Patent Description:
As one of the pollutants discharged into air by the combustion of fuel, nitrogen oxides (NO, NO<NUM>, NO<NUM>, N<NUM>O, N<NUM>O<NUM>, N<NUM>O<NUM>, N<NUM>O<NUM>) can be exemplified. The nitrogen oxides induce acid rain, ozone layer depletion, photochemical smog, etc., and have a serious influence on the environment and human bodies; therefore, treatment thereof is an important problem.

As technology for removing the above-mentioned nitrogen oxides, the selective catalytic reduction reaction (NH<NUM>-SCR) with ammonia (NH<NUM>) as the reductant has been known. As disclosed in Patent Document <NUM>, a catalyst using titanium oxide as the carrier and supporting vanadium oxide is being widely used as the catalyst used in the selective catalytic reduction reaction. Titanium oxide has low activity for sulfur oxides, and has high stability; therefore, it is best established as the carrier.

On the other hand, although vanadium oxide plays a main role in NH<NUM>-SCR, since it oxidizes SO<NUM> to SO<NUM>, it has not been able to support on the order of <NUM> wt% or more of vanadium oxide. In addition, with conventional NH<NUM>-SCR, since the catalyst made by supporting vanadium oxide on a titanium oxide carrier almost does not react at low temperature, it must be used at high temperatures such as <NUM> to <NUM>. However, in order to raise the degrees of freedom of design in devices and facilities realizing NH<NUM>-SCR and make more efficient, the development of a catalyst exhibiting high nitrogen oxide reduction rate activity at low temperatures has been demanded.

Subsequently, the present inventors have found a denitration catalyst in which vanadium pentoxide is present in at least <NUM> wt%, having a BET specific surface area of at least <NUM><NUM>/g, and which can be used in denitration at <NUM> or lower (Patent Document <NUM>).

<CIT> discloses a combustion system according to the preamble of claim <NUM>. <CIT> and <CIT> show other related combustion systems with denitration catalysts.

The present inventors, as a result of thorough research trying to achieve a further improvement of the above Patent Document <NUM>, found a denitration catalyst exhibiting a more superior reduction rate activity of nitrogen oxides.

The present invention has an object of providing a combustion system using a catalyst having better denitration efficiency at low temperature compared to the conventional technology, upon the selective catalytic reduction reaction with ammonia as the reductant.

The present invention relates to a combustion system including: a combustion device which combusts a fuel; an exhaust channel through which exhaust gas generated by the fuel combusting in the combustion device flows; a dust collector which is disposed in the exhaust channel, and collects ash dust in the exhaust gas; and a denitration device which is disposed in the exhaust channel, and removes nitrogen oxides from the exhaust gas by way of a denitration catalyst, in which the denitration device is disposed on a downstream side of the dust collector in the exhaust channel, and the denitration catalyst contains vanadium oxide, the vanadium oxide including vanadium pentoxide, and the denitration catalyst has a defect site at which oxygen atoms are deficient in the crystal structure of the vanadium pentoxide, wherein having a defect site at which oxygen atoms are deficient indicates an intensity ratio of peak intensity (P<NUM>-<NUM>) on the (<NUM>) plane of V<NUM>O<NUM>, relative to the peak intensity (P<NUM>-<NUM>) on the (<NUM>) plane of V<NUM>O<NUM>, detected by powder X-ray diffraction method, being at least <NUM> and no more than <NUM>.

In addition, it is preferable for the combustion system to further include an air preheater disposed in the exhaust channel, and recovers heat from the exhaust gas, and the air preheater to be disposed on an upstream side of the dust collector.

A combustion system according to the present invention has better denitration efficiency at low temperature compared to the conventional technology, upon the selective catalytic reduction reaction with ammonia as the reductant.

Hereinafter, embodiments of the present invention will be explained.

The denitration catalyst of the present invention is a denitration catalyst containing vanadium oxide, in which this vanadium oxide includes vanadium pentoxide, and has defect sites at which oxygen atoms are deficient in the crystal structure of this vanadium pentoxide. Such a denitration catalyst can exhibit a high denitration effect even under a low temperature environment, compared to a denitration catalyst such as a vanadium/titanium catalyst which is conventionally used.

Firstly, the denitration catalyst of the present invention contains vanadium oxide. This vanadium oxide includes vanadium oxide (II) (VO), vanadium trioxide (III) (V<NUM>O<NUM>), vanadium tetroxide (IV) (V<NUM>O<NUM>), and vanadium pentoxide (V) (V<NUM>O<NUM>), and the V element of vanadium pentoxide (V<NUM>O<NUM>) may assume the pentavalent, tetravalent, trivalent and divalent form in the denitration reaction. It should be noted that this vanadium oxide is a main component of the denitration catalyst of the present invention, and may contain other substances within a range no inhibiting the effects of the present invention; however, it is preferably present in at least <NUM> wt% by vanadium pentoxide conversion, in the denitration catalyst of the present invention. More preferably, the vanadium oxide preferably exists in at least <NUM> wt% by vanadium pentoxide conversion. More preferably, vanadium oxide is preferably present in at least <NUM> wt% by vanadium pentoxide conversion, in the denitration catalyst of the present invention.

Secondly, the denitration catalyst of the present invention has defect sites at which oxygen atoms are deficient in the crystal structure of vanadium pentoxide included in the above-mentioned vanadium oxide. It should be noted that, herein, "defect site" indicates being a position (site) at which a certain type of atom is not occupied, while being a position (site) which be occupied by this certain atom in the crystal. In the denitration catalyst of the present invention, the structure of the vanadium pentoxide crystal contained in this denitration catalyst is locally disordered due to firing at a relatively low temperature, and can exhibit high denitration effect; however, above all, it is assumed that a high denitration effect is exhibited by sites appearing at which oxygen atoms are deficient in the crystal structure of vanadium pentoxide. It should be noted that "site at which oxygen atoms are deficient" is also abbreviated as "oxygen defect site".

It should be noted that, herein, according to the invention, "having a defect site at which oxygen atoms are deficient" indicates an intensity ratio of peak intensity (P<NUM>-<NUM>) on the (<NUM>) plane of V<NUM>O<NUM>, relative to the peak intensity (P<NUM>-<NUM>) on the (<NUM>) plane of V<NUM>O<NUM>, detected by powder X-ray diffraction method, being at least <NUM> and no more than <NUM>, as disclosed in the Examples described later.

In addition, the denitration catalyst of the present invention has a state in which the degree of crystallinity declines due to the existence of vanadium pentoxide in which the crystal structure of vanadium pentoxide included in the above-mentioned vanadium oxide contains crystal water. In the denitration catalyst of the present invention, the structure of the vanadium pentoxide crystal included in this denitration catalyst is locally disordered by firing at relatively low temperature, and can exhibit high denitration effect; however, by the crystal structure of vanadium pentoxide and crystal water-containing vanadium pentoxide coexisting, it is assumed that high denitration effect is exhibited by inhibiting growth of vanadium pentoxide crystals, and generating a local disorder in the structure of the vanadium pentoxide crystal.

In the embodiment of the present invention, in the selective catalytic reduction reaction using the denitration catalyst in which the intensity ratio (PV6O13/PV2O5) of the peak intensity (PV6O13) of the.

