JPS6255055B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for regenerating a fluidized medium, and in particular, to remove substances attached to a fluidized medium used in a fluidized bed incinerator for incinerating dust collected ash (hereinafter referred to as EP ash) collected from exhaust gas, and to regenerate it in the incinerator. Regarding how to play it for use. Large amounts of EP ash containing unburned carbon are emitted from boilers such as large thermal power plants that burn large amounts of crude oil and heavy oil. Due to its properties, this EP ash is not suitable for landfilling. For this reason, it has recently become possible to reduce the volume and weight of EP ash, as well as effectively utilize the energy it possesses, and it is also possible to recover metals such as vanadium contained in EP ash.
The method of incinerating EP ash has been attracting attention. There are various types of incinerators, but each has its advantages and disadvantages, which indicates that incineration of EP ash is not easy. Among these, equipment that processes EP ash using a fluidized bed furnace is considered important because it can respond well to load fluctuations, changes in ash composition, etc. However, this fluidized bed furnace also has the following drawbacks. In other words, the fluid medium (mainly sand is used) becomes swollen with deposits over time, causing poor flow.
This makes long-term continuous operation difficult. For this reason, it is necessary to stop the operation of the furnace and replace the medium, resulting in disadvantages in terms of work costs, operating costs, medium costs, etc., and improvements in these are desired. The object of the present invention is to eliminate these drawbacks of the prior art and to provide a method for regenerating a fluidized medium without stopping the operation of the furnace and refeeding the regenerated medium to the furnace. In short, this invention extracts a fluidized medium from an operating fluidized bed furnace, mechanically strips and removes deposits from the fluidized medium in the presence of water or a liquid that dissolves deposits, and further leaches out water-soluble components of the deposits. The method is characterized in that the temperature of the solution is raised to such an extent that insoluble components can be easily peeled off. Table 1 shows an example of analysis of substances that adhered to the surface of the fluidized medium when EP ash was incinerated in a fluidized bed furnace.

[Table] The main components are sodium oxide (Na ₂ O) and sulfuric anhydride (SO ₃ ), and these are thought to exist in the form of sodium sulfate (Na ₂ SO ₄ ). Other components include vanadium (V), iron (Fe), and nickel (Ni). As a method to separate deposits of this composition from the medium (mainly natural sand),
It is conceivable to apply mechanical force to crush and separate the two. However, in this method, it is difficult to peel off the deposits on the surface with a force that does not crush the sand medium. In other words, if a force capable of crushing the deposits is applied, the medium itself will also be crushed and powdered, making it impossible to achieve the original purpose of recycling the medium. This is because the adhesion is more elastic than the medium.
This is thought to be due to its strong impact force. On the other hand, Na ₂ SO ₄ , which is thought to account for about 50% of the attached substances,
It is soluble in certain liquids such as water, and its adhesive strength and elasticity are expected to decrease rapidly in the presence of these liquids. This shows that if the crushing operation of the substances adhered to the fluid medium is performed in the presence of these liquids, it is possible to peel off and remove the adhered substances without crushing the fluid medium. By the way, the solubility of Na ₂ SO ₄ in the liquid depends largely on the temperature of the solution.
It is known that when the temperature is above ℃, the amount of liquid required to dissolve Na ₂ SO ₄ becomes very small.
The inventors tested the solubility of soluble components in deposits, including Na ₂ SO ₄ , using water as the dissolving solution. Figure 1 is a graph showing this result, with curve 1
represents the amount of water required to dissolve 1 kg of water-soluble matter, the horizontal axis represents the water temperature, and the vertical axis represents the amount of water.
As is clear from this curve 1, when the water temperature is about 30°C, the amount of water required to dissolve the water-soluble matter is extremely small. Curve 2 shows the water soluble content as Na ₂ SO ₄
In this case, the same results as above are obtained, especially when the water temperature is around 30°, the amount of water is the lowest. In other words, from these results, if the fluidized medium is crushed in the presence of a dissolving solution that maintains a temperature of 30°C or higher, deposits can be easily removed, and the amount of dissolving solution added can be reduced. . In order to further confirm the rate of detachment of the deposits, the inventors changed the water temperature, added water at a weight ratio of 1:0.3 to a fluid medium containing 24.5% deposits, and crushed the mixture in a ball mill for 10 minutes. be. The water temperature is 10℃
and 90°C. Table 2 shows the results of this test.

