JPS623791B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a continuous gypsum firing apparatus. Natural gypsum or chemical gypsum is used as raw material gypsum for gypsum boards, but recently chemical gypsum has been mostly used. Among the by-product gypsum produced by chemical factories, the ones used as raw materials for gypsum board are:
The main materials are phosphate gypsum and flue gas desulfurization gypsum. The process of firing these raw material gypsum is divided into preliminary drying and firing. The former is dried by co-current airflow drying to the extent that the water adhering to the raw gypsum is almost completely eliminated.
When phosphogypsum is used as a raw material, calcium carbonate is added to adjust the pH, inactivating residual phosphoric acid and fluorine in the raw gypsum, and eliminating any negative effects on the condensation time and strength of the gypsum. Thereafter, by firing the raw gypsum, dihydrate gypsum is converted into hemihydrate gypsum and reformed. When gypsum hemihydrate is mixed with water, it hardens back to gypsum dihydrate, and this property is used to make products such as gypsum board. Conventional gypsum firing equipment for performing the above-mentioned firing uses a normal pressure, batch type kettle pot, as disclosed in Japanese Patent Publication No. 46-31125. There are problems in terms of service life and processing capacity. In other words, the quality of board gypsum depends on the firing conditions: α-type hemihydrate gypsum and β-type gypsum.
Compared to the latter, the former requires less mixing water, requires less heat to dry the gypsum board, has greater tensile and compressive strength, and has better adhesion between the core and paper. However, in the conventional gypsum firing apparatus described above, the ratio of β-type hemihydrate gypsum was high. On the other hand, as a method to increase the production ratio of α-type hemihydrate gypsum, for example, dehydration of dihydrate gypsum is performed in a state where as much water vapor as possible is condensed on the surface of the gypsum, and dihydrate gypsum is dehydrated without adding an aqueous solution separately. Dissolution and recrystallization can be carried out by applying pressure in a small amount of aqueous solution, such as the crystallization water released by gypsum crystals during the process of dehydration, or dihydrate gypsum can be dissolved and recrystallized in water or an aqueous salt solution. There are methods such as causing crystallization. An object of the present invention is to provide a gypsum firing apparatus that can perform continuous firing and has a high production ratio of α-type hemihydrate gypsum. The present invention achieves this objective by providing a vertically elongated pressurizing chamber with a vertical axis, and
A charging device is installed at the upper end and a discharging device is installed at the lower end.
A heating means for indirectly heating the inside of the pressure chamber is divided into upper and lower stages, and these heating means are
A heating jacket disposed around the outer periphery of the pressurizing chamber, a heating tube disposed inside the pressurizing chamber, a heat medium supply pipe connected to the heating jacket and the heating pipe, and a heat medium discharge pipe. By constructing the chamber, firing is performed under saturated steam pressure of 120 to 180°C in a pressurized chamber without adding an aqueous solution, and the vertically long pressurized chamber allows as much water vapor as possible to condense on the plaster surface. By ensuring that dihydrate gypsum is dehydrated in a condition that
The generation ratio of mold hemihydrate gypsum is increased, and stirring blades are provided at the top of the pressure chamber to bake the gypsum evenly and efficiently.The power is reduced by providing only the top, and the stirring in the middle part is reduced to boiling. Furthermore, by providing the heating means divided into upper and lower stages, α-type hemihydrate gypsum is matured while preventing the formation of soluble anhydrite due to secondary dehydration at the lower part of the chamber. The present invention provides a continuous type gypsum firing device that can control the temperature. Hereinafter, one embodiment of the present invention will be described based on the drawings. In FIG. 1, reference numeral 1 denotes a vertically elongated pressure chamber with a vertical axis and a diameter-to-height ratio of 1:3 to 1:10, and has a pressure-resistant and sealed structure. Reference numeral 2 denotes an input device disposed at the upper end of the pressurizing chamber 1, and numeral 3 denotes a discharging device disposed at the lower end of the pressurizing chamber 1. An eccentric ball valve 5 for powder sealing and a gas It is equipped with a swing valve 6 for sealing. Heating jackets 7, 8, and 9 are arranged on the outer periphery of the pressure chamber 1 and are divided into an upper part, an intermediate part, and a lower part in the longitudinal direction, and a heating medium such as dowsum is supplied to each lower part. Supply pipes 10a, 10b, 10c are connected, and heat medium discharge pipes 11a, 11b, 11c are connected to the upper part. Reference numerals 12a, 12b, and 12c are flow rate regulating valves disposed in the heat medium supply pipes 10a, 10b, and 10c, which receive signals from the temperature detection devices 13a, 13b, and 13c in the upper, middle, and lower portions of the pressurizing chamber 1, respectively. It is configured to be controlled by. 14,15,1
Reference numeral 6 denotes heating tubes arranged in a coil shape at the upper, middle, and lower parts of the pressurizing chamber 1, and one end located on the lower side is connected to the heating medium supply tubes 10a, 10b, 10c.