(<NUM>) plane of V<NUM>O<NUM> relative to the peak intensity (PV2O5) of the (<NUM>) plane of V<NUM>O<NUM> detected by powder X-ray diffraction method of the denitration catalyst being at least <NUM> and no more than <NUM>, it exhibited a NO conversion rate of <NUM>% to <NUM>% at the reaction temperature of <NUM>, and a NO conversion rate of <NUM>% to <NUM>% at the reaction temperature of <NUM>. On the other hand, in the selective catalytic reduction reaction using the denitration catalyst in which the intensity ratio (PV6O13/PV2O5) of the peak intensity (PV6O13) of the (<NUM>) plane of V<NUM>O<NUM> relative to the peak intensity (PV2O5) of the (<NUM>) plane of V<NUM>O<NUM> detected by powder X-ray diffraction method of the denitration catalyst being <NUM>, it only exhibited a NO conversion rate of <NUM>% at the reaction temperature of <NUM>, and a NO conversion rate of <NUM>% at the reaction temperature of <NUM>.

In addition, the intensity ratio (PV6O13/PV2O5) of the peak intensity (PV6O13) of the (<NUM>) plane of V<NUM>O<NUM> relative to the peak intensity (PV2O5) of the (<NUM>) plane of V<NUM>O<NUM> detected by powder X-ray diffraction method of the denitration catalyst is preferably at least <NUM> and no more than <NUM>; however, more preferably, it may be at least <NUM> and no more than <NUM>.

More preferably, it may be at least <NUM> and no more than <NUM>.

Not in accordance with the invention, "having a defect site at which oxygen atoms are deficient" may be the matter of transmittance at a wavelength <NUM> normalized with transmittance at wavelength <NUM> as <NUM> in ultraviolet-visible near-infrared absorption spectrum being no more than <NUM>, as disclosed in the Examples described later.

In a selective catalytic reduction reaction using a denitration catalyst having a reflectance at a wavelength <NUM> normalized with reflectance at a wavelength <NUM> as <NUM> in ultraviolet-visible near-infrared absorption spectrum of at least <NUM> and no more than <NUM>, it exhibited a NO conversion rate of <NUM>% to <NUM>% at a reaction temperature of <NUM>, and a NO conversion rate of <NUM>% to <NUM>% at a reaction temperature of <NUM>.

On the other hand, in the selective catalytic reduction reaction using a denitration catalyst having a reflectance at a wavelength <NUM> normalized with reflectance at a wavelength <NUM> as <NUM> in ultraviolet-visible near-infrared absorption spectrum of <NUM>, it only exhibited a NO conversion rate of <NUM>% at a reaction temperature of <NUM>, and a NO conversion rate of <NUM>% at a reaction temperature of <NUM>.

In addition, the reflectance of wavelength <NUM> normalized with reflectance of wavelength <NUM> as <NUM> in ultraviolet-visible near-infrared absorption spectrum is preferably no more than <NUM>; however, more preferably, it may be at last <NUM> and no more than <NUM>.

Not in accordance with the invention, "having a defect site at which oxygen atoms are deficient" may be the matter of the ratio of tetravalent vanadium relative to overall vanadium of the catalyst surface detected by X-ray photoelectron spectroscopy being at least <NUM>, as disclosed in the Examples described later.

In a selective catalytic reduction reaction using a denitration catalyst having a ratio of tetravalent vanadium relative to overall vanadium at the catalyst surface detected by X-ray photoelectron spectroscopy of at least <NUM> and no more than <NUM>, for example, it exhibited a NO conversion rate of <NUM>% to <NUM>% at a reaction temperature of <NUM>, and a NO conversion rate of <NUM>% to <NUM>% at a reaction temperature of <NUM>.

On the other hand, in the selective catalytic reduction reaction using a denitration catalyst having a ratio of tetravalent vanadium relative to overall vanadium at the catalyst surface detected by X-ray photoelectron spectroscopy of <NUM>, it only exhibited a NO conversion rate of <NUM>% at a reaction temperature of <NUM>, and a NO conversion rate of <NUM>% at a reaction temperature of <NUM>.

In addition, the ratio of tetravalent vanadium relative to overall vanadium at the catalyst surface detected by X-ray photoelectron spectroscopy is preferably at least <NUM>; however, more preferably, it may be at least <NUM> and no more than <NUM>.

Not in accordance with the invention, "having a defect site at which oxygen atoms are deficient" may refer to the ratio (P1/P3) of the peak intensity P1 of wavenumber <NUM> to <NUM>-<NUM> originating from crosslinked V-OB-V bending vibration, relative to the peak intensity P3 of wavenumber <NUM> to <NUM>-<NUM> originating from edge-sharing 3V-OC bending vibration, as described in the Examples later being no more than <NUM>. The wavenumber for calculating this "P1/P3" is the wavenumber in a case of the beginning to the end of the peak; however, in the case of calculating using the wavenumber of the peak top, it may be calculated as the ratio (P1/P3) of the peak intensity P1 of wavenumber <NUM> to <NUM>-<NUM> originating from the crosslinked V-OB-V bending vibration, relative to the peak intensity P3 of wavenumber <NUM> to <NUM>-<NUM> originating from edge-sharing 3V-OC bending vibration.

In a selective catalytic reduction reaction using a denitration catalyst having a ratio (P1/P3) of the peak intensity P1 of wavenumber <NUM> to <NUM>-<NUM> originating from the crosslinked V-OB-V bending vibration, relative to the peak intensity P3 of wavenumber <NUM> to <NUM>-<NUM> originating from edge-sharing 3V-OC bending vibration of <NUM> to <NUM>, it exhibited a NO conversion rate of <NUM>% to <NUM>% at the reaction temperature of <NUM>, and exhibited a NO conversion rate of <NUM>% to <NUM>% at the reaction temperature of <NUM>.

On the other hand, in the selective catalytic reduction reaction using a denitration catalyst having a ratio (P1/P3) of the peak intensity P1 of wavenumber <NUM> to <NUM>-<NUM> originating from the crosslinked V-OB-V bending vibration, relative to the peak intensity P3 of wavenumber <NUM> to <NUM>-<NUM> originating from edge-sharing 3V-OC bending vibration of <NUM>, it only exhibited a NO conversion rate of <NUM>% at the reaction temperature of <NUM>, and exhibited a NO conversion rate of <NUM>% at the reaction temperature of <NUM>.

In addition, the ratio (P1/P3) of the peak intensity P1 of wavenumber <NUM> to <NUM>-<NUM> originating from the crosslinked V-OB-V bending vibration, relative to the peak intensity P3 of wavenumber <NUM> to <NUM>-<NUM> originating from edge-sharing 3V-OC bending vibration is preferably no more than <NUM>; however, more preferably, it may be at least <NUM> and no more than <NUM>.

Furthermore, the denitration catalyst may have a line defect in which point defects such as the "defect site at which an oxygen atoms are deficient occurs" are continuously arranged one-dimensionally, a plane defect in which the point defects are continuously arranged two-dimensionally, or a lattice defect such as lattice strain, for example.

In addition, the denitration catalyst of the present invention is preferably used in denitration at <NUM> or lower. This is derived from the firing temperature of denitration catalyst of the present invention being <NUM>. On the other hand, in the Examples described later, the denitration catalyst of the present invention exhibits high denitration effect in the selective catalytic reduction reaction at the reaction temperature of <NUM> or lower, and thus the denitration catalyst of the present invention is capable of use in denitration at <NUM> or lower. During the selective catalytic reduction reaction, oxidation of SO<NUM> to SO<NUM> is thereby not accompanied, as in the knowledge obtained by the above Patent Document <NUM>.

