JPS6317990A - Wet production of coal-water slurry in high concentration - Google Patents

Abstract

PURPOSE:To readily obtain a coal.water slurry in a high concentration without containing coarse particles, by separating the coarse particles from a wet pulverized coal.water slurry, blending the coarse particulate slurry with part of fine particulate slurry, circulating the resultant blend and preparing the residual fine particulate slurry. CONSTITUTION:Coal, together with water, a dispersing agent and adjusted slurry, is pulverized in a wet ball mill to give a coal slurry. Coarse particles are then separated from the above-mentioned slurry with a wet classifier. The classified coarse particulate coal slurry is then blended with part of fine particulate coal slurry to give as an adjusted slurry, which is then circulated and fed to the above-mentioned wet ball mill.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wet method for producing a highly concentrated coal/water slurry that does not contain coarse particles.

[Prior Art] A highly concentrated coal/water slurry can be used not only for transportation and storage but also for direct combustion by fluidizing coal, which is a solid fuel.

Furthermore, it is an effective fuel because it can reduce ash and sulfur content.

When a highly concentrated coal/water slurry is burned in a combustion device such as a power generation wheeler, the combustion time is affected by the coal fuel ratio, ash content, particle size, oxygen concentration, combustion temperature, etc. If the residence time in the combustion equipment is not sufficient compared to the combustion time, unburned carbon will remain in the combustion residue such as fly ash that is discharged with the combustion gas, and the unburned This will result in a loss. Furthermore, when reducing the air ratio and lowering the combustion temperature to some extent in order to suppress NOx emissions in the combustion gas, the combustion time similarly increases.

In particular, when burning highly concentrated coal/water slurries containing coarse particles, NOx emissions are observed in the combustion gas due to an increase in the unburned carbon content in the combustion residue, such as fly ash, and an increase in the air-to-air ratio. .

Therefore, as a manufacturing method for highly concentrated coal/water slurry, it is a challenge to realize a wet manufacturing method for highly concentrated coal/water slurry made of fine particles that do not contain coarse particles, and it is required that these be realized economically. has been done.

Conventionally, this type of wet production method for highly concentrated coal/water slurry involves adding appropriate amounts of water and a dispersant to coal from one end of a wet ball mill, as described in, for example, JP-A-60-13887. Grinding media (steel balls) with different diameters, large and small, are supplied with the agent.
The coal is wet-pulverized by rotating the multiple crushers of a wet-type ball mill, each of which is filled with coal, to produce coal slurry, and it is possible to wet-manufacture a highly concentrated coal/water slurry.

Furthermore, as a wet method for producing highly concentrated coal/water slurry that does not contain coarse particles, attempts have been made to apply the open circuit wet pulverization method used in wet processing of ores, etc. The coal slurry is classified into coarse coal slurry and fine coal slurry, and the coarse coal slurry is returned to the wet ball mill, where it is circulated and wet-pulverized repeatedly, and the fine coal slurry is adjusted to produce a high-quality coal slurry that does not contain coarse particles. Wet production of concentrated coal/water slurry is carried out.

[Problems to be Solved by the Invention] However, in the conventional wet manufacturing method of highly concentrated coal/water slurry described above, it is not possible to produce a highly concentrated coal/water slurry that does not contain coarse particles using a simple manufacturing method. The problem was that it was difficult.

In other words, when using highly concentrated coal/water slurry in power generation boilers, etc., a wet classifier with large capacity is required, but the coal slurry produced by a wet ball mill has high viscosity and low fluidity. Due to the fact that
If a suitable method that can meet the above requirements is not found and, for example, a wet sieving method is applied, the processing capacity will be limited by the sieve opening size depending on the particle size of the required fine coal slurry. Furthermore, the coal slurry is prevented from moving uniformly on the sieve surface and being discharged from the bottom end, and the coal slurry moves irregularly on the sieve surface, causing the coal concentration of coarse coal slurry and fine coal slurry to decrease. There is a problem in that slurry properties such as viscosity change, significantly reducing the separation efficiency and processing capacity of wet sieving. There was a problem that sufficient separation could not be achieved.