The other end on the upper side is connected to a heat medium supply pipe 17. In addition, the upper 1/3 of the pressure chamber 1
A stirring blade 18 is disposed in the 1/2 range so as not to interfere with the heating tube 14, and its rotating shaft 19 passes through the pressure chamber 1 and is connected to a rotation drive device 20 on the pressure chamber 1. has been done. A bottom plow 21 is installed at the lower end of the pressure chamber 1 to prevent bridging and rathole phenomena.
The fired gypsum is discharged evenly.
22 is a drive device for this bottom plow 21, and 23 is a device for discharging the gypsum discharged from the discharge device 3 into a hot pit 2.
This is the feeding conveyor that feeds into 4. 25 is a steam outlet provided at the upper end of the pressurizing chamber 1, and 26 is its pressure regulating valve. 27 is a raw gypsum supply pipe connected to the charging device 2, 28 is a level meter, and 29 is a heat insulating material covering the outer surfaces of the pressurizing chamber 1 and the heating jackets 7, 8, and 9. In addition, as shown in FIG. 2, the heating tube 14 is
Heating may be performed evenly and efficiently by winding the heating tubes 14, 15, and 16 two or three times in the radial direction, and the shape and arrangement of the heating tubes 14, 15, and 16 may be appropriately selected. In the above configuration, the heat medium supply pipes 10a, 10
A heating medium is supplied from b and 10c, and raw gypsum is sequentially supplied to the pressurizing chamber 1 while maintaining the pressure inside the pressurizing chamber 1 through the feeding device 2 from the raw gypsum supply pipe 27.
supply within. The raw gypsum is fired while descending inside the pressure chamber 1, and the fired gypsum is successively taken out by the discharge device 3 while maintaining the pressure inside the pressure chamber 1, and is transferred to the hot pit 2 by the input conveyor 23. will be put into the In the pressure chamber 1, the raw gypsum is
Through a dry process under saturated vapor pressure of 120 to 180°C and without the addition of an aqueous solution, dihydrate crystals are dissolved and recrystallized using the crystal water released by themselves in the process of dehydration. α-type hemihydrate gypsum is produced. In addition, because the pressurizing chamber 1 is vertically long, dihydrate gypsum is dehydrated in a state where a large amount of water vapor can condense on the gypsum surface, and in this respect, α-type hemihydrate gypsum is easily obtained. . In addition, by providing a stirring blade 18 in the upper part of the pressure chamber 1, the gypsum is effectively stirred and baked uniformly and efficiently. Since a stirring effect is produced by utilizing this phenomenon, stirring can be achieved reliably while reducing the power required for the stirring blades. thus,
While the raw gypsum flows down inside the pressure chamber 1, it is heated by the heating pipes 14, 15 and the heating jackets 7, 8, and its temperature rises, and when it reaches 120°C to 130°C,
Crystal water is desorbed and vaporized, increasing the volume by 10-14%.
