JP5352079B2 - Biodesulfurization apparatus and method for digestion gas - Google Patents
Biodesulfurization apparatus and method for digestion gas Download PDFInfo
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- 230000029087 digestion Effects 0.000 title claims description 45
- 238000000034 method Methods 0.000 title description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 117
- 238000006477 desulfuration reaction Methods 0.000 claims description 113
- 230000023556 desulfurization Effects 0.000 claims description 113
- 239000007789 gas Substances 0.000 claims description 65
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims description 45
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims description 44
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 40
- 239000007921 spray Substances 0.000 claims description 28
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 24
- 239000000945 filler Substances 0.000 claims description 16
- 241000894006 Bacteria Species 0.000 claims description 14
- 239000010815 organic waste Substances 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 11
- 229910052760 oxygen Inorganic materials 0.000 claims description 11
- 239000001301 oxygen Substances 0.000 claims description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 238000000855 fermentation Methods 0.000 claims description 10
- 230000004151 fermentation Effects 0.000 claims description 10
- 238000002347 injection Methods 0.000 claims description 8
- 239000007924 injection Substances 0.000 claims description 8
- 238000011017 operating method Methods 0.000 claims 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 63
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 24
- 229910052717 sulfur Inorganic materials 0.000 description 22
- 239000011593 sulfur Substances 0.000 description 22
- 235000011121 sodium hydroxide Nutrition 0.000 description 21
- 238000006386 neutralization reaction Methods 0.000 description 18
- 238000006243 chemical reaction Methods 0.000 description 15
- 239000007787 solid Substances 0.000 description 14
- 239000007788 liquid Substances 0.000 description 12
- 239000002351 wastewater Substances 0.000 description 12
- 238000003756 stirring Methods 0.000 description 10
- HYHCSLBZRBJJCH-UHFFFAOYSA-M sodium hydrosulfide Chemical compound [Na+].[SH-] HYHCSLBZRBJJCH-UHFFFAOYSA-M 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 239000013505 freshwater Substances 0.000 description 5
- 238000012423 maintenance Methods 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 239000005708 Sodium hypochlorite Substances 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 238000004140 cleaning Methods 0.000 description 4
- 239000004570 mortar (masonry) Substances 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 235000011149 sulphuric acid Nutrition 0.000 description 4
- 238000005273 aeration Methods 0.000 description 3
- 238000013019 agitation Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 150000003464 sulfur compounds Chemical class 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 239000002250 absorbent Substances 0.000 description 2
- 230000002745 absorbent Effects 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- -1 polypropylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 2
- 229910052815 sulfur oxide Inorganic materials 0.000 description 2
- 229920003002 synthetic resin Polymers 0.000 description 2
- 239000000057 synthetic resin Substances 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- QWPPOHNGKGFGJK-UHFFFAOYSA-N hypochlorous acid Chemical compound ClO QWPPOHNGKGFGJK-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000010525 oxidative degradation reaction Methods 0.000 description 1
- 150000002926 oxygen Chemical class 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000010801 sewage sludge Substances 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 235000017557 sodium bicarbonate Nutrition 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
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- Treatment Of Water By Oxidation Or Reduction (AREA)
Description
本発明は、有機性廃棄物をメタン発酵させて得られたメタンガスに含まれている硫黄化合物を除去する装置と方法に関するものである。 The present invention relates to an apparatus and method for removing sulfur compounds contained in methane gas obtained by subjecting organic waste to methane fermentation.
農作物加工場からの廃棄物、水産物加工場からの廃棄物、厨芥、下水汚泥などの比較的水分の多い有機性廃棄物の処理には、現在、メタン発酵処理が多用されている。このメタン発酵処理は、有機性廃棄物を含む水スラリーを消化槽と称する反応容器に供給し、適温（３０〜６０℃）に加熱して所定時間保持し、有機性廃棄物からガスを発生させて、回収するものである。その際、発生するガス中の成分は、メタンガスが６０〜７０容量％及び二酸化炭素が３０〜４０容量％である。また、不純物として、通常１００〜３０００ｐｐｍの硫化水素ガスも含まれている。 Currently, methane fermentation treatment is frequently used for the treatment of waste from agricultural products processing plants, waste from marine products processing plants, organic wastes with relatively high water content such as dredging and sewage sludge. In this methane fermentation treatment, a water slurry containing organic waste is supplied to a reaction vessel called a digester, heated to an appropriate temperature (30 to 60 ° C.) and held for a predetermined time to generate gas from the organic waste. To be collected. At that time, components in the generated gas are 60 to 70% by volume of methane gas and 30 to 40% by volume of carbon dioxide. Further, 100 to 3000 ppm of hydrogen sulfide gas is usually contained as an impurity.
ところで、このガスは、通常「消化ガス」と呼ばれ、燃料ガスとして利用される。例えば、発電用のガスエンジン、ガスタービン、燃料電池等、温水や蒸気を製造するボイラー等の燃料である。そして、硫化水素が混入していると燃焼によって硫黄酸化物が生成するので、いずれの用途でも、エンジン等の機械部分を腐食させたり、あるいは排ガス中の硫黄酸化物濃度を高くするという問題が起きる。そのため、硫化水素を低減させてから利用する必要がある。 By the way, this gas is usually called “digestion gas” and used as fuel gas. For example, it is a fuel such as a boiler for producing hot water or steam, such as a gas engine for power generation, a gas turbine, or a fuel cell. And if hydrogen sulfide is mixed in, sulfur oxides are generated by combustion. Therefore, in any application, problems such as corroding mechanical parts such as engines or increasing the concentration of sulfur oxides in exhaust gas occur. . Therefore, it is necessary to use after reducing hydrogen sulfide.
この硫化水素の低減には、従来より、酸化鉄等の吸着剤を用いて吸着除去する乾式の脱硫装置やアルカリを用いたスクラバー処理による湿式の脱硫装置が利用されてきた。乾式の脱硫装置は日常の操作が不要であり、脱硫性能が高いのが特長であるが、劣化した脱硫剤の交換が必要であり、交換作業費コストが嵩むことと、劣化した脱硫剤は産業廃棄物として処分しなければならないが、その処分先が少なく、処分費が高いことが問題である。 In order to reduce this hydrogen sulfide, conventionally, a dry desulfurization apparatus that adsorbs and removes using an adsorbent such as iron oxide and a wet desulfurization apparatus that uses a scrubber treatment using an alkali have been used. The dry-type desulfurization equipment does not require daily operations and is characterized by high desulfurization performance. However, it requires replacement of the desulfurization agent, which increases the cost of replacement work. Although it must be disposed of as waste, there are few disposal destinations and high disposal costs.
水酸化ナトリウムとの中和反応によるスクラバー処理（湿式）の脱硫装置においては、水の使用量を低減するため循環散水するが、消化ガス中の炭酸ガスと以下の式１、２の反応を起こすため、重炭酸ナトリウムや炭酸ナトリウムのスケールが析出され、吸収液のノズルや塔の壁に付着し、その清掃が煩雑である。
ＮａＯＨ ＋ ＣＯ２→ＮａＨＣＯ３↓・・・・・式１
２ＮａＯＨ ＋ ＣＯ２→Ｎａ２ＣＯ３↓＋Ｈ２Ｏ・・・・・式２
In a desulfurization apparatus for scrubber treatment (wet) by neutralization reaction with sodium hydroxide, water is circulated to reduce the amount of water used, but the reaction of carbon dioxide in digestion gas and the following formulas 1 and 2 occurs. Therefore, the scale of sodium bicarbonate or sodium carbonate is deposited and adheres to the nozzle of the absorbing liquid or the wall of the tower, and the cleaning thereof is complicated.
