JPS5919540A - Continuous hydrothermal synthesis apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform stable treatment continuously without generating the lowering in product quality caused by the mixing of an unreacted stock material into product at all in hydrothermal synthesis, by a simple structure comprising the combination of a perfect mixing type reaction tank and a tubular reactor. CONSTITUTION:The titled apparatus is constituted from a perfect mixing type reaction tank 1 and a tubular reactor 6 having a screw type stirrer 7 connected thereto while a pressure balance adjusting pipe 10 for adjusting pressure is separately provided between both of them other than a reaction product transfer pipe 5. As the aforementioned screw type stirrer 7, one wherein at least one pitch or more of a screw blade is left at an appropriate position in the axial direction and other screw blades are cut off every other blade along the surface of the spiral direction thereof at 20-40 practical intervals is used. That is, the mixing of an unreacted stock material is eliminated by providing the tubular reactor having no fear leaving the unreacted stock material in an outlet slurry at all according to a reaction condition in the downstream side.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous hydrothermal synthesis apparatus that combines a seed reactor and a tubular reactor.

Reactors can be broadly categorized by device shape: seed-type reactors,
It becomes a front type reactor and a base type reactor.

There are two types of flow states: ideal flow and non-ideal flow.
The former is further extrusion flow (pjston flow)
and completely mixed flow (m1xed flow).

The ideal flow is an idealized flow, and in an actual reactor it is thought to exhibit a non-ideal flow with characteristics intermediate between an extrusion flow and a complete mixing flow.

In general, a seed reactor is designed to provide a completely mixed flow by providing an agitator, and a front reactor is designed to provide extrusion flow. The basic reactor is mainly used as a packed column for catalysts, etc., and the flow state within the device exhibits a non-ideal flow.

In continuous operation using a fully mixed reactor (a stirrer-equipped seed reactor exhibiting a completely mixed flow), the liquid composition within the tank is uniform in all parts, and the outlet liquid composition is the same as that inside the tank. Therefore, depending on various factors such as throughput, capacity of the apparatus, reaction rate, etc., in a single reaction tank, the amount of unreacted substances in the composition of the outlet liquid may not be negligible. For this reason, in continuous operation, it is generally rare to use a single complete mixing type reaction tank, and a multi-stage type in which several such reactors are connected is often used.

On the other hand, in a tube wall reactor, the composition within the reactor is not uniform and changes continuously along the flow direction. Reaction engineering l-i
A tubular reactor can be thought of as an infinite number of complete mixing reactors connected together.

The present invention relates to a continuous hydrothermal synthesis apparatus having these complete mixing type reaction vessels and tube wall reactors as basic components.

Hydrothermal synthesis is a compound synthesis and crystal growth method carried out in the presence of high-temperature water, especially high-temperature and high-pressure water.A typical example is α-type hemihydrate gypsum (α-CaSO4
HzO), boehmite (Alool()) and xonotlite (6Ca0.6SiO1.HzO).

In this hydrothermal synthesis reaction, the raw material is almost always provided in the form of a slurry, and in the above example, in the synthesis of α-type hemihydrate gypsum, it is gypsum < caso4°2H20) - aqueous slurry, and in the synthesis of boehmite, it is provided as dibzite ( AL(OIL)s
) An aqueous slurry, or in the case of xonotrite, a quicklime (Cab)-silica (St(h))-aqueous slurry is each used as a raw material slurry for the reaction.

The hydrothermal synthesis reaction proceeds through two stages: nucleation and crystal growth, but the first stage of nucleation requires a relatively large space like a stirring tank, and is evenly stirred. The one that is the best. As mentioned above, the most effective equipment for hydrothermal synthesis, where raw materials are often provided in the form of slurry, is a stirred tank type reaction tank with uniform stirring, that is, a complete mixing type reaction tank. This is a decrease in product quality due to the contamination of reaction raw materials into the product. In order to prevent unreacted raw materials from being mixed into the product, if it is a batch operation, it is sufficient to allow sufficient reaction time, but if it is a continuous operation, it is most common to use a multi-stage stirring tank, and the fruiting equipment is It has no choice but to become complex and large in scale. Although continuous operation generally has many advantages over batch operation as an industrial operation, at present there are almost no hydrothermal synthesis apparatuses that can stably process slurry raw materials in a continuous manner.

