JP6540104B2 - Exhaust purification system for internal combustion engine - Google Patents
Exhaust purification system for internal combustion engine Download PDFInfo
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- JP6540104B2 JP6540104B2 JP2015044247A JP2015044247A JP6540104B2 JP 6540104 B2 JP6540104 B2 JP 6540104B2 JP 2015044247 A JP2015044247 A JP 2015044247A JP 2015044247 A JP2015044247 A JP 2015044247A JP 6540104 B2 JP6540104 B2 JP 6540104B2
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本発明は、内燃機関からの排気中に含まれる有害成分を浄化するための内燃機関の排気浄化装置に関する。 The present invention relates to an exhaust gas purification apparatus for an internal combustion engine for purifying harmful components contained in exhaust gas from the internal combustion engine.
排気中に含まれる有害成分を浄化するための技術としては、例えば下記特許文献１，２による技術が公知である。下記特許文献１では、排気中に含まれる硫黄酸化物を除去するために吸収液と気液接触させる湿式脱硫装置において、脱硫塔本体内に水蒸気を吹き込む水蒸気管を設けている。脱硫塔本体内に水蒸気を吹き込むと周囲のガスにより冷却され、水蒸気はその温度における飽和濃度となり余剰の水蒸気は凝縮して液滴となり、この液滴がガス中に浮遊しているダスト等を核として成長するため、微細なこれらの粒子が見かけ上肥大化する。粒子が大きくなると慣性により液滴が衝突して捕集されやすくなり、ダスト等の捕集効率が向上する。 As a technique for purifying harmful components contained in exhaust gas, for example, techniques according to Patent Documents 1 and 2 below are known. In the following Patent Document 1, in a wet desulfurization apparatus in which the absorbent is brought into gas-liquid contact to remove sulfur oxides contained in the exhaust gas, a steam pipe for blowing water vapor into the desulfurization tower main body is provided. When steam is blown into the desulfurization tower main body, it is cooled by the surrounding gas, the steam becomes saturated concentration at that temperature and the excess steam condenses and becomes droplets, and these droplets are suspended in the gas, etc. These fine particles seem to grow in size as they grow. When the particles become large, the droplets collide with each other and easily collected due to inertia, and the collection efficiency of dust and the like is improved.
また、下記特許文献２では、被処理ガス中の窒素酸化物（ＮＯｘ）を除去するために、被処理ガス中のＮＯｘをオゾン酸化し、このオゾン酸化後の被処理ガス中の残存ＮＯｘ成分を吸収液によって吸収除去している。その際に、オゾンを被処理ガス中と吸収液中の双方に添加している。 Moreover, in the following Patent Document 2, in order to remove nitrogen oxides (NOx) in the gas to be treated, NOx in the gas to be treated is oxidized with ozone, and the remaining NOx component in the gas to be treated after this ozone oxidation is Absorbed by absorption solution. At that time, ozone is added to both the gas to be treated and the absorbing solution.
ガソリンエンジンやディーゼルエンジン等の内燃機関からの排気中には、燃料の燃焼で生成された水が水蒸気として存在しており、さらに、排気中の窒素酸化物が水（水蒸気）と反応することで硝酸（ＨＮＯ3）が生成される。そこで、排気中の水蒸気を凝縮させた水に排気中の窒素酸化物（例えばＮＯ2）や硝酸等の水溶性ガスを吸収させることで、排気中の窒素酸化物や硝酸等の水溶性ガスを浄化することが可能となる。ただし、例えば酸素過剰の希薄燃焼（リーンバーン）等、内燃機関の空燃比が理論空燃比から離れることで排気中の水蒸気濃度が低くなると、排気中の水蒸気が凝縮する露点温度が低くなる。また、内燃機関の排気温度が高くなると、排気中の飽和水蒸気濃度が増加する。それらの内燃機関の運転状態においては、排気中の水蒸気が凝縮しにくくなり、排気中の窒素酸化物や硝酸等の水溶性ガスを凝縮後の水に吸収させて浄化する性能が低下しやすくなる。 In the exhaust from internal combustion engines such as gasoline engines and diesel engines, water generated by combustion of fuel is present as steam, and further, nitrogen oxides in the exhaust react with water (steam). Nitric acid (HNO 3 ) is produced. Therefore, by making water condensed from water vapor in the exhaust absorb water-soluble gas such as nitrogen oxide (for example, NO 2 ) and nitric acid in the exhaust, water-soluble gas such as nitrogen oxide and nitric acid in the exhaust can be It becomes possible to purify. However, if the water vapor concentration in the exhaust gas is lowered due to the air fuel ratio of the internal combustion engine being separated from the stoichiometric air fuel ratio, such as lean combustion (lean burn) with excess oxygen, for example, the dew point temperature at which the water vapor in the exhaust gas condenses is lowered. In addition, when the exhaust gas temperature of the internal combustion engine becomes high, the saturated water vapor concentration in the exhaust gas increases. Under the operating conditions of those internal combustion engines, the water vapor in the exhaust gas is less likely to condense, and the ability to absorb and purify water-soluble gases such as nitrogen oxides and nitric acid in the exhaust gas is likely to deteriorate. .
本発明に係る内燃機関の排気浄化装置は、内燃機関の運転状態が変化しても排気浄化性能の低下を抑制することを目的とする。 An exhaust gas purification apparatus for an internal combustion engine according to the present invention aims to suppress a decrease in exhaust gas purification performance even if the operating state of the internal combustion engine changes.
本発明に係る内燃機関の排気浄化装置は、上述した目的を達成するために以下の手段を採った。 The exhaust gas purification apparatus for an internal combustion engine according to the present invention adopts the following means in order to achieve the above-mentioned object.
本発明に係る内燃機関の排気浄化装置は、内燃機関からの排気が流入する容器内に、排気と接触するデミスタ部と、デミスタ部の温度を調整する温度調整部とを備え、デミスタ部に接触する排気中の水分を排気中の水溶性ガスとともにデミスタ部で捕捉する温度調整型デミスタユニットを有することを要旨とする。 The exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a demister unit in contact with the exhaust gas and a temperature control unit for adjusting the temperature of the demister unit in a container into which exhaust gas from the internal combustion engine flows. The gist of the present invention is to have a temperature control type demister unit that captures moisture in the exhaust gas together with the water-soluble gas in the exhaust gas at the demister section.
本発明の一態様では、温度調整部は、容器内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように、デミスタ部の温度を調整することが好適である。 In one aspect of the present invention, the temperature control unit preferably adjusts the temperature of the demister unit such that the water vapor concentration in the exhaust flowing into the container is higher than the saturated water vapor concentration.
本発明の一態様では、容器内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように、内燃機関の空燃比が制御されることで、排気中の水蒸気濃度が制御されることが好適である。 In one aspect of the present invention, the water vapor concentration in the exhaust gas is controlled by controlling the air-fuel ratio of the internal combustion engine such that the water vapor concentration in the exhaust flowing into the container becomes higher than the saturated water vapor concentration. It is suitable.
本発明の一態様では、容器内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように、内燃機関からの排気に水を添加する水添加装置を有することが好適である。 In one aspect of the present invention, it is preferable to have a water addition device that adds water to the exhaust from the internal combustion engine so that the water vapor concentration in the exhaust flowing into the container becomes higher than the saturated water vapor concentration.