NaOH + CO 2 → NaHCO 3 ↓ ・ ・ ・ ・ ・ Formula 1
2NaOH + CO 2 → Na 2 CO 3 ↓ + H 2 O ····· Formula 2
そこで、硫黄細菌を用いて脱硫する方法が開発されている。例えば、特許文献１、２には、硫化水素を酸化分解する微生物が付着した充填材層を有する生物脱硫塔を用いた脱硫装置が開示されている。
この生物脱硫塔での反応を式３に示す。
Ｈ２Ｓ ＋ ２Ｏ２ →Ｈ２ＳＯ４・・・・式３
Therefore, a method for desulfurization using sulfur bacteria has been developed. For example, Patent Documents 1 and 2 disclose a desulfurization apparatus using a biological desulfurization tower having a filler layer to which microorganisms that oxidize and decompose hydrogen sulfide are attached.
The reaction in this biological desulfurization tower is shown in Formula 3.
H 2 S + 2O 2 → H 2 SO 4 ... Formula 3
この生物脱硫塔における維持費は、循環水のポンプ動力と消化ガスに微量の空気を注入するファンの動力と循環水の補給水だけであり、非常に維持費が安価であることが特長である。 The maintenance cost of this biological desulfurization tower is only the power of the circulating water pump, the power of the fan that injects a small amount of air into the digestion gas, and the supplementary water of the circulating water, and the maintenance cost is very low. .
しかしながら、この生物脱硫塔においては、以下のような問題点が指摘されている。
（１）硫化水素の酸化は硫黄酸化細菌の生物反応処理のため、初期の立ち上げ時における菌の馴致時期や負荷変動が極めて大きい場合、循環水の温度やｐＨが最適範囲から外れた場合においては、生物反応が負荷量に追いつかず、処理性能が低下し、生物脱硫塔出口の消化ガス中の硫化水素濃度が設計値以上に残留する。
（２）前述（１）の対策のため、生物脱硫塔の下流側に乾式脱硫塔を設置する事例が多く、この場合では設備投資額が過大となるという問題がある。また、生物脱硫塔で十分に硫化水素を除去できている場合においても、下流側の乾式脱硫塔に消化ガスを常時通過させるため、乾式脱硫剤に反応による劣化はないものの、生物脱硫塔の循環水から消化ガスに持ち出された水分により脱硫剤が湿ることにより膨潤し、通気抵抗が大となり、約１年経過にて、脱硫剤を交換しなければならなく、維持費が安価にならないという問題がある。
（３）前述（２）の対策のため、生物脱硫塔の下流側に湿式脱硫塔を設置する場合が考えられる。アルカリによる中和反応にて硫化水素を除去する湿式脱硫塔では以下の式４の反応により、水硫化ナトリウムが生成される。その排水が生物脱硫塔の硫酸排水と混じると、式５の反応により、ただちに硫化水素が発生し、その近傍に人が立ち入った場合には非常に危険である。また、硫化水素が大気開放されるので、近隣に悪臭公害をもたらす。
ＮａＯＨ＋Ｈ２Ｓ→ＮａＨＳ ＋ Ｈ２Ｏ・・・式４
２ＮａＨＳ＋Ｈ２ＳＯ４→２Ｈ２Ｓ↑ ＋Ｎａ２ＳＯ４・・・・式５
（４）生物脱硫では硫化水素の酸化のために注入する空気は処理ガスである可燃性ガス中の酸素をなるべく少なくするため、硫化水素の酸化に必要な酸素量とそれを少し過剰にする量しか注入しないように制御する。このため、硫化水素の酸化が不完全となりやすく、この場合の反応は式６のように、生物脱硫塔内にて固体硫黄が蓄積し、塔内底部に蓄積し、また充填物に固着することで通気ガスの圧力損失が大となるため、これを定期的に除去する必要がある。
Ｈ２Ｓ＋Ｏ２→ Ｓ＋Ｈ２Ｏ・・・・式６
生物脱硫塔内に蓄積した固体硫黄の除去方法については特許文献２において詳細に記載されているが、そのためには生物脱硫塔を停止しなければならず、また、固体硫黄を含んだ吸収液を産業廃棄処分する必要があり、液状では水分がほとんどであるため、処分量が過大となり、産業廃棄処分費は非常に嵩むことが問題となる。さらに、硫黄は危険物質であり、その産業廃棄処分先が限られ、輸送先が遠距離となる場合、輸送費が嵩み、またその処分費が高いことも問題であるが、国内では処分先が枯渇しつつある。
従って、生物脱硫塔内に固体硫黄が残留蓄積しないようにする必要がある。
However, the following problems are pointed out in this biological desulfurization tower.
(1) Oxidation of hydrogen sulfide is a biological reaction treatment of sulfur-oxidizing bacteria, so if the acclimatization time and load fluctuation of the bacteria at the initial start-up are extremely large, or if the temperature or pH of the circulating water deviates from the optimum range In this case, the biological reaction cannot keep up with the load, the processing performance decreases, and the hydrogen sulfide concentration in the digestion gas at the outlet of the biological desulfurization tower remains above the design value.
(2) There are many cases where a dry desulfurization tower is installed on the downstream side of the biological desulfurization tower as a countermeasure against the above-mentioned (1). In this case, there is a problem that the amount of capital investment becomes excessive. Even when hydrogen sulfide is sufficiently removed by the biological desulfurization tower, the digestion gas is always passed through the downstream dry desulfurization tower. The desulfurization agent swells when it is moistened by the water taken into the digestion gas from the water, and the ventilation resistance becomes large. After about one year, the desulfurization agent must be replaced, and the maintenance cost is not reduced. There's a problem.
(3) As a countermeasure against the above (2), there may be a case where a wet desulfurization tower is installed downstream of the biological desulfurization tower. In a wet desulfurization tower that removes hydrogen sulfide by a neutralization reaction with an alkali, sodium hydrosulfide is produced by the reaction of the following formula 4. When the wastewater is mixed with the sulfuric acid wastewater from the biological desulfurization tower, hydrogen sulfide is immediately generated by the reaction of Formula 5, and it is very dangerous if a person enters the vicinity. Moreover, since hydrogen sulfide is opened to the atmosphere, it causes bad odor pollution in the vicinity.
NaOH + H 2 S → NaHS + H 2 O Formula 4
2NaHS + H 2 SO 4 → 2H 2 S ↑ + Na 2 SO 4 ... Formula 5
(4) In biodesulfurization, the air injected for the oxidation of hydrogen sulfide reduces the amount of oxygen necessary for the oxidation of hydrogen sulfide and an amount that slightly increases it in order to minimize the oxygen in the combustible gas that is the processing gas. Control to only inject. For this reason, oxidation of hydrogen sulfide is likely to be incomplete. In this case, as shown in Equation 6, solid sulfur accumulates in the biological desulfurization tower, accumulates at the bottom of the tower, and adheres to the packing. Since the pressure loss of the aeration gas becomes large, it is necessary to remove it periodically.
H 2 S + O 2 → S + H 2 O... Formula 6
The method for removing solid sulfur accumulated in the biological desulfurization tower is described in detail in Patent Document 2, but for this purpose, the biological desulfurization tower must be stopped, and an absorbent containing solid sulfur is removed. There is a need for industrial disposal, and since the liquid is almost moisture, the disposal amount becomes excessive, and the industrial disposal cost is very high. In addition, sulfur is a hazardous substance, and its disposal destinations are limited. If the transportation destination is a long distance, the transportation cost increases and the disposal cost is high. Is being depleted.
