JPH06108067A - Process and apparatus for producing coal/water paste - Google Patents

Abstract

PURPOSE:To provide a process and apparatus for producing a low-cost low- water-content coal/water paste(CWP) which can be stably fed to a combustion furnace. CONSTITUTION:This apparatus is provided with an at least two-stage agitation means comprising the first agitation means 6 and 8 for mixing a part of the ground coal necessary for the production of a coal/water paste with the total water necessary for the production to form the coal/water paste, and the second or subsequent agitation means 7 and 9 for mixing the above coal/water paste with the remainder of the coal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a coal / water paste, and more particularly to burning a solid fuel such as coal in a pressurized fluidized bed, driving a steam turbine with the generated steam, and The present invention relates to a method and apparatus for producing a mixture of coal and water to be supplied to a combustion furnace of a pressurized fluidized bed boiler combined cycle power plant that drives a gas turbine with high-temperature combustion gas to obtain electric power with high efficiency.

[0002]

2. Description of the Related Art A pressurized fluidized bed boiler can obtain energy from steam and high-pressure combustion gas that are generated, so that highly efficient power generation is possible. However, one issue is to continuously and stably supply solid coal particles into the combustion furnace under pressure. Conventionally, as a method of supplying coal to a fluidized bed combustion furnace, coal particles and water are mixed to form a paste-like fluid (hereinafter, referred to as Coal-Water Paste; hereinafter abbreviated as CWP), and the CWP is pressurized and pumped and sprayed. There is a wet supply system (for example, Japanese Patent Laid-Open No. 62-155433) which is supplied from a nozzle. The CWP supply method does not require pretreatment such as drying and is low in cost, as compared with a dry supply method, for example, a method of pneumatically transporting after the pressure of the lock hopper is increased. However, it is important to minimize the amount of water added to coal in order to maintain the power generation efficiency at a high level. For this reason, CW with a limited amount of added water
P has a high viscosity, and since it does not contain an agent for dispersing coal particles in order to reduce the manufacturing cost, it has extremely poor fluidity.

CWP has a maximum diameter of 6 mm and a weight average diameter of 1
Although the particle size is as coarse as ~ 2 mm, a particle size structure containing a considerable amount of fine particles is required in order to obtain CWP with low water content. Therefore, the coal particles in the CWP are characterized in that they exist in a wide range of particle sizes from fine particles of several tens of μm to coarse particles of maximum 6 mm. Generally, the particle diameter of the solid used for the mixing operation of the solid and the liquid is about 2 mm at the maximum, and most of them are fine particles of several tens μm. Moreover, if the solid and liquid are difficult to mix with each other,
It is common to use a chemical to make the solid surface wettable by the liquid. For example, Japanese Examined Patent Publication (Kokoku) No. 62-44038 discloses a device for continuously producing a high-concentration coal water slurry having a weight average diameter of 10 to 30 μm in the presence of a surfactant, which has a high concentration by a combination of high speed stirring and low speed stirring. A method of making a coal water slurry is disclosed.

However, in spite of the fact that the CWP has a particle size constitution containing a large amount of fine particles, in the manufacture thereof, no chemicals are used in order to reduce the manufacturing cost, and in order to suppress the decrease in power generation efficiency due to water, the amount of water is minimized. It is desired to reduce. That is, the coal particles in the above particle size range are mixed with water in a condition of low water content without using a chemical agent, in other words, highly hydrophobic coal particles under high viscosity conditions,
Problems such as piping blockage occurred during pumping, and a large amount of stirring power was required to make pumping possible.

[0005]

As described above, in the prior art, coal particles in the CWP aggregate due to the fact that water is mixed with highly hydrophobic coal particles under a condition of a smaller water content, that is, a highly viscous condition. However, it was in a heterogeneous state in which coal particles and water were unevenly distributed. A large amount of stirring power was required to bring this into a homogeneous state. An object of the present invention is to provide a low-cost coal / water paste production method and apparatus capable of producing low-moisture CWP with low stirring power and stably supplying it to a combustion furnace.