The present invention has an extremely simple and compact structure that combines a complete mixing type reaction tank and a tube wall reactor.
To provide a hydrothermal synthesis apparatus capable of continuous and stable processing without causing any deterioration in product quality caused by unreacted raw materials mixed into the product in hydrothermal synthesis where raw materials are often provided in the form of slurry.

That is, O's invention of the present invention is composed of a complete mixing type reaction tank and a tube wall reactor equipped with a screw type stirrer, and a pressure is applied separately from the tube for transferring reactants between the two. This is a continuous hydrothermal synthesis device characterized by the installation of a pressure balance adjustment tube for adjustment. In addition, in the second invention V, as the screw type agitator of the first invention, the screw blades are left at least 1 pitch or more at appropriate positions in the axial direction, and the other screw blades are arranged along the helical direction surface of 20 or more. One piece was cut out at 40 degree intervals.

As mentioned above, in a complete mixing type reaction tank, the outlet composition and the inside composition are the same in the case of continuous operation, so if this alone is used, it is essentially unavoidable that unreacted raw materials will be mixed into the outlet slurry. In the present invention, from a reaction engineering point of view, it is analyzed that an infinite number of completely mixed reaction vessels are connected in series, that is, a tube wall reactor in which there is no risk of unreacted raw materials remaining in the outlet slurry depending on the reaction conditions. By installing this later, it is possible to eliminate the contamination of unreacted raw materials. As a result, the scale of the apparatus is smaller and the structure is simpler than in the case of using multiple stages of complete mixing type reaction vessels, and the equipment cost can also be reduced.

゛Also, if we divide the combination of a completely mixed reactor and a tube wall reactor into each stage of hydrothermal synthesis, namely nucleation and crystal growth, we can see that in a completely mixed reactor, nucleation mainly occurs as described in t'1nIJ. After the formation and subsequent crystal growth, it enters the tube wall reactor where further crystal growth occurs.

Furthermore, the tube reactor is equipped with a screw type stirrer inside thereof. A tube reactor is generally used for single-phase reactions such as gas phase or liquid phase, and is not suitable for solid-liquid processing such as slurry. 5. The tube reactor according to the present invention is equipped with a screw-type stirrer and stirrer, so that even when the raw material is provided as a slurry, it is possible to carry out stable hydrothermal synthesis treatment continuously.

Also, this stirrer is basically a screw type,
Even thick slurry can be passed through the cylindrical reactor.

In other words, the tube reactor of the present invention not only allows reactions to occur, but also has the function of transporting reactants to the next process.

Hereinafter, five aspects of the present invention will be explained with reference to the drawings.

FIG. 1'1 is an explanatory longitudinal cross-sectional view showing an example of a continuous hydrothermal synthesis apparatus according to the present invention. In the figure, 1 is a complete mixing type reaction tank, where the raw materials fed through the raw material inlet 2 are hydrothermally synthesized while being uniformly stirred by the stirrer 3.
Generation of crystal nuclei and crystal growth are performed. 4 is a heating jacket. The inside of this jacket is partitioned into a spiral flow path as shown in the figure, and the heat medium flows along the flow path inside the jacket. The reactants are further led to the pipe-type reactor 6 via the transport pipe 5, and are uniformly stirred by the screw-type stirrer 7 to completely react the unreacted substances, further crystal growth, and then to the discharge port 8. be transferred to. 9 is a heating jacket similar to 4.

As mentioned above, the screw type stirrer 7 prevents the slurry reactant from separating into solid and liquid and depositing in the tube, and also plays the role of transport, which is the original function of the screw. In other words, the slurry is uniformly stirred inside the tubular reactor by the screw type stirrer and is transported to the discharge port while crystal growth occurs. As a screw type stirrer, it is a normal helical screw! , but it is preferable to leave the screw blades at a pitch of at least 1 at an appropriate position in the axial direction, and leave the other screw blades at a pitch of 20 to 40 along the helical direction.
It is effective to remove every other blade at intervals of 100°C from the viewpoint of both stirring performance and maintaining product quality.

