AU2004231120A1

AU2004231120A1 - Determining gas volume, porosity, and intrinsic oxidation rate

Info

Publication number: AU2004231120A1
Application number: AU2004231120A
Authority: AU
Inventors: Sreten Askraba; John William Bennett; Alan Stanley Boyd; Andrew McKay Garvie
Original assignee: Australian Nuclear Science and Technology Organization
Current assignee: Srk Consulting (australasia) Pty Ltd
Priority date: 2003-04-16
Filing date: 2004-04-16
Publication date: 2004-10-28
Anticipated expiration: 2024-04-16
Also published as: AU2004231120B2

Description

WO 2004/092690 PCT/AU2004/000512 DETERMINING GAS VOLUME, POROSITY, AND INTRINSIC OXIDATION RATE Technical Field s This invention relates to a method for measuring the oxidation rate of a sample of porous material. In particular, the invention relates to a method for determining the intrinsic oxidation rate (IOR) of waste rock from a mine by measuring changes as a function of time in oxygen levels in the gas which has been in contact with a sample of the waste. 10 Background Art Pyrite and other sulfidic minerals commonly occur in many of the base metal, precious metal and coal deposits which are mined around the world. Sulfidic materials below cut-off grade are routinely consigned to waste rock dumps and sulfidic wastes from 15 ore processing are piped to tailings storage facilities. In these piles the sulfides may be exposed to air and may undergo oxidation reactions, generating sulfate and iron salts, sulfuric acid and possibly mobilising trace metals present in the wastes such as nickel, copper, cobalt, zinc etc. Such low quality drainage may be referred to as acid mine drainage (AMD) or acid rock drainage (ARD). 20 The presence of metal species in drainage waters from sulfidic waste piles may cause receiving ecosystems to be adversely affected. There is a need for a means to predict whether a particular mine waste might present an ecological risk and, if it does so, to manage the waste in order to reduce the risk to an acceptable level. To meet this need, a numerical model is required which can be used with confidence to predict the chemical 25 composition of drainage waters from a full-sized waste pile. The intrinsic oxidation rate (IOR) is the rate of oxidation of material at a point in a system (for example a column, stockpile or a dump), under the particular conditions which pertain at that point. The IOR is a function of many parameters, such as oxygen concentration, sulfide sulfur concentration, temperature, pH, sulfide mineral morphology, 30 microbial ecology etc. Since there currently exists no method for predicting the functional dependence of the IOR by measuring individual material characteristics, a reasonable alternative approach uses direct measurements of oxidation rate, either of samples in the laboratory or in-situ. Field measurements of IOR are usually expressed as mass of oxygen consumed 35 per cubic metre of material per second [kg(0 2 ) m-3s1]. If the mass or bulk density of the WO 2004/092690 PCT/AU2004/000512 2 material is known, then IOR may be expressed as the mass of oxygen consumed per mass of material per second [kg(0 2 ) kg(material) s-l]. The use of JOR in predictive modelling of sulfidic piles has been well described by Ritchie (Ritchie, A.I.M, "Bio-oxidation heaps and AMD from waste rock dumps - the 5 importance of the intrinsic oxidation rate", in Proceedings of the AusIMM Annual Conference, Darwin, 5-9 August 1994, pp. 473-476). IOR is the property of the material which enables oxidation and primary pollutant generation rates in a system to be described as a function of space and time. Various forms of the functional dependence of the IOR have been proposed. 10 Ritchie (Ritchie, A.I.M. "Sulfide oxidation mechanisms: controls and rates of oxygen transport" in Short Course Handbook on Environmental Geochemistry of Sulfide Mine Wastes, vol. 22, eds. D.W.Blowes and J..L Jambour, pp 201-245, Mineralogical Association of Canada, May 1994, Waterloo) has shown that the overall oxidation rate in a waste rock dump is comparatively insensitive to detailed changes in the intrinsic 15 oxidation rate unless the IOR is very low. It follows that in many situations, knowledge of the detailed dependencies of the IOR are not required for the practical purposes of decision-making in the management of sulfidic wastes. The management of waste material in the mining industry is expensive. It is believed that characterising and selecting materials with respect to their intrinsic 20 oxidation rate during a mining operation would be a cost-effective element of a strategy for management of waste materials. There is no conventional instrument available that is capable of determining the IOR of material at an accuracy of the order 10-1 kg(0 2 )m-s<' in the time frame of less than about 12 hours. A typical time for laboratory measurements is between 2 and 3 days. 25 The data obtained from an instrument that could accurately measure IOR of waste material in a period of, say, less than about 12 hours, would, if such an instrument were available, be beneficial for characterising and selecting waste material. There is therefore a need for an instrument capable of measuring IOR of mine waste material in a relatively short period of time. 30 A device for measuring the rate of oxygen consumption by waste rock from mining operations has been disclosed in a paper by Anderson, Scharer and Nicholson (Sudbury 1999, Mining and the Environment, Sudbury, Canada pp. 1133 to 1142). The authors specify in that paper that their device requires a measurement time of 1 to 3 days, which is too long to provide the rapid results necessary for efficient management of waste 35 rock piles. In addition, although the authors claim the ability to measure multiple samples WO 2004/092690 PCT/AU2004/000512 3 simultaneously, to do so using their system has the disadvantage that it would require the use of multiple oxygen sensors. High sensitivity oxygen sensors are required in order to enable accurate measurement of the IOR of samples of a conveniently small size for laboratory testing. Further, the gas within the sample in the device described by 5 Anderson, Scharer and Nicholson is static, since the device has no means to circulate the gas. Consequently, the system must rely on diffusion through a porous mass of rock to the headspace above in order to achieve a representative measurement of gaseous oxygen concentration. In addition, the oxygen sensor is inserted directly into the sample container. This arrangement can allow damage or contamination of the oxygen sensor. 10 The presence of moisture and CO 2 can damage sensitive oxygen sensors, or lead to inaccurate results. Further, in that device there are no means to determine whether the sample container has leaks. Since typical samples for the device are waste rock material, the potential for particulate contamination of the seals is considerable. Such contamination could cause leaks, and consequently allow oxygen diffusion from the is outside atmosphere, which would lead to measurement errors. Objects of the Invention It is an object of this invention to address the aforementioned need. It is another object of this invention to overcome at least one of the disadvantages of the prior art. It is 20 a further object to provide methods and systems for determining the intrinsic oxidation rate (IOR) of one or more samples of waste material in a period of time sufficiently short to allow for timely characterisation and selection of waste material. Disclosure of Invention 25 According to a first aspect of this invention, there is provided a method for determining internal gas volume in a sealed enclosure, said method comprising: a) measuring a first gas pressure in the sealed enclosure; b) changing the internal volume of the sealed enclosure by a known volume; c) measuring a second gas pressure in the sealed enclosure after said changing; and 30 d) determining the internal gas volume of the sealed enclosure from the first and second gas pressures and the known volume. According to a second aspect of this invention, there is provided a method for determining at least one of internal gas volume in a sealed enclosure and whether there is gas leakage into or from the sealed enclosure, said method comprising: 35 a) measuring a first gas pressure in the sealed enclosure; WO 2004/092690 PCT/AU2004/000512 4 b) changing the internal volume of the sealed enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) measuring a second gas pressure in the sealed enclosure after said changing as a 5 function of time; d) determining from said second gas pressure as a function of time whether there is gas leakage from or into said sealed enclosure; e) where there is no gas leakage from or into said sealed enclosure, determining the internal gas volume of the sealed enclosure from the first and second gas pressures 10 and the known volume. Where there is a gas leak from or into the sealed enclosure, the second gas pressure will vary as a function of time. According to a third aspect of this invention there is provided a method for determining at least one of internal gas volume in a sealed enclosure and whether there is is gas leakage into or from a sealed enclosure, said method comprising: a) changing the internal volume of the sealed enclosure by a first known volume whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; b) measuring a first gas pressure in the sealed enclosure after said changing as a 20 function of time; and c) determining from said first gas pressure as a function of time whether there is gas leakage from or into said sealed enclosure. Where there is no gas leakage from or into said sealed enclosure, said method further comprises: 25 d) further changing the internal volume of the sealed enclosure by a second known volume; e) measuring a second gas pressure in the sealed enclosure after said further changing; and f) determining the internal gas volume of the sealed enclosure from the first and 30 second gas pressures and the known volumes. The first known volume may be the same as or different from the second known volume. According to a fourth aspect of this invention, there is provided a method for determining whether there is gas leakage into or from a sealed enclosure, said method comprising: WO 2004/092690 PCT/AU2004/000512 5 a) changing the internal volume of the sealed enclosure whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; b) measuring gas pressure in the sealed enclosure after said changing as a function of time; and 5 c) determining from said gas pressure as a function of time whether there is gas leakage from or into said sealed enclosure. Where there is a gas leak from or into the sealed enclosure, the gas pressure will vary as a function of time. According to a fifth aspect of this invention, there is provided a method for 10 determining the volume of a sample of material, said method comprising: a) placing the sample of material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first pressure within said enclosure; d) changing the internal volume of said enclosure by a known volume, whereby the 15 gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; e) measuring a second pressure within said enclosure as a function of time; f) determining from said second pressure as a function of time whether the enclosure has a leak; and 20 g) where the enclosure has no leak, determining the volume of the sample from the volume of the enclosure, the first and second gas pressures, the known volume and the porosity of the sample. In an embodiment there is provided a method for determining the volume of a sample of material, said method comprising: 25 a) placing the sample of material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first gas pressure in the enclosure; d) changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the 30 enclosure; e) measuring a second gas pressure in the enclosure after said changing as a function of time; f) determining from said second gas pressure as a function of time whether there is a gas leak from or into said enclosure; WO 2004/092690 PCT/AU2004/000512 6 g) where there is no gas leak from or into said enclosure, determining the internal gas volume of the enclosure from the first and second gas pressures and the known volume; and h) determining the volume of the sample from the internal gas volume of the 5 enclosure, the first and second gas pressures, the known volume and the porosity of the sample. In this specification, porosity is taken to mean the proportion of a material that is gas, and includes interstitial gas and gas in open pores, but excludes gas in totally sealed inclusions in the solid portion of the material as well as gas dissolved in any portion of the 10 sample. The porosity is a gas-filled porosity, and does not include the portion of pores that are filled with liquid. Such liquid-containing pores may be common in waste rock samples. For waste rock samples, the porosity may be in the range of 0.1 to 0.6, for example, or may be 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6, for example. In particular the porosity may, depending on the nature of the waste rock, be taken to be 0.4, but may be 15 determined independently. The volume of the enclosure may be determined by the method of the first aspect of this invention, or by some other means. According to a sixth aspect of this invention, there is provided a method for determining the density of a sample of material, comprising: 20 a) placing a known mass of the sample of material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first pressure within said enclosure; d) changing the internal volume of said enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the 25 enclosure; e) measuring a second gas pressure within said enclosure as a function of time; f) determining from said second gas pressure as a function of time whether the enclosure has a leak; g) where the enclosure has no leak, determining a volume of the sample; and 30 h) determining the density of the sample from the volume of the sample and the mass of the sample. The volume of the sample may be determined from volume of the enclosure, the volume of gas in the enclosure when the sample is present and the porosity of the sample. The volume of gas in the enclosure when the sample is present may be determined from the 35 first and second gas pressures, the known volume. Details of these calculations are WO 2004/092690 PCT/AU2004/000512 7 provided later in this specification. The sample referred to in this aspect of the invention includes all portions of the sample including solid matter, moisture included in the sample and gaseous material in pores, interstitial spaces, inclusions and other spaces. Alternatively, the mass of the sample may be determined after it has been placed 5 inside the openable enclosure. This may for example comprise: a) measuring the mass of the openable enclosure or a part thereof capable of holding the sample, before the sample has been placed therein; b) measuring the mass of the openable enclosure or the part thereof after the sample has been placed therein; and 10 c) subtracting the mass of step a) from the mass of step b). According to a seventh aspect of the invention, there is provided a method for determining a gas-filled porosity of a material that contains both gas phase and solid phase intermingled. The gas phase may be included in the solid phase either in the form of open pores or cavities within the solid particles or in the form of interstitial spaces 15 between solid particles or both. The method may include the steps of: a) placing the sample in an openable enclosure capable of holding the sample; b) sealing the enclosure; c) measuring a first gas pressure in the enclosure; d) changing the internal volume of the enclosure by a known volume; 20 e) measuring a second gas pressure in the enclosure after said changing; f) determining a volume occupied by the sample; and g) determining the gas-filled porosity of the sample from the volume occupied by the sample, the volume of the enclosure and the volume of gas in the enclosure when the sample is in the enclosure. 25 The step of measuring a second gas pressure may comprise measuring said second gas pressure as a function of time, and the method may comprise the step of determining whether the enclosure has a leak. The volume occupied by the sample may be determined by calculation using a measured depth of the sample and the known geometry and dimensions of the sealed 30 enclosure. For example, if the sealed enclosure is a vertical cylinder of radius R, and the depth of the sample is D, then the volume Vm may be determined from the equation: Vm = .R 2 .D (1) Alternatively, the volume may be determined by removing the sample from the enclosure and inserting into the enclosure sufficient quantity of a reference material of known 35 density, for example water, to occupy the same volume as had been occupied by the WO 2004/092690 PCT/AU2004/000512 8 sample. The mass of that quantity of the reference material may then be determined, and the volume of the sample determined from the equation: Vm = m/d (2) where: m is the mass of the reference material 5 d is the bulk density of the reference material The total volume of the gas phase in the enclosure may be calculated from the equation: VS = 2 P (3) P -Pz Vg = volume of gas in the enclosure (which may conveniently be expressed 10 in m 3 ) when the sample is in the enclosure. This will include interstitial gas and gas in open pores in the sample. VP the known volume (which may conveniently be expressed in M 3 ), which may conveniently be 140x1 0 6 m 3 PI = pressure of the gas within the enclosure before changing the volume of 15 the container (which may conveniently be expressed in kPa), which may be the same as the pressure outside the enclosure.