[0006]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors on a method for producing a coal / water paste in a pressurized fluidized bed, the above object of the present invention has been achieved by the following constitution. That is, in a method for producing a coal / water paste comprising a step of pulverizing raw coal and a step of mixing pulverized coal with water, first, a part of the amount of pulverized coal necessary for producing the coal / water paste is This is a method for producing a coal / water paste, which is prepared by mixing together with the total amount of water necessary for production into a coal / water paste, and then mixing and stirring the rest of the crushed coal amount. At this time, 60 to 90% by weight of the amount of pulverized coal required for the production of the coal / water paste at the time of the first mixing of coal and water can be mixed with the total amount of water required for the production to form a coal / water paste. If the crushed coal lacks fine particles, it is possible to add a step of crushing again the remaining amount of crushed coal added at the time of stirring and mixing the coal and water paste from the second stage to finely crushed coal. it can.

The above object of the present invention can also be achieved by the following configuration. In other words, in a coal / water paste manufacturing device consisting of a raw coal crushing device and a stirring device that mixes the crushed coal with water, a part of the crushed coal amount required to produce the coal / water paste is used to produce a total amount of water. Coal provided with at least two or more stirrers consisting of a first stirrer that is mixed together with it to form a coal / water paste, and a second and subsequent stirrer that mixes and stirs the rest of the crushed coal amount.・ It is a water paste manufacturing device. At this time, if the crushed coal lacks fine particles, it is possible to provide a crushing means for crushing again the remaining amount of the crushed coal added during the stirring and mixing of the second and subsequent stages of the coal / water paste.

[0008]

When the total amount of coal is added to the amount of added water required for CWP production as in the conventional method, it is difficult to mix the coal and water because the mixture is agitated and mixed under high viscosity. as a result,
The coal particles and water that compose the CWP are unevenly distributed, and the coal particles also agglomerate with each other, resulting in a CWP in an extremely inhomogeneous state by stirring for a short time. In the method of the present invention, first, a part of the amount of pulverized coal necessary for the production of CWP is added to the total amount of water required by the first-stage stirring means, so that uniform mixing with low power can be realized. It is desirable to add 60 to 90% by weight of the total amount of crushed coal required for the production of CWP to the amount of crushed coal added by the first-stage stirring means. That is, when the distribution ratio of the amount of pulverized coal to the first-stage stirring means is 60% by weight or less, the viscosity of CWP is 0.1 Pa · s or less, and the coarse particles in CWP are likely to selectively precipitate, resulting in uniform Good mixing is not achieved.
On the other hand, when the distribution ratio is 90% by weight or more, the viscosity is 1.5.
It becomes Pa · s or more and there is no settling of particles, but it is difficult to be uniform at low power because of high viscosity. Therefore, the distribution ratio of the pulverized coal amount to the first-stage stirring means is 60 to 90% by weight.
By so doing, coarse particles are less likely to settle during stirring and mixing, and the viscosity range is such that the contact frequency of coal particles and water increases, and uniform mixing is achieved in a short time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below.
FIG. 1 shows an example of the flow of an apparatus suitable for implementing the present invention. The raw coal in the raw coal bunker 1 is quantitatively cut by a raw coal feeder 2 and supplied to a roll crusher 3. The coarse particles in the crushed carbon obtained in the roll crusher 3 are removed by the sieve 4. The crushed carbon after the coarse particles are removed is supplied to a distributor 5, and a part of the crushed carbon (hereinafter, abbreviated as crushed carbon I) is supplied to a stirring tank 6 and the rest of the crushed carbon (hereinafter, crushed carbon).
(Abbreviated as II) is distributed to the stirring tank 7. Stirring tank 6
In addition to the crushed carbon I, limestone as a desulfurizing agent and water necessary for producing CWP are added, and the mixture is stirred by a stirrer 8.
Mixed. Since the above operation is continuously performed, the CWP having a low coal concentration in the stirring tank 6 is extruded into the stirring tank 7, and is stirred and mixed in the stirring tank 7 with the remaining pulverized coal II by the stirrer 9. The manufactured CWP is supplied to a furnace (not shown) by the CWP pump 10.

The roll crusher 3 has a maximum diameter of about 50 m.
Conditions are set so that m of raw coal can be crushed to a particle size of 6 mm or less. The raw coal may be crushed by any kind of crusher as long as it can crush to a predetermined particle size. Also,
The mesh size of the sieve 4 was determined so that the maximum diameter of the coal particles in the CWP was 6 mm. The distributor 5 has a function of distributing the crushed coal at a predetermined ratio, and in this embodiment, the ratio of the crushed coal I and the crushed coal II is set according to the coal property. In the above manufacturing apparatus, limestone particles having a maximum diameter of about 3 mm are used as the desulfurizing agent. The agitation tanks 6 and 7 and the agitators 8 and 9 are shown schematically and do not limit the present invention.