Therefore, it is necessary to prevent solid sulfur from remaining in the biological desulfurization tower.
前記（１）の問題点については、高いレベルで脱硫性能を保持するためには、循環水のｐＨを常に最適帯に維持する必要がある。この最適帯はｐＨが１〜２の範囲であることが経験的にわかった。この理由としては、ｐＨ２以下にて硫黄酸化細菌の活動が最も盛んとなることが考えられる。
ｐＨが２より大となると、生物脱硫塔出口の消化ガスの硫化水素濃度は１０ｐｐｍを超える場合が出てくるため、後段に設置した乾式または湿式の脱硫塔を運転する必要があり、維持費が嵩む。
Regarding the problem (1), in order to maintain the desulfurization performance at a high level, it is necessary to always maintain the pH of the circulating water in the optimum zone. It has been empirically found that this optimum band has a pH range of 1-2. This is probably because the activity of sulfur-oxidizing bacteria is most active at pH 2 or lower.
If the pH is higher than 2, the concentration of hydrogen sulfide in the digestion gas at the outlet of the biological desulfurization tower may exceed 10 ppm. Therefore, it is necessary to operate a dry or wet desulfurization tower installed in the subsequent stage, and maintenance costs are low. Bulky.
特許文献２では、循環水ラインにｐＨ計を設置して、そのｐＨが１〜６になるように新水の補給で調整するとしているが、ｐＨが２以上では脱硫性能が劣ることが問題である。ｐＨの設定値を１〜２と狭い範囲で設定するには、特許文献２では「極端なｐＨの低下を防ぐため、新水を補給して循環水の一部を適宜入れ替える」としか記載されてなく、具体的な新水の制御方法が詳しく述べられていない。
一方、連続計測するために現場に設置したｐＨ計は、前述の式６の反応に生成される固体硫黄や他のスケールの影響やｐＨ計自体の校正不備の原因により、正常に作動していない場合がある。また、補給水をバッチ式にて補給するには、ｐＨの設定レベルが狭すぎることと、生物脱硫塔内の保有水量があまり多くないので、過注入をしやすく、この場合はｐＨ値が設定値より大となり、脱硫性能が落ちる。
In Patent Document 2, a pH meter is installed in the circulating water line, and the pH is adjusted to 1 to 6 by replenishing with fresh water. However, when the pH is 2 or more, the desulfurization performance is inferior. is there. In order to set the pH setting value within a narrow range of 1 to 2, Patent Document 2 only describes that “a part of circulating water is appropriately replaced by replenishing fresh water in order to prevent an extreme drop in pH”. The specific control method of new water is not described in detail.
On the other hand, the pH meter installed at the site for continuous measurement is not operating normally due to the influence of solid sulfur and other scales generated in the reaction of the above-mentioned formula 6 and the cause of the calibration failure of the pH meter itself. There is a case. In addition, in order to replenish makeup water in a batch system, the pH setting level is too narrow and the amount of water retained in the biological desulfurization tower is not so large, so it is easy to over-inject. In this case, the pH value is set. It becomes larger than the value and desulfurization performance falls.
有機性廃棄物のメタン発酵処理によって生成される消化ガス中の硫化水素濃度は、原料である有機性廃棄物の性状に由来するものであり、有機性廃棄物の性状が大きく変わらない場合には硫化水素濃度は変動が少ない。そこでこの硫化水素濃度の変動が少ないことを利用して、新水の補給量を生物脱硫塔内で生成される硫酸負荷と比例させて、連続にて定量注入する方法を考案した。具体的には、硫酸負荷を消化ガス量と硫化水素濃度より求め、生物脱硫塔内において最適ｐＨとなるような硫酸濃度を算出し、その硫酸濃度となるように補給水の注入量を算出する。一般的には消化ガス量と硫化水素濃度の変動が少ないので、この設定は最初だけでよい。設備としては、定量注入ポンプが必要であり、好ましくは注入量を積算測定できる水道メータを設置することにより、新水の注入量が正確に把握できる。
この場合では、循環水のｐＨ計による制御は不要となる。新水を連続注入することで、生物脱硫塔内にて連続生成される硫酸が常に一定割合にて薄められるため、常時、ｐＨが最適値内に平衡状態に保たれる。
The concentration of hydrogen sulfide in digestion gas produced by methane fermentation treatment of organic waste is derived from the properties of the organic waste that is the raw material, and if the properties of the organic waste do not change significantly There is little fluctuation in the hydrogen sulfide concentration. In view of this, we have devised a method for continuously injecting a fixed amount of water in proportion to the sulfuric acid load generated in the biological desulfurization tower by taking advantage of the small fluctuation of the hydrogen sulfide concentration. Specifically, the sulfuric acid load is obtained from the digestion gas amount and the hydrogen sulfide concentration, the sulfuric acid concentration is calculated so as to obtain the optimum pH in the biological desulfurization tower, and the injection amount of makeup water is calculated so as to obtain the sulfuric acid concentration. . This setting is only necessary at first because the amount of digestion gas and hydrogen sulfide concentration are generally small. As the equipment, a metering injection pump is required. Preferably, by installing a water meter capable of integrating and measuring the injection amount, the injection amount of fresh water can be accurately grasped.
In this case, control with circulating water pH meter becomes unnecessary. By continuously injecting fresh water, the sulfuric acid continuously produced in the biological desulfurization tower is always diluted at a constant rate, so that the pH is always kept in an optimum state within the optimum value.
そこで、本願の第１に係る発明では、内部に硫黄酸化細菌が生息する充填材が充填され、該充填材に水を供給する散布水給水管および散布水排水管が接続され、かつ、酸素含有ガスの供給口と、消化ガスの導入口および排出口を有する生物脱硫塔を備えた脱硫装置において、前記散布水給水管にまたは、生物脱硫塔に直接補給水を供給する定量供給装置が設けられていることを特徴とする、有機性廃棄物をメタン発酵させて得られる消化ガスの脱硫装置を提供する。 Therefore, in the invention according to the first aspect of the present application, a filler in which sulfur-oxidizing bacteria inhabit is filled, a spray water supply pipe and a spray water drain pipe for supplying water to the filler are connected, and oxygen-containing In a desulfurization apparatus comprising a biological desulfurization tower having a gas supply port and a digestion gas inlet and exhaust port, a fixed-quantity supply device for supplying makeup water directly to the spray water supply pipe or to the biological desulfurization tower is provided. The present invention provides a desulfurization apparatus for digestion gas obtained by subjecting organic waste to methane fermentation.
次に、前記（１）において、高いレベルで脱硫性能を保持するためには、循環水の温度を常に最適帯に維持する必要がある。特許文献２では循環水の温度を１５〜４０℃に保つことが望ましいとしているが、実際は２５℃以下になると脱硫性能が低下することが経験的にわかり、最適帯は２５℃以上である。そこで、冬季では循環水の加温操作が必須となるが、循環水を直接加温するには循環水のｐＨが非常に低いため、ヒータや熱交換器が腐食しやすく、問題である。また、熱交換器を高価なチタンなどの腐食に強い材質を使わざるを得ないが、高価である。 Next, in the above (1), in order to maintain the desulfurization performance at a high level, it is necessary to always maintain the temperature of the circulating water in the optimum zone. Patent Document 2 states that it is desirable to maintain the temperature of the circulating water at 15 to 40 ° C. However, it is empirically found that the desulfurization performance is lowered when the temperature is 25 ° C or lower, and the optimum zone is 25 ° C or higher. Therefore, in the winter season, the operation of heating the circulating water is indispensable. However, since the pH of the circulating water is very low for directly heating the circulating water, the heater and the heat exchanger are easily corroded. In addition, the heat exchanger must be made of corrosion-resistant material such as expensive titanium, but it is expensive.
