WO2013035743A1 - 脱硝触媒のso2酸化率上昇低減方法 - Google Patents
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Definitions
- the present invention relates to a method for reducing an increase in SO 2 oxidation rate of a denitration catalyst.
- NOx nitrogen oxides
- ammonia is used as a reducing agent, and catalytically decomposed into nitrogen and water.
- Ammonia catalytic reduction is widely used.
- the NOx removal catalyst currently in practical use is mainly a honeycomb-shaped catalyst having a square hole shape in order to prevent clogging by dust in the exhaust gas and to widen the gas contact area.
- the catalyst component those containing titanium oxide as a main component are excellent, and those containing vanadium, tungsten and the like as active components are generally used, and mainly a binary TiO 2 -WO 3 catalyst or TiO 2 -MoO 3 catalyst, and a ternary TiO 2 -V 2 O 5 -WO 3 catalyst or TiO 2 -V 2 O 5 -MoO 3 catalysts such is used.
- the present inventors confirmed that the regeneration effect of the SO 2 oxidation rate is hardly seen in the conventional cleaning process. .
- the denitration catalyst regenerated by the above method is impregnated or coated with a catalytically active component containing, for example, vanadium, there is a problem that the SO 2 oxidation rate increases.
- a catalytically active component containing, for example, vanadium there is a problem that the SO 2 oxidation rate increases.
- an object of the present invention is to provide a method for reducing an increase in the SO 2 oxidation rate of a denitration catalyst that removes an inhibitory factor of a silicon compound such as silica adhering to the denitration catalyst.
- the first invention of the present invention for solving the above-mentioned problems is an alkali treatment step for washing and removing an inhibitor that causes an increase in the SO 2 oxidation rate with an alkaline aqueous solution when regenerating the denitration catalyst, and the alkali treatment step. And an activation treatment step of activating the catalyst with an aqueous acid solution, and a method for reducing the increase in the SO 2 oxidation rate of the denitration catalyst.
- the carrier of the denitration catalyst is titanium oxide
- the inhibitor is a silicon compound
- the strength ratio of titanium and silicon on the surface of the denitration catalyst (Si / Ti strength ratio) is obtained.
- the third invention is the second invention, the measurement of the titanium and silicon intensity ratio is in the SO 2 oxidation rate increase method of reducing denitration catalyst, which comprises carrying out an electron beam analyzer analysis (EPMA).
- EPMA electron beam analyzer analysis
- the alkaline aqueous solution is an aqueous solution of NaOH, KOH, Na 2 CO 3 , NaHCO 3, or K 2 CO 3
- the acid aqueous solution is HCl, HNO 3.
- a method for reducing an increase in the SO 2 oxidation rate of a denitration catalyst wherein the denitration catalyst is washed and then pulverized to form a raw material for the denitration catalyst. is there.
- a denitration catalyst according to the first or second aspect wherein after the denitration catalyst is washed, the denitration catalyst slurry is recoated on the surface of the denitration catalyst.
- the method is to reduce the increase in SO 2 oxidation rate.
- an inhibitor such as a silicon compound covering the surface of a denitration catalyst can be removed by an alkali treatment with an alkaline aqueous solution and an activation treatment with an acid aqueous solution, and there is no increase in the SO 2 oxidation rate of the regenerated denitration catalyst.
- by regenerating and using the catalyst it contributes to the reduction of industrial waste, and has significant industrial significance in terms of the environment.
- FIG. 1 is a drawing in which the horizontal axis represents the Si / Ti intensity ratio and the vertical axis represents the ratio between the measured value and the predicted value of the SO 2 oxidation rate (actual value / predicted value).
- the present invention relates to a denitration catalyst used for removal of nitrogen oxides in combustion exhaust gas, when a silica component (silicon compound) that is an inhibitor of an increase factor in SO 2 oxidation rate accumulates on the catalyst surface, The silica component accumulated on the surface is dissolved to regenerate the catalyst.