P

2 = pressure of the gas in the sealed enclosure (which may conveniently be expressed in kPa) when the volume of the enclosure is increased by V,. The porosity s of in the sample may then be calculated using the equation: 20 E =1- (4) Vm Vc =volume of the enclosure The method according to this aspect of the invention may be employed for the determination of the volume of gas in the interstitial spaces and open pores in a particulate material, whereby the particulate material is placed inside the sealed enclosure 25 also containing a gas phase, the internal volume of the enclosure is changed by a known volume, and the pressures of the gas phase in the enclosure before and after the change in volume are used to calculate said volume of gas. With reference to the sixth and the seventh aspects of this invention, the moisture levels in the sample may not be the same as the moisture levels in the bulk of the material 30 from which the sample was taken. This may lead to some inaccuracy in extrapolating the determined values of density and of porosity for the sample to values of those properties for the bulk of the material, although this inaccuracy is likely to be small in many instances.

WO 2004/092690 PCT/AU2004/000512 9 According to an eighth aspect of this invention, there is provided a method for measuring the intrinsic oxidation rate of a sample comprising: a) placing the sample in an openable enclosure capable of holding the sample; b) sealing the enclosure; 5 c) determining at least one of the volume of the sample and the mass of the sample in the enclosure; d) determining changes in gaseous oxygen mass as a function of time; and e) determining the intrinsic oxidation rate of the sample. Preferably the enclosure is not opened and the sample is not disturbed after said sealing 10 but before said determining changes in gaseous oxygen mass as a function of time. The intrinsic oxidation rate (IOR) is the rate at which oxygen is consumed by the sample. It depends on the concentration of oxygen in the gas in which the sample is located. IOR is conveniently measured at atmospheric oxygen concentration, however the actual IOR of a sample will vary with the local oxygen concentration. For example, in the 15 centre of a mineral waste dump, if the oxygen has been depleted by the material in the dump, the IOR of a sample may be considerably lower than it would be if the same sample were located in a region of atmospheric oxygen concentration. IOR may conveniently be expressed as: IOR - A (5) Vm At) 20 where: IOR = intrinsic oxidation rate (kg(oxygen)m 3 s 1 ). Am changes in mass of oxygen (kg). At = time period (s) Vm volume of material (M 3 ). 25 Equation 5 provides a volume based IOR. A similar equation, Equation 5a, may also be used to determine a mass based IOR, which may be expressed in kg(oxygen)kg4l (material)s"': IOR = - (Sa) MmAt where Mm = dry mass of the sample. 30 Mm may be determined by weighing the dried sample. Vm may be calculated using the equation: V -V Vm = " g (6) 1- 8 WO 2004/092690 PCT/AU2004/000512 10 Vc= volume of enclosure, which may be about 4.1x10- 3 m 3 Vg = volume of gas in enclosure (M 3 ). S = porosity (a typical value for the materials commonly investigated by this instrument is s=0.4 although it may commonly have a different value. 6 may be 5 determined independently). The mass of oxygen is defined by the equation: p C M= px V (7) RT 100 g where: m = mass of oxygen (which may conveniently expressed in kg), 10 p = molar mass of oxygen (p=32 x 10-3 kg mol-), p = pressure, which may be atmospheric pressure (which may conveniently expressed in kPa). R = universal gas constant (R=8.314 m 2 kgK~'s- 2 mol-), T = temperature (K), 15 C = oxygen concentration in enclosure measured using oxygen analyser (expressed in molar %), Vg = volume of gas in enclosure (which may conveniently expressed in M 3 ). In an embodiment, there is provided a method for measuring the intrinsic oxidation rate of a sample comprising: 20 a) placing the sample of material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first gas pressure in the enclosure; d) changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the 25 enclosure; e) measuring a second gas pressure in the enclosure after said changing as a function of time; f) determining from said second gas pressure as a function of time whether there is a gas leak from or into said enclosure; 30 g) where there is no gas leak from or into said enclosure, determining the internal gas volume of the enclosure from the first and second gas pressures and the known volume; WO 2004/092690 PCT/AU2004/000512 11 h) determining the volume of the sample from the internal gas volume of the enclosure, the first and second gas pressures, the known volume and the porosity of the sample; i) determining a change in gaseous oxygen mass in the enclosure as a function of 5 time; and j) determining the intrinsic oxidation rate of the sample. In one particular embodiment of the invention, the method for measuring the intrinsic oxidation rate of a sample comprises: a) placing the sample in an openable enclosure capable of holding the sample; 10 b) sealing the enclosure; c) measuring a first gas pressure in the sealed enclosure having a first volume; d) changing the internal volume of the sealed enclosure by a known volume; e) measuring a second gas pressure in the sealed enclosure after said changing; f) restoring the internal volume of the sealed enclosure to the first volume; 15 g) measuring gaseous oxygen concentration in the enclosure as a function of time for a time sufficient to enable a determination of intrinsic oxidation rate of the sample; h) determining at least one of the volume of the sample and the mass of the sample in the enclosure; 20 i) determining changes in gaseous oxygen mass as a function of time; and j) determining the intrinsic oxidation rate of the sample from the measuring of the gaseous oxygen concentration, the resultant changes in mass of gaseous oxygen in the enclosure as a function of time, from at least one of the volume of the sample and the mass of the sample and from temperature and pressure. 25 The measurement of gaseous oxygen concentration may be conducted over a period of less than about 24 hours, preferably less than about 12 hours, more preferably, less than about 10 hours. Still more preferably, individual values of gaseous oxygen concentration are obtained at least once every hour throughout the overall measurement period. Measurement of temperature may be made outside the sample container and may be 30 assumed to be the same as inside the sample container, or it may be measured inside the sample container. Measurements of temperature and/or pressure may be taken once only at the beginning of the test, or they may be measured each time a measurement of oxygen concentration is made or they may be measured a different number of times through the progress of the test.

WO 2004/092690 PCT/AU2004/000512 12 Optionally, during all or a portion of a period in which measurements of gaseous oxygen concentration are taken, gas in the enclosure in which the sample is located may be circulated by means of a pump or other similar means. Each individual value of gaseous oxygen concentration may be calculated from a 5 plurality of separate measurements of oxygen concentration, all of which may be measured within a relatively short period of time, by taking an average of some or all of the separate measurements. Alternatively, each individual value of gaseous oxygen concentration may be calculated from a continuous measurement over a short period of time. 10 Preferably, the gas from an enclosure is passed through a filter or a plurality of filters before a measurement of gaseous oxygen concentration is made. Said filter(s) may be designed to remove one or more of moisture, carbon dioxide, particulate matter and other material that could damage an oxygen sensor or that could alter its ability to accurately measure a concentration of oxygen in a gas. It is known that for some types of is oxygen measuring devices, carbon dioxide may affect the accuracy of the measurement of oxygen concentration. Thus carbon dioxide may be filtered out of the gas before a measurement of oxygen is made. Alternatively the carbon dioxide concentration in the gas from an enclosure may be measured, and the method may comprise the step of compensating the measurement of oxygen concentration for the concentration of carbon 20 dioxide. The IOR so measured may be used, for example, to make decisions in advance regarding the disposition of waste rock generated during blasting in an open cut mining operation. According to a ninth aspect of this invention, there is provided a method for 25 measuring the intrinsic oxidation rate of a sample comprising: a) placing the sample in an openable enclosure capable of holding the sample; b) sealing the enclosure; c) measuring a first gas pressure in the sealed enclosure; d) changing the internal volume of the sealed enclosure by a known volume; 30 e) measuring a second gas pressure in the sealed enclosure as a function of time, to ascertain whether there is gas leakage from or into the enclosure; f) where there is no gas leakage from the enclosure, determining the intrinsic oxidation rate of the sample. The step of placing the sample in the openable enclosure may, if desired, comprise 35 placing a known mass of the sample in the openable enclosure, or it may comprise placing WO 2004/092690 PCT/AU2004/000512 13 a quantity of the sample in the openable enclosure and then determining the mass of said quantity of the sample. Alternatively, the step of placing the sample in the openable enclosure may, if desired, comprise the step of placing a known volume of sample in the openable enclosure, or it may comprise the step of placing a quantity of the sample in the 5 openable enclosure and then determining the volume of said quantity of the sample. The step of determining the intrinsic oxidation rate of the sample may include: a) restoring the internal volume of the sealed enclosure to the first volume; b) measuring gaseous oxygen concentration in the enclosure as a function of time for a time sufficient to enable a determination of intrinsic oxidation rate of the 10 sample; c) determining the volume of the sample in the enclosure; d) determining changes in gaseous oxygen mass as a function of time; and e) determining the intrinsic oxidation rate of the sample from the measuring of the gaseous oxygen concentration, the resultant changes in mass of gaseous oxygen in is the enclosure as a function of time and from the volume of the sample. The step of measuring the gaseous oxygen concentration may be repeated, and may be repeated more than once. An oxygen concentration may be determined for each step of determining oxygen mass in said enclosure. The value of the oxygen concentration used in a determination of oxygen mass may be derived from a plurality of measurements of 20 said oxygen concentration or from a continuous measurement thereof, conveniently over a short period of time. The value of oxygen concentration used in the determination of oxygen mass is preferably derived from a plurality of measurements of oxygen concentration by determining an average of some or all of said measurements of oxygen concentration. Alternatively, each value of oxygen mass may be derived from more than 25 one individual measurement of oxygen mass, preferably by taking an average of some or all of said individual values of oxygen mass. Each of said individual values of oxygen mass may be determined from a measurement of oxygen concentration in the gas. According to a tenth aspect of this invention, there is provided a method of estimating a rate of oxygen consumption in a pile of material which is oxygenated, 30 comprising: a) determining a volume of a sample of the material from the pile of material; b) determining an IOR of the sample of material; c) determining a volume of the pile of material; and d) estimating the rate of oxygen consumption of the pile of material from the 35 volume of the sample, the IOR of the sample and the volume of the pile of material.

