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Title:
AN ARRANGEMENT AND A METHOD OF UTILIZING LANDFILL GASES
Document Type and Number:
WIPO Patent Application WO/1998/007974
Kind Code:
A1
Abstract:
An arrangement for utilizing biogas or landfill gas includes a plurality of gas-collecting units (2) disposed in at least one waste-material landfill (1). The gas-collecting units are connected via conduits (3) to a common collecting station (4) which generates a subpressure in the conduits and from which collected gas is used to fuel an internal combustion engine (6), preferably an engine intended for powering an electric generator. The suction side (7) of the engine (6) is connected to the conduits (3) such as to generate in the conduits the subpressure required for said gas collection. In a method of utilizing landfill gas, the gas is collected at the gas-collecting sites (2) and transported therefrom to the collection station (4). The suction side (7) of the engine (6) is connected to the conduits (3), suitably after being started-up with conventional fuel, so as to generate in the conduits the subpressure necessary to collect the gas.

Inventors:
HANSSON HANS-ERIK (SE)
Application Number:
PCT/SE1997/001378
Publication Date:
February 26, 1998
Filing Date:
August 21, 1997
Export Citation:
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Assignee:
ABB POWERMAN AB (SE)
HANSSON HANS ERIK (SE)
International Classes:
F02B43/10; F02M21/02; C02F11/04; (IPC1-7): F02M21/02; F02B43/10; C02F11/04
Foreign References:
Other References:
PATENT ABSTRACTS OF JAPAN, Vol. 7, No. 151, C-174; & JP,A,58 064 199 (TOKYO SHIBAURA DENKI K.K.), 16 April 1983.
PATENT ABSTRACTS OF JAPAN, Vol. 7, No. 175, C-179; & JP,A,58 081 497 (MITSUBISHI DENKI K.K.), 16 May 1983.
PATENT ABSTRACTS OF JAPAN, Vol. 7, No. 191, C-182; & JP,A,58 092 500 (TOKYO SHIBAURA DENKI K.K.), 1 June 1983.
Attorney, Agent or Firm:
Nilsson, Karl (P.O. Box 4630, Stockholm, SE)
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Claims:
CLAIMS
1. An arrangement for utilizing biogas or landfill gas, comprising a plurality of gas collecting units (2) disposed in at least one wastematerial landfill (1) and connected by conduits (3) to a collecting station (4) which is common to said conduits and which generates a subpressure therein, wherein gas collected in said collecting station is used to fuel an internal combustion engine (6) intended preferably for powering an electric generator, characterized in that the suction side (7) of the engine (6) is connected to said conduits (3) in a manner to generate therein the subpressure required for said gas collection.
2. An arrangement according to Claim 1, characterized in that the gas conduits (3) are connected to a fuel/air mixer (10) which works at a subpressure and which functions to mix the collected landfill gas with combustion air prior to delivery to the engine (6), and in that a pressure reduction device (12) for reducing the pressure of said combustion air is connected upstream of the mixer (10) and functions to adapt the pressure of said air to the pressure of the incoming landfill gas.
3. An arrangement according to Claim 2, characterized in that the outlet side of the mixer (10) is connected to a fuel/air mixture supercharger (1517) driven by engine exhaust gases.
4. An arrangement according to Claim 3, characterized in that the outlet of the fuel/air mixture supercharger (1. 517) is connected to a further mixer (24) whose inlet side is also connected to the outlet side of a compressor (17) for compressing additional combustion air, said compressor being driven by engine exhaust gases.
5. An arrangement according to Claim 1, characterized in that the gas conduits (3) are connected to the subpressure side of an exhaustgas driven compressor (17) whose outlet side is connected to a fuel/air mixer (10), and in that the inlet side of the mixer (10) is also connected to the outlet side of an exhaustgas driven combustion air compressor (17), while the outlet side of said mixer is connected to the fuel/air inlet (7) of said engine (6).
6. An arrangement according to Claim 4 or Claim 5, characterized by means (20) for setting the flows of exhaust gases used to operate the two compressors (17).
7. An arrangement according to any one of Claims 16, characterized in that the engine (6) is also connected to a conventional fuel supply (25) for starting said engine.
8. A method of utilizing biogas or landfill gas in which the gas is collected at a plurality of sites (2) disposed throughout at least one landfill (1), from which the gas is transported through conduits (3) to a collecting station (4) that generates a subpressure in said conduits, and in which collected gas is utilized to fuel an internal combustion engine (6), preferably an engine for powering an electric generator, characterized by connecting the suction side (7) of said engine (6) to said conduits (3), suitably after starting the engine with conventional fuel, such as to generate in said conduits the subpressure necessary for said gas collection.
9. A method according to Claim 8, characterized by mixing the landfill gas with combustion air prior to delivering said gas to the engine (6), optionally after demoisturizing the gas to a given extent, and reducing the pressure of the combustion air to the pressure of the landfill gas prior to mixing said air with said gas.
10. A method according to Claim 9, characterized by compressing the mixture of landfill gas and combustion air in a supercharger (1517) which is driven by engine exhaust gas prior to delivering said mixture to the engine (6) and optionally after admixing said mixture with further combustion air.
Description:
AN ARRANGEMENT AND A METHOD OF UTILIZING LANDFILL GASES The present invention relates to an arrangement for utilizing biogases or landfill gases, said arrangement including a plurality of gas-collecting units dispersed throughout at least one landfill and connected by conduits to a common gas collecting station that generates a subpressure in respective conduits, wherewith collected gas is used to fuel an internal combustion engine, preferably an engine that powers an electric generator. The invention also relates to a novel method of utilizing landfill gas.