- the denitration catalyst regenerated by the present invention contains titanium oxide as a main component and contains vanadium, tungsten, molybdenum or the like as an active component.
- the regeneration treatment method of the present invention is a treatment method that undergoes an activation treatment step after the alkali treatment step, and further, if necessary, a treatment method that suitably undergoes an impregnation supporting step of a catalyst active component. It is.
- a determination step is also included in which it is determined that a predetermined amount of an inhibitor that increases the SO 2 oxidation rate, such as a silica component (silicon compound), is not present on the surface of the denitration catalyst.
- the denitration catalyst whose performance has been reduced by the accumulation of the silica component accumulated on the surface of the denitration catalyst is washed with an alkaline aqueous solution to remove silica as an inhibitory substance from the denitration catalyst.
- the cleaning method is not particularly limited, and the purpose of cleaning is achieved by contacting the denitration catalyst with an alkaline aqueous solution.
- a method of immersing a denitration catalyst in an alkaline aqueous solution a method of leaving a denitration catalyst in an aqueous sulfuric acid solution or an aqueous ammonia solution, or generating bubbling air or forced convection in the stationary denitration catalyst to update the solution
- the method etc. which promote are mentioned.
- an alkaline aqueous solution of a strongly basic substance is used as the alkaline aqueous solution, and a compound capable of generating a sodium compound or potassium compound is suitably used as having an ability to remove silica.
- alkaline aqueous solution used in the present invention include any one of NaOH, KOH, Na 2 CO 3 , NaHCO 3, and K 2 CO 3 aqueous solutions.
- the alkali concentration in the aqueous solution is usually in the range of 0.05 to 20% by weight. It is effective that the temperature of the alkaline aqueous solution serving as the cleaning liquid is in the range of 10 to 90 ° C.
- the cleaning effect may not be sufficient when the concentration of the alkaline aqueous solution is less than 0.05% by weight or the temperature of the cleaning solution is less than 10 ° C., conversely, the concentration of the alkaline aqueous solution is greater than 20% by weight or the cleaning solution. This is because if the temperature is higher than 90 ° C., the cost of the processing equipment may increase.
- the activated denitration catalyst after the treatment in the previous alkali treatment step is activated using an acid aqueous solution. That is, in the alkali treatment step, silica can be removed from the denitration catalyst by washing, but since the alkali component used for washing and removal remains in the catalyst, the denitration catalyst is poisoned by alkali. Alkali metal itself is a substance that can cause degradation of the denitration catalyst. Therefore, even if the performance degradation due to the accumulation of the silica component (silicon compound) can be avoided in this state, degradation due to alkali metal occurs. Therefore, in the present invention, activation treatment using an aqueous acid solution is performed after alkali washing to remove the alkali on the catalyst and remove all poisonous substances from the denitration catalyst.
- an acid aqueous solution of an organic acid or an inorganic acid is used as the acid aqueous solution, but it is preferable to use an acid aqueous solution using an inorganic acid in consideration of the post-treatment burden and the like.
- Any inorganic acid that can be ion-exchanged with sodium or potassium can be used regardless of whether it is a strong acid or a weak acid.
- aqueous acid solution used in the present invention examples include any aqueous solution such as HCl, HNO 3 , HF, and H 2 SO 4 .
- aqueous solution of HCl, HNO 3 , HF or H 2 SO 4 is used as the acid aqueous solution
- the concentration in the aqueous solution is usually in the range of 0.1 to 25% by weight, and the temperature of the aqueous solution is 10 to 90%. It is effective to make the temperature range.
- the ion exchange may not be sufficient when the concentration of the aqueous acid solution is less than 0.1% by weight, or the temperature of the aqueous solution is less than 10 ° C., conversely, the concentration of the aqueous acid solution is greater than 20% by weight, or the aqueous solution. This is because if the temperature is higher than 90 ° C., the cost of the processing equipment may increase.