WO 2004/092690 PCT/AU2004/000512 14 In an embodiment of the tenth aspect the method comprises: a) placing a sample of the material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first gas pressure in the enclosure; 5 d) changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; e) measuring a second gas pressure in the enclosure after said changing as a function of time; l0 f) determining from said second gas pressure as a function of time whether there is a gas leak from or into said enclosure; g) where there is no gas leak from or into said enclosure, determining the internal gas volume of the enclosure from the first and second gas pressures and the known volume; is h) determining the volume of the sample from the internal gas volume of the enclosure, the first and second gas pressures, the known volume and the porosity of the sample; i) determining a change in gaseous oxygen mass in the enclosure as a function of time; 20 j) determining the intrinsic oxidation rate of the sample; k) determining a volume of the pile of material; and 1) estimating the rate of oxygen consumption in the pile of material from the volume of the sample, the intrinsic oxidation rate of the sample and the volume of the pile of material. 25 The volume of the pile of material may conveniently be determined from the dimensions of said pile. The rate of oxygen consumption of the pile of material may conveniently be calculated using the equation: Am AmV At (pile) = IOR x Vpii, = - (sample) x Y* (8) At At Vsample where: 30 Am = change in mass of oxygen (which may be expressed in kg) At = time over which change in mass of oxygen occurs (which may be expressed in s) IOR = intrinsic oxidation rate (which may be expressed in kg(oxygen)m 3 s-) VpiIe = volume of the pile of material (which may be expressed in M 3

)

