JPH08270930A - Dust removing filter for coal burning and pressurized fluidized bed boiler - Google Patents

Abstract

PURPOSE: To reduce a thermal shock to be given at the time of backwash to a filter used for a coal burning and pressurized fluidized bed boiler in a coal burning and pressurized fluidized bed power generation system by allowing a ceramic porous body to carry a combustion negative catalyst, preferably a combustion negative catalyst composed of TiO2 and/or Nb2 O5 . CONSTITUTION: A ceramic porous body is allowed to carry a combustion negative catalyst, preferably a combustion negative catalyst composed of TiO2 and/or Nb2 O5 . The ceramic porous body may be the one which is selected from cordierite or from a-Al2 O3 and which has fine pores being-of the order of micron or submicron. A dust removing filter is made by such a method that the powder of a raw material for a ceramic filter, with which the combustion negative catalyst of TiO2 and/or Nb2 O5 is mixed, is sintered, or that a sintered ceramic porous body is impregnated with a solvent with the combustion negative catalyst dispersed therein, or such a solvent is applied to a sintered ceramic porous body, so that the combustion negative catalyst can be carried on the dust removing filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressurized fluidized bed boiler for a coal pressurized fluidized bed power generation system, and more particularly to a dedusting filter for a coal pressurized fluidized bed boiler using a ceramic filter as a dust removing means.

[0002]

2. Description of the Related Art For the purpose of energy saving and measures against oil resource depletion, high efficiency utilization of coal has been reviewed and attention has been paid to a coal pressure fluidized bed power generation system having high power generation efficiency.

A coal pressurized fluidized bed power generation system is a system for directly sending high temperature coal combustion gas generated in a pressurized fluidized bed boiler to a gas turbine for power generation, and a high efficiency dedusting technique at high temperature is essential.

The coal combustion gas (referred to as combustion gas) of the pressurized fluidized bed boiler has a high temperature of about 800 ° C. and contains a large amount of dust, which is mainly composed of unburned solid carbon, of several 100 mg / Nm ³ .
When the combustion gas containing a large amount of dust is sent to the gas turbine, the gas turbine parts are eroded violently, and therefore the dust needs to be removed from the combustion gas with high efficiency.

A multi-stage cyclone can be used as the dust removing means, but the dust collecting efficiency is low, and in particular, if the dust collecting efficiency of the cyclone is reduced due to fluctuations in the amount of combustion gas, there is concern that the turbine blades of the gas turbine will be damaged. To be done.

From this point of view, recently, Ceramics B
ulltin, vol. 70, No. 9 (1991) 1491,
Asahi Glass Research Report vol. 42, No. 1 (1992) 81
As can be seen from the above, the use of a ceramic filter has attracted attention as a highly efficient dust removing means in high temperature combustion gas.

This is a filter provided with a porous ceramic such as cordierite, alumina, mullite, or SiC, which has micropores of micron or submicron order. Due to the fine pores of the porous ceramic, high dust collection efficiency is obtained, and the problem of erosion of the gas turbine is solved.

[0008]

However, since the ceramic filter is vulnerable to thermal shock, it has a problem that it is easily damaged. In particular, when unburned solid carbon (called unburned carbon), which tends to be generated at startup or when operating conditions are changed, accumulates on the filter surface, the differential pressure increases, so the accumulated dust is regularly removed from the surface. There is a need.

This is done by blowing air from the opposite direction of the normal gas flow instantly once every few minutes. The unburned carbon content generated from the pressurized fluidized bed boiler is very small during normal load operation, but it is large at the time of start-up of the power generation system or when the load is changed. If backwashing is performed on the filter where dust containing a large amount of unburned carbon is deposited,
The unburned carbon may be abruptly combusted by the backwash air, and the surface temperature of the filter may be rapidly increased from a normal operating temperature of about 800 ° C to about 1200 ° C in a short time. For this reason, the temperature of the filter also rises sharply, and the thermal shock may damage the filter and stop the power generation system. As described above, the reliability of the filter affects the reliability of the entire power generation system, and in particular, the thermal shock during backwashing is one of the factors that reduce the reliability of the coal pressurized fluidized bed power generation system.

An object of the present invention is to reduce the thermal shock at the time of backwashing a filter used in a coal pressure fluidized bed boiler of a coal pressure fluidized bed power generation system to prevent the filter from being damaged, and It is to provide a dust filter that can improve the reliability of a floor power generation system.