In other words, screws are originally used as a means of transportation and are not suitable for stirring slurry due to their structure.
As mentioned above, by removing the screw blades, the stirring performance is improved, but since the original helical structure of the screw is basically retained, it also has the function of transportation. Further, it is not necessary to cut out all the screw blades in this way, but to leave the screw blades as they are at a suitable position in the axial direction at least one pitch or more is meaningful from the viewpoint of maintaining the quality of the product. In other words, the portion of the screw blade left as it is serves as a kind of dam band and has the effect of promoting the retention of slurry in the reactor, and as a result, it prevents unreacted raw materials from passing through, so there is no unreacted material in the product. Contamination can be avoided. Considering that in the area between the dam bands, stirring is uniformly performed by the cut-out screw blades as described above, the W-type reactor according to the present invention can be constructed by constructing a complete mixing type reaction tank in multiple stages. Although it can be considered equivalent to a connected device, in that case, the device would be more complex and larger than in the case of the present invention.

The number of damming bands is determined by the characteristics of the reaction system, operational advantages, quality characteristics of the product, etc.

In addition, the portion on the discharge port 8 side of this screw type agitator can smoothly discharge the slurry by arranging the screw blades in a 2- to 3-pitch inverted spiral as shown in Figure O1.

In addition, in Fig. 1, there is a pressure balance adjustment pipe 1O between the complete mixing type reaction tank 1 and the pipe reactor 6, in addition to the slurry transport pipe 5, for adjusting the pressure. Completely mixed reaction 41il
Fluctuations in the pressure balance between the complete mixing type reaction tank 1 and the pipe reactor 6 that occur when the slurry is transferred from the slurry to the pipe reactor 6 via the transport pipe 5 result in vapor movement within the pipe 10. This means that the entire fruiting system can be operated stably.

As described above, the present invention provides a continuous hydrothermal synthesis apparatus capable of continuous and stable processing in hydrothermal synthesis where raw materials are often provided in the form of slurry.

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 α-type hemihydrate gypsum was continuously produced using flue gas desulfurization gypsum (dihydrate gypsum) as a raw material by the silo pressure aqueous solution method.

The continuous reactor has a complete mixing type reaction tank with a diameter of 512 mm, a height of 975 mm, and a capacity of 200 tons, followed by a 10 mm diameter
A continuous hydrothermal synthesis apparatus consisting of a tubular reactor with a diameter of 0 mm, a length of 4200 mm, and a volume of 1st was used. The tubular reactor was equipped with screws in which two pitches of screw blades were left at three equal intervals in the axial direction, and screws were cut out every other blade at 30° intervals in the helical direction. In addition, pressure balance tubes were installed at the top of the complete mixing reactor and near the inlet of the tubular reactor.

The raw material gypsum and water are mixed to form a slurry, which is continuously supplied to the hydrothermal synthesis equipment using a slurry pump.Production conditions: temperature 130°C, pressure 2. After staying at sKg/cJ for a predetermined time, it was recovered as α-type hemihydrate gypsum. In addition, 0.1 g of sodium succinate was added as a crystal modifier to the raw gypsum. The pH of the slurry was adjusted by Na0)i. No unreacted dihydrate gypsum was observed.

Table 1 shows the manufacturing conditions, and Table 2 shows the quality test results for the α-type hemihydrate gypsum product obtained in Table 1 and the commercial product. The quality test was conducted using JIS R9112-195 (Example 1 in Table 2 Example 2 Flue gas desulfurization stone-1lv: as a raw material and υα by the pressurized aqueous solution method.
Continuous production of type hemihydrate gypsum was carried out. The continuous reactor consists of a complete mixing type reaction tank with a diameter of 300 mm, a height of 700 mm, and a capacity of FP47t, followed by a complete mixing type reaction tank with a diameter of 100 mm and a length of 420 mm.
A continuous hydrothermal synthesis apparatus consisting of a tubular reactor with a volume of 18 t was used. The tubular reactor is actual/kU19
The same one as 1Jl was used.

