CN102053054A - Method for on-site measuring permeability coefficient of landfill gas - Google Patents

Abstract

A method for on-site measuring permeability coefficient of landfill gas adopts a measurement system comprising a lower opened tube well, a gas pressure sensor, a gas pressure display recording instrument, an extraction pipeline valve, a leachate emptying valve, a leachate emptying pipe, a gas measuring apparatus and a centrifugal fan. The method adopting extraction mode comprises the following step tube well internal pressure and extraction flow rate are recorded after the gas is stable; and the permeability coefficient of landfill gas is obtained after the substitution to a stationary model. In the method, not only are the conventional extraction pipeline and equipment in a landfill utilized, but also the defects of easy explosion and high hazards which are caused after air and methane are mixed when gas injection mode is adopted are overcome, further the characteristics of landfill covering permeability and permeability coefficient difference in horizontal direction and vertical direction of the landfill caused by layered landfilling and compaction are fully considered. Therefore, the method provided by the invention has the advantages of high measurement accuracy, simple system, and convenience in operation; in addition, key parameters are provided for the pollution control and the recycling of the landfill gas, so that the method has a promised application prospect.

Description

A kind of method of in-site measurement landfill heap body gas permeability coefficient

Technical field

The present invention is a kind of method of in-site measurement landfill heap body gas permeability coefficient, belongs to the resource and environment technical field.

Background technology

Sanitary Landfill Technology is the main mode of long duration interior China urban garbage disposal after reaching at present.The dirty landfill gas of garbage loading embeading gas (landfill gas is called for short LFG) is one of major pollutants of house refuse sanitary landfill generation, and it is a kind of inflammable, explosive and greenhouse gas, and environment and health are had potential threat.According to the relevent statistics, the whole nation was total to about 7.5 hundred million tons of landfill waste in nearly ten years, growth rate according to the present garbage loading embeading of China, landfill gas yield model according to IPCC calculates, since calendar year 2001 landfill to the year two thousand thirty landfill finish to end, discharge 1.3 hundred million tons in methane altogether, the year two thousand thirty methane production reach 1,000 ten thousand tons of peak.(reduce landfill or recycle landfill gas) if can not adopt an effective measure to landfill yard, a large amount of discharge of methane will aggravate climate change, and the surrounding enviroment to landfill yard cause severe contamination simultaneously.

Simultaneously landfill gas is again a kind of energy of recyclable utilization, if recycle, but then pollution abatement, turns harm into good.The Clean Development Mechanism (CDM) of Kyoto Protocol regulation has been established economic base for large-scale developing and utilizing of landfill gas undoubtedly.The introducing of Clean Development Mechanism (CDM) makes general landfill gas recycle project and can obtain huge foreign capitals support, and the project that can guarantee cost-recovering in 3 or five years makes that the owner is ready to invest, thereby developed widely in China.

Understand the data that weather department announces according to China national State Development and Reform Commission person, by on April 14th, 2010, the CDM project of China's approved had 2497, estimated that a year reduction of discharging total amount is about 4.35 hundred million tons of CO ₂E (CO ₂Equivalent), the wherein garbage disposal number of entry only accounts for 2.7% of project sum, and a year CER accounts for 2.1% of total amount.According to the statistics of UNFCCC, by on March 31st, 2010, the registration CDM project of the United Nations had 2121, wherein 781 (36.82%) of China; Garbage disposal project in the United Nations's registration has 465 (18.02%).Present China has 48 landfill gas and utilizes the CDM project to obtain National Development and Reform Committee's approval, has 23 projects to obtain registration, and the registration project is with 4,000,000 tons of average annual reducing emission of carbon dioxide.About 400,000 tons CER that amounts to that 6 projects have obtained to sign and issue is arranged in the landfill gas project of these 23 registrations, account for and all sign and issue 17% of project, brought 4,000 ten thousand yuan considerable income for China owner.These projects have obtained economy and environmental benefit by collecting landfill gas and combustion power generation or heat supply air feed.