[0011]

The present inventor has conducted various studies on a method of suppressing combustion of accumulated unburned carbon in order to alleviate thermal shock applied to a filter during backwashing, and arrived at the present invention. The gist of the present invention for solving the above problems is as follows.

[1] A dust removal filter for a coal pressurized fluidized bed boiler, characterized in that a combustion negative catalyst is supported on a porous ceramic body.

[2] TiO ₂ is added to the ceramic porous body.
And / or a combustion negative catalyst composed of Nb ₂ O ₅ is carried, and a dust filter for a coal pressurized fluidized bed boiler.

[3] A dedusting filter for a coal pressurized fluidized bed boiler, characterized in that a negative combustion catalyst is supported on the surface layer of a porous ceramic body.

[4] A dedusting filter for a coal pressurized fluidized bed boiler, wherein a combustion negative catalyst made of TiO ₂ and / or Nb ₂ O ₅ is carried on the surface layer of the ceramic porous body.

[5] For the coal pressurized fluidized bed boiler, wherein the ceramic porous body is cordierite or a porous ceramic having fine pores of micron to submicron order selected from α-Al ₂ O ₃ . Dust filter.

The dust filter according to the present invention comprises TiO ₂ ,
The Nb ₂ O ₅ combustion negative catalyst is mixed with the raw material powder of the ceramic filter and sintered, or the sintered ceramic porous body is impregnated or coated with a solvent in which the combustion negative catalyst is dispersed. It can be supported.

The above-mentioned combustion negative catalyst should be supported on the ceramic porous body in an amount of 1% by weight or more, preferably 1 to 20% by weight.

Further, it is preferable that the ceramic porous body is composed of continuous ventilation holes and has a porosity of 10 to 40% (volume ratio).

[0020]

Operation: Generally, the thermal shock that a high temperature member receives during use is
The growth of minute defects such as cracks and pores inherent in the member leads to a decrease in strength, and the member is destroyed. In order to prevent such a destruction phenomenon, the thermal shock received by the member may be reduced.

As described above, the thermal shock of the porous filter used in the pressurized fluidized bed boiler is particularly large during backwashing. This is because the unburned carbon deposited on the filter surface is rapidly burned by the air for backwashing and the temperature rises. Therefore,
If the combustion of unburned carbon on the filter can be suppressed, abrupt heat generation can be suppressed and the thermal shock received by the filter can be mitigated.

By supporting TiO ₂ or Nb ₂ O ₅ having a negative catalytic effect on the porous filter, it is possible to suppress the rapid combustion of unburned carbon deposited on the filter during backwashing with air, and A sudden temperature rise can be prevented.

[0023]

The present invention will be described in more detail by way of examples.

[Example 1] Graphite as carbon,
As a ceramic filter, α-Al ₂ O ₃ (average particle size:
6 μm), BaO as a carbon burning negative catalyst (average particle size of 0.1).
3 μm), MgO (average particle size 0.7 μm), Nb ₂ O
₅ (average particle size 0.6 μm), SiO ₂ (average particle size 0.4 μm
m) and TiO ₂ (average particle size 0.6 μm) were selected and their carbon combustion catalytic activities were investigated.

Α-Al ₂ for 60 parts by weight of graphite
For each 30 parts by weight of O ₃ , one carbon combustion negative catalyst was used.
The powder in which 0 part by weight was mixed was subjected to thermal analysis using a thermogravimetric balance (TG), and the starting point of weight reduction was defined as the combustion starting temperature.

The activity of the carbon burning negative catalyst (negative catalyst) is
The combustion start temperature of the mixed powder of (graphite) + (α-Al ₂ O ₃ ) and (negative catalyst) + (graphite) + (α-A
(1 ₂ O ₃ ) It is shown by the difference from the combustion start temperature of the mixed powder. The smaller the temperature difference, the greater the negative catalyst activity.

First, when the combustion starting temperature of only graphite was measured, the temperature was 630 ° C. On the other hand, the combustion starting temperature of the mixed powder of graphite and α-Al ₂ O ₃ was 573 ° C. The negative catalytic activity of α-Al ₂ O ₃ was 57 ° C. as compared with the combustion starting temperature of graphite alone.

Α-Al ₂ O ₃ promotes the combustion of carbon,
That is, it has a carbon combustion catalytic effect, and may promote the combustion of unburned carbon that has accumulated during backwashing and increase the thermal shock applied to the filter.

Next, BaO, MgO, Nb ₂ O ₅ , SiO
₂ and TiO ₂ are graphite and α-Al ₂ O _{3 respectively.}
And the negative catalytic activity thereof was measured.

