JP4029230B2 - Coal / water paste manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, solid fuel such as coal is burned in a pressurized fluidized bed, a steam turbine is driven by the generated steam, and a gas turbine is further driven by high-pressure and high-temperature combustion gas to obtain electric power with high efficiency. More particularly, the present invention relates to a method for producing a mixture of coal and water supplied to the combustion furnace.
[0002]
[Prior art]
Pressurized fluidized bed boilers can sell energy from the generated steam and high-pressure combustion gases. However, one of the problems is to supply the solid coal particles continuously and stably into the pressurized combustion furnace. Conventionally, as a method for supplying coal to a fluidized bed combustion furnace, coal particles and water are mixed to form a paste fluid (hereinafter referred to as CWP), and the CWP is pressurized and pumped by a pump and supplied from a spray nozzle. A supply system is known (for example, JP-A-62-155433). This wet supply method does not require a pretreatment such as drying as compared with a dry supply method, for example, a method in which the pressure is increased by a lock hopper and then pneumatically transported.
[0003]
As shown in FIG. 8, conventionally, the raw coal 1 is supplied to the crusher 3 by the raw coal conveyor 2 and is crushed to have a weight average diameter of 1 to 2 mm. Here, a calculation method of the weight average diameter is shown. In the particle size analysis by sieving, the relationship between the opening of the sieve as shown in FIG. 9 and the weight of particles passing through the sieve (hereinafter referred to as cumulative weight under the sieve) is drawn on the basis of dry coal. At this time, the opening of the sieve corresponds to the maximum value of the particle diameter that has passed through the sieve. From this relationship, the value of the particle size when the cumulative weight ratio under the sieve (= 100 × (cumulative weight under the sieve) / (crushed coal weight)) is 50% (the opening value of the sieve, F in FIG. 9) The weight average diameter is used.
[0004]
Part of the crushed coal obtained by crushing the raw coal 1 with the crusher 3 is introduced into the pulverizer 5 through the crushed coal hopper 4, and the weight average diameter 0. The finely divided slurry 20 is produced by wet pulverization at a coal concentration of 50% or less so as to be 03 to 0.07 mm. The produced fine slurry 20, crushed charcoal 19 and limestone 22 are mixed by the kneader 6 while adjusting the amount of water injected so as to have a predetermined viscosity to produce CWP 21. The CWP is stored in the tank 7 while being stirred by the CWP stirrer 10 and then pumped to the furnace 9 by the CWP pump 8. The viscosity of the CWP is adjusted with moisture so that clogging in the pipe does not occur, and water is injected and mixed with the kneader 6 so that the viscosity of the pin viscometer 23 is about 10 Pa · s at 100 rpm. ing. The water content of CWP at this time is about 20 to 30 wt% although it varies depending on the coal type.
[0005]
The viscosity of CWP is 5 to 15 Pa · s, preferably 10 Pa · s, using a pin type viscometer. When the viscosity is higher than this, the CWP is likely to be clogged in the pipe, and when the viscosity is lower, the coal and water are easily separated.
[0006]
Here, lines A and B shown in FIG. 3 indicate that particles having a size of 75 μm or less, that is, particles having passed through a sieve having a mesh size of 75 μm, pass through the fine powder slurry finely pulverized by the fine pulverizer 5. It shows what percentage is present, and if the ratio is in the range of 60-70%, it indicates that it is an acceptable range. When pulverizing at a coal concentration of 50% or more in the fine pulverizer 5, the viscosity of the fine powder slurry in the fine pulverizer 5 is increased and the coal particle size becomes coarse as shown by line A in FIG. Therefore, it becomes difficult to adjust the particle size. Accordingly, the coal concentration during pulverization is 50% or less.
[0007]
The mixing ratio of the fine slurry 20 and the crushed coal 19 in the kneader 6 is 20 to 25 wt% of the fine slurry on the basis of dry coal as shown in FIG. If it is outside this range, the moisture for making the viscosity 10 Pa · s cannot be lowered. If it is 20 wt% or less, coal and water are easily separated, and if it is 25 wt% or more, CWP tends to be high in viscosity. That is, mixing fine powder with a particle size of 60 to 70% of 75 μm or less with 20 to 25% of the coal particles of all CWP has the most moisture, so it has good combustibility, and there is almost no separation between water and coal, so transportability is improved. Is an excellent and optimal CWP.