WO 2004/092690 PCT/AU2004/000512 15 Vsampie = volume of the sample of material (which may be expressed in in 3 ) Alternatively, the method of estimating the rate of oxygen consumption in the pile may comprise: a) determining a mass of a sample from the pile of material; 5 b) determining a density of the sample; c) determining a mass-based IOR of the sample; d) estimating a mass of the pile of material; and e) calculating the rate of oxygen consumption in the pile. The mass-based TOR may be determined by a modification of Equation 5 in which the 10 mass of the sample replaces the volume of the sample, and is conveniently expressed in kg(oxygen)kg-1(material)s 4 . The mass of the pile of material may be estimated, for example, from the dimensions of the pile of material and the bulk density of the sample. The rate of oxygen consumption in the pile of material may be used to estimate the rate of production of pollutant materials from the pile, and may be used to predict future rates of is production of pollutant materials from the pile. This may be useful in the management of piles such as waste rock dumps from mining operations. According to an eleventh aspect of this invention, there is provided a method of determining IOR of each of a plurality of samples, wherein the IOR of all of the plurality of samples is measured over the same period of time, comprising: 20 a) loading each of said plurality of samples into the same enclosure, or into a different enclosure, or into an enclosure that shares some regions with other enclosures; b) determining if any one or more of the enclosures have gas leaks; c) for those enclosures with no gas leak, measuring an internal gas volume for each 25 enclosure; and d) for each enclosure with no gas leak, determining an IOR. In an embodiment the method comprises: a) loading said plurality of samples into a plurality of enclosures; b) determining if any of the enclosures has a gas leak; 30 c) for each enclosure with no gas leak, measuring an internal gas volume for said enclosure; and d) for each enclosure with no gas leak, determining an intrinsic oxidation rate of the sample therein. Optionally, the plurality of samples may be obtained from different locations in a waste 35 heap, so that a determination of the spatial distribution of TOR within the waste heap may WO 2004/092690 PCT/AU2004/000512 16 be derived from the IORs of the samples. Alternatively, the plurality of samples may be taken from the same location in the waste heap, and the IORs obtained from said plurality of samples may be used to determine an average IOR and optionally, the variation of IOR at such single location. As a further alternative, the plurality of samples may be taken 5 from different waste heaps in order to compare the IOR for those different heaps with each other. Yet another alternative is to measure the IOR of samples taken from different locations in an open cut mining operation, in order to make decisions in advance regarding the disposition of waste rock from blasting in those different locations. For example, in one application, samples of rock from different locations in an open cut mine 10 where blasting is planned may be tested to determine their IORs. Waste rock with similar IOR from different areas of the blasting operation may then be grouped into allocated waste piles so that the appropriate management of those piles can be effectively implemented. In an embodiment, there is provided a method for determination of a spatial is distribution of intrinsic oxidation rate within a waste heap comprising the steps of: a) obtaining samples from different locations in the waste heap, b) measuring an intrinsic oxidation rate for at least two of the samples, and c) determining a spatial distribution of intrinsic oxidation rate within the waste heap. 20 According to a twelfth aspect of this invention, there is provided a system for determining at least one of an internal gas volume in, and whether there is gas leakage into or from, a sealed enclosure, said system comprising: a) an enclosure selected from the group consisting of a salable enclosure and a sealed enclosure; 25 b) means for changing the internal volume of the sealed enclosure by a known volume whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) means for measuring the gas pressure in the sealed enclosure. The system may include means for determining the internal gas volume of the sealed 30 enclosure from the first and second gas pressures and the known volume. The means for measuring gas pressure in the sealed enclosure may be a means for measuring gas pressure in the sealed enclosure as a function of time. In an embodiment there is provided a system for determining an internal gas volume in a sealed enclosure, comprising: 35 a) an openable sealable enclosure; WO 2004/092690 PCT/AU2004/000512 17 b) a volume adjustor for changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) a pressure measuring device for measuring the gas pressure in the enclosure as a 5 function of time. In another embodiment there is provided a system for determining the porosity of a sample of material comprising: a) an openable salable enclosure; b) a volume adjustor for changing the internal volume of the enclosure by a known 10 volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) a pressure measuring device for measuring the gas pressure in'the enclosure as a function of time; d) a volume calculator for calculating the volume of the sample; and 15 e) a porosity calculator. The volume calculator and the porosity calculator may be the same or they may be different. They may for example comprise a computer or other calculating device. According to a thirteenth aspect of this invention, there is provided a system for determining at least one of the volume of a sample and the density of a sample, 20 comprising: a) an enclosure selected from the group consisting of an openable salable enclosure and an openable sealed enclosure; b) means for changing the internal volume of the enclosure by a known volume whereby the gas pressure in the enclosure is less than or greater than the gas 25 pressure outside the enclosure; and c) means for measuring the gas pressure in the sealed enclosure. The system may also include means for determining the mass of a sample placed in the enclosure, and may also include a means for calculating at least one of the volume of the sample and the density of the sample. 30 In an embodiment there is provided a system for determining the volume of a sample of material comprising: a) an openable salable enclosure; b) a volume adjustor for changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the 35 gas pressure outside the enclosure; WO 2004/092690 PCT/AU2004/000512 18 c) a pressure measuring device for measuring the gas pressure in the enclosure as a function of time; and d) a volume calculator for calculating the volume of the sample. According to a fourteenth aspect of this invention, there is provided a system for 5 measuring the intrinsic oxidation rate of a sample comprising: a) an openable enclosure capable of holding the sample said enclosure being selected from the group consisting of a sealable openable enclosure and a sealed openable enclosure; b) means for changing the internal volume of the sealed enclosure by a known 10 volume, said means for changing being coupled to the enclosure; c) means for measuring gas pressure and temperature; and d) means for measuring gaseous oxygen concentration in the enclosure. The means for measuring gaseous oxygen concentration may be located outside the openable enclosure, and there may be a means to transport some or all of the gas in the is enclosure to said means for measuring gaseous oxygen concentration. There may additionally be means to prevent access to said means for measuring gaseous oxygen concentration by materials that could damage it or that could alter its ability to accurately measure a concentration of oxygen in a gas. Said means to prevent access may comprise, for example, one or more of a moisture filter, a carbon dioxide filter and a filter for 20 removing particulate matter. The means for measuring temperature may be inside the enclosure or it may be outside the enclosure. According to this aspect of the invention, there may also be a means for determining IOR of the sample from the temperature, the pressure, the volume of the sample and the gaseous oxygen concentration in the enclosure as a function of time. 25 According to a fifteenth aspect of this invention there is provided a system for determining at least one of an internal gas volume in a sealed enclosure and whether there is gas leakage into or from a sealed enclosure, said system comprising: a) an openable enclosure, said enclosure being selected from the group consisting of a salable openable enclosure and a sealed openable enclosure; 30 b) means for changing the internal volume of the sealed enclosure by a first known volume whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) means for measuring a first gas pressure in the sealed enclosure after changing the internal volume of the sealed enclosure by a first known volume whereby the WO 2004/092690 PCT/AU2004/000512 19 gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure as a function of time; d) means for determining whether there is gas leakage from or into said sealed enclosure; 5 e) means for further changing the internal volume of the sealed enclosure by a second known volume; f) means for measuring a second gas pressure in the sealed enclosure after said further changing; and g) means for determining the internal gas volume of the sealed enclosure from the 10 first and second gas pressures and the known volumes. The first known volume may be the same as or different from the second known volume. The means for measuring a first gas pressure may be the same as or different from the means for measuring a second gas pressure. The means for changing the internal volume of the sealed enclosure may be the same as or different from the means for further is changing the internal volume of the sealed enclosure. According to a sixteenth aspect of this invention, there is provided a system for measuring the intrinsic oxidation rate of a sample comprising: a) an openable enclosure capable of holding the sample said enclosure being selected from the group consisting of a salable openable enclosure and a sealed 20 openable enclosure; b) means for sealing the enclosure; c) means for determining the volume of the sample in the enclosure; d) means for determining changes in gaseous oxygen mass as a function of time; and 25 e) means for determining the intrinsic oxidation rate of the sample. The means for determining the intrinsic oxidation rate may be an IOR determiner. The means for sealing the enclosure may comprise complementary screw threads on each of two portions of the enclosure and a seal that may be compressed when the two portions are screwed together. Alternatively the means may comprise some other device for 30 sealing the enclosure. In an embodiment there is provided a system for measuring an intrinsic oxidation rate of a sample comprising: a) an openable salable enclosure capable of holding the sample; b) a volume adjustor for changing the internal volume of the sealed enclosure by a 35 known volume, said adjustor being coupled to the enclosure; WO 2004/092690 PCT/AU2004/000512 20 c) a pressure measuring device for measuring gas pressure and a temperature measuring device for measuring temperature; and d) an oxygen meter for measuring gaseous oxygen concentration of a gas in the enclosure. 5 In one particular embodiment, the system for measuring the intrinsic oxidation rate of a sample comprises: a) an openable enclosure capable of holding the sample said enclosure being selected from the group consisting of a sealable openable enclosure and a sealed openable enclosure; 10 b) means for sealing the enclosure; c) means for measuring a first gas pressure in the sealed enclosure having a first volume; d) means for changing the internal volume of the sealed enclosure by a known volume; is e) means for measuring a second gas pressure in the sealed enclosure; f) means for restoring the internal volume of the sealed enclosure to the first volume; g) means for measuring gaseous oxygen concentration and measurement gas pressure in the enclosure as a function of time for a time sufficient to enable a 20 determination of intrinsic oxidation rate of the sample; h) means for determining the volume of the sample in the enclosure; i) means for determining temperature; j) means for determining changes in gaseous oxygen mass as a function of time; and 25 k) means for determining the intrinsic oxidation rate of the sample from the measuring of the gaseous oxygen concentration and the resultant changes in mass of oxygen as a function of time and from the volume of the sample. Optionally said system may also include means to recirculate a gas within an enclosure containing the sample. Said means may be a gas circulator. 30 Preferably the means for measuring gaseous oxygen concentration is not located within the enclosure in which the sample is located and there is a means to transport air from the enclosure to the means for measuring gaseous oxygen concentration. The means to transport may be a transport system. Advantageously there may also be a filter or a plurality of filters which is (are) capable of removing one or more of moisture, carbon 35 dioxide, particulate matter and other material that could damage an oxygen sensor or that WO 2004/092690 PCT/AU2004/000512 21 could alter its ability to detect an accurate concentration of oxygen in a gas. Said filter(s) may be located such that gas passes through said filter(s) before reaching the means for measuring gaseous oxygen concentration. The means for measuring gaseous oxygen concentration may be an oxygen meter, or an oxygen sensor. The oxygen sensor may be 5 for example an oxygen fuel cell. The system for measuring the intrinsic oxidation rate may have a carbon dioxide filter for removing carbon dioxide from the gas before it reaches the oxygen sensor, since carbon dioxide is capable of affecting the accuracy of an oxygen sensor. Alternatively, the system may comprise a carbon- dioxide meter for measuring the concentration of carbon dioxide in the gas. In this case, the oxygen sensor 10 may have a compensator so that the measurement of oxygen is compensated for the concentration of carbon dioxide. According to a seventeenth aspect of this invention, there is provided a system for measuring the intrinsic oxidation rate of a sample comprising: a) an openable enclosure capable of holding the sample said enclosure being is selected from the group consisting of a sealable openable enclosure and a sealed openable enclosure; b) means for sealing the enclosure; c) means for measuring a first gas pressure in the sealed enclosure; d) means for changing the internal volume of the sealed enclosure by a known 20 volume; e) means for measuring a second gas pressure in the sealed enclosure as a function of time to ascertain whether there is gas leakage from or into the enclosure; and f) where there is no gas leakage from the enclosure, means for determining the intrinsic oxidation rate of the sample. 25 The means for determining the intrinsic oxidation rate of the sample may include: a) means for restoring the internal volume of the sealed enclosure to the first volume; b) means for measuring gaseous oxygen concentration and for measuring gas pressure in the enclosure as a function of time for a time sufficient to enable a 30 determination of intrinsic oxidation rate of the sample; c) means for determining the volume of the sample in the enclosure; d) means for determining the temperature; e) means for determining changes in gaseous oxygen mass as a function of time; and WO 2004/092690 PCT/AU2004/000512 22 f) means for determining the intrinsic oxidation rate of the sample from the measuring of the gaseous oxygen concentration and the resultant changes in mass of oxygen as a function of time and from the volume of the sample. According to an eighteenth aspect of the invention there is provided a system for 5 determining an IOR for a plurality of samples comprising: a) a plurality of an openable enclosures capable of holding the samples, said enclosures being selected from the group consisting of a sealable openable enclosures and a sealed openable enclosures; b) means for determining the gas volume of each of said enclosures individually; 10 c) means for determining for each enclosure separately whether that enclosure has a gas leak; and d) means for determining for each enclosure separately the IOR of the sample in said enclosure. The system may also include means to isolate an enclosure. Said means may be for is example an isolator. In one form the system may include means to isolate an enclosure, or a portion of an enclosure that contains the sample, or more than one such enclosure or portion of an enclosure, if it is determined that there is a leakage into or from said enclosure or enclosures. All of the enclosures may be connected to a single means for changing the 20 volume of the enclosure, a single means for measuring the pressure in the enclosure and a single means for measuring oxygen concentration, which may be a single oxygen sensor. Alternatively, one of the following options may be used: a) single means for changing the volumes of the all of the enclosures, separate means for measuring the pressure in each enclosure and single means for 25 measuring oxygen concentration in all of the enclosures; b) separate means for changing the volume of each enclosure, single means for measuring the pressures in all of the enclosures and single means for measuring oxygen concentration in all of the enclosures; c) separate means for changing the volume of each enclosure, separate means for 30 measuring the pressure in each enclosure and single means for measuring oxygen concentration in all of the enclosures; d) single means for changing the volumes of all of the enclosures, single means for measuring the pressures in all of the enclosures and separate means for measuring oxygen concentration in each enclosure; WO 2004/092690 PCT/AU2004/000512 23 e) single means for changing the volumes of all of the enclosures, separate means for measuring the pressure in each enclosure and separate means for measuring oxygen concentration in each enclosure; f) separate means for changing the volume of each enclosure, single means for 5 measuring the pressures in all of the enclosures and separate means for measuring oxygen concentration in each enclosure; g) separate means for changing the volume of each enclosure, separate means for measuring the pressure in each enclosure and separate means for measuring oxygen concentration in each enclosure. 10 Herein, "single means" indicates that all enclosures are connected to the same means, whereas "separate means" indicates that at least two of the enclosures are connected to one means. In addition, each enclosure may have a separate means for measuring temperature, or there may be one means for measuring temperature. Said means may be a voltage divider circuit incorporating a thermistor as a temperature sensor, or a 15 thennocouple or a thermometer or may be some other suitable means for measuring temperature. Preferably, the volume of the system, excluding the sample containers in which the samples are placed, is kept to a minimum in order to minimise dilution of the sample container air during measurement of oxygen content. 