No matter be effective control that landfill gas pollutes, still collect and utilize, all must grasp Penetration Signature and the migration rule of landfill gas in junk-heap body.Gas permeability coefficient is the key parameter of landfill gas migration, is the underlying parameter that carries out engineering design.And the data of order landfill heap body gas permeability coefficient are also fewer, and data and field condition (landfill structure, landfill age, rubbish kind and water cut etc.) close relation, need badly and carry out on-site measurement.

At present domestic relevant landfill heap body gas permeability coefficient on-site measurement method and study and do not appear in the newspapers, external only Rasmussen (1993), Massmann (1994), Cestaro (2003) and P.Jain (2005) etc. adopt the mode of injecting compressed air to measure pressure and extraction flow under the certain flow per capita, adopt Model Calculation landfill heap body gas permeability coefficient, the concentration of methane is 5～15% o'clock and because air mixes afterwards with landfill gas, very easily blast, dangerous high, therefore in actual landfill yard, be difficult to promote.

Summary of the invention

The method that the purpose of this invention is to provide a kind of in-site measurement landfill heap body gas permeability coefficient, adopt air suction mode, can utilize existing exhaust pipe of landfill yard and equipment, can overcome again when adopting method of gas injection very easily blast behind the air and methane blended, dangerous high shortcoming, pollute for landfill gas and to control and recycling provides key parameter.

Technical scheme of the present invention is as follows:

A kind of method of in-site measurement landfill heap body gas permeability coefficient, it is characterized in that: the measuring system that this method adopts comprises bottom perforate pipe well, gas pressure sensor, gaseous tension display recorder, pump-line valve, gas meter and centrifugal blower; Described gas pressure sensor is installed in the top of pipe well, is connected with described gaseous tension display recorder by data line; Described centrifugal blower is communicated with the upper end of pipe well by gas piping, and described pump-line valve and gas meter are installed on the gas piping; Percolate blow-down pipe and percolate emptying valve also are housed on the gas piping between pump-line valve and the gas meter;

Described method comprises the steps:

1) on landfill heap body, holes, the running casing while boring, put into bottom perforate pipe well and gravel packing after waiting to reach projected depth, then sleeve pipe is pulled up, backfill boring is taken out between pipe well perforate part top and the overlayer below landfill material and compacting, the clay sealing is adopted in the top, prevents to produce the advantage passage;

2) open percolate emptying valve, with the percolate emptying of accumulating in the percolate blow-down pipe;

3) closing percolate emptying valve, open the pump-line valve, start centrifugal blower, and open gas pressure sensor and gaseous tension display recorder, is 20～100m with the gas meter flow set ³/ h;

4) treat the stable reading of gaseous tension display recorder and gas meter after, extraction flow Q and the pressure P of record this moment _wNumerical value;

5) according to extraction flow Q and pressure P _wBetween corresponding relation:

$P_w^2=P_{\mathrm{arm}}^2-\frac{{\mathrm{QP}}_{\mathrm{arm}}{\mathrm{\μ}}_a}{{\mathrm{\πk}}_r}f---\left(1\right)$

Wherein

$f=\frac{a}{r_w}\{\frac{K_o\left(M_o\frac{r_w}{a}\right)}{{\mathrm{bK}}_z\left(M_o\frac{r_w}{a}\right)}+\frac{2}{\mathrm{\π}(l-d)}{\mathrm{\Σ}}_{n=1}^{\∞}[\frac{\sin \left(\frac{\mathrm{n\πt}}{b}\right)-\sin \left(\frac{\mathrm{n\πd}}{b}\right)}{{\mathrm{nM}}_n{K}_z\left(M_n\frac{r_w}{a}\right)}\left]\cos \left(\frac{\mathrm{n\πd}}{b}\right)K_o\left(M_n\frac{r_w}{a}\right)\right\}---\left(2\right)$

$a^2=\frac{k_r}{k_z}---\left(3\right)$

$M_n=\sqrt{\left(\frac{k_c}{{\mathrm{bb}}_c{k}_z}\right)+{\left(\frac{\mathrm{n\π}}{b}\right)}^2},$ n＝0，1，2，...(4)

