JPH0547598B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for efficiently drying and pulverizing solid fuels such as coal and coke. [Prior Art] Conventionally, when coal is burnt as pulverized coal in a coal-fired boiler or the like, coal from a coal storage yard is dried in a hot gas type vertical roller mill 1 or the like as shown in Fig. 3. After drying in a mill to a moisture content of 2% or less, it was separated using a separator 2 to obtain product coal, which was then supplied to boiler coal feeders and the like. [Problems to be solved by the invention] Coal stored in a coal storage yard normally contains around 10% moisture, but during the rainy season, the moisture content changes seasonally to over 15% and also changes over time. On the other hand, in hot gas drying mills, when the moisture content in raw coal becomes high, the crushing capacity decreases significantly. For this reason, in the conventional method, a mill with excessive capacity had to be installed in consideration of moisture fluctuations in the raw coal. Although pre-drying may be considered, the particle size of coal in coal storage yards is coarse (usually about 20 mm in diameter), and it is difficult to pre-dry it by airflow drying or the like. The present invention was developed in view of the above points, and by pre-drying solid fuel such as coal and coke to maintain the moisture content in the solid fuel supplied to the mill within a certain range, product quality is stabilized and The object of the present invention is to provide a drying and pulverizing method that can reduce the capacity of a mill. [Means and effects for solving the problem] The solid fuel drying and pulverizing method of the first invention of the present application is such that solid fuel having a relatively high moisture content discharged from a solid fuel storage yard is shafted in an inclined rotating cylinder. The solid fuel is introduced into a material inch tube type tube dryer, which has a large number of tubes arranged in the direction of the tube, circulates the solid fuel inside the tubes, and circulates a heating medium outside the tubes to indirectly heat the solid fuel. The solid fuel is supplied to a hot gas drying mill after the moisture content is adjusted to 6% by weight or less. In addition, the solid fuel drying and pulverizing method of the second invention of the present application pre-pulverizes solid fuel with a relatively high water content discharged from a solid fuel storage yard to a particle size of 10 mm or less, and then rotates the pre-pulverized product by rotating it at an inclined angle. The solid fuel is introduced into a material inch tube type tube dryer in which a large number of tubes are disposed in the axial direction within a cylinder, the solid fuel is passed through the tubes, and a heating medium is passed outside the tubes to indirectly heat the solid fuel. The method is characterized in that after the moisture content of the solid fuel is adjusted to 6% by weight or less, the solid fuel is supplied to a hot gas drying mill. According to the method of the present invention, if the moisture content is adjusted in advance to 6% by weight or less, preferably 3% by weight or less using a tube dryer, the mill in the next process can be used at the maximum efficiency of approximately 100% mill capacity. can. Furthermore, variations in the moisture content of the solid fuel that occur in the solid fuel storage yard can be adjusted using the tube dryer. When the moisture content in the solid fuel at the outlet of the tube dryer exceeds 3% by weight, the milling capacity begins to decrease, reaching 90% with a moisture content of 7% by weight and 80% with a moisture content of 10% by weight.
% or less. Since the tube dryer is an indirect heating dryer, it has high thermal efficiency and can easily respond to fluctuations in the amount of processing and drying by increasing the pressure of the heating medium such as steam. Absorbs moisture fluctuations in fuel. Furthermore, the solid fuel in the solid fuel storage yard has a particle size of about 50 mm or less, usually about 20 mm, and it is desirable to pre-pulverize it to a particle size of 10 mm or less before supplying it to the tube dryer. This pre-grinding significantly improves the grinding efficiency of the mill, as shown in the Examples below.
In the preliminary crushing, if the particle size exceeds 10 mm, the crushing efficiency of the mill will not improve that much, and furthermore, the efficiency of drying with a tube dryer will decrease. [Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings, in the case where coal is used as the solid fuel. However, unless there is a specific description, the shapes of the components described in this example, their relative positions, etc. are not intended to limit the scope of the present invention to these, but are merely illustrative examples. Only. As shown in Figure 1, raw coal with a relatively high moisture content (usually 10% or more) discharged from a coal storage yard is pre-pulverized to a particle size of 10 mm or less in a crusher 3, and this pre-pulverized coal is introduced into a tube dryer 4. After controlling the moisture content of the coal to 5% or less, the coal is supplied to a hot gas drying mill such as a hot gas type vertical roller mill 1 or a fan mill to reduce the moisture content to 2% or less. A mixture of exhaust gas and pulverized coal from the vertical roller mill 1 is introduced into a separator 2 and separated into the exhaust gas and product pulverized coal having a water content of 2% or less. If the grain size of the raw coal in the coal storage yard is small,
The pre-pulverization step in the crusher is omitted and the powder is directly introduced into the tube dryer 4. As the tube dryer 4, a large number of tubes 6 are disposed in the axial direction in an inclined rotating cylinder 5, coal in the form of powder and granules is passed through the tubes, and a heating medium such as steam is passed outside the tubes to dry the coal. Use a Ube-type material that heats the material indirectly. 7 is a heating medium flow path. Note that instead of separating the product pulverized coal with the separator 2, as shown in FIG. 2, the mixture of exhaust gas and pulverized coal may be directly supplied to the boiler 8 without providing a separator. Next, an experimental example conducted by the present inventors will be explained. In this experimental example, a conventional method shown in FIG. 3 and a method of the present invention shown in FIG. 2 were conducted using a vertical roller mill of the same capacity. The conditions and results are shown in the table below.

〔Effect of the invention〕

Since the present invention is configured as described above, there is no need to increase the capacity of the mill, and the capacity of the mill can be reduced, thereby reducing operating costs. In addition, product quality is stabilized and improved by pre-drying with a tube dryer and keeping the moisture content of the solid fuel supplied to the mill within a certain range. Furthermore, by charging the pre-dried solid fuel into the mill, the amount of water vapor generated in the mill is reduced, and even when the pulverized solid fuel is supplied directly from the mill to the boiler together with the exhaust gas, it has favorable effects in terms of thermal efficiency.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of an apparatus for carrying out the solid fuel drying and pulverizing method of the present invention, FIG. 2 is a flow sheet showing another example of an apparatus for carrying out the method of the present invention, and FIG. This is a flow sheet of an apparatus for carrying out a conventional solid fuel drying and pulverizing method. 1... Vertical roller mill, 2... Separator, 3
...Crushier, 4...Tube dryer, 5...
... inclined rotating cylinder, 6 ... tube, 7 ... heating medium channel, 8 ... boiler.

Claims (1)

[Scope of Claims] 1. Solid fuel with a relatively high moisture content discharged from a solid fuel storage yard is collected by disposing a large number of tubes in the axial direction in an inclined rotating cylinder, and flowing the solid fuel through the tubes. The solid fuel is introduced into a material inch tube type tube dryer that indirectly heats the solid fuel by circulating a heating medium to the outside, and after controlling the moisture content of the solid fuel to 6% by weight or less, the solid fuel is transferred to a hot gas drying mill. A method for drying and pulverizing solid fuel, characterized by supplying solid fuel. 2. Solid fuel with a relatively high moisture content discharged from a solid fuel storage yard is pre-pulverized to a particle size of 10 mm or less, and this pre-pulverized material is placed in a tilted rotating cylinder with a number of tubes arranged in the axial direction. After introducing the solid fuel into a material tube type tube dryer that indirectly heats the solid fuel by circulating solid fuel inside the tube and circulating a heating medium outside the tube, the moisture content of the solid fuel is adjusted to 6% by weight or less. A method for drying and pulverizing solid fuel, which comprises supplying this solid fuel to a hot gas drying mill.