JP4919844B2 - Fuel adjustment device and fuel adjustment method - Google Patents

Description

  The present invention relates to a fuel adjustment device and a fuel adjustment method for a boiler for thermal power generation, and more particularly, to mix and burn biomass fuel in coal which is fuel for a boiler for thermal power generation. The present invention relates to a fuel adjustment device and a fuel adjustment method suitable for obtaining a product.

  In recent years, the emission of carbon dioxide (hereinafter referred to as CO2), a causative agent of global warming, has become a problem, and in particular, in order to reduce the increase in CO2 concentration due to fossil fuel consumption, the movement to effectively use biomass as renewable energy Has become active. Biomass generally means a resource substance derived from living organisms, and is a substance that does not increase CO2 in the atmosphere in the carbon cycle by photosynthesis (CO2 neutral). That is, even if CO2 is generated, biomass absorbs CO2 in the atmosphere and does not lead to an increase in CO2 concentration in the atmosphere, so it is said that it is effective for measures to prevent global warming. ing.

In addition to biomass, solar power, wind power, geothermal power, small-scale hydropower, etc. are attracting attention as energy sources, but in order to stabilize the supply of these energies, preparation periods such as facility maintenance are necessary. There are also problems such as high costs.
Therefore, biomass can be said to be the most practical of the above energy sources, and is expected as a renewable energy that can reduce CO2 emissions.

  In recent years, in order to reduce the amount of CO2 emitted into the atmosphere, for example, in a conventional coal fired boiler for thermal power generation, plant-derived biomass, such as woody biomass fuel, is mixed with fuel coal. Burning is done. Among biomass fuels, woody biomass, in particular, has a more stable supply than other biomass, and its price is stable. For example, when wood-based biomass is combusted in a power generation boiler, for example, wood-based biomass requires a larger pulverization power compared to coal pulverization, and the introduction of dedicated pulverization equipment for wood-based biomass. The cost is high.

  That is, it is difficult to stably supply woody biomass and it is difficult to obtain a large amount of woody biomass. Therefore, from the viewpoint of economy, it is desirable to combust these coal and biomass fuel with as little as possible operating cost as much as possible by using existing equipment as effectively as possible without providing new equipment.

  On the other hand, from the aspect of equipment operation and the effect of reducing CO2 emissions, various woody biomass fuels (hereinafter also simply referred to as biomass) must be burned at various mixing ratios (preferably high mixing ratios). It has been. From the viewpoint of economy and operability as a whole boiler, there are cases where conventional pulverized coal and pulverized biomass are air-conveyed as a mixed fuel and burned in the same combustion apparatus. Here, coal and biomass have different flammability such as pulverization and burning rate, so in order to burn various biomass at various mixing ratios, pulverization / classification using coal and biomass, respectively, using separate pulverizers. It is also conceivable to obtain a fuel having an optimum particle size distribution according to the mixing ratio.

  Patent Document 3 describes a configuration in which the particle size distribution of a fine sample is measured and the adjustment of the rotation speed of the classification blade is automated to perform the optimum particle size management for the product. Further, Patent Document 2 describes a configuration including a particle size distribution measuring device capable of continuously measuring the particle size distribution of pulverized coal. As in the configurations described in these documents, it is possible to measure the particle size distribution of coal and biomass separately to adjust the rotation speed of the classification blade, or to measure the particle size distribution continuously.

However, one coal pulverizer conventionally used is required for every 6 to 10 combustion devices. For example, in a 1000 MW class boiler, about 6 combustion devices are usually installed. If a pulverizer, classifier, particle size distribution measuring device, etc. for biomass are installed, the equipment cost will increase significantly.
Therefore, Patent Document 1 below proposes a configuration in which biomass is pulverized and classified by the same pulverizer as coal and supplied to the combustion apparatus.

JP 2005-42970 A JP 2005-241480 A JP 62-132559 A

  According to Patent Document 1, in a boiler using coal or the like as a main fuel, carbonized fuel such as biomass is co-fired as a secondary fuel to reduce the emission amount of nitrogen oxides (NOx). And the reduction effect of NOx discharge | emission amount at the time of co-firing carbonized fuel as a secondary fuel to main fuels, such as coal, is confirmed.

  However, when biomass is introduced into an existing coal crusher, the pulverization power tends to increase. When the biomass mixing ratio is increased, the power margin of the pulverizer such as a mill exceeds the allowable range of the crusher. End up. If the pulverization power is simply reduced in this case, the particle size of the entire fuel becomes coarse, so that the fuel is not efficiently used for combustion, and there is a concern that the amount of NOx and unburned emissions increases. Therefore, there is a problem that the biomass mixing rate (mixed firing rate) cannot be increased when combustion is performed mainly with coal and mixed with woody biomass fuel.

  As in the configuration described in Patent Document 3, in the case of a single sample, it is possible to continuously measure the particle size using a particle size distribution measuring device described in Patent Document 2 and adjust the particle size to an optimum particle size. It is. However, in the case of a mixture sample, substances with different properties are mixed, so the entire particle size of the mixture sample is simply considered in the same way as in the case of a single sample, and the particle size of the mixture is measured to determine the optimum particle size for the entire sample. It is difficult to do. And the focus of mixed grinding is concentrated only on the maximum mixed firing rate of biomass, and it cannot be said that proper mixed grinding is being used.

  An object of the present invention is to increase the cost of biomass fuel without significantly increasing the cost of equipment such as a fuel pulverizer, without increasing the pulverization power, and maintaining a certain level of NOx and unburned emissions. To provide a fuel adjustment device and a fuel adjustment method capable of increasing the mixing rate (mixed combustion rate).