In addition, in the aforementioned disclosure, the denitration catalyst of the present invention is preferably used in denitration at <NUM> or lower; however, it may be preferably used in denitration at <NUM> or lower, and even more preferably, it may be used in denitration with a reaction temperature of <NUM> to <NUM>. More preferably, it may be used in denitration with a reaction temperature of <NUM> to <NUM>. Alternatively, it may be used in denitration with a reaction temperature of <NUM> to <NUM>.

The denitration catalyst containing vanadium oxide, and having a defect site at which oxygen atoms are deficient occurs in the crystal structure of vanadium pentoxide included in this vanadium oxide can be prepared by the sol gel method for the most part.

The sol gel method includes a step of mixing vanadate and chelate compound, and firing after dissolving this mixture in pure water. As the vanadate, for example, ammonium vanadate, magnesium vanadate, strontium vanadate, barium vanadate, zinc vanadate, lead vanadate, lithium vanadate, etc. may be used. In addition, as the chelate compound, for example, that having a plurality of carboxyl groups such as oxalic acid and citric acid, that having a plurality of amino groups such as acetylacetonate and ethylenediamine, that having a plurality of hydroxyl groups such as ethylene glycol, etc. may be used. It should be noted that, in the present embodiment, after dissolving the vanadate in chelate compound and drying, it is fired at a temperature of <NUM> or less.

The denitration catalyst produced by the method including a step of dissolving ammonium vanadate in an oxalic acid aqueous solution, and a step of subsequently drying, and then firing at a temperature of <NUM>, exhibited a NO conversion rate of <NUM> to <NUM>% at a reaction temperature of <NUM>, and exhibited a NO conversion rate of <NUM> to <NUM>% at a reaction temperature of <NUM>.

On the other hand, as a denitration catalyst produced by a method differing from such a process, for example, a denitration catalyst produced by a method including a step of dissolving ammonium vanadate in an oxalic acid aqueous solution, and a step of subsequently drying, and then firing at a temperature of <NUM> for <NUM> hours only exhibited a NO conversion rate of <NUM>% at a reaction temperature of <NUM>, and exhibited a NO conversion rate of <NUM>% at a reaction temperature of <NUM>.

The denitration catalyst prepared in this way is normally a denitration catalyst containing vanadium oxide, in which this vanadium oxide includes vanadium pentoxide, and has a defect site at which an oxygen deficiency occurs in the crystal structure of this vanadium pentoxide.

It should be noted that the present invention is not to be limited to the above embodiment, and that modifications, improvements, etc. within the scope of the appended claims are also encompassed by the present invention.

Hereinafter, Examples of the present invention will be specifically explained together with Comparative Examples. It should be noted that the present invention is not limited to these Examples.

Ammonium vanadate was dissolved in an oxalic acid aqueous solution.

Herein, the molar ratio of ammonium vanadate : oxalic acid is <NUM>:<NUM>. After completely dissolving, the moisture in the solution was evaporated on a hot stirrer, and was dried overnight at <NUM> in a dryer.

Subsequently, the dried powder was fired for <NUM> hour at <NUM> in air. The fired vanadium pentoxide was defined as the denitration catalyst of Example <NUM>.

It should be noted that the sample name of this denitration catalyst of Example <NUM> was set as "V270-<NUM>".

Ammonium vanadate was dissolved in a oxalic acid aqueous solution. Herein, the molar ratio of ammonium vanadate : oxalic acid is <NUM>:<NUM>. After completely dissolving, the moisture in the solution was evaporated on a hot stirrer, and dried overnight at <NUM> in a dryer. Subsequently, the dried powder was fired for <NUM> hours at <NUM> in air. The dried vanadium pentoxide was defined as the denitration catalyst of Example <NUM>.

Ammonium vanadate was dissolved in a oxalic acid aqueous solution.

Herein, the molar ratio of ammonium vanadate : oxalic acid is <NUM>:<NUM>. After completely dissolving, the moisture in the solution was evaporated on a hot stirrer, and dried overnight at <NUM> in a dryer. Subsequently, the dried powder was fired for <NUM> hours at <NUM> in air. The dried vanadium pentoxide was defined as the denitration catalyst of Example <NUM>.

Ammonium vanadate was dissolved in a oxalic acid aqueous solution. Herein, the molar ratio of ammonium vanadate : oxalic acid is <NUM>:<NUM>. After completely dissolving, the moisture in the solution was evaporated on a hot stirrer, and dried overnight at <NUM> in a dryer. Subsequently, the dried powder was fired for <NUM> hours at <NUM> in air. The dried vanadium pentoxide was defined as the denitration catalyst of Comparative Example <NUM>.

It should be noted that the sample name of this denitration catalyst of Comparative Example <NUM> was set as "V300-<NUM>".

It should be noted that this Comparative Example <NUM> is a denitration catalyst disclosed in Patent Document <NUM> noted above.

Under the conditions of Table <NUM> below, the NH<NUM>-SCR reaction was carried out using a fixed bed flow-type reactor at a reaction temperature of <NUM> to <NUM>.

In the gas passing through the catalyst layer, NO was analyzed by a Jasco FT-IR-<NUM>.

In addition, the NO conversion rate was calculated by Formula (<NUM>) noted below. It should be noted that Noin is the NO concentration at the reaction tube inlet, and NOout is the NO concentration of the reaction tube outlet. Formula <NUM> <MAT>.

Table <NUM> shows the NO conversion rates of each vanadium pentoxide catalyst for both a case of a reaction temperature of <NUM> and a case of a reaction temperature of <NUM>.

<FIG> is a plot graphing this Table <NUM>.

In both a case of a reaction temperature of <NUM> and a case of a reaction temperature of <NUM>, the denitration catalyst of the Examples exhibited a higher NO conversion rate than the denitration catalyst of the Comparative Example. Above all, the denitration catalysts fired for <NUM> to <NUM> hours at <NUM> exhibited a high NO conversion rate.

Thereamong, Example <NUM> (V270-<NUM>) exhibited the highest NO conversion rate.

Under the conditions of a reaction temperature of <NUM> in Table <NUM> above, using the catalyst of Example <NUM> (V270-<NUM>), the NH<NUM>-SCR reaction was carried out over <NUM> hours by the same method as measurement method <NUM>, under conditions in which moisture is not coexisting (dry) and <NUM> vol% moisture coexistence (<NUM> vol% water).

<FIG> is a graph showing the change in NO conversion rate at <NUM> hours of the catalyst of Example <NUM> (V270-<NUM>).

As is evident from the graph of <FIG>, the NO conversion rate of the catalyst of Example <NUM> (V270-<NUM>) showed stable numerical values over at least <NUM> hours in both the condition in which moisture does not coexist, and under moisture coexistence.

<FIG> show TEM images of Example <NUM> (V270-<NUM>).

It should be noted that <FIG> is a TEM image of <NUM>,<NUM> times magnification, and <FIG> is a TEM image of <NUM>,<NUM>,<NUM> times magnification.

In addition, <FIG> show TEM images of Example <NUM> (V270-<NUM>).

On the other hand, <FIG> show TEM images of Comparative Example <NUM> (V300-<NUM>).