The results are shown in Table 1, which all have a negative catalytic action. However, the negative catalytic activity of BaO, MgO and SiO ₂ is low, and that of TiO ₂ and Nb ₂ O ₅ is high. Therefore, TiO ₂ and Nb ₂ O are used as the negative catalyst.
It turns out that ₅ is preferred.

[0031]

[Table 1]

Next, TiO ₂ exhibiting a negative catalytic effect was loaded on a ceramic filter, and the effect of suppressing deterioration of mechanical properties of the filter due to thermal shock during backwashing was confirmed.

Α-Al ₂ O ₃ powder 8 having an average particle size of 0.6 μm
300 parts by weight of ethyl alcohol and 3 parts by weight of polyvinyl butyral as a binder were added to a mixed powder of 0 parts by weight and 20 parts by weight of TiO ₂ powder having an average particle size of 0.7 μm,
Mix for 24 hours on a ball mill.

The obtained slurry was spray granulated with a spray dryer to obtain granulated powder. This granulated powder is molded with a mold,
It was calcined at 0 ° C. for 2 hours and then sintered at 1250 ° C. for 30 minutes to obtain a porous ceramics sintered body having a porosity of 25%. The surface of the obtained ceramic filter is SEM / ED
Observations and analyzes were performed at X. TiO ₂ was uniformly dispersed on the surface. This confirmed that the TiO ₂ negative catalyst was supported on the surface of the porous ceramic filter.

The TiO ₂ -supported ceramics filter thus obtained was incorporated in a small-sized simulation test apparatus, and a dust removal experiment was conducted while measuring the surface temperature.

The surface temperature during normal operation was 796 ° C. on average, but the surface temperature rose to a maximum of 996 ° C. during backwashing.
After repeating the cycle of normal operation ⇔ backwash 100 times, a part of the TiO ₂ -supported ceramic filter tested was cut out and the strength test results are shown in FIG. 1. The 4-point bending strength decreased from 83 MPa in the initial stage to 75 MPa,
A strength decrease of about 10% was observed.

The ceramic filter was not damaged until 1000 cycles, and the 4-point bending strength was 72 MPa.
Met.

[0038] As a comparative example, a catalyst with a porosity of 25% α-Al ₂ O ₃ porous ceramic that has not been supported was subjected to the same dust removal experiment above. The surface temperature of the filter during normal operation was 803 ° C. on average, but the surface temperature rose to a maximum of 1220 ° C. during backwashing. Normal operation ⇔ backwash 1
After 00 cycles, a part of the test ceramic filter was cut out and the strength was evaluated.

The four-point bending strength is 7 MPa from the initial 85 MPa.
The strength decreased to 1 MPa, and a strength decrease of about 17% was observed. After 1000 cycles, the 4-point bending strength is 54MP.
to 36%, and a strength reduction of about 36% was observed.

Example 2 300 parts by weight of ethyl alcohol and 3 parts by weight of polyvinyl butyral as a binder were mixed with 100 parts by weight of crystallized cordierite powder having an average particle size of 1 μm in a ball mill for 24 hours. The obtained slurry was spray granulated with a spray dryer to obtain granulated powder. This granulated powder is molded in a mold, calcined at 800 ° C. for 2 hours, and then sintered at 1300 ° C. for 30 minutes to give a porosity of 1
A 5% porous ceramics sintered body was obtained.

This cordierite sintered body was formed into Ti (OC)
A 5% by weight solution of H (CH ₃ ) ₂ ) ₄ in ethyl alcohol was impregnated and heated until the ethyl alcohol solution had evaporated. Then, it was fired at 1000 ° C. for 1 hour to obtain a TiO ₂ -supported ceramic filter.

The surface of the obtained TiO ₂ -supported ceramic filter was observed and analyzed by SEM / EDX. It was confirmed to be a porous cordierite filter in which TiO ₂ was uniformly dispersed on the surface. This TiO ₂ -supported cordierite filter was incorporated into a small-sized simulated test device, and a dust removal experiment was conducted while measuring the surface temperature.

The surface temperature during normal operation was 805 ° C. on average, but the surface temperature rose to a maximum of 984 ° C. during backwashing.
After 100 cycles of normal operation and backwashing, a part of the TiO ₂ -supported ceramic filter was cut out and the strength was evaluated. Four
The point bending strength decreased from 90 MPa in the initial stage to 83 MPa, and a strength decrease of about 10% was observed. The ceramic filter was not damaged even after 1000 cycles, and the 4-point bending strength was 81 MPa.