- the denitration catalyst after passing through the alkali treatment step and the activation treatment step, the denitration catalyst can be regenerated through an impregnation / supporting step of the catalytic active component described below, if necessary.
- vanadium or tungsten which are active components of the catalyst, may be eluted from the catalyst, resulting in a decrease in denitration performance due to a decrease in the concentration of the active component in the catalyst. is there.
- the silica component (silicon compound) is washed and removed, and after washing with water and drying, vanadium and / or tungsten may be impregnated and supported so that the active component concentration in the catalyst is the same as that before the regeneration. it can.
- the method for supporting vanadium include a method of immersing the catalyst in an aqueous solution in which vanadium compounds such as vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate are dissolved in water, an organic acid, and an amine solution.
- tungsten compound such as ammonium paratungstate, ammonium metatungstate, tungsten trioxide, or tungsten chloride is dissolved in water, hydrochloric acid, an amine solution, or an organic acid.
- a tungsten compound such as ammonium paratungstate, ammonium metatungstate, tungsten trioxide, or tungsten chloride is dissolved in water, hydrochloric acid, an amine solution, or an organic acid.
- the silica component (silicon compound) accumulated in the catalyst is first washed with an alkaline aqueous solution and accumulated on the catalyst surface (silicon compound) in the alkali treatment step. ) Can be removed.
- Na + ions can remain in the catalyst. Therefore, in the activation treatment step subsequent to the above step, Na + ions that remain on the catalyst and become poisonous substances of the catalyst are ion-exchanged using an aqueous acid solution such as HCl. Thereby, Na + ions are converted into H + ions, and Na + ions are removed from the catalyst, so that the activity of the denitration catalyst can be recovered.
- an inhibiting factor such as gaseous silica (for example, silicon compound such as organic silica) present in the exhaust gas in the form of high-temperature vapor in the unburned portion is the surface of the denitration catalyst.
- gaseous silica for example, silicon compound such as organic silica
- an inhibitor such as a silica component (silicon compound) covering the surface of the denitration catalyst can be removed by alkali treatment with an alkaline aqueous solution and activation treatment with an acid aqueous solution, A catalyst that does not increase the SO 2 oxidation rate of the regenerated denitration catalyst can be provided.
- regenerating and using the catalyst it contributes to the reduction of industrial waste, and has significant industrial significance in terms of the environment.
- This determination step is to determine that a predetermined amount of silica component is not present on the surface of the denitration catalyst in the regenerated denitration catalyst.
- This determination step measures the strength ratio between titanium and silicon on the surface of the denitration catalyst. This measurement is preferably performed by an electron beam analyzer analysis (EPMA: Electro Probe MicroAnalyzer). In addition to EPMA, the intensity ratio can also be measured by X-ray Fluorescence Analysis (XRF).
- EPMA Electro Probe MicroAnalyzer
- the Si / Ti strength ratio is, for example, 0.1 or less, more preferably 0.08 or less.
- the ratio between the measured value and the predicted value of the SO 2 oxidation rate of the denitration catalyst is preferably in the range of 1.00 to 1.30. This is because if the actually measured value / predicted value exceeds 1.30, the SO 2 oxidation rate increases remarkably, the regeneration of the denitration catalyst becomes insufficient, and cannot be reused.
- the Si / Ti intensity ratio exceeds a predetermined threshold (for example, 0.1)
- a predetermined threshold for example, 0.1
- the alkali treatment step and the activation treatment step are performed again, and silica (inhibitor of the increase factor of SO 2 oxidation rate)
- the silicon compound is removed, and the determination process is performed again to determine whether the catalyst can be reused.
- a catalytically active component such as vanadium (V), for example, is reliably supported on the surface of Ti, which is a carrier, and the catalytic activity is improved. That is, when the Si / Ti intensity ratio exceeds a predetermined threshold (for example, 0.1), the surface of titanium (Ti) as a support is covered with a silica component (silicon compound).