20 In an embodiment there is provided a system for determining an intrinsic oxidation rate for a plurality of samples comprising: a) a plurality of openable sealable enclosures capable of holding the samples; b) a volume measuring system for determining the gas volume of each of said enclosures individually; 25 c) a leak detection system for determining for each enclosure separately whether that enclosure has a gas leak; and d) an intrinsic oxidation rate detection system for determining for each enclosure separately the intrinsic oxidation rate of the sample in said enclosure. In another embodiment there is provided a system for determining a spatial 30 distribution of intrinsic oxidation rates within a waste heap comprising: a) a sampling system for obtaining samples from different locations within the heap; b) a plurality of openable sealable enclosures capable of holding the samples; c) a volume measuring system for determining the gas volume of each of said 35 enclosures individually; WO 2004/092690 PCT/AU2004/000512 24 d) a leak detection system for determining for each enclosure separately whether that enclosure has a gas leak; e) an intrinsic oxidation rate detection system for determining for each enclosure separately an intrinsic oxidation rate of the sample in said enclosure; and 5 f) distribution determiner for determining a spatial distribution of intrinsic oxidation rates. According to a nineteenth aspect of the invention, there is provided a system for estimating a rate of oxygen consumption of a pile of material which is oxygenated, comprising; 10 a) means for determining a volume of a sample from the pile of material; b) means for determining an IOR of said sample; c) means for estimating a volume of the pile of material; and d) means for calculating the rate of oxygen consumption of the pile from the IOR and the volumes of the sample and of the pile. is The means for determining the volume of the sample may comprise: (i) an enclosure selected from the group consisting of an openable salable enclosure and an openable sealed enclosure; (ii) means for changing the internal volume of the enclosure by a known volume whereby the gas pressure in the enclosure is less than or greater than the gas 20 pressure outside the enclosure; (iii) means for measuring a gas pressure in the sealed enclosure; and (iv) means for calculating a volume of the sample. The system may additionally include means to estimate the rate of production of pollutant materials from the pile of material from the rate of oxygen consumption of the 25 pile. In an embodiment there is provided a system for estimating a rate of oxygen consumption of a pile of material which is oxygenated, comprising; a) an openable salable enclosure capable of holding a sample of the material; b) a volume adjustor for changing the internal volume of the enclosure by a known 30 volume, said adjustor being coupled to the enclosure; c) a pressure measuring device for measuring gas pressure and a temperature measuring device for measuring temperature; d) an oxygen meter for measuring gaseous oxygen concentration of a gas in the enclosure in order to determine an intrinsic oxidation rate of the sample; 35 e) a volume estimator for estimating a volume of the pile of material; and WO 2004/092690 PCT/AU2004/000512 25 f) an oxygen consumption calculator for calculating the rate of oxygen consumption of the pile from the intrinsic oxidation rate and the volumes of the sample and of the pile. According to a twentieth aspect of the invention, there is provided a system for 5 determining the proportion of a gas phase in a material that contains both gas phase and solid phase intermingled, comprising: a) an enclosure selected from the group consisting of a sealable enclosure and a sealed enclosure; b) means for changing the internal volume of the sealed enclosure by a known 10 volume whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) means for measuring the gas pressure in the sealed enclosure; and d) means for determining the volume of the sample in the enclosure. The system may include means for determining the internal gas volume of the 15 sealed enclosure from the first and second gas pressures and the known volume. With reference to the eighth, ninth, tenth, eleventh, fourteenth, sixteenth, seventeenth, eighteenth and nineteenth aspects of the invention, the IOR may be measured at any desired combination of values of oxygen concentration, pressure and temperature. Conveniently, IOR is Smax, where Smax is the IOR determined at atmospheric oxygen 20 concentration. Conveniently also, IOR is determined at the same conditions of atmospheric oxygen concentration, temperature and pressure as pertain outside the enclosure(s) in the vicinity of the system for detennining IOR. These conditions may be 25*C, 101.3kPapressure and 20.95% (v/v) oxygen, or one or more of these conditions may be different from these values, depending on local conditions when and at the 25 location at which the IOR is determined. In assessing management options for AMD it is useful for the mining industry to quantify the following: a) the time between dumping waste materials and the time for AMD to appear, b) the time for all sulfide material in waste piles to be used up, and 30 c) magnitude of pollution load in drainage as a function of time. Measurement of IOR can assist in providing estimates for all of these parameters. It is an advantage of the present invention that the rapidity and sensitivity of the system described herein allows a fast and accurate indication of the IOR of a body of waste material, and enables a timely estimate of the prospective environmental impact of 35 the material tested. This allows a user to make informed decisions concerning waste rock WO 2004/092690 PCT/AU2004/000512 26 pile management. It is a further advantage of the invention that there is no need to pretreat the sample before testing, although pretreatment of a sample, for example drying of a particularly wet sample, may be practiced within the scope of this invention. In addition, the volume of the sample is determined, and the IOR is able to be determined, on the 5 same sample without further processing or manipulation of the sample. This simplifies the test, and helps to minimise the time required to conduct a test, and thereby allows the results of the testing to be made available in a relatively short timeframe. Whereas the IOR systems and methods described in this invention are designed to measure the oxygen consumption rate of sulfidic waste rock and tailing waste materials 10 for the mining industry, this instrument could be easily applied in other applications. For example, determination of IOR is of use in management of biooxidation and bioleach heaps, where IOR is used to determine what improvements may be necessary in the operating conditions of such heaps in order to improve the yield of valuable metals from mining operations, and to predict the effective lifetimes of such heaps. The decision about 15 whether to treat a particular sulfidic material in a biooxidation or bioleach heap may be based on economic criteria that may include the time for a pre-determined amount of material to oxidise. Determining the IOR of materials during mining may provide cost effective and timely information to be used in choosing suitable materials for use in production heaps. The systems and methods in this invention may also find use in other 20 industries such as the food industry, and the scope of the invention is to be construed as including such applications. Brief Description of Drawings The invention will now be described, by way of example, with reference to the 25 accompanying drawings wherein: Figure 1 is a diagrammatic representation of a voltage divider circuit which may be used to measure temperature; Figure 2 is a graph of temperature as a function of calculated voltage in the voltage divider circuit of Figure 1; 30 Figure 3 is a diagrammatic representation of a system in accordance with the invention; Figure 4 is a graph showing mass of oxygen consumed by a sample as a function of time, as determined in the course of the Example; Figure 5 is a diagrammatic representation of a sealing system that may optionally be used to seal plastic (PVC) sample containers forming part of the system of Figure 3; WO 2004/092690 PCT/AU2004/000512 27 Figure 6 is a diagrammatic representation of a mechanism which may optionally be used to control a force urging an upper edge of a sample container against a foam rubber seal forming part of the system of Figure 3; Figure 7 shows diagrammatic representations of a variety of systems that may be used in 5 accordance with the invention; and Figure 8 is a diagrammatic representation of another system in accordance with the invention, said system being not the same as the system represented in Figure 3. Best Mode And Other Modes For Carrying Out The Invention 10 Referring to Figure 1, circuit 100 may be used to measure temperature. Circuit 100 comprises thermistor 101 with nominal resistance Rthermistor of 100 kOhm for use within the range of from 0*C to 70*C. The thermistor is used as a sensor in the voltage divider. The maximum power dissipation of thermistor 101 is 28tW in the temperature range from 04C to 70*C. To satisfy this manufacturer requirement, the excitation voltage 15 (Ucit.) provided by power source 102 and fixed resistor (R) 103 were determined to be 1.5V and 20 kOhm, respectively. From the manufacturer's specification for thermistor 101, the voltage Uf across tenninals 104 and 105 was calculated by using the equation: (Rf Uf = UeXci. Rf (9) SR f + R thermi~stor ) Figure 2 shows the temperature on the ordinate axis as a function of voltage Uf on the 20 abscissa. For calculated data, the fourth order polynomial fit was obtained and it is given by: T = -56.429 (Uf) 4 + 185.39 (Uf) 3 -216.5 (Uf) 2 + 177.46 (Uf) - 8.4761 (10) Equation 10 is used to calculate the temperature corresponding to a particular measured voltage Uf. 25 Referring to Figure 3, there is shown a system 300 for determining the intrinsic oxidation rate (IOR) of a plurality of samples of material. System 300 measures the intrinsic oxidation rate of up to eight different samples. The invention is, however, not limited to the use of up to eight samples. Any number of samples may be used at the same time. System 300 includes cylinder 301 having a piston 302, and a pressure sensor 303. 30 System 300 further includes a manifold of valves 304 which incorporates solenoid valves 305a, 306a, 307a, 308a, 309a, 310a, 311a and 312a, and spare solenoid valves 395 and 396 (which in this description remain closed throughout), as well as a manifold of solenoid valves 313 which incorporates solenoid valves 305b, 306b, 307b, 308b, 309b, 310b, 311b and 312b, and also solenoid valve 391 leading to the atmosphere and solenoid WO 2004/092690 PCT/AU2004/000512 28 valve 317 leading to the oxygen detection system described below. System 300 also includes eight air pumps 305c, 306c, 307c, 308c, 309c, 310c, 311c and 312c, and eight sample containers 305d, 306d, 307d, 308d, 309d, 310d, 311d and 312d. Each of the sample containers 305d, 306d, 307d, 308d, 309d, 310d, 311d and 312d is openable to 5 enable a sample to be placed into and/or to be removed from it. System 300 also includes an air pump 314, a moisture filter 315, a CO 2 filter 316, an oxygen analyser 318 (with a resolution better than 0.001% corresponding to a mass of oxygen less than 3 x 10- 9 g) and a computer 319. Cylinder 301 having piston 302 is coupled to pressure sensor 303 by lines 320 and 321 and to the manifold of valves 313 by lines 320 and 322. Sample 10 containers 305d to 312d are connected to valves 305b to 312b respectively by lines 325, 328, 331, 334, 337, 340, 343 and 390 respectively. Air pumps 305c, 306c, 307c, 308c, 309c, 3 10c, 311c and 312c are coupled to the sample containers 305d, 306d, 307d, 308d, 309d, 310d, 311d and 312d respectively by lines (a) 346, 347, 324; (b) 348, 349, 327; (c) 350, 351, 330; (d) 352, 353, 333; (e) 354, 355, 336; (f) 356, 357, 339; (g) 358, 359, 342; is (h) 360, 361, 345; respectively. During measurement of intrinsic oxygen rate each of the sample containers 305d, 306d, 307d, 308d, 309d, 310d, 311d and 312d is sealably connected into the system 300 by lines (a) 323, 324, 325; (b) 326, 327, 328; (c) 329, 330, 331; (d) 332, 333, 334; (e) 335, 336, 337; (f) 338, 339, 340; (g) 341, 342, 343; (h) 344, 345, 390; respectively. The manifold of valves 313 is coupled via valve 317 to moisture 20 filter 315 by line 362, whilst moisture filter 315 is coupled to CO 2 filter 316 by line 364, and CO 2 filter 316 is coupled to the pump 314 by line 365, and pump 314 is coupled to oxygen analyser 318 by line 366, and oxygen analyser 318 is coupled to manifold of valves 304 by line 367. The computer 319 is electrically coupled to air pump 314 by line 368, to oxygen analyser 318 by line 371, to piston 302 by line 372, to the pressure sensor 25 303 by line 373, to manifold of valves 313 which incorporates valves 305b, 306b, 307b, 308b, 309b, 310b, 311b, 312b, 391 and 317 by a plurality of lines capable of controlling each of the solenoid valves in manifold 313 individually (for the sake of clarity, only one of said lines, 374, is shown in Figure 3), to the manifold of valves 304 which incorporates inlet valves 305a, 306a, 307a, 308a, 309a, 310a, 31 la, 312a, 395 and 396 by a plurality of 30 lines capable of controlling each of the solenoid valves in manifold 304 individually (for the sake of clarity, only one of said lines, 375, is shown in Figure 3), and to the air pumps 305c, 306c, 307c, 308c, 309c, 310c, 311c and 312c by lines 376, 377, 378, 379, 380, 381, 382, and 383 respectively. Figure 4 shows experimental data for variation of oxygen content as a function 35 of time, obtained in the Example. The abscissa of the graph represents the time expired WO 2004/092690 PCT/AU2004/000512 29 since the start of the test, and the ordinate axis represents the mass of oxygen detected in an enclosure containing a sample. Individual points on the graph represent individual values of oxygen mass at the corresponding time shown on the abscissa. Figure 5 shows a mechanism which may optionally be used for sealing sample 5 containers in the system of Figure 3. In Figure 5, only those four sample containers that are located at the front of system 300 of Figure 3 are shown. A similar assembly containing a further four sample containers is located at the rear, behind the assembly shown. With reference to Figure 5, individual sample containers 501, 502, 503 and 504 may be located in complementary sample bases 531, 532, 533 and 534, which are 10 attached to a movable. sample container holder 506. Sample container holder 506 is located above the fixed base 508 of the system 300. Fixed base 508 is a portion of frame 550. Shelves 551 and 552 are provided for convenient storage of other components of the system, tools, samples or other items. Linear actuators 510, 511 and 512 are used to move the sample container holder 506, and thereby the sample containers 501, 502, 503 and is 504, in a vertical direction. The top plate 514 is in a fixed position, and is attached to the sample container lids 516, 517, 518 and 519, each of which is fitted with a 6mm thick closed cell neoprene foam rubber seal 522, 523, 524 and 525 respectively. The sample container lids 516, 517, 518 and 519 are located above the sample bases 531, 532, 533 and 534 in such positions that, when the sample containers 501, 502, 503 and 504 are 20 located in the bases 531, 532, 533 and 534, and when the linear actuators 510, 511 and 512 are operated so as to move the sample container holder 506 upwards, the sample containers 501, 502, 503 and 504 are sealed against the sample container lids 516, 517, 518 and 519 by means of seals 522, 523, 524 and 525. By adjusting the height of the linear activators 510, 511 and 512, and by adjusting the force applied by the sample 25 container bases (shown in Figure 6), the force applied by the rims of the sample containers 501, 502, 503 and 504 to the seals 522, 523, 524 and 525 maybe adjusted. Figure 6 shows a diagrammatic representation of a spring loaded system located in sample container bases 531, 532, 533 and 534 of Figure 5 in order to allow for adjustment of the force applied by the rim of sample containers 501, 502, 503 and 504 of 30 Figure 5 to the seals 522, 523, 524 and 525 of Figure 5. As is shown in Figure 6, sample container 601 fits into sample container base 602. Located within base 602 is fixed cylindrical plate 604 with 3 holes 642, 644 and 646. Above fixed plate 604 is located movable plate 606, with 3 holes 652, 654 and 656, located so that when plate 604 is placed above plate 606, the two sets of holes in the two plates can be aligned. Bolts 610, 35 611 and 612 are fitted with washers 615, 616 and 617, springs 620, 621 and 622 and WO 2004/092690 PCT/AU2004/000512 30 washers 625, 626 and 627, and connect plates 604 and 606, fitting through both sets of holes in those plates. Bolts 610, 611 and 612 are held in place by nuts 630, 631 and 632, located beneath fixed plate 604. The length of stainless steel springs 620, 621 and 622, and the position of bottom nuts 630, 631 and 632, regulate the distance between plates 5 604 and 606. Figure 7 shows a variety of diagrams representing systems that may be used in accordance with the invention. In all of the diagrams in Figure 7, there may additionally be means for collecting and optionally for processing data, and there may be means to control one or more of the components in the system. Such means are commonly a 10 computer, connected to the relevant components of the system, however, for the sake of simplicity, said means are not shown. Openable container 702 may have a means for sealing so that the enclosure is sealed. Piston 706 is used to alter the volume of the enclosure by a known volume, and may additionally be capable of altering the volume of the enclosure by a second known volume. The pressure in the enclosure may be measured 15 using manometer 704. Oxygen meter 708 may be used to determine the concentration of oxygen in container 702. The oxygen probe, which forms a part of meter 708 (but is not shown separately in these diagrams) may be located in container 702, as shown in diagrams 7a, 7b and 7c, or it may be located outside container 702, as shown in diagrams 7d and 7e. Recirculation pump 710 may be used to ensure that the gas within the 20 container is approximately homogeneous. If the oxygen probe is located outside container 702, pump 714 is provided to transfer gas from container 702 to the oxygen probe. One or more filters 712 may be provided such that the gas from the container passes through the filters 712 before reaching the oxygen probe, in order to remove materials such as C0 2 , moisture and dust which might damage the probe or cause it to be inaccurate. 25 Thus Figure 7a is a diagrammatic representation of a system which may be used in accordance with the first aspect of the invention. When using the system in accordance with the first aspect, container 702 is sealed. Manometer 704 may be used for measuring a first pressure and also for measuring a second gas pressure, and piston 706 can be used for changing the internal volume of the sealed enclosure. In this system, the enclosure 30 comprises the internal portions of container 702, manometer 704, the cylinder in which piston 706 moves and the tubing that connects those components. The system of Figure 7a may also be used in accordance with other aspects of the invention, for example the second aspect. Figure 7b is a diagrammatic representation of a system which may be used in 35 accordance with the eighth aspect of the invention. When using the system in accordance WO 2004/092690 PCT/AU2004/000512 31 with the eighth aspect, container 702 is openable and sealable, using a system that may be similar to that shown in Figure 5. The volume of the sample may be determined using the method of the fifth aspect of this invention (which may include using manometer 704 to measure a first and a second pressure, and using piston 706 to change the internal volume 5 of the enclosure by a known volume), and changes in oxygen mass as a function of time may be determined using the oxygen meter 708. In this system, the enclosure comprises the internal portions of container 702, manometer 704, the cylinder in which piston 706 moves and the tubing that connects those components. The system of Figure 7b may also be used in accordance with other aspects of the invention, for example the ninth aspect. 10 Figure 7c is a diagrammatic representation of another system which may be used in accordance with the eighth aspect of the invention. When using the system in accordance with the eighth aspect, it is used in a manner similar to that described for Figure 7b, however during all or a portion of the period in which measurements of gaseous oxygen concentration are taken using oxygen meter 708, gas in container 702 is may be circulated by means of pump 710. The system of Figure 7c may also be used in accordance with other aspects of the invention, for example the ninth aspect. Figure 7d is a diagrammatic representation of yet another system which may be used in accordance with the eighth aspect of the invention. When using the system in accordance with the eighth aspect, it is used in a manner similar to that described for 20 Figure 7b, however the gas from container 702 is passed through filter or plurality of filters 712 using pump 714 before a measurement of gaseous oxygen concentration is made by oxygen meter 708. Said filter(s) may be designed to remove one or more of moisture, carbon dioxide, particulate matter and other material that could damage an oxygen sensor or that could alter its ability to accurately measure a concentration of 25 oxygen in a gas. The system of Figure 7d may also be used in accordance with other aspects of the invention, for example the ninth aspect. Figure 7e is a diagrammatic representation of a further system which may be used in accordance with the eighth aspect of the invention. When using the system in accordance with the eighth aspect, it is used in a manner similar to that described for 30 Figure 7d, however during all or a portion of the period in which measurements of gaseous oxygen concentration are taken using oxygen meter 708, gas in container 702 may be circulated by means of pump 710. The system of Figure 7e may also be used in accordance with other aspects of the invention, for example the ninth aspect.