そこで、本発明では、設置する連続注入の補給水の新水ラインに電気ヒータを設置し、補給水を加温することで、循環水を加温することを考案した。この場合は、新水は腐食液でないので、高価な材質は必要がなく、安価となる。制御としては、循環水の温度が２５℃以下になると、ヒータの電源をいれ、２７℃以上となるとヒータの電源を切る操作でよい。 Therefore, in the present invention, it has been devised that the circulating water is heated by installing an electric heater in the new water line of the continuously injected makeup water to be installed and heating the makeup water. In this case, since fresh water is not a corrosive liquid, an expensive material is not necessary and the cost is low. As control, when the temperature of the circulating water is 25 ° C. or lower, the heater is turned on, and when it is 27 ° C. or higher, the heater is turned off.
そこで、本願の第２に係る発明では、前記給水管に加熱装置が設けられていることを特徴としている。
以上のｐＨと水温の改善を加えることで、生物脱硫塔出口の消化ガス中の硫化水素濃度は常時、１０ｐｐｍ以下となり、後段の脱硫操作は不要であるが、生物脱硫塔の馴致の期間や生物脱硫塔内の固体硫黄の清掃作業時、また消化ガスの硫化水素負荷変動が過大となった場合には、生物脱硫塔出口の消化ガスに硫化水素が残留するので、やはり後段に別途の脱硫装置が必要である。
Therefore, the second aspect of the present invention is characterized in that a heating device is provided in the water supply pipe.
By adding the above-mentioned improvements in pH and water temperature, the concentration of hydrogen sulfide in the digestion gas at the outlet of the biological desulfurization tower is always 10 ppm or less, and no subsequent desulfurization operation is required. When cleaning the solid sulfur in the desulfurization tower or when the fluctuation of the hydrogen sulfide load of the digestion gas becomes excessive, hydrogen sulfide remains in the digestion gas at the exit of the biodesulfurization tower. is necessary.
前記（２）に記載したように、後段の脱硫装置として、乾式脱硫塔を用いるのは、操作は簡単であるが、設備投資面、維持費の面より得策でない。従って、後段の脱硫装置は水酸化ナトリウムによる中和反応をさせる１パス式のスクラバー処理がよいが、（３）に示すように生物脱硫塔からの硫酸排水と後段の湿式での水酸化ナトリウムが混ざることで式５に示すように硫化水素が発生する問題がある。この対象として、湿式脱硫塔の排水に次亜塩素酸ナトリウムなどの酸化剤を注入し、水硫化ナトリウムを酸化させることを考案した。この反応式を式７に示す。
ＮａＨＳ ＋ ＮａＣｌＯ → Ｓ↓ ＋ＮａＣｌ＋ＮａＯＨ・・・式７
As described in (2) above, using a dry desulfurization tower as a subsequent desulfurization apparatus is simple in operation, but is not advantageous from the viewpoint of capital investment and maintenance costs. Therefore, the latter-stage desulfurization apparatus is preferably a one-pass scrubber treatment that neutralizes with sodium hydroxide. However, as shown in (3), the sulfuric acid waste water from the biological desulfurization tower and the latter-stage wet sodium hydroxide When mixed, there is a problem that hydrogen sulfide is generated as shown in Formula 5. As an object, we devised to oxidize sodium hydrosulfide by injecting an oxidizing agent such as sodium hypochlorite into the drainage of the wet desulfurization tower. This reaction formula is shown in Formula 7.
NaHS + NaClO → S ↓ + NaCl + NaOH Formula 7
そこで、本願の第３に係る発明では、消化ガスの排出口に湿式脱硫塔が接続され、該湿式脱硫塔のアルカリ水溶液の排出側に次亜塩素酸又はその塩の供給管が接続されていることを特徴としている。 Therefore, in the third invention of the present application, a wet desulfurization tower is connected to the digestion gas discharge port, and a hypochlorous acid or salt supply pipe is connected to the alkaline aqueous solution discharge side of the wet desulfurization tower. It is characterized by that.
前記（４）において、生物脱硫塔内に固体硫黄が蓄積しやすく、定期的な清掃のため、生物脱硫塔を停止させる必要がある。また、固体硫黄を含んだ吸収液を産業廃棄処分しなければならず、その処分費が嵩む。
固体硫黄比重が約２と比較的重く、生物脱硫塔の底部に溜まりやすい。ただし、ｐＨを１〜２に保持している生物脱硫にて生成される硫黄の性状は粘着性が少なく、さらさらしており、充填剤への付着は少ないことがわかった。
In said (4), solid sulfur tends to accumulate in the biological desulfurization tower, and it is necessary to stop the biological desulfurization tower for periodic cleaning. Moreover, the absorbent containing solid sulfur must be industrially disposed of, which increases the disposal cost.
The specific gravity of solid sulfur is relatively heavy at about 2 and tends to accumulate at the bottom of the biological desulfurization tower. However, it was found that the property of sulfur produced by biodesulfurization maintaining the pH at 1 to 2 is less sticky, free flowing, and has little adhesion to the filler.
そこで、生物脱硫塔にて硫黄が蓄積しないように、底部をすり鉢状にする。さらに、槽底部を攪拌するポンプを循環ポンプとは別に設置し、常時、槽底部から吸い込んだ液を攪拌ポンプにて昇圧し、槽底部に向けて吐出させ槽内を攪拌する。この際、吐出口の配管口径を絞って、流速を早くし、流速の大である吐出流にて槽底部に沈積している固体硫黄を常時巻き上がらせて、浮遊させる。なお、この攪拌ポンプの吐出先を槽内攪拌とは別にバルブ切り替えにて中和槽に移送させるラインを設けることで、補給水により生物脱硫塔の水位が規定値を超えた場合に、排水させることができ、固体硫黄を系外に排出することができる。
このような工夫により、生物脱硫塔に固体硫黄は蓄積されず、定期的な清掃は不要であり、固体硫黄の処分は不要となる。
Therefore, the bottom is mortared so that sulfur does not accumulate in the biological desulfurization tower. Further, a pump for stirring the tank bottom is provided separately from the circulation pump, and the liquid sucked from the tank bottom is constantly pressurized by the stirring pump and discharged toward the tank bottom to stir the inside of the tank. At this time, the pipe diameter of the discharge port is reduced to increase the flow rate, and the solid sulfur deposited on the bottom of the tank is constantly lifted and floated by the discharge flow having a high flow rate. In addition, by providing a line that transfers the discharge destination of this agitation pump to the neutralization tank by switching the valve separately from the agitation in the tank, when the water level of the biological desulfurization tower exceeds the specified value due to make-up water, it is drained. And solid sulfur can be discharged out of the system.
With such a device, solid sulfur is not accumulated in the biological desulfurization tower, periodic cleaning is unnecessary, and disposal of solid sulfur is unnecessary.
そこで、本願の第４に係る発明では、生物脱硫塔の底部をすり鉢状にするとともにそこにある液を攪拌する攪拌ポンプが設けられていることを特徴としている。 Therefore, the invention according to the fourth aspect of the present invention is characterized in that a stirring pump for stirring the liquid in the bottom of the biological desulfurization tower is provided.
