JP2919906B2 - Fluid medium and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a combustion furnace, an incinerator,
The present invention relates to a fluid medium used in a firing furnace, a heating furnace, and the like, and a method for producing the same.

(Prior Art) combustion furnace according to the fluidized bed method, combustion efficiency can be better yet use solid fuel, also low NO _x, because of the advantages such as more equipment costs at a low SO _x is small, urban dust, multi It tends to be widely used in mud incinerators, general industrial boilers, and the like.

Conventionally, as a fluidized medium used in a fluidized bed furnace,
Natural minerals mainly composed of CaO and MgO, such as limestone and dolomite, are also used as desulfurizing agents.

Although these natural minerals have the advantage that they can be obtained at low cost, it has been pointed out that, when used, they are disintegrated, powdered, and scattered by heat shock, dehydration, decarboxylation and the like in a combustion furnace. Therefore, in the case where these minerals are used as a fluid medium, it is necessary to sequentially feed the fluid medium in order to maintain the height of the fluidized bed at a predetermined height.

In particular, when a low-sulfur solid fuel is used, there is a problem that a fluid medium in excess of the amount contributing to desulfurization has to be charged, and the fuel is discharged from the fluid due to excessive use of the fluid medium. The amount of generated ash was also large. Further, since decarboxylation is an endothermic reaction, there is a problem that heat contributing to this reaction is lost in the combustion furnace. All of these problems have caused an increase in the operating cost of the fluidized bed furnace, and a solution to this problem has long been desired.

(Problems to be Solved by the Invention) The present invention seeks to obtain a fluid medium that is less likely to be powdered than conventional limestone and dolomite in a fluidized state at 800 to 900 ° C. and that has no endothermic reaction due to decarboxylation. is there.

(Means for Solving the Problems) The present invention is a sintered body using gypsum as a raw material, and is a fluid medium having a particle size of 0.2 to 4.0 mm. Of water to make the particle size 0.2 ~
This is a method for producing a fluid medium, which comprises granulating to a size of 4.0 mm and firing the granulated material. Hereinafter, these inventions will be further described.

In the present invention, gypsum is used as a fluid medium instead of conventional limestone or dolomite, and granulated and fired. The plaster used here is natural plaster,
Any gypsum such as chemical gypsum can be used. Those containing a small amount of fluorine or fluoride in addition to CaO and SO ₃ which are the main components of gypsum have excellent strength both in the strength after granulation and in the final product after firing. Therefore, the fluorine component is reduced to 0.
Phosphogypsum containing more than 7% can be suitably used,
Of course, various types of gypsum, such as waste gypsum, which have almost no fluorine or fluoride components, can obtain excellent fluid media by adding a hardening agent, which will be described later. is not.

The raw gypsum is first heated at a temperature of 100-250 ° C,
Dry to make hemihydrate gypsum or anhydrous gypsum. By using semi-hydrated water or anhydrous gypsum, the amount of granulated water at the time of granulation becomes constant, and a stable granulated product is obtained. Next, this is crushed to a specific surface area of 2000 to 8000 cm ² / g, and a retarder and, if necessary, a curing agent are added and mixed.

The retarder adjusts the hydration setting time at the time of granulation of gypsum, and facilitates granulation.One or more of gelatin, peptone, starch, alkali tartrate, citric acid, succinic acid, etc., as a powder, Or 0.05 to gypsum as an aqueous solution
Add 5%. If it is less than 0.05%, the effect of retarding setting is not sufficient, and the granulation property is poor. Even if it is added in an amount of 5% or more, the granulation effect does not change for the addition, which is not economically preferable. When citric acid is used as a retarder, a suitable amount is 0.2 to 2%.

Next, the curing agent, those which when fluorinated or fluoride component in the raw material gypsum is small as described above, NaF, by adding an inorganic fluoride such as CaF _2, so that good fluid medium is obtained is there. This acts as a high-temperature binder during the firing step and strengthens the bonding by firing, which results in a suitable flowing medium. That is, a good fluid medium that is hard to be powdered and hard to break due to the presence of fluorine or a fluorine compound is obtained. The inorganic fluoride as a hardener is added to the gypsum as a powder or as an aqueous solution in an amount of 0.5 to 10%. If it is less than 0.5%, a fluid medium having sufficient strength cannot be obtained. Further, even if it is added in excess of 10%, the granulated material melts or defluoridates during firing, which is not preferable. When using waste gypsum as the raw material gypsum, it is preferable to add 1 to 3% of NaF or ₂ to 5% of CaF2.