WO 2004/092690 PCT/AU2004/000512 32 Figure 7 is not intended to represent all of the possible systems that may be used in accordance with this invention, and should not be taken as in any way limiting the invention to those systems shown diagrammatically in Figure 7. Referring to Figure 8, there is represented a system 800, wherein those 5 components of the system that are in common with Figure 3 are described above, and serve the same functions as described for Figure 3. In Figure 8, moisture filter 315 and

CO

2 filter 316, together with lines 362, 364 and 365 are omitted, and manifold of valves 313 is connected via valve 317 to pump 314 by line 862. Also sample containers 305d, 306d, 307d, 308d, 309d, 310d, 311d and 312d are connected to valves 305b, 306b, 307b, 10 308b, 309b, 3 10b, 311b and 312b respectively by a) line 805a, CO 2 filter 805b, line 805c, moisture filter 805d and lines 805e and 805f; b) line 806a, CO 2 filter 806b, line 806c, moisture filter 806d and lines 806e and 806f; c) line 807a, CO 2 filter 807b, line 807c, moisture filter 807d and lines 807e and 807f; d) line 808a, CO 2 filter 808b, line 808c, moisture filter 808d and lines 808e and 808f; e) line 809a, CO 2 filter 809b, line 809c, 15 moisture filter 809d and lines 809e and 809f; f) line 810a, CO 2 filter 810b, line 810c, moisture filter 810d and lines 810e and 810f; g) line 81la, CO 2 filter 811b, line 811c, moisture filter 811d and lines 811e and 811f; and h) line 812a, CO 2 filter 812b, line 812c, moisture filter 812d and lines 812e and 812f respectively. Moisture filters 805d, 806d, 807d, 808d, 809d, 810d, 811d and 812d are connected to air pumps 305c, 306c, 307c, 20 308c, 309c, 310c, 311c and 312c respectively by lines a) 805e and 805g; b) 806e and 806g; c) 807e and 807g; d) 808e and 808g; e) 809e and 809g; f) 810e and 810g; g) 811e and 811g; and h) 812e and 812g respectively. A preferred mode of operation of an IOR meter is described below with reference to the Figures 1 to 3, 5 and 6. In this description, when reference is made to 25 Figure 5, it is understood that there is a similar assembly of four sample containers and housings behind the four shown in the diagram. Similarly, when reference is made to Figure 6, it is understood that the system shown in Figure 6 is representative of all of the eight sample container bases. In addition, an enclosure, as used in this description, comprises cylinder 301, pressure sensor 303, manifold 313, one of solenoid valves 305b 30 to 312b, the corresponding one of pumps 305c to 312c, the corresponding one of sample containers 305d to 312d, together with tubing connecting the above to each other and to the corresponding solenoid valve of 305a to 312a, as shown diagrammatically in Figure 3. The enclosure that incorporates sample container 305d will be referred to as enclosure 1, the enclosure that incorporates sample container 306d will be referred to as enclosure 2 WO 2004/092690 PCT/AU2004/000512 33 and so forth, such that the enclosure that incorporates sample container 312d will be referred to as enclosure 8. A program written in LabVIEW computer language controls the data acquisition device, solenoid valves, air pumps, linear actuators, thermistor, pressure sensor and 5 oxygen analyser. In order to seal each sealable enclosure, the following procedure is followed. Each sample container is placed in a sample container base, represented by the sample bases 501, 502, 503 and 504 of Figure 5, and shown in detail in Figure 6. By selecting appropriate springs 620, 621 and 622 (Figure 6), by adjusting nuts 630, 631 and 632 10 (Figure 6) and by adjusting linear actuators 510, 511 and 512 (Figure 5), the force with which the sample containers (represented by the sample containers 501, 502, 503 and 504 of Figure 5) impinge on the seals 522, 523, 524 and 525 (Figure 5) may be set to an appropriate value. The linear actuators 510, 511 and 512 (Figure 5) are then used to raise the movable sample container holder 506 (Figure 5) so that the sample containers seal 15 against the sample container lids 516, 517, 518 and 519 (Figure 5) by means of seals 522, 523, 524 and 525. In order to determine the volume of each sealable enclosure, and whether it has a leak, the following procedure is followed. Initially the sealable containers are sealed into system 300 as described above. Then solenoid valves 305a to 312a, 305b to 312b and 317 20 (Figure 3) are closed. In order to determine the internal gas volume in enclosure 1 and whether there is a gas leakage into or from enclosure 1, solenoid valves 305b and 391 are opened, and the system is allowed to equilibrate with atmospheric pressure for 60 seconds. A first gas pressure P 1 is then measured using pressure sensor 303, after which solenoid valve 391 is closed. Piston 302 is then used to change the internal volume of 25 enclosure 1 by a known volume Vp. The system is then allowed to equilibrate for 60 seconds. A second pressure P 2 is then measured using pressure sensor 303. A third pressure P 3 is measured after a further 40 seconds, using pressure sensor 303. If the difference between P 2 and P 3 is less than or equal to 80Pa, and if P 1

#P

2 , then there is not a 30 leakage into or from enclosure 1. In that case, the internal gas volume of sealed enclosure 1, V., is calculated using a modification of Equation 3 in which V, replaces V9. Using piston 302, the internal volume of the enclosure is then restored to its original value. If the difference between P 2 and P 3 is greater than 80Pa, or if Pi=P 2 , then there is a leakage into or from enclosure 1. In this case, by adjusting the position of seal (522 or similar in 35 Figure 5) and of the linear actuators 510, 511 and 512 (Figure 5) and of the nuts 630, 631 WO 2004/092690 PCT/AU2004/000512 34 and 632 (Figure 6) or by other appropriate actions, the quality of the seal is improved until the procedure described above shows that there is not a leakage into or from enclosure 1. The acceptable amount of the difference between P 2 and P 3 may be chosen to be less than 200, 150, 100, 80, 60, 40, 20, 10, 5 or 1Pa, or some other acceptable value if 5 required. The above method for determining the internal gas volume of enclosure 1 is then repeated using the appropriate combinations of valves and other elements in order to determine the internal gas volumes of enclosures 2 to 8 in turn, although it is not necessary to measure a new value of the first gas pressure P 1 for each enclosure, since P 1 10 is the same as the ambient atmospheric pressure. Once the internal gas volume of each enclosure has been determined, that value may be stored. The stored value may then be used for subsequent tests, rather than redetermining the volume of the enclosure as described above. Enclosures 1 to 8 are then opened by using linear actuators 510, 511 and 512 to '1s lower sample container holder 506. A sample of material to be tested is then placed in each of the sample containers 305d to 312d (although one or more containers may be left empty if desired), the sample containers are located in the corresponding sample container bases, and the enclosures are sealed by using linear actuators 510, 511 and 512 to raise the sample container holder 506. 20 In order to determine whether there is a gas leakage into or from enclosure 1 and to determine the volume of gas in enclosure 1, a similar procedure is followed to that described above to determine whether there is a gas leakage into or from enclosure 1 and to determine the internal gas volume of enclosure 1 before the sample was loaded into container 305d. If the difference between P 2 and P 3 is less than or equal to 80Pa, and 25 PimP 2 , then there is not a leakage into or from enclosure 1. In that case, the volume of gas in sealed enclosure 1, Vg, is calculated using Equation 3. Using piston 302, the internal volume of the enclosure is then restored to its original value. If the difference between P 2 and P 3 is greater than 8OPa, or if P1=P 2 , then there is a leakage into or from enclosure 1. In that case, solenoid valves 305a and 305b are used to isolate the portion of enclosure 1 30 between those solenoid valves, and no data is acquired for the sample in sample container 305d, since the results may be inaccurate due to diffusion of oxygen into or out of the container. The acceptable amount of the difference between P 2 and P 3 may be chosen to be less 200, 150, 100, 80, 60, 40, 20, 10, 5 or lPa, or some other acceptable value if required.

WO 2004/092690 PCT/AU2004/000512 35 The method for determining whether there is a gas leakage into or from an enclosure, and for determining the volume of gas in an enclosure and for restoring the internal volume of the enclosure to its original value, as described above, is then repeated for each of the enclosures 2 to 8 in turn, although it is not necessary to measure a new 5 value of P 1 for each enclosure, since P 1 is the same as the ambient atmospheric pressure. For the purpose of the remainder of this description, it is assumed that all of the enclosures 1 to 8 are found not to have a gas leakage into or from the enclosure and not to have any other unacceptable defects, although this will not always be the case. The ambient temperature is then measured, using a voltage divider circuit 10 containing a thermistor, as shown diagrammatically in Figure 1. The voltage Uf determined by the circuit shown in Figure 1 is used to determine the temperature by use of a calibration curve such as that shown in Figure 2. Alternatively temperature may be measured by some other convenient means. This temperature used in all calculations relating to this invention where temperature is required. 15 After determining whether there is a gas leakage into or from enclosures 1 to 8, and determining the volume of gas in enclosures 1 to 8, and restoring the internal volume of enclosures 1 to 8 to their original values, as described above, valves 305a to 312a and 305b to 312b, and valves 391 and 317 are all closed. A gaseous oxygen concentration in enclosure 1 is measured as follows. Solenoid 20 valves 305a, 305b and 317 are opened, while solenoid valves 306a to 312a, 306b to 312b and 391 are closed. Air is then circulated for approximately 5 minutes from sample container 305d through moisture and carbon dioxide filters 315 and 316 respectively to oxygen sensor 318 using pump 314 at a rate of approximately 4x10- 4 m 3 /min. A representative value of oxygen concentration of the air so circulated is detennined, and 25 the time of said determination is recorded. Solenoid valves 305a and 305b are then closed. In a similar manner to that described above for enclosure 1, the oxygen concentrations in enclosures 2 to 8 are measured individually in turn, using the appropriate combinations of solenoid valves, pumps and other components of system 300 shown diagrammatically in Figure 3. 30 After an initial value of gaseous oxygen concentration is measured for each enclosure, pumps 305c to 312c are started and are used continuously throughout the remainder of the test to circulate gas through containers 305d to 312d respectively. The measurement of oxygen concentration of the gas in the enclosures is performed for each enclosure as described above, at approximately hourly intervals over an approximately ten 35 hour period.

WO 2004/092690 PCT/AU2004/000512 36 The volume of sample in each cylindrical sample container is also determined. This may conveniently be done by measuring the depth of the sample in the sample container, and then applying Equation 1 to determine the volume Vm. Alternatively, if the porosity s is known, then the volume Vm may be calculated using Equation 6. If F is not 5 known, it may be determined from known values of Vm (determined by the first method described above) and of V, and Vg by applying Equation 4. The data acquired as described above is stored in computer 319 (Figure 3) or similar data processing device. Once all of the data has been acquired and stored in computer 319 (Figure 3), 10 values of oxygen concentration for each enclosure at each measurement time are converted to a value of oxygen mass using Equation 7. Alternatively, these calculations can be performed during the time that data is being acquired, and the results then stored in the computer. Curves of mass of oxygen against time are then constructed. An example of Am such a curve is shown in Figure 4. The slope of this curve, A, is then determined for 15 each enclosure, and the IOR of the material in each enclosure is calculated using Equation 5. An alternative instrument that may also be used in accordance with the invention is showed diagrammatically in Figure 8. In the following description of the operation of the alternative instrument, an enclosure comprises cylinder 301, pressure sensor 303, 20 manifold 313, one of solenoid valves 305b to 312b, the corresponding one of pumps 305c to 312c, the corresponding one of sample containers 305d to 312d, the corresponding one of CO 2 filters 805b to 812b, the corresponding one of moisture filters 805d to 812e together with tubing connection the above to each other and to the corresponding solenoid valve of 305a to 312a, as shown diagrammatically in Figure 3. The enclosure that 25 incorporates sample container 305d will be referred to as enclosure 1, the enclosure that incorporates sample container 306d will be referred to as enclosure 2 and so forth, such that the enclosure that incorporates sample container 312d will be referred to as enclosure 8. A program written in LabVIEW computer language controls the data acquisition 30 device, solenoid valves, air pumps, linear actuators, thermistor, pressure sensor and oxygen analyser. The methods for determining the volume of each salable container, for determining whether there is a gas leakage into or from each enclosure and for measuring the ambient temperature are the same as was described above for the earlier mode of operation.

