JPS5971921A - Method for purging fuel tube to feed burner for highly concentrated slurry - Google Patents

Abstract

PURPOSE:To prevent a fuel tube from being choked by highly concentrated slurry when it is solidified, by an easy method by introducing water to the fuel tube at the starting or/and stopping time of operation of a highly concentrated slurry burner. CONSTITUTION:Fuel 4 is fed to a burner chip 2 via a fuel feed valve 10 and a fuel tube 3. Spray medium 6 is fed into a burner gun 1 via a spray medium feed tube 5, being mixed with the fuel immediately before the burner chip 2, and is injected from a plurality of injection ports of a burner chip 2, being atomized. A purging medium 8 is fed into the fuel tube 3 via a purging medium feed tube 7 and a purging medium feed valve 9, purging the fuel tube 3 by pushing out the solidified fuel stagnating in the tube. When the burner is normally operated, the purging medium feed valve 9 is closed, while at the purging operation, the purging medium feed valve 9 is opened, immediately after the fuel feed valve 10 is closed. The highly concentrated slurry is evaporated and boiled nearly at 100 deg.C, and is solidified when water content is decreased. When the slurry is solidified, the burner chip 2 is easily choked, as a result, the function of a burner is stopped.

Description

[Detailed Description of the Invention] In the wake of the oil crisis, research and development on the use of coal as an alternative fuel to petroleum has been actively conducted, and various forms of fuel have begun to be produced. One of them is highly concentrated coal slurry, which is made by fluidizing coal using water as a medium, and is a mixed liquid fuel in which the weight ratio of coal and water is approximately 70%:30%. Since the highly concentrated slurry is a fluid, good spray combustion is possible by basically using a burner similar to oil.

The present invention relates to a fuel pipe purging method for starting and stopping operations of a high-concentration slurry burner that burns high-concentration slurry. This was discovered after repeated experiences and intensive research into countermeasures.

A two-fluid spray type burner that blows high-pressure steam or compressed air onto the fuel slurry is suitable for the burner that burns the highly concentrated slurry. In tests conducted by the present inventors, burner chips for high-concentration slurries were found to be of the (1) internal mixing type in which the high-concentration slurry and the atomizing medium (compressed air or steam) are mixed inside the burner; (3) An external mixing type, in which the fuel and atomizing medium are mixed outside the burner after the concentrated slurry is ejected; (3) an intermediate mixing type, in which the highly concentrated slurry is mixed with the atomizing medium immediately before being ejected from the burner;
It was possible to burn highly concentrated slurry well with either method. Therefore, the structure of the high-concentration slurry burner can be applied by slightly modifying a conventional oil burner, and no special consideration is required for burner operation under continuous operation conditions.

However, when starting and stopping a high-concentration slurry burner, it has been found that if the operating method is similar to that of an oil burner, the moisture in the high-concentration slurry evaporates within the burner, making it difficult to avoid solidification of the fuel and blockage of the burner. In other words, when starting and stopping a high-concentration slurry burner, sufficient purge performance cannot be obtained unless a completely different method is used to purge (clean) the fuel pipes in an oil burner. discovered the present invention as a result of intensive research.

The present invention is characterized in that during starting and/or stopping operations of a high concentration slurry burner, water is introduced into the fuel pipe to purge the fuel pipe in order to prevent solidification and clogging of the high concentration slurry within the fuel pipe. The present invention provides a method for purging a fuel pipe of a high concentration slurry burner. Further, the second invention of the present invention is characterized in that when starting the high concentration slurry burner, water is first introduced into the fuel pipe and then the high concentration slurry is supplied. When the slurry burner is stopped, water is introduced into the fuel pipe to purge the fuel pipe after the fuel supply is stopped. Furthermore, the fourth aspect of the present invention is that when the high-concentration slurry burner is started, the combustion is stopped! '1 Water is introduced into the pipe and high concentration slurry is continuously supplied, while when the high concentration slurry burner is stopped, water is introduced into the fuel pipe and the fuel pipe is purged after the fuel supply is stopped. There is.

Further, in the second, third, and fourth inventions, it is more effective if the driving operations are sequentially controlled.

Due to practical constraints, high-concentration slurry has a coal concentration of 50% or more.
However, the present invention applies to all types of solid content (all combustible solids such as coal, pitch, asphalt, etc.) as long as the solid content is slurried using water as a medium. It can be applied regardless of solid content concentration (50% or more or less), and all burners that fire these will be collectively referred to as high-concentration slurry burners and will be explained below.

Next, a comparative example of an oil burner and an example of a high concentration slurry burner will be described.