The present invention solves these conventional problems,
It is possible to wet-produce a highly concentrated coal/water slurry that does not contain coarse particles, and when it is fed to a combustion equipment and burned, it is an excellent highly concentrated coal that has little unburned carbon content in the combustion residue and can suppress NOx emission concentration. - Provides a wet manufacturing method for water slurry.

[Means for solving problems] In order to achieve the above object, the present invention converts coal into water.

The coal slurry is supplied together with the dispersant and the adjustment slurry to a wet-type whole mill and wet-pulverized to form a coal slurry.The coal slurry is classified into a coarse-grained coal slurry and a fine-grained coal slurry by a wet classifier that separates the coarse-grained coal slurry. and some part of the fine coal slurry to form a adjusted slurry, and the adjusted slurry is circulated and supplied to a wet ball mill,
The remaining part of the fine coal slurry is adjusted.

[Function] The present invention has the following effects due to the above configuration. That is, coal is wet-pulverized with water 2 dispersant and adjusted slurry to obtain a coal slurry, and the adjusted slurry prepared from the coal slurry has a constant flow rate of fine coal slurry related to the production amount of highly concentrated coal/water slurry. Because the ratio is adjusted and a high concentration of coal is circulated and supplied to the wet ball mill, wet grinding in the wet ball mill proceeds under an extremely stable steady state, and closed circuit wet grinding is performed. By repeatedly crushing coarse particles,
The coal concentration of the wet-pulverized coal slurry is 9 particles, the fluidity is significantly improved, and the crushing performance of the wet ball mill can be improved. As a result, the slurry properties such as coal concentration and viscosity of coarse coal slurry and fine coal slurry did not change, and coarse particles were sufficiently separated without reducing separation efficiency and processing capacity in wet sieving. Highly concentrated coal/water slurry can be produced.

Wet sieving is performed without diluting the coal concentration of the coal slurry with water, etc., so coarse particles can be sufficiently separated without the need for additional operations such as dewatering or adjusting the dehydrated cake. It is possible to produce high-concentration coal/water slurry, and when it is supplied to a combustion equipment and burned, it is possible to reduce the unburned carbon content in the combustion residue and suppress the NOx emission concentration in the combustion exhaust gas. can.

[Example] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 10 indicates a wet ball mill, and coal 14 is supplied to the wet ball mill 10 by a coal feeder 12, and at the same time, water 16, a dispersant 18, and a adjusted slurry 42, which will be described later, are supplied at a required ratio. Wet pulverization is performed to obtain a coal slurry 22 having a coal concentration of about 60% by weight or more. Subsequently, the wet sieving portion is machine 20.
Coarse coal slurry 26 and fine coal slurry 2 are continuously supplied to a wet classifier using
It is classified into 4. For the wet sieving portion, the sieve opening size of the machine 20 is selected so as to obtain the required particle size of the granular coal slurry 24, and
The coal concentration of No. 4 is approximately 60% by weight or more, and the difference from the coal concentration of coal slurry 22 is slight. The granular coal slurry 24 is transported from the storage tank 30 via the piping 32 by the pump 36, passes through the control valve 66, and is further transported to the stabilizer 5.
2 is added and mixed in the kneader 50.

After adjustment by cross-talk, a highly concentrated coal/water slurry 54 having a coal concentration of about 60% by weight or more, containing no coarse particles, and having excellent fluidity and stability is continuously produced.

The coarse coal slurry 26 is supplied to the storage tank 40 using a suitable transportation means, and a part of the fine coal slurry retained in the storage tank 30 is transported by a pump 38 via a pipe 34. , is supplied to the storage tank 40 described above. Therefore, the coarse coal slurry 26 and some of the fine coal water slurry are mixed to form the adjusted slurry 42,
The adjusted slurry 42 containing coarse particles and having a coal concentration of approximately 60% by weight or more is transported by the pump 46, passed through the adjustment valve 68, and returned to the wet ball mill 10 for circulation.

