JP2010054241A - Methods for measurement and generation control of methane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide methods for measurement and generation control of methane in a gas generated from a compost production facility or a storage tank of excessive sludge or a storage place of dehydrated cake within a water treatment facility. <P>SOLUTION: The method for measurement of methane comprises steps of collecting a gas generated from a methane generation facility, the gas containing at least methane, carbon dioxide and volatile organic acid; passing the collected gas through an alkaline absorbent to separate the carbon dioxide and the volatile organic acid; and measuring methane concentration by a hydrogen flame ionization detector (FID). The method for generation control of methane comprises measuring concentration of methane generated from a methane generation facility, and performing aerobic operation when the measured concentration exceeds a reference value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for measuring methane and a method for suppressing generation thereof, and more particularly, controls a method for measuring and generating methane in a gas generated from a compost manufacturing facility, a storage tank for excess sludge in a water treatment facility, or a storage place for dehydrated cake. On how to do.

  Currently, the most serious environmental problem is global warming.

  The most interesting greenhouse gas that causes global warming is carbon dioxide, but methane, along with dinitrogen monoxide (nitrous oxide), chlorofluorocarbons known as a type of chlorofluorocarbon, etc. Also mentioned.

  The greenhouse effect of methane is said to be 21 times that of carbon dioxide. Like carbon dioxide, the concentration of methane in the atmosphere tends to increase. According to Non-Patent Document 1, methane is generated by the activity of anaerobic microorganisms in animal intestinal fermentation, natural wetlands and paddy fields, natural gas mining, biomass combustion, etc. It is expected that specific control measures will be required for each source in the future.

Patent Document 1 describes an inhibitor that suppresses methane generated from the digestive organs of animals, particularly rumen (ruminals) of ruminants.
JP 2006-166853 A “2.2 Methane”, [online], Japan Meteorological Agency website, Air and Ocean Environment Observation Report No. 7 (2005 observations), [March 19, 2008 search], Internet, <URL: http: // www.data.kishou.go.jp/obs-env/cdrom/report2005/html/2_2_0.htm>

  On the other hand, the present inventors have found that methane is also generated from a compost manufacturing facility, a storage tank for excess sludge in a water treatment facility, and a storage place for dehydrated cake.

  Microbial activities such as bacteria and fungi also become active in surplus sludge storage tanks and dewatered cake storage in composting and water treatment facilities.

  Then, compost, excess sludge and oxygen inside the dehydrated cake are consumed by the activity of microorganisms. In an environment where the supply of air (oxygen) is not sufficient, the interior becomes partially anaerobic as the consumption of oxygen proceeds.

  Under anaerobic conditions, the atmosphere is reduced and the activity of anaerobic methane-producing bacteria converts excess sludge in the compost raw material and low-molecular organic substances and carbon dioxide contained in the dehydrated cake into methane.

  The situation in which such methane is generated is also a situation in which hydrogen sulfide and ammonia are generated by other microorganisms. Also, since methane is an odorless flammable gas, it is difficult to notice the generation, and if methane accumulates in the building, it may cause an explosion accident. From a macro perspective, it also causes global warming.

  Therefore, the present inventor paid attention to methane generated in the anaerobic state of the facility, completed a method for easily measuring the methane, and took measures to eliminate the anaerobic state using the concentration as a trigger. As a result, the present inventors have found that greenhouse gas reduction can be achieved without stopping the operation.

  Accordingly, an object of the present invention is to provide a method for measuring and controlling the generation of methane in a gas generated from a compost manufacturing facility, a storage tank for excess sludge in a water treatment facility, or a storage place for dehydrated cake. .

  The other subject of this invention becomes clear by the following description.

  The above problems are solved by the following inventions.

(Claim 1)
A step of collecting a gas containing at least methane, carbon dioxide gas and volatile organic acid generated from a methane generation facility, and separating the carbon dioxide gas and the volatile organic acid by passing the collected gas through an alkaline absorbent And a step of measuring the methane concentration with a flame ionization detector (FID).

(Claim 2)
The method for measuring methane according to claim 1, wherein hydrogen gas supplied to the alkaline absorbent and the flame ionization detector (FID) is generated by water electrolysis.