CWPs of charcoal A and charcoal B were produced using the apparatus shown in FIG. An example at this time is shown below. Example 1 Charcoal A (water content = 4%, fuel ratio = 1.8, ash = 15.5)
%) On a dry coal basis and crushed by a roll crusher 3 to 6 mm or less. At this time, the roll gap was set to 3 mm. After removing coarse particles of 6 mm or less, which are mixed in a small amount with the sieve 4, it is supplied to the distributor 5 and distributed so that the ratio of the crushed coal I to the total amount of the crushed coal is 74.4% by weight. Here, the distribution ratio is such that the CWP viscosity is 0.1 in the stirring tank 6 based on the result of the basic experiment.
It is determined to be ~ 1.5 Pa · s, and the distribution ratio differs depending on the coal type. Table 1 shows the flow rates of the pulverized coal, water and the desulfurizing agent supplied to the stirring tank and the C in the tank at that time.
The analytical values of the coal concentration and viscosity of WP are shown by comparing the conventional method and this example. The capacities of the stirring tanks 6 and 7 and the power required for stirring are also shown.

[0012]

[Table 1]

In the present embodiment, in the first-stage stirring tank 6, crushed coal I (18
6 kg / h) and the required amount of desulfurizing agent (4 kg / h) are stirred and mixed together with the total amount of added water, so that C in the stirring tank 6
WP has a low viscosity of 0.55 Pa · s, and the required power is low with respect to the tank capacity. The low-concentration CWP efficiently stirred with low power in the first-stage stirring tank 6 is stirred and mixed in the second-stage stirring tank 7 with the remaining pulverized coal II (64 kg / h). The required power required to obtain the properties equivalent to those of the CWP manufactured by the conventional method is 1.3 kW. The total power required for this example is 3.6 kW, which can be reduced by 20% compared to the conventional method of 4.5 kW.

Example 2 In this example, A charcoal was supplied at 655 kg / h on a dry coal basis, and the stirring tank capacity was large. Example 1
A charcoal is crushed with a roll crusher 3 in the same way as
After classifying with a sieve 4, it is supplied to a distributor 5 and distributed so that the ratio of crushed coal I to the total amount of crushed coal is 74.4% by weight. The flow rate and the measurement result in this case are shown in Table 2.

[0015]

[Table 2]

The required power of this embodiment is 8.1 kW,
28% reduction compared to 11.3 kW of the conventional method. The power reduction rate is higher than that in the first embodiment because the agitation tank 6,
This is because the larger the capacity of 7, the higher the stirring efficiency under the condition of low viscosity, and the required power for obtaining the same stirring effect was lower than expected.

Example 3 Charcoal B (water content = 7.0%, fuel ratio = 1.0, ash content = 42)
%) On a dry coal basis at a rate of 250 kg / h, the B carbon is crushed and classified in the same manner as in Example 1, and then supplied to the distributor 5.
Distribute so that the ratio of crushed coal I to the total amount of crushed coal is 61.7% by weight. Table 3 shows the flow rate and measurement results in this case.
It was shown to.

[0018]

[Table 3]

Table 3 shows the analysis values of the coal concentration and viscosity of the CWP in the tanks supplied to the stirring tanks 6 and 7 in comparison with the conventional method and this embodiment. The capacity of each tank 6 and 7 and the power required for stirring are also shown. Since charcoal B has a large amount of ash, yield stress is likely to occur in the manufactured CWP and sedimentation is difficult to occur. On the other hand, viscosity is not lowered unless the coal concentration is considerably lowered, and the distribution ratio is lowered.
Nevertheless, the required power of this example was 3.5 kW, which was 19% less than the conventional method of 4.3 kW.

Embodiment 4 This embodiment is an example which was examined by focusing on making the device compact rather than reducing the power. A charcoal on a dry coal basis 2
When 50 kg / h was supplied, the carbon A was crushed and classified in the same manner as in Example 1 except that the stirring tanks 6 and 7 had a small capacity. Is 74.4% by weight. Table 4 shows the pulverization degree supplied to the stirring tank, the flow rates of water and the desulfurizing agent, the analysis values of the coal concentration and viscosity of the CWP in the tank at that time, the capacity of each tank, and the power required for stirring in the conventional method. This is shown in comparison with this example.

