in accordance with the present invention.

Best Mode(s) for Carrying Out the Invention

[0061] In Figure 1 there is shown a prior art arrangement 10 of a reactor vessel 12 in which a body of organic material 14 is provided for the purposes of microbiological degradation or composting. The body of organic material 14 is composed of a plurality of generally solid particles 16 of differing shapes and sizes. The reactor vessel 12 comprises an outer wall 18 in which is provided one or more fluid inlets 20 and through which fluids may be introduced to the body of organic material 14 during the process of composting or the microbiological degradation of the organic material. [0062] The introduction of fluid through the fluid inlet 20 may result in a flow path described by arrow 22, in which a significant proportion of the particles 16 are not exposed to the fluid flow. Areas of acid accumulation 24 between solid particles 16 may result from this short circuiting by the fluid flow 22. Acid accumulation of this nature may result in the inhibition of microbial activity and consequent inhibition of the degradation process and inhibition of the production of biogas.

[0063] In Figure 2 there is shown an apparatus 30 in accordance with the present invention, being for the introduction of a fluid to a body of material that is undergoing a microbiological process. The apparatus 30 is similar in many respects to the arrangement 10 described hereinabove and like numerals denote like parts. The apparatus 30 further comprises an internal perforated or mesh screen 32 that contains or constrains the body of organic material 14. The fluid inlets 20 are further provided with a pulsing means (not shown) whereby the flow of fluid therethrough may be pulsed as it is introduced to the body of organic material 14. The pulsing of this fluid flow is such that the body of organic material is disturbed, particularly in the immediate vicinity of the inlet 20, causing the particles 16 to shift, alter shape or orientation with respect to one another. This action creates new flow paths 34 that branch off from the original flow path 22 that was typical of the prior art. This action exposes additional material to the fluid being introduced to the reactor vessel 12. In this manner the areas of acid accumulation 24 of the prior art may be reduced or avoided as shown at area 36 through which the new flow paths now pass.

[0064] The pulsed fluid flow comprises a series of pulses of about every 1 second to 10 minutes. Each pulse within the series of pulses lasts between about 0.001 to 1 second.

[0065] The fluid is introduced to the body of material over a period of four or more days. For example, the fluid is introduced to the body of material over a period of between about four to twelve days, depending upon what fluid is being injected and what stage of the microbiological process is being undertaken. [0066] The pulsing means is envisaged to be capable of varying a non-pulsed pressure of about 250 kPa either to 0 kPa, or to as high as about 2000 kPa.

[0067] The fluid inlets 20 are arranged about the reactor vessel 12 so as to further facilitate the distribution of fluid when such is introduced to the body of Organic material 14. It is envisaged that the fluid inlets 20 may be provided in spaced apart relation to one another, either in an equidistant or irregular manner.

[0068] In Figure 3 there is shown the external appearance of one embodiment of the reactor vessel 12. The reactor vessel 12 has a height of 20 m, a diameter of 10 m and a volume of about 1 150 m ³ , about 1000 m ³ of which is filled with the body of organic material 14. The body of organic material 14 weighs about 700 tonnes and has a surface area of about 350 m ² .

[0069] The reactor vessel 12 has a generally cylindrical upper portion 40, a tapered intermediate portion 42 and a base 44 at which is provided an outlet 46, the detail of which is not shown. A first band 48 of eight fluid inlets 20 is arranged about intermediate portion 42 of the reactor vessel 12 at a point just above the base 44 and outlet 46. The fluid inlets 20 in the first band 48 are spaced equidistant apart. A second band 50 of eight fluid inlets 20 is arranged about the upper portion 40 of the reactor vessel 12 at a point just above the intermediate portion 42. The fluid inlets 20 of the second band 50 are spaced equidistant apart. A third band 52 of eight fluid inlets 20 is arranged about the upper portion 40 of the reactor vessel 12 at a point spaced apart from the second band 50. Again, the fluid inlets 20 of the third band 52 are spaced equidistant apart. The fluid inlets 20 of the second and third bands, 50 and 52 respectively, are offset or staggered relative to one another, as can be understood most clearly with reference to Figure 3.