When waste materials that have a high content of organic materials decompose, or rot, anaerobically there are generated gases of high methane content which must be recovered in order to avoid troublesome greenhouse effects.

Although the gases generated in landfills can be simply burned off, it is desirable to recover the energy content of these gases when such recovery can be achieved economically.

Accordingly, the object of the present invention is to provide an arrangement which is of such simple construction and which demands such low investment costs as to enable the energy content of landfill gases to be recovered with good economy.

It is proposed to this end in accordance with the invention that the suction side of the internal combustion engine in an arrangement of the kind mentioned in the introduction is connected to said conduits in a manner to generate therein the subpressure that is required in order to achieve said gas collection. This avoids beneficially the need for separate pumps and/or compressors to collect and handle the landfill gases. The engine may be a standard engine, with or without supercharging, in addition to which only simple and

inexpensive auxiliary equipment is required for recovering the energy content of the landfill gases.

The invention also relates to a method of achieving the advantages indicated in the aforegoing. To this end, there is provided a method according to the preamble of Claim 8 that also comprises the method steps set forth in the characterizing clause of Claim 8.

Other advantages and features characteristic of the invention will be apparent from the depending Claims and also from the following description of chosen exemplifying embodiments of the inventive arrangement illustrated in the accompanying drawings, in which Figs. 1-4 are respective schematic illustrations of a first, a second, a third and a fourth embodiment of the invention.

Those features of these embodiments that coincide or generally coincide with one another have been identified by the same reference signs in respective Figures.

In Fig. 1, the reference numeral 1 identifies a landfill in which decomposition of organic material occurs under anaerobic conditions such as to generate essentially moist methane gas. This gas is collected typically with the aid of a plurality of gas-collecting units 2, for instance perforated pipes buried in the landfill. The gas is conducted in conduits 3 to a collecting station 4 that is common to said conduits and from which the gas is further conducted through a conduit 5, optionally after demoisturizing the gas.

The landfill gas is utilized in an arrangement that includes an internal combustion piston-engine 6 having a suction side 7 and an exhaust side 8. Although not shown, the engine 6 may be conveniently arranged to drive an electric generator.

The engine 6 is driven on a mixture of landfill gas and air.

The air enters through a conduit 9 and the air and gas are mixed together in a gas/air mixer 10 whose outlet is connected to the suction side 7 of the engine via a conduit 11. When the plant is working, the engine will thus generate a subpressure in the conduit 11 and, via the mixer 10, also in the conduits 5 and 9. Because of the subpressure generated in the conduit 5, the landfill gas will be transported from the landfill 1 to the collecting station 4, via the units 2 and the conduits 3. Mounted in the conduit 9, whose inlet side is connected to atmosphere, is a pressure reduction device 12 by means of which the pressure immediately upstream of the mixer 10 is reduced to a value at which air will enter the mixer 10 instead of being forced into the gas conduit 5, such as to obtain a desired gas/air mixture in said mixer, this gas/air mixture being led to the engine 6 via a throttle valve 13 mounted in the conduit 11, e. g. a typical gas throttle, by means of which the power output of the engine 6 can be regulated. As a result of the illustrated arrangement, the pressure reduction device 12 is the sole means required in utilizing the landfill gas additional to the engine 6 and its standard accessories. Reference numeral 25 indicates a conventional fuel tank, e. g. for gasoline, gasol, ethanol, for instance. The fuel can be delivered to the engine 6 via a control valve 26, for the purpose of starting the engine and optionally also to support engine combustion temporarily, if necessary.

The embodiment illustrated in Fig. 2 differs from the embodiment illustrated in Fig. 1 insomuch that the engine 6 is fitted with a conventional, exhaust-gas driven supercharger that includes a turbine 15 which is driven by the exhaust gases exiting through the conduit 14 and which, in turn, drives, via a shaft 16, the compressor 17 that generates the subpressure in the mixer 10 and in the conduits

5 and 9, and also generates an overpressure in the conduit 11 in a known manner.

The embodiment illustrated in Fig. 3 includes two turbines 15 that are driven by exhaust gases and that each drive a respective compressor 17 via respective shafts 16. One of the compressors 17 draws-in combustion air through the conduit 9 and the other compressor draws-in landfill gas through the conduit 5, wherewith the air and the gas are compressed in respective compressors 17 prior to entering the fuel/air mixer 10. The exhaust conduit 14 is branched to form two exhaust conduits 18 and 19 which each supply a respective exhaust gas turbine 15, wherewith a throttle 20 mounted in one branch conduit 19 is used to set the flow of exhaust gas in the conduits 18 and 19, and therewith set the capacity of the compressors 17.

In the case of the Fig. 4 embodiment, gas and air are drawn into a mixer 10 via a supercharger 15,16,17 in the same way as that described above with reference to Fig. 2. Further air entering through a branch conduit 21 is compressed in a further supercharger 15,16,17. The compressed gas/air mixture and the compressed air exiting through respective conduits 22,23 are mixed together in a second mixer 24, from which the gas/air mixture produced therein is delivered to the engine 6 via the throttle 13 and the conduit 11. The throttle 20 is also adjusted for the ratio between the exhaust-gas flows in the conduits 18 and 19.

It will be understood that the invention is not restricted to the aforedescribed and illustrated exemplifying embodiments thereof and that it can be implemented in any desired manner within the scope of the inventive concept as defined in the following Claims.