- regeneration with alkali washing with 1N NaOH at 40 ° C. may be insufficient (Si / Ti strength ratio is 0.10 or more).
- the washing may be performed by raising the alkaline washing condition with 1N-NaOH to 60 ° C.
- the surface of the denitration catalyst is covered by confirming that the Si / Ti intensity ratio does not exceed a predetermined threshold (for example, 0.1) while performing the alkali treatment with the alkali aqueous solution and the activation treatment with the acid aqueous solution. It is possible to provide a regenerative denitration catalyst in which the residual rate of substances that inhibit the increase in the SO 2 oxidation rate, such as silica components (silicon compounds), is reduced and the SO 2 oxidation rate is not increased.
- a predetermined threshold for example, 0.1
- test Examples 1 and 2 are denitration catalysts that have been sufficiently washed with alkali
- Comparative Examples are denitration catalysts that have not been sufficiently washed with alkali.
- the SO 3 is measured at the inlet and the outlet of the regenerated NO x removal catalyst, to confirm the increase, from the measured value and the predicted value, the predicted and measured values of SO 2 oxidation rate
- the ratio (actual value / expected value) was determined.
- the catalyst used was 91.4% by weight of TiO 2 , 8.0% by weight of WO 3 and 0.63% by weight of V 2 O 5 .
- the catalyst used was 91.4% by weight of TiO 2 , 8.0% by weight of WO 3 and 0.59% by weight of V 2 O 5 .
- the catalyst used was 91.2% by weight of TiO 2 , 8.0% by weight of WO 3 and 0.83% by weight of V 2 O 5 .
- FIG. 1 is a drawing in which the horizontal axis represents the Si / Ti intensity ratio and the vertical axis represents the ratio between the measured value and the predicted value of the SO 2 oxidation rate (actual value / predicted value).
- Table 1 shows the ratio (measured value / predicted value) between the actually measured value and the predicted value of the SO 2 oxidation rate in Test Examples 1 and 2 and the Comparative Example.
- the catalyst of Test Example 1 has a Si / Ti strength ratio of 0.036
- the catalyst of Test Example 2 has a Si / Ti strength ratio of 0.072. 2
- the ratio of the measured value and the predicted value of the oxidation rate is lower than 1.3, 1.03 and 1.05, which is close to 1.0 and is higher than that of a fresh catalyst. There was a slight increase in the SO 2 oxidation rate.
- the catalyst of the comparative example has Si / Ti intensity ratios greatly exceeding 0.132 and 0.1, and the ratio between the measured value and the predicted value of the SO 2 oxidation rate (actual value / predicted value). Was 1.94, exceeding 1.3, and the SO 2 oxidation rate was significantly higher than that of the fresh catalyst.
- the regenerated catalyst has a SO 2 oxidation rate that does not increase as compared with a fresh catalyst.