The above problems can be achieved by employing the following configuration.
The invention according to claim 1 is a pulverizer for pulverizing a mixture of woody biomass fuel and coal, a rotary classifier having a rotation mechanism for classifying the pulverized material pulverized by the pulverizer, and the rotary classifier A fuel adjustment device comprising a supply device for supplying the pulverized material classified by the above to a combustion device including a boiler, a sampling device for taking out a part of the pulverized material classified by the rotary classifier, and the sampling device A fuel comprising: a particle size analyzer that analyzes the particle size of coal among the pulverized matter taken out by the method; and a control device that controls the rotational speed of the rotary classifier based on the particle size of the coal analyzed by the particle size analyzer It is an adjustment device.

  According to a second aspect of the present invention, the particle size analyzer includes a centrifuge for separating the woody biomass fuel and coal in heavy liquid from the pulverized matter taken out by the sampling device and separating the gravity, and the centrifuge. A particle size measuring device that measures the particle size of coal separated by specific gravity by a separating device, and the control device rotates the rotating classifier so that the coal particle size measured by the particle size measuring device falls within a predetermined range. The fuel adjustment device according to claim 1, wherein the fuel adjustment device has a configuration for controlling the number.

  The invention according to claim 3 is a fuel adjustment method in which a mixture of woody biomass fuel and coal is pulverized, and the obtained pulverized material is classified by a classifying means having a rotation mechanism and then supplied to a combustion apparatus including a boiler. Then, the particle size of the coal in the pulverized product after classification is analyzed by the classification means, and the fuel adjustment method controls the rotational speed of the classification means based on the analyzed coal particle size.

  The invention according to claim 4 is a method in which a part of the pulverized product after the classification is dispersed in heavy liquid, and the woody biomass fuel and coal are separated by specific gravity by centrifugation, and then the particle size of the coal is measured. The fuel adjustment method according to claim 3, wherein the rotational speed of the classification means is controlled so that the measured coal particle size falls within a predetermined range.

(Function)
The present invention is that the biomass can be regarded as clean energy and the combustion of biomass fuel does not generate harmful substances such as NOx, but the amount of NOx emission can be reduced to make existing combustion exhaust gas cleaner. It is the feature. And the focus of current mixing and grinding is concentrated only on the maximum mixed combustion rate of biomass, and the idea of controlling milling devices such as mills is not followed, and proper mixing and grinding is being used. Although it cannot be said, according to the present invention, it is possible to perform an optimum operation related to mixed pulverization of biomass and pulverized coal.

  In order to simultaneously burn wood biomass fuel with coal in a combustion furnace, if both are pulverized and classified by the same pulverizer and supplied to the combustion device, the respective NOx, unburned content is reduced, that is, NOx, unburned Therefore, it is difficult to grind so that both proper particle size ranges can be accommodated simultaneously.

  In addition, as described above with respect to the problems of the prior art, there has been a problem that the biomass mixing rate (mixed firing rate) cannot be increased when combustion is performed by mixing woody biomass fuel with coal as the main fuel. And, when trying to pulverize the woody biomass fuel to the required particle size that can satisfy the generation of NOx and unburnt, the woody biomass fuel tends to be excessively pulverized, and the pulverization power becomes enormous. End up.

When pulverizing biomass and pulverized coal at the same time, the particle size of biomass and the particle size of pulverized coal change depending on the mixing ratio.
For example, when the mixing ratio of biomass is high, the particle size of biomass and pulverized coal when pulverized at the same time are larger than those when simultaneously pulverizing with the same power and lowering the mixing ratio of biomass.

  Moreover, the characteristics differ also with the kind of biomass. It is known that the particle size distribution of biomass differs depending on the part even in the same woody biomass. For example, herbs (skin parts) have similar grindability to coal and are relatively easy to grind. Even with a small amount of biomass, for example, the pulverization power of a pulverizer such as a mill becomes large, and the pulverization power when mixing and pulverizing about 5% biomass based on the calorific value of biomass with respect to pulverized coal is only pulverized coal. Is increased by 20% or more compared with the case of adjusting the particle size to the same particle size.

By the way, as a general example, FIG. 4 shows an example in which the pulverized coal and biomass are compared with the pulverized coal and the biomass having a substantially equivalent burning rate for pulverized coal and biomass that are crushed exclusively.
In FIG. 4, pulverized coal is pulverized with pulverized coal alone and shows a particle size distribution when the cumulative passing weight after passing through a 200-mesh sieve is 80%. The particle size distribution when the particle size is adjusted so that the particle size distribution with an accumulated passing weight of 100%) is a particle size distribution of 2 mm or less is shown.

  Here, the pulverized coal and biomass when pulverizing pulverized coal are not one kind, and FIG. 4 passed through a sieve having a certain opening (corresponding to the particle size of the sample) with respect to the sample pulverized under a certain condition. The accumulated passing weight of the sample is measured, and the particle size distribution of the sample is displayed. 200 mesh represents the number of wires per inch, and the specific mesh is 75 μm. That is, 200 mesh corresponds to a mesh of 75 μm × 75 μm. The pulverized coal and biomass having the particle size distribution shown in FIG. 4 have the same burning rate when individually burned.

  And, as shown in FIG. 4, pulverized coal and biomass with the same burning rate have a considerable difference in particle size, and if the particle size is the same, biomass has a lighter cumulative weight than coal, It turns out that it is easy to burn even with a small amount. That is, it can be seen that the burning rate of biomass is greater than that of ordinary pulverized coal.