[0021]

[Table 4]

In this embodiment, the capacities of the agitation tanks 6 and 7 were reduced, and the average residence time during agitation and mixing was shortened.
The required power required is higher than that in the first embodiment. as a result,
The required power is 4.5 kW, which is the same as the conventional method.
However, the total volume of the stirring tanks 6 and 7 was reduced by 28% as compared with the conventional method, and the manufacturing apparatus was made compact.

Next, the flow of another apparatus to which the present invention is applied is shown in FIG. In FIG. 2, the raw coal in the raw coal bunker 1 is quantitatively cut out from the feeder 2 and supplied to the roll crusher 3. The crushed carbon obtained in the roll crusher 3 is supplied to the distributor 5, and a part of the crushed carbon (hereinafter, crushed carbon
(Abbreviated as I) is supplied to the sieve 4 to remove coarse particles.
The remaining crushed coal (hereinafter abbreviated as crushing degree II) of the crushed coal is further crushed by the hammer crusher 11. The crushed coal discharged from the sieve 4 and the hammer crusher 11 is supplied to the stirring tank 12. The inside of the stirring tank 12 is divided into two chambers. In the first chamber 12a, water necessary for producing limestone and CWP is added as a desulfurizing agent in addition to the ground coal I supplied from the sieve 4, and the stirring machine Stir and mix with 8. Since the above operation is continuously performed, the CWP having a low coal concentration in the stirring tank 12a is extruded into the second chamber 12b, and the hammer crusher 11 in the second chamber 12b.
It is stirred and mixed by the stirrer 9 with the remaining crushed carbon II supplied from. The manufactured CWP is supplied to a furnace (not shown) by the CWP pump 10.

The roll crusher 3 has a maximum diameter of about 50 m.
Conditions are set so that m of raw coal can be crushed to a particle size of 10 mm or less. On the other hand, the hammer crusher 11 is 6m
It is set so that crushed carbon of m or less can be crushed to a particle size of 2 mm or less. Other conditions are the same as those of the device shown in FIG.

Using the apparatus shown in FIG. 2, C charcoal (1.5
%, Fuel ratio = 2.8, ash content = 9%). An example at this time is shown below. Example 5 C charcoal was supplied at 300 kg / h on a dry coal basis and crushed to 6 mm or less by a roll crusher 3. Distributor 5 distributed so that the ratio of crushed coal I to the total amount of crushed coal was 85.4%, and a small amount was mixed in with sieve 4 6m
After removing coarse particles of m or more, the coarse particles are supplied to the first chamber 12a of the stirring tank 12. Crushed carbon II is hammer crusher 1
After re-grinding with No. 1, it is supplied to the second chamber 12b of the stirring tank 12. In the case of coal having a low ash content and a large fuel ratio, such as C coal, it is necessary to separately re-grind and produce a fine particle group because fine particles are insufficient in the crushed carbon of 6 mm or less. Table 5
Shows the flow rates of the pulverized coal, water, and the desulfurizing agent supplied to the stirring tank 12, and the analysis values of the coal concentration and viscosity of the CWP in the tank at that time in comparison with the conventional method and this example. The capacities of the first chamber 12a and the second chamber 12b of the stirring tank 12 and the power required for stirring are also shown.

[0026]

[Table 5]

In this embodiment, the first chamber 1 of the stirring tank 12 is
85.4% of the total amount of crushed coal in 2a I
(256 kg / h) and the required amount of desulfurizing agent (5 kg / h) are stirred and mixed together with the total amount of added water, so that C
WP has a low viscosity of 0.3 Pa · s, and requires less power for the tank capacity. The low-concentration CWP efficiently stirred with low power in the first chamber 12a is stirred and mixed with the remaining pulverized coal II (44 kg / h) in the second chamber 12b.
In this example, the required power required to obtain the properties equivalent to the properties of the CWP manufactured by the conventional method is 2.9 kW, which can be reduced by 40% compared with 4.8 kW of the conventional method. As described above, the present embodiment has been described in detail, but a container rotating type (for example, a concrete mixer) stirring device may be used as the stirring devices 8 and 9 other than those in which the stirring blades rotate, and the purpose can be sufficiently achieved. Can be achieved.