Abstract
Description
また、排ガス中に存在するヒ素(As2O3)の蓄積による脱硝性能が低下した脱硝触媒の再生にあたり、アルカリ水溶液で触媒蓄積物質を洗浄除去した後、酸水溶液で触媒の活性化処理を行う技術を提案した(特許文献1)。
この要因について調査研究した結果、脱硝触媒に付着したシリカの存在であることが判明した。
この結果、脱硝触媒に再生工程を施した場合でも、再生が良好に行われず、脱硝触媒のSO2酸化率上昇の要因となる、という問題がある。
ここで、本発明により再生される脱硝触媒は、酸化チタンを主成分とし、活性成分としてバナジウム、タングステン又はモリブデン等を含んだものであり、具体的には、二元系のTiO2-WO3触媒、TiO2-MoO3触媒、あるいは三元系のTiO2-V2O5-WO3触媒、TiO2-V2O5-MoO3触媒等が挙げられる。
また、シリカ成分(ケイ素化合物)等のSO2酸化率の上昇要因の阻害物質が脱硝触媒の表面に所定量存在しないことを判定する判定工程も含まれる。
先ず、アルカリ処理工程では、脱硝触媒の表面に蓄積したシリカ成分の蓄積により性能低下した脱硝触媒を、アルカリ水溶液により洗浄し、該脱硝触媒から阻害物質であるシリカを除去するものである。
洗浄方法は特に限定されることはなく、アルカリ水溶液に脱硝触媒が接触することによって洗浄の目的は達成される。
また、このアルカリ処理工程では、アルカリ水溶液として、強塩基性物質のアルカリ水溶液が用いられ、シリカを除去する能力があるものとして、ナトリウム化合物又はカリ化合物を生成するような化合物が好適に用いられる。
そして、アルカリ水溶液として前記NaOH、KOH、Na2CO3、NaHCO3又はK2CO3の水溶液を用いるような場合には、通常、水溶液中のアルカリ濃度は0.05~20重量%の範囲とし、洗浄液であるアルカリ水溶液の温度は10~90℃の範囲とすることが有効である。
これは、アルカリ水溶液の濃度が0.05重量%未満、あるいは洗浄液の温度が10℃未満では、洗浄効果が十分でない場合があり、逆に、アルカリ水溶液の濃度が20重量%より大きい、あるいは洗浄液の温度が90℃より高い範囲では、処理設備のコストが高くなる場合が生じるからである。
この活性化処理工程では、先のアルカリ処理工程での処理後の洗浄された脱硝触媒について、酸水溶液を用いて活性化処理を行うものである。
すなわち、前記アルカリ処理工程では、脱硝触媒中からシリカを洗浄除去することができるが、洗浄除去に用いたアルカリ成分が触媒中に残存するため、脱硝触媒がアルカリにより被毒されることになる。アルカリ金属は、それ自体が脱硝触媒の劣化原因になりうる物質であるため、このままでは、シリカ成分(ケイ素化合物)の蓄積による性能低下は回避できても、アルカリ金属による劣化が生じてしまう。
そこで、本発明においては、アルカリ洗浄後に酸水溶液を用いた活性化処理を行うことにより、触媒上のアルカリを除去して、脱硝触媒から被毒物を全て除去するものである。
一方、この処理工程後には、Na+イオンが触媒に残留しうることになる。よって、前記工程に続く活性化処理工程においては、触媒上に残留して触媒の被毒物質となりうるNa+イオンを、HCl等の酸水溶液を用いてイオン交換する。これにより、Na+イオンをH+イオンに変換し、触媒上からNa+イオンが除去されて、脱硝触媒の活性を回復させることができる。
この判定工程は、再生処理した脱硝触媒において、シリカ成分が脱硝触媒の表面に所定量存在しないことを判定するものである。
この判定工程は、脱硝触媒の表面のチタンとケイ素との強度比を測定するものである。この測定は、電子線アナライザ分析(EPMA:Electron Probe MicroAnalyser)により行うのが好ましい。
また、EPMA以外としては、蛍光X線分析(X-ray Fluorescence Analysis:XRF)により、強度比を測定することもできる。
これによりガラス繊維の影響がない、Si/Ti強度比を定量することが可能となる。
このSi/Ti強度比としては、例えば0.1以下、より好ましくは0.08以下とするのが良い。
