JPH01310220A - Combustion method for coal and water mud - Google Patents

Abstract

PURPOSE:To prevent consumption of boiler-generating steam and to prevent lowering of boiler efficiency due to the vaporizing latent heat of a moisture content in CWM, by a method wherein a coal and water mud drier to dry coal and water mud by means of exhaust gas is mounted in a boiler exhaust gas flue, and dried coal and water mud is fed to a boiler. CONSTITUTION:A coal and water mud (CWM) drier 3 is disposed in a duct running between the outlet of an electric dust collector 10 located in the middle of an exhaust gas duct 9 and a chimney, and a dried CWM collector 11 in a duct between the drier 3 and a chimney 12. CWM stored in a CWM storage tank 1 is boosted with the aid of a pump and fed in the drier 3 through a CWM piping 2. CWM is brought into direct contact with boiler exhaust gas and dried so that a weight ratio between coal and water is kept at approximate 85:15-95:5, and CWM forms a small lumpform substance which is discharged. Boiler exhaust gas enters the collector 11 in a state that a part of dried pulverized coal in the CWM is brought into a floating state, and after floating dried pulverized coal is separated, the boiler exhaust gas is discharged to the atmosphere. Pulverized coal is dropped onto a conveyor and carried on a concentralized conveyor togetherwith the CWM for recombustion.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for burning coal-water slurry (hereinafter referred to as CWM), which is made by mixing finely pulverized coal and water to form a slurry. It is.

[Conventional technology] CWM was developed as a method for using coal as an alternative fuel to petroleum, and it involves pulverizing coal into fine powder using a mill, etc., and mixing it with water to obtain a coal concentration of approximately 65 to 70%. By making it into a slurry, it can be transported by pipe on land in the same way as liquid fuel, and when loading and unloading onto and from transport ships, lignite equipment, etc. can be transported via pipes without the need for military quays. In addition to being able to transport
It has been researched and developed as an excellent fuel type that has the advantage of being able to be handled almost in the same way as heavy oil when burned in boilers, etc., and has already been put into practical use in some areas.

However, as mentioned above, in CWM, the mixing ratio of coal and water is about 65:35 to 70; In addition to having a large amount of heat, it also required spraying with an atomizing medium when burning in a combustion furnace of a boiler. C.W.
It is preferable for M to have a higher coal concentration from the point of view of reducing transportation costs or improving combustion efficiency, but along with this, CWM
As the viscosity of fuel increases dramatically, the amount of atomizing medium required for conventional heavy oil combustion is approximately 5% of the amount of fuel, whereas in the case of CWM, approximately 20% of the amount of vapor is required. . When considering a boiler, the amount of steam required for this spraying corresponds to about 4% of the amount of steam obtained by burning the CWM, and has a large effect on the overall efficiency of the boiler. FIG. 3 is a system diagram of a CWM-fired boiler facility based on a conventional combustion method. In Fig. 3, 51 is a CWM storage tank, 52 is a CWM pipe, 53 is a boiler, 54 is a CWM spraying steam pipe, 55
5 is a duct for boiler exhaust gas, 56 is an electric precipitator, and 57 is a chimney. The CWM stored in the CWM storage tank 51 is pressurized by a pump or the like, and is sent to a burner attached to a boiler 53 via a CWM pipe 52. The CWM fed into the burner is atomized by the atomizing steam supplied from the boiler via the atomizing steam pipe 54, and is atomized into the combustion chamber, where it is combusted. The gas generated by combustion undergoes heat exchange in the boiler, and is cooled down to about 140°C. After that, it is led to an electrostatic precipitator 56 through an exhaust gas duct 55 to remove dust such as fly ash in the exhaust gas, and then the chimney. 57 and released into the atmosphere.

[Problems to be Solved by the Invention] As described above, even in the above-mentioned conventional technology, coal, which is originally solid, is pulverized and mixed with water to form a slurry, which makes it possible to handle it as a liquid fuel. This has the advantage that combustion equipment can be used to carry out combustion using almost the same equipment as when burning heavy oil. However, when spraying CWM with a burner, CWM
When a large pressure is applied to the CWM, local concentration changes occur in the CWM in the pipe, and the CWM in the high concentration area becomes extremely viscous, loses fluidity, and creates a blockage in the pipe.
Steam was usually used as the medium for spraying. The atomizing steam consumed at this time corresponds to about 4% of the total amount of steam obtained by burning the CWM, which has the disadvantage of reducing the overall efficiency of the boiler.