In the formula, P _wBe gas absolute pressure in the pipe well, Pa; P _AtmBe atmospheric pressure, Pa; Q is an extraction flow, m ³/ s; k _rBe landfill heap body horizontal direction gas permeability coefficient, m ²k _zBe landfill heap body vertical direction gas permeability coefficient, m ²μ _aBe the kinematic viscosity of landfill gas, Pas; B is the distance of lining to the overlayer bottom, m; b _cBe cover thickness, m; L is the distance between overlayer bottom to the pipe well bottom, m; D is the distance of overlayer bottom to pipe well perforate part top, m; r _wBe the internal diameter of pipe well, m; A is the ratio of landfill heap body level and vertical direction gas permeability coefficient; F, M _nBe model parameter, m ^-1

Therefore landfill is piled body horizontal direction gas permeability coefficient k _rAvailablely reach as shown in the formula sublist:

$k_r=\frac{Q{P}_{\mathrm{arm}}{\mathrm{\μ}}_z}{\mathrm{\π}(P_{\mathrm{arm}}^2-P_w^2)}f---\left(5\right)$

Calculate model parameter f according to field condition, with extraction flow Q and pressure P _wNumerical value substitution formula (5) is promptly tried to achieve landfill heap body horizontal direction gas permeability coefficient k _r, try to achieve vertical direction gas permeability coefficient k by the ratio a of landfill heap body level and vertical direction gas permeability coefficient _z

The caliber of perforate pipe well in bottom of the present invention is preferably 5～15cm, and perforate length is preferably 1.5～6m, and described extraction flow preferably is set to 20～60m ³/ h.

The present invention has the following advantages and the high-lighting effect: the present invention adopts air suction mode, can utilize existing exhaust pipe of landfill yard and equipment, very easily blast after air and the methane blended in the time of can overcoming the employing method of gas injection again, dangerous high shortcoming, and taken into full account the covering layer of landfill site perviousness and because the landfill heap body horizontal direction that layering landfill and compacting cause and the characteristics of vertical direction infiltration coefficient otherness, so accuracy of measurement height, and system is simple, easy to operate, pollute control and recycling provides key parameter for landfill gas, have a extensive future.

Description of drawings

Fig. 1 is the system architecture synoptic diagram of a kind of in-site measurement landfill heap body gas permeability coefficient provided by the invention.

Among the figure: 1-bottom perforate pipe well; The 2-gas pressure sensor; 3-gaseous tension display recorder; 4-pump-line valve; 5-percolate emptying valve; 6-percolate blow-down pipe; The 7-gas meter; The 8-centrifugal blower.

Model parameter f value was with overlayer and landfill heap body vertical direction gas permeability coefficient ratio k when Fig. 2 measured Beijing's sanitary filling field for adopting the present invention _c/ k _zThe curve that changes.

Embodiment

Below in conjunction with the drawings and specific embodiments the present invention is described in further details.

Fig. 1 is the system architecture synoptic diagram of a kind of in-site measurement landfill heap body gas permeability coefficient provided by the invention.The measuring system that this method adopts comprises bottom perforate pipe well 1, gas pressure sensor 2, gaseous tension display recorder 3, pump-line valve 4, gas meter 7 and centrifugal blower 8; Described gas pressure sensor 2 is installed in the top of pipe well, is connected with described gaseous tension display recorder by data line; Described centrifugal blower is communicated with the upper end of pipe well by gas piping, and described pump-line valve and gas meter are installed on the gas piping; Percolate blow-down pipe 6 and percolate emptying valve 5 also are housed on the gas piping between pump-line valve and the gas meter; Centrifugal blower installs fire proof motor additional;

Described method comprises the steps:

1) on landfill heap body, holes, the running casing while boring, put into bottom perforate pipe well and gravel packing after waiting to reach projected depth, then sleeve pipe is pulled up, backfill boring is taken out between pipe well perforate part top and the overlayer below landfill material and compacting, the clay sealing is adopted in the top, prevents to produce the advantage passage;

2) open percolate emptying valve, with the percolate emptying of accumulating in the percolate blow-down pipe;

3) closing percolate emptying valve, open the pump-line valve, start centrifugal blower, and open gas pressure sensor and gaseous tension display recorder, is 20～100m with the gas meter flow set ³/ h;

4) treat the stable reading of gaseous tension display recorder and gas meter after, extraction flow Q and the pressure P of record this moment _wNumerical value;