この範囲であると、脱硝触媒のSO2酸化率の実測値と予想値との比(実測値/予想値)が、1.00~1.30の範囲となるので好ましい。
これは、実測値/予想値が1.30を超えると、SO2酸化率の上昇が著しく多くなり、脱硝触媒の再生が不十分となり、再利用できないからである。
これにより、担体であるTiの表面に例えばバナジウム(V)等の触媒活性成分が確実に担持され、触媒活性が良好となる。
すなわち、Si/Ti強度比が所定の閾値(例えば0.1)を超える場合には、担体であるチタン(Ti)の表面に、シリカ成分(ケイ素化合物)が覆われており、このような場合に、活性成分であるバナジウム(V)を担持しても、チタンの表面に直接バナジウムが担持できる割合が減少する結果、バナジウムの触媒活性が十分とならず、SO2酸化率の上昇要因となるからである。
以下、試験例により本発明をより詳細に説明するが、本発明はこれらの実施例によって何ら制限されるものではない。
使用済脱硝触媒として、触媒表面にシリカ(ケイ素化合物)が堆積されている使用済脱硝触媒(6孔×7孔×900mmのハニカム触媒)を準備した。
この使用済脱硝触媒を用いて、アルカリ洗浄及び活性処理を行い、再生処理を行った。
処理後の再生脱硝触媒の表面のSi/Ti強度比をEPMA分析した。
EPMA分析の際、電子顕微鏡(SEM)でその表面に存在するガラス繊維を避けて、電子線を照射した。
EPMA分析には、X線マイクロアナライザ(日本電子社製「XA-8900RL(商品名)」を用いた。
試験例1及び2はアルカリ洗浄を十分に行った脱硝触媒であり、比較例はアルカリ洗浄が十分ではなかった脱硝触媒である。
なお、使用した触媒は、試験例1では、TiO2が91.4重量%、WO3が8.0重量%、V2O5が0.63重量%である。
なお、使用した触媒は、試験例2では、TiO2が91.4重量%、WO3が8.0重量%、V2O5が0.59重量%である。
なお、使用した触媒は、比較例では、TiO2が91.2重量%、WO3が8.0重量%、V2O5が0.83重量%である。
試験例1及び2、比較例のSO2酸化率の実測値と予想値との比(実測値/予想値)を表1に示す。
Claims (7)
- 脱硝触媒の再生にあたり、アルカリ水溶液でSO2酸化率上昇要因となる阻害物質を洗浄除去するアルカリ処理工程と、
このアルカリ処理工程の後、酸水溶液で触媒の活性化処理を行う活性化処理工程とを有することを特徴とする脱硝触媒のSO2酸化率上昇低減方法。 - 請求項1において、
脱硝触媒の担体が酸化チタンであり、阻害物質がケイ素化合物であると共に、
脱硝触媒表面のチタンとケイ素の強度比(Si/Ti強度比)を求め、
Si/Ti強度比が所定の閾値を超える場合には、
再度アルカリ処理工程と活性化処理工程とを行うことを特徴とする脱硝触媒のSO2酸化率上昇低減方法。 - 請求項2において、
前記チタンとケイ素の強度比の測定は、電子線アナライザ分析(EPMA)により行うことを特徴とする脱硝触媒のSO2酸化率上昇低減方法。 - 請求項1又は2において、
前記アルカリ水溶液が、NaOH、KOH、Na2CO3、NaHCO3又はK2CO3の水溶液であり、かつ、前記酸水溶液が、HCl、HNO3、HF又はH2SO4の水溶液であることを特徴とする脱硝触媒のSO2酸化率上昇低減方法。 - 請求項1又は2において、
脱硝触媒を洗浄した後、該脱硝触媒に触媒活性成分を含浸担持することを特徴とする脱硝触媒のSO2酸化率上昇低減方法。 - 請求項1又は2において、
脱硝触媒を洗浄した後、該脱硝触媒を粉砕し、脱硝触媒の原料とすることを特徴とする脱硝触媒のSO2酸化率上昇低減方法。 - 請求項1又は2において、
脱硝触媒を洗浄した後、該脱硝触媒に脱硝触媒のスラリー状の原料を該脱硝触媒の表面に再コートすることを特徴とする脱硝触媒のSO2酸化率上昇低減方法。
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CN112473650B (zh) * | 2019-09-12 | 2024-04-09 | 国家能源投资集团有限责任公司 | 一种脱硝催化剂及其制备方法 |
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