In the comparative examples and examples, a two-fluid spray type internal mixing burner as shown in the drawings was used.・1 in the drawing
is the burner gun which is the main body of the burner, 2 is the burner tip which is the tip of the burner, 6 is the fuel pipe, 4 is the highly concentrated slurry or oil fuel, 5 is the spray medium supply pipe for atomizing the fuel, 6 is the spray A medium (steam or compressed air), 7 is a purge medium supply pipe, 8 is a purge medium (water, steam or compressed air), 9 is a purge medium supply valve, and 10 is a fuel supply valve. The fuel 4 reaches the burner tip 2 via the fuel supply valve 10 and the fuel pipe 6, and the spray medium 6 enters the inside of the burner gun 1 via the spray medium supply pipe 5, mixes with the fuel just before the burner tip 2, and then enters the burner tip 2. The fuel is ejected from the plurality of ejection holes of No. 2, and the fuel is atomized at that time. The purge medium 8 enters the fuel pipe B through the purge medium supply pipe 7 and the purge medium supply valve 9, and purges the fuel pipe 3 by pushing out the fuel inside. During normal burner operation, the purge medium supply valve 9 is closed, and during a purge operation, the purge medium supply valve 9 is opened immediately after the fuel supply valve 10 is closed. Highly concentrated slurry evaporates and boils when the temperature approaches 100°C, and solidifies when the water content decreases. When solidified, the burner tip 2 is easily blocked and the burner stops functioning.

Comparative Example 1 This example shows the startup of an oil-fired burner. For example, in the case of cold startup of C heavy oil firing, steam is introduced from the purge medium supply pipe 7 into the burner fuel pipe B, and
In some cases, preheating the fuel reduces the viscosity of the fuel and maintains the granulation performance, but when burning kerosene or light oil, which have a low viscosity, the fuel pipe purge operation may be omitted. many. On the other hand, in a boiler equipped with multiple burners, the combustion air temperature is 30°C when the burners are started.
When the burner gun 1 is preheated to about 0°C, the burner gun 1 itself is also superheated to nearly the same temperature, but no special operation is required during normal startup.

The reason for this is that if the fuel is oil, even if the fuel temperature rises excessively, it will not cause trouble in combustion performance as long as the burner is started for a short time. As described above, when an oil-fired burner is started, there are cases in which an operation is performed to introduce steam into the fuel pipe for the purpose of preheating the fuel pipe, but in many cases, the purge operation of the fuel pipe is omitted.

Comparative Example 2 This example shows the case when the oil-fired burner is stopped. If you do not purge the fuel pipes when you stop the oil-fired burner, oil will remain in the fuel pipes, which may (1) cause the oil to gradually escape from the burner and cause an explosion or fire. (2) When the burner receives radiant heat from the furnace and convection heat from the combustion air, the burner is overheated, and the oil inside the fuel pipe is thermally decomposed and a part of it solidifies, causing the burner tip 2 to become clogged.
(3) Oils with a higher viscosity than C heavy oil may cause trouble in that the oil may solidify inside the fuel pipe O when the oil temperature drops, so the fuel pipe must be purged. Steam is usually used as the purge medium, and sometimes compressed air is used.

Example 1 This example shows the startup of a burner for high concentration slurry. A power generation boiler is assumed to be one type of combustion furnace that burns highly concentrated slurry, but in such a boiler, light oil or heavy oil is first burned to preheat the furnace, and the combustion air temperature reaches 300°C.
When it reaches a certain level, the slurry will be switched to a high concentration slurry. If high-concentration slurry is supplied directly to the burner under such conditions, burner gun 1, combustion tube 3
Because the fuel pipe was overheated to about 0.000°C, water in the highly concentrated slurry rapidly boiled on the surface of the fuel pipe, solidified the highly concentrated slurry, and the burner tip 2 was instantaneously blocked. Therefore, it is necessary to perform a purge operation to cool the fuel pipes before supplying high-concentration slurry, and an attempt was made to use steam as the purge medium, which is practiced in oil-fired systems. Blockage of the burner tip also occurred because the temperature of the tube did not drop below the steam temperature (usually 100-odd degrees Celsius). On the other hand, even with the method of cooling fuel pipes using compressed air, it takes a very long time to lower the temperature of the fuel pipe, and methods that use steam as the spray medium take a long time. However, it was found that there was a limit to the temperature drop in the fuel pipe, and it was not possible to completely prevent burner tip clogging. Based on these experiences, the best purging method that the present inventors have arrived at is the method of the present invention, which uses water as the purge medium 8. When water is used as a purge medium, as water is introduced into the fuel pipe, the water evaporates within the fuel pipe, cooling the fuel pipe and bringing it to the same temperature as the water in a short time. Thereafter, by closing the purge medium supply line and opening the high concentration slurry line, it was possible to shift to high concentration slurry combustion without any trouble.