It should be noted that the images in the lower right included in each image of <FIG>, <FIG>, <FIG>, <FIG> and <FIG> show electron diffraction patterns of vanadium oxide catalysts.

From these images, it was clarified that a crystalline portion and amorphous portion exist in the crystal structure of the Examples.

As powder X-ray diffraction, measurement was performed using Cu-Kα by a Rigaku Smart Lab.

<FIG> shows the powder XRD (X-Ray Diffraction) patterns of Example <NUM> (V270-<NUM>), Example <NUM> (V270-<NUM>), Example <NUM> (V270-<NUM>) and Example <NUM> (V270-<NUM>).

Mainly, a peak of the (<NUM>) plane of V<NUM>O<NUM>·<NUM><NUM>O was found at 2θ=<NUM>°, a peak of the (<NUM>) plane of V<NUM>O<NUM> was found at 2θ=<NUM>°, and a peak of the (<NUM>) plane of V<NUM>O<NUM> was found at 2θ=<NUM>°.

<FIG> is a view showing an outline of the change in internal structure in the case of firing VO<NUM>(C<NUM>O<NUM>), which is the precursor. At the stage of firing at <NUM> for <NUM> to <NUM> hours, V<NUM>O<NUM>·<NUM><NUM>O, V<NUM>O<NUM> and V<NUM>O<NUM> are mainly generated in the denitration catalyst, and a component other than these is amorphous V<NUM>O<NUM>.

Subsequently, at the stage of firing at <NUM> for <NUM> to <NUM> hours, V<NUM>O<NUM>, V<NUM>O<NUM>·<NUM><NUM>O, and V<NUM>O<NUM> are mainly generated in the denitration catalyst, and a component other than these is amorphous V<NUM>O<NUM>.

Eventually, at the stage completely fired, V<NUM>O<NUM> is mainly generated in the denitration catalyst, and a component other than these is amorphous V<NUM>O<NUM>.

Therefore, for each catalyst, the intensity ratio (P<NUM>-<NUM>/P<NUM>-<NUM>) of the peak intensity (P<NUM>-<NUM>) of the (<NUM>) plane of V<NUM>O<NUM> relative to the peak intensity (P<NUM>-<NUM>) of the (<NUM>) plane of V<NUM>O<NUM> was calculated, and this was set as an index of each catalyst.

Table <NUM> shows the intensity ratio of each vanadium catalyst, and the NOx conversion rates for both the case of a reaction temperature of <NUM> and the case of a reaction temperature of <NUM>. <FIG> is a plot graphing this Table <NUM>.

From Table <NUM> and <FIG>, it was found that the catalysts according to the Examples having an intensity ratio of at least <NUM> exhibited higher NO conversion rate than the Comparative Example.

The color of the vanadium catalyst itself according to the above Examples and Comparative Examples changes from green to yellow as firing progresses.

Therefore, for each catalyst, UV-Vis-NIR spectra was calculated using a diffuse reflection microscope.

In more detail, a sample of each catalyst was filled into a sample holder including a white sheet of barium sulfate, and UV-Vis-NIR spectra were measured by the diffuse reflectance method.

As the measuring apparatus, a UV-3100PC UV-visible spectrophotometer manufactured by Shimadzu was used.

<FIG> shows, as the UV-Vis-NIR spectra for each catalyst, a graph establishing the wavelength as the horizontal axis, and establishing the reflectance normalizing the reflectance of wavelength <NUM> as <NUM> as the vertical axis.

According to the graph of <FIG>, it was shown that the value of reflectance dropped within a wide range of wavelengths after <NUM>, as the tetravalent vanadium increased.

It should be noted that Table <NUM> below shows the absorption edge wavelength of each catalyst and the reflectance of wavelength <NUM>.

<FIG> is a graph showing the relationship between the reflectance of wavelength <NUM> of each catalyst and the NO conversion rate.

For both a case of a reaction temperature of <NUM> and a case of a reaction temperature of <NUM>, the NO conversion rates of catalysts according to the Examples having a reflectance of no more than <NUM> exhibited a higher value than the NO conversion rate of the catalyst according to the Comparative Example having a reflectance exceeding <NUM>.

In order to analyze the crystal structure of each catalyst, the Raman spectra was measured by Raman spectroscopy.

In more detail, a small amount of a sample of each catalyst was placed on a slide of glass, and the Raman spectra were measured by a Raman spectroscopic device.

As the measurement apparatus, an NRS-<NUM> Raman spectrophotometer manufactured by JASCO Corp.

<FIG> shows the Raman spectra of each catalyst.

From <FIG>, the peaks originating from the crystal structure of each catalyst could be confirmed.

Above all, it showed that there is a defect portion and a site of V<NUM>+ in the crystal structure of each catalyst according to the Examples.

The infrared absorption spectra of each catalyst was measured.

It should be noted that, upon measurement, <NUM> of sample of each catalyst and <NUM> of potassium bromide were mixed, and molded by pressurizing by a tablet molding machine.

Furthermore, infrared absorption spectra was measured by the transmission method using a TGS detector.

As the measurement apparatus, an FT/IR-<NUM> infrared spectrometer manufactured by JASCO Corp.

<FIG> shows the spectral curve of each catalyst obtained as a result of measuring the infrared absorption spectra of the fingerprint region: <NUM> to <NUM>-<NUM>.

In addition, <FIG> shows crystal structures of vanadium pentoxide according to each of the Examples.

In the crystal structure of vanadium pentoxide, the terminal V=O (<NUM> in <FIG>), edge-shared 3V-OC (<NUM> in <FIG>) and crosslinked V-OB-V (<NUM> in <FIG>) exist.

As shown in <FIG>, the peak (Peak <NUM>) originating from crosslinked V-CB-V bending vibration overlaps the peak (Peak <NUM>) originating from edge-shared 3V-OC stretching vibration. Therefore, the ratio (P1/P3) of intensity P1 of the peak (Peak <NUM>) of wavenumber <NUM> to <NUM>-<NUM> originating from the crosslinked V-OB-V bending vibration relative to intensity P3 of the peak (Peak <NUM>) of wavenumber <NUM> to <NUM>-<NUM> originating from edge-shared 3V-OC stretching vibration was calculated. Table <NUM> below shows the wavenumber, transmittance and ratio of P1/P3 of each peak for every catalyst. In addition, <FIG> is a graph establishing the ratio of P1/P3 in Table <NUM> as the horizontal axis, and establishing the NO conversion rate of each catalyst as the vertical axis.

As found from Table <NUM> and <FIG>, according to the Examples, the catalysts according to the Examples having a P1/P3 of <NUM> or less showed a higher NO conversion rate than the catalyst according to the Comparative Example having a P1/P3 of <NUM>.

For the catalysts according to each of the Examples and Comparative Example, the X-ray photoelectron spectrum (XPS) was measured in order to analyze the electronic state.

In more detail, powder samples of each catalyst of the Examples and Comparative Examples were fixed to a sample holder using carbon tape, and the X-ray photoelectron spectrum was measured.

As the measurement device, a JPS-9010MX photoelectron spectrometer manufactured by JEOL Ltd.

<FIG> shows the XPS spectra for the V2p region.

From <FIG>, it is shown that there is a defect portion and V<NUM>+ site in the crystal structure of each catalyst according to the Examples, similarly to <FIG>.

