JP2005319421A - Filter for treating exhaust gas and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter for treating exhaust gas with which soot is captured when an engine is started and the differential pressure rise of which after the engine is started is prevented, and to provide a method for manufacturing the filter. <P>SOLUTION: The filter for treating exhaust gas is used for introducing the exhaust gas flowing from an exhaust gas inlet-side gas flow passage into an adjacent outlet-side gas flow passage through an oxidation catalyst-deposited porous partition wall of the exhaust gas inlet-side gas flow passage and discharging the treated exhaust gas from the outlet-side flow passage. Inorganic particles 2 having 2-20 μm average particle size are stuck to the catalyst-deposited porous partition wall 1 of a DPF (diesel particulate filter) by 0.2-2 wt.% of the filter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、排ガス処理用フィルタおよびその製法に係り、特に自動車用及び定置用の排ガスへ中に含まれる粒子状物質（PM）を除去するための排ガス処理用フィルタおよびその製法に関する。   The present invention relates to an exhaust gas treatment filter and a method for producing the same, and more particularly to an exhaust gas treatment filter for removing particulate matter (PM) contained in automobile and stationary exhaust gas and a method for producing the same.

最近、内燃機関である分散型電源用ディーゼルエンジンを利用したコジェネレーションシステム、自動車等の輸送機関が都市部を中心として増加しており、これらの排ガスに対して、PM、窒素酸化物（NOx）の排出規制が適用され、かつ地域によっては強化されるため、大型プラントと同様に排ガス処理装置の設置が急務となっている。特に排ガス処理装置に用いられるディーゼルパティキュレートフィルタ（DPF）は排ガス中に含まれるPMを除去するもので重要である。   Recently, the number of cogeneration systems using diesel engines for distributed power sources, which are internal combustion engines, and transportation systems such as automobiles are increasing mainly in urban areas. As the large-scale plant is installed, exhaust gas treatment equipment is urgently needed. In particular, a diesel particulate filter (DPF) used in an exhaust gas treatment apparatus is important because it removes PM contained in exhaust gas.

DPFは、典型的には多孔質隔壁によって区分されたハニカムのガス流路の流入部および排出部の一方が隣り合う流路で交互に封じたもので、排ガスを該多孔質隔壁に通過させて排ガス中のPMを除去するものである。DPFには、セラミック製ハニカム構造体によりPMをハニカム壁で捕捉するものが最も多いが（特許文献１および２）、耐熱性繊維の積層体フィルタによりPMを捕捉するものも知られている（特許文献３および４）。
特開2003-205245号公報 特開2002-309923号公報 特開2002-357113号公報 特開2002-27918号公報 DPF is typically a honeycomb gas flow path divided by porous partition walls, and one of the inflow and discharge sections of the honeycomb is alternately sealed by adjacent flow paths, and exhaust gas is allowed to pass through the porous partition walls. It removes PM in exhaust gas. Most DPFs capture PM with a honeycomb wall using a ceramic honeycomb structure (Patent Documents 1 and 2), but those that capture PM with a laminated filter of heat-resistant fibers are also known (patents). References 3 and 4).
Japanese Patent Laid-Open No. 2003-205245 JP 2002-309923 A JP 2002-357113 A JP 2002-27918

上記した従来技術において、特許文献１および２に記載された方法はDPFのハニカム壁の気孔率が小さい場合、ハニカム壁にPMが次第に蓄積して、最終的に閉塞(上限差圧)する場合がある。逆に気孔率が大きい場合、DPF担体の製造時の成形性が不良となり、歩留まりが低いため、コストがかかったり、ハニカム壁をPMが通過することがある。   In the above-described prior art, in the methods described in Patent Documents 1 and 2, when the porosity of the DPF honeycomb wall is small, PM may gradually accumulate on the honeycomb wall and eventually clog (upper differential pressure). is there. On the other hand, when the porosity is high, the formability during the production of the DPF carrier becomes poor and the yield is low, so that the cost may be increased and PM may pass through the honeycomb wall.