FIG. 5 shows an example of the particle size distribution in the case where the same coal and woody biomass as in FIG. 4 are mixed and pulverized with 5 cal% of biomass in the coal based on the calorific value of the biomass.
In FIG. 5, 5 cal% (mixing ratio based on calorific value) of biomass is mixed with coal and pulverized, and the total particle size is adjusted so that the cumulative passing weight with a particle size of 75 μm or less (200 mesh pass) is 65 wt%. The particle size of the mixture at that time, the particle size of the pulverized coal alone in the mixture, and the particle size of the biomass alone in the mixture (the relationship between the particle size and the cumulative passing weight wt%) are compared.

  Here, the reason why the particle size of the mixture is adjusted so that the cumulative passing weight with a particle size of 75 μm or less is 65 wt% is conventionally required to burn only this coal without any problems in terms of NOx and unburned content. In contrast to the target particle size of 70 μm and the accumulated particle weight of 75 μm or less, the mixture is a little rough as a mixture, considering the significant increase in power by biomass mixing and NOx reduction effect by biomass co-firing. The weight was set to 65 wt%.

Note that the target particle size necessary for combustion without problems in terms of NOx and unburned content, and the value of the cumulative passing weight with a particle size of 75 μm or less vary depending on the coal type.
In the case of coal that is easy to burn, a particle size of about 65 wt% cumulative passage weight with a particle size of 75 μm or less may be used, but in the case of coal that is difficult to burn, a particle size of about 85 wt% cumulative passage weight with a particle size of 75 μm or less is required.

  Here, regarding the method of obtaining the particle size (individual curves in FIG. 5) of coal alone and biomass alone from the mixture of coal and biomass, the ash content is based on the ash contained in the coal and biomass, regardless of the particle size. Assuming that the content of ss does not change, each fraction was calculated arithmetically.

As shown in FIG. 5, the mixture has a cumulative weight of 65 wt% with a particle size of 75 μm or less.
On the other hand, it can be seen that the cumulative passing weight of the pulverized coal constituting the mixture with a particle size of 75 μm or less is as small as 80 wt%, and the biomass is as large as 20 wt%. Moreover, although the particle size of biomass is coarse compared with the particle size of pulverized coal, the top size is not so different compared with the top size of coal.

  As mentioned above, as the cumulative passing weight of the mixture for the target particle size and cumulative passing weight 70 wt% with particle size of 75 μm or less, which was necessary for burning NOx and unburned matter without problems in the combustion of only coal, Was pulverized to 65 wt%, but the pulverized coal composing the mixture had a cumulative passing weight with a particle size of 75 μm or less of 80 wt%.

  On the other hand, although it depends on the type of biomass, generally the particle size required for the biomass to burn without problems in terms of NOx and unburned content is about 2 mm or less. Therefore, according to FIG. 5, the particle size at which the cumulative passing weight of biomass alone becomes 100%, that is, the top size is about 200 μm, so it is extremely small compared to 2 mm, and the pulverization power may be greatly reduced. I understand.

  Considering the NOx and unburned matter generated during the combustion of the above mixture, the particles may be atomized in order to combust the fuel without any problem. However, in order to atomize, the pulverization power becomes enormous. And it can be seen that pulverized coal becomes finer as described above compared to the case where the particle size of the mixture is based. Will lead to an increase in power. That is, according to the example of FIG. 5, it means that the grinding power of the mill is excessively applied, and it cannot be said that the grinding is proper.

  As described above, when biomass is introduced into an existing coal pulverizer, the pulverization power tends to increase. When the mixing ratio of biomass is increased, the power margin of the mill is exceeded. Therefore, the existing coal crusher has a problem that the mixing ratio of biomass cannot be increased.

  However, as described above, it has been found that the influence of coal particle size is dominant in the conditions for burning the mixed fuel without problems in terms of NOx and unburned content. Therefore, according to the present invention, by controlling the power of the mill, that is, the rotational speed of the classifier so that the coal in the mixed fuel has an appropriate particle size, the power of the biomass can be exceeded without exceeding the margin of power of the mill. The mixed fuel can be pulverized. The real value of the number of revolutions of the classifier shifts according to the scale of the classifier. Since the real value is adjusted by the balance between the centrifugal force and the centripetal force applied to the rotating particles by the rotary classifier, the absolute value of the rotational speed is reduced in an apparatus having a large scale. Therefore, for example, specifically, in order to control the coal particle size in the mixture to a rotational speed that can be adjusted so that the 200 mesh cumulative passing weight is 65 wt%, the rotational classification is compared with the 200 mesh cumulative passing weight of 70 wt%. It is recommended to reduce the number of machine rotations according to the scale of implementation.

Therefore, it becomes possible to increase the mixing ratio of biomass. However, since the mixing ratio of biomass is at most about 5% and the ratio of pulverized coal is as high as 95%, appropriate fuel adjustment can be made by measuring only the particle size of pulverized coal.
When the grindability of biomass and the biomass crushing rate change, the particle sizes of each change also subordinately. Therefore, it is not possible to adjust to an appropriate particle size just by knowing the particle size of the mixture.

  However, if the particle size is equal to or less than the same particle size (same as the particle size), the biomass has a lighter cumulative weight than coal, so it is easy to burn even in small amounts, that is, the burning rate of biomass is higher than that of ordinary pulverized coal. You can see that it ’s big. Moreover, if the particle size of the biomass is rough enough not to exceed 2 mm, the top size is not much different from the top size of coal, so the pulverization power may be greatly reduced. I understand.

  That is, since it was found that the condition for burning the mixed fuel without problems in terms of NOx and unburned content is more influenced by the coal particle size than the biomass particle size, according to the present invention, By controlling the power of the pulverizer, that is, the rotational speed of the classifier so that the coal has an appropriate particle size, the mixed fuel of biomass can be pulverized without exceeding the power margin of the pulverizer. And, as shown in the example of FIG. 5, the top size of the biomass alone is a value that is one or more orders of magnitude smaller than the top size of the biomass necessary to burn without problems in terms of NOx and unburned content. According to the above, it is possible to use biomass having a particle size necessary for burning without any problem in terms of the NOx and unburned content. Therefore, it becomes possible to increase the mixing ratio of biomass.