Water used for granulation of gypsum is 10-40% by weight of gypsum
And If this is less than 10%, granulation cannot be performed well,
If it exceeds 40%, the strength after granulation and after firing is inferior. The granulation may be performed by any method such as an extrusion method, a tumbling method, an injection method, and a crushing method. The tumbling granulator may be of any type of bread type, drum type and cone type. The size of the granulated material is 0.20 ~ 4.0m
m, preferably 0.3 to 2.0 mm.

The granulate is then cured, preferably cured in air for one or more days before firing. Firing is, for example, in a rotary kiln, and the firing temperature is preferably 850 to 1200 ° C. If sintering is performed outside this range, the strength of the fluidized medium is not sufficient. The firing temperature is more preferably 950 to 1100 ° C
It is. By this calcination, the granulated material is subjected to a temperature history up to the temperature at which it is used as a fluidized medium.There is no CO ₂ gas generated by decarbonation during use in the fluidized bed, so heat loss due to gas and endothermic reaction A fluid medium free from heat loss due to heat and less powdered due to rapid thermal quenching impact can be obtained.
After sintering, sieving is performed and the particle size is finally 0.2 to 4.0
Grain to mm. If it is less than 0.2, scattering occurs more frequently when used as a fluid medium, and if it exceeds 4.0 mm, the ability to form a fluidized state is reduced, which is not preferable.

Hereinafter, experimental examples using the fluid medium according to the present invention will be described, and the present invention will be further described.

Experimental Example 1. Gypsum of the chemical composition (anhydrous base) shown in Table 1 was used as a raw material, and was dried by heating at about 200 ° C., and then crushed to a specific surface area of about 6000 cm ² / g. Was added and mixed. Next, 35% of water was added thereto, and the mixture was granulated by using a small-sized pan pelletizer (diameter: 1000 mm). This granulated product was cured in the air for 72 hours and then calcined at 1000 ° C. in a rotary kiln (diameter: 446 mm, length: 8688 mm) (residence time in the kiln: about 10 minutes). Thereafter, this was cooled to room temperature and then sieved to adjust to a granulated product having a particle size of 1.0 to 3.0 mm.

The granulated material prepared as described above was subjected to a powdering test using a fluidized bed test apparatus shown in FIG. As a comparative example, limestone was pulverized and sieved to adjust the particle size to a particle size of 1.0 to 3.0 mm.

In FIG. 1, reference numeral 1 denotes a fluid tube into which the above-mentioned raw material is introduced from a hopper 2. Reference numeral 3 denotes an annular heater, which heats the raw material inside the flow tube 1. In this experiment, before charging the granular material, 500 g of silica sand was placed in the fluidized tube, and heated with the heater 3 to obtain 100 g of the granular material from the hopper 2 when the fluidized bed was stabilized. It was supplied in batch mode. Reference numeral 4 denotes a compressor, which feeds air at a predetermined pressure into the flow tube 1 to
Was fluidized so that a fluidized bed was formed there. The powder that has been pulverized and scattered in the fluidized bed is guided to the cyclone 6 by a tube attached to the upper part of the fluidized tube 1,
It was collected here and measured intermittently. This measurement is 10
It was carried out for 0 minutes, after which the blowing was stopped and the weight of the residue in the flow tube 1 was measured. From the results of these experiments,
Granulation of raw materials and scattering rate of limestone, initial powdering rate,
The wear powdering ratio was measured. The scattering rate, initial powdering rate, and wear powdering rate are defined as follows, respectively, and the time-dependent change of the scattering state (scattering rate), the initial scattering state (initial powdering rate) due to heat shock, etc., and the flow A steady state of wear powdering due to the flow in the layer (wear powdering rate) was observed.

The measurement conditions were as follows.

Bed temperature; 800 ° C Air flow velocity: 1.2 m / sec Measurement time: 100 minutes Silica sand: JIS No. 4 equivalent. Average particle size (D _SO ) ≒ 0.
8 mmφ Measurement material particle size; 1-3 mmφ Fluid medium / silica sand = 100 g / 500 g Changes over time in the scattering rate are shown in FIG. 2. Table 2 shows the initial powdering rate and the wear powdering rate.

