JP2948401B2 - Method for producing flue gas desulfurization agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a desulfurizing agent (calcium carbonate) useful for desulfurization in exhaust gas generated from a thermal power plant or the like from a shell.

[0002]

2. Description of the Related Art A large amount of shellfish is generated in an intake channel of a thermal power plant and adheres to the inside of the channel. As the adhesion of shellfish progresses, the waterway is blocked and it becomes difficult to take normal water. Therefore, the shellfish attached to the waterway are regularly removed and cleaned. At this time, the amount of attached shellfish is enormous, and at present, landfill disposal or ocean input is being performed as a disposal method, but in recent years it has become difficult to secure landfill sites, and furthermore, local There is no agreement. Therefore, volume reduction by incineration has been partially performed, but there is a drawback that the processing cost is high.

[0003] As described above, shellfish attached to an intake channel is waste, and if industrially useful resources can be recovered from this waste, its technical value is high. Therefore, it is conceivable to use it effectively as a substitute for calcium carbonate, which is the main component of shells of shellfish, and to dry shellfish that has already been dried and most of the attached meat is removed at about 450-600 ° C for 30 minutes or more. There has been proposed a method of producing a flue gas desulfurization absorbent from shellfish powder that has been subjected to a heat treatment or a heat treatment in which the COD value of a supernatant of a shell powder slurry is 30 ppm or less, that is, calcium carbonate. (JP-A-63-49
No. 230).

In the above proposed method, the heating condition is set to CO
Focusing on the D value, the temperature at which the COD value decreases is 450 ° C.
The upper limit temperature is set to 600 ° C. or lower as a temperature at which calcium carbonate is decarbonated by the following reaction formula and does not change into calcium oxide. CaCO ₃ → CaO + CO ₂

[0005]

However, as a method for producing calcium carbonate for flue gas desulfurization from shell powder, the above-mentioned conventional method requires a high heating temperature, requires a large amount of heat energy, and is not economical.

[0006]

Under the circumstances described above, the present inventors have conducted repeated studies and researches on a method for efficiently producing calcium carbonate for flue gas desulfurization from shell powder. It is important to pay attention to the foaming of the liquid when the shell powder is dissolved in the flue gas desulfurization absorbing liquid, not the COD value pointed out by the above-mentioned proposal, but the foaming of the liquid is important. It was clarified that it was caused by the protein contained in the shell.

The present invention has been completed on the basis of the above-mentioned findings, and comprises the steps of:
This is a method for producing a flue gas desulfurizing agent, which comprises performing heat treatment for at least 0 minute.

In the present invention, the shell powder used in the present invention is not limited to mussels and green mussels, but also clams, clams,
All kinds of shell powder, such as clams, oysters and scallops, are used. The shell powder is pulverized to about 10 μm to 3 mm and heated at 300 to 400 ° C.

Hereinafter, specific examples of the present invention will be described, and their effects will be clarified.

[0010]

FIG. 1 shows the changes in the organic carbon content and the nitrogen content when the shell powder (shellfish powder containing mussels as a main component and slightly containing green mussels and having an average particle size of 10 μm) was treated by changing the heating temperature. Indicates a change. From this figure, it can be seen that COD in the heating condition of the present invention in the range of 300 to 400 ° C.
It is clear that the amount of organic carbon which may cause the above is not reduced, but the amount of nitrogen, which indicates the amount of protein, has disappeared, indicating that this temperature range is a sufficient heat treatment to suppress foaming.

Next, FIG. 2 shows the effect of the heating time. From this figure, it can be seen that the nitrogen amount disappears in the same manner as the temperature in the range of 30 minutes or more which is the heating condition of the present invention.

FIG. 3 shows an example of a test result in which reduction in foaming of the shell powder subjected to the above-mentioned heat treatment was confirmed. The test was performed as follows. 200 ml of the test solution was placed in the bottom of a vertically installed cylindrical tube having an inner diameter of 35 mm, and fine bubbles were blown from the bottom of the solution to measure a foam layer formed on the upper surface of the solution. The test liquid was prepared as follows. After dissolving 4 g of shell powder in 160 ml of pure water and 4.7 ml of hydrochloric acid, the solution was made up to 200 ml with pure water to obtain a test solution. From FIG. 3, it was confirmed that foaming can be significantly reduced under the heating conditions of the present invention as described with reference to FIGS. In addition, the foaming property of the normally used calcium carbonate for flue gas desulfurization was equivalent to that shown as the treatment at 350 ° C. in FIG.

The properties of the shellfish used in the above test are as follows. Calcium carbonate purity: 92.6%, organic carbon content:
1.6%, nitrogen content: 0.6%

Table 1 shows the results of using calcium carbonate obtained by the method for producing calcium carbonate for flue gas desulfurization using shell powder according to the present invention in a flue gas desulfurization test apparatus by the wet lime gypsum method. As a comparative example, the results of calcium carbonate produced by pulverizing limestone normally used in flue gas desulfurization equipment are also shown in Table 1.

[Table 1]

As is apparent from Table 1, the suitability of calcium carbonate prepared from the shellfish produced according to the present invention as an absorbent is not inferior to that of calcium carbonate usually used in flue gas desulfurization equipment. I understand. Also,
When untreated shell powder was tested under the same conditions, foaming occurred in the tank, causing problems such as overflow of the foam layer. However, such a problem did not occur with the calcium carbonate according to the present invention. Furthermore, the COD value of concern in the above-mentioned publication method was detected in the wastewater even when the calcium carbonate according to the present invention was used. However, when this wastewater was treated with a simple activated carbon or treated with chlorine, the COD value was reduced. C
The OD value was 5 ppm or less, and the wastewater had no problem.

[0016]

As described in detail in the embodiments, according to the present invention, compared with the prior art, the treatment is performed at a lower temperature, so that heat energy can be saved and industrially useful resources can be obtained from shellfish as waste. Can be recovered.

[Brief description of the drawings]

FIG. 1 is a chart showing changes in the amount of organic carbon and the amount of nitrogen with respect to the heat treatment temperature of shellfish.

FIG. 2 is a chart showing changes in the amount of organic carbon and the amount of nitrogen with respect to the heat treatment temperature of shellfish.

FIG. 3 is a chart showing the effervescence of shellfish.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tokuma Arai 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Heavy Industries, Ltd. (56) References JP-A-63-49230 (JP, A) JP-A Sho JP-A-4-346882 (JP, A) JP-A-53-34376 (JP, A) JP-A-48-51000 (JP, A) JP-A-2-202957 (JP, A) A) Actual opening 57-77632 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 20/00-20/34 B01D 53/34-53/34 136 C01F 11/00 -11/48

Claims (1)

(57) [Claims] 1. A method for producing a flue gas desulfurizing agent, comprising heating a ground shell powder at 300 to 400 ° C. for 30 minutes or more.