In addition, the ratio of tetravalent vanadium relative to overall vanadium from the catalyst surface until <NUM> which is the photoelectron escape depth becomes <NUM> in Example <NUM>, <NUM> in Example <NUM>, <NUM> in Example <NUM>, and <NUM> in Example <NUM>.

On the other hand, it was merely <NUM> in the Comparative Example.

<FIG> is a graph establishing the proportion of tetravalent vanadium in the overall vanadium of the catalyst surface of each of the Examples and Comparative Examples as the horizontal axis, and establishing the NO conversion rate as the vertical axis.

It was shown that the NO conversion rates of the catalysts according to the Examples in which the proportion of tetravalent vanadium of the overall vanadium of the catalyst surface was at least <NUM> is higher than the NO conversion rate of the catalyst according to the Comparative Example in which the proportion of tetravalent vanadium of the overall vanadium of the catalyst surface was <NUM>.

In the above way, a denitration catalyst containing vanadium oxide has a high denitration efficiency at low temperatures of <NUM> or lower, in the selective catalytic reduction reaction with ammonia as the reductant, using a denitration catalyst having a defect site at which oxygen atoms are deficient in the crystal structure of vanadium pentoxide.

Hereinafter, a first application example of the present invention will be explained while referencing the drawings.

<FIG> is a view showing the configuration of a combustion system <NUM> according to the first application example.

The combustion system <NUM> is a combustion system establishing pulverized coal as the fuel.

As shown in <FIG>, the combustion system <NUM> assumes a thermal power generation system as an example, and includes: a boiler <NUM> as a combustion device, a coal pulverizer <NUM>, an exhaust channel L1, an air preheater <NUM>, a gas heater <NUM> as a heat recovery device, a dust collector <NUM>, an induced-draft fan <NUM>, desulfurization equipment <NUM>, a gas heater <NUM> as a heater, a denitration device <NUM>, and a smoke stack <NUM>.

The boiler <NUM> combusts the pulverized coal as fuel together with air.

In the boiler <NUM>, exhaust gas is produced by the pulverized coal combusting.

It should be noted that coal ash such as clinker ash and fly ash is produced by pulverized coal combusting.

The clinker ash produced in the boiler <NUM> is discharged to the clinker hopper <NUM> arranged below the boiler <NUM>, and is then carried to a coal ash collection silo which is not illustrated.

The boiler <NUM> is formed in a substantially reversed U-shape as a whole.

The exhaust gas produced in the boiler <NUM> moves in reverse U shape along the shape of the boiler <NUM>.

The temperature of the exhaust gas near the outlet of the exhaust gas of the boiler <NUM> is <NUM> to <NUM>, for example.

The coal pulverizer <NUM> forms pulverized coal by crushing coal supplied from the coal hopper which is not illustrated, into a fine particle size.

The coal pulverizer <NUM> preheats and dries the pulverized coal, by mixing the pulverized coal and air.

The pulverized coal formed in the coal pulverizer <NUM> is supplied to the boiler <NUM> by air being blown.

The exhaust channel L1 has an upstream side connected to the boiler <NUM>.

The exhaust channel L1 is a flow path through which the exhaust gas produced in the boiler <NUM> flows.

The air preheater <NUM> is arranged in the exhaust channel L1. The air preheater <NUM> performs heat exchange between the exhaust gas and air used for combustion fed from a pusher-type blower which is not illustrated, and recovers heat from the exhaust gas.

The air for combustion is supplied to the boiler <NUM> after being heated in the air preheater <NUM>.

The gas heater <NUM> is arranged on the downstream side of the air preheater <NUM> in the exhaust channel L1.

Exhaust gas which was heat recovered in the air preheater <NUM> is supplied to the gas heater <NUM>.

The gas heater <NUM> further recovers heat from the exhaust gas.

The dust collector <NUM> is arranged on the downstream side of the gas heater <NUM> in the exhaust channel L1.

The exhaust gas which was heat recovered in the gas heater <NUM> is supplied to the dust collector <NUM>.

The dust collector <NUM> is a device which collects dust such as coal ash (fly ash) in the exhaust gas by applying voltage to electrodes.

Fly ash collected in the dust collector <NUM> is carried to a coal ash collection silo which is not illustrated.

The temperature of exhaust gas in the dust collector <NUM> is <NUM> to <NUM>, for example.

The induced-draft fan <NUM> is arranged on the downstream side of the dust collector <NUM> in the exhaust channel L1.

The induced-draft fan <NUM> draws in exhaust gas from which fly ash was removed in the dust collector <NUM> from a first side and sends out to a second side.

The desulfurization equipment <NUM> is arranged on the downstream side of the induced-draft fan <NUM> in the exhaust channel L1.

The exhaust gas sent out from the induced-draft fan <NUM> is supplied to the desulfurization equipment <NUM>.

The desulfurization equipment <NUM> removes sulfur oxides from the exhaust gas.

In detail, the desulfurization equipment <NUM> removes sulfur oxides from the exhaust gas, by absorbing sulfur oxides contained in the exhaust gas into a mixed solution, by spraying mixed solution (limestone slurry) of limestone and water to the exhaust gas.

The temperature of exhaust gas in the desulfurization device <NUM> is <NUM> to <NUM>, for example.

The gas heater <NUM> is arranged on the downstream side of the desulfurization device <NUM> in the exhaust channel L1.

The exhaust gas from which the sulfur oxides were removed in the desulfurization equipment <NUM> is supplied to the gas heater <NUM>.

The gas heater <NUM> heats the exhaust gas.

The gas heater <NUM> and gas heater <NUM> may be configured as gas-gas heaters performing heat exchange between exhaust gas flowing between the air preheater <NUM> and the dust collector <NUM> in the exhaust channel L1, and exhaust gas flowing between the desulfurization equipment <NUM> and denitration device <NUM> described later.

Above all, the gas heater <NUM> heats the exhaust gas up to a temperature suited to the denitration reaction of the denitration device <NUM> at a later stage.

The denitration device <NUM> is arranged on the downstream side of the gas heater <NUM> in the exhaust channel L1.

The exhaust gas heated in the gas heater <NUM> is supplied to the denitration device <NUM>.

The denitration device <NUM> removes nitrogen oxides from the exhaust gas by way of the denitration catalyst.

The denitration device <NUM> uses a denitration catalyst containing vanadium oxide, having a carbon content of at least <NUM> wt%, and having a defect site at which an oxygen deficiency occurs in the crystal structure.

The temperature of exhaust gas in the denitration device <NUM> is <NUM> to <NUM>, for example.

The denitration device <NUM> removes nitrogen oxides from exhaust gas by a selective catalytic reduction process.

According to the selective catalytic reduction process, it is possible to remove nitrogen oxides efficiently from exhaust gas, by generating nitrogen and water from the nitrogen oxides by reductant and the above-mentioned denitration catalyst.

The reductant used in the selective catalytic reduction process contains at least one of ammonia and urea.

In the case of using ammonia as the reductant, ammonia in any state of ammonia gas, liquid ammonia and ammonia aqueous solution may be used.

More specifically, the denitration device <NUM> can be a configuration which injects ammonia gas to the introduced exhaust gas, and then contacts this mixed gas with the denitration catalyst.