[Means for solving the problem] As described in the claims, the means for solving the above problem is as described in the claims, in a boiler that burns a coal/water slurry, the coal that is dried by the boiler exhaust gas is placed in the boiler exhaust gas flue.・A coal/water slurry combustion method characterized by installing a water slurry dryer and supplying the dried coal/water slurry to a boiler, or a coal/water slurry combustion method characterized by installing a mill and supplying the dried coal/water slurry to a boiler. This is a coal/water slurry combustion method in which dried coal/water slurry is crushed and supplied to a boiler.

[Function] A CWM dryer is installed in the duct between the outlet of the electrostatic precipitator and the chimney, which is installed in the middle of the exhaust gas duct of the boiler, and the CW
A dry CWM dust collector is installed in the duct between the M dryer and the chimney. The CWM stored in the CWM storage tank is pressurized by a pump or the like and sent into the CWM dryer via CWM piping. The injected CWM is discharged from the CWM piping and comes into direct contact with the boiler exhaust gas, resulting in a coal-to-water weight ratio of 8.
It is dried to a ratio of about 5+15 to 95:5, and is discharged onto a conveying facility, for example, a conveyor, in the form of small lumps. C.W.
In the M dryer, the boiler exhaust gas that comes into contact with the CWM and dries the CWM enters the dry CWM dust collector with a part of the dry pulverized coal in the CWM suspended, and the suspended dry pulverized coal is separated. It is then released into the atmosphere through chimneys. C.W.M.
The dry-dried pulverized coal collected in the duster falls onto the conveyor and is fed onto the gathering conveyor together with the dry CWM discharged from the CWM dryer. If the boiler is capable of burning lump coal, such as a fluidized bed boiler, the dry lump CWM discharged from the CWM dryer described above is fed and combusted, but if the boiler is a pulverized coal-fired boiler, the mill is Install and CWM
The lumpy dry CWM discharged from the dryer is again pulverized and supplied to the boiler. Therefore, according to the present invention, the CWM is dried by using the boiler exhaust gas that was conventionally discharged from the chimney, and the CWM spraying steam is sent to the boiler without being consumed, thereby preventing the consumption of the boiler-generated steam. This has the effect of preventing a decrease in boiler efficiency due to the latent heat of vaporization of water in the CWM and increasing the overall efficiency of the boiler equipment.

[Example] Examples of the present invention will be described below based on drawings and tables.

Figure 1 shows the CWM in a boiler that burns CWM according to the present invention, in which a CWM dryer and a dry CWM @ duster are installed in the exhaust gas system, and a mill is installed in the fuel system that feeds the boiler to the burner. A system diagram of the boiler-fired equipment, Fig. 2 is a system diagram when the mill is not installed in the fuel system in Fig. 1, and Table 1 shows the system diagram of the conventional CWM-fired boiler and the CWM-fired boiler based on the present invention. This is a table showing a comparison of efficiency, steam savings, etc. In Figures 1 and 2, 1 is a CWM storage tank;
2 is a CWM pipe, 3 is a CWM dryer, and 4 is a drying CWM stiff conveyor discharged from the CWM dryer.
The dust conveyor for dry CWM discharged from the M dust collector is a collection conveyor for dry CWM, 6 is a mill for re-pulverizing the dry CWM, 7 is a transport pipe for dry CWM re-pulverized into fine powder, 8 is a boiler, and 9 is a conveyor for dry CWM. A duct for boiler exhaust gas, 10 an electric precipitator, 11 a dust collector for collecting dry CWM, and 12 a chimney. In FIG. 1, the exhaust gas duct 9 of the boiler 1
Electrostatic precipitator 10 and chimney used in military service (Note) (1)
11 is the dryness of CWM that is not in a fluidized state.

(2) Pull out the CWM dryer and check the temperature of the exhaust gas at the exit of the dryer.

(3) The annual operating time of the boiler was 11,000 hours.

CWM dryer 3 and 12 dryer C in the duct between Nu1 Table 12
A WM$ duster 11 will be installed. The CWM stored in the CWM storage tank 1 is pressurized by a pump or the like, and is sent into the CWM dryer 3 via the CWM piping 2. The injected CWM directly contacts the boiler exhaust gas from which dust has been removed by the electrostatic precipitator 10 in the CWM dryer 3, and the weight ratio of coal to water is approximately 85:1.
It is dried to a ratio of about 5 to 95:5 and is discharged onto the conveyor 4 in the form of relatively brittle small lumps.