本発明の一態様では、内燃機関からの排気に水を添加する水添加装置を有し、容器内に流入する排気中の水蒸気濃度を飽和水蒸気濃度より高くするための優先順位が、温度調整部によるデミスタ部の温度調整、内燃機関の空燃比制御、水添加装置による水添加の順に設定されていることが好適である。 In one aspect of the present invention, there is provided a water addition device for adding water to exhaust gas from an internal combustion engine, and the priority order for making the water vapor concentration in the exhaust gas flowing into the container higher than the saturated water vapor concentration is a temperature control unit It is preferable that the temperature adjustment of the demister part by this, the air-fuel ratio control of the internal combustion engine, and the water addition by the water addition device are set in this order.
本発明の一態様では、温度調整型デミスタユニットは、温度調整部として、冷媒が流れる冷却管を備えることが好適である。 In one aspect of the present invention, the temperature controlled demister unit preferably includes, as a temperature control unit, a cooling pipe through which a refrigerant flows.
本発明によれば、デミスタ部に接触する排気中の水分を排気中の水溶性ガスとともにデミスタ部で捕捉することで、排気中の水溶性ガスを浄化することができる。その際には、温度調整部によりデミスタ部の温度を調整することで、排気中の水蒸気濃度が低くなったり、排気温度が高くなる等、内燃機関の運転状態が変化しても、排気中の水蒸気をデミスタ部で安定して凝縮させることができ、排気中の水溶性ガスを浄化する性能の低下を抑制することができる。 According to the present invention, the water-soluble gas in the exhaust gas can be purified by capturing water in the exhaust gas contacting the demister part together with the water-soluble gas in the exhaust gas in the demister part. At that time, by adjusting the temperature of the demister section by the temperature adjustment section, even if the operating condition of the internal combustion engine changes, for example, the water vapor concentration in the exhaust gas becomes low or the exhaust gas temperature becomes high. Water vapor can be stably condensed in the demister portion, and a decrease in the performance of purifying the water-soluble gas in the exhaust can be suppressed.
以下、本発明を実施するための形態（以下実施形態という）を図面に従って説明する。 Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described according to the drawings.
図１は、本発明の実施形態に係る内燃機関の排気浄化装置の概略構成を示す図である。本実施形態に係る排気浄化装置は、例えば内燃機関とともに車両に搭載される。内燃機関（エンジン）１０は、シリンダ内で燃料を燃焼させることで動力を発生する。ここでの内燃機関１０は、例えばガソリンエンジン等の火花点火機関であってもよいし、例えばディーゼルエンジン等の圧縮着火機関であってもよい。内燃機関１０での燃焼後の排気は、排気管１２内へ排出される。内燃機関１０から排気管１２内へ排出される排気中には、窒素酸化物（ＮＯｘ）等の有害成分が含まれており、本実施形態では、内燃機関１０からの排気中の窒素酸化物を含む有害成分を浄化するために、温度調整型デミスタユニット２０が排気管１２の下流側の位置に設けられている。 FIG. 1 is a view showing a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. The exhaust purification system according to the present embodiment is mounted on a vehicle together with an internal combustion engine, for example. The internal combustion engine (engine) 10 generates power by burning fuel in a cylinder. The internal combustion engine 10 here may be, for example, a spark ignition engine such as a gasoline engine, or may be a compression ignition engine such as a diesel engine. Exhaust gas after combustion in internal combustion engine 10 is discharged into exhaust pipe 12. The exhaust gas discharged from the internal combustion engine 10 into the exhaust pipe 12 contains harmful components such as nitrogen oxides (NOx). In the present embodiment, nitrogen oxides in the exhaust gas from the internal combustion engine 10 are contained. A temperature controlled demister unit 20 is provided at a position downstream of the exhaust pipe 12 in order to purify harmful components contained therein.
温度調整型デミスタユニット２０において、容器２１には流入口２１ａ及び流出口２１ｂが形成されており、内燃機関１０から排気管１２内に排出された排気は、流入口２１ａから容器２１内に流入し、流出口２１ｂから容器２１外へ流出する。容器２１内には、流入口２１ａから流入した排気と接触するデミスタ部２２と、デミスタ部２２の温度を調整する温度調整部２３が収容されている。 In the temperature controlled demister unit 20, an inlet 21a and an outlet 21b are formed in the container 21, and the exhaust gas discharged from the internal combustion engine 10 into the exhaust pipe 12 flows into the container 21 from the inlet 21a. , And flow out of the container 21 from the outlet 21b. In the container 21, a demister portion 22 in contact with the exhaust gas flowing from the inflow port 21a and a temperature control portion 23 for adjusting the temperature of the demister portion 22 are accommodated.
容器２１内のデミスタ部２２及び温度調整部２３の構成例を図２，３に示す。図２は１層あたりの構造例を示し、図３は図２の構造を多層化した構成例を示す。図２に示すように、温度調整部として冷却管２３が蛇行して設けられ、デミスタ部として針金２２が冷却管２３に巻き付けられた状態で編目状に形成されている。そして、冷却管２３に針金２２を巻き付けた構造が、図３に示すように、容器２１内における排気流れ方向（矢印Ａに示す方向）に沿って多数並べられている。 The structural example of the demister part 22 and the temperature control part 23 in the container 21 is shown to FIG. FIG. 2 shows a structural example per layer, and FIG. 3 shows a structural example in which the structure of FIG. 2 is multilayered. As shown in FIG. 2, a cooling pipe 23 is provided in a meandering manner as a temperature control section, and a wire 22 is formed in a mesh shape in a state of being wound around the cooling pipe 23 as a demister section. Then, as shown in FIG. 3, many structures in which the wire 22 is wound around the cooling pipe 23 are arranged along the exhaust flow direction (the direction shown by the arrow A) in the container 21.
図２，３の矢印Ｂに示すように冷却管２３内を冷却水等の液体冷媒が流れることで、冷却管２３に接触するデミスタ部（針金）２２が冷却され、デミスタ部２２の温度が調整される。冷却水は、容器２１外に設置された冷却水貯蔵タンク２４内に貯留され、電動ポンプ２５の駆動により冷却管２３内へ供給されて循環する。冷却水貯蔵タンク２４内の冷却水量レベルＬｗは水量レベルセンサ２６で監視され、水量レベル維持装置により冷却水量レベルＬｗが規定範囲内に維持される。冷却管２３内を通る冷却水温度Ｔｗは水温センサ２７で監視され、水温調整装置により冷却水温度Ｔｗが設定温度に調整される。 The liquid refrigerant such as cooling water flows in the cooling pipe 23 as shown by the arrow B in FIGS. 2 and 3 to cool the demister part (wire) 22 in contact with the cooling pipe 23, and the temperature of the demister part 22 is adjusted. Be done. The cooling water is stored in a cooling water storage tank 24 installed outside the container 21 and is supplied into the cooling pipe 23 by the drive of the electric pump 25 and circulated. The coolant level Lw in the coolant storage tank 24 is monitored by the water level sensor 26, and the coolant level maintenance device maintains the coolant level Lw within a specified range. The coolant temperature Tw passing through the inside of the cooling pipe 23 is monitored by the coolant temperature sensor 27, and the coolant temperature Tw is adjusted to the set temperature by the coolant temperature control device.
