JPS6349230A - Production of absorbent for wet flue gas desulfurization from shell - Google Patents

Abstract

PURPOSE:To produce the title good-quality desulfurization absorbent by drying shells to remove most of the stuck flesh, and then heating the dried shells within the applicable range of heating temp. and time. CONSTITUTION:Shells are dried to mechanically remove most of the flesh, and the dried shells are quantitatively charged into an incinerator 3 from a dried shell hopper 1 through a screw feeder 2. The dried shells are burned at 450-600 deg.C in the incinerator, hence the remaining org. matter is completely decomposed and removed, and the purity of CaCO3 is enhanced. Although the burning time is related to the heating temp., the time is usually controlled to about 30min-2hr. The incinerated shells are stored in a crushed calcium carbonate hopper 6 through a line 11, the crushed material is then pulverized by a crusher 7, and the obtained fine powder is utilized as the absorbent 8 for desulfurization.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing an absorbent for wet flue gas desulfurization, and more specifically, the present invention relates to a method for producing an absorbent for wet flue gas desulfurization, and more specifically, it involves incinerating dried seashells to obtain a high-purity product suitable for a desulfurization absorbent. The present invention relates to a method for obtaining calcium carbonate.

[Conventional technology]

In the present invention, shellfish is a term that collectively refers to crustaceans such as mussels, scallops, oyster shells, and even crabs and shrimps.

At thermal and nuclear power plants, large amounts of shellfish grow in the cooling waterway systems, causing various problems such as a reduction in the amount of water available for intake. For this reason, shellfish are removed by inspection at a similar rate every year. It is well known that these shellfishes contain a considerable amount of organic matter both as their flesh and as residues attached to their shells, so that they gradually decompose and emit a foul odor when they are disposed of or piled up.

For this reason, power plants have dumped the removed shellfish into the sea or disposed of them in landfills, but this has caused problems with the odor emitted during transportation.
This type of dumping is becoming increasingly difficult due to issues such as securing landfill sites. After drying and disposing of the shellfish removed there, it is desired to make effective use of the shells by coarsely crushing them and mechanically removing the meat attached to the shellfish. KEPCO, Research Institute of Technology Materials: Shellfish removed from the cooling waterway system Experimental research on shell/meat separation method). After the shell and meat have been separated, the shell has a high moisture content and strong foul-smelling organic matter is removed, making it easier to handle for recycling.

The present inventor conducted various studies as to whether or not the shells treated in this way could be used as a calcium carbonate agent as a desulfurization absorbent, but the small amount of organic matter remaining in the shells had an adverse effect and it was not immediately adopted. I don't get it. Therefore, we conducted studies to remove this organic matter and use it as a desulfurization absorbent, which led to the present invention.

[Problem that the invention seeks to solve]

The removed shellfish collected from the cooling channel system are mussels with an average shell length of 10 cm, and after being crushed and dried to about 0.5 to 3 cm, the attached shellfish meat is removed using a classifier (as described above). Document). Dry shell fragments obtained here (0.6 to 10.0 mark m) (hereinafter abbreviated as dry shell)
After pulverizing it into a fine powder, add water to it for 10 minutes.
The color rendering of the slurry prepared to a concentration of wt% was brown to yellow, and the C0Dun (potassium permanganate oxygen consumption at 100'C) was measured to be approximately 1.0
It showed a high value of 00 ppm.

Also, add H2SO and water to this and add calcium sulfite (
After preparing CaSO)' 1/2H-0), we oxidized it by blowing air into it, and as a result, as shown in Figure 1 (marked 0 in the figure), the oxidation rate was significantly lower than that of limestone. , and the resulting plaster emitted a foul odor.

An object of the present invention is to provide a method for completely removing organic matter contained in such dried shells and obtaining highly pure calcium carbonate that can be used as a desulfurization absorbent.

[Means for solving problems]

The dried shells obtained by drying the removed shellfish and mechanically separating the shells from the meat cannot be used as a desulfurization absorbent because the organic matter originating from the remaining meat has an adverse effect on the dried shells. Therefore, in order to apply it as a desulfurization absorbent, it is necessary to completely remove this organic matter. Therefore, the oxidation treatment of calcium sulfite was performed by the method described above using incinerated shells that had been heated in an electric furnace at a predetermined temperature for a predetermined period of time or longer, but the oxidation rate was significantly improved.

It was found that it can be made almost equivalent to limestone, which is normally used as an absorbent for flue gas desulfurization.

In addition, in order to be able to utilize dried shells as desulfurization absorbent for limestone-gypsum wet desulfurization equipment, Ca CO
3, the organic matter must be removed without decomposing the organic matter at a predetermined temperature;
The heat treatment must be performed for a specified time or less.

These two ranges of heating temperature and heating time are ranges that both satisfy the applicable range shown in FIGS. 2 and 3, as described later.

The ranges of these heating temperatures and heating times will be explained below.