For this reason, the denitration device <NUM> includes one or a plurality of denitration catalyst layers, and these denitration catalyst layers may include a plurality of casings, a plurality of honeycomb catalysts accommodated in this plurality of casing, and a sealing member.

In more detail, the casing is configured from a square tubular metal member in which one end and the other end are open, and may be arranged so that the opened one end and other end are opposite in the flow path of the exhaust gas in the denitration reactor, i.e. so that exhaust gas flows inside of the casing.

In addition, the plurality of casings may be arranged to be connected in an abutted state so as to block the flow path of exhaust gas.

The honeycomb catalyst may be formed in a long shape (rectangular parallelepiped shape) in which a plurality of exhaust gas circulation holes extending in the longitudinal direction is formed, and may be arranged so that the extending direction of exhaust gas circulation holes follows the flow path of exhaust gas.

The smoke stack <NUM> has a downstream side of the exhaust channel L1 connected.

The exhaust gas from which nitrogen oxides were removed in the denitration device <NUM> is introduced to the smoke stack <NUM>.

The exhaust gas introduced to the smoke stack <NUM> is effectively discharged from the top of the smoke stack <NUM> by the stack effect, by being heated by the gas heater <NUM>.

In addition, by the exhaust gas being heated in the gas heater <NUM>, it is possible to prevent water vapor from condensing above the smoke stack <NUM> and white smoke generating.

The temperature of exhaust gas near the outlet of the smoke stack <NUM> is <NUM>, for example.

<FIG> is a view showing the configuration of a combustion system 1A according to a second application example.

The combustion system 1A is a combustion system establishing pulverized coal as fuel, similarly to the combustion system <NUM>.

In the combustion system 1A, for constituent elements identical to the combustion system <NUM>, the same reference numbers are used, and explanations of the functions thereof will be omitted.

The combustion system 1A differs from the combustion system <NUM> in the point of the denitration device <NUM> being installed immediately after the dust collector <NUM>.

Furthermore, the induced-draft fan <NUM>, desulfurization equipment <NUM>, and a gas heater <NUM> are provided in order from upstream at the downstream of the denitration device <NUM>.

The gas heater <NUM> in the combustion system <NUM> heats the exhaust gas up to the temperature suited to the denitration reaction of the denitration device <NUM> of a later stage.

On the other hand, the gas heater <NUM> of the combustion system 1A heats the exhaust gas up to the suitable temperature to diffuse from the smoke stack <NUM> at a later stage.

By installing the denitration device <NUM> immediately after the dust collector <NUM>, it is possible to set the temperature of exhaust gas in the denitration device <NUM> as <NUM> to <NUM>, without requiring to provide a gas heater before the denitration device <NUM>.

<FIG> is a view showing the configuration of a combustion system 1B according to a third application example.

The combustion system 1B differs from the combustion systems <NUM> and 1A, and is a combustion system establishing natural gas as the fuel.

In the combustion system 1B, for constituent elements identical to the combustion system <NUM> and the combustion system 1A, the same reference numbers are used, and explanations of the functions thereof will be omitted.

As shown in <FIG>, the combustion system 1B includes the boiler <NUM> as a combustion device, a vaporizer <NUM> of natural gas, the exhaust channel L1, the air preheater <NUM>, the denitration device <NUM>, the induced-draft fan <NUM>, and the smoke stack <NUM>.

On the other hand, the combustion system 1B does not establish the dust collector and desulfurization equipment as essential constituent elements.

The vaporizer <NUM> vaporizes natural gas supplied from an LNG tank which is not illustrated and supplies to the boiler <NUM>.

Upon vaporizing, a system using seawater (open rack system) may be used, a system making hot water by heating with a gas burner (submerged combustion system) may be used, or a system performing heat exchange of a plurality of stages using a mediator may be used.

The denitration device <NUM> is arranged on the downstream side of the air preheater <NUM> in the exhaust channel L1.

Exhaust gas cooled in the air preheater <NUM> is supplied to the denitration device <NUM>.

The denitration device <NUM> removes nitrogen oxides from the exhaust gas by the denitration catalyst.

The temperature of each gas in the denitration device <NUM> is <NUM> to <NUM>, for example.

The downstream side of the exhaust channel L1 is connected to the smoke stack <NUM>.

Exhaust gas from which nitrogen oxides were removed in the denitration device <NUM> is introduced to the smoke stack <NUM>.

Due to the temperature of the exhaust gas in the denitration device <NUM> being <NUM> to <NUM>, for example, the exhaust gas introduced to the smoke stack <NUM> is effectively discharged from the top of the smoke stack <NUM> by the stack effect.

In addition, the temperature of exhaust gas near the outlet of the smoke stack <NUM> is <NUM>, for example.

By arranging the denitration device <NUM> on the downstream side of the air preheater <NUM>, the temperature of exhaust gas denitrated by the denitration catalyst becomes lower, and it becomes possible to decrease the deterioration of the denitration catalyst.

<FIG> is a view showing the configuration of a combustion system 1C according to a fourth application example.

As shown in FIG. <NUM>, the combustion system 1C is a combustion system used for the propulsion of ships, and includes: a fuel supply device <NUM>, an internal combustion engine <NUM> as a combustion device, a dust collector <NUM>, an exhaust recovery device <NUM>, a denitration device <NUM>, a smoke stack <NUM>, a shaft motor <NUM>, a fuel channel R1, exhaust channels R2 and R3, a steam channel R4, and a power line R5.

The fuel supply device <NUM> supplies fuel using the fuel channel R1 to the internal combustion engine <NUM>.

As the fuel, for example, it is possible to use petroleum fuel such as light oil or heavy oil.

The fuel channel R1 has an upstream side connected to the fuel supply device <NUM>, and a downstream side connected to the internal combustion engine <NUM>.

The fuel channel R1 is a flow path to which fuel is transported from the fuel supply device <NUM> to the internal combustion engine <NUM>.

The internal combustion engine <NUM> combusts the petroleum fuel together with air.

In the internal combustion engine <NUM>, the exhaust gas is produced by the petroleum fuel combusting.

The produced exhaust gas is discharged to the dust collector <NUM> via the exhaust channel R2.

It should be noted that the internal combustion engine <NUM> may be a <NUM>-stroke low-speed diesel engine used in a large ship, may be a <NUM>-stroke high-speed diesel engine used in a ferry or the like, or may be a <NUM>-stroke high-speed diesel engine used in a high-speed boat or small ship.

The exhaust channel R2 has an upstream side connected to the internal combustion engine <NUM>. The exhaust channel R2 is a flow path through which exhaust gas produced by the internal combustion engine <NUM> flows.

The dust collector <NUM> is arranged on the downstream side of the internal combustion engine <NUM> in the exhaust channel R2, and the exhaust gas discharged from the internal combustion engine <NUM> is supplied thereto. The dust collector <NUM> is a device which collects ash dust in the exhaust gas. As the ash dust collection method, for example, a method may be used which charges the ash dust by applying voltage to electrodes, and collects using Coulomb force. Alternatively, a method may be used which collects ash dust by gas-liquid contact, by supplying a ash dust absorption liquid to a venturi portion, and atomizing the ash dust absorption liquid by exhaust gas which reaches high speed by this venturi portion, as in the method conducted by a venturi scrubber.

The exhaust heat recovery device <NUM> is arranged on the downstream side of the dust collector <NUM> in the exhaust channel, and exhaust gas from which ash dust was removed by the dust collector <NUM> is supplied thereto.