5) according to extraction flow Q and pressure P _wBetween corresponding relation:

$P_w^2=P_{\mathrm{arm}}^2-\frac{{\mathrm{QP}}_{\mathrm{arm}}{\mathrm{\μ}}_a}{{\mathrm{\πk}}_r}f---\left(1\right)$

Wherein

$f=\frac{a}{r_w}\{\frac{K_o\left(M_o\frac{r_w}{a}\right)}{{\mathrm{bK}}_z\left(M_o\frac{r_w}{a}\right)}+\frac{2}{\mathrm{\π}(l-d)}{\mathrm{\Σ}}_{n=1}^{\∞}[\frac{\sin \left(\frac{\mathrm{n\πt}}{b}\right)-\sin \left(\frac{\mathrm{n\πd}}{b}\right)}{{\mathrm{nM}}_n{K}_z\left(M_n\frac{r_w}{a}\right)}\left]\cos \left(\frac{\mathrm{n\πd}}{b}\right)K_o\left(M_n\frac{r_w}{a}\right)\right\}---\left(2\right)$

$a^2=\frac{k_r}{k_z}---\left(3\right)$

$M_n=\sqrt{\left(\frac{k_c}{{\mathrm{bb}}_c{k}_z}\right)+{\left(\frac{\mathrm{n\π}}{b}\right)}^2},$ n＝0，1，2，...(4)

In the formula, P _wBe gas absolute pressure in the pipe well, Pa; P _AtmBe atmospheric pressure, Pa; Q is an extraction flow, m ³/ s; k _rBe landfill heap body horizontal direction gas permeability coefficient, m ²k _zBe landfill heap body vertical direction gas permeability coefficient, m ²μ _aBe the kinematic viscosity of landfill gas, Pas; B is the distance of lining to the overlayer bottom, m; b _cBe cover thickness, m; L is the distance between overlayer bottom to the pipe well bottom, m; D is the distance of overlayer bottom to pipe well perforate part top, m; r _wBe the internal diameter of pipe well, m; A is the ratio of landfill heap body level and vertical direction gas permeability coefficient; F, M _nBe model parameter, m ^-1

Therefore landfill is piled body horizontal direction gas permeability coefficient k _rAvailablely reach as shown in the formula sublist:

$k_r=\frac{Q{P}_{\mathrm{arm}}{\mathrm{\μ}}_z}{\mathrm{\π}(P_{\mathrm{arm}}^2-P_w^2)}f---\left(5\right)$

Calculate model parameter f according to field condition, with extraction flow Q and pressure P _wNumerical value substitution formula (5) is promptly tried to achieve landfill heap body horizontal direction gas permeability coefficient k _r, try to achieve vertical direction gas permeability coefficient k by the ratio a of landfill heap body level and vertical direction gas permeability coefficient _z

The caliber of perforate pipe well in bottom of the present invention is preferably 5～15cm, and perforate length is preferably 1.5～6m, and described extraction flow preferably is set to 20～60m ³/ h.

Use method of the present invention and measure Beijing's sanitary filling field different depth heap body gas permeability coefficient, according to field condition, model parameter f value is with blanket gas infiltration coefficient and the vertical gas permeability coefficient ratio k of landfill heap body _c/ k _zThe curve that changes is seen shown in Figure 2, corresponding different heap body level and vertical direction gas permeability coefficient ratio k _r/ k _zWith overlayer and heap body vertical direction gas permeability coefficient ratio k _c/ k _zThe heap body horizontal direction gas permeability coefficient that ratio records is as shown in table 1.