A predetermined amount (2 og) of dried shells was weighed and incinerated using an electric furnace (inner volume: 3Q) at a heating temperature of 400 to 600°C and a heating time of 0.5 to 2 hours. The incinerated shells were ground in a ball mill, water was added to prepare a slurry (10wt%), and the amount of residual organic matter was investigated by measuring C and 0DHn in the supernatant, as shown in Figure 2. be.

By heat treatment at a heating temperature of 450°C or higher, CO
DMn is less than 10 ppm, and organic matter (COD value: 1,000 ppm) attached to dried shells is 99%.
The above is decomposed. Among the shells obtained in this way, the first
As shown in the figure, oxidation of calcium sulfite to gypsum progresses at the same rate as limestone, making it possible to use it as an absorbent for desulfurization.

Further, as shown in FIG. 2, complete incineration and removal of attached organic matter can be achieved by increasing the heating temperature. However, the reagent CaCO2 is usually heated to 700°C.
It is known that CaC○ gradually decomposes into calcium oxide (C; ao) from the vicinity according to the following formula.

CaC0, → CaO+GO, ↑=-・-(1)>7
00℃ When used as a desulfurization absorbent, the presence of a large amount of CaO will increase the pH of the slurry, causing problems such as a decrease in the dissolution rate of CaC0℃ (decrease in desulfurization performance), scaling in the tower, and a decrease in the purity of by-product gypsum. There are concerns that this may cause problems. Therefore, it is necessary to determine a temperature that does not cause decomposition of CaC0°. Therefore, dried shells were incinerated at different heating temperatures and times, and the incinerated product was examined for the presence or absence of CaO detection using X-ray diffraction. The results are shown in Figure 3, and when heated at 650°C for over 1 hour, CaO was detected (C
(containing a01% or more) was not detected at all at temperatures below 600°C.

Figure 4 shows a comparison of the results of differential thermal/thermogravimetric analysis of dried seashells and limestone. (650°C), and the melting point of shells (740°C) is also lower than that of limestone (770°C).

From the above results, it has become clear that the heating temperature must be 600° C. or lower in order to maintain the Ca CO form.

In addition, Table 1 shows dried shells, burned shells (550°C, lh
(r treatment) and limestone composition analysis results are shown below. When the shells are incinerated, the purity of CaCO3 becomes 97%, which is approximately 0% higher in purity than untreated shells, resulting in products with properties similar to limestone.

In addition, combustible C, H, N, etc. caused by organic matter are reduced,
The product did not generate any bad odor and had properties that could be used as a desulfurization absorbent.

〔Example〕

FIG. 5 is a flow diagram illustrating the minimum necessary equipment for implementing the present invention.

The dried shells (crushed material) from which most of the shellfish meat has been mechanically removed are quantitatively fed into the incinerator 3 from the dry shell hopper 1 through the screw feeder 2, where they are incinerated while being maintained at a temperature range of 450 to 600°C. The treatment completely decomposes and removes residual organic matter to improve CaCO3 purity. The incinerated shells are passed through the incineration process to produce charcoal (calcium carbonate).

The same applies hereinafter)) The crushed material is stored in a hopper 6, and then pulverized by a pulverizer 7 to be used as an absorbent 8 for desulfurization. In addition,
The gas discharged from the incinerator uses a bag filter 4 to collect scattered carbonaceous gas, and furthermore, a deodorizing tower 5 removes odorous gas generated from the decomposition of organic matter in the exhaust gas and releases it into the atmosphere. In addition, 11, 12.1 in the figure
3 is a coal cal recovery line, 14 is a cyclone recovery line,
15°16.17 is the exhaust gas line.

〔Effect of the invention〕

Traditionally, shells are reduced in volume by separating the meat from shellfish, but
This could not be used effectively as a resource.

According to the present invention, by incinerating and removing the organic matter contained in the dried shells, the composition becomes suitable for use as an absorbent for desulfurization, and furthermore, the by-product gypsum does not emit a bad odor, and limestone can be used. It is possible to obtain products of almost the same quality as those obtained by using the method, and the effective use of shells can be achieved.

[Brief explanation of the drawing]

Figure 1 shows a comparison of oxidation rates when sulfites produced by adding sulfite water to dried shells, shell incineration, and limestone are oxidized. CODM in the slurry supernatant of the obtained shellfish incineration
Figure 3 is a diagram showing the n value, Figure 3 is a diagram showing the results of examining the presence or absence of Ca○ formation by X-ray diffraction of the incinerated matter obtained under various incineration conditions, Figure 4 is the differential heat and heat of dried shells and limestone. FIG. 5, which is a diagram showing the results of gravimetric analysis, is a minimum necessary flow chart for carrying out the present invention.

Claims (2)

[Claims] (1) Using dried shells from which most of the attached meat has been removed by drying shellfish, the temperature and time ranges that satisfy both the applicable heating temperature and heating time ranges shown in Figures 2 and 3 are used. A method for producing a desulfurization absorbent, which comprises heating and incinerating it. (2) In claim 1, the COD_Mn value of the supernatant liquid of the incinerated pulverized shell slurry (10 wt%) is 3.
A method for producing a desulfurization absorbent characterized by carrying out heating and incineration treatment until the concentration becomes 0 ppm or less.