The exhaust heat recovery device <NUM> recovers exhaust heat from exhaust gas supplied from the dust collector <NUM>.

More specifically, the exhaust heat recovery device <NUM> includes a turbine device <NUM> and exhaust gas economizer <NUM>.

The turbine device <NUM> includes a gas turbine <NUM>, steam turbine <NUM> and generator <NUM>.

The gas turbine <NUM> and generator <NUM>, and the steam turbine <NUM> and generator <NUM> are connected to each other.

The gas turbine <NUM> is driven by exhaust gas supplied from the dust collector <NUM> through the exhaust channel R3.

When the gas turbine <NUM> is driven, the generator <NUM> connected to the gas turbine <NUM> is also driven in connection to perform power generation.

In addition, the steam turbine <NUM> is driven by steam supplied from the exhaust gas economizer <NUM> described later, through the steam channel R4.

When the steam turbine <NUM> is driven, the generator <NUM> connected to the steam turbine <NUM> also operates in connection to perform power generation.

The electric power generated by the generator <NUM> is supplied to the shaft motor <NUM> through the power line R5.

The exhaust gas economizer <NUM> generates steam from water stored in a water supply tank (not illustrated), with the exhaust gas supplied from the dust collector <NUM> through the exhaust channel R2, and exhaust gas supplied from the gas turbine <NUM> through the exhaust channel R3 as the heat source.

The steam generated by the exhaust gas economizer <NUM> is supplied to the steam turbine <NUM> through the steam channel R4.

The exhaust channel R3 is a different exhaust channel than the exhaust channel R2, with the upstream side being connected to the dust collector <NUM> and the downstream side being connected to the exhaust gas economizer <NUM>, and midstream thereof, goes through the gas turbine <NUM>.

The exhaust channel R3 is a flow path which flows the exhaust gas supplied from the dust collector <NUM> to the exhaust gas economizer <NUM> through the gas turbine <NUM>.

The steam channel R4 has an upstream side connected to the exhaust gas economizer <NUM>, and a downstream side connected to the steam turbine <NUM>.

The steam channel R4 is a flow path through which steam generated by the exhaust gas economizer <NUM> flows.

The power line R5 has an upstream side connected to the generator <NUM>, and a downstream side connected to the shaft motor <NUM>.

The power line is a flow path through which electricity generated by the generator <NUM> flows.

The denitration device <NUM> is arranged on the downstream side of the exhaust heat recovery device <NUM> in the exhaust channel R2, and the exhaust gas from which exhaust heat was recovered is supplied thereto.

The denitration device <NUM> uses a denitration catalyst containing vanadium oxide, in which the carbon content is at least <NUM> wt%, and the above-mentioned denitration catalyst has a defect site at which an oxygen deficiency occurs in the crystal structure.

Since the denitration device <NUM> is installed on the downstream side of the exhaust heat recovery device <NUM>, the temperature of exhaust gas in the denitration device <NUM> is <NUM> to <NUM>, for example.

The denitration device <NUM> removes nitrogen oxides from exhaust gas by way of a selective catalytic reduction process.

According to the selective catalytic reduction process, it is possible to remove nitrogen oxides efficiently from exhaust gas, by generating nitrogen and water from the nitrogen oxides by way of a reductant and denitration catalyst.

The smoke stack <NUM> is connected at a downstream side of the exhaust channel R2.

The exhaust gas from which nitrogen oxides have been removed in the denitration device <NUM> is introduced to the smoke stack <NUM>.

The exhaust gas introduced to the smoke stack <NUM> is effectively discharged from the top of the smoke stack <NUM> by way of the stack effect, due to the temperature of the exhaust gas in the denitration device <NUM> being <NUM> to <NUM>, for example.

In addition, it is possible to prevent water vapor from condensing above the smoke stack <NUM> and white smoke generating.

The temperature of the exhaust gas near the outlet of the smoke stack <NUM> is <NUM>, for example.

The shaft motor <NUM> is installed on the downstream side of the generator <NUM> in the power line R5, and is driven so as to aid rotation around the propeller shaft of the internal combustion engine <NUM>.

Electric power is supplied to the shaft motor <NUM> from the generator <NUM> through the power line R5, and by using this electric power, drives so as to aid the motive power generated by the internal combustion engine <NUM>.

In addition, although not illustrated, a fifth application example may be a denitration device which equips, to a combustion system that incinerates raw garbage, etc., a denitration catalyst containing vanadium oxide, and having a carbon content of at least <NUM> wt%, and the above denitration catalyst having a defect site at which an oxygen deficiency occurs in the crystal structure.

In the denitration device installed at a later stage than the boiler combusting raw garbage, although the temperature of exhaust gas may be no more than <NUM>, since the above-mentioned denitration catalyst can be used in denitration having a reaction temperature of <NUM> to <NUM>, it is useful also for such a denitration system.

The above-mentioned denitration catalyst is basically powder form; however, for example, a honeycomb-type catalyst made by coating catalyst component on a honeycomb shape substrate may be used in a flue gas denitration apparatus installed at a thermal power plant, as disclosed in <CIT>.

As a sixth application example, it is possible to coat the above-mentioned denitration catalyst as the catalyst component on a substrate.

So long as deformation, etc. does not occur at temperatures of <NUM> or higher, any substrate can be used as the above-mentioned substrate.

For example, ceramics, pottery and metals such as titanium may be used as the substrate.

Alternatively, as the substrate, a corrugated honeycomb filter made from a ceramic fiber paper, glass fiber paper, flame-retardant paper, activated carbon paper, deodorizing paper, honeycomb filter nonwoven fabric, felt, or plastic sheet may be used.

Alternatively, the catalyst component may be further coated on a new catalyst or a used catalyst.

In addition, the substrate can be made into any form, and can be established as any among a plate-like shape, pellet shape, fluid form, columnar shape, star shape, ring shape, extruded shape, spherical shape, flake shape, pastille shape, rib extruded shape, or ribbed ring shape, for example.

For example, the corrugated honeycomb filter can assume any form such as block type, rotor type, diagonal type, deformed block, strip type and mini pleats.

Furthermore, a catalyst block such as a honeycomb catalyst may be used in the denitration device equipped to a coal-fired power generation facility; however, it is possible to produce a catalyst block with the above-mentioned denitration catalyst as the catalyst component as a seventh application example, as disclosed in <CIT>, for example.

More specifically, it is possible to produce the catalyst block by mixing and kneading <NUM> to <NUM> wt% of CMC (carboxymethyl cellulose) or PVA (polyvinyl alcohol), for example, as a binder to the above-mentioned denitration catalyst of powder form, extrusion molding by a molder such as a pellet mill or vacuum extruder, or press molding, then drying, followed by firing.

It should be noted that, upon firing, since the above-mentioned binder is burned off, the weight ratio of the above-mentioned denitration catalyst in the catalyst block after firing becomes <NUM> wt%.

In addition, it is possible to produce the catalyst block by, after further mixing titanium molybdenum, tungsten and/or other compounds (particularly oxides), or silica, etc. to the above-mentioned denitration catalyst of powder form, then kneading, and extrusion molding.

The catalyst block can assume any form, for example, and it is possible to make into plate-like shape, pellet shape, fluid form, columnar shape, star shape, ring shape, extruded shape, spherical shape, flake shape, honeycomb shape, pastille shape, rib extruded shape, or ribbed ring shape.