ディ−ゼルエンジンは始動直後に短時間であるが比較的多量の煤を排出するため、酸化触媒を担持した、DPFを使用すれば煤を捕捉でき、捕捉された煤は熱および酸化触媒によって徐々に燃焼されるが、気孔率の小さいDPFは煤の燃焼速度より煤の捕捉速度が高い場合、煤が徐々に蓄積することによってDPF差圧が大きくなる。この気孔率の小さいDPFを使用し続けるとDPF差圧が上限に達し、DPF自身の破壊やエンジントラブルの原因となる。特に定置式ディ−ゼルエンジンは使用する燃料が重油系になるため始動直後の煤量は多い傾向がある。そのため気孔率が50〜65％と比較的高いDPFが使用される。しかし気孔率が比較的高いDPFを使用した場合であっても、新品のDPFを使用するとエンジン始動後数分から約120分の間、DPFの差圧がかなり高くなる場合がある。この現象はDPFの断面積に対して長さが短いDPFを使用した場合に顕著に表れる。DPF差圧が上限に達すると、DPF自身の破壊やエンジントラブルの原因となる。DPFの設置する数を増加させると差圧の上昇は緩和されるが、DPFはコストがかかり、かつDPF設置用の治具が大きくなるなどの問題があった。   The diesel engine discharges a relatively large amount of soot immediately after start-up, so that the soot can be captured using DPF carrying an oxidation catalyst, and the trapped soot is gradually absorbed by heat and the oxidation catalyst. However, if the trapping speed of soot is higher than the burning speed of soot, the DPF differential pressure increases as the soot gradually accumulates. If you continue to use this low-porosity DPF, the DPF differential pressure reaches the upper limit, causing DPF damage and engine trouble. In particular, stationary diesel engines tend to have a large amount of soot immediately after starting because the fuel used is heavy oil. Therefore, a relatively high DPF with a porosity of 50 to 65% is used. However, even when a DPF having a relatively high porosity is used, if a new DPF is used, the differential pressure of the DPF may become considerably high for a few minutes to about 120 minutes after the engine is started. This phenomenon is noticeable when a DPF having a short length relative to the cross-sectional area of the DPF is used. If the DPF differential pressure reaches the upper limit, it will cause damage to the DPF itself and engine trouble. Increasing the number of DPF installations alleviates the rise in differential pressure, but DPF is costly and has problems such as an increased DPF installation jig.

本発明の課題は、エンジン始動時の煤を捕捉し、エンジン始動後の差圧上昇を防止した排ガス処理用フィルタおよびその製法を提供することにある。   An object of the present invention is to provide an exhaust gas treatment filter that captures soot at the time of engine startup and prevents an increase in differential pressure after engine startup, and a method for manufacturing the same.

上記課題を解決するため、本願で特許請求される発明は下記のとおりである。
（１）排ガス入口側のガス流路から流入した排ガスを、酸化触媒を担持した該ガス流路の多孔質隔壁を経て隣接する出口側のガス流路に導入し、該出口側のガス流路から流出させる排ガス処理用フィルタであって、前記触媒を担持した多孔質隔壁に、平均粒径２〜２０μｍの無機質粒子を該フィルタの重量の０．２〜２重量％付着させたことを特徴とする排ガス処理用フィルタ。
（２）前記無機質粒子がシリカ（SiO₂）またはアルミナ（AlO₃）であることを特徴とする（１）記載のフィルタ。 In order to solve the above problems, the invention claimed in the present application is as follows.
(1) The exhaust gas flowing in from the gas channel on the exhaust gas inlet side is introduced into the adjacent gas channel on the outlet side through the porous partition wall of the gas channel carrying the oxidation catalyst, and the gas channel on the outlet side An exhaust gas treatment filter that flows out of the filter, wherein 0.2 to 2% by weight of inorganic particles having an average particle diameter of 2 to 20 μm are attached to the porous partition wall supporting the catalyst. Filter for exhaust gas treatment.
(2) The filter according to (1), wherein the inorganic particles are silica (SiO ₂ ) or alumina (AlO ₃ ).