As is evident from FIG. 2, the scattering rate is much less for the exfoliated gypsum granules than for limestone, and even less for gypsum phosphate. Further, as shown in Table 2, it can be seen that the gypsum phosphate granules are the lowest in both the initial powdering rate and the wear powdering rate, and are hardly powdered. .

EXPERIMENTAL EXAMPLE 2. The granulated material and limestone adjusted in the same manner as in Experimental Example 1 were further sized to a particle size of 0.105 to 0.5 mm in order to keep the test condition constant, and the blasting device shown in FIG. 3 was used. The wear properties of the heat transfer tube material were measured.

In the spray wear device shown in FIG. 3, reference numeral 8 denotes a granulated material transfer pipe. For this, the granulated material is supplied from granulated material supply devices 9 provided on both sides. An electric furnace (A) of a heating device is provided on the outer periphery of the granule transfer tube 8, and heats the granules inside through the granule transfer tube 8. A test piece 10 is attached to the tip of the granule transfer tube 8 at a predetermined inclination by a test piece attachment jig 11. The electric furnace (B) of the heating device is also provided on the outer periphery of the portion where the granulated material is sprayed from the nozzle at the end of the transfer pipe 8. A collection box 12 for collecting the sprayed granules is provided below the test piece 10. Granulated material transfer pipe 8
Is supplied with pressurized air 13
The granulated material supplied into the granulated material transfer pipe 1 is ejected from the nozzle toward the test piece 10.

Using the above-mentioned apparatus, the state where the sized granules abraded the test piece was examined.

 The measurement conditions were as follows.

Specimen material: Alloy steel pipe for piping (JIS G 345
8) STBA24 test piece temperature; 500 ° C Injection speed; 100m / sec Test piece mounting angle; 10 ゜ Measurement time; 120 minutes The wear test results show that the maximum wear of the test pieces was gypsum phosphate, gypsum, and limestone. The depth is about 2-3μm / hr, less than 1/10 compared to silica sand, and compared to the residue in the bed in a conventional fluidized bed boiler using limestone
It was 1/2. The phosphate gypsum and the waste gypsum are hard and hard to powder, but have substantially no difference from conventional limestone in that they do not wear the heat transfer tubes in the furnace.

Experimental Example 3. Except for adding 0.2% of citric acid as a retarder and adding and mixing CaF ₂ and NaF as hardeners in advance to the gypsum after granulation with a pan pelletizer, respectively, Similarly, various fluid media were obtained, and the scattering rate and the initial powdering rate were measured. The results were as shown in Table 3.
FIG. 4 shows representative data.

As is clear from Table 3 and FIG. 4, all of the fluidized media according to the present invention were good ones having a low powdering and scattering rate.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a powdering test apparatus for a fluidized medium according to the present invention, and FIGS. 2 and 4 are diagrams each showing a particulate matter of limestone, waste gypsum and phosphate gypsum in a fluidized bed test apparatus. FIG. 3 is a diagram showing the relationship between the elapsed time and the scattering rate, FIG. 3 is an explanatory diagram showing an experimental apparatus for an electrothermal wear test using a fluid medium according to the present invention, and FIG. 4 is a diagram showing the relationship between the elapsed time and the scattering rate. FIG. DESCRIPTION OF SYMBOLS 1 ... Flow pipe, 3 ... Annular heater, 4 ... Compressor, 5 ... Raw material, 6 ... Cyclone, 8 ... Granular material transfer pipe, 10 ... Test piece, 13 ... Pressurized air.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Nakamura 6276 Onoda, Onoda-shi, Yamaguchi Pref.Onoda Cement Co., Ltd. (72) Inventor Tadayoshi Iwamoto, Onoda City, Yamaguchi Pref., 6276 Onoda, Onoda Cement Co., Ltd. (72) Inventor, Nao Takagi 1-8-2, Marunouchi, Chiyoda-ku, Tokyo (58) Field surveyed (Int.Cl. ⁶ , DB name) F27B 15/02 F23G 5/30

Claims (2)

(57) [Claims] 1. A fluid medium which is a sintered body made of gypsum and has a particle size of 0.2 to 4.0 mm. 2. A process for producing a fluid medium, comprising adding 10 to 40% of water to gypsum, granulating the resulting granules to a particle size of 0.2 to 4.0 mm, and calcining the granules.