In addition, for example, the catalyst block of honeycomb shape may have a honeycomb surface which is a polygonal shape such as triangular, quadrilateral, pentagonal or hexagonal, or circular form.

As applications of the above-mentioned denitration catalyst, a combustion system is mentioned in <NUM>, a denitration catalyst made by coating the denitration component on a substrate is mentioned in <NUM>, and a denitration catalyst molded into block form is mentioned in <NUM>; however, the applications of the denitration catalyst are not limited thereto.

For example, a combustion system with pulverized coal as the fuel is mentioned in <NUM>. <NUM> and <NUM>. <NUM>, and a combustion system with natural gas as the fuel is mentioned in <NUM>. <NUM>; however, the above-mentioned denitration catalyst may be used in a combustion system using oil or biomass fuel in place of pulverized coal or natural gas.

In addition, a combustion system used for the propulsion of ships was mentioned in <NUM>. <NUM>; however, the above-mentioned denitration catalyst may be used in a combustion system used for propelling automobiles instead of ships.

According to the combustion system related to the above-mentioned application examples, the following effects are exerted. (<NUM>) As mentioned above, the combustion system <NUM> according to the above application example arranged the denitration device <NUM> on the downstream side of the dust collector <NUM>, in the exhaust channel L1 through which exhaust gas generated in the boiler (combustion device) <NUM> flows.

Furthermore, the above embodiment uses, in the denitration device <NUM>, a denitration catalyst containing vanadium oxide, the vanadium oxide including vanadium pentoxide, and having defect sites at which oxygen atoms are deficient in the crystal structure of the vanadium pentoxide. By using the above-mentioned denitration catalyst, the combustion system <NUM> according to the above embodiment can exhibit an effect whereby the denitration efficiency at low temperature is even higher compared to the conventional technology, upon a selective catalytic reduction reaction with ammonia as the reductant.

(<NUM>) The combustion system 1A according to the above application example further includes the air preheater <NUM> which recovers heat from the exhaust gas, and the air preheater <NUM> is arranged on the upstream side of the dust collector <NUM>.

By the exhaust gas which has been heat recovered by the air preheater <NUM> being supplied to the dust collector <NUM>, the load on the dust collector <NUM> by the heat of exhaust gas can be suppressed.

In addition, since the denitration device <NUM> is not arranged upstream of the air preheater <NUM> which is normally arranged near the boiler (combustion device) <NUM> in the exhaust channel L1, clogging of the air preheater <NUM> caused by ammonium sulfate produced by ammonia and sulfur component in exhaust gas reacting will not occur.

The cost of operation of the combustion system 1A is thereby low.

(<NUM>) The combustion system 1B according to the above application example arranges the denitration device <NUM> on the downstream side of the air preheater <NUM>, in the exhaust channel L1 through which exhaust gas produced in the boiler (combustion device) <NUM> flows. Furthermore, the above-mentioned embodiment uses a denitration catalyst containing vanadium oxide in the denitration device <NUM>, the vanadium oxide including vanadium pentoxide, and having defect sites at which oxygen atoms are deficient in the crystal structure of the vanadium pentoxide.

By using the above-mentioned denitration catalyst, the combustion system 1A according to the above embodiment can exhibit an effect whereby the denitration efficiency at low temperature is even higher compared to the conventional technology, upon selective catalytic reduction reaction with ammonia as the reductant.

In addition, since it is thereby possible to arrange the denitration device <NUM> on the downstream side of the air preheater <NUM>, the temperature of the exhaust gas denitrated by the denitration catalyst is lower, and it is possible to decrease deterioration of the denitration catalyst.

In addition, the combustion system <NUM> of the above embodiment does not establish the desulfurization device as an essential constituent element.

Therefore, by simplifying the configuration of the combustion system 1B, it becomes possible to lower the installation cost.

(<NUM>) The combustion system 1C according to the above-mentioned application example includes: the exhaust channel R2 through which exhaust gas generated by fuel combusting in the internal combustion engine <NUM> flows; the exhaust heat recovery device <NUM> which is arranged in the exhaust channel R2 and recovers exhaust heat from the exhaust gas discharged from the internal combustion engine <NUM>; and the denitration device <NUM> which is arranged in the exhaust channel R2 and removes nitrogen oxides from exhaust gas by way of the denitration catalyst, in which the denitration device <NUM> is arranged on the downstream side of the exhaust heat recovery device <NUM> in the exhaust channel R2, and the denitration catalyst contains vanadium oxide, the vanadium oxide includes vanadium pentoxide, and has a defect site at which oxygen atoms are deficient in the crystal structure of the vanadium pentoxide.

By using the above-mentioned denitration catalyst, the combustion system 1C according to the above embodiment can exhibit an effect whereby the denitration efficiency at low temperature is even higher compared to the conventional technology, upon selective catalytic reduction reaction with ammonia as the reductant.

Furthermore, immediately before introducing exhaust gas to the denitration device <NUM>, it is not essential to heat the exhaust gas. Since the denitration catalyst is thereby no longer exposed to high temperatures, the deterioration of denitration catalyst is decreased, and the cost of operation of the combustion system 1C becomes lower.

In addition, the combustion system 1C of the above embodiment can be made a more compact configuration by the amount by which heaters for warming the exhaust gas are not essential.

It thereby becomes possible to install the combustion system with a denitration device in a narrow space such as that of a ship.

(<NUM>) As mentioned above, it is preferable for the exhaust heat recovery device <NUM> to include the turbine device <NUM> and exhaust gas economizer <NUM>, in which the exhaust gas economizer <NUM> produces steam with exhaust gas discharged from the internal combustion engine <NUM> and exhaust gas supplied from the turbine device <NUM> as heat sources, and the turbine device <NUM> conducts power generation using the exhaust gas discharged from the internal combustion engine <NUM> and steam supplied from the exhaust gas economizer <NUM>.

Claim 1:
A combustion system (<NUM>, 1A, 1C) comprising:
A combustion device (<NUM>, <NUM>) which combusts a fuel;
an exhaust channel (L1, R2) through which exhaust gas generated by the fuel combusting in the combustion device (<NUM>, <NUM>) flows;
a dust collector (<NUM>, <NUM>) which is disposed in the exhaust channel (L1, R2), and collects ash dust in the exhaust gas; and
a denitration device (<NUM>, <NUM>) which is disposed in the exhaust channel (L1, R2), and removes nitrogen oxides from the exhaust gas by way of a denitration catalyst,
wherein the denitration device (<NUM>, <NUM>) is disposed on a downstream side of the dust collector (<NUM>, <NUM>) in the exhaust channel (L1, R2),
wherein the denitration catalyst contains vanadium oxide, the vanadium oxide including vanadium pentoxide,
characterised in that
the denitration catalyst has a defect site at which oxygen atoms are deficient in the crystal structure of the vanadium pentoxide,
and in that having the defect site at which oxygen atoms are deficient indicates an intensity ratio of peak intensity (P<NUM>-<NUM>) on the (<NUM>) plane of V<NUM>O<NUM>, relative to peak intensity (P<NUM>-<NUM>) on the (<NUM>) plane of V<NUM>O<NUM>, detected by powder X-ray diffraction of the denitration catalyst, being at least <NUM> and no more than <NUM>.