(Claim 3)
The method for measuring methane according to claim 1 or 2, wherein the methane generation facility is a facility for producing a compost by aerobic fermentation of a compost raw material.

(Claim 4)
The method for measuring methane according to claim 1 or 2, wherein the methane generation facility is a storage tank for excess sludge in the water treatment facility or a storage place for the dehydrated cake.

(Claim 5)
The concentration of methane generated from the methane generation facility is measured by the method for measuring methane according to any one of claims 1 to 4, and when the measured concentration exceeds a reference value, an aerobic operation is performed. A characteristic methane generation control method.

(Claim 6)
6. The methane generation control method according to claim 5, wherein when the methane generation facility is a facility for producing a compost by aerobic fermentation of a compost raw material, the methane generation facility performs reversal as an aerobic operation.

(Claim 7)
The methane generation control method according to claim 5, wherein when the methane generation facility is an excess sludge storage tank in the water treatment facility, sludge aeration is performed as an aerobic operation.

  ADVANTAGE OF THE INVENTION According to this invention, the measurement method and the method of controlling generation | occurrence | production of the methane in the gas which generate | occur | produce from the storage place of the excess sludge in the compost manufacturing facility and the water treatment facility, and the storage place of a dewatering cake can be provided.

  Embodiments of the present invention will be described below.

  The compost manufacturing facility in the present invention is a sludge cake obtained by dewatering sludge generated from a sewage treatment plant or a rural settlement wastewater treatment plant, etc., and organic waste such as livestock manure and straw is used as a main compost raw material, and is subjected to aerobic fermentation. It is a facility that produces compost that is mainly used as fertilizer for plants such as agricultural crops and parks.

  In the present invention, the facility for manufacturing the compost is not limited at all. It is preferable that there is a covering structure such as a roof or a cover, and an opening for exhausting the air inside is provided so that the gas generated from the compost can be taken out. Even if there is no structure to cover and the gas generated from compost is released to the atmosphere in a normal state, the present invention can be used effectively if the gas generated from compost can be sampled. it can.

  The excess sludge storage tank in the water treatment facility is the sludge that is temporarily stored in the process of being transferred from the sludge concentration tank or sludge concentration tank to a dehydrator (if it is not dewatered, it is transported to the outside by a tank truck, etc.) For example, a storage tank. The storage location for the dehydrated cake corresponds to the temporary storage location when the dehydrated cake is transferred to an incineration facility and incinerated.

  FIG. 1 is a schematic view of an apparatus for measuring a warming gas from a sampling gas sampled from a facility for generating a greenhouse gas.

  In the present invention, the greenhouse gas to be measured is methane.

  The sampling gas removes volatile organic acids (for example, acetic acid and propionic acid), carbon dioxide, and hydrogen sulfide in the sampling gas through the alkali absorption tube 1 containing the filler 10 immersed in an alkali absorbent.

  Alkali absorbents include alkaline water generated on the cathode side by electrolyzing water (water electrolysis), alkali metal hydroxides (for example, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution), alkaline earth metal water. Oxides (for example, calcium hydroxide aqueous solution), ammonium hydroxide aqueous solution and the like can be mentioned. Among them, alkaline water generated on the cathode side by water electrolysis or sodium hydroxide having excellent absorbability is preferable, and water electrolysis is preferable on the cathode side. The resulting alkaline water is particularly preferred.

  This is because, in water electrolysis, the cathode-side liquid becomes alkaline due to proton consumption, and this is excellent in terms of maintainability and handling during disposal.

  The pH of the alkali absorbent is at least 8 or more, and absorption close to saturation is also preferable.

  The filler 10 may be a general porous body, preferably activated carbon.

  In the present invention, instead of the alkali absorption tube 1, a vial 3 containing an alkali absorbent inside may be used as shown in FIG. In the vial 3, a liquid phase 3b composed of a gas phase 3a and an alkaline absorbent is formed.

  When the vial 3 is used, in order to enhance the absorption effect, the gas in the gas phase 3a can be sucked by the pump 31, returned to the liquid phase 3b in the vial 3, and aerated again.