  In the present invention, the mixture after pulverization is sampled from the outlet portion of the pulverizer, and the particles of the pulverized product taken out are separated into biomass and pulverized coal particles. Among these, the particle size of the pulverized coal particles is analyzed, and the rotational speed of the rotary classifier is adjusted so as to obtain the target particle size. The rotational speed of the rotary classifier is controlled based on the particle size obtained by pulverizing only ordinary coal.

  This makes it possible to obtain an appropriate pulverized coal particle size, so that it can be burned with appropriate pulverization power without excessively pulverizing fine pulverized coal, or on the contrary, generating coarse particles that are not sufficiently pulverized. It is possible to produce pulverized coal with the required appropriate particle size.

  According to invention of Claim 1 and 3, it measures the particle size of the pulverized coal particle which is dominant as a condition which burns without problems in terms of NOx and unburned content in the mixture after pulverization of coal and biomass. Therefore, proper operation of mixing and pulverizing coal and biomass is easily performed.

  According to the second and fourth aspects of the invention, in addition to the above-described action of the first and third aspects of the invention, the sampled biomass and coal pulverized material are dispersed in heavy liquid, and the difference in specific gravity between the two is utilized. Then, by separating the specific gravity by centrifugation, the mixed pulverized product can be easily separated into coal and biomass, and the particle size of only coal can be accurately measured. And based on the said measurement result, the rotation speed of a classifier can be controlled so that the particle size of coal may be settled in a predetermined range.

  According to the present invention, in the case of coal combustion, only a biomass mixing facility for mixing with coal is required, and no major facility modification is required. And since the boiler main body and the modification of a combustion apparatus are unnecessary, a low-cost and effective biomass combustion system can be constructed | assembled. In addition, the mixing rate of the biomass (mixed-combustion rate) is maintained while maintaining a constant level of NOx and unburned emissions without significantly increasing the cost of equipment such as a fuel pulverizer and without significantly increasing the pulverization power. ) Can be increased.

  According to the first and third aspects of the invention, since proper mixing and pulverization of coal and biomass is performed, an increase in equipment costs such as a fuel pulverizing apparatus is prevented, and the pulverization power is suppressed to reduce NOx and unburned fuel. Fuel adjustment that can increase the mixing rate (mixed firing rate) of biomass fuel while maintaining the discharge of water at a certain level becomes possible.

  According to the inventions of claims 2 and 4, in addition to the above effects of the inventions of claims 1 and 3, the particle size of only coal in the mixed fuel can be accurately measured easily and easily. Can be precisely controlled so that is within a predetermined range.

FIG. 1 shows a system configuration diagram of a system of a fuel adjustment device according to an embodiment of the present invention.
As shown in FIG. 1, a plurality of (six in the figure) main burners 4 for combusting pulverized coal are disposed on a water cooling wall of a boiler body 1 of a pulverized coal burning boiler, and are provided so as to surround the main burner 4. Combustion air is supplied from the wind box 3. Further, an OFA (Over Firing Airport) 2 is provided above the main burner 4. The main burner 4 is a conventional pulverized coal burner.

Coal, which is the main fuel, is transported in large quantities in a short time from the coal storage facility 10 and is temporarily stored in the coal bunker 9. Although there is no limitation here as a transportation method, specifically, a relatively inexpensive and highly reliable belt conveyor system is usually used.
The biomass 32 (FIG. 6) is roughly crushed to a size that can be conveyed by a belt conveyor, for example, about 50 mm or less, and then supplied from the biomass bunker 7 to the conveyor by a fixed amount by a fixed amount supply device 8. And supplied to the bunker 9.
Here, “mixing” means to the extent that it merges with the coal conveyance line. When the situation of the coal and biomass 32 on the belt conveyor is locally observed, the biomass 32 is only a small amount on top of the coal bed.

  The mixed fuel of coal and biomass 32 is temporarily stored in the bunker 9, then is cut out by a fixed amount supply device 8 provided at the bottom of the bunker 9, and supplied to a plurality of corresponding mills 6. The fixed amount supply device 8 may be, for example, a general fixed amount coal supply device of a pulverized coal fired boiler that adjusts the supply amount by rotating the feeder 33 (FIG. 6). Each mill 6 is a pulverizer that finely pulverizes the mixed fuel, and a rotary classifier 11 that rotates when the motor 16 is driven is installed in the upper part of the mill 6 (FIG. 2). The mixed fuel finely pulverized by each mill 6 is air-transported upward in the mill 6, classified by a rotary classifier 11 provided on the upper part of the mill 6, and then, respectively, via a pipe 30 for air-current transport. It is supplied to the main burner 4 of the corresponding boiler body 1. And it burns stably at the same time it is blown into the boiler body 1 by the main burner 4.

Normally, as shown in FIG. 1, the bunker 9 and the mill 6 are combined in a one-to-one relationship, and the remaining amount of fuel in the bunker 9 depends on the operation of the boiler, that is, the on / off state of each burner 4 according to the combustion load. Different for each bunker 9.
On the other hand, since coal and biomass 32 have different specific gravities, one may segregate during temporary storage. Therefore, even if coal 32 and biomass 32 are mixed on the conveyor, even if biomass 32 is supplied at a constant mixing ratio, the mixing ratio of the mixed fuel cut out from the bunker 9 to the mill 6 is different for each mill 6. This point is also significant in the present invention. That is, according to the present invention, since the rotation speed of the rotary classifier 11 can be controlled for each mill 6, even if the mixing ratio of coal and biomass 32 is different for each mill 6, an appropriate fuel is provided for each mill 6. Adjustment control is possible.