Raw gypsum and water were mixed to form a slurry, and sodium succinate was added as a crystal modifier at a weight ratio of 0.1% to the raw gypsum. The raw material slurry was continuously supplied to the hydrothermal synthesis apparatus using a slurry pump, and after residence for a predetermined period of time, it was recovered as α-type hemihydrate gypsum. The water/gypsum ratio of the raw material slurry is 1.
5. Slurry pl+ was operated at 9.5 and residence time 1.5 hours.

Table 3 shows the quality test results of the α-type hemihydrate gypsum product.

Example 3 α-type hemihydrate gypsum was continuously produced using flue gas desulfurization gypsum as a raw material by a pressurized aqueous solution method. Continuous hydrothermal synthesis equipment has a diameter of 5
121, a complete mixing type reaction tank with a height of 975 m and a capacity of 200 t, followed by a reactor with a diameter of 100 mw and a length of 4200 m.
A continuous hydrothermal synthesis apparatus consisting of a tubular reactor with a capacity of 18 t and a diameter of 18 t was used. The tubular reactor was equipped with a screw type stirrer, and a 3 mm thick silicon gonor plate was adhered to the screw blade to prevent product from adhering. A pressure balance tube was installed at the top of the complete mixing reactor and near the inlet of the nail reactor.

Raw F1 gypsum and water are mixed to form a slurry, which is continuously supplied to the hydrothermal synthesis equipment using a slurry pump, with a manufacturing temperature of 130°C.
After staying at a pressure of 2.8 Kg/cm2 for a predetermined time, it was recovered as α-type hemihydrate gypsum. In addition, 0.1 g of sodium succinate was added as a crystal modifier to the raw gypsum at a monthly ratio of 0.1 g.

The pH of the slurry was adjusted with NaOH.

Table 4 shows the manufacturing conditions, and Table 5 shows the quality test results of the α-type hemihydrate gypsum product.

TS・4Table 5 Table Example 4 Gypzite AL (01()s) is bound as a raw material and boehmite/
Continuous synthesis of JH was performed. The continuous hydrothermal synthesis apparatus was the same as that used in Example 1. The production conditions were a slurry with a water/gibsite ratio of 5 by weight, and a temperature of 160~ 180℃, pressure (i, 3-10.3 Kg/
cn? The experiment was carried out under the 11th water vapor pressure. Table 6 shows the manufacturing conditions and boehmite percentage (%).

Table 6 (Note) The boehmite rate is the diffraction angle 2θ of boehmite by CII Kα rays = 14.5°, the diffraction angle 2θ of gibzite =
This value was determined from the intensity ratio of the X-ray diffraction peak at 20.3°.

Example 5 A type zeolite was continuously synthesized using silica sol and sodium aluminate as raw materials. The continuous hydrothermal synthesizer N is the same as that used in Example 1.

The manufacturing conditions are silica sol and sodium aluminate with NaO/5
i02 =0.5.5iOz/A403= 4, H*
0/Naz O=246 to make a slurry,
The experiment was carried out at a temperature of 110°C and a pressure of 1.5 Kg/cm'' under saturated steam pressure.A with almost 100% purity was obtained with a residence time of 5 hours.
type zeolite was synthesized.

Example 6 A-type zeolite was continuously synthesized using waste alumina gel (aluminum treated with sulfuric acid) and water glass as raw materials. The continuous hydrothermal synthesis apparatus was the same as that used in Example 1. Manufacturing conditions: alumina gel and water glass are mixed with Na2O
/5i02=2.0, S i O□/A1203=2
．． 0, I120/NazO=100 to form a slurry, and the test was carried out at a temperature of 105°C and a pressure of t and saturated steam pressure of zKp/♂. 7111 residence time 5 hr A
Type zeolite (purity 95%) was obtained.