ガソリンエンジンやディーゼルエンジン等の内燃機関１０から排気管１２内へ排出される排気中には、燃料の燃焼で生成された水が水蒸気として存在しており、さらに、排気中のＮＯｘが水（水蒸気）と反応することで硝酸（ＨＮＯ3）や硝酸イオンが生成される。温度調整型デミスタユニット２０において、流入口２１ａから容器２１内に流入した排気は、図２，３の矢印Ａの方向に流れ、デミスタ部（針金）２２に接触しながら編目状の針金２２間の隙間を通過する。その際には、排気中の水蒸気が凝縮して水滴（液体）となって針金２２に付着し、この水滴に、ＮＯｘ（例えばＮＯ2）、硝酸、硝酸イオン、アルデヒド等、排気中の水溶性ガスが溶け込むことで、これらの水溶性ガスが水とともに排気から分離・除去される。水溶性ガスが溶け込んだ水滴は、重力によって鉛直下方に落下して凝集液貯蔵タンク２８内に貯留される。凝集液貯蔵タンク２８内の水に吸収された硝酸や硝酸イオンについては、硝酸イオン濃度計やｐＨ計等を用いて硝酸量を監視することが好ましい。また、針金２２間の隙間を通過した排気は、流出口２１ｂから容器２１外へ流出する。このように、温度調整型デミスタユニット２０は、デミスタ部２２に接触する排気中の水分を排気中の水溶性ガスとともにデミスタ部２２で捕捉することで、排気中の水溶性ガスを浄化する。なお、デミスタ部２２の構成は、排気中の水分を捕捉可能な構成であればどのような構成でもよく、図２，３の構成に限定されるものではない。そして、温度調整部２３の構成も、デミスタ部２２の温度を調整可能な構成であればどのような構成でもよく、図２，３の構成に限定されるものではない。 In the exhaust discharged from the internal combustion engine 10 such as a gasoline engine or a diesel engine into the exhaust pipe 12, water generated by combustion of the fuel is present as water vapor, and NOx in the exhaust is water (water vapor Nitric acid (HNO 3 ) and nitrate ions are produced by reacting with. In the temperature-controlled demister unit 20, the exhaust gas flowing into the container 21 from the inflow port 21a flows in the direction of arrow A in FIGS. 2 and 3 and contacts the demister portion (wire) 22 between the meshed wires 22. Pass through the gap. At this time, the water vapor in the exhaust condenses to form water droplets (liquid) and adheres to the wire 22. In this water droplet, NOx (for example, NO 2 ), nitric acid, nitrate ion, aldehyde, etc. As the gas dissolves, these water-soluble gases are separated and removed from the exhaust together with the water. The water droplets in which the water-soluble gas is dissolved fall vertically downward by gravity and are stored in the coagulated liquid storage tank 28. With regard to nitric acid and nitrate ions absorbed in water in the coagulated liquid storage tank 28, it is preferable to monitor the amount of nitric acid using a nitrate ion concentration meter or a pH meter. Further, the exhaust gas having passed through the gap between the wires 22 flows out of the container 21 from the outlet 21 b. As described above, the temperature control type demister unit 20 purifies water-soluble gas in the exhaust gas by capturing moisture in the exhaust gas contacting the demister portion 22 together with water-soluble gas in the exhaust gas by the demister portion 22. The configuration of the demister unit 22 may be any configuration as long as it can capture moisture in the exhaust gas, and is not limited to the configurations shown in FIGS. Further, the configuration of the temperature adjustment unit 23 may be any configuration as long as the temperature of the demister unit 22 can be adjusted, and is not limited to the configurations of FIGS.
排気中の水蒸気は、温度が低くなれば露点温度で凝縮して液体の水になるが、その露点温度は排気中の水蒸気濃度に応じて変化し、排気中の水蒸気濃度の低下に対して露点温度が低下する。排気中の飽和水蒸気濃度は排気温度に応じて変化し、図４に示すように、排気温度の低下に対して排気中の飽和水蒸気濃度が低下する。したがって、排気中の水蒸気をデミスタ部２２で凝縮させて水溶性ガスを吸収する性能は、デミスタ部２２の温度や排気中の水蒸気濃度に依存して変化する。一例としてデミスタ部２２の温度に対するＨＮＯ3吸収率の関係を図５に示す。図５に示すように、デミスタ部２２の温度の低下に対してＨＮＯ3吸収率が高くなる。 The water vapor in the exhaust condenses at the dew point temperature and becomes liquid water when the temperature decreases, but the dew point temperature changes according to the water vapor concentration in the exhaust, and the dew point against the reduction of the water vapor concentration in the exhaust The temperature drops. The saturated water vapor concentration in the exhaust gas changes in accordance with the exhaust gas temperature, and as shown in FIG. 4, the saturated water vapor concentration in the exhaust gas decreases as the exhaust gas temperature decreases. Therefore, the ability to condense water vapor in the exhaust gas by the demister 22 and absorb the water-soluble gas varies depending on the temperature of the demister 22 and the water vapor concentration in the exhaust gas. The relationship between the HNO 3 absorptivity and the temperature of the demister portion 22 is shown in FIG. 5 as an example. As shown in FIG. 5, the HNO 3 absorptivity increases as the temperature of the demister portion 22 decreases.
また、内燃機関１０からの排気中の水蒸気濃度は、内燃機関１０の空燃比Ａ／Ｆに応じて変化する。例えば理論空燃比Ａ／Ｆ＝１４．７で燃焼させた場合の排気中には、理論上約１５％程度の水蒸気が含まれるが、酸素過剰雰囲気のＡ／Ｆ＝４０では、排気中に含まれる水蒸気が約６％程度に減少する。また、空燃比Ａ／Ｆがリッチである（理論空燃比より小さい）場合も、排気中に含まれる水蒸気が理論空燃比に比べて減少する。したがって、内燃機関１０の空燃比Ａ／Ｆに応じて排気中の水蒸気が凝縮する露点温度が変化し、例えば酸素過剰の希薄燃焼（リーンバーン）等、空燃比Ａ／Ｆが理論空燃比から離れるほど露点温度が低下する。空燃比Ａ／Ｆが理論空燃比から離れる等、排気中の水蒸気濃度が低下して露点温度が低下すると、排気中の水蒸気がデミスタ部２２で凝縮しにくくなり、ＨＮＯ3等、排気中の水溶性ガスが吸収されにくくなる。排気中の水蒸気をデミスタ部２２で凝縮させて水溶性ガスを吸収する性能を向上させるためには、容器２１内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなる、つまりデミスタ部２２に接触する排気中の水分が露点温度より低くなる結露条件が成立することが望ましい。 Further, the water vapor concentration in the exhaust gas from the internal combustion engine 10 changes in accordance with the air-fuel ratio A / F of the internal combustion engine 10. For example, the exhaust gas when burned at the theoretical air-fuel ratio A / F = 14.7 theoretically contains about 15% of water vapor, but when A / F = 40 in the oxygen excess atmosphere, it is contained in the exhaust gas Water vapor is reduced to about 6%. Also, when the air-fuel ratio A / F is rich (less than the stoichiometric air-fuel ratio), the water vapor contained in the exhaust gas is reduced compared to the stoichiometric air-fuel ratio. Therefore, the dew point temperature at which the water vapor in the exhaust condenses changes according to the air-fuel ratio A / F of the internal combustion engine 10, and the air-fuel ratio A / F deviates from the theoretical air-fuel ratio As the dew point temperature decreases. When the water vapor concentration in the exhaust gas decreases such that the air fuel ratio A / F deviates from the theoretical air fuel ratio and the dew point temperature decreases, the water vapor in the exhaust gas is less likely to condense in the demister 22 and HNO 3 etc. It is difficult to absorb sexual gases. In order to condense the water vapor in the exhaust gas in the demister portion 22 and improve the ability to absorb the water-soluble gas, the water vapor concentration in the exhaust gas flowing into the container 21 becomes higher than the saturated water vapor concentration. It is desirable that the dew condensation condition in which the moisture in the exhaust gas in contact is lower than the dew point temperature is satisfied.