（３）前記無機質粒子が酸化触媒粒子、または酸化触媒を担持した粒子であることを特徴とする（１）または（２）記載のフィルタ。
（４）排ガス入口側のガス流路と、排ガス出口側のガス流路から多孔質隔壁を経て隣接し、排ガス入口側から導入された排ガスを酸化触媒を担持した該ガス流路の多孔質隔壁を経て前記出口側のガス流路から流出させる排ガス処理用フィルタの製法において、前記排ガス入口側から無機質粒子を含むガスを流通させ、前記多孔質隔壁に該無機質粒子を均一に付着させることを特徴とする排ガス処理用フィルタの製法。 (3) The filter according to (1) or (2), wherein the inorganic particles are oxidation catalyst particles or particles carrying an oxidation catalyst.
(4) The gas partition on the exhaust gas inlet side and the gas partition on the exhaust gas outlet side adjacent to each other through the porous partition wall, and the exhaust gas introduced from the exhaust gas inlet side carries the oxidation catalyst. In the manufacturing method of the exhaust gas treatment filter that flows out from the gas channel on the outlet side through the gas, the gas containing inorganic particles is circulated from the exhaust gas inlet side, and the inorganic particles are uniformly attached to the porous partition wall. Manufacturing method of exhaust gas treatment filter.

本発明者らは、DPFの形状および添加する触媒を検討した結果、DPFの形状を変えるよりも特定の粒子をDPF内壁に付着、保持させることによってエンジン始動時の差圧上昇を緩和できることを見出した。DPFの排ガス流路壁面に特定の粒子を少量保持させておくと、エンジン始動時の煤は直接DPF壁面に接触せずに一旦添加した粒子に接触する。粒子に接触した煤は微細化してDPF壁面に接触するため、煤が一気にDPF壁面の細孔に蓄積し、閉塞(完全な閉塞ではない)することを防ぐものと考えられる。   As a result of examining the shape of the DPF and the catalyst to be added, the present inventors have found that rather than changing the shape of the DPF, it is possible to mitigate the increase in the differential pressure at the start of the engine by attaching and holding specific particles on the DPF inner wall. It was. If a small amount of specific particles are held on the wall surface of the exhaust gas flow path of the DPF, the soot at the time of starting the engine does not directly contact the DPF wall surface but contacts the once added particles. It is considered that the soot in contact with the particles is refined and comes into contact with the DPF wall surface, preventing the soot from accumulating in the pores of the DPF wall surface and blocking (not completely closing).

本発明において、DPFの多孔質隔壁に付着させる無機質粒子は、平均粒子径2〜20μm（好ましくは2〜10μm）で、その付着量はDPF重量の0.2〜2重量％（好ましくは0.2〜1.5重量％）の範囲が効果的である。平均粒子径が2μm未満では、DPFを通過、または壁面から奥側へ保持されるため、効果は小さくなる。また平均粒子径が20μmを越えると粒子間どうしの隙間が大きいため、大部分の煤がすり抜け、直接DPF壁面に接触してしまい、粒子の付着効果がなくなってしまう。無機質粒子の付着量が０．２重量％未満では付着粒子の層が薄くなるため、効果が低下し、また2重量％を越えると付着粒子層の差圧が発生するため、効果は低下する。無機質粒子としてはシリカ（SiO₂）またはアルミナ（AlO₃）が好ましいが、DPFに担持された触媒に影響しないものであれば他の物で代用できる。また無機質粒子として酸化触媒粒子、または予め触媒成分を担持した粒子を用いると、煤の酸化燃焼効果が増大するため、より効果的である。
本発明のDPFの後流部にSCR(脱硝装置)を設置すれば、煤等の粒子状物質の除去とともに、窒素酸化物（NOx）を除去することができる。 In the present invention, the inorganic particles adhered to the porous partition walls of the DPF have an average particle diameter of 2 to 20 μm (preferably 2 to 10 μm), and the amount of adhesion is 0.2 to 2% by weight (preferably 0.2 to 1.5% by weight) of the DPF weight. %) Is effective. When the average particle size is less than 2 μm, the effect is small because it passes through the DPF or is retained from the wall surface to the back side. On the other hand, when the average particle diameter exceeds 20 μm, the gap between the particles is large, so that most of the wrinkles slip through and directly contact the DPF wall surface, and the adhesion effect of the particles is lost. If the adhesion amount of the inorganic particles is less than 0.2% by weight, the layer of the adhered particles becomes thin, so that the effect is lowered. If the amount exceeds 2% by weight, the differential pressure of the adhered particle layer is generated, and thus the effect is lowered. Silica (SiO ₂ ) or alumina (AlO ₃ ) is preferable as the inorganic particles, but other materials can be substituted as long as they do not affect the catalyst supported on the DPF. In addition, it is more effective to use oxidation catalyst particles or particles that previously support a catalyst component as the inorganic particles, because the effect of soot oxidation combustion increases.
If an SCR (denitration device) is installed in the downstream portion of the DPF of the present invention, nitrogen oxides (NOx) can be removed along with removal of particulate matter such as soot.