[0008]
[Problems to be solved by the invention]
The moisture content of the raw coal 1 varies depending on the type of coal, the environment of the coal yard, the weather, and the like. Usually, it is about 9 wt%, but if raw coal is left in a high humidity state, it may be about 14 wt%. When the mixing ratio of coal and water in the pulverizer 5 and the kneader 6 in FIG. 8 is manufactured as in the prior art, moisture having a viscosity of 5 to 15 Pa · s as shown by the dotted line in FIG. 6 (see FIG. 5). When the amount of water injected in the kneading machine 6 becomes small and the water content of the raw coal 1 becomes 14 wt%, the kneading machine 6 cannot add water. Here, the water injection percentage in the kneader in FIG.
Water injection ratio in kneader = {(water addition amount in kneader) / (total CWP amount)} × 100
(The total amount of CWP is the weight of CWP including coal).
[0009]
At the same time, if the water is not reduced by a fine pulverizer, the water does not become moisture for making the viscosity of CWP21 5-15 Pa · s. However, as described above, when the coal concentration in the fine pulverizer is 50 wt% or more and pulverized, the pulverization ability is lowered. This is a problem.
[0010]
It is an object of the present invention to detect that the viscosity at the kneader outlet has decreased to adjust water with only a kneader, even when using raw coal whose water content exceeds 10 wt%, The moisture content is reduced to facilitate moisture adjustment in the kneader.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention detects a decrease in CWP viscosity at the kneader outlet when controlling the CWP properties at the kneader outlet and controlling the amount of water injected into the kneader. The amount of water supplied to the water is reduced. For this purpose, a surfactant is injected into the pulverizer together with water to reduce the viscosity of the pulverized slurry in the pulverizer, and the pulverization capacity is the same as when the surfactant is not injected or the water content is not decreased. Is to be manufactured.
[0012]
According to this method, conventionally, even if it is not possible to adjust the CWP viscosity to be easy to transport with a kneader because the moisture content of the raw coal exceeds 10 wt%, the moisture content of the raw coal is not directly controlled, It becomes possible to produce CWP whose properties are kept in a required range.
[0013]
This onset bright to achieve the above object, after crushing the raw coal, a portion of the crushed coal is mixed with water while pulverized using a fine grinding mill to produce a fine slurry, further remainder of crushed coal with a kneading machine In a method for producing a coal / water paste (hereinafter, referred to as CWP) by mixing limestone, limestone slurry, water, and water , a note to the kneader is based on the viscosity of the CWP at the kneader outlet. Controlling the amount of water, detecting a decrease in the amount of water injected into the kneader, adjusting the amount of surfactant supplied to the fine pulverizer, and adjusting the amount of water supplied to the fine pulverizer Features.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIG. The illustrated CWP manufacturing apparatus includes a raw coal conveyor 2 that conveys the raw coal 1, a crusher 3 that crushes the raw coal 1 conveyed by the raw coal conveyor 2 to a weight average diameter of 1 to 2 mm, and a crusher 3. A plurality of crushed coal hoppers 4 for storing the generated crushed coal 19, an additive tank 12 having an additive stirrer 14 for storing the surfactant 17, and an additive tank 12 connected to the suction side. The additive pump 15 that pressurizes and discharges the surfactant 17, the additive amount adjustment valve 24 interposed in the discharge side pipe 29 of the additive pump 15, and the water that sucks and discharges the water 11 from the water source. A pump 16, a fine pulverizer-side water amount adjustment valve 26 interposed in a first pipe 27 connected to the discharge side of the water pump 16, and an upstream of the pulverizer-side water amount adjustment valve 26 of the first pipe. A second branch provided on the side and provided with a kneader-side water amount adjustment valve 25. A fine crusher 5 connected to a pipe 28, one of the plurality of crushed coal hoppers 4, a downstream end of the discharge side pipe 29 and the first pipe 27, and among the plurality of crushed coal hoppers 4 The kneading machine 6 arranged in connection with the other side of the kneading machine 5, the downstream end of the second pipe 28, and the storage tank of the limestone 22; The tank 7 which is disposed and connected to the outlet side of the kneader 6 via a pipe 30 to store CWP, the pin viscometer 23 interposed in the pipe 30, and the tank 7 is installed inside the tank 7. A CWP stirrer 10 that stirs CWP and a CWP pump 9 that sucks CWP from the tank 7 and sends the CWP to the furnace 9 are configured.