そこで、温度調整部２３は、容器２１内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように、デミスタ部２２の温度を調整する。図１に示すように、温度調整型デミスタユニット２０より上流側の排気管１２には水蒸気濃度センサ３２が付設されており、容器２１内に流入する排気中の水蒸気濃度Ｄが水蒸気濃度センサ３２により検出されて電子制御装置（ＥＣＵ）４０に入力される。電子制御装置４０は、水蒸気濃度Ｄが飽和水蒸気濃度より高くなる、つまり容器２１内のデミスタ部２２雰囲気温度Ｔｄが露点温度より低くなるように、電動ポンプ２５の駆動制御により冷却管２３内に流す冷却水流量を制御する。ここでの露点温度については、水蒸気濃度Ｄに対応する露点温度として算出可能であり、ここでの飽和水蒸気濃度については、デミスタ部２２雰囲気温度Ｔｄに対応する飽和水蒸気濃度として算出可能である。デミスタ部２２雰囲気温度Ｔｄについては、容器２１内の雰囲気温度を温度センサにより直接検出してもよいし、水温センサ２７により検出された冷却水温度Ｔｗをデミスタ部２２の温度として代用することも可能である。これによって、容器２１内に流入する排気中の水蒸気濃度Ｄがデミスタ部２２雰囲気温度Ｔｄに対応する飽和水蒸気濃度より高くなる、つまりデミスタ部２２に接触する排気中の水分が排気中の水蒸気濃度Ｄに対応する露点温度より低くなる結露条件が成立するように、冷却管２３によりデミスタ部２２が冷却される。なお、前述のように、排気中の水蒸気濃度Ｄは内燃機関１０の空燃比Ａ／Ｆと相関があるため、排気中の水蒸気濃度Ｄについては、水蒸気濃度センサ３２により直接検出する以外に、内燃機関１０の空燃比Ａ／Ｆ（例えば空燃比センサにより検出）から算出することも可能である。 Therefore, the temperature adjustment unit 23 adjusts the temperature of the demister unit 22 so that the water vapor concentration in the exhaust flowing into the container 21 becomes higher than the saturated water vapor concentration. As shown in FIG. 1, a water vapor concentration sensor 32 is attached to the exhaust pipe 12 upstream of the temperature control type demister unit 20, and the water vapor concentration D in the exhaust flowing into the container 21 is detected by the water vapor concentration sensor 32. It is detected and input to the electronic control unit (ECU) 40. The electronic control unit 40 causes the electric pump 25 to drive and control flow into the cooling pipe 23 so that the water vapor concentration D becomes higher than the saturated water vapor concentration, that is, the atmosphere temperature Td of the demister 22 in the container 21 becomes lower than the dew point temperature. Control the coolant flow rate. The dew point temperature here can be calculated as the dew point temperature corresponding to the water vapor concentration D, and the saturated water vapor concentration here can be calculated as the saturated water vapor concentration corresponding to the demister portion 22 ambient temperature Td. For the demister portion 22 ambient temperature Td, the ambient temperature in the container 21 may be directly detected by a temperature sensor, or the coolant temperature Tw detected by the water temperature sensor 27 may be substituted as the temperature of the demister portion 22. It is. As a result, the water vapor concentration D in the exhaust flowing into the container 21 becomes higher than the saturated water vapor concentration corresponding to the demister portion 22 atmosphere temperature Td, that is, the water concentration in the exhaust water of the exhaust gas in contact with the demister portion 22 The demister portion 22 is cooled by the cooling pipe 23 such that the dew condensation condition which becomes lower than the dew point temperature corresponding to the above is satisfied. As described above, since the water vapor concentration D in the exhaust gas is correlated with the air-fuel ratio A / F of the internal combustion engine 10, the water vapor concentration D in the exhaust gas is not detected directly by the water vapor concentration sensor 32. It is also possible to calculate from the air-fuel ratio A / F of the engine 10 (for example, detected by an air-fuel ratio sensor).
以上説明した本実施形態によれば、排気中の水蒸気をデミスタ部２２で凝縮させて排気中のＮＯｘ（例えばＮＯ2）、硝酸、硝酸イオン、アルデヒド等の水溶性ガスを凝縮後の水に吸収することで、排気中の水溶性ガスを浄化することができる。その際には、上記の結露条件が成立するように、温度調整部２３によりデミスタ部２２の温度調整（冷却）を行うことで、内燃機関１０からの排気中の水蒸気濃度が低くなったり、内燃機関１０からの排気温度が高くなる等、内燃機関１０の運転状態が変化しても、排気中の水蒸気をデミスタ部２２で安定して効率よく凝縮させることができ、排気中の水溶性ガスを浄化する性能の低下を抑制することができる。 According to the present embodiment described above, the water vapor in the exhaust gas is condensed by the demister portion 22 and the water-soluble gas such as NOx (eg, NO 2 ), nitric acid, nitrate ion, and aldehyde in the exhaust gas is absorbed in water after condensation. Thus, the water-soluble gas in the exhaust can be purified. At that time, the temperature adjustment unit 23 performs temperature adjustment (cooling) of the demister unit 22 so that the above-described dew condensation condition is satisfied, so that the water vapor concentration in the exhaust gas from the internal combustion engine 10 decreases, or the internal combustion engine Even if the operating condition of the internal combustion engine 10 changes, such as the exhaust temperature from the engine 10 becomes high, the water vapor in the exhaust can be stably and efficiently condensed by the demister 22 and the water soluble gas in the exhaust can be It is possible to suppress the decrease in the purification performance.
なお、電子制御装置４０は、容器２１内に流入する排気中の水蒸気濃度Ｄが飽和水蒸気濃度より高くなるように、内燃機関１０の空燃比Ａ／Ｆを制御することで、排気中の水蒸気濃度Ｄを制御することも可能である。その際には、水蒸気濃度Ｄがデミスタ部２２雰囲気温度Ｔｄに対応する飽和水蒸気濃度より高くなる（デミスタ部２２に接触する排気中の水分が水蒸気濃度Ｄに対応する露点温度より低くなる）結露条件が成立するように、内燃機関１０の空燃比Ａ／Ｆが制御される。これによって、内燃機関１０からの排気温度が高くなる等、内燃機関１０の運転状態が変化しても、排気中の水蒸気をデミスタ部２２で安定して効率よく凝縮させることができ、排気中の水溶性ガスを浄化する性能の低下を抑制することができる。 Note that the electronic control unit 40 controls the air-fuel ratio A / F of the internal combustion engine 10 so that the water vapor concentration D in the exhaust flowing into the container 21 becomes higher than the saturated water vapor concentration, to thereby control the water vapor concentration in the exhaust gas. It is also possible to control D. In this case, the water vapor concentration D becomes higher than the saturated water vapor concentration corresponding to the atmosphere temperature Td of the demister portion 22 (the water content in the exhaust contacting the demister portion 22 becomes lower than the dew point temperature corresponding to the water vapor concentration D) The air-fuel ratio A / F of the internal combustion engine 10 is controlled such that As a result, even if the operating state of the internal combustion engine 10 changes, such as the exhaust gas temperature from the internal combustion engine 10 becomes high, the water vapor in the exhaust can be stably and efficiently condensed by the demister portion 22. It is possible to suppress the decrease in the performance of purifying the water-soluble gas.