  And in the exit part of the mill 6, a part of the mixed pulverized product of coal and biomass 32 is sampled and used as a sample, and the particle size of the sample is measured by the particle size measurement control system 5. Direct measurement of coal particle size. And the particle size of coal required when co-firing coal and biomass 32 from the measured coal particle size is estimated.

  And the rotation speed of the rotary classifier 11 which controls a particle size with respect to the variable which concerns on a particle size adjustment among the particle size adjustment apparatuses of the mill 6 is controlled. That is, when the rotational speed of the rotary classifier 11 is increased, the particle size becomes finer and the proportion of fine particles increases, and when the rotational speed of the rotary classifier 11 is decreased, the particle size becomes coarse and the proportion of coarse particles increases.

In FIG. 2, the block diagram of the particle size measurement control system 5 of FIG. 1 is shown. Furthermore, FIG. 3 shows a configuration diagram of a two-component automatic particle size measuring apparatus 13 of pulverized coal and biomass 32 as a center in the particle size measurement control system 5.
As shown in FIG. 2, the particle size measurement control system 5 includes an automatic particle sampling device (autosampler) 12, an individual particle size measurement device 13 for fine coal and biomass 32, and a mill rotary classifier control device 14. Then, the particle size distribution of each of the pulverized coal and biomass 32 of the sample taken out by the automatic particle sampling device 12 is measured by the individual particle size measuring device 13, and the rotation speed of the rotary classifier 11 in the mill 6 is determined based on the measurement result. Control is performed by the mill rotary classifier controller 14.

  As shown in FIG. 1, the biomass 32 and the coal cut out by the quantitative supply device 8 provided at the bottom of the bunker 9 are mixed at a predetermined ratio, and then charged into the mill 6 and pulverized. Since the material to be crushed is conveyed to the main burner 4 by air, as shown in FIG. 2, in the pipe 30 for air current conveyance, the mixed particles of coal and biomass 32 are mixed at regular intervals from the middle (for example, (1 hour interval) A small amount is taken out by the automatic particle sampling device 12. Then, the particle size of coal among the mixed particles is measured by the individual particle size measuring device 13 for the extracted mixed particles. Then, based on the measured particle size of the coal alone, an appropriate rotational speed of the classifier 11 is predicted, and the motor 16 is controlled by the mill rotational classifier controller 14 so as to be the predicted rotational speed.

  In FIG. 2, the automatic particle sampling device 12 is used for sampling when the mixed particles of coal and biomass 32 are taken out from the pipe 30 for airflow conveyance. Since the automatic particle sampling apparatus 12 is a commonly used apparatus, details thereof are not particularly shown in FIG.

FIG. 3 shows a process when a mixture of coal particles and biomass particles is obtained, and will be described below.
The mixed particles of coal and biomass 32 taken out by the automatic particle sampling device 12 are put in a plurality of ampoules 18 whose lower portions can be easily cut, dispersed in heavy liquid, and subjected to specific gravity separation by a centrifugal separator 17 for short. Settling in time (eg about 10 minutes). The heavy liquid may be a transparent substance for adjusting specific gravity which is generally used.

  At this time, only the coal particles having a specific gravity higher than that of water are settled, and the wood biomass particles generally have a specific gravity lower than that of water and thus do not settle. Therefore, the coal particles and the biomass particles are separated into two poles in the depth direction of the ampoule 18. The Here, the specific gravity of the coal particles is considered to be about 1.3 to 1.5, and the specific gravity of the woody biomass particles is considered to be about 0.6 to 0.8 (each is a general value).

Depending on the type of biomass 32, it is considered that there is a thing close to the specific gravity of coal. For example, there is coconut husk. In that case, a water-soluble additive is added to water, and the specific gravity is adjusted so as to be intermediate between the specific gravity of coal and the specific gravity of general biomass 32, that is, separation is possible.
In addition, although the specific gravity of the biomass 32 is measured beforehand, since the biomass 32 in a mixture has dispersion | variation, it may be necessary to throw in an additive later.

  When the two poles are separated inside the ampoule 18, the lower part of the ampoule 18 is cut by the ampoule cutter 19 so that the coal is fed into the optical cell (measurement cell) 23 of the automatic particle size analyzer 5, and the particle size of the coal is reduced. measure. Of the sample solution in the ampoule 18, the channel solution is switched by the channel switching device 22 to separate the sample solution that flows to the measurement side and the waste side.

  Since the specific gravity of coal is large, it accumulates in the lower part of the ampoule 18, so that only the coal can be taken out by cutting the lower part of the ampoule 18. And a part of coal is discarded and a part is used as a measurement sample. Discard the sample after measurement. For the measurement of the sample, a laser diffraction type particle size measuring device 26 which can be measured quickly with a non-contact type is used.

  Then, based on the coal particle size detected by the detection unit 25, the rotational speed of the rotary classifier 11 in the mill 6 is automatically adjusted so as to be in the following state. The adjustment criteria are shown below.

1) The particle size (200 mesh passing weight) of pulverized coal alone at the time of biomass mixed pulverization is the particle size at the time of coal pulverization alone × biomass correction coefficient.
2) The particle size of biomass alone at the time of biomass pulverization is under 2 mm.

  Here, the biomass correction coefficient is set to 0.9 to 1.0, and a numerical value in consideration of the influence on the combustibility due to the co-firing of the biomass 32 is selected. In other words, the combustibility of the whole fuel changes depending on the mixing ratio of the biomass 32, and thus correction is made. Specifically, since biomass 32 is generally easier to burn than coal, the biomass correction coefficient is set to 1.0 or less. The finer the particle size of the fuel, the easier it is to burn, but if the mixing ratio of the biomass 32 is increased, the particle size may be coarser. Needless to say, it also depends on the type of biomass 32.