本発明によれば、エンジン始動時の煤を捕捉し、 DPFの差圧上昇を緩和することができる。   According to the present invention, the soot at the time of starting the engine can be captured, and the increase in the DPF differential pressure can be mitigated.

以下、本発明を図１〜図４によってさらに詳細に説明する。図１は、本発明の一実施例を示す排ガス処理用フィルタ（DPF）の断面を模式的に示した説明図である。DPFの壁1には、無機質粒子層２が形成されている。この粒子層２は、DPFの排ガス入口側から無機質粒子を気体流によって導入し、DPF壁面に所定量均一に付着させることにより形成される。このDPFを排ガス管内に設置した後、ディーゼル排ガスを通過させると、排ガス中の煤3は、図１に示すようにDPFの壁1に直接接触せずに一旦、粒子層2に接触する。煤3は排ガス圧によって粒子層2の隙間を通過し、同時に微細化され、次いで微細化された煤3はDPFに担持された酸化触媒によって酸化燃焼され、ほとんど残留することなくガス化し、DPFの壁1を通過する。   Hereinafter, the present invention will be described in more detail with reference to FIGS. FIG. 1 is an explanatory view schematically showing a cross section of an exhaust gas treatment filter (DPF) showing an embodiment of the present invention. An inorganic particle layer 2 is formed on the wall 1 of the DPF. The particle layer 2 is formed by introducing inorganic particles by gas flow from the DPF exhaust gas inlet side and uniformly depositing them on the DPF wall surface. When the diesel exhaust gas is allowed to pass after the DPF is installed in the exhaust gas pipe, the soot 3 in the exhaust gas once contacts the particle layer 2 without directly contacting the DPF wall 1 as shown in FIG. The soot 3 passes through the gap between the particle layers 2 due to the exhaust gas pressure, and is simultaneously refined, and then the refined soot 3 is oxidized and burned by the oxidation catalyst supported on the DPF, and is gasified with almost no residue, Pass through wall 1.

図２は、本発明のDPFの差圧の経時変化の一例を示す図である。図から明らかなように本発明のDPFの方が従来のDPFに較べて差圧変化が極めて小さいことがわかる。
図３は、DPFに付着させた無機質粒子の粒子径と定常運転時の差圧上昇を付着量（重量％）をパラメータとして示した図である。付着させる粒子の粒子径と付着量が増大するにつれて定常運転時のDPF差圧が上昇することが分かる。この図から無機質粒子の粒径(平均粒径）は、差圧がそれ程上昇しない2〜20μｍの範囲、付着量は2重量％以下が好ましいことが分かる。 FIG. 2 is a diagram showing an example of the temporal change of the differential pressure of the DPF of the present invention. As can be seen from the figure, the DPF of the present invention has a much smaller differential pressure change than the conventional DPF.
FIG. 3 is a graph showing the particle size of the inorganic particles adhered to the DPF and the differential pressure increase during steady operation using the amount of adhesion (% by weight) as a parameter. It can be seen that the DPF differential pressure during steady operation increases as the particle size and amount of particles to be deposited increase. From this figure, it is understood that the particle size (average particle size) of the inorganic particles is preferably in the range of 2 to 20 μm where the differential pressure does not increase so much, and the adhesion amount is preferably 2% by weight or less.