Example 7 Quicklime (purity 96%) and silica (silica dust purity 94%)
%)' Continuous synthesis of xonotlite was carried out as fc raw material. The continuous hydrothermal synthesis apparatus was the same as that used in Example 1. After digesting quicklime with warm water, M
, to a fft ratio of CaO/5i02 = 0.9, add silica and add water to make a slurry so that the ratio of water/solidification is 12 times.The slurry is continuously supplied with a slurry pump, and after residence for a predetermined time, xonotlite etc. and collected it. The production conditions were a temperature of 190°C, a pressure of 12°C, and a residence time of 6 hours under a saturated steam pressure of 8 K9/lyn2. The product xonotlite was a needle-like crystal of 0.5μΦ×10μ, and was recovered as a spherical aggregate with an average size of about 20μ.

Comparative Example 1 Using flue gas desulfurization gypsum as a raw material, α-type hemihydrate gypsum was continuously produced by a pressurized aqueous solution method. The continuous hydrothermal synthesis apparatus used a single complete mixing type reaction tank with a diameter of 512 mm, a height of 975 mm, and a volume of 200 tons.

The manufacturing conditions were a temperature of 130° C. and a pressure of 2.8 Kmc* under saturated steam pressure. Raw material gypsum and water were mixed to form a slurry, which was continuously supplied using a slurry pump and, after residence for a predetermined period of time, was recovered as α-type hemihydrate gypsum. In addition, sodium succinate was used as a crystal modifier at a weight ratio of 0.0% to gypsum.
05-0.2% was added. The production conditions and the proportion of dihydrate gypsum remaining in the α-type hemihydrate gypsum product (unreacted rate) are shown in the off-line table. The unreacted rate was measured by DTA and TG.

E7 Table (Note) Crystal form ○: short columnar shape with large crystals Δ: columnar shape with small crystals ×: sword shape with small crystals A combination of continuous hydrothermal synthesis equipment (in the experiments using the equipment in Example 1, no trace of dihydrate was observed in any of the experiments. In addition, when carried out using a single complete mixing type reaction tank with a batch line attached) It took more than 5 hours for 2 Suiseki π to disappear.

Comparative Example 2 Flue gas desulfurization gypsum was used as raw material, and pa
Continuous production of α-type hemihydrate gypsum was carried out. Continuous hydrothermal synthesis system!
Only a control reactor (control reactor of Example 1) having a diameter of 100 mm, a length of 4200 mm, and a volume of 18 tons was used. The manufacturing conditions are temperature 130℃, pressure 2, 8 kg/
The experiment was carried out under a saturated vapor pressure of cm. Original) 1 Gypsum and water were mixed to make a slurry, which was continuously supplied using a slurry pump and after residence for a predetermined period of time, was recovered as α-type hemihydrate gypsum. In addition, the crystal modifier is sodium succinate in a weight ratio of 0 to the raw gypsum.
．． Added 1 inch. Manufacturing information is shown in table O8, and product α is shown in table O9.
The quality test results of type hemihydrate gypsum are shown.

E 8 Table

[Brief explanation of the drawing]

FIG. 1 is an explanatory longitudinal cross-sectional view of an example of a continuous hydrothermal synthesis apparatus according to the present invention. l...Complete mixing type reaction tank 2...Hara Kyo) Inlet port 3.
... Stirrer 4 ... Jacket 5 ... Feed pipe 6 ... Management reactor 7 - ... Screw type stirrer 8 ... Discharge port 9 ... Jacket I
O...Pressure balance adjustment tube

Claims (2)

[Claims] (1) Composed of a complete mixing type reaction tank and a subsequent tubular reactor equipped with a screw type stirrer, and pressure balance adjustment to adjust the pressure separately from the tube that transfers reactants between the two. A continuous hydrothermal synthesis device characterized by the installation of pipes. (2) Leave at least one pitch of screw blades at appropriate positions in the axial direction following the complete mixing type reaction tank, and leave one screw blade at intervals of 20 to 40 degrees along the helical direction of the other screw blades. It consists of a tubular reactor equipped with a screw-type stirrer cut out at intervals.
A continuous hydrothermal synthesis apparatus characterized in that a pressure balance adjustment tube for adjusting the pressure is placed between the two, separate from the tube for transferring the reactant.