本発明により、有機性廃棄物をメタン発酵させて得られる消化ガスに含まれる硫黄化合物を簡便な方法で安価に効率よく除去することができる。 According to the present invention, sulfur compounds contained in digestion gas obtained by subjecting organic waste to methane fermentation can be efficiently and inexpensively removed by a simple method.
本発明の脱硫装置の生物脱硫塔は、消化ガスの導入口と排出口、酸素含有ガスの供給口、散布水給水口と散布水排出口が設けられ、内部に硫黄酸化細菌を生息させる充填材が収容されているものである。 The biological desulfurization tower of the desulfurization apparatus of the present invention is provided with a digestion gas inlet and outlet, an oxygen-containing gas supply port, a spray water supply port and a spray water discharge port, and a filler for inhabiting sulfur-oxidizing bacteria inside Is contained.
塔本体の形状は、通常は円筒形であるが、箱形等であってもよい。中央部には充填材が収容され、上下には空間が設けられている。底部は平底でもよいがすり鉢状とすることが好ましい。 The shape of the tower body is usually a cylindrical shape, but may be a box shape or the like. A filler is accommodated in the central portion, and spaces are provided above and below. The bottom may be a flat bottom but is preferably mortar-shaped.
充填材は、硫黄酸化細菌を生息させられるものであればよく、通常は気液接触充填物である。形状は粒径の外、管状、シート状などであってもよい。好ましいものとして、比重が０．９〜１．０５で容積率で８０〜９５％空隙を有する合成樹脂粒子がある。この合成樹脂として好ましいものは、例えば、ポリプロピレンである。 The filler may be any material that can be inhabited by sulfur-oxidizing bacteria, and is usually a gas-liquid contact filler. The shape may be a particle shape, a tubular shape, a sheet shape, or the like. Preferable examples include synthetic resin particles having a specific gravity of 0.9 to 1.05 and a void ratio of 80 to 95%. A preferable example of the synthetic resin is polypropylene.
充填材に植え付ける細菌は、硫化水素を酸化して硫酸を生成させるものであり、いわゆる硫黄酸化細菌と称されるものである。硫黄酸化細菌は下水処理場の活性汚泥処理をしている曝気槽の液に存在しており、曝気槽の液を生物脱硫塔に少量投入すればよい。 Bacteria to be planted in the filler are those that oxidize hydrogen sulfide to produce sulfuric acid, and are so-called sulfur-oxidizing bacteria. Sulfur-oxidizing bacteria are present in the liquid in the aeration tank that performs the activated sludge treatment in the sewage treatment plant, and a small amount of the liquid in the aeration tank may be introduced into the biological desulfurization tower.
消化ガスは、生物脱硫塔内を下降流、上昇流のいずれで移動させてもよく、それに応じて導入口と排出口の一方を上部に、他方を下部に設ける。
酸素含有ガスは、硫化水素の酸化に使用されるものであり、通常は空気が用いられ、消化ガスとともに生物脱硫塔に供給させる。その場合には、消化ガスの導入口が酸素含有ガスの供給口をかねることになる。この酸素含有ガス供給口は独立して設けてもよい。
The digestion gas may be moved in the biological desulfurization tower by either a downward flow or an upward flow, and one of the introduction port and the discharge port is provided at the upper part and the other is provided at the lower part accordingly.
The oxygen-containing gas is used for the oxidation of hydrogen sulfide. Usually, air is used and supplied to the biological desulfurization tower together with the digestion gas. In this case, the digestion gas inlet serves as the oxygen-containing gas supply port. This oxygen-containing gas supply port may be provided independently.
生物脱硫塔内への給水は、硫黄細菌を生育させて脱硫を行わせるためであり、通常は充填材の層の上から散水することにより行う。従って、通常は、散布水給水口は塔の上部に、散布水排水口は下部に設ける。そして、さらに、散布水給水口と散布水排水口の間には、散布水の循環ラインを設けて、散布水を塔内を循環させるようにする。
また、補給水の供給口は散布水循環ラインに合流させてもよいし、生物脱硫塔に独立して設けてもよい。
The water supply to the biological desulfurization tower is for growing sulfur bacteria to perform desulfurization, and is usually performed by sprinkling water from above the filler layer. Therefore, normally, the spray water supply port is provided in the upper part of the tower and the spray water drain port is provided in the lower part. Further, a spray water circulation line is provided between the spray water supply port and the spray water discharge port so that the spray water is circulated in the tower.
Further, the makeup water supply port may be joined to the spray water circulation line or may be provided independently in the biological desulfurization tower.
散布水循環ラインに接続される補給水管には定量供給装置を設ける。この定量供給装置には、流量調整機構を有する定量供給ポンプを用いることができるが、その外、供給される水に水圧があれば、ノズルや弁を用いることもできる。本発明では、この定量供給装置で水を定量供給することにより、生物脱硫塔内の水のｐＨを１〜２に保つ。 A fixed amount supply device is provided in the makeup water pipe connected to the spray water circulation line. In this fixed quantity supply device, a fixed quantity supply pump having a flow rate adjusting mechanism can be used, but in addition, if the supplied water has water pressure, a nozzle or a valve can be used. In the present invention, the pH of water in the biological desulfurization tower is kept at 1 to 2 by quantitatively supplying water with this quantitative supply device.
この補給水管には、さらに、補給される水の加熱装置を設ける。この加熱装置は、生物脱硫塔内の水を２５℃以上に保って、菌による脱硫を活発にするためである。加熱装置の種類は特に限定されず、熱交換器を設けて、蒸気やその他の熱媒を供給するとか、電気ヒータを用いるとか、各種の公知の加熱装置を用いることができる。 The replenishing water pipe is further provided with a heating device for water to be replenished. This heating device is for keeping the water in the biological desulfurization tower at 25 ° C. or more and activating desulfurization by bacteria. The type of the heating device is not particularly limited, and various known heating devices can be used such as providing a heat exchanger to supply steam or other heat medium, using an electric heater, or the like.
排水管の途中には、中和槽を設ける。これは、生物脱硫塔から排出される水がｐＨ１〜２であるため中性付近に調整するためである。
生物脱硫塔には硫黄が蓄積しないように、底部をすり鉢状にすることが好ましい。底部が平底の場合には、底部の側壁はコンクリートなどでハンチをつけてすり鉢状にする。さらに、槽底部を攪拌するポンプを循環ポンプとは別に設置し、常時、槽底部から吸い込んだ循環液を攪拌ポンプにて昇圧し、槽底部に向けて吐出させ槽内を攪拌する。この際、吐出口の配管口径を絞って、流速を早くし、流速の大である吐出流にて槽底部に沈積している固体硫黄を常時巻き上がらせて、浮遊させる。この際以下の条件が望ましい。すり鉢部の勾配は硫黄のスラリーが堆積しにくい３０度〜６０度が望ましい。底部中央の平面の径は攪拌の吐出流が届く範囲の０．３〜１．０ｍが望ましい。ちなみに塔径は１〜３ｍ程度である。攪拌流の吐出速度は底部の硫黄スラリーを巻き上げることができる３ｍ／秒〜１０ｍ／秒が望ましい。上記底面平面の径では攪拌流の吐出口は１０ｍｍ〜５０ｍｍが望ましい。
A neutralization tank is installed in the middle of the drain pipe. This is because the water discharged from the biological desulfurization tower has a pH of 1-2, so that the water is adjusted to near neutrality.