[0018]
Next, the operation of the apparatus having the above configuration will be described. The raw coal 1 is supplied to the crusher 3 by the raw coal conveyor 2, is crushed so as to have a weight average diameter of 1 to 2 mm, becomes crushed coal 19, and is put into the crushed coal hopper 4. Part of the crushed coal in the crushed coal hopper 4 is supplied to the fine pulverizer 5, finely pulverized while mixing the water 11 that is pressurized by the water pump 16 and supplied via the fine pulverizer-side water amount adjustment valve 26. A slurry 20 is obtained. In the pulverizer 5, the surfactant 17 pressurized from the additive tank 12 to the additive pump 15 and supplied through the additive amount adjusting valve 24 is 0.01 to 0.9% with respect to the dry coal. Injected at a rate of
[0019]
The produced fine powder slurry 20 is sent to the kneader 6, and kneaded together with the crushed coal 19, limestone 22, and water 11 supplied to the kneader 6 to become a CWP 21. At that time, the amount of water to be supplied is supplied to the kneader 6 while being adjusted by the kneader-side water amount adjustment valve 25 so that the viscosity of the produced CWP becomes a predetermined viscosity. The manufactured CWP 21 is measured for viscosity by a pin viscometer 23 and then stored in the tank 7. The CWP 21 in the tank is pumped to the furnace 9 by the CWP pump 8.
[0020]
The kneader-side water amount adjustment valve 25 controls the amount of water sent to the kneader 6 so that the CWP viscosity detected by the pin viscometer 23 is in the range of 5 to 15 Pa · s. If the raw coal water is high, the CWP viscosity is low. When the pin type viscometer 23 detects that the CWP viscosity is low, the additive amount adjusting valve 24 is opened and the opening of the fine pulverizer side water amount adjusting valve 26 is simultaneously reduced to reduce the coal concentration of the fine slurry 20. The mixture is then pulverized and the fine slurry is supplied to the kneader 6. As a result, the water content at the outlet of the kneader 6 is reduced, so that the viscosity of the CWP 21 increases. This is detected by the pin-type viscometer 23, and the water injection ratio in the kneading machine is adjusted so that the total water content in FIG. The viscosity of CWP is managed again so that the relationship between the ratio of water injection in the kneader represented by the oblique line and the total water content of CWP falls within the range of region E.
[0021]
According to this method, as shown by the solid line in FIG. 6, even if the coal has a moisture content of 14 wt%, it is possible to adjust the moisture only with a kneader. In addition, when a surfactant is added to the fine pulverizer, even if the coal concentration of the fine pulverizer is increased and pulverized, as shown by the line B in FIG. It can be seen that the particle size of 20 is maintained in the desired particle size range, and the pulverization performance is not deteriorated.
[0022]
Since it is also important to reduce fuel costs, it is better not to use a surfactant except when the coal has water that cannot be injected with a kneader (coal with a water content of 10% or more). When coal has a moisture content of 10% or more, proper moisture adjustment and particle size adjustment cannot be performed unless a surfactant is used. Therefore, it is necessary to properly use the conventional technique and the operation method according to the present invention depending on the moisture content of the received coal. However, as in the prior art, when a surfactant is suddenly introduced into a fine powder slurry in a fine pulverizer with a large amount of water, dispersion is advanced and coal is easily separated. Moreover, if the grinding | pulverization density | concentration (coal density | concentration) of the fine powder slurry in the fine pulverizer which does not contain surfactant is raised rapidly, a grinding | pulverization capability will fall as mentioned above. For this reason, it is important to simultaneously add the surfactant and increase the pulverization concentration.
[0023]
For example, when the pulverization concentration is increased from 50% to 60% and the additive is added in an amount of 0.35 wt% with respect to the dry coal, the additive amount is gradually changed as shown in FIG. Operate to increase grinding density.