  Reference numeral 2 denotes a methane measuring device equipped with a hydrogen flame ionization detector (FID).

  The FID detector can detect an organic compound with high sensitivity.

  In the present invention, the composition of the sampled gas (gas) is assumed to be air containing at least methane, carbon dioxide, and a volatile organic acid. It may contain hydrogen sulfide and ammonia.

  It is essential for the FID detector to supply hydrogen gas on the measurement principle.

  In the present invention, the hydrogen gas supplied to the FID detector is preferably supplied by water electrolysis instead of being introduced from the provided hydrogen gas cylinder. Supplying from a water electrolysis supply device is superior in terms of maintainability. Further, as described above, since the liquid on the cathode side is alkaline, it can be used for the preceding stage of alkali absorption, so that it is more rational.

  These series of methane concentration measurements are carried out constantly or intermittently. When a concentration exceeding the set standard is detected, generation is controlled by performing aerobic processing.

  Since the state of methane generation varies depending on the level of anaerobic microorganism activity, it may change sequentially depending on the facility, season, temperature, and time zone. A uniform aerobic process (for example, every fixed time) without dealing with the state of generation cannot exhibit a sufficient control effect on the generation of methane.

  By performing the aerobic treatment as necessary while measuring the methane concentration as in the present invention, more effective control can be realized more efficiently.

  Here, the range of the reference value is a value that is appropriately determined within a range of several ppm or less, and this concentration is below the detection limit (lower limit) of a normal semiconductor detector.

  The aerobic treatment at the compost manufacturing facility includes turning over.

  As a method of turning back, a method of agitating compost and contacting with the atmosphere, a method of aerobing by sending compressed air from an air introduction pipe provided under the compost, a method of agitating and aerobicizing with a machine, etc. However, it is not limited at all.

  The aerobic treatment in the storage tank for excess sludge in the water treatment facility and the storage place for the dewatered cake includes measures such as aeration, stirring, and turning over.

  These treatments may be performed until the concentration of the greenhouse gas to be measured falls below a predetermined value, or after a specified number of times and then re-measured, the effect of the aerobic treatment is insufficient (specified) If the concentration exceeds), the aerobic treatment may be performed again.

  In the present invention, by measuring the methane concentration, inputting the measurement result, and when the measurement result exceeds the reference value, by providing the control unit 5 that outputs an instruction signal to perform the aerobic processing, The generation of methane can be controlled automatically.

  FIG. 3 will be described by taking a compost manufacturing apparatus as an example.

  In FIG. 3, 7 is a compost manufacturing apparatus. The compost production apparatus 7 has a plurality of tanks 703 in which a rectangular or cylindrical compost production apparatus main body 701 is partitioned by a plurality of partition walls 702, and the compost is fermented and aged in the tank 703.

  The compost raw material charged into the tank 703 from the compost raw material inlet 704 is fermented and matured while moving from the tank close to the compost raw material inlet 704 to the tank near the compost product outlet 705.

  An inclined portion 706 is provided at the bottom of each tank 703 to eliminate dead space, and the lower part of the tank 703 is formed in a conical shape or a pyramid shape.

  A space is formed between the lower portion of the inclined portion 706 and the compost manufacturing apparatus main body 701, and a heater 707 for adjusting the temperature is provided in each space.

  At the bottom of the tank 703, one or more air supply pipes 708 for introducing air into the compost are installed, and the air supply pipe 708 is connected to a compressor 709 for supplying pressurized air. The tip of the air supply pipe 708 is in the tank 703, and air is supplied into the compost by supplying pressurized air from the air supply pipe 708, and at the same time, the compost can be stirred. In the compost production apparatus of FIG. 3, “turning back” is performed by this air introduction and stirring.

  The air introduced from the air supply pipe 708 is preferably configured to be temperature-controllable, and is preferably supplied with air heated by a heater (not shown) or the like.

  It is also preferable to provide another air supply pipe (not shown) in the tank 703 and connect it to a blower that supplies humidified air so as to supply humidified air in addition to pressurized air.

  Reference numeral 710 denotes an exhaust port provided in the upper part of the compost manufacturing apparatus main body 701. An exhaust introduction pipe 61 is connected to the exhaust port 710 so that a part of the exhaust can be sampled.