The boiler exhaust gas that contacts the CWM in the CWM dryer 3 and dries the CWM causes a part of the dried CWM to be suspended in the exhaust gas in a fine powder state, and enters the dry CWM dust collector 11 . Dry CWM# & dust container 11 The pulverized coal in the internal container 11 is separated from the exhaust gas, and the exhaust gas is sent into the chimney and released into the atmosphere, while the separated and collected pulverized coal is discharged onto the conveyor 4°. do. CWM dryer 3 and dry CWM dust collector 11
The dry CWM discharged from conveyors 4 and 4
' and then sent onto the collecting conveyor 5. When the boiler 8 is a pulverized coal combustion boiler, since most of the dry CWM conveyed by the collection conveyor 5 is in the form of small lumps, a mill 6 is provided to send the entire amount of dry CWM into the mill 6. After being re-pulverized into a fine powder, the primary air sent from the primary blower 13 is sent to the burner of the boiler 8 for combustion. Because of its high brittleness, it can be re-pulverized in a short time with extremely low power. FIG. 2 shows the case of a boiler capable of burning lump coal, such as a fluidized bed boiler. It is possible to carry out combustion by directly feeding the dry CWM in the form of small pieces conveyed by the collection conveyor 5 into the combustion chamber of the boiler 8 without any installation. Table 1 is a table showing a comparison of boiler efficiency, steam savings, etc. between a conventional CWM-fired boiler and a CWM-fired boiler based on the present invention.
Steam generation amount 1'OOt/h, steam pressure 100A/c
Calculated for one boiler with x2G and steam temperature of 500°C. Based on the present invention in the word list (CWM
Assuming three concentrations of CWM to be fed into the boiler, the weight ratio of coal to water is 85:15, 90:10, and 95:5.
A comparison is made for each.

[Effects of the Invention] Since the present invention is configured as described above, it produces effects as described below.

By using the exhaust gas that was originally released into the atmosphere from the chimney as a heat source for CWM drying, there is no cost for the heat source itself.

It becomes possible to use CWM as a fuel in conventional pulverized coal-fired boilers or fluidized bed boilers, etc., without sacrificing the advantages of CWM in transportation or storage.

Dry the CWM and reduce the coal to water weight ratio to the original 65:
The economic advantage of increasing the ratio from 35 to 85 + 15 to 95:5 and not using steam as a medium when feeding the boiler is that the boiler efficiency increases by about 4 to 5%, and the amount of steam saved is equal to the amount of steam generated. In a 100 t/h boiler, the annual output reaches approximately 32,000 tons. The economic benefits obtained from this are due to the equipment required to carry out the invention, such as CWM dryers, dry CWM precipitators, conveyors, mills or lower temperatures due to lower exhaust gas temperatures.
Even when considering the cost of facilities such as desulfurization equipment as food countermeasures, it has the effect of ensuring sufficient economic efficiency.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a boiler facility based on the present invention in which a CWM dryer and a dry CWM precipitator are installed in the exhaust gas system and a mill is installed in the fuel system. It is a system diagram when a mill is not arranged. FIG. 3 is an example of the prior art. 1... CWM storage tank, 2... CWM piping, 3... CWM dryer, 4.4', 5...
・・Conveyor for drying CWM, 6・・・・Mill, 7・
...Dry CWM transport pipe, 8...Boiler,
9...Exhaust gas duct, 10...Electric precipitator, 11...Dry CWM dust collector, 12...
...Chimney, 51...CWM storage tank, 52...
...CWM piping, 53...Boiler, 54...
... CWM spraying steam piping, 55 ... Exhaust gas duct, 56 ... Electric precipitator, 57 ...
··chimney.

Claims (1)

[Claims] 1. In a boiler that burns coal/water slurry, a coal/water slurry dryer that is dried by boiler exhaust gas is installed in the boiler exhaust gas flue, and the dried coal/water slurry is supplied to the boiler. A method for burning coal/water slurry, characterized by: 2. The method for combustion of a coal/water slurry according to claim 1, wherein a mill is provided, and the coal/water slurry dried by the coal/water slurry dryer is pulverized and supplied to the boiler. 3. The coal/water slurry according to claim 1 or 2, wherein a dust collector for collecting the dried coal/water slurry is installed in the exhaust gas flue between the coal/water slurry dryer and the chimney, which are dried by the boiler exhaust gas. How to burn water slurry.