WO 2004/092690 PCT/AU2004/000512 37 After determining whether there is a gas leakage into or from enclosures 1 to 8, and determining the volume of gas in enclosures 1 to 8, and restoring the internal volume of enclosures 1 to 8 to their original values, as described above, valves 305a to 312a and 305b to 312b, and valves 391 and 317 are all closed. 5 A gaseous oxygen concentration in enclosure 1 is measured as follows. Solenoid valves 305a, 305b and 317 are opened, while solenoid valves 306a to 312a, 306b to 312b and 391 are closed. Air is then circulated for approximately 5 minutes from sample container 305d through moisture and CO 2 filters 805d and 805b respectively to oxygen sensor 318 using pump 314 at a rate of approximately 4x1 0 4 m 3 /min. A representative 10 value of oxygen concentration of the air so circulated is determined, and the time of said determination is recorded. Solenoid valves 305a and 305b are then closed. In a similar manner to that described above for enclosure 1, the oxygen concentrations in enclosures 2 to 8 are measured individually in turn, using the appropriate combinations of solenoid valves, pumps and other components of system 800 shown diagrammatically in Figure 8. 15 After an initial value of gaseous oxygen concentration is measured for each enclosure, pumps 305c to 312c are started and are used continuously throughout the remainder of the test to circulate gas through containers 305d to 312d and moisture filters 805d to 812d and CO 2 filters 805b to 812b respectively. The measurement of oxygen concentration of the gas in the enclosures is performed for each enclosure as described 20 above, at approximately hourly intervals over an approximately ten hour period. The determination of the volume of sample in each cylindrical container and the data acquisition and calculations are the same as was described for the earlier mode of operation. An advantage of the alternative instrument, as described above and as 25 represented in Figure 8, is that the volume of the system that is not within any of the enclosures is reduced relative to the instrument represented in Figure 3. This reduces the contamination of gases between enclosures when switching from measurement of oxygen concentration in a particular enclosure to measurement of oxygen concentration in another enclosure. However, the choice of which mode of operation is used may depend 30 on the nature of the sample. Samples with very low initial moisture levels may dry out to the point where their IOR is affected if the alternative instrument of Figure 8 is used, whereas the drying effect is less severe when using the instrument of Figure 3. Example I An IOR meter, as shown diagrammatically in Figure 3, was used to measure the 35 IOR of reactive rock samples over a period of approximately 12 hours. Reactive rock WO 2004/092690 PCT/AU2004/000512 38 samples were placed in eight plastic (PVC) sample containers of volume approximately 4x 10-m 3 , which were then sealed in a reversible manner into the IOR meter. Data in this example is provided for the sample in only one representative enclosure of the IOR meter, although similar data might be obtained from the other seven 5 samples. By means of changing the internal volume of a sealed enclosure by a known volume (using piston 302), measuring a pressure in the enclosure after said changing (using pressure sensor 303), and measuring a pressure in the enclosure at a time 40 seconds after the initial measuring, it was determined that there was no leakage from or 10 into the enclosure. This procedure was conducted for each of the enclosures in the IOR meter. In addition, after measurement of the ambient atmospheric pressure, the volume of gas in the representative enclosure was determined to be 3.2x10- 3 m 3 using Equation 3. The volume of material placed into the sample container of the representative enclosure was calculated to be 1.48 x10- 3 m 3 using Equation 6. Pumps 305c to 312c, with flow of 15 4x1 0 4 m 3 /min, were then used to continuously circulate gas through the enclosures, which had been shown to be correctly sealed. At regular intervals of approximately 5000 seconds, the gas from each enclosure was circulated through moisture and carbon dioxide filters to an oxygen analyser which had a resolution better than 0.001% (corresponding to a mass of oxygen less than 3x10 9 g) and then back to the enclosure, at a constant flow of 20 4x1 0-4m 3 /min. The ambient temperature was measured using a thermistor, forming part of a voltage divider circuit shown diagrammatically in Figure 1, and the pressure was measured using a pressure sensor. The mass of oxygen in an enclosure was then calculated for each measurement time, using Equation 7. The values of temperature, oxygen concentration and mass of oxygen for the representative enclosure are shown in 25 Table 1. Table 1: Measured temperature and oxygen concentrations and calculated mass of oxygen at each measurement time. Time (s) Temperature ("C) Oxygen concentration Mass of oxygen (kg) (molar %) 1487 25.9 20.54 8.63x10-4 6115 25.68 20.29 8.53x10 4 10783 25.28 20.07 8.44x10-4 WO 2004/092690 PCT/AU2004/000512 39 15478 24.88 19.86 8.35x10-4 20162 24.49 19.67 8.26x1O~4 24882 24.17 19.48 8.18x10~ 4 29602 23.87 19.31 8.11x10- 4 34322 23.62 19.14 8.04x 104 39043 23.39 18.99 7.97x10~4 43763 23.64 18.81 7.89x1O The values of mass of oxygen in the representative enclosure, obtained from the IOR meter, are shown graphically in Figure 4 as a function of time. This data was used to Am detennine the rate of change of the oxygen mass with time, - in the representative At enclosure. Using Equation 5, the value of IOR for the sample in the representative 5 enclosure was calculated to be 1. 17x10- 6 kg(oxygen)m-3s-1. Example 2 This example describes a process that may be used to control the operation of, and acquire data from, a system for measuring IOR of a plurality of samples in accordance with this invention. The steps of the process are described with reference to 10 Figure 1, Figure 3 and Figure 5. With regard to Figure 3, there is a linear actuator, not shown in Figure 3, which may be used to move piston 302 in order to change the internal gas volume of one or more of enclosures 1 to 8. With regard to Figure 5, as was described above, a similar assembly containing a further four sample containers is located at the rear, behind the assembly shown. Elements in the rear assembly will be referred to in this 15 example with a suffix b. Thus, for example, behind linear actuators 510, 511 and 512 are similar linear actuators 510b, 51 lb and 512b respectively. This does not apply to any numbers representing components in Figures other than Figure 5. In this example there may optionally be a mass flow controller (MFC) which may be inserted into line 366 (Figure 3), between pump 314 and oxygen detector 318. 20 The sequences of operation for startup commence with opening are as follows. The computer opens communications with the following modules: linear actuators, solenoid valves, pumps, mass flow controller (if present), oxygen sensor, pressure sensor, thermistor, then blanks the display panels and initialises graphs. The operator should then input into the computer program the sample containers that are to be tested. The screen of 25 computer 319 then displays the text "test/no test" for the 8 sample containers 305d, 306d, 307d, 308d, 309d, 310d, 311d and 302d. The operator should input the details of the contents of each sample container. The operator is then prompted for a file name. The file WO 2004/092690 PCT/AU2004/000512 40 is then created, and the file name, date, time, contents of sample containers and file headers are saved to a file for each sample container. In order to reset all channels to the OFF state, the following sequence of operations is followed. The voltages for thermistor, MFC (if present) and oxygen air 5 pump to are set to OV. Valves 305a to 312a are closed and the linear actuators are reset to the start position, fully extended (relay OFF): Group A (510, 511 and 512) and Group B (510b, 511b and 512b). Valves 305b to 312b and air valve 391 are then opened. This ensures that there is no pressure built up inside the sample containers so that they will not get stuck and will move down with the sample container holder. Piston 303 is then reset 10 to the start position. After an 8 second delay, the power to linear actuators (510, 511, 512, 510b, 511b and 512b) for the sample container holders (506 and 506b), and the power to piston 302 and linear actuator are turned off. Air valve 391, oxygen pump valve 317 and valves 305b to 312b are then closed, and air pumps 305c to 312c for sample containers are turned off. The operator then places the sample containers on the holders. A prompt 15 appears on the screen of computer 319: "Are the canisters in place on the holders? Press OK when you are ready to begin testing." The start time is displayed on screen of computer 319 and time is set to to for test. To establish a starting pressure, the following procedure is followed. Linear actuators 510, 511, 512, 510b, 511b and 512b are activated. If only testing any or all of 20 sample containers 501 to 504 then only front sample container holder 506 is activated using linear actuators 510, 511 and 512. If only testing any or all of sample containers 501b to 504b then only back sample container holder 506b is activated using linear actuators 5 1Ob, 51 lb and 512b. If testing a plurality of sample containers, at least one of which is one of 501, 502, 503 and 504 and at least one of which is one of 501b, 502b, 25 503b and 504b, then both sample container holders are activated. This operation lifts up and seals the sample containers. The screen of computer 319 displays the text "sealing canister" for each sample container that will be tested. After an 8 second delay to allow for the sample containers to be lifted up, the power to the linear actuators 510, 511, 512, 510b, 511b and 512b is turned off. Air valve 391 and valves 305b to 312b are then 30 opened. This equalises the pressure in all sample containers to atmospheric pressure. The screen of computer 319 displays the text "Equalising Canister" for each sample container to be tested. After waiting 60s for the sample containers and gas lines to equalise to atmospheric pressure, the barometric pressure (ic Pat, atmospheric pressure) is determined and displayed, and the value is saved to file. Solenoid valves 305b to 312b are 35 then closed.

WO 2004/092690 PCT/AU2004/000512 41 In order to check if there is a leak in each sample container to be tested, and to calculate the volume of gas (Vg) in each sample container to be tested, the following procedure is followed. First, the screen of computer 319 displays "measuring pressure in canister/waiting/pressure test completed" for each enclosure that is to be tested. Then, for 5 each enclosure that is being tested, the following procedure is performed. The solenoid valve in manifold 313 that corresponds to the enclosure to be tested is opened, and also air valve 391 is opened for 10 seconds to equalise the single enclosure to atmospheric pressure again. Then air valve 391 is closed. The computer then reads, calculates and stores pressure P 1 from pressure sensor 303. The actuator for piston 302 is activated, to 10 withdraw gas from the enclosure. After waiting 40 seconds for the piston to move and for system to stabilise, the power to the linear actuator is turned off. The computer then reads pressure P 2 from the pressure sensor. After waiting a further 40 seconds to check for a leak in the enclosure seal, the computer reads pressure P 3 from pressure sensor and calculates P 1

-P

2 and P 3

-P

2 . If PI - P 2 < 3 kPa then sample container is not present and this is enclosure is not tested any further, and the screen of computer 319 displays the text "canister not present". If P 3 - P 2 < 0.08 kPa then there is no leak. Otherwise, testing on the enclosure is discontinued and the screen of computer 319 displays the text "leak". If the sample container is present and the enclosure has no leak, then gas volume, Vg is calculated and stored, and the piston returned to its starting position. After waiting a 20 further 8 seconds, the solenoid valve in manifold 313 that corresponds to the enclosure is closed. The screen of computer 319 then displays either the text "Leak" or the text "No Leak" for each enclosure. If all of the enclosures have a leak or they are not present the system will shutdown. Otherwise it proceeds to determine IOR for those enclosures that have no leak. 25 In order to determine the air temperature, measure oxygen concentration, determine change in mass of oxygen and determine the IOR the following procedure is followed. First the text "Waiting" is displayed for the sample containers that are being tested. 1.5V is applied to thermistor (see Figure 1) so that the temperature can be read. After waiting for 5 seconds, voltage Uf is read the from the voltage divider of the 30 thennistor, and the temperature is calculated, displayed and stored. The voltage that was applied to the thermistor is then turned off. If present, the MFC is activated and flow rate set to 0.4 L/min. Then, for each cycle the following procedure is followed. Firstly, for each enclosure that is being tested the following operations are conducted, in order to determine a mass of oxygen in each of the enclosures. The two solenoid air valves (one in 35 each of manifolds 304 and 313) corresponding to the enclosure being tested, are opened at WO 2004/092690 PCT/AU2004/000512 42 the same time. Air pump valve 317 is also opened, and air pump 314 is turned on by setting the voltage of the pump to 1.75V. After eight minutes of running air pump 318, the output from oxygen analyser 318 is read, calculated and stored every 10 seconds for 60s, and the average reading for the 60s is calculated, display and stored, and the time txi 5 seconds when the average value was calculated is also recorded. Therefore, air pump 318 runs for nine minutes in total. The mass of oxygen, mx, 1 is then calculated, displayed and then stored in the file. After each measurement of the mass of oxygen except for the first measurement for each sample, the IOR for the sample is then calculated using a linear fit to the data stored in the file, and is then displayed on the screen of computer 319. (IOR is 10 expressed in either units kg(0 2 )kg(material)'s 1 or kg(0 2 )m 3 s 1 depending on which units were selected on the main screen of computer 319 by the user. If in kg(material) then user should enter mass of material on the computer 319 before test started and if m 3 then user should have entered volume of material on the computer 319 before test started.) The mean square error to the 15 fit of the IOR is then calculated and stored in the file. Air pump 314 is then turned off by setting the voltage to the pump to OV, and the air pump valve 317 and solenoid valves in manifolds 304 and 313 corresponding to the enclosure being tested are closed. Then the air pumps in all of the enclosures, 305c to 312c are turned on, and the screen of computer 319 displays the text "Waiting till next oxygen measurement". After a delay of several 20 minutes (the exact time is set by the user on the computer) for the gas in the sample containers may to circulate and mix, the air pumps, 305c to 312c are turned off. After all cycles are complete, separate graphs of the mass of oxygen vs time are displayed for each of the enclosures that are being tested. In order to shut down the system, the following process is followed. The screen 25 of computer 319 displays the text "Testing completed". The voltages for thermistor, MFC (if present) and oxygen air pump are set to OV. Valves 305a to 312a are closed, the linear actuators are reset to the start position, fully extended (turn the relay OFF): Group A (510, 511 and 512) and Group B (510b, 51lb and 512b). Valves 305b to 312b and air valve 391 are opened. This ensures that there is no pressure built up inside the sample containers so 30 that they will not get stuck and will move down with the sample container holder. Piston 302 is reset to the start position. After waiting for 8 seconds, power to linear actuators 510, 511, 512, 510b, 511b and 512b for the sample container holders and power to piston 302 and linear actuator are turned off. Then air valve 391, oxygen pump valve 317 and valves 305b to 312b are closed. Air pumps 305c to 312c are turned off, and WO 2004/092690 PCT/AU2004/000512 43 communications to linear actuators, solenoid valves, pumps, mass flow controller (if present), oxygen sensor, pressure sensor, thermistor are then closed.