In FIG. 6, the result of having compared the combustion rate of woody biomass and pulverized coal is shown.
In the measurement, a DTF (Drop Tube Furnace) having a configuration shown in FIG. DTF is a vertical tubular electric furnace that drops solids and samples from the top of the furnace and analyzes the product gas and solids that have reacted in the furnace to perform reaction analysis. As shown in FIG. 6A, the primary air 31 and the biomass 32 are supplied together with the secondary air 35 from the top of the heater 40 by the feeder 33. Then, the supplied biomass 32 is burned in the furnace 36 in the heater 40, and the combustion efficiency of the char sampled by the water-cooled sampling probe 37 is analyzed to obtain the burning rate of the biomass 32. The gas analysis monitor 39 is used as an index for adjusting the flow rate ratio of combustion air and fuel (here, biomass).

  The vertical axis in FIG. 6 (b) is the combustion speed, indicating the ratio of burning in one second, and the horizontal axis indicating the reciprocal of absolute temperature. And the result using the biomass sample whose particle size is 2 mm or less and the pulverized coal sample of 200 mesh cumulative passing weight 70% is shown. FIG. 6 (b) does not show the optimum value of the particle size of the biomass 32. From this figure, it can be seen that the combustion rate of the biomass 32 may be higher than that of the pulverized coal depending on the temperature conditions. . However, from FIG. 6 (b), it can be said that biomass particles having a particle size of approximately 2 mm or less exhibit combustibility equivalent to that of pulverized coal having a cumulative passing weight of approximately 200 mesh of approximately 70%.

  FIG. 7 shows the effect on exhaust gas when biomass 32 (pine: moisture 21%) is mixed with 15% of the main fuel based on the calorific value in a pilot test with a coal input of 200 kg / h. Results are shown. That is, FIG. 7 is a diagram showing environmental characteristics when the particle size of pulverized coal is constant and the co-firing rate of biomass 32 having a predetermined particle size is increased. 7A shows the relationship between the NOx concentration and the mixed combustion rate, and FIG. 7B shows the relationship between the unburned ash content (UBC) and the mixed combustion rate.

  From FIG. 7A, it can be seen that when the co-firing rate of biomass 32 is 15 cal%, the concentration of NOx in the exhaust gas is reduced by about 20% as compared with the case of coal-firing (mixing rate 0 cal%). Moreover, there is an unburned component in ash as an item representing burnout in the combustion performance. According to the present embodiment, from FIG. 7 (b), the unburned amount in the ash is 6% to 4% in the mixed combustion rate of 15 cal% of the biomass 32 as compared with the unburned amount in the ash based on the pulverized coal. It turns out that it fell to%. Therefore, it was confirmed that when the mixed combustion rate of the biomass 32 is increased, the concentration of NOx in the exhaust gas is reduced, and further, the ratio of unburned content in the ash is also reduced. That is, it can be seen that when biomass 32 is co-fired as main fuel such as coal as a secondary fuel, the NOx emission reduction effect and the ratio of unburned fuel in the ash are also reduced.

  From the above, according to the embodiment of the present invention, only a biomass mixing facility for mixing with coal is required, and no major facility modification is required. And since the boiler main body and the modification of a combustion apparatus are unnecessary, a low-cost and effective biomass combustion system can be constructed | assembled. And the mixing rate of the biomass (mixed firing rate) while maintaining the emission level of NOx and unburned fuel at a certain level without significantly increasing the cost of equipment such as a fuel pulverizer and without increasing the pulverization power. ) Can be increased.

FIG. 8 shows a system configuration diagram of a system of a fuel adjustment device according to another embodiment of the present invention. Note that description of members denoted by the same reference numerals as those in FIG. 1 is omitted.
According to FIG. 8, for the biomass 32, an original biomass bunker 7 and an original quantitative supply device 8 are installed, and the biomass 32 is directly supplied to the mill 6 before being mixed with coal. Compared with the method of supplying to the coal bunker 9 while maintaining the mixing ratio with coal as shown in FIG. 1, it is possible to control at an accurate mixing rate. As shown in FIG. 1, when mixing on a conveyor, it is difficult to avoid segregation with time in the bunker 9 due to the difference in specific gravity between coal and biomass 32.

  However, by providing the unique biomass bunker 7 and the unique supply device 8 as shown in FIG. 8, the supply method of the biomass 32 becomes highly accurate, and the risk of segregation as described above can be avoided. Driving at a rate is possible. FIG. 8 shows a method of supplying biomass to two mills 6 and a control method of two mills 6, that is, only two systems are shown, but application to a six-mill system is also possible. .

  The mixed fuel of biomass 32 and coal was adjusted based on the system flow of the fuel adjustment device shown in FIG. The biomass 32 is cedar (20 mm under) and the coal is Barga coal. The calorific value of the biomass 32 is used as a reference, and the coal 32 is mixed with 5 cal% of the biomass 32 and pulverized. At 1.2 t / h. The rotational speed of the rotary classifier 11 (SLS-50) is 140 rpm, and a part (about 10 mg) of the mixed pulverized product of coal and biomass 32 is taken out from the outlet part of the mill 6 by the automatic particle sampling device 12 and put in the ampoule 18. Then, after the biomass 32 and the pulverized coal mixture were dispersed in a heavy liquid (calcium chloride aqueous solution), separation was performed using a CP100WX automatic centrifugal separator 17 manufactured by Hitachi.