図４は、DPFに付着させる無機質粒子(平均粒径5μm)の付着量とDPFの差圧ピークの関係を示す図であるが、付着量が0.2重量％に達しないと差圧ピークが増大することが分かる。これより、無機質粒子の付着量は、DPFの0.2重量％以上であることが好適である。     FIG. 4 is a diagram showing the relationship between the adhesion amount of inorganic particles (average particle size 5 μm) adhered to the DPF and the differential pressure peak of the DPF, and the differential pressure peak increases when the adhesion amount does not reach 0.2% by weight. I understand that. From this, the adhesion amount of the inorganic particles is preferably 0.2% by weight or more of DPF.

実施例１
本発明による定置ディ−ゼルエンジンの排ガス処理実験を行った。酸化触媒を担持した直径150mm、長さ100mmのセラミックDPF(気孔率65%)を直径155mm、長さ2ｍの配管の一端内に設置し、配管のもう一端にブロワ装置を取付けた。配管の中央部に新たに粒子付着用の外径6mmΦ、内径4mmΦの導入管を取付け、一端を配管中心部に位置するように調整した。導入管のもう一端には平均粒子径3μmのSiO₂を充填したテーブルフィーダ装置に接続した。ブロワ装置にて流量50m³/hの空気ガスをDPFに流し、続いてテーブルフィーダ装置内のSiO₂を空気ガス4Ｌ/ｍｉｎの流量で2g/minの速度で配管中心部にフィードした。6分後に平均粒子径3μmのSiO₂がDPF重量の1％付着された。
定置ディ−ゼルエンジン排ガス管のエンジンから1ｍ後流に上記DPFを設置し、排ガス流量をドライ条件で120m³/hＮとしてエンジン始動後のDPF差圧を測定した。その結果、差圧は、最大2ｋＰａをピ−クに減少し、2時間後には1.8kPaで安定した。 Example 1
An exhaust gas treatment experiment of a stationary diesel engine according to the present invention was conducted. A ceramic DPF with a diameter of 150 mm and a length of 100 mm carrying an oxidation catalyst was installed in one end of a pipe with a diameter of 155 mm and a length of 2 m, and a blower device was attached to the other end of the pipe. A new inlet pipe with an outer diameter of 6 mmΦ and an inner diameter of 4 mmΦ for attaching particles was newly attached to the center of the pipe, and one end was adjusted to be located at the center of the pipe. The other end of the introduction tube was connected to a table feeder device filled with SiO ₂ having an average particle diameter of 3 μm. A blower unit was used to flow air gas at a flow rate of 50 m ³ / h to the DPF, and then SiO ₂ in the table feeder was fed to the center of the pipe at a flow rate of 2 g / min at a flow rate of 4 L / min. After 6 minutes, SiO ₂ having an average particle size of 3 μm was deposited by 1% of the weight of DPF.
The DPF was installed 1 m behind the engine of the stationary diesel engine exhaust pipe, and the DPF differential pressure after starting the engine was measured with the exhaust gas flow rate set to 120 m ³ / hN under dry conditions. As a result, the differential pressure decreased from a maximum of 2 kPa to a peak and stabilized at 1.8 kPa after 2 hours.

実施例２
実施例1と同様の定置ディ−ゼルエンジンの排ガス処理実験を行った。酸化触媒を担持した長さ100mmのセラミックDPF(気孔率65%)に、 DPFに担持されている酸化触媒と同じものを担持した平均粒子径4μmのSiO₂をDPF重量の1％付着させたDPFを使用した。実施例１と同様にエンジン始動後のDPF差圧を測定した結果、差圧は、最大2ｋＰａをピ−クに減少し、2時間後には1.8kPaで安定した。 Example 2
An exhaust gas treatment experiment of a stationary diesel engine similar to that in Example 1 was performed. The ceramic DPF length 100mm carrying an oxidation catalyst (65% porosity), and the SiO ₂ having an average particle diameter of 4μm carrying same as the oxidation catalyst carried on the DPF deposited 1% DPF weight DPF It was used. As a result of measuring the DPF differential pressure after starting the engine in the same manner as in Example 1, the differential pressure decreased to a maximum of 2 kPa and stabilized at 1.8 kPa after 2 hours.