[0024]
Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is different from the first embodiment shown in FIG. 1 in that the opening degree of the fine pulverizer side water amount adjusting valve 26 and the additive amount adjusting valve 24 is controlled by the output of the pin type viscometer 23. Instead, it is configured to be controlled based on the opening degree of the kneader-side water amount adjustment valve 25. Since the other components are the same as those in the first embodiment, the same reference numerals are given and description thereof is omitted. Also in this embodiment, based on the output of the pin viscometer 23, the CWP viscosity is controlled to be in the range of 5 to 15 Pa · s. When the CWP viscosity output from the pin type viscometer 23 falls below a set value, the kneader-side water amount adjustment valve 25 is controlled so that the amount of water injection decreases. When it is detected that the opening degree of the kneader-side water amount adjustment valve 25 is reduced, the additive amount adjustment valve 24 is opened, and at the same time, the opening degree of the fine pulverizer-side water amount adjustment valve 26 is reduced. When the fine powder slurry 20 manufactured in this way is supplied to the kneader 6, the CWP viscosity increases. This increase in viscosity is detected by the pin type viscometer 23, and the viscosity of the CWP 21 is again managed by the kneader-side water amount adjustment valve 25 as shown by the solid line in FIG.
[0025]
【The invention's effect】
According to the present invention, even when the moisture content of the received coal exceeds 10%, the moisture can be adjusted by the kneader by suppressing the moisture in the pulverizer by adding the surfactant. Is possible. As a result, even when the moisture content of the received coal exceeds 10%, it is possible to produce CWP without reducing the particle size of the coal pulverized by the fine pulverizer.
[Brief description of the drawings]
FIG. 1 is a system diagram showing a main configuration of a CWP manufacturing apparatus according to a first embodiment of the present invention.
FIG. 2 is a system diagram showing a main configuration of a CWP manufacturing apparatus according to a first embodiment of the present invention.
FIG. 3 is a graph showing a comparison of the relationship between the coal concentration and the generated fine powder slurry particle size in the pulverizer according to an embodiment of the present invention and the prior art.
FIG. 4 is a graph showing the relationship between the total water content of CWP in the prior art and the mixing ratio (fine powder mixing ratio) of fine slurry and crushed coal in a kneader.
FIG. 5 is a graph showing the relationship between CWP total moisture and CWP viscosity in the prior art.
FIG. 6 is a graph showing the relationship between the ratio of water added to the kneader and the total water content of CWP in the prior art and the example of the present invention, with the water content of coal in the pulverizer as a parameter.
FIG. 7 is a graph showing a comparison of changes over time in the coal concentration (pulverization concentration) and surfactant addition amount of a fine pulverizer in the prior art and an example of the present invention.
FIG. 8 is a system diagram showing a main configuration of a CWP manufacturing apparatus according to the prior art.
FIG. 9 is a conceptual diagram showing a particle size distribution measured by sieving.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Raw coal 2 Raw coal conveyor 3 Crusher 4 Crushing coal hopper 5 Fine crusher 6 Kneading machine 7 Tank 8 CWP pump 9 Furnace 10 CWP stirrer 11 Water 12 Additive tank 14 Additive stirrer 15 Additive pump 16 Water pump 17 Surfactant 19 Crushed coal 20 Fine powder slurry 21 CWP
22 Limestone 23 Pin type viscometer 24 Additive amount adjustment valve 25 Kneader side water amount adjustment valve 26 Fine crusher side water amount adjustment valve 27 First piping 28 Second piping 29 Discharge side piping 30 Piping

Claims (1)

After crushing the raw coal, a portion of the crushed coal is mixed with water while being pulverized with a fine pulverizer to produce a finely divided slurry, and the remaining crushed coal, limestone, the finely divided slurry and water are mixed with a kneader. In the method for producing coal / water paste, which produces coal / water paste (hereinafter referred to as CWP),
The amount of surfactant to be supplied to the fine pulverizer by controlling the amount of water injected to the kneader based on the viscosity of the CWP at the kneader outlet and detecting that the amount of water injected to the kneader decreases. And adjusting the amount of water supplied to the pulverizer .

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