また、図１に示すように、排気管１２（水蒸気濃度センサ３２より上流側の位置）に水添加装置３４を設け、水添加装置３４から排気管１２内の排気に水（水蒸気）を添加することで、容器２１内に流入する排気中の水蒸気濃度Ｄを調整することも可能である。そして、水添加装置３４は、容器２１内に流入する排気中の水蒸気濃度Ｄが飽和水蒸気濃度より高くなるように、内燃機関１０からの排気に水（水蒸気）を添加することも可能である。その際に、電子制御装置４０は、水蒸気濃度Ｄがデミスタ部２２雰囲気温度Ｔｄに対応する飽和水蒸気濃度より高くなる（デミスタ部２２に接触する排気中の水分が水蒸気濃度Ｄに対応する露点温度より低くなる）結露条件が成立するように、水添加装置３４により添加する水蒸気量を制御することで、容器２１内に流入する排気中の水蒸気濃度Ｄを制御する。これによって、内燃機関１０からの排気中の水蒸気濃度が低くなったり、内燃機関１０からの排気温度が高くなる等、内燃機関１０の運転状態が変化しても、排気中の水蒸気をデミスタ部２２で安定して効率よく凝縮させることができ、排気中の水溶性ガスを浄化する性能の低下を抑制することができる。なお、水添加装置３４は、容器２１内に流入する排気中の水蒸気濃度Ｄを調整可能な構成であればどのような構成でもよく、例えばスプレノズル等で水を排気管１２内へ噴霧してもよいし、多孔質膜型の加湿器を用いてもよい。 Further, as shown in FIG. 1, the water addition device 34 is provided in the exhaust pipe 12 (a position upstream of the water vapor concentration sensor 32), and water (water vapor) is added from the water addition apparatus 34 to the exhaust in the exhaust pipe 12. Thus, it is also possible to adjust the water vapor concentration D in the exhaust flowing into the container 21. The water addition device 34 can also add water (water vapor) to the exhaust from the internal combustion engine 10 so that the water vapor concentration D in the exhaust flowing into the container 21 becomes higher than the saturated water vapor concentration. At that time, the electronic control unit 40 makes the water vapor concentration D higher than the saturated water vapor concentration corresponding to the demister portion 22 atmosphere temperature Td (the dew point temperature of the water in the exhaust gas contacting the demister portion 22 corresponds to the water vapor concentration D The water vapor concentration D in the exhaust flowing into the container 21 is controlled by controlling the amount of water vapor to be added by the water addition device 34 so that the dew condensation condition becomes low. As a result, even if the operating condition of the internal combustion engine 10 changes, such as the water vapor concentration in the exhaust gas from the internal combustion engine 10 decreases, the exhaust gas temperature from the internal combustion engine 10 increases, etc. Thus, condensation can be stably and efficiently performed, and deterioration in the ability to purify the water-soluble gas in the exhaust can be suppressed. The water addition device 34 may have any configuration as long as it can adjust the water vapor concentration D in the exhaust flowing into the container 21. For example, even if water is sprayed into the exhaust pipe 12 with a spray nozzle or the like. A porous membrane type humidifier may be used.
また、内燃機関１０の運転時には、電子制御装置４０が図６のフローチャートに示す処理を実行することも可能である。まずステップＳ１０１では、水蒸気濃度Ｄがデミスタ部２２雰囲気温度Ｔｄに対応する飽和水蒸気濃度より高くなる（デミスタ部２２に接触する排気中の水分が水蒸気濃度Ｄに対応する露点温度より低くなる）結露条件が成立するか否かが判定される。結露条件が成立する場合（ステップＳ１０１の判定結果がＹＥＳの場合）は、本処理の実行を終了する。一方、結露条件が成立しない場合（ステップＳ１０１の判定結果がＮＯの場合）は、ステップＳ１０２に進む。 Further, at the time of operation of the internal combustion engine 10, the electronic control device 40 can also execute the processing shown in the flowchart of FIG. First, in step S101, the water vapor concentration D becomes higher than the saturated water vapor concentration corresponding to the atmosphere temperature Td of the demister portion 22 (the water content in the exhaust contacting the demister portion 22 becomes lower than the dew point temperature corresponding to the water vapor concentration D) It is determined whether or not If the dew condensation condition is satisfied (if the determination result in step S101 is YES), the execution of this process ends. On the other hand, when the dew condensation condition is not satisfied (when the determination result of step S101 is NO), the process proceeds to step S102.
ステップＳ１０２では、電動ポンプ２５の駆動制御により冷却管２３内に流す冷却水流量が制御されることで、デミスタ部２２の温度が低下するように温度調整（冷却）が行われる。その際には、電動ポンプ２５の回転数が設定回転数以下に制限されることで、冷却管２３内に流す冷却水流量が設定流量以下に制限される。次にステップＳ１０３では、冷却管２３内に流す冷却水流量が設定流量以下の条件でデミスタ部２２の冷却を行うことで、上記の結露条件が成立するか否かが判定される。冷却水流量が設定流量以下の条件で結露条件が成立する場合（ステップＳ１０３の判定結果がＹＥＳの場合）は、本処理の実行を終了する。一方、冷却水流量を設定流量まで増加させても結露条件が成立しない場合（ステップＳ１０３の判定結果がＮＯの場合）は、ステップＳ１０４に進む。 In step S102, the temperature control (cooling) is performed such that the temperature of the demister unit 22 is lowered by controlling the flow rate of the cooling water flowing into the cooling pipe 23 by the drive control of the electric pump 25. At that time, the rotational speed of the electric pump 25 is limited to the set rotational speed or less, whereby the flow rate of the cooling water flowing in the cooling pipe 23 is restricted to the set flow rate or less. Next, in step S103, by performing cooling of the demister portion 22 under the condition that the flow rate of the cooling water flowing into the cooling pipe 23 is equal to or less than the set flow rate, it is determined whether the above-described condensation condition is satisfied. If the condensation condition is satisfied under the condition that the coolant flow rate is equal to or less than the set flow rate (if the determination result in step S103 is YES), the execution of this process is ended. On the other hand, when the condensation condition is not satisfied even if the coolant flow rate is increased to the set flow rate (when the determination result in step S103 is NO), the process proceeds to step S104.
ステップＳ１０４では、内燃機関１０の空燃比Ａ／Ｆが理論空燃比に近づくように制御されることで、容器２１内に流入する排気中の水蒸気濃度Ｄを増加させる。次にステップＳ１０５では、内燃機関１０の空燃比制御を行うことで、上記の結露条件が成立するか否かが判定される。内燃機関１０の空燃比制御により排気中の水蒸気濃度Ｄを増加させることで結露条件が成立する場合（ステップＳ１０５の判定結果がＹＥＳの場合）は、本処理の実行を終了する。一方、内燃機関１０の空燃比Ａ／Ｆを理論空燃比に制御しても結露条件が成立しない場合（ステップＳ１０５の判定結果がＮＯの場合）は、ステップＳ１０６に進む。 In step S104, the air-fuel ratio A / F of the internal combustion engine 10 is controlled to approach the stoichiometric air-fuel ratio, whereby the water vapor concentration D in the exhaust flowing into the container 21 is increased. Next, in step S105, by performing air-fuel ratio control of the internal combustion engine 10, it is determined whether the above-described condensation condition is satisfied. If the condensation condition is satisfied by increasing the water vapor concentration D in the exhaust gas by air-fuel ratio control of the internal combustion engine 10 (if the determination result in step S105 is YES), the execution of the present process is ended. On the other hand, if the condensation condition is not satisfied even if the air-fuel ratio A / F of the internal combustion engine 10 is controlled to the stoichiometric air-fuel ratio (if the determination result in step S105 is NO), the process proceeds to step S106.