Claims

1. A method for determining an internal gas volume in a sealed enclosure comprising: a) measuring a first gas pressure in the sealed enclosure; 5 b) changing the internal volume of the sealed enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; c) measuring a second gas pressure in the sealed enclosure after said changing as a function of time; 10 d) determining from said second gas pressure as a function of time whether there is a gas leak from or into said sealed enclosure; e) where there is no gas leak from or into said sealed enclosure, determining the internal gas volume of the sealed enclosure from the first and second gas pressures and the known volume. 15

2. A method for determining a gas-filled porosity of a sample of material, said method comprising: a) placing the sample in an openable sealable enclosure capable of holding the sample; 20 b) sealing the enclosure; c) measuring a first gas pressure in the enclosure; d) changing the internal volume of the enclosure by a known volume; e) measuring a second gas pressure in the enclosure after said changing; f) determining a volume occupied by the sample; and 25 g) determining the gas-filled porosity of the sample from the volume occupied by the sample, the volume of the enclosure and the volume of gas in the enclosure when the sample is in the enclosure.

3. A method for measuring an intrinsic oxidation rate of a sample 30 comprising: a) placing the sample of material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first gas pressure in the enclosure; WO 2004/092690 PCT/AU2004/000512 45 d) changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; e) measuring a second gas pressure in the enclosure after said changing as a 5 function of time; f) determining from said second gas pressure as a function of time whether there is a gas leak from or into said enclosure; g) where there is no gas leak from or into said enclosure, determining the internal gas volume of the enclosure from the first and second gas pressures and the known 10 volume; h) determining the volume of the sample from the internal gas volume of the enclosure, the first and second gas pressures, the known volume and the porosity of the sample; i) determining a change in gaseous oxygen mass in the enclosure as a function of 15 time; and j) determining the intrinsic oxidation rate of the sample.

4. The method of claim 3 wherein the intrinsic oxidation rate is determined using a formula selected from the group consisting of: 20 IOR = Am (5) and IOR = (Sa) where: IOR = intrinsic oxidation rate 25 Am = change in gaseous oxygen mass At = time period Vm = volume of the sample Mm = dry mass of the sample, wherein equation 5 is used to determine a volume based intrinsic oxidation rate and 30 equation 5a is used to determine a mass based intrinsic oxidation rate.

5. The method of claim 3 wherein the step of determining a change in gaseous oxygen mass comprises measurement of gaseous oxygen concentration. WO 2004/092690 PCT/AU2004/000512 46

6. The method of claim 5 wherein the measurement of gaseous oxygen concentration is conducted over a period of less than about 24 hours. 5

7. The method of claim 5 wherein individual values of gaseous oxygen concentration are obtained at least once every hour throughout an overall measurement period.

8. The method of claim 5 further comprising measuring a concentration of 10 carbon dioxide in the enclosure

9. The method of claim 8 comprising compensating the measurement of gaseous oxygen concentration for the concentration of carbon dioxide. 15

10. The method of claim 5 wherein gas from the enclosure is passed through a filter before a measurement of gaseous oxygen concentration is made.

11. The method of claim 3 wherein a gas in the enclosure is circulated. 20

12. A method of estimating a rate of oxygen consumption in a pile of material which is oxygenated, comprising: a) placing a sample of the material in a closable sealable enclosure; b) closing and sealing said enclosure; c) measuring a first gas pressure in the enclosure; 25 d) changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; e) measuring a second gas pressure in the enclosure after said changing as a function of time; 30 f) determining from said second gas pressure as a function of time whether there is a gas leak from or into said enclosure; g) where there is no gas leak from or into said enclosure, determining the internal gas volume of the enclosure from the first and second gas pressures and the known volume; WO 2004/092690 PCT/AU2004/000512 47 h) determining the volume of the sample from the internal gas volume of the enclosure, the first and second gas pressures, the known volume and the porosity of the sample; i) determining a change in gaseous oxygen mass in the enclosure as a function of 5 time; j) determining the intrinsic oxidation rate of the sample; k) determining a volume of the pile of material; and 1) estimating the rate of oxygen consumption in the pile of material from the volume of the sample, the intrinsic oxidation rate of the sample and the volume of 10 the pile of material.

13. A method of determining intrinsic oxidation rates of a plurality of samples, wherein the intrinsic oxidation rates are measured over the same period of time, comprising: 15 a) loading said plurality of samples into a plurality of enclosures; b) determining if any of the enclosures has a gas leak; c) for each enclosure with no gas leak, measuring an internal gas volume for said enclosure; and d) for each enclosure with no gas leak, determining an intrinsic oxidation rate of the 20 sample therein.

14. The method of claim 13 wherein the intrinsic oxidation rate of each sample in an enclosure with no gas leak is determined using a formula selected from the group consisting of: 25 IOR =- (5) and IOR - (5a) MmAt where: IOR = intrinsic oxidation rate 30 Am = change in gaseous oxygen mass At = time period Vm volume of the sample Mm dry mass of the sample WO 2004/092690 PCT/AU2004/000512 48 wherein equation 5 is used to determine a volume based intrinsic oxidation rate and equation 5a is used to determine a mass based intrinsic oxidation rate.

15. A method for determination of a spatial distribution of intrinsic 5 oxidation rate within a waste heap comprising the steps of: a) obtaining samples from different locations in the waste heap, b) measuring an intrinsic oxidation rate for at least two of the samples, and c) detennining a spatial distribution of intrinsic oxidation rate within the waste heap. 10

16. A system for determining an internal gas volume in a sealed enclosure, comprising: a) an openable salable enclosure; b) a volume adjustor for changing the internal volume of the enclosure by a known 15 volume, whereby the gas pressure in the enclosure is less than or greater than the gas pressure outside the enclosure; and c) a pressure measuring device for measuring the gas pressure in the enclosure as a function of time. 20

17. A system for determining a gas-filled porosity of a sample of material comprising: a) an openable salable enclosure; b) a volume adjustor for changing the internal volume of the enclosure by a known volume, whereby the gas pressure in the enclosure is less than or greater than the 25 gas pressure outside the enclosure; c) a pressure measuring device for measuring the gas pressure in the enclosure as a function of time; d) a volume calculator for calculating the volume of the sample; and e) a porosity calculator. 30

18. A system for measuring an intrinsic oxidation rate of a sample comprising: a) an openable salable enclosure capable of holding the sample; b) a volume adjustor for changing the internal volume of the sealed enclosure by a 35 known volume, said adjustor being coupled to the enclosure; WO 2004/092690 PCT/AU2004/000512 49 c) a pressure measuring device for measuring gas pressure and a temperature measuring device for measuring temperature; and d) an oxygen meter for measuring gaseous oxygen concentration of a gas in the enclosure. 5

19. The system of claim 18 wherein the oxygen meter is capable of measuring gaseous oxygen concentration as a function of time.

20. The system of claim 19 additionally comprising an intrinsic oxidation 10 rate determiner for determining the intrinsic oxidation rate of the sample from the measuring of gaseous oxygen concentration and the resultant change in gaseous oxygen mass as a function of time and from the volume of the sample.

21. The system of claim 18 additionally comprising a gas circulator for 15 circulating the gas.

22. The system of claim 18 wherein the oxygen meter is located outside the enclosure, and there is a transport system to transport some or all of the gas in the enclosure to said oxygen meter. 20

23. The system of claim 18 additionally comprising a carbon dioxide meter for measuring a concentration of carbon dioxide in the gas.

24. The system of claim 18 having a compensator for compensating the 25 measurement of gaseous oxygen concentration for the concentration of carbon dioxide.

25. The system of claim 18 additionally comprising a filter to prevent access to said oxygen meter by a material that is capable of damaging said meter or of altering its ability to accurately measure a concentration of oxygen in a gas. 30

26. A system for determining an intrinsic oxidation rate for a plurality of samples comprising: a) a plurality of openable sealable enclosures capable of holding the samples; b) a volume measuring system for determining the gas volume of each of said 35 enclosures individually; WO 2004/092690 PCT/AU2004/000512 50 c) a leak detection system for determining for each enclosure separately whether that enclosure has a gas leak; d) an intrinsic oxidation rate detection system for determining for each enclosure separately the intrinsic oxidation rate of the sample in said enclosure. 5

27. The system of claim 26 wherein the intrinsic oxidation rate detection system comprises an oxygen meter for measurement of a gaseous oxygen concentration.

28. The system of claim 27 wherein more than one of the enclosures is 10 connected to the oxygen meter, said oxygen meter being located outside the enclosures.

29. The system of claim 26 additionally comprising a carbon dioxide meter for measuring a concentration of carbon dioxide in each enclosure. is

30. The system of claim 29 having a compensator for compensating the measurement of gaseous oxygen concentration for the concentration of carbon dioxide.

31. The system of claim 26 additionally including an isolator to isolate an enclosure. 20

32. A system for determining a spatial distribution of intrinsic oxidation rates within a waste heap comprising: a) a sampling system for obtaining samples from different locations within the heap; 25 b) a plurality of openable sealable enclosures capable of holding the samples; c) a volume measuring system for determining the gas volume of each of said enclosures individually; d) a leak detection system for determining for each enclosure separately whether that enclosure has a gas leak; 30 e) an intrinsic oxidation rate detection system for determining for each enclosure separately an intrinsic oxidation rate of the sample in said enclosure; and f) distribution determiner for determining a spatial distribution of intrinsic oxidation rates. WO 2004/092690 PCT/AU2004/000512 51

33. A system for estimating a rate of oxygen consumption of a pile of material which is oxygenated, comprising; a) an openable sealable enclosure capable of holding a sample of the material; b) a volume adjustor for changing the internal volume of the enclosure by a known 5 volume, said adjustor being coupled to the enclosure; c) a pressure measuring device for measuring gas pressure and a temperature measuring device for measuring temperature; d) an oxygen meter for measuring gaseous oxygen concentration of a gas in the enclosure in order to determine an intrinsic oxidation rate of the sample; 10 e) a volume estimator for estimating a volume of the pile of material; and f) an oxygen consumption calculator for calculating the rate of oxygen consumption of the pile from the intrinsic oxidation rate and the volumes of the sample and of the pile.