  Excess exhaust gas that is not used for the measurement of the warming gas is directly discharged from the exhaust port 710.

  An example of a control flow in the control unit 5 that controls the compost manufacturing apparatus 7 is shown in FIG.

  First, the control unit 5 operates the sampling fan 6 and sucks the exhaust (sampling gas) of the compost manufacturing apparatus 7 from the exhaust introduction pipe 61 provided at the exhaust port of the facility and introduces it into the vial 3 (S1).

  The vial 3 is brought into contact with the alkaline absorbent and the introduced exhaust to absorb carbon dioxide and the like in the exhaust that hinders the measurement of the greenhouse gas (S2). Further, the pump 31 is operated as necessary.

  The methane concentration is measured by the methane measuring device 2 (S3).

  It is determined whether the greenhouse gas concentration exceeds a reference value (S4).

  If the reference value is not exceeded, it is determined that the anaerobic state has not been reached and the process ends.

  When it exceeds the reference value, the control unit 5 operates the compressor 709 to introduce air into the tank 703 and perform switching (S5). Thereafter, the process returns to S1.

  When the compost manufacturing apparatus is equipped with a motor-driven stirring blade or the like as the stirring means and a blower or the like as the air supply means, the control unit 5 can be controlled to perform reversal by operating the motor and the blower. it can.

  In the present invention, when the methane concentration exceeds the reference value, the above control can be performed and a warning can be issued. The warning can be performed, for example, on a monitor screen (not shown).

Example 1
A gas sampling unit is installed on the indoor sludge storage tank of the sewage activated sludge treatment facility, and the collected gas is continuously measured by a gas analyzer (alkaline scrubber-FID) having a separate FID detector. The sludge storage tank was agitated and aerated so that it could be maintained at 1 ppm or less.

The generation amount per unit area of the storage tank could be suppressed to 1 Nm ³ / day or less.

Comparative Example 1
In the same sludge storage tank as in Example 1, control by methane gas concentration was not performed.

The generation amount per unit area of the storage tank was 10 Nm ³ / day.

Schematic diagram of a device for measuring greenhouse gases Schematic showing another example of a device for measuring greenhouse gases The figure which shows the one aspect | mode used for the compost manufacturing method of this invention. Control flow chart in the control unit that controls the compost manufacturing equipment

Explanation of symbols

1: Alkali absorption tube 2: Methane meter 3: Vials
3a: Gas phase 3b: Liquid phase 5: Control unit 6: Sampling fan 61: Exhaust pipe 7: Compost manufacturing device 701: Compost manufacturing device main body 702: Partition wall 703: Tank 704: Compost raw material input port 705: Compost product collection Outlet 706: Inclined portion 707: Heater 708: Air supply pipe 709: Compressor 710: Exhaust port

Claims (7)

Collecting at least methane, carbon dioxide and volatile organic acid gas generated from the methane generation facility;
Passing the collected gas through an alkaline absorbent to separate the carbon dioxide gas and the volatile organic acid;
And measuring the methane concentration with a flame ionization detector (FID).   The method for measuring methane according to claim 1, wherein the alkaline absorbent and the hydrogen gas supplied to the flame ionization detector (FID) are generated by water electrolysis.   The method for measuring methane according to claim 1 or 2, wherein the methane generation facility is a facility for producing a compost by aerobic fermentation of a compost raw material.   The method for measuring methane according to claim 1 or 2, wherein the methane generation facility is a storage place for excess sludge storage tank or dewatered cake in the water treatment facility.   The concentration of methane generated from the methane generation facility is measured by the method for measuring methane according to any one of claims 1 to 4, and when the measured concentration exceeds a reference value, an aerobic operation is performed. A characteristic methane generation control method.   6. The method for controlling the generation of methane according to claim 5, wherein when the methane generation facility is a facility for producing a compost by aerobic fermentation of a compost raw material, the methane generation facility performs reversal as an aerobic operation. The methane generation control method according to claim 5, wherein when the methane generation facility is an excess sludge storage tank in the water treatment facility, sludge aeration is performed as an aerobic operation.

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