[Table] It was observed that more than 90% of the deposits were removed when the water temperature was 25°C or higher, especially about 30°C or higher. When the water temperature is below 20℃, the rate of detachment of deposits decreases rapidly.
In particular, it does not reach 50% at temperatures below 15°C. Although not shown in the table, as a result of analyzing the peeled materials, it was confirmed that the medium, sand, was hardly powdered at any water temperature. The experimental results demonstrated that it is very important to increase the temperature of the solution in order to remove the deposits. In addition to the improvement in the dissolution rate of soluble components, a change in the viscosity of the solution can also be considered as a factor for the improvement in the peeling rate due to the temperature increase of the dissolving solution. FIG. 2 shows a specific example of implementing the method of the present invention based on the above experimental examples. A fluid medium such as sand extracted from the EP ash incinerator 1 is introduced into the crusher 2 through a line 11. Water or a solution heated to 30° C. or higher by a heater 3 is injected into the crusher 2 through a line 21. In the crusher 2, mechanical force is applied in the presence of this water or solution to peel off the deposits. The medium and deposits after crushing are separated by a separator 4 located at the rear of the crusher 2, and the medium is re-supplied to the EP ash incinerator via line 31,
On the other hand, the deposits are discharged and disposed of through line 41. In this case, in order to separate the medium and the deposits,
A separate separation device such as a sieve may be provided, and a device for washing the regenerated medium with water or a washing liquid may also be provided. In addition, the heat source of the heater 3 is exhaust heat,
It is economical to use steam or waste heat from other processes. FIG. 3 shows another embodiment in which the heated medium for deposit removal is used directly as the heating source for the water or solution. A heated medium is introduced from the EP ash incinerator 1 into the crusher 2 via a line 11 via an automatic opening/closing valve 5. Water or a solution is added to the crusher 2 in advance through a line 21, and the temperature is raised by a heated medium. A temperature sensor 6 installed in the crusher 2 detects the liquid temperature and transmits this signal to the automatic opening/closing valve 5 via the line 10. Based on this signal, the automatic opening/closing valve 5 adjusts the amount of medium introduced and removes the liquid. The temperature is maintained at 25°C or higher, preferably 30°C or higher. The deposits crushed in the crusher 2 are separated in the separator 4 as in the previous embodiment, and the regenerated medium is supplied to the incinerator 1 through the line 31. Note that a stirring device 7 may be provided in the crusher 2 in order to keep the liquid temperature and concentration in the crusher 2 uniform. According to this invention, continuous operation of the fluidized bed incinerator is possible, and workability and economical efficiency can be improved. Furthermore, by setting the temperature of the dissolving solution to 30° C. or higher, the amount of dissolving solution can be reduced and damage to the medium for deposits is less likely.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the dissolution characteristics of soluble components in deposits, Fig. 2 is a systematic diagram showing an example of the present invention,
FIG. 3 is a system diagram showing another embodiment. 1...EP ash incinerator, 2...Crusher, 3...Heater, 4...Separator, 5...Automatic opening/closing valve, 6
... Temperature detector, 7... Stirrer.

Claims (1)

[Claims] 1. Recycle and use the fluidized medium by mechanically peeling off and removing deposits containing Na ₂ SO ₄ attached to the fluidized medium in the presence of a liquid that dissolves them in a fluidized bed furnace. A method for regenerating a fluidized medium, characterized in that the temperature of the dissolving liquid is set to 30°C or higher. 2. The method for regenerating a fluidized medium according to claim 1, wherein the water or solution is heated by a fluidized medium in a heated state. 3. The method for regenerating a fluidized medium according to claim 2, characterized in that the temperature of the aqueous solution is maintained by controlling the amount of the fluidized medium to be withdrawn, and the concentration of the aqueous solution is kept uniform by stirring the solution.