Example 2 This example shows the case when the burner of high concentration slurry is stopped. Regarding the purging operation of the fuel pipe when the burner stops operating, in the method using steam similar to oil-fired, (1) a mutual phase change occurs at the interface between the low-temperature, high-concentration slurry and the high-temperature steam, and the temperature inside the fuel pipe increases. (2) If the burner tip 2 is made of ceramic material, the burner tip is likely to be damaged due to thermal stress caused by temperature fluctuations. (3) The flow velocity in the fuel pipe increases significantly. ,
(4) If the purge is not sufficient, the water in the highly concentrated slurry will evaporate and some solid particles will remain in the fuel pipe, causing burner blockage when restarting the burner. It has the disadvantage of. On the other hand, methods using compressed air have fewer disadvantages than steam, but when water is used as a purge medium, these problems are almost eliminated and can be the most reliable method.

As shown in the comparative examples and examples above, the present invention introduces water into the fuel pipe in order to prevent solidification and clogging of the high concentration slurry in the fuel pipe during startup and stop operations of the high concentration slurry burner. The present invention provides a method for purging fuel lines.

The reason why there has never been an example of using water as a purge medium is because the conventional technology was developed based on oil-fired burners, and (1) fuel pipes could be purged using steam or air. (2) Since the design is based on the assumption that water will not enter the fuel pipe, using water as a purge medium will cause unstable combustion and corrosion of the fuel pipe.
This is based on two reasons. However, originally 3
Regarding the newly developed fuel, which is a highly concentrated slurry containing about 0% water, the burner design assumes that it contains water, so there is no problem when using water as a purge medium. Rather, it has been found that the purging operation cannot be carried out effectively unless by the method using water as described above.

Although the present invention provides a method for performing a purge operation using water as a medium, conventional purge operations using steam or air may be used in combination as appropriate.

In addition, this method can be applied regardless of the burner structure or slurry properties (type of solid content such as coal or asphalt, solid content concentration), and can be applied not only to boilers, industrial furnaces, gasifiers, and liquefaction furnaces, but also to high-concentration slurry. Applicable to all combustion devices and reaction devices that use slurry as fuel.

On the other hand, purge operations can also be performed manually,
A sequential control circuit is constructed to automatically open the purge medium supply valve 9 before starting the burner, introduce water for a certain period of time to purge the fuel pipe, and then close the purge medium supply valve 9 and open the fuel supply valve 10. It can also be controlled.

Similarly, when the burner is stopped, the fuel supply valve 10 may be closed first, and the purge medium supply valve 9 may be immediately opened to introduce water for a certain period of time to purge the fuel pipe.

As explained above, according to the method of the present invention, by introducing water into the fuel pipe when starting and/or stopping the high-concentration slurry burner, solidification and clogging of high-concentration slurry in the fuel pipe can be easily prevented. It has the excellent effect of preventing

[Brief explanation of the drawing]

The drawing is an explanatory cross-sectional view showing an example of a two-fluid spray type internal mixing burner used in comparative examples and examples. 1... burner gun, 2... burner tip, 3...
Fuel pipe, 4...High concentration slurry or oil fuel, 5.
... Spray medium supply pipe, 6... Spray medium, 7... Purge medium supply pipe, 8... Purge medium, 9... Purge medium supply valve, 10... Fuel supply valve agent patent attorney Makoto Shiide

Claims (1)

[Claims] 1. In order to prevent solidification and clogging of the high concentration slurry in the fuel pipe when starting and/or stopping the high concentration slurry burner, water is introduced into the fuel pipe to purge the fuel pipe. A fuel pipe purging method for a high concentration slurry burner characterized by: 2. A method for purging a fuel pipe of a high-concentration slurry burner, characterized by first introducing water into the fuel pipe when starting the high-concentration slurry burner, and then continuously supplying high-concentration slurry. 3. A method for purging a fuel pipe of a high concentration slurry burner, characterized in that when the high concentration slurry burner is stopped, water is introduced into the fuel pipe to purge the fuel pipe after the fuel supply is stopped. 4 When the high-concentration slurry burner is started, water is introduced into the fuel pipe and high-concentration slurry is continuously supplied. On the other hand, when the high-concentration slurry burner is stopped, water is introduced into the fuel pipe after the fuel supply is stopped and fuel is supplied. A method for purging a fuel pipe of a high concentration slurry burner, the method comprising purging the pipe. 5. A method for purging a fuel pipe of a high-concentration slurry burner according to claim 2, 6, or 4, wherein the operation is sequentially controlled.