比較例１
排ガス管のエンジンから1ｍ後流に酸化触媒を担持した長さ100mmのセラミックDPFを設置し、実施例1と同様の実験を行った。その結果、エンジン始動後のDPF差圧は最大3.6ｋＰａまで上昇し、安全弁が開いて排ガスの煤は排出された。 Comparative Example 1
A 100 mm long ceramic DPF carrying an oxidation catalyst was installed 1 m behind the exhaust pipe engine and the same experiment as in Example 1 was performed. As a result, the DPF differential pressure after engine startup rose to a maximum of 3.6 kPa, the safety valve opened, and exhaust gas soot was discharged.

本発明は、自動車やディーゼルエンジン等の排ガス中に含まれる粒子状物質の除去に有用である。   The present invention is useful for removing particulate matter contained in exhaust gas from automobiles, diesel engines and the like.

本発明の一実施例を示す排ガス処理用フィルタ（DPF）の断面を模式的に示した説明図。BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which showed typically the cross section of the filter for exhaust gas treatment (DPF) which shows one Example of this invention. 本発明のDPFの差圧の経時変化の一例を示す図。The figure which shows an example of the time-dependent change of the differential pressure | voltage of DPF of this invention. DPFに付着させた無機質粒子の粒子径と定常運転時の差圧上昇を付着量（重量％）をパラメータとして示した図。The figure which showed the particle size of the inorganic particle adhering to DPF, and the differential pressure increase at the time of steady operation as an adhesion amount (weight%) as a parameter. DPFに付着させた粒子(平均粒子径5μm)の付着量とDPFの差圧ピークの関係を示す図。The figure which shows the relationship between the adhesion amount of the particle | grains (average particle diameter of 5 micrometers) adhering to DPF, and the differential pressure peak of DPF.

符号の説明Explanation of symbols

１…DPF、２…粒子層、３… 煤。   1 ... DPF, 2 ... particle layer, 3 ...….

Claims (4)

排ガス入口側のガス流路から流入した排ガスを、酸化触媒を担持した該ガス流路の多孔質隔壁を経て隣接する出口側のガス流路に導入し、該出口側のガス流路から流出させる排ガス処理用フィルタであって、前記触媒を担持した多孔質隔壁に、平均粒径２〜２０μｍの無機質粒子を該フィルタの重量の０．２〜２重量％付着させたことを特徴とする排ガス処理用フィルタ。 The exhaust gas flowing in from the gas flow path on the exhaust gas inlet side is introduced into the adjacent gas flow path on the outlet side through the porous partition wall of the gas flow path carrying the oxidation catalyst, and is discharged from the gas flow path on the outlet side. An exhaust gas treatment filter characterized in that inorganic particles having an average particle diameter of 2 to 20 μm are adhered to the porous partition wall supporting the catalyst in an amount of 0.2 to 2% by weight of the weight of the filter. Filter. 前記無機質粒子がシリカ（SiO₂）またはアルミナ（AlO₃）であることを特徴とする請求項１記載のフィルタ。 The filter according to claim 1, wherein the inorganic particles are silica (SiO ₂ ) or alumina (AlO ₃ ). 前記無機質粒子が酸化触媒粒子、または酸化触媒を担持した粒子であることを特徴とする請求項１または２記載のフィルタ。         The filter according to claim 1 or 2, wherein the inorganic particles are oxidation catalyst particles or particles carrying an oxidation catalyst. 排ガス入口側のガス流路と、排ガス出口側のガス流路から多孔質隔壁を経て隣接し、排ガス入口側から導入された排ガスを酸化触媒を担持した該ガス流路の多孔質隔壁を経て前記出口側のガス流路から流出させる排ガス処理用フィルタの製法において、前記排ガス入口側から無機質粒子を含むガスを流通させ、前記多孔質隔壁に該無機質粒子を均一に付着させることを特徴とする排ガス処理用フィルタの製法。








The gas channel on the exhaust gas inlet side is adjacent to the gas channel on the exhaust gas outlet side through the porous partition wall, and the exhaust gas introduced from the exhaust gas inlet side passes through the porous partition wall of the gas channel carrying the oxidation catalyst. In a method for producing an exhaust gas treatment filter that flows out from a gas channel on an outlet side, a gas containing inorganic particles is circulated from the exhaust gas inlet side, and the inorganic particles are uniformly attached to the porous partition wall. Processing filter manufacturing method.

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