The bottom of the biological desulfurization tower is preferably formed in a mortar shape so that sulfur does not accumulate. When the bottom is flat, the bottom side wall is mortared with concrete or the like to form a mortar. Further, a pump for agitating the tank bottom is installed separately from the circulation pump, and the circulating fluid sucked from the tank bottom is constantly pressurized by the agitation pump and discharged toward the tank bottom to stir the inside of the tank. At this time, the pipe diameter of the discharge port is reduced to increase the flow rate, and the solid sulfur deposited on the bottom of the tank is constantly lifted and floated by the discharge flow having a high flow rate. In this case, the following conditions are desirable. The gradient of the mortar portion is preferably 30 to 60 degrees where sulfur slurry is difficult to deposit. The diameter of the flat surface at the center of the bottom is desirably 0.3 to 1.0 m within a range where the stirring discharge flow can reach. Incidentally, the tower diameter is about 1 to 3 m. The discharge speed of the stirring flow is desirably 3 m / sec to 10 m / sec, which can wind up the sulfur slurry at the bottom. As for the diameter of the bottom plane, the stirring outlet is preferably 10 mm to 50 mm.
本発明の脱硫装置を用いて生物脱硫塔内の循環水のｐＨを最適域に保持するための方法を説明する。
消化ガス量１００Ｎｍ３／Ｈで硫化水素濃度が１，０００ｐｐｍの場合に、ｐＨ値を２以下にする場合の補給水量を以下に計算する。
A method for maintaining the pH of the circulating water in the biological desulfurization tower in the optimum region using the desulfurization apparatus of the present invention will be described.
When the digestion gas amount is 100 Nm 3 / H and the hydrogen sulfide concentration is 1,000 ppm, the makeup water amount when the pH value is 2 or less is calculated as follows.
処理風量 ＱＧ：１００Ｎｍ３／Ｈ
硫化水素濃度Ｃ：１，０００ｐｐｍ
硫化水素負荷ｑＨ２Ｓ：
ｑＨ２Ｓ＝１００Ｎｍ３／Ｈ×２４Ｈ×１０００ｐｐｍ×１０−６÷２２．４＝０．１０７ｋｍｏｌ／日
生物による酸化分解反応：
Ｈ２Ｓ＋２Ｏ２→Ｈ２ＳＯ４
生成硫酸負荷ｑＨ２ＳＯ４：０．１０７ｋｍｏｌ／日（硫化水素と硫酸は等量反応のため）
循環水の上限ｐＨ：２
水素イオン濃度とｐＨの関係：ｐＨ＝−ｌｏｇ［Ｈ＋］→［Ｈ＋］＝１０−ｐＨ
上限［Ｈ＋］濃度（ｇイオン／Ｌ）：０．０１
下限硫酸濃度ＣＨ２ＳＯ４（ｍｏｌ／Ｌ）：０．００５（硫酸の価数：２、電離度：１より）
上限補給水量Ｑｗ＝ｑＨ２ＳＯ４÷ＣＨ２ＳＯ４＝２１．４（ｋＬ／日）
補給水の消化ガスとの上限の割合л：
л＝Ｑｗ÷（ＱＧ×２４Ｈ）×１００＝０．８９％
このように、硫化水素濃度が１０００ｐｐｍの場合には消化ガス量に対し、約０．８９％以下の補給水を定量注入すればよいことになる。
以上より、消化ガス量に対する補給水量の比лの上限値を消化ガス中の硫化水素濃度Ｃに対し比例させればよい。
л（％）＜０．８９％×Ｃ（ｐｐｍ）÷１０００（ｐｐｍ）
もし、消化ガスの硫化水素濃度は季節的な増減がある場合は、このлを上記計算にて算出し、定量ポンプの吐出量を調整すればよい。この程度の吐出量に対しては、定量ポンプとしてはダイヤフラムポンプを用いるのが一般的であり、このタイプのポンプ吐出量の調整は、ダイヤルゲージにて吐出ストロークを調整するだけであり、安価で操作も簡単である。
Processed air volume Q G : 100Nm 3 / H
Hydrogen sulfide concentration C: 1,000 ppm
Hydrogen sulfide load q H2S :
q H2S = 100 Nm 3 / H × 24H × 1000 ppm × 10 −6 ÷ 22.4 = 0.107 kmol / day Oxidative degradation reaction by organism:
H 2 S + 2O 2 → H 2 SO 4
Sulfuric acid load q H2SO4 : 0.107 kmol / day (because hydrogen sulfide and sulfuric acid are equivalent reactions)
Maximum pH of circulating water: 2
Relationship between hydrogen ion concentration and pH: pH = −log [H + ] → [H + ] = 10 −pH
Upper limit [H + ] concentration (g ion / L): 0.01
Lower limit sulfuric acid concentration C H2SO4 (mol / L): 0.005 (from sulfuric acid valence : 2, ionization degree: 1)
Upper limit water supply amount Qw = q H2SO4 ÷ C H2SO4 = 21.4 (kL / day)
Percentage ratio of upper limit to digestion gas for make-up water:
л = Qw ÷ (Q G × 24H) × 100 = 0.89%
As described above, when the hydrogen sulfide concentration is 1000 ppm, it is sufficient to quantitatively inject makeup water of about 0.89% or less with respect to the digestion gas amount.
From the above, the upper limit value of the ratio of the makeup water amount to the digestion gas amount л may be made proportional to the hydrogen sulfide concentration C in the digestion gas.
л (%) <0.89% × C (ppm) ÷ 1000 (ppm)
If the hydrogen sulfide concentration in the digestion gas changes seasonally, this л can be calculated by the above calculation and the discharge rate of the metering pump can be adjusted. For this amount of discharge, it is common to use a diaphragm pump as a metering pump, and this type of pump discharge amount can be adjusted simply by adjusting the discharge stroke with a dial gauge. The operation is also easy.
ただし、上記の割合лは式３の反応が１００％起きる場合であり、実際は中間の単体硫黄に留まり、単体硫黄の形態で系外に搬出されるものがある割合で存在する。従って現実にこの計算で算出した割合より若干低い割合にて補給水を注入すればよい。 However, the above-mentioned ratio л is the case where the reaction of Formula 3 occurs 100%. Actually, it remains in the intermediate elemental sulfur, and there is a ratio in which some elemental sulfur is carried out of the system. Therefore, it is only necessary to inject makeup water at a rate slightly lower than the rate actually calculated in this calculation.
次に生物脱硫塔内の循環水の温度を最適域に保持するための方法を説明する。
生物脱硫の循環水温度が２０℃以下になると脱硫性能が低下することが経験的にわかり、最適帯は２５℃以上であり、外気温が低下する冬季では加温する必要がある。
循環水の温度を低下させる要因としては、（１）消化ガスの温度低下、（２）補給水の温度低下、（３）外気の温度低下がある。（３）の対策としては、外気に接している生物脱硫塔の外側を保温材により被覆することで防げるものである。ある実施例では被覆を実施した後における放散熱の割合（１）：（２）：（３）は、４５％：４０％：１５％程度であった。
Next, a method for maintaining the temperature of the circulating water in the biological desulfurization tower in the optimum range will be described.
It is empirically known that the desulfurization performance is lowered when the circulating water temperature of biological desulfurization is 20 ° C. or lower. The optimum zone is 25 ° C. or higher, and it is necessary to heat in the winter when the outside air temperature decreases.
Factors that reduce the temperature of the circulating water include (1) a decrease in digestion gas temperature, (2) a decrease in makeup water temperature, and (3) a decrease in the temperature of outside air. As a measure of (3), it can be prevented by covering the outside of the biological desulfurization tower in contact with the outside air with a heat insulating material. In a certain example, the ratio (1) :( 2) :( 3) of the heat dissipated after coating was about 45%: 40%: 15%.