In addition, when rotating with the rotary classifier 11, centripetal force and centrifugal force are applied to the particles, and for large particles, the centrifugal force exceeds the centripetal force and is returned to the mill 6 side. That is, the magnitude of the rotational speed gives the magnitude of the centrifugal force. Centrifugal force is expressed by MRω ^2, M is the mass of a single particle, R is the radius of the rotary classifier 11, omega is angular velocity. The rotational speed of the rotary classifier 11 is ω, which is 140 rpm in this embodiment.

  And in the case of the apparatus which can disperse | distribute the mixed ground material particle | grains of coal and biomass 32 to the ampoule 18, centrifuge, and cut | disconnect the lower part and can extract only a separated material, after coal settled in about 10 minutes, The lower part of the ampoule 18 was cut with an ampoule cutter 19 to feed a coal sample into the optical cell (measuring cell) 23 of the automatic particle size analyzer 5 and the particle size of the coal was measured using a laser diffraction particle size measuring device 26. The pulverized coal particles that were centrifuged were introduced into the optical cell 23 of the Malvern Masterizer 2000 as the laser diffraction particle size measuring device 26, and the particle size distribution was measured.

  Further, when a mechanism capable of automatically extracting a centrifugal separation is added to the centrifugal separator 17, the extract (coal sample) is sent to the optical cell (measurement cell) 23 of the automatic particle size analyzer 5, as described above. In addition, the particle size of coal may be measured using the laser diffraction particle size measuring device 26.

The particle size of the coal at this time was 200 mesh cumulative passing weight 70 wt%. Therefore, the motor 16 is controlled by the mill rotary classifier control device 14 so that the 200 mesh cumulative passing weight is changed from 70 wt% to 65% wt, and the rotational speed of the rotary classifier 11 is decreased from 140 rpm to 110 rpm. Adjustments were made.
The above sampling and analysis operations were performed every hour, and the rotational speed of the rotary classifier 11 was appropriately adjusted so that the sampled coal particle size was 200 mesh cumulative passing weight 65% wt.

  FIG. 9 shows an example of the relationship between the spindle power (kW) of the mill and the load factor (%) of the mill, and compares the operation by the method of Example 1 of the present invention with the operation by the conventional method. . The main shaft power is the power directly applied to the pulverization and excludes the mechanical power loss of the power transmission system of the mill 6.

  The mill 6 shown in FIG. 9 is a pilot-scale test mill, and the rated mill power (corresponding to the power margin of the mill 6 described above) is 14 kW, and operation that does not exceed this value is required. The results are obtained when coal and woody biomass are simultaneously ground using a mill 6 having a rated coal grinding capacity of 2 t / h. The horizontal axis of FIG. 9 is the load factor of the mill 6 and is a value obtained by dividing the supply amount of raw materials such as coal and biomass 32 by the rated pulverization amount. In the case of coal alone, 70% load factor operation is the standard.

  According to FIG. 9, it can be seen that the main shaft power shown on the vertical axis in FIG. When the biomass 32 is mixed and pulverized by 5 cal%, the limit value of 14 kW is exceeded by the operation at a load factor of 70%, and the power at point B is obtained.

  This case corresponds to a case where the particle size is constant, for example, the rotational speed of the rotary classifier is fixed at 140 rpm and the fuel is switched from coal alone to a mixed fuel in which 5 cal% of biomass 32 is mixed. Thereafter, in order to keep the main shaft power below the rated power (14 kW), the rotational speed of the rotary classifier is decreased to 110 rpm, the power is moved to the point C in the figure, and the power is decreased from the point B.

  By such a fuel adjustment method, mixing is performed by maintaining the proper mill power by controlling the rotation speed of the rotary classifier 11 without exceeding the rated mill power line when the load factor of the mill 6 shown in FIG. 9 is 70%. Fuel adjustment can be made.

  And if it is the fuel adjustment method by a present Example, the particle size of the coal in mixed fuel can be analyzed, and motive power can be immediately reduced from 140 rpm to 110 rpm based on the result. Therefore, with respect to the operation of the rotary classifier 11, the particle size of the coal is instantly reflected in the method according to this embodiment. However, according to the conventional method, the power of the mill 6 increases with a delay of 30 minutes or more with respect to the operation of the rotary classifier 11. Therefore, in the method according to the present embodiment, even if the number of rotations of the classifier 11 is changed after the measurement of the particle size, it is sufficiently in time before the load is applied.

  Thus, compared with the case where the power of the mill 6 is moved from the above point A to the point B and from the point B to the point C, when the power is actually coal alone before the load factor of the mill 6 increases to 70%. Because it is possible to control movement directly from point A to point C without passing point B exceeding the rated mil power, it is possible to control quickly by preventing problems such as adverse effects on devices and trips due to exceeding the rated power There is.

FIG. 10 shows an example in which the rotational speed of the rotary classifier 11 is adjusted.
The sampled coal particle size is less than the target particle size (200 mesh cumulative passing weight is 65% or more), and the rotational classifier rotation speed VS.200 mesh passing weight characteristic curve (solid line A) obtained when pulverized coal alone is pulverized. ), The characteristic curve (solid line A) of the pulverized coal alone is shifted so as to match the measured value (dotted line B) of the coal particle size, and the rotational speed of the rotary classifier 11 so as to reach the target particle size. Correct. This procedure will be described below.

Step 1: For example, the rotational speed of the rotary classifier 11 is started at R0 (initial value). The actual measured value of the 200 mesh cumulative passing weight analyzed from the coal particle size at this time is defined as an actual measured value 1.
Step 2: Then, assuming that the solid line A, which is the characteristic curve of pulverized coal alone, is correct, shift to the left so as to overlap the actual measurement value 1 (dotted line B).