Table 1 Beijing sanitary filling field different depth heap body gas permeability coefficient measured value

Claims (3)

1. the method for in-site measurement landfill heap body gas permeability coefficient, it is characterized in that: the measuring system that this method adopts comprises bottom perforate pipe well (1), gas pressure sensor (2), gaseous tension display recorder (3), pump-line valve (4), gas meter (7) and centrifugal blower (8); Described gas pressure sensor (2) is installed in the top of pipe well, is connected with described gaseous tension display recorder by data line; Described centrifugal blower is communicated with the upper end of pipe well by gas piping, and described pump-line valve and gas meter are installed on the gas piping; Percolate blow-down pipe (6) and percolate emptying valve (5) also are housed on the gas piping between pump-line valve and the gas meter;

Described method comprises the steps:

1) on landfill heap body, holes, the running casing while boring, put into bottom perforate pipe well and gravel packing after waiting to reach projected depth, then sleeve pipe is pulled up, backfill boring is taken out between pipe well perforate part top and the overlayer below landfill material and compacting, the clay sealing is adopted in the top, prevents to produce the advantage passage;

2) open percolate emptying valve, with the percolate emptying of accumulating in the percolate blow-down pipe;

3) closing percolate emptying valve, open the pump-line valve, start centrifugal blower, and open gas pressure sensor and gaseous tension display recorder, is 20～100m with the gas meter flow set ³/ h;

4) treat the stable reading of gaseous tension display recorder and gas meter after, extraction flow Q and the pressure P of record this moment _wNumerical value;

5) according to extraction flow Q and pressure P _wBetween corresponding relation:

$P_w^2=P_{\mathrm{arm}}^2-\frac{{\mathrm{QP}}_{\mathrm{arm}}{\mathrm{\μ}}_a}{{\mathrm{\πk}}_r}f---\left(1\right)$

Wherein

$f=\frac{a}{r_w}\{\frac{K_o\left(M_o\frac{r_w}{a}\right)}{{\mathrm{bK}}_z\left(M_o\frac{r_w}{a}\right)}+\frac{2}{\mathrm{\π}(l-d)}{\mathrm{\Σ}}_{n=1}^{\∞}[\frac{\sin \left(\frac{\mathrm{n\πt}}{b}\right)-\sin \left(\frac{\mathrm{n\πd}}{b}\right)}{{\mathrm{nM}}_n{K}_z\left(M_n\frac{r_w}{a}\right)}\left]\cos \left(\frac{\mathrm{n\πd}}{b}\right)K_o\left(M_n\frac{r_w}{a}\right)\right\}---\left(2\right)$

$a^2=\frac{k_r}{k_z}---\left(3\right)$

$M_n=\sqrt{\left(\frac{k_c}{{\mathrm{bb}}_c{k}_z}\right)+{\left(\frac{\mathrm{n\π}}{b}\right)}^2},$ n＝0，1，2，...(4)

In the formula, P _wBe gas absolute pressure in the pipe well, Pa; P _AtmBe atmospheric pressure, Pa; Q is an extraction flow, m ³/ s; k _rBe landfill heap body horizontal direction gas permeability coefficient, m ²k _zBe landfill heap body vertical direction gas permeability coefficient, m ²μ _aBe the kinematic viscosity of landfill gas, Pas; B is the distance of lining to the overlayer bottom, m; b _cBe cover thickness, m; L is the distance between overlayer bottom to the pipe well bottom, m; D is the distance of overlayer bottom to pipe well perforate part top, m; r _wBe the internal diameter of pipe well, m; A is the ratio of landfill heap body level and vertical direction gas permeability coefficient; F, M _nBe model parameter, m ^-1

Therefore landfill is piled body horizontal direction gas permeability coefficient k _rAvailablely reach as shown in the formula sublist:

$k_r=\frac{Q{P}_{\mathrm{arm}}{\mathrm{\μ}}_z}{\mathrm{\π}(P_{\mathrm{arm}}^2-P_w^2)}f---\left(5\right)$

Calculate model parameter f according to field condition, with extraction flow Q and pressure P _wNumerical value substitution formula (5) is promptly tried to achieve landfill heap body horizontal direction gas permeability coefficient k _r, try to achieve vertical direction gas permeability coefficient k by the ratio a of landfill heap body level and vertical direction gas permeability coefficient _z

2. the method for a kind of in-site measurement landfill heap body gas permeability coefficient according to claim 1, it is characterized in that: the caliber of described bottom perforate pipe well is 5～15cm, perforate length is 1.5～6m.

3. the method for a kind of in-site measurement landfill heap body gas permeability coefficient according to claim 1 and 2, it is characterized in that: described extraction flow is set to 20～60m ³/ h.

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