ステップＳ１０６では、水添加装置３４により排気管１２内の排気に水蒸気が添加されることで、容器２１内に流入する排気中の水蒸気濃度Ｄを増加させる。その際には、上記の結露条件が成立するように、水添加装置３４により排気に添加される水蒸気量が制御される。そして、本処理の実行を終了する。 In step S106, water vapor is added to the exhaust gas in the exhaust pipe 12 by the water addition device 34, whereby the water vapor concentration D in the exhaust gas flowing into the container 21 is increased. At this time, the amount of water vapor added to the exhaust gas is controlled by the water addition device 34 so that the above-described condensation condition is satisfied. Then, the execution of this process ends.
図６のフローチャートによれば、容器２１内に流入する排気中の水蒸気濃度Ｄを飽和水蒸気濃度より高くする（デミスタ部２２に接触する排気中の水分を露点温度より低くする）ための優先順位が、温度調整部２３によるデミスタ部２２の温度調整、内燃機関１０の空燃比制御、水添加装置３４による水添加の順に設定される。温度調整部（冷却管）２３によるデミスタ部２２の温度調整の際に、冷却管２３内に流す冷却水流量が設定流量以下の条件で上記の結露条件が成立しないと判定された場合は、内燃機関１０の空燃比制御により排気中の水蒸気濃度Ｄを増加させることで、電動ポンプ２５の消費電力を削減することができる。そして、内燃機関１０の空燃比Ａ／Ｆを理論空燃比に制御しても上記の結露条件が成立しないと判定された場合に、水添加装置３４からの水添加により排気中の水蒸気濃度Ｄを増加させることで、水添加装置３４による水添加のために必要な水の量を抑えることができる。 According to the flowchart of FIG. 6, the priority for setting the water vapor concentration D in the exhaust flowing into the container 21 higher than the saturated water vapor concentration (lowering the water content in the exhaust contacting the demister portion 22 than the dew point temperature) is The temperature adjustment of the demister unit 22 by the temperature adjustment unit 23, the air-fuel ratio control of the internal combustion engine 10, and the water addition by the water addition device 34 are set in this order. When it is determined that the above-described dew condensation condition does not hold under the condition that the flow rate of the cooling water flowing into the cooling pipe 23 is equal to or less than the set flow rate when adjusting the temperature of the demister section 22 by the temperature adjusting section (cooling pipe) By increasing the water vapor concentration D in the exhaust gas by air-fuel ratio control of the engine 10, the power consumption of the electric pump 25 can be reduced. Then, when it is determined that the above condensation condition does not hold even if the air fuel ratio A / F of the internal combustion engine 10 is controlled to the theoretical air fuel ratio, the water vapor concentration D in the exhaust gas is added by water addition from the water addition device 34 By increasing the amount, the amount of water required for water addition by the water addition device 34 can be reduced.
本実施形態に係る内燃機関の排気浄化装置の他の概略構成を図７に示す。図７の構成例では、図１の構成例と比較して、排気管１２における水添加装置３４より上流側の位置に改質装置１４が設けられ、排気管１２における改質装置１４より上流側の位置に熱交換器１３が設けられている。 Another schematic configuration of the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment is shown in FIG. In the configuration example of FIG. 7, in comparison with the configuration example of FIG. 1, the reforming device 14 is provided at a position upstream of the water adding device 34 in the exhaust pipe 12, and the upstream side of the exhaust pipe 12 from the reforming device 14 The heat exchanger 13 is provided at the position of.
改質装置１４は、窒素酸化物を硝酸（ＨＮＯ3）に変換する反応を促進するための硝酸生成触媒１４ａを有し、内燃機関１０からの排気中の有害成分に含まれる窒素酸化物を硝酸生成触媒１４ａ上で硝酸に改質する。硝酸生成触媒１４ａは、酸点を有する触媒、または酸点を有する担体に銀（Ａｇ）や鉄（Ｆｅ）や銅（Ｃｕ）等の金属が担持された触媒により構成することができる。酸点を有する触媒／担体としては、例えばＺＳＭ−５、ＢＥＡ、ＭＯＲ、ＳＡＰＯ等のゼオライトや、ＳｉＯ2／Ａｌ2Ｏ3、ＳＯ4／ＴｉＯ2の他、ＳｉＯ2／ＴｉＯ2、ＷＯ3／ＴｉＯ2、ＷＯ3／ＺｒＯ2、ＷＯ3／ＳｎＯ2、ＳＯ4／ＺｒＯ2等の複合酸化物を用いることが可能である。改質装置１４での酸化反応のために、排気管１２における改質装置１４より上流側の位置（熱交換器１３と改質装置１４との間の位置）には、オゾン添加弁１９が設けられている。オゾン添加弁１９から改質装置１４へ向けて酸化剤としてのオゾン（Ｏ3）が噴射されることで、改質装置１４に流入する排気中の有害成分にオゾンが添加される。改質装置１４では、一酸化窒素（ＮＯ）や二酸化窒素（ＮＯ2）等の窒素酸化物が、オゾン添加弁１９により添加されたオゾン（Ｏ3）及び内燃機関１０からの排気中に含まれる水分とともに硝酸生成触媒１４ａに接触することで、硝酸（ＨＮＯ3）に酸化改質する。硝酸に転化した有害成分を含む排気は、下流側の温度調整型デミスタユニット２０へ供給される。 The reformer 14 has a nitric acid generation catalyst 14 a for promoting a reaction of converting nitrogen oxides to nitric acid (HNO 3 ), and nitrogen oxides contained in harmful components in exhaust gas from the internal combustion engine 10 are nitrated. It reforms to nitric acid on the formation catalyst 14a. The nitric acid generation catalyst 14a can be configured by a catalyst having an acid point or a catalyst in which a metal such as silver (Ag), iron (Fe), copper (Cu) or the like is supported on a carrier having an acid point. As a catalyst / support having an acid point, for example, zeolites such as ZSM-5, BEA, MOR, SAPO, etc., SiO 2 / Al 2 O 3 , SO 4 / TiO 2 , SiO 2 / TiO 2 , WO 3 / It is possible to use composite oxides such as TiO 2 , WO 3 / ZrO 2 , WO 3 / SnO 2 , SO 4 / ZrO 2 and the like. An ozone addition valve 19 is provided at a position upstream of the reformer 14 in the exhaust pipe 12 (position between the heat exchanger 13 and the reformer 14) for the oxidation reaction in the reformer 14. It is done. By injecting ozone (O 3 ) as an oxidizing agent from the ozone addition valve 19 toward the reformer 14, ozone is added to harmful components in the exhaust flowing into the reformer 14. In the reformer 14, nitrogen oxides such as nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) are contained in ozone (O 3 ) added by the ozone addition valve 19 and exhaust gas from the internal combustion engine 10. By contacting with the nitric acid generation catalyst 14 a together with the moisture, it is oxidized and reformed to nitric acid (HNO 3 ). Exhaust gas containing harmful components converted to nitric acid is supplied to the downstream temperature controlled demister unit 20.