Step 3: The rotational speed R at the time when the 200 mesh passes 65% is predicted with the curve of the dotted line B (predicted value 1), and the rotational speed R1 obtained from the dotted line B is given.
Step 4: At this time, the absolute value of the difference between the rotation speed initial values R0 and R1 should be 10% of the initial value R0, so that the particle size is not significantly changed due to the change in the rotation speed of the rotary classifier 11. . That is, | R0−R1 | does not exceed R0 / 10, and if it exceeds, R1 = R0 × 0.9 (or 1.1) is given.

  Step 5: If the rotational speed of R1 is given and the coal particle size deviates from 65% passing through 200 mesh (predicted value 1) (estimated value 2), the characteristics obtained from R0 and R1 are The base R predicts R at 65% when passing through 200 mesh (predicted value 2), and gives the rotation speed of R2. Again, as in step 4, | R1−R2 | is made not to exceed R1 / 10, and if it exceeds, R2 = R1 × 0.9 (or 1.1) is given. Then, when the actual measurement value 3 is obtained, the process returns to Step 3 and the curve of the dotted line B (solid line A) is shifted again so as to overlap the actual measurement value 3 to predict the rotation speed R when the 200 mesh passes 65%. Follow the steps and adjust to approach 65% infinitely. In the second embodiment, a maximum value of 10% of the change width of one rotation speed is provided so that a measurement error occurs and the rotation speed does not change suddenly. This range of change varies depending on the apparatus and implementation scale.

  The adjusting device and adjusting method of the auxiliary fuel co-fired with coal as a fuel in a combustion apparatus such as a boiler can be applied not only to biomass fuel but also to other waste materials as auxiliary fuel.

It is a system configuration | structure figure of the system of the fuel adjustment apparatus which is one Embodiment of this invention. It is a block diagram of the particle size measurement control system of FIG. It is a block diagram of the two-component automatic particle size measuring apparatus of pulverized coal and biomass of FIG. It is the figure which showed the example which compared the particle size of the sample from which pulverized coal and biomass were each grind | pulverized exclusively, and the combustion speed | velocity | rate becomes substantially equivalent by pulverized coal and biomass. It is the figure which showed the particle size at the time of mixing and crushing 5% on the basis of the calorific value of biomass about the same coal and woody biomass as FIG. It is the figure which showed the result of having compared the combustion rate of woody biomass and pulverized coal. FIG. 6A is a diagram showing the configuration of the used DTF (Drop Tube Furnace), and FIG. 6B is a diagram showing the burning rate of woody biomass and pulverized coal. It is the figure which showed the result of having investigated about the influence on the exhaust gas at the time of biomass co-firing 15% of main fuel on the basis of calorific value. FIG. 7A is a diagram showing the relationship between the NOx concentration and the mixed combustion rate, and FIG. 7B is a diagram showing the relationship between the unburned ash (UBC) and the mixed combustion rate. It is a system configuration | structure figure of the system of the fuel adjustment apparatus by other embodiment of this invention. It is a figure which shows an example of the relationship between the spindle power (kW) of a mill, and the load factor (%) of a mill. It is the figure which showed the example which adjusted the rotation speed of the rotary classifier by Example 2 of this invention.

Explanation of symbols

1 Boiler body 2 OFA
3 Wind box 4 Main burner 5 Particle size measurement control system 6 Mill 7 Biomass bunker 8 Fixed supply device 9 Coal bunker 10 Coal handling equipment 11 Rotating classifier 12 Automatic particle sampling device 13 Particle size measuring device 14 Rotating classifier controller 16 Motor 17 Centrifugal Separator 18 Ampoule 19 Ampoule cutter 22 Flow path switch 23 Measurement cell 25 Detector 26 Laser diffraction particle size measuring device
30 Piping for air flow 31 Primary air 32 Biomass 33 Feeder 35 Secondary air 36 Furnace 37 Water-cooled sampling probe 39 Gas analysis monitor 40 Heater

Claims (4)

A crusher for crushing a mixture of woody biomass fuel and coal;
A rotating classifier having a rotating mechanism for classifying the pulverized product pulverized by the pulverizer;
A fuel adjusting device comprising a supply device for supplying the pulverized material classified by the rotary classifying device to a combustion device including a boiler,
A sampling device for taking out a part of the pulverized material classified by the rotary classifier;
A particle size analyzer for analyzing the particle size of coal among the pulverized material taken out by the sampling device;
And a control device for controlling the rotational speed of the rotary classifier based on the coal particle size analyzed by the particle size analyzer. The particle size analyzer is a centrifugal separator that separates the woody biomass fuel and coal in a heavy liquid from the pulverized matter taken out by the sampling device and separates them in specific gravity.
It consists of a particle size measuring device that measures the particle size of coal separated by specific gravity by the centrifugal separator,
2. The fuel adjustment device according to claim 1, wherein the control device has a configuration for controlling the rotational speed of the rotary classifier so that the coal particle size measured by the particle size measurement device falls within a predetermined range. . A fuel adjustment method for pulverizing a mixture of woody biomass fuel and coal, classifying the obtained pulverized material by a classifying means having a rotation mechanism, and then supplying it to a combustion device including a boiler,
A fuel adjustment method, wherein the classification means analyzes the coal particle size in the pulverized product after classification, and controls the rotational speed of the classification means based on the analyzed coal particle size.   A part of the pulverized product after the classification is dispersed in heavy liquid, and the woody biomass fuel and coal are separated by specific gravity by centrifugation, then the particle size of the coal is measured, and the measured coal particle size is predetermined. 4. The fuel adjustment method according to claim 3, wherein the number of revolutions of the classifying means is controlled so as to fall within a range.

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