このように、（２）の補給水の温度低下が循環水の温度低下に占める割合が比較的多いので、循環水を加温するのではなく、腐食問題がない補給水を加温することにより、循環水の温度保持ができれば好都合である。
そこで、［００３２］で実施する補給水の連続注入のラインに、加温ヒータを取り付け、循環水の温度が２５℃〜２７℃程度となるように、２５℃でヒータがＯＮとし、２７℃でヒータをＯＦＦする。
Thus, since the ratio of the temperature drop of the makeup water in (2) accounts for a relatively large proportion of the temperature drop of the circulating water, it is not necessary to heat the circulating water, but to warm the makeup water without corrosion problems. It is advantageous if the circulating water temperature can be maintained.
Therefore, a heating heater is attached to the line for continuously injecting makeup water performed in [0032], and the heater is turned on at 25 ° C. so that the temperature of the circulating water is about 25 ° C. to 27 ° C. Turn off the heater.
ヒータは電気ヒータが価格も安く、取り付けも簡単である。また、設備容量が大きい場合で、廃熱回収による安価な温水が供給できる場合は、温水を直接加温するか、もしくは、温水を補給水の一部として少量注入してもよい。 Electric heaters are cheaper and easier to install. When the equipment capacity is large and cheap hot water can be supplied by waste heat recovery, the hot water may be heated directly, or a small amount of hot water may be injected as part of the makeup water.
後段の湿式脱硫の排水と生物脱硫排水の中和方法を説明する。
生物脱硫塔出口の消化ガス中の硫化水素濃度が規定値を超える場合を想定して、後段に湿式脱硫塔を設置する。湿式脱硫塔の反応は以下であり、残留量の硫化水素と等量または少し過剰の水酸化ナトリウム水溶液を供給する。
ＮａＯＨ＋Ｈ２Ｓ→ＮａＨＳ＋Ｈ２Ｏ・・・・式４
ただし、消化ガスには炭酸ガスが多量に含まれ、循環式では消化ガス中の炭酸ガスと以下の式１、２の反応を起こすため、重炭酸ナトリウムや炭酸ナトリウムのスケールを析出させ、吸収液のノズルや塔の壁に付着し、その清掃が煩雑である。そのため、循環式ではなく、１パス（一過式）でしかもスケールがつきにくいスプレー塔とするのが望ましい。
ＮａＯＨ ＋ ＣＯ２→ＮａＨＣＯ３↓・・・・・式１
２ＮａＯＨ ＋ ＣＯ２→ Ｎａ２ＣＯ３↓＋Ｈ２Ｏ・・・・・式２
The neutralization method of the waste water of wet desulfurization and biological desulfurization waste water of the latter stage is demonstrated.
A wet desulfurization tower is installed in the latter stage assuming that the hydrogen sulfide concentration in the digestion gas at the biological desulfurization tower outlet exceeds the specified value. The reaction of the wet desulfurization tower is as follows, and a sodium hydroxide aqueous solution equivalent to or slightly in excess of the residual amount of hydrogen sulfide is supplied.
NaOH + H 2 S → NaHS + H 2 O... Formula 4
However, the digestion gas contains a large amount of carbon dioxide, and in the circulation type, the reaction of the following formulas 1 and 2 occurs with the carbon dioxide in the digestion gas. It adheres to the nozzles and tower walls and is complicated to clean. For this reason, it is desirable to use a spray tower which is not a circulation type but has one pass (one-time type) and is difficult to scale.
NaOH + CO 2 → NaHCO 3 ↓ ・ ・ ・ ・ ・ Formula 1
2NaOH + CO 2 → Na 2 CO 3 ↓ + H 2 O ····· Formula 2
消化ガスは硫化水素が残留の有無にかかわらず常に、後段の湿式塔を通過させ、硫化水素の残留が許容値を超えた場合に、残留する硫化水素濃度と等量または少し過剰の水酸化ナトリウムを注入する。硫化水素は連続測定器を設置しても良いが、検知管などの簡易測定器を用いても良い。
この時に重要なのは炭酸ガスと反応しスケールがつかないように、水酸化ナトリウム水溶液のｐＨを下げるため、水に希釈して０．００１〜０．０１％程度望ましくは０．００４％程度にして噴霧することである。
The digestion gas is always passed through the wet column in the latter stage regardless of whether hydrogen sulfide remains, and when the hydrogen sulfide residue exceeds the allowable value, it is equivalent to the residual hydrogen sulfide concentration or a little excess sodium hydroxide. Inject. For hydrogen sulfide, a continuous measuring device may be installed, but a simple measuring device such as a detector tube may be used.
In order to reduce the pH of the aqueous sodium hydroxide solution, it is important to dilute it with water to make it 0.001 to 0.01%, preferably about 0.004%. It is to be.
式４の中和反応により、生成された水硫化ナトリウムはその排水が生物脱硫塔の硫酸排水と混じると、式５の反応により、ただちに硫化水素が発生し、その近傍に人が立ち入った場合には非常に危険である。また、硫化水素が大気開放されるので、近隣に悪臭公害をもたらす。
２ＮａＨＳ＋Ｈ２ＳＯ４→２Ｈ２Ｓ↑ ＋Ｎａ２ＳＯ４・・・・式５
この対策として、湿式脱硫塔の排水に次亜塩素酸ナトリウムなどの酸化剤を注入し、水硫化ナトリウムを酸化させる。この反応式を式７に示す。
ＮａＨＳ ＋ ＮａＣｌＯ → Ｓ↓ ＋ＮａＣｌ＋ＮａＯＨ・・・式７
When the drainage of sodium hydrosulfide produced by the neutralization reaction of Formula 4 is mixed with the sulfuric acid drainage of the biological desulfurization tower, hydrogen sulfide is generated immediately by the reaction of Formula 5, and a person enters the vicinity. Is very dangerous. Moreover, since hydrogen sulfide is opened to the atmosphere, it causes bad odor pollution in the vicinity.
2NaHS + H 2 SO 4 → 2H 2 S ↑ + Na 2 SO 4 ... Formula 5
As a countermeasure, an oxidizing agent such as sodium hypochlorite is injected into the waste water of the wet desulfurization tower to oxidize sodium hydrosulfide. This reaction formula is shown in Formula 7.
NaHS + NaClO → S ↓ + NaCl + NaOH Formula 7
なお、注入量は湿式脱硫塔に注入した水酸化ナトリウムと等量でよく、市販の１２％程度の次亜塩素酸ナトリウムを定量ポンプでスプレー塔の底部または排水管に注入しても良い。
この排水は生物脱硫塔の中和槽に入れれば、水酸化ナトリウムを含んでいるので、生物脱硫塔の硫酸排水の中和を助けるので、経済的である。
The injection amount may be the same as sodium hydroxide injected into the wet desulfurization tower, and about 12% of commercially available sodium hypochlorite may be injected into the bottom of the spray tower or the drain pipe with a metering pump.
If this waste water is placed in the neutralization tank of the biological desulfurization tower, it contains sodium hydroxide, which helps to neutralize the sulfuric acid waste water of the biological desulfurization tower, and is economical.