改質装置１４に流入する有害成分に添加されるオゾンを生成するために、オゾン発生装置１８が設けられており、オゾン発生装置１８で生成されたオゾンが、オゾン導管１７内を通ってオゾン添加弁１９から改質装置１４へ向けて噴射される。オゾン発生装置１８では、オゾンはどのような方法で作られてもよいが、例えば水電解装置やプラズマ放電等が挙げられる。なかでも水電解装置を用いることで、高濃度・高純度のオゾンが生成・供給可能となり、効率、コスト、スペース等の点からも有利である。水電解装置とは、水の電気分解によりオゾンと水素を生成する装置のことであり、陽イオン交換膜で隔てられた陽極側で水を分解してオゾンが生成されるとともに、陰極側で陽イオン膜を通過してきた水素イオンから水素ガスが生成される。水電解装置で電気分解に用いられる水については、外部から供給することも可能であるし、排気中の水を回収して供給することも可能である。 An ozone generator 18 is provided to generate ozone to be added to harmful components flowing into the reformer 14, and the ozone generated by the ozone generator 18 passes through the ozone conduit 17 and is added with ozone. The fuel is injected from the valve 19 toward the reformer 14. In the ozone generator 18, ozone may be produced by any method, and examples thereof include a water electrolysis apparatus and plasma discharge. Above all, by using a water electrolysis apparatus, ozone with high concentration and high purity can be generated and supplied, which is advantageous also from the viewpoint of efficiency, cost, space and the like. A water electrolysis apparatus is an apparatus that generates ozone and hydrogen by electrolysis of water, and water is decomposed on the anode side separated by a cation exchange membrane to generate ozone, and the cathode side Hydrogen gas is generated from hydrogen ions that have passed through the ion membrane. The water used for electrolysis in the water electrolysis apparatus can be supplied from the outside, or the water in the exhaust can be recovered and supplied.
改質装置１４の上流側に設けられた熱交換器１３は、内燃機関１０からの排気との熱交換を行うことで、改質装置１４に流入する排気の温度を調整する。これによって、排気と接触する硝酸生成触媒１４ａの温度が調整される。例えば熱交換器１３に冷媒を供給して内燃機関１０からの排気を冷却することで、改質装置１４に流入する排気の温度を下げることができ、硝酸生成触媒１４ａの温度を下げることができる。このように、熱交換器１３は、硝酸生成触媒１４ａの温度を調整するための温度調整装置として機能する。なお、硝酸生成触媒１４ａの温度が高くなると、硝酸の生成に用いられるオゾンが分解されやすくなるとともに、生成された硝酸が逆反応により窒素酸化物に戻りやすくなる。そこで、熱交換器１３は、硝酸生成触媒１４ａの温度を３５０℃以下（より好ましくは３００℃以下）に保持するように、内燃機関１０からの排気との熱交換により硝酸生成触媒１４ａの温度を調整することが好ましい。例えば温度センサで検出した硝酸生成触媒１４ａの温度が３５０℃（より好ましくは３００℃）を超えたら、熱交換器１３に冷媒を供給して硝酸生成触媒１４ａに接触する排気の温度を下げることで、硝酸生成触媒１４ａの温度を３５０℃以下（より好ましくは３００℃以下）に下げることが好ましい。 The heat exchanger 13 provided on the upstream side of the reformer 14 exchanges heat with the exhaust from the internal combustion engine 10 to adjust the temperature of the exhaust flowing into the reformer 14. Thus, the temperature of the nitric acid generation catalyst 14a in contact with the exhaust is adjusted. For example, by supplying the refrigerant to the heat exchanger 13 to cool the exhaust gas from the internal combustion engine 10, the temperature of the exhaust gas flowing into the reforming device 14 can be lowered, and the temperature of the nitric acid generation catalyst 14a can be lowered. . Thus, the heat exchanger 13 functions as a temperature control device for adjusting the temperature of the nitric acid generation catalyst 14a. When the temperature of the nitric acid generation catalyst 14a becomes high, ozone used for the generation of nitric acid is easily decomposed, and the generated nitric acid is easily returned to the nitrogen oxide by the reverse reaction. Therefore, the heat exchanger 13 exchanges the temperature of the nitric acid generation catalyst 14a by heat exchange with the exhaust gas from the internal combustion engine 10 so as to maintain the temperature of the nitric acid generation catalyst 14a at 350 ° C. or lower (more preferably 300 ° C. or lower). It is preferable to adjust. For example, when the temperature of the nitric acid generation catalyst 14a detected by the temperature sensor exceeds 350 ° C. (more preferably 300 ° C.), a refrigerant is supplied to the heat exchanger 13 to lower the temperature of the exhaust contacting the nitric acid generation catalyst 14a. It is preferable to lower the temperature of the nitric acid generation catalyst 14a to 350 ° C. or less (more preferably 300 ° C. or less).
図７の構成例によれば、排気中の窒素酸化物をデミスタ部２２で水に吸収させて捕捉する前に硝酸へ変換しておくことで、水への吸収速度を大幅に向上させることができ、窒素酸化物の浄化率をさらに向上させることができる。さらに、酸点を有する硝酸生成触媒１４ａに窒素酸化物をオゾン及び水とともに接触させることで、硝酸生成触媒１４ａ上で硝酸を高い反応速度で連続的に生成することができる。 According to the configuration example of FIG. 7, the absorption rate to water can be significantly improved by converting the nitrogen oxides in the exhaust into nitric acid before absorption and capture in water by the demister 22. It is possible to further improve the purification rate of nitrogen oxides. Furthermore, nitric acid can be continuously produced at a high reaction rate on the nitric acid production catalyst 14a by bringing the nitrogen oxide into contact with the nitric acid production catalyst 14a having an acid point together with ozone and water.
ただし、ＮＯｘの共存ガスとして、プロピレン（Ｃ3Ｈ6）、エチレン（Ｃ2Ｈ4）等の不飽和炭化水素（オレフィン）や、芳香族の炭化水素が共存する場合は、これら炭化水素とＯ3の反応性が高いため、これら炭化水素との反応にＯ3が消費されてしまい、ＨＮＯ3生成反応に用いられるＯ3量が低下する。そこで、図７の構成例では、排気管１２における改質装置１４及び熱交換器１３より上流側の位置に酸化触媒１６がさらに設けられている。酸化触媒１６は、内燃機関１０からの排気中に含まれる炭化水素（ＴＨＣ）、特にプロピレン（Ｃ3Ｈ6）、エチレン（Ｃ2Ｈ4）等の不飽和炭化水素（オレフィン）や、芳香族の炭化水素を、水（Ｈ2Ｏ）と二酸化炭素（ＣＯ2）に酸化し、排気中に含まれる一酸化炭素（ＣＯ）を二酸化炭素（ＣＯ2）に酸化する。さらに、酸化触媒１６は、内燃機関１０からの排気中に含まれる一酸化窒素（ＮＯ）を二酸化窒素（ＮＯ2）に酸化する。 However, when coexisting unsaturated hydrocarbons (olefins) such as propylene (C 3 H 6 ) and ethylene (C 2 H 4 ) and aromatic hydrocarbons as coexisting gases of NOx, these hydrocarbons and O Since the reactivity of 3 is high, O 3 is consumed in the reaction with these hydrocarbons, and the amount of O 3 used for the HNO 3 generation reaction is reduced. So, in the structural example of FIG. 7, the oxidation catalyst 16 is further provided in the position more upstream than the reforming device 14 and the heat exchanger 13 in the exhaust pipe 12. The oxidation catalyst 16 is a hydrocarbon (THC) contained in the exhaust gas from the internal combustion engine 10, particularly an unsaturated hydrocarbon (olefin) such as propylene (C 3 H 6 ) and ethylene (C 2 H 4 ), and an aromatic Are oxidized to water (H 2 O) and carbon dioxide (CO 2 ), and carbon monoxide (CO) contained in the exhaust is oxidized to carbon dioxide (CO 2 ). Furthermore, the oxidation catalyst 16 oxidizes nitrogen monoxide (NO) contained in the exhaust gas from the internal combustion engine 10 to nitrogen dioxide (NO 2 ).