The liquid water reaches a state similar to boiling, and primary dehydration occurs as described above, and at this time the gypsum has become hemihydrate gypsum. And if the temperature continues to rise,
The volume begins to gradually decrease, and at 180°C, a slight increase in volume and boiling occur again, and the remaining water of crystallization is desorbed, resulting in secondary dehydration, and in this state, calcined gypsum becomes soluble anhydrite. It is better to use as little soluble anhydrite as possible as a raw material for gypsum board. Therefore, after the primary dehydration, heating pipes 15 and 16 and heating jackets 8 and 9 in the middle and lower portions were installed so that the ripening process could proceed without secondary dehydration occurring.
The temperature is adjusted by controlling the flow rate regulating valves 12b, 12c of the heat medium supply pipes 10b, 10c, so that a large amount of α-type hemihydrate gypsum can be obtained. The table below compares the quality of the by-product gypsum fired products obtained by the apparatus of the present invention and conventional products.

[Table] The other firing conditions for the fired product according to the present invention are that the moisture adhering to the supplied gypsum is 10.5%, and the addition rate of a modifier that acts to alleviate dehydration is 0.05%. From the above data, it can be seen that in the firing according to the present invention, the amount of mixed water is low and the production ratio of α-type hemihydrate gypsum with high strength is high. According to the continuous gypsum firing apparatus of the present invention, as is clear from the above explanation, the gypsum firing apparatus in the pressurized chamber can
Continuous firing is possible without adding an aqueous solution under saturated steam pressure of 180℃, and by using a vertically long pressurized chamber, dihydrate gypsum can be dehydrated in a state where as much water vapor as possible can condense on the gypsum surface. This eliminates unevenness in the quality of hemihydrate gypsum, improves the ratio of α-type hemihydrate gypsum, improves the strength of the molded product, and improves the adhesion between the core and paper. Since less water is needed for kneading, less heat is required for drying, and there is no sudden temperature change in the pressure chamber unlike in the batch type, so the lifespan is extended. In addition, the stirring blades provided at the top of the pressure chamber allow the gypsum to be baked uniformly and efficiently, and by providing only the top, the power can be reduced, and boiling can be used for stirring in the middle part. By providing the heating means divided into upper and lower stages, it is possible to prevent the formation of soluble anhydrite due to secondary dehydration in the lower part of the chamber,
The temperature can be adjusted so that α-type hemihydrate gypsum is fired.
Furthermore, since each heating means is indirect heating, the exhaust gas dust collector can be made smaller than, for example, direct heating using high-temperature gas, and the quality can be made uniform without partial over-firing.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, FIG. 1 is a longitudinal sectional front view showing a schematic configuration, and FIG. 2 shows another example of the arrangement of stirring blades and heating tubes, a is a longitudinal sectional front view, b is
is a cross-sectional plan view. 1... Pressure chamber, 2... Insertion device, 3...
Ejection device, 4... Intermediate chamber, 7, 8, 9...
Heating jacket, 10a, 10b, 10c...
Heat medium supply pipe, 12a, 12b, 12c...Flow rate adjustment valve, 13a, 13b, 13c...Temperature detection device, 14, 15, 16...Heating tube, 18...Stirring blade.

Claims (1)

[Claims] 1. A charging device is provided at the upper end of a vertically long pressurizing chamber whose axis is vertical, a discharging device is provided at the lower end, a stirring blade is provided at the top of the pressurizing chamber, and a heating means for indirectly heating the inside of the pressurizing chamber is installed above and below. The heating means is divided into a plurality of stages, and these heating means are connected to a heating jacket disposed around the outer periphery of the pressurizing chamber, a heating tube disposed inside the pressurizing chamber, and the heating jacket and the heating tube. A continuous gypsum firing device characterized by comprising a heat medium supply pipe and a heat medium discharge pipe connected to each other.