生物脱硫排水の中和の必要性は次の通りである。すなわち、連続注入により、生物脱硫塔内の液が増量するので、規定水位を超えた場合に、ポンプにて系外に排出する。この排水は、ｐＨ１〜２で下水道への放流基準のｐＨ５．８〜８．６を超えるため、中和処理が必要である。中和処理の手順は、硫酸排水を一旦中和槽にいれ、中和槽に設置したｐＨ計により、水酸化ナトリウムを徐々に注入し、また、攪拌機にて硫酸と水酸化ナトリウムを混合し、基準ｐＨの範囲に入れば、水酸化ナトリウムの注入を停止し、これを下水道に排水する。生物脱硫塔のｐＨ値は中和槽に設置しているｐＨ計と記録チャートにて、生物塔内の排水が流入した時点のｐＨ値として得られるので、特許文献２にて記載している生物脱硫塔内または循環水に設置するｐＨ計は不要である。 The necessity of neutralization of biological desulfurization wastewater is as follows. That is, since the liquid in the biological desulfurization tower increases due to continuous injection, the liquid is discharged out of the system by a pump when the specified water level is exceeded. Since this waste water exceeds pH 5.8 to 8.6 on the basis of discharge to sewer at pH 1 to 2, neutralization is necessary. The neutralization treatment procedure is as follows. Sulfuric acid wastewater is once put in a neutralization tank, and sodium hydroxide is gradually injected with a pH meter installed in the neutralization tank, and sulfuric acid and sodium hydroxide are mixed with a stirrer. If it enters the range of the reference pH, the injection of sodium hydroxide is stopped, and this is drained into the sewer. Since the pH value of the biological desulfurization tower is obtained as the pH value at the time when the wastewater in the biological tower flows in with a pH meter and a recording chart installed in the neutralization tank, the biological value described in Patent Document 2 A pH meter installed in the desulfurization tower or in the circulating water is unnecessary.
本発明の一実施例である脱硫装置の構成を図１に示す。
この装置は、生物脱硫塔と湿式脱硫塔と中和槽よりなっている。
生物脱硫塔は、直径２ｍ、高さ５．５ｍの円筒状で、外面には保温材が装着されている。内部には充填材としてポリプロピレン製気液接触充填材が収容されている。頂部には、消化ガス供給管が接続され、その途中には、酸素含有ガスとしての空気の供給管が接続されている。消化ガス供給管と空気供給管にはいずれも流量計が取り付けられている。塔の上部には給水管が接続され、塔内には全面に散水できるように散水ノズルが配置されている。塔の下部は、ハンチをつけてすり鉢状にされ、そこに散布水排水管が接続されている。この散布水排水管はポンプを介して散布水給水管に接続されて循環ラインを形成されている。
FIG. 1 shows the configuration of a desulfurization apparatus which is an embodiment of the present invention.
This apparatus comprises a biological desulfurization tower, a wet desulfurization tower, and a neutralization tank.
The biological desulfurization tower has a cylindrical shape with a diameter of 2 m and a height of 5.5 m, and a heat insulating material is mounted on the outer surface. Inside, a gas-liquid contact filler made of polypropylene is accommodated as a filler. A digestion gas supply pipe is connected to the top, and an air supply pipe as an oxygen-containing gas is connected to the top. A flow meter is attached to both the digestion gas supply pipe and the air supply pipe. A water supply pipe is connected to the upper part of the tower, and a watering nozzle is arranged in the tower so that water can be sprayed over the entire surface. The lower part of the tower is shaped like a mortar with a haunch, and a spray water drain pipe is connected to it. The spray water drain pipe is connected to the spray water supply pipe via a pump to form a circulation line.
水を供給する補給水タンクはこの循環ラインの途中に配管接続され、この配管も給水管を構成している。配管の途中には、定量ポンプ、流量計、ヒータ、弁が取り付けられている。
消化ガスの排出口は塔の下部に設けられ、そこから湿式脱硫塔に配管接続されている。配管の途中にはＨ２Ｓ計が取り付けられている。
A makeup water tank for supplying water is connected to a pipe in the middle of this circulation line, and this pipe also constitutes a water supply pipe. A metering pump, a flow meter, a heater, and a valve are attached in the middle of the piping.
Digestion gas outlets are provided in the lower part of the tower and are connected to a wet desulfurization tower by piping. An H 2 S meter is attached in the middle of the piping.
塔の下部には排水管も接続されており、この排水管の他端は排水弁を介して中和槽に接続されている。また、この排水管の途中から分岐してポンプを介して塔内の下部に戻る循環ラインが形成されている。この循環ラインによって塔内下部の液を攪拌する。この模様を図２に示す。 A drain pipe is also connected to the lower part of the tower, and the other end of the drain pipe is connected to a neutralization tank through a drain valve. In addition, a circulation line is formed which branches from the middle of the drain pipe and returns to the lower part of the tower via a pump. The liquid in the lower part of the tower is stirred by this circulation line. This pattern is shown in FIG.
湿式脱硫塔は下部に消化ガスの入口が、頂部に出口が設けられている。また、上部には苛性ソーダタンクからポンプを介して配管接続され、その途中には苛性ソーダを希釈する補給水タンクからの配管が接続されている。塔内上部には、この苛性ソーダ溶液を全面に散布しうるようノズルが配置されている。 The wet desulfurization tower has a digestion gas inlet at the bottom and an outlet at the top. Further, a pipe is connected to the upper part through a pump from a caustic soda tank, and a pipe from a makeup water tank for diluting the caustic soda is connected in the middle. In the upper part of the tower, a nozzle is arranged so that this caustic soda solution can be sprayed over the entire surface.
湿式脱硫塔の下部には、Ｈ２Ｓを吸収した水硫化ナトリウム溶液の排出口が設けられ、そこからポンプを介して中和槽に配管接続されている。この配管の途中には次亜塩素酸ソーダ水溶液のタンクからの配管がポンプを介して接続されている。 At the lower part of the wet desulfurization tower, a discharge port for a sodium hydrosulfide solution that has absorbed H 2 S is provided, and is connected to a neutralization tank through a pump from there. In the middle of this pipe, a pipe from a tank of sodium hypochlorite aqueous solution is connected via a pump.
中和槽には、前記の生物脱硫塔の排水管、湿式脱硫塔からの排水管に加えて、
苛性ソーダタンクからの供給管もポンプを介して接続され、中和槽に設けられた
ｐＨ計の指令によって、このポンプを作動させるようになっている。
In the neutralization tank, in addition to the drainage pipe of the biological desulfurization tower and the drainage pipe from the wet desulfurization tower,
A supply pipe from a caustic soda tank is also connected via a pump, and this pump is operated by a command from a pH meter provided in the neutralization tank.
本発明の脱硫装置は、有機性廃棄物をメタン発酵させて得られた消化ガスに含まれている硫黄化合物を安価に効率よく除去できるので、この、メタン発酵装置に広く付設して使用しうるものである。 Since the desulfurization apparatus of the present invention can efficiently remove sulfur compounds contained in digestion gas obtained by subjecting organic waste to methane fermentation at low cost, it can be widely used in this methane fermentation apparatus. Is.
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| JP3750648B2 (en) * | 2001-11-02 | 2006-03-01 | Ｊｆｅエンジニアリング株式会社 | Digestion gas desulfurization apparatus and desulfurization method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111154524A (en) * | 2020-01-19 | 2020-05-15 | 中国石油天然气股份有限公司 | Low-gas-content oil well sulfur-containing associated gas interval type in-situ purification treatment method |
| CN111154524B (en) * | 2020-01-19 | 2021-04-30 | 中国石油天然气股份有限公司 | Low-gas-content oil well sulfur-containing associated gas interval type in-situ purification treatment method |
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