図７の構成例によれば、排気中に含まれる不飽和炭化水素や芳香族の炭化水素が改質装置１４上流側の酸化触媒１６で酸化されて除去されるため、これら炭化水素との反応にＯ3が消費されるのを抑制することができ、改質装置１４でのＨＮＯ3生成反応に用いられるＯ3量の低下を抑制することができる。さらに、排気中に含まれるＮＯが改質装置１４上流側の酸化触媒１６でＮＯ2に酸化されることによっても、改質装置１４でのＨＮＯ3生成反応に用いられるＯ3量の低下を抑制することができる。したがって、オゾン添加量を増加させることなくＮＯｘ浄化率の低下を抑制することができる。 According to the configuration example of FIG. 7, since the unsaturated hydrocarbon and the aromatic hydrocarbon contained in the exhaust gas are oxidized and removed by the oxidation catalyst 16 on the upstream side of the reformer 14, the reaction with these hydrocarbons is carried out Thus, the consumption of O 3 can be suppressed, and the decrease in the amount of O 3 used for the HNO 3 generation reaction in the reformer 14 can be suppressed. Furthermore, the reduction of the amount of O 3 used for the HNO 3 generation reaction in the reformer 14 is suppressed also by the NO contained in the exhaust being oxidized to NO 2 by the oxidation catalyst 16 on the upstream side of the reformer 14 can do. Therefore, the decrease in the NOx purification rate can be suppressed without increasing the ozone addition amount.
以上、本発明を実施するための形態について説明したが、本発明はこうした実施形態に何等限定されるものではなく、本発明の要旨を逸脱しない範囲内において、種々なる形態で実施し得ることは勿論である。 As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited at all by such embodiment, It can be implemented with various forms in the range which does not deviate from the summary of this invention. Of course.
１０ 内燃機関、１２ 排気管、１３ 熱交換器、１４ 改質装置、１４ａ 硝酸生成触媒、１６ 酸化触媒、１７ オゾン導管、１８ オゾン発生装置、１９ オゾン添加弁、２０ 温度調整型デミスタユニット、２１ 容器、２１ａ 流入口、２１ｂ 流出口、２２ デミスタ部（針金）、２３ 温度調整部（冷却管）、２４ 冷却水貯蔵タンク、２５ 電動ポンプ、２６ 水量レベルセンサ、２７ 水温センサ、２８ 凝集液貯蔵タンク、３２ 水蒸気濃度センサ、３４ 水添加装置、４０ 電子制御装置。 DESCRIPTION OF SYMBOLS 10 internal combustion engine, 12 exhaust pipe, 13 heat exchanger, 14 reformer, 14a nitric acid generation catalyst, 16 oxidation catalyst, 17 ozone conduit, 18 ozone generator, 19 ozone addition valve, 20 temperature control type demister unit, 21 container , 21a inlet, 21b outlet, 22 demister part (wire), 23 temperature control part (cooling pipe), 24 cooling water storage tank, 25 electric pump, 26 water level sensor, 27 water temperature sensor, 28 condensed liquid storage tank, 32 water vapor concentration sensor, 34 water addition device, 40 electronic control device.
Claims (6)
内燃機関からの排気が流入する容器内に、排気と接触するデミスタ部と、デミスタ部の温度を調整する温度調整部とを備え、デミスタ部に接触する排気中の水分を排気中の水溶性ガスとともにデミスタ部で捕捉する温度調整型デミスタユニットと、
排気中の水蒸気濃度を検出する水蒸気濃度センサと、
検出された水蒸気濃度に基づき、デミスタ部における排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように温度調整部を制御する制御部と、
を有する、内燃機関の排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine
A demister portion in contact with the exhaust gas and a temperature control portion for adjusting the temperature of the demister portion are provided in a container into which exhaust gas from the internal combustion engine flows, and water soluble gas in the exhaust gas is supplied with water in the exhaust gas contacting the demister portion. a temperature adjusting type demister unit that captures in demister with,
A water vapor concentration sensor that detects the water vapor concentration in the exhaust;
A control unit that controls the temperature adjustment unit such that the water vapor concentration in the exhaust in the demister unit is higher than the saturated water vapor concentration based on the detected water vapor concentration;
An exhaust purification system for an internal combustion engine, comprising:
制御部が、容器内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように、内燃機関の空燃比を制御する、内燃機関の排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine according to claim 1 , wherein
Control unit, so that the water vapor concentration in the exhaust gas flowing into the container becomes higher than the saturated water vapor concentration, to control the air-fuel ratio of an internal combustion engine, an exhaust purifying apparatus for an internal combustion engine.
容器内に流入する排気中の水蒸気濃度が飽和水蒸気濃度より高くなるように、内燃機関からの排気に水を添加する水添加装置を有する、内燃機関の排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2 , wherein
An exhaust gas purification apparatus for an internal combustion engine, comprising: a water addition device that adds water to exhaust gas from the internal combustion engine such that the water vapor concentration in the exhaust flowing into the container becomes higher than the saturated water vapor concentration.
容器内に流入する排気中の水蒸気濃度を飽和水蒸気濃度より高くするための優先順位が、温度調整部によるデミスタ部の温度調整、内燃機関の空燃比制御、水添加装置による水添加の順に設定されている、内燃機関の排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein a second aspect is cited .
Priority for higher than the saturated steam concentration of water vapor concentration in the exhaust gas flowing into the container is, the temperature adjustment of the demister by the temperature adjustment unit, the air-fuel ratio control of the internal combustion engine, setting the order of addition of water by water addition device The exhaust gas purification system for internal combustion engines.
内燃機関からの排気が流入する容器内に、排気と接触するデミスタ部と、デミスタ部の温度を調整する温度調整部とを備え、デミスタ部に接触する排気中の水分を排気中の水溶性ガスとともにデミスタ部で捕捉する温度調整型デミスタユニットと、
内燃機関からの排気に水を添加する水添加装置と、
を有し、
容器内に流入する排気中の水蒸気濃度を飽和水蒸気濃度より高くするための優先順位が、温度調整部によるデミスタ部の温度調整、内燃機関の空燃比制御、水添加装置による水添加の順に設定されている、内燃機関の排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine
A demister portion in contact with the exhaust gas and a temperature control portion for adjusting the temperature of the demister portion are provided in a container into which exhaust gas from the internal combustion engine flows, and water soluble gas in the exhaust gas is supplied with water in the exhaust gas contacting the demister portion. Temperature controlled demister unit to be captured by the demister section together with
A water addition device for adding water to exhaust gas from an internal combustion engine ;
Have
Priorities for making the water vapor concentration in the exhaust flowing into the container higher than the saturated water vapor concentration are set in the order of temperature adjustment of the demister by the temperature adjustment unit, air-fuel ratio control of the internal combustion engine, and water addition by the water addition device. The exhaust purification system for internal combustion engines.
温度調整型デミスタユニットは、温度調整部として、冷媒が流れる冷却管を備える、内燃機関の排気浄化装置。 An exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein
The temperature control type demister unit includes, as a temperature control unit, a cooling pipe through which a refrigerant flows, and an exhaust gas purification apparatus for an internal combustion engine.
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