As a comparative example, the same dedusting experiment as described above was carried out using a cordierite porous ceramic filter having a porosity of 15% which does not support a catalyst. The surface temperature of the filter during normal operation was 807 ° C. on average, but the surface temperature rose to a maximum of 1215 ° C. during backwashing. Normal operation ⇔
After 10 cycles of backwashing, a part of the sample cordierite filter was cut out and the strength was evaluated.

The four-point bending strength is from the initial 90 MPa to 7
The strength decreased to 5 MPa, and a strength decrease of about 17% was observed. After 1000 cycles, the 4-point bending strength is 58MP.
to 36%, and a strength reduction of about 36% was observed.

Example 3 α-Al having an average particle size of 1 μm
Ethyl alcohol 300 per 100 parts by weight of ₂ O ₃ powder
Part by weight and polyvinyl butyral as a binder were mixed by weight for 24 hours using a ball mill to prepare a slurry. This was spray-granulated with a spray dryer to obtain granulated powder. This granulated powder was molded into a mold, calcined at 800 ° C. for 2 hours, and then sintered at 1300 ° C. for 30 minutes to obtain a porous ceramics sintered body having a porosity of about 20%.

[0047] Nb (OC ₃ in the α-Al ₂ O ₃ porous surface
A 5% by weight solution of H ₅ ) ₅ in ethylethyl alcohol was sprayed at 10 ml per 1 cm ² of surface area, and dried in a dryer at 200 ° C. for 5 hours. Then baked 1 hour at 1000 ° C., to obtain a Nb ₂ 0 ₅ supported ceramic filter.

[0048] The resulting Nb ₂ 0 ₅ surface bearing ceramic filter was observed and analyzed by SEM / EDX. Nb ₂ O ₅ -supporting α-Al ₂ with Nb ₂ O ₅ uniformly dispersed on the surface
It was confirmed to be an O ₃ ceramic filter. This N
A b ₂ O ₅ -supporting α-Al ₂ O ₃ ceramic filter was incorporated into a small-sized simulation test apparatus, and a dust removal experiment was conducted while measuring the surface temperature.

The surface temperature during normal operation was 805 ° C. on average, but the surface temperature rose to a maximum of 984 ° C. during backwashing.
After 100 cycles of normal operation and backwash, a part of the Nb ₂ O ₅ -supported ceramic filter was cut out and the strength was evaluated. Four
The point bending strength decreased from 90 MPa in the initial stage to 83 MPa, and a strength decrease of about 10% was observed. The ceramic filter was not damaged even after 1000 cycles, and the 4-point bending strength was 81 MPa.

As a comparative example, a dusting test similar to the above was carried out using an α-Al ₂ O ₃ porous ceramic filter having no porosity of 20% and supporting no catalyst. The 4-point bending strength after 100 cycles was 71 MPa, and after 1000 cycles it was reduced to 60 MPa.

[0051]

INDUSTRIAL APPLICABILITY The present invention makes a ceramic filter used as a dust removing means for coal combustion gas of a pressurized fluidized bed boiler of a coal pressurized fluidized bed power generation system carry a combustion negative catalyst, thereby providing a filter on the filter. Thermal shock due to rapid combustion during backwashing of dust containing unburned solid carbon that accumulates is mitigated,
The reliability of the filter could be improved. This effect can improve the reliability of the coal pressurized fluidized bed power generation system.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the number of thermal shock cycles by backwashing and the four-point bending strength of a filter.

Claims (6)

[Claims] 1. A dedusting filter for a coal pressurized fluidized bed boiler, which comprises a porous ceramics carrying a combustion negative catalyst. 2. A dedusting filter for a coal pressure fluidized bed boiler, comprising a porous ceramics carrying a combustion negative catalyst composed of TiO ₂ and / or Nb ₂ O ₅ . 3. A dedusting filter for a coal pressurized fluidized bed boiler, wherein a combustion negative catalyst is supported on a surface layer of a ceramic porous body. 4. The surface layer of the porous ceramic body is made of TiO.
_A dedusting filter for a coal pressurized fluidized bed boiler, which carries a combustion negative catalyst composed of ₂ and / or Nb ₂ O ₅ . 5. The porous ceramic body according to claim 1, which is a cordierite or a porous ceramic having fine pores of micron to submicron order selected from α-Al ₂ O _3. Dust filter for coal pressurized fluidized bed boiler. 6. The porosity of the ceramic porous body is 10.
4. A porous ceramic of -40% (volume ratio).
The dust removal filter for coal pressurization fluidized bed boilers in any one of Claims 1-4.