[0070] The arrangement of the fluid inlets 20 in bands about the reactor vessel 12 as described hereinabove enables the introduction of fluids to the body of organic material 14 about its entire diameter. Further, the vertical spacing of the bands on the reactor vessel 12 allows fluids to be injected to the body of material 14 at multiple points across its height.

[0071] In one example, the fluid being introduced is an anaerobic digestate liquor, that is a liquor generated through the anaerobic digestion of a body of organic material and removed therefrom, and which will contain a variety of microorganisms that contribute to biological degradation of organic material. The pulsing flow of the liquor creates the new flow paths 34 referred to above and distributes liquor throughout the body of organic material more effectively than the arrangements and methods of the prior art. This improved distribution throughout the body of organic material increases the yield of biogas during the anaerobic digestion phase and positively influences the energy balance achieved. The introduction of digestate liquor occurs over a period of between 7 to 2 days.

[0072] In a further example, the fluid being introduced may be an inert gas or a biogas. This may be undertaken during an anaerobic digestion phase. Still further, air, enriched air or oxygen rich gas may be injected to the body of organic material in a method in accordance with the present invention during the initial aerobic phase and/or the aerobic conditioning phase post-anaerobic digestion, so as to improve the composting process and thereby aiding compost conditioning and pasteurisation. Such introduction of air, enriched air or oxygen rich gas may occur over a period of greater than 4 days, for example about 4 to 7 days.

[0073] It is envisaged that a pulsed fluid flow may be achieved by a variety of means, including the use of a fluid moving apparatus, such as a pump or compressor, of which the output flow or pressure characteristic is of a cyclical nature, as provided by a piston-type pump, or progressive cavity or peristaltic- type. Further, a ram or piston of which the stroke or volume can be altered with time may be utilised. Valves that are rapidly opened or closed may also be utilised, particularly those in which the actuation is external to the fluid, such as is provided by ball valves, gate valves, pinch valves and the like. Alternatively, an in-line self oscillating valve may be provided in the fluid flow, such as a hammer valve or a flapper valve. A wave generator might also be used to set up a pulse flow, such as a sonic or ultrasonic wave generator. Still further, pulsing may also be achieved through the introduction of an external pressure source, such as an explosive release of gas as may be achieved using a carbon dioxide Cardox™ system. It follows that the means for producing a flow in a series of pulses may be provided in one of the abovementioned forms.

[0074] It is envisaged that the introduction of pulsed fluids as described herein may be achieved in combination with a variety of mechanical means, including but not limited to one or more elongate perforated lances such as are described in International Patent Application PCT/AUOO/00865 (WO 01 /05729).

[0075] As can be seen from the above, the method and apparatus of the present invention allow the fluids that contribute to the anaerobic and aerobic composting phases of organic material to be introduced in a pulsed manner, at multiple points, to a body of organic material provided in a digestion or reactor vessel. The introduction at multiple points improves the fluid distribution throughout the body of organic material. The introduction points are preferably distributed both vertically and horizontally about the vessel. The introduction points may be provided in a repeating pattern or in a random manner.

[0076] During anaerobic digestion, the pulsed introduction of the fluids is understood to improve contact between the microorganisms and the body of organic material, which in turn improves the anaerobic degradation or digestion process through the reduction of preferential flow paths (paths of least resistance) in the body of material. This in turn produces greater volumes of biogas and greater degradation of the organic material than might otherwise have been achieved. During aerobic phases of the digestion process, the pulsed introduction of fluids is envisaged to increase the availability of oxygen to aerobic microorganisms. [0077] It is envisaged that an existing reactor vessel may be retrofitted such that the method of the present invention may be practised using same. Such retrofitting would require, at a basic level, the provision of a plurality of fluid inlets and the associated pipe work and pulsing means.

[0078] It is further envisaged that the method of the present invention may find broader application in processes where improved contact between different media is required so as to aid microbiological leaching processes, for example microbiological heap leaching processes.

[0079] Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.