Next, the results of preliminary experiments for determining the distribution ratio of coal suitable for stirring and mixing CWP are shown. A charcoal of 6 mm or less (water content = 4%, fuel ratio = 1.8, ash content = 15.5%) in a beaker with a capacity of 0.5 liters 300
g (dry coal base) with a stirrer (blade diameter φ60)
C while mixing with 4.6 g and 4 g of desulfurizing agent of 3 mm or less
Adjust WP. This adjustment condition is standard for A coal, and the coal concentration in CWP is 78 wt%. Here, the stirring condition was 1000 rpm × 10 minutes. Table 6 shows the distribution ratio of A charcoal to a predetermined amount of 300 g when the distribution amount of A charcoal is changed (distribution ratio for producing pulverized coal I in which water and a desulfurizing agent are mixed in each of the examples). And the measured values of the coal concentration and viscosity of the prepared CWP are shown. Furthermore, the CWP prepared under each condition was arbitrarily sampled 10 times, and the particle size passing through a 1 mm sieve was measured.

[0029]

[Table 6]

FIG. 3 shows the relationship between the distribution ratio φ of A charcoal and the variation of the measured sieve passage ratio with respect to the average value. Here, the variation is displayed as an absolute value. The large variation means that the prepared CWP is inhomogeneous and particles are easily aggregated or separated by sedimentation. From this figure, it can be seen that the variation is minimum when the distribution ratio φ is in the range of 60 to 90% by weight. This suggests that there are suitable conditions for stirring and mixing the CWP. The variation is large when φ <60% by weight because of CW
This is because P has a low viscosity and coarse particles in CWP tend to settle out easily. Even if φ> 90% by weight, the variation becomes large because the viscosity of CWP increases and coal particles are less likely to mix with water. Is.

From the above examination, it has been clarified that in the case of producing CWP, crushed coal and water are not simply mixed, but the mixing method is very important. The coal / water paste of the present invention is not limited to the pressurized fluidized bed boiler and can be used as a fluid fuel used in other combustion furnaces.

[0032]

As described above, according to the present invention, the CW is used.
It is possible to stably supply P with a smaller amount of water and to provide a CWP manufacturing method that requires no manufacturing power.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a distribution ratio of coal and a CWP property.

[Explanation of symbols]

1 ... Raw coal bunker, 2 ... Feeder, 3 ... Roll crusher, 4 ... Sieve, 5 ... Distributor, 6, 7, 12 ... Stirring tank, 8, 9 ... Stirrer, 10 ... CWP pump, 11 ... Hammer crusher

Continued front page (72) Inventor Katsuya Oki 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Kure factory (72) Inventor Kodai Nonaka 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Kure factory Within

Claims (5)

[Claims] 1. A method for producing a coal / water paste comprising the steps of crushing raw coal and mixing crushed coal with water,
First, after mixing a part of the amount of crushed coal required for the production of coal / water paste with the total amount of water required for the production of coal / water paste to form a coal / water paste, the rest of the amount of crushed coal is mixed. A method for producing a coal / water paste, which comprises stirring. 2. A coal / water paste is prepared by mixing 60 to 90% by weight of the amount of crushed coal required for the production of the coal / water paste at the time of first mixing the coal and water together with the total amount of water required for the production. The method for producing a coal / water paste according to claim 1, which is characterized in that. 3. A method for producing a coal / water paste, comprising the steps of crushing raw coal and mixing crushed coal with water,
First, a part of the amount of crushed coal required for the production of coal / water paste is mixed with the total amount of water required for the production of coal / water paste to form a coal / water paste, and then the rest of the amount of crushed coal is pulverized again. A method for producing a coal / water paste, which comprises mixing the coal / water paste as finely ground pulverized coal and stirring the mixture. 4. A coal / water paste manufacturing device comprising a raw coal crushing device and a stirring device for mixing the crushed coal with water, wherein a part of the amount of crushed coal required for manufacturing the coal / water paste is required for the production. At least two or more stirrers comprising a first-stage stirrer that mixes with the total amount of water to form a coal / water paste, and a second-stage and below stirrer that mixes and stirs the remaining amount of crushed coal. A coal / water paste manufacturing device characterized by being provided. 5. A coal / water paste manufacturing device comprising a raw coal crushing device and a stirring device for mixing the crushed coal with water, wherein a part of the amount of crushed coal required for manufacturing the coal / water paste is required for the production. At least two or more stirrers comprising a first-stage stirrer that mixes with the total amount of water to form a coal / water paste, and a second- or lower stirrer that mixes and stirs the remaining amount of crushed coal. An apparatus for producing a coal / water paste, comprising crushing means for crushing the crushed coal supplied to the stirring means at the second and subsequent stages again.