Landfill gas production testing and extraction method
First Claim
1. A method of determining flow of a gas component through a surface of ground, the method comprising the steps of:
- measuring a gas pressure at a selected depth below the surface multiple times at each of a first plurality of locations with respect to the surface over a predetermined period to obtain a temporal average gas pressure for the predetermined period at each of the first plurality of locations and a spatial distribution of the average gas pressure;
determining pneumatic permeability of the ground at a second plurality of locations with respect to the surface to obtain a spatial distribution of permeability;
measuring a gas component at a third plurality of locations to obtain a spatial distribution thereof; and
determining gas component flow through the surface based on the temporal average gas pressures and their spatial distribution and the spatial distributions of permeability and gas component.
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Accused Products
Abstract
A method for determining total landfill gas production capability and pollutant emission rates involves measuring gas pressure in a soil cover at various locations around the landfill. These measurements are preferably made successively and repeated. The tester determines an average gas pressure and its spatial uncertainty envelope and measures soil pneumatic permeabilities by taking soil samples, preferably at various locations. The soil is tested to determine viscous and inertial resistance coefficients to characterize permeability. The gas composition is determined preferably at each pressure measuring location, and the coefficients, gas pressure and composition measurements are used to calculate total gas emission. A method of controlling gas extraction so that gas pressure in the soil cover approaches or becomes atmospheric pressure includes measuring gas pressure and relative permeability of the soil at various locations, relative flows of air into, or landfill gas out of, the surface are determined, and the extraction pressures at collection wells are adjusted in view of the flow through the soil until the relative flow at each location is zero or substantially zero.
71 Citations
24 Claims
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1. A method of determining flow of a gas component through a surface of ground, the method comprising the steps of:
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measuring a gas pressure at a selected depth below the surface multiple times at each of a first plurality of locations with respect to the surface over a predetermined period to obtain a temporal average gas pressure for the predetermined period at each of the first plurality of locations and a spatial distribution of the average gas pressure; determining pneumatic permeability of the ground at a second plurality of locations with respect to the surface to obtain a spatial distribution of permeability; measuring a gas component at a third plurality of locations to obtain a spatial distribution thereof; and determining gas component flow through the surface based on the temporal average gas pressures and their spatial distribution and the spatial distributions of permeability and gas component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of controlling an extraction rate of gas from ground at various positions in the ground at which the gas is extracted, the method comprising the steps of:
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determining gas pressure below a surface of the ground at multiple locations with respect to the surface; determining a relative permeability of the ground to the gas at each of the locations; calculating an adjusted value of the gas pressure at each of the multiple locations based on the relative permeability; and adjusting the extraction rate at each of the positions in the ground at which the gas is extracted based on relative flow of the gas into and out of the ground as indicated by the adjusted values of the gas pressure. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method of controlling an extraction rate of gas from underground positions in a landfill comprising trash and a cover layer, the method comprising the steps of:
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determining gas pressure relative to a reference pressure at a predetermined depth in the cover layer at multiple locations with respect to a surface of the landfill; determining permeability of the cover layer to the predetermined depth at each of the multiple locations relative to a reference amount; dividing each gas pressure by each relative permeability, respectively, to obtain a relative flow; obtaining a spatial distribution of the relative flow; and increasing the extraction rate at positions corresponding to positive flow and decreasing the extraction rate at positions corresponding to negative flow, where positive flow represents gas flow out of the landfill and negative flow represents air flow into the landfill. - View Dependent Claims (20, 21, 22)
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23. A method of extracting gas from various underground positions and determining an additional amount of gas that can be extracted from the underground, the method comprising the steps of:
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extracting the gas; determining gas pressure relative to a reference pressure at a predetermined depth underground at multiple locations with respect to a surface of the ground; determining permeability of the ground to the predetermined depth at each of the multiple locations relative to a reference amount; dividing each gas pressure by each relative permeability, respectively, to obtain a relative flow having areas of negative relative flow and positive relative flow; obtaining a spatial distribution of the relative flow; and determining an amount of additional gas that can be extracted by summing up relative positive flow amounts to obtain a total positive relative flow and multiplying the positive relative flow by a calibration factor, the calibration factor being obtained by determining a total flow rate of air into the ground, summing up the negative relative flow rate to obtain a total negative relative flow, and taking a ratio of the total flow rate of air and the total negative relative flow. - View Dependent Claims (24)
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Specification