The regulating valves 66 and 68 each receive a control signal 64 from the controller 60.
65, the flow rate of the remaining granular coal slurry and the flow rate of the adjusted slurry are adjusted to be a constant ratio, and by the above adjustment, the flow rate of coal newly supplied to the wet ball mill 10 and the flow rate of coal in the adjusted slurry are adjusted. Closed-circuit wet pulverization is performed with a circulation ratio that is a constant ratio, and coarse particles contained in the adjusted slurry 42 are gradually pulverized and reduced as the number of circulation increases, and are transferred to the granular coal slurry 24. Ital. The input signal 62 to the controller 60 is the flow rate of the highly concentrated coal/water slurry 54 .

Various parameters including coal concentration and E coal particle size are input. Further, in the storage tanks 30 and 40, liquid level control is performed so that a required slurry liquid level is maintained. Thus, the wet ball mill 10 contains coal 14. The new feed consisting of water 169 and dispersant 18 and the returned adjusted slurry are mixed so as to have the same coal concentration and are supplied so as to obtain the required circulation ratio. As wet pulverization progresses under an extremely stable steady state without any change in the concentration of the mixing system, and coarse particles gradually decrease through closed-circuit wet pulverization, the coal concentration of the coal slurry decreases to 9. Particle size and fluidity are significantly improved, and the grinding performance of the wet ball mill 10 can be improved, and coarse particle separation in the wet classifier 20 is carried out so that the coal slurry 22 is moved uniformly on the sieve surface. As a result, the slurry properties such as the coal concentration and viscosity of the coarse coal slurry 26 and the fine coal slurry 24 are unchanged, and the coarse particles are sufficiently removed without reducing the separation efficiency and processing capacity in wet sieving. The separated high-concentration coal/water slurry 54 can be produced, and can also be prepared to exhibit good slurry properties.

As described above, according to the above embodiment, a highly concentrated coal/water slurry in which coarse particles are sufficiently separated can be obtained, and additional operations such as dewatering operation and dewatering cake adjustment are not required.
The effect is that highly concentrated coal/water slurry can be produced using a simple method.

It goes without saying that the aspects of the wet ball mill, wet classifier, control means, etc. in the present invention are not limited to those of the above-mentioned embodiments.

[・Effects of the invention] As is clear from the above examples, the present invention
In wet production of water slurry, closed-circuit wet pulverization can be performed to return the adjusted slurry in a wet ball mill, resulting in high-concentration coal/water slurry that does not contain coarse particles, resulting in good pulverization efficiency, pulverization performance, and reliable separation in wet classification. It can be produced in large quantities due to its efficiency and throughput, and when burned in large-capacity power generation boilers, it can have great effects in improving combustion efficiency and NOx suppression. can.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a wet manufacturing method for highly concentrated coal/water slurry according to an embodiment of the present invention. 10... Wet ball mill 14... Coal 16...
・Water 18...Dispersant 20...Wet classifier 22...Coal slurry 24...Fine coal slurry 26...Coarse coal slurry 42...
Adjusted slurry

Claims (1)

[Claims] Coal is supplied to a wet ball mill along with water, a dispersant, and a controlled slurry, and wet-pulverized to form a coal slurry.
The coal slurry is classified into a coarse coal slurry and a fine coal slurry by a wet classifier that separates the coarse particles, and the coarse coal slurry and a part of the fine coal slurry are mixed to form an adjusted slurry, and the adjusted slurry is A wet method for producing a highly concentrated coal/water slurry, characterized in that the fine coal slurry is circulated and supplied to a wet